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171.
172.
In order to elucidate the mechanism of suppression of plasma aldosterone by chronic ACTH administration, especially the role of the renin-angiotensin system and dopamine, we administered ACTH with or without MK422, a converting enzyme inhibitor, to reduce the endogenous angiotensin II in rats, and measured the plasma renin activity, plasma corticoid concentrations and urinary dopamine excretion. The plasma aldosterone concentration (PAC) was decreased after chronic ACTH administration. However, in the ACTH + MK422 administered group, aldosterone suppression was not observed. It appeared therefore that the aldosterone suppressing mechanism was independent of the weakened renin-angiotensin system following chronic ACTH administration, since PAC was not decreased in the ACTH + MK422 administered group when angiotensin II might be completely eliminated. The urinary excretion of dopamine was significantly increased in the chronic ACTH + MK422 administered group as well as in the chronic ACTH administered group. This suggested that the inhibitory effect of dopamine on aldosterone did not contribute significantly to the suppression of plasma aldosterone. The present results suggest therefore that the mechanism of suppression of plasma aldosterone following chronic ACTH administration was not dependent on the renin-angiotensin system and dopamine. 相似文献
173.
174.
Fukuda T Uchida H Takashima Y Uwajima T Kawabata T Suzuki M 《Biochemical and biophysical research communications》2001,284(3):704-706
Degradation of bisphenol A (BPA), an endocrine-disrupting chemical, was studied with a purified laccase from the basidiomycete Trametes villosa. SDS--polyacrylamide gel electrophoresis of the purified laccase gave one single band with a mobility corresponding to MW 65 kDa. The absorption spectrum showed the characteristics of a blue copper protein with a maximum peak at 600 nm. HPLC analysis revealed that 2.2 micromol BPA were degraded by incubation with 1.5 units of the purified laccase in a total volume of 1.0 ml at pH 6.0 and 60 degrees C for 3 h. The enzyme reaction proceeded rapidly without requirement of mediators for the electron transfer. Isolation and identification of several reaction products are in progress, in which one product was identified as 4-isopropenylphenol by a gas chromatography--mass spectrophotometer. 相似文献
175.
Effects of nitric oxide on matrix metalloproteinase-2 production by rheumatoid synovial cells 总被引:9,自引:0,他引:9
Hirai Y Migita K Honda S Ueki Y Yamasaki S Urayama S Kamachi M Kawakami A Ida H Kita M Fukuda T Shibatomi K Kawabe Y Aoyagi T Eguchi K 《Life sciences》2001,68(8):913-920
Nitric oxide (NO) is a multifunctional messenger molecule generated from L-arginine by a family of enzymes, including nitric oxide synthase (NOS). This study was performed to examine whether NO modulates the production of matrix metalloproteinases (MMPs), which degrade all components of extracellular matrix (ECM), in rheumatoid synovial cells. We investigated the effects of exogenously generated NO by a NO donor, S-nitroso-N-acetyl-DL-penicillamine (SNAP), on the MMPs production by rheumatoid synovial cells. Culture media conditioned by SNAP-treated synovial cells were examined by gelatin zymography and immunoblot analysis. Incubation of synovial cells with SNAP resulted in gelatinase A production in a dose-dependent fashion. Furthermore, RT-PCR analysis demonstrated that MMP-2 mRNA expression was induced in SNAP-treated synovial cells. In contrast, SNAP did not influence the production of TIMP-1 and TIMP-2, which preferentially inhibit MMP-2, by rheumatoid synovial cells. Our data indicate that NO could modulate MMP production by rheumatoid synovial cells and therefore contribute to ECM degradation of articular components in RA. 相似文献
176.
Involvement of local intercellular communication in the differentiation of zinnia mesophyll cells into tracheary elements 总被引:4,自引:0,他引:4
The transdifferentiation of isolated mesophyll cells of zinnia (Zinnia elegans L.) into tracheary elements (TEs) has been well studied as a model of plant cell differentiation. In order to investigate
intercellular communication in this phenomenon, two types of culture method were developed, in which mesophyll cells were
embedded in a thin sheet of agarose gel and cultured on solid medium, or embedded in microbeads of agarose gel and cultured
in liquid medium. A statistical analysis of the two-dimensional distribution of TEs in the thin-sheet cultures demonstrated
their aggregation. In the microbead cultures, the frequency of TE differentiation was shown to depend on the local cell density
(the cell density in each microbead): TE differentiation required local cell densities of more than 105 cells ml−1. These results suggest that TE differentiation involves cell-cell communication mediated by a locally acting diffusible factor.
