Evolution of supermassive black holes

Supermassive black holes (SMBHs) are nowadays believed to reside in most local galaxies, and the available data show an empirical correlation between bulge luminosity - or stellar velocity dispersion - and black hole mass, suggesting a single mechanism for assembling black holes and forming spheroids in galaxy halos. The evidence is therefore in favour of a co-evolution between galaxies, black holes and quasars. In cold dark matter cosmogonies, small-mass subgalactic systems form first to merge later into larger and larger structures. In this paradigm galaxy halos experience multiple mergers during their lifetime. If every galaxy with a bulge hosts a SMBH in its center, and a local galaxy has been made up by multiple mergers, then a black hole binary is a natural evolutionary stage. The evolution of the supermassive black hole population clearly has to be investigated taking into account both the cosmological framework and the dynamical evolution of SMBHs and their hosts. The seeds of SMBHs have to be looked for in the early Universe, as very luminous quasars are detected up to redshift higher than z=6. These black holes evolve then in a hierarchical fashion, following the merger hierarchy of their host halos. Accretion of gas, traced by quasar activity, plays a fundamental role in determining the two parameters defining a black hole: mass and spin. A particularly intriguing epoch is the initial phase of SMBH growth. It is very challenging to meet the observational constraints at z=6 if BHs are not fed at very high rates in their infancy.Comment: Extended version of the invited paper to appear in the Proceedings of the Conference "Relativistic Astrophysics and Cosmology - Einstein's Legacy

Combined heterozygosity for methylenetetrahydrofolate reductase (MTHFR) mutations C677T and A1298C is associated with abruptio placentae but not with intrauterine growth restriction

Objective: This study was undertaken to investigate the involvement of MTHFR gene mutations C677T and A1298C implicated in vascular disease, in patients with abruptio placentae and intrauterine growth restriction (IUGR). Study Design: DNA was extracted from blood samples of 54 patients with placental vasculopathy (18 patients with abruptio placentae and 36 with IUGR) and 114 control patients and amplified by the polymerase chain reaction (PCR). The resulting fragments were subjected to restriction enzyme analysis and resolved by gel electrophoresis. Results: A significant association could be demonstrated between mutation A1298C and both abruptio placentae and IUGR. Combined heterozygosity for mutations C677T and A1298C was detected in 22.2% of abruptio placentae cases. Conclusions: Combined heterozygosity for MTHFR mutations C677T and A1298C may represent a genetic marker for abruptio placentae. Copyright © 2001 Elsevier Science Ireland Ltd.Objective: This study was undertaken to investigate the involvement of MTHFR gene mutations C677T and A1298C implicated in vascular disease, in patients with abruptio placentae and intrauterine growth restriction (IUGR). Study Design: DNA was extracted from blood samples of 54 patients with placental vasculopathy (18 patients with abruptio placentae and 36 with IUGR) and 114 control patients and amplified by the polymerase chain reaction (PCR). The resulting fragments were subjected to restriction enzyme analysis and resolved by gel electrophoresis. Results: A significant association could be demonstrated between mutation A1298C and both abruptio placentae and IUGR. Combined heterozygosity for mutations C677T and A1298C was detected in 22.2% of abruptio placentae cases. Conclusions: Combined heterozygosity for MTHFR mutations C677T and A1298C may represent a genetic marker for abruptio placentae. Copyright © 2001 Elsevier Science Ireland Ltd.ArticleArticl

α-Melanocyte stimulating hormone promotes muscle glucose uptake via melanocortin 5 receptors.

OBJECTIVE: Central melanocortin pathways are well-established regulators of energy balance. However, scant data exist about the role of systemic melanocortin peptides. We set out to determine if peripheral α-melanocyte stimulating hormone (α-MSH) plays a role in glucose homeostasis and tested the hypothesis that the pituitary is able to sense a physiological increase in circulating glucose and responds by secreting α-MSH. METHODS: We established glucose-stimulated α-MSH secretion using humans, non-human primates, and mouse models. Continuous α-MSH infusions were performed during glucose tolerance tests and hyperinsulinemic-euglycemic clamps to evaluate the systemic effect of α-MSH in glucose regulation. Complementary ex vivo and in vitro techniques were employed to delineate the direct action of α-MSH via the melanocortin 5 receptor (MC5R)-PKA axis in skeletal muscles. Combined treatment of non-selective/selective phosphodiesterase inhibitor and α-MSH was adopted to restore glucose tolerance in obese mice. RESULTS: Here we demonstrate that pituitary secretion of α-MSH is increased by glucose. Peripheral α-MSH increases temperature in skeletal muscles, acts directly on soleus and gastrocnemius muscles to significantly increase glucose uptake, and enhances whole-body glucose clearance via the activation of muscle MC5R and protein kinase A. These actions are absent in obese mice, accompanied by a blunting of α-MSH-induced cAMP levels in skeletal muscles of obese mice. Both selective and non-selective phosphodiesterase inhibition restores α-MSH induced skeletal muscle glucose uptake and improves glucose disposal in obese mice. CONCLUSION: These data describe a novel endocrine circuit that modulates glucose homeostasis by pituitary α-MSH, which increases muscle glucose uptake and thermogenesis through the activation of a MC5R-PKA-pathway, which is disrupted in obesity

Pressure ulcers: guideline development and economic modelling.

AIM: This paper presents the development process for clinical guidelines on the use of pressure-relieving devices (beds, mattresses and overlays), with emphasis on incorporating economic evidence. BACKGROUND: Previous UK guidelines on the use of pressure-relieving devices to prevent pressure ulcers have not considered whether any recommendations made are cost effective. The routine inclusion of cost effectiveness evidence in guidelines is a recent policy development, and there has been little research into its potential role in the guideline process. METHODS: We systematically reviewed the literature to assess both the clinical and cost effectiveness of pressure-relieving devices for prevention of pressure ulcers. Where there was sufficient evidence on the comparative clinical effectiveness between alternative devices, economic modelling was undertaken to assess comparative cost effectiveness. A guideline development group (comprising both clinicians and patient representatives) reviewed all the available evidence to formulate clinical practice guidelines and recommendations for further research. RESULTS: Studies showed that caring for people vulnerable to developing pressure ulcers on high-specification foam mattresses compared with standard hospital mattresses significantly reduced their risk of developing a pressure ulcer. Cost effectiveness modelling indicated that, because of savings accruing through treating fewer pressure ulcers, high-specification foam mattresses are likely to cost less overall and are more effective. The resulting clinical practice guideline was uncompromising on the use of high-specification foam mattresses as the minimum provision in patients vulnerable to pressure ulcers. Significant weaknesses were identified in both the quality and availability of evidence for most of the other pressure relieving devices considered. CONCLUSIONS: Cost effectiveness assessment was an integral part of the guideline development process. It clarified the shortcomings of some of the clinical effectiveness evidence and helped in formulating pragmatic clinical practice recommendations

Host Plant Records for Fruit Flies (Diptera: Tephritidae: Dacini) in the Pacific Islands: 2. Infestation Statistics on Economic Hosts

Detailed host records are listed for 39 species of Bactrocera and 2 species of Dacus fruit flies, infesting 98 species of commercial and edible fruits in the Pacific Island Countries and Territories, based on sampling and incubating in laboratory almost 13,000 field collected samples, or over 380,000 fruits. For each host-fly-country association, quantitative data are presented on the weight and number of fruits collected, the proportion of infested samples, the number of adult flies emerged per kg of fruits and, whenever available, the percentage of individual fruits infested. All the published records of each fly-host-country association are cited and erroneous or dubious published records are rectified or commented. Laboratory forced infestation data are also cited and reviewed