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Biomedical subjects

M Ashraf

Publications and source records attributed to M Ashraf.

At least 181 records · Page 10Linked to original sources
PubMed1978

Sporulation in single-spore isolates from amitrole-induced multispored asci of Saccharomyces cerevisiae.

Amitrole treatment causes multispored ascus production by cells of a yeast strain whose asci normally contain two diploid spores. Single spores were isolated from asci containing two to eight spores and their ability to germinate was determined. Cells in colonies grown from single spores sporulated in the same manner as the parent strain indicating that amitrole had not induced meiotic division in the developing asci.

Amitrole↗
PubMed1978

Ultrastructural influence of reperfusing dog myocardium with calcium-free blood after coronary artery occlusion.

The ultrastructural effects of perfusing ischemic myocardium with calcium-free blood were determined in 12 dogs. In 6 dogs, the left anterior descending coronary artery was ligated for 45 minutes and was released for 5, 10, or 20 minutes. In 6 other dogs, the ischemic zone was perfused with blood free of calcium which was chelated with EGTA (ethylene glycol bis [B-aminoethylether-N,N'-tetraacetic acid] for 5, 10, or 20 minutes. After reperfusion with whole blood, the sarcomeres either were mildly contracted or formed contracted bands. The cells were usually pulled apart at the intercalated disk. The mitochondria were swollen and contained electron-dense deposits. Lanthanum was used as a marker for monitoring changes in cell membrane permeability and permeated into many ischemic myocardial cells. The hearts treated with calcium-free plasma showed well preserved morphology. Mitochondria were slightly swollen, their cristae were occasionally disrupted, and they lacked electron-dense deposits. No lanthanum leaked into these cells, with a few scattered exceptions. Even in the leaky cells, the mitochondria did not show any deposits. It is suggested that calcium overload plays a significant role in the pathogenesis of cell injury and that reduction in plasma levels of calcium, at least for a limited period may delay the onset of calcium overload and improve cell morphology. Alterations in the cell membrane are followed by lethal intracellular changes leading to events associated with cell death.

Animals↗
PubMed1977

Induction of multispored asci in two-spored strains of Saccharomyces cerevisiae by amitrole.

Although growth of two yeast strains characterized by consistent production of two diploid spores per ascus was inhibited in complex presporulation media containing amitrole, a fraction of the cells produced were able to form asci with more than two spores after transfer to acetate sporulation medium. Cells grown in a defined presporulation medium containing amitrole did not acquire this ability. The increase in spore numbers per ascus is attributed either to the induction by amitrole in growth medium of cells with more than one nucleus or to the restoration of normal meioses in the multispored asci.

Amitrole↗
PubMed1977

Structural changes in the freeze-fractured sarcolemma of ischemic myocardium.

Ultrastructural alterations in the sarcolemma of ischemic myocardium were studied with the freeze-fracture technique. In normal myocardial sarcolemma, the P fracture face contained many intramembranous particles which were randomly distributed, while the E fracture face had few intramembranous particles; no structural abnormalities were seen within the lipid bilayer on either face. Myocardium ischemic for 45 minutes displayed no, or only slight, aggregation of intramembranous particles, but upon reperfusion for 5 to 20 minutes, the particles became significantly aggregated in the P face. Scattered nicks within the lipid bilayer were observed on both fracture faces. Intramembranous particles were similarly aggregated in myocardium ischemic for 2 hours; however, the number of nicks were greatly increased on the P and E fracture faces. These structural alterations, which were undetected in thin sections, are likely to be associated with altered function in the sarcolemma of ischemic myocardium.

Animals↗
PubMed1976

X-ray microanalysis of mitochondrial deposits in ischemic myocardium.

