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91.
Robert Baur Vladimír Koál Bruno Patrian Erich Städler 《Entomologia Experimentalis et Applicata》1996,81(3):353-364
In laboratory dual-choice assays females of the cabbage root fly, Delia radicum, prefer for oviposition plants with roots damaged by conspecific larvae to undamaged controls. Cauliflower and kale plants were inoculated with root fly eggs (25 per plant) and the hatching larvae were allowed to feed on the roots for various periods of time (1–17 days). After 4 (cauliflower) or 5 (kale) days of larval feeding the oviposition preference was most pronounced and flies laid between 64% and 68% of their eggs near plants with damaged roots. Later, with increasing damage but fewer surviving, and thus actively feeding, larvae, the magnitude of the preference declined. The preference for plants already damaged by conspecific larvae may contribute to the previously observed aggregated distribution of D. radicum eggs in Brassica crop fields.Further experiments revealed that the sensory cues inducing this oviposition preference originate from the complex consisting of the damaged roots, the surrounding substrate (soil) and associated microbes, rather than from the aerial plant parts. In choice assays using the root-substrate complex of damaged and control plants (aerial parts removed), the observed preference for damaged roots was similar to that found for the entire plant but was more pronounced. The damaged roots alone, compared to control roots, received up to 72% (cauliflower) and 75% (kale) of the eggs. By contrast, surrogate leaves sprayed with methanolic leaf surface extracts from the most preferred plants which had been damaged were not discriminated from surrogate leaved sprayed with extracts of the respective control plants. Analysis of glucosinolate levels in methanolic leaf surface extracts revealed that root damage resulted in enhanced concentrations of indole-glucosinolates on the leaf surface in kale but not in cauliflower. Although indole-glucosinolates are oviposition stimulants for the cabbage root fly, the induced changes were apparently too small to influence oviposition behaviour. 相似文献
92.
Caterina Crescimanno Jean-Michel Foidart Agns Noël Myriam Polette Erik Maquoi Philippe Birembaut Eugenia Baramova Peter Kaufmann Mario Castellucci 《Experimental cell research》1996,227(2):240
Implantation and placental development are dependent upon trophoblast invasion of the endometrium. While the villous trophoblast does not display invasive behavior, the extravillous cytotrophoblast is highly invasive. By cloning BeWo choriocarcinoma cells, we have isolated two distinct clones that share similarities with villous and extravillous cytotrophoblasts. When cultured at the surface of a type I collagen gel, BeWo MC-1 cells were not invasive, whereas BeWo MC-2 cells rapidly invaded this matrix. When injected subcutaneously in nude mice, BeWo MC-1 cells developed a localized tumor and BeWo MC-2 cells developed larger tumors with micrometastases. Gelatinase A expression and minute amounts of gelatinase B were detected in the parental cell line and in both clones. However, the parental and the BeWo MC-2 cells secreted 5- to 10-fold more gelatinase A than the BeWo MC-1 cells. Laminin and matrigel stimulated the production of gelatinase A in BeWo MC-2 cells. Type I collagen promoted the conversion of the 72-kDa progelatinase A in an active enzyme only in parental BeWo and in BeWo MC-2 cells. These clones provide an interesting model for studying the complex mechanisms regulating implantation as well as the controlled invasiveness during implantation compared to tumor invasion. 相似文献
93.
Transformation of the extremely thermoacidophilic archaeon Sulfolobus solfataricus via a self-spreading vector 总被引:1,自引:0,他引:1
Abstract The comparative chromosomal locations of polymeric β-fructosidase SUC genes have been determined by Southern blot hybridization with the SUC2 probe in 91 different strains of Saccharomyces cerevisiae . Most of the strains exhibited a single SUC2 gene, but in some strains two or three SUC genes were found. All Suc− strains carried a silent suc20 sequence. The accumulation of SUC genes was observed in populations derived from sources containing sucrose and seems to be absent in strains from sources promoting the MEL gene. 相似文献
94.
C. Sauvain-Dugerdil G. Boëtsch C. Serrano-Sanchez 《International Journal of Anthropology》1996,11(2-4):3-11
this first paper introduces the topic of the volume, outcomes of a symposium organised at the 13th ICAES held in Mexico in
August 1993. It briefly reminds of the convergence between anthropology and demography up to date and stresses on the need
of real transdisciplinary work in this challenging domain. The aim of the symposium was to make a contribution on the central
theme chosen by the congress — the cultural and biological dimensions of global change — while examining the place of demographic
anthropology in the study of change. The papers presented at the symposium have been organised in three parts which form the
present volume: the composition of population, the choice of spouse and mobility, the reproduction and dynamics of populations.
The basic mechanisms of change are considered through examples at the level of local populations. This also leads to question
the definitions of human groups and to make a “declaration” stressing on the importance of individual heterogeneity and the
arbitrariness and reductive nature of any grouping of individuals, stating therefore the misapprehension of the most recent
scientific work inherent to the rationale of programs of “ethnic cleasing”.
Translated from the french by prof. Derek F. Roberts 相似文献
95.
