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Here we describe recent breakthroughs in our understanding of microbial life in dry volcanic tephra (“soil”) that covers much of the surface area of the highest elevation volcanoes on Earth. Dry tephra above 6000 m.a.s.l. is perhaps the best Earth analog for the surface of Mars because these “soils” are acidic, extremely oligotrophic, exposed to a thin atmosphere, high UV fluxes, and extreme temperature fluctuations across the freezing point. The simple microbial communities found in these extreme sites have among the lowest alpha diversity of any known earthly ecosystem and contain bacteria and eukaryotes that are uniquely adapted to these extreme conditions. The most abundant eukaryotic organism across the highest elevation sites is a Naganishia species that is metabolically versatile, can withstand high levels of UV radiation and can grow at sub-zero temperatures, and during extreme diurnal freeze–thaw cycles (e.g. − 10 to + 30 °C). The most abundant bacterial phylotype at the highest dry sites sampled (6330 m.a.s.l. on Volcán Llullaillaco) belongs to the enigmatic B12-WMSP1 clade which is related to the Ktedonobacter/Thermosporothrix clade that includes versatile organisms with the largest known bacterial genomes. Close relatives of B12-WMSP1 are also found in fumarolic soils on Volcán Socompa and in oligotrophic, fumarolic caves on Mt. Erebus in Antarctica. In contrast to the extremely low diversity of dry tephra, fumaroles found at over 6000 m.a.s.l. on Volcán Socompa support very diverse microbial communities with alpha diversity levels rivalling those of low elevation temperate soils. Overall, the high-elevation biome of the Atacama region provides perhaps the best “natural experiment” in which to study microbial life in both its most extreme setting (dry tephra) and in one of its least extreme settings (fumarolic soils).

Many galaxies are thought to have supermassive black holes at their centres 1 —more than a million times the mass of the Sun. Measurements of stellar velocities 2 , 3 , 4 , 5 , 6 , 7 and the discovery of variable X-ray emission 8 have provided strong evidence in favour of such a black hole at the centre of the Milky Way, but have hitherto been unable to rule out conclusively the presence of alternative concentrations of mass. Here we report ten years of high-resolution astrometric imaging that allows us to trace two-thirds of the orbit of the star currently closest to the compact radio source (and massive black-hole candidate) Sagittarius A*. The observations, which include both pericentre and apocentre passages, show that the star is on a bound, highly elliptical keplerian orbit around Sgr A*, with an orbital period of 15.2 years and a pericentre distance of only 17 light hours. The orbit with the best fit to the observations requires a central point mass of (3.7 ± 1.5) × 10 6 solar masses ( M ⊙ ). The data no longer allow for a central mass composed of a dense cluster of dark stellar objects or a ball of massive, degenerate fermions.

Background and purpose: High resting heart rate is a predictor for total and cardiovascular mortality independent of other risk factors in patients with coronary artery disease. We tested the hypothesis that a reduction of resting heart rate with the cardiac pacemaker If current inhibitor ivabradine prevents the endothelial dysfunction associated with dyslipidaemia. Experimental approach: Three‐month‐old dyslipidaemic (DL) male mice expressing the human ApoB‐100 were assigned or not (DL, n=16), to treatment for 3 months with ivabradine (10 mg kg−1 d−1, n=17). Wild‐type C57Bl/6 mice (WT, n=15) were used as controls. Heart rate was measured at 3, 4.5 and 6 months. Dilatation to acetylcholine (ACh) of isolated cerebral and renal arteries was investigated at 6 months. Key results: Heart rate remained stable in anaesthetized WT mice, increased (25%, P<0.05) with age in DL mice but was limited (11%, P<0.05) by ivabradine. At 6 months, left ventricular maximal pressure was similar in all groups. The minimal and end‐diastolic left ventricular pressures were increased (P<0.05) in DL (10.2±1.0 and 18.7±1.4 mm Hg) compared to WT (−0.4±0.7 and 6.3±1.0 mm Hg) and reduced (P<0.05) by ivabradine (4.2±1.3 and 11.5±1.5 mm Hg). ACh‐induced maximal dilatation was impaired (P<0.05) in renal and cerebral arteries isolated from DL compared to WT (56±7 versus 83±3% in renal arteries; 22±2 versus 42±2% in cerebral arteries). Ivabradine completely prevented (P<0.05) this dysfunction in renal and cerebral arteries. Conclusions and implications: Selective heart rate reduction with ivabradine limits cardiac dysfunction and prevents the renovascular and cerebrovascular endothelial dysfunction associated with dyslipidaemia. British Journal of Pharmacology (2008) 154, 749–757; doi:fn2; published online 14 April 2008

