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.

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.

The solar nebula origin of (486958) Arrokoth, a primordial contact binary in the Kuiper Belt

The New Horizons spacecraft's encounter with the cold classical Kuiper Belt object (486958) Arrokoth (provisional designation 2014 MU₆₉) revealed a contact-binary planetesimal. We investigated how Arrokoth formed and found that it is the product of a gentle, low-speed merger in the early Solar System. Its two lenticular lobes suggest low-velocity accumulation of numerous smaller planetesimals within a gravitationally collapsing cloud of solid particles. The geometric alignment of the lobes indicates that they were a co-orbiting binary that experienced angular momentum loss and subsequent merger, possibly because of dynamical friction and collisions within the cloud or later gas drag. Arrokoth's contact-binary shape was preserved by the benign dynamical and collisional environment of the cold classical Kuiper Belt and therefore informs the accretion processes that operated in the early Solar System.

Pluto's Interaction With Energetic Heliospheric Ions

Pluto energies of a few kiloelectron volts and suprathermal ions with tens of kiloelectron volts and above. We measure this population using the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board the New Horizons spacecraft that flew by Pluto in 2015. Even though the measured ions have gyroradii larger than the size of Pluto and the cross section of its magnetosphere, we find that the boundary of the magnetosphere is depleting the energetic ion intensities by about an order of magnitude close to Pluto. The intensity is increasing exponentially with distance to Pluto and reaches nominal levels of the interplanetary medium at about 190R _P distance. Inside the wake of Pluto, we observe oscillations of the ion intensities with a periodicity of about 0.2 hr. We show that these can be quantitatively explained by the electric field of an ultralow-frequency wave and discuss possible physical drivers for such a field. We find no evidence for the presence of plutogenic ions in the considered energy range.

Prebiotic Chemistry of Pluto

We present the case for the presence of complex organic molecules, such as amino acids and nucleobases, formed by abiotic processes on the surface and in near-subsurface regions of Pluto. Pluto's surface is tinted with a range of non-ice substances with colors ranging from light yellow to red to dark brown; the colors match those of laboratory organic residues called tholins. Tholins are broadly characterized as complex, macromolecular organic solids consisting of a network of aromatic structures connected by aliphatic bridging units (e.g., Imanaka et al., 2004; Materese et al., 2014, 2015). The synthesis of tholins in planetary atmospheres and in surface ices has been explored in numerous laboratory experiments, and both gas- and solid-phase varieties are found on Pluto. A third variety of tholins, exposed at a site of tectonic surface fracturing called Virgil Fossae, appears to have come from a reservoir in the subsurface. Eruptions of tholin-laden liquid H₂O from a subsurface aqueous repository appear to have covered portions of Virgil Fossae and its surroundings with a uniquely colored deposit (D.P. Cruikshank, personal communication) that is geographically correlated with an exposure of H₂O ice that includes spectroscopically detected NH₃ (C.M. Dalle Ore, personal communication). The subsurface organic material could have been derived from presolar or solar nebula processes, or might have formed in situ. Photolysis and radiolysis of a mixture of ices relevant to Pluto's surface composition (N₂, CH₄, CO) have produced strongly colored, complex organics with a significant aromatic content having a high degree of nitrogen substitution similar to the aromatic heterocycles pyrimidine and purine (Materese et al., 2014, 2015; Cruikshank et al., 2016). Experiments with pyrimidines and purines frozen in H₂O-NH₃ ice resulted in the formation of numerous nucleobases, including the biologically relevant guanine, cytosine, adenine, uracil, and thymine (Materese et al., 2017). The red material associated with the H₂O ice may contain nucleobases resulting from energetic processing on Pluto's surface or in the interior. Some other Kuiper Belt objects also exhibit red colors similar to those found on Pluto and may therefore carry similar inventories of complex organic materials. The widespread and ubiquitous nature of similarly complex organic materials observed in a variety of astronomical settings drives the need for additional laboratory and modeling efforts to explain the origin and evolution of organic molecules. Pluto observations reveal complex organics on a small body that remains close to its place of origin in the outermost regions of the Solar System.

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.

Detection of ammonia on Pluto's surface in a region of geologically recent tectonism

We report the detection of ammonia (NH3) on Pluto's surface in spectral images obtained with the New Horizons spacecraft that show absorption bands at 1.65 and 2.2 μm. The ammonia signature is spatially coincident with a region of past extensional tectonic activity (Virgil Fossae) where the presence of H2O ice is prominent. Ammonia in liquid water profoundly depresses the freezing point of the mixture. Ammoniated ices are believed to be geologically short lived when irradiated with ultraviolet photons or charged particles. Thus, the presence of NH3 on a planetary surface is indicative of a relatively recent deposition or possibly through exposure by some geological process. In the present case, the areal distribution is more suggestive of cryovolcanic emplacement, however, adding to the evidence for ongoing geological activity on Pluto and the possible presence of liquid water at depth today.

