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排序方式: 共有68条查询结果,搜索用时 31 毫秒
31.
Background
In a number of species males damage females during copulation, but the reasons for this remain unclear. It may be that males are trying to manipulate female mating behaviour or their life histories. Alternatively, damage may be a side-effect of male-male competition. In the black scavenger or dung fly Sepsis cynipsea (Diptera: Sepsidae) mating reduces female survival, apparently because males wound females during copulation. However, this damage does not seem to relate to attempted manipulation of female reproduction by males. Here we tested the hypothesis that harming females during mating is an incidental by-product of characters favoured during pre-copulatory male-male competition. We assessed whether males and their sons vary genetically in their ability to obtain matings and harm females, and whether more successful males were also more damaging. We did this by ranking males' mating success in paired competitions across several females whose longevity under starvation was subsequently measured. 相似文献32.
David G. Cotter Baris Ercal D. André d'Avignon Dennis J. Dietzen Peter A. Crawford 《The Journal of biological chemistry》2013,288(27):19739-19749
Preservation of bioenergetic homeostasis during the transition from the carbohydrate-laden fetal diet to the high fat, low carbohydrate neonatal diet requires inductions of hepatic fatty acid oxidation, gluconeogenesis, and ketogenesis. Mice with loss-of-function mutation in the extrahepatic mitochondrial enzyme CoA transferase (succinyl-CoA:3-oxoacid CoA transferase, SCOT, encoded by nuclear Oxct1) cannot terminally oxidize ketone bodies and develop lethal hyperketonemic hypoglycemia within 48 h of birth. Here we use this model to demonstrate that loss of ketone body oxidation, an exclusively extrahepatic process, disrupts hepatic intermediary metabolic homeostasis after high fat mother''s milk is ingested. Livers of SCOT-knock-out (SCOT-KO) neonates induce the expression of the genes encoding peroxisome proliferator-activated receptor γ co-activator-1a (PGC-1α), phosphoenolpyruvate carboxykinase (PEPCK), pyruvate carboxylase, and glucose-6-phosphatase, and the neonate''s pools of gluconeogenic alanine and lactate are each diminished by 50%. NMR-based quantitative fate mapping of 13C-labeled substrates revealed that livers of SCOT-KO newborn mice synthesize glucose from exogenously administered pyruvate. However, the contribution of exogenous pyruvate to the tricarboxylic acid cycle as acetyl-CoA is increased in SCOT-KO livers and is associated with diminished terminal oxidation of fatty acids. After mother''s milk provokes hyperketonemia, livers of SCOT-KO mice diminish de novo hepatic β-hydroxybutyrate synthesis by 90%. Disruption of β-hydroxybutyrate production increases hepatic NAD+/NADH ratios 3-fold, oxidizing redox potential in liver but not skeletal muscle. Together, these results indicate that peripheral ketone body oxidation prevents hypoglycemia and supports hepatic metabolic homeostasis, which is critical for the maintenance of glycemia during the adaptation to birth. 相似文献
33.
34.
Application of ultrasound for pregnancy diagnosis has been tested and evaluated in 15 Iranian camels (Camelus dromedarius), all of which ultimately calved. Transabdominal examinations were unsuccessful, while intrapelvic application resulted in the reception of sounds characteristic for foetal life, similar to those found in other domestic animals. Signals of foetal heart, pulse of umbilical vessels and uterine artery as well as foetal movement could be recognized as distinct sounds and have been recorded for further studies. An attempt was made to verify the findings of the ultrasonic diagnosis through rectal palpation. The ultrasonic technique resulted in 12 correct and three incorrect diagnoses. 相似文献
35.
Ribosomal protein S14 genes (RPS14) in eukaryotic species from protozoa to
primates exhibit dramatically different intron-exon structures yet share
homologous polypeptide-coding sequences. To recognize common features of
RPS14 gene architectures in closely related mammalian species and to
evaluate similarities in their noncoding DNA sequences, we isolated the
intron-containing S14 locus from Chinese hamster ovary (CHO) cell DNA by
using a PCR strategy and compared it with human RPS14. We found that rodent
and primate S14 genes are composed of identical protein-coding exons
interrupted by introns at four conserved DNA sites. However, the structures
of corresponding CHO and human RPS14 introns differ significantly.
Nonetheless, individual intron splice donor, splice acceptor, and upstream
flanking motifs have been conserved within mammalian S14 homologues as well
as within RPS14 gene fragments PCR amplified from other vertebrate genera
(birds and bony fish). Our data indicate that noncoding, intronic DNA
sequences within highly conserved, single-copy ribosomal protein genes are
useful molecular landmarks for phylogenetic analysis of closely related
vertebrate species.
相似文献
36.
