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141.
Summary The permeability and partition coefficients of tetraphenylarsonium (TPA) and several other organic cations were studied in the human erythrocyte using an ion-selective electrode. The permeability constant for the different cations could be explained quite well by differences in oil/water partition coefficients. No evidence for facilitated transport could be found. Binding of the organic ions occurred to both the cell membrane and to intracellular contents. Partitioning to the membrane remained relatively constant despite variation from ion intracellular binding with blood samples from different donors. TPA flux is stimulated by substoichiometric amounts of tetraphenylboron and other organic anions, suggesting an ion-pairing mechanism. 相似文献
142.
Application of an acid solution to the dorsal skin of conscious toads having intact nervous system induces a scratching reflex and escape movements, as well as autonomic alterations (hypertension and tachycardia) that are part of the defense response. The motor components of this response are abolished or reduced by microinjection of 60, 30, 15 or 7.5 ng carbachol into the midbrain tegmentum. The cardiovascular components, however, continue to be present, although their amplitude is reduced. The depression of the motor response is statistically significant up to 15 minutes for the 60 ng dose, up to 10 minutes for the 15 and 30 ng doses, and only up to 5 minutes for the 7.5 ng dose. The data suggest that the midbrain tegmentum may modulate the reflex motor response triggered by a noxious stimulus and also participate in the organization of the escape movements. The importance of cholinergic agents in this modulation is discussed. The persistence of the cardiovascular component of the response shows the importance of this parameter as an indicator of alert situations. 相似文献
143.
Thigmomorphogenesis: The induction of callose formation and ethylene evolution by mechanical perturbation in bean stems 总被引:1,自引:0,他引:1
Mordecai J. Jaffe Moshe Huberman James Johnson Frank W. Telewski 《Physiologia plantarum》1985,64(2):271-279
Mechanical perturbation by rubbing of the first internode of 11–12 day old plants of Phaseolus vulgaris L. cv. Cherokee wax induces the rapid deposition of callose in the cells of phloem and other tissues. Callose deposition begins immediately after mechanical perturbation, and shows a minor transient peak 1.5 h, and a major peak 6 h later. The callose gradually disappears and is gone after 3 days. If the stems are perturbed every day, the amount of callose decreases by day 2 but then gradually increases again through day 12. Both the top and bottom of the internode produce callose in response to mechanical perturbation. The evolution of ethylene in response to mechanical perturbation begins after 1 h, peaks at 2–3 h and is gone by 5–6 h. A spray of 10−2 M 2-deoxy-D-glucose (DDG) completely blocks stem thickening, callose deposition and ethylene evolution due to mechanical perturbation. DDG at 10−5 to 10−4 M blocks callose production in mechanically perturbed stem segments and increases ethylene evolution from unperturbed stem segments to greater levels than those obtained by mechanically perturbed segments. It is concluded that mechanical perturbation of bean stems tissue induces deposition of callose more rapidly than it induces evolution of ethylene and that DDG can block both processes. 相似文献
144.
Infection of wound tissue of Avicennia marina seedlings by a fungus belonging to the genus Phytophthora induced the production of three chemically-related phytoalexins. After isolation by extraction, partition HPLC separation, one was identified as naphtho[1,2-b]furan-4,5-dione, and the other two tentatively as 3-hydroxynaphtho[1,2-b]furan-4,5-dione and 2-[2′-(2′-hydroxy)propyl]-naphtho[1,2-b]furan-4,5-dione. 相似文献
145.
