Spacecraft sample collection and subsurface excavation of asteroid (101955) Bennu

Carbonaceous asteroids, such as (101955) Bennu, preserve material from the early Solar System, including volatile compounds and organic molecules. We report spacecraft imaging and spectral data collected during and after retrieval of a sample from Bennu’s surface. The sampling event mobilized rocks and dust into a debris plume, excavating a 9-m-long elliptical crater. This exposed material that is darker, spectrally redder, and more abundant in fine particulates than the original surface. The bulk density of the displaced subsurface material was 500–700 kg per cubic meter, about half that of the whole asteroid. Particulates that landed on instrument optics spectrally resemble aqueously altered carbonaceous meteorites. The spacecraft stored 250 ± 101 g of material, which will be delivered to Earth in 2023.

Fine-regolith production on asteroids controlled by rock porosity

Spacecraft missions have observed regolith blankets of unconsolidated subcentimetre particles on stony asteroids^1-3. Telescopic data have suggested the presence of regolith blankets also on carbonaceous asteroids, including (101955) Bennu⁴ and (162173) Ryugu⁵. However, despite observations of processes that are capable of comminuting boulders into unconsolidated materials, such as meteoroid bombardment^6,7 and thermal cracking⁸, Bennu and Ryugu lack extensive areas covered in subcentimetre particles^7,9. Here we report an inverse correlation between the local abundance of subcentimetre particles and the porosity of rocks on Bennu. We interpret this finding to mean that accumulation of unconsolidated subcentimetre particles is frustrated where the rocks are highly porous, which appears to be most of the surface¹⁰. The highly porous rocks are compressed rather than fragmented by meteoroid impacts, consistent with laboratory experiments^11,12, and thermal cracking proceeds more slowly than in denser rocks. We infer that regolith blankets are uncommon on carbonaceous asteroids, which are the most numerous type of asteroid¹³. By contrast, these terrains should be common on stony asteroids, which have less porous rocks and are the second-most populous group by composition¹³. The higher porosity of carbonaceous asteroid materials may have aided in their compaction and cementation to form breccias, which dominate the carbonaceous chondrite meteorites¹⁴.

Bright carbonate veins on asteroid (101955) Bennu: Implications for aqueous alteration history

The composition of asteroids and their connection to meteorites provide insight into geologic processes that occurred in the early Solar System. We present spectra of the Nightingale crater region on near-Earth asteroid Bennu with a distinct infrared absorption around 3.4 micrometers. Corresponding images of boulders show centimeters-thick, roughly meter-long bright veins. We interpret the veins as being composed of carbonates, similar to those found in aqueously altered carbonaceous chondrite meteorites. If the veins on Bennu are carbonates, fluid flow and hydrothermal deposition on Bennu's parent body would have occurred on kilometer scales for thousands to millions of years. This suggests large-scale, open-system hydrothermal alteration of carbonaceous asteroids in the early Solar System.

Variations in color and reflectance on the surface of asteroid (101955) Bennu

Visible-wavelength color and reflectance provide information about the geologic history of planetary surfaces. Here we present multispectral images (0.44 to 0.89 micrometers) of near-Earth asteroid (101955) Bennu. The surface has variable colors overlain on a moderately blue global terrain. Two primary boulder types are distinguishable by their reflectance and texture. Space weathering of Bennu surface materials does not simply progress from red to blue (or vice versa). Instead, freshly exposed, redder surfaces initially brighten in the near-ultraviolet region (i.e., become bluer at shorter wavelengths), then brighten in the visible to near-infrared region, leading to Bennu's moderately blue average color. Craters indicate that the time scale of these color changes is ~10⁵ years. We attribute the reflectance and color variation to a combination of primordial heterogeneity and varying exposure ages.

Asteroid (101955) Bennu's weak boulders and thermally anomalous equator

Thermal inertia and surface roughness are proxies for the physical characteristics of planetary surfaces. Global maps of these two properties distinguish the boulder population on near-Earth asteroid (NEA) (101955) Bennu into two types that differ in strength, and both have lower thermal inertia than expected for boulders and meteorites. Neither has strongly temperature-dependent thermal properties. The weaker boulder type probably would not survive atmospheric entry and thus may not be represented in the meteorite collection. The maps also show a high-thermal inertia band at Bennu's equator, which might be explained by processes such as compaction or strength sorting during mass movement, but these explanations are not wholly consistent with other data. Our findings imply that other C-complex NEAs likely have boulders similar to those on Bennu rather than finer-particulate regoliths. A tentative correlation between albedo and thermal inertia of C-complex NEAs may be due to relative abundances of boulder types.

In situ evidence of thermally induced rock breakdown widespread on Bennu's surface

Rock breakdown due to diurnal thermal cycling has been hypothesized to drive boulder degradation and regolith production on airless bodies. Numerous studies have invoked its importance in driving landscape evolution, yet morphological features produced by thermal fracture processes have never been definitively observed on an airless body, or any surface where other weathering mechanisms may be ruled out. The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission provides an opportunity to search for evidence of thermal breakdown and assess its significance on asteroid surfaces. Here we show boulder morphologies observed on Bennu that are consistent with terrestrial observations and models of fatigue-driven exfoliation and demonstrate how crack propagation via thermal stress can lead to their development. The rate and expression of this process will vary with asteroid composition and location, influencing how different bodies evolve and their apparent relative surface ages from space weathering and cratering records.

