Studies on the mechanisms of histidase development in rat skin and liver. I. Basis for tissue specific developmental changes in catalytic activity.

Skin and liver histidases of the rat follow markedly differing developmental courses. In skin, the enzyme activity emerges in late fetal life, rises to a maximum during the first postnatal week and then declines; in liver, histidase activity initially appears in the neonatal period and progressively rises thereafter. The enzymes in both tissues, however, are immunologically identical, as demonstrated by Ouchterlony double diffusion, immunoelectrophoresis, and immunotitration analyses of histidase in adult animals. Furthermore, although crude preparations of skin and liver histidase differ slightly in electrophoretic mobility on acrylamide gels, the isoelectric points and Michaelis constants of the enzyme from both skin and liver are the same. During development neither dissociable activators nor inhibitors of the enzyme are evident, which might account for the divergent developmental patterns, nor are enzyme inhibitors found in tissues devoid of histidase activity. No immunologically cross-reacting materials are detectable in skin and liver at developmental stages prior to the emergence of enzyme activity, nor in tissues not expressing histidase catalytic activity. Furthermore, there is no evidence of elaboration of immunological variants of histidase in skin and liver during development. These data are compatible with the view that all developmental changes in catalytic activity are due to altered amounts of the same enzyme antigen.     

Alterations in liver chromatin during perinatal development of the rat

Chromatins were isolated from liver nuclei of 19-day fetuses, 2-, 5-, 21-day old and adult rats. Very little variation was observed in the mass ratio of total histones to DNA or in the spectrum of histones as determined by polyacrylamide gel electrophoresis. On the other hand, the amount and banding pattern of acidic proteins indicated pronounced changes during liver development.The composition of acidic proteins may be specific for the stage of development as evidenced immunochemically. Antibody against acidic protein-DNA complexes from adult rat liver were produced in rabbits. Whereas adult liver acidic protein-DNA complexes interacted strongly with the antibody, fetal liver preparations showed very little affinity. Complexes from 2-day-old animals reacted more strongly than fetal complexes while preparations from 5-day-old and 21-day-old displayed further increases in affinity. The results support the idea that chromatin acidic proteins play an important role in genetic expression during the ontogeny.     

Alterations in fucosyl oligosaccharides of glycoproteins during rat liver regeneration.

[3H]Fucose-labelled glycopeptides in the slices of liver 24h after partial hepatectomy were fractionated on Sephadex G-50. Glycopeptides from regenerating liver contained a higher proportion of lower-Mr components than did controls. Regenerating liver contained a higher proportion of glycopeptides that were bound to concanavalin A-Sepharose and were subsequently eluted with 20mM-methyl alpha-D-glucopyranoside than did controls. Concanavalin A-bound glycopeptides from each source were entirely bound to a lentil lectin-Sepharose column. Both the concanavalin A-bound and -unbound fractions from regenerating liver were indistinguishable from the respective controls by Bio-Gel P6 column chromatography and neuraminidase digestion. These results show that fucosyl glycopeptides from regenerating liver contain a higher proportion of biantennary species with core fucose residues than do controls. Glycopeptides from regenerating livers 12h, 72h and 144h after partial hepatectomy were also examined; however, the difference was not significant. These observations suggest that the alterations in fucosyl glycopeptides may be related to rapid growth of hepatocytes 24h after partial hepatectomy. No significant difference was found in either [3H]mannose- or [3H]fucose-labelled glycoproteins from regenerating liver and from controls by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, suggesting that the alteration in glycopeptides should depend on some differences in the late stage of oligosaccharide processing.     

A study of lactate dehydrogenase levels and turnover rates during postnatal development in the rat

Specific radioimmunoassays for lactate dehydrogenase A and B subunits have been employed to quantify cellular contents of these proteins more precisely than hitherto possible and to monitor changes during postnatal development. Liver, skeletal muscle, heart muscle and kidney cortex all demonstrated alterations in cellular levels of lactate dehydrogenase subunits over the first 56 days of life, the particular pattern being specific to each tissue. Studies on the turnover of lactate dehydrogenase in vivo and in vitro indicated that the developmental changes in total lactate dehydrogenase content in liver and kidney were regulated at some point(s) during both the biosynthesis and the degradation of the proteins.     

Alterations in cation levels and Na-K ATPase activity in rat cerebral cortex during the development of cobalt-induced epilepsy

Abstract— This study was carried out to ascertain what biochemical changes might be present in cobalt-induced epilepsy in the rat. Sodium, potassium, calcium, magnesium, Na-K ATPase activity, water content, protein content and the ability of the tissue to utilize oxygen were measured in (1) the area of the cerebral cortex in which the cobalt was implanted; (2) in an area adjacent to but not including the area of the lesion; and (3) in the homotopic area of the contralateral cerebral cortex. The greatest changes were observed in the area of the lesion itself, with marked increases in calcium, magnesium and sodium contents and decreases in potassium content, Na-K ATPase activity, protein content and the ability of the tissue to utilize oxygen. The only significant findings in the area adjacent to the lesion and in the contralateral cortex were a modest elevation of sodium and a modest decrease in potassium at different time periods after implantation of the cobalt. We feel that the changes observed at the site of cobalt implantation may reflect tissue destruction which is unrelated to the epileptic process.     

N-Acetylglutamate in rat liver during foetal development.

N-Acetylglutamate is present in foetal rat liver at 17 days' gestation. The tissue content (approx. 50 nmol/g wet wt.) remains constant during later foetal life. The appearance of N-acetylglutamate does not parallel the developmental pattern of the urea cycle.     

Changes in immunoreactive malic enzyme in liver and brown adipose tissue during development of the rat

There is a good correlation between changes in malic enzyme activity and immunoreactive protein in both hepatic and brown adipose tissue during postnatal development of the rat. Furthermore, the previously observed premature appearance of hepatic malic enzyme during the suckling period, in response to triiodothyronine, can also be achieved through dichloroacetate administration. A combination of triiodothyronine and dichloroacetate induces malic enzyme activity and immunoreactive protein in a synergistic manner, indicating different sites of action in the control of synthesis of hepatic malic enzyme although neither agent was found to affect the level of malic enzyme in brown adipose tissue. There is evidence to suggest that changes in the ability of the liver to express malic enzyme in response to triiodothyronine administration occur early in postnatal life.