Out of Africa and back again: nested cladistic analysis of human Y chromosome variation

We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.      

Synthesis of 1-(β-D-Glycopyranosyl)-3-Deazapyrimidines from 2-Hydroxy and 2-Mercaptopyridines

Abstract

The synthesis of new 4- and 5-substituted-3-cyanopyridine nucleosides has been performed by reacting the silylated pyridines and penta-O-acetyl-α -D-glycopyranose in dichloroethane in the presence of SnCl₄. The free nucleosides were tested for their potential activity against HIV and different types of tumor.     

Salt-imposed restrictions on the uptake of macroelements by roots of Arabidopsis thaliana

The aim of this investigation was to identify the growth limiting factors in Arabidopsis thaliana subjected to a mild salt stress. Two natural accessions (Col and N1438) were compared. In spite of their morphological and developmental similarity, they have been previously shown to differ in the response of their superoxide dismutase genes to salt stress (Physiol Plant 132:293–305, 2008). Thirty-day-old seedlings were grown for 15 days using a split-root configuration in which the root system was divided into two equal parts: the first was immersed in a complete nutrient solution with 50 mM NaCl added, while the second part was immersed in either complete or incomplete K-, Ca-, or N-free medium. Using this approach, we demonstrated that K⁺ and Ca²⁺ uptake was impaired in the roots subjected to NaCl. There was no indication of the salt-induced inhibition of N uptake. If K⁺ or Ca²⁺ were available from salt-free medium, plants were able to grow at normal rate and accumulate large amounts of Na⁺ in the shoots. These results indicate that the sensitivity of Arabidopsis growth to mild salinity was probably due to an inhibition of K⁺ or Ca²⁺ root transport by salt rather than due to salt accumulation in shoots. Furthermore, the salt sensitivity of ion transport in roots seemed to depend on the genotype, since K⁺ was limiting for Col growth, in contrast to N1438, the growth of which was limited by Ca²⁺.     

Analysis of salinity effects on basil leaf surface area, photosynthetic activity, and growth

Basil (Ocimum basilicum L.) seedlings were cultured on liquid medium in controlled conditions. Two varieties differing in leaf size were compared. When plants were 30?days old, the medium was supplemented with 50?mM NaCl. After 15?days of treatment, root, stem and leaf biomass, leaf number, and leaf surface area were measured. Ion accumulation was determined in roots, stems, and leaves. Photosynthetic parameters (CO₂ fixation rate, internal CO₂ concentration, stomatal conductance) as well as transpiration rate were determined on separate leaves. Electrolyte leakage and malondialdehyde content were used to estimate damage to membranes and lipid peroxidation, respectively. Several antioxidant enzymatic activities were used as proxies of oxidative stress. High Na⁺ concentration was reached in leaf tissues. Salt restricted whole plant biomass deposition rate by diminishing leaf number and leaf expansion, as well as photosynthetic activity were estimated from whole plant biomass production per unit leaf surface area. Diminished stomatal conductance restricted CO₂ fixation rate, and decrease in chlorophyll content presumably limited photosynthetic activity. Lipid peroxidation revealed damages to membranes. The magnitude of these responses differed between the two varieties, indicating that an intraspecific variability in salt response exists in basil.     

蓖麻蚕卵受精的研究

我们从细胞形态上的研究, 证明:蓖麻蚕卵在成熟期分裂的中期(同一横剖面), 基组数染色体是14;分作两圈, 内层4个, 外层10个。成熟卵停止在第一次中期分裂, 纺锤体与卵膜垂直, 待精子入卵后继续向前分裂, 并发现有染色质消散的现象。第二次成熟期分裂结果获得3个极体和1个雌性原核。正常的卵平均能接受2-3条精子, 它们入卵后起收缩、囊化成雄性原核;其中一个与雌性原核合并为“双组核”。剩余的过数精核分裂缓慢, 终于中心体离纺锤体作异形的分裂。     