In their study, the authors discuss the potential of thermal weathering on airless bodies. As a case study, they use boulder and fracture morphologies on asteroid Bennu.

Episodes of particle ejection from the surface of the active asteroid (101955) Bennu

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

The unexpected surface of asteroid (101955) Bennu

NASA'S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine-that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu's global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5-11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid's properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu's thermal inertia12 and radar polarization ratios13-which indicated a generally smooth surface covered by centimetre-scale particles-resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.

Shape of (101955) Bennu indicative of a rubble pile with internal stiffness

The shapes of asteroids reflect interplay between their interior properties and the processes responsible for their formation and evolution as they journey through the Solar System. Prior to the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission, Earth-based radar imaging gave an overview of (101955) Bennu's shape. Here, we construct a high-resolution shape model from OSIRIS-REx images. We find that Bennu's top-like shape, considerable macroporosity, and prominent surface boulders suggest that it is a rubble pile. High-standing, north-south ridges that extend from pole to pole, many long grooves, and surface mass wasting indicate some low levels of internal friction and/or cohesion. Our shape model indicates that, similar to other top-shaped asteroids, Bennu formed by reaccumulation and underwent past periods of fast spin leading to its current shape. Today, Bennu might follow a different evolutionary pathway, with interior stiffness permitting surface cracking and mass wasting.

Impact of Weekend Physiotherapy Service on the Cost Effectiveness of Elective Orthopaedic Hip and Knee Arthroplasty

We performed a prospective correlational study to evaluate the efficiency and cost effectiveness of weekend physiotherapy in accelerating rehabilitation, reducing hospital stay as well as hospital costs for joint arthroplasty patients in a busy Scottish district general hospital. Patients that underwent elective hip (470) and knee (321) arthroplasty were analysed over a 12 month period. A four month period with weekend physiotherapy provision was arranged to ascertain its effectiveness on the length of stay and the achievement of set physiotherapy milestones. Data collected included length of stay and progression in a defined set of physiotherapy milestones. The relationship between time to discharge, mobilisation with sticks, straight leg raise, 90º knee flexion and cost effectiveness of service were used to determine the correlation, and analysis of the interactions of these factors separately. Our Outcome data demonstrate a statistical significance for the time to mobilisation with two sticks for hip (p=0.0030) and knee (p= 0.0037) arthroplasty patients. There was a trend towards earlier discharge times for all patients receiving weekend physiotherapy, but this was not statistically significant. We conclude that the provision of a continuous programme of weekend physiotherapy for all arthroplasty patients has the potential benefit of a quicker rehabilitation that would results in a cost saving.

Phylogenetic and morphological analysis of Aspergillus ochraceoroseus

Aspergillus ochraceoroseus produces the yellow-gold conidia and other characteristics of Aspergillus subgenus Circumdati section Circumdati. However, this species produces aflatoxin, a secondary metabolite characteristic of some members of subgenus Circumdati section Flavi and sterigmatocystin, a related secondary metabolite usually associated with subgenus Nidulantes sections Nidulantes and Versicolores, as well as members of several other genera. Our morphological data support the placement of A. ochraceoroseus in subgenus Circumdati. Sequence data from A. ochraceoroseus aflatoxin and sterigmatocystin genes aflR and nor-1/stcE, as well as 5.8S ITS and beta tubulin genes, were compared to those of aspergilli in sections Circumdati, Flavi, Nidulantes and Versicolores. In the sequence comparisons, A. ochraceoroseus was related more closely to the species in subgenus Nidulantes than to species from subgenus Circumdati.

A descriptive report of the effects of a 16-month xylitol chewing-gum programme subsequent to a 40-month sucrose gum programme

A previous caries trial (Belize studies) involved the usage of sucrose chewing-gum for a period of 40 months in one group of initially 10-year-old subjects in an environment of high sugar consumption, high caries activity, and limited access to restorative care. After the termination of the 40-month supervised sucrose gum usage, the 109 subjects of the original sucrose group retrieved at the endpoint of the original trial were invited to participate in a xylitol chewing-gum programme (involving the usage of the '100% pellet-shaped formular') for 16 months. The average daily consumption level of xylitol was up to 14 g per subject, normally used in seven daily chewing episodes. Although most subjects used chewing-gum at schools and received their gum portions from a school official, gum chewing during these 16 months was mostly unsupervised. After 16 months, 83 subjects (76%; mean age 14.9 years) were retrieved. The caries status of these subjects was examined by the same calibrated, blinded examiners as in the original trial. To mask the examiners, 141 similar non-participating subjects were recruited from the same school classes and were examined in a random order with the gum-using subjects, according to the same standard routine. The intensified xylitol gum usage for 16 months was associated with a reduction of the mean DMFS score from 10.9 (at 40 months) to 9.3 (at 56 months, p = 0.0013) and a reduction in caries rate from 20.1 caries onsets per 1,000 surface-years (40-month period average rate) to 10.2 caries onsets per 1,000 surface-years. The reduction in DMFS score resulted mostly from the change in the D component of the index and possibly reflected a stabilisation of the caries process and rehardening of some caries lesions to a non-progressive carious state.

