Coevolution of costly mate choice and condition-dependent display of good genes.

Females often choose their mates, instead of mating at random, even when a father contributes nothing but genes to his offspring. Costly female preferences for males with exaggerated traits that reduce viability, such as the peacock's tail, are particularly puzzling. Such preferences can evolve if directly favoured by natural selection or when the exaggerated trait, although maladaptive per se, indicates high overall quality of the male's genotype. Two recent analyses suggested that the advantage to mate choice based on genetic quality is too weak to explain extreme cases of exaggeration of display traits and the corresponding preferences. We studied coevolution of a female mate-preference function and a genotype-dependent male display function where mutation supplies variation in genotype quality and mate preference is costly. Preference readily evolves, often causing extreme exaggeration of the display. Mate choice and trait expression can approach an equilibrium, or a limit cycle, or exaggeration can proceed forever, eventually causing extinction.     

Targeted Selection Experiments and Enzyme Polymorphism: Negative Evidence for Octanoate Selection at the G6PD Locus in DROSOPHILA MELANOGASTER

Published studies have reported significant selection with respect to the G6pd locus for Drosophila melanogaster reared on Na-octanoate food. We have reexamined the selective effects of Na-octanoate on egg to adult viability with respect to the G6pd polymorphism using specially constructed X chromosomes. Four experiments were carried out using different 6Pgd backgrounds in two recombinant sets of chromosomes segregating for the G6pd locus but constructed so as to minimize variation over most of the X chromosome. In addition, two measures of viability were used, and the size of the experiments and their associated degrees of freedom are approximately double those reported in the former studies. Our results find no evidence for differential selection on G6pd genotypes (males and females) by Na-octanoate and, therefore, do not corroborate the positive results of selection reported by other investigators. The reasons for our different results are discussed.     

Intracellular pH plays a role in regulating protein synthesis in Xenopus oocytes

Full-grown Xenopus oocytes undergo meiotic maturation in response to progesterone stimulation. Using [¹⁴C]dimethyloxazolidine dione (DMO), we have measured a cytoplasmic alkalization in these oocytes starting at pH 7.14 ± 0.17 during the germinal vesicle (GV) stage, and increasing to 7.56 ± 0.14 at the time of germinal vesicle breakdown (GVBD). During this period, the rate of protein synthesis increases 2-fold from 18.9 ± 3.1 to 37.7 ± 8.8 ng/hr/oocyte. Artificial alkalization of GV stage oocytes to pH_i 7.68 ± 0.16, by exposure to the weak bases trimethylamine, methylamine, procaine, or imidazole, led to a 1.8-fold increase in the synthetic rate. Intracellular acidification from 7.5 back to 7.0 had no apparent effect on the elevated rate of protein synthesis following GVBD. Therefore, a cytoplasmic alkalization in the range of 7.5 to 7.6 seems to be one of the events that is necessary for initiating the increase in protein synthesis in maturing Xenopus oocytes; however, it does not appear that an elevated pH_i is necessary to maintain the increased synthetic rate following GVBD.     

Apoptosis: mode of cell death induced in T cell leukemia lines by dexamethasone and other agents

Glucocorticoids can mediate the destruction of thymocytes and T cell-derived leukemia cells through a mechanism known as apoptosis. The characteristic feature of apoptosis is fragmentation of DNA at internucleosomal linkers through the activity of a specific endonuclease. In this study, an attempt was made to compare dexamethasone-induced apoptosis in two T cell-derived human leukemia lines (CEM-C1 and CEM-C7) to the cell killing brought about by selected cytotoxic agents. In the CEM-C7 cell line (dexamethasone-sensitive), apoptosis was induced not only by dexamethasone but by actinomycin D, cycloheximide, and 25-OH cholesterol. In the CEM-C1 cell line (dexamethasone-resistant) cycloheximide, 25-OH cholesterol, or cell starvation could induce apoptosis. It appears that in leukemic cells apoptosis may be induced by a variety of unrelated toxic agents and is not limited to glucocorticoids.     

Copper regulation of ceruloplasmin in copper-deficient rats.

