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Biomedical subjects

A Mathur

Publications and source records attributed to A Mathur.

At least 235 records · Page 13Linked to original sources
PubMed1983

Induction of suppressor cells in Japanese encephalitis virus infected mice.

Adoptive transfer of spleen cells obtained from mice primed with Japanese encephalitis virus (JEV) suppressed IgM antibody plaque forming cells (PFC) against JEV in the spleen. Similar suppression of PFC was also shown in vitro by adding primed spleen cells to JEV-stimulated spleen cell cultures. The suppressor activity appeared sharply in the third week after priming and persisted up to 6 weeks. By using various cell separation procedures it was found that the suppressor activity resided in the T cell enriched fraction and not in B cells or macrophages. Sensitivity of the cells to treatment with anti-Thy 1.2 antiserum and complement confirmed that suppressor cells were T lymphocytes. It was noted that the suppression was effective against dengue virus antigen also. Our findings thus show generation of suppressor T lymphocytes in JEV-infected mice.

Animals↗
PubMed1983

A scanning electron microscopy evaluation of peripheral nerve regeneration.

Regeneration of a transected peripheral nerve following repair is often impeded by scar formation and misdirection of axon sprouts. This paper describes the use of the scanning electron microscope (SEM) in conjunction with other physiologic tests to evaluate nerve regeneration. A central one centimeter segment was removed from the peroneal branch of both sciatic nerves in 37 white New Zealand rabbits. Sectioned nerves were divided into four experimental groups according to type of repair performed: (A) no repair; (B) mobilization and direct epineural repair; (C) interpositional nerve graft repair; (D) polyglycolic acid (PGA) conduit repair. Each animal was reexplored eight months later and nerves examined by electrophysiologic testing and scanning electron microscopy. Unrepaired nerves viewed by SEM showed impaired axonal regeneration and loss of fascicular morphology with increased scar tissue. Nerve sections of direct epineural and interpositional graft repairs showed the best return of axonal morphology. Nerves regenerated across a one centimeter gap through a PGA conduit demonstrated regrowth of small and large myelinated axons grouped into "mini-fascicles" with increased connective tissue. PGA conduit repairs were electrically inferior to graft and direct repairs as measured by conduction velocity and the amplitude of evoked response. These findings correlated well with anatomy seen on scanning electron micrographs. The scanning electron microscope proved an excellent adjunctive tool for the study of peripheral nerve regeneration.

Animals↗
PubMed1983

Dengue virus-induced cytotoxic factor induces macrophages to produce a cytotoxin.

In our earlier studies we have observed that T lymphocytes of dengue type 2 virus (DV)-infected mouse spleen produce a cytotoxic factor (CF). In the present study it has been observed that CF induces mouse spleen and peritoneal macrophages to produce a cytotoxin (CF2) as has been revealed by DEAE-cellulose chromatography. CF2 is produced by an induction process and is present intracellularly as well as leaking out of the cells. CF2 kills most of the macrophages and some of the T cells, as observed with CF. It appears that CF2 is produced to amplify the effect of CF and/or for cooperative action with CF.

Animals↗
PubMed1983

Characterization of the cytotoxin produced by macrophages in response to dengue virus-induced cytotoxic factor.

We have observed earlier that dengue type 2 virus-induced cytotoxic factor (CF) induces macrophages to produce a cytotoxin (CF2) which kills mainly the macrophages, some of the T lymphocytes and has no effect on B-lymphocytes of normal mouse spleen. The findings of the present study show that CF2 is heat-labile, trypsin-sensitive and unstable at acid and alkaline pH. It is a low molecular weight product as it is dialysable, non-sedimentable on ultracentrifugation at 103,500 g for 3 h and passes through 0.22 micron Millipore filter. It is adsorbed onto the target normal mouse spleen cells. The properties of CF and CF2 have been compared.

Adsorption↗
PubMed1982

Transplacental Japanese encephalitis virus (JEV) infection in mice during consecutive pregnancies.

Transplacental transmission of Japanese encephalitis virus (JEV) has been demonstrated in consecutive pregnancies of mice. Pregnant mice inoculated intraperitoneally with JEV transmit the virus to the foetus. When such female mice were mated again after 6 months, the virus could be isolated from the foetuses of the ensuing pregnancy. The incidence of abortion was increased significantly though the neonatal deaths were considerably less than during the first pregnancy. Intra-uterine infection occurred in spite of the presence of HAI antibodies against JEV in the preconceptional sera of the mice. The findings of the present study indicate the value of such a system for further investigations of the pathogenesis of JEV infection during pregnancy in humans.

