Biomedica biochimica acta最新文献

12 rabbits ("Deutscher Riese") were exposed to a hypoxic atmosphere (FiO2 = 0.05) for 3 h at their 1st day of life. At the 7th or 13th day of life, steel wire electrodes were chronically implanted into 3 leg muscles in order to record the electromyograms (EMG). The myographic activity was derived during free fall (height of drop = 0.5 m) until the age of 20 days. The quantitatively analysed EMG data were compared with corresponding data of undisturbed growing control animals. Using various EMG parameters, a quantitative separation of hypoxic animals from the controls was successfully done by a discriminant analysis, the animals being 8 and 20 days of age, respectively. It can be concluded that 1. already a single perinatal hypoxic load influences the supraspinal motor system permanently at least up to the age of 20 days, and that 2. this supraspinal influence on the investigated vestibulospinal reaction changes with increasing age of the rabbits.

DL-omega-phenyl amino acid esters turned out to be inhibitors of the sheep vesicular gland prostaglandin H synthase in addition to their antiphlogistic action on the carrageenan-induced oedema of the rat paw and weak antihistaminic actions. The inhibition of the prostaglandin H synthase was dose-dependent, the inhibitory potencies were however much lower than that of indomethacin. Some but not all derivatives, such as DL-4-amino-4-phenylbutyric acid octyl ester, also caused inhibition of the pure lipoxygenase from rabbit reticulocytes and the conversion of arachidonic acid to leukotriene B4 and 5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid by human polymorphonuclear leukocytes as well as inhibition of antigen-induced release of histamine from mast cells of ovalbumin-sensibilized rats. Since no clear relations between the data of the in vitro and in vivo models were obtained, further studies on the pharmacokinetics and possible biotransformations are required.

The multicatalytic proteinase complex is a high molecular weight nonlysosomal proteinase. Kinetic studies of the proteolytic activities of the complex have shown that there are at least three distinct types of catalytic centre, each of which has a different specificity. All of the activities can be inhibited by the serine protease inhibitor 3,4-dichloroisocoumarin. Viewed under the electron microscope, the multicatalytic proteinase purified from rat liver appears to have a hollow cylindrical structure. It is composed of many different types of subunit and on two-dimensional polyacrylamide gels gives rise to a complex pattern of about 20 spots with pI values ranging between 5 and 8.5 and molecular masses between 22 and 34 kDa. Immunoblot analysis has shown that many of the major polypeptides are antigenically distinct. However, there are some relationships between the proteinase polypeptides. For example, although N-terminal sequences of five of the polypeptides are unique, they show considerable sequence similarity suggesting that these proteins are encoded by members of the same gene family. Also, there is some cross-reactivity between certain polypeptides when blots are probed with affinity purified, subunit-specific antisera. In addition to the variety of polypeptide components of the proteinase, a small RNA species (80 nucleotides) can be found associated with the complex even after purification by chromatographic procedures.

An easy and rapid enzymatic method is described which allows replacement of P'-residues in bovine pancreatic trypsin inhibitor. Insertion of Xaa-Arg or Xaa-Lys into a BPTI fragment lacking P1' = Ala16 and P2' = Arg17 was carried out in a "one pot" reaction catalysed by trypsin in the presence of 80% 1,4 butanediol.

In addition to previous observations indicating that membrane potential changes generated by various Donnan- and Nernst-potentials lead to erythrocyte shape transformations, we show in this paper that diffusion potential change, induced by valinomycin, governs erythrocyte shape transformations. In low KCl-medium valinomycin, transferring the positive Nernst-potential into a negative diffusion potential, transforms stomatocytes into echinocytes. Using modified erythrocytes with a reversed K/Na ratio, even positive diffusion potentials can be induced by valinomycin. In these cases, stomatocytes can be generated by valinomycin. It is shown that, additionally, valinomycin in large concentrations is itself stomatocytogenic, and that the fluorescent dye diS-C3-(5) also induces stomatocytes. This, however, is a side effect which does not contradict the potential dependence of shape transformation. Using non washed erythrocytes, resuspended in plasma, valinomycin, inducing negative diffusion potential, transforms most erythrocytes to echinocytes despite the stomatocytogenic effect of albumin.

