34. The toxic effects of chemicals are determined by a) The nature of the chemic
ID: 272295 • Letter: 3
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34. The toxic effects of chemicals are determined by a) The nature of the chemical hazard b) The dose or quantity to which the individual is exposed c) The pathwayls) of exposure d) all of the above e) a and c only Multiple test (34 x2.5 85)+ essay (5 x3 15) 35. Let's say the therapeutic dose of Drug X is 50 mg, and the lethal dose IS 50 mg, and the lethal dose is 800 mg. Which drug is safer in terms o is 60 mg. For Drug Y, the therapeu f therapeutic index? (5) 36. Please describe several types of specialized cells in epidermis (5) mphoid stem cell (5) 37. Please describe the process of antibody production from lyExplanation / Answer
34. (d) all of the above.
35. Drug Y is more safer than X drug because the therapeutic dose of the drug is 50mg and its Lethal Dose (LD) value is 800mg. Where as X drug's therapeutic dose is 50mg and LD is 60mg. So its obivous at low contration also this drug x is detrimental for the test animal or individual taking this. On the other hand therapeutic dose of Y drug is working fine in low dose as 50 mg and its Lethal dose is 800mg which is very high. So this difference between therapeutic dose and lethal dose make Y drug more safer than the X drung.
36.
The epidermis contains three specialized cells:
37.Hematopoietic stem cells (HSCs) give rise to two predominant populations, the common myeloid progenitor (CMP) and the common lymphocyte progenitor (CLP). It is from the CLP from which B cells arise, commitment to the B cell lineage is a result of contact with the stromal cells as well as growth factor and cytokine production that results in initiating gene regulation that drives B cell commitment. This becomes a progenitor B (or pro-B) cell. In these early differentiation stages, IL-7, stem cell factor, Flt3 ligand, and specific adhesion molecules are important to support growth and survival of the pro-B cells. In the pro-B cells heavy chain (HC) immunoglobulin (Ig) rearrangement begins which is the beginning of antibody production. Once HC Ig gene rearrangement has successfully initiated, the cells become precursor B (or pre-B) cells. During the pre-B cell stage (which can be divided into different phases) HC Ig gene rearrangement is completed and tested (I’ll get back to this in a moment) and light chain (LC) gene rearrangement takes place to generate a fully functional B cell receptor (BCR, which is a membrane bound antibody). At this stage the cell is called an immature B cell. The immature B cells that successfully make it through this process (only about 10%) enter into the bloodstream and migrate to the spleen. The immature B cells have both IgM and IgG (BCRs) expressed on their surface at this point and once they enter into the spleen are called transitional type 1 (T1) B cells. In the spleen B cells, T cells, and follicular dendritic cells, form what is known as a primary follicle or sometimes the white pulp. The T1 B cells are located outside of the follicle (extrafollicular) in an area known as the red pulp (as this is where all of the red cells are flowing through the spleen). At this point, the T1 B cells are exposed to more self cells and circulating proteins and if they respond strongly it would indicate autoreactivity and the cells are typically induced to become T3 B cells, which are anergic (which means they become non-responsive to antigen), and will likely die off.
If the T1 B cells survive through this they can then migrate into the follicle and become T2 B cells . At this point they will be responsive to antigen, and become naive follicular B cells, which are fully mature B cells that can participate in immune responses. The mature B cells will circulate through all lymphoid tissues (spleen, lymph nodes, and lymphoid associated tissue) being exposed to antigens. If they encounter antigens that stimulate a response then they will migrate to the border of the B cell/T cell boundary and interact with stimulated T cells. B cells present antigen to the T cells and those that are specific for that antigen will activate the B cell to become an antibody producing B cell, as well as generate a germinal center, where B cells undergo affinity maturation and class switching. This will generate B cells that can produce antibodies with increased specificity to the antigen and also memory B cells, which will be able to respond much more quickly upon subsequent exposures to the same antigen.
The terminal differentiation of a B cell is becoming a plasma cell which is essentially a cell devoted to secreting antibodies.
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