Search PubMed⌕ Search

Biomedical subjects

S Chandrasekhar

Publications and source records attributed to S Chandrasekhar.

At least 91 records · Page 5Linked to original sources
PubMed1977

Mast cell response during the early phase of tuberculosis: an electron-microscopic study.

Guinea pig lungs were infected with Mycobacterium tuberculosis by intratracheal route and examined under electron microscope to investigate the morphological alterations of the organisms, if any, and the response of the host tissue. The bacilli showed no changes in their morphology, while the host tissues revealed several cells containing many electron-dense intracytoplasmic granules. These cells were predominantly seen during the 1st week of infection. The electron-dense bodies of these cells may be the ones observed by earlier workers and suggested to be the altered forms of tubercle bacilli. The present investigation, however, revealed them to be the granules of the mast cells. These cells were observed to respond to tuberculous infection during the first few days by appearing in large numbers crowded with intracytoplasmic granules and soon disintegrating as the result of subsequent degranulation. The above observation is presented and its significance discussed.

Animals↗
PubMed1976

The effect of gravitational forces on the viability of spheroplasts of mycobacteria.

Spheroplasts of Mycobacterium smegmatis and Mycobacterium tuberculosis were subjected to a wide range of centrifugal forces ranging from 583 g to 15 000 g after which their viability was determined by plating them on two types of media; one containing stabilizing agents and the other without them. Though there were minor fluctuations in the viable counts, there was no consistent decrease in their viability even in the absence of osmotic stabilizers.

Cycloserine↗
PubMed1976

The pathogenicity of spheroplasts of Mycobacterium tuberculosis.

Guinea pigs were injected with spheroplasts of Mycobacterium tuberculosis and were sacrificed after various intervals to study the state of the organisms and to evaluate the extent of disease. The spheroplasts persisted in the body of the animals for a considerable length of time. Their presence, however, was not associated with either the development of tuberculin hypersensitivity or pathologic changes. It was found that the spheroplasts were pathogenic only when reverted in the animals to bacterial forms. The reversion of the spheroplasts to bacillary state and the subsequent initiation of infection were dependent on the duration of their stay within the host.

Animals↗
PubMed1972

Macrophage accumulation, division, maturation, and digestive and microbicidal capacities in tuberculous lesions. I. Studies involving their incorporation of tritiated thymidine and their content of lysosomal enzymes and bacilli.

Dermal and pulmonary tuberculous lesions were produced in rabbits with BCG, biopsied, incubated in vitro with tritiated thymidine ((3)HT) under hyperbaric oxygen, quickly frozen, sectioned in a cryostat, stained for the lysosomal enzyme beta-galactosidase, autoradiographed, stained for acid-fast bacilli and counterstained with hematoxylin. As macrophages developed into epithelioid cells, they could still divide-ie, incorporate (3)HT. However, once they became fully mature epithelioid cells that were 4-plus in beta-galactosidase, they could not do so. Tuberclebacilli did not stimulate macrophage division. On the contrary, macrophages containing bacilli did not divide, except when the lesions began. During the development of tuberculous lesions, macrophages (including those rich in enzymes and those containing bacilli) died, forming caseous centers. Therefore, local cell division did not seem to be the main mechanism by which macrophages reduced their bacillary load. Such division seemed mainly to occur in young macrophages that had recently immigrated into the lesions from the bloodstream and had not yet ingested bacilli.

Animals↗
PubMed1971

Radiation, Infection, and Macrophage Function IV. Effect of Radiation on the Proliferative Abilities of Mononuclear Phagocytes in Tuberculous Lesions of Rabbits.

Rabbits were irradiated with 400 to 600 rads 2 to 3 days before they were infected with BCG or with virulent tubercle bacilli. Biopsies were periodically removed from the resulting lesions and incubated for 1 hr with (3)H-thymidine in vitro under hyperbaric oxygen. Twelve to 16 days after radiation there was a reduction in the percentage of mononuclear cells (macrophages and some lymphocytes) that had incorporated (3)H-thymidine in the lesions. At this time, the lesions of the irradiated group were smaller than those of controls. These results can be explained by the reduction in the number of new mononuclear cells that entered the lesions of the irradiated group and support the tenet that local mononuclear cell division occurs mainly in cells that have recently emigrated from the blood stream. An alternate, but less likely, explanation of these results would be that radiation caused the bone marrow to release a higher percentage of "defective" mononuclear cells that were unable to divide, i.e., incorporate (3)H-thymidine, in the lesions. The reduction produced by radiation in both local cell infiltration and local cell division would decrease the number of macrophages available to control the tuberculous infection in the host.

Journal Article↗