Recruitment of the nuclear receptor corepressor N-CoR by the TEL moiety of the childhood leukemia-associated TEL-AML1 oncoprotein

The t(12;21)(p13;q22) chromosomal translocation is the most frequent illegitimate gene recombination in a pediatric cancer and occurs in approximately 25% of common acute lymphoblastic leukemia (cALL) cases. This rearrangement results in the in frame fusion of the 5'-region of the ETS-related gene, TEL (ETV6), to almost the entire acute myeloid leukemia 1 (AML1) (also called CBFA2 or PEBP2AB1) locus and expression of the TEL-AML1 chimeric protein. Although AML1 stimulates transcription, TEL-AML1 functions as a repressor of some AML1 target genes. In contrast to the wild type AML1 protein, both TEL and TEL-AML1 interact with N-CoR, a component of the nuclear receptor corepressor complex with histone deacetylase activity. The interaction between TEL and N-CoR requires the central region of TEL, which is retained in TEL-AML1, and TEL lacking this domain is impaired in transcriptional repression. Taken together, our results suggest that TEL-AML1 may contribute to leukemogenesis by recruiting N-CoR to AML1 target genes and thus imposing an altered pattern of their expression.

TEL-AML1 fusion gene frequency in paediatric acute lymphoblastic leukaemia in Brazil

We analysed 67 samples from Brazilian children of diverse ethnic origins with acute lymphoblastic leukaemia (ALL) for the presence of the TEL-AML1 fusion gene transcripts using reverse transcription polymerase chain reaction (RT-PCR). All 12 positive cases (20% of the 60 B-cell precursor ALL) had common (CD10+) ALL with a mean age of 4 years (range 1-10 years). We conclude that the frequency, age, distribution and clinical features of the TEL-AML1 fusion gene-positive ALL is similar in the diverse ethnic backgrounds of the Brazilian children to that in other countries with predominantly white Caucasian or oriental ethnicity. Apparent exceptions to this generality are discussed.

Application of the fundamental parameter method to the in vivo x-ray fluorescence analysis of Pt

The application of the fundamental parameter method (FPM) to the in vivo x-ray fluorescence (XRF) analysis of Pt has been investigated. The FPM is conventionally used to carry out elemental analysis of samples in vitro without the need to use standard samples of accurately known composition for system calibration. The present work has involved the use of the FPM to calculate the concentration of Pt solutions in phantoms, with concentrations ranging from 25-1000 ppm. The phantoms simulate the measurement of Pt-based chemotherapy drugs in head and neck tumours. The radiation sources were a 150 kV tungsten-anode x-ray tube and the isotope 99mTc. The minimum detection limit measured for Pt was in the range 8-30 ppm (depending on radiation source and geometry), using a narrow (5 mm) diameter beam. Dose rates in the phantom were 0.1-5 mGy h(-1). Average differences between nominal and calculated values of Pt concentration were <8% using the phantoms in air to simulate measurement of Pt in superficial body sites. If the phantoms were placed in a water bath, to simulate measurement at greater depths of overlying tissue, higher systematic differences (15-20%) were observed. This effect is probably due to multiple scattering processes in the surrounding medium.

The optimum time to initiate habitual xylitol gum-chewing for obtaining long-term caries prevention

Habitual xylitol gum-chewing may have a long-term preventive effect by reducing the caries risk for several years after the habitual chewing has ended. The goal of this report was (1) to determine if sorbitol and sorbitol/xylitol mixtures provide a long-term benefit, and (2) to determine which teeth benefit most from two-year habitual gum-chewing - those erupting before, during, or after habitual gum-chewing. Children, on average 6 years old, chewed gums sweetened with xylitol, sorbitol, or xylitol/sorbitol mixtures. There was a "no-gum" control group. Five years after the two-year program of habitual gum-chewing ended, 288 children were re-examined. Compared with the no-gum group, sorbitol gums had no significant long-term effect (relative risk [RR], 0.65; 95% confidence interval [c.i.], 0.39 to 1.07; p < 0.18). Xylitol gum and, to a lesser extent, xylitol/sorbitol gum had a long-term preventive effect. During the 5 years after habitual gum-chewing ended, xylitol gums reduced the caries risk 59% (RR, 0.41; 95% c.i., 0.23 to 0.75; p < 0.0034). Xylitol-sorbitol gums reduced the caries risk 44% (RR, 0.56; 95% c.i., 0.36 to 0.89; p < 0.02). The long-term caries risk reduction associated with xylitol strongly depended on when teeth erupted (p < 0.02). Teeth that erupted after 1 year of gum-chewing or after the two-year habitual gum use ended had long-term caries risk reductions of 93% (p < 0.0054) and 88% (p < 0.0004), respectively. Teeth that erupted before the gum-chewing started had no significant long-term prevention (p < 0.30). We concluded that for long-term caries-preventive effects to be maximized, habitual xylitol gum-chewing should be started at least one year before permanent teeth erupt.