This presumptive factor was characterized by applying a modified version of the sheet culture, which used two sheets of different
cell densities, a low-density sheet and a high-density sheet. Differentiation of TEs in the former could be induced only by
bringing it into contact with the latter. Insertion of a 25-kDa-cutoff membrane between the high-density and low-density sheets
severely suppressed such induction of TEs in the low-density sheet while a 300-kDa-cutoff membrane suppressed induction only
slightly. Insertion of agarose sheets containing immobilized pronase E or trypsin also interfered with the induction of TEs
in the low-density sheets. Thus, a proteinaceous macromolecule of 25–300 kDa in molecular weight was assumed to mediate the
local intercellular communication required for TE differentiation. This substance was designated “xylogen” with reference
to its xylogenic activity. The time of requirement for xylogen during TE differentiation was assessed by experiments in which
cells in the low-density sheet were separated from xylogen produced in the high-density sheet at various times by insertion
of a 25-kDa-cutoff membrane between the two sheets, and was estimated to be from the 36th hour to the 60th hour of culture
(12–36 h before visible thickening of secondary cell walls of TEs).
Received: 13 July 2000 / Accepted: 4 October 2000 相似文献
177.
Brassinosteroid levels increase drastically prior to morphogenesis of tracheary elements 总被引:6,自引:0,他引:6
As the first step toward understanding the involvement of endogenous brassinosteroids (BRs) in cytodifferentiation, we analyzed biosynthetic activities of BRs in zinnia (Zinnia elegans L. cv Canary Bird) cells differentiating into tracheary elements. The results of feeding experiments suggested that both the early and late C6-oxidation pathways occur during tracheary element differentiation. Gas chromatography-mass spectrometry analysis revealed that five BRs, castasterone, typhasterol, 6-deoxocastasterone, 6-deoxotyphasterol, and 6-deoxoteasterone, actually existed in cultured zinnia cells and culture medium. Quantification of endogenous BRs in each stage of tracheary element differentiation by gas chromatography-mass spectrometry exhibited that they increased dramatically prior to the morphogenesis, which was consistent with the idea that BRs are necessary for the initiation of the final stage of tracheary element differentiation. Moreover, the proportion of each BR in culture medium was quite different from that in cells, suggesting that specific BRs are selectively secreted into medium and may function outside the cells. 相似文献
178.
HEMPAS. Hereditary erythroblastic multinuclearity with positive acidified serum lysis test 总被引:2,自引:0,他引:2
Fukuda MN 《Biochimica et biophysica acta》1999,1455(2-3):231-239
Congenital dyserythropoietic anemia type II or HEMPAS (hereditary erythroblastic multinuclearity with positive acidified serum lysis test) is a genetic anemia in humans caused by a glycosylation deficiency. Erythrocyte membrane glycoproteins, such as band 3 and band 4.5, which are normally glycosylated with polylactosamines lack these carbohydrates in HEMPAS. Polylactosamines accumulate as glycolipids in HEMPAS erythrocytes. Analysis of N-glycans from HEMPAS erythrocyte membranes revealed a series of incompletely processed N-glycan structures, indicating defective glycosylation at N-acetylglucosaminyltransferase II (GnT-II) and/or alpha-mannosidase II (MII) steps. Genetic analysis has identified two cases from England in which the MII gene is defective. Mutant mice in which the MII gene was inactivated by homologous recombination resulted in a HEMPAS-like phenotype. On the other hand, linkage analysis of HEMPAS cases from southern Italy excluded MII and GnT-II as the causative gene, but identified a gene on chromosome 20q11. HEMPAS is therefore genetically heterogeneous. Regardless of which gene is defective, HEMPAS is characterized by incomplete processing of N-glycans. The study of HEMPAS will identify hitherto unknown factors affecting N-glycan synthesis. 相似文献
179.
180.
Human heterochromatin protein HP1(Hsalpha) possesses two evolutionarily conserved regions in the N- and C-terminal halves, so-called chromo and chromo-shadow domains, and DNA-binding domain in the internal non-conserved region. Here, to examine its in vivo properties, we expressed HP1(Hsalpha) as a fusion product with green fluorescent protein in human cells. HP1(Hsalpha) was observed to form discrete dots in interphase nuclei and to localize in the centromeric region of metaphase chromosomes by fluorescence microscopy. Interestingly, this dot-forming activity was also found in the N-terminal half retaining the chromo and DNA-binding domains and in the C-terminal chromo-shadow domain. However, the chromo domain alone stained nuclei homogeneously. To correlate this dot-forming activity with self-associating activity in vitro, the chromo and chromo-shadow domain peptides were independently expressed in Escherichia coli, affinity purified, and chemically cross-linked with glutaraldehyde. In a SDS-polyacrylamide gel, the former mainly produced a dimer, while the latter produced a ladder of bands up to a tetramer. When passed through a gel filtration column in a native state, these peptides were exclusively separated as a dimer and a tetramer, respectively. These results suggested that the internal DNA-binding and C-terminal chromo-shadow domains are both involved in heterochromatin formation in vivo. 相似文献