Aftab Ahmed - Academia.edu (original) (raw)

Papers by Aftab Ahmed

T and B Lymphocytes: Recognition and Function, 1979

Radio Science, 1977

Male CBA/J mice were exposed to 2450-MHz microwave radiation (each exposure: 30 minutes at an ave... more Male CBA/J mice were exposed to 2450-MHz microwave radiation (each exposure: 30 minutes at an averaged dose rate near 14 mW/g). The mice were tested later to determine effects of the radiation on (1) the relative frequency of T and B cells; (2) the functional capacity of spleen cells from irradiated mice to respond to T-and B-cell-specific membrane stimuli; and (3) the ability to respond to sheep red blood cells and dinitrophenyl-lyslyl-Ficoll. Results demonstrated that microwave radiation has weak stimulatory effects on B-but not T-lymphoid cells in the spleen. Single exposures to radiation produced an increase in the incidence of cells with complement receptor on the cell's surface. Three exposures to radiation induced increases in the total number of splenic cells, in the incidence of immunoglobin-positive cells, and in the incidence of complement receptor-positive cells. The total number of T cells was unaffected by single or triple exposures of mice to the radiation.

Immunologic Defects in Laboratory Animals 1, 1981

Science, 1977

Nonirradiated mice of the W/Wv genotype were injected with normal (+/+) bone marrow cells that ha... more Nonirradiated mice of the W/Wv genotype were injected with normal (+/+) bone marrow cells that had been treated with antiserum to Thy 1.2 and complement (C'). Such bone marrow cells had no effect on the number of macroscopic colonies formed in the spleens of these mice, but did not cure the anemia. The addition of +/+ thymocytes to these bone marrow cells restored their ability to cure the anemia in W/Wv mice. These data suggest that a theta-sensitive cell is required in the promotion of differentiation of murine hematopoietic stem cells into erythrocytes, and that there is a deficiency of such a cell in the W/Wv mouse.

The Protein Journal, 2014

Taxon specific lens crystallins in vertebrates are either similar or identical with various metab... more Taxon specific lens crystallins in vertebrates are either similar or identical with various metabolic enzymes. These bifunctional crystallins serve as structural protein in lens along with their catalytic role. In the present study, we have partially purified and characterized lens crystallin from Indian spiny-tailed lizard (Uromastyx hardwickii). We have found lactate dehydrogenase (LDH) activity in lens indicating presence of an enzyme crystallin with dual functions. Taxon specific lens crystallins are product of gene sharing or gene duplication phenomenon where a pre-existing enzyme is recruited as lens crystallin in addition to structural role. In lens, same gene adopts refractive role in lens without modification or loss of preexisting function during gene sharing phenomenon. Apart from conventional role of structural protein, LDH activity containing crystallin in U. hardwickii lens is likely to have adaptive characteristics to offer protection against toxic effects of oxidative stress and ultraviolet light, hence justifying its recruitment. Taxon specific crystallins may serve as good models to understand structure-function relationship of these proteins.

Proceedings of The National Academy of Sciences - PNAS, 1981

Thymosin (fraction 5 and synthetic α 1 peptide) induced prothymocytes in mouse bone marrow and sp... more Thymosin (fraction 5 and synthetic α 1 peptide) induced prothymocytes in mouse bone marrow and spleen to express terminal deoxynucleotidyl transferase (TdT; DNA nucleotidylexotransferase; nucleosidetriphosphate:DNA deoxynucleotidylexotransferase, EC 2.7.7.31) or Lyt-1+, 2+, 3+ alloantigens (or both) after brief incubation in vitro. Three antigenic phenotypes were generated: (i) TdT+ Lyt+, (ii) TdT- Lyt+, and (iii) TdT+ Lyt-. The TdT+ Lyt+ phenotype was expressed by 80% of prothymocytes in bone marrow and 30% of prothymocytes in spleen from normal mice. The TdT- Lyt+ phenotype was expressed by 81% of prothymocytes in bone marrow from athymic mice. More than 80% of TdT+ bone marrow cells from normal and athymic mice expressed Lyt antigens after thymosin treatment. We interpret these observations as suggesting that (i) most TdT+ hemopoietic cells in normal and athymic mice are thymocyte progenitors; (ii) two independent lineages of prothymocytes exist, one that expresses TdT and another that does not; (iii) commitment of prothymocytes to the TdT+ cell pathway is partially regulated by a thymic feedback mechanism; and (iv) the bone marrow preferentially produces TdT+ prothymocytes, whereas the spleen may serve as a repository for TdT- prothymocytes. A model of T-cell development is presented in which the thymus functions as a compound organ to process TdT+ and TdT- thymocyte progenitors and to generate two lines of T cells.

Annals of The New York Academy of Sciences, 1979

It has been at least a decade since the first reports that cell-free diffusible factors from the ... more It has been at least a decade since the first reports that cell-free diffusible factors from the thymus could partially reverse the deficiencies caused by neonatal thymectomy in a variety of species including mice, rats, hamsters, rabbits, and Humoral factors have also been found to be involved in the many pathways that lead from the pluripotent, hemopoietic stem cell ( H E ) to mature elements of the blood. A classic example of the latter is the discovery that the hormone, erythropoietin, interacts with erythroid precursors and leads to the differentiation of mature red blood cells in vitro.6.7 Differentiation of the HSC along the thymusderived (T-cell) lymphoid pathway has been a subject of intensive investigation. The underlying principle in these investigations is the concept that there are at least three distinct steps in the life of a T-cell: 1. A precursor stage that is devoid of phenotypic characteristics of a mature T-cell and lacking immunological function ascribed to mature T-cells.

Immunogenetics, 1980

All means had SEM< 12~ o. Preliminary experiments indicated that all antigens being analyzed c... more All means had SEM< 12~ o. Preliminary experiments indicated that all antigens being analyzed could be detected in the heterozygous state, ie, in the (C3H/HeJ x AKR/J) F 1 (data not shown), making backcross analysis feasible. Twenty-eight C3H/HeJ x (C3H/HeJ x ...

Cryobiology, 1974

Experiments were carried out to determine if thymic-derived lymphocytes (T-cells) could be differ... more Experiments were carried out to determine if thymic-derived lymphocytes (T-cells) could be differentially damaged by hypotonic and/or freeze-thaw stress. The uptake of 3 H-thymidine after stimulation of murine spleen cells with phytohemagglutinin-P (PHA-P) or bacterial endotoxin (LPS) ...

Cellular Immunology, 1977

The minor lymphocyte stimulating (Mls) locus codes for lymphocyte activating determinants (LADS) ... more The minor lymphocyte stimulating (Mls) locus codes for lymphocyte activating determinants (LADS) on murine B lymphocytes, but not T lymphocytes. This observation was strengthened by a series of techniques which allow deletion and addition of T and B cells. These included the use of cytotoxic antisera such as anti-Thy 1.2, anti-MTLA, anti-MBLA, and complement, and the use of a goat anti-p antisera, and finally the use of a fluorescence activated cell sorter (FACS).