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1.
Twenty-eight strains of pectolytic clostridia were isolated from sugar beet pulp silages. Seventeen non-pigmented strains were presumed to be Clostridium acetobutylicum ; the remaining 11 pigmented strains were similar to Cl. felsineum. The addition of molasses to sugar beet pulps favoured the growth of other bacteria, particularly lactic acid organisms, whereas pectolytic clostridia were only occasionally found. The pectolytic clostridia promoted the structure loss of simulated silages. The use of molasses in sugar beet pulp ensiling was suggested to prevent texture loss of the ensiled mass. 相似文献
2.
S Papa M Vitale G Mazzotti R Rizzoli M Falconi A Bartoletti F A Manzoli 《Histochemistry》1988,89(3):241-245
A number of techniques are currently employed for the fractionation of heterogeneous cell populations or for the separation of cells in different phases of their cycle. With the development of osmotically inert colloidal silica particles media, density gradient centrifugation became an established method for the separation and purification of cells and subcellular particles. We have applied this technique to the separation of cycling from resting Friend erythroleukemia cells, to obtain purified populations for further biological assays. The flow cytometric analysis of DNA content of the different fractions obtained by the gradient and stained with Propidium Iodide (PI), showed the S compartment highly concentrated in the 1.073/77 g/ml interface, while the upper levels of the gradient were highly enriched of cells in G1 phase. Moreover, the dual parameter analysis of DNA content by means of Bromodeoxyuridine (BrdUrd) incorporation and PI staining, showed that part of the cells in the 1.067/73 fraction represented the early S phase even if their DNA level, measured on the basis of PI fluorescence was within the diploid cell cluster. This method seems to be suitable to obtain pure cell fractions even when dealing with numerically large populations. 相似文献
3.
J Hupert S Mobarhan T J Layden V M Papa D J Lucchesi 《Biochimie et biologie cellulaire》1991,69(8):509-514
Enzymatic conversion of retinal to retinoic acid in rat liver cytosol was detected using a rapid and sensitive assay based on high pressure liquid chromatography (HPLC). This retinal oxidase assay system did not require extraction steps or any other manipulation of the sample mixture once the sample vial was sealed for incubation. The product (retinoic acid) and the reactant (retinal) were separated by HPLC in 14.0 min with a sensitivity of 15 and 40 pmol per injection for retinoic acid and retinal, respectively. Enzymatic activity was observed to be linear with protein concentration (0-2.4 mg/mL) and time (0-30 min) and displayed a broad pH maximum of 7.7-9.7. The enzyme exhibited Michaelis-Menten single-substrate kinetics with an apparent Km of 0.25 mM. The average specific activity in nine normal rats was 35.6 +/- 3.3 nmol retinoic acid formed/h per mg protein. Incubation of the enzyme with zinc did not affect the rate of retinoic acid synthesis. Dithiothreitol inhibited the reaction. Both NAD and NADH stimulated retinoic acid formation. Formation of retinol was also observed when these pyridine nucleotides were added to the reaction mixture, indicating the presence of retinal reductase activity. The results of kinetic studies suggest that NADH may act indirectly to stimulate retinoic acid formation. 相似文献
4.
S Papa S Capitani A Matteucci M Vitale P Santi A M Martelli N M Maraldi F A Manzoli 《Cytometry》1987,8(6):595-601
The development of hepatocyte polyploidy in rats aged up to 4 months was analyzed by flow cytometry using both scatter and fluorescent parameters to distinguish DNA diploid and DNA tetraploid populations and to discriminate between parenchymal and non-parenchymal compartments. The precise origin of each class of nuclei was assessed in whole liver homogenate using purified hepatocytes, obtained by liver perfusion followed by separation on Percoll gradient, and identifying the peaks corresponding to parenchymal nuclei. The results indicate that preparative procedures involving homogenization of the rat liver tissue caused loss of the DNA octaploid population. Data on the relative proportion of the different DNA ploidy elements during rat liver development, which are in good agreement with those observed by cell analysis by means of microspectrophotometry, indicate the usefulness of flow cytometry as a choice method for the analysis of ploidy distribution. 相似文献
5.
Genetics of Aspergillus flavus: linkage of aflatoxin mutants 总被引:6,自引:0,他引:6
K E Papa 《Canadian journal of microbiology》1984,30(1):68-73
Eight aflatoxin (afl) mutants of Aspergillus flavus were induced with N-methyl-N'-nitro-N-nitrosoguanidine. Heterozygous diploids formed between afl mutants and tester strains revealed that each afl mutant was recessive. Haploids selected from these heterozygous diploids indicated the linkage of all eight afl mutants to markers on group VII. These include previously mapped arg-7 (arginine), leu (leucine), dominant afl-1, and nor which accumulates norsolorinic acid that is visible as an orange-red pigment. Diploid complementation tests indicated that all but two afl mutants were nonallelic. Diploids homozygous for nor, resulting from crossing-over, were isolated and used to map new afl genes. 相似文献
6.
N M Maraldi F Marinelli A Galanzi N Zini A Ognibene R Del Coco A Matteucci S Papa 《Biology of the cell / under the auspices of the European Cell Biology Organization》1986,56(1):31-39
The morphology of intact or membrane-deprived interphase nuclei has been analysed by freeze-fracture electron microscopy. This method appears particularly useful for providing information on the distribution and organisation of chromatin and ribonucleoproteins in the absence of dehydration and embedding artifacts of conventional electron microscope techniques which, among other effects, appear to affect heterochromatin distribution, inducing its aggregation along the nuclear envelope. The main levels of chromatin superstructure, from nucleosome to solenoid fibres, are detectable in the replicas of freeze-fractured nuclei on the basis of the size of their shadow, a parameter particularly suitable for automated image analyses. 相似文献
7.
Experimental observations reveal a number of characteristics of the redox-linked proton ejection from cytochrome c oxidase vesicles, which apparently cannot be explained by a proton pumping activity of the oxidase. These observations seem, on the other hand, to provide useful elements for alternative explanation(s) of the proton ejection. It is proposed here that the process is scalar and not vectorial and can derive from redox-linked rupture of protonated salt-bridges in the oxidase-lipid complex. 相似文献
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