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991.
992.
993.
The effect of ten derivatives of carbonylcyanide phenylhydrazone on growth of bacteria, yeast and different species of filamentous
fungi was investigated. In yeast and mitochondria isolated from rat liver the effect of these derivatives on the respiratory
activity was also followed. The relative efficiency of the individual derivatives of earbonylcyanide phenylhydrazone was determined
on the basis of the results obtained. It was shown that derivatives, in which the substituent on the benzene ring causes simultaneously
an increase of acidity and lipophilicity of the derivative as compared with the non-substituted carbonylcyanide phenylhydrazone
(4-trifluoromethoxy-, 3-chloro-, 4-chloro and 3,4-dichloroderivatives) were most effective. 相似文献
994.
Separation and properties of α-mannosidase and mannanase from the basidiomycetePhellinus abietis 总被引:1,自引:1,他引:0
Proteins of a crude enzyme preparation obtained from the cultivation medium of the basidiomycetePhellinus abietis were separated by gel filtration and ion-exchange chromatography. The preparation contained a minimum of three enzymes capable
of splitting α-d-mannosidic bonds: α-mannosidase, exomannanase, and endomannanase, which were separated. Some properties of the mannanase
complex of the crude enzyme preparation, and of a partially purified α-mannosidase were examined. The mannanase complex exhibited
two pH optima, its temperature optimum being at 46 °C The pH optimum of purified α-mannosidase was at pH 5.0, the temperature
optimum was at 60 °C; the enzyme had a relatively high heat stability. The Km of α-mannosidase forp-nitrophenyl α-d-mannopyranoside was 1.5 x 10−5 M. Pure α-mannosidase did not split mannan. 相似文献
995.
Summary Microelectrode techniques were employed to study the mechanisms of the transepithelial voltage transients (V
ms
) observed during transmural current clamps in the isolatedNecturus gallbladder. The results indicate that: a) part of V
ms
is due to a transepithelial resistance change (R
t
), and part to a tissue emf change. b) R
t
is entirely caused by changes of the resistance of the paracellular pathway. At all current densities employed, the measured changes are probably due to changes in both fluid conductivity and width of the lateral intercellular spaces. At high currents, in addition to the effects on the lateral spaces, the resistance of other elements of the pathway (probably the limiting junction) drops, regardless of the direction of the current. c) The magnitude and polarity of the R
t
-independent transepithelial and cell membrane potential transients indicate that the largest emf change takes place at the basolateral membrane (E
b
), with smaller changes at the luminal membrane (E
a
) and the paracellular (shunt) pathway (E
s
). It is shown that two-thirds of the transient are caused by E
s
, and one-third by (E
b
–E
a
). E
s
can be explained by a diffusion potential generated by a current-dependent NaCl concentration gradient across the tissue. E
a
and E
b
are caused by [K] changes, mainly at the unstirred layer in contact with the basolateral membrane. 相似文献
996.
The cell-cell adhesion characteristic of C-6 astrocytoma cells changes as a function of cell density. Cell suspensions prepared from monolayers having a density lower than 1 × 105 cells/cm2 show maximal affinity for plasma membranes and cells obtained from monolayers at densities greater than 1 × 106 cells/cm2 shows minimal affinity for plasma membranes. The adhesive component retained on plasma membranes is present at essentially equal levels in membranes prepared from cells at different density. This modulation in cell surface affinity appears to be due to cell-cell contact and appears to represent a suitable model for the study of the modulation of cell-cell adhesion as a result of cell contact. 相似文献
997.
998.
Crystal-containing organelles in cells of virus infected plants lying at chloroplasts and mitochondria are identical with single membrane-bound microbodies containing crystals of catalase described in healthy plants. Massive complex inclusions caused by turnip mosaic virus very frequently contain the same microbodies with crystal inclusions; that phenomenon may be related to some pathophysiological changes of virus infected plants. Comparable proteinaceous crystals, but not lying within microbodies limited by a membrane, may also be found in cytoplasm of infected cells. These crystals are sometimes surrounded by a substance resembling the microbody matrix. Disintegrated cytoplasm of virus infected cells may also contain the same crystals lying free in “empty spaces”. Cytopathological effects responsible for this phenomenon and possible artifacts as well are discussed. 相似文献
999.
1000.
Judith Huerta-Bahena Rafael Villalobos-Molina J.Adolfo García-Sáinz 《Life sciences》1982,30(20):1757-1762
Cycloheximide, a widely used inhibitor of protein synthesis, stimulates glycogenolysis, gluconeogenesis and ureogenesis in isolated rat hepatocytes. The effects of cycloheximide were compared to those of norepinephrine. Both agents, cycloheximide and norepinephrine, produced slight increases in the levels of cyclic AMP (30% increases) which were blocked by propranolol. Interestingly, it was found that the metabolic actions of norepinephrine and cycloheximide (stimulation of glycogenolysis, gluconeogenesis and ureogenesis) were only slightly diminished by the β adrenergic antagonist propranolol but abolished by the selective α1 adrenergic antagonist prazosin. The ability of cycloheximide to inhibit protein synthesis was not affected by either prazosin or propranolol. It is concluded that the stimulation of glycogenolysis, gluconeogenesis and ureogenesis by cycloheximide in rat hepatocytes, is an effect of the antibiotic independent of its ability to inhibit protein synthesis and that is mediated through activation of α1 adrenoceptors. The adrenergic activity of cycloheximide should be considered when this drug is used as an inhibitor of protein synthesis. 相似文献