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1.
DW Cameron 《Canadian Metallurgical Quarterly》1998,82(1):47-58
The lipid bilayer technique was used to examine the effects of the ATP-sensitive K+ channel inhibitor (glibenclamide) and openers (diazoxide, minoxidil and cromakalim) and Cl- channel activators (GABA and diazepam) on two types of chloride channels in the sarcoplasmic reticulum (SR) from rabbit skeletal muscle. Neither diazepam at 100 microM nor GABA at 150 microM had any significant effect on the conductance and kinetics of the 75 pS small chloride (SCl) channel. Unlike the 150 pS channel, the SCl channel is sensitive to cytoplasmic glibenclamide with Ki approximately 30 microM. Glibenclamide induced reversible decline in the values of current (maximal current amplitude, Imax and average mean current, I') and kinetic parameters (frequency of opening Fo, probability of the channel being open Po and mean open time, To, of the SCl channel. Glibenclamide increased mean closed time, Tc, and was a more potent blocker from the cytoplasmic side (cis) than from the luminal side (trans) of the channel. Diazoxide increased I', Po, and To in the absence of ATP and Mg2+ but it had no effect on Imax and also failed to activate or remove the glibenclamide- and ATP-induced inhibition of the SCl channel. Minoxidil induced a transient increase in I' followed by an inhibition of Imax, whereas cromakalim reduced Po and I' by increasing channel transitions to the closed state and reducing To without affecting Imax. The presence of diazoxide, minoxidil or cromakalim on the cytoplasmic side of the channel did not prevent [ATP]cis or [glibenclamide]cis from blocking the channel. The data suggest that the action(s) of these drugs are not due to their effects on the phosphorylation of the channel protein. The glibenclamide- and cromakalim-induced effects on the SCl channel are mediated via a "flicker" type block mechanism. Modulation of the SCl channel by [diazoxide]cis and [glibenclamide]cis highlights the therapeutic potential of these drugs in regulating the Ca2+-counter current through this channel. 相似文献
2.
Previous studies have found that the volume of several song control nuclei is larger in male songbirds than in female songbirds. The degree of this volumetric sex difference within a given species appears to be systematically related to the degree of the behavioral sex difference. The largest volumetric differences have been reported in species in which the male sings and the female sings little, if at all, and the smallest sex differences in volume have been reported in species in which males and females both sing in nearly equal amounts. We compared the volume of three song control nuclei in male and female European starlings (Sturnus vulgaris), a species in which females are known to sing, though at a much lower rate than males. We investigated the volume of hyperstriatum ventrale, pars caudale, nucleus robustus archistriatalis, and area X of the lobus parolfactorius as defined with the use of a Nissl stain. In addition, we measured the volume of area X as defined by the density of muscarinic cholinergic receptors visualized by in vitro receptor autoradiographic methods. The volumes of all three of the song nuclei, as defined by Nissl staining, are significantly larger in males than in females. For area X, Nissl staining and receptor autoradiography indicate the same significant volumetric sex difference. The three nuclei are approximately one and one half to two times larger in males than in females, a degree of dimorphism that is intermediate to those reported for other species. Previous investigations of sex differences in the avian vocal control system have used only Nissl stains to define nuclear volumes. We demonstrate in this paper that receptor autoradiography can be used to assess dimorphisms in nuclear volume. Broad application of this approach to a number of neurotransmitter receptor systems will better characterize the dimorphisms in the song system, and therefore will provide greater insight into the neuroanatomical and neurochemical control of birdsong. 相似文献
3.
