Valacyclovir

Nancy S. Yunker, PharmD, FCCP, BCPS

• Assistant Professor of Pharmacy, Department of Pharmacotherapy and Outcomes Science, Virginia Commonwealth University School of Pharmacy
• Clinical Pharmacy SpecialistﾗInternal Medicine, VCU Health, Richmond, Virginia

https://app.pharmacy.vcu.edu/nyunker

Spindle fibers: Structures needed for proper alignment and separation of chromosomes during mitosis and meiosis joint infection hiv purchase valacyclovir 500 mg without prescription. Spinous process: A structure of the spinal vertebrae that is formed when two plates called laminae fuse hiv infection rates nsw effective valacyclovir 1000 mg. Spirometer: An instrument for measuring the air taken into and exhaled by the lungs hiv infection in newborn buy discount valacyclovir 1000 mg on line. Spirometry: Laboratory evaluation of the air capacity of the lungs hiv infection detection generic valacyclovir 1000 mg buy, by means of a spirometer antiviral kleenex side effects purchase 1000 mg valacyclovir. Splanchnic circulation: the arteries that branch from the abdominal aorta, serving the digestive organs and hepatic portal circulation. Splanchnic nerves: the nerves that synapse in the collateral ganglia, anterior to the vertebral column. Spleen: the largest lymphatic organ, it is filled with blood instead of lymph and filters the blood via the actions of lymphocytes and macrophages. Splenic cords: Areas of reticular connective tissue in the red pulp of the spleen. Splenic sinusoids: Blood-filled structures in the red pulp of the spleen that are also known as venous sinuses; they are separated by the splenic cords. Splenic vein: the blood vessels that drain blood from the spleen, stomach fundus, and part of the pancreas. Spongy bone: Similarly composed to compact bone, but its cells do not aggregate around the central canals; its cells lie inside the trabeculae and take their nutrients from diffused substances that enter the canaliculi. Spongy urethra: the part of the male urethra that is surrounded by erectile tissue; also called the penile urethra. Sprain: Stretching or tearing of the ligaments reinforcing a joint, most commonly occurring in the ankle, knee, and lumbar region of the spine. Squamous cell carcinoma: A slow-growing malignant tumor of squamous epithelia, frequently found in the lungs and skin, but also occurring in the anus, cervix, larynx, nose, and bladder. Squamous part: the squama; a convex and irregular area of the temporal bone that borders the squamous suture. Squamous suture: the point at which the temporal bones join the parietal bone, on each side of the skull. Stapes: the auditory ossicle attached to the oval window; it transmits sound vibrations from the incus to the internal ear. Static equilibrium: the maintenance of balance when the head and body are motionless. Statoconia: Tiny stones of calcium carbonate crystals (otoliths) that increase the weight of the otolith membrane as well as its resistance to changes in motion; important in equilibrium. Stem cells: Cells that retain the ability to divide repeatedly without specializing and that allow for continual growth and renewal. Striate: Striped, grooved, or ridged; such as the primary visual (striate) cortex. Striated involuntary muscle: Cardiac muscle, which is not under voluntary control by the nervous system; instead pacemaker cells control the individual cardiac muscle cells, though the nervous system can alter their rate; this muscle has striations similar to those of skeletal muscle. Striatum: Also called the corpus striatum; a collective term for the caudate nucleus, putamen, and globus pallidus. Stroke volume: the volume of blood discharged from the ventricle with each contraction; in adults, it is usually about 70 mL. Styloid process: One of two projections below each external acoustic meatuses; it provides a point of attachment, and is attached to muscles of the tongue and pharynx. A different styloid process emerges from the distal end of the radius bone, providing ligament attachments to the wrist. Stylomastoid foramen: the opening, posterior to the base of the styloid process, that allows the facial nerve to pass through. Subarachnoid hemorrhage: Bleeding into the subarachnoid space, which is between the arachnoid membrane and the pia mater. Subcapsular sinus: Also called a lymphatic sinus; channel in a lymph node crossed by a reticulum of cells and fibers, and bounded by littoral cells; there are also trabecular and medullary sinuses. Subclavian vein: A paired large vein, one on either side of the body, with a diameter about the size of an adult pinky finger. Subcostal nerve: the 12th thoracic nerve; its anterior division is larger than the others, running along the lower border of the twelfth rib; it communicates with the first lumbar nerve and transversus. Subcutaneous layer: the hypodermis; it is a loose connective tissue below the dermis that binds the skin to the organs underneath. Subdural hemorrhage: Also called subdural hematoma; a form of traumatic brain injury in which blood gathers in the outermost meningeal layer, between the dura mater and arachnoid mater. Subdural space: the potential space between the dura mater and the arachnoid membrane. Submucosa: the second level of the alimentary canal, made up of loose connective tissue, glands, blood vessels, lymphatic vessels, and nerves. Stercobilinogens: Bilirubin metabolites; precursors of stercobilin, formed by reduction of urobilinogen. Stercobilins: Bile pigment derivatives formed by air oxidation of stercobilinogens; brown-orange-red pigments contributing to the color of feces and urine. Sternal angle: A horizontal ridge across the front of the sternum where the manubrium meets the sternal body; it is cartilaginous and acts as a hinge to allow the gladiolus to move anteriorly during inhalation. Steroid: Molecules with four connected rings of carbon atoms, including cholesterol, estrogen, progesterone, testosterone, cortisol, and estradiol. Stomach: A pouch-like organ that mixes food from the esophagus with gastric juice, begins protein digestion and limited absorption, and moves food into the small intestine. Straight sinus: the sinus that receives blood from the superior cerebellar veins and inferior sagittal sinus; it drains into the confluence of sinuses. Straight tubule: A tubule through with the rete testis receives sperm; it is formed by the seminiferous tubules of each lobule. Stratified columnar epithelium: Thick tissue found in the male urethra, ductus deferens, and areas of the pharynx. Stratified cuboidal epithelium: Thick tissue that lines the mammary gland ducts, sweat glands, salivary glands, pancreas, ovaries, and seminiferous tubules. Stratified squamous epithelium: Thick tissue that forms the epidermis and lines the mouth, esophagus, vagina, and anus. Stratum basale: the deepest layer of the epidermis, also known as the stratum germinativum or stratum basalis. Stratum basalis: Also called the stratum basale or stratum germinativum; the deepest layer of the five layers of the epidermis. Stratum corneum: the outermost layer of the epidermis, consisting of dead and desquamating cells. Stratum germinativum: the deepest layer of the epidermis, also known as the stratum basale; in this layer, cell division occurs. Stratum granulosum: the epidermal layer between the stratum lucidum and stratum spinosum, in which keratin is accumulated. Stratum lucidum: the clear, translucent layer of the epidermis just below the stratum corneum. Stratum spinosum: the epidermal layer between the stratum granulosum and stratum basale, characterized by the presence of prickle cells. Glossary Submucosal nerve plexus: A gangliated plexus of unmyelinated nerve fibers, derived chiefly from the superior mesenteric plexus, ramifying in the intestinal submucosa. Substance P: A polypeptide neurotransmitter that stimulates vasodilation and contraction of intestinal and other smooth muscles; it also plays a part in salivary secretion, diuresis, natriuresis, and pain sensation. Substantia nigra: the layer of gray matter separating the covering (tegmentum) of the midbrain from the crus cerebri. Sucrase: A digestive enzyme secreted in the intestine that catalyzes the hydrolysis of sucrose nad maltose to produce glucose and fructose. Sucrose: A disaccharide obtained from sugar cane, sugar beet, or other sources; used as a food and sweetening agent. Summation: the temporal or spatial addition of contractile force or neural stimuli. Superficial temporal artery: A major artery of the head; its pulse can be felt above the zygomatic arch. Superior mesenteric vein: the vessel that drains blood from the small intestine and forms the hepatic portal vein. Superior vena cava: the second largest vein in the body, formed by the joining of the brachiocephalic veins, which return deoxygenated blood from the upper half of the body to the right atrium. In the anatomic position, the hand is supinated while the radius and ulnae are parallel. Supporting cells: the cells that provide support and protection, and may contribute to the nutrition of principal or other cells of certain organs; they are found in the labyrinth of the inner ear, organ of Corti, olfactory epithelium, taste buds, and seminiferous tubules. Supporting connective tissue: Cartilage and bone, the strong, durable tissues that support other types of tissues in the body. Supraorbital foramen: the notch in each eye orbit (socket), part of the formation of the anterior skull above the eyes, via the frontal bone. Suprarenal glands: Two secretory organs on the upper kidneys, surrounded by their protective fat capsules; each has two parts with independent functions: the cortex and medulla. Surface anatomy: the study of internal body structures related to overlying skin surfaces. Surface tension: An effect that makes it difficult for the alveoli to inflate; it is caused by attraction of water molecules. Suspensions: