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1.
The role of the Trp6 residue in the biological activity of the hypotensive peptide xenopsin (<Glu-Gly-Lys-Arg-Pro-Trp-Ile-Leu-OH) was investigated. This residue was satisfactorily reduced to 2,3-dihydro-Trp on treatment with excess pyridine-borane in trifluoroacetic acid without any detectable change in other parts of the molecule. The analogous peptide, (Lys2, Gly3) xenopsin, was also reduced in a similar manner. Both reduction products were purified by gel filtration and characterized by UV absorption, amino acid composition, and structural analysis.The reduced peptides were assayed on the fundus strip of isolated rat stomach and were found to possess less than 1 percent of the activity of the original peptides. Although each of the reduced analogs had an indoline substituted for an indole in the tryptophyl residue, their biological activity was virtually lost. This suggests that the tryptophyl residue of xenopsin is crucial for its biological activity. 相似文献
2.
Tatsuya Matsunami Toshihiro Suzuki Yasuo Hisa Kuniaki Takata Tetsuro Takamatsu Masahito Oyamada 《Cell communication & adhesion》2006,13(1):93-102
To elucidate the role of the spiral limbus in glucose transport in the cochlea, we analyzed the expression and localization of GLUT1, connexin26, connexin30, and occludin in the spiral limbus of the rat cochlea. GLUT1 and occludin were detected in blood vessels. GLUT1, connexin26, connexin30, and occludin were also expressed in fibrocytes just basal to the supralimbal lining cells. Connexin26 and connexin30 were present among not only these GLUT1-positive fibrocytes but also GLUT1-negative fibrocytes. In vivo glucose imaging using 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-6-deoxyglucose (6-NBDG, MW 342) together with Evans Blue Albumin (EBA, MW 68,000) showed that 6-NBDG was rapidly distributed throughout the spiral limbus, whereas EBA was localized only in the vessels. Moreover, the gap junctional uncoupler heptanol inhibited the distribution of 6-NBDG. These findings suggest that gap junctions play an important role in glucose transport in the spiral limbus, i.e., that gap junctions mediate glucose transport from GLUT1-positive fibrocytes to GLUT1-negative fibrocytes in the spiral limbus. 相似文献
3.
Madhusoodana P. Nambiar Tatsuya Oda Chaohua Chen Yasuo Kuwazuru Henry C. Wu 《Journal of cellular physiology》1993,154(2):222-228
The intracellular pathway following receptor-mediated endocytosis of cholera toxin was studied using brefeldin A (BFA), which inhibited protein secretion and induced dramatic morphological changes in the Golgi region. In both mouse Y1 adrenal cells and CHO cells, BFA at 1 μg/ml caused a 80–90% inhibition of the cholera toxin (CT)-elevation of intracellular cAMP. The inhibition of the cytotoxicity of CT by BFA was also observed in a rounding assay of Y1 adrenal cells. The inhibition of CT cytotoxicity by BFA was dose dependent, with the ID50 value similar to the LD50 of BFA in Y1 adrenal cells. Binding and internalization of [125I]-cholera toxin in Y1 adrenal cells was not affected by BFA. Unlike the BFA-sensitive cell lines such as Y1 adrenal and CHO cells, BFA at 1 μg/ml did not inhibit the cytotoxicity of CT in PtK1 cells, of which the Golgi structure was BFA-resistant. These results strongly suggest that a BFA-sensitive Golgi is required for the protection of CT cytotoxicity by BFA. In contrast, elevation of the intracellular cAMP by forskolin, which acts directly on the plasma membrane adenylate cyclase, was not affected by BFA. These observations indicate that the intoxication of target cells by CT requires an intact Golgi region for its intracellular trafficking and/or processing. In this respect, CT shares a common intracellular pathway with ricin, Pseudomonas toxin, and modeccin, even though their structures and modes of action are very different. © 1993 Wiley-Liss, Inc. 相似文献
4.
