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Biomedical subjects

E Chin

Publications and source records attributed to E Chin.

60 records · Page 4Linked to original sources
PubMed1981

Susceptibility of Zygomycetes to human serum.

Seven members of the class Zygomycetes were tested for serum susceptibility. Five of the isolates were inhibited to different degrees by pooled fresh human serum. Heating the serum at 56 degrees C for 30 min to inactivate complement did not abolish the inhibitory activity in the serum. Members of the genera Cunninghamella and Absidia appeared most susceptable to the inhibitory effects of serum while members of the genus Rhizopus were most resistant. One isolate of R. arrhizus appeared to have enhanced growth in the presence of human serum. Our findings suggest certain species of the class Zygomycetes are strongly inhibited by serum, and this may account for the rarity of human infections by these species.

Blood Physiological Phenomena↗
PubMed1978

Flow-cytometric analysis of chicken red blood cells.

Flow-cytometric analysis of acriflavin-Feulgen stained chicken erythrocytes shows a complex distribution of amounts of deoxyribonucleic acid fluorescence, the profile consisting of a main peak and a right hand shoulder. This bimodal distribution, an artifact characteristically seen on analysis of flattened cells using orthogonal flow systems, results from fluorescence emission in preferred directions stemming from the combined effects of refractility and orientation of the cells. The shoulder disappears on analysis of lysed erythrocyte ghosts, also on analysis of cells in a medium whose refractive index approximates that the cells. An orientation effect for matrue erythrocytes was indicated by reanalysis of fractions after sorting on the basis of high and low fluorescence or scatter signals. Both fractions gave the original range of values on reanalysis, although some changes in shape of the profile and in the peak positions for the sorted cells were seen. Sodium dodecyl sulfate treatment of stained cells "loosened" the cells' structure, yielding lowered scatter values, and fluorescence values approaching those of the shoulder. The average fluorescence emission of the erythrocytes was lower than that of reticulocytes and lymphocytes. The values of the latter correspond closely, although coincidently, to that the erythrocyte shoulder values. Dual parameter analysis of forward light scatter, and fluorescence, which was detected at 90 degrees to the laser beam, showed the low fluorescence to be accompanied by low scatter signal, and the high fluorescence among the cells with the high scatter signal. The lowered forward scatter signal is due to a wider scattering of light from cells oriented edge-on to the detector, and loss of signal beyond the acceptance angle of the detector. These results suggest that the preferred directions for fluorescence are in the plane of the cells, and the values are dependent on the cells' orientation in the stream. These interpretations were supported by the results of analysis of partially oriented cells. The approaches used and conclusions arrived at are similar to those of Gledhill et al (16), Van Dilla et al (37), in their analysis of fluorescence of flat sperm cells although the affects in the case of the erythrocytes are less extreme.

Animals↗
PubMedDate not supplied

Streptozotocin, an analog of N-acetylglucosamine, blocks the removal of O-GlcNAc from intracellular proteins.

Streptozotocin (STZ), an analog of N-acetylglucosamine (GlcNAc), is a specific toxin for the pancreatic beta cell. We found that treatment of rats with STZ results in an early beta-cell-specific increase in the level of intracellular protein modification by O-linked GlcNAc (O-GlcNAc). Using a model O-GlcNAc peptide based on the transcription factor Sp1, we show that treatment of cultured cells with STZ during peptide biosynthesis results in hyperglycosylation of the peptide as a result of the ability of STZ to specifically inhibit the activity of O-GlcNAc-selective N-acetyl-beta-D-glucosaminidase. Although this inhibitory activity of STZ probably can occur in all cells, we found, using in situ hybridization, that beta cells express very high levels of the mRNA encoding the enzyme responsible for cytoplasmic protein O-glycosylation, O-GlcNAc transferase (OGT). These findings suggest that the pancreatic beta cell is particularly sensitive to the toxicity of STZ because it expresses such high levels of OGT. When STZ blocks O-GlcNAc removal from intracellular proteins, the cell with the most rapid on-rate for O-GlcNAc, the beta cell, will experience the most rapid accumulation of this protein modification. Because we also show that the on-rate of O-GlcNAc is substrate driven in several cell types, we speculate that the beta cell, with its high level of OGT, may also respond to elevations of blood sugar with increased protein modification by O-GlcNAc. Thus, this proposed mechanism of STZ toxicity on the beta cell may result from an exaggeration of a heretofore unrecognized physiological response to glucose mediated through the high level of OGT in these cells.

Acetylglucosamine↗