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Biomedical subjects

D Casper

Publications and source records attributed to D Casper.

51 records · Page 3Linked to original sources
PubMed1988

Regulation of choline acetyltransferase activity by cell density in a cultured human neuroblastoma cell line.

Choline acetyltransferase (ChAT), the biosynthetic enzyme for acetylcholine metabolism, is expressed in a human cholinergic neuroblastoma cell line; MC-IXC. We demonstrate that ChAT activity is regulated in this cell line by cell density. It is believed that the mechanism of stimulation of enzyme activity involves cellular contact, as medium conditioned by cells of high density failed to mimic the effect of density alone, and trypsinization reversed this effect. Density did not increase acetylcholinesterase activity, another marker for the cholinergic phenotype, in MC-IXC cultures, demonstrating the independent regulation of these two cholinergic enzymes. Since increased density slows the rate of cell division, we used a DNA synthesis inhibitor to uncouple DNA replication from cell density. This had no effect on the specific activity of ChAT, suggesting that a cell-cell contact was the mediating factor. Other neuroblastoma cell lines were tested, and only cell lines which already contain ChAT activity were sensitive to its regulation by cell-cell contact, suggesting that cell-cell contact is permissive rather than instructive in this process. The effect of cell passage on ChAT activity is also discussed.

Cell Count↗
PubMed1980

Differences between intracellular platelet and brain proteins that bind serotonin.

Two proteins with binding capacity highly specific for serotonin are present in the 100,000 g supernatant obtained from rat platelets: a glycoprotein and albumin. They were purified by means of (NH4)2SO4 fractionation, Sephadex sieve chromatography, and affinity column chromatography. The two proteins differed in most of their physical and chemical properties: (a) migration on 7.5% acrylamide gel of the complex (protein-Fe+2-[3H]serotonin); (b) molecular weight (sodium dodecyl sulfate gels); (c) carbohydrate reaction; (d) binding capacity and binding constants; (e) effect of reserpine; (f) heat stability; and (g) isoelectric point. However, they showed two similar properties: sensitivity to trypsin and dependence on Fe+2 for serotonin binding. The properties of both the glycoprotein and albumin differ considerably from those of serotonin binding protein of brain (SBP), which was not detected in platelets. Since brain serotonin binding protein is thought to be involved in storage of the amine, these results suggest that the storage form of serotonin in rat platelets is different from that in rat brain. These results also imply that the storage of serotonin in platelets may not serve as a model for the storage of serotonin in nerve terminals of the brain.

Albumins↗
PubMedDate not supplied

Strategies toward maximum detergent efficiency.

Detergent Z demonstrated the most reliable cleaning and detergent delivery system. After the initial detergent evaluation, the data were compared against all detergents. It was found that acceptably cleaned items ranged from 37% to 85% per evaluation. Labor and material costs could be reduced greatly with the use of detergent Z, which had the best cleaning results. We also observed the advantage of a sensor in the detergent delivery system which can override some less obvious equipment malfunctions. Since detergent Z also exhibited the least amount of residue build-up, a savings in maintenance costs could be expected later on. The vendor of detergent Z showed great interest and concern for our department's needs and quality assurance by offering us numerous technical resources during the evaluation. One year following our detergent studies, detergent Z and its related line of cleaning products are being utilized in our hospital. We found that the four months spent analyzing detergents used in our utensil washers provided an interesting resource project that has been a positive investment in improved operations for the decontamination area. In Central Service alone, 61.7 hours a week were saved by the change in products. Quality of cleaning continues to be high. The practice of a weekly acid bath for the utensil washers has been discontinued; the acid bath will now be given when necessary, and has not been done since detergent Z was put into use six months ago. During the next fiscal year, savings of detergent, utilities and labor are conservatively projected at $30,000.

Central Supply, Hospital↗