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31.
The kinetics of anaerobic degradation of a molasses wastewater were measured under constant pH conditions in a laboratory scale packed bed reactor. In continuous and batch experiments the formation and degradation rates of the organic acids (butyric, propionic and acetic) have been followed. The influence of hydrogen gas on the acid degradation rates has been measured and, contrary to the literature and the thermo-dynamic calculations, no inhibition was detected, biofilm diffusional effects may be the reason. Two dynamic simulation models were tested, a heterogeneous model, which considered the biofilm diffusion-reaction phenomena and a quasihomogeneous model with the same kinetics. Except for hydrogen, the diffusion effects were found to be negligible. Otherwise both models gave essentially the same results and the time profiles of acids, hydrogen, carbon dioxide and methane agreed relatively well with dynamic startup experiments. Batch experiments showed the acid concentrations to be highly sensitive to the initial molasses concentration. This aspect was not included in the model but is being investigated further. 相似文献
32.
Contact sensitization to components of the urushiol oils of poison oak and poison ivy appears to require covalent bond formation between the o-quinones derived from urushiol catechols and nucleophilic groups on proteins. Previous studies using a murine delayed hypersensitivity model demonstrated that 5-methyl-3-pentadecylcatechol (5-Me-PDC) is an epicutaneous tolerogen to the parent compound and a weak sensitizer to itself. To investigate further the structural requirements for sensitization vs suppression, 5,6-dimethyl-3-pentadecylcatechol (5,6-di-Me-PDC) and 4,5,6-trimethylpentadecylcatechol (4,5,6-tri-Me-PDC) were synthesized. The former compound is blocked at both preferred sites for covalent bond formation and the latter is completely blocked towards conjugate addition reactions. These compounds were tested for sensitizing and suppressive ability. Epicutaneous application of both analogs suppressed subsequent induction of sensitization to 3-pentadecylcatechol (PDC) and 3-heptadecylcatechol (HDC). Lymph node cells from animals treated with 5,6-di-Me-PDC could transfer suppression. The dimethyl analog, 5,6-di-Me-PDC, but not the trimethyl analog also exhibited weak sensitizing capacity. The urushiol analogs 5-pentadecylresorcinol (PDR) and 3-heptadecylveratrole (HDV) which cannot form o-quinones were found to be ineffective sensitizers as well. HDV in addition produced no blastogenesis in draining lymph nodes whereas lymph node cell proliferation induced by 4,5,6-tri-Me-PDC followed the same kinetics as previously observed for HDC. PDR elicited weak proliferation with a different time course. These and previous studies indicate that blocking the C5-position on the catechol ring favors the induction of suppression, although some sensitizing capacity may be retained. Covalent bond formation may not be necessary for the induction of active suppressor cell populations. 相似文献
33.
Column centrifugation generates an intersubunit disulfide bridge in Escherichia coli F1-ATPase 总被引:1,自引:0,他引:1
Passage of F1-ATPase through a centrifuge column [Penefsky, H. S. (1979) Methods Enzymol. 56, 527-530] caused formation of a product with a relative molecular mass of 72,000 as determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The product was identified as cross-linked alpha and delta subunits by using Western blots and subunit-specific monoclonal antibodies. The cross-link was reversed by 50 mM dithiothreitol implying that it was a disulfide bridge. Formation of the cross-link was inhibited by 2 mM EDTA and was stimulated in some buffers by the addition of 10 microM CuCl2. Time course experiments indicated that the majority of the cross-link formed while the enzyme was passing through the column. Thus the cross-link induced by column centrifugation arose from the rapid, heavy-metal-ion-catalysed oxidation of two sulfhydryl groups, one on the alpha subunit and one on the delta subunit, to a disulfide. These results demonstrate that care must be exercised when running proteins through centrifuge columns as potentially deleterious disulfide formation can result. An anti-beta monoclonal antibody was capable of immunoprecipitating the entire enzyme including the cross-linked subunits, implying that the cross-linked alpha and delta subunits were still a part of F1. The formation of the cross-link affected neither the hydrolytic activity of the enzyme nor its susceptibility to inhibition by epsilon subunit. The cross-linked enzyme was unable to bind to F1-depleted membranes in experiments in which soluble F1 and membranes were separated by centrifugation. Column centrifugation did not generate the cross-link on membrane-bound enzyme. These results indicate that the alpha-delta cross-link results in a loss of binding affinity between F1 and F0. 相似文献
34.
Factors affecting the reliability of the McMaster technique 总被引:3,自引:0,他引:3
Factors detracting from the reliability of faecal egg counts based on the McMaster technique include variation in flotation time (interval between loading chamber and counting eggs) and sample dilution (ratio of faecal material to salt solution). We recommend standardization of both these variables as normal laboratory procedure, and propose optima of a 30 minute flotation time and a sample dilution of 15 ml salt solution/g faeces for use of the McMaster technique in the estimation of the fecundity of Heligmosomoides polygyrus (Nematoda). 相似文献
35.
Anti-VPg antibody precipitation of product RNA synthesized in vitro by the poliovirus polymerase and host factor is mediated by VPg on the poliovirion RNA template. 总被引:11,自引:10,他引:1
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Antibody to the poliovirus genome-linked protein, VPg, specifically immunoprecipitated the product RNA synthesized in vitro by the poliovirus RNA polymerase and HeLa cell host factor when VPg-linked poliovirion RNA was used as a template. The largest product RNA that was immunoprecipitated was twice the size of the template RNA. The complete denaturation of the product RNA with CH3HgOH had no effect on the immunoprecipitation reaction. In contrast, CH3HgOH denaturation prevented the immunoprecipitation of the oligo(U)-primed product RNA. Immunoprecipitation of the product RNA synthesized in the host-factor-dependent reaction was prevented if VPg was removed from the template RNA by pretreatment with proteinase K or if an RNA template without VPg was used in the reaction. The results support our previous evidence that a covalent linkage exists between the labeled negative-strand product RNA and the VPg-linked template RNA and suggest that the purified polymerase and host factor initiated RNA synthesis in vitro in the absence of VPg or a VPg-precursor protein. 相似文献
36.
