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A Weber

Publications and source records attributed to A Weber.

At least 541 records · Page 30Linked to original sources
PubMed1981

Cooperativity of the calcium switch of regulated rabbit actomyosin system.

The concentration range required for calcium activation of skeletal myofibrillar ATPase activity has previously been attributed to simultaneous binding of two calcium ions to each troponin. We present data representative of the majority of myofibrillar preparations and data with acto subfragment-1 (S-1) whose calcium activation of ATPase activity occurs over a much too narrow range of calcium concentrations to be so explained. S-1 binding significantly broadened the range of Ca2+ concentrations over which activation occurred but not to the extent that is associated with simultaneous binding of 2 calcium ions.

Actins↗
PubMed1981

7-Chloro-4-nitrobenzeno-2-oxa-1,3-diazole actin as a probe for actin polymerization.

Lysine 372 of N-ethylmaleimide actin was specifically (60%) labeled by 7-chloro-4-nitrobenzeno-2-oxa-1,3-diazole chloride (NBD-Cl), which also reacted with lysines on cyanogen bromide fragment 17 (20%) and other undetermined residues (20%). Isolation of N-ethylmaleimide peptides and two-dimensional peptide mapping demonstrated that 90% of bound N-ethylmaleimide was attached to an adjacent residue, cysteine 373, independent of the polymerization state of actin during the labeling reaction. Formation of NBD cysteine severely inhibited lysine modification. After N-ethylmaleimide blockage of cysteine 373, lysine labeling with NBD was greatly accelerated. The kinetics of formation of fluorescent compounds were biphasic, with fluorescence decreasing upon prolonged incubation of actin in NBD-Cl. Lysine 372 of purified NBD actin reproducibly responded to polymerization by a 2.2- to 2.3-fold enhancement of fluorescence. By contrast, interaction of NBD actin with several actin-binding proteins caused only very small or undetectable changes in fluorescence intensity: 10% enhancement on myosin subfragment 1 binding, about 6% quenching by DNase I, and no change at all by tropomyosin-troponin. Despite its sensitivity to polymerization the probe did not affect it. Native and modified actin polymerized randomly indicating that the rate constants for polymerization remained the same. Labeling actin with NBD did not diminish its cofactor activity for myosin ATPase activity. Contrary to previous reports we observed that myosin subfragment 1 (single myosin heads) caused actin polymerization in the absence of salt.

4-Chloro-7-nitrobenzofurazan↗
PubMed1981

Cell types involved in the expression of foetal aldolases during rat azo-dye hepatocarcinogenesis.

Cellular and subcellular immunolocalization of aldose isozymes and alpha-foetoprotein (AFP) was performed in rat liver during the different stages of carcinogenesis induced by 3'-methyl-4-dimethylaminoazobenzene. During the early stages, double-labelling experiments showed that oval and transitional cells that expressed foetal aldolases did not contain adult aldolase B; this isozyme was only found in small and "normal' hepatocytes. AFP was present in transitional cells and in small hepatocytes. During hyperplastic nodule development, neither foetal aldolases nor AFP were located in hepatocytes. These foetal proteins were still observed in transitional cells. In hepatocellular carcinomas, both foetal proteins (aldolase isozymes and AFP) and adult aldolase B were present in malignant cells. Moreover, during the different stages foetal aldolases were also found in sinusoidal cells. These results indicate that, during azo-dye hepatocarcinogenesis, (a) several cell types synthesize foetal aldolases: oval and transitional cells, hepatoma cells and sinusoidal cells; (b) only hepatoma cells and not hepatocytes located in hyperplastic nodules can express both foetal and adult aldolases. This suggests that in primary, as in transplanted, hepatoma the resurgence of foetal isozymes is the consequence of a disturbance of control gene expression.

Animals↗
PubMed1981

Differential effect of several inducers on hepatic and mammary benzo(A)pyrene metabolism in rat and hamster.

Rat and hamster mammary gland, in comparison with the liver, were examined for their in vitro ability to metabolize polycyclic aromatic hydrocarbons, and for the effects of pretreatment with various mixed function oxidase inducers on this metabolism. Hamster mammary microsomal benzo(a)pyrene (BP) hydroxylase activity was 4-fold greater than that in the rat, and this activity was induced 3- to 5-fold in the hamster, and 7- to 13-fold in the rat, by pretreatment with 7,12-dimethylbenz(a)anthracene, beta-naphthoflavone, Aroclor 1254 or 3-methylcholanthrene. Hamster hepatic microsomal BP-hydroxylase activity was 80-fold greater than in the rat. Whereas pretreatment with these enzyme inducers enhanced rat hepatic activity by 20- to 30-fold, little effect of "inducers" was observed on the hamster hepatic enzyme, even when the formation of the various BP metabolites was determined by high pressure liquid chromatography.

Animals↗
PubMed1981

Correlation of blood lymphocyte nuclear pocket prevalence with enzootic bovine leukemia p24 viral antibody titers.