Human urine from smokers and nonsmokers on strictly controlled diets was assayed for mutagenic activity. Two distinct diets were employed in this study. Diet study A consisted of a high-meat, high-fat diet, observed for 5 days, followed by a vegan diet, adhered to for the next 5 days. The vegan diet contained no meat, fish, eggs, or dairy products. It was comprised of soy products, prepackaged vegan dinners, seeds, nuts, fruits, vegetables, beans and herbal teas. Diet study B consisted of 3 days on a typical western diet followed by a macrobiotic diet of grains and fresh vegetables for 5 days. Portions of 24-h urine samples were assayed in Salmonella typhimurium TA1538. The levels of urinary creatinine and cotinine were measured. Mutagenic activity was observed in the urine of most smokers. However, the levels of mutagens in the urine of light smokers were similar to those of nonsmokers. For both nonsmokers and smokers there was a significant increase in urine mutagenicity when volunteers were on the vegan diet. Several nonsmokers on the vegan diet in diet study A had pronounced mutagenic activity in their urine samples, in some instances at higher levels than that in the urine of smokers on a meat diet. In diet study B no clear differences were observed between the meat diet and the macrobiotic diet. In diet studies A and B the mutagenic potency of smokers' urine could not be correlated with cotinine levels alone or with urinary pH. These data suggest that dietary factors can play a dominant role in the mutagenicity of urine concentrates. 相似文献
146.
Computer-Assisted Image Analysis of Plant Growth, Thigmomorphogenesis, and Gravitropism 总被引:2,自引:0,他引:2
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Mordecai J. Jaffe Andrew H. Wakefield Frank Telewski Edward Gulley Ronald Biro 《Plant physiology》1985,77(3):722-730
A nonintrusive auxonometric system, based on the DARWIN image processor (Telewski et al. 1983 Plant Physiol 72: 177-181), is described and demonstrated in the analysis of gravitropism and thigmomorphogenesis in corn seedlings (Zea mays). Using this system, growth and bending of regularly shaped plants or organs can be quickly and accurately measured without, in any way, interfering with the plant. Furthermore, the growth and bending curves are automatically plotted. Thigmomorphogenesis in the aerial part of corn seedlings involves growth promotion at a low force load and growth retardation at higher force loads. The time courses of the two kinds of response are somewhat different, with retardation occurring immeditely after mechanical perturbation and growth promotion taking somewhat longer to begin. Gravitropic experiments show that when dark-grown corn seedlings are placed on their side in the light, the resulting curvature is due to two consecutive morphological mechanisms. In the first instance, lasting for about 15 minutes, the elongation of the bottom edge of the plant accelerates, while the elongation of the top edge remains constant. After that, for the next 1.75 hours, the elongation of the top edge decelerates and stops while that of the bottom edge remains constant at the increased rate for most of the period. The measurements taken from both experiments at relatively high resolution (0.08-0.1 millimeter) show that the growth curves are not smooth but show many small irregularities which may or may not involve micronutations. 相似文献
147.
T van Houwelingen G W Canters G Stobbelaar J A Duine J Frank A Tsugita 《European journal of biochemistry》1985,153(1):75-80
The blue copper protein induced during growth of Thiobacillus versutus on methylamine was purified and characterized. It is an acidic protein (isoelectric point 4.7), contains one Cu2+ ion/enzyme molecule, is a monomeric protein (molecular mass about 14 kDa), has a maximum in its absorption spectrum at 596 nm (molar absorption coefficient 3.9 X 10(3) M-1 cm-1), shows an axial type-I electron paramagnetic resonance spectrum (g parallel = 2.239, g perpendicular = 2.046 and A parallel = 5.6 mT) and has a redox potential (Eo) of + 260 mV. In view of these properties and in view of the fact that the protein is active as an electron carrier between methylamine dehydrogenase and cytochrome c, it is concluded that it is similar to the amicyanins isolated from Methylomonas sp. strain J and Pseudomonas sp. strain AM 1. 相似文献
148.
Zusammenfassung In Burkina Faso ließ ein Mangrovereiher offensichtlich gezielt eine Asclepiadaceen-Blüte aus 20 cm Höhe auf die Wasseroberfläche fallen und verharrte danach einige Sekunden mit halb-gestrecktem Hals. Bei einer weiteren Beobachtung in Niger plazierte ein Mangrovereiher einen kleinen Gegenstand auf der Wasseroberfläche. Bevor der Gegenstand mit dem Wind außer Reichweite trieb, holte ihn der Reiher und legte ihn auf der Luvseite wieder auf der Wasseroberfläche ab. Der Vorgang wiederholte sich mehrere Male, dabei gelang es dem Reiher, einen Fisch zu erbeuten, der allerdings wieder entkam. Anderntags setzte an derselben Stelle ein Mangrovereiher in gleicher Weise offensichtlich einen Käfer ein. Ähnliche Beobachtungen werden kurz diskutiert. 相似文献
149.
