Surface Ices and the Atmospheric Composition of Pluto

Observations of the 1.4- to 2.4-micrometer spectrum of Pluto reveal absorptions of carbon monoxide and nitrogen ices and confirm the presence of solid methane. Frozen nitrogen is more abundant than the other two ices by a factor of about 50; gaseous nitrogen must therefore be the major atmospheric constituent. The absence of carbon dioxide absorptions is one of several differences between the spectra of Pluto and Triton in this region. Both worlds carry information about the composition of the solar nebula and the processes by which icy planetesimals formed.

Evaluating Community-Based Collaborative Mechanisms: Implications for Practitioners

This article examines the possible reasons why the published literature on community-based coalition strategies offers only marginal evidence that such approaches lead to health status/health systems change. Three possible explanations are proposed: (a) collaborative mechanisms are inefficient and/or insufficient mechanisms for carrying out critical planning and implementation tasks, (b) expectations of health status/health systems change outcomes are unrealistic, and/or (c) Health status/health systems changes may occur but may go undetected because it is difficult to evaluate and demonstrate a cause-and-effect relationship. The implications of each possible explanation are addressed through a review of the literature on stages of coalition building, focusing on key factors for success at each stage. The authors conclude that funders and practitioners may be expecting too much from these increasingly popular mechanisms and may not be asking the right questions when evaluating collaborative activity.

Home use of a bihormonal bionic pancreas versus insulin pump therapy in adults with type 1 diabetes: a multicentre randomised crossover trial

BACKGROUND

The safety and effectiveness of a continuous, day-and-night automated glycaemic control system using insulin and glucagon has not been shown in a free-living, home-use setting. We aimed to assess whether bihormonal bionic pancreas initialised only with body mass can safely reduce mean glycaemia and hypoglycaemia in adults with type 1 diabetes who were living at home and participating in their normal daily routines without restrictions on diet or physical activity.

METHODS

We did a random-order crossover study in volunteers at least 18 years old who had type 1 diabetes and lived within a 30 min drive of four sites in the USA. Participants were randomly assigned (1:1) in blocks of two using sequentially numbered sealed envelopes to glycaemic regulation with a bihormonal bionic pancreas or usual care (conventional or sensor-augmented insulin pump therapy) first, followed by the opposite intervention. Both study periods were 11 days in length, during which time participants continued all normal activities, including athletics and driving. The bionic pancreas was initialised with only the participant's body mass. Autonomously adaptive dosing algorithms used data from a continuous glucose monitor to control subcutaneous delivery of insulin and glucagon. The coprimary outcomes were the mean glucose concentration and time with continuous glucose monitoring (CGM) glucose concentration less than 3·3 mmol/L, analysed over days 2-11 in participants who completed both periods of the study. This trial is registered with ClinicalTrials.gov, number NCT02092220.

FINDINGS

We randomly assigned 43 participants between May 6, 2014, and July 3, 2015, 39 of whom completed the study: 20 who were assigned to bionic pancreas first and 19 who were assigned to the comparator first. The mean CGM glucose concentration was 7·8 mmol/L (SD 0·6) in the bionic pancreas period versus 9·0 mmol/L (1·6) in the comparator period (difference 1·1 mmol/L, 95% CI 0·7-1·6; p<0·0001), and the mean time with CGM glucose concentration less than 3·3 mmol/L was 0·6% (0·6) in the bionic pancreas period versus 1·9% (1·7) in the comparator period (difference 1·3%, 95% CI 0·8-1·8; p<0·0001). The mean nausea score on the Visual Analogue Scale (score 0-10) was greater during the bionic pancreas period (0·52 [SD 0·83]) than in the comparator period (0·05 [0·17]; difference 0·47, 95% CI 0·21-0·73; p=0·0024). Body mass and laboratory parameters did not differ between periods. There were no serious or unexpected adverse events in the bionic pancreas period of the study.

INTERPRETATION

Relative to conventional and sensor-augmented insulin pump therapy, the bihormonal bionic pancreas, initialised only with participant weight, was able to achieve superior glycaemic regulation without the need for carbohydrate counting. Larger and longer studies are needed to establish the long-term benefits and risks of automated glycaemic management with a bihormonal bionic pancreas.

FUNDING

National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, and National Center for Advancing Translational Sciences.

