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1.
Cheng TH Shih NL Chen CH Lin H Liu JC Chao HH Liou JY Chen YL Tsai HW Chen YS Cheng CF Chen JJ 《Journal of biomedical science》2005,12(1):123-133
Endothelin-1 (ET-1) has been found to increase cardiac -myosin heavy chain (-MyHC) gene expression and induce hypertrophy in cardiomyocytes. ET-1 has been demonstrated to increase intracellular reactive oxygen species (ROS) in cardiomyocytes. The exact molecular mechanism by which ROS regulate ET-1-induced -MyHC gene expression and hypertrophy in cardiomyocytes, however, has not yet been fully described. We aim to elucidate the molecular regulatory mechanism of ROS on ET-1-induced -MyHC gene expression and hypertrophic signaling in neonatal rat cardiomyocytes. Following stimulation with ET-1, cultured neonatal rat cardiomyocytes were examined for 3H-leucine incorporation and -MyHC promoter activities. The effects of antioxidant pretreatment on ET-1-induced cardiac hypertrophy and mitogen-activated protein kinase (MAPKs) phosphorylation were studied to elucidate the redox-sensitive pathway in cardiomyocyte hypertrophy and -MyHC gene expression. ET-1 increased 3H-leucine incorporation and -MyHC promoter activities, which were blocked by the specific ETA receptor antagonist BQ-485. Antioxidants significantly reduced ET-1-induced 3H-leucine incorporation, -MyHC gene promoter activities and MAPK (extracellular signal-regulated kinase, p38, and c-Jun NH2 -terminal kinase) phosphorylation. Both PD98059 and SB203580 inhibited ET-1-increased 3H-leucine incorporation and -MyHC promoter activities. Co-transfection of the dominant negative mutant of Ras, Raf, and MEK1 decreased the ET-1-induced -MyHC promoter activities, suggesting that the Ras-Raf-MAPK pathway is required for ET-1 action. Truncation analysis of the -MyHC gene promoter showed that the activator protein-2 (AP-2)/specificity protein-1 (SP-1) binding site(s) were(was) important cis-element(s) in ET-1-induced -MyHC gene expression. Moreover, ET-1-induced AP-2 and SP-1 binding activities were also inhibited by antioxidant. These data demonstrate the involvement of ROS in ET-1-induced hypertrophic responses and -MyHC expression. ROS mediate ET-1-induced activation of MAPK pathways, which culminates in hypertrophic responses and -MyHC expression.
Tzu-Hurng Cheng, Neng-Lang Shih: These authors have equally contributed to this work 相似文献
2.
Eighteen month old spontaneously hypertensive rats (SHR-rats) showed myocardial dysfunction and autoantibodies directed against the 1-adrenoceptor similarly as known in human dilated cardiomyopathy or Chagas' disease. The agonist-like antibodies were able to activate the 1-adrenoceptor mediated signal transduction cascade in cultured rat cardiomyocytes and induced a long-lasting stimulatory effect resulting in a harmful adrenergic overdrive. The antibodies recognized an epitope of the second extracellular loop of the 1-adrenoceptor identical to that epitope identified in Chagas' disease. In conclusion, our assumption is supported that old SHR-rat are an useful animal model for investigating the role of anti-1-adrenoceptor antibodies in the induction of human cardiomyopathy. 相似文献
3.