Mixtures with large, often visible solutes that usually settle; they are heterogeneous mixtures, an example of which is blood. Suspensory ligaments: the ligaments that anchor the ovarian ligament laterally to the pelvic wall; also, those that extend inward to help support the weight of the breast. Sutures: Seams that occur only between the bones of the skull; they are a type of fibrous joints. Sweat glands (sudoriferous glands): Those that originate in the deep dermis or superficial subcutaneous layers and secrete sweat out of the skin through the pores; they include merocrine (eccrine) and apocrine glands. Symmetry: Having a similar dimension, proportion, or arrangement; it describes the appearance of many body structures, such as the right and left hemispheres of the brain. Sympathetic ganglia: Groups of cell bodies of adrenergic neurons of the sympathetic nervous system, arranged on either side of the spinal cord. Sympathetic trunk: A bundle of nerve fibers running from the base of the skull to the coccyx. Sympathetic venoconstriction: the action that reduces the amount of blood in the veins. Sympathetic: the part of the nervous system that increases heart and breathing rates; part of the "fight-orflight" response. Synapse: A junction between any two communicating neurons; a synapse is the site of intracellular communications between neurons. Synaptic cleft: A fluid-filled space between presynaptic and postsynaptic membranes. Synaptic delay: the period between the arrival of an impulse at the presynaptic membrane and the initiation of an action potential in the postsynaptic membrane. Synaptic vesicles: Tiny membrane-bounded sacs on axon terminals of presynaptic neurons; they each contain thousands of neurotransmitter molecules. Synarthrotic: A joint that is immovable; mostly found in the axial skeleton, along with amphiarthrotic joints. Synchondroses: Cartilaginous joints in which plates or bars of hyaline cartilage unite bones; nearly all of these are synarthrotic. Syndesmoses: Fibrous joints in which ligaments connect their related bones, and the connecting fibers are longer than those found in sutures. Synergists: Muscles that work with a prime mover to make its action more effective. Taste pores: Minute openings of taste buds on the surface of the oral mucosa, through which gustatory hairs of specialized neuroepithelial gustatory cells project. Tectorial membrane: One of two acellular membranes in the cochlea of the inner ear, lying above the spiral limbus and organ of Corti; the other is the basilar membrane. Tectospinal tracts: Also called the colliculospinal tracts; nerve pathways that coordinate head and eye movements. Teeth: the structures used for chewing inside the mouth; humans have two sets-primary (deciduous) and secondary (permanent) teeth. Temporal summation: the type of summation that occurs when stimuli are added in rapid succession at just one synapse that is repeatedly active. Tendon sheath: Lengthened bursae wrapping completely around a tendon subjected to friction; common in areas such as the wrist, where several tendons are tightly crowded inside narrow canals. Teniae coli: the three bands in which the longitudinal muscular fibers of the large intestine, except the rectum, are collected. Tensor tympani: A muscle originating in the cartilaginous portion of the auditory tube and inserting in the manubrium of the malleus; it tenses the tympanic membrane as sounds occur. Tentorium cerebelli: A horizontal projection of the meningeal dura mater that covers and separates the cerebellum, in the posterior cranial fossa, from the posterior parts of the cerebral hemispheres. Teratogens: Environmental factors that cause congenital malformations by interfering with prenatal growth or development. Terminal arteriole: An arteriole that has no branches, but splits into capillaries. Terminal branches: Structures of axons that allow information from the neuron to travel to more than cell at a time. Terminal cisterns: End sacs in the sarcoplasmic reticulum of skeletal muscle fibers that form perpendicular cross-channels at the A band and I band junctions; they occur in pairs and are larger cross-channels. Synostoses: Unions between adjacent bones or parts of single bones formed by osseous material. Synovial fluid: the fluid secreted by synovial membranes that lubricates synovial joints.

The onset of clinically appreciable hepatic encephalopathy heralds liver failure and differentiates it from patients with a severe acute liver injury [4] antiviral zdv best 1000 mg valacyclovir. Firstly antiviral youwatch buy cheap valacyclovir, there is a preponderance among females (67% of cases in a large series of 1147 patients) and relatively young patients (mean age 38 years) [5 hiv infection rates homosexual cheap valacyclovir 1000 mg buy line,6] hiv infection after 1 year symptoms generic valacyclovir 1000 mg amex. Historically it was assumed that unidentified pathogenic viruses or hepatotoxic drugs were the most likely cause for the majority of these cases; the term "seronegative" was introduced more recently antiviral and antibiotics purchase valacyclovir paypal, which recognized the possibility of an uncharacterized autoimmune or immunemediated liver injury. It is associated with a high incidence of cerebral edema, but paradoxically has the best outcomes and patients in this group are more likely to survive without liver transplantation. Finally, "subacute liver failure" pertains to individuals with a more insidious onset of encephalopathy, which develops 5­12 weeks after the onset of jaundice; in this group the incidence of cerebral edema is low but prognosis is very poor without transplantation. Patients with indeterminate or seronegative hepatitis most commonly present with subacute liver failure, which can be difficult to differentiate clinically from decompensated liver cirrhosis or acuteonchronic liver failure. Such cases have poor spontaneous recovery and survival rates and represent a common indication for emergency liver transplantation [4,12]. Most common in pregnant or immunosuppressed patients and may not be associated with mucocutaneous lesions; empiric aciclovir can be considered in these patients. Chapter 10 Managing Acute and Chronic Seronegative Liver Disease 187 A thorough patient history is critical in determining etiology, as offending drugs or toxins may have been ingested weeks or months before presentation. Unintentional acetaminophen overdoses are also common, with patients inadvertently consuming toxic levels of acetaminophen from multiple different products or when mentation is impaired with drug and/or alcohol ingestion. It is often necessary to take repeat histories from patients and gain collateral history from relatives or friends. In this group, some patients are suspected of having an autoimmune pathogenesis on the basis of characteristics such as being a young female, a history of other autoimmune diseases, hyperglobulinemia, and positive autoantibodies. Autoantibodies were absent in acetaminophenrelated cases but present in 23 of 53 (43%) of nonacetaminophen cases. Prodromal symptoms are typically nonspecific and include fatigue, myalgia and nausea, and can often be mistaken for a viral prodrome. Other clinical features include a lesser degree of coagulopathy, and less renal failure and acidosis when compared with acetaminophen toxicity. Acute renal failure, bacterial and fungal infections, and respiratory distress requiring ventilation are also common manifestations [6]. A number of risk stratification algorithms are used throughout the world; common elements among these algorithms include patient age, the degree of coagulopathy, and jaundice. Multiple studies, including systematic reviews and meta analyses, have consistently shown these criteria to have high specificity but lower sensitivity and negative predictive value. Patients identified as having the lowest transplantfree survival included those with hepatic encephalopathy and low factor V levels and these criteria predicted mortality with a positive predictive value of 82% and negative predictive value of 98% [20]. The significant heterogeneity between studies included in the metaanalysis made conclusions difficult and the authors suggested that neither scoring system is optimal for all patients [24]. Patients often develop hypoglycemia which should be monitored and glucose infusions commenced as appropriate. Coagulopathy should not be corrected unless there is evidence of active bleeding and stress ulcer prophylaxis should be provided. Patients should undergo rapid assessment to determine the etiology and severity of the liver injury, along with the suitability for liver transplantation. Early identification of patients with a significantly reduced chance of spontaneous survival is imperative as this increases the chance for successful liver transplantation. In these situations, clinicians are faced with the conundrum of whether to deny corticosteroids to patients who may respond but otherwise die or to introduce corticosteroids to patients who will not improve and may deteriorate. Once instituted, this treatment should not delay transfer to a transplant center, should be given for a defined period which should be less than 2 weeks, and patients must be intensively monitored for signs of deterioration. Survival after transplantation improved from 66 to 86% and overall transplantfree survival also increased to 48%. This minimizes the chance the patient will become too unwell to transplant and maximizes the time to find a suitable donor organ. Consideration of survival potential following transplantation, including factors such as age, comorbidities, and sepsis. Psychological assessment of the patient to assess expected compliance, social supports, past history of suicide attempts, and high risk substance and alcohol abuse. This is a complex area and collateral history should be