Discovery of two new satellites of Pluto

Pluto's first known satellite, Charon, was discovered in 1978. It has a diameter (approximately 1,200 km) about half that of Pluto, which makes it larger, relative to its primary, than any other moon in the Solar System. Previous searches for other satellites around Pluto have been unsuccessful, but they were not sensitive to objects less, similar150 km in diameter and there are no fundamental reasons why Pluto should not have more satellites. Here we report the discovery of two additional moons around Pluto, provisionally designated S/2005 P 1 (hereafter P1) and S/2005 P 2 (hereafter P2), which makes Pluto the first Kuiper belt object known to have multiple satellites. These new satellites are much smaller than Charon, with estimates of P1's diameter ranging from 60 km to 165 km, depending on the surface reflectivity; P2 is about 20 per cent smaller than P1. Although definitive orbits cannot be derived, both new satellites appear to be moving in circular orbits in the same orbital plane as Charon, with orbital periods of approximately 38 days (P1) and approximately 25 days (P2).

Placebo-controlled trial of gabapentin in patients with amyotrophic lateral sclerosis. WALS Study Group. Western Amyotrophic Lateral Sclerosis Study Group

We designed a phase II trial to evaluate the efficacy of gabapentin in slowing the rate of decline in muscle strength of patients with amyotrophic lateral sclerosis (ALS) and to assess safety and tolerability. Gabapentin (800 mg) or placebo was administered t.i.d. in a randomized, double-blinded, placebo-controlled, trial for 6 months. We enrolled 152 patients at eight sites in the United States. The primary outcome measure was the slope of the arm megascore, the average maximum voluntary isometric strength from eight arm muscles standardized against a reference ALS population. A secondary outcome measure was forced vital capacity. Slopes of arm megascores for patients on gabapentin were compared with slopes of those taking placebo using a two-way ANOVA. We observed a nonstatistically significant trend (p = 0.057-0.08) toward slower decline of arm strength in patients taking gabapentin compared with those taking placebo (mean difference 24%, median 37%). We observed no treatment effect on forced vital capacity. Gabapentin was well tolerated by patients with ALS. These results suggest that further studies of gabapentin in ALS are warranted.

A giant impact origin for Pluto's small moons and satellite multiplicity in the Kuiper belt

The two newly discovered satellites of Pluto (P1 and P2) have masses that are small compared to both Pluto and Charon-that is, between 5 x 10(-4) and 1 x 10(-5) of Pluto's mass, and between 5 x 10(-3) and 1 x 10(-4) of Charon's mass. This discovery, combined with the constraints on the absence of more distant satellites of Pluto, reveal that Pluto and its moons comprise an unusual, highly compact, quadruple system. These facts naturally raise the question of how this puzzling satellite system came to be. Here we show that P1 and P2's proximity to Pluto and Charon, the fact that P1 and P2 are on near-circular orbits in the same plane as Pluto's large satellite Charon, along with their apparent locations in or near high-order mean-motion resonances, all probably result from their being constructed from collisional ejecta that originated from the Pluto-Charon formation event. We also argue that dust-ice rings of variable optical depths form sporadically in the Pluto system, and that rich satellite systems may be found--perhaps frequently--around other large Kuiper belt objects.

Multicenter, Randomized Trial of a Bionic Pancreas in Type 1 Diabetes

BACKGROUND

Currently available semiautomated insulin-delivery systems require individualized insulin regimens for the initialization of therapy and meal doses based on carbohydrate counting for routine operation. In contrast, the bionic pancreas is initialized only on the basis of body weight, makes all dose decisions and delivers insulin autonomously, and uses meal announcements without carbohydrate counting.

METHODS

In this 13-week, multicenter, randomized trial, we randomly assigned in a 2:1 ratio persons at least 6 years of age with type 1 diabetes either to receive bionic pancreas treatment with insulin aspart or insulin lispro or to receive standard care (defined as any insulin-delivery method with unblinded, real-time continuous glucose monitoring). The primary outcome was the glycated hemoglobin level at 13 weeks. The key secondary outcome was the percentage of time that the glucose level as assessed by continuous glucose monitoring was below 54 mg per deciliter; the prespecified noninferiority limit for this outcome was 1 percentage point. Safety was also assessed.

