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Biomedical subjects

A Hossain

Publications and source records attributed to A Hossain.

116 records · Page 7Linked to original sources
PubMed1981

Bacillus stearothermophilus from Saudi Arabian Soils.

Ten thermophilic Gram-positive bacteria were isolated from various soils of Saudi Arabia. The strains are spore-forming rods belonging to the species Bacillus stearothermophilus. The cells are motile, strictly aerobic, catalase and oxidase positive. The sporangia appear to be swollen and their position varies from terminal in some to sub-terminal in others. The thermal stability of some enzymes of these bacteria was investigated; extracellular alpha-amylase appears to be very sensitive to pH and temperature. The ultrastructure of these bacteria shows specific changes in the cell wall when grown at the maximum, minimum and optimum growth temperatures, respectively.

Geobacillus stearothermophilus↗
PubMed1975

Purification and properties of phenylalanyl-tRNA synthetase from baker's yeast.

In an effort to avoid proteolytic fragmentation of enzymes extracted from yeast cells, the (L-phenylalanine:tRNAPhe ligase (AMP-forming) phenylalanyl-tRNA synthetase (EC6.1.1.20)) has been isolated from toluene lysates of baker's yeast in the presence of the protease inhibitor, phenylmethylsulfonyl fluoride. The procedure includes ammonium sulfate fractionation and chromatography on DEAE-cellulose and hydroxylapatite columns. Acrylamide gel electrophoresis of the enzyme in the presence of sodium dodecyl sulfate indicates a single subunit of 75 000; other isolations have led to two subunits of 75 000 and 63 000, respectively, in agreement with other workers. Steady state kinetic analysis of the enzyme has also been carried out. The apparent kinetic patterns resulting from application of Cleland's procedure, in which the substrates are varied pairwise in the presence of saturating concentrations of the third component, suggest a reaction mechanism in which ATP and phenylalanine enter the reaction in an obligatory ordered fashion but do not completely eliminate a random mechanism.

Adenosine Triphosphate↗
PubMedDate not supplied

Mixed inocula of mouse mammary tumour cell subpopulations result in changes of organ-specific metastasis.

Tumour and metastatic phenotypes, the pattern of mouse mammary tumour virus (MMTV) integration and expression, and the expression of a metastasis associated gene, nm23, were examined in three mammary tumour cell subpopulations, 66, 168 and 4526. Tumour growth, host survival, metastatic aggressiveness, and the distribution of different cell types in metastasis resulting from mixed cell inocula were also analysed. The results of these studies indicated that the cell lines were distinguishable from each other both phenotypically and genotypically. However, a rearrangement of the mammary tumour specific protooncogene, int-1, caused by MMTV was found to be a unique characteristic of the cell line 4526. Therefore, int-1 was used as a stable marker to examine the genotype of the metastatic colonies that developed in mice bearing tumours of mixed cell inocula. Highly metastatic 4526 cells influenced the metastatic range of poorly metastatic 66 cells. Line 66 cells that normally colonize only to lungs were also found to colonize liver when inoculated together with the liver-metastasizing 4526 cells. This acquired metastatic phenotype of 66 cells was transient. On the contrary, mixed cell inocula of 4526 and non-metastatic 168 cells did not produce any colony of 168 cells. The metastatic aggressiveness of 4526 cells was inhibited by both 66 and 168 cells. Furthermore, the metastatic behaviour of mixed inocula differed depending on the relative abundance of the component populations in the mixtures. These findings suggest that interaction between cells of different metastatic phenotypes may result in changes of their metastatic behaviour.

Animals↗
PubMedDate not supplied

Colonization characteristics of a murine mammary tumor cell line that metastasizes frequently to the heart.

Metastasis by mouse mammary tumor cells is usually confined to lung. This paper describes the metastatic behavior of an established mouse mammary tumor cell line, 4526, that in addition to lung and liver metastasis, shows a high rate of heart metastases. The tumor cells were inoculated into the fourth mammary fat pad of syngeneic mice and their pattern of distant colonization was analysed qualitatively as well as quantitatively. We found that the cell line produced 100, 70 and 40% metastases to the lung, liver and heart, respectively. While the lung metastases appeared primarily as nodular masses, the liver metastases occurred both as nodular and diffuse masses. In addition, we observed that the metastatic load of each of the different lung lobes of individual mice was proportional directly to its relative size, and there seemed to be an inverse relationship between the occurrence of lung and liver metastases in individual mice. As compared to lung and liver metastases, heart metastases were found to be localized internally, usually in the cavity and wall of the ventricle. Furthermore, hearts with metastases revealed destruction of cardiac tissue and blockage of the cavity space. Our results show that 4526 cells are phenotypically stable, since the metastatic behavior of several clonal derivatives of the cell line obtained from lung, liver and heart colonies were found to be identical to that of the parental cell line. Thus this cell line, because of its unparalleled metastatic characteristics, offers a model for investigations into the biology of mammary tumor cell metastasis, especially heart metastasis.

Animals↗