Carotenoid photobleaching induced by photosystem II action in the membrane fragments of the blue-green alga Anabaena variabilis : Action of O2

Carotenoid photobleaching induced by photosystem II action wasstudied using membrane fragments of the blue-green alga Anabaenavariabilis. Special attention was paid to the action of O₂. Carotenoid photobleaching elicited by carbonyl cyanide m-chlorophenylhydrazone(CCCP) depended on O₂. However, the addition of H₂O₂, sodiumsilicotungstate or potassium ferricyanide (Ferri), an electronacceptor for reaction center II action, removed the O₂-dependency.These results indicate that O₂ acts as the electron acceptorfor this reaction. When both CGCP and Ferri were present, a short illumination(0.25 sec) caused a rapid photobleaching followed by a slowrecovery in the subsequent dark period. The spectrum of theabsorption decrease in the light was identical with that ofthe absorption increase in the subsequent dark, indicating thata reversible process is involved in the carotenoid photobleaching.The size in the dark recovery relative to the light bleachingbecame larger under anaerobic conditions and smaller under higherpartial pressure of O₂. The reuslts were interpreted as indicatingthat O₂ does not function in the primary process including areversible bleaching step, but is involved in the slow and irreversiblebleaching process. (Received April 3, 1978; )     

A tryptic peptide from beta-casein depresses protein synthesis and degradation and enhances ureogenesis in primary cultures of rat hepatocytes

1. A peptide which enhances ureogenesis in primary cultured hepatocytes of rats was isolated from a tryptic digest of bovine beta-casein. 2. The structure of the peptide was Ala-Val-Pro-Tyr-Pro-Gln-Arg which is located from 177th to 183rd residues from N-terminal of beta-casein. 3. The peptide also showed the activity to inhibit protein synthesis and protein degradation. 4. It also inhibited DNA synthesis of hepatocytes induced by insulin and/or epidermal growth factor.     

Comparison of cytochrome P-450 species which catalyze the hydroxylations of the aromatic ring of estradiol and estradiol 17-sulfate

For identification of microsomal cytochrome P-450 (P-450) enzymes which catalyze 2- or 4-hydroxylations of estrogens in the rat liver, estradiol (E₂) and estradiol 17-sulfate (E₂-17-S) were selected as the substrates and incubated with various kinds of purified P-450 enzymes: PB-1, PB-2, PB-4 and PB-5 obtained from phenobarbital-treated male rats (Sprague-Dawley); MC-1 and MC-5 from 3-methylcholanthrene-treated male rats; and UT-1, UT-2, UT-4 and UT-5 from untreated animals. The reactions were carried out under the P-450-reconstructed system, and the resulting products were determined by HPLC using electrochemical detection. All the enzymes tested were shown to have varying degrees of catalytic activities for 2-hydroxylation of the two substrates; UT-1 and UT-2 had the highest activity. Of the induced P-450 enzymes, PB-2 and MC-1 showed fairly high catalytic activity for 4-hydroxylation of E₂. The P-450 enzymes obtained from the untreated male rats, especially UT-4, showed the highest catalytic activity for 4-hydroxylation of the two substrates. From these results and also from kinetic experiments, the P-450 enzymes which catalyze 2- and 4-hydroxylations of estrogen were considered to be different species. A part of E₂ was converted to such metabolites as estrone and those having a hydroxyl group at positions 6β, 15 or 16, each production of which was estimated to be catalyzed by single or multiple P-450s.     

Constitutive expression of FosB and its short form, FosB/SF, induces malignant cell transformation in rat-1A cells

We have established Rat-1A cell lines constitutively expressing c-Fos and the two products of the fosB gene, FosB and its short form, FosB/SF. The expressed proteins in the different stable transfectants have been characterized by immunofluorescence and immunoprecipitation analysis. Our results demonstrate that constitutive expression of FosB, like the constitutive expression of c-Fos and, to a lesser extent, FosB/SF, results in cells that grow to increased saturation densities and have the ability to grow in an anchorage-independent manner. Most important is the finding that expression of these proteins augments the tumorigenic potential of Rat-1A cells. These results show that both forms of FosB have a stimulatory effect on cell proliferation.     