RESULTS

A total of 219 participants 6 to 79 years of age were assigned to the bionic-pancreas group, and 107 to the standard-care group. The glycated hemoglobin level decreased from 7.9% to 7.3% in the bionic-pancreas group and did not change (was at 7.7% at both time points) in the standard-care group (mean adjusted difference at 13 weeks, -0.5 percentage points; 95% confidence interval [CI], -0.6 to -0.3; P<0.001). The percentage of time that the glucose level as assessed by continuous glucose monitoring was below 54 mg per deciliter did not differ significantly between the two groups (13-week adjusted difference, 0.0 percentage points; 95% CI, -0.1 to 0.04; P<0.001 for noninferiority). The rate of severe hypoglycemia was 17.7 events per 100 participant-years in the bionic-pancreas group and 10.8 events per 100 participant-years in the standard-care group (P = 0.39). No episodes of diabetic ketoacidosis occurred in either group.

CONCLUSIONS

In this 13-week, randomized trial involving adults and children with type 1 diabetes, use of a bionic pancreas was associated with a greater reduction than standard care in the glycated hemoglobin level. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; ClinicalTrials.gov number, NCT04200313.).

Impact craters on Pluto and Charon indicate a deficit of small Kuiper belt objects

The flyby of Pluto and Charon by the New Horizons spacecraft provided high-resolution images of cratered surfaces embedded in the Kuiper belt, an extensive region of bodies orbiting beyond Neptune. Impact craters on Pluto and Charon were formed by collisions with other Kuiper belt objects (KBOs) with diameters from ~40 kilometers to ~300 meters, smaller than most KBOs observed directly by telescopes. We find a relative paucity of small craters ≲13 kilometers in diameter, which cannot be explained solely by geological resurfacing. This implies a deficit of small KBOs (≲1 to 2 kilometers in diameter). Some surfaces on Pluto and Charon are likely ≳4 billion years old, thus their crater records provide information on the size-frequency distribution of KBOs in the early Solar System.

Glucose Self-monitoring in Non-Insulin-Treated Patients With Type 2 Diabetes in Primary Care Settings: A Randomized Trial

IMPORTANCE

The value of self-monitoring of blood glucose (SMBG) levels in patients with non-insulin-treated type 2 diabetes has been debated.

OBJECTIVE

To compare 3 approaches of SMBG for effects on hemoglobin A1c levels and health-related quality of life (HRQOL) among people with non-insulin-treated type 2 diabetes in primary care practice.

DESIGN, SETTING, AND PARTICIPANTS

The Monitor Trial study was a pragmatic, open-label randomized trial conducted in 15 primary care practices in central North Carolina. Participants were randomized between January 2014 and July 2015. Eligible patients with type 2 non-insulin-treated diabetes were: older than 30 years, established with a primary care physician at a participating practice, had glycemic control (hemoglobin A1c) levels higher than 6.5% but lower than 9.5% within the 6 months preceding screening, as obtained from the electronic medical record, and willing to comply with the results of random assignment into a study group. Of the 1032 assessed for eligibility, 450 were randomized.

INTERVENTIONS

No SMBG, once-daily SMBG, and once-daily SMBG with enhanced patient feedback including automatic tailored messages delivered via the meter.

MAIN OUTCOMES AND MEASURES

Coprimary outcomes included hemoglobin A1c levels and HRQOL at 52 weeks.

RESULTS

A total of 450 patients were randomized and 418 (92.9%) completed the final visit. There were no significant differences in hemoglobin A1c levels across all 3 groups (P = .74; estimated adjusted mean hemoglobin A1c difference, SMBG with messaging vs no SMBG, -0.09%; 95% CI, -0.31% to 0.14%; SMBG vs no SMBG, -0.05%; 95% CI, -0.27% to 0.17%). There were also no significant differences found in HRQOL. There were no notable differences in key adverse events including hypoglycemia frequency, health care utilization, or insulin initiation.

CONCLUSIONS AND RELEVANCE

In patients with non-insulin-treated type 2 diabetes, we observed no clinically or statistically significant differences at 1 year in glycemic control or HRQOL between patients who performed SMBG compared with those who did not perform SMBG. The addition of this type of tailored feedback provided through messaging via a meter did not provide any advantage in glycemic control.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02033499.

Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU₆₉, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU₆₉ is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU₆₉'s origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

Gravity Waves in Jupiter's Thermosphere

The Atmosphere Structure Instrument on the Galileo probe detected wavelike temperature fluctuations superimposed on a 700-kelvin temperature increase in Jupiter's thermosphere. These fluctuations are consistent with gravity waves that are viscously damped in the thermosphere. Moreover, heating by these waves can explain the temperature increase measured by the probe. This heating mechanism should be applicable to the thermospheres of the other giant planets and may help solve the long-standing question of the source of their high thermospheric temperatures.

Thermal Structure of Jupiter's Upper Atmosphere Derived from the Galileo Probe

Temperatures in Jupiter's atmosphere derived from Galileo Probe deceleration data increase from 109 kelvin at the 175-millibar level to 900 &plusmn; 40 kelvin at 1 nanobar, consistent with Voyager remote sensing data. Wavelike oscillations are present at all levels. Vertical wavelengths are 10 to 25 kilometers in the deep isothermal layer, which extends from 12 to 0.003 millibars. Above the 0.003-millibar level, only 90- to 270- kilometer vertical wavelengths survive, suggesting dissipation of wave energy as the probable source of upper atmosphere heating.

The small satellites of Pluto as observed by New Horizons

The New Horizons mission has provided resolved measurements of Pluto's moons Styx, Nix, Kerberos, and Hydra. All four are small, with equivalent spherical diameters of ~40 kilometers for Nix and Hydra and ~10 kilometers for Styx and Kerberos. They are also highly elongated, with maximum to minimum axis ratios of ~2. All four moons have high albedos (~50 to 90%) suggestive of a water-ice surface composition. Crater densities on Nix and Hydra imply surface ages of at least 4 billion years. The small moons rotate much faster than synchronous, with rotational poles clustered nearly orthogonal to the common pole directions of Pluto and Charon. These results reinforce the hypothesis that the small moons formed in the aftermath of a collision that produced the Pluto-Charon binary.

Depression in adults in the T1D Exchange Clinic Registry

OBJECTIVE

Little is known about the frequency of depression in adults with type 1 diabetes (T1D) or its relationship to diabetes outcomes. The T1D Exchange clinic registry allowed us to explore depression in a large, heterogeneous sample.

RESEARCH DESIGN AND METHODS

Participants ≥18 years old (N = 6,172; median age 34 years; median diabetes duration 16 years; 55% female; and 89% non-Hispanic white) completed the eight-item Patient Health Questionnaire (PHQ-8), a validated, reliable measure of current depression. Probable major depression was defined in four ways: PHQ-8 ≥10, PHQ-8 ≥12, per diagnostic algorithm, and as a continuous variable. Characteristics and clinical outcomes of those with and without depression were compared using logistic and linear regression models.

RESULTS

A total of 4.6-10.3% of participants were classified as probable major depression depending on how defined. Participants classified as depressed were more likely female, nonwhite race/ethnicity, to have a lower household income and lower education level, to exercise less often, to miss insulin doses, and to have one or more complications (neuropathy, nephropathy, treatment for retinopathy, or cardiovascular/cerebrovascular disease) (all P < 0.01). HbA1c was higher in the depressed versus not depressed groups (8.4 ± 1.7% [68 ± 8.6 mmol/mol] vs. 7.8 ± 1.4% [62 ± 15.3 mmol/mol]; P < 0.001). Occurrence of one or more diabetic ketoacidosis events (11 vs. 4%; P < 0.001) and one or more severe hypoglycemic events (18 vs. 9%; P < 0.001) in the past 3 months was higher among depressed participants.

CONCLUSIONS

In the T1D Exchange clinic registry, adults with probable major depression have worse clinical outcomes than those not depressed. Whether identification and treatment of depression improves diabetes outcomes requires study. Depression is common in T1D, and better identification and treatment of this comorbid condition is needed.