P Frank A Licht T D Tullius K O Hodgson I Pecht 《The Journal of biological chemistry》1985,260(9):5518-5525
The production and spectroscopic properties of an L-selenomethionine-containing homolog of Pseudomonas aeruginosa azurin are described. The amino acid substitution was carried out by developing an L-methionine-dependent bacterial strain from a fully functional ATCC culture. Uptake studies monitored using L-[75Se]methionine indicated that L-selenomethionine was incorporated into the protein synthetic pathway of Pseudomonas bacteria in a manner analogous to L-methionine. Several batches of bacteria were grown, and one sample of isolated and purified selenoazurin (azurin in which methionine was substituted by selenomethionine) was found (by neutron activation analysis) to contain 5.2 +/- 0.8 seleniums/copper. Correspondingly, a residual 0.35 methionines, relative to 6.0 in the native protein, were found by amino acid analysis in this azurin sample. The redox potential and extinction coefficient of this selenoazurin were found to be 333 +/- 1 mV (pH 7.0, I = 0.22) and 5855 +/- 160 M-1 cm-1 at 626 +/- 1 nm, respectively. Visible electronic, CD, and EPR spectra are reported and Gaussian curve fitting to the former spectrum allowed assignment of the selenomethionine Se----Cu(II) transition to a band found at 18034 cm-1, based upon an observed 450 cm-1 shift to the red from the analogous band position in the native protein. The data are consistent with a relatively more covalent copper site stabilizing the reduced, Cu(I), form in the selenoprotein. A role for the methionine as a modulator of the blue copper site redox potential by metal----ligand back bonding from Cu(I) is discussed in terms of a ligand sphere which limits the valence change at copper to much less than 1 during a redox cycle. 相似文献
150.
Wolfgang Löscher Gerhard Böhme Frank Müller Sonia Pagliusi 《Journal of neurochemistry》1985,45(3):879-889
A procedure is described for the rapid preparation of nerve ending particles (synaptosomes) from 11 regions of one rat brain. The synaptosomal fractions have been characterized by electron microscopy and determination of four marker enzymes, i.e., glutamate decarboxylase (GAD), acetylcholinesterase, succinate dehydrogenase, and glycerol 3-phosphate dehydrogenase. Comparison with a much lengthier standard (Ficoll-sucrose) preparation showed that the synaptosomal yield of the new procedure was substantially better as judged by both morphological evaluation and protein recovery. The improved synaptosome preparation was used for determination of regional gamma-aminobutyric acid (GABA) levels in synaptosomal fractions. The postmortem increase in GABA level during removal and dissection of brain tissue and homogenization and fractionation procedures could be minimized by rapid processing of the tissue at low temperatures and inclusion of the GAD inhibitor 3-mercaptopropionic acid (3-MP; 1 mM) in the homogenizing medium. The addition of GABA (0.2 mM) to the homogenizing medium did not alter the GABA levels in the synaptosomes, indicating that no significant redistribution of GABA occurred during subcellular fractionation in sodium-free media. Synaptosomal GABA levels determined in the 11 rat brain areas showed the same regional distribution as the GABA-synthesizing enzyme GAD. On the basis of these findings, it was suggested that the synaptosome preparation could be used to evaluate the in vivo effects of drugs on nerve terminal GABA. Treatment of rats with a convulsant dose of 3-MP (50 mg/kg i.p.) 3 min before decapitation significantly lowered synaptosomal GABA levels in olfactory bulb, hippocampus, thalamus, tectum, and cerebellum. The 3-MP-induced seizures and reduction of GABA levels could be prevented by administration of valproic acid (200 mg/kg i.p.) 15 min before the 3-MP injection. The data indicate that the improved synaptosome preparation offers a convenient method of preparing highly purified synaptosomes from a large number of small tissue samples and can provide useful information on the in vivo effects of drugs on regional GABA levels in nerve terminals. 相似文献