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排序方式: 共有423条查询结果,搜索用时 15 毫秒
1.
D. R. Anderson K. P. Burnham B. R. Crain 《Biometrical journal. Biometrische Zeitschrift》1985,27(7):723-731
ANDERSON and POSPAHALA (1970) investigated the estimation of wildlife population size using the belt or line transect sampling method and devised a correction for bias, thus leading to a class of estimators with desirable characteristics. This work was given a basic and rigorous mathematica framework by BURNHAM and ANDERSON (1976). In the present article we use this mathematical framework to develop an estimator of population size and density using weighted least squares. The approach is a two-stage Method. 相似文献
2.
3.
Dose Response Curve Linearization and Computer Potency Calculation of Turbidimetric Microbiological Vitamin Assays
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The dose response curves of various turbidimetric microbiological assays, including vitamin B12, Ca pantothenate, and pyridoxine (vitamin B6), were linear with logarithmic transformation of the responses by use of the equation derived, ln[T(x) - T(∞)] = ln A - Bx. A Fortran computer program which used the slope ratio potency calculation was written. The assay potencies calculated by the computer program showed excellent agreement with those obtained by the manual calculation. 相似文献
4.
The incubation of beta-carotene-(14)C with the soluble fraction of the intestinal mucosa resulted in the formation of small amounts of acidic material. The addition of NAD or NADH to the soluble fraction caused a tenfold increase in this material. Incubation of retinal-15-(14)C with the soluble fraction of the intestinal mucosa plus NAD or NADH resulted in the conversion of 80-90% of the retinal to acidic material, which has been shown to contain retinoic acid. In vivo studies on the formation of retinoic acid in the intestinal mucosa after the administration of beta-carotene-(14)C revealed that an appreciable amount of beta-carotene was converted to acidic compounds. When retinal-15-(14)C was administered, portal blood contained 30-40% of the absorbed radioactivity. 24% of this radioactivity was found in acidic material, which has been shown to contain retinoic acid. It is suggested that enzymes in rat intestine cleave beta-carotene to retinal and oxidize the latter to retinoic acid, which is then transported via the portal circulation to the liver. 相似文献
5.
Transduction of light and hormone signals in plants may utilize a mechanism similar to one widely used in animal systems, that of accelerated phosphatidylinositol (PI) turnover. The elements of this central mechanism and consequences of the acceleration as well as recent evidence for its operation in plants are described. 相似文献
6.
Structure determination of a nucleoside Q precursor isolated from E. coli tRNA: 7-(aminomethyl)-7-deazaguanosine. 总被引:5,自引:3,他引:2
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N Okada S Noguchi S Nishimura T Ohgi T Goto P F Crain J A McCloskey 《Nucleic acids research》1978,5(7):2289-2296
A precursor of modified nucleoside Q isolated from E. coli methyl-deficient tRNA was determined to be 7-(aminomethyl)-7-deazaguanosine. The structure was deduced by means of its chromatographic and electrophoretic mobilities, and UV and mass spectra, in addition to comparison with the synthesized authentic compound. The same molecule is also found in tRNA of an E. coli mutant selected for deficient synthesis of modified nucleosides. 相似文献
7.
8.
Inositol phospholipid metabolism may trigger flagellar excision in Chlamydomonas reinhardtii 总被引:3,自引:0,他引:3
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L M Quarmby Y G Yueh J L Cheshire L R Keller W J Snell R C Crain 《The Journal of cell biology》1992,116(3):737-744
Chlamydomonas reinhardtii cells shed their flagella in response to environmental stress. Under favorable conditions, flagella are quickly regrown. To learn more about the signals that trigger flagellar excision and regrowth we have investigated inositol phospholipid metabolites, molecules implicated in signal transduction in several other systems. After deflagellation by low pH or mastoparan, a potent activator of G proteins, there was a rapid increase in levels of inositol 1,4,5-trisphosphate measured by use of receptor-binding assays and HPLC. This increase was concomitant with a decrease in levels of phosphatidylinositol 4,5-bisphosphate and was followed by an increase in phosphatidic acid, results consistent with activation of phospholipase C and diacylglycerol kinase. Additional experiments suggest that this activated phospholipase C is not important for flagellar regrowth but plays a role in informing the excision apparatus of the environmental stress. Addition of neomycin (an inhibitor of phospholipase C) before exposure of cells to low pH or mastoparan prevented the increase in inositol 1,4,5-trisphosphate and also prevented deflagellation. Addition of neomycin after deflagellation blocked increases in inositol 1,4,5-trisphosphate that normally followed deflagellation, but did not block flagellar assembly. Furthermore, a flagellar excision-defective mutant, fa-1, did not shed its flagella in response to low pH or mastoparan, yet both of these agents activated phospholipase C in these cells. The results suggest that activation of phospholipase C, possibly via a G protein, is a proximal step in the signal transduction pathway inducing deflagellation in Chlamydomonas. 相似文献
9.
The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs. 相似文献
10.
Robert B. Goldberg William R. Crain Joan V. Ruderman Gordon P. Moore Thomas R. Barnett Ratchford C. Higgins Robert A. Gelfand Glenn A. Galau Roy J. Britten Eric H. Davidson 《Chromosoma》1975,51(3):225-251
The arrangement of repetitive and non-repetitive sequence was studied in the genomic DNA of the oyster (Crassostrea virginica), the surf clam (Spisula solidissima), the horseshoe crab (Limulus polyphemus), a nemertean worm (Cerebratulus lacteus) and a jelly-fish (Aurelia aurita). Except for the jellyfish these animals belong to the protostomial branch of animal evolution, for which little information regarding DNA sequence organization has previously been available. The reassociation kinetics of short (250-300 nucleotide) and long (2,000-3,000 nucleotide) DNA fragments was studied by the hydroxyapatite method. It was shown that in each case a major fraction of the DNA consists of single copy sequences less than about 3,000 nucleotides in length, interspersed with short repetitive sequences. The lengths of the repetitive sequences were estimated by optical hyperchromicity and S1 nuclease measurements made on renaturation products. All the genomes studied include a prominent fraction of interspersed repetitive sequences about 300 nucleotides in length, as well as longer repetitive sequence regions. 相似文献