BACKGROUND/AIMS Vascular insufficiency due to abnormal autoregulation has been proposed as a major factor in the development of glaucoma. The anterior optic nerve is primarily perfused by the short posterior ciliary arteries. The autoregulatory capacity of these vessels in response to acutely elevated intraocular pressure (IOP) was examined in normal human subjects. METHODS Colour Doppler imaging was performed on the short posterior ciliary arteries of 10 normal subjects at baseline and during four incremental IOP elevations. Using a scleral suction cup placed temporally, IOP was elevated to approximately 25, 30, 40, and 50 mm Hg. Additional measurements were performed immediately after pressure release. Systolic and diastolic flow velocities were measured and Pourcelot’s resistivity index was calculated. RESULTS Systolic and diastolic flow velocities decreased linearly with each incremental increase in IOP (p<0.001). Pourcelot’s resistivity index increased linearly with each incremental increase in IOP (p<0.001). Changes in end diastolic velocity, peak systolic velocity, and Pourcelot’s resistivity index were linearly related to changes in IOP. CONCLUSION The normal healthy eye is not able to autoregulate to maintain PCA blood flow velocities in response to acute large elevations in IOP.

Pluto's tenuous nitrogen atmosphere was first detected by the imprint left on the light curve of a star that was occulted by the planet in 1985 (ref. 1 ), and studied more extensively during a second occultation event in 1988 (refs 2–6 ). These events are, however, quite rare and Pluto's atmosphere remains poorly understood, as in particular the planet has not yet been visited by a spacecraft. Here we report data from the first occultations by Pluto since 1988. We find that, during the intervening 14 years, there seems to have been a doubling of the atmospheric pressure, a probable seasonal effect on Pluto.

Abstract The Savvy Caregiver Program (SCP) is a well-established psychoeducation intervention for dementia caregivers. Though many evidence-based caregiver interventions exist, little research has examined effectiveness of these interventions in the community. Past work has overlooked the question of therapeutic mechanisms, though extensive theoretical and empirical findings suggest that caregiver preparedness may be one such mechanism. Primary goals of this study were A) to replicate past work examining the efficacy of SCP, and B) to examine caregiver preparedness as a prospective therapeutic mechanism. Subjects include dementia caregivers who completed the Savvy Caregiver protocol conducted by a community nonprofit organization in the metropolitan Orlando area. Measures administered before and after the 6-week Savvy Caregiver program include the Zarit Burden Inventory (short-form), the Center for Epidemiological Studies-Despression-10, the Anticipatory Grief Scale, and the Preparedness for Caregiving Scale. The modal participant was female (n=15, 83.3%), white (n=14, 77.8%), a college graduate (n=10, 55.6%) and reported her age as between 40 and 64 years (n=12, 66.7%). Results of paired-samples t-tests were that caregiver preparedness (t(16)=-4.31, p<.000), caregiver burden (t(16)=3.08, p<.007), and anticipatory grief (t(16)=3.22,p<.005) all improved over the course of the intervention. Mean scores on the depression measure were unchanged (t(16)=.52, p>.608). Change in caregiver burden from pre- to post-intervention was significantly moderated by change in caregiver preparedness (F=5.23, p<.05, ηρ2=.26). These findings are consistent with past work supporting use of the SCP with dementia caregivers, and builds on this work by identifying caregiver preparedness as one therapeutic mechanism by which this intervention influences caregiver distress.

