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451.
Ivar Paulson 《American anthropologist》1961,63(4):832-833
452.
453.
Ole Brix Renate Grüner Ivar R?nnestad Sven Gemballa 《Proceedings. Biological sciences / The Royal Society》2009,276(1674):3777-3782
In fish, the relative amount of tissues of different densities changes significantly over short periods throughout the year, depending on the availability of food, nutrition and their developmental status, such as sexual maturation. If a land-living animal accumulates fat it influences not only its general state of health, but also markedly increases its energy expenditure for locomotion owing to the force of gravity. On a body submerged in water, this force, which acts on the centre of gravity (COG), is counterbalanced by a lifting force that is negligible in air and which acts on the centre of buoyancy (COB). Any difference in the longitudinal positions of the two centres will therefore result in pitching moments that must be counteracted by body or fin movements. The displacement of the COG away from the COB is a result of tissues of different density (e.g. bones and fat) not being distributed homogeneously along the body axis. Moreover, the proportions of tissues of different densities change significantly with feeding status. It is still unknown whether these changes produce a displacement of the COG and thus affect the hydrostatic stability of fish. Analysis of computed tomography and magnetic resonance imaging images of Atlantic herring, Atlantic salmon and Atlantic mackerel reveals that the COG is fairly constant in each species, although we recorded major interspecies differences in the relative amount of fat, muscle and bone. We conclude that the distribution of different tissues along the body axis is very closely adjusted to the swimming mode of the fish by keeping the COG constant, independent of the body fat status, and that fish can cope with large variations in energy intake without jeopardizing their COG and thus their swimming performance. 相似文献
454.
Chlorpromazine, in parallel with reduced fluid accumulation in ligated loops, interfered with the basement membrane and caused shedding of intestinal mucosal epithelium. This was examined by electron microscopy of rat ileum maintained both in vitro and in situ. 相似文献
455.
Strains of Vibrio alginolyticus were regularly isolated from mussels, fish, bottom sediment and seawater from April to October. Vibrio parahaemolyticus was isolated occasionally in samples from mussels and bottom sediment in July and August. None of the species were detected in the cold season. Isolated strains were characterized by growth requirement, morphological characteristics and biochemical tests. In addition the cellular fatty acid composition was determined and compared with standard strains from the family Vibrionaceae. With the exception of some biochemical reactions which distinguish Vibrio alginolyticus from Vibrio parahaemolyticus, growth requirement, morphological characteristics and biochemical reactions are similar for these strains. The close relation between Vibrio alginolyticus and Vibrio parahaemolyticus was also revealed by cluster analyses of fatty acid patterns which combined these two species into one cluster which, however, was clearly separated from the standard strains of Vibrio anguillarum. 相似文献
456.
Erling Johan Solberg Christer M. Rolandsen Morten Heim John D. C. Linnell Ivar Herfindal Bernt-Erik Sæther 《European Journal of Wildlife Research》2010,56(6):871-881
The sustainability of wild ungulate harvests can be greatly enhanced if monitoring data are available to permit an adaptive
management approach. Utilising data provided by hunters is potentially the most cost-effective approach. In Scandinavia, observations
recorded by moose (Alces alces) hunters provide a range of indices of population density, composition and reproductive performance. These are routinely
used in practical management, but there are still many questions about their accuracy and precision. In this study, we availed
of the fact that virtually all individual moose on the island of Vega in central Norway were marked during the period 1992–2005.
Thus, we were able to compare the observation indices provided by hunters to the known size and composition of the population.
The results indicate that the hunter observation indices provided accurate estimates of variation in moose cow recruitment
and twinning rates. The estimates of sex ratio closely followed the pattern of annual variation but showed a consistent pattern
of over-estimating the proportion of males. Thus, males seem to visually expose themselves more often for hunters than do
females. The density index, measured as number of moose seen per hunter day did not to the same extent follow the variation
in population density, possibly because moose were more naive in the first years after hunting was introduced or because of
reduced detection conditions due to increasing scrub and tree encroachment during the study period. The results are discussed
in light of their application to management and the evolutionary pressures in moose anti-predator behaviour. 相似文献
457.
The antisecretory factor: synthesis and intracellular localisation in porcine tissues 总被引:1,自引:0,他引:1
The antisecretory factor, AF, is a 41-kDa protein, cloned and sequenced from a human pituitary library. AF is a potent inhibitor of experimental intestinal hypersecretion in rats and pigs. An antiserum against the C-terminal of the truncated, recombinantly produced AF protein was raised in rabbits. The affinity-purified antiserum was used to study the expression of AF in mucosal membranes and in the pituitary gland of the pig; distinctly stained cells were found in lymphoid cells in the connective tissue of all parts of the gastrointestinal, respiratory and urinary tracts. Cytoplasmic AF was demonstrated in endocrine and epithelial cells in the pituitary gland. In situ hybridisation with a digoxigenin-labelled mRNA probe also demonstrated specific cytoplasmic staining in epithelial and lymphoid cells in all of these tissues. The cells stained by either method were similarly distributed topographically within the tissues. The results suggest that a specific defined cell population in these various tissues possesses the capability of both synthesising and storing the AF protein within the cellular cytoplasmic compartment. 相似文献