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.

In Situ Observations of Preferential Pickup Ion Heating at an Interplanetary Shock

Nonthermal pickup ions (PUIs) are created in the solar wind (SW) by charge-exchange between SW ions (SWIs) and slow interstellar neutral atoms. It has long been theorized, but not directly observed that PUIs should be preferentially heated at quasiperpendicular shocks compared to thermal SWIs. We present in situ observations of interstellar hydrogen (H^{+}) PUIs at an interplanetary shock by the New Horizons' Solar Wind Around Pluto (SWAP) instrument at ∼34  au from the Sun. At this shock, H^{+} PUIs are only a few percent of the total proton density but contain most of the internal particle pressure. A gradual reduction in SW flow speed and simultaneous heating of H^{+} SWIs is observed ahead of the shock, suggesting an upstream energetic particle pressure gradient. H^{+} SWIs lose ∼85% of their energy flux across the shock and H^{+} PUIs are preferentially heated. Moreover, a PUI tail is observed downstream of the shock, such that the energy flux of all H^{+} PUIs is approximately six times that of H^{+} SWIs. We find that H^{+} PUIs, including their suprathermal tail, contain almost half of the total downstream energy flux in the shock frame.

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.

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.

Pluto's interaction with its space environment: Solar wind, energetic particles, and dust

The New Horizons spacecraft carried three instruments that measured the space environment near Pluto as it flew by on 14 July 2015. The Solar Wind Around Pluto (SWAP) instrument revealed an interaction region confined sunward of Pluto to within about 6 Pluto radii. The region's surprisingly small size is consistent with a reduced atmospheric escape rate, as well as a particularly high solar wind flux. Observations from the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument suggest that ions are accelerated and/or deflected around Pluto. In the wake of the interaction region, PEPSSI observed suprathermal particle fluxes equal to about 1/10 of the flux in the interplanetary medium and increasing with distance downstream. The Venetia Burney Student Dust Counter, which measures grains with radii larger than 1.4 micrometers, detected one candidate impact in ±5 days around New Horizons' closest approach, indicating an upper limit of <4.6 kilometers(-3) for the dust density in the Pluto system.

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.

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.

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).

Strengthening relationships for a successful nurse directed center within an academic setting

This article focuses on the evolvement of a nurse-directed student health center within an academic setting. The advantages of having a student health center located under academic affairs versus the traditional model of being placed under student affairs is discusses. How this organizational arrangement can be used to develop and strengthen relationships, as well as promote collaboration among various disciplines within the college is discussed. Such an arrangement can provide resources, student practicum experiences on campus as well as strengthen and develop relationships within the surrounding community. These strategies can be used to create a forum for discussion of various strategies which will assist in establishing a vision, overcoming obstacles, expanding the center's scope of services as well as provide mentoring opportunities for student nurses and faculty.

Validation of K-edge 125I brachytherapy enhancement with silver compounds

Brachytherapy with radioactive seeds implanted within the tumour volume has demonstrated good success rates in treating certain cancers. In an effort to improve the curative rates in cancer patients, ongoing research is being conducted to enhance the amount of radiation dose that is absorbed within the tumour volume while minimizing the dose absorbed by the surrounding normal tissue. One method for enhancing tumour dose absorption with 125I brachytherapy seeds is to increase the number of photoelectric atomic interactions within the tumour volume by introducing small quantities of a silver compound, taking advantage of the K-edge effect. Because low-energy electrons and Auger electrons are the primary sources of brachytherapy dose enhancement, acquiring accurate experimental measurements of absorbed dose increases is a major challenge. To circumvent this problem, an x ray fluorescence excitation spectroscopy dosimetry technique supplemented with clinically accepted dosimetry calculations was developed to estimate relative absorbed dose increases in a water phantom containing up to 7.5 mM of silver. Excellent agreement was observed between theoretically derived Monte Carlo dosimetric predictions and experimental measurements. These results successfully demonstrated that K-edge enhanced 125I brachytherapy is indeed possible with future development of a non-toxic silver chelate.

