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Sex differences in the fitness effects of alleles at a single locus (intralocus sexual antagonism, or SA) have several evolutionary consequences. Among the consequences of SA, polymorphisms at genes partially linked to the sex-determining region of the sex chromosome pair potentially drive the evolution of suppressed recombination between the sex chromosomes. Understanding the conditions under which SA polymorphism can exist at such pseudo-autosomal (or PAR) loci should increase understanding of the evolution of recombination between sex chromosome pairs, and can help predict when we may expect potentially empirically detectable allele frequency differences between the sexes. Models so far published have concluded that PAR genes can maintain SA polymorphisms over a wider range of selection coefficients than autosomal ones, but have used restrictive assumptions. We expand the modeling of SA alleles at a single locus with the full range of degrees of linkage to the male-specific region, to include strong or weak selection and the possibility of different dominance coefficients in the two sexes. We confirm the previous major conclusion that SA polymorphisms are generally maintained in a larger region of parameter space if the locus is in the PAR than if it is autosomal. 相似文献
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Crispin M. Mutshinda Robert B. O'Hara Ian P. Woiwod 《Proceedings. Biological sciences / The Royal Society》2009,276(1669):2923-2929
The search for general mechanisms of community assembly is a major focus of community ecology. The common practice so far has been to examine alternative assembly theories using dichotomist approaches of the form neutrality versus niche, or compensatory dynamics versus environmental forcing. In reality, all these mechanisms will be operating, albeit with different strengths. While there have been different approaches to community structure and dynamics, including neutrality and niche differentiation, less work has gone into separating out the temporal variation in species abundances into relative contributions from different components. Here we use a refined statistical machinery to decompose temporal fluctuations in species abundances into contributions from environmental stochasticity and inter-/intraspecific interactions, to see which ones dominate. We apply the methodology to community data from a range of taxa. Our results show that communities are largely driven by environmental fluctuations, and that member populations are, to different extents, regulated through intraspecific interactions, the effects of interspecific interactions remaining broadly minor. By decomposing the temporal variation in this way, we have been able to show directly what has been previously inferred indirectly: compensatory dynamics are in fact largely outweighed by environmental forcing, and the latter tends to synchronize the population dynamics. 相似文献
35.
Michel Halbwax Crispin Kamate Mahamba Anne-Marie Ngalula & Claudine André 《Journal of medical primatology》2009,38(3):171-174
Background This case report describes the first placental retention in an 11-year-old female bonobo ( Pan paniscus ) following the delivery of a healthy infant.
Methods After unsuccessful medical treatment with oxytocin, the placenta was manually extracted.
Results and conclusions Both the dam and infant survived. 相似文献
Methods After unsuccessful medical treatment with oxytocin, the placenta was manually extracted.
Results and conclusions Both the dam and infant survived. 相似文献
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Julia W. Neilson Lin Zhang Tracey A. Veres-Schalnat Kevin B. Chandler Charlotte H. Neilson Jennifer D. Crispin Jeanne E. Pemberton Raina M. Maier 《Applied microbiology and biotechnology》2010,88(4):953-963
While variable production of the biosurfactant, rhamnolipid, by Pseudomonas aeruginosa has been shown to be dependent on growth conditions, no research has evaluated potential relationships between rhamnolipid
production and the presence of heavy metals. The current investigation evaluates the influence of Cd2+ on rhamnolipid synthesis. Cultures grown in the presence of 0.45 and 0.89 mM Cd2+ were monitored for rhlB/rhlC expression, rhamnolipid yield, and the ratio of monorhamnolipid (RL1) and dirhamnolipid (RL2) produced. Results show a Cd-induced
enhancement of rhlB expression in mid-stationary phase (53 h). In addition, sustained production of rhamnolipid through late stationary growth
phase (96 h) was observed for Cd-amended cultures, unlike Cd-free control cultures that ceased rhamnolipid production by mid-stationary
growth phase. Most significant was an observed increase in the ratio of RL2 to RL1 congeners produced by cultures grown in
the presence of Cd2+. Previous results have shown that the complexation constant for RL2–Cd is several orders of magnitude larger than that of
RL1–Cd thus the preferential production of RL2 in the presence of Cd2+ impacts its bioavailability and toxicity both for the cell and in the surrounding environment. 相似文献
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Cationic (positively charged) liposomes have been tested in various gene therapy clinical trials for neoplastic and other
diseases. They have demonstrated selectivity for tumour vascular endothelial cells raising hopes for both antiangiogenic and
antivascular therapies. They are also capable of being selectively delivered to the lungs and liver when administered intravenously.
These vesicles are being targeted to the tumour in various parts of the body by using advanced liposomal systems such as ligand-receptor
and antibody-antigen combinations. At present, the transferrin receptor is commonly used for cancer-targeted drug delivery
systems including cationic liposomes. This review looks at the growing utility of these vesicles for delivery of small molecule
anticancer drugs. 相似文献
40.
Crispin MD Ritchie GE Critchley AJ Morgan BP Wilson IA Dwek RA Sim RB Rudd PM 《FEBS letters》2004,566(1-3):270-274
The monoglucosylated oligomannose N-linked oligosaccharide (Glc(1)Man(9)GlcNAc(2)) is a retention signal for the calnexin-calreticulin quality control pathway in the endoplasmic reticulum. We report here the presence of such monoglucosylated N-glycans on the human complement serum glycoprotein C3. This finding represents the first report of monoglucosylated glycans on a human serum glycoprotein from non-diseased individuals. The presence of the glucose moiety in 5% of the human C3 glycoprotein suggests that this glycosylation site is sequestered within the protein and is consistent with previous studies identifying a cryptic conglutinin binding site on C3 that becomes exposed upon its conversion to iC3b. 相似文献