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排序方式: 共有508条查询结果,搜索用时 15 毫秒
1.
J F Searle 《BMJ (Clinical research ed.)》1984,288(6435):1998-1999
2.
B F BuSha B G Judd H L Manning P M Simon B C Searle J A Daubenspeck J C Leiter 《Journal of applied physiology》2001,90(6):2330-2340
Evidence of the Hering-Breuer reflex has been found in humans during anesthesia and sleep but not during wakefulness. Cortical influences, present during wakefulness, may mask the effects of this reflex in awake humans. We hypothesized that, if lung volume were increased in awake subjects unaware of the stimulus, vagal feedback would modulate breathing on a breath-to-breath basis. To test this hypothesis, we employed proportional assist ventilation in a pseudorandom sequence to unload the respiratory system above and below the perceptual threshold in 17 normal subjects. Tidal volume, integrated respiratory muscle pressure per breath, and inspiratory time were recorded. Both sub- and suprathreshold stimulation evoked a significant increase in tidal volume and inspiratory flow rate, but a significant decrease in inspiratory time was present only during the application of a subthreshold stimulus. We conclude that vagal feedback modulates respiratory timing on a breath-by-breath basis in awake humans, as long as there is no awareness of the stimulus. 相似文献
3.
J. Paupério J. S. Herman J. Melo‐Ferreira M. Jaarola P. C. Alves J.B. Searle 《Molecular ecology》2012,21(24):6015-6032
Species are generally described from morphological features, but there is growing recognition of sister forms that show substantial genetic differentiation without obvious morphological variation and may therefore be considered ‘cryptic species’. Here, we investigate the field vole (Microtus agrestis), a Eurasian mammal with little apparent morphological differentiation but which, on the basis of previous sex‐linked nuclear and mitochondrial DNA (mtDNA) analyses, is subdivided into a Northern and a Southern lineage, sufficiently divergent that they may represent two cryptic species. These earlier studies also provided limited evidence for two major mtDNA lineages within Iberia. In our present study, we extend these findings through a multilocus approach. We sampled 163 individuals from 46 localities, mainly in Iberia, and sequenced seven loci, maternally, paternally and biparentally inherited. Our results show that the mtDNA lineage identified in Portugal is indeed a distinct third lineage on the basis of other markers as well. In fact, multilocus coalescent‐based methods clearly support three separate evolutionary units that may represent cryptic species: Northern, Southern and Portuguese. Divergence among these units was inferred to have occurred during the last glacial period; the Portuguese lineage split occurred first (estimated at c. 70 000 bp ), and the Northern and Southern lineages separated at around the last glacial maximum (estimated at c. 18 500 bp ). Such recent formation of evolutionary units that might be considered species has repercussions in terms of understanding evolutionary processes and the diversity of small mammals in a European context. 相似文献
4.
The development of gene therapy is hampered by the difficulty of producing large stocks of retroviral vectors at high titer. This study aimed to improve culture conditions and to intensify the production of retroviruses by FLYRD18, a packaging cell line derived from the HT1080 human fibrosarcoma line. Batch virus production proved to be feasible in unsupplemented basal medium and provided significantly higher titers and productivities than medium supplemented with 10% serum. For longer-term production, however, AIM-V complete serum-free medium and basal medium supplemented with 2% serum gave superior results. Serum supplementation should nevertheless be optimized to take into account the presence of inhibitors of viral production. In monolayer cultures with 0.2 mL/cm(2), the cell concentration was increased up to 2 x 10(6) cells/mL without loss of cell productivity. A semicontinuous production process, which enables the collection of larger amounts of viruses from the same culture, has also been successfully used. Suspension culture processes were prevented by the anchorage dependency of the FLYRD18 cell line. Microcarrier cultures were able to produce viruses but will require further investigation and optimization for their performance to become competitive with monolayer cultures. In the course of this study, more than a 10-fold increase of titer has been achieved. 相似文献
5.
This work is concerned with the extent of behavioural discrimination between three chromosomal races of the house mouse (the standard 40-chromosome race and a 32- and 36-chromosome races) found in the vicinity of a hybrid zone in northern Scotland. Mice were investigated for several elements of their social behaviour. Within-population dyadic encounters did not show consistent behavioural differences attributable to karyotype among five populations (two standard race, two 36-chromosome race, one 32-chromosome race). Between-population dyadic encounters revealed significant differences between three populations. The standard population examined appeared to be the most “open” to foreigners, the 32-chromosome population the most “closed” while the 36-chromosome mice displayed an intermediate response. Differences in behaviour displayed during between-population as compared to within-population dyadic encounters revealed the occurrence of behavioural discrimination between populations. The implication of these results on the dynamics of the hybrid zone are discussed. 相似文献
6.
The NK cell functional capacity of first trimester human decidua against K562 targets was assessed in a 3-hr CRA. Collagenase dispersal combined with plastic adherence, nylon wool passage, and density gradient centrifugation yielded NKH-1 (Leu 19) positive enriched decidual large granular lymphocyte fraction (mean 75% positive). Decidual effectors displayed reduced lytic activity compared with autologous PB effectors at every effector:target ratio but this difference in cytotoxicity was abolished by short-term culture before the CRA. Decidual effectors treated with 50 units rIL-2 showed increased lytic activity compared to untreated decidual cells. By FACS analysis the majority of NKH-1 positive decidual effectors were CD3 and CD16 negative which corresponds with a minority PB NK population. The implications of a population of functional NK cells in early pregnancy decidua for the materno-fetal relationship is discussed. 相似文献
7.