Plane polarized x-ray fluorescence system for the in vivo measurement of platinum in head and neck tumours

A plane polarized x-ray fluorescence system based on an orthovoltage radiotherapy treatment unit, the Pantak DXT-300, has been developed and optimized to measure tumour platinum concentration. The platinum derives from platinum based chemotherapy agents, such as cisplatin and carboplatin used to treat tumours in the head and neck region. Photons from an x-ray tube are polarized by scattering through 90 degrees, and used to stimulate the emission of characteristic platinum x-rays from the tumour. Information about the drug in the tumour could be of use in establishing dose-response relationships, in order to optimize the treatment and reduce the toxicity of the drug. The performance of the system was optimized with respect to the applied x-ray tube voltage, the current and the filter material; the effect on the minimum detection limit (MDL) of the thickness of the overlying tissue surrounding the tumour was investigated in detail. The lowest MDL is achieved using 0.25 mm of tin filter and x-ray tube voltage of 220 kV. This is 5.6 ppm for a tumour surrounded with 20 mm of overlying tissue, a measurement time of 2000 s and an estimated skin dose of 3.0 mGy. This represents the most sensitive in vivo XRF system to date. We have embarked on a clinical pilot study to measure the platinum concentration in tumours of the head and neck, and expect initial results to be available in the near future.

Fetal origins of the TEL-AML1 fusion gene in identical twins with leukemia

The TEL (ETV6)-AML1 (CBFA2) gene fusion is the most common reciprocal chromosomal rearrangement in childhood cancer occurring in approximately 25% of the most predominant subtype of leukemia- common acute lymphoblastic leukemia. The TEL-AML1 genomic sequence has been characterized in a pair of monozygotic twins diagnosed at ages 3 years, 6 months and 4 years, 10 months with common acute lymphoblastic leukemia. The twin leukemic DNA shared the same unique (or clonotypic) but nonconstitutive TEL-AML1 fusion sequence. The most plausible explanation for this finding is a single cell origin of the TEL-AML fusion in one fetus in utero, probably as a leukemia-initiating mutation, followed by intraplacental metastasis of clonal progeny to the other twin. Clonal identity is further supported by the finding that the leukemic cells in the two twins shared an identical rearranged IGH allele. These data have implications for the etiology and natural history of childhood leukemia.

Characterization of the heparin-binding properties of human clusterin

Clusterin is a highly conserved mammalian glycoprotein which has been predicted to contain heparin-binding sites. We tested this prediction by studying the interactions between heparin and clusterin using ELISA and heparin affinity chromatography methodologies. Two forms of biotinylated heparin were used in ELISA: heparin which had been directly biotinylated with a biotin-N-hydroxysuccinimide ester and heparin which had been activated using epichlorohydrin and 1,6-diaminohexane prior to biotinylation. Both gave dose-dependent increases in ELISA signal with increasing concentrations of biotinylated heparin, with the latter giving signals an order of magnitude greater than the former. There was a dose-dependent increase in the ELISA signal from bound biotinylated heparin with increasing concentrations of plate-bound clusterin. The apparent affinity constant for binding of biotinylated heparin to plate-bound clusterin at pH 6.0 was estimated as 0.06 +/- 0.02 microM. Unlabeled heparin blocked the binding of biotinylated heparin to clusterin over a concentration range similar to that of the binding of biotinylated heparin to plate-bound clusterin. The binding of biotinylated heparin to clusterin was independent of the presence or absence of Ca2+. The binding of biotinylated heparin to plate-bound clusterin increased with decreasing pH over the range 5.5-8.0 and was characterized by an apparent pKa of 6.9. Clusterin in human serum bound to heparin-Sepharose at pH 6.0 but not at pH 7.4. Dot-blot experiments showed that one of the polypeptide chains of clusterin which had been reduced and alkylated under denaturing conditions bound to heparin-Sepharose. This chain was identified as the alpha chain from its N-terminal amino acid sequence.

Coherent imaging with two-dimensional focal-plane arrays: design and applications

Scanned, single-channel optical heterodyne detection has been used in a variety of lidar applications from ranging and velocity measurements to differential absorption spectroscopy. We describe the design of a coherent camera system that is based on a two-dimensional staring array of heterodyne receivers for coherent imaging applications. Experimental results with a single HgCdTe detector translated in the image plane to form a synthetic two-dimensional array demonstrate the ability to obtain passive heterodyne images of chemical vapor plumes that are invisible to normal video infrared cameras. We describe active heterodyne imaging experiments with use of focal-plane arrays that yield hard-body Doppler lidar images and also demonstrate spatial averaging to reduce speckle effects in static coherent images.

Hospital charges for stroke patients

BACKGROUND AND PURPOSE

Stroke is a common disease with a yearly cost in the United States of approximately $30 billion. The increasing prevalence of managed care and cost-containment measures may affect the delivery of stroke care now and in the future. This study was performed to determine (1) hospital charges and test utilization for stroke patients and (2) the effectiveness of educational efforts in modifying test utilization and related hospital charges.

METHODS

Patients with a diagnosis of stroke who were discharged from either the neurology service or another service of the Department of Medicine (DOM) were identified. Data on test utilization and hospital charges were collected and analyzed. Following this analysis, educational sessions were held in an effort to reduce the use of specific diagnostic tests. The effectiveness of these methods was studied in a second group of stroke patients.

