首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The ovary in which a CL was observed by laparoscopy in Finnish Landrace, Tasmanian Merino and Scottish Blackface ewes had no apparent effect on the location of the CL during the succeeding oestrous cycles, on the duration of the associated oestrous cycles, or on the peripheral progesterone concentrations on Days 7 and 11. Although 53% of CL were present in the right ovaries, the difference between the two sides was not significant.  相似文献   

2.
3.
Mori M 《Bioethics》1993,7(2-3):141-148
In this paper I want to try to clarify the nature of the two different problems indicated in the title: there is a lively debate on whether or not genetic selection is a morally licit practice, and there are strong disagreements on whether or not the embryo is a person. I think that most of such controversies depend on confusions and/or unclearness about specific problems involved in each issue, I have no precise normative proposal on the morality of genetic selection, but I hope that my analysis will be helpful in avoiding some current confusions.  相似文献   

4.
The effect of vasopressin on learning, habituation and habit recovery in rat before and after electrolytic ablation of locus coeruleus, nuclei dorsalis et medialis raphe and pars compacta substantiae nigrae was studied by behavioural methods. The rats were learned with positive reinforcement in a T-shaped maze and with negative reinforcement in a U-shaped maze. It was found that improvement of trace consolidation and acceleration of learning were in many cases dependent on the activity level of the dophaminergic, noradrenergic and to a lesser degree on that of serotoninergic brain systems.  相似文献   

5.
The experiments on the immature female rats were carried out to show the effects of damage or stimulation of the lateral septal nucleus (LSN) on the ovary function and its response to chorionic gonadotrophin. The damage of the LSN decreases the ovary weight, but enlarges mature ovarian follicles and increases the estrogen production. LSN lesions in hypophysectomized rats have no effect on the ovary and uterus weights as compared to hypophysectomized ones, but decrease the size of mature ovarian follicles against a background of hypophysectomy or LSN lesions. Damage of the LSN increases ovary and uterus sensitivity to the chorionic gonadotrophin injections. A conclusion is drawn on the existence of parahypophysial way to transfer the influence of LSN on the rat ovaries. The possible mechanisms of LSN influence on the reproduction system of female rats is under discussion.  相似文献   

6.
The effects of a synthetic antioxidant ionol (dibunol) on the biosynthesis and content of catecholamines in the heart and adrenal glands were studied. It was shown that in stress a mobilization of catecholamine reserve is combined with a considerable increase in dopamine concentration. In conditions of physiological rest, ionol did not affect the studied indices of adrenal catecholamine biosynthesis, while in the heart it enhanced the dopamine synthesis and content. With ionol administration, stress did not suppress but, on the contrary, increased the neuronal uptake and noradrenaline biosynthesis, catecholamine concentration remaining practically unchanged. Simultaneously, a manyfold increase in the biosynthesis along with a considerable increase in the concentration of dopamine developed in both organs. The data obtained suggest that ionol realizes its stress-defensive effect to a great extent due to the activation of catecholamine biosynthesis and to a concomitant increase in dopamine accumulation.  相似文献   

7.
The germination of the spores of Thermoactinomyces vulgaris formed on a complex medium is stimulated by suspending them in solutions containing Mg2+ and Ca2+ ions. The stimulation is not the result of the initiation of the spores in the presence of the ions since the experiments were carried out at a temperature of 20 degrees C at which the initiation did not virtually take place. The ions of Na+ and K+ have almost no effect on the germination of the spores. The fraction of the resting spores of Thermoactinomyces vulgaris depends on the composition of the growth medium, especially on its amino acid composition. The addition of Mg2+ and Ca2+ ions to a minimal synthetic growth medium stimulates the growth of the cultures and decreases the dormancy of the spores. The spores formed on the synthetic medium are less thermostable than the spores formed on the complex medium. Thermostability of the spores increases upon the addition of Mg2+ to the synthetic medium. Spore suspensions obtained on the synthetic medium with Mg2+ or Ca2+ are initiated more completely than spore suspensions obtained on the complex medium.  相似文献   

