Wednesday, April 28, 2010

Plague?


It is a infectious disease or deadly Bacterial disease.for example:

Bubonic Plague(BLACK DEATH DISEASE):It is due to.....................

1.High fever

2.Swelling

3.Bleeding

4.Necrosis of Lymph Nodes.


Wednesday, April 21, 2010

Paralysis Agitans

This is a chronic affection of the
nervous system, characterized by muscular weakness, trembling and
rigidity.

Causes. It usually occurs after the fortieth year, and is more common in
men than in women. The exciting causes are exposure to cold and wet,
business worries, anxieties, violent emotional excitement and specific
fevers.

Symptoms. The four prominent symptoms are trembling, weakness, rigidity,
and a peculiar attitude. It generally develops gradually, usually in one
or the other hand. There is at first a fine trembling, beginning in the
hands or feet, gradually extending to the arms, the legs and sometimes the
whole body. The head is not involved so frequently. This trembling
(tremor) consists of rapid, uniform "shakings." At first it may come in
spells, but as the disease advances it is continuous. Any excitement makes
it worse. It is very marked in the hands. The trembling generally ceases
during sleep. The muscles become rigid and shortened; the head is bent and
the body is bent forward; the arms are flexed (bent) and the thumbs are
turned into the palms and grasped by the fingers; the legs are bent,
movement soon becomes impaired and the extremities show some stiffness in
motion. There is great weakness of the muscles and it is most marked,
where the trembling is most developed. There is no expression on the face,
and the person has a slow and measured speech. The walk is very peculiar,
and in attempting to walk the steps are short and hurried. The steps
gradually become faster and faster, while the body is bent forward and the
patient must keep on going faster to keep from falling. It is difficult to
go around in a short circle. The patient cannot change his position in bed
easily. The mind is rarely affected.

Recovery. It is an incurable disease. It may run on for twenty years or
more. There may be times of improvement, but the tendency is to grow,
gradually worse.

PHYSICIANS' TREATMENT for Shaking Palsy. This is simply to make the
patient as comfortable as possible. Regulate the diet. The patient should
not worry or have much exercise. Frequent warm baths are sometimes
beneficial with gentle massage of the muscles.

Tuesday, April 20, 2010

HLA

The human leukocyte antigen system (HLA) is the name of the major histocompatibility complex (MHC) in humans. The superlocus contains a large number of genes related to immune system function in humans. This group of genes reside on chromosome 6, and encode cell-surface antigen-presenting proteins and many other genes. The HLA genes are the human versions of the MHC genes that are found in most vertebrates (and thus are the most studied of the MHC genes). The proteins encoded by certain genes are also known as antigens, as a result of their historic discovery as factors in organ transplantations. The major HLA antigens are essential elements for immune function. Different classes have different functions:
HLA class I antigens (A, B & C) present peptides from inside the cell (including viral peptides if present). These peptides are produced from digested proteins that are broken down in the proteasomes. The peptides are generally small polymers, about 9 amino acids in length. Foreign antigens attract killer T-cells (also called CD8 positive- or cytotoxic T-cells) that destroy cells.
HLA class II antigens (DP,DM, DOA,DOB,DQ, & DR) present antigens from outside of the cell to T-lymphocytes. These particular antigens stimulate T-helper cells to multiply, and these T-helper cells then stimulate antibody-producing B-cells to produce Antibodies to that specific antigen. Self-antigens are suppressed by suppressor T-cells.
HLA class III antigens encode components of the complement system.
HLA have other roles. They are important in disease defense. They may be the cause of organ transplant rejections. They may protect against or fail to protect (if down regulated by an infection) cancers. They may mediate autoimmune disease (examples: type I diabetes, coeliac disease). Also, in reproduction, HLA may be related to the individual smell of people and may be involved in mate selection.
Aside from the genes encoding the 6 major antigens, there are a large number of other genes, many involved in immune function, located on the HLA complex. Diversity of HLA in human population is one aspect of disease defense, and, as a result, the chance of two unrelated individuals having identical HLA molecules on all loci is very low. Historically, HLA genes were identified as a result of the ability to successfully transplant organs between HLA similar individuals.

Sunday, April 11, 2010

Mediators of inflammation


Once leukocytes have arrived at a site of infection or inflammation, they release mediators which control the later accumulation and activation of other cells. However, in inflammatory reactions initiated by the immune system, the ultimate control is exerted by the antigen itself, in the same way as it controls the immune response itself. For this reason, the cellular accumulation at the site of chronic infection, or in autoimmune reactions (where the antigen cannot ultimately be eradicated), is quite different from that at sites where the antigenic stimulus is rapidly cleared.

There are four major plasma enzyme systems which have an important role in haemostasis and control of inflammation. These are the complement system, the clotting system, the fibrinolytic (plasmin) system and the kinin system.

Inflammatory mediators are soluble, diffusible molecules that act locally at the site of tissue damage and infection, and at more distant sites. They can be divided into exogenous and endogenous mediators.

Bacterial products and toxins can act as exogenous mediators of inflammation. Notable among these is endotoxin, or LPS of Gram-negative bacteria. The immune system of higher organisms has probably evolved in a veritable sea of endotoxin, so it is perhaps not surprising that this substance avokes powerful responses. For example, endotoxin can trigger complement activation, resulting in the formation of anaphylatoxins C3a and C5a which cause vasodilation and increase vascular permeability. Endotoxin also activates the Hageman factor, leading to activation of both the coagulation and fibrinolytic pathways as well as the kinin system. In addition, endotoxin elicit T cell proliferation, and have been described as superantigen for T cells.

Endogenous mediators of inflammation are produced from within the (innate and adaptive) immune system itself, as well as other systems. For example, they can be derived from molecules that are normally present in the plasma in an inactive form, such as peptide fragments of some components of complement, coagulation, and kinin systems. Mediators of inflammatory responses are also released at the site of injury by a number of cell types that either contain them as preformed molecules within storage granules, e.g. histamine, or which can rapidly switch on the machinery required to synthesize the mediators when they are required, for example to produce metabolites of arachidonic acid.

Mononuclear phagocytes (monocytes and macrophages) are central to inflammation, as they produce many components which participate in or regulate the different plasma enzyme systems, and hence the mediators of the inflammatory response. They are also actively phagocytic and are involved in microbial killing, as are neutrophils. While the latter can be thought of as short-lived kamikaze cells that need to be continually replaced from the bone marrow, mononuclear phagocytes are long-lived and some can proliferate in situ. Other cells such as mast cells and basophils are much less phagocytic, but together with platelets, these cells are particularly important for secretion of vasoactive mediators. The function of these cell types is at least partially under the control of cytokines. All inflammatory cells have receptors for Fc domains of immunoglobulins and for complement components, and they possess specialized granules containing an immerse variety of products that are released perhaps by common mechanisms. Cytotoxic T lymphocytes and NK cells, in general, also possess granules which are important for their cytotoxic function. In general, lymphocytes are involved in the adaptive response to inflammation, and the early events of inflammation are mediated in part by molecules produced by cells of the innate arm of the immune system.

Early phase mediators are produced by mast cells and platelets. They are especially important in acute inflammation and include mainly histamine, serotonin and other vasoactive substances. Platelets may contribute to inflammatory responses resulting as a consequence of tissue injury, through a variety of mechanisms including:

the release of vasoactive amines and other permeability factors,
the release of lysosomal enzymes,
the release of coagulation factors which lead to localized and generalized fibrin deposition, and
the formation of platelet aggregates or trombi which result in the blocking of vessels and capillaries.

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