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Biomedical subjects

S Jayaraman

Publications and source records attributed to S Jayaraman.

At least 91 records · Page 5Linked to original sources
PubMed1984

Repair studies utilizing a fly-pupariation model of postmitotic cell response.

Delay in pupariation of irradiated fly (and other insect) larvae results from a neuroendocrine disturbance and represents a dose-dependent response of differentiated postmitotic tissue. Many experimental manipulations (e.g. heating) may themselves upset timing, limiting usefulness of this phenomenon as a model of postmitotic tissue response. Doses greater than 20 Gy inhibit retraction of specific muscles at time of pupariation, leading to formation of elongate puparia. Degree of elongation (ratio of length: breadth) was also a function of dose. Peak sensitivity for elongation occurs later than that for delay, but both endpoints exhibit rapid kinetics for sparing effect of dose fractionations (sdf). With degree of elongation as endpoint, we demonstrated synergism between heat and radiation, and heat markedly inhibited sdf. Maintenance of irradiated larvae under wet conditions greatly prolonged the larval stage, and degree of elongation was reduced. This recovery, analogous to repair of potentially-lethal damage (PLD) in plateau-phase cell cultures, proceeds much more slowly than sdf.

Animals↗
PubMed1983

Shift of glycolysis as a marker of sperm maturation.

The presence of glycogen-phosphorylase (A and B forms), glucose-6-phosphatase and fructose-1, 6-diphosphatase in bonnet monkey spermatozoa was determined. The process of glycolysis gradually decreased and the process of reversal of glycolysis steadily increased in monkey spermatozoa as they move from testis to caput to corpus to cauda to vas deferens and finally in ejaculate. Hence in bonnet monkeys, the functional maturity of spermatozoa and the shift in glycolysis are closely related.

Animals↗
PubMed1983

Effect of chronic administration of inhibin and testosterone on spermatogenesis in adult male rats.

Inhibin (Inh) and testosterone (T) were administered to adult male rats for 32 days to evaluate their effect on spermatogenesis. Fifty micrograms of Inh was injected subcutaneously twice daily, and T was administered as Silastic implants 2.5 cm in length. Weights of testes and epididymides were significantly decreased in (Inh + T)- and T-treated groups, but not in Inh-treated rats. Although Inh alone could suppress both the testicular and the epididymal sperm count, maximum suppression was observed in the (Inh + T)-treated group. The effect on the epididymal sperm count, however, was pronounced. The accessory organ weights remained unaffected in all treated groups. Chronic administration of Inh and T results in partial impairment of spermatogenesis.

Animals↗
PubMed1983

Hapten-specific responses to the phenyltrimethylamino hapten. IV. Occurrence of mechanistically distinct idiotypic suppressor T cells before the appearance of anti-idiotypic suppressor T cells induced by the monovalent antigen L-tyrosine-p-azophenyltrimethylammonium.

We have previously shown that a single i.p. injection of the monovalent synthetic antigen, L-tyrosine-p-azophenyltrimethylammonium [tyr(TMA)] in complete Freund's adjuvant induces an anti-idiotypic T suppressor cell (Ts2) population that can be detected 6 wk later by its ability to shut down delayed-type hypersensitivity (DTH) specific for the TMA hapten. In this paper we present evidence that 2 wk after tyr(TMA) administration, a subset of Ts, termed Ts1, appears that is both functionally and phenotypically distinct from the late appearing Ts2 population. The early occurring Ts1 act only at the induction phase of the DTH response and can also suppress this response intrinsically. This latter point is in marked contrast to our previous observation that the tyr(TMA)-induced anti-idiotypic Ts2 fail to function intrinsically and can only be detected upon adoptive transfer into naive mice. Ts1 bear idiotypic receptors and are Ly-1+,2- in contrast to the anti-idiotypic Ly-1-,2+ Ts2 population. In addition, unlike the Ts2 population, Ts1 are comparatively nylon wool-adherent. Adsorption of Ts1 on either antigen- or idiotype-coated petri dishes indicate that the suppressor activity can be transferred only by antigen-binding cells. Cellfree factors prepared from spleens containing the Ts1 population can suppress DTH only if administered at the induction phase of the response, in contrast to the factors derived from the Ts2 population that act both at induction as well as effector phases, suggesting that Ts1 and Ts2 can function via soluble mediators. Finally, we show that when Ts1-bearing mice are primed and boosted for anti-TMA antibody formation, the resulting response was overall reduced with respect to the idiotype-positive and negative plaque-forming cells that differs from the Ts2-bearing hosts wherein the idiotypic component is preferentially suppressed. The appearance of Ts1 before the detection of Ts2 in the same experimental animals is discussed with reference to a normal physiologic sequence of events involved in suppressor pathways.

Animals↗
PubMed1983

Centrioles, primary cilia and calcium in the growth of Balb/c 3T3 cells.

