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31.
T. M. Blackburn K. J. Gaston R. M. Quinn H. Arnold R. D. Gregory 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1997,352(1352):419-427
We examine the relation between population size and geographic range size for British breeding birds and mammals. As for most other assemblages studied, a strong positive interspecific correlation is found in both taxa. The relation is also recovered once the phylogenetic relatedness of species has been controlled for using an evolutionary comparative method. The slope of the relation is steeper for birds than for mammals, but this is due in large part to two species of mammals that have much higher population sizes than expected from their small geographic ranges. These outlying mammal species are the only ones in Britain to be found only on small offshore islands, and so may be exhibiting density compensation effects. With them excluded, the slope of the abundance–range size relation for mammals is not significantly different to that for birds. However, the elevation of the relation is higher for mammals than for birds, indicating that mammals are approximately 30 times more abundant than birds of equivalent geographic range size. An earlier study of these assemblages showed that, for a given body mass, bats had abundances more similar to birds than to non-volant mammals, suggesting that the difference in abundance between mammals and birds might be due to constraints of flight. Our analyses show that the abundance–range size relation for bats is not different for that from other mammals, and that the anomalously low abundance of bats for their body mass may result because they have smaller than expected geographic extents for their size. Other reasons why birds and mammals might have different elevations for the relation between population size and geographic range size are discussed, together with possible reasons for why the slopes of these relations might be similar. 相似文献
32.
Synopsis Two groups of coho salmon,Oncorhynchus kisutch, were raised under identical regimes to test the hypothesis that the group from a stream with lower and less variable temperatures would have a lower and less variable preferred temperature than would the group from a stream with warmer and more variable temperatures. The preferred (modal) temperatures in an electronic shuttlebox of coho salmon young from a relatively cool, groundwater-fed stream were slightly lower and less variable than those of young from a warmer and more heterothermal stream (mean = 9.6° C, range: 6–16° C vs. mean = 11.6° C, range: 7–21° C). However, there was a great deal of variation within and among individual fish. While some genetic variation in thermal preference may exist, the species seems best characterized as tolerant of relatively large temperature fluctuations. 相似文献
33.
N. Quinn 《BMJ (Clinical research ed.)》1995,310(6979):575-579
A wide variety of drugs is available for treating Parkinson''s disease, including anticholinergics, amantadine levodopa, dopamine agonists, and selegiline. In younger patients (less than 50) levodopa is usually delayed provided that adequate relief of symptoms can be achieved with other drugs. In older patients (greater than 70) levodopa should be started as soon as symptom relief is required. Between these ages there is no consensus, but at present most such patients should probably be given controlled release levodopa before a dopamine agonist is added. Fluctuations can often be alleviated by giving controlled release preparations of levodopa, by giving small doses at frequent intervals, by adding selegiline or a long acting oral agonist, or by subcutaneous apomorphine. Dyskinesia can be peak dose, diphasic, or "off period." The diphasic form is hardest to alleviate. Psychiatric side effects should initially be managed by changing the antiparkinsonian treatment before resorting to antipsychotic drugs. 相似文献
34.
Soft rot Erwinia bacteria in surface and underground waters in southern Scotland and in Colorado, United States 总被引:7,自引:6,他引:1
Nancy J. McCarter-Zorner G.D. Franc M.D. Harrison Janet E. Michaud C.E. Quinn I. Ann Sells D.C. Graham 《Journal of applied microbiology》1984,57(1):95-105
An anaerobic liquid enrichment method followed by plating on a selective medium revealed that the soft rot coliform bacterium Erwinia carotovora subsp. carotovora was generally present in water from drains, ditches, streams, rivers and lakes (including reservoirs) in southern Scotland and in Colorado, United States, in mountainous, upland and arable areas through the year. Many sites were remote from susceptible or diseased crops. Erwinia carotovora subsp. atroseptica was isolated much less frequently and no Erwinia bacteria were isolated from underground waters. Erwinia bacteria were also found in rain-water in Scotland, in winter snow from mountain passes in Colorado, and in sea water from the west and east coasts of Scotland and from the coasts of Oregon, California, Texas, Louisiana and Florida. The significance of the occurrence of these bacteria in water is discussed in relation to the control of blackleg and soft rot diseases of potato by production of Erwinia -free stocks. 相似文献
35.
Individual myogenic cells were isolated from the pectoralis muscles of chick embryos from days 8-14 of embryogenesis. When separately cloned, these cells produced three types of colonies in culture: (1) Positive: all cells in the clone were terminally differentiated muscle cells; (2) negative: no cells in the clone were terminally differentiated muscle; (3) mixed: some cells in the clone were terminally differentiated muscle. Positive clones from all ages tended to contain 2n cells (n = 0, 1, 2, 3, 4). Negative clones were found in all sizes and did not cluster around powers of 2 in cell number. Mixed clones were, by far, the most common type among those clones larger than 24 in cell number. Estimates of cell numbers in embryonic muscle tissue revealed that, while the numbers of cells in all myogenic compartments increased steadily with embryonic age, the number and percentage of precursor cells that produced large mixed clones increased dramatically. Subclones, prepared from populations of cells equivalent to large mixed clones, yielded both small positive and large mixed colonies. This indicated that the precursors to the large mixed clones were also precursors to the smaller positive clones. These observations suggest a model for the myogenic lineage in which there exists a stem cell that can generate, by a series of asymmetric divisions, cohorts of terminally differentiated muscle cells. The model can explain the asynchrony of production of terminally differentiated muscle cells both in vitro and in vivo. 相似文献
36.