The conformational properties of the oligosaccharide chain of GM1 ganglioside containingN-glycolyl-neuraminic acid, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer, were studied through NMR nuclear Overhauser effect investigations on the monomeric ganglioside in dimethylsulfoxide, and on mixed micelles of ganglioside and dodecylphosphocholine in water. Several interresidual contacts for the trisaccharide core--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-were found to fix the relative orientitation of the three saccharides, while the glycosidic linkage of the terminal -Gal-was found to be quite mobile as the -Gal-(1-3)--GalNAc-disaccharide exists in different conformations. These results are similar to those found for two GM1 gangliosides containingN-acetyl-neuraminic acid and neuraminic acid [1].Abbreviations Ganglioside nomenclature is in accordance with Svennerholm [23] and the IUPAC-IUB Recommendations [24] GM3(Neu5Ac)
II3Neu5AcLacCer, -Neu5Ac-(2-3)--Gal-(1-4)--Glc-(1-1)-Cer
- GM3(Neu5Gc)
II3Neu5GcLacCer, -Neu5Gc-(2-3)--Gal-(1-4)--Glc-(1-1)-Cer
- GM1(Neu5Ac)
II3Neu5AcGgOse4Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- GM1(Neu5Gc)
II3Neu5GcGgOse4Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- GM1(Neu)
II3NeuGgOse4Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu-(2-3)]--Glc-(1-1)-Cer
- GD1a
IV3Neu5AcII3Neu5AcGgOse4Cer, -Neu5Ac-(2-3)--Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- GalNAc-GD1a
IV4GalNAcIV3Neu5AcII3Neu5AcGgOse4Cer, -GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- Neu
neuraminic acid
- Neu5Ac
N-acetyl-neuraminic acid
- Neu5Gc
N-glycolyl-neuraminic acid
- Cer
ceramide 相似文献
4.
MHC class I molecules are heterotrimeric complexes composed of heavy chain, 2-microglobulin (2m) and short peptide. This trimeric complex is generated in the endoplasmic reticulum (ER), where a peptide loading complex (PLC) facilitates transport from the cytosol and binding of the peptide to the preassembled ER resident heavy chain/2m dimers. Association of mouse MHC class I heavy chain with 2m is characterized by allelic differences in the number and/or positions of amino acid interactions. It is unclear, however, whether all alleles follow common binding patterns with minimal contributions by allele-specific contacts, or whether essential contacts with 2m are different for each allele. While searching for the PLC binding site in the 3 domain of the mouse MHC class I molecule H-2Db, we unexpectedly discovered a site critical for binding mouse, but not human, 2m. Interestingly, amino acids in the corresponding region of another MHC class I heavy chain allele do not make contacts with the mouse 2m. Thus, there are allelic differences in the modes of binding of 2m to the heavy chain of MHC class I. 相似文献
5.
van Wamel AJ Ruwhof C van der Valk-Kokshoom LE Schrier PI van der Laarse A 《Molecular and cellular biochemistry》2001,218(1-2):113-124
Cardiac hypertrophy is a compensatory response of myocardial tissue upon increased mechanical load. Of the mechanical factors, stretch is rapidly followed by hypertrophic responses. We tried to elucidate the role of angiotensin II (AII), endothelin-1 (ET-1) and transforming growth factor- (TGF-) as autocrine/paracrine mediators of stretch-induced cardiomyocyte hypertrophy. We collected conditioned medium (CM) from stretched cardiomyocytes and from other stretched cardiac cells, such as cardiac fibroblasts, endothelial cells and vascular smooth muscle cells (VSMCs). These CMs were administered to stationary cardiomyocytes with or without an AII type 1 (AT1) receptor antagonist (losartan), an ET-1 type A (ETA) receptor antagonist (BQ610), or anti-TGF- antibodies. By measuring the mRNA levels of the proto-oncogene c-fos and the hypertrophy marker gene atrial natriuretic peptide (ANP), the molecular phenotype of the CM-treated stationary cardiomyocytes was characterized.Our results showed that c-fos and ANP expression in stationary cardiomyocytes was increased by AII release from cardiomyocytes that had been stretched for 60 min. Stretched cardiomyocytes, cardiac fibroblasts and endothelial cells released ET-1 which led to increased c-fos and ANP expression in stationary cardiomyocytes. ET-1 released by stretched VSMCs, and TGF- released by stretched cardiac fibroblasts and endothelial cells, appeared to be paracrine mediators of ANP expression in stationary cardiomyocytes.These results indicate that AII, ET-1 and TGF- (released by cardiac and vascular cell types) act as autocrine/paracrine mediators of stretch-induced cardiomyocyte hypertrophy. Therefore, it is likely that in stretched myocardium the cardiomyocytes, cardiac fibroblasts, endothelial cells and VSMCs take part in intercellular interactions contributing to cardiomyocyte hypertrophy. 相似文献
6.