obtained from family and friends. A comprehensive patient history is mandatory, including: Chapter 10 Managing Acute and Chronic Seronegative Liver Disease 193 Table 10. Established associations Nonalcoholic steatohepatitis Seronegative autoimmune hepatitis Occult viral hepatitis Concealed ethanol Sarcoidosis Wilson disease Occult biliary disease Hepatic vascular disease Celiac disease Mitochondriopathies Familial Mediterranean fever Systemic lupus erythematosus Alstrom syndrome Keratin 18 mutations Telomerase gene mutations Less established Other associations risk factors for viral hepatitis. Other investigations such as IgG4 levels and celiac serology should also be considered. Often, interpretation of biopsies necessitates close cooperation between the hepatologist and pathologist, looking for residual "histologic footprints" or pre-existing disorders (Table 10. Autoantibody titers at presentation also correlate poorly with disease severity, degree of liver injury, and response to treatment [47]. In such cases, the diagnosis is made typically on the basis of a transaminitis, elevated serum IgG levels, typical histologic findings, and careful exclusion of other causes of liver disease [48]. It is now recognized that a spectrum of other histologic findings may coexist with interface hepatitis without negating the diagnosis [44,49]. The presence of centrilobular necrosis may confer a good response to corticosteroid therapy [50]. Conclusion Patients with seronegative or cryptogenic liver disease represent a heterogeneous and challenging group. A systematic, comprehensive and multidisciplinary approach is essential in evaluating such patients and this, coupled with ongoing improvements in diagnostic technology, is likely to result in fewer and fewer patients diagnosed with true cryptogenic liver disease. Atypical presentations of autoimmune liver disease undoubtedly represent the underlying etiology in a significant proportion of seronegative patients presenting with both acute and chronic liver disease. Timely diagnosis is essential and may result in improved outcomes for the patient. Systematic review: non A­E, seronegative or indeterminate hepatitis; what is this deadly disease Etiology and outcome of fulminant hepatic failure managed at an Australian liver transplant unit. Outcomes in adults with acute liver failure between 1998 and 2013: an 10 11 12 13 14 15 16 17 observational cohort study. Outcomes following liver transplantation for seronegative acute liver failure: experience during a 12year period with more than 100 patients. The significance of autoantibodies and immunoglobulins in acute liver failure: a cohort study. Acute liver failure of indeterminate etiology: a comprehensive systematic approach by an expert committee to establish causality. Acute liver failure in Scotland: changes in aetiology and outcomes over time (the Scottish LookBack study). Chapter 10 Managing Acute and Chronic Seronegative Liver Disease 199 18 McPhail, M. Coagulation factor V levels as a prognostic indicator in fulminant hepatic failure. Patients with acute liver failure listed for superurgent liver transplantation in France: reevaluation of the Clichy Villejuif criteria. Introduction to the Revised American Association for the Study of Liver Diseases Position Paper on Acute Liver Failure 2011. Intravenous Nacetylcysteine 28 29 30 31 32 33 34 35 36 37 improves transplantfree survival in early stage nonacetaminophen acute liver failure. Effects of N acetylcysteine on cytokines in nonacetaminophen acute liver failure: potential mechanism of improvement in transplantfree survival. Efficacy and safety of acetylcysteine in "nonacetaminophen" acute liver failure: a metaanalysis of prospective clinical trials. Effect of N acetylcysteine on mortality and liver transplantation rate in nonacetaminophen induced acute liver failure: a multicenter study. Corticosteroid responsive cryptogenic chronic hepatitis: evidence for seronegative autoimmune hepatitis. The natural history of nonalcoholic steatohepatitis: a followup study of fortytwo patients for up to 21 years. Prevalence of obesity, diabetes mellitus and hyperlipidaemia in patients with cryptogenic liver cirrhosis. Cryptogenic cirrhosis: clinical characterization and risk factors for underlying disease. Wilson disease: pathogenesis and clinical considerations in diagnosis and treatment. Serologic markers do not predict histologic severity or response to treatment in patients with autoimmune hepatitis. Seronegative autoimmune hepatitis presents with more severe disease but has similar outcomes as compared to seropositive patients. Comparison of the clinical features and clinical course of antimitochondrial antibodypositive and negative primary biliary cirrhosis. The risk of maternal complications is closely linked to the presence of cirrhosis and disease activity, and can be reduced with optimization of medical management. Women with cirrhosis are at risk of decompensation, in particular those with higher model for end-stage liver disease score at conception. Flare-up of disease activity is more common in the postpartum period but can also occur during pregnancy, and can precipitate liver-related complications and adverse maternal and fetal outcomes. The widespread use of azathioprine in rheumatologic disorders and inflammatory bowel diseases has provided increasing evidence on the safety of azathioprine in pregnancy. Flareup of disease activity is more common in the postpartum period but can also occur during pregnancy, and can precipitate liverrelated complications Autoimmune Liver Disease: Management and Clinical Practice, First Edition. These women should undergo surveillance and therapy of gastroesophageal varices usually prior to conception as well as in the second trimester of gestation. Its activity can be altered during pregnancy and in the postpartum period, and women with cirrhosis are at risk of developing liverrelated complications. The safety of medications in pregnancy has been a significant concern among women and obstetricians. Menstruation and ovulation usually return to normal after optimal control of their disease has been achieved [2]. A significant proportion of female patients with endstage liver disease experience amenorrhea and anovulation, the etiology of which is presumably dysfunction of the hypothalamic­pituitary axis. A study of 12 young women (age 19­33 years) with cirrhosis and amenorrhea of at least 3 months demonstrated that seven women were hypogonadotrophic and five were normogonadotrophic based on luteinizing hormone levels [1]. The former had significantly lower testosterone and estradiol levels, were thinner, and exhibited lower breast development stage. It was therefore hypothesized that undernutrition, which is common in advanced liver disease, could potentially be the cause of hypothalamic mediated amenorrhea. The landscape has changed dramatically in the last one to two decades with the emergence of increasing evidence showing encouraging fetal and maternal outcomes. Their main limitations are the relatively small number of patients/pregnancies, their retrospective nature, the lack of control group, and in some cohorts the methodology used to record outcomes (self reported outcomes via response to questionnaires). Chapter 11 Managing Pregnant Women with Autoimmune Liver Disease 205 In these studies the miscarriage rate, defined as fetal loss before weeks 20­22 of gestation, ranged between 5. The highest miscarriage rate was reported among women with cirrhosis in the study by Borssen et al. In this study, there were 131 pregnancies in 71 women, including 43 pregnancies in 33 women with cirrhosis. There were 13 terminations of pregnancy in this cohort, several of which occurred following clinician advice. The number of stillbirths, defined as fetal loss beyond weeks 20­22 of gestation, in all studies was very low (0­2). The rate of preterm birth (delivery before weeks 36­37 of gestation) was on average 20% in the majority of studies [3,4,7,8]. The risk was 21% in noncirrhotic and 23% in cirrhotic women in the study by Borssen et al. The reported congenital abnormality and neonatal death rate was low in the majority of studies, and did not seem to be associated with fetal exposure to azathioprine. All previous studies included small numbers of patients given the rarity of the disease, and more importantly did not compare pregnancy outcomes to those in the general population. The risk of intrahepatic cholestasis of pregnancy was also higher in the same group compared to the general population (11. Pregnancy in this population is associated with increased risk of preterm birth and smallforgestational age neonates, but not congenital malformations. The risk of miscarriage is likely increased mainly in women with cirrhosis [6,14­16]. The loss of self tolerance is the result of impaired balance between liverspecific Tregulatory cells and effector cells of liver damage [17]. Under normal circumstances, Tregulatory cells exert control over the effector cells ensuring immune tolerance. Impaired Tregulatory cell control function or impaired effector cell responsiveness results in recognition of liverspecific autoantigens, cytokine release and cytotoxicity, leading to liver damage [18]. A number of immunologic changes occur in the advent of conception in an effort to ensure immune tolerance to paternally derived fetal antigens. The immune system reacts to the recognition of fetal antigens with the development of protective mechanisms. Pregnancy is characterized by a shift from proinflammatory Th1 to antiinflammatory Th2 immune responses and cytokine balance. Increased levels of cortisol, estrogen and progesterone likely play a role in this shift. Of particular interest is the induction of Tregulatory cells during pregnancy that facilitate tolerance to fetal antigens, but which also maintain tolerance to selfantigens [21].

