By M. Georg. Roberts Wesleyan College.
Antigenic variants escape recognition by the rst wave of specic host defense against the initial antigenic type buy medrol 16mg low price, extending the length of infection discount medrol 4 mg without a prescription. Trypanosoma brucei changes its dominant antigenic surface glyco- protein at a rate of 103 to 102 percell division (Turner 1997) discount 4 mg medrol with amex. The trypanosome changes to another surface coat by altering expression be- tween dierent genes already present in the genome. Infections lead to successive waves of parasitemia and clearance as novel antigenic types spread and are then checked by specic immunity. Mutational changes to new, successful epitopes may be rare in each replication of the virus. Butthe very large population size of viruses within a host means that mutations, rare in each replication, often occur at least once in the host in each parasite generation. For parasites that produce antigenic variants within hosts, the infec- tion continues until the host controls all variants, raises an immune response against a nonvarying epitope, or clears the parasite by non- specic defenses. Extended infection benets the parasite by increasing the chances for transmission to new hosts. Host memory of particular antigens blocks reinfection by parasites car- rying those antigens. Cross-reaction between antigenic variants occurs when a host can use its specic recognition from exposuretoapriorvariant to ght against alater,slightlydierent variant. Cross-reactive protection may provide only partial defense, allowing infection but clearing the parasite more rapidly than in naive hosts. The distribution of anti- genic variants will be inuenced by the rate at which new variants arise andspread and the rate at which old variants are lost from the popula- tion. As host individuals age, they become infected by and recover from dierent antigenic variants. Thus, the host population can be classied by resistance proles based on the past infection and recovery of each individual (Andreasen et al. On the one hand, each variant may occasionally spread epidemically through the host pop- ulation. This leaves a large fraction of the hosts resistant upon recov- ery, driving that particular variant down in frequency because it has few hosts it can infect. The variant can spread again only after many resis- tant hosts die and are replaced by young hosts without prior exposure to that antigen. In this case, three factors set the temporal pacing for each antigenic variant: host age structure, the rapidity with which vari- ants can spread and be cleared, and the waiting time until a potentially successful variant arises. Variants may, on the other hand, be maintained endemically in the host population. This requires a balance between the rate at which in- fections lead to host death or recovery and the rate at which new suscep- tible hosts enter the population. The parasite population maintains as many variants as arise and do not cross-react, subject to birth-death processes governing the stochastic origin of new variants and the loss of existing variants. In reality, vari- ants may dier in their ability to transmit between hosts and to grow within hosts. Nonspecic immunity or partial resistance to nonvarying or secondary epitopes also complicate the dynamics. Nonetheless, the epidemiology of the parasite, the hostagestructure and resistance pro- les, and the processes that generate new variants drive many aspects of the dynamics. The resistance proles of individual hosts can still be described by history of exposure. However, a new variants ability to infect a particular host depends on the impedance to the variant caused by the hosts exposure prole and the cross-reactivity between antigens. From the parasites point of view, a particular antigenic variant may be able to attack some host ge- notypes but not others. Host genotype can also aect the structure of the cellular receptors to which parasites attach. It is not clear whether minor variants of cellular receptors occur suf- ciently frequently to favor widespread matching variation of parasite surface antigens. Several cases of this sort may eventually be found, but in vertebrate hosts genetic variation of cellular receptors may be a relatively minor cause of parasite diversity. Varying these attachment characters allows attack of dierent cell types or ad- hesion to various tissues. Such variability can provide the parasite with additional resources or protection from host defenses. Several species of the spirochete genus Borrelia cause relapsing fever (Barbour and Hayes 1986; Barbour 1987, 1993). Relapses occur because the parasite switches expression between dierent genetic copies of the major surface antigen. A subset of antigenic variants of these blood-borne bacteria have a tendency to accumulate in thebrain,where they can avoid the hosts immune response (Cadavid et al. Those bacteria in the brain may cause later relapses after the host has cleared the pathogens from the blood. The diering tissue tropisms of the antigenic variants may combine to increase the total parasitemia.