Penny von Wettstein-Knowles 《Planta》1972,106(2):113-130
Summary Five eceriferum, (cer) mutants in barley which influence -diketone and hydroxy--diketone synthesis in spike and internode epicuticular waxes have been characterized. The mutation cer-u
69 blocks the synthesis of hydroxy--diketones and leads to a compensatory increase in the amount of -diketones, indicating that -diketones are precursors of the hydroxy--diketones. Furthermore, highly lobed wax plates were observed for the first time on barley lemmas, in addition to the characteristic wax tubes. Both diketone classes are selectively and proportionally reduced in the spike wax of cer-i
16, which has shorter wax tubes. The three mutants cer-c
36, -q
42, and -c,u
108 synthesize neither diketone class and form no wax tubes. In contrast to the variable composition of most individual barley wax classes, only a single -diketone was identified, namely hentriacontan-14,16-dione. 相似文献
7.
Young S. Kim Ze Wang Robert M. Levin Samuel Chacko 《Molecular and cellular biochemistry》1994,131(2):115-124
The obstruction of the bladder outlet induces a marked increase in bladder mass, and this is accompanied by reduced contractility of bladder smooth muscle and alteration in the cellular architecture. In this study, we show that the composition of various isoforms of actin, a major component of the contractile apparatus and the cytoskeletal structure of smooth muscle, is altered in response to the obstruction-induced bladder hypertrophy. Northern blot analysis of the total RNA isolated from hypertrophied urinary bladder muscle, using a cDNA probe specific for smooth muscle -actin, shows over 200% increase in the -actin mRNA. However, the estimate of the amount of actin from the 2D gel reveals only a 16% increase in -actin, since the 2D gel electrophoresis does not distinguish -smooth muscle actin from -cytoplasmic actin. The bladder smooth muscle -actin and the smooth muscle -actin mRNA are not altered in response to the hypertrophy. The obstructed bladder also reveals a decrease in the -cytoplasmic actin (37%) and a concomitant diminution in the -cytoplasmic actin mRNA (29%). Hence, the composition of the actin isoforms in bladder smooth muscle is altered in response to the obstruction-induced hypertrophy. This alteration of the actin isoforms is observed at both the protein and mRNA levels. 相似文献
8.
Avigdor Shafferman Yehuda Flashner Israel Hertman Menachem Lion 《Molecular & general genetics : MGG》1987,208(1-2):263-270
Summary The functional R6K origin is composed of two DNA elements, one of 580 bp carrying the origin sequences and the other of 277 bp containing the seven 22 bp direct repeats previosly identified as also required for and origin activity. These two genetic elements are separated by approximately 3,000 bp of R6K sequences which are dispensable for origin activity. The function of the origin depends on the presence in cis of the 580 bp and the 277 bp fragments and requires that they be oriented as in the intact R6K. Activation of the origin depends on the R6K replication initiation protein .Within the 580 bp of the origin, there is a sequence of 98 bp which appears as an inverted repeat of 96 bp in the replicon. Deletion of the 96 bp or 98 bp results in inactivation of the and the origins respectively. These long repeats are palindromic and it is suggested that these may serve as the recognition signals for initiation of DNA replication in the and the origins of R6K. DNA homology analysis performed on , and origin sequences, also reveals 10–23 bp sequences in the and the origins that are related to the family of 22 bp direct repeats in the origin which were shown previously to be binding sites for the protein. 相似文献
9.
