Genetic sex determination,sex chromosome size and sex-specific lifespans across tetrapods

Sex differences in lifespan are ubiquitous across the tree of life and exhibit broad taxonomic patterns that remain a puzzle, such as males living longer than females in birds and vice versa in mammals. The prevailing unguarded X hypothesis explains sex differences in lifespan by differential expression of recessive mutations on the X or Z chromosome of the heterogametic sex, but has only received indirect support to date. An alternative hypothesis is that the accumulation of deleterious mutations and repetitive elements on the Y or W chromosome might lower the survival of the heterogametic sex (‘toxic Y’ hypothesis). Here, we use a new database to report lower survival of the heterogametic relative to the homogametic sex across 136 species of birds, mammals, reptiles and amphibians, as expected if sex chromosomes shape sex-specific lifespans, and consistent with previous findings. We also found that the relative sizes of both the X and the Y chromosomes in mammals (but not the Z or the W chromosomes in birds) are associated with sex differences in lifespan, as predicted by the unguarded X and the ‘toxic Y’. Furthermore, we report that the relative size of the Y is negatively associated with male lifespan in mammals, so that small Y size correlates with increased male lifespan. In theory, toxic Y effects are expected to be particularly strong in mammals, and we did not find similar effects in birds. Our results confirm the role of sex chromosomes in explaining sex differences in lifespan across tetrapods and further suggest that, at least in mammals, ‘toxic Y’ effects may play an important part in this role.     

Aberrant Mitochondria in a Bethlem Myopathy Patient with a Homozygous Amino Acid Substitution That Destabilizes the Collagen VI α2(VI) Chain

Bethlem myopathy and Ullrich congenital muscular dystrophy (UCMD) sit at opposite ends of a clinical spectrum caused by mutations in the extracellular matrix protein collagen VI. Bethlem myopathy is relatively mild, and patients remain ambulant in adulthood while many UCMD patients lose ambulation by their teenage years and require respiratory interventions. Dominant and recessive mutations are found across the entire clinical spectrum; however, recessive Bethlem myopathy is rare, and our understanding of the molecular pathology is limited. We studied a patient with Bethlem myopathy. Electron microscopy of his muscle biopsy revealed abnormal mitochondria. We identified a homozygous COL6A2 p.D871N amino acid substitution in the C-terminal C2 A-domain. Mutant α2(VI) chains are unable to associate with α1(VI) and α3(VI) and are degraded by the proteasomal pathway. Some collagen VI is assembled, albeit more slowly than normal, and is secreted. These molecules contain the minor α2(VI) C2a splice form that has an alternative C terminus that does include the mutation. Collagen VI tetramers containing the α2(VI) C2a chain do not assemble efficiently into microfibrils and there is a severe collagen VI deficiency in the extracellular matrix. We expressed wild-type and mutant α2(VI) C2 domains in mammalian cells and showed that while wild-type C2 domains are efficiently secreted, the mutant p.D871N domain is retained in the cell. These studies shed new light on the protein domains important for intracellular and extracellular collagen VI assembly and emphasize the importance of molecular investigations for families with collagen VI disorders to ensure accurate diagnosis and genetic counseling.     

Release of hypothalamic neuropeptide Y and effects of exogenous NPY on the release of hypothalamic GnRH and pituitary gonadotropins in intact and ovariectomized does in vitro

The effect of NPY on the hypothalamic release of GnRH and pituitary release of gonadotropins was examined in intact and ovariectomized (OVEX) rabbits in a superfusion system. Exposure of mediobasal hypothalami (MBH) from intact rabbits to NPY (8 X 10(-8) M) resulted in a sustained stimulation of GnRH secretion into the medium. The same dose of NPY had no effect on MBH-GnRH release from OVEX rabbits. NPY also produced a sustained stimulation of LH and FSH release by pituitary fragments from intact rabbits, but NPY caused only a transient release of these hormones by pituitaries from OVEX does. Media samples from MBH superfusions were also measured for NPY concentrations. NPY was released episodically into the medium. The amplitude and frequency of NPY pulses in intact and OVEX rabbits did not differ; nor were mean levels of NPY significantly affected by castration. These results suggest that NPY has direct effects on both the hypothalamus and pituitary to modulate the the activities of GnRH neurons and gonadotropes. The pattern of GnRH and gonadotropin response to NPY exposure is determined by ovarian factors.     

