Effect of glucocorticoids on fetoprotein production by an established cell line from Morris hepatoma 8994

Glucocorticoids at concentrations equal to or higher than 10^?7M lead to an increase of alpha-fetoprotein production by an established cell line from Morris hepatoma 8994. These cells also secreted alpha_M-fetoprotein into the culture medium but only after addition of at least 4×10^?7M hydrocortisone or 5×10^?8M dexamethasone. The effects on both fetoproteins were observed in spite of a decrease of cell multiplication and an increase of cell detachment.     

Metabolic cooperation studied by a quantitative enzyme assay of single cells

A new method making use of a radiochemical enzyme assay at the single cell level is presented to investigate metabolic cooperation, a widely studied form of cellular communication. In this case metabolic cooperation between normal human fibroblasts and fibroblasts derived from a patient deficient for the enzyme hypoxanthine-guanine phosphoribosyl transferase has been studied.A mixture of an equal number of both cell types was cultured in close physical contact and after trypsinisation, replating and culturing the cells for several hours in a high dilution, quantitative enzyme measurements with individual cells isolated from the mixture were carried out. From the distribution curve of the enzyme activities of the individual cells the conclusion could be drawn that a macromolecule, either the enzyme itself or DNA or mRNA, coding for that enzyme, is transferred from normal to mutant cells.     

Multiple forms of acetylcholinesterase from rat erythrocytes. Effect of fat-free diet.

Electrophoretic patterns of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) from rat erythrocyte were studied. The enzyme was solubilized by the following treatments: a) Triton X-100, b) sodium deoxycholate, or c) ultrasonic irradiation. When the erythrocyte membrane was solubilized by Triton X-100 at concentrations higher than 0.3%, by 10 mM sodium deoxycholate, or by ultrasonic irradiation for more than 5 min, a single band of acetylcholinesterase activity appeared in the gel. Two bands of activity were stained in the gel when the membrane was solubilized by Triton X-100 at concentrations between 0.1--0.2%, or by ultrasound for 5 min. Electrophoretic patterns of acetylcholinesterase from rats fed a fat-sufficient diet were similar to those for the enzyme from animals fed a fat-free diet. The recombination of lipids with the enzyme eluted from the gels confirmed the "phenotypic allosteric desensitization phenomenon".     

The fusion of abnormal plasma lipoprotein (LP-X) and the erythrocyte membrane in patients with cholestasis studied by electronmicroscopy.

Adhesion followed by fusion of LP-X vesicles with the erythrocyte membrane is an important contribution to the erythrocyte enlargement in patients with intra or extra hepatic cholestasis. Adhesion of LP-X vesicles is demonstrated by thin section and freeze-etch electronmicroscopy. Fusion of LP-X with the erythrocyte membrane is deduced from biochemical data and freeze-etch electronmicroscopy in that the uptake of cholesterol and lecithin coincides with the increase in smooth areas on the fracture faces of the erythrocyte membrane.     

Lysophospholipase activity in cell-wall fragments contaminating mitochondrial fractions of Neurospora crassa.

Crude mitochondrial preparations from Neurospora crassa contain high levels of lysophospholipase (EC 3.1.1.5) activity when assayed with lysophosphatidylcholine as a substrate. In mitochondria purified by centrifugation on a sucrose-density gradient this activity is virtually absent. The enzyme was shown to be linked to a contaminating cell fraction which mainly consists of cell-wall material as was demonstrated by electron microscopy and chemical analysis. The enzyme has no absolute Ca2+ requirement but it is slightly stimulated by 10 mM CaCl2. The pH optimum is 5.8 in presence of CaCl2 and is shifted to 4.2 when EDTA is present. In contrast to other lysophospholipases this enzyme is only slightly inhibited by deoxycholate. This detergent is able to release part of the lysophospholipase activity from the wall fragments without producing an increase in specific activity. The enzyme is possibly secreted by the cells as high lysophospholipase activities were also found in the culture medium.     

Effect of 6-hydroxydopamine on diet-induced hyperlipidemia and atherosclerosis in the rat.

The effect of 6-hydroxydopamine (6-OH-dopamine) and of a cholesterol rich diet on the plasma and aortic cholesterol of female rats were studied. Both the diet and the 6-OH-dopamine produced an important increase in plasmatic and aortic cholesterol. A synergistic effect of these two treatments was observed on the plasma but not on the aortic cholesterol. The mechanism by which 6-OH-dopamine produces hypercholesterolemia and a increase in aortic cholesterol remains to be explained.     

Intercellular exchange of lysosomal enzymes: enzyme assays in single human fibroblasts after co-cultivation.

Intercellular exchange of N-acetyl-β-D-glucosaminidase (EC 3.2.1.30) β-galactosidase (EC 3.2.1.23) and acid α-glucosidase (EC 3.2.1.20) was studied after cocultivation of normal and enzyme deficient human fibroblasts in confluent cultures. Enzyme activities were measured in single cells using microchemical procedures. After co-cultivation of normal control fibroblasts and those from a patient with Sandhoff's disease an increase of activity of N-acetyl-β-D-glucosaminidase was found in Sandhoff cells, together with a decrease of activity in normal control cells. After co-cultivation of normal fibroblasts and those from patients with glycogenosis II and GM1-gangliosidosis, no indication was found for intercellular transfer of acid α-glucosidase and β-galactosidase respectively. The significance of the results is discussed in respect of the hypothesis of Hickman and Neufeld about secretion and uptake of lysosomal enzymes.