Carmen A. Mannella 《Journal of bioenergetics and biomembranes》1997,29(6):525-531
There is considerable evidence that the voltage-gated mitochondrial channel VDAC forms a -barrel pore. Inferences about the number and tilt of -strands can be drawn from comparisons with bacterial -barrel pores whose structures have been determined by x-ray crystallography. A structural model for VDAC is proposed (based on sequence analysis and electron crystallography) in which the open state is like that of bacterial porins with several important differences. Because VDAC does not occur as close-packed trimers, there are probably fewer interpore contacts than in the bacterial porins. VDAC also appears to lack a large, fixed intraluminal segment and may not have as extensive a region of uniformly 35°-tilted -strands as do the bacterial porins. These structural differences would be expected to render VDAC's -barrel less stable than its bacterial counterparts, making major conformational changes like those associated with gating more energetically feasible. A possible gating mechanism is suggested in which movement of the N-terminal -helix out of the lumen wall triggers larger-scale structural changes. 相似文献
10.
Tubulin, the major component of microtubules, has a tendency to lose its ability to assemble or to bind to ligands in a time-dependent process known as decay. The decay process also causes tubulin to expose sulfhydryl groups and hydrophobic areas. The antimitotic drug phomopsin A strongly protects the tubulin molecule from decay. Here we have studied the interaction of phomopsin A with tubulin and tubulin which has been treated with subtilisin to remove selectively the C-termini of the and chains (ss). The binding of phomopsin A to tubulin decreases the sulfhydryl titer by approximately 1.0 mol/mol. Selective removal of the peptides from the C-terminal ends does not affect phomopsin A's interaction with tubulin. Moreover, the ss tubulin–phomopsin A complex appears to be more stable than the tubulin–phomopsin A complex as determined by the time-dependent increase in exposure of sulfhydryl groups and hydrophobic areas on tubulin. In fact, phomopsin A inhibits the decay process of ss tubulin completely. This observation raises the possibility of determining the conformtion of this configuration of tubulin. 相似文献
11.
Stretch-induced paracrine hypertrophic stimuli increase TGF-β1 expression in cardiomyocytes 总被引:2,自引:0,他引:2
van Wamel AJ Ruwhof C van der Valk-Kokshoorn LJ Schrier PI van der Laarse A 《Molecular and cellular biochemistry》2002,236(1-2):147-153
Cardiac hypertrophy refers to the abnormal growth of cardiomyocytes, and is often caused by valvular heart disease and hypertension. It involves the activation of growth, including increased protein synthesis and changes in gene expression. Transforming growth factor-1 (TGF-1) may play a central role in protecting the heart during the hypertrophic response by helping to restore normal functions of the affected myocardium. We tested the hypothesis that cardiomyocytes respond to stretch-induced paracrine hypertrophic stimuli with increased expression of TGF-1. To that purpose, we investigated whether angiotensin II (AII), endothelin-1 (ET-1) and TGF-, secreted by stretched cardiac and vascular cells, are involved in the paracrine mechanisms of stretch-induced changes of TGF-1 mRNA expression in stationary (i.e. non-stretched) cardiomyocytes.Our results indicated that TGF-1 mRNA expression in stationary cardiomyocytes was increased by AII release from cardiomyocytes that had been stretched for 30–60 min. Furthermore, it is likely that ET-1 and TGF- were released by stretched cardiac fibroblasts and endothelial cells to induce TGF-1 mRNA expression in stationary cardiomyocytes. Stretched vascular smooth muscle cells did not influence TGF-1 mRNA expression in stationary cardiomyocytes. These results indicate that AII, ET-1 and TGF-, released by cardiac cell types, act as paracrine mediators of TGF-1 mRNA expression in cardiomyocytes. Therefore, we conclude that in stretched myocardium the cardiomyocytes, cardiac fibroblasts and endothelial cells take part in intercellular interactions contributing to cardiomyocyte hypertrophy. 相似文献
12.