Structural analysis of intrinsically disordered proteins by small-angle X-ray scattering

Small-angle scattering of X-rays (SAXS) is an established method to study the overall structure and structural transitions of biological macromolecules in solution. For folded proteins, the technique provides three-dimensional low resolution structures ab initio or it can be used to drive rigid-body modeling. SAXS is also a powerful tool for the quantitative analysis of flexible systems, including intrinsically disordered proteins (IDPs), and is highly complementary to the high resolution methods of X-ray crystallography and NMR. Here we present the basic principles of SAXS and review the main approaches to the characterization of IDPs and flexible multidomain proteins using SAXS. Together with the standard approaches based on the analysis of overall parameters, a recently developed Ensemble Optimization Method (EOM) is now available. The latter method allows for the co-existence of multiple protein conformations in solution compatible with the scattering data. Analysis of the selected ensembles provides quantitative information about flexibility and also offers insights into structural features. Examples of the use of SAXS and combined approaches with NMR, X-ray crystallography, and computational methods to characterize completely or partially disordered proteins are presented.     

A review of the genus Rusa in the indo-malayan archipelago and conservation efforts

Genus Rusa, belonging to the deer family Cervidae is native to the Indo-Malaya Archipelago (IMA). However, detailed information on the Rusa genus in the IMA is limited. This review provides comprehensive information on the Rusa genus in the IMA including, threats and conservation efforts. There are four species of deer in Rusa genus, which is Sambar deer (Rusa unicolor), Javan deer (Rusa timorensis), Visayan spotted deer (Rusa alfredi) and Philippine deer (Rusa marianna). Despite their wide distribution in the South Asian and Southeast Asian regions, they are under serious threats. Some conservation efforts that are being done to protect and conserve them among others are; (1) facilities protection, (2) habitat enrichment programme, (3) Ex-situ conservation, (4) legislations, and (5) captive breeding. Conservation through genetics is also an important step in conserving these species. Recommendations for conservation of the genus are also discussed; 1. maintenance of ecosystem. 2. more effective monitoring system on the existing protected area. 3. ex-situ conservation, and 4. habitat monitoring.     

B. thuringiensis is a Poor Colonist of Leaf Surfaces

The ability of several Bacillus thuringiensis strains to colonize plant surfaces was assessed and compared with that of more common epiphytic bacteria. While all B. thuringiensis strains multiplied to some extent after inoculation on bean plants, their maximum epiphytic population sizes of 10⁶ cfu/g of leaf were always much less than that achieved by other resident epiphytic bacteria or an epiphytically fit Pseudomonas fluorescens strain, which attained population sizes of about 10⁷ cfu/g of leaf. However B. thuringiensis strains exhibited much less decline in culturable populations upon imposition of desiccation stress than did other resident bacteria or an inoculated P. fluorescens strain, and most cells were in a spore form soon after inoculation onto plants. B. thuringiensis strains produced commercially for insect control were not less epiphytically fit than strains recently isolated from leaf surfaces. The growth of B. thuringiensis was not affected by the presence of Pseudomonas syringae when co-inoculated, and vice versa. B. thuringiensis strains harboring a green fluorescent protein marker gene did not form large cell aggregates, were not associated with other epiphytic bacteria, and were not found associated with leaf structures, such as stomata, trichomes, or veins when directly observed on bean leaves by epifluorescent microscopy. Thus, B. thuringiensis appears unable to grow extensively on leaves and its common isolation from plants may reflect immigration from more abundant reservoirs elsewhere.     

Quantum Dot Based Heterostructures for Unassisted Photoelectrochemical Hydrogen Generation

TiO₂ hollow nanowires (HNWs) and nanoparticles (NPs) constitute promising architectures for QDs sensitized photoanodes for H₂ generation. We sensitize these structures with CdS/CdSe quantum dots by two different methods (chemical bath deposition, CBD and succesive ionic layer adsorption and reaction, SILAR) and evaluate the performance of these photoelectrodes. Remarkable photocurrents of 4 mA·cm and 8 mA·cm^?2 and hydrogen generation rates of 40 ml·cm^?2·day^?1 and 80 ml·cm^?2·day^?1 have been obtained in a three electrode configuration with sacrificial hole scavengers (Na₂S and Na₂SO₃), for HNWs and NPs respectively, which is confirmed through gas analysis. More importantly, autonomous generation of H₂ (20 ml·cm^?2·day^?1 corresponding to 2 mA·cm^?2 photocurrent) is obtained in a two electrode configuration at short circuit under 100 mW·cm^?2 illumination, clearly showing that these photoanodes can produce hydrogen without the assistance of any external bias. To the best of the authors' knowledge, this is the highest unbiased solar H₂ generation rate reported for these of QDs based heterostructures. Impedance spectroscopy measurements show similar electron density of trap states below the TiO₂ conduction band while the recombination resistance was higher for HNWs, consistently with the much lower surface area compared to NPs. However, the conductivity of both structures is similar, in spite of the one dimensional character of HNWs, which leaves some room for improvement of these nanowired structures. The effect of the QDs deposition method is also evaluated. Both structures show remarkable stability without any appreciable photocurrent loss after 0.5 hour of operation. The findings of this study constitute a relevant step towards the feasibility of hydrogen generation with wide bandgap semiconductors/quantum dots based heterostructures.     

