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 7 毫秒
1.
2.
Testing of animals with different degrees of manifestation of attraction to ethanol showed that in conditions of zoosocial conflict rats--potential dipsomaniacs have less competition abilities in their struggle for the aims of biological value as compared to the rats, who are not dipsomaniacs. Their failure in a conflict situation leads to the fact, that while getting in the same or some other stress conditions for the second time, the animal fully gives up activity and makes no attempts to overcome these situations. This weak behavioural activity of such rats is based on a great tendency to the development of depressive-like state. Alcohol in certain doses (0.5 g/kg) normalizes the behaviour of rats--potential dipsomaniacs. This, probably, explains the appearance of alcoholic motivation in these animals.  相似文献   

3.
Comparative analysis of levels of the allozymic variation in the vertebrates is conducted using evaluation of a) within population heterozygosity of ferment coding homologous loci, b) average (per each species) allele frequencies of homologous loci, and c) overall sample of the loci being analyzed. It is established that amphibians and reptiles are characterized by the highest, birds and mammals--by the lowest, and fishes--by the middle level of genetic diversity. The diversity of genetic systems, if the constant heterozygosity of duplicated loci is taken into consideration, decreases from fishes to mammals and from cold-blooded to warm-blooded vertebrates. This tendency could be considered as an extrapolation of the "progressive specialization" rule on molecular level. Three basic factors determining certain level of genetic diversity of a species are acknowledged position in the phylogenetic system, population structure, and level of introgressive hybridization. From methodological viewpoint, evaluation of the genetic diversity by homologous loci seems to be most valid in comparative studies.  相似文献   

4.
Blood serum samples of 3,448 schoolchildren of grades 1-10 in 35 schools of Dushanbe were examined in the passive hemagglutination test in 1988 and 1989. The proportion of persons unprotected against diphtheria and tetanus was estimated by common methods in different kinds of selective serologic survey: mass screening (43.4-83.0%), testing in selected groups reduced 2, 3 and 5 times, cluster sampling. The reduction of the groups to be examined (from 3,033 to 250 persons) was not accompanied by essential changes (t < 2) in the characteristics of mass immunity against diphtheria and tetanus. The cluster method was shown to be highly reliable also in the study of population immunity.  相似文献   

5.
6.
In spite of increasing application of presence-only models in ecology and conservation and the growing number of such models, little is known about the relative performance of different modelling methods, and some of the leading models (e.g. GARP and ENFA) have never been compared with one another. Here we compare the performance of six presence-only models that have been selected to represent an increasing level of model complexity [BIOCLIM, HABITAT, Mahalanobis distance (MD), DOMAIN, ENFA, and GARP] using data on the distribution of 42 species of land snails, nesting birds, and insectivorous bats in Israel. The models were calibrated using data from museum collections and observation databases, and their predictions were evaluated using Cohen's Kappa based on field data collected in a standardized sampling design covering most parts of Israel. Predictive accuracy varied between modelling methods with GARP and MD showing the highest accuracy, BIOCLIM and ENFA showing the lowest accuracy, and HABITAT and DOMAIN showing intermediate accuracy levels. Yet, differences between the various models were relatively small except for GARP and MD that were significantly more accurate than BIOCLIM and ENFA. In spite of large differences among species in prevalence and niche width, neither prevalence nor niche width interacted with the modelling method in determining predictive accuracy. However, species with relatively narrow niches were modelled more accurately than species with wider niches. Differences among species in predictive accuracy were highly consistent over all modelling methods, indicating the need for a better understanding of the ecological and geographical factors that influence the performance of species distribution models.  相似文献   

7.
8.
9.
The study of ingestive behaviour has an extensive history, starting as early as 1918 when Wallace Craig, an animal behaviourist, coined the terms ‘appetitive’ and ‘consummatory’ for the two-part sequence of eating, drinking and sexual behaviours. Since then, most ingestive behaviour research has focused on the neuroendocrine control of food ingestion (consummatory behaviour). The quantity of food eaten, however, is also influenced by the drive both to acquire and to store food (appetitive behaviour). For example, hamster species have a natural proclivity to hoard food and preferentially alter appetitive ingestive behaviours in response to environmental changes and/or metabolic hormones and neuropeptides, whereas other species would instead primarily increase their food intake. Therefore, with the strong appetitive component to their ingestive behaviour that is relatively separate from their consummatory behaviour, they seem an ideal model for elucidating the neuroendocrine mechanisms underlying the control of food hoarding and foraging. This review focuses on the appetitive side of ingestive behaviour, in particular food hoarding, attempting to integrate what is known about the neuroendocrine mechanisms regulating this relatively poorly studied behaviour. An hypothesis is formed stating that the direction of ‘energy flux’ is a unifying factor for the control of food hoarding.  相似文献   

10.
11.
Understanding taste processing in the nervous system is a fundamental challenge of modern neuroscience. Recent research on the neural bases of taste coding in invertebrates and vertebrates allows discussion of whether labelled-line or across-fibre pattern encoding applies to taste perception. While the former posits that each gustatory receptor responds to one stimulus or a very limited range of stimuli and sends a direct 'line' to the central nervous system to communicate taste information, the latter postulates that each gustatory receptor responds to a wider range of stimuli so that the entire population of taste-responsive neurons participates in the taste code. Tastes are represented in the brain of the fruitfly and of the rat by spatial patterns of neural activity containing both distinct and overlapping regions, which are in accord with both labelled-line and across-fibre pattern processing of taste, respectively. In both animal models, taste representations seem to relate to the hedonic value of the tastant (e.g. palatable versus non-palatable). Thus, although the labelled-line hypothesis can account for peripheral taste processing, central processing remains either unknown or differs from a pure labelled-line coding. The essential task for a neuroscience of taste is, therefore, to determine the connectivity of taste-processing circuits in central nervous systems. Such connectivity may determine coding strategies that differ significantly from both the labelled-line and the across-fibre pattern models.  相似文献   

