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21.
It is well known that catalase is transformed to nitric oxide-Fe2+-catalase by hydrogen peroxide (H2O2) plus azide. In this report, we show that myeloperoxidase is also inactivated by H2O2 plus azide. Utilizing this system, we studied the presence and source of intracellular H2O2 generated by activated neutrophils. Stimulation of neutrophils with phorbol myristate acetate (PMA, 100 ng/ml) plus azide (5 mM) for 30 min completely inactivated intragranular myeloperoxidase and reduced cytosolic catalase to 35% of resting cells. This intracellular inactivation of heme enzymes did not occur in normal neutrophils incubated with either PMA or azide alone or in neutrophils from patients with chronic granulomatous disease (CDG) which cannot produce H2O2 in response to PMA. Incubation of neutrophils with azide and a H2O2 generating system (glucose-glucose oxidase) inactivated 41% of neutrophil myeloperoxidase. Glutathione-glutathione peroxidase (GSH-GSH peroxidase), an extracellular H2O2 scavenger, totally protected neutrophil myeloperoxidase from inactivation by azide plus glucose-glucose oxidase. In addition, when a mixture of normal and CGD cells was stimulated with PMA in the presence of azide, 90% of the myeloperoxidase in CGD neutrophils was inactivated. Therefore, H2O2 released extracellularly from activated neutrophils can diffuse into cells. In contrast, myeloperoxidase in normal polymorphonuclear leukocytes stimulated with PMA in the presence of azide and GSH-GSH peroxidase was 75% inactivated. Thus, the results indicate that a GSH-GSH peroxidase-insensitive pool of H2O2 is also generated, presumably at the plasma membrane, and this pool of H2O2 can undergo direct internal diffusion to inactivate myeloperoxidase. 相似文献
22.
An oxygen-evolving complex has been highly purified from the thermophilic cyanobacterium Synechococcus sp. The complex, which reproducibly showed 5 major polypeptide bands of 47, 40, 35, 30 and 9 kDa on SDS-polyacrylamide gel electrophoresis and contained 3.2 Mn per QA, had an oxygen-evolving activity of 300–400 μmol/mg chl per h in the presence of 5 mM MnCl2; or CaCl2. The complex most likely represents a minimum functional unit of the photosynthetic oxygen evolution. 相似文献
23.
Summary Since viable intergeneric hybrids between the chicken (Gallus domesticus) and the pheasant (Phasianus colchicus) have been reported, as well as interfamilial hybrids between the chicken and the turkey (Meleagris gallopavo), the chromosome complements of the pheasant and the turkey were compared with that of the chicken. In these three species belonging to the order Galli, the Z-chromosomes appeared to be identical, while the autosomal complements of the pheasant and the turkey differed radically from that of the chicken. It was noted with some surprise that the pheasant of the family Phasianidae and the turkey of the family Meleagridae have very similar chromosome complements, at least so far as gross morphology of somatic metaphase chromosomes is concerned.This work was supported in part by grant C-5138 from the National Cancer Institute, U.S. Public Health Service, and grant C-17601 from the National Science Foundation.The authors gratefully acknowledge the generosity of Rea's Game Birds, Paramount, California, who supplied the pheasant chicks, and the McPherin Hatcheries, Sunnymead, California, who furnished the turkey chicks. The authors also appreciate the editorial assistance of'Patricia A. Ray. 相似文献
24.