The symptoms of fibromyalgia include chronic burning or gnawing pain quality medrol 4 mg, multiple tender points medrol 16mg generic, sleep disturbances generic 16 mg medrol with amex, and fatigue. The tender points are located in the muscle insertions at both sides of the body (3). No clear structural abnormalities have been found in their biopsies and no inflammation can be detected (4). Pain and fatigue often lead to psychological disturbances and depression is a common problem. Approximately every second patient attributes the onset of symptoms to an injury, infection, or other stress (4,5). The individual course of symptoms is variable, which also makes the diagnosis difficult. If the tenderness in palpation of at least 11 of these is found in a patient whose diffuse musculoskeletal pains have lasted at least 3 months, then the fibromyalgia diagnosis can be made. Simply identi- fying the diagnosis helps significantly in alleviating the patients suffering by assuring the patient that this disease is not dangerous, despite the suffering and the limited ability to work that it causes. Patients should be encouraged to continue working because it has been shown that when they stop working, their symptoms seem to worsen (4). As a nutritional approach for the treatment of rheumatoid diseases in general is poorly understood, it is easy to understand that the dietary treatment of fibromyalgia in particular is also not known. In all chronic diseases, nutritional status tends, however, to be altered and physical activity tends to be depressed. The first course of action should always be the correction of nutritional deficits, and only then should drug treatment be considered. Often, patients have tried a variety of drug treatments themselves, albeit with limited success. Many drugs may interfere with the normal regulation of food intake, which exacerbates the effect of the disease, per se, on nutritional status (8). Instead, patients are advised to eliminate or supplement their diet depending on their symptoms. Typically, patients with fibromyalgia have looked for alleviation of their symptoms by using different kinds of vegetarian diets or having specific remedy foods or supplements such as herbs, wheatgrass juice, or purified antioxidants. Theories on the pathophysiology of fibromyalgia have included alterations in neuro- transmitter regulation (especially serotonin); hormonal control problems (especially of the hypothalamicpituitaryadrenal and growth hormone axes); immune system dysfunction; problems in sleep physiology; abnormal perception of bodily sensa- tions; stress; viral pathologies; local hypoxia; and disturbances in muscle microcir- culation, adenosine monophosphate, and creatinine concentrations. Current evidence most strongly supports a neurochemical or neurohormonal hypothesis (1,9). The following sections focus on the brain functions, followed by nutritional inter- ventions for patients with fibromyalgia, especially vegan and vegetarian approaches. Patients with fibromyalgia have lowered blood circulation in the pain-sensitive areas of their brains, which may be the origin of several symptoms reported, including pain and fatigue (11). Pain signals reach the consciousness only when the signals are handled in the brain. Patients with fibromyalgia have exaggerated pain responses to various stimuli and show allodynia (i. The autonomic nervous system shows higher activity of the sympathetic component, and blocking of these fibers alleviates the pain sensation in patients. As one can expect, pain causes poor sleep quality (12), which is one of the most common problems reported in fibromyalgia. Excessive serotonin levels are not desirable either, however, because serotonin causes vasoconstriction, as in migraine headaches (14). Blood platelets share some properties of neurons and therefore, they can be used as a model for studying fibromyalgia. A significant increase in benzodiazepine receptors occurs in platelet membranes of patients affected by primary fibromyalgia, and this seems to be related to the severity of fibromyalgic symptoms (15). Patients with fibromyalgia have some similarities with subjects whose glucocorticoid administration has been withdrawn in that both cause fatigue, sleep disturbances, and pain. Persistent pain and poor sleep quantity and quality make it easy to understand the feeling of fatigue. A vicious cycle is created whereby fatigue leads to reduced physical activity and poor appetite, which then further exacerbate feelings of fatigue and lethargy. It has been shown that fibromyalgia symptoms are alleviated by exercise and physical therapy (4). Nutrition therapy can be helpful by promoting physical activity, which creates a positive feedback loop and reduces symptoms. Therefore, patients with fibromyalgia tend to search for help from alternative and complementary methods, including herbal remedies. The aim of nutrition therapy in rheumatoid diseases is to maintain optimal nutritional status. Instead, patients are advised to eliminate or supplement the diet depending on their symptoms. It is also recommended to consume adequate liquids and to participate in exercises (17,18). Balanced nutrition promotes the intake of all necessary nutrients and no supplementation is needed.
