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Biomedical subjects

F Beck

Publications and source records attributed to F Beck.

At least 163 records · Page 9Linked to original sources
PubMed1976

Inhibition of pinocytosis in rat yolk sac by trypan blue.

Day 17.5 yolk sacs from rats injected with partially denatured 125I-labeled bovine serum albumin (I-BSA) were cultured in vitro by a raft technique. The rates of release of [125I]iodotyrosine were similar in control yolk sacs and in yolk sacs from rats preinjected with trypan blue. Day 17.5 rat yolk sacs were also cultured in medium containing I-BSA. Following pinocytic uptake the substrate was degraded intracellularly and [135I]iodotyrosine released into the medium. Trypan blue, when present in the medium in concentrations above 100 mug/ml, inhibited pinocytosis of I-BSA and so decreased the rate of [125I]iodotyrosine production. Trypan blue similarly decreased the rate of pinocytic uptake of 125I-labeled polyvinylpyrrolidone. Pinocytic uptake of macromolecules was not decreased in yolk sacs from rats pretreated with trypan blue. The relevance of these results to the mechanism of teratogenic action of trypan blue is discussed. It is proposed that if trypan blue in teratogenic doses similarly inhibits pinocytosis by the yolk sac during the organogenetic period teratogenesis might result from a transient interruption in the flow of metabolites through the yolk sac to the embryo.

Animals↗
PubMed1976

Comparative placental morphology and function.

The distinction between histiotrophic nutrition (in which local macromolecules are chiefly responsible for the maintenance of the embryo) and hemotrophic nutrition (which results from a transfer of material between the maternal and fetal circulations) is made. Placentation in a number of commonly used laboratory animals and in man is described, and it is shown that dependence upon histiotroph and hemotroph varies greatly, not only between species but also at different stages of gestation in a single species. These facts are likely to be reflected in considerably differences in response to certain teratogens; they must be carefully considered when experimental results are extrapolated between species. The significance to man of an agent which has been shown to be teratogenic in a single species of experimental animals should be evaluated in terms of possible differences in placental function between man and that species. This is particularly so if there is a suspicion that the potential teratogen may affect the fetal membranes.

Animals↗
PubMed1976

[The controlled TUR: a new method for the measurement of intraoperative blood-loss during TUR (author's transl)].

The measurement of intraoperative blood-loss during TUR is concerned as a compulsory procedure for this kind of operation. After testing so far known methods for measuring blood-volume in blood-water-mixtures and demonstrating greater disadvantages of these methods, we developed a new photometer, which allows an immediate and exact estimation of the blood-loss. We compared this new method with other also exact but more complicated methods, had laboratory tests and tests in the daily operative routine and excluded possible mistakes.

Aged↗
PubMed1975

Quantitative studies of pinocytosis. I. Kinetics of uptake of (125I)polyvinylpyrrolidone by rat yolk sac cultured in vitro.

A method is described for the in vitro culture of 17.5-day rat visceral yolk sac. Tissue survival was good as judged by light and electron microscopy. The rate of pinocytic uptake of 125I-labeled polyvinylpyrrolidone by the tissue was constant both within and between experiments. Within the concentration range 0.15-24 mug/ml, the 125I-labeled polyvinylpyrrolidone neither stimulated nor inhibited pinocytosis. The system offers many advantages in the quantitative study of the physical basis of pinocytosis.

Animals↗
PubMed1975

Quantitative studies of pinocytosis. II. Kinetics of protein uptake and digestion by rat yolk sac cultured in vitro.

Pinocytic uptake of 125I-labeled bovine serum albumin by 17.5-day rat visceral yolk sac cultured in vitro has been examined. Uptake was followed by intracellular digestion and, after an initial period, the content of radioactivity in the tissue itself remained constant during the incubation. Radiolabel was returned to the culture medium predominantly as (125I)iodotyrosine; exocytosis of undigested protein did not occur. The rate of uptake of labeled protein, which was constant within an experiment and reproducible between experiments, was much higher than that of a nondigestible macromolecule, 125I-labeled polyvinylpyrrolidone. The higher rate of uptake was a consequence of the protein entering the cells chiefly by adsorption to the plasma membrane being internalized; 125I-labeled albumin did not stimualte, nor did 125I-labeled polyvinylpyrrolidone inhibit pinocytosis. Different preparations of 125I-labeled albumin had characteristically different rates of uptake, probably reflecting differences in affinity for plasma membrane receptors. The physiological significance of the findings is discussed.

Animals↗
PubMed1975

Development and structure of the extra-embryonic membranes of the ferret. A light microscopic and ultrastructural study.

