The central Siberian origin for native American Y chromosomes.

Y chromosomal DNA polymorphisms were used to investigate Pleistocene male migrations to the American continent. In a worldwide sample of 306 men, we obtained 32 haplotypes constructed with the variation found in 30 distinct polymorphic sites. The major Y haplotype present in most Native Americans was traced back to recent ancestors common with Siberians, namely, the Kets and Altaians from the Yenissey River Basin and Altai Mountains, respectively. Going further back, the next common ancestor gave rise also to Caucasoid Y chromosomes, probably from the central Eurasian region. This study, therefore, suggests a predominantly central Siberian origin for Native American paternal lineages for those who could have migrated to the Americas during the Upper Pleistocene.     

Salt stress and respiration inAspergillus repens

Studies with whole cells and mitochondrial fractions revealed increased respiratory activity inAspergillus repens grown under salt stress conditions. The state 3 and state 4 respiration rates, PO ratios, and Mg²⁺-dependent ATPase were higher in mitochondria of stressed cells than in control cells.A. repens respires via an antimycin A-and cyanide-sensitive pathway. Oligomycin, dicyclohexylcarbodiimide (DCCD) and rotenone inhibited respiration rates less in mitochondria of stressed cells than in controls. Though 2,4-dinitrophenol (DNP), carbonyl cyanide-m-chlorophenylhydrazone (m-Cl-CCP), and carbonyl cyanide-p-trifluoromethylhydrazone (p-F₃-CCP) did not stimulate Mg²⁺-ATPase activity, DNP enhanced the respiration rates, whereasm-Cl-CCP andp-F₃-CCP decreased the respiration rates in either condition; mitochondria of stressed cells exhibited a lower degree of inhibition than controls. Addition of DNP, oligomycin, and DCCD inhibited the basal Mg²⁺-ATPase (ATPase activity without Mg²⁺ addition). Oligomycin inhibited the Mg²⁺-ATPase. DCCD showed less inhibition in mitochondria under stress than did the controls. Levels of some respiratory enzymes were higher in the culture grown under stress than in the controls.     

Convergent evolution of cysteine residues in sperm protamines of one genus of marsupials, the Planigales

A characteristic feature of the sperm P1 protamines of eutherian mammals is the constant presence of six to nine cysteine residues per molecule. During spermiogenesis these residues become oxidized to form a three-dimensional network of disulfide bridges between, and within, protamine molecules in the sperm chromatin. This covalent cross linking strongly stabilizes eutherian sperm nuclei. In contrast, protamines sequenced from teleost fish, birds, monotremes, and marsupials all lack cysteine residues and their sperm nuclei, without the stabilizing cross links, are easily decondensed in vitro. We have now found that one genus of tiny, shrewlike dasyurid marsupials, the Planigales, possess P1 protamines containing five to six cysteine residues. These residues appear to have evolved since the divergence of Planigales from other members of the family Dasyuridae, such as the marsupial mouse, Sminthopsis crassicaudata. We believe this constitutes a case of convergent evolution in a subfamily of dasyurid marsupials toward the cysteine-rich eutherian form of sperm protamine P1.      

A selective difference between human Y-chromosomal DNA haplotypes

DNA analysis is making a valuable contribution to the understanding of human evolution [1]. Much attention has focused on mitochondrial DNA (mtDNA) [2] and the Y chromosome [3] and [4], both of which escape recombination and so provide information on maternal and paternal lineages, respectively. It is often assumed that the polymorphisms observed at loci on mtDNA and the Y chromosome are selectively neutral and, therefore, that existing patterns of molecular variation can be used to deduce the histories of populations in terms of drift, population movements, and cultural practices. The coalescence of the molecular phylogenies of mtDNA and the Y chromosome to recent common ancestors in Africa [5] and [6], for example, has been taken to reflect a recent origin of modern human populations in Africa. An alternative explanation, though, could be the recent selective spread of mtDNA and Y chromosome haplotypes from Africa in a population with a more complex history [7]. It is therefore important to establish whether there are selective differences between classes (haplotypes) of mtDNA and Y chromosomes and, if so, whether these differences could have been sufficient to influence the distributions of haplotypes in existing populations. A precedent for this hypothesis has been established for mtDNA in that one mtDNA background increases susceptibility to Leber hereditary optic neuropathy [8]. Although studies of nucleotide diversity in global samples of Y chromosomes have suggested an absence of recent selective sweeps or bottlenecks [9], selection may, in principle, be very important for the Y chromosome because it carries several loci affecting male fertility [10] and [11] and as many as 5% of males are infertile [11] and [12]. Here, we show that one class of infertile males, PRKX/PRKY translocation XX males, arises predominantly on a particular Y haplotypic background. Selection is, therefore, acting on Y haplotype distributions in the population.     