The ontogenetic development of the vestibulospinal reaction following the free fall was studied in 11 rabbits ("Deutscher Riese") 8 to 20 days old by means of myographical recordings (EMG) synchronously derived from 3 muscles (M. triceps brachii caput lateralis, M. brachialis, M. quadriceps femoris vastus lateralis) by chronically implanted steel wire electrodes. With increasing age, rabbits show a sustained rise of EMG activity during fall and develop the ability to change the generated EMG activity under the condition of repeated stimulation. It is concluded, firstly, that more typical EMG reactions are produced with growing age, and secondly, that the ability to modify the intensity of the response to repeated free falls increases during postnatal development.

A hybrid protein containing the N-terminal part of the murine stress protein hsp25 (amino acids 1 to 110) and the C-terminal part of the human stress protein hsp27 (amino acids 111 to 208) was expressed in E. coli using a T7 polymerase/promoter system. The recombinant hybrid protein was purified and used for immunization of rabbits. In contrast to immunization experiments using hsp25 and hsp27 alone, immunization with the hybrid protein hsp25/27 leads to antibodies which can be used for detection of both hsp25 and hsp27.

The known proportional increase in the amplitude of the pattern reversal visually evoked potential (VEP) with increasing stimulus area does not occur for the motion-onset VEP. When the stimulus area of the total field (6 degrees x 6 degrees) is compared to that of the half-field (6 degrees x 3 degrees), the N200 amplitude of the motion-onset VEP is not changed proportionally but remains almost constant. Reducing the pattern contrast beyond the saturation value for the motion-VEP yields essentially the same results. Contrary to the pattern reversal VEP, the amplitudes of the motion-onset VEP are found to be more pronounced for the nasal than for the temporal hemiretina. Our results support the notion of a genuine difference between the pattern- and the motion-analyzing visual system.

The activities of human erythrocyte glutathione-S-transferase (EC 2.5.1.18) obtained from 53 subjects of both sexes aged between 5 and 25 years of HbAA (20), HbAS (13) and HbSS (20) were determined. The results, expressed in IU/g Hb, obtained for the various genotypes were: HbSS = 14.6 +/- 3.4; HbAS = 4.7 +/- 1.1; HbAA = 2.7 +/- 0.8. The observed differences were found to be statistically significant (p less than 0.001). Kinetic analysis showed similar Michaelis constants (Km) of the enzyme irrespective of the genotype, indicating structural and functional similarities of the enzyme from the various genotypes. A mean (+/- SD) percentage increase of 63.8 +/- 4.9 was obtained for the red cell glutathione-S-transferase activity in the presence of dithionite, while a mean (+/- SD) decrease of 38.8 +/- 1.9% was obtained in the presence of 0.3 mM haemin. These findings suggest an increased activation of the enzyme in HbSS and HbAS subjects (as compared with HbAA subjects) possibly by an increased generation of electrophilic substrates in the red cell of these subjects.

Cellular proteins may be designated to fast degradation by their N-terminal amino acids, and especially a N-terminal arginine residue should have an extremely destabilizing effect on cytosol proteins. We investigated the post-translational arginylation of cytosol proteins and especially of ornithine decarboxylase (ODC) by the cytosolic enzyme arginyl transferase by incubation with radioactive L-arginyl-tRNA and isolation of ODC with our monoclonal antibody. Arginylated ODC had a specific radioactivity 8600 times that of the bulk of cytosolic proteins and Edman-degradation of this ODC showed that the post-translational arginylation occurred only at the L-amino-end of the enzyme. The inhibitor of arginyltransferase, L-Glutamyl-L-Valyl-L-Phenylalanine, increased the half-life of ODC in cultured hepatocytes from 39 min to more than 90 min. This post-translational arginylation of ODC and also of other cytosol proteins is reversible. At least 25 different cytosol proteins in addition to ODC can be arginylated in hepatocytes, and at least 15 different proteins can be arginylated in Dictyostelium discoideum. The arginylated proteins are much more rapidly degraded by cellular proteinases, especially by calpains, than those cytosolic proteins which are not arginylated.