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排序方式: 共有234条查询结果,搜索用时 15 毫秒
1.
To analyze the sexual behavior of male black-legged deer ticks Ixodes dammini,we collected ticks infesting 202 white-tailed deer. On average, 17.7 males and 8.8 females infested each deer. Field-collected males copulated with a mean of 2.25 females, and virgin males mated with 2.4 females. On experimental hosts, males established sexual contact with feeding females and repelled other males, and about half remained paired after their mate detached. Engorged females continue to be receptive, and males mate more readily with them than with nonfed females. We conclude that male I. damminiare endowed with a repertoire of behaviors which favor an opportunistic mating before seeking a host and a preference for mating with feeding females on the host accompanied by tenacious mate guarding. 相似文献
2.
Role of fructose 2,6-bisphosphate in the regulation of glycolysis and gluconeogenesis in chicken liver 总被引:3,自引:0,他引:3
O K Chaekal J C Boaz T Sugano R A Harris 《Archives of biochemistry and biophysics》1983,225(2):771-778
Glucagon and dibutyryl cyclic AMP inhibited glucose utilization and lowered fructose 2,6-bisphosphate levels of hepatocytes prepared from fed chickens. Partially purified preparations of chicken liver 6-phosphofructo-1-kinase and fructose 1,6-bisphosphatase were activated and inhibited by fructose 2,6-bisphosphate, respectively. The sensitivities of these enzymes and the changes observed in fructose 2,6-bisphosphate levels are consistent with an important role for this allosteric effector in hormonal regulation of carbohydrate metabolism in chicken liver. In contrast, oleate inhibition of glucose utilization by chicken hepatocytes occurred without change in fructose, 2,6-bisphosphate levels. Likewise, pyruvate inhibition of lactate gluconeogenesis in chicken hepatocytes cannot be explained by changes in fructose 2,6-bisphosphate levels. Exogenous glucose caused a marked increase in fructose 2,6-bisphosphate content of hepatocytes from fasted but not fed birds. Both glucagon and lactate prevented this glucose effect. Fasted chicken hepatocytes responded to lower glucose concentrations than fasted rat hepatocytes, perhaps reflecting the species difference in hexokinase isozymes. 相似文献
3.
N T Boaz 《American journal of physical anthropology》1980,53(1):49-54
The first definitive hominoid from the Libyan Mio-Pliocene site of Sahabi is described. The specimen is a left clavicle, lacking a portion of the acromial end. In superior view it shows a marked sternal curvature, similar to homonids, but it also shows a curvature in the coronal plane, similar to the pongid condition. Muscle attachments for sternocleidomastoid, pectoralis major and the anterior portion of deltoid are preserved. The robust attachment for the latter suggests relative hypertrophy of this muscle. These considerations and certain morphological similarities to hominids do not suggest a functional reconstruction of locomotor behavior similar to Miocene dryopithecines. Nevertheless, more complete functional and taxonomic discussions must await further work at Sahabi. 相似文献
4.
Boaz Luz 《Palaeogeography, Palaeoclimatology, Palaeoecology》1977,22(1):61-78
Statistical analysis applied to foraminiferal data from 78 South Pacific core tops enables the derivation of a transfer function that relates sea surface temperature to foraminiferal assemblages. Application of this transfer function to eight cores from the southern part of the East Pacific Rise yields estimates of the sea surface temperatures of the last glacial maximum, as well as the paleotemperature record of the past 150,000 years. Comparison of the last glacial temperature estimates with the recent sea surface temperature shows that the greatest change between glacial and present conditions (about 5°C) occurs in a climatically sensitive area near 50°S. Stratigraphic correlation of two cores from this area suggests that the last glacial started in this area with rapid cooling, and that the climate stayed generally cold until the end of the glacial. Similar general shape of the climatic record is found in the high latitudes of the North Atlantic as well as in the ice sheets of Greenland and Antarctica. In contrast to the similarity in the shape of these high-latitude records, they differ distinctly from the foraminiferal oxygen isotope record of several deep-sea cores which indicates a general gradual increase of ice volume from the beginning of the last glacial to the maximum glaciation which occurred about 18,000 years B.P.In the study area the rate of sediment accumulation during the last glacial is about two to three times less than in the last interglacial. There is no indication of increased carbonate solution during the glacial, and it is suggested that the change in the accumulation rate results from a reduction in the supply of calcareous shells to the sediment. It seems that with cooling, the environment becomes less favorable to organisms producing calcium carbonate tests, and therefore carbonate production decreases during the glacial. 相似文献
5.