The region encompassing theMa, Mb1, Mb2, andLmp2 genes of the mouse class II major histocompatibility complex (MHC) was sequenced. Since this region contains clusters of genes required for efficient class I and class II antigen presentation, it was interesting to search for putative additional genes in the 21 kilobase gap between theMb1 andLmp2 genes. Computer predictions of coding regions and CpG islands, exon trapping experiments, and cross-species comparison with the corresponding human sequence indicate that no additional functional gene is present in that stretch. However, computer analysis revealed the possible existence of an alternative 3 exon forMb1. Except for the fact that the mouse MHC contains twoMb genes, the genomic organization of theH2-M loci was found to be almost identical to the organization of the humanHLA-DM genes. The promoter regions of theMa andMb genes also resemble classical class II promoters, containing typical S, X, and Y boxes. Like the human genes, the threeH2-M genes displayed very limited polymorphism when we compared the cDNA sequences from six haplotypes. Finally, comparison ofDMB withMb1 andMb2, both at the genomic level and in their coding regions, suggests that theMb gene was recently duplicated, probably only in certain rodents. 相似文献
96.
Solveig Persson-Sjögren Sture Forsgren Pål Rooth Inge-Bert Täljedal 《Cell and tissue research》1996,284(3):391-400
Collagenase-isolated pancreatic islets from C57BL/6J mice were cultured overnight and transplanted under the kidney capsule of non-diabetic syngeneic hosts. Cryostat sections of grafts and fresh islets were stained for acetylcholinesterase (AChE) and vasoactive intestinal polypeptide-like immunoreactivity (VIP-LI). Immediately after isolation, as well as 2-5 days after transplantation, VIP-LI- and AChE-positive nerve cell bodies were clearly seen in the periphery of the islets. Grafts 3-5 days old exhibited a transient and marked increase in VIP-LI nerve cell bodies and fibers. Seven days after transplantation VIP-LI nerve structures began to decrease in number and after 26-52 weeks they were no longer detectable. In contrast, AChE-positive nerve cell bodies and fibers, which showed a relatively constant pattern of distribution, were observed throughout the entire observation period. Restaining experiments demonstrated the coexistence of VIP-LI and AChE activity in the neurons. It is concluded that the grafts were extensively equipped with an intrinsic VIP-ergic and AChE-positive innervation. The initial, transient enhancement of VIP-LI expression probably reflects an adaptation of the neuro-insular complex to the preganglionic denervation, or to the ectopic environment, or both. 相似文献
97.
On Normandy coasts, the red alga Delesseria sanguinea perennates by its stipe; fronds grow in January and disappear in June. Seasonal variations in sterol composition in relation to the biology of D. sanguinea are reported. Sterols in cellular membranes are free or conjugated by esterification with fatty acids, heterosides or lipid complexes like phospholipids. Both kinds of sterols were analyzed by GC-MS. The major sterol (80%) found in fronds was cholesterol whereas in stipes, cholesterol was also the major sterol in spring, but in September, an important reduction in cholesterol yield was noted with proportional increase in sitosterol content. It appears that cholesterol is synthesized in fronds in spring, then transferred to the stipe, which loses an important amount of cholesterol with loss of the blades. 相似文献
98.
Vascular endothelial cells: Targets for studying the activity of hair follicle cell-produced VEGF 总被引:1,自引:0,他引:1
S. Lachgar M. Charvéron Y. Gall J. Plouët J. L. Bonafé 《Cell biology and toxicology》1996,12(4-6):331-334
Fetal bovine aortic endothelial cells (FBAEC) were exposed to purified fractions of conditioned medium from cultures of hair dermal papilla cells (DPC) to determine the existence of any vascular endothelial growth factor (VEGF)-like paracrine activity of the latter. Such fractions were tested for stimulation of growth and migration of cultured FBAEC. In addition, VEGF secretion by DPC was measured by radioassay of VEGF receptors using FBAEC as target cells. The results showed that stimulation of FBAEC proliferation and migration following exposure to purified conditioned medium was dose-dependent. Radioreceptor assays of recombinant VEGF and purified DPC-conditioned medium showed competitive VEGF binding in FBAEC.Abbreviations CM
conditioned medium
- DMEM
Dulbecco's modified eagle's medium
- DPC
dermal papilla cells
- EDTA
ethylenediaminetetra-acetic acid
- FBAEC
fetal bovine aortic endothelial cells
- FCS
fetal calf serum
- VEGF
vascular endothelial growth factor 相似文献
99.
J. Hallborn N. Meinander B. Hahn-Hëgerdal M. -F. Gorwa M. Pentillä S. Keränen 《Applied microbiology and biotechnology》1994,42(2-3):326-333
Xylitol formation by a recombinantSaccharomyces cerevisiae strain containing theXYL1 gene fromPichia stipitis CBS 6054 was investigated under three sets of conditions: (a) with glucose, ethanol, acetate, or glycerol as cosubstrates, (b) with different oxygenation levels, and (c) with different ratios of xylose to cosubstrate. With both glucose and ethanol the conversion yields were close to 1 g xylitol/g consumed xylose. Decreased aeration increased the xylitol yield on the basis of consumed cosubstrate, while the rate of xylitol formation decreased. The xylitol yield based on consumed cosubstrate also increased with increased-xylose:cosubstrate ratios. The transformant utilized the cosubstrate more efficiently than did a reference strain in terms of utilization rate and growth rate, implying that the regeneration of NAD(P)+ during xylitol formation by the transformant balanced the intracellular redox potential. 相似文献
100.
Gold-labeled insulin is bound first of all to the cilia of the oral field of Tetrahymena. A primary treatment (hormonal imprinting) with insulin increases the binding capacity even after 24h and makes it more sensitive for appearance a week later, within a minute of giving insulin-gold. The food vacuoles contain insulin-gold in pretreated cells or without pretreatment as well, though in imprinted situations the label can be found in pinocytotic vesicles at the bases of cilia in the oral field. Altogether, a functional difference can be observed between the cilia of the oral and non-oral surfaces of Tetrahymena and hormonal imprinting has a specifying effect on the binding of labeled hormone. 相似文献