Advances in genetics hiv aids infection rate washington dc valacyclovir 1000 mg order online, including the outstanding results of the Human Genome Project antiviral bacteria buy valacyclovir in united states online, are improving treatments and even cures for a large variety of diseases and disorders linked to gene and chromosomal defects hiv infection vectors purchase valacyclovir 1000 mg on-line. Geneticists can now manipulate and engineer human genes and examine their expression for genetic screening and drug development highest hiv infection rates us valacyclovir 500 mg buy line. Humans inherit two alleles for each gene hiv infection prognosis buy discount valacyclovir 1000 mg, but some genes have more than two allele forms, which leads to multiple allele inheritance. Factors that may influence or override gene expression include the sun, exercise, drugs, pathogens, nutrition, and the effects of other genes. Prader­Willi syndrome causes moderate retardation, shortness, and extreme obesity. It is caused by deletion of a particular region of chromosome 15, but the defect comes from the father. It is caused by the same chromosome deletion, but the defect comes from the mother. Mitochondrial (extranuclear) genes are transmitted almost always by the mother because her ovum donates nearly all the cytoplasm in the fertilized egg. It is able to test for fetal chromosomal abnormalities and information about the fetal genome, including mutations. Gene therapy can involve defective cells being injected with a virus that has already had functional genes inserted into it. The percentage of people with a certain genotype that show the expected phenotype is referred to as A. Which of the following is the most common abnormality of the Klinefelter syndrome karyotype Autosomes Which of the following factors may result in multiple allele inheritance Explain why recessive genetic disorders are more frequent than those caused by dominant alleles. Identify the amounts of genes carried by the X and Y chromosomes and give a brief overview of their functions. Discuss tests used to screen for the sickling gene, Tay-Sachs disease, and cystic fibrosis. Abdominal aorta: the largest artery in the abdominal cavity; a direct continuation of the descending aorta of the thorax. Abduction: Moving a part away from the midline (longitudinal axis), or median plane, of the body. Absolute refractory period: the period from the opening of sodium channels until they begin to reset to their original resting state. Accessory organs: In the digestive system, these include the salivary glands, liver, gallbladder, and pancreas. Accessory pancreatic duct: the excretory duct of the head of the pancreas, formed from the proximal part of the duct of the embryonic dorsal pancreatic bud; it opens into the duodenum at the lesser duodenal papilla. Acetabular labrum: A circular rim of fibrocartilage of the hip joint that increases the depth of the acetabulum. Acetabulum: A structure created by the fusing of the three parts of the hipbones; it houses the rounded head of the femur. Acetylcholinesterase: the enzyme that causes muscle relaxation by the decomposition of acetylcholine; abbreviated as "AchE. Acidosis: Also known as acidemia; the accumulation of acid and hydrogen ions or depletion of the bicarbonate content in the blood and body tissues, decreasing the pH. Acromegaly: A disorder marked by progressive enlargement of the head, face, hands, and feet because of excessive secretion of growth hormone from the anterior lobe of the pituitary gland, occurring after puberty. Acromion process: An extension from the scapula that provides muscle attachments for the upper limbs and chest; it is continuous with the scapular spine. Actin: the component that makes up most of the thin protein filaments of the myofibrils. Action potential: the basis for a nerve impulse, based on the cell membrane reaching its threshold potential; it is a brief reversal of membrane potential with a change in voltage of approximately 100 millivolts. Active humoral immunity: Signified by antibodies produced by B-cells after encountering antigens; it may be acquired naturally or artificially. Active transport: the movement of particles through membranes from regions of lower concentration to regions of higher concentration. Active tubular reabsorption: A selective process that reclaims materials from the tubular fluid and returns them to the bloodstream; it can move a solute against an electrochemical gradient and requires energy derived from metabolism. Adaptation: Any characteristic of anatomy, physiology, or behavior that promotes survival and reproduction. Adaptive (specific) defense: Immunity; it targets specific pathogens and acts more slowly than innate defenses. Adductor tubercle: the bump on the superior region of the medial epicondyle of the femur. Adenocarcinoma: Any one of a large group of malignant epithelial cell tumors of the glandular tissue. Adenohypophysis: the anterior pituitary; the glandular part of the pituitary gland. Adipocytes: Fat cells, in which the organelles and cytoplasm are squeezed to one side. Adiponectin: A hormone produced exclusively in adipose tissue that is involved in many metabolic processes, including glucose regulation and the metabolism of fat for energy production. Adrenal androgens: Sex hormones from the adrenal cortex; may be converted to estrogens, progesterone, or testosterone. Adrenal cortex: the outer, firm layer making up most of the adrenal gland; it secretes mineralocorticoids, androgens, and glucocorticoids. Adrenal medulla: the inner portion of the adrenal gland, where epinephrine and norepinephrine are produced. Adrenergic fibers: Sympathetic postganglionic neurons that secrete norepinephrine (noradrenalin). Aerobic respiration: the release of energy from glucose or another organic substrate in the presence of oxygen. Afferent arterioles: the final branches of the interlobular arteries of the kidneys; they lead to the nephrons. Afterload: the pressure that the heart must push against when it ejects blood into the circulatory system. Agglutinins: Antibodies that interact with antigens, resulting in agglutination; agglutinins are used in blood typing, and in identifying or estimating the strength of immunoglobulins. Alae: In the spine, the expanded superior regions that have a wing-like appearance and are lateral to the anterior sacral foramina. Albumins: the smallest of plasma proteins; they make up around 60% of these proteins by weight. Aldosterone: A mineralocorticoid produced by the adrenal cortex that helps the kidneys to balance sodium and potassium as well as stimulating water retention via osmosis. Alimentary canal: the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus. Alkaline phosphatase: An enzyme that is lost in matrix vesicles by osteoblasts; it is critical for mineralization of bones. Alkalosis: Also known as alkalemia; the accumulation of bases, or loss of acids from the blood and body tissues, increasing the pH. Allantois: A structure that forms during the third week of development as a tube extending from the early yolk sac into the connecting stalk of the embryo. Allergens: Antigens; chemicals that stimulate B cells to produce antibodies or allergies. All-or-none phenomenon: the description of how an action potential occurs, which is either completely or not at all; the action potential is generated and propagated once it reaches threshold whether or not the stimulus continues, and it cannot occur if threshold is never reached, even only by a slight amount. Alpha cells: the cells located in the adenohypophysis of pancreatic islets; in the pancreas, they produce glucagon, which raises the level of glucose in the blood. Alternative pathway: the pathway that activates the complement system when antibody molecules are absent. Alveolar arch: the curved portion of the mandible that contains the hollow sockets for the lower teeth. Alveolar macrophages: Cells of the reticuloendothelial system in the lungs, which engulf and digest foreign substances inhaled into the alveoli. Alveoli: Microscopic air sacs inside capillary networks of the lungs; they are composed mainly of simple squamous epithelial cells called pneumocytes. Angiotensinogen: A serum globulin formed by the liver that is cleaved by renin to form angiotensin I. Angular movements: Those that decrease or increase the angle between two bones, including extension, flexion, hyperextension, abduction, adduction, and circumduction. Annular ligament: the ligament that surrounds the heat of the radius and is part of the elbow joint. Antagonists: Muscles that cause movement in the opposite direction of prime movers. Anterior cardiac veins: Two or three small veins in the anterior wall of the right ventricle, opening directly into the right atrium, independently of the coronary sinus. Anterior cerebral artery: One of the two terminal branches of the internal carotid. Anterior communicating artery: A short vessel joining the two anterior