Boel Lanne Jeana Cîopraga Jörgen Bergström Cecilia Motas Karl-Anders Karlsson 《Glycoconjugate journal》1994,11(4):292-298
The carbohydrate-binding specificity ofPseudomonas aeruginosa lectin I (PA-I) in iodinated or biotinylated form was studied. A large number of glycosphingolipids, as well as some glycoproteins and neoglycoproteins were used as ligands. Also, inhibition by free saccharides of PA-I binding to glycosphingolipids was tested. It was found that the lectin binds most strongly to terminal and nonsubstituted Gal3Gal- or Gal4Gal-structures.Abbreviations PA-I
Pseudomonas aeruginosa lectin I
- Cer
ceramide
- lactosylceramide
Gal4GlcCer
- iso globotriaosylcerami
Gal3Gal4GlcCer
- globotriaosylceramide
Gal4Gal4GlcCer
- globoside or globotetraosylceramide
GalNAc3Gal4Gal4GlcCer
- Forssman glycolipid
GalNAc3GalNAc3Gal4Gal4GlcCer
- P1 glycolipid
Gal4Gal4GlcNAc3Gal4GlcCer
- lactoneotetraosylceramide
Gal4GlcNAc3Gal4GlcCer
- B5 glycolipid
Gal3Gal4GlcNAc3Gal4GlcCer
- gangliotetraosylceramide
Gal3GalNAc4Gal4GlcCer
- GM1
Gal3GalNAc4(NeuAc3)Gal4GlcCer
- RBC
red blood cells
- BSA
bovine serum albumin
- PBS
phosphate-buffered saline
- SDS
sodium dodecyl sulfate
- TLC
thin-layer chromatography
- HPLC
high pressure liquid chromatography
- MS
mass spectrometry
- FAB
fast-atom bombardment
- EI
electron impact 相似文献
13.
The acrylamide quenching of the intrinsic tryptophanyl fluorescence of normal and sickle apohemoglobins has been studied in 0.05 M potassium phosphate buffer,pH 7.5, at 5°C over a protein concentration range from 1 to 50M. Analysis of quenching dynamics revealed a strong dependence on acrylamide concentration for the intrinsic fluorescence of both normal and sickle apohemoglobins, suggesting that one tryptophanyl residue [presumably that at position 37(C3)], was more accessible to collisional quencher than the other tryptophanyl residue [15(A12)]. Additional studies, which altered viscosity and subunit assembly experimental parameters, supported the assignment of residue 37 as the more dynamically accessible residue. Finally, the quenching data were also found to be dependent on protein concentration, implying that this difference in the mobility between the two residues is a sensitive probe of self-aggregation. Extrapolated dynamic quenching constants at low concentration of acrylamide were used to estimate the dimer-monomer equilibrium dissociation constants of normal and sickle apohemoglobins, and were found to be 5.6 and 2.4M, respectively, thus demonstrating distinct self-association properties of
A and
S apohemoglobins. 相似文献
14.
A. S. U. Choughuley A. S. Subbaraman Z. A. Kazi M. S. Chadha 《Origins of life and evolution of the biosphere》1975,6(4):527-535
It has been observed that -hydroxy--amino acids are transformed into other amino acids, when heated in dilute solutions with phosphorous acid, phosphoric acid or their ammonium salts. It has been shown that as in the case of previously reported glycine-aldehyde reactions, glycine also reacts with acetone to give -hydroxyvaline under prebiologically feasible conditions. It is suggested, therefore, that the formation of -hydroxy--amino acids and their transformation to other amino acids may have been a pathway for the synthesis of amino acids under primitive earth conditions. 相似文献
15.
