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991.
Maintenance and reversibility of active albumin secretion by adult rat hepatocytes co-cultured with another liver epithelial cell type 总被引:19,自引:0,他引:19
C Guguen-Guillouzo B Clément G Baffet C Beaumont E Morel-Chany D Glaise A Guillouzo 《Experimental cell research》1983,143(1):47-54
When adult rat hepatocytes were co-cultured with another liver epithelial cell type in a medium supplemented or not with fetal calf serum (FCS), it was found that 1. They survived for more than 2 months 2. Albumin secretion levels remained high over the whole culture period 3. Decreased secretion might be reversed 4. This protein secretion activity appeared to be dependent upon both the presence of cell-cell contacts and the production of an extracellular material. The results demonstrate for the first time long-term stabilization and reversibility of a specific function (albumin secretion) at high levels by adult hepatocytes cultured in serum-free medium and suggest that both the presence of other liver cell type(s) and the production of an extracellular matrix are needed for the maintenance of specific functions in cultured hepatocytes. 相似文献
992.
Clathrin-associated proteins contain bound nucleotide 总被引:2,自引:0,他引:2
An alcohol dehydrogenase isolated from Zymomonas mobilis was found to be activated by ferrous ions but not by zinc, after inactivation with metal-complexing agents. Cobaltous ions also re-activated to a lesser extent. It is suggested that in this species the alcohol dehydrogenase naturally contains iron. Kinetic studies on the iron-treated enzyme indicate an 'alcohol activation' phenomenon, which may have physiological relevance in overcoming product inhibition during fermentation. 相似文献
993.
Trypanosoma cruzi: 4-aminopyrazolopyrimidine in the treatment of experimental Chagas' disease 总被引:1,自引:0,他引:1
JoséLuis Avila Angela Avila Edgar Mun̄oz Héctor Monzón 《Experimental parasitology》1983,56(2):236-240
An allopurinol metabolite, 4-aminopyrazolopyrimidine, was tested on two different strains of mice (NMRI-IVIC and C57Bl/6J) that had been infected 4 days earlier with the virulent Ya strain of Trypanosoma cruzi. Low doses of 4-aminopyrazolopyrimidine (0.125-0.500 mg/kg body wt/day) for 10 days induced a significant reduction in parasitemia (direct counts and subinoculation experiments) and increased survival time (without any evidence of toxicity) compared with untreated animals. When tested in vitro, 4-aminopyrazolopyrimidine was sixfold more active than allopurinol as a trypanostatic drug. The low therapeutic doses of 4-aminopyrazolopyrimidine suggest that this drug may be useful in the treatment of acute Chagas' disease. 相似文献
994.
The effects of nine drugs on the CD spectra of a synthetic calcium binding analog of site III of rabbit skeletal troponin C, can generally be divided into 3 groups: (1) that consisting of haloperidol, benperidol, molindone and promethazine, had no effect on the CD spectrum or calcium sensitivity of the apopeptide; (2) that composed of structurally rigid thioxanthenes, induced CD-detectable structural change in the apopeptide but prevented Ca2+-induced structural change; (3) that consisting of chlorpromazine, trifluoperazine and fluphenazine, induced structural change in the peptide but had no effect on the Ca2+-induced structural change. 相似文献
995.
PPi driven ATP synthesis has been reconstituted in a liposomal system containing the membrane-bound energy-linked PPiase and coupling factor complex, both highly purified from Rhodospirillum rubrum. This energy converting model system was made by mixing both enzyme preparations with an aqueous suspension of sonicated soybean phospholipids and subjecting to a freeze-thaw procedure. In the presence of ADP, Mg2+, Pi and PPi the system catalyzed phosphorylation by up to 25 nmol ATP formed X mg protein-1 X min-1, at 20 degrees C, which was sensitive to uncouplers and inhibitors of phosphorylation such as oligomycin, efrapeptin and N,N'-dicyclohexylcarbodiimide. 相似文献
996.
997.
A chronic intoxication with carbaryl, fenthion and lindane was induced in young snails. The parameter k of the von Bertalanffy's equation showed clearly the growth changes induced by these insecticides. In all cases the fecundity of intoxicated snails was reduced. Among these three insecticides, lindane was the most toxic, carbaryl the least. 相似文献
998.
Acute toxicity and degradation of an aqueous suspension of Thiram were studied in Cloeon dipterum. Lethal concentrations for 50% of the larvae (LC 50) after 24 to 96 h of exposure and thresholds were calculated. LC 50 varied from 0.39 to 1.92 mg·l?1 according to the time and the physiological state of the larvae. It was demonstrated that: the sensitivity of the larvae increased with the time during which they were kept in the laboratory; while the toxicity of the aqueous suspension (1 mg·l?1) of Thiram decreased with time, another toxic product was formed. 相似文献
999.
N Ellfolk M R?nnberg R Aasa L E Andréasson T V?nng?rd 《Biochimica et biophysica acta》1983,743(1):23-30
The oxidation-reduction potentials of the two c-type hemes of Pseudomonas aeruginosa cytochrome c peroxidase (ferrocytochrome c:hydrogen-peroxide oxidoreductase EC 1.11.1.5) have been determined and found to be widely different, about +320 and -330 mV, respectively. The EPR spectrum at temperatures below 77 K reveals only low-spin signals (gz 3.24 and 2.93), whereas optical spectra at room temperature indicate the presence of one high-spin and one low-spin heme in the enzyme. Optical absorption spectra of both resting and half-reduced enzyme at 77 K lack features of a high-spin compound. It is concluded that the heme ligand arrangement changes on cooling from 298 to 77 K with a concomitant change in the spin state. The active form of the peroxidase is the half-reduced enzyme, in which one heme is in the ferrous and the other in the ferric state (low-spin below 77 K with gz 2.84). Reaction of the half-reduced enzyme with hydrogen peroxide forms Compound I with the hemes predominantly in the ferric (gz 3.15) and the ferryl states. Compound I has a half-life of several seconds and is converted into Compound II apparently having a ferric-ferric structure, characterized by an EPR peak at g 3.6 with unusual temperature and relaxation behavior. Rapid-freeze experiments showed that Compound II is formed in a one-electron reduction of Compound I. The rates of formation of both compounds are consistent with the notion that they are involved in the catalytic cycle. 相似文献
1000.
In vitro cleavage specificity of the adenovirus type 2 proteinase 总被引:10,自引:0,他引:10
Two in vitro proteinase assay systems were developed and used to study the peptide bond specificity and substrate specificity of the adenovirus endoproteinase. Five adenovirus precursor proteins (PVI, PVII, PVIII, 87K, 11K), all found in the virion of the ts1 mutant grown at the nonpermissive temperature, were digested by the proteinase. All, except 11K, were cleaved to their mature counterparts. Some of the proteins, particularly the 87K terminal protein, were processed via cleavage intermediates similar to those found in vivo. The data suggest that the proteinase specifically hydrolyses Gly-Ala bonds. The high specificity for the natural substrates and the failure to cleave foreign proteins suggest that cleavage activity is determined not only by primary sequence but also by other physical features of the substrate. Enzyme activity was inhibited by diisopropylfluorophosphate, showing that it is a serine proteinase. 相似文献