Mindfulness-Based Stress Reduction: Effect on Emotional Distress in Older Adults

Objectives: Mindfulness training may help seniors successfully manage the physical and psychological challenges of aging in a manner that reduces distress and promotes vitality. The purpose of this retrospective analysis is to evaluate the impact of mindfulness-based stress reduction (MBSR) training on mood states in older adults. Methods: The authors identified 141 older adults (>60 years) who completed MBSR training. All participants completed the Profile of Mood States-Short Form (POMS-SF) at baseline and following 8 weeks of MBSR. Using paired t tests, the authors evaluated changes in mood following training in MBSR. In a subset analysis, the authors further examined the impact of MBSR training in individuals with the highest scores on depression and anxiety. Primary reasons cited for MBSR enrollment are also reported. Results: Overall emotional distress and all sub-scale mood measurements improved significantly following MBSR training. MBSR training resulted in >50% reduction in the number of older people reporting clinically significant depression and anxiety. Most enrolled in MBSR training to improve stress management skills. Discussion: MBSR training is a promising, group-based intervention for decreasing psychological distress in older adults. Larger randomized controlled trials are needed to confirm study findings.

Cognition is not modified by large but temporary changes in sex hormones in men

CONTEXT

Little is known about the role of testosterone and estradiol on cognition in healthy older men.

OBJECTIVE

The cognitive effects of increasing or lowering testosterone or estradiol were examined.

DESIGN

Cognition was assessed before and after 6 wk of double-blind placebo-controlled hormone modification.

SETTING

The study was conducted at an academic medical center.

PARTICIPANTS

Healthy older (ages 60-80 yr) and younger men (ages 25-35 yr) were recruited from the community.

INTERVENTION

Men were randomized to one of four treatments: 1) maintain testosterone and estradiol at eugonadal levels for young men (GnRH agonist + testosterone gel); 2) block testosterone's conversion to estradiol (GnRH agonist + testosterone gel + aromatase inhibitor); 3) induce hypogonadism (GnRH agonist alone); and 4) all placebo.

MAIN OUTCOME MEASURES

Measures of executive function, memory, and spatial cognition were obtained before and after treatment. Hormone levels were obtained 10 times over the course of the study.

RESULTS

Counter to expectations, hormone treatment did not affect cognition (P > 0.10). Free testosterone was positively related to spatial cognition in older men after treatment and controlling for age and estradiol level or exclusion of the hypogonadal men (P = 0.02). Estradiol was negatively associated with working memory controlling for the same variables (P = 0.01). Blinding to treatment assignment was maintained, with the exception of the hypogonadal group.

CONCLUSIONS

A significant change in sex hormone status, including complete hypogonadism, does not modify cognition in men. These findings, along with studies that show a risk for neurodegenerative disease in those with low testosterone, suggest that sex hormone status may be important for neuroprotection in aging but not modulation of normal day-to-day cognitive function.

The geology and geophysics of Kuiper Belt object (486958) Arrokoth

The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, is composed of primitive objects preserving information about Solar System formation. In January 2019, the New Horizons spacecraft flew past one of these objects, the 36-kilometer-long contact binary (486958) Arrokoth (provisional designation 2014 MU₆₉). Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters in diameter) within a radius of 8000 kilometers. Arrokoth has a lightly cratered, smooth surface with complex geological features, unlike those on previously visited Solar System bodies. The density of impact craters indicates the surface dates from the formation of the Solar System. The two lobes of the contact binary have closely aligned poles and equators, constraining their accretion mechanism.

Jupiter cloud composition, stratification, convection, and wave motion: a view from new horizons

Several observations of Jupiter's atmosphere made by instruments on the New Horizons spacecraft have implications for the stability and dynamics of Jupiter's weather layer. Mesoscale waves, first seen by Voyager, have been observed at a spatial resolution of 11 to 45 kilometers. These waves have a 300-kilometer wavelength and phase velocities greater than the local zonal flow by 100 meters per second, much higher than predicted by models. Additionally, infrared spectral measurements over five successive Jupiter rotations at spatial resolutions of 200 to 140 kilometers have shown the development of transient ammonia ice clouds (lifetimes of 40 hours or less) in regions of strong atmospheric upwelling. Both of these phenomena serve as probes of atmospheric dynamics below the visible cloud tops.

Color, composition, and thermal environment of Kuiper Belt object (486958) Arrokoth

The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU₆₉) has been largely undisturbed since its formation. We studied its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through irradiation of simple molecules. Water ice was not detected. This composition indicates hydrogenation of carbon monoxide-rich ice and/or energetic processing of methane condensed on water ice grains in the cold, outer edge of the early Solar System. There are only small regional variations in color and spectra across the surface, which suggests that Arrokoth formed from a homogeneous or well-mixed reservoir of solids. Microwave thermal emission from the winter night side is consistent with a mean brightness temperature of 29 ± 5 kelvin.

