Search PubMed⌕ Search

Biomedical subjects

R Michel

Publications and source records attributed to R Michel.

At least 145 records · Page 8Linked to original sources

The two human trypsinogens: catalytic properties of the corresponding trypsins.

The catalytic properties of the two human trypsins obtained from purified trypsinogens have been studied. The catalytic rate constant kcat and the pK of the ionisable residue implicated in the active site have been determined with Bz-Arg-OEt. The hydrolysis of Tos-Arg-OMe by human trypsins does not follow the simple Michaelis-Menten scheme and indicates a difference in the conformational flexibility of the active site-regions of the two enzymes. Both enzyme are readily autolyzed and calcium ion plays a fundamental role in stabilizing trypsin activity. However trypsin 2 self-digests more rapidly than trypsin 1. These results are a prerequisite to the elucidation of the fate of pancreatic enzymes in human digestive tract.

Animals↗

[Invasion of erythrocytes by toxoplasma gondii (author's transl)].

The in vitro-invasion of mouse erythrocytes by Toxoplasma gondii could be detected and analysed by electron microscopy. The sequence of events observed during erythrocyte invasion led to the assumption of an actively penetrating parasite into the non-phagocytic host cell.

Animals↗

[Binding of 3,3',5'-triiodo-L-thyronine (rT3) to human serum proteins].

The rT3-binding and human serum proteins was directly studied with tracer doses of radioactive rT3. Polyacrylamide gel electrophoresis showed 125I-rT3 added to human serum was distributed among two proteins: albumin (carrying 57% of tracer rT3) and TBPA )22%). No binding was observed to TBG, protein binding T4.

Humans↗

[Effect of thryoidectomy on the properties of rat liver mitochondria during liver regeneration].

The properties of regenerating rat liver mitochondria are not changed by the thyroidectomy. Thus, hepatectomy induces, in thyroidectomized rats as in normal ones, a decrease in the activity of the outer membrane enzymes, a stimulation of oxidative phosphorylations and an increase of the turn over rate of mitochondrial proteins. Thyroid hormones do not seem to have a major effect upon the liver regeneration mechanism.

Animals↗

[Studies on the presence of metal traces in tissue surrounding A.O. angle plates, based on neutron activation analysis (author's transl)].

Using instrumental neutron activation analysis, 11 samples of tissue in contact with A.O. angle plates and 8 samples of fascial tissue were examined for their content of trace elements, half a year to 5 1/2 years after hip joint intertrochanteric osteotomies. Significant increases in the concentrations of the elements Cr, Fe, Co, Ni and Mo, all of which are contained in the A. O. steel plates (V4A steel), were found both in the contact tissue and in the tissue of the fascia lata femoris about 4--8 cm away from the angle plates, whereas the levels of concentration of elements not specific for the alloy in question, namely, Zn, Se, Rb and Cs, were normal or just subnormal. It was possible to prove by means of element correlations that the elements Cr, Co, Ni and Mo are present in constant ratios in those tissue samples which are loaded with traces of metals foreign to the body. However, only the Mo:Cr ratio corresponds to that of the angle plates. The authors considered Ni to be a useful indicator for the degree of metal loading of a tissue, since Ni will normally occur in human tissue in very low concentrations (less than or equal to 10(-6) g/g dry substance) and was identified by the authors--contrary to previous studies--even in the fascial tissue located up to 8 cm away from the contact tissue. Non-linear correlations were found between iron and the other components of the steel, reflecting the complicated regulatory mechanisms governing the presence of iron in the organism. The results of the analysis are discussed in respect of possible long-term action of the implantate components liberated by corrosion, which, in case of long-term implantates might place an overall burden of foreign ions on the body.

Chromium↗

Structural changes on Entamoeba histolytica trophozoites after cryopreservation in liquid nitrogen.