RESULTS

In the baseline period there were 303 stroke patients, of which 262 (86%) were discharged from the neurology service and 41 (14%) were discharged from other services of the DOM. Patients on the neurology service had a lower mean length of stay than patients on the other services of the DOM (9.2 days versus 10.5 days) and lower mean total charges per case ($13,149 versus $15,727), although the respective differences were not statistically significant. Patient on the neurology service were more likely to have both brain CT and MRI performed (82 of 262 patients, 31.3%) than patients on the other services of the DOM (4 of 41, 9.8%, P = .005). In addition, patients on the neurology service were more likely to undergo a transthoracic echocardiogram than patients on the other services of the DOM (71.8% versus 53.7%, P = .025). After educational sessions, the percentage of stroke patients on the neurology service having both CT and MRI fell from 31.3% to 17.7% (P = .005), and the number of stroke patients having a transthoracic echocardiogram fell from 71.8% to 60.3% (P = .025). However, the overall charges for stroke patients on the neurology services did not decrease.

CONCLUSIONS

Education can be successful in reducing the utilization of and associated charges for specific diagnostic tests for some stroke patients. A multidisciplinary approach to case management, using tools such as care maps, may be necessary to realize significant cost savings in certain groups of stroke patients.

Regulation of the myeloperoxidase enhancer binding proteins Pu1, C-EBP alpha, -beta, and -delta during granulocyte-lineage specification

We have compared the molecular architecture and function of the myeloperoxidase upstream enhancer in multipotential versus granulocyte-committed hematopoietic progenitor cells. We show that the enhancer is accessible in multipotential cell chromatin but functionally incompetent before granulocyte commitment. Multipotential cells contain both Pu1 and C-EBP alpha as enhancer-binding activities. Pu1 is unphosphorylated in both multipotential and granulocyte-committed cells but is phosphorylated in B lymphocytes, raising the possibility that differential phosphorylation may play a role in specifying its lymphoid versus myeloid functions. C-EBP alpha exists as multiple phosphorylated forms in the nucleus of both multipotential and granulocyte-committed cells. C-EBP beta is unphosphorylated and cytoplasmically localized in multipotential cells but exists as a phosphorylated nuclear enhancer-binding activity in granulocyte-committed cells. Granulocyte colony-stimulating factor-induced granulocytic differentiation of multipotential progenitor cells results in activation of C-EBP delta expression and functional recruitment of C-EBP delta and C-EBP beta to the nucleus. Our results implicate Pu1 and the C-EBP family as critical regulators of myeloperoxidase gene expression and are consistent with a model in which a temporal exchange of C-EBP isoforms at the myeloperoxidase enhancer mediates the transition from a primed state in multipotential cells to a transcriptionally active configuration in promyelocytes.

Polyol chewing gums and caries rates in primary dentition: a 24-month cohort study

The effect of 2-year chewing-gum use on the caries rates of primary teeth was studied in a combined school and home program in a sample of 510 initially 6-year-old subjects with high caries experience, low availability of fluoride, and difficult access to dental care. The gum, formed into either sticks or pellets, comprised either xylitol, sorbitol, or mixtures thereof. The gum was chewed for 5 min under supervision five times a day during the school year, and for variable times during nonschool days. Seven groups were studied. One group received no gum; two xylitol gum groups received either pellet or stick gum as did, two sorbitol gum groups, and two groups received either of two types of xylitol/sorbitol pellet gum. The response variable was the development of a frank carious lesion detectable by physical loss of enamel and probable extension to the dentin for those surfaces of primary teeth that were not cavitated at baseline. Caries rates associated with the use of each of the gum types were compared to the caries rates in the no-gum group. The usage of all polyol gums resulted in a significant decrease of the caries onset rate (p < 0.05). The caries onset risk for a primary surface in the xylitol pellet and the sorbitol pellet groups was 35 and 44% of that in the no-gum group (relative risk, 0.35; 95% confidence interval, 0.21-0.59; relative risk, 0.44; 95% confidence interval, 0.30-0.63, respectively). The caries onset risk in the xylitol stick gum group was 53% of that in the no-gum group (relative risk, 0.53; 95% confidence interval, 0.39-0.72), which was marginally (p = 0.1520) lower than in the sorbitol stick gum group (relative risk, 0.70; 95% confidence interval, 0.52-0.94). The usage of both xylitol/sorbitol mixtures in pellet form was associated with a caries onset rate comparable with the usage of the xylitol stick gum. The largest caries risk reduction was observed in the group receiving xylitol pellet gum.