8.
Aquaculture is a generic term that covers a wide variety of culture techniques and cultured species under different conditions and in different geographical localities. It is typically a littoral and rural activity, and is rapidly expanding. An assessment of available literature concerning the interaction of aquaculture and the environment was conducted using the Aquatic Science and Fisheries Abstract (ASFA) database from 1978 to December 1991, incorporating a variety of definitive key word strategies together with a classical search of the available literature. Of the 2692 references collected, 70% were made up of publications from the ASFA database, while 30% consisted of ‘gre’ publications (i.e. Government reports, Working Group reports and publications not included in the ASFA database). The literature gleaned from the ASFA database tends to refer to specific interactions of environment and a given culture species in a given location, while the grey literature tends to deal with the broader implications. Most or the research focuses on the most commonly cultured species in developed Western countries. Consequently, information on extensive aquaculture is based on the interactions arising from cyprinid (12%), oyster (13%) and mussel culture (8%), while information on intensive culture is concerned mainly with trout culture in fresh water (20%) and salmonid culture in shallow marine localities (6%). There is a general lack of information on the waste output of commercial farming systems of marine finfish species new to the aquaculture industry and on their basic biological requirements in cultivation, as well as their environmental interactions. Other gaps in the literature relate to the discharge of chemicals into the environment and the effects on the immediate environs and adjacent ecosystems and the accidental or intentional release of cultured species.  相似文献   

9.
We examined first the behavior of a single animal (Macacus Rhesus), partially free to move on a Brady chair, before and after direct electrical stimulation of the amygdala and the hippocampus; then the social behavior of two animals, completely free to move in a large behavioral cage, before and after stimulation, by radio, of the amygdala. Certain ventromedial areas of the amygdala have a short and long term inhibitory effect on feeding and social behavior and the hippocampus has a short and long term facilitating effect on feeding behavior, especially during the after discharge.  相似文献   

10.
The ozone molecule contains three atoms of oxygen and is mainly formed by the action of the ultraviolet rays of the sun on the diatomic oxygen molecules in the upper part of the Earth's atmosphere (called the stratosphere). Atmospheric pollution near the Earth's surface can form localized areas of ozone. The stratospheric ozone layer protects life on Earth by absorbing most of the harmful ultraviolet radiation from the sun. In the mid 1970s it was discovered that some manmade products destroy ozone molecules in the stratosphere. This destruction can result in damage to ecosystems and to materials such as plastics. It may cause an increase in human diseases such as skin cancers and cataracts. The discovery of the role of the synthetic ozone-depleting chemicals such as chlorofluorocarbons (CFCs) stimulated increased research and monitoring in this field. Computer models predicted a disaster if no action was taken to protect the ozone layer. Based on this research and monitoring, the nations of the world took action in 1985 with the Vienna Convention for the Protection of the Ozone Layer followed by the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987. The Convention and Protocol were amended and adjusted several times as new knowledge was obtained. The Meetings of the Parties to the Montreal Protocol appointed three Assessment Panels to review the progress in scientific knowledge on their behalf. These panels are the Scientific Assessment Panel, the Technological and Economic Assessment Panel and the Environmental Effects Assessment Panel. Each panel covers a designated area and there is a natural level of overlap. The main reports of the Panels are published every four years as required by the Meeting of the Parties. All the reports have an executive summary that is distributed more widely than the main report itself. It became customary to add a set of questions and answers--mainly for non-expert readers--to the executive summaries. This document contains the questions and answers prepared by experts who comprise the Environmental Assessment Panel. It is based mainly on the 2006 report of the Panel but also contains information from previous assessments. Readers who need detailed information on any question should consult the full reports for a more complete scientific discussion. This set of questions refers mainly to the environmental effects of ozone depletion and climate change. The report of the Scientific Assessment Panel contains questions and answers related to the other scientific issues addressed by that Panel. All these reports can be found on the UNEP website (http://ozone.unep.org).  相似文献   

11.
In the Indo-Pacific and the Caribbean regions, isolated rivers are host to amphidromous Gobiidae with a life cycle adapted to extreme climatic and hydrological seasonal variation. Although this is the most diverse family of freshwater fish, their biological cycle and the parameters and evolutionary processes that lead to such diversity are poorly understood. This paper reports on the current knowledge on reproduction (nidification, spawning, larval life and sexuality), recruitment into the rivers, upstream migration and distribution in the rivers. Management and restoration strategies to preserve amphidromous gobies, often endemic and bordering on extinction, require the development of research to have a better understanding of their life cycle.  相似文献   

