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91.
Kenneth Garson Gregory J. Matlashewski Khosrow Adeli Laurian S. Robert Illimar Altosaar 《Analytical biochemistry》1983,134(2):512-516
A rapid method for obtaining large quantities of developing groats suitable for the isolation of highly intact polysomes has been developed. Developing spikelets were harvested directly from oat panicles into liquid nitrogen and then quickly passed through a dehuller. Chaff was removed by air aspiration and the resultant groats were collected directly back into liquid nitrogen. Approximately 250 g of groats could be isolated each man-hour by the above method. In comparison, only 10 g of endosperm could be collected by squeezing it out of spikelets using an endosperm mangle. Membrane-bound polysomes extracted from the immature groats were compared to those extracted from endosperm. The largest polysomes discernable as unique peaks on sucrose gradients were ten-mers and nine-mers for groats and endosperm, respectively. Polysomes isolated from both starting materials stimulated similar incorporations of [35S]methionine into trichloroacetic acid-insoluble products during in vitro translations in wheat germ extract. Both polysome preparations directed the synthesis of similar high-molecular-weight proteins. Based on these criteria, polysomes from both preparations were found to be of similar intactness, although the groat starting material was much more readily obtained. The polysome classes having the maximum absorbance peak for endosperm and groat polysomes were six-mers and eight-mers, respectively. 相似文献
92.
Some Properties of Thiosulfate-Oxidizing Enzyme from Marine Heterotroph 16B 总被引:3,自引:1,他引:2 下载免费PDF全文
Thiosulfate-oxidizing enzyme has been demonstrated in cell-free extracts of the marine, thiosulfate-oxidizing pseudomonad strain 16B. The enzyme, partially purified by ion-exchange chromatography and calcium phosphate gel treatment, catalyzed the oxidation of thiosulfate to tetrathionate with the concomitant reduction of ferricyanide. Native but not mammalian cytochrome c was also reduced by the enzyme in the presence of thiosulfate. The enzyme was located exclusively in the supernatant of ultracentrifuged cell extracts. The most purified enzyme preparation, like intact cells, exhibited a temperature optimum of 30 to 31°C. However, it exhibited no definite pH optimum. At pH 6.1 to 6.3 and 30°C, the Km for thiosulfate was 1.57 mM. At lower temperatures, the apparent Km for thiosulfate increased, but the apparent maximum velocity remained virtually unchanged. Thiosulfate oxidation in intact cells exhibited an increase in the pH optimum at lower temperatures. The thiosulfate-oxidizing enzyme of marine heterotroph 16B is compared with thiosulfate-oxidizing enzymes from other bacteria, and the effect of temperature on the relationship between pH and thiosulfate oxidation is discussed with reference to the natural habitat of the bacterium. 相似文献
93.
L B Nguyen J F Gregory J J Cerda 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1983,173(4):568-573
Previous research has indicated that dietary fiber may affect the absorption and utilization of certain nutrients. To determine the effect of certain fiber materials on the absorption of B-6 vitamers, jejunal segments from young male adult rats were perfused in situ with a control solution containing 0.02 mM pyridoxine (PN), 0.02 mM pyridoxal (PL), and 0.02 mM pyridoxamine (PM), followed by a test solution containing the same vitamin B-6 mixture and one of five fiber-rich test materials (cellulose, pectin, lignin, homogenized fresh carrot, or carrot homogenized after 10 min boiling) added at a concentration of 1-3%. The mean absorption rates of PL, PN, and PM from the control solution were, respectively, 3.66 +/- 0.23, 2.06 +/- 0.23, and 1.74 +/- 0.37 nmole/min/20 cm jejunal segment. There were no significant differences between the absorption rates of B-6 vitamers from control and test solutions containing cellulose, pectin, and lignin. The absorption rates of PM and PL were significantly depressed (P less than 0.05 and P less than 0.01, respectively) by the presence of fresh or cooked carrot. The absorption rate of PN in presence of cooked carrot was also decreased relative to the control value but the difference was only marginally significant (P less than 0.10). When the concentration of fresh carrot in the test solution was increased to 10% by weight and the perfusion rate was decreased from 1.91 to 0.49 ml/min in a second perfusion experiment, there was a significant increase in variability and the differences between absorption rates of the B-6 vitamers in control and test solutions were not statistically significant. The limited evidence of adverse effect of carrot on absorption of vitamin B-6 suggested the need for further clarification of the influence of dietary fiber in an unrefined state on the bioavailability of vitamin B-6. 相似文献
94.