Properties of whole saliva and dental plaque in relation to 40-month consumption of chewing gums containing xylitol, sorbitol of sucrose

Samples of whole saliva and dental plaque were collected from initially 10-year old subjects who participated in a 40-month cohort study investigating the effect of chewing gum usage on caries rates. The subjects represented nine cohorts of which one did not receive gum, while in eight cohorts the subjects received gum containing either xylitol, sorbitol, their mixtures, or sucrose as bulk sweeteners, the maximum sweetener consumption in the form of gums being up to 10.7 g/day, used in 3-5 daily chewing episodes. Gum usage had no significant effect on the levels of salivary protein, IgA, alpha-amylase, peroxidase, lysozyme, SCN and buffer capacity. At the endpoint, the group that received 100% xylitol pellet-shaped gum five times/day, had significantly lower levels of sucrase (p <0.05) and free sialic acid (p < 0.001) in whole saliva than at baseline. This group showed significantly (p <0.05) smaller plaque index scores at two cross-sectional measurements, and exhibited the lowest log(10) counts of salivary lactobacilli at endpoint than most other groups. The salivary levels of peptidase(s) (oligopeptidase B-like enzymes) hydrolyzing N-alpha-benzoyl-DL-arginyl-p-nitroaniline were significantly (p<0.05) or almost significantly lower in groups which received 100% xylitol pellet gums. All groups exhibited obviously an aging-related increase of salivary mutans streptococcus scores, except the above xylitol group in which the mean scores did not change.

Xylitol chewing gums and caries rates: a 40-month cohort study

Dental caries is a pandemic infectious disease which can affect the quality of life and consumes considerable health care resources. The chewing of xylitol, sorbitol, and even sugar gum has been suggested to reduce caries rates. No clinical study has simultaneously investigated the effectiveness of these gums when compared with a group receiving no chewing gum. A 40-month double-blind cohort study on the relationship between the use of chewing gum and dental caries was performed in 1989-1993 in Belize, Central America. One thousand two hundred and seventy-seven subjects (mean age, 10.2 years) were assigned to nine treatment groups: one control group (no supervised gum use), four xylitol groups (range of supervised xylitol consumption: 4.3 to 9.0 g/day), two xylitol-sorbitol groups (range of supervised consumption of total polyols: 8.0 to 9.7 g/day), one sorbitol group (supervised consumption: 9.0 g/day). The gum use during school hours was supervised. Four calibrated dentists performed the caries registrations by means of a modified WHO procedure. The primary endpoint was the development of an unequivocal caries lesion on a non-cavitated tooth surface. Compared with the no-gum group, sucrose gum usage resulted in a marginal increase in the caries rate (relative risk, 1.20; 95% confidence interval,0.96 to 1.49; p = 0.1128). Sorbitol gum significantly reduced caries rates (relative risk 0.74; 95% confidence interval, 0.6 to 0.92 ; p = 0.0074). The four xylitol gums were most effective in reducing caries rates, the most effective agent being a 100% xylitol pellet gum (relative risk, 0.27; 95% confidence interval, 0.20 to 0.36; p = 0.0001). This gum was superior to any other gum (p < 0.01). The xylitol-sorbitol mixtures were less effective than xylitol, but they reduced caries rates significantly compared with the no-gum group. DMFS analyses were consistent with these conclusions. The results suggest that systematic usage of polyol-based chewing gums reduces caries rates in young subjects, with xylitol gums being more effective than sorbitol gums.

Stabilisation of rampant caries: polyol gums and arrest of dentine caries in two long-term cohort studies in young subjects

The purpose of this paper is to report clinical observations on the stabilisation of dentine caries in two chewing gum studies carried out in young subjects. One study focused on the permanent dentition of 1,277 initially 10-year old subjects, while the other study was carried out on 510 initially 6-year old subjects and focused on the primary dentition. In both trials, several chewing gum formulas containing dietary polyols (xylitol and sorbitol, or their combinations) were used for up to 40 months (10-year olds) or up to 24 months (6-year olds). The daily consumption level of both polyols was up to 10.7 g per subject, used normally in 5-minute chewing episodes 3 to 5 times per day. Supervised chewing in schools lasted 5 min per episode, and for variable times during non-school days. Rehardening of dentine caries lesions was observed clinically by experienced, blinded examiners using sharp dental explorers and fibre optic light. After 40 months (permanent dentition) or after 18 months (primary dentition), rehardening (caries arrest) generally occurred more frequently in subjects who used polyol gums than in subjects who did not receive gum as part of the programmes, or who received sucrose gum. Arrest or non-progression of dentine caries was most frequently observed in subjects who used 100 per cent xylitol gums or mixtures of xylitol and sorbitol, but the differences between gums were not consistently significant. However, the usage of 100 per cent xylitol pellet-shaped gum was more frequently associated with arrest of dentine caries than other treatments. These results and previous studies suggest that high-xylitol chewing gum usage can retard or arrest even rampant dentine caries in conditions where effective restoration and prevention programmes have not been instituted, and can also provide additional protection against further caries development during full implementation of restorative procedures by holding the lesion in a non-progressive condition.

A myeloid-lineage-specific enhancer upstream of the mouse myeloperoxidase (MPO) gene

The myeloperoxidase (MPO) gene is selectively expressed during haemopoiesis in the granulocytic lineage. Compared with the erythroid (beta-globin) and B-cell (immunoglobulin) lineages, little is known of the regulatory sequences and transcription factors involved in the regulation of genes specific for granulopoiesis. We have approached this issue by identifying a strong enhancer for the murine MPO gene. A candidate enhancer region was mapped by the detection of a strong DNase I hypersensitive site, -3.4 to -3.2 kb upstream of the MPO gene. A 301 bp fragment encompassing the DNase I site was shown to have strong enhancer function in a transient assay following transfection of a reporter gene into a MPO-expressing cell (WEHI 3BD+), but was inactive in lymphoid cells. Analysis of sub-fragments revealed that the whole 301 bp fragment is required for maximal enhancer function.