George?M?WarimweEmail author Gema?Lorenzo Elena?Lopez-Gil Arturo?Reyes-Sandoval Matthew?G?Cottingham Alexandra?J?Spencer Katharine?A?Collins Matthew?DJ?Dicks Anita?Milicic Amar?Lall Julie?Furze Alison?V?Turner Adrian?VS?Hill Alejandro?Brun Sarah?C?Gilbert 《Virology journal》2013,10(1):349
Background
Rift Valley Fever (RVF) is a viral zoonosis that historically affects livestock production and human health in sub-Saharan Africa, though epizootics have also occurred in the Arabian Peninsula. Whilst an effective live-attenuated vaccine is available for livestock, there is currently no licensed human RVF vaccine. Replication-deficient chimpanzee adenovirus (ChAd) vectors are an ideal platform for development of a human RVF vaccine, given the low prevalence of neutralizing antibodies against them in the human population, and their excellent safety and immunogenicity profile in human clinical trials of vaccines against a wide range of pathogens.Methods
Here, in BALB/c mice, we evaluated the immunogenicity and efficacy of a replication-deficient chimpanzee adenovirus vector, ChAdOx1, encoding the RVF virus envelope glycoproteins, Gn and Gc, which are targets of virus neutralizing antibodies. The ChAdOx1-GnGc vaccine was assessed in comparison to a replication-deficient human adenovirus type 5 vector encoding Gn and Gc (HAdV5-GnGc), a strategy previously shown to confer protective immunity against RVF in mice.Results
A single immunization with either of the vaccines conferred protection against RVF virus challenge eight weeks post-immunization. Both vaccines elicited RVF virus neutralizing antibody and a robust CD8+ T cell response.Conclusions
Together the results support further development of RVF vaccines based on replication-deficient adenovirus vectors, with ChAdOx1-GnGc being a potential candidate for use in future human clinical trials.37.
38.
Andrew C Doxey Daniel A Kurtz Michael DJ Lynch Laura A Sauder Josh D Neufeld 《The ISME journal》2015,9(2):461-471
Cobalamin (vitamin B12) is a complex metabolite and essential cofactor required by many branches of life, including most eukaryotic phytoplankton. Algae and other cobalamin auxotrophs rely on environmental cobalamin supplied from a relatively small set of cobalamin-producing prokaryotic taxa. Although several Bacteria have been implicated in cobalamin biosynthesis and associated with algal symbiosis, the involvement of Archaea in cobalamin production is poorly understood, especially with respect to the Thaumarchaeota. Based on the detection of cobalamin synthesis genes in available thaumarchaeotal genomes, we hypothesized that Thaumarchaeota, which are ubiquitous and abundant in aquatic environments, have an important role in cobalamin biosynthesis within global aquatic ecosystems. To test this hypothesis, we examined cobalamin synthesis genes across sequenced thaumarchaeotal genomes and 430 metagenomes from a diverse range of marine, freshwater and hypersaline environments. Our analysis demonstrates that all available thaumarchaeotal genomes possess cobalamin synthesis genes, predominantly from the anaerobic pathway, suggesting widespread genetic capacity for cobalamin synthesis. Furthermore, although bacterial cobalamin genes dominated most surface marine metagenomes, thaumarchaeotal cobalamin genes dominated metagenomes from polar marine environments, increased with depth in marine water columns, and displayed seasonality, with increased winter abundance observed in time-series datasets (e.g., L4 surface water in the English Channel). Our results also suggest niche partitioning between thaumarchaeotal and cyanobacterial ribosomal and cobalamin synthesis genes across all metagenomic datasets analyzed. These results provide strong evidence for specific biogeographical distributions of thaumarchaeotal cobalamin genes, expanding our understanding of the global biogeochemical roles played by Thaumarchaeota in aquatic environments. 相似文献
39.
This article selectively reviews research concerning nicotine's effects on cognition, including the neurobiological mechanism for these effects, task and experimental features that may be important for elucidating these effects, and why these effects may have amplified motivational significance among smokers with cognitive deficit. Nicotine has effects on various cognitive processes, though most studies in humans have focused on the amelioration of cognitive deficits experienced during drug withdrawal. The direct cognitive-enhancing effect of nicotine remains a controversial topic. The relationship between attentional and non-attentional cognitive effects of nicotine is discussed in the context of cognitive self-medication. Further research should include theory-driven examination of cognitive effects of nicotine, and develop targeted smoking cessation programs based on an improved understanding of the role of cognitive self-medication in high-risk individuals. 相似文献
40.
Andrew C Doxey Michael DJ Lynch Kirsten M Müller Elizabeth M Meiering Brendan J McConkey 《BMC evolutionary biology》2008,8(1):316