Acta biologica et medica Germanica最新文献

The distribution of membrane potential (Em) of aortic media cells and fibroblastoid kidney cells (both derived from calf and monkey) was investigated by using dense cell layers. Fibroblastoid kidney cells showed a symmetric distribution of Em with a mean of -10.6 +/- 0.29 mV for calf and -12.1 +/- 0.31 mV for monkey (m +/- sm). In aortic media cell lines, however, a wide bimodal distribution of Em was found (between -4 mV and -32 mV). The peaks were at about -17 mV and -27 mV in calf aortic media cells, and at about -13 mV and -22 mV in monkey aortic media cells. The bimodality of Em distribution of cultured aortic media cells may be typical for this cell type. Presumably, this pattern reflects two cell populations in different states of differentiation or maturation.

Out of nine compounds known to induce accumulation of autophagosomes, seven were found to inhibit degradation of endogenous protein and all of them to inhibit degradation of an exogenous protein (asialofetuin) in isolated rat hepatocytes. On the basis of these findings we propose two possible common mechanisms by which the drugs may cause autophagosome accumulation: 1) The inhibition of protein degradation may result in a decrease in the intracellular amino acid levels, a change which in turn serves as a stimulus for increased autophagic sequestration. 2) Disturbance of the function of the lysosomes may reduce their ability to fuse with newly formed autophagosomes, thereby causing accumulation of the latter.

The relative proportions of alpha-, beta-, and pre-beta-lipoproteins in the fetal serum of mouse, rat, rabbit, guinea pig, mini-pig, and man were determined by agarose gel electrophoresis and subsequent scan evaluation. No distinct species-independent, fetal-specific common features could be detected. In mouse, rabbit and rat an increase in alpha-lipoproteins and a decrease of the proportion of beta-lipoproteins can be observed during prenatal development. In human cord serum of the 30th week alpha-LP are prevalent; at delivery their proportion is still 50%, like in the serum of adults. Five of the species investigated reveal low, if any, pre-beta-lipoprotein levels in fetal serum, while those in the adult organism amount to 19-33%. The lipoprotein spectrum of the mini-pig at the end of the gestational period is identical with that of the adult animal. In the serum of the fetal and adult guinea pig no alpha-lipoprotein band is detectable. On the other hand, a pre-albumin fraction appeared in the prenatal period, amounting to 25% of total lipoproteins. In total, the findings reported here reflect a largely species-specific development of the fetal lipoprotein patterns.

Leucocytes and spleen contain four different types of protein proteinase inhibitors. Two of them can be inactivated by cathepsin D. In this work biochemical and immunological studies of the inactivation of I-2 by cathepsin D are presented. Polyacrylamide gel electrophoretic examinations indicate that cathepsin D inactivates I-2 by hydrolysis of the inhibitor molecule. The conversion of the active inhibitor into inactive protein proceeds catalytically. The studies on the inhibitor mechanism of the isoinhibitors of I-1 type explain the unusual inhibitor property of this type of inhibitor to inhibit two different types of proteinases, cysteine and serine. The evidence suggests that the inhibitory mechanism is based on an active sulfhydryl group of the inhibitor which may interact with the disulfide bridge of the inhibited proteinase.

The biosynthesis of porphyrins after incubation with 6.25 mmoles/l delta-aminolevulinic acid (ALA) for 4 h, the synthesis of porphobilinogen, the residual ALA, and the activity of the porphobilinogen synthase were determined in erythrocytes. Examined were 568 individuals: healthy males and female, normal pregnancy and nephropathy of pregnancy, newborn infants and various diseases of the kidney. The biosynthesis of porphyrin in erythrocytes after incubation with ALA and the activity of porphobilinogen synthase in erythrocytes in chronic renal disorders progressively decreased depending on the stages of the pathologic process and the development of chronic renal insufficiency. The high correlation between the level of synthesized porphyrins and hemoglobin led us to assume that disorders in porphyrin biosynthesis represent in fact one of the pathogenetic mechanisms of nephrogenic anemia.

Methods for the production of antibodies against Paraoxon in rabbits are described. The highest-titre antisera were produced with conjugates containing a succinyl spacer group with a degree of derivatisation between 8 and 12 haptens per albumin molecule. The antibody response was tested by immunoprecipitation in agar gel with a hapten-rabbit-albumin-complex and by a radioimmunoassay. The synthesis of 125I labelled tracers is reported. The most potent antisera bound 50% of the radioactive tracer after 1:10(5) dilution and showed apparent affinity constants of 10(6) to 10(7) M-1 for Paraoxon. Compared to Paraoxon these antisera possessed cross reactivities with Parathion of 8.8 to 13.8%, with Methylparathion of 0.35 to 0.82%, and with Dimethoat of 0.0006 to 0.0012%.

5-Hydroxytryptamine (5-HT) and dopamine were found to inhibit glucose-induced insulin release and 45Ca2+ net uptake in islets microdissected from ob/ob-mice. Dopamine was more potent than 5-HT. L-DOPA, the precursor of dopamine, had an effect similar to that of dopamine and this effect was reduced by benserazide. L-5-hydroxytryptophan, the precursor of 5-HT, potentiated glucose-induced insulin release and stimulated 45Ca2+ uptake. This effect was also blocked by benserazide. It is concluded that dopamine is a stronger inhibitor than 5-HT and that the different actions of 5-HTP and L-DOPA might be explained by this difference in the magnitude of inhibition.

An aqueous extract from the unripe fruits of the tropical plant Momordica charantia was found to be a potent stimulator of insulin release from beta-cell-rich pancreatic islets isolated from obese-hyperglycemic mice. The stimulation of insulin release was partially reversible. It differed from that of D-glucose and other commonly employed insulin secretagogues in not being suppressed by L-epinephrine and in even being potentiated by the removal of Ca2+. This anomalous behaviour was not associated with general effects on the metabolism of the beta-cells as indicated by an unaltered oxidation of D-glucose. Studies of 45Ca fluxes suggest that the insulin-releasing action is the result of perturbations of membrane functions. In support for the idea of direct effects on membrane lipids, the action of the extract was found to mimic that of saponin in inhibiting the Ca2+/H+ exchange mediated by the ionophore A23187 in isolated chromaffin granules and release Ca2+ from preloaded liposomes.

Rat islets, rat insulinoma cells and islets from three different mouse strains were labelled with 35S-cysteine and/or 35S-methionine. Detergent lysates of the cells were subjected to immunoprecipitation with sera from 5 newly diagnosed diabetic children and 5 control sera. The immunoprecipitates were analysed by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis followed by autoradiography. One of the sera immunoprecipitated a protein of Mr 64K from lysates of rat islets, rat insulinoma cells, A. TH and NMRI but not CBA/H mouse islets. This protein was not consistently immunoprecipitated by the other diabetic sera, however, it was never found with control sera nor was it detected in rodent lymphocytes. Some proteins of lower molecular weight (59K, 57K, 40K, 29K) were specifically immunoprecipitated by one or more diabetic sera from some of the rodent islet cell preparations. It is concluded that rodent islet cells contain a protein of Mr 64K which may be antigenically related to a 64K protein previously detected in immunoprecipitates of human islet cells with the same diabetic sera. The variable results with rat and mouse islet cell material suggest that the level of cross-reactivity is low. Further studies are needed to clarify whether the lower molecular components detected in some immunoprecipitates represent other antigenic determinants or degradation products of the 64K protein.