cerebral arteries across the midline, completing the cerebral arterial circle (of Willis) anteriorly. Anterior intercostal arteries: the arteries supplying the anterior portions of the intercostal spaces of the thoracic wall. Anterior interventricular artery: Also called the left anterior descending artery; a branch of the left coronary artery originating at the left margin of the pulmonary trunk. Anterior interventricular sulcus: A groove on the anterosuperior surface of the heart, marking the location of the septum between the two ventricles. Anterograde amnesia: Loss of memory of events during a specific period of time after the occurrence of a precipitating event. Antibodies: Immunoglobulins or agglutinins; they are gamma globulin proteins that react to destroy antigens or antigen-containing particles and are produced from B cells. Ammonia: A compound of nitrogen and hydrogen that is secreted by the kidneys to neutralize excess acid; however, in sufficient quantities, it is toxic to body cells. A wide-bore needle is used to remove amniotic fluid, using ultrasound to visualize the position of the fetus and the sac. Amnion: A membrane that develops, during the embryonic period, around the embryo; it appears during the second week. Amniotic fluid: A liquid that fills the space between the amnion and embryonic disc. Amphiarthrotic: A joint that is slightly movable; mostly found in the axial skeleton, along with synarthrotic joints. Amplitude: the width or breadth of range or extent, such as an amplitude of convergence. Ampulla: An expansion at the end of each semicircular canal containing a crista ampullaris. Amygdaloid body: An almond-shaped nucleus on the tail of the caudate nucleus and is part of the limbic system. Anaerobic endurance: the ability to endure activity or function without molecular oxygen. Anaerobic respiration: A form of respiration in which molecular oxygen is not consumed, such as nitrate or sulfate respiration. Anastomoses: Surgical, traumatic, or pathologic formations of connections between two normally distinct structures, such as between arteries and veins. Anastomosis: A single communication between vessels, via a collateral channel or channels; anastomoses are multiple communications between vessels via collateral channels. Anatomical neck: the narrow depression in the humerus that separates it from the greater and lesser tubercles. Androgens: Male sex hormones mostly produced by the testicular interstitial cells. Aneurysm: A blood-filled sac in an artery wall caused by dilation or weakening of the wall. In each monomer arm, each antibody monomer has two antigen-binding sites or regions. Antigenic determinants: Sites on an antigen molecule to which antibody molecules bind. Antigen-presenting cell: An accessory cell, which may be a macrophage, B cell, or other type of cell that has processed antigen fragments on its surface. Antigens: Also called agglutinogens, they are proteins, polysaccharides, glycoproteins, or glycolipids commonly found on red blood cell surfaces; cells learn to recognize antigens as either "self " or "nonself " (foreign). Anus: the opening of the distal end of the anal canal; feces pass out of the anus to outside of the body. Aorta: the largest artery in the body, it originates from the left ventricle of the heart and extends down to the abdomen, where it branches off and sends oxygenated blood to all body tissues. Aortic arch: the second section of the aorta; it branches into the brachiocephalic trunk, left common carotid artery, and left subclavian artery. Aortic bodies: Receptors in the aortic arch sensitive to changing oxygen, carbon dioxide, and pH of the blood. Aortic reflex: Also called the cardiac depressor reflex; a fall in blood pressure due to peripheral vasodilation and cardiac inhibition by stimulations of terminations of a cardiac depressor nerve in the aortic arch and base of the heart. Aortic sinus: the space between the superior portion of each of the three aortic valve cusps, and the dilated portion of the wall of the ascending aorta. Aortic valve: Located at the base of the aorta, it has three cusps and opens to allow blood to leave the left ventricle during contraction. Apex: the lowest superficial part of the heart, formed by the inferolateral part of the left ventricle; also the narrow superior tip of each lung. Apneustic breathing: A pattern of breathing characterized by a prolonged inspiratory phase, followed by expiration apnea.

Decreased intestinal absorption anti viral cleanse and regimen reviews cheap valacyclovir master card, hyperparathyroidism hiv symptoms directly after infection cheap valacyclovir online amex, or increased urinary output hiv infection gas station cheap valacyclovir 500 mg otc. Dehydration hiv infection rates louisiana valacyclovir 500 mg amex, increased retention or intake hiv infection prophylaxis generic 500 mg valacyclovir amex, hyperparathyroidism, or metabolic acidosis. Outcomes (for both hyperchloremia and hypochloremia) have no direct clinical symptoms because they are usually associated with the underlying cause, which is often related to abnormalities in the pH. Metabolic alkalosis, such as caused by vomiting or excessive ingestion of alkaline substances, and aldosterone deficiency. Although rare, it occurs in kidney failure when magnesium is not excreted normally. Outcomes include lethargy, impaired central nervous system functioning, respiratory depression, coma, and cardiac arrest. Outcomes include tremors, increased neuromuscular excitability, convulsions, and tetany. It is not difficult for us to obtain the amounts of electrolytes we need, however. Natural foods contain plenty of sodium, whereas processed foods contain too much sodium. Salts are mostly lost from the body via sweating, vomiting, and in the urine and feces. Sweat is usually hypotonic, but large amounts of salt can be lost when sweating becomes profuse. Large losses of salt in vomit or feces may be linked to disorders of the gastrointestinal tract. Aldosterone secretion is also directly stimulated by high plasma potassium ion concentrations. The ways aldosterone influences the amounts of conserved sodium and the amounts of potassium excreted via the urine are closely related. Calcium Balance There is more calcium in the body than any other mineral, and 99% of body calcium is deposited in the skeleton. Calcium is vital for controlling muscular and neural activities, for blood clotting, for forming the crystalline components of bones, as a cofactor for enzymatic reactions, and because of its second messenger functions. Calcium homeostasis is maintained in the extracellular fluid by parathyroid hormone and calcitriol but also by calcitonin to a smaller degree. Calcium ion concentrations are raised by parathyroid hormone and calcitriol, whereas calcitonin opposes their actions. Although a small amount of calcium is lost every day in the bile, only tiny amounts are lost via the urine or feces. It is absorbed in the digestive tract and reabsorbed in the distal convoluted tubule. Hypercalcemia is present when the extracellular fluid calcium ion concentration is higher than 5. In adults, it is usually caused by hyperparathyroidism, which is over-secretion of parathyroid hormone. Additional causes include malignant cancers of the breast, kidneys, bone marrow, or lungs. Excessive use of supplements containing calcium or vitamin D may also cause hypercalcemia. Hypercalcemia is considered severe when calcium ion concentration exceeds 12­13 mEq/L in the extracellular fluid. Signs and symptoms include confusion, fatigue, calcification of soft tissues such as the kidneys, and cardiac arrhythmias. The opposite condition is hypocalcemia, in which there is a calcium ion concentration under 4. This electrolyte diffuses out of the cellular cytoplasm into the extracellular fluid and therefore requires the cells to expend energy to recover its ions. The potassium ion concentration in the extracellular fluid is based on a balance between the rate at which the ions are gained across the digestive epithelium and the rate at which they are lost into the urine. The actions of the ion pumps in the distal parts of nephrons and the collection system regulate potassium loss in the urine. When a sodium ion is reabsorbed from the tubular fluid, there is usually an exchange between it and a cation, most commonly potassium, from the peritubular fluid. Normally, between 50 and 150 mEq of urinary potassium ions are lost, whereas the same amount is absorbed across the digestive epithelium. In the extracellular fluid, potassium ion concentration is controlled by regulating active secretion rates along the distal convoluted tubule and nephron collecting system. Three factors relate to how the rate of tubular secretion of potassium ions varies: changes in the potassium ion concentration of the extracellular fluid, changes in pH, and aldosterone levels. Basically, the higher the concentration of potassium in the extracellular fluid, the higher the