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1.
2.
Nitrous oxide (N2O) decreased in vivo oxidation of histidine in rats fed a basal diet marginally deficient in methionine, although hepatic levels of S-adenosylmethionine (AdoMet) were not significantly altered. Excess dietary methionine increased hepatic levels of AdoMet and increased histidine oxidation. However, it did not protect histidine oxidation when the rats were treated with N2O. Parenteral administration of methionine greatly increased hepatic levels of AdoMet and increased histidine oxidation in normal and N2O treated rats. This indicates that when hepatic levels of AdoMet are greatly elevated by administration of methionine, N2O does not affect in vivo histidine oxidation. 相似文献
3.
Summary Maximum lipase production byAspergillus foetidus was obtained from cultures grown in the medium of 2% olive oil and 0.5% sucrose. The optimal conditions for the production of lipases in the Multigen fermenters were found to be at 500rpm with an airflow of 1.5 liter per mimute. Immobilization of the fungal source was found to be infeasible in natural polymers. 相似文献
4.
It is shown for the first time that the content of ubiquinone of liver increases (2.5 fold) on dietary administration of the
widely-used industrial Plasticizer diethylhexyl Phthalate to the rat. The increase is localized almost entirely in mitochondria
in which the concentration of the quinone Per mg Protein is 1.7 times the control. IncorPoration of the radioactive Precursor
(acetate) reveals that the biosynthesis of ubiquinone is increased in the livers of Plasticizer-administered animals. The
rate of degradation is not altered. 相似文献
5.
Lectins, the divalent or polyvalent (glyco) proteins of non-immune origin of the cells agglutinate cells or other materials,
that display more than one saccharide of sufficient complementarity. Lectins considered ‘identical’ in terms of mono-and disaccharide
specificity can be differentiated by their ability to recognise the fine differences in more complex structures. The present
review discusses the interaction of lectins with various oligosaccharides and their resultant separations due to structural
variations. 相似文献
6.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
7.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
8.
The development of sclerotia of Botrytis cinerea was examined at four stages during their maturation. The surface structure developed a network of profusely branched hyphae through their coalescence to a compact sclerotial body which was maturated by the deposition of melanin pigment. A characteristic feature of the hyphal cells of B. cinerea during the later stages of development was the presence of paramural bodies (plasmalemmasomes and lomasomes). Electrondense bodies with a limiting double-membrane congregated against the transverse septa of hyphal cells as sclerotia matured and may migrate from cell to cell through septal pores. We suggest that these and the lipid bodies found in hyphal cells may have a storage function in the resting sclerotia. 相似文献
9.
The -galactosidase (EC 3.2.1.32) of Corynebacterium murisepticum (inducible by lactose and galactose) was purified by successive column chromatography on Sephadex G-200, DEAE-Sephadex A-50 and DEAE-cellulose (DE52). The enzyme was found to be a dimer of identical subunits of molecular mass 100,000 daltons. The K
m values of the enzyme for the substrates lactose and o-nitrophenyl--d-galactopyranoside (ONPG) are 16.7 mM and 4.4 mM, respectively, indicating, its low affinity for the substrates. The Ouchterlony immunodiffusion method exhibited immunological homogeneity of the enzyme preparation. The catalytic site of the enzyme does not take part in antigen-antibody reaction. 相似文献
10.
P R Taylor M H Schiffman D Y Jones J Judd A Schatzkin P P Nair R Van Tassell G Block 《Mutation research》1988,206(1):3-9
Correlation studies suggest that fecal mutagenicity is increased in groups eating high-fat diets, the same groups who are often found to have high colorectal cancer incidence and mortality. The fecapentaenes are the best characterized class of fecal mutagens, but the relationship of dietary fat intake to the excretion of these potent genotoxins is unknown. We studied the effect of changes in amount and type of dietary fat on fecapentaene levels in 31 premenopausal women 20-40 years of age who participated in a controlled feeding study. After a pre-diet free-living period lasting 1 menstrual cycle, women were placed on a high-fat (40% energy from fat) diet for 4 menstrual cycles and then switched to a low-fat (20% energy from fat) diet for an additional 4 menstrual cycles. One-half the subjects were maintained throughout the study at a ratio of polyunsaturated-to-saturated fatty acids (P/S ratio) of 1.0, the other half at 0.3; body weight was constant. All meals during the controlled diet periods were prepared at the Human Study Facility of the Beltsville Human Nutrition Research Center. Fecapentaene and fecapentaene precursor levels were measured in acetone extracts from 3-day pooled stool samples collected during the study. No differences in fecapentaene or precursor levels were observed between the high- and low-fat diets at either P/S ratio. Fecapentaene and precursor levels were higher while on controlled diets than during the pre-diet free-living period, and levels declined again in the post-diet free-living period. We conclude that dietary fat has no significant effect on fecapentaene or precursor levels in acetone extracts of stool in premenopausal women. The effect of other dietary or non-dietary factors on fecapentaenes remains unknown. 相似文献