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21.
22.
Taurine entered the alga Chlorella fusca Shihira et Krauss strain 21l-8b via a pH and energy-dependent system ("permease"). Transport followed triphasic kinetics from 10−6 to 10−2 M with Km values for taurine of 5.4 × 10−5 , 4.1 × l0−4 and l.5 × 10−3 M. This uptake system was specific for sulfonic acids and showed no affinity for α- and β -amino acids or Na+ ; thus the permease of C. fusca is different from all known taurine transport systems with respect to structural specificity and lack of Na+ -dependence. Uptake was not observed in sulfate-grown algae but developed as a response to sulfate limitation within 2 h. Sulfate addition caused a rapid decline in taurine transport capacity. Labeled taurine was rapidly metabolized in C. fusca to sulfate and ethanolamine, suggesting oxidative hydrolysis as the mechanism of C-S bond cleavage. Further incorporation of these catabolic products in C - and S -metabolism was demonstrated. Taurine catabolism was also detected in other green algae and some cyanobacteria. 相似文献
23.
Summary The uptake of deoxyguanosine by rat liver mitochondria was characterized. The process required an intact mitochondrial membrane and exhibited a dependence on added phosphate. Deoxyguanosine uptake was minimally influenced by Mg2+ or Mn2+, but Ca2+ at concentrations above 0.5 mM were detrimental. Of the deoxynucleosides tested, only deoxyinosine inhibited the uptake of deoxyguanosine. The ribonucleoside guanosine was not observed to compete with its deoxynucleoside analog. Known inhibitors of nucleoside transport, cytochalasin B and NBMPR, did not block deoxyguanosine uptake, but the sulfhydryl reagents NEM and pCMB were both inhibitory. The uptake of deoxyguanosine was shown to be a saturable process and an apparent Km of 0.64 M was calculated from a Hanes plot. 相似文献
24.
C. M. B. Duwel F. C. Visser M. J. van Eenige J. P. Roos 《Molecular and cellular biochemistry》1989,88(1-2):191-194
Summary Under normal and ischemic conditions backdiffusion of radiolabeled non-esterified fatty acids (NEFA) has been demonstrated. In the fasted normal canine heart the extraction fraction (EF) during interventions with glucose or lactate loading, vasodilation, and metabolic level augmentation was determined, and compared with the control EF. Backdiffusion alterations were deduced from the EF changes. After iv injection of 17-iodo-131 heptadecanoic acid (IHDA), 11 blood samples were drawn from aorta and coronary sinus in a time period of 60 minutes. In the control and vasodilation group the EF slowly decreased from 40 to 10%. In contrast, the EF in the noradrenaline group was constant. During glucose and lactate infusion the EF became negative within 10 min and remained negative. These results suggest that during physiological circumstances backdiffusion is determined by the metabolic level of the heart and its substrate availability. 相似文献
25.
This report deals with the modulation of activity and expression of the hepatic asialoglycoprotein receptor, in pregnant or diethylstilbestrol-treated rats.The results show a two-fold increase in the total cell associated binding activity, both in pregnant and in estrogen-treated animals, with respect to normal values. On the contrary the surface expression was shown to be strongly enhanced only in the liver of pregnant rat. Therefore the modulation shown by this receptor system in pregnancy seems to be only partially estrogen-dependent. 相似文献
26.
We studied in the rat the effects of the drug etretinate (Tigason), given at three doses 3, 10, and 30 mg/kg body wt for 1 mo, on the concentrations of Na, K, Ca, Mg, Fe, S, P, Cu, and Zn in the plasma, brain, thymus, heart, liver, lung, kidney, testicle, muscle, and bone. The elements were simultaneously determined in tissues after nitric acid dissolution by inductively coupled plasma emission spectrometry using a JY 48 instrument. At the dose of 3 mg/kg, etretinate did not induce any statistically significant modifications of the element distribution. At the dose of 10 mg/kg, the main observed modifications were in plasma an increase of copper (+38%) and a decrease of zinc (-25%). At the highest dose of 30 mg/kg, some variations of the concentrations of elements in tissues were observed. But, on no account did retinoids induce an alteration of the mineral composition of bone, despite obvious macroscopic bone alterations. 相似文献
27.
