These resistance mutations are amino acid changes in the primary structure of reverse transcriptase that facilitate the removal of the chain-terminators NRTI-triphosphate from the 3’ end of the DNA chain after it has been incorporated (eg. In experiments with wild-type and mutant reverse transcriptase carrying the K65R mutation measuring the polymerisation activity for 3TC-triphosphate, the mutant reverse transcriptase was shown to reduce the rate of incorporation of 3TC-triphospate resulting in a 13.1 fold increase in resistance. Decrease the rate of incorporation of the NRTI-triphosphate over the natural nucleotide (eg.In experiments with wild-type and mutant reverse transcriptase carrying the M184V mutation measuring the binding affinity for 3TC-triphosphate, the mutant reverse transcriptase was shown to bind the 3TC-triphospate with a reduced affinity over the wild-type enzyme resulting in a 48.8 fold increase in resistance. Decrease the binding affinity of the NRTI-triphosphate over the natural nucleotide in the reverse transcriptase active site (eg.There are two ways in which discrimination can be achieved: These resistance mutationsare amino acid changes in the primary structure of reverse transcriptase that increase the selective ability of the enzyme to incorporate the natural nucleotid e over the NRTI-triphosphate(eg. There are two ways in which NRTI resistance can be achieved: The additional phosphorylation is carried out by host cellular enzymes (kinases). Tenofovir contains a single phosphonate group to which only two phosphate groups need to be added to generate the active compound. With the exception of Tenofovir, the NRTI compounds that are taken up by the cell do not contain phosphate groups and require three phosphate groups to generate the triphosphate form of the base analogue before it can be used as a substrate by reverse transcriptase. The NRTI compounds permit correct base-pairing and incorporation into the DNA chain, however, an important hydroxyl grouprequired for addition of the next nucleotide has been replaced by a non-reactive chemical group. They function as chain-terminators during the extension of the DNA chain during the reverse transcription process which is carried out by HIV reverse transcriptase. The NRTI class of antiretroviral drugs are chemical compounds that are nucleotide base analogues. Nucleoside reverse transcriptase inhibitors (NRTI) Mechanisms of HIV antiretroviral drug action and drug resistance Usually two drugs from this class are used to form the backbone of HAART. This was the first group of antiretroviral agents to be used against HIV. For these drugs to be active they need to be phosphorylated intracellularly. Further exploration of its relationship to psychological well being, medication adherence and other aspects of medical care is indicated.Nucleoside Reverse Transcriptase Inhibitors (NRTIs) inhibit reverse transcriptionby causing chain termination after they have been incorporated into viral DNA. We conclude that the BIS has good construct validity and is a highly reproducible measure of self-perceptive of body image in HIV-infected patients. The presence of symptomatic disease ( p < 0.001) and a diagnosis of AIDS ( p = 0.02) were associated with a less favorable body image, although laboratory markers of disease progression (CD4 count and plasma HIV viral load) were not. Patients' current perception of their body image was worse then what they perceived it to be prior to HIV infection ( p < 0.001), but better than their perception of how others view people with HIV ( p < 0.001). The BIS had unidimensional factor structure, good internal consistency reliability (Chronbach α = 0.91), and good test–retest reliability ( r = 0.71, p < 0.001) after controlling for the length of interval between assessments. Nearly half of the sample (46%) had AIDS and 25% had a CD4 count below 200 cells/mm 3 within the prior 3 months. A subset ( n = 38) were administered the survey on two occasions to assess test-retest reliability. HIV-positive men ( n = 129) and women ( n = 21) attending two outpatient HIV clinics were administered the BIS survey along with a one-page questionnaire. We assessed the psychometric properties of a newly developed Body Image Scale (BIS), a subjective measure of body image perception in persons with HIV infection, as well as the scale's relationship to disease progression, symptoms, and demographic factors. HIV infection and its treatment can have significant effects on physical appearance and functioning, which can affect self-perceived body image.
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