12.
Interconnection between predisposition to depressive-like state (DS) in stress situation and heightened addiction to ethanol was studied in nonlinear male white rats. Electrolytic lesion of the septum in animals inclined to the development of DS, led to a change from the passive type of reaction in stress conditions to the active type. The rate of formation of alcoholic motivation in these animals decreased in comparison with sham-operated rats. The effect of the septal lesion in rats with formed addiction to alcohol was less expressed. Conclusion is made that the passive type of reaction in extreme conditions is significant for the formation of alcohol motivation in rats, especially at early stages.  相似文献   

13.
14.
A comparative study of distant hybridization in plants and animals   总被引:1,自引:0,他引:1  
Distant hybridization refers to crosses between two different species, genera, or higher-ranking taxa, which can break species limits, increase genetic variation, and combine the biological characteristics of existing species. It is an important way of creating genetic variation, fertile strains, and excellent characteristics in new strains and populations. Combining analyses and summaries from many inter-related documents in plants and animals, both domestic and international, including examples and long-standing research on distant hybridization in fish from our laboratory, we summarize and compare the similarities and differences in plant and animal distant hybridization. In addition, we analyze and review the biological characteristics of their different ploidy progenies and the possible causes of disparity in survival rates. Mechanisms of sterility in animal and plant distant hybrids are also discussed, and research methods for the study of biological characteristics of hybrids, including morphology, cytology,and molecular cytogenetics are presented. This paper aims to provide comprehensive research materials and to systematically compare the general and specific characteristics of plant and animal hybrids with regards to reproduction, genetics, growth traits,and other biological characteristics. It is hoped that this paper will have great theoretical and practical significance for the study of genetic breeding and biological evolution of plant and animal distant hybridization.  相似文献   

15.
The action of bicillin-3 on Brucella directly in the body of animals enhances their potential ability to convert into L-forms. One of the factors contributing to the generalization of the infection caused by the L-forms of Brucella and to their prolonged persistance in the body is the presence of an L-transforming agent (in this case, bicillin-3), which indicate that the appearing L-forms of Brucella are obviously antibiotic-dependent.  相似文献   

16.
Comparative randomized opened pharmacokinetic evaluation of benzathine benzylpenicillin in three dosage forms was performed. Benzathine benzylpenicillin was used as extencilline (2.4 million U or 1.2 million U, "Rh?ne-Poulenc Rorer", France) and as bicillin-5 (1.5 million U, "Synthesis" Russia). 33 patients were included in investigation (23 women and 10 men aged 16-60 years). 25 persons had verified rheumatism without blood circulation failure signs, 4--had chronic tonsillitis and 4 were healthy volunteers. Benzylpenicillin concentration was estimated by microbiology test in blood samples taken at 1, 3, 24 hours and 7, 14 and 21 days after intramuscular drug injection. After 2.4 million U extencilline injection (12 patients) its concentration, was at the inhibition level for beta-hemolytic streptococcus group A (25 ng/ml) for 3 weeks-period in 83.3 per cent of patients. After 1.2 million U extencilline injection (10 patients) or 1.5 million U bicillin-5 injection (12 patients) the above mentioned concentration was achieved on the 21st day in 30 and 0 per cent of patients respectively. Thus the treatment with benzathine benzylpenicillin at the 1.2 million U dose in the form of extencilline or bicillin-5 doesn't provide adequate antistreptococcal concentration in blood in prolonged period and is not suitable for correct rheumatism prophylaxis in adult patients.  相似文献   

17.
18.
The experiments carried out on albino male rats have shown a decreased zinc content in the brain of active animals selected under conditions of forced swimming test, as compared to passive animals. 10-day intraperitoneal injection of biotic zinc sulfate dose (50 micrograms/kg) resulted in the prevention of alcohol motivation in active animals. There was no such effect in passive animals. The differences between basic mechanisms of alcohol motivation in different groups of animals are suggested.  相似文献   

19.
In this work the comparative evaluation of the sensitivity and serological specificity of the microcapsular agglutination (MCA) test, the passive hemagglutination (PHA) test and the microagglutination (MA) test are presented. In the MCA test leptospiral antigens, adsorbed on synthetic carrier capsules produced by Japan Lyophilization Laboratory, were used and the PHA test was made with the use of polyvalent erythrocyte diagnosticum. The study of blood serum samples from 46 leptospirosis patients revealed that the values of antibody titers in the PHA and MCA tests were 5.5-8.1 times higher than the traditional MA test. In the MCA and PHA tests antileptospiral antibodies could be detected as early as on days 1-3 of the disease when the results of the MA test were negative or very low. The maximum values of antibody titers in the MCA and PHA tests were detected on days 11-15 of the disease and in the MA test, on days 21-25. The MCA and PHA tests are genus-specific and permit the detection of antileptospiral antibodies irrespective of the serogroup of the infective agent. In the study of the blood sera of 40 patients with diseases of nonleptospiral etiology the MCA and MA tests yielded false positive results in 7.5% and the PHA test, in 12.5% of cases in titers below the diagnostic level. These data are indicative of high sensitivity and specificity of the serological tests used in this study.  相似文献   

20.
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