Cell extracts (27000xg supernatant) of acetate grown Methanosarcina barkeri were found to have carbonic anhydrase activity (0.41 U/mg protein), which was lost upon heating or incubation with proteinase K. The activity was inhibited by Diamox (apparent K
i=0.5 mM), by azide (apparent K
i=1 mM), and by cyanide (apparent K
i=0.02 mM). These and other properties indicate that the archaebacterium contains the enzyme carbonic anhydrase (EC 4.2.1.1). Evidence is presented that the protein is probably located in the cytoplasm. Methanol or H2/CO2 grown cells of M. barkeri showed no or only very little carbonic anhydrase activity. After transfer of these cells to acetate medium the activity was induced suggesting a function of this enzyme in acetate fermentation to CO2 and CH4. Interestingly, Desulfobacter postgatei and Desulfotomaculum acetoxidans, which oxidize acetate to 2 CO2 with sulfate as electron acceptor, were also found to exhibit carbonic anhydrase activity (0.2 U/mg protein). 相似文献
28.
The in vitro acetylation of HMG proteins was studied using liver slices of young (18-week) and old (138-week) male rats. Acetylation of total HMG proteins is lower in old age. The incorporation of (14C) acetate into individual HMG proteins varies remarkably with advancing age. Whereas acetylation of high mol. wt. proteins (HMG 1 and 2) is higher, that of low mol. wt. proteins (HMG 14 and 17) is lower in the liver of young rats as compared to the old ones. Spermine stimulates the acetylation of HMG 1 and 14 in young and HMG 1, 2 and 14 in old age. It inhibits the acetylation of HMG 17 in both ages. Dexamethasone decreases the level of incorporation of (14C) into HMG 1 and 17 in young and HMG 14 and 17 in old rats. On the other hand, it stimulates the acetylation of HMG 14 by two-fold in young and that of HMG 1 and 2 by more than three-fold in old rats. Such alteration in the acetylation of HMG proteins may account for age-related changes in the structure and function of chromatin. 相似文献
29.
Hepatic coma was induced in rats chronically treated with CCl4, by means of a single injection of ammonium acetate. The activities of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T), as well as the synaptosomal uptake and release of [3H]GABA, were measured in the following brain areas of the comatose rats: cortex, striatum, hypothalamus, hippocampus, midbrain and cerebellum. Hepatic coma was associated with a general decrease of GAD activity, whereas GABA-T activity was diminished only in the hypothalamus, striatum and midbrain. During hepatic coma, the K+-stimulated [3H]GABA release was notably diminished in the striatum and cerebellum, whereas a significant increase was observed in the hippocampus. [3H]GABA uptake increased in most regions after CCl4 treatment, independently of the presence of coma. The results indicate that GABAergic transmission seems to be decreased in most cerebral regions during hepatic coma. 相似文献
30.
Immunocytochemical investigations on the presence of neuron-specific antibodies in the CSF of Parkinson's disease cases 总被引:2,自引:0,他引:2
A. McRae-Degueurce L. Rosengren K. Haglid S. Bööj C. -G. Gottfries A. C. Granérus Dr. A. Dahlström 《Neurochemical research》1988,13(7):679-684
The CSF and sera of 7 patients with Parkinson's disease were investigated immunocytochemically, in order to see if antibodies were present which recognized DA-ergic cell bodies in glutaraldehyde fixed rat brain. In 2 patients a marked labeling of DA-ergic neurons in the substantia nigra was observed, identified by anti-DA antiserum and by 6-OHDA induced degeneration, but also other neurons in the ventral mesencephalon were recognized. The other patients were weakly positive or negative. Sera gave unspecific labelling of all neurons. In one patient the sub-classes of IgG were investigated and found to be of IgG3 (labeling nerve terminals) and of IgG1–2, low affinity type (recognizing perikarya). The epitopes recognized have not been identified, but are unlikely to be DA-like, since blocking experiments and ELISA-tests gave negative results. The possible clinical importance of the results are discussed.Special Issue dedicated to Prof. Holger Hydén. 相似文献