Acta biologica et medica Germanica最新文献

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%.

The changes of lipid parameters induced in male Wistar rats by feeding a high-fat diet for several weeks were studied in cell fractions of the liver. For this purpose subcellular fractionations of liver tissue from 12-week-old animals receiving food containing, respectively, 3% fat (controls) and 50% fat, were performed by means of differential centrifugation, and the lipids in the cell fractions were determined quantitatively. The levels of triglycerides and cholesteryl esters both in total liver and in the cell fractions had risen several fold against the controls. Most of the accumulated lipids were retrieved in the cytosolic supernatant. In contrast, for the phospholipids and the free cholesterol only a slight increase in free cholesterol was observed in total liver, and increases of both lipids had occurred in the cytosolic supernatant, while the particulate fractions showed no alterations. It is pointed out in the discussion that the accumulation of triglycerides and cholesteryl esters in the liver largely concerns the particulate fractions too (observed so far in the literature only for single particulate fractions), which might be of interest for the function of the cell nucleus, the mitochondria and the endoplasmatic reticulum. The increase of phospholipids and free cholesterol in the supernatant has to be considered not only as a passive process of deposition, but could represent necessary contributions to the building up of lipid droplets in the cytosol during deposition of triglycerides and cholesterol in this region of the cell. The studies confirm that the fatty degeneration of the liver, true, is always the result of triglyceride accumulation but that, under certain conditions, cholesterol is also enriched in the form of its esters.

A decrease of the acetylcholine concentration in the brain of infantile rats was induced by maternal deprivation in neonatal life, which was associated with emotional and mental ill-effects in later life. The decreased acetylcholine concentration in the infantile brain as well as the permanent emotional and mental ill-effects, which were produced by neonatal deprivation, could be prevented by neonatal administration of the acetylcholinesterase inhibitor pyridostigmine. These findings suggest that acetylcholine can be considered as an important, environment-dependent local organizer of the brain.

Nonhistone proteins (NHPs) of salt-soluble chromatin (Chromatin S) and of the residual nuclei (Chromatin P) from rat liver and thymus were studied by SDS-polyacrylamide gel electrophoresis. The two chromatin fractions of the liver showed significant differences in their NHP patterns with most of the hnRNP and matrix proteins occurring in Chromatin P. In accordance with the low protein content of thymus nuclei, the corresponding thymus fractions exhibited electrophoretic patterns with a markedly lower amount of NHPs than in liver. Chromatin P from thymus, in contrast to the liver fraction, revealed only a very low content of hnRNP-specific proteins of molecular weight 30,000-40,000 (30 K to 40 K) (informosomal proteins) consistent with the significantly lower RNA content of thymus nuclei. In the region of the matrix proteins (60-75 K) Chromatin P showed only two bands of about 64 K and 73 K in thymus, whereas in liver five strong bands at 64 K, 66 K, 69 K, 73 K, and 75 K were found. RNase digestion was employed to discriminate hnRNP-specific protein from "real" chromosomal NHPs. At least about 65% and 25% of the NHPs from Chromatin P and S of liver, respectively, were found to be RNP-specific. The two chromatin fractions were further fractionated by sucrose gradient centrifugation and isopycnic banding in metrizamide. After centrifugation the main peaks, both of Chromatin S and P, contained only minor amounts of NHPs with a predominating protein of 38 K. By the centrifugation procedures described in this paper, a small subfraction of chromatin could be separated which was enriched in newly synthesized RNA, informosomal proteins, matrix- and other high molecular weight proteins. This subfraction might be related to transcriptionally active chromatin.

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.

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.