Modulatory role of substance P on gonadotropin and prolactin secretion in the rabbit.

Substance P (SP) is present in large quantities in the brainstem and hypophysiotropic areas of the brain, but its roles in gonadotropin and prolactin secretion are controversial. The aim of this study was to measure luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (PRL) release from the pituitary after either intracerebroventricular (ICV) injection or infusion of SP or its C- and N-terminal fragments in intact (INT) and ovariectomized (OVX) conscious rabbits. A single injection of SP into the 3rd cerebral ventricle (3CVT) in INT and OVX rabbits augmented plasma LH concentrations, especially when SP was applied during the initial phase of an LH peak. Injection of SP during the declining phase of LH release was not effective. Injection of SP into the 3CVT was followed by increased plasma PRL concentrations in OVX but not in INT rabbits. Both SP 1-11 and SP 1-7 failed to alter LH, FSH, and PRL secretion when the peptides were slowly infused into the 3CVT, although ICV infusion of SP 6-11 did cause a delayed increase in LH release. The results support a stimulatory role of SP on LH and prolactin release. The results further indicate that although the stimulatory effect of SP on LH is ovarian steroid-independent, in the absence of ovarian steroids, SP is stimulatory only during the rising phase of an LH pulse. A dual role of SP-ergic transmission in modulating LH secretion is discussed.     

Coordinated action of the Fanconi anemia and ataxia telangiectasia pathways in response to oxidative damage

Fanconi anemia (FA) and ataxia telangiectasia (AT) share common traits such chromosomal instability and proneness to hematological cancers. Both AT and FA cell lines, and patients, are characterized by abnormally high levels of oxidative stress markers. The key FA protein FANCD2 is phosphorylated on Ser 222 by ATM after ionizing radiation (IR), thus allowing normal activation of the S-phase checkpoint, and ATM cells are known to be hypersensitive to oxidative damage. In this work we show that FANCD2 deficient cells have a defective S-phase checkpoint after Hydrogen Peroxide (H(2)O(2)) induced oxidative damage. ATM dependent phosphorylation of FANCD2 at the S222 residue is necessary for normal S-phase checkpoint activation after oxidative stress, while FANCD2 monoubiquitination at K561 is dispensable. We also show that FANCD2 is not required for base excision repair of 8-oxoG and other DNA lesions (abasic sites, uracils), while treatments that exclusively induce 8-oxoG, but not DNA double strand breaks, fail to activate FANCD2 monoubiquitination, thus indicating that the known accumulation of 8-oxoG in FA cells reflects an overproduction of ROS rather than defective processing of oxidized bases. We conclude that the handling of DNA damage after H(2)O(2)-induced oxidative stress requires the coordinated action of FANCD2 and ATM.     

Activation of hypothalamic RIP‐Cre neurons promotes beiging of WAT via sympathetic nervous system

Activation of brown adipose tissue (BAT) and beige fat by cold increases energy expenditure. Although their activation is known to be differentially regulated in part by hypothalamus, the underlying neural pathways and populations remain poorly characterized. Here, we show that activation of rat‐insulin‐promoter‐Cre (RIP‐Cre) neurons in ventromedial hypothalamus (VMH) preferentially promotes recruitment of beige fat via a selective control of sympathetic nervous system (SNS) outflow to subcutaneous white adipose tissue (sWAT), but has no effect on BAT. Genetic ablation of APPL2 in RIP‐Cre neurons diminishes beiging in sWAT without affecting BAT, leading to cold intolerance and obesity in mice. Such defects are reversed by activation of RIP‐Cre neurons, inactivation of VMH AMPK, or treatment with a β3‐adrenergic receptor agonist. Hypothalamic APPL2 enhances neuronal activation in VMH RIP‐Cre neurons and raphe pallidus, thereby eliciting SNS outflow to sWAT and subsequent beiging. These data suggest that beige fat can be selectively activated by VMH RIP‐Cre neurons, in which the APPL2–AMPK signaling axis is crucial for this defending mechanism to cold and obesity.