Acta biologica Academiae Scientiarum Hungaricae最新文献

The effects of barium ions (Ba2+) on the release of growth hormone (GH), and prolactin (PRL) and ultrastructural changes accompanying altered hormone secretion in primary cultures of the rat anterior pituitary gland were studied in the presence or absence of calcium ions (Ca2+) in the medium. In four days old cultures previously labelled with 14C-L-leucine radiolabelled PRL release was stimulated in the presence of both Ba2+ and Ca2+, while GH release remained unchanged. In the absence of Ca2+, Ba2+ caused a more marked PRL and a significant GH release. In seven days old cultures, Ba2+ stimulated immunoreactive GH release in the presence of Ca2+ three-fold and a dramatic GH release occurred when Ca2+ was omitted from the incubation medium. Many parenchymal cells contracted profoundly in the presence of Ba2+ without Ca2+ in the incubation medium and the discharge of secretory material was frequent in a number of granular cells that did not contract. The observation on contraction suggests that Ba2+ may activate the microtubular-microfilamentous system in pituitary parenchymal cells.

The mutagenic activity of the pentacyanonitrosylferrate (II) (NP) was studied by the prophage induction and the Drosophila mosaic test. On the basis of plaque and mosaic spot induction freqauencies it is concluded that both NP and its adenine complex are nonmutagenic as for induction of chromosome breaks and point mutations. The nonmutagenic activity of the NP can be attributed to its nonpermeability through cell membranes.

The composition of myofibrillar proteins was studied in the soleus and gastrocnemius muscles of rabbit hind limbs immobilized by plaster cast in experiments lasting 1--4 weeks. The amounts of actin, M protein and C protein increased relative to the normal composition. The ratio of the light chain peptides of the fast muscle myosin changed from 1 : 2 : 1 to 1 : 2 : 0.5 as a result of 4 weeks of disuse. The LC-1 : LC-2 ratio of slow myosin did not change considerably while the amount of fast LC-3 peptide, hardly detectable in soleus muscle, increased more than tenfold. The amount of tropomyosin decreased significantly in both muscles. The submolecular composition of troponin changed, mostly in the slow muscle; TN--C and TN--I decreased significantly, whereas there was an increase in the TN--T values. It is concluded that the phenotype of the structural proteins of muscles with different functions is de-differentiated by disuse, while the genetic functions of the muscle cells is reprogrammed to the synthesis of contractile proteins (e.g. myosin) characteristic of the other type of muscle.

The purpose of the present study was to compare the ATPase activities of cardiac SR in two species in which the different intrinsic myocardial contractility can only partially be explained by the different properties of cardiac myosins. In cardiac SR isolated from rat heart, the total ATPase activity was 1512.5 +/- 23.3 nmol Pi/mg protein/min, nearly four times as high as in dog cardiac SR (408.8 +/- 28.9 nmol Pi/mg protein/min). The Ca2+-activated ATPase in rat cardiac SR represented only 23.8% of the total ATPase activity, while in dog cardiac SR it was approximately 50% of the total. Thus, the specific Ca2+-activated ATPase was nearly two times higher in the cardiac SR of the rat than in that of the dog. This higher rate of ATP hydrolysis in rat cardiac SR may be, at least in part, responsible for the increased intensity and shorter duration of the active state in the rat myocardium. Polyacrylamide gel electrophoresis of SR showed that the relative amount of Ca2+-pump protein was two times higher in dog heart, similar to the percentage of Ca2+-activated ATPase activity. At the same time, the specific Ca2+-activated ATPase activity and the relative amount of Ca2+ pump protein in both the rat and dog cardiac SR were inversely related.

The distribution by individual chromosomes of early centromere divisions was investigated in two series of G-banded lymphocyte culture preparations. 1. Photographs of mitoses of routinely karyotyped 201 healthy persons were retrospectively analysed. 2. In a prospective study, 48 h and 72 h cultures of 12 girl infants were examined. The results were very similar in both series. They confirm a non-randomness of centromere separation which seems to be independent of sex and technical factors. The earliest dividing chromosomes were Nos 18, 2, 5, 12 and X, in that order, whereas the acrocentrics were the last to separate. The investigation of asynchronous division may be interesting from the point of view of mechanism of non-disjunction, and of testing mutagenicity.

Forty male guinea pigs weighting 400--600 g, 8 months old, were given metribuzin directly into the gastric lumen over a period of 30 days (20 animals) or 90 days (20 animals), 6 times a week. The intoxicated animals showed in the gastric mucosa a significant decrease in glucosamine isomerase activity and a significant increased in beta-glucosidase and beta-galactosidase activity. The results suggest that the biosynthesis of the sugar moiety of glycoproteins is depressed, the degradation of glycoproteins is stimulated by metribuzin.

Histamine antagonists bind to the histamine receptors of Tetrahymena, and their presence can be shown by immunocytofluorimetry. The binding of histamine is inhibited by antagonists structurally similar to histamine, regardless whether they bind to H1 or H2 receptors, but it is not inhibited by phenindamine, a compound structurally highly different from histamine. That part of H1 receptor which binds to both concanavalin A (con-A) and histamine probably contains primarily simple sugars, and secondly, glycosamine oligomers. At the H2 binding sites, on the other hand, acetylgalactosamine and its derivatives dominate. The present findings in the light of earlier functional experiments, suggest that in Tetrahymena, binding and effect are separated from each other to a certain degree.

A stable recombinant clone was constructed by inserting a 1.5 kb mouse satellite DNA HindIII restriction fragment into the plasmid pBR-322. The cloned fragment according to both hybridisation data and restriction analysis seems to be identical with the major component of the mouse satellite DNA. It contains two Atu4001 (EcoRII) monomers, one dimer and one "1.5-mer". HindIII restriction sites are either in position around 95 or 140 of the Atu4001 monomer. Our results and the recently published prototype sequence of the mouse satellite DNA Sau961 monomer (15) suggest that HindIII cleavage of the mouse satellite DNA follows the B type restriction pattern.

The effects of hypoxaemia on the synthesis of prostacyclin and prostaglandins in the cerebral microvessels and on the ultrastructure of brain cortex capillaries were investigated in three groups of rats. Series I: rat embryos were kept in hypoxic-hypobaric condition for 42 hours. It resulted in the enhancement of synthesis of PG2alfa and PGE2 even two months after birth. The fine structure of the capillary endothelium remained without any pathological change. Series II: adult male rats were on hypoxic-hypobaric environment for 42 hours. There was a slight increase in the synthesis of PGE2 and PGD2 while the ultrastructure of brain capillaries was found to be normal. Series III: the hypoxic-hypobaric condition lasted for 240 hours in adult male rats. This long term hypoxaemia affected greatly the prostaglandin synthesis of brain cortex capillaries and resulted in changes in the fine structure of brain microvessels as well. The possible molecular mechanism activated by hypoxaemia in brain capillaries is discussed.