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721.
The green flagellate Euglena gracilis has been used as a model organism to elucidate the possible large-scale and short-term
effects of waste substances from the pulp and paper industry on photosynthetic efficiency (PE). Different concentrations of
waste substances before and after treatment in a cleaning system were studied. The uncleaned sample at concentrations up to
1:10 and the cleaned sample at concentrations up to 1:5 showed stimulating effects on the PE after 7 days of incubation compared
to the control. The effects of waste substances on the PE of E. gracilis were also studied in combination with short-term
studies (20 and 40 min) of ultraviolet-B radiation (UV-B, 280–320 nm). It was shown that increasing concentrations of the
uncleaned sample had continuously stimulating effects on the PE and worked protectively against UV-B radiation. The cleaned
sample exhibited no effects, or negative effects, on the PE of E. gracilis together with UV-B radiation compared to the experiments
with only UV-B radiation. At the concentration 1:1 of the cleaned sample an increase in the PE was detected due to the high
concentration of the coloured substances and a decrease in the UV-B penetration. PE revealed itself to be highly sensitive
for detecting toxic effects on E. gracilis and is thus very promising for use in regular toxicity tests of waste water from
pulp and paper industry.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
722.
In this paper, a statistical model for clinical trials is presented for the special situation that a varying and unstructered number of binary responses is obtained from each subject. The assumptions of the model are the following: 1.) For each subject there is a (constant) individual Bernoulli parameter determining the distribution of the binary responses of this subject. 2.) The Bernoulli parameters associated with the subjects are realizations of independent random variables with distributions Pg in treatment group g(g = 1, 2, …, G). 3.) Given the value of the Bernoulli parameter, the observations are stochastically independent within each subject. Under these assumptions, a test statistic is derived to test the hypothesis H0:E(P1) = E(P2) = … = E(PG). It is proven and demonstrated by simulations, that the test statistic asymptotically (i.e. for a large number of subjects) follows the X2-distribution. 相似文献
723.
A binary random variable depends on nonstochastic covariates through a density function. The equations that determine the maximum likelihood estimators of the parameters are intractable and difficult to solve iteratively. We develop modified maximum likelihood estimators for both logistic and nonlo-gistic densities. These estimators are explicit functions of sample observations and are, therefore, easy to compute. They are asymptotically fully efficient and, for small samples, are almost fully efficient. The appropriateness of the logistic density function is also discussed. 相似文献
724.
The relationship between binding of the hemolytic toxin (prymnesin) to bovine erythrocytes and the amount of heat liberated was examined as a function of pH using a flow microcalorimeter and 3H-labelled toxin isolated from the euryhaline alga Prymnesium parvum. A high degree of correlation (correlation coefficient = 0.986) was found between the amount of heat generated and the quantity of toxin that was allowed to interact with the erythrocytes. No significant binding of toxin was observed at pH 7 but it increased linearly as the pH was reduced to 5.5. Maximum heat and binding occured at a pH range 4.5–5.5. The same pattern was followed in terms of the amount of heat liberated and the hemolytic activity of the toxin. The differences in the maximum binding and heat production as a function of pH was independent of the average red cell volume which remained constant at pH 5.5 and 6.2 (102.4 and 102.6 μm3, respectively). 相似文献
725.
This paper is concerned with the properties of a stochastic integral which arises in the study of a modified Markov branching process. Explicit expressions are found for the mean and the limit distribution of the integral. 相似文献
726.
The paper proposes a general model for analysizing two-period change-over designs with binary data. The model includes tests for carry-over effects, treatment and period effects in analogy to the well-known ANOVA-model for continuous data. Minimum modified χ2-statistics are derived and formulas for desk calculators are given. 相似文献
727.
J E Bishop W Hunziker A W Norman 《Biochemical and biophysical research communications》1982,108(1):140-145
Studies from many laboratories have reported apparent molecular weights for the chick intestinal 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] receptor varying from 47,000 to 67,000 daltons. We report here that in the presence of the protease inhibitor phenylmethylsulfonyl fluoride (PMSF, 0.3 mM) and in the presence or absence of ligand, the apparent molecular weight of the receptor is 99,700 ± 9,400 (SD) daltons (as determined by gel filtration). In the absence of PMSF, however, the unoccupied receptor migrates with an apparent molecular weight of 51,400 ± 5,700 (SD) daltons. This smaller form of the 1,25(OH)2D3 receptor, upon incubation with [3H]-1,25(OH)2D3 in the presence of PMSF, then migrates with an apparent molecular weight of 95,900 ± 7,300 (SD) daltons. These results suggest the presence of heretofore unappreciated multiple molecular forms of the chick intestinal 1,25(OH)2D3 receptor. 相似文献
728.
We have isolated poly(A)+ RNA from four antigenic variants (117, 118, 121, 221) of one clone of Trypanosoma brucei. Translation of these poly(A)+ RNAs in a rabbit reticulocyte lysate gave rise to proteins that could be precipitated with antisera against homologous variant surface glycoprotein, the protein responsible for antigenic variation in trypanosomes. From the electrophoretic mobility of these in vitro products in sodium dodecyl sulphate (SDS) gels we infer that variant surface glycoproteins (VSGs) are made as pre-proteins, which require trimming to yield mature VSGs.The total translation products from the four poly(A)+ RNAs produced a complex set of bands on SDS gels, which only differed in the region where the variant pre-glycoproteins migrated. The only detectable variation in the messenger RNA populations of these variants is, therefore, in the messenger RNA for variant pre-glycoproteins.We have made duplex DNA copies of these poly(A)+ RNAs, linked the complementary DNA to plasmid pBR322 by GC tailing and cloned this recombinant DNA in Escherichia coli. Colony hybridization with complementary DNA made on poly(A)+ RNA showed that 7–10% of the colonies contained DNA that hybridized only with the homologous probe. Plasmid DNA was isolated from ten such colonies (two or three of each variant complementary DNA), bound to diazobenzyloxymethyl-cellulose (DBM) paper and used to select complementary messenger RNA from total poly(A)+ RNA by hybridization. In eight cases the RNA recovered from the filter gave variant pre-glycoprotein as the predominant product of in vitro translation.Poly(A)+ RNA from each of the variants only hybridized to the homologous complementary DNA in filter hybridizations. Each trypanosome variant, therefore, contains no detectable messenger RNAs for the three heterologous variant-specific glycoproteins tested. We conclude from this lack of cross-hybridization that antigenic diversity in trypanosomes, unlike antibody diversity in mammals, does not involve the linkage of a repertoire of genes for the variable N-terminal half to a single gene for the C-terminal half of the VSGs. 相似文献
729.
In a recent paper, MARASCUILO [19] has provided an asymptotic solution to the important question on how to test for differences in change parameters when paired observation of binary type (+, -) have been made on two or more independent samples of individuals. In this article, an alternative approach is presented implying asymptotic as well as exact tests for changes. They are based on pre-post test designs from clinical research and allow for controlled evaluation of one treatment modality as well as for comparing 2 or more than 2 treatment modalities. The rationale of the tests is based on McNEMARS [21] test for paired binary observations in one, two, or k samples. 相似文献
730.