Interleukin-6 regulates expression of the syndecan-1 proteoglycan on B lymphoid cells

Proteoglycans participate in hematopoiesis and immune responses by mediating cell adhesion and by binding and presenting growth factors to cells. However, the mechanisms that regulate proteoglycan expression on cells of the immune system have not been defined. Syndecan-1, a member of the syndecan family of integral membrane proteoglycans, is expressed by pre-B cells and plasma cells but is absent from circulating B cells. Because IL-6 is an important cytokine in both B cell differentiation and in the progression of B cell-related diseases, we examined the effect of IL-6 on syndecan-1 expression. Following growth of murine B lymphoid cells in medium containing IL-6, the level of syndecan-1 detected is dramatically reduced. This reduction in syndecan-1 expression is dependent on the concentration of IL-6 present in the medium, with syndecan-1 levels being 2.5- to 5-fold lower than those of controls when cells are grown in media containing 10 and 1000 U/ml of IL-6, respectively. The effect of IL-6 on syndecan-1 expression is time dependent, with syndecan-1 levels declining over the first 48 hr. This trend is reversible because following removal of exogenous IL-6, syndecan-1 levels increase within 24 hr to 80% of their control levels. The regulation of syndecan-1 expression by IL-6 appears to be via post-transcriptional mechanisms because syndecan-1 mRNA levels are not decreased following growth of cells in the presence of IL-6. Furthermore, IL-6 does not alter syndecan-1 structure and therefore its effect is different from that of TGF-beta which alters syndecan-1 glycosylation but not the number of syndecan-1 molecules at the cell surface. We conclude that IL-6 participates in the regulation of syndecan-1 expression on B lymphoid cells and, given its broad distribution, IL-6 may regulate proteoglycan expression on other cell types as well.

Dysthyroid ophthalmopathy in children

The observation in this study of 33 pediatric patients with thyroid disfunction supports the view that ocular changes are uncommon in this age group. If ophthalmopathy does occur, it is mild. No patient was found to have clinical myopathy, corneal involvement, or visual loss. B Scan Ultrasonography demonstrated extraocular muscle involvement despite the absence of clinical signs and symptoms of myopathy. There was no HLA antigen prevalence in those patients with ophthalmopathy as compared with those free of ocular change. It is suggested that the conservative medical management of the pediatric group with thyroid disease may account for the low incidence of severe ocular changes.

The rapid formation of Sputnik Planitia early in Pluto's history

Pluto's Sputnik Planitia is a bright, roughly circular feature that resembles a polar ice cap. It is approximately 1,000 kilometres across and is centred on a latitude of 25 degrees north and a longitude of 175 degrees, almost directly opposite the side of Pluto that always faces Charon as a result of tidal locking. One explanation for its location includes the formation of a basin in a giant impact, with subsequent upwelling of a dense interior ocean. Once the basin was established, ice would naturally have accumulated there. Then, provided that the basin was a positive gravity anomaly (with or without the ocean), true polar wander could have moved the feature towards the Pluto-Charon tidal axis, on the far side of Pluto from Charon. Here we report modelling that shows that ice quickly accumulates on Pluto near latitudes of 30 degrees north and south, even in the absence of a basin, because, averaged over its orbital period, those are Pluto's coldest regions. Within a million years of Charon's formation, ice deposits on Pluto concentrate into a single cap centred near a latitude of 30 degrees, owing to the runaway albedo effect. This accumulation of ice causes a positive gravity signature that locks, as Pluto's rotation slows, to a longitude directly opposite Charon. Once locked, Charon raises a permanent tidal bulge on Pluto, which greatly enhances the gravity signature of the ice cap. Meanwhile, the weight of the ice in Sputnik Planitia causes the crust under it to slump, creating its own basin (as has happened on Earth in Greenland). Even if the feature is now a modest negative gravity anomaly, it remains locked in place because of the permanent tidal bulge raised by Charon. Any movement of the feature away from 30 degrees latitude is countered by the preferential recondensation of ices near the coldest extremities of the cap. Therefore, our modelling suggests that Sputnik Planitia formed shortly after Charon did and has been stable, albeit gradually losing volume, over the age of the Solar System.

