Acta biologica et medica Germanica最新文献

An extensive comparative analysis of more than fifty available sequences of ribosomal 5S RNA has been made. Both for prokaryotic and eukaryotic 5S RNA a generalized secondary structure is presented which is similar to that suggested by Nishikawa and Takemura modified in few positions only. Both generalized secondary structures contain five main helical regions and a high base-pairing content of about 65 +/- 5%. The general structural architecture of prokaryotic and eukaryotic 5S RNA molecules appears to be very similar with minor modifications within particular subgroups of organisms. Conserved and semiconserved nucleotides are accumulated in the single stranded parts of 5S RNA. Functional importance was suggested for some of these regions; other short conserved nucleotide stretches may be involved in the folding of 5S RNA molecules. In particular, we propose a tertiary base-pairing interaction between the universal invariant GUA sequence (positions 76-78 and 75-77 in prokaryotic and eukaryotic 5S RNA, respectively) and the complementary conserved CPuU sequence (positions 38-40 and 36-38) in a parallel manner. A molecular model of the 5S RNA of human KB cells was constructed, which verifies the proposed tertiary interaction, probably stabilizing the two neighboured helices E and D and a stacking arrangement of the bases in the sequence positions 67-108 (and 70-106) in eukaryotic (and prokaryotic) 5S RNAs, respectively.

A decrease of the collagenolytic cathepsin activity was found in foetal and adult hepatic slices cultured in vitro with acetylsalicylic acid, phenylbutazone, aminophenazone, indomethacin and naproxen. The most marked decrease was found in slices treated with naproxen and indomethacin. Acetylsalicylic acid produced only a slight diminution of the enzyme activity. Studies on hepatotoxicity indicated that acetylsalicylic acid and phenylbutazone are very toxic drugs, whereas the naproxen toxicity was very low.

Spontaneously hypertensive rats (SHR) and normotensive Wistar rats were fed a linoleic acid-rich (LAR) and -deficient (LAD) diet for 22 weeks, respectively. Although linoleic acid (LA) and arachidonic acid (AA) in serum and liver triglycerides markedly increased after a LAR diet, LA was significantly lower and AA was higher in SHR when compared to normotensive control rats. Thus, the percentage of both fatty acids remained different like in animals fed a commercial diet. On the contrary, in SHR and normotensive rats fed a LAD diet no differences in the LA and AA content could be found between the groups. In these rats, however, n-3 fatty acids (eicosapentaenoic and docosahexaenoic acids) in serum triglycerides were increased. Blood pressure, serum triglycerides and total cholesterol appeared unchanged, whereas HDL-cholesterol was increased after a LAR diet. Dopamine, adrenaline and noradrenaline content as well as dopamine-beta-hydroxylase activity were augmented in adrenal glands of SHR fed a LAR diet. In spite of distinct biochemical alterations the genetically determined hypertension in rats could not be influenced by a long-lasting diet containing a high amount of LA which has been proved to be effective on lowering blood pressure in other hypertensive rat models.

To characterize consequences of cholesterol induced increases of the Na content on the Ca regulation in rabbit myocardium the influence of increasing extracellular Ca (Cae) on isometric contraction and relaxation of papillary muscles has been investigated after a 12 weeks lasting cholesterol-rich diet. After cholesterol-rich diet increasing Cae caused a higher augmentation in peak tension T, accompanied by a decreased index in contractility [Formula: see text], an insignificantly prolonged time to peak tension TPT, and a decrease in the refractory period, which was extended compared with the control group. A delay in relaxation is demonstrated by the maximum relaxation rate [Formula: see text], the half time of relaxation RT 1/2 and more pronounced by a prolonged relaxation time RT. The results correspond with changes in the Na content published earlier and are in agreement with the assumption that a Na-Ca exchange is involved in beat-to-beat regulation in rabbit myocardium; thereby the cholesterol component of atherogenic diet promotes Ca enhancement in rabbit cardiac cells.

The LD50, the spontaneous locomotor activity, and the circadian rhythm of mortality were determined in male ICR-mice following intraperitoneal injection of 1,1,2,2-tetrabromoethane. By solving the substance in ethanol its toxicity increased significantly, in case of the LD50 by the factor 3.4 and threefold concerning the general mortality. The regression lines calculated for the spontaneous locomotor activity differed significantly with regard to the distance. Significant circadian rhythms of mortality were demonstrated after injections of 1,1,2,2-tetrabromoethane, of tetrabromoethane in ethanol, and of ethanol.

The influence of litter size on the development of the endocrine rat pancreas in the fetal period has been investigated. Rats from 3 spontaneously different litter sizes were chosen to estimate sex, body weight, food uptake, pancreatic wet weight, insulin and glucagon concentrations, plasma glucose and insulin. With increasing litter size we could observe an enhancement of the pancreatic insulin concentration whereas the glucagon content was decreased. Food uptake caused an increase of insulin and glucagon in the pancreas. The observed changes were not sex dependent. Our results show that the litter size has an obvious effect on the endocrine pancreas already in the fetal and early neonatal phase of development.

Isolated pancreatic islets from 7-10 days old Wistar rats were incubated in freshly prepared human serum. The cytotoxic insulin leakage from the islets was correlated with the presence in the sera of islet cell surface antibodies (ICSA) determined by indirect immunofluorescence. Such cytotoxic ICSA were found to be common in Type-I diabetics as well as in nondiabetic subjects who had contact with laboratory rats.

Proteolytic activities associated with plasma membrane preparations from cells of tumourous lymph nodes in enzootic bovine leukosis and from normal bovine lymphoid cells have been studied. 125I-Casein-Sepharose has been used as a substrate. No significant difference between both cell types has been found in total proteolytic activity at different pH-values as well as in the number and type of proteinases, the membranes seem to be equipped with. The main proteolytic activities present in both types of membranes are: One (or two) pepstatin-inhibitable aspartate-proteinase(s) with maximum activity at pH 3 and 5, a leupeptin-inhibitable, presumably cysteine-proteinase, maximally active at pH 4, very small activity(ies?) between pH 7 and 8 of uncertain nature, and a plasminogen-activator with maximum activity around pH 8. Autodigestion of plasma membranes from normal lymph node lymphocytes has been performed choosing conditions optimal for the different proteinases. The only specific proteolysis observed is the splitting of a glycoprotein (151.5 kD), which is present in the plasma membranes of normal lymph node lymphocytes but not in the plasma membranes of peripheral blood lymphocytes and tumour cells, under conditions optimal for the aspartate-proteinase. A possible role of this specific proteolysis is suggested for tumouri-genesis and/or loss of sessility of normal lymphocytes.