Polymerization site in the beta chain of fibrin: mapping of the B beta 1-55 sequence

The formation of a fibrin clot occurs through binding of putative complementary sites, called fibrin polymerization sites, located in the NH2- and COOH-terminal domains of fibrin monomer molecules. In this study, we have investigated the structure of the NH2-terminal fibrin polymerization site by using fibrinogen-derived peptides and fragments. Fibrinogen was digested with Crotalus atrox protease III, to two major molecular species: a Mr 325,000 derivative (Fg325) and a peptide of Mr 5000. The peptide and its thrombin-cleavage product were purified by ion-exchange and reverse-phase HPLC; the authenticity of the B beta 1-42 and beta 15-42 peptides, respectively, was confirmed by amino acid sequencing. Since Fg325 had decreased thrombin coagulability, we addressed the question of whether the peptide B beta 1-42 contained a fibrin polymerization site. In order to identify and map the site, the peptides B beta 1-42 and beta 15-42 were tested for their ability to inhibit fibrin monomer polymerization. In addition the following peptides prepared by chemical synthesis were also tested: beta 15-18, beta 15-26, beta 24-42, beta 40-54, beta 50-55, and alpha 17-19-Pro. While B beta 1-42 had no inhibitory activity, the peptide devoid of fibrinopeptide B, beta 15-42, was a strong inhibitor. The peptides beta 15-18, beta 15-26, and beta 15-42 decreased the rate of fibrin polymerization by 50% at a molar excess of the peptide to fibrin monomer of 500, 430, and 50, respectively. The peptides beta 24-42, beta 40-54, and beta 50-55 were inactive.(ABSTRACT TRUNCATED AT 250 WORDS)     

TGF-β activates APC through Cdh1 binding for Cks1 and Skp2 proteasomal destruction stabilizing p27kip1 for normal endometrial growth

We previously reported that aberrant TGF-β/Smad2/3 signaling in endometrial cancer (ECA) leads to continuous ubiquitylation of p27^kip1(p27) by the E3 ligase SCF-Skp2/Cks1 causing its degradation, as a putative mechanism involved in the pathogenesis of this cancer. In contrast, normal intact TGF-β signaling prevents degradation of nuclear p27 by SCF-Skp2/Cks1 thereby accumulating p27 to block Cdk2 for growth arrest. Here we show that in ECA cell lines and normal primary endometrial epithelial cells, TGF-β increases Cdh1 and its binding to APC/C to form the E3 ligase complex that ubiquitylates Cks1 and Skp2 prompting their proteasomal degradation and thus, leaving p27 intact. Knocking-down Cdh1 in ECA cell lines increased Skp2/Cks1 E3 ligase activity, completely diminished nuclear and cytoplasmic p27, and obviated TGF-β-mediated inhibition of proliferation. Protein synthesis was not required for TGF-β-induced increase in nuclear p27 and decrease in Cks1 and Skp2. Moreover, half-lives of Cks1 and Skp2 were extended in the Cdh1-depleted cells. These results suggest that the levels of p27, Skp2 and Cks1 are strongly or solely regulated by proteasomal degradation. Finally, an inverse relationship of low p27 and high Cks1 in the nucleus was shown in patients in normal proliferative endometrium and grade I-III ECAs whereas differentiated secretory endometrium showed the reverse. These studies implicate Cdh1 as the master regulator of TGF-β-induced preservation of p27 tumor suppressor activity. Thus, Cdh1 is a potential therapeutic target for ECA and other human cancers showing an inverse relationship between Cks1/Skp2 and p27 and/or dysregulated TGF-β signaling.     

Modeling the Cost Effectiveness of Neuroimaging-Based Treatment of Acute Wake-Up Stroke

Background

Thrombolytic treatment (tissue-type plasminogen activator [tPA]) is only recommended for acute ischemic stroke patients with stroke onset time <4.5 hours. tPA is not recommended when stroke onset time is unknown. Diffusion-weighted MRI (DWI) and fluid attenuated inversion recovery (FLAIR) MRI mismatch information has been found to approximate stroke onset time with some accuracy. Therefore, we developed a micro-simulation model to project health outcomes and costs of MRI-based treatment decisions versus no treatment for acute wake-up stroke patients.

Methods and Findings

The model assigned simulated patients a true stroke onset time from a specified probability distribution. DWI-FLAIR mismatch estimated stroke onset <4.5 hours with sensitivity and specificity of 0.62 and 0.78, respectively. Modified Rankin Scale (mRS) scores reflected tPA treatment effectiveness accounting for patients’ true stroke onset time. Discounted lifetime costs and benefits (quality-adjusted life years [QALYs]) were projected for each strategy. Incremental cost-effectiveness ratios (ICERs) were calculated for the MRI-based strategy in base-case and sensitivity analyses. With no treatment, 45.1% of simulated patients experienced a good stroke outcome (mRS score 0–1). Under the MRI-based strategy, in which 17.0% of all patients received tPA despite stroke onset times >4.5 hours, 46.3% experienced a good stroke outcome. Lifetime discounted QALYs and costs were 5.312 and $88,247 for the no treatment strategy and 5.342 and $90,869 for the MRI-based strategy, resulting in an ICER of $88,000/QALY. Results were sensitive to variations in patient- and provider-specific factors such as sleep duration, hospital travel and door-to-needle times, as well as onset probability distribution, MRI specificity, and mRS utility values.

Conclusions

Our model-based findings suggest that an MRI-based treatment strategy for this population could be cost-effective and quantifies the impact that patient- and provider-specific factors, such as sleep duration, hospital travel and door-to-needle times, could have on the optimal decision for wake-up stroke patients.