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Biomedical subjects

A Marshak

Publications and source records attributed to A Marshak.

18 recordsLinked to original sources
PubMed1996

Synergy, activity and tolerability of zidovudine and interferon-alpha in patients with symptomatic HIV-1 infection: AIDS Clincal Trial Group 068.

Thirty-four subjects with symptomatic HIV-1 infection, p24 antigenaemia, and CD4 cell counts > 200/mm3 were randomly assigned to receive treatment with either zidovudine (ZDV) orally, interferon-alpha (IFN-alpha) subcutaneously, or both at respective low (200 mg ZDV/ 2 million international units IFN-alpha (MIU)), middle (400 mg/4 MIU) or high (600 mg/6 MIU) daily dose levels for 12 weeks. Thereafter, all patients received combination therapy at the initially assigned dose level to a total of 96 weeks. This design permitted analysis by the combination index (CI) method, which demonstrated antiretroviral synergy between ZDV and IFN-alpha with respect to p24 antigen suppression. Over the first 12 weeks, combination therapy was acceptably tolerated, more so than IFN-alpha monotherapy, and it was significantly more active in suppressing antigenaemia than either of the monotherapies. Similarly, the high-dose combination was the most active dose level over weeks 12 to 96. Combination ZDV/IFN-alpha at the optimal dose level defined by this trial merits further study. In addition, the CI design strategy employed here may be useful for the investigation of new antiretroviral combinations.

Administration, Cutaneous↗
PubMed1986

Tryptic digestion of myosin light chain kinase produces an inactive fragment that is activated on continued digestion.

Trypsin digestion of chicken gizzard myosin light chain kinase at limiting trypsin concentrations proceeds in stages. In the first stage, catalytic activity in the presence or absence of calcium and calmodulin decreases. In the second stage, activity in the absence of calcium increases, and the calcium-calmodulin complex no longer stimulates activity. The initial loss of activity is associated with the appearance of a 59,000-Da peptide that has been isolated and shown to have low catalytic activity. This peptide was further digested to a 55,000-Da peptide that has calcium-independent catalytic activity. This peptide has been isolated, and its affinities for the peptide substrate Kemptamide (Lys-Lys-Arg-Pro-Gln-Arg-Ala-Thr-Ser-Asn-Val-Phe-Ser-NH2) and ATP have been shown to be the same as those of the intact enzyme. Neither the 59,000-Da nor the 55,000-Da fragment binds calmodulin.

Calcium↗
PubMed1977

The control of specificity of cytotoxic T lymphocytes by the major histocompatibility complex (AG-B) in rats and identification of a new alloantigen system showing no AG-B restriction.

The regulatory influence of the rat major histocompatibility complex (MHC) (Ag-B complex) on the specificity of cytotoxic T lymphocytes was investigated. It was shown that the effector cells were specific for the original Ag-B phenotype in rat systems in which the responder and stimulator cell populations were unquestionably MHC identical but expressed different minor alloantigens of viral antigens. However, combined in vivo immunization and restimulation in culture of lymphocytes from rat strains previously thought to be MHC compatible resulted in the generation of cytotoxic T lymphocytes which effectively lyse not only target cells from the specific stimulating strains but also, to varying degrees, target cells from third party strains regardless of their Ag-B haplotypes. Genetic analysis indicates that expression of these cytotoxic T-cell-defined ("CT") antigens, found on both T and B lymphocytes, detectable thus far only with cytotoxic lymphocytes, is controlled by a single locus which segregates in backcross populations with the rat MHC. Discrepancies between the nature of CT antigens of the rat Ag-B and I-region specificities of the mouse H-2 are discussed.

Animals↗
PubMed1976

SPECIFIC positive and negative selection of rat lymphocytes reactive to strong histocompatibility antigens: activation with alloantigens in vitro and in vivo.