The x-ray microanalysis technique was used to determine the chemical composition of intramitochondrial electron-dense deposits in ischemic myocardial cells. Semi-thin sections were cut from Araldite-embedded tissue and analyzed in a scanning electron microscope equipped with energy- and wavelength-dispersive spectrometers. The energy dispersive spectrum revealed calcium and phosphorus peaks over many mitochondrial deposits. Peak to background ratios of calcium, phosphorus and magnesium obtained with the wavelength dispersive spectrometer were 1.7, 8.8 and 1.2, respectively. There was no consistent relationship in the characteristic peaks of calcium and phosphorus in a given mitochondrial granule. Magnesium appears to be negligible, except in some mitochondrial deposits which lacked calcium, where it was present with a peak to background ratio of two. These results suggest formation of calcium or magnesium phosphate in the mitochondria during ischemia. X-ray microanalysis can provide detailed information on subcellular electrolyte distribution in normal and ischemic myocardial cells and should be attempted with improved methods of tissue preparation.

Animals↗
PubMed1976

The effect of amitrole (3-amino-1H-1,2-4-triazole) on cytokinin activity and sexual reproduction in the yeast Schizosaccharomyces octosporus.

Cytokinin activity in extracts from actively growing cultures of Schizosaccharomyces octosporus was greatly reduced by exposure to amitrole (5 X 10--3M). Amitrole treatment, at the same concentration, stimulated cell enlargment and ascus production in this organism. These data suggest that a relationship may exist between low levels of endogenous cytokinins, cell expansion in preference to cell division, and ascus formation.

Amitrole↗
PubMed1975

Scanning electron microscopy of the heart after coronary occlusion.

The scanning electron microscope was used to study the ultrastructural alterations which occur following periods of myocardial ischemia of 30 minutes and 1, 2, 5, 10, and 24 hours. The alterations were compared with those seen with the transmission electron microscope. The early changes consist of swelling of organelles and clumping of nuclear chromatin. After 5 hours, disintegration of the transverse tubular system becomes apparent, and breakdown of the connections between the nucleus and the sarcoplasmic reticulum is seen coincident with distortion of the shape of the nucleus. It is suggested that the sarcoplasmic reticulum may be a part of the "endoskeleton" of the cell and may play a role in maintaining the shape and location of the nucleus. After 10 hours, extensive membrane alterations have occurred in many of the intracellular organelles. It is concluded that the changes seen with scanning electron microscopy are consistent with those seen with transmission electron microscopy.

Animals↗
PubMed1975

Scanning electron microscopy of the heart.

Dog hearts were studied with the scanning electron microscope. This technique provides a better perspective of the relationships between organelles than can be obtained with other methods. Extensive communications between mitochondria, sarcoplasmic retiuclum, and nuclear envelop were demonstrated; this suggests the presence of a direct pathway between mitochondria and nuclei for the transport of ATP and perhaps other substances.

Animals↗
PubMed1975

Myofibrillar alterations in ischemic myocardium after glucose-insulin-potassium infusion.

GIK infusion after experimental coronary artery ligation in dogs appears to reduce the size of the infarct and influence the ultrastructure of some of the cells bordering the infarct. These cells contain fine filamentous material thought to be actin, which appears to originate near the intercalated disc and is thought to represent a reparative process in reversibly injured cells and a hypertrophic response in normal cells adjacent to the infarct.

Actins↗
PubMed1975

Scanning electron microscopy of infarcted myocardium.

The scanning electron microscope had been applied to the study of cellular alterations which are caused by myocardial ischemia. This instrument allows rapid tissue preparation and, while resolution is less than can be obtained with the transmission electron microscope, it provides a somewhat three-dimensional appearance of the cell's ultrastructure. The early alterations consist mainly of swelling of organelles, separation of fibrils, and clumping of nuclear chromatin. Within 5 hr disruption of the T-tubules and sarcoplasmic reticulum occurs, nuclear distortion is frequent, and fibrillar destruction is commonly seen but is often focal. Extensive fibrillar alterations occur after 10 hr and become more exaggerated at 24 hr after the onset of ischemia. However, even after 24 hr many mitochondria and nuclei, though damaged, are recognizable. This study suggests that scanning electron microscopy may play a useful role in the study of pathological alterations at the ultrastructural level.

Animals↗