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61.
MARIANNE J. VAN DIJKEN PETER NEUENSCHWANDER JACQUES J. M. VAN ALPHEN WINFRED N. O. HAMMOND 《Ecological Entomology》1991,16(2):233-240
Abstract.
- 1 In cassava fields in Africa, population sex ratios of Epidinocarsis fopezi vaned from 0.44 (males to total parasitoids) at low host densities to highly male-biased ratios of 0.70 at high host densities.
- 2 This variability is caused by the difference in allocation of sons and daughters to hosts of different sizes, through the following mechanisms: (a) small, i.e. second instar, hosts are mainly used for the production of male offspring, whereas in large, i.e. third instar, hosts a variable, female-biased sex ratio is produced; (b) E.fopezi does not selectively oviposit into large hosts but always accepts both small and large hosts for oviposition upon encountering; (c) in the field, this parasitoid is time-limited, and not egg-limited. On the basis of an optimal diet model, such general host acceptance is shown to be the best strategy.
- 3 Thus, sex ratio increases with host density for three reasons: the proportion of small hosts encountered in the field increases with increasing host density, small hosts are used for male production, and hosts are always accepted when encountered.
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63.
DAVID M. GOLDENBERG ROSE A. PAVIA HANS J. HANSEN JACQUES P. VANDEVOORDE 《Nature: New biology》1972,239(93):189-190
NORMAL and neoplastic mammalian cells cultivated in vitro retain a number of functions that characterize their cellular origin, even after extensive passage1. It therefore seems reasonable to expect that cell products such as tumour-associated antigens could, if present from the outset, be retained in a demonstrable state when the tumour cells are cultivated outside the original host organism. The discovery by Gold and Freedman2 of an antigenic substance specific for entodermally-derived cancers of the digestive system, carcinoembryonic antigen (CEA), provides a suitable candidate for studying one such property related to a particular type of human cancer. It has been proposed, however, that tumour-specific antigens such as CEA are not indigenous to the tumours, but are glycoproteins produced elsewhere in the body and coating the tumour cells secondarily3. If this were the case, then human colonic cancer cells in long-term propagation in vitro should not synthesize this material. We now present evidence to the contrary. 相似文献
64.
Observations on Idiotypy of Rabbit Antibodies against <Emphasis Type="Italic">Salmonella abortus-equi</Emphasis> 总被引:4,自引:0,他引:4
IDIOTYPIC specificities are antigenic specificities each of which seems to be peculiar to antibodies of one given individual (or perhaps of one group of individuals) against one given antigen1,2. They are detected by reactions—usually of specific precipitation-using anti-idiotypic sera3. We have used anti-Salmonella abortus-equi (SAE) sera of two rabbits to agglutinate bacteria which were injected into two series of six rabbits; three rabbits of each series gave precipitating anti-idiotypic sera. 相似文献
65.
JEAN-FRANÇOIS RIOU DE-LI SHI THIERRY DARRIBÈRE JEAN-CLAUDE BOUCAUT JACQUES CHARLEMAGNE 《Development, growth & differentiation》1987,29(5):443-454
We have previously reported the identification of cell surface glycoproteins in Pleurodeles waltlii gastrulae. In an attempt to study the expression of three of these cell surface glycoproteins (proteins referred to 1, 11 and 14), we have produced monoclonal and polyclonal antibodies by immunizing mice with the spots of the three selected glycoproteins excised from 2D-gels. Expression of the three glycoproteins was detected on the surfaces of all cells during embryonic development. Before hatching, proteins 1, 11 and 14 become expressed in a limited number of tissues. 相似文献
66.
Abstract. An acid phosphatase is isolated and purified to homogeneity from sycamore cell walls. The enzyme, which has a molecular weight close to 100,000, is a glycoprotein and is most probably made up of one polypeptide chain only. Its amino acid composition has been determined. Although homogeneous to polyacrylamide gel electrophoresis under non-denaturing conditions, the enzyme preparation still contains protease traces that tend to split polypeptide chain in two fragments. 相似文献
67.
JEAN GRUENBERG BERNARD SCHWENDIMANN PUKH RAJ SHARMA JACQUES DESHUSSES 《The Journal of eukaryotic microbiology》1980,27(4):484-491
SYNOPSIS. Under aerobic conditions, we have determined glycerol uptake in the long slender (LS) bloodstream form of Trypanosoma (Trypanozoon) brucei brucei by studying glycerophosphate accumulation in the parasites. The coupled enzyme theory applies to the permeation-phosphorylation sequence. Glycerol passage through the plasma membrane is asymmetric, the efflux process being favored over the influx process. No free diffusion of glycerol can be detected even under conditions under which free glycerol accumulates within the cells; most probably, glycerol permeation is mediated by a specific transport system. In the absence of respiratory activities, glycerol is known to be an end-product of T. brucei glycolysis; its production from glycerophosphate should allow ATP synthesis. The observed efflux of free glycerol following intracellular accumulation of glycerophosphate confirms the hypothesis that glycerol production occurs through reversal of glycerol kinase activity. We conclude that in vivo the role of the carrier-mediated asymmetric permeation process is to prevent inhibition of the reversal of the glycerol kinase-mediated reaction by removing free glycerol. 相似文献
68.
Long-day conditions increase internode length, leaf area, anddry weight and reduce the interval between the appearance ofsuccessive leaf pairs in S. rebaudiana as compared with shortdays. Total soluble leaf sugars, protein, and stevioside contentare also augmented in both absolute and relative terms and thebiosynthesis of steviol, the aglucone present in stevioside,is increased by 45%. The interaction between dry matter, steviosidecontent, and day length is discussed and a theory for the biologicalrole of stevioside as a possible defence mechanism against insectherbivory is proposed: as such this is the first known caseof a tetracyclic diterpene glycoside assuming this function. 相似文献
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