George W. Alal James E. Barasa Emily J. Chemoiwa Boaz Kaunda-Arara Peter Akoll Charles Masembe 《Zeitschrift fur angewandte Ichthyologie》2021,37(3):427-438
Determining the genetic characteristics of natural fish stocks is useful for conservation and aquaculture programs. For African catfish, Clarias gariepinus, genetic characterization could help identify populations suitable as brood stock for culture, and those in need of conservation. This study determined the genetic diversity, population structure, and demographic history of C. gariepinus from Lakes Victoria (LV), Kenyatta (LKE), Kamnarok (LKA), and Rivers Nyando (NR), Tana (TR) and Sosiani (SR) in Kenya. Using 128 DNA sequences of D-loop control region, 34 haplotypes were recovered, of which 79.4% were singletons. Only 7 haplotypes were shared between sites, implying little gene flow between sites. Number of haplotypes was highest in LKE and NR populations and lowest in SR. Haplotype diversity was highest in LV, and lowest in SR, while, nucleotide diversity was highest in LKA and lowest in LV. Phylogenetic analyses revealed five clusters: Lakes Victoria, Kamnarok and Kenyatta, and Rivers Tana and Nyando, from both maximum likelihood tree and minimum spanning network. This, together with significant F ST values among the sites imply population differentiation. Mismatch distributions were multi-modal in LKA, LKE, NR and TR, signifying demographic equilibria. Neutrality tests Tajima`s D values for the sampled populations were negative and significantly different, suggesting stable populations. These results show the existence of genetically distinct populations of C. gariepinus that require spatially explicit management actions such as reducing fishing pressure, pollution, minimizing habitat destruction and fragmentation for sustainable utilisation of stocks. 相似文献
6.
Boaz G. Oliveira Tamires F. Costa Regiane C. M. U. Araújo 《Journal of molecular modeling》2013,19(9):3551-3568
In this theoretical work, a new idea about cooperativity in intermolecular clusters of CnHm???HCN???HW stabilized by hydrogen bonds composed by lone-electron pairs (nitrogen) and π clouds (C?=?C and C?≡?C) as proton acceptors is developed. The structural study and vibrational analysis have pointed out deformations in the intermolecular clusters caused by the HW terminal proton-donor, in which if W?=?fluorine the largest perturbation occurs. On the contrary, the HCN molecule is considered an intermolecular mediator because its structure is practically unaltered upon the formation of the trimolecular complexes. In order to understand the real contribution of the proton-donor either mediator (HCN) or terminal (HW with W?=?CN or F), a chemometric analysis was performed uniquely to discover which interaction plays a key role in the collapse of the cooperative effect. The formation of strongest interactions leads to more drastic variations in the energy distribution. In this way, the application of the quantum theory of atoms in molecules (QTAIM) has been extremely important because the hydrogen bond strengths followed by indiciums of covalence were predicted, and therefore the cooperative effect could be understood at last. 相似文献
7.
Elad Asher Shay Dvir Daniel S. Seidman Sari Greenberg-Dotan Alon Kedem Boaz Sheizaf Haim Reuveni 《PloS one》2013,8(3)
Objective
To describe the daily work practice under the threat of defensive medicine among obstetricians and gynecologists.Study Design
A prospective cross-sectional survey of obstetricians and gynecologists working at tertiary medical centers in Israel.Results
Among the 117 obstetricians and gynecologists who participated in the survey, representing 10% of the obstetricians and gynecologists registered by the Israel Medical Association, 113 (97%) felt that their daily work practice is influenced by concern about being sued for medical negligence and not only by genuine medical considerations. As a result, 102 (87%) physicians are more likely to offer the cesarean section option, even in the absence of a clear medical indication, 70 (60%) follow court rulings concerning medical practices, and 85 (73%) physicians mentioned that discussions about medical negligence court rulings are included in their departments'' meetings.Conclusions
Defensive medicine is a well-embedded phenomenon affecting the medical decision process of obstetricians and gynecologists. 相似文献8.
Yael Aharon Zohar Pasternak Michael Ben Yosef Adi Behar Carol Lauzon Boaz Yuval Edouard Jurkevitch 《Applied and environmental microbiology》2013,79(1):303-313
The Mediterranean fruit fly (medfly) (Ceratitis capitata) lays eggs in fruits, where larvae subsequently develop, causing large-scale agricultural damage. Within its digestive tract, the fly supports an extended bacterial community that is composed of multiple strains of a variety of enterobacterial species. Most of these bacteria appear to be functionally redundant, with most strains sustaining diazotrophy and/or pectinolysis. At least some of these bacteria were shown to be vertically inherited, but colonization, structural, and metabolic aspects of the community''s dynamics have not been investigated. We used fluorescent in situ hybridization, metabolic profiling, plate cultures, and pyrosequencing to show that an initial, egg-borne, diverse community expands throughout the fly''s life cycle. While keeping “core” diazotrophic and pectinolytic functions, it also harbors diverse and fluctuating populations that express varied metabolic capabilities. We suggest that the metabolic and compositional plasticity of the fly''s microbiota provides potential adaptive advantages to the medfly host and that its acquisition and dynamics are affected by mixed processes that include stochastic effects, host behavior, and molecular barriers. 相似文献
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