rate of secretion. When pH falls in the extracellular fluid, the pH of the peritubular fluid also falls. This is because hydrogen ions, not potassium ions, are secreted as part of an exchange with sodium ions in the tubular fluid. Aldosterone greatly affects the rate at which potassium ions are lost in the urine. This results from the ion pumps being sensitive to aldosterone and therefore reabsorbing sodium ions from the filtrate, 606 Chapter 23 Fluid, Electrolyte, and Acid-Base Balance caused by hypoparathyroidism, which is under-secretion of parathyroid hormone, chronic renal failure, or vitamin D deficiency. Signs and symptoms include osteoporosis, weak heartbeat, muscle spasms that may be accompanied by generalized convulsions, and cardiac arrhythmias. Acid-Base Balance Phosphate Balance Phosphate ions are essential for the mineralization of bones. Phosphate most significantly affects the intracellular fluid, where it helps to activate enzymes, form high-energy compounds, and synthesize nucleic acids. The major sources of hydrogen ions are as follows: Chloride Balance Chloride ions are the most common ions found in the extracellular fluid, with normal plasma concentrations between 100 and 108 mEq/L. In the renal tubules, chloride and sodium ions are absorbed by several carrier proteins. Aerobic respiration of glucose: produces carbon dioxide and water, forms carbonic acid, and releases hydrogen and bicarbonate ions Anaerobic respiration of glucose: produces lactic acid, adding hydrogen ions to body fluids Incomplete oxidation of fatty acids: produces acidic ketone bodies to increase hydrogen ion concentration Oxidation of sulfur-containing amino acids: yields sulfuric acid, releasing hydrogen ions Hydrolysis of phosphoproteins and nucleic acids: produces phosphoric acid, releasing hydrogen ions Strengths of Acids and Bases Strong acids dissociate to release hydrogen ions more completely, whereas weak acids release them less completely. An example of a strong acid is hydrochloric acid and of a weak acid is carbonic acid. Bases release ions, such as hydroxide ions, that combine with hydrogen ions, lowering their own concentration. They may combine with strong acids; for example, bicarbonate ions may combine with hydrogen ions from hydrochloric acid to form carbonic acid. All functioning proteins, including enzymes, cytochromes, and hemoglobin, are influenced by hydrogen concentrations. Therefore, nearly all biochemical reactions are influenced by fluid environment pH, and there is close regulation of acid-base balance. The lower pH in venous blood and the cells is because of their larger amounts of carbon dioxide and acidic metabolites. If a person lacks sufficient iron, he or she may "crave" chalk, clay, or starch-a condition known as pica. However, because it is higher than the optimal hydrogen concentration for most cells, a pH between 7. The three sequential regulators of hydrogen ion concentration in the blood are chemical buffers, brain stem respiratory centers, and renal mechanisms. The first line of defense consists of chemical buffers, which act in less than a second to resist changes in pH. In one to three minutes, respiration changes in rate and depth, compensating for acidosis or alkalosis. The kidneys are the slowest to act, requiring several hours to days to alter the blood pH, but are the strongest regulators of acid-base balance. Acid-Base Buffer Systems Acid-base buffer systems consist of chemicals that combine with excess acids or bases. Buffer system chemicals can combine with strong acids, which release more hydrogen ions, to convert them into weak acids, which release fewer hydrogen ions. The three Bicarbonate buffer system: this system is present in both intracellular and extracellular fluids, using the bicarbonate ion as a weak base and carbonic acid as a weak acid. Carbonic acid is formed when hydrogen ions are excessive and dissociates when conditions are basic or alkaline. Phosphate buffer system: this system also operates in both intracellular and extracellular fluids and is very important in controlling hydrogen ion concentrations in the fluid of the nephrons and in urine. For red blood cells, which are densely packed with hemoglobin molecules that buffer hydrogen ions, a chloride shift occurs. This involves dissociation of carbonic acid and bicarbonate ions diffusing into the plasma in exchange for chloride ions. As carbonic acid dissociates, hydrogen ions increase and the internal environment pH drops. These actions stimulate chemoreceptors in the medulla oblongata, increasing breathing so the lungs can excrete more carbon dioxide. If cells are less active, production of these components is low and breathing may be closer to resting levels. Nephrons excrete hydrogen ions in urine to help regulate hydrogen ion concentration. Epithelial cells in the renal tubules secrete hydrogen ions into the tubular fluid. The partial pressure of carbon dioxide (Pco2) is the most important indicator of normal respiratory function. Dangerous acidosis and alkalosis conditions may be linked to cardiovascular, respiratory, urinary, digestive, or nervous system abnormalities. To correctly diagnose these conditions, most blood tests include screenings of pH and buffer system function. Additional tests include measuring the anion gap and using nomograms or diagnostic charts to plot test results. These steps help to correctly identify the condition, its severity, its causes, and whether it is compensated or uncompensated. It is usually caused Acid-Base Imbalances 609 by hypoventilation, which is an abnormally low respiratory rate. When the Pco2 rises in the extracellular fluid compartment, hydrogen and bicarbonate ion concentrations also rise. This is normally accomplished by chemoreceptors that stimulate an increase in breathing rate. In uncompensated acidosis, the pH continues to drop, and the patient can become comatose and eventually die. Therefore, for victims of cardiac arrest or drowning, reversing acute respiratory acidosis is the major goal. Chronic respiratory acidosis occurs because normal respiratory function is compromised but compensatory mechanisms have not completely failed. In a patient with central nervous system damage, normal respiratory compensation may not occur even when stimulated by chemoreceptors. People whose respiratory centers are desensitized by barbiturates or alcohol may also be unable to achieve normal respiratory compensation. Other factors, such as congestive heart failure, emphysema, pneumonia, pneumothorax, and respiratory muscle paralysis, can influence the development of chronic respiratory acidosis. When normal pulmonary responses are disabled, the kidneys increase hydrogen ion secretion into the tubular fluid, slowing the rate of pH change. Unfortunately, the kidneys are not able to return pH to normal levels on their own. Breathing efficiency may be temporarily improved with bronchodilators or mechanical devices providing air that is under positive pressure. Artificial respiration or mechanical ventilation are required once breathing has ceased. If the respiratory acidosis was not severe or prolonged, normal pH can still be restored. Respiratory acidosis treatment is made more difficult because the condition also causes metabolic acidosis as lactic acid is generated in tissues that do not have sufficient oxygen. Respiratory Alkalosis Respiratory alkalosis is a less common condition that results from excessive carbon dioxide and carbonic acid loss. A temporary hypocapnia can be produced by hyperventilation, often in response to anxiety, pain, fever, or poisoning due to salicylates. Hyperventilation depletes carbon dioxide and increases body fluid pH to as high as 8. Fortunately, respiratory alkalosis is usually self-corrected, because chemoreceptor stimulation stops and the urge to breathe reduces. Hyperventilation often results from pain or other physical stressors and extreme anxiety or other psychological stressors. It gradually elevates the pH of the cerebrospinal fluid, affecting central nervous system function. The individual may be light-headed and lose consciousness if the condition continues. Because unconsciousness stops perception of causative psychological stimuli, breathing rate declines and the condition is self-corrected. Hyperventilation is easily treated by having the patient rebreathe air that has been exhaled into a small paper bag. Rising Pco2 in the bag results in similar rises in the arterial and alveolar carbon dioxide concentrations. Rare situations that may involve respiratory alkalosis include high altitudes that cause hyperventilation, use of mechanical respirators, and those with brain stem injuries that cause them to be unable to respond to changes in plasma carbon dioxide concentrations. Metabolic Acidosis Metabolic acidosis is the second most common type of acid-base imbalance. Metabolic imbalances such as this are indicated by bicarbonate levels below or above the normal range, which is 22­26 mEq/L.