Trophozoites of Entamoeba histolytica cultures which had been deep-frozen in the presence of 5% DMSO, along with untreated cells and cells treated with DMSO (5%), were examined for fine-structural changes. After deep-freezing in liquid nitrogen only a few amoebae exhibited normal nuclear and cytoplasmic structure. One frequently observed but unspecific finding pertaining to recovered cells is the separation of the cytoplasm into large vacuolated (coarse-granular) and electron-optically fine-granular (hyaline) zones. The glycogen which normally lies in the cytoplasm is always eluted. In many cases numerous short RNP helices are scattered unevenly in the vesicular plasma, but they are also found in larger masses adjacent to the membranes of still intact and already damaged nuclei. Moderately damaged nuclei have a poorly folded membrane and their chromatin is markedly denatured. More heavily damaged nuclei have a membrane which has partly fibrillated or ruptured and then formed conspicuous folds, where the nuclear membrane has ruptured nucleoplasmic remnants of chromatin and button-like bodies appear to pour into the surrounding cytoplasm. The final destruction of the cell is marked by coalescing autolytic zones, first in the vacuolated and later in the fine-granular cytoplasm. Finally only remnants of the nuclear membrane and of the membranes of numerous vacuoles remain. It is assumed that most of the changes in the cytoplasm are of a secondary nature and are caused by the early functional disturbance of the nucleus.

Animals↗

Human pancreatic lipase: a glycoprotein.

Human lipase has been purified from pancreatic juice. The protein has a molecular weight of 48 000 and an N-terminal residue of lysine. It has been characterized as a glycoprotein containing 4.7 mol of glucosamine, 2.8 mol of mannose, 2.9 mol of fucose, 3.0 mol. of galactose and 1.1 mol of glucose per mol of protein. Two isolipases have been separated by polyacrylamide gel electrophoresis. Their isoelectric points are 5.80 and 5.85, respectively and both are glycoproteins. Immunological cross reactions have been obtained between human lipase and other mammalian lipases (porcine, bovine, ovine, canine and rat).

Amino Acids↗

[Cytophysiology of the glandular lobe of the corpora cardiaca: ergastoplasmic granules and their significance].

The number of ergastoplasmic granules in the glandular lobe of the corpora cardiaca is counted in Locusta migratoria migratorioides R. and F. and Schistocerca gregaria Forsk., male adults of different ages, grouped or isolated, having flown or not, and reared in various conditions of hygrometry and temperature. A good correlation was found between the number of ergastoplasmic granules and the utilization of the adipokinetic hormone. Ergastoplasmic granules may représent an original mechanism of hormonal storage used in view of heavy metabolic requirements.

Age Factors↗

Action of intracellular proteinases on mitochondrial translation products of Neurospora crassa Schizosaccharomyces pombe.

Gel electrophoretic analysis of mitochondrial membranes from Neurospora crassa shows the presence of a polypeptide fraction with apparent molecular weights of 7000 - 1200, which is synthesized on mitochondrial ribosomes. This fraction comprises between 10 and 50% of total mitochondrial translation products. Evidence is presented that the major part of this fraction is derived from components with higher apparent molecular weights by proteolytic activity. The proteolytic activity is located in vesicles which are co-isolated with mitochondria upon differential centrifugation. The activity is strongly enhanced by application of detergents such as sodium dodecylsulfate and Triton. Proteins synthesized on mitochondrial as well as cytoplasmic ribosomes are subject to proteolytic breakdown. This proteolysis can be blocked by addition of inhibitors such as diisopropylfluorphosphate to isolated mitochondria. Similar observations were made with Schizosaccharomyces pombe. In Neurospora, the amount of mitochondrial translation products with apparent molecular weights of less than 12000 is low in mitochondria from cells treated with cycloheximide for 1 h and high in mitochondria from cells treated with cycloheximide for 5 min. This observation is explained by the finding that proteinase activity in mitochondrial preparations decreases exponentially with a t1/2 of 20 min during preincubation of cells with cycloheximide. Procedures are described to remove or block contaminating proteinase activity. The results appear to be relevant for the interpretation of many data obtained from experiments in which this puzzling kind of artifact has not been sufficiently considered.

Ascomycota↗

Nonparallel courses of intrapancreatic levels of exportable enzymes after a fatty meal.

Stimulation of pancreatic secretion by a fatty meal resulted in a nonparallel time-course of intrapancreatic amylase, lipase, trypsinogen, and chymotrypsinogen levels. Concomitant variations in the rate of pancreatic protein biosynthesis are observed. Those results support the hypothesis that nonparallelism in exportable enzyme levels is a consequence of a nonparallel regulation by the stimulus of the individual rates of enzyme biosynthesis.

Amylases↗