This study compares the functional properties of rat thoracic duct lymphocytes (TDL) after stimulation with strong alloantigens of the major histocompatibility complex (MHC) either in vitro in preparative mixed lymphocyte interactions (MLI) or in vivo in systemic graft-vs-host (GVH) reactions. Comparisons were made of PHA responses and reactivity to the specific priming haplotypes or to third party haplotypes in analytical MLI and in GVH reactions either before or after the activated populations were "parked" in syngenetic T cell-deprived (B) rats. These comparisons can be summarized as follows: 1) TDL populations primed in bulk MLI cultures (MLI-TDL) slowed some evidence of specific positive selection when tested immediately; MLI responses to specific alloantigens were both relatively large and accelerated in tempo, whereas responses to third party alloantigens were diminished but also accelerated in tempo. Specific GVH responses were more marked than in third party recipients but they were also decreased relative to normal, and displayed an abberant dose/response slope. MLI-TDL populations tested after they had been stored in syngeneic B rats showed clear evidence of stable-specific positive selection; specific MLI and GVH responses were enriched relative to third party responses and also in comparison to normal, unselected TDL populations. This finding indicates that GVH and MLI reactivity are probably both functional capacities of the same lymphocyte subpopulation since positive selection by one function (MLI) also enriched for a second (GVH). 2) Parental strain TDL activated in vivo in the systemic GVH reaction in irradiated F1 animals and recovered from the thoracic duct 3 to 4 days later (late GVH-TDL) consisted mainly of blast cells, however, in contrast to MLI-TDL these populations showed no evidence of positive selection when tested before or after parking in B rats. MLI responses to specific alloantigens were minimal, and greatly reduced in magnitude compared to normal. GVH responses to specific haplotypes could be detected, but these were not enriched compared to normal, despite the content in the late GVH-TDL populations of a significant proportion of blast cells presumably activated by host alloantigens. 3) Early collections (less than 40 hr) of parental strain GVH-TDL collected from F1 recipients contained no blast cells and showed impressive degrees of negative selection; they were markedly depleted of both GVH and MLI activity to specific alloantigens but displayed normal reactivity to third party alloantigens. Moreover, specific negative selection was persistent in these populations parked for several weeks in B rats, and indication that a specific subpopulation of reactive cells had been physically eliminated. 4) PHA responses of both MLI- and GVH-activated TDL populations tested either before or after parking in B rats were approximately normal on a per T cell basis...

Animals↗
PubMed1976

Specific selection of cytotoxic effector cells: the generation of cytotoxic T cells in rat thoracic duct lymphocyte populations positively or negatively selected for reactivity to specific strong histocompatibility alloantigens.

These studies consider the generation of cytotoxic T lymphocytes (CTL) from precursors (CTLP) present in rat thoracic duct lymphocytes after stimulation with strong alloantigens. Also, they explore the relationship between CTLP and "initiator" (I) lymphocytes responsible for specific GVH and MLI reactions. Positively selected TDL populations prepared in bulk MLI cultures show enriched GVH and MLI reactivity for the selecting major histocompatibility complex (MHC) haplotype, but no cytotoxic activity, raising the possibility that I and CTLP may belong to different subpopulations, and the latter failed to differentiate or to survive under these culture conditions. Restimulation of these cells in Marbrook culture vessels with the original priming haplotype under conditions suitable for generating killer cells in vitro resulted in greatly increased specific CTL activity with accelerated kinetics soon after priming and normal kinetics later. These findings indicate that "memory" killer cells can be generated in a previously stimulated lymphocyte population that had no overt cytotoxic activity. Restimulation with third party haplotypes failed to give CTL activity either to specific or to third party targets. Negatively selected TDL populations prepared by "filtration" through x-irradiated F1 rats, depleted of specific GVH and MLI responses, were also depleted of the ability to generate CTL in Marbrook cultures stimulated with the selecting haplotype. Stimulation with third party haplotypes, or with both third party and specific haplotypes together, gave CTL effective only against the third party target.

Animals↗