In every mammalian cell the interphase centriole forms a primary cilium during some part of the cell cycle. Many sensory receptors are modifications of primary cilia, but a sensory role for primary cilia in mammalian cells has not been proven. Nevertheless, we have found that both growth factors and calcium ionophore (A23187) induce calcium fluxes and shortening of the primary cilium. This evidence raises the question of whether the primary cilium is involved in calcium fluxes that are necessary for growth stimulation in mammalian cells.

Animals↗
PubMed1982

Hapten-specific responses to the phenyltrimethylamino hapten. III. Mice whose delayed-type hypersensitivity responses cannot be abrogated by the presence of anti-idiotypic suppressor T cells lack a critical modulatory T cell function.

A single intraperitoneal injection of the monovalent synthetic antigen, tyrosinated trimethylaminoaniline [tyr(TMA)] in Freund's complete adjuvant induces an antiidiotypic second-order T suppressor (Ts2) cell population 6 wk later. This population was able to suppress TMA-specific delayed-type hypersensitivity (DTH) responses when adoptively transferred into normal syngeneic recipients. However, they failed to function intrinsically. The inability of the Ts2 to function intrinsically was not caused by compensating idiotype-negative T cells that mediate DTH. Rather, this paradoxical observation was found to be caused by the absence or loss of function of a critical modulatory T cell population in the suppressor cell-bearing mice. This cell is functionally active in normal mice immunized for DTH responses and is sensitive to cyclophosphamide treatment. In addition, this cell type bears idiotype on its surface and is Thy-1+ and Lyt-1-,2+. It was demonstrated that by adoptively transferring the activated modulatory T cells from normal mice into tyr(TMA)-immune recipients, it was possible to observe suppressor cell function intrinsically. The potential importance of modulatory T cell function in the regulation of antibody and DTH responses is discussed.

Animals↗
PubMed1982

T cell replacing factor substitutes for an I-J+ idiotype-specific T helper cell.

An in vitro system for the study of idiotype (Id) expression on antitrimethylamino hapten antibody-producing cells and its regulation by two classes of helper T cells is described. These cells are distinguished in four ways: one requires a hapten-carrier bridge and gives a good response that is low in Id; it does not bind to Id-coated dishes and is not affected by anti-I-J plus complement. The other requires antigen but not a hapten-carrier bridge, is bound by Id-coated dishes and is killed by anti-I-J and complement. The Id-specific cell appears to be antigen specific and acts via a soluble factor(s).

Animals↗
PubMed1982

Hapten-specific responses to the phenyltrimethyl-amino hapten. I. Evidence for idiotype-anti-idiotype interactions in delayed-type hypersensitivity in mice.

The delayed-type hypersensitivity (DTH) reaction to the phenyltrimethylamino (TMA) hapten in mice has been investigated. TMA-derivatized syngeneic spleen cells (TMA-SC) administered s.c. in several strains of mice consistently evoked DTH reactivity, as measured by footpad swelling after challenge with the diazonium salt of TMA. DTH could be induced by low levels of anti-idiotypic antisera (anti-Id) in lieu of antigen. The DTH reaction induced by either mode was hapten-specific, could be transferred into naive recipients by viable lymph node cells but not with serum from immune mice and was not influenced by cyclophoshamide pretreatment. Unlike TMA-SC which induced DTH in all of the strains of the mice tested, anti-Id induced DTH only in strains of the Igh-1e allotype. Positive DTH reactions were induced by anti-Id in the C57.Ige strain (H-2b, Igh-1e) but not in its allotype-congenic partner C57BL/6J (H-2b, Igh-1b). Interestingly this reaction could be suppressed if relatively high amounts of anti-Id were inoculated i.v. just prior to antigen challenge. In addition, the administration of anti-Id 1 h prior to antigen challenge in TMA-SC-sensitized mice significantly blocked the DTH reaction only in the Igh-1e strains. These results demonstrate that the induction and abrogation of TMA-specific DTH by anti-Id is linked to the IgCh locus.

Animals↗
PubMed1981

Computer generation of cobalt-60 single beam dose distribution using an analytical beam model.

A beam dose calculation model based on evaluation of tissue air ratios (TAR) and scatter air ratios (SAR) for cobalt-60 beams of rectangular cross section has been developed. Off-central axis fall-off of primary radiation intensity is derived by an empirical formulation involving an arctangent function with the slope of the geometrical penumbra acting as an essential constant. Central axis TAR and SAR values are assessed by semi-empirical polynomial expressions employing the two sides of the rectangular field as the variables. The model utilises a minimum number of parametric constants and is useful for computer generation of isodose curves. The model is capable of accounting for situations where wedge filters or split field shielding blocks, are encountered. Further it could be widely applied with minor modifications to several makes of the currently available cobalt-60 units. The paper explains the model and shows examples of the results obtained in comparison with the corresponding experimentally determined dose distributions.

Absorption↗