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71.
Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes 总被引:3,自引:0,他引:3
Portions of two mitochondrial genes (12S and 16S ribosomal RNA) were
sequenced to determine the phylogenetic relationships among the major
clades of snakes. Thirty-six species, representing nearly all extant
families, were examined and compared with sequences of a tuatara and three
families of lizards. Snakes were found to constitute a monophyletic group
(confidence probability [CP] = 96%), with the scolecophidians (blind
snakes) as the most basal lineages (CP = 99%). This finding supports the
hypothesis that snakes underwent a subterranean period early in their
evolution. Caenophidians (advanced snakes), excluding Acrochordus, were
found to be monophyletic (CP = 99%). Among the caenophidians, viperids were
monophyletic (CP = 98%) and formed the sister group to the elapids plus
colubrids (CP = 94%). Within the viperids, two monophyletic groups were
identified: true vipers (CP = 98%) and pit vipers plus Azemiops (CP = 99%).
The elapids plus Atractaspis formed a monophyletic clade (CP = 99%). Within
the paraphyletic Colubridae, the largely Holarctic Colubrinae was found to
be a monophyletic assemblage (CP = 98%), and the Xenodontinae was found to
be polyphyletic (CP = 91%). Monophyly of the henophidians (primitive
snakes) was neither supported nor rejected because of the weak resolution
of relationships among those taxa, except for the clustering of Calabaria
with a uropeltid, Rhinophis (CP = 94%).
相似文献
72.
House mice ( Mus rnusculus muralis ) on St Kilda became extinct within about 18 months of the human population leaving the island in 1930. Although it was argued at the time that they died out because they were unable to find enough food, house mice flourish on a number of uninhabited islands and it seems more probable that they could not successfully compete with the Long-tailed field mouse ( Apodemus sylvaticus ) in the absence of man.
A study of the distribution and diet of both house and field mice on the Shetland islands of Foula and Fair Isle shows that the house mouse populations tend to be centred on human dwellings, although both species were found apparently living together on Foula away from habitation. The natural history of the two species is reviewed, and it is concluded that the breeding of the house mouse is the most probable characteristic to be upset by disturbance, and that the disappearance of man on St Kilda allowed Apodemus to enter a habitat previously occupied almost exclusively by Mus . 相似文献
A study of the distribution and diet of both house and field mice on the Shetland islands of Foula and Fair Isle shows that the house mouse populations tend to be centred on human dwellings, although both species were found apparently living together on Foula away from habitation. The natural history of the two species is reviewed, and it is concluded that the breeding of the house mouse is the most probable characteristic to be upset by disturbance, and that the disappearance of man on St Kilda allowed Apodemus to enter a habitat previously occupied almost exclusively by Mus . 相似文献
73.
Many mainland populations of kiwi are declining because stoats (Mustela erminea) kill most of their chicks. Stoats are often trapped during conservation programmes, but the long-term effectiveness of trapping has not been measured. During continuous trapping of mammalian predators in the 9800?ha Whangarei Kiwi Sanctuary, the survival of brown kiwi (Apteryx mantelli) chicks declined over time. Following the use of sodium fluoroacetate (1080) to kill rats (Rattus spp.) and possums (Trichosurus vulpecula) and likely secondary poisoning of stoats, chick survival at Riponui increased from 5% to 56%, and the 62% chick survival at Rarewarewa was better than the 20% recorded in a trapped-only area nearby. We suggest that untrappable stoats accumulate in areas subjected to continuous predator trapping. Conservation managers should build into their long-term pest control programmes a periodic pulse of an alternative tool to kill pests that, for whatever reason, actively avoid the primary control tool. 相似文献
74.
Background
Leucine-rich repeats are one of the more common modules found in proteins. The leucine-rich repeat consensus motif is LxxLxLxxNxLxxLxxLxxLxx- where the first 11–12 residues are highly conserved and the remainder of the repeat can vary in size Leucine-rich repeat proteins have been subdivided into seven subfamilies, none of which include members of the epidermal growth factor receptor or insulin receptor families despite the similarity between the 3D structure of the L domains of the type I insulin-like growth factor receptor and some leucine-rich repeat proteins. 相似文献75.
A Bell OA Rodríguez LA de Castro e Paula MB Padua J Hernández-Cerón CG Gutiérrez A De Vries PJ Hansen 《BMC veterinary research》2008,4(1):22
Background
Results regarding the use of bovine somatotropin for enhancing fertility in dairy cattle are variable. Here, the hypothesis was tested that a single injection of a sustained-release preparation of bovine somatotropin (bST) during the preovulatory period would improve pregnancy success of lactating dairy cows at first service.Results
The first experiment was conducted in a temperate region of Mexico. Cows inseminated following natural estrus or timed artificial insemination were given a single injection of bST or a placebo injection at insemination (n = 100 cows per group). There was no significant difference between bST and control groups in the proportion of inseminated cows diagnosed pregnant (29 vs 31% pregnant). The second experiment was performed during heat stress in Florida. Cows were subjected to an ovulation synchronization regimen for first insemination. Cows treated with bST received a single injection at 3 days before insemination. Controls received no additional treatment. As expected, bST did not increase vaginal temperature. Treatment with bST did not significantly increase the proportion of inseminated cows diagnosed pregnant although it was numerically greater for the bST group (24.2% vs 17.8%, 124–132 cows per group). There was a tendency (p = 0.10) for a smaller percent of control cows to have high plasma progesterone concentrations (≥ 1 ng/ml) at Day 7 after insemination than for bST-treated cows (72.6 vs 81.1%). When only cows that were successfully synchronized were considered, the magnitude of the absolute difference in the percentage of inseminated cows that were diagnosed pregnant between bST and control cows was reduced (24.8 vs 22.4% pregnant for bST and control).Conclusion
Results failed to indicate a beneficial effect of bST treatment on fertility of lactating dairy cows.76.
David M Markusic Niek P van Til Johan K Hiralall PJ Oude Ronald Elferink Jurgen Seppen 《BMC biotechnology》2009,9(1):85
Background
Lentiviral vectors are well suited for gene therapy because they can mediate long-term expression in both dividing and nondividing cells. However, lentiviral vectors seem less suitable for liver gene therapy because systemically administered lentiviral vectors are preferentially sequestered by liver macrophages. This results in a reduction of available virus and might also increase the immune response to the vector and vector products. 相似文献77.
Bayesian analysis of factorial experiments by mixture modelling 总被引:3,自引:0,他引:3
78.
79.
Primary antibody-forming cells and secondary B cells are generated from separate precursor cell subpopulations 总被引:22,自引:0,他引:22
Two precursor cell subpopulations have been isolated from the spleen cells of nonimmune mice. The major B cell subpopulation binds high levels of the J11D monoclonal antibody and, upon T cell-dependent antigenic stimulation, gives rise to primary antibody-forming cell clones but not secondary B cells. A minority of the 10%-14% of Ia+ precursors that bind low levels of J11D (J11Dlo) also generate antibody-forming cell clones after primary stimulation. However, over 70% of J11Dlo precursors yield no primary antibody-forming cell clones but instead give rise to secondarily responsive B cells. The existence of a distinct precursor cell subpopulation that is responsible for the generation of B cell memory is further evidenced by the distribution of variable region clonotypes among J11Dlo primary precursors, which resembles the clonotype patterns of secondary B cells, and by the accumulation of somatic mutations in their clonal progeny. 相似文献