It was originally discovered by a German chemist Martin Heinric Klaproth cheap medrol 4 mg line, but misidentified as tellurium discount medrol 16 mg on line. Later purchase medrol 16 mg with amex, in 1818 a Swedish chemist Jons Jacob Berzelius discovered selenium and was named after the Greek goddess of the moon, Selene  and its name was associated with tellurium, a name for earth. It ranks seventieth in abundance among the elements and is distributed in the Earths crust at concentrations averaging 0. Selenium has six major stable isotopes have been reported and the most abundant in nature are 80Se (49. In general, selenium is present in the environment in elemental form or in the form of sele nide (Se ), selenate (SeO2- 2-), or selenite (SeO 2-). The identity and amounts of the various oxi 4 3 dation-state species in soils depends enormously on the redox-potential conditions. The lower oxidation states predominate in anaerobic conditions, acidic soils, and the higher oxi dation states are favored in alkaline and aerobic conditions. Both selenites and selenates are taken up by plants and converted to protein-bound selenocysteine and selenomethionine, soluble inorganic forms, several free amino acids, and volatile organoselenium compounds. The elemental form of selenium, selenium dioxide, and volatile organoselenium compounds produced by industries and plants are incorporated in the environment. Selenium occurs naturally in water in trace amounts as a result of geochemical processes, such as weathering of rocks and erosion of soils, and is usually present in water as selenate or selenite; however the elemental form may be carried in suspension . Interest in selenium and health was focused primarily on the potentially toxic effects of high intakes in humans, stimulated by reports of alkali disease in livestock raised in seleniferous areas, in the last century . Selenium is a trace mineral that is essential to good health but required only small amounts [6,7]. Selenium is considered as essential human micronutrient and is incorporated into proteins to make selenoproteins. Selenium is present in the seleno proteins, as the aminoacid selenocysteine (Se-Cys) [8-12]. Dietary levels of the desired amount of Se are in a very narrow range: consumption of foods containing less than 0. Se status varies significantly across different populations and different ethnic groups [14-15]. Selenium enters the food chain through plants, and the amount and bioavailability of seleni um in the soil typically reflects the plant level. Plants convert Se mainly into selenomethionine (Se-Met) and incorporated it into protein place of methionine. More than 50% of the total Se content of the plant exist as Se-Met, the rest exist as selenocysteine (Se-Cys), methyl-Se-Cys and c- glutamyl-Se-methyl-Cys. Higher animals are unable to synthesize Se-Met and only Se-Cys was detected in rats supplemented with Se as selenite . Most ingested forms of selenium ultimately are metabolized to low molecular weight inor ganic and organic compounds that play a central role in human health either via incorpora tion into selenoproteins or binding to selenium binding proteins . Several excellent books and re views appeared in literature describing the biological function of organoselenium com pounds [20-22]. The essentiality of selenium results as a necessary component of the active center of a num ber of selenoenzymes. The term selenoprotein is any protein that includes in its primary sequence of amino acids, the selenocysteine (Se-Cys) res idue . The glutathione and thioredoxin systems in particular have long been considered the major pathways through which selenium exerts its potential chemopreventive effect , while some investigations have also suggested growth inhibito ry, proapoptotic activity for selenometabolites in premalignant cells . Selenium is also in volved in thyroid function, T cell immunity, and spermatogenesis , and is a competitive antagonist of potentially carcinogenic heavy metals such as arsenic and cadmium . Vitamin E is a fat-soluble vitamin known for its antioxidant capacity that is why it is well known as a lipophilic antioxidant that protects membranes from being oxidatively damaged as an electron donor to free radicals . It is well known that all forms of vitamin E are lipid soluble they easily absorbed from the intestinal lumen after dietary intake via micelles created by biliary and pancreatic secretions [34-35]. Vitamin E is then incorporated into chylomicrons and secreted into the circulation where, transported by various lipoproteins, it travels to the liver . Plasma -tocopherol 422 Oxidative Stress and Chronic Degenerative Diseases - A Role for Antioxidants concentrations in humans range from 11 to 37 mol/L, whereas -tocopherol are between 2 and 5 mol/L. The liver plays a central role in regulating -tocopherol levels by directly act ing on the distribution, metabolism, and excretion of this vitamin . This protein facilitates secretion of -toco pherol from the liver into the bloodstream, by acquiring it from endosomes and then deliv ering it to the plasma membrane where it is released and promptly associates with the different nascent lipoproteins . Plasma concentration of vitamin E depends completely on the absorption, tissue delivery, and excretion rate. The estimated -tocopherol half-life in plasma of healthy individuals is ~ 48 to 60 H, which is much longer than the half-life of - tocopherol approximately 15 H. These kinetic data underscore an interesting concept that while -tocopherol levels are maintained, the other forms of vitamin E are removed much more rapidly . The list of clinical disorders expected to be influenced by Se deficiency is rapidly growing with time.