Nestling white-crowned sparrows (Z. l. nuttalli) were handreared in sound-isolation chambers under a variety of conditions. The songs of 9 total isolates were compared with songs of 2 Ss tutored with song, and the number of inputs sufficient for an S to produce a normal song was explored. The flexibility of the song-learning system was investigated with a range of tape-recorded tutor songs: alien dialects, alien subspecies, alien species, alternating alien dialects, and an aberrant song. Adult songs were obtained for 40 males and 7 testosterone-injected females. All of the tutor songs could be learned; some Ss learned elements of an alien species' song. Ss tutored with 2 songs copied 1 or the other, were bilingual, or sang a hybrid of the 2. No S presented with fewer than 120 songs learned the tutor song; 2 Ss tutored with 252 songs copied the tutor song. It is concluded that the song learning system is quite flexible, that the results obtained with tape-tutors are different from those with social tutors, and that there may be an interaction between total number of song inputs and the number presented on a single day. Implications for physiological mechanisms and the possible functional significance of the acquisition system are discussed. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Identification of sex from the skeleton is an important demographic assessment in medicolegal investigations. Studies have demonstrated that populations differ from each other in size and proportions and that these differences can affect the metric assessment of sex. It is therefore vital to determine if population differences are great enough to necessitate group-specific standards. To date, there have been no attempts to create standards of assessment for modern Thais. Therefore the purpose of this research is to establish standards from which to determine sex from the femur using a new skeletal collection housed at the Chiang Mai University Department of Anatomy. The sample is composed of 104 individuals (70 males, 34 females). Six standard osteometric dimensions including maximum length, maximum head diameter, midshaft circumference, midshaft anterior-posterior and transverse diameters, and bicondylar breadth were measured and analyzed by stepwise discriminant function statistics. To understand population differences, formulas derived from Chinese, South African whites and American whites and blacks using the same method and variables were tested on the Thai sample. Results indicated that maximum head diameter and bicondylar breadth are the optimal combination for sex diagnosis and yielded 94.2% accuracy. Direct analysis using predetermined single or multiple variables also revealed bicondylar breadth as the best single dimension (93.3%). In cross-tests on the Thais, the Chinese formula gave the most favorable outcome with unsatisfactory results for all other groups. The present research confirms that sexual dimorphism is better reflected in breadth dimensions than in bone length. Comparisons showed that Thais are very different metrically from whites and blacks, and although they most resemble the Chinese, these two groups are not identical. These findings underscore the need for population-specific formulas for identification of sex from the skeleton. 相似文献
5.
PURPOSE: The authors present the "pattern" visual evoked potentials (VEP) analysis with use of the artificial neural networks (ANN). MATERIALS AND METHODS: The study involved 11 patients with compressive chiasmal optic neuropathy, 20 patients with optic neuritis, 12 patients with anterior ischaemic optic neuropathy, 20 patients with optic nerve atrophy from neuritis, 8 patients with demyelinative neuropathy, 5 patients with oedema optic nerve, 20 healthy persons. The tests of visual evoked potentials were performed with the use of computer system UTAS-E1000. Classification of potentials was made by correlation of outputs of ANN with results of confirmed neuro-ophthalmology conditions. RESULTS: ANN of different architecture were classified correctly in 80-100% of VEP record samples. CONCLUSIONS: The obtained correctness of classification confirms usefulness of VEP analysis as the objective diagnostic method in some neuro-ophthalmological diseases and indicates application of ANN in multifactor analysis. 相似文献
6.
MP Faillace MI Keller Sarmiento RE Rosenstein 《Canadian Metallurgical Quarterly》1996,711(1-2):112-117
Melatonin effect on retinal cyclic GMP accumulation, guanylate cyclase activity, cyclic GMP content and cyclic GMP phospho-diesterase activity was examined in the Syrian hamster retina. Melatonin increased significantly cyclic GMP accumulation at picomolar concentrations and in a time-dependent manner. The kinetic analysis of guanylate cyclase activity revealed a significant increase of both apparent Vmax and K(m), induced by 10 nM melatonin. The effect of melatonin was higher in the absence, than in the presence of the phoshodiesterase inhibitor (IBMX), suggesting an effect on cyclic GMP catabolism. Phosphodiesterase activity was significantly decreased by melatonin. The results show a dual effect of melatonin on cyclic GMP levels, i.e. by increasing the synthesis and inhibiting the degradation, both resulting in an increase of cyclic GMP levels. Taking into account the key role of cyclic GMP in visual mechanisms, the results would suggest the participation of melatonin in retinal physiology. 相似文献
7.