Billger Martin Nilsson Elisabeth Karlsson Jan-Olof Wallin Margareta 《Molecular and cellular biochemistry》1993,122(1):85-92
Viral infection of cultured cells with transforming viruses causes an increase in cell-surface N-linked 1-6 (GlcNAc1-6Man) branching of complex-type oligosaccharides. Similar observations have been made after transfection of cells with activated oncogenes, which is associated with an induction of tumorigenic and metastatic properties. In this study, the effects of transfection of both activated and proto-Ha-ras oncogenes into NIH3T3 cells were analyzed. The results showed that, in comparison with NIH3T3 cells, bothras transfectants have increased sensitivity to the cytotoxic action of L-PHA. An increase in 1-6 branching and an increased level of N-acetylglucosaminyltransferase V (GlcNAc-T V), the enzyme which initiates the 1-6 branching were also observed. The levels of GlcNAc-T I and 1-4 Gal-T remained unchanged in activated Ha-ras transfected NIH3T3 cells. These data suggest that a specific induction of GlcNAc-T V occurs after transfection with either the proto- or activated Ha-ras oncogenes, which is responsible for the increased 1-6 branching previously observed. (Mol Cell Biochem122: 85–92, 1993)Abbreviations Asn
Asparagine
- BHK
Baby Hamster Kidney (cells)
- 1-4 Gal-T or Gal-T
1-4 Galactosyltransferase
- BSL-II
Banderia Simplifolia Lectin II
- CHO
Chinese Hamster Ovary (cells)
- ConA
Concanavalin A
- D-MEM
Dulbecco's Modified Eagle's Medium
- E-PHA
Erythroagglutinin of Phytohemagglutinin
- Fuc
Fucose
- Gn or GlcNAc
N-acetylglucosamine
- GlcNAc-T I
N-acetylglucosaminyltransferase I
- LCA
Lens Culinaris Agglutinin
- L-PHA
Leukoagglutinin of Phytohemagglutinin
- M or Man
Mannose
- PBS
Phosphate-Buffered Saline
- PL
Pea Lectin
- RIC
Ricin
- SDS-PAGE
Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis
- UDP-Gal
Uridine-Diphosphate-Galactose
- UDP-Gn
Uridine-Diphosphate-N-acetylglucosamine
- WGA
Wheat Germ Agglutinin 相似文献
16.
The roles of transforming growth factor-beta (TGF) in heart or skeletal muscle development and physiology are still the subject of controversies. Our aim was to block, in transgenic mice, the TGF signalling pathway by a dominant negative mutant of the TGF type II receptor fused to the enhanced green fluorescent protein (TRII-KR-EGFP) under the control of a 7.1 kbp mouse beta-myosin heavy chain (MHC) promoter to investigate the roles of TGF in the heart and slow skeletal muscles. First, we generated two transgenic lines overexpressing EGFP under the control of the 7.1 kbp MHC promoter. In embryos, EGFP was detectable as early as 7.5 days post coitum. In embryos, newborns and adults, EGFP was expressed mainly in the cardiac ventricles and in slow skeletal muscles. EGFP expression was intense in the bladder but weak in the intestines. In contrast to the endogenous MHC promoter, the activity of the 7.1 kbp MHC promoter in the transgene was not repressed after birth and remained high in adult transgenic mice. We obtained two founders with the transgene comprising the TRII-KR-EGFP sequence under the control of the 7.1 kbp MHC promoter. These founders were generated at a very low frequency and expressed barely detectable levels of TRII-KR-EGFP mRNA. Our failure to obtain transgenic lines overexpressing the dominant negative receptor suggests that the blocking of the TGF signalling pathway in the heart and slow skeletal muscles could be embryonically lethal. To conclude, the 7.1 kbp MHC promoter directs high levels of transgene expression in the cardiac ventricles and in slow skeletal muscles of the mouse. Analysis of the consequences of the blocking of the TGF signalling pathway in the heart will require the use of tissue specific means of conditional gene invalidation. 相似文献
17.