Perpetuation of pathogenic autoreactive cells associated with a lesser expression and differentiation of Tregs would be another condition for autoimmunity development 4mg medrol mastercard. The expression of surface molecules order medrol 4mg on line, phenotype discount medrol 16 mg free shipping, discloses the history of antigenic exposure (Appay, Dunbar et al. Therefore, the antigen-specific response can be well characterized by specific intracellular markers of phosphorylation and development of antibodies for specific epitopes of cytoplasmic proteins (Rosette, Werlen et al. There are few studies of autoimmune diseases that have studied the pattern of intracellular signaling of T lymphocytes and possible dysfunctions in T cell activation and immune response, except in rheumatic diseases such as systemic lupus erythematosus (Pang, Setoyama et al. Immune Profile and Tyrosine Phosphorylation of T-Cell Receptor in Autoimmune Thyroid Diseases 105 Gobert, M. Immune Profile and Tyrosine Phosphorylation of T-Cell Receptor in Autoimmune Thyroid Diseases 107 Ueda, H. Introduction The development of thyroid cancer is a multifactorial and multistep process. Several factors are thought to predispose people to thyroid cancer, including genetics, environment, and sex hormones. The incidence of thyroid cancer is three to four times higher in women than in men (Libutti, 2005; Machens et al. Animal studies support these epidemiological data, and suggest that exogenous estrogen (17-estradiol, E2) can promote thyroid tumors (Mori et al. Several studies have been carried out to address the role of estrogens in the pathogenesis of proliferative and neoplastic disorders. Although the precise mechanism still remains ill- defined, a range of plausible mechanisms explaining their carcinogenic effects has been proposed. On one hand, estrogens may promote cellular proliferation through their receptor-mediated activity (Arnold et al. Thyroid cancer Thyroid carcinoma is the most common and prevalent of all endocrine malignancies, accounting for more than 95% of all endocrine-related cancers (Hodgson et al. Anaplastic carcinomas are undifferentiated tumors deriving from thyroid epithelial cells. They are usually lethal with 110 Thyroid and Parathyroid Diseases New Insights into Some Old and Some New Issues no effective system therapy. The factors leading to thyroid carcinoma development are not fully understood despite some well-established associations, such as between ionizing radiation and papillary carcinoma, and between iodine deficiency and follicular carcinoma. From the molecular point of view, papillary and follicular thyroid cancers are completely different diseases. Although estrogens are present in both men and women, their levels are significantly higher in women of reproductive age. The three major naturally occurring estrogens in women are: estrone, estradiol and estriol (Speroff et al. In premenopausal women, 17-estradiol (E2), produced by the ovary, is the estrogen formed in the largest quantity and is the most potent since it has the highest affinity for estrogen receptors. In premenopausal women, the level of circulating E2 varies from 40 to 400 pg/mL during the menstrual cycle (Ruggiero et al. In postmenopausal women, the ovary ceases to produce E2 while the adrenal gland continues to produce androstenedione, with the result that the level of estrone remains unchanged while the level of E2 falls significantly. E3 is the main estrogen produced by the placenta during pregnancy, and is found in smaller quantities than E2 and E1 in nonpregnant women (Jones, 1992; Ruggiero et al. It can also result in an increase of Ca2+ or nitric oxide and the promotion of cell cycle progression. Therefore, integrative signaling by E2 from several places in the cell can lead to both rapid and sustained actions, which synergize to provide plasticity for cell response. These findings suggest that mitochondria could also be a target site for the action of estrogens. As a consequence, E2 may exert coordinated effects on both nuclear and mitochondrial gene expression. Bcl-2 proteins localize or translocate to the mitochondrial membrane and modulate apoptosis by permeabilization of the inner and/or outer membrane, leading to the release of citochrome c or stabilization of the barrier function. It is well established that cathepsin D expression is elevated in thyroid tumors and correlates with disease aggressiveness (Leto et al. Rajoria and colleagues observed that E2 dramatically increases the ability of thyroid cells to adhere (137-140%) and migrate (27-75%). They also found downregulation of -catenin in the thyroid cells treated with E2 (Rajoria et al. Akt1 deficient mice show normal glucose tolerance and insulin-stimulated glucose clearance from blood, but display severe growth retardation (Cho et al. It has Estrogen Signaling and Thyrocyte Proliferation 115 also been shown that cells derived from Akt1 deficient mouse embryos are also more susceptible to pro-apoptotic stimuli (Chen et al. Phosphorylation at Ser473 appears to precede and facilitate phosphorylation at Thr308 (Sarbassov et al. This difference leads to increased cellularity in the thyroids of female mutants at a young age, to an increased incidence of thyroid adenomas in mutant females at 8 months of age (Yeager et 116 Thyroid and Parathyroid Diseases New Insights into Some Old and Some New Issues al. Several groups had anticipated a role for estrogen in thyroid proliferation, based on the effects of estradiol on thyroid carcinoma cells in culture (Manole et al.