- 1.
Competition experiments between
125 I-insulin (1 nM) and an excess of native insulin (30 μM) indicate a specific hormone fixation to membrane crude extracts from unfertilized and fertilized eggs. The magnitude of specific binding'is comparable to values recorded for mammalian cells.- 2.
Inhibition of insulin fixation by concanavalin A (100 μg/ml) suggests the glycoprotein composition of plasma membrane receptors.
- 3.
A 30-min incubation of unfertilized and fertilized eggs in the presence of insulin leads to a significant increase in cyclic AMP content.
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An immunocytochemical method demonstrates that insulin is selectively and specifically bound to the plasma membrane of eggs incubated in the presence of insulin before fixation.
It can be concluded that insulin receptor sites are components of sea urchin eggs plasma membrane. Insulin binding which leads to cyclic AMP accumulation is not deeply modified by fertilization and does not induce visible morphological changes in the eggs. 相似文献8.9.Giada Cordoni Elisabetta Palagi Silvana Borgognini Tarli 《International journal of primatology》2006,27(5):1365-1382We studied post-aggression mechanisms in a captive group of western gorillas (Apenheul Primate Park, The Netherlands) and compared them with those of wild mountain gorillas (Gorilla beringei). We found the same trend for reconciliation that wild mountain gorillas show: reconciliation occurred only between adult male-female dyads, while it was absent in the other sex-age class combination. There were both solicited and nonsolicited contacts; the latter finding is in contrast with the result obtained in wild mountain gorillas, in which consolation was absent. Immature females were more likely to offer consolation toward both related and unrelated individuals. Consolation did not reduce the likelihood of further attacks among group members. It may be that, as the α-male plays a fundamental role in preventing the spread of conflicts throughout the entire group, triadic contacts become ineffective for the function. The levels of consolation were higher in absence of reconciliation than in its presence, suggesting that consolation may function as an alternative mechanism in stress reduction of the victim. 相似文献10.Peter M. Kappeler Carel P. van Schaik 《Ethology : formerly Zeitschrift fur Tierpsychologie》1992,92(1):51-69Affinitive contact between former opponents soon after a conflict has been demonstrated in a growing number of primate species. Several recent studies show that such contact reduces the probability of future conflicts, allows the recipient of aggression to reduce its anxiety, and restores tolerance between former opponents. Hence, these contacts can be termed reconciliation. In this paper, we critically discuss common methodological problems of studying reconciliation, examine functional aspects, and evaluate the existing variation in primate reconciliation in light of predictions derived from four untested hypotheses about its evolutionary origins. We find that the occurrence of reconciliation in primates is not limited to anthropoids. Neither is it limited to species with formalized dominance relations. Reconciliation is also not a prerequisite for life in permanent social groups. Instead, several lines of evidence support the hypothesis that reconciliation serves to maintain valuable social relationships between individuals. We suggest several more specific versions of this hypothesis and discuss reconciliation between kin, mates, and alliance partners, as well as a number of open questions pertaining to the mechanisms, functions and origins of reconciliation among primates. 相似文献11.12.Sites of Synthesis and Transport Pathways of Insect Hydrocarbons: Cuticle and Ovary as Target Tissues 总被引:3,自引:0,他引:3SCHAL COBY; SEVALA VEERESH L.; YOUNG HUGH P.; BACHMANN JANE A.S. 《Integrative and comparative biology》1998,38(2):382-393SYNOPSIS. The outer surface of insects is covered with a lipidlayer that provides water-proofing and protection against environmentalstresses. Hydrocarbons (HC) are major constituents of this epicuticularwax and they also serve as semiochemicals. In some insects HCare also exploited as biosynthetic precursors for pheromones.HC are synthesized by oenocyteswhich are situated in the integumentor hemocoel. Shuttling of HC to the epicuticie, fat body, andgonads requires transport through an aqueous medium. Insects,unlike vertebrates, use a versatile lipoprotein to effect lipidtransport and to selectively deliver lipids to specific tissues.A high-density hemolymph lipoprotein (lipophorin [Lp]) servesthis function.In adult females of the German cockroach (Blattellagermanica), Lp carries both HC and a contact sex pheromone.Lipophorin is a multi-functional lipid carrier serving alsoas a juvenile hormone binding protein in many insects. Studiesofthe interactions between Lp and HC are beginning to unravelthe routes used in delivering HC to target tissues. We discussthepathways and dynamics of loading of Lp with HC and HC-derivedpheromones, their transport through the hemolymph, and depositionin various tissues, including the epicuticie, ovaries, and pheromone-emittingglands. 相似文献13.Frans B. M. de Waal RenMei Ren 《Ethology : formerly Zeitschrift fur Tierpsychologie》1988,78(2):129-142Observations were made following spontaneous aggressive incidents in a breeding group of captive stumptail macaques (Macaca arctoides). Participants were observed both during the first 10 min following the aggressive incident, and during matched-control observations. Data on 670 pairs of former opponents were collected, and compared with a sample of 573 such pairs of rhesus macaques (M. mulatta), which had been observed with identical methods in a previous study. Selective attraction between opponents was confirmed for the stumptail monkeys, i.e. both the absolute and the relative rate of nonagonistic body contact between individuals increased after aggression between them. The species was found to be considerably more conciliatory than rhesus monkeys, and to have a remarkably rich repertoire of reassurance gestures. The most characteristic conciliatory behavior is the hold-bottom ritual, in which one individual (usually the subordinate) presents its hindquarters, and the other (usually the dominant) clasps the other's haunches. The high rate of reconciliation among stumptail monkeys extended to all relationship classes, and a correlation with the closeness of social bonds (measured as time spent in association) could not be demonstrated. Because of the generality of the species' high peacemaking tendencies it is assumed that group cohesiveness is of great survival value in the wild. 