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111.
D. W. DUSZYNSKI S. A. ROY J. STEWERT G. A. CASTRO 《The Journal of eukaryotic microbiology》1978,25(3):370-374
SYNOPSIS. Experiments were designed to test whether or not intestinal transit time increases significantly during severe coccidiosis in the rat. Intraduodenal catheters were surgically implanted into 25 rats. Six to 12 days after surgery 11 rats were inoculated orally with 104 sporulated oocysts of Eimeria nieschulzi Dieben, and 11 were inoculated with 106 oocysts; 3 rats were retained as uninfected controls. At 2, 4, 8, 9, and 16 days postinoculation (PI) Na251CrO4 was injected through the catheter into the duodenum of fasted rats and allowed to progress through the small bowel for 15 min, at which time the rats were killed. The distribution of 51Cr in the gut was plotted as a function of gut length. The leading edge of radioactivity traversed 70% of the gut length in controls, and ~ 50–60% in parasitized rats on days 2, 4, 8, and 9 PI. Also, a reflux of gut contents, as evidenced by radioactivity in the stomach, occurred early (PI days 2 & 4) in rats infected with 104 oocysts and throughout patency in rats infected with 106 oocysts. A 2nd study was undertaken to determine if chemically induced suppression of gut transit time during early infection would enhance infectivity as measured by increased parasite fecundity. Nine rats were injected subcutaneously with an antidiarrheal agent, Loperamide®, known to slow small bowel motility significantly. Another group of 9 control rats was injected with the ethanol-propylene glycol solvent. Ten min after injection, all rats were inoculated per os with 104E. nieschulzi oocysts. The daily number of oocysts discharged/rat was followed from PI days 5–11. Patency began for all rats on PI day 7. The total number of oocysts discharged by the drugged rats as compared with controls was not significantly different. 相似文献
112.
A canonical analysis of multiple time series 总被引:2,自引:0,他引:2
113.
The rotational correlation time of two homologous cytoplasmic aspartate aminotransferase molecules isolated from pig and chicken hearts was obtained by spin-labeling technique. The maleimide and iodoacetamide spin-labels modyfying external SH-groups of a protein were used. In the interpretation of ESR spectra a rotational motion of nitroxide group relative to the protein molecule was taken into account. To determine the macromolecule rotational correlation time two methods of the immobilization of a protein molecule were used: 1) by means of increasing protein solution viscosity and 2) by fixation of the protein molecule on adsorbent. From comparison of experimental and theoretical values of rotational correlation time it was conclude that the both enzymes exhibits an intramolecular flexibility. 相似文献
114.
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116.
Partial residuals for the proportional hazards regression model 总被引:34,自引:0,他引:34
117.
High performance liquid chromatography (HPLC) was used to follow the kinetics of the alkaline induced opening of the imidazole ring of 7-methylguanosine (7-meGuo). The kinetics show an initial rapid formation of a major transient intermediate and some minor products that were chromato-graphically separable into seven peaks. This phase of the reaction is followed by the formation of a dominant pyrimidine derivative whose liquid chromatography retention time in a 6% methanol, 0.01 M NH4H2PO4 (pH 5.1) solvent is 6 min; during the rest of the reaction time this dominant species was progressively converted to a co-dominant species that has a 4.5-min column retention. Mass spectroscopy confirmed the existence of two species of ring opened 7-methylguanine (7-meGua), one formylated and another deformylated. Schiff's reaction demonstrated that the species in the second HPLC peak is the formylated one. The ring opened 7-methylguanine (rom7Gua) released by formamidopyrimidine (FAPy)-DNA glycosylase was shown to coelute with the formylated species. These results demonstrate that the enzyme excises formylated rom7Gua from DNA Analysis of rom7Guo by NMR showed that there are two signals assignable to methyl protons and two to formyl protons. These chemical shifts were interpreted as being due to the opening of the imidazole ring at two sites and to the formation of formylated and deformylated rom7Gua. 相似文献
118.
Louise R. Romanow Orlando M. B. Ponti Chris Mollema 《Entomologia Experimentalis et Applicata》1991,60(3):247-259
Life history parameters including longevity, developmental time, and reproduction were determined for whiteflies, Trialeurodes vaporariorum (Westwood), kept in clip-on cages on susceptible parent, Lycopersicon esculentum, resistant parent, L. hirsutum glabratum, and intermediate breeding lines of tomato. Using the Lewontin triangular reproductive function, the intrinsic rate of increase (rm) was calculated for each genotype. This is an elegant tool for detecting resistance, as it incorporates all salient factors of life history. Comparing rm to the other parameters measured, selection criteria were chosen. Developmental time is not a suitable selection criterion as it varies very little even between the most susceptible and the most resistant genotypes. Additionally, developmental time of T. vaporariorum offspring was found to be highly significantly correlated to parental age on all tomato genotypes except L. hirsutum glabratum. Total reproduction, truncated population counts, and longevity appear good criteria for selection. This test, focusing on antibiotic factors, shows large differences between the resistant and susceptible parent genotypes, but much smaller differences between the breeding lines and the susceptible parent. Earlier screenings relying on a variety of tests appear to have maintained antixenotic rather than antibiotic properties in the breeding lines. 相似文献
119.
Determination of window size for analyzing DNA sequences 总被引:4,自引:0,他引:4
Fumio Tajima 《Journal of molecular evolution》1991,33(5):470-473
Summary DNA sequences are generally not random sequences. To show such nonrandomness visually, DNA sequence data are often plotted as moving averages for a certain length of window slid along a sequence. Here a simple algorithm is presented for determining the window size and for finding a nonrandom region of sequence. 相似文献
120.
Primary productivity has been measured routinely at Lake Tahoe since 1967, and a number of mechanisms underlying variability in the productivity record have now been identified. A long-term trend due to nutrient loading dominates the series. Seasonality also is prominent, apparently controlled by direct physical factors unrelated to the trophic cascade. A 3-yr cycle has been detected and several possible mechanisms are considered. Irregular fluctuations also are present, caused in part by isolated events (a forest fire) and recurring but variable phenomena (spring mixing). Except possibly for the 3-yr cycle, the known sources of variability appear to operate bottom-up through direct physical and chemical effects on the phytoplankton. 相似文献