Gregory A. Osenga Bruce C. Coull 《Journal of experimental marine biology and ecology》1983,67(3):221-225
Meiofauna were collected from adjacent areas with and without Spartina alterniflora Loisel culms. Environmental complexity resulting from root structure cannot be determined by simply observing S. alterniflora culm distribution. There were no significant differences between the two areas with respect to root density or root sizes; however, the number of live roots was significantly higher in the area containing Spartina culms. Nematodes, the most abundant taxon were positively correlated with live root density. In contrast, the number of dead roots and harpacticoid copepods were higher in the area without culms. This study suggests that nematodes are positively associated with micro-oxygenated zones produced by live S. alterniflora roots. Other measures of biogenic structure, such as total root density or root size fractions are not important in affecting nematode abundance. 相似文献
95.
Thirty-six mares which foaled over a 10-day period were given 1 to 10 daily intramuscular injections of a combination of 150 mg. progesterone and 10 mg. estradiol 17β. The first injection was given within 18 hours after parturition. Because individual mares foaled on different dates during the 10 day period, commencement of treatment varied, but treatment for all mares ceased on the same day. Teasing and breeding began seven days after the final treatment. The mares were teased daily for 10 days and artifically inseminated every second day until ovulation occurred. The mean interval from the end of treatment to beginning of estrus was 9.4 days (range 7 to 14) and 33 of 26 mares (94.7%) ovulated 10 to 16 days after the final treatment. Both estrus and ovulation were effectively synchronized, resulting in a first estrus pregnancy rate of 80.6% (29 of 36). 相似文献
96.
97.
Specific Inhibition of the Cyanide-insensitive Respiratory Pathway in Plant Mitochondria by Hydroxamic Acids 总被引:77,自引:44,他引:33 下载免费PDF全文
Gregory R. Schonbaum Walter D. Bonner Jr. Bayard T. Storey James T. Bahr 《Plant physiology》1971,47(1):124-128
Hydroxamic acids, R-CONHOH, are inhibitors specific to the respiratory pathway through the alternate, cyanide-insensitive terminal oxidase of plant mitochondria. The nature of the R group in these compounds affects the concentration at which the hydroxamic acids are effective, but it appears that all hydroxamic acids inhibit if high enough concentrations are used. The benzhydroxamic acids are effective at relatively low concentrations; of these, the most effective are m-chlorobenzhydroxamic acid and m-iodobenzhydroxamic acid. The concentrations required for half-maximal inhibition of the alternate oxidase pathway in mung bean (Phaseolus aureus) mitochondria are 0.03 mm for m-chlorobenzhydroxamic acid and 0.02 mm for m-iodobenzhydroxamic acid. With skunk cabbage (Symplocarpus foetidus) mitochondria, the required concentrations are 0.16 for m-chlorobenzhydroxamic acid and 0.05 for m-iodobenzhydroxamic acid. At concentrations which inhibit completely the alternate oxidase pathway, these two compounds have no discernible effect on either the respiratory pathway through cytochrome oxidase, or on the energy coupling reactions of these mitochondria. These inhibitors make it possible to isolate the two respiratory pathways and study their mode of action separately. These inhibitors also enhance an electron paramagnetic resonance signal near g = 2 in anaerobic, submitochondrial particles from skunk cabbage, which appears to be specific to the alternate oxidase and thus provides a means for its assay. 相似文献
98.
Changes in Ribonucleic Acid Fractions During Maturation of Mimosa Epicotyl Tissues 总被引:1,自引:1,他引:0 下载免费PDF全文
Gregory N. Brown 《Plant physiology》1969,44(2):272-276
Total RNA and DNA of mimosa epicotyl tissues were extracted and the RNA fractionated into specific soluble RNAs (sRNAs) at different times during late germination. Epicotyls collected at each time contained qualitatively comparable meristematic and developing tissues, while mature tissues increased. Quantitative ratios of total RNA to DNA and total sRNAs to approximated ribosomal RNA (rRNA) varied consistently during development. Terminal nucleosides of sRNA did not vary in any consistent pattern through development. On the other hand, regular changes in quantitative ratios of specific sRNA groups were observed during development. 相似文献
99.
Cellular evolution in induced inflammation in uremic patients 总被引:2,自引:0,他引:2
100.