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201.
The transport of carnitine by rat kidney cortex slices against a concentration gradient has been demonstrated. Similarities to other transport systems included a linear period of uptake, as well as indications of saturability of the system with increasing concentrations of substrate. The transport of carnitine was inhibited by anoxia, and carbonyl cyanide-m-chloro-phenylhydroxazone (CCC1P), an uncoupler of oxidative phosphorylation. Carnitine uptake was stimulated approximately 50% when kidney slices were treated with dibutyryl cAMP. 相似文献
202.
203.
Automated determinations of 5-hydroxytryptamine and its main metabolite, 5-hydroxyindoleacetic acid, have been described (Technicon autoanalyzer). The determinations are based on an extraction procedure from deproteinized tissue extracts or cerebrospinal fluid by means of butanolheptane mixtures. The indoles are transferred from the organic phase to a water phase and determined fluormetrically with the cysteine-o-phthaldialdehyde method. The method is highly sensitive: solutions containing 1 ng/ml can be reproducibly determined. Twenty samples per hour can be passed through the system. The determination of both 5-hydroxyindoles is performed with the same manifold. 相似文献
204.
G. Kozianowski F. Canganella F. A. Rainey H. Hippe G. Antranikian 《Extremophiles : life under extreme conditions》1997,1(4):171-182
A novel thermophilic spore-forming anaerobic microorganism (strain Ab9) able to grow on citrus pectin and polygalacturonic
acid (pectate) was isolated from a thermal spa in Italy. The newly isolated strain grows optimally at 70°C with a growth rate
of 0.23 h−1 with pectin and 0.12 h−1 with pectate as substrates. Xylan, starch, and glycogen are also utilized as carbon sources and thermoactive xylanolytic
(highest activity at 70°–75°C), amylolytic as well as pullulolytic enzymes (highest activity at 80°–85°C) are formed. Two
thermoactive pectate lyases were isolated from the supernatant of a 300-l culture of isolate Ab9 after growth on citrus pectin.
The two enzymes (lyases a and b) were purified to homogeneity by ammonium sulfate treatment, anion exchange chromatography, hydrophobic chromatography and
finally by preparative gel electrophoresis. After sodium dodecylsulfate (SDS) gel electrophoresis, lyase a appeared as a single polypeptide with a molecular mass of 135 000 Da whereas lyase b consisted of two subunits with molecular masses of 93 000 Da and 158 000 Da. Both enzymes displayed similar catalytic properties
with optimal activity at pH 9.0 and 80°C. The enzymes were very stable at 70°C and at 80°C with a half-life of more than 60
min. The maximal activity of the purified lyases was observed with orange pectate (100%) and pectate-sodium salt (90%), whereas
pectin was attacked to a much lesser extent (50%). The K
m values of both lyases for pectate and citrus pectin were 0.5 g·l−1 and 5.0 g·l−1, respectively. After incubation with polygalacturonic acid, mono-, di-, and tri-galacturonate were detected as final products.
A 2.5-fold increase of activity was obtained when pectate lyases were incubated in the presence of 1 mM Ca2+. The addition of 1 mM ethylenediaminetetraacetic acid (EDTA) resulted in complete inhibition of the enzymes. These heat-stable
enzymes represent the first pectate-lyases isolated and characterized from a thermophilic anaerobic bacterium. On the basis
of the results of the 16S rRNA sequence comparisons and the observed phenotypic differences, we propose strain Ab9 as a new
species of Thermoanaerobacter, namely Thermoanaerobacter italicus sp. nov.
Received: May 25, 1997 / Accepted: June 5, 1997 相似文献
205.
A rapid, simple, and reproducible method for determination of iron in biological material is suggested using the oxidation of p-phenetidine hydrochloride with hydrogen peroxide in a reaction catalyzed by Fe(III) and activated by 1,10-phenanthroline. The high sensitivity of the reaction allows a single determination to be carried out with as much as 1–5 mg fresh tissue. 相似文献
206.
Gerhart Drews 《Archives of microbiology》1981,130(4):325-327
The name Rhodospirillum salexigens, spec. nov., was proposed for the strain WS 68, isolated by W. R. Sistrom at the Oregon coast from salt water. The spiral-shaped phototrophically or chemotrophically growing, salt demanding bacterium contains intracytoplasmic membranes arranged parallel to the cytoplasmic membrane. Bacteriochlorophyll a and spirilloxanthin are the major pigments. Growth occurs between 20 and 45°C at a neutral pH. The DNA base composition was 64 mol % guanine plus cytosine. The cell wall contains peptidoglycan and proteins but no glycolipids. 相似文献
207.
Analysis of the effects of cesium ions on potassium channel currents in biological membranes 总被引:3,自引:0,他引:3
Cesium ions block potassium channels in biological membranes in a voltage dependent manner. For example, external cesium blocks inward current with little or no effect on outward current. Consequently, it produces a characteristic N-shaped current-voltage relationship. We have modeled this result by single file diffusion of ions in a narrow channel spanning the membrane with a special blocking site in the channel for cesium ions. The model enables us to make detailed comparisons of the effects of cesium on potassium channels in different types of biological membranes. 相似文献
208.
Cardiomegaly was observed in rats severely intoxicated with ethanol for a 4 day period. It was apparent at 48 hours of treatment, a time at which cardiac protein was elevated and continued into withdrawal. During a 4 day abstinence period the degree of hypertrophy declined towards normal. Cardiac noradrenaline was reduced at the 48 hour time of intoxication, then increased gradually in the further experimental period. As the cardiac hypertrophy occurs at a time that urinary catecholamines are elevated and the adrenal medulla is intensely stimulated, it is proposed that increased levels of circulating catecholamines are largely responsible for the enlargement of the heart. 相似文献
209.
210.
A large series of mouse monoclonal antibodies was found to inhibit the proliferation of T-cell growth factor (TCGF)-dependent human T-cell blasts as measured by the incorporation of tritiated thymidine. The specificity of the antibody appeared to be irrelevant for inhibition and two T-cell-specific antibodies did not prevent the absorption of TCGF by treated T cells. It is suggested that the antibodies function by the indirect release of suppressor factors by Fc receptor-bearing TCGF-dependent cells. 相似文献