The quantitative relationship between radioimmunoassay serotiters to p24 enzootic bovine leukemia viral antigen and the prevalence of lymphocytic nuclear pockets (LNP) was studied in 554 clinically normal dairy cows and bulls. Of the animals, 69% were seronegative. Of the seronegative animals, 44% had no observed LNP, whereas 93% of the seronegative animals had less than 1% LNP. However, 2.3% of the seronegative animals had substantially increased (greater than 2%) numbers of LNP, and conversely, 24% of the seropositive animals had no observed LNP. Statistical evaluation of the data, using contingency table and regression methods, provide significant (P less than 0.0001) evidence for a positive association between LNP prevalence and p24 bovine leukemia viral serotiters. Although significant, the association was weak, and hence LNP number had little value for predicting serotiter.

Animals↗
PubMed1981

[Comparison of two enrichment methods and five selective media for the isolation of Yersinia enterocolitica from tonsils of slaughter pigs (author's transl)].

115 tonsils of healthy slaughter pigs were culturally examined for presence of Yersinia (Y.) enterocolitica. For this purpose each sample was enriched both in phosphate buffered saline solution (pH 7.6; stored at 4 degrees C and plated every week, thrice all together) and modified Rappaport broth (plated after an incubation of two days at 22 degrees C). Each such enrichment was plated on 5 different selective media: Yersinia selective agar proposed by Wauters (1973), deoxycholate-citrate-mannitol agar (Saari and Jansen, 1979), pectin agar (Bowen and Kominos), MacConkey and Leifson agar as used in the routine, diagnostic of Enterobacteriaceae. Each agar plate was incubated at 28 degrees C for two days. By cold enrichment method were isolated 11 strains of human pathogenic Y. enterocolitica (9 X O-group I syn. serotype O:3; 2X O-group V syn. serotype O:9). With the modified Rappaport medium were recovered 33 strains (24X O-group I, 9 X O O-group V). The most recoveries were done over the Yersinia selective agar with 65.2%, then followed deoxycholate-citrate-mannitol agar with 57.6%, Leifson agar with 45.5%, MacConkey agar with 42.3% and pectin agar only with 18.2% of the isolations. Not only the type of enrichment medium has a marked effect in the recovery efficiency of Y. enterocolitica out of samples but also number and type of the used selective media on which the enrichment is plated.

Abattoirs↗
PubMed1981

[Isolation of H2S-producing escherichia coli from urine samples (author's transl)].

The correct identification of isolated E. coli strains is usually without problems in the bacteriological routine diagnostic. We recently isolated H2S-producing strains from urine samples of two patients. 4 strains isolated at different times from one patient were serotyped, as O21:H25 and 2 strains from another patient belonged to the serotype O86:H-. The isolates biochemically differed both in the reaction of ornithine decarboxylase and in the fermentation of sucrose (Table 1). Differences were ascertained in the agar diffusion test in the sensitivity against discs of ampicillin, carbenicillin, chloramphenicol, tetracycline and trimethoprim-sulfamethoxazole (Table 2). The present knowledge of the mechanisms for producing H2S by E. coli is discussed.

Aged↗
PubMed1981

[Seasonal isolation of Yersinia enterocolitica and Yersinia pseudotuberculosis from tonsils of healthy slaughter pigs (author's transl)].

45 strains of Yersinia (Y.) enterocolitica from which 36 respectively 9 belonged to O-group I or V and 28 strains of Y. pseudotuberculosis from which 15 respectively 13 isolates belonged to serotype I or II were isolated from 70 tonsils of 480 examined, clinically healthy slaughter pigs. In the tonsils of three animals were found both species together. Y. enterocolitica was isolated during the whole year, but especially in the months of November (17.5%) and December (32.5%). Y. pseudotuberculosis was found during the time of winter and spring, most frequently in the months of January (30%) and December (17.5%). The bacteriological findings and the possible significance for human infections are discussed.

Abattoirs↗
PubMed1981

Chloramphenicol succinate pharmacokinetics in Macaca nemestrina: dose dependency study.

Chloramphenicol succinate ester in doses equivalent to 25, 100 and 250 mg/kg of chloramphenicol were administered by rapid i.v. infusion in a randomized crossover fashion to five adolescent ((18-36 month) male Macaca nemestrina monkeys. Thirteen serum samples and all voided urine were collected over a 5- to 6-hr period. Urinary excretion of unhydrolyzed ester was independent of dose and averaged 26.3 +/- 6.2% of the administered dose. Dose dependency was observed for the elimination rate constant, total body clearance and metabolic clearance of chloramphenicol succinate. Dose dependency was also observed for the apparent volume of distribution, total body clearance, metabolic clearance and time to peak concentration of chloramphenicol. Although significant dose dependency of various pharmacokinetic parameters ws demonstrated, the peak chloramphenicol concentration and the elimination rate constant of chloramphenicol after administration of chloramphenicol succinate showed no significant dose-dependent changes. Therefore, peak chloramphenicol concentrations would be expected to reflect changes in dose in a linear or proportional manner.

Animals↗