Fang-Sheng Wu 《Planta》1987,171(3):346-357
The positively-charged fluorescent dye rhodamine 123 (r-123) specifically stains mitochondria in living plant protoplasts, suspensionculture cells, and root hairs. This dye functions as a vital stain and permits visualization of the localization, distribution and movement of the mitochondria. Dehydration of root hairs caused mitochondria to aggregate into clumps. Mitochondria were either homogenous or heterogeneous and were frequently seen to accumulate in the perinuclear regions of suspension-culture cells but not in those of protoplasts or root-hair cells. Dinitrophenol and high concentrations of ethyleneglycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid and KCl immediately eliminated fluorescence in r-123-stained mitochondria whereas ionomycin enhanced it. Treatment of seedlings with r-123 resulted in differential brightness of fluorescence in different tissues. Meristematic tissues, such as root and shoot tips, exhibited the brightest fluorescence. The cytotoxicity of r-123 in both germinating seedlings and suspension-culture cells was low. The specificity, sensitivity and low toxicity of r-123 should make it a useful tool in experiments designed to examine agents and conditions which affect the location, the physiological status or the viability of mitochondria.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethyl ether)N,N,N,N-tetraacetic acid
- DAPI
46-diamidino-2-phenylindole
- r-123
rhodamine 123 相似文献
18.
Conditions which induce a transmembrane electrical potential, positive with respect to the inside of membrane vesicles, result in a substantial (4–12-fold) stimulation of the activity of membrane-associated -glucan synthetases in a membrane preparation derived from the developing cotton (Gossypium hirsutum L.) fiber. Induction of electrical potentials which are negative with respect to the inside of the membrane vesicle results in little or no stimulation of -glucan synthesis. Those products whose synthesis is stimulated are mainly -1,3-glucan, but there is also a considerable increase in -1,4-glucan. No -1,4-glucan (starch) was detected in the reaction products. A transmembrane pH gradient was found to have no effect on -glucan synthesis. The results indicate that a transmembrane electrical potential can influence, either directly or indirectly, the activity of membrane-associated polysaccharide synthetases.Abbreviations UDP-glucose
uridine-5-diphosphoglucose
- PEG
polyethylene glycol
- BTP
bistrispropane (1,3-bis[tris(hydroxymethyl)methylamino]propane)
- MES
2(N-morpholino)ethanesulfonic acid
- VAL
valinomycin 相似文献
19.
Summary The localization of luteinizing hormone beta (LH)-mRNA was studied by in situ hybridization in the pars tuberalis of sheep using a homologous sheep double-stranded 32P-or 35S-cDNA. The labelled cDNA probe detected one mRNA sequence in the pars tuberalis by Northern blot analysis; this sequence was similar to that detected in the pituitary. In situ, the labelling of LH-mRNA in the horizontal and sagittal tissue sections was found throughout the pars tuberalis. This labelling was prevented by adding an excess of cold probe or treating the sections by ribonuclease before in situ hybridization. Controls showed a labelling in the pars distalis, but not in the median eminence, hypothalamus, cerebral cortex and liver sections. Double labelling by using a specific LH-antiserum indicated that the labelling of LH-mRNA appeared more intense in LH-containing cells that were found only in the ventral part of the pars tuberalis. These results suggest that the entire pars tuberalis is able to produce the LH subunit, but that the level of translation greatly varies according to the location of the cells. 相似文献
20.
A study was made of contractile activity produced in isolated muscle strips from human umbilical vessels by adrenomimetics and adrenoblockers. Activation of -as well as -adrenoceptors was found to cause contraction in the smooth muscle of the umbilical arteries and veins — a different effect from that occurring in other vessels. Selective shut-down of - or -receptors under the action of phentolamine and obsidane would indicate that activation of - and -adrenoceptors are responsible for mainly phasic and tonic components (respectively) of smooth muscle contraction in the umbilical vein. Obsidane was also found to inhibit the tonic component of contraction induced by oxytocin. In the smooth muscle cells of the umbilical artery, - and -receptors produce nonselective inhibition of noradrenaline-induced contraction, which obviously indicates limited differentiation in the adrenoceptors of this vessel. In view of the experimental findings obtained, application of obsidane either separately or in combination with oxytocin might be recommended for obstetrical use.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 547–551, July–August, 1989. 相似文献