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.

A change in conformation of fibrinogen, caused by cobaltous ions after parenteral application or incubation of plasma, is dependent on the presence of species specific plasma proteins. These proteins, which can be found only in some animals, have not yet been identified. An glycoprotein, responsible for the cobalt effect, was isolated from rabbit serum. It migrates immunoelectrophoretically as an alpha-globulin. In the SDS electrophoresis it was shown to migrate in front of albumin. The actions of this protein, induced by cobaltous ions, could be inhibited by complexing and SH groups alkylating compounds.

Alpha-Amylase preparations often contain small quantities of proteolytic activity which are difficult to remove. On the example of fungal alpha-amylase, such associated proteases have been shown to possess a specific activity to the denatured amylase molecules. The amylase is not attacked under native conditions, whereas in the thermal denaturation a rapid degradation of only the inactivated molecules occurs. A specific metabolic function of these associated proteases in the return of denatured amylase molecules to the amino acid pool is suggested.

Tolerance in carps can be induced by intracardial injection of 10-30 mg of ultracentrifuged human gamma globulin (HGGu), with strong individual variation being observable. Out of 21 carps pretreated with 10 mg HGGu, 10 animals showed 14 days after i.p. test immunization with 1 mg HGGu a log2 anti-HGG titre of 1.55 +/- 0.60 (control group - log2 7.33 +/- 1.47), while 11 animals exhibited a log2 titre of 7.45 +/- 2.75. Low doses of HGGu (0.01-1.0 mg) led to stimulation of immune response. If 1-2 mg of a human IgG myeloma protein are applied i.p. after intracardial injection of 10 mg HGGu either simultaneously or after a longer break, then a high-titre anti-idiotypical antiserum with low activity against HGG can be obtained in single cases. The experiments have shown wide individual variation in tolerance induction which may be due also to seasonal factors.

The activity of glucose-6-phosphatase (G6Pase) and fructose-1,6-bisphosphatase (FDPase) was determined in the homogenate of the liver of 69 pig fetuses during the last third of gestation (80th to 114th day), 47 piglets from birth to 4 weeks old (suckling period) and to slaughter pigs. G6Pase is evident in fetal liver at an early date and raises steadily during gestation. In newborn piglets, the enzyme activity increases rapidly during the first hours of life and remains at this high level during the first week of life. Afterwards the enzyme activity returns to birth level, which exists also in pigs at slaughtering. The activity of FDPase is constant during the fetal period. After birth enzyme activity rises at a lower rate than the G6Pase during the first week of life. This level remains constant during the suckling period and increases thereafter until the time of slaughtering of pigs. The role of hormones in the perinatal development of these enzymes is described. Probably, thyroxine causes the prenatal increase of the activity of both the enzymes. The rapid postnatal rise of G6Pase activity may be induced by the high level of hydrocortisone at parturition, and furthermore, glucagon may have a permissive effect.