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31.
32.
Stomatal movement in Zea mays: Shuttle of potassium and chloride between guard cells and subsidiary cells 总被引:2,自引:2,他引:0
Summary When stomates of Zea mays open K and Cl migrate from the subsidiary cells into the guard cells; when the stomates close both elements return to the subsidiary cells. Subsidiary cells function as reservoirs for K and Cl. Import of K and Cl into the guard cells and loss of both elements from the guard cells become observable 1 or 2 min after light is turned on or off, both when histochemical methods and the electron-probe microanalyzer are used for detection. Each stomatal complex of maize contains on the average 10±3×10-13 gram equivalents (eq) of K and 4±1×10-13 eq of Cl. Guard cells accumulate K in the light and CO2-free air at an average rate of 10×10-15 eq K per minute, and Cl at approximately half that rate. 相似文献
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34.
DISTRIBUTION OF PEROXISOMES (MICROBODIES) IN THE NEPHRON OF THE RAT : A Cytochemical Study 总被引:24,自引:9,他引:15 下载免费PDF全文
The distribution of peroxisomes (microbodies) in the rat nephron was studied cytochemically, using glutaraldehyde- or formaldehyde-fixed tissue, by means of α-hydroxy acid oxidase activity in light microscopy or oxidation of 3,3'-diaminobenzidine (DAB) at pH 9 in both light and electron microscopy.The two cytochemical methods show peroxisomes to be nearly sperical particles found only in cells of the proximal convoluted tubule. Lysosomes were identified in the same or parallel sections, with β-glycerophosphate or 5'-cytidylic acid as substrate. They are found in all cells of the nephron. These cytochemical methods visualize the two organelles for light microscopy; they also permit unequivocal differentiation of all kidney peroxisomes from lysosomes in electron micrographs. Peroxisomes are larger and more reactive in the cells of the pars descendens (P3 segment) of the proximal convolution, located in the outer medulla and medullary rays, than in the cells of the pars convoluta (P1 and P2 segments), situated in the cortex. In contrast, lysosomes are much smaller in the P3 segment and larger and more reactive in the P1 and P2 segments. In all cells of the proximal convolution, peroxisomes tend to be concentrated nearer the base of the cells than do lysosomes. Mitochondria in P3 cells also show low levels of DAB oxidation at pH 6, in contrast to those in P1 and P2 cells. The possibility is discussed that P3 cells possess an extramitochondrial means of oxidation in which peroxisome oxidases play an important role. 相似文献
35.
Correlation Between Degradation of Bacteriophage T2 Deoxyribonucleic Acid and the Resistance of Escherichia coli to Infection 总被引:3,自引:2,他引:1 下载免费PDF全文
The ability of certain strains of Escherichia coli to degrade T2 deoxyribonucleic acid to acid-soluble fragments is correlated with their high capacity to survive T2 infection. 相似文献
36.
During the past two years a pilot project was conducted in which 19 inactive physicians were retrained in preparation for resumption of active practice. The initial program consisted of a flexible training program of six months to one year patterned after conventional internship-residency concepts. During the second year the program was modified by providing an initial condensed indoctrination period of two months'' duration especially designed for this purpose, followed by a preceptorship type of training.The project was considered successful in permitting trainees to enter some form of active medical work, or to enroll in formal specialty training. The observations made by the faculty of the program and its accomplishments are discussed in the light of the effort expended and the cost of the project. 相似文献
37.
The reversal of phenylarsenoxide inhibition of keto acid oxidation in mitochondrial and bacterial suspensions by lipoic acid and other disulphides 总被引:2,自引:1,他引:1 下载免费PDF全文
1. Inhibition of pyruvate oxidation in suspensions of Aerobacter aerogenes cells and of isolated mitochondria from rat heart and liver by phenylarsenoxide is prevented by an excess of lipoic acid, whereas inhibition due to certain bivalent cations is not. 2. In both systems inhibition persists when the bacteria and mitochondria are recovered and resuspended in fresh media in the absence of the inhibitor. Persistent inhibition due to preincubation with phenylarsenoxide, but not with the metal ions, is reversed by lipoic acid and by certain other disulphides. 3. 2,3-Dimercaptopropan-1-ol prevents the inhibition of pyruvate oxidation by phenylarsenoxide and by bivalent cations in both mitochondria and bacterial cells. 4. In aerobic suspensions of mitochondria and bacteria disulphides such as lipoic acid are reduced rapidly to dithiols. Reduction is inhibited by Co(2+), Ni(2+), Cd(2+) and Zn(2+), but not by phenylarsenoxide. 5. It is concluded that the inability of lipoic acid to prevent the action of the metal ions on pyruvate oxidation is due to the inhibition of its reduction to the effective dithiol. 相似文献
38.
Summary Methods for countingAzotobacter species in soil have been examined. The highest counts were obtained from soil suspensions shaken in sterile distilled water containing 10-g glass beads and plated on to glucose agar. Mannitol has been rejected as a suitable substrate in agar media because it gives lower counts of Azotobacter than glucose, an effect which is further enhanced by drying the agar plates. A clear medium free from precipitated phosphate and CaCO3 is recommended for the agar-plate method; the Azotobacter count is affected by the phosphate concentration.The agar-plate and dilution-tube methods were compared; the latter is less accurate but more convenient when many soil samples have to be examined. 相似文献
39.
I. Chanarin M. Hutchinson Anne McLean Margaret Moule 《BMJ (Clinical research ed.)》1966,1(5484):396-399
40.
Substitution of Manganese for Tomato Juice in the Cultivation of Lactic Acid Bacteria 总被引:10,自引:7,他引:3 下载免费PDF全文
Tomato juice was separated by chemical and physical methods into various active fractions, as measured by growth response and acid production by numerous lactic acid bacteria. Incineration of the treated extracts with little apparent loss in activity established the fact that the stimulatory component was of inorganic composition. Of the various cations tested, manganese was the only element that produced biological activity comparable to that of the original extract. Of the 71 strains of lactic acid bacteria tested, 63 strains showed a definite requirement for manganese or tomato juice. 相似文献