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排序方式: 共有802条查询结果,搜索用时 15 毫秒
81.
Cannabinoid CB(1) receptor agonists exhibit potent analgesic effects in rodents and humans, but their clinical utility as analgesic drugs is often limited by centrally mediated side effects. We report herein the preparation of N-methyl-3-(tetrahydro-2H-pyran-4-yl)-2,3,4,9-tetrahydro-1H-carbazole-6-carboxamides as a novel class of hCB(1)/hCB(2) dual agonists with attractive physicochemical properties. More specifically, (R)-N,9-dimethyl-N-(4-(methylamino)-4-oxobutyl)-3-(tetrahydro-2H-pyran-4-yl)-2,3,4,9-tetrahydro-1H-carbazole-6-carboxamide, displayed an extremely low level of CNS penetration (Rat Cbr/Cplasma=0.005 or 0.5%) and was devoid of CNS side effects during pharmaco-dynamic testing.  相似文献   
82.
Current models of parent-offspring communication do not explicitly predict the effect of parental food supply on offspring demand (ESD). However, existing theory is frequently interpreted as predicting a negative ESD, such that offspring beg less when parental supply is high. While empirical evidence largely supports this interpretation, several studies have identified the opposite case, with well-fed offspring begging more than those in poorer condition. Here, we show that signalling theory can give rise to either a negative or a positive ESD depending on the precise form of costs and benefits. Introducing variation among parents in the cost of care, we show that the ESD may change sign depending upon the quantitative relation between two effects: (i) decreased supply leads to increased begging because of an increase in marginal fitness benefit of additional resources to offspring, (ii) decreased supply leads to reduced begging because it is associated with a decrease in parental responsiveness, rendering begging less effective. To illustrate the interplay between these two effects, we show that Godfray's seminal model of begging yields a negative ESD when care is generally cheap, because the impact of supply on the marginal benefits of additional resources then outweighs the associated changes in parental responsiveness to begging. By contrast, the same model predicts a positive ESD when care is generally costly, because the impact of care costs on parental responsiveness then outweighs the change in marginal benefits.  相似文献   
83.
In his famous haplodiploidy hypothesis, W. D. Hamilton proposed that high sister-sister relatedness facilitates the evolution of kin-selected reproductive altruism among Hymenopteran females. Subsequent analyses, however, suggested that haplodiploidy cannot promote altruism unless altruists capitalize on relatedness asymmetries by helping to raise offspring whose sex ratio is more female-biased than the population at large. Here, we show that haplodiploidy is in fact more favourable than is diploidy to the evolution of reproductive altruism on the part of females, provided only that dispersal is male-biased (no sex-ratio bias or active kin discrimination is required). The effect is strong, and applies to the evolution both of sterile female helpers and of helping among breeding females. Moreover, a review of existing data suggests that female philopatry and non-local mating are widespread among nest-building Hymenoptera. We thus conclude that Hamilton was correct in his claim that 'family relationships in the Hymenoptera are potentially very favourable to the evolution of reproductive altruism'.  相似文献   
84.
Observations on the bioecology and damage of Teratopactus nodicollis Boheman on Phaseolus vulgaris were carried out on field samples by assessing the number of larvae and root damage in 40?ha of a dry bean field from the Federal District, Brazil (16°4??28.41???W; 47°30??21.13???S). Larvae caused the greatest damage at the stage of germination, emergence, and primary leaves, producing 50?% stand reduction. Most larvae pupated in August and September, and adult emergence occurred in middle October. Some larvae were infected with the fungus Metarhizium spp., a biological agent that would be naturally controlling this insect.  相似文献   
85.
There is significant interest in treating cancers by blocking protein synthesis, to which hematological malignancies seem particularly sensitive. The translation elongation inhibitor homoharringtonine (Omacetaxine mepesuccinate) is undergoing clinical trials for chronic myeloid leukemia, whereas the translation initiation inhibitor silvestrol has shown promise in mouse models of cancer. Precisely how these compounds induce cell death is unclear, but reduction in Mcl-1, a labile pro-survival Bcl-2 family member, has been proposed to constitute the critical event. Moreover, the contribution of translation inhibitors to neutropenia and lymphopenia has not been precisely defined. Herein, we demonstrate that primary B cells and neutrophils are highly sensitive to translation inhibitors, which trigger the Bax/Bak-mediated apoptotic pathway. However, contrary to expectations, reduction of Mcl-1 did not significantly enhance cytotoxicity of these compounds, suggesting that it does not have a principal role and cautions that strong correlations do not always signify causality. On the other hand, the killing of T lymphocytes was less dependent on Bax and Bak, indicating that translation inhibitors can also induce cell death via alternative mechanisms. Indeed, loss of clonogenic survival proved to be independent of the Bax/Bak-mediated apoptosis altogether. Our findings warn of potential toxicity as these translation inhibitors are cytotoxic to many differentiated non-cycling cells.  相似文献   
86.

Background

Congenital hereditary sensorineural deafness (CHSD) occurs in many dog breeds, including Australian Cattle Dogs. In some breeds, CHSD is associated with a lack of cochlear melanocytes in the stria vascularis, certain coat characteristics, and potentially, abnormalities in neuroepithelial pigment production. This study investigates phenotypic markers for CHSD in 899 Australian Cattle Dogs.