Purchase 500 mg valacyclovir with visa. Infectious Diseases - How do we control them?.

Their secretory function is believed to be mostly regulated by intracellular calcium hiv infection and aids-ppt valacyclovir 500 mg buy low cost. More recently hiv infection lymph nodes 500 mg valacyclovir mastercard, other important biological properties restricted to cholangiocytes lining the smaller bile ducts have been reported hiv infection hindi order valacyclovir 500 mg, especially with regard to their plasticity (the ability to undergo limited phenotypic changes) hiv infection essay valacyclovir 500 mg fast delivery, reactivity (the ability to participate in the inflammatory reaction to liver damage) hiv infection rates wikipedia 1000 mg valacyclovir purchase free shipping, and ability to behave as liver progenitor cells. The Kupffer cells are specialized tissue macrophages and account for up to 90% of Chapter 1 Physiology, Immunology and Pathology of the Liver and Biliary Tree 7 the total population of fixed macrophages in the body. These are macrophages attached to the endothelial lining of the sinusoid, in greater numbers in the periportal areas. They are responsible for removing old and damaged blood cells or cellular debris, bacteria, viruses, parasites, and tumor cells. They lie within the subendothelial space, and their long cytoplasmic extensions have close contact with parenchymal cells and sinusoids, where they may regulate blood flow and hence influence portal hypertension. Pit cells show spontaneous cytotoxicity against tumor and virusinfected hepatocytes. In turns, the metabolic function of the liver is regulated by hormones secreted by the pancreas, adrenal gland, and thyroid. Bilirubin formed in the monocytic­macrophage cell system of liver, spleen and bone marrow and some of the bil irubin formed in the hepatocytes from hepatic heme are released into plasma where bilirubin is bound to albumin at highaffinity binding sites. An increase in free bilirubin would allow the pigment to enter tissues where it can have toxic effects; this is what is observed in neonates with defective conjugation and in Crigler­Najjar syndrome, when diffusion of unbound bilirubin into the brain can cause kernicterus. In normal conditions, bilirubin is effi ciently taken up by the liver whereas the albumin remains in plasma. In the liver, bilirubin is bound initially to glutathione Stransferase, then glucuronidated and excreted into bile. Bilirubin diglucuro nide is not reabsorbed from the small intestine; in the colon it may be hydrolyzed by bacterial glucuronidases, producing urobilinogens and urobilin, which are excreted in the stool or urine. Two enzymes are involved in bilirubin formation: the microsomal heme oxygenase converts heme to biliverdin and a cytosolic reductase subsequently reduces biliverdin to bilirubin. The majority (up to 85%) of heme is derived from hemoglobin and only a small fraction from other hemecontaining proteins such as cytochrome P450, myoglobin and immature the liver plays a key role in carbohydrate metabolism. It maintains carbohydrate stores by synthesizing glycogen and generating glucose from precursors such as lactate, pyru vate, and amino acids. Glycogen stored in the liver is the main source of rapidly available glucose for the whole organism. In the fed state, glycogen synthesis occurs preferentially in the perivenous hepatocytes whereas in the fasting state, glucose release via glycogenolysis 8 Section I Scientific Basis of Clinical Autoimmune Liver Diseases and gluconeogenesis initially occurs in peri portal hepatocytes. The liver glycogen stores contain up to a 2day supply of glucose, after which glucogenesis occurs mainly from lac tate. In acute liver failure, the blood glucose level may drop whereas this is infrequent in chronic liver disease, where it is more common to observe hyperglycemia and insulin resis tance. This may be related to decreased glucose uptake by muscle and reduced gly cogen storage in the liver and muscle. Lipid Metabolism A major role of the liver in lipid metabolism is to synthesize large quantities of cholesterol and phospholipids, many of which are pack aged with lipoproteins and made available to the rest of the body. Free cholesterol also derives from the uptake of chylomicron rem nants and lipoproteins from the circulation. Synthesis is increased in biliary duct obstruction, terminal ileal resection, biliary or intestinal lymph fistula, and with medications such as colestyramine, corticosteroids and thyroid hormones. This is mainly secondary to reten tion of cholesterol normally excreted in bile but also to increased hepatic synthesis of cholesterol, reduced plasma lecithincholes terol acyltransferase activity, and regurgita tion of biliary lecithin, which produces a shift of cholesterol from preexisting tissue cho lesterol into the plasma. Elevated cholesterol levels are clini cally associated with skin xanthomas and xanthelasma. In addition, the liver has other roles in lipid metabolism such as oxidizing triglycerides to produce energy; synthesizing lipoproteins; and converting excess carbohydrates and proteins into fatty acids and triglyceride, which are then exported and stored in adipose tissue. Protein Metabolism Amino acids are derived from the diet and from tissue breakdown and they reach the liver via the portal vein. Many critical aspects of protein metabolism occur in the liver, such as the deamination and transamination of amino acids, followed by conversion of the nonnitrogenous parts of these molecules to glucose or lipids. The liver is also responsible for a number of vital metabolic processes, including the removal of ammonia (an important factor in the development of hepatic encephalopathy) via the synthesis of urea; the synthesis of nonessential amino acids; and the synthesis of most plasma proteins such as albumin (the major plasma protein), fibrinogen, 1 antitrypsin, haptoglobin, ceruloplasmin, transferrin, and several coagulation factors. Metabolic Zonation the multiple functions of the liver are facilitated by a functional specialization Chapter 1 Physiology, Immunology and Pathology of the Liver and Biliary Tree 9 of the liver parenchyma, known as meta bolic zonation, where hepatocytes show different functional and structural char acteristics according to their location in the liver acinus. Within each acinus, the functional unit in terms of blood flow, blood rich in nutrients and hormones enters at the portal triad through the portal vein, mixes with oxygenrich blood from the hepatic artery, flows through the sinusoids and eventually exits the lobule through the central vein. As the blood flows through the sinusoids there is free exchange of nutrients and metabo lites between blood and hepatocytes. Functional variation is observed in hepa tocytes based on their location along the portal­central axis. Hepatocytes exhibit a distinct gene expression based on their location within the acinus, which mani fests as diverse availability of substrates and concentration of enzymes in different parts of the acinus. Based on this organi zation and heterogeneity of hepatocytes, the acinus comprises three geographical areas or zones: periportal or zone 1, midzonal or zone 2, and perivenous or zone 3. Hepatocytes in zone 3 contain the drugmetabolizing P450 enzymes, have a reduced oxygen supply, receive a higher concentration of any toxic product of drug metabolism, and have a reduced glutathione concentration compared with zone 1. Also, hepatocytes in zone 1 receive blood with a high bile salt concentration and are therefore particu larly important in bile saltdependent bile formation, whereas hepatocytes in zone 3 are important in nonbile saltdependent bile formation. Functions such as gluco neogenesis, glycolysis, and ketogenesis appear to be dependent on the direction of blood flow along the sinusoid. For others, such as cytochrome P450 activity, the gene transcription rate differs bet ween perivenular and periportal hepato cytes. Hepatic Transport Systems Hepatic uptake and efflux of electrolytes and solutes involved in bile formation are main tained by distinct transport systems expressed at the two surface domains of hepatocytes. Basolateral (Sinusoidal) Transporters the uptake of exogenous and endogenous compounds from the portal circulation is facilitated by a number of basolaterally located, sodiumdependent and sodium independent transporters. Green arrows indicate stimulatory and red lines suppressive effects on target genes. Hepatocellular transporters are subject to extensive transcriptional and posttran scriptional regulation, allowing for adapta tional changes in response to the intracellular accumulation of bile salts. Canalicular phospholipids are then solubilized by canalic ular bile salts to form mixed micelles, thereby protecting cholangiocytes from the