Summary In contrast to the situation found in two classes of warm-blooded vertebrates, mammals and birds, the class Reptilia is not uniform with regard to total genetic content; rather, it contains two distinct categories. The close cytological kinship between snakes and birds was revealed. Both are almost identical in total genetic content, which is about 50 per cent that of placental mammals. Both have microchromosomes, as well as Z-chromosomes very similar in absolute size, comprising nearly 10 per cent of the homogametic haploid (AZ) set. This leads to the implication that snakes and birds originated from the same lineage, and that their Z-chromosomes have not changed substantially since the Jurassic period of the Mesozoic era, about 180 million years ago.Within the reptilian suborder Serpentes, the step-by-step differentiation from the primitive ZW pair to the grossly heteromorphic ZW pair could be observed. In the ancient family Boidae, the sex chromosomes were still homomorphic to each other. In the family Colubridae, the beginning of heteromorphism was manifested in two ways. In some species, a pericentric inversion on the W caused it to differ from the Z; in others, duplication of the W occurred. In the family Crotalidae, the W had apparently achieved its very specialized status; it was a distinctly smaller element.In Säo Paulo, this work was supported by Fundacão de Amparo a Pesquisa do Estado de São Paulo e Fundo de Pesquisas do Instituto Butantan. In Duarte, this work was supported in part by grant CA-05138-05, National Cancer Institute, U. S. Public Health Service. Contribution No. 36-64, Department of Biology, City of Hope Medical Center. 相似文献
25.
The reaction to C-banding was investigated throughout the mitotic cycle ofCrepis capillaris (2n=6): (1) 18–22 C-bodies or C-bands were found during mid telophase and interphase to prophase and metaphase, and also
12–14 at late anaphase to early telophase in the mitotic cycle. Fewer C-bands in late anaphase to early telophase were due
to the absence of minute bands; (2) large and medium sized C-bands were strongly stained by Giemsa, while small and minute
bands stained palely. It is suggested that inCrepis capillaris the difference of color in C-banded segments following Giemsa staining is referable to the amount of constitutive heterochromatin
rather than to the difference in the condensation and decondensation; (3) the size of C-bodies changed during telophase to
interphase and prophase. It is inferred that the extent of C-bodies is regulated by both the length of DNA sequences of constitutive
heterochromatin and the amount of proteins combined with C-banded DNA. It was shown that the reaction to C-banding is neither
due to the differential condensation of chromatin nor to a higher concentration of DNA in the C-banded regions, in the C-banding
mechanism as has been suggested so far at least. 相似文献
26.
J Ohno K Fukuyama A Hara W L Epstein 《The journal of histochemistry and cytochemistry》1989,37(5):629-634
A phosphoprotein phosphatase (PPase: EC 3.1.3.2) was recently purified from rat epidermis. The enzyme dephosphorylates phosphoprotein, and its properties, such as pH optimum, inhibitor spectrum, and Fe2+ activation, differ from those of other soluble phosphatases. We investigated in 2-day-old rat skin the distribution of immunologically detectable PPase and intracellular localization of PPase activity. The reaction of rabbit monospecific anti-PPase IgG was identified in granular and cornified cells by the avidin-biotin complex method. For activity staining, basic principles of the Gomori lead-salt method and azo dye technique with the substrates p-nitrophenylphosphate (p-NPP) and alpha-naphthyl phosphate (NP), respectively, were modified according to the biochemical properties of PPase activity which is resistant to formalin, Na tartrate, and NaF. Activity was detectable in granular cells including keratohyalin granules and the lower strata of cornified cells. The activity was inhibited by 1 mM CuSO4 and enhanced by a mixture of 0.5 mM FeSO4 and 1 mM ascorbic acid. We consider that PPase may be involved in dephosphorylation of histidine-rich proteins in granular and cornified cells and may play a key role in intracellular catabolism associated with epidermal cell differentiation. 相似文献
27.