12.
We present ab-initio periodic Hartree–Fock calculations (crystal program) of small molecules on TiO2 and MgO. The adsorption of the molecules may be molecular or dissociative. This depends on their acid and basic properties in the gas phase. For the molecular adsorption, the molecules are adsorbed as bases on Ti(+IV) sites, the adsorption energies correlate with the proton affinities. The dissociations on the surface correlate with the gas phase cleavages: thus, the dissociation of MeOH leads to a preferential basic cleavage (the fragment HO– is adsorbed on a Ti+4 ion and the fragment Me+ is adsorbed on a O2– ion of the oxide). The opposite result is obtained with MeSH. Another important factor is the adsorbate–adsorbate interaction: favorable cases are a sequence of H-bonds for the hydroxyl groups resulting from the water dissociation and the mode of adsorption for the ammonium ions. Lateral interactions also force the adsorbed CO2 molecules to bend over the surface so that their mutual orientation resembles the geometry of the CO2 dimer. With respect to water adsorption, MgO appears to be a basic oxide. As experimentally observed, NH3 adsorbs preferentially on TiO2 and CO2 on MgO. However, this difference of reactivity should not be expressed in terms of acid vs. basic behaviour but in terms of hard and soft acidity. The MgO surface is a 'soft' acidic surface that reacts preferentially with the soft base, CO2.  相似文献   

13.
The gynoecium is syncarpous in all Ochnaceae. In the Ochnoideae carpels are peltate with a conventional cross-zone bearing one ovule, or, in Lophira , a very broad cross-zone with an horizontal ovular row. In Ochna and Brackenridgea , the style is gynobasic, each carpel develops transmitting tissue on its morphologically dorsal surface, and this tissue lines a canal or originates a solid inner strand in each carpel at style level. The style is tubular, with an inner cuticle, and compound, each component with its own transmitting tissue. In Ouratea the style is solid with a single compound transmitting strand. In Lophira and Elvasia the transmitting tissue seems to be developed by the morphologically ventral carpellary surfaces. Ovules are unitegmic with a bivalent integument.
In the Sauvagesioideae carpels are peltate, but with ovules above the cross-zones, on margins of the symplicate zone. In Euthemis , there is one ovule on each side of, and close to, each cross-zone. The single stylar canal is bounded by the morphologically dorsal carpellary surfaces. In Sauvagesia ovules occur on both sides of the cross-zones but most of them are above on carpel margins, as are all ovules of Cespedesia. The stylar canal of Sauvagesia is bounded by the ventral carpel surfaces, three strips of the outer surface passing inside at the sutures and developing into transmitting tissue. The stylar canal of Cespedesia is bounded by the dorsal carpel surfaces. The gynoecium of Wallacea has two epeltate carpels with a laminar placentation, the carpel margins being displaced on to the topographically ventral carpel surfaces with a row of ovules along each margin. Ovules are bitegmic.
The Ochnoideae, which shows relationships with the Rutaceae, Meliaceae, Simaroubaceae and Hippocastanaceae, is more advanced than the Sauvagesioideae, which clearly belongs in the Violales. The Ochnaceae is to be placed in the Violales.  相似文献   

14.
The significance of Behaviourism is examined in relation to its far conceptual roots, i.e. comparative animal studies initiated by Darwin, mechanistic physiological thinking initiated by Descartes and empiricist associationism. The Behaviourist anti-mentalist position induced neuromechanistic interpretations based on Pavlovian reflexes, stimulus-response connectionism and the very first hypotheses on synaptic plasticity. As a result, the evolutionary tradition was dropped and the two other trends were combined into a new adaptive version of Cartesian automaton, with persisting influences in modern reductionist thinking, from robotics and cognitive science to the neuroscience of learning and memory.  相似文献   