detergent properties of bile salts. The main hepatocyte enzymes involved in metabolism belong to the cytochrome P450 group, a large family of related enzymes housed in the smooth endoplasmic reticulum of the hepatocyte. Phase 1 involves reduction, hydrolysis or oxidation of the drug, the latter being the most common process. After phase 1 reactions, the resulting drug metabolite is still often chem ically active. Phase 2 metabolism involves 12 Section I Scientific Basis of Clinical Autoimmune Liver Diseases conjugation with glutathione, methyl or acetyl groups, which usually occurs in the cytoplasm of the hepatocyte and makes the metabolite more hydrosoluble. Some drugs may undergo just phase 1 or just phase 2 metab olism, but more often the drug will undergo phase 1 and then phase 2 sequentially. The numbers of hepatocytes and enzyme activity can decline, with a reduction in the metabolic potential of the liver, follow ing aging, acute and chronic liver disease, and conditions that affect hepatic blood flow. Metabolism can also be altered due to ge netic deficiency of a particular enzyme and secondary to the use of other drugs as well as dietary and environmental factors. Capillarization of sinusoids during chronic liver disease increases the bioavailability of drugs at high hepatic extraction, possibly increasing the side effects. Druginduced liver injury is a major clinical problem, is often favored by exposure to a combination of drugs and, at times, may be mediated by immunologic mechanisms. Bile Formation, Secretion and the Enterohepatic Circulation Bile is a complex secretion that originates from hepatocytes and is modified distally by absorptive and secretory transport systems in the bile duct epithelium. Bile formation by the hepatocytes involves secretion of osmot ically active inorganic and organic anions into the canalicular lumen, followed by passive water movement. Bile then enters the gallbladder where it is concentrated or is delivered directly to the bowel. Bile Acid Synthesis and Metabolism secondary bile salt species are contained in human bile, although primary bile salts are usually predominant. Death and Regeneration of Hepatocytes Cell Death Hepatocytes can die because of either necrosis or apoptosis. Necrosis is the loss of plasma membrane integrity with release of the cel lular contents locally, which triggers an inflammatory response. Apoptosis is a highly regulated process in which cells that are dam aged, senescent or deregulated selfdestruct with a lower release of inflammatory prod ucts. Dying cells undergo morphologic modi fications including chromatin condensation, nuclear fragmentation, and generation of apo ptotic bodies. Furthermore, they express sig nals on the cell surface that allow macrophage recognition. Apoptosis is essential to avoid the outflow of intracellular contents and to limit the immunologic response against intracel lular autoantigens. Nevertheless, apoptotic bodies and fragments can under some cir cumstances constitute a major source of immunogens in autoimmune diseases that involve the targeting of ubiquitous autoanti gens. Liver Regeneration Liver possesses a unique capacity to replace its mass after tissue injury or loss. The majority of research on liver regeneration has focused on cytokine and growth factor mediated pathways involved in initiation and progression through the cell cycle. During more extensive acute liver injury, Canals of Hering which far exceeds the capacity of remaining healthy hepatocytes to replicate and restore liver function, resident liver progenitor cells. Biliary progenitors support the renewal of large intrahepatic and extrahe patic bile ducts. Stem cells are present in the canals of Hering, and participate in the renewal of the small intrahepatic bile ducts and in the regeneration of liver parenchyma. Small hepa tocytes located in pericentral positions are also believed to act as progenitor cells on certain occasions. Distinct subpopulations of mature hepatocytes and stem/progenitor cell com partments are differentially activated depend ing on the nature and duration of the liver damage versus different human pathologies. Resistance against these noxious compounds and their cytolytic poten tial is therefore essential. They may derive from hepatocytes undergoing a process of ductular metaplasia, or from activation of the hepatic progenitor cell compartment and/or from proliferation and dedifferentiation of preexisting cholangio cytes. The biliary epithelium stands as a first line of defense against bacteria, fungi and other pathogens by secreting antimicrobial pep tides such as defensin and cathelicidin. Since the biliary epithelium is continu ously in contact with bacterial products of intestinal origin, changes in one or more regulatory checkpoints may trigger an exag gerated inflammatory response in the liver. Cell senescence is a mechanism of irreversible cell arrest in G1 stage induced by different stimuli. All these signals lead to different physiologic responses generally leading to tumor suppres sion; however, in some cases it could promote cancer development or induce a fibrosing response and mediate agerelated degenerative diseases. This indicates that senescence could not only act as a barrier to tumor growth, but also paracrinally stimulate the activation of aberrant reparative/ regenerative responses. In chronic biliary diseases, cholangiocyte senescence is likely the result of ongoing inflammation, a sort of "exhaustion" of the activated cholangiocytes. Biochemical Markers and Patterns of Hepatic Injury Contrary to the kidney, no single test can be used to assess liver function. These patterns are valuable in directing specific serologic tests, imaging, and liver biopsy. However, they are not diagnostic for a specific cause, nor are they able to distin guish whether cholestasis is intrahepatic or extrahepatic. Autoimmune hepatitis can sometimes have an acute outset with striking elevation of aminotransferases. Rarely, bile duct stones can manifest as marked rise in aminotransferase, although this is fol lowed by a rapid fall within 48 hours. Cholestasis Cholestasis is an overarching term applied to conditions in which there is impairment of bile formation and/or bile flow. It occurs where there is a failure at any point along the biliary tree, between the basolateral (sinusoidal) membrane of the hepatocyte and the ampulla of Vater, as a result of congenital or acquired injuries, that leads to impaired secretion of bile such that biliary constituents spill into blood. The liver isoenzyme is located on the cana licular side of the hepatocyte plasma mem brane and the luminal surface of bile duct epithelium. This is the Regan isoenzyme, bio chemically different from the liver isoen zyme, that has been described in lung cancer, Hodgkin disease, and renal cell carcinoma. It is mainly localized in hepatocytes and bil iary epithelia, and is also present in extrahepatic tissues such as kidney, spleen, pancreas, heart, lung, and brain, but not bone. Nomenclature of the finer branches of the biliary tree: canals, ductules, and ductular reactions in human livers. New therapeutic concepts in bile acid transport and signaling for management of cholestasis. Contribution of resident stem cells to liver and biliary tree regeneration in human diseases. Multipotent stem/progenitor cells in human biliary tree give rise to hepatocytes, cholangiocytes, and pancreatic islets. Pathophysiologic implications of innate immunity and autoinflammation in the biliary epithelium. This article addresses major themes: innate and adaptive immunity in the context of the liver as an immune organ; generation and maintenance of tolerance to autoantigens; and risk factors for autoimmunity. The themes discussed also include: loss of immune tolerance to autoantigens and perpetuation of autoimmune diseases; and prospects for prevention of autoimmunity and therapeutic control of autoimmune diseases. Bacterial, fungal or viral infections can instigate innate and adaptive immune responses that result in autoimmunity. The increasing incidence of autoimmunity and inflammatory diseases observed worldwide is correlated with changes in environmental factors, including a more modern lifestyle, improved hygiene, a Western diet, use of antibiotics, and elimination of childhood parasitic infections.

References

• Longo M, Levra MG, Capelletto E, et al. Fetal adenocarcinoma of the lung in a 25-year-old woman. J Thorac Oncol 2008;3:441-3.
• De Bakey M. Bezoars and concretions. Surgery 1938;4:934.
• PURSUIT Investigators: Inhibition of platelet glycoprotein IIb/IIIa with eptifibatide in patients with acute coronary syndromes. The PURSUIT Trial Investigators. Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy. N Engl J Med 1998;339:436-443.
• I. Goldberg and Y. Becker, J. Pharm. Sci. 76, 259, 1987.