Clonal characteristics of acute lymphoblastic cells derived from BCR/ABL p190 transgenic mice

The clonal and immunophenotypic characteristics of blood leukemic cells from BCR/ABL p190 transgenic mice were investigated. All cell populations evaluated in vivo and in vitro had B-lymphocyte progenitor immunophenotypes. Immunoglobulin (JH) rearrangement patterns provided evidence for clonal diversification at different sites in vivo. Multiple clones were established in vitro from two of these mice (nos. 730 and 753). These cells expressed BCR/ABL p190 protein tyrosine kinase (PTK) and were highly malignant on transfer to secondary recipients. Cells independently cloned in vitro shared identical immunophenotypes and clonal IgH rearrangements, but these were distinct from those of the dominant clones in the mouse from which they were derived. Nevertheless, in vitro clones from mouse no. 753 had an abnormal karyotype (chromosome 14 trisomy) in common with the dominant clone in blood, providing evidence for a hierarchy or clonal selection in vivo and in vitro. Two sets of in vitro clones proliferated independently of exogenous growth factors and stroma and released autocrine interleukin 7 growth factor activity. These data provide evidence for rapid divergent clonal evolution and selection of B-cell progenitors initiated by BCR/ABL p190, followed by other, secondary genetic events mirroring similar changes in the equivalent, highly malignant human leukemia Philadelphia (Ph)-positive/B-precursor acute lymphoblastic leukemia (ALL).

Circulating stem cells in mice treated with cyclophosphamide

Chemotherapy has been used clinically to mobilize hematopoietic progenitor cells into the peripheral blood so that they can be harvested for autologous transplantation. In humans, this is demonstrated by the presence of circulating granulocyte-macrophage colony-forming cells (CFU-GM) and CD34-positive cells, but it has not been possible to confirm the presence of marrow-repopulating stem cells. In this study, we treated mice with 200 mg/kg cyclophosphamide (CY) and measured the numbers of white blood cells, day 12 CFU-S (CFU-S12), and CFU-GM in the peripheral blood. There was a peak in the numbers of CFU-S12 and CFU-GM 8 days after treatment with cyclophosphamide. Peripheral blood cells taken at this time rescued lethally irradiated mice and engraftment of donor cells was confirmed after 140 days in sex mismatched recipients using a Y chromosome-specific probe. In vitro culture of the blood cells harvested after cyclophosphamide showed that they proliferated in suspension cultures for at least a year in the presence of interleukin-3. The cultured cells rapidly lost their abilities to rescue irradiated mice and to form colonies in vitro, but they did not become leukemic. Also, CY-treated mice were irradiated with a leukemogenic dose of x-rays to coincide with peak circulating cell numbers but these animals did not develop an excess of leukemias over mice given irradiation alone.

Immunoglobulin heavy-chain and CD3 delta-chain gene enhancers are DNase I-hypersensitive in hemopoietic progenitor cells

Multipotential interleukin 3-dependent non-immortalized murine hemopoietic progenitor cells have DNase I-hypersensitive sites in the immunoglobulin heavy-chain and CD3 delta enhancers and transcribe germ-line T-cell antigen receptor gamma-chain (TCR gamma), but not IgM or TCR beta, genes. Induction of myeloid differentiation in these cells clones down expression and/or transcriptional accessibility of the immunoglobulin heavy-chain and TCR gamma genes. The CD3 delta enhancer region remains DNase I-hypersensitive but closes down in B cells. In embryonic stem cells and pan-mesodermal cells, these genes or enhancer regions are neither expressed nor DNase I-hypersensitive. These data suggest that lineage potential may be programmed, at least in part, by alterations in the accessibility or conformation of regulatory regions of genes and that some promiscuity of gene expression and/or accessibility can precede lineage commitment and maturation in progenitor cells induced to self-renew by interleukin 3.

Multilineage phenotypes of interleukin-3-dependent progenitor cells

Interleukin-3 (IL-3)-dependent murine FDCP-mix cells have multilineage differentiation capacity; they are nonleukemic, have a normal karyotype, and are nonimmortalized. These cells coexpress on their cell surface the "early" B-lineage marker B220/CD45R and the myeloid marker Mac-1/iC3b receptor (CR3), transcribe germline T-cell receptor gamma genes, and express the macrophage lineage growth factor receptor gene c-fms as a predominant 8.4-kb transcript. They do not detectably express at the stable mRNA or protein level other lymphoid precursor cell genes including CD2, TdT, lambda 5, and BP1. Induction of granulocyte/macrophage differentiation in these cells closes down expression of the lymphoid genes and activates stable expression of genes specific to the myeloid lineage, including myeloperoxidase. Expression of the c-fms gene at the mRNA level is upregulated and the dominant stable transcript is now in the 4.1-kb form typical of the macrophage lineage. These data provide a plausible explanation for the coexpression of lymphoid and myeloid lineage markers on human leukemic cells of stem cell or progenitor cell origin and have implications for the programming of lineage potential in normal multipotential hematopoiteic progenitor cells.