The present study was designed to compare alterations of endothelium-dependent vasorelaxation in coronary epicardial arteries and subendocardial arterioles occurring in left ventricular hypertrophy (LVH) secondary to 60 days of aortic banding in a porcine model. Development of LVH was documented by echocardiogram and the endothelial function of subendocardial and epicardial vessels was studied by constructing concentration-response curves in a pressure myograph and standard organ chambers, respectively. 5-HT induced relaxations were reduced (p<0.05) in both vessel types isolated from pigs with LVH. Dilations of subendocardial arterioles and epicardial vessels to UK14304 were depressed by LVH. In the presence of Nomega-nitro-L-arginine (L-NNA), EDHF solely accounts for BK-induced relaxations; it fully compensates for the loss of NO in arterioles, but only partially in epicardial arteries isolated from LVH swine. Endothelium-independent relaxations induced by SNP were not altered in both vessel types from the LVH group. In a porcine model of LVH secondary to 60 days of aortic banding, the associated coronary endothelial dysfunction preferentially involves Gi-protein mediated relaxations in arterioles and arteries but also affects Gq-protein mediated relaxations in epicardial coronary arteries.

As anemonefishes of the genus Amphiprion are emerging as a model organism for marine science, it is critical to have standardization in housing and husbandry protocols for research laboratories. Here, we conducted a literature review, a questionnaire survey, and two experiments regarding the housing and husbandry of anemonefishes for use in research. The literature review identified the need for standardization and optimization of multiple variables including tank volume, diet composition, and lighting type for the housing of broodstock pairs. The questionnaire survey was completed by 27 laboratories, with a 45% response rate, across 11 different countries in Europe, North America, Asia, and Australia. Results from the survey confirmed the need for standardization or optimization of laboratory protocols. The experimental manipulation of housing of Amphiprion percula was conducted over a 3-month period, where reproduction was monitored for 8 breeding pairs housed in large, 120-liter (30-gallon) tanks versus 7 breeding pairs housed in small, 9-liter (2-gallon) tanks. Results suggest that reproductive output was significantly reduced among breeding pairs in experimental 9-liter tanks when compared to those housed in standard 120-liter tanks. The experimental manipulation of husbandry of A. percula was conducted over a 3-month period, where reproduction was monitored across 19 breeding pairs on a high ration diet (1 mL scoop of pellets) versus 15 breeding pairs on a low ration diet (0.5 mL scoop of pellets). Results suggest that reproductive output was significantly reduced among breeding pairs on a low ration diet when compared to those on a high ration diet. Although the experimental 9-liter tanks were likely below the optimum for reproductive output, the fact that reproduction still occurred suggests that the fish will reproduce in tanks smaller than 120 liters and that 20-75 liter tanks may be the best option for housing large numbers of A. percula and similar species. The reproductive output of broodstock pairs fed a high ration diet is similar to that seen in the wild, and provision of higher quality foods (e.g., cuttlefish, shrimp, fish eggs, etc.) beyond commercial pellets may enhance survival of larvae. In conclusion, our research suggests that the anemonefish research community should be discussing the optimization and standardization of housing and husbandry or, minimally, recognize that housing and husbandry influence a wide range of traits and will influence the results and conclusions drawn from experiments.

Charon among the stars Stellar occultations, when a Solar System object passes between us and a star and blocks its light, are eagerly awaited by astronomers as they provide a chance to make measurements that are not normally possible. It had been 25 years since a solitary observation of a stellar occultation by Pluto's moon Charon. But on 11 July 2005 another occurred and this time observatories across South America were ideally placed to track it. The resulting haul of data has been used to obtain an accurate measure of Charon's radius, of close to 605 km, and to establish an upper limit (a rather low one) on the density of its atmosphere. Visit tinyurl.com/9c56s for a QuickTime movie of the event. Pluto and its satellite, Charon (discovered in 1978; ref. 1 ), appear to form a double planet, rather than a hierarchical planet/satellite couple. Charon is about half Pluto's size and about one-eighth its mass. The precise radii of Pluto and Charon have remained uncertain, leading to large uncertainties on their densities 2 . Although stellar occultations by Charon are in principle a powerful way of measuring its size, they are rare, as the satellite subtends less than 0.3 microradians (0.06 arcsec) on the sky. One occultation (in 1980) yielded a lower limit of 600 km for the satellite's radius 3 , which was later refined to 601.5 km (ref. 4 ). Here we report observations from a multi-station stellar occultation by Charon, which we use to derive a radius, R C = 603.6 ± 1.4 km (1 σ ), and a density of ρ = 1.71 ± 0.08 g cm -3 . This occultation also provides upper limits of 110 and 15 (3 σ ) nanobar for an atmosphere around Charon, assuming respectively a pure nitrogen or pure methane atmosphere.