A histochemical study has been made of seasonal fluctuations in the follicular atresia and interstitial gland tissue with the ovarian cycles of the house sparrow (Passer domesticus). The atresia of primordial oocytes forms the predominant feature of the quiescent-winter ovary. The building up of interstitial gland tissue of thecal origin. which precedes the breeding activity, is closely related to the atresia of previtellogenic follicles of variable sizes. Interstitial gland cells which accumulate lipid droplets consisting of cholesterol, and/or its esters, triglycerides and some phospholipids, are the steroid secretors. The possible functional significance of different-sized follicular atresia in relation to follicular growth and breeding activity is discussed. 相似文献
8.
The courtship song of Drosophila is thought to be involved in sexual selection and species recognition. Because of the mating system of flies, however, directly demonstrating that song influences female preference is difficult. The majority of previous studies have used an experimental design that potentially confounds male and female reactions to song. In D. montana, correlational evidence has suggested that males that produce short sound pulses consisting of a high number of sound cycles (i.e. a high carrier frequency) have a higher mating success than other males. In this study, we played synthetic song that varied in pulse length and carrier frequency to individual females in the laboratory, both alone and in the presence of mute males. We scored female preference via an acceptance posture, 'wing spreading', which the females of this species usually display prior to mounting by a male. Females responded to synthetic song in the absence of males. The presence of mute males significantly increased their overall responsiveness, but the relative effectiveness of the songs did not change, eliminating male reaction to song as a possible confounding factor in the results. The interaction between pulse length and carrier frequency determined the discrimination between song types, with females responding most readily to song consisting of short pulses with a high carrier frequency. Thus, direct examination of female preferences supports the previous studies of male mating success, and confirms female song preference as a likely determinant of male mating success. Copyright 1998 The Association for the Study of Animal Behaviour 相似文献
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A novel binding site for angiotensin II has been identified in certain murine tissues. This site, denoted ATm, is distinct from both the AT1 and AT2 sites, as well as the various atypical sites that have been described. The site has a low affinity for angiotensin II (100 nM) and is not blocked by losartan, PD123177 or saralasin. The site shows structural specificity for angiotensin II since both angiotensin III and angiotensin II (1-7) failed to inhibit the binding. Numerous standard drugs, including various receptor blockers, enzyme inhibitors and therapeutic agents, showed no affinity for the site. In murine tissues the site is associated with active tissue generation, as found in spleen, placenta and growing tumors, but its occurrence appears to be rare outside of the mouse. 相似文献
11.
JM Guerrero A Menendez-Pelaez JR Calvo C Osuna A Rubio MA Lopez-Gonzalez 《Canadian Metallurgical Quarterly》1994,3(2):99-106
Specific melatonin binding sites in the harderian gland of both rat and Syrian hamster were studied using [125I]melatonin. In both species, binding of [125I]melatonin by harderian gland membranes exhibited properties such as dependence on time, temperature, membrane concentration, saturability, and high specificity. Only one class of high-affinity binding sites was found with a Kd of 0.19 and 6.47 nM for the rat and Syrian hamster, respectively. The binding capacity in the rat harderian gland was 4.00 fmol/mg protein; in the Syrian hamster it was 7.58 fmol/mg protein. In the rat, no sex differences were found in the binding of the tracer to the membranes. However, in the Syrian hamster, binding of [125I]melatonin by the harderian gland was twice higher in the female than in the male. No changes were found in the Kd values (6.47 vs. 6.94 nM), while binding capacity was significantly increased in the female (13.50 fmol/mg protein) when compared to the male hamster (7.58 fmol/mg protein). Binding of [125I]melatonin by the harderian gland of male hamsters was modified by castration but not by melatonin treatment. Castration induced an increase of binding up to the level of females. However, chronic melatonin administration did not alter the [125I]melatonin binding in either intact or gonadectomized male hamsters. Binding studies also showed diurnal variations. There was a diurnal rhythm of [125I]melatonin binding by Syrian hamster harderian glands with the peak at the end of the light period and the trough late in the dark period. This rhythm in the binding is observed in both male and female hamsters, although binding in females was always higher than that in males.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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Chin morphology and sexual dimorphism in the fossil hominid mandible sample from Klasies River Mouth
The site of Klasies River Mouth (KRM) in South Africa has produced a small sample of early Upper Pleistocene hominid remains that have been a focus for discussions of the origins of modern humans. Despite certain primitive characteristics exhibited by these fossils, proponents of a single recent origin have attributed them to early modern humans. Critics of this hypothesis have emphasized the significance of the archaic features evident in this sample, including the absence of pronounced chins among the mandibular specimens. This study compares the size range and chin morphology exhibited by the KRM mandibles with that of Neandertals, Upper Pleistocene humans, and recent humans. The extreme sexual dimorphism documented among the KRM fossils reflects the presence of a very small individual, and previous efforts to classify the KRM sample as archaic on the basis of their robusticity have failed to address the significance of this diminutive hominid. While each KRM fossil falls within the 95% envelope of variability established for chin development in a comparative modern sample, a similarly low frequency of pronounced chins is very unlikely to be found in any recent human population. The morphological pattern of the KRM mandibles is clearly distinct from that of Neandertals and of recent humans. 相似文献
14.