Opines, in particular nopaline and octopine, are specific compounds found in crown gall tumor tissues induced by infections with Agrobacterium species, and are synthesized by well-studied NAD(P)H-dependent dehydrogenases (synthases), which catalyze the reductive condensation of α-ketoglutarate or pyruvate with L-arginine. The corresponding genes are transferred into plant cells via a tumor-inducing (Ti) plasmid. In addition to the reverse oxidative reaction(s), the genes noxB-noxA and ooxB-ooxA are considered to be involved in opine catabolism as (membrane-associated) oxidases; however, their properties have not yet been elucidated in detail due to the difficulties associated with purification (and preservation). We herein successfully expressed Nox/Oox-like genes from Pseudomonas putida in P. putida cells. The purified protein consisted of different α-, β-, and γ-subunits encoded by the OdhA, OdhB, and OdhC genes, which were arranged in tandem on the chromosome (OdhB-C-A), and exhibited dehydrogenase (but not oxidase) activity toward nopaline in the presence of artificial electron acceptors such as 2,6-dichloroindophenol. The enzyme contained FAD, FMN, and [2Fe-2S]-iron sulfur as prosthetic groups. On the other hand, the gene cluster from Bradyrhizobium japonicum consisted of OdhB
1
-C-A-B
2, from which two proteins, OdhAB1C and OdhAB2C, appeared through the assembly of each β-subunit together with common α- and γ-subunits. A poor phylogenetic relationship was detected between OdhB1 and OdhB2 in spite of them both functioning as octopine dehydrogenases, which provided clear evidence for the acquisition of novel functions by “subunit-exchange”. To the best of our knowledge, this is the first study to have examined flavin-containing opine dehydrogenase. 相似文献
5.
Summary Subcellular structures of type II alveolar epithelial cells in the rat lung were analyzed at six evenly spaced times over 24 h (light period: 06.00 h–18.00 h), using a morphometric technique. The cell volumes were maximal at 16.00 h and minimal at 08.00 h. The volume and surface densities of rough endoplasmic reticulum and mitochondria were low during the light period, and high during the dark period. Morphometric parameters of multivesicular bodies did not significantly fluctuate over 24 h, but they increased from 04.00 h to 08.00 h. The volume densities of lamellar bodies increased from 16.00 h to 20.00 h, and decreased from 00.00 h to 08.00 h. The change in numerical densities of lamellar bodies was inversely correlated to that in the volume densities. As shown by electron microscopy, small lamellar bodies predominated at 08.00 h, larger lamellar bodies increasing at 16.00h. Composite bodies often appeared at 08.00 h and 12.00 h. Type II cells thus appear to fluctuate, showing three phases over 24 h: formation, accumulation and secretion of lamellar bodies. In particular, it is noteworthy that the accumulation stage occurs during the resting phase of the rat, whereas the secretion stage occurs during its body-active phase. 相似文献
6.
Acyl carrier protein is present in the mitochondria of plants and eucaryotic micro-organisms 总被引:5,自引:0,他引:5
Proteins antigenically similar to the acyl carrier protein (ACP) found in the mitochondria of Neurospora crassa were detected by immunoblotting and radioimmunoassay techniques in mitochondria isolated from yeast, potatoes, and pea leaves. These mitochondrial proteins were similar to Neurospora ACP both in their electrophoretic mobility and in their unusual decrease in mobility upon reduction. Authentic ACP(s) show this type of change upon conversion of the acylated to the unacylated form. Purified ACP from both spinach chloroplasts and Escherichia coli cells cross-reacted with antibodies raised against Neurospora ACP. Purified ACP from Neurospora cross-reacted with antibodies raised against spinach chloroplast ACP and E. coli ACP. Mitochondria isolated from beef heart and rat brain were tested extensively and exhibited no cross-reaction with any of the three anti-ACP preparations. The discovery of ACP in the mitochondria of other organisms raises questions concerning the possible relationship between ACP and beta-oxidation in mitochondria, the involvement of ACP in de novo biosynthesis of some of the acyl chains in mitochondria and the subcellular locations of fatty acid biosynthesis in plants and eucaryotic micro-organisms. 相似文献
7.
Shigeru Kumano Masashi Ihira Yasuo Maeda Misako Yamauchi Eiji Matsumoto Isao Matsuda 《Ecological Research》1990,5(2):221-235
Diatom assemblages of sediments obtained from three sites on Kushiro Moor were analyzed to investigate the Holocene sedimentary
history. The results showed that: 1) The Takkobu site was originally at the bottom of the paleo-Kushiro Bay, and after-wards
the paleo-Takkobu Lagoon developed, became sealed off, and changed to a freshwater lake. The succession to peat moor probably
began about 2000 yr B.P. at the Takkobu site. 2) The Tsurui site was originally at the bottom of the paleo-Kushiro Bay, then
changed to the paleo-Kushiro Lagoon and became peat moor as a result of the first Holocene regression, which finished about
3600 yr B.P. The site then returned to a brackish lake again, probably due to the second Holocene transgression between 3600
and 3000 yr B.P., thereafter passing through brackish lake and freshwater lake stages, and eventually becaming peat moor at
about 2000 yr B.P., 3) At the Chuo site, the second paleo-Kushiro Bay developed again as a result of the second Holocene transgression,
which finished about 3000 yr B.P. Thereafter, brackish or freshwater lakes, rivers, and then peat moor developed in the central
area of Kushiro Moor. 4) The second marine diatom zone (MD2 Zone), which indicates the second Holocene transgression, complete by about 3000 yr B.P., is detected only at the Chuo site
in the central area of Kushiro Moor. 相似文献
8.