Nocturnal blood pressure in young patients with insulin-dependent diabetes mellitus: correlation with cardiac function

Lack of a decline in nocturnal blood pressure is associated with an adverse effect on end organs in adults with insulin-dependent diabetes mellitus (IDDM). The role of the decline in nocturnal blood pressure in young patients with IDDM is not known. We studied 25 white subjects with IDDM (age = 20.8 +/- 3.7 years, mean +/- SD), 8 of whom were female. The duration of IDDM in these subjects was 12.9 +/- 5.4 years (mean +/- SD). We determined the values for glycosylated hemoglobin (HgbA1), 24-hour ambulatory blood pressure, diastolic cardiac function (the ratio of peak E wave to peak A wave velocity (E/A) and indexed peak filling rate ¿PFR/SV¿ by Doppler echocardiography), and albumin excretion rate. The HgbA1 level was 10.9% +/- 1.9% (mean +/- SD; normal range = 4.5%-8.5%). The HgbA1 concentration was inversely correlated (p < 0.005) with the decline in systolic (r = 0.57) and diastolic (r = -0.55) nocturnal blood pressure. Diastolic cardiac dysfunction ¿E/A ratio [r = 0.42, p < 0.03) and PFR/SV (r = 0.52, p < 0.01)¿ correlated with a smaller decrease in nocturnal diastolic blood pressure. An inverse correlation between decline in nocturnal systolic blood pressure and log albumin excretion rate (r = -0.37, p = 0.07) approached statistical significance. We conclude that poor glycemic control adversely affects nocturnal blood pressure and that the latter may play an important role in cardiac and possibly renal dysfunction in early IDDM.

125I brachytherapy k-edge dose enhancement with AgTPPS4

Photon activation is a radiotherapy technique in which an element is added to the absorbing medium to raise the probability that a photoelectric interaction will occur, thus causing an increase in the absorption of ionizing radiation. Binding energies of key elements within an absorbing medium are closely matched with the incident photon energies to maximize the production of free electrons and subsequent absorption of their kinetic energies. The purpose of this research was to quantify potential dose enhancement using a silver tetraphenyl sulfonato porphyrin (AgTPPS4) in tumors as a photon activator for use with interstitial 125I brachytherapy. A three-dimensional Monte Carlo dosimetry model was developed using the EGS4 coding system. The photon source was modeled using spectral gamma emissions from models 6702 or 6711 brachytherapy seeds for comparison. Absorbed dose within the tumor volume was calculated for AgTPPS4 concentrations ranging between 0 and 20 mmol/kg tumor weight. These theoretical studies demonstrated linear increases in dose absorbed by the tumor with corresponding increases in AgTPPS4 concentration. The required AgTPPS4 concentration (RSC) to achieve at least a ten percent absorbed dose increase is approximately 6.5 mmol/kg tumor weight for model 6702 seeds. In vivo biodistribution and in vitro toxicity studies were conducted to determine if the theoretically derived RSC could be achieved biologically. Cell toxicity studies showed that TPPS4 porphyrin derivatives were cytotoxic at concentrations required to provide significant brachytherapy dose enhancement. Reverse phase HPLC confirmed that toxicity was due to intrinsic properties of the TPPS4 molecule, not the presence of free silver, drug impurities, or metabolites. Further research is necessary to develop a nontoxic molecular carrier for delivering silver to the DNA of tumor cells.

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.

Disposition of enrofloxacin and its metabolite ciprofloxacin after intramuscular injection in juvenile Burmese pythons (Python molurus bivittatus)

Eleven juvenile Burmese pythons (Python molurus bivittatus) weighing 0.75-1.75 kg were randomly divided into two groups. Blood samples were obtained through surgically placed anterior carotid artery cannulas. Six pythons received a single i.m. injection of enrofloxacin at 5 mg/kg. Blood samples were obtained at 0.5, 1, 3, 6, 12, 24, 48, 72, and 96 hr postinjection. A mean (+/- SD) maximal plasma concentration of 1.66 (+/- 0.42) micrograms/ml was measured at 5.75 hr postinjection. The harmonic mean half-life was calculated to be 6.37 hr. The second group of five snakes received enrofloxacin at 5 mg/kg i.m. s.i.d. for 5 days. Blood was collected immediately before each injection and at 6 hr after each injection. Over the 5-day period, there was a stepwise increase in mean trough plasma concentrations of enrofloxacin. Clinically effective peak plasma enrofloxacin concentrations were attained after the first injection but did not significantly increase during the sampling period. Pharmacokinetic data were assessed against minimum inhibitory concentrations of enrofloxacin for Pseudomonas ssp. isolates in snakes obtained from historical data at the Veterinary Medical Teaching Hospital, University of Florida. Enrofloxacin should be administered at 10 mg/kg i.m. every 48 hr when treating Pseudomonas ssp. infections in juvenile Burmese pythons. Treatment of infections of more enrofloxacin-sensitive gram-negative bacteria could be achieved with the administration of an initial i.m. dose of 10 mg/kg followed by 5 mg/kg every 48 hr.