D Pontier E Fromont F Courchamp M Artois NG Yoccoz 《Canadian Metallurgical Quarterly》1998,265(1392):167-173
Hochberg and co-workers have predicted that an increase in host adult mortality due to parasites is balanced by an earlier age at first reproduction. In polygynous species we hypothesize that such a pattern would lead to diverging selection pressure on body size between sexes and increased sexual size dimorphism. In polygynous mammals, male body size is considered to be an important factor for reproductive success. Thus, under the pressure of a virulent infection, males should be selected for rapid growth and/or higher body size to be able to compete successfully as soon as possible with opponents. In contrast, under the same selection pressure, females should be selected for lighter adult body size or rapid growth to reach sexual maturity earlier. We investigated this hypothesis in the domestic cat Felis catus. Orange cats have greater body size dimorphism than non-orange cats. Orange females are lighter than non-orange females, and orange males are heavier than non-orange males. Here, we report the extent to which orange and non-orange individuals differ in infection prevelance for two retroviruses, feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). FIV is thought to be transmitted almost exclusively through aggressive contacts between individuals, whereas FeLV transmission occurs mainly through social contacts. The pattern of infection of both diseases is consistent with the higher aggressiveness of orange cats. In both sexes, orange cats are significantly more infected by FIV, and tend to be less infected by FeLV than other cats. The pattern of infection is also consistent with an earlier age at first reproduction in orange than in non-orange cats, at least for females. These results suggest that microparasitism may have played an important role in the evolution of sexual size dimorphism of domestic cats. 相似文献
15.
ND Fisher C Ferri C Bellini A Santucci R Gleason GH Williams NK Hollenberg EW Seely 《Canadian Metallurgical Quarterly》1997,29(4):980-985
The angiotensinogen gene is one of the very few related by linkage analysis to human hypertension, but the linkage has been consistently shown only among males. Moreover, polymorphisms in this gene predict an abnormal renal responsiveness to angiotensin II, a feature of non-modulation, but again, only among males. To pursue these related bridges between genetics and physiology, we evaluated the effects of sex on a second feature of non-modulation, the aldosterone response to infused angiotensin II during low sodium balance. We tested the resultant hypothesis-that non-modulation would be less frequent in women-by conducting identical protocols on 225 hypertensive inpatients (70 women, 155 men). Non-modulation was strikingly less frequent among women (26%; 95% confidence interval, 16% to 37%) than men (49%; 95% confidence interval, 40% to 57% (P = .001). We tested the hypothesis that sex steroids play a role by comparing young, premenopausal women (< 35 years) with women who were perimenopausal (45 to 55 years) and postmenopausal (> 55 years). Among the youngest women, the frequency of non-modulation was only 7%, significantly less than in young men (41%, P = .02). A steady increase in non-modulation frequency accompanied advancing age in women, reaching 47% in those older than 55 years, equal to the fraction of men affected. Age influenced non-modulation frequency in men far less. We conclude that a striking sex difference underlies the non-modulation phenotype and that female sex hormones may confer protection against a genotypic predisposition in women. This "override" of genotype, manifest by a very low frequency of non-modulation in young women, may participate in their known protection against cardiovascular disease. 相似文献
16.