15.
The fine structure of the trophozoite and cyst of Entamoeba histolytica from the stool of a patient was compared using the freeze-fracture method. The intramembranous particles (IMP's) were heterogeneously distributed on the plasma membrane of the trophozoite and their density was 1139 +/- 105/micron 2 on the P face. Particle-rich depressions and linear particle arrays, reported by other investigators on cultured trophozoites, were also observed on the P face while on the E face such special particle arrangement was not recognized. Particle-free, small protrusions were frequently observed on the P face of the trophozoite membrane. The existence of these protrusions is a new finding. In the cyst, the IMP's were also distributed heterogeneously on both the P and E faces of the plasma membrane. The density of the IMP's, however, was much lower than in the trophozoite: 6 +/- 2/micron 2 on the P face and averaging less than 1/micron 2 on the E face. In freeze-fracture images, the plasma membrane of the cyst showed a variety of configurations from smooth to uneven or ridged surfaces. These morphological alterations of the plasma membrane may be attributed to the aging of the cyst. The thick wall of the cyst had a filamentous tri- or tetra-lamellar structure. The cytoplasm of the cyst was similar in structure to that of the trophozoite and the diameter of the nuclear pores was equal in both trophozoites and cysts.  相似文献   

16.
This paper presents the main results of a 10-year zooarchaeological study on the origin of the present-day terrestrial mammals of Corsica. Thousands of teeth and bones from Corsican archaeological sites comprise an almost complete succession from the end of the Pleistocene ( c. 10,000 years BP) to the present. Human activities brought about the extinction of the entire autochthonous mammalian fauna and the gradual introduction of more than 25 taxa which constitute the present wild and domestic fauna. Such a complete turnover has also been recorded on other large Mediterranean islands and on some of the smaller ones. Preliminary data indicate how these events may have occurred in Corsica. This article emphasizes the important role which zooarchaeology can play in biogeographical research.  相似文献   

17.
In experiments on thirteen rats with electrodes in the lateral hypothalamus, with a simultaneous change in current intensity I and of stimulation duration T, two variants were obtained of the empirical response surface of the self-stimulation (SS) frequency: with the maximum SS frequency, located within the surface boundaries (peak variant), and with the maximum at one of its boundaries (side variant). An equation has also been deduced on the regression of SS frequency on the parameters I and T, which quite accurately defines the experimental and rated data (R = 0.57 divided by 0.97). It has been established that current intensity has a greater effect on SS frequency as compared with the stimulation duration and that the influences of these parameters are relatively independent of one another.  相似文献   

18.
Hair patterns of the dorsum proper of the hand and foot are similar in occupying comparable anatomical positions. The more extensive hair patterns have a higher incidence in whites than in Negroes. And digital hair is more frequently absent on the lateral side of the hand and foot than on the medial side.  相似文献   

19.
ABSTRACT The fine structure of the trophozoite and cyst of Entamoeba histolytica from the stool of a patient was compared using the freeze-fracture method. The intramembranous particles (IMP's) were heterogeneously distributed on the plasma membrane of the trophozoite and their density was 1139 ± 105/μm2 on the P face and 27 ± 9/μm2 on the E face. Particle-rich depressions and linear particle arrays, reported by other investigators on cultured trophozoites, were also observed on the P face while on the E face such special particle arrangement was not recognized. Particle-free, small protrusions were frequently observed on the P face of the trophozoite membrane. The existence of these protrusions is a new finding. In the cyst, the IMP's were also distributed heterogeneously on both the P and E faces of the plasma membrane. The density of the IMP's, however, was much lower than in the trophozoite: 6 ± 2/μm2 on the P face and averaging less than 1/μm2 on the E face. In freeze-fracture images, the plasma membrane of the cyst showed a variety of configurations from smooth to uneven or ridged surfaces. These morphological alterations of the plasma membrane may be attributed to the aging of the cyst. The thick wall of the cyst had a filamentous tri- or tetra-lamellar structure. The cytoplasm of the cyst was similar in structure to that of the trophozoite and the diameter of the nuclear pores was equal in both trophozoites and cysts.  相似文献   

20.
Intrinsic noise and the design of the genetic machinery   总被引:1,自引:0,他引:1  
Darwinian theory envisages 'selection pressure' as a stress imposed on the genotype by the environment. However, noise in the replicative and translational mechanisms in itself imposes a significant 'pressure' on the adaptive fitness of the organism. We propose that the biosphere has been shaped by both extrinsic (environmental) and intrinsic (noise-generated) factors. Because noise has been a remorseless and ever-present background to the evolutionary process, adaptations to this intrinsic pressure include not only a variety of familiar genetic mechanisms but also many anatomical and life-style characteristics that focus on the transmission of information between generations.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号