Increased production of growth factors and epidermal growth factor receptor by gastric carcinoma

Four growth factors and one growth factor receptor have been studied in carcinomas from 22 gastrectomy specimens and compared to non-malignant tissue from the same specimen. cDNA probes for transforming growth factors alpha and beta, platelet-derived growth factor A and B, insulin-like growth factor II and epidermal growth factor receptor were used to assay messenger RNA transcripts for the growth factors by dot hybridization. Increased levels of all the transcripts were found in carcinomas compared to benign tissue (P less than 0.05). No correlation was found between any of the growth factors studied and tumour stage or patient survival. Increased growth factor production by gastric cancers may be important in the pathogenesis of these tumours and further work is required to establish their role.

Far field propagation of the truncated EH(11) dielectric waveguide mode

The Fraunhofer diffraction pattern from hole-coupled and nonhole-coupled waveguides is obtained in analytical form. Nonlinear regression is used to fit a Gaussian beam to the far field pattern, and the effective beam waist is computed and compared to previous measurements. The ratio of the effective beam waist and the output aperture radius is found to depend on the ratio of the aperture and waveguide diameters. The percentage of power contained in nonzero diffraction orders is computed.

Comparison of high and low sodium bicarbonate and acetate dialysis in stable chronic hemodialysis patients

Eight stable center dialysis patients completed four, 10-week study periods in which either acetate or bicarbonate dialysis was used, each with high or low sodium concentration. During high sodium dialysis, blood pressure was better controlled, weight loss more easily tolerated and dialysis was most satisfactory from the patient's point-of-view with regard to dialysis-associated symptoms. Low sodium dialysis, whether with acetate or bicarbonate, was less satisfactory. In contrast to the beneficial effect of an increased sodium concentration, the use of bicarbonate instead of acetate appeared to make little difference either to the patient's symptoms, to the control of blood pressure or to changes in blood gases or biochemistry. Careful choice of dialysate sodium concentration appears to be important in lessening dialysis side-effects. Substitution of bicarbonate for acetate in chronic stable dialysis patients has comparatively little benefit and the choice can legitimately be made on the basis of cost and technical considerations.

The perception of flicker and glare on computer CRT displays

Subjects rated their discomfort due to direct glare, reflected glare, and flicker while viewing a CRT display under various conditions of ambient illuminance, video luminance, and video polarity. The angle away from the CRT at which the subjects first noticed flicker was also measured. Levels of these design and environmental variables that minimize discomfort are suggested. Video luminance was shown to have the greatest impact on comfort. Methods of reducing glare and flicker are discussed.

Monitoring particulate carbon collected on Teflon filters: an evaluation of photoacoustic and transmission techniques

The Colorado State University Aerosol Workshop provided an excellent opportunity to obtain various particulate samples collected on filters. Our results indicate that the photoacoustic technique is preferable to the transmission technique (integrating plate method) for ambient samples with low-filter loadings since the presence of a nonabsorbing scattering aerosol (ammonium sulfate) only slightly perturbs the photoacoustic signal and significantly affects the transmitted signal. Measurements indicate that the photoacoustic signal depends not only on the energy absorbed from the incident beam but also on the existence of thermal wave interference effects and, especially for heavily loaded filters, on the presence of a nonabsorbing scattering aerosol.

Thermal wave interferometry: a potential application of the photoacoustic effect

The Rosencwaig-Gersho equation for the photoacoustic signal is recast in a manner that emphasizes the crucial role thermal wave interference plays in the production of the photoacoustic signal. This formalism is then used to suggest a technique for extracting thermal information from the structure in the photoacoustic signal resulting from thermal wave interference. Experimental measurements illustrating this technique are presented.

Increased levels of threonyl-tRNA synthetase in a borrelidin-resistant Chinese hamster ovary cell line

The growth of Chinese hamster ovary cells in medium containing reduced concentrations of threonine is inhibited by borrelidin, a macrolide antibiotic. Borrelidin-resistant clones have been isolated after ethyl methanesulfonate mutagenesis. One clone, 1C-1, has a 3-fold increased level of threonyl-tRNA synthetase [L-threonine:tRNAThr ligase (AMP-forming), EC 6.1.1.3] as determined by both activity measurements and antiserum titrations. The levels of four other aminoacyl-tRNA synthetases and of tRNAThr are the same in strain 1C-1 and in the wild-type parent. The phenotype of increased threonyl-tRNA synthetase activity is recessive to wild type in cell hybrids.

Helmholtz resonator enhancement of photoacoustic signals

A Helmholtz resonator attached to a nonresonant photoacoustic cell enhances the responsivity to trace gas absorption by as much as a factor of 15.3. A simple system model based on a lumped parameter approach predicts the experimentally determined resonance frequency f(0) within 6% for all five resonator volumes tried and gives a pressure amplitude response at resonance proportional to f(0)(-5/2), which is the approximate experimental dependence. Optimization of response based on the model shows a pressure amplitude dependence on a(1/2), the square root of the radius of the cylindrical tube connecting the cell and the resonator.