Results

Auditory function was tested in 899 Australian Cattle Dogs in family groups using brainstem auditory evoked response testing. Coat colour and patterns, facial and body markings, gender and parental hearing status were recorded. Deafness prevalence among all 899 dogs was 10.8% with 7.5% unilaterally deaf, and 3.3% bilaterally deaf, and amongst pups from completely tested litters (n = 696) was 11.1%, with 7.5% unilaterally deaf, and 3.6% bilaterally deaf. Univariable and multivariable analyses revealed a negative association between deafness and bilateral facial masks (odds ratio 0.2; P ?? 0.001). Using multivariable logistic animal modelling, the risk of deafness was lower in dogs with pigmented body spots (odds ratio 0.4; P = 0.050). No significant associations were found between deafness and coat colour. Within unilaterally deaf dogs with unilateral facial masks, no association was observed between the side of deafness and side of mask. The side of unilateral deafness was not significantly clustered amongst unilaterally deaf dogs from the same litter. Females were at increased risk of deafness (odds ratio from a logistic animal model 1.9; P = 0.034) after adjusting for any confounding by mask type and pigmented body spots.

Conclusions

Australian Cattle Dogs suffer from CHSD, and this disease is more common in dogs with mask-free faces, and in those without pigmented body patches. In unilaterally deaf dogs with unilateral masks, the lack of observed association between side of deafness and side of mask suggests that if CHSD is due to defects in molecular pigment pathways, the molecular control of embryonic melanoblast migration from ectoderm to skin differs from control of migration from ectoderm to cochlea. In Australian Cattle Dogs, CHSD may be more common in females.  相似文献   
87.
Hepatocyte growth factor (HGF) is a potent mitogenic and angiogenic factor produced in human adipose tissue. In this study, we use 3T3-F442A preadipocytes to study the contribution of HGF to angiogenesis in an in vivo fat pad development model. As observed for human adipocytes, HGF is synthesized and secreted by 3T3-F442A preadipocytes and mature adipocytes. HGF knockdown with small-interfering RNA reduced HGF mRNA expression 82.3 +/- 4.2% and protein secretion 82.9 +/- 1.4% from 3T3-F442A preadipocytes. Silencing of HGF resulted in a 70.5 +/- 19.0% reduction in endothelial progenitor cell migration to 3T3-F442A-conditioned medium in vitro. 3T3-F442A preadipocytes injected under the skin of mice form a fat pad containing mature, lipid-filled adipocytes and a functional vasculature. At 72 h postinjection, expression of the endothelial cell genes TIE-1 and platelet endothelial cell adhesion molecule (PECAM)-1 was decreased 94.4 +/- 2.2 and 91.5 +/- 2.5%, respectively, in 3T3-F442A fat pads with HGF silencing. Knockdown of HGF had no effect on differentiation of 3T3-F442A preadipocytes to mature adipocytes in vitro or in vivo. In developing fat pads under the skin of HGF overexpressing transgenic mice, TIE-1 and PECAM-1 mRNA was increased 16.5- and 21.4-fold, respectively, at 72 h postinjection. The increase in gene expression correlated with immunohistochemical evidence of endothelial cell migration in the developing fat pad. These data suggest that HGF has a central role in regulating angiogenesis in adipose tissue.  相似文献   
88.
The level of mRNA encoding the nuclear enzyme poly(ADP-ribose) polymerase (ADP-ribosyltransferase, EC 2.4.2.30) was found to be very low in quiescent human lymphocytes and to increase at least 10-fold between 1 and 2 dyas after stimulation with the mitogen phytohaemagglutinin, staying high for several days thereafter. This increase was inhibited by 3-methoxybenzamide (a competitive inhibitor of poly(ADP-ribose) polymerase) but was not affected significantly by aphidicolin. Incubation of activated cells with cycloheximide for 2 h increased the expression slightly. These data demonstrate that, during lymphocyte activation, the level of mRNA of the poly(ADP-ribose) polymerase gene correlates with, and hence is presumably responsible for, the increase in poly(ADP-ribose) polymerase protein detectable by enzyme assay or immunochemistry.  相似文献   
89.
By using an electrical impedance plethysmorgraph and a pressure applicator to a rabbit's earlobe artery, it became possible to monitor the blood pressure for periods of several months. A study of the correlations of the blood pressure from carotid and ear was also made at varied blood pressures under different conditions which showed excellent correlations. This method could effectively replace the encannulation technique for monitoring rabbit's blood pressure in chronic experiments.  相似文献   
90.
Abundance and length of the highly-targeted snapper Chysophrys auratus were compared between sites in ''no take'' areas (Sanctuary Zones: SZ), partial protected areas which are fished (Habitat Protection Zones: HPZ), and areas outside (Outside) the Solitary Islands Marine Park (SIMP), Australia. Baited Remote Underwater Video (BRUV) sampling on shallow rocky reef (15 - 25 m) was conducted annually from 2002 until 2014 in the Austral-winter, covering the decade after these marine park zones were established (2002). Additional deeper sites (25 - 40 m) were sampled in 2010-2011 to assess if findings were more-broadly applicable. Lengths were measured using stereo-BRUVs from 2011-2014. Snapper were significantly more abundant in SZ overall and in most years compared with the other two management types, which did not significantly differ. Snapper rapidly increased after 2 - 3 years protection in all management types, especially SZ. Snapper were present on more SZ deployments than HPZ and Outside after the same period. The positive SZ response in snapper abundance on shallower reef was also found at a broader spatial scale on deeper sites. Again the two fished management types did not show significant differences among each other. There was considerable variation in snapper abundance between years, with strong peaks in 2005, 2009 and 2014 especially in SZ. Abundances remained higher in SZ in the year or two following a strong peak, but decreased to similar abundances to fished areas before the next peak. Snapper length frequency distribution significantly differed between SZ and both fished management types, with more larger snapper within SZ including a higher proportion (58%) that were legal-sized (>25.7 cm FL). HPZ and Outside did not significantly differ from each other, and were dominated by individuals below legal size. Overall, SZ''s have positively influenced abundance and length of snapper on these subtropical rocky reefs.  相似文献   
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