Stimulatory Effects of Exogenous Thyroid Hormone and Growth Hormone on sn-Glycerol-3-Phosphate Dehydrogenase Activity in the Genetic-Hypothyroid Mutant Mouse Cerebellum: Restricted to the Second 20 Days of Postnatal Life

We recently reported that by postnatal day 40 the activity of sn-glycerol-3-phosphate dehydrogenase (GPDH) was significantly depressed in the cerebellum of genetic-hypothyroid mutant mice. This mutant mouse-GPDH combination was used in the present study to define the critical time period during which thyroid hormone (T4) and growth hormone (GH) are essential for maturation of Bergmann glial cells. Our findings are that (a) induction of GPDH activity in the Bergmann glial cell is dependent on T4, (b) T4 is most effective when administered during the second 20 days of postnatal life, (c) the effect of GH on GPDH activity is complementary to or synergistic with that of T4, and (d) Bergmann glial cells and radial glial fibers of the mutant mice contain immunoreactive GPDH following various hormonal treatments. These results suggest that T4 is indispensable for the maturation of Bergmann glial cells.     

Mouse Offspring Derived from Fetal Ovaries or Reaggregates Which were Cultured and Transplanted into Adult Females

Primordial germ cells (PGCs) and gonia could be promising novel targets and vehicles for manipulation of the mammalian germ line. To make such manipulation a practical possibility, PGCs or gonia must be allowed to produce gametes and offspring after they were isolated from embryos and manipulated in culture. As the first step to develop such research strategy, we obtained offspring from mouse oogonia which were isolated from embryonic ovaries and cultured as dispersed cells before transplantation into female mice as reaggregates.     

Purification and characterization of peroxisomal apo and holo alanine:glyoxylate aminotransferase from bird liver.

Alanine:glyoxylate aminotransferase has been reported to be present as the apo enzyme in the peroxisomes and as the holo enzyme in the mitochondria in chick (white leghorn) embryonic liver. However, surprisingly, birds were found to be classified into two groups on the basis of intraperoxisomal forms of liver alanine:glyoxylate aminotransferase. In the peroxisomes, the enzyme was present as the holo form in group 1 (pigeon, sparrow, Java sparrow, Australian budgerigar, canary, goose, and duck), and as the apo form in group 2 (white leghorn, bantam, pheasant, and Japanese mannikin). In the mitochondria, the enzyme was present as the holo form in both groups. The peroxisomal holo enzyme was purified from pigeon liver, and the peroxisomal apo enzyme from chicken (white leghorn) liver. The pigeon holo enzyme was composed of two identical subunits with a molecular weight of about 45,000, whereas the chicken apo enzyme was a single peptide with the same molecular weight as the subunit of the pigeon enzyme. The peroxisomal holo enzyme of pigeon liver was not immunologically cross-reactive with the peroxisomal apo enzyme of chicken liver, the mitochondrial holo enzymes from pigeon and chicken liver, and mammalian alanine:glyoxylate aminotransferases 1 and 2. The mitochondrial holo enzymes from both pigeon and chicken liver had molecular weights of about 200,000 with four identical subunits and were cross-reactive with mammalian alanine:glyoxylate aminotransferase 2 but not with mammalian alanine:glyoxylate aminotransferase 1.     

Local formation and degradation of endothelin-1 in guinea pig airway tissues

Endothelin(ET)-1 and big ET-1 caused potent and sustained constriction of isolated guinea pig bronchus. The response to ET-1 was enhanced by phosphoramidon in a simple dose-related manner (0.01-1000 microM), while the response to big ET-1 was enhanced at lower doses (0.01-0.1 microM) but was suppressed at higher doses (100-1000 microM) of phosphoramidon. Big ET-1, when given intravenously (i.v.) to anesthetized guinea pigs, increased both bronchopulmonary inflation pressure and mean arterial blood pressure (2.5, 5, 10 nmol/kg i.v.). The pressor response to big ET-1 was attenuated by phosphoramidon dose-relatedly, while the pulmonary response was modified in a complex fashion composed of delayed onset and prolonged duration of action. These results suggest that ET converting as well as degrading enzymes coexist in the airway tissue and both enzymes are sensitive to phosphoramidon, so that phosphoramidon acts bifunctionally to reduce and stimulate the airway responses to big ET-1.     

Purification and properties of extracellularβ-fructofuranosidases fromAureobasidium sp. ATCC 20524

Summary Two extracellular -fructofuranosidases (E-1 andE-2) fromAureobasidium sp. ATCC 20524, producing 1-kestose (1^F--fructofuranosyl-sucrose) from sucrose, were purified to homogeneity. Molecular weights of the enzymes were estimated to be about 304000 (E-1) and 315000 (E-2) Da by gel filtration. The enzymes contained 33% (w/w) (E-1) and 27% (w/w) (E-2) carbohydrate. TheK _m values for sucrose ofE-1 andE-2 andE-2 were 0.34 and 0.28 M, respectively. were 0.34 and 0.28 M, respectively. The enzymatic profiles of these enzymes were almost identical to intracellular enzymesP-1 andP-2 except for the differences in carbohydrate content andK _m values ofE-2 andP-2.