Behavioral effects of acute and chronic triazolam treatments in albino rats

Previous behavioral studies on triazolam (TZ), which are small in number, could only speculate about tolerance to the anxiolytic effect of TZ, as the experiments did not cover sufficient time (of 4 to 7 days) for tolerance to develop. Therefore longer time for chronic TZ administration is used. We investigated the effects of TZ on motor activity and exploratory behavior using plus maze and open field. Three experiments were conducted. In the first, five groups of rats were acutely treated with different doses of TZ (0.25 mg/kg-4.0 mg/kg). In the second set of experiments, rats were treated chronically with a single daily dose of TZ (started with 0.25 mg/kg and increased by time to 1.0 mg/kg) for 5 weeks (representing clinical use). In the third, rats were treated chronically with three daily doses of TZ (started with 0.25 mg/kg and increased by time to 0.5 mg/kg) for 20 days (mimicking drug abuse). Acute TZ administration produced dose dependent anxiolytic effects and a decrease in motor activity with higher doses. Chronically treated rats, either once daily or three times daily doses, showed tolerance to both anxiolytic and sedative effects of TZ. It may be concluded that tolerance to the anxiolytic and sedative effects of TZ would develop after chronic administration either with clinical use or its abuse.     

Sodium transport in basil

In order to diversify the production of plants with pharmacological interest, it is important to understand the mechanisms involved in their tolerance to environmental constraints, such as salinity. Basil (Ocimum basilicum), known for its therapeutic uses, has been claimed to be salt tolerant, but physiological aspects of this behavior remain unknown. Since salt tolerance is known to be associated with several characteristics concerning Na⁺ transport to leaves, we studied this function in hydroponically grown basil. We analyzed the response of 30-day-old seedlings to 25–50 mM NaCl applied for 15 days. Growth was poorly affected, indicating that these concentrations corresponded to the tolerated salinity range. Leaves accumulated Na⁺ at relatively high concentration, without dehydrating. Potassium concentration in leaf tissues was maintained close to control level, indicating that K⁺ was 15- to 25-fold preferred over Na⁺ for ion transport and deposition. Collection of xylem sap on detopped plants revealed that this preference was only 10-fold for ion introduction into root xylem sap. Short-term (24 h) changes in Na⁺ distribution between organs after stem (steam) girdling suggested that Na⁺ downward recirculation by phloem occurred. Although modest, this transport might have augmented K⁺ selectivity of ion deposition in leaves.     

The Timing of the Shrew: Continuous Melatonin Treatment Maintains Youthful Rhythmic Activity in Aging Crocidura russula

Background

Laboratory conditions nullify the extrinsic factors that determine the wild expected lifespan and release the intrinsic or potential lifespan. Thus, wild animals reared in a laboratory often show an increased lifespan, and consequently an increased senescence phase. Senescence is associated with a broad suite of physiological changes, including a decreased responsiveness of the circadian system. The time-keeping hormone melatonin, an important chemical player in this system, is suspected to have an anti-aging role. The Greater White-toothed shrew Crocidura russula is an ideal study model to address questions related to aging and associated changes in biological functions: its lifespan is short and is substantially increased in captivity; daily and seasonal rhythms, while very marked the first year of life, are dramatically altered during the senescence process which starts during the second year. Here we report on an investigation of the effects of melatonin administration on locomotor activity of aging shrews.

Methodology/Principal Findings

1) The diel fluctuations of melatonin levels in young, adult and aging shrews were quantified in the pineal gland and plasma. In both, a marked diel rhythm (low diurnal concentration; high nocturnal concentration) was present in young animals but then decreased in adults, and, as a result of a loss in the nocturnal production, was absent in old animals. 2) Daily locomotor activity rhythm was monitored in pre-senescent animals that had received either a subcutaneous melatonin implant, an empty implant or no implant at all. In non-implanted and sham-implanted shrews, the rhythm was well marked in adults. A marked degradation in both period and amplitude, however, started after the age of 14–16 months. This pattern was considerably delayed in melatonin-implanted shrews who maintained the daily rhythm for significantly longer.

Conclusions

This is the first long term study (>500 days observation of the same individuals) that investigates the effects of continuous melatonin delivery. As such, it sheds new light on the putative anti-aging role of melatonin by demonstrating that continuous melatonin administration delays the onset of senescence. In addition, the shrew appears to be a promising mammalian model for elucidating the precise relationships between melatonin and aging.