8.
Phylogenetic distribution in the genus Mus of t-complex-specific DNA and protein markers: inferences on the origin of t-haplotypes 总被引:8,自引:0,他引:8
Delarbre C; Kashi Y; Boursot P; Beckmann JS; Kourilsky P; Bonhomme F; Gachelin G 《Molecular biology and evolution》1988,5(2):120-133
We have examined the phylogenetic distribution of two t-specific markers
among representatives of various taxa belonging to the genus Mus. The
centromeric TCP-1a marker (a testicular protein variant specific for all
t-haplotypes so far studied) has also been apparently detected in several
non-t representatives of the Mus IVA, Mus IVB, and probably M. cervicolor
species. By contrast, a t-specific restriction- fragment-length
polymorphism allele (RFLP) of the telomeric alpha- globin pseudogene DNA
marker alpha-psi-4 was found only in animals belonging to the M.
musculus-complex species either bearing genuine t- haplotypes or, like the
M. m. bactrianus specimen studied here, likely to do so. This t-specific
alpha-psi-4 RFLP allele was found to be as divergent from the RFLP alleles
of the latter, non-t, taxonomical groups as it is from Mus 4A, Mus 4B, or
M. spretus ones. These results suggest the presence of t-haplotypes and of
t-specific markers in populations other than those belonging to the M. m.
domesticus and M. m. musculus subspecies, implying a possible origin for
t-haplotypes prior to the radiation of the most recent offshoot of the Mus
genus (i.e., the spretus/domesticus divergence), some 1-3 Myr ago.
相似文献
9.
Differential and analytical subfractionation of rat liver components internalizing insulin and prolactin 总被引:4,自引:0,他引:4
Receptor-mediated endocytosis of 125I-insulin and 125I-prolactin into liver parenchymal cells has been studied by quantitative subcellular fractionation. Differential centrifugation yielded three particulate fractions, N (nuclear), ML (large granule), and P (microsomes), and a final supernatant (S). Quantitative differences in the extent and rates of accumulation of 125I-insulin and 125I-prolactin into the fractions were observed. The acidotropic agent chloroquine and the microtubule disrupting agent colchicine were administered separately to rats. The agents increased significantly the T 1/2 of hormone clearance from the liver and augmented the accumulation of both ligands in the low-speed ML fraction. However, differences in the rates of accumulation of insulin and prolactin into all cell fractions were still maintained. Analytical centrifugation of each of the particulate fractions was carried out in order to determine if different endocytic components were specific to insulin or prolactin internalization. This was not the case. An "early" endosomal component of density 1.11 was identified in microsomes. A "late" endosome of density 1.10 was identified in the large granule (ML) fraction. Both endosomal components appeared to accumulate insulin and prolactin but at different rates. Marker enzyme analysis identified the presumed plasma membrane component in microsomes (density approximately 1.155). This component showed a significant difference in the rate of loss of 125I-insulin (T 1/2 approximately 4.1 min) as compared to that of 125I-prolactin (T 1/2 approximately 12.7 min). A further difference in the handling of the ligands was observed in early endosomes.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
10.
Trimethoprim binding to Lactobacillus casei dihydrofolate reductase: a 13C NMR study using selectively 13C-enriched trimethoprim 总被引:1,自引:0,他引:1
H T Cheung M S Searle J Feeney B Birdsall G C Roberts I Kompis S J Hammond 《Biochemistry》1986,25(8):1925-1931
We have measured the 13C chemical shifts for trimethoprim molecules selectively enriched with 13C at the 2-, 4-, 5-, 6-, and 7-positions and the p-OCH3 position in their complexes with Lactobacillus casei dihydrofolate reductase in the presence and absence of coenzyme analogues. The C2 carbon shifts indicate that the pyrimidine ring is protonated at N1 in all the complexes of trimethoprim with the enzyme and coenzymes and in each case the pyrimidine ring is binding in a similar way to that of the corresponding part of methotrexate in the enzyme-methotrexate complex. The C6 carbon of trimethoprim shows a large upfield shift in all complexes (3.51 to 4.70 ppm) but no shift in the complex of 2,4-diaminopyrimidine with the enzyme: these shifts probably arise from steric interactions between the C1' and C2' carbons and the H6 proton, which approach van der Waals contact in the folded conformation adopted by trimethoprim when bound to the enzyme. The large shift observed for C6 in all complexes indicates that the basic folded conformation is present in all of them. A comparison of the 13C shifts in the enzyme-trimethoprim-NADPH complex with those in the enzyme-trimethoprim binary complex shows substantial changes even for carbons such as C6 and p-OCH3 (0.46 and -0.36 ppm, respectively), which are remote from the coenzyme: these are caused by ligand-induced conformational changes that may involve displacement of the helix containing residues 42-49.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献