Abortion, Spontaneous↗
PubMed1982

Inhibition of E-rosette formation and phagocytosis by human blood leucocytes after treatment with the dengue virus-induced cytotoxic factor.

We have observed earlier that T lymphocytes of dengue type 2 virus (DV)-infected mouse spleen produce a cytotoxic factor (CF) which kills T lymphocytes and macrophages of the spleen of normal mice or animals of other species. In the present study an effort was made to study the effect of CF treatment on human peripheral blood leucocytes. After treatment with various dilutions of CF at 4 degrees for 1 hr 25%-36% of T lymphocytes lost their capacity to form E rosettes and 25%-36% of monocytes lost their phagocytic function. Cytotoxic-factor treatment had no effect on formation of EAC rosettes by B lymphocytes and the phagocytic functions of polymorphonuclear cells. Pretreatment of cells with 2,4 dinitrophenol, reduced glutathione or ouabain, which act on the cell membrane, inhibited the effect of CF on E-rosette formation and phagocytosis. This indicated that CF acts by inducing changes in the cell membrane. It is likely that production of a similar factor in DV-infected humans is responsible for similar alterations observed in their blood.

Animals↗
PubMed1982

Depressed macrophage functions in dengue virus-infected mice: role of the cytotoxic factor.

Dengue virus Type 2 (DV) infection causes immunosuppression in mice. Since macrophages are crucial for immune response, we have studied their functions in this condition and report our findings here. It was observed that in DV-infected mice the phagocytosis of neutral-red and latex particles by splenic and peritoneal-cavity macrophages was significantly reduced (P less than 0.001) from Days 3 to 10 after inoculation. Similarly the migration of splenic and peritoneal macrophages on a glass surface was reduced significantly (P less than 0.001) from Days 4 to 10 after inoculation. Pre-treatment of normal mouse spleen cells with DV-induced cytotoxic factor (CF) inhibited the phagocytic and migratory functions in the same way as observed in DV-infected mice. Higher dilutions of CF (10(-3) and 10(-3.7)) did not kill the cells but affected their functions. It was concluded that macrophage functions are affected by killing and metabolic changes in these cells by DV-induced CF, thus producing immunosuppression.

Animals↗
PubMed1981

Target lymphoid cells for the cytotoxic factor produced in the spleen of dengue virus-infected mice.

In previous studies we have observed the production of a cytotoxic factor by the T-lymphocytes in the spleen of dengue type-2 virus- (DV) infected mice which killed normal mouse spleen cells in vitro. In the present study types of spleen cells affected in vitro by the cytotoxic factor (CF) have been investigated. It was observed that it kills of the macrophages, one-third of T-lymphocytes and a few of the granulocytes, normoblasts and megakaryocytes. It had no effect on B-lymphocytes. The proportion of killed cells could not be significantly enhanced by retreatment of cells by additional CF. The cytotoxic activity of CF is not affected by adsorption with susceptible or non-susceptible cells. CF also kills lymphoid cells of animals of other species, viz. albino rats, rabbits, guinea pigs but had no effect on those of rooster. It had no effect on various cell cultures.

Animals↗
PubMed1981

Congenital infection of mice with Japanese encephalitis virus.

Transplacental transmission of Japanese encephalitis virus (JEV) when given intraperitoneally was demonstrated in pregnant mice as shown by isolation of the virus from placenta and fetal tissues. Furthermore, JEV could be isolated from the brain, liver, and spleen of newborn mice. The effect of JEV at different periods of gestation in pregnant mice was demonstrated for the first time, and the consequences of maternal infection on fetuses and neonates were studied. JEV infection during the 1st week of gestation caused a significantly higher number of fetal and neonatal deaths (66%) than during the 3rd week of gestation (13.8%). The number of abortions, stillbirths, and neonatal deaths was higher in infected mothers than in controls. No congenital abnormalities were found in any of the newborn mice. Sera obtained from 5-week-old health mice delivered by mothers infected during the 3rd week of gestation contained JEV hemagglutination inhibiting and immunoglobulin M antibodies. The results of these preliminary experiments show the usefulness of mice as a model for further elucidation of JEV infection during pregnancy and its effects on the fetus.

Abortion, Spontaneous↗