BB creatine kinase and myogenic differentiation 总被引:1,自引:0,他引:1
Mark M. Robinson LeBris Smith Quinn Mark Nameroff 《Differentiation; research in biological diversity》1984,26(1-3):112-120
Abstract. Antisera specific for the B monomer of creatine kinase (B-CK), the M monomer of creatine kinase (M-CK), and muscle-specific myosin heavy chain (MHC) were used to investigate the biochemical characteristics of individual cells in primary myogenic cultures. Through the use of immunocytochemical techniques, in conjunction with 3H-thy-midine autoradiography, it was determined that (1) all of the terminally differentiated myoblasts contained B-CK in addition to M-CK and MHC, (2) none of the cycling cells contained M-CK or MHC, (3) a fraction (7.5%) of the cycling cells contained B-CK, and (4) the cycling, B-CK positive cells divided once, and only once, and produced two terminally differentiated myoblasts. These results indicate that myogenic precursors in vitro are a phenotypically heterogeneous cell population and that the appearance of B-CK in cycling myogenic cells is a biochemical manifestation of a distinct precursor compartment in the chicken skeletal myogenic lineage. 相似文献
37.
J.H. Kennedy M.A. Quinn P.W. Howie A.A. Calder 《Prostaglandins & other lipid mediators》1978,15(1):169-173
A viscous suspension of prostaglandin E2 was introduced endocervically to induce labor in patients with favourable induction features. The method was found to be effective and compared favourably with the conventional practices of amniotomy and intravenous oxytocin infusion or oral prostaglandin therapy. Several advantages were found including a high degree of patient acceptability. 相似文献
38.
Foetal and placental growth in the mouse after pre-implantation development in vitro under oxygen concentrations of 5 and 20% 总被引:2,自引:0,他引:2
Blastocysts which developed from two-cell mouse embryos in culture tubes containing an atmosphere with 20% oxygen had approximately 20% fewer blastomeres than blastocysts which developed under an oxygen concentration of 5%. When these smaller blastocysts were transferred to the uteri of pseudopregnant foster mothers, the foetuses developing were as viable as those developing from blastocysts cultured under 5% oxygen, indicating their ability to regulate for a lower blastomere number by at least day 17 of development. The transfer operation itself had no adverse effect on foetal or placental growth. However, culture of blastocysts in vitro did depress foetal though not placental growth, suggesting that the inner cell mass is more susceptible than the trophectoderm to culture in vitro. Foetal but not placental growth was lower following the transfer of blastocysts to a day-3 rather than a day-4 uterus. Four cases of placental fusion were found. In one case, the foetuses were contained within the same embryonic sac and may have been twins. 相似文献
39.
Colin J. Restall Patrick Williams Michael P. Percival Peter J. Quinn Dennis Chapman 《生物化学与生物物理学报:生物膜》1979,555(1):119-130
A method is reported for the in situ modification of the lipids of isolated spinach chloroplast membranes. The technique is based on a direct hydrogenation of the lipid double bonds in the presence of the catalyst, chlorotris(triphenylphosphine)rhodium (I). The pattern of hydrogenation achieved suggests that the catalyst distributes amongst all of the membranes. The polyunsaturated lipids within the membranes are hydrogenated at a faster rate and at an earlier stage than are the monoenoic lipids.Whilst addition of the catalyst to the chloroplast causes an initial 10–20% decrease in Hill activity, saturation of up to 40% of the double bonds present can be accomplished without causing further significant alterations in photosynthetic electron transport processes or marked morphological changes of the chloroplast structure as observed in the electron microscope. 相似文献
40.
P Quinn 《The Journal of experimental zoology》1979,210(3):497-505
When incubated for 8 to 26 hours with zona-free mouse or rat ova, human spermatozoa failed to attach to or penetrate any of the ova. The ova were capable of being fertilized since both intra- and inter-species penetration of spermatozoa and formation of pronuclei occurred between rat and mouse gametes. When mouse spermatozoa were incubated for three to eight hours with rat ova, a high proportion of the ova were penetrated, formation of pronuclei occurred and in 9 out of 36 ova incubated for 40 hours after insemination, regular cleavage and formation of morphologically normal 2-cell embryos occurred. Human spermatozoa retained their morphological integrity and motility only when the culture medium contained purified bovine serum albumin (3 mg/ml) or human serum (5% v/v) and not when unpurified BSA from several different commercial sources was used as a protein source. In this latter medium, the ova of both rats and mice degenerated after 8-hour incubation in the presence of human spermatozoa but not when human spermatozoa were absent or in the presence of either rat or mouse spermatozoa. Electron microscopy indicated that the human spermatozoa incubated for eight hours in medium containing purified BSA had undergone an acrosome reaction. These spermatozoa also attached to and penetrated human oocytes which had been matured in vitro. 相似文献