In copper-deficient rats, oral intubation of copper increases the rate of ceruloplasmin synthesis without affecting general synthesis of plasma or liver proteins. It also restores the enzyme from half to full activity. Copper given by injection at doses commonly employed has additional nonspecific effects on protein synthesis and in some strains of rats produces severe hemolysis. In contrast to deficient rats, in normal rats copper does not elevate plasma ceruloplasmin unless hemolysis also occurs. Thus, at least in deficiency, copper availability controls the rate of synthesis, acitvation, and plasma concentration of ceruloplasmin.     

盐泽螺旋藻藻胆蛋白的分离和特性研究

盐泽螺旋藻(Spirulina subsalsa)的水溶性色素粗提物经过硫酸铵沉淀和羟基磷灰石(HA)柱层析后可以分出两种藻胆蛋白,即藻蓝蛋白(c-PC)和别藻蓝蛋白(APC)。它们的纯度(指其在可见光部分的最大吸收与280nm处吸收之比)可分别达到7．27(c-PC)和6．55(APC)。而一般认可的纯度标准,PC为5,APC为6。纯化后的c—PC和APC在聚丙烯酰胺凝胶电泳(PAGE)中仅见一条色带,其最大吸收峰分别在620nm和650nm,其室温荧光发射峰分别为642nm和657nm。     

Young Children's Probability of Dying Before and After Their Mother's Death: A Rural South African Population-Based Surveillance Study

Background

There is evidence that a young child''s risk of dying increases following the mother''s death, but little is known about the risk when the mother becomes very ill prior to her death. We hypothesized that children would be more likely to die during the period several months before their mother''s death, as well as for several months after her death. Therefore we investigated the relationship between young children''s likelihood of dying and the timing of their mother''s death and, in particular, the existence of a critical period of increased risk.

Methods and Findings

Data from a health and socio-demographic surveillance system in rural South Africa were collected on children 0–5 y of age from 1 January 1994 to 31 December 2008. Discrete time survival analysis was used to estimate children''s probability of dying before and after their mother''s death, accounting for moderators. 1,244 children (3% of sample) died from 1994 to 2008. The probability of child death began to rise 6–11 mo prior to the mother''s death and increased markedly during the 2 mo immediately before the month of her death (odds ratio [OR] 7.1 [95% CI 3.9–12.7]), in the month of her death (OR 12.6 [6.2–25.3]), and during the 2 mo following her death (OR 7.0 [3.2–15.6]). This increase in the probability of dying was more pronounced for children whose mothers died of AIDS or tuberculosis compared to other causes of death, but the pattern remained for causes unrelated to AIDS/tuberculosis. Infants aged 0–6 mo at the time of their mother''s death were nine times more likely to die than children aged 2–5 y. The limitations of the study included the lack of knowledge about precisely when a very ill mother will die, a lack of information about child nutrition and care, and the diagnosis of AIDS deaths by verbal autopsy rather than serostatus.

Conclusions

Young children in lower income settings are more likely to die not only after their mother''s death but also in the months before, when she is seriously ill. Interventions are urgently needed to support families both when the mother becomes very ill and after her death. Please see later in the article for the Editors'' Summary     

Cross‐sex genetic covariances limit the evolvability of wing‐shape within and among species of Drosophila

The independent evolution of males and females is potentially constrained by both sexes inheriting the same alleles from their parents. This genetic constraint can limit the evolvability of complex traits; however, there are few studies of multivariate evolution that incorporate cross‐sex genetic covariances in their predictions. Drosophila wing‐shape has emerged as a model high‐dimensional phenotype; wing‐shape is highly evolvable in contemporary populations, and yet perplexingly stable across phylogenetic timescales. Here, we show that cross‐sex covariances in Drosophila melanogaster, given by the B ‐matrix, may considerably bias wing‐shape evolution. Using random skewers, we show that B would constrain the response to antagonistic selection by 90%, on average, but would double the response to concordant selection. Both cross‐sex within‐trait and cross‐sex cross‐trait covariances determined the predicted response to antagonistic selection, but only cross‐sex within‐trait covariances facilitated the predicted response to concordant selection. Similar patterns were observed in the direction of extant sexual dimorphism in D. melanogaster, and in directions of most and least dimorphic variation across the Drosophila phylogeny. Our results highlight the importance of considering between‐sex genetic covariances when making predictions about evolution on both macro‐ and microevolutionary timescales, and may provide one more explanatory piece in the puzzle of stasis.