N Masumoto K Tasaka J Mizuki A Miyake O Tanizawa 《Biochemical and biophysical research communications》1992,182(2):906-912
Changes of intracellular free Mg2+ concentration ([Mg2+]i) in human amnion cells induced by superoxide anion were determined using a highly Mg(2+)-sensitive fluorescent dye Mg(2+)-fura2 or Mg(2+)-indol. Superoxide anion, produced by addition of xanthine oxidase to hypoxanthine, induced decrease of [Mg2+]i. The decrease was significantly inhibited by an anion channel blocker, 4,4'diisothiocyano-2,2' disulfonic acid stilbene (DIDS). Superoxide dismutase (SOD), injected into cells by cell fusion, also inhibited the change of [Mg2+]i, but catalase did not. Superoxide anion induced prompt increase of intracellular pH (pHi) as well as decrease of [Mg2+]i and subsequently activated the increase of intracellular free Ca2+ ([Ca2+]i) and the release of arachidonate. In contrast to superoxide anion, NH4Cl which induces increase of pHi in amnion cells increased [Mg2+]i. The elevation of basal level of [Mg2+]i by Mg(2+)-ionophore inhibited the change of [Ca2+]i and the release of arachidonate induced by superoxide anion. These results suggest that superoxide anion, transported through anion channels into cells, decreases [Mg2+]i directly, not due to a pH-effect and that the decrease of [Mg2+]i may regulate biological functions of the cells via increase of [Ca2+]i. 相似文献
28.
Kaoru Nakamura Takehiko Miyai Kiyoko Inoue Seiji Kawasaki Shinzaburo Oka Atsuyoshi Ohno 《Biocatalysis and Biotransformation》1990,3(1):17-24
Esters of 3-methyl-2-oxobutanoic acid are reduced with bakers' yeast by three methods: free bakers' yeast in water, immobilized bakers' yeast in water, and immobilized bakers' yeast in hexane. Although (R)-hydroxy esters are obtained in all cases, the enantiomeric excess varies from 3% (reduction of the methyl ester with free bakers' yeast in water) to 93% (reduction of the butyl ester with immobilized bakers' yeast in hexane) depending on the structure of substrate and on the reaction conditions. The mechanism of the present stereochemical control is discussed. 相似文献
29.
Sequence requirements for the recognition of tyrosine-based endocytic signals by clathrin AP-2 complexes. 总被引:21,自引:4,他引:17 下载免费PDF全文
W Boll H Ohno Z Songyang I Rapoport L C Cantley J S Bonifacino T Kirchhausen 《The EMBO journal》1996,15(21):5789-5795
We recently determined that fusion proteins containing tyrosine-based endocytic signals bind to the mu 2 subunit of AP-2, the complex that drives clathrin coat formation and mediates endocytosis from the plasma membrane. Here we analyze the selectivity of peptide recognition by mu 2 and by AP-2 using combinatorial selection methods and surface plasmon resonance. Both mu 2 and AP-2 are shown to interact with various sequences of the form tyrosine-polar-polar-hydrophobic (Yppø) found on receptors that follow the clathrin pathway. The optimal sequence for interaction with mu 2 and with AP-2 has tyrosine as an anchor and prefers arginine at position Y + 2 and leucine at position Y + 3. In contrast, no preferred sequence is detected surrounding the Yppø signal, indicating that recognition of the Yppø endocytic signal does not require a prefolded structure. We conclude that sorting into the endocytic pathway is governed by a surprisingly simple interaction between the mu 2 chain and a tyrosine-containing tetrapeptide sequence. 相似文献
30.
The carrageenan-producing red algaKappaphycus alvarezii (Doty) Doty was brought to Vietnam from Japan in 1993. Branch fragments of this species were cultivated in a pond, lagoon, inlet and offshore in Vietnam for the first time. The best daily growth rate (DGR) of plants grown in the lagoon area attained 9–11 % day–1 in May to June (cold season). The water temperature and salinity in this area ranged from 27.2–32.4 °C and 31.4–33.7 °C, respectively. DGR of plants grown in the inlet ranged from 7 to 9% day–1 in June. Grazing by fish has been observed to occur in this area. The DGR of plants grown in the pond ranged from 5–6% in January–July, but decreased to less than 4% day–1 in August (hot season).
K. alvarezii in Vietnam showed a carrageenan yield of 18.8–24.6% and gel strength of 1566–1712 g cm–2. These values are similar ones obtained fromK. alvarezii cultivated in the Philippines and Indonesia. 相似文献