A re-evaluation of the cytology of cat Pacinian corpuscles 总被引:1,自引:0,他引:1
Bryce L. Munger Yasuo Yoshida Shuichiro Hayashi Tokuji Osawa Chizuka Ide 《Cell and tissue research》1988,253(1):83-93
Summary The ultrastructure of cat mesenteric Pacinian corpuscles in cross and longitudinal sections has been examined. The terminal ends of lamellar cells of the inner core have been identified in longitudinal sections through the proximal portion of the inner core. These terminal bulbous expansions contain characteristic concentric membranes of rough endoplasmic reticulum and in some cases masses of oval membranous inclusions. The central axon as seen in cross section is oval in profile, having X-(short) and Y-(long) axes, and each axonal face is characterized by specializations of the axolemma. At the X-axis, the inner lamellae of the inner core tightly abut a smooth axolemma, with no intervening connective tissue matrix, in a manner reminiscent of a neuroepithelium. The axolemma of the Y-axis has numerous axonal spines (microspikes) that project into the cleft in the inner core. The extent of the axolemma having axonal spines can only be appreciated in longitudinal sections. The clefts contain a specialized connective tissue with elastic and collagen fibrils. The connective tissue compartment of fibers and matrix separating individual inner core lamellae is unique, in that it contains extremely thin collagen fibrils measuring approximately 15 nm in diameter. The diameter of collagen fibrils increases as the cleft is approached. Here the fibrils resemble typical endoneural collagen. 相似文献
9.
Solubilization and Characterization of Calcitonin Gene-Related Peptide Binding Site from Porcine Spinal Cord 总被引:1,自引:1,他引:0
Osamu Hiroshima Yoshihisa Sano Teruaki Yuzuriha Chiyuki Yamato Akira Saito Naomichi Okamura† Yasuo Uchiyama† Sadao Kimura † Katsutoshi Goto 《Journal of neurochemistry》1988,50(2):480-485
The binding site for calcitonin gene-related peptide (CGRP) was solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS) in an active form from porcine spinal cord. 125I-labeled human alpha-CGRP (125I-CGRP) binding to the solubilized protein was determined by filtration using a GF/B glass filter. The maximal binding activity (approximately 60% of the crude membrane fraction) was obtained with 5 mM CHAPS. 125I-CGRP binding to the solubilized protein was of high affinity, saturability, and high specificity, having KD and Bmax values of 3.69 pM and 338 fmol/mg of protein, respectively. The binding activity was eluted in a single peak with a molecular mass of 400,000 daltons by gel filtration on TSK gel G4000SW. These results suggest that the solubilized protein may be responsible for the specific binding site. 相似文献
10.
Motoki Tagami Kazuo Yamagata Hideaki Fujino Akiyoshi Kubota Yasuo Nara Yukio Yamori 《Cell and tissue research》1992,268(2):225-232
Summary In this study bovine aortic endothelial cells were co-cultured with astrocytes from fetal Wistar Kyoto rats. Endothelial cells growing on type-I collagen, development. Although some cells appeared to be mature, horseradish peroxidase penetrated within 1 min of incubation through the intercellular junctions of these endothelial elements maintained on type-I collagen. In contrast, endothelial cells on type-IV collagen, co-cultured with astrocytes, were well developed; their intercellular junctions were well established, and plasmalemmal vesicles reduced in number. As a result, horseradish peroxidase was unable to penetrate through the endothelial cells grown on type-IV collagen and co-cultured with astrocytes because of the reduced extent of the junctional and vesicular transport. These findings reveal that (1) type-IV collagen is essential for the differentiation of endothelial cells, (2) endothelial cell-astrocyte interactions occur during co-culture, and (3) endothelial permeability depends on astrocyte-produced factors, in addition to type-IV collagen. 相似文献