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.

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.

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.

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.

A finite difference heat transfer analysis of a percutaneous transluminal microwave angioplasty system

Finite difference time domain (FDTD) techniques have been developed to calculate the specific absorption rates (SAR) in hyperthermia models. The University of Utah Hyperthermia Research Group has extended these numerical techniques for developing a percutaneous transluminal microwave angioplasty applicator, calculating the SARs produced by a high energy electromagnetic field to remove atherosclerotic plaques in blood vessels. The objective of this research was to derive a method for calculating the bioheat transfer in biological tissue surrounding a microwave angioplasty applicator. A hypothetical model was developed and observations are discussed based on the numerical results of this study. A limited analysis on the thermal effects of microwave pulsing was also completed. Preliminary numerical calculations yielded reasonable results. Experimental laboratory tests are required to validate the accuracy of the numerical results found in this study. Further development of this thermal analysis method may greatly assist in future studies of new applicator configurations to ensure safe atherosclerotic plaque removal and to predict the resulting thermal environments.

An encounter with homeless mothers and children: gaining an awareness

This article describes the experience of two nurses who established and conducted concurrent support groups for homeless mothers and their preschool children. The group sessions were 75 minutes in length and occurred once a week for 10 weeks. Both mothers and children were depressed and felt hopeless. Mothers manifested signs of grief and made statements indicative of severely eroded self-concepts. This resulted in a diminished ability to provide for the basic needs of their children. Most of the children demonstrated social, motor, and language skills far below the levels appropriate for their ages. Poor health was a consistent finding, especially among the children. An incentive program used to promote attendance in parent's group is described. Other successful and unsuccessful interventions are reviewed and specific recommendations for successful intervention with homeless families are provided.

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.

Adhesion of B lymphoid (MPC-11) cells to type I collagen is mediated by integral membrane proteoglycan, syndecan

Differentiating B lymphocytes undergo changes in cell-cell and cell-matrix adhesion that control their movement through a series of distinct microenvironments. The integral membrane proteoglycan, syndecan, is a candidate for mediating B lymphocyte-matrix interactions because it is expressed on B lymphocytes only at times when they associate with matrix, and because syndecan is known to behave as a matrix receptor on simple epithelia. However, syndecan from B lymphocytes is significantly smaller in molecular mass than syndecan from simple epithelia (85 vs 160 kDa) suggesting that syndecan may have distinct functions on these two cell types. Our study was undertaken to determine if syndecan mediates adhesion of B lineage cells to extracellular matrix. The murine myeloma cell line MPC-11 was used because syndecan is the only major heparan sulfate proteoglycan detected on these cells and because they express a form of syndecan almost identical to that found on normal B lymphocytes. Cell binding assays demonstrate that syndecan binds MPC-11 cells to type I collagen. Binding is inhibited by heparin, by pretreatment of cells with heparitinase or by growth of cells before the assay in chlorate, an inhibitor of sulfation. Solid phase assays show that syndecan purified from MPC-11 cells binds to type I collagen but not type IV collagen, laminin, or fibronectin. The interaction of MPC-11-derived syndecan with type I collagen is of relatively high affinity (Kd app = 143 nM) as measured by affinity coelectrophoresis. However, the 160-kDa form of syndecan isolated from epithelial cells has a greater than fourfold higher affinity for type I collagen (Kd app = 31 nM) than does the MPC-11 syndecan, suggesting that different molecular forms of syndecan have distinct ligand binding properties. These results demonstrate that syndecan can mediate B lymphocyte interactions with matrix and suggest that changes in syndecan expression during B cell differentiation are a mechanism for controlling B cell localization within specific microenvironments.