Light and electron microscopic observations on the development and structure of the extra-embryonic membranes of the ferret are described. By day 16 of pregnancy trophoblastic villi consisting of a cytotrophoblastic core with a peripherally located phagocytic syncytiotrophoblast have penetrated deeply into the endometrium. During its invasion the syncytiotrophoblast removes endometrial glandular cells and some of the adjacent stromal tissue. The maternal blood vessels remain intact and eventually become surrounded by the syncytiotrophoblast. A marked hypertrophy of the maternal capillary endothelium then begine. By day 28 the maternal capillary endothelial cells attain their maximum height. The cytoplasm of these cells contains numerous cisternae of rough endoplasmic reticulum and a well-developed Golgi apparatus, features which are typical of protein-secreting cells. The maternal blood vessels are separated from the syncytiotrophoblast by a thick layer of amorphous material which stains positively with PAS. Alcian blue staining in the presence of critical concentrations of magnesium chloride indicates the presence of both sulphated and carboxylated acid mucopolysaccharides. It may be that the amorphous material contributes significantly to the nutritional requirements of the developing fetus. Invaginations of the syncytiotrophoblast plasma membrane facing this amorphous layer are often seen. Coated vesicles and substances in contact with the outer surface of the membrane are therefore likely to be endocytozed. The acid phosphatase in the syncytiotrophoblast is consistent with the presence of lysosomes and catabolic function. Regions of paraplacental cellular trophoblast which lie in close association with the endometrium, but do not penetrate it, appear to specialize in endocytosis. The haemophagus organ, which is located at the antimesometrial pole, is the site of rupture of maternal blood vessels, and the extravasated blood lies in close association with the chorio-allantoic membrane. The maternal blood cells ingested by the trophoblast in this area are presumably an important source of iron for the embryo. The cellular trophoblast in the paraplacental regions is well equipped with hydrolytic enzymes, as shown by histochemical tests for acid phosphatase. It seems likely that these regions are concerned with embryotrophic endocytotic nutrition supplementing endothelio-chorial nutrition.

Animals↗
PubMed1971

The effect of Trypan Blue, suramin and aurothiomalate on the breakdown of 125 I-labelled albumin within rat liver lysosomes.

1. A fraction enriched in lysosomes was prepared by centrifugation from the livers of rats that had been injected 0.5h before death with (125)I-labelled albumin. When suspended in sucrose-protected buffer, pH7.4, and incubated at 22 degrees C for 2h, the particles progressively released iodotyrosine into the medium. Albumin digestion did not occur if the particles were subjected to treatments known to break lysosomes or if particles from uninjected rats were incubated in medium containing (125)I-labelled albumin. It is concluded that the observed production of iodotyrosine results from protein hydrolysis within intact heterolysosomes. 2. Particles from rats pre-treated with Trypan Blue, suramin or aurothiomalate released iodotyrosine more slowly than controls. Since these compounds are enzyme inhibitors that concentrate in liver lysosomes after administration in vivo, their effect is ascribed to intralysosomal inhibition of proteolysis. The doses used did not decrease endocytosis of albumin into liver or cause increased lysosome breakage during incubation, thus allowing some alternative explanations of the decreased proteolysis to be eliminated. Particulate carbon, a non-inhibitor that also concentrates in lysosomes, did not affect albumin hydrolysis.

Animals↗
PubMed1971

Digestion of an exogenous protein by rat yolk-sac cultured in vitro.

Yolk-sacs were removed from 17.5-day pregnant rats injected 2-5h previously with (125)I-labelled bovine serum albumin. The specific activities of acid phosphatase and acid proteinase, and the specific radioactivities (trichloroacetic acid-insoluble and trichloroacetic acid-soluble) were measured in subcellular fractions prepared by homogenization and differential centrifugation. The conversion of acid-insoluble into acid-soluble radioactivity within cultured tissue was followed and the nature of the liberated products was investigated by gel chromatography. The results are consistent with the protein entering lysosomes and being digested there. The radiolabel was released chiefly as free iodotyrosine.

Acid Phosphatase↗
PubMed1969

Protein digestion in isolated lysosomes inhibited by intralysosomal trypan blue.

Control rats and rats treated with subcutaneous trypan blue were injected intravenously with denatured albumin-I(125). Lysosome-rich fractions of their livers, when incubated at 22 degrees C in osmotically protected medium (pH 7.4), retained their capacit to digest albumin-I(125). The rate of digestion was lower in suspensions pre-pared from rats treated with trypan blue than in control suspensions, but rates of lysosome breakage were not different. T'hese results and other experimental evidence suggest that trypanblue concentrated within lysosomes can inhibit intralysosomal digestion, probably by inhibition of lysosomal proteinases.

Acid Phosphatase↗