相似文献14.Reconciliation in three groups of lion-tailed macaques 总被引:1,自引:0,他引:1We studied postconflict behavior in three captive groups of lion-tailed macaques (Macaca silenus). After a conflict, we monitored the aggressee as the focal individual during a 10-min postconflict period and made control observations the following day on the same individual. Selective attraction between former opponents occurred in the first minutes of the postconflict period. The conciliatory tendency was relatively high, about 40%. Although no specific behavior was used to reconcile, postconflict contacts were especially intense and a rich repertoire of affiliative patterns was exihibited. With regard to the rate and form of reconciliation, lion-tailed macaques resemble Sulawesi macaques, which belong to the same phyletic lineage. We also discuss the possible interrelations between conciliatory patterns and other characteristics of social organization. 相似文献15.16.Willy J. Malaisse Abdullah Sener Francine Malaisse-Lagae 《Molecular and cellular biochemistry》1981,37(3):157-165Summary Nutrients which stimulate insulin secretion are currently thought to initiate the series of cellular events eventually leading to insulin release either by interacting with a stereospecific receptor system (the regulatory site hypothesis) or by acting as a fuel (the substrate site hypothesis) in the pancreaticB-cell. The latter hypothesis is supported by a number of observations indicating that the capacity of nutrients to stimulate insulin release is indeed highly dependent on their capacity to increase catabolic fluxes in isolated pancreatic islets. However, these observations do not rule out the existence of nutrient receptors in islet cells. For instance, a nonmetabolized analog of L-leucine stimulates insulin release by causing allosteric activation of glutamate dehydrogenase, which should be considered, therefore, as a receptor for certain amino acids. Likewise, the increase in glycolytic flux, which is associated with the process of glucose-stimulated insulin release, is attributable not solely to a mass action phenomenon but also to the activation of phosphofructokinase by fructose 2.6-bisphosphate. The biosynthesis of this activator may involve a glucose receptor system. The fact that certain nutrient secretagogues (e.g D-glucose and L-leucine) act in the B-cell both as substrates and enzyme activators permits reconciliation of the substrate site and regulatory site hypotheses for insulin release. 相似文献17.In previous studies we have shown that recombination across a 299-bp interspersed sequence accounts for the diversity of the mitochondrial genome in wild and cultivated soybeans. In this study, a computer-assisted survey of databases was performed using sequences of the repeat and its neighboring regions as query sequences. The sequences of soybean were found to be present as many short segments that include repeated sequences in the mitochondrial genomes of Arabidopsis and liverwort. Taken together with the results of a DNA gel-blot analysis, this suggests that the soybean sequences were found to have originated during land plant evolution and are present as small-interspersed segments in many taxa of land plants. 相似文献18.19.Emma Varley 《Culture, medicine and psychiatry》2016,40(2):159-180Using data collected over nearly three years of ethnographic fieldwork in the Gilgit-Baltistan region of northern Pakistan, my paper explores hospital spaces, clinical services and treatment encounters as conduits for the expression and propagation of conflictive Shia-Sunni sectarianism. Where my prior research has investigated the political etiologies (Hamdy in Am Ethnol 35(4):553–569, 2008) associated with Gilgiti women’s experiences of childbirth during ‘tensions’, as Shia-Sunni hostilities are locally known, this paper focuses on healthcare providers’ professional and personal navigations of an episode of conflict whose epicentre was at the District Headquarter Hospital, Gilgit-Baltistan’s foremost government hospital. Through critical evaluation of the impacts of Shia-Sunni tensions on the social, administrative and clinical practices and consequences of medicine, my paper analyses the complex ways that clinics in crisis serve as zones of contact (Pratt in Profession 91:33–40, 1991) and abandonment (Biehl in Soc Text 68(19):131–149, 2001; Subjectivity: ethnographic investigations, 2007), in which neglect and harm are directed along lines of sectarian affiliation to produce vulnerability, spectacular violence and death for healthcare providers and patients. 相似文献20.Most previous studies of the evolution of codon usage bias (CUB) and intronic GC content (iGC) in Drosophila melanogaster were based on between-species comparisons, reflecting long-term evolutionary events. However, a complete picture of the evolution of CUB and iGC cannot be drawn without knowledge of their more recent evolutionary history. Here, we used a polymorphism dataset collected from Zimbabwe to study patterns of the recent evolution of CUB and iGC. Analyzing coding and intronic data jointly with a model which can simultaneously estimate selection, mutational, and demographic parameters, we have found that: (1) natural selection is probably acting on synonymous codons; (2) a constant population size model seems to be sufficient to explain most of the observed synonymous polymorphism patterns; (3) GC is favored over AT in introns. In agreement with the long-term evolutionary patterns, ongoing selection acting on X-linked synonymous codons is stronger than that acting on autosomal codons. The selective differences between preferred and unpreferred codons tend to be greater than the differences between GC and AT in introns, suggesting that natural selection, not just biased gene conversion, may have influenced the evolution of CUB. Interestingly, evidence for non-equilibrium evolution comes exclusively from the intronic data. However, three different models, an equilibrium model with two classes of selected sites and two non-equilibrium models with changes in either population size or mutational parameters, fit the intronic data equally well. These results show that using inadequate selection (or demographic) models can result in incorrect estimates of demographic (or selection) parameters. 相似文献 - 2.