Two objects with homologous landmarks are said to be of the same shape if the configuration of landmarks of one object can be exactly matched with that of the other by translation, rotation/reflection, and scaling. In an earlier paper, the authors proposed statistical analysis of shape by considering logarithmic differences of all possible Euclidean distances between landmarks. Tests of significance for differences in the shape of objects and methods of discrimination between populations were developed with such data. In the present paper, the corresponding statistical methodology is developed by triangulation of the landmarks and by considering the angles as natural measurements of shape. This method is applied to the study of sexual dimorphism in hominids. 相似文献
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Coturnix kept in a 14L:10D photoperiod from hatch began to lay their first eggs at a mean age of 42.8 days (range 38-55). Approximately 2/3 of Coturnix held from hatch in photoperiods of 6L:16D light were laying at 165 days of age. Mean age at first egg was 112.7 days (range 68-162 days) in 8L:16D and 130.8 days (range 117-158 days) in 6L:18D photoperiod. Coturnix transferred from a non-stimulatory (8L:16D) photoperiod to a stimulatory one (14L:10D or 24L) begun laying in 15-20 days if less than 140 days old, and in about 5 days if greater than 140 days old, when trasferred. Birds which has spontaneously begun to lay in an 8L:16D photoperiod did not stop laying when the photoperiod was reduced to 6L:18D. Those which began laying under 14L:10D photoperiod ceased laying in about 15 days if 89 or fewer days old when switched to 8L:16D, or in about 6 days if 140 or more days old. Those switched from 14L:10D to 6L:18D ceased laying in about 13 days when 76 days old, and 7 days when 89 days old. 相似文献
19.
Sexual dimorphism in catecholamine and indoleamine content in the brain preoptic area and mediobasal hypothalamus was studied in 10-day-old rat pups whose mothers had been exposed to the daily 1-h immobilization stress during the last week of pregnancy. Concentration of noradrenaline in the preoptic area and 5-hydroxyindoleacetic acid in the mediobasal hypothalamus of the prenatally stressed male offspring as well as dopamine content in the mediobasal hypothalamus and 5-hydroxyindoleacetic acid content in the preoptic area of the females were increased by 59%, 45%, 34%, 76%, respectively. Dopamine content in the preoptic area of the female pups was decreased. In addition, an increase of 5-hydroxytryptamine metabolism in the female preoptic area has been revealed. As a result of prenatal stress, sex-related differences in noradrenaline and 5-hydroxyindoleacetic acid concentrations in the preoptic area and those in dopamine concentration in the mediobasal hypothalamus disappeared. The suggestion is made that the early changes in sexual dimorphism of the brain catecholamines and 5-hydroxytryptamine metabolism in prenatally stressed rats may be responsible for the development of the long-term disorders of sexual differentiation of the neuroendocrine functions. 相似文献
20.
Previous studies have suggested a causal relation between sex differences in behavior such as singing and sex differences in the size of brain areas such as the forebrain song control areas of songbirds. In the present study we show that the size of the forebrain vocal control areas nucleus hyperstriatalis ventrale pars caudale (HVC) and nucleus robustus archistriatalis (RA) and its neuron numbers are about twice as large in males as in females of the African dueting bush shrike Laniarius funebris. However, song types are of similar complexity (number of elements per song type, physical properties of elements) in both sexes, and repertoire size does not differ between males and females. Furthermore, in captivity male and female shrikes are able to learn the same song types. This demonstrates for the shrike that sex differences in the size of vocal control areas and in its neuron numbers do not predict the type of sex-typical vocal behavior. This result is supported by a statistical comparison of the sex differences in HVC size, RA size, and song repertoire size of all songbird species studied to date. Sex differences in species in which only the males sing are indeed larger than in species in which the females also sing; in songbird species with singing females, however, the sex differences in HVC and RA volume appear to be independent of the vocal repertoire size of females. The songbird model therefore does not support the notion that sex differences in area size and neuron number explain sex differences in a behavior that occurs in both sexes. Furthermore, in the shrike, neuron soma size is similar in males and females in the song motonucleus hypoglossus pars tracheosyringealis (nXIIts) and in the premotor nucleus RA, but is sexually dimorphic in the higher vocal center HVC. Thus, male and female shrikes produce songs of similar complexity with different neuron phenotypes. 相似文献