Prospective, randomized, double-blind, placebo-controlled comparison of metoclopramide and ondansetron for prevention of posttonsillectomy or adenotonsillectomy emesis

STUDY OBJECTIVE

To compare the antimetic efficacy of prophylactic ondansetron, metoclopramide, and placebo for prevention of postoperative vomiting in pediatric tonsillectomy or adenotonsillectomy patients.

DESIGN

Prospective, randomized, double-blind, placebo controlled study.

SETTING

Children's hospital.

PATIENTS

132 ASA status I and II children, ages 2 to 12 years, undergoing tonsillectomy or adenotonsillectomy.

INTERVENTIONS

Patients received intravenous (IV) melodopramide 0.25 mg/kg, IV on dansetron 0.15 mg/kg, or IV saline placebo after induction of standardized halothane, nitrous oxide, and oxygen anesthesia. Muscle relaxants and their antagonists were allowed. Patients received postoperative analgesics as needed.

MEASUREMENTS AND MAIN RESULTS

Incidence of postoperative vomiting, time of vomitting onset, and hospital length of stay (LOS) were measured. Patients who were admitted were excluded from LOS analysis. The postoperative incidence of vomiting was 54% for patients receiving metoclopramide, 26% for patients receiving ondansetron, and 69% for the placebo group. These differences were significant for ondansetron versus metoclopramide (p = 0.008) and placebo (p = 0.001). The mean (SD) LOS was significantly shorter for patients not vomiting 488 (88) minutes for vomiters versus 435 (65) minutes for non-vomiters.

CONCLUSIONS

Prophylactic ondansetron is more effective than metoclopramide or placebo for the prevention of vomiting after tonsillectomy or adenotonsillectomy. Patients who do not vomit postoperatively have shorter LOS.

Acquired inflammatory superior oblique tendon sheath (Brown's) syndrome. Report of a case following frontal sinus surgery

A case of acquired Brown's syndrome secondary to fibrous proliferation about the trochlea and the superior oblique tendon developed following frontal sinus surgery. This syndrome is a restrictive ocular motility disorder characterized by vertical diplopia and inability to elevate the affected eye above the midline on medial gaze. The purpose of this report is to bring to the attention of otolaryngologists this sequela of sinus surgery, to offer suggestions for modification of surgical technique to avoid this complication, and to emphasize the importance of identifying any signs or symptoms of eye muscle dysfunction prior to surgery.

Genomic fingerprinting for epidemiological differentiation of Staphylococcus aureus clinical isolates

We used genomic fingerprinting to investigate an outbreak of methicillin-resistant Staphylococcus aureus in the neonatal intensive care units (NICUs) of two hospitals. The hospitals are located in the same city and are part of the same medical care system. Fingerprinting was done by Southern blot hybridization with DNA probes for the genes encoding the S. aureus collagen adhesin (cna), fibronectin-binding proteins (fnbA and fnbB), and beta-toxin (hlb). Genomic DNA was digested with HaeIII (cna and fnbA-fnbB probes) or HindIII (hlb probe). Hybridization patterns could be distinguished on the basis of (i) the presence or absence of cna, (ii) the size of the restriction fragment containing the cna gene, (iii) restriction fragment length polymorphisms within fnbA and fnbB, (iv) the presence of a lysogenic phage within hlb, and (v) the sizes of the restriction fragments containing the phage-bacterial DNA junction fragments. Over a period of 4 months we examined a total of 46 isolates obtained from various wards within each hospital. Among these 46 isolates, we observed a total of 4 cna patterns, 11 fnbA-fnbB patterns, and 11 hlb patterns. Southern blots with HaeIII-digested genomic DNA and a combination of all three gene probes revealed a total of 16 clearly distinguishable patterns. A total of 22 of the 46 isolates were identical with respect to every genomic marker examined. A total of 21 of these 22 isolates were obtained from patients within an NICU. Nineteen of 21 isolates also exhibited identical antibiotic resistance profiles (antibiogram). Although 5 of the remaining 24 strains exhibited an antibiogram identical to those of the NICU isolates, all 24 strains could be distinguished from the NICU isolates by at least one genomic marker. These results suggest that the NICU isolates had a common origin and that genomic fingerprinting with the cna, fnbA, fnbB, and hlb gene probes can provide an important epidemiological tool for the identification of clinical isolates of S. aureus.