Adhesion of B lymphoid (MPC-11) cells to type I collagen is mediated by integral membrane proteoglycan, syndecan

Differentiating B lymphocytes undergo changes in cell-cell and cell-matrix adhesion that control their movement through a series of distinct microenvironments. The integral membrane proteoglycan, syndecan, is a candidate for mediating B lymphocyte-matrix interactions because it is expressed on B lymphocytes only at times when they associate with matrix, and because syndecan is known to behave as a matrix receptor on simple epithelia. However, syndecan from B lymphocytes is significantly smaller in molecular mass than syndecan from simple epithelia (85 vs 160 kDa) suggesting that syndecan may have distinct functions on these two cell types. Our study was undertaken to determine if syndecan mediates adhesion of B lineage cells to extracellular matrix. The murine myeloma cell line MPC-11 was used because syndecan is the only major heparan sulfate proteoglycan detected on these cells and because they express a form of syndecan almost identical to that found on normal B lymphocytes. Cell binding assays demonstrate that syndecan binds MPC-11 cells to type I collagen. Binding is inhibited by heparin, by pretreatment of cells with heparitinase or by growth of cells before the assay in chlorate, an inhibitor of sulfation. Solid phase assays show that syndecan purified from MPC-11 cells binds to type I collagen but not type IV collagen, laminin, or fibronectin. The interaction of MPC-11-derived syndecan with type I collagen is of relatively high affinity (Kd app = 143 nM) as measured by affinity coelectrophoresis. However, the 160-kDa form of syndecan isolated from epithelial cells has a greater than fourfold higher affinity for type I collagen (Kd app = 31 nM) than does the MPC-11 syndecan, suggesting that different molecular forms of syndecan have distinct ligand binding properties. These results demonstrate that syndecan can mediate B lymphocyte interactions with matrix and suggest that changes in syndecan expression during B cell differentiation are a mechanism for controlling B cell localization within specific microenvironments.

The human tumor clonogenic assay in human breast cancer

The human tumor clonogenic assay (HTCA) was evaluated in 407 fresh samples of breast cancer from 288 patients. Seventy samples were inadequate for testing. Adequate in vitro growth for drug testing (greater than 30 colonies/plate) was obtained in 91 (27%) of the 337 viable samples, inadequate growth for drug evaluation (5 to 30 colonies/plate) in 17%, and no colony formation (less than 5 colonies/plate) in 56%. Operationally defining a greater than or equal to 50% inhibition of colony formation as in vitro drug sensitivity, the in vitro response rates to 12 anticancer drugs tested against ten to 36 different cancers (arranged in decreasing order according to the number of tests performed) were as follows: doxorubicin (14%), bisantrene (54%), vinblastine (33%), mitomycin (36%), interferon clone A (23%), 5-fluorouracil (20%), methotrexate (17%), leukocyte interferon (33%), mitoxantrone (42%), cyclophosphamide (25%), m-AMSA (16%), and melphalan (10%). Among 25 patients receiving single-agent therapy, there were ten (59%) of 17 with in vitro sensitivity who responded; resistance was correctly predicted in nine patients (100%), P = .01. Among 34 patients treated with combination chemotherapy, seven (50%) of 14 with in vitro sensitivity responded, and resistance was predicted in 13 (65%) of 20 patients. Difficulties in using the HTCA in breast cancer (including small specimen size, difficulties in disaggregation, and inadequacy of growth) will require additional research. Nonetheless, the assay appears to detect in vitro activity as well as resistance of a variety of anticancer agents and appears to predict clinical responsiveness to standard as well as some investigational single agents.

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.

Human myeloma in vitro colony growth: interrelationships between drug sensitivity, cell kinetics, and patient survival duration

Ninety-seven patients with multiple myeloma evaluated serially had both a tritiated thymidine labeling index of bone marrow plasma cells (LI%) and in vitro myeloma stem cell culture performed. Thirty-three patients with myeloma colony growth had in vitro drug sensitivity testing carried out, 18 having in addition in vitro thymidine suicide determinations. The LI% and the likelihood of in vitro myeloma colony growth were highly correlated: the higher the LI%, the more likely was colony or cluster growth (p less than 0.001). The tritiated thymidine suicide of myeloma stem cells was usually very high. There was excellent correlation between in vitro and in vivo drug sensitivity. Both pretreatment drug resistance and selective sensitivity (e.g., interferon, bisantrene, methotrexate, vinblastine) at the time of relapse were accurately detected and correlated well with survival duration (p = 0.01 Wilcoxan). Although LI% and in vitro sensitivity were clearly independent variables, a high LI% (greater than 3%) plus in vitro resistance were associated with a subsequent survival duration of less than 6 mo. The studies allowed dissection of the complex interrelationship between cell kinetics and drug sensitivity.

Dysthyroid ophthalmopathy: an update

Since the original description of dysthyroid ophthalmopathy, much has been learned about its etiology, pathology, course, and management. The subject is reviewed in depth and the author suggests explanations relating to some of the poorly understood aspects of the disorder.

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.