Production of pea lectin in Escherichia coli 总被引:2,自引:0,他引:2
In order to explore the molecular basis for the glycopeptide specificity of legume lectins, we have developed an experimental system in which specific amino acid alterations can be introduced into the carbohydrate binding site of pea lectin. This system is based on the production of pea lectin in Escherichia coli. The plasmid coding for the lectin was constructed from two lectin cDNA sequences isolated from Pisum sativum seeds (Higgins, T. J. V., Chandler, P. M., Zurawski, G., Button, S. C., and Spencer, D. (1983) J. Biol. Chem. 258, 9544-9549) and an expression vector based on the gene for the outer membrane lipoprotein of E. coli (Nakamura, K., and Inouye, M. (1982) EMBO J. 1, 771-775). The lectin is produced as a single polypeptide chain and forms insoluble aggregates in E. coli cells (2-5 mg/liter). Functional lectin is recovered by solubilization of the aggregates in guanidinium hydrochloride, renaturation in the presence of MnCl2 and CaCl2, and affinity purification on Sephadex. This procedure yields a homogeneous 28,000-dalton protein. Comparison of the recombinant lectin with natural pea lectin in an inhibition of hemagglutination assay demonstrated that there is no detectable difference in the carbohydrate binding properties of the two lectins. 相似文献
37.
Prominent early effects of irradiation include neutrophilic vasculitis and interstitial inflammation. To examine the role of the endothelium in these events, bovine aortic endothelial cells (EC) were irradiated (5 Gy) under ambient conditions followed by measurements of neutrophil chemotaxis toward conditioned media and adherence to EC. Neutrophil chemotactic activity increased at 4, 24, and 72 h in both the sham-treated (4.2 +/- 2.5, 15.2 +/- 4.8, and 20.0 +/- 2.7 microns, respectively) and irradiated EC-conditioned media (5.0 +/- 2.1, 18.7 +/- 4.5, and 24.1 +/- 3.4 microns, respectively), and the difference between them was significant at 72 h. The chemoattractant was trypsin sensitive, heat resistant, and chemotactic. It was not present in the EC sonicate. Adherence of neutrophils to EC that were irradiated 4 h earlier (19.3 +/- 4.2%) increased compared with controls (11.1 +/- 2.4%) and was similar to EC pretreated with zymosan-activated serum (22.0 +/- 4.0%), which is a potent inducer of adherence. Thus, following irradiation, bovine aortic EC have greater neutrophil chemotactic activity in their media and are more adherent to polymorphonuclear leukocytes. 相似文献
38.
The A, B, O, D, Du, C, c, E, e, M, N, S, s, Kell and Duffy antigens were determined on 190 blood samples from Hausas in the north of Nigeria. The highest gene frequencies in the rhesus system were cDe (0.648) and cde (0.176). Su gene frequency was 0.270. The great majority of subjects were Kell negative (98.9%) and Duffy negative (98.8%). As the MNSs group determinants are carried by glycophorins, which are also receptor sites for Plasmodium falciparum, and the Duffy antigen marks the receptor for P. vivax, the present study provides data of interest in the epidemiology and genetics of malaria. 相似文献
39.
Summary Fifteen lectin-horseradish peroxidase conjugates have been used in a comprehensive histochemical study of human skeletal muscle. The staining patterns of many lectins were found to be coincident with the known distributions of types I, III, IV and V collagen, fibronectin and laminin. One lectin,Bandeiraea simplicifolia (BSA I), selectively stained capillaries in a blood group-specific manner, the significance of which is unknown. The results show that although lectins are useful cytochemical probes for identifying tissue glycoconjugates, lectin binding is not solely determined by monosaccharide specificity as lectins which interact with the same sugars may have completely different staining patterns. Factors such as accessibility, glycan conformation and oligosaccharide sequence also affect lectin binding in tissues. For these reasons, we conclude that a comprehensive histochemical investigation of tissue glycoconjugates should employ a large number of lectins, preferably with overlapping sugar specificities. 相似文献
40.
Most of the mucosal epithelium in the anterior small intestine of B10A mice infected with Trichinella spiralis showed no cytopathology. However, isolated foci of damaged cells or dense masses of multinucleate cytoplasm were seen in the crypt-villus junction, or the base of the villi. Cells occupied by the nematode ranged from a nearly normal appearance, showing only compressed nuclei and organelles, to progressive inflation and vesiculation of endoplasmic reticulum, loss of terminal web and hence disoriented and reduced microvilli, and pycnosis of nuclei. Damaged cells and multinucleate cytoplasmic masses may be derived from the cells previously occupied by the nematode that were linked together by fusion of their lateral cell membranes. Damaged cells and multinucleate masses are apparently sloughed from the epithelium at the villus base without migrating up the villi. Eosinophils were seen in the lamina propria, in the mucosal epithelium (usually associated with damaged cells) and in the intestinal lumen (also with damaged cells). As no eosinophils were seen in contact with the nematode, their activities may be related more to the cells killed by the worm than to the worm itself. 相似文献