The randomized shortened dental arch study: oral health-related quality of life.

OBJECTIVES: Although the shortened dental arch (SDA) concept is a widely accepted strategy to avoid overtreatment, little is known on its impact on oral health-related quality of life (OHRQoL). This multicenter randomized controlled trial aimed to investigate the OHRQoL for removable partial dental prostheses (RPDP) with molar replacement versus the SDA concept. MATERIAL AND METHODS: In both groups, missing anterior teeth were replaced with fixed dental prosthesis. Two hundred fifteen patients with bilateral molar loss in at least one jaw were included. The Oral Health Impact Profile (OHIP-49) was completed before; 6 weeks (baseline), 6 months, and 12 months after treatment; and thereafter annually until 5 years. RESULTS: Of the initial cohort, 81 patients were assigned to the RPDP group and 71 to the SDA group (age, 34 to 86 years). Before treatment, the median OHIP score was similar in both groups (RPDP, 38.0; SDA, 40.0; n.s.). Results indicate marked improvements in OHRQoL in both groups between pretreatment and baseline (RPDP, 27.0; SDA, 19.0; p ≤ 0.0001) which continued in the RPDP group until the 1-year follow-up (p = 0.0002). These significant reductions in OHIP scores are reflected in its subscales. No further differences were seen within and between groups during the remainder observation period. CONCLUSION: Both treatments show a significant improvement in OHRQoL which continued in the RPDP group until the 1-year follow-up. No significant differences were seen between groups. CLINICAL RELEVANCE: For improving OHRQoL, it is not necessary to replace missing molars with a RPDP.

The randomized shortened dental arch study: tooth loss over five years.

OBJECTIVES: The study was designed to provide clinical outcome data for two treatments of the shortened dental arch (SDA). MATERIAL AND METHODS: In a multicenter randomized controlled clinical trial, patients with complete molar loss in one jaw were provided with either a partial removable dental prosthesis (PRDP) retained with precision attachments or treated according to the SDA concept preserving or restoring a premolar occlusion. No implants were placed. The primary outcome was tooth loss. RESULTS: Of 152 treated patients, 132 patients reached the 5-year examination. Over 5 years, 38 patients experienced tooth loss. For the primary outcome tooth loss, the Kaplan-Meier survival rates at 5 years were 0.74 (95% CI 0.64, 0.84) in the PRDP group and 0.74 (95% CI 0.63, 0.85) in the SDA group. For tooth loss in the study jaw, the survival rates at 5 years were 0.88 (95% CI 0.80, 0.95) in the PRDP group and 0.84 (95% CI 0.74, 0.93) in the SDA group. The differences were not significant. No Cox regression models of appropriate fit explaining tooth loss on the patient level could be found. CONCLUSIONS: The overall treatment goals of a sustainable oral rehabilitation and the avoidance of further tooth loss over longer periods were not reliably achievable. The influence of the type of prosthetic treatment on tooth loss might have been overestimated. CLINICAL RELEVANCE: Regarding our results, the patient's view will gain even more importance in the clinical decision between removable and fixed restorations in SDAs.

An experimental setup to evaluate innovative therapy options for the enhancement of bone healing using BMP as a benchmark--a pilot study.

Critical or delayed bone healing in rat osteotomy (OT) models is mostly achieved through large defects or instability. We aimed to design a rat OT model for impaired bone healing based on age, gender and parity. The outcome should be controllable through variations of the haematoma in the OT including a bone morphogenetic protein (BMP) 2 guided positive control. Using external fixation to stabilise femoral a 2 mm double OT in 12 month old, female Sprague Dawley rats after a minimum of 3 litters healing was characterised following in situ haematoma formation (ISH-group)), transplantation of a BMP charged autologous blood clot (BMP-group) and the artificial blood clot only (ABC-group) into the OT-gap. In vivo micro-computer tomography (µCT) scans were performed after 2, 4 and 6 weeks. After 6 weeks specimens underwent histological analyses. In µCT examinations and histological analyses no bony bridging was observed in all but one animal in the ISH-group. In the BMP group complete bridging was achieved in all animals. The ABC-group showed less mineralised tissue formation and smaller bridging scores during the course of healing than the ISH-group. In this pilot study we introduce a model for impaired bone healing taking the major biological risk factors into account. We could show that the in situ fracture haematoma is essential for bone regeneration. Using BMP as a positive control the presented experimental setup can serve to evaluate innovative therapeutical concepts in long bone application.

Influence of exposure route and oral dosage regimen on 1, 1-dichloroethylene toxicokinetics and target organ toxicity.

The objective of this investigation was to elucidate the effects of route of exposure and oral dosage regimen on the toxicokinetics (TK) of 1,1-dichloroethylene (DCE). Fasted male Sprague-Dawley rats that inhaled 100 or 300 ppm for 2 h absorbed total systemic doses of (10 or 30 mg/kg DCE, respectively. Other groups of rats received 10 or 30 mg/kg DCE by intravenous injection, bolus gavage (by mouth), or gastric infusion (g.i.) over a 2-h period. Serial microblood samples were taken from the cannulated, unanesthetized animals and analyzed for DCE content by gas chromatography to obtain concentration versus time profiles. Inhalation resulted in substantially higher peak blood concentrations and area under blood-concentration time curves (AUC(0)(2)) than did gastric infusion of the same dose over the same time frame at each dosage level, although inhalation (AUC(0)(infinity)) values were only modestly higher. Urinary N-acetyl-beta-D-glucosaminidase (NAG) and gamma-glutamyltranspeptidase (GGT) activities were monitored as indices of kidney injury in the high-dose groups. NAG and GGT excretion were much more pronounced after inhalation than gastric infusion. Administration of DCE by gavage also produced much higher Cmax and AUC(0)(2) values than did 2-h g.i., although AUC(0)(infinity) values were not very different. The 30 mg/kg bolus dose produced marked elevation in serum sorbitol dehydrogenase, an index of hepatocellular injury. Administration of this dose by inhalation and gastric infusion was only marginally hepatotoxic. These findings demonstrate the TK and target organ toxicity of DCE vary substantially between different exposure routes, as well as dosage regimens, making direct extrapolations untenable in health risk assessments.

Presystemic elimination of trichloroethylene in rats following environmentally relevant oral exposures.

1,1,2-Trichloroethylene (TCE), a volatile organic contaminant (VOC) of drinking water in the Unites States, is frequently present in trace amounts. TCE is currently classified by the International Agency for Research on Cancer and the U.S. Environmental Protection Agency as a probable human carcinogen, because it produces tumors in some organs of certain strains of mice or rats in chronic, high-dose bioassays. Previous studies (Toxicol Appl Pharmacol 60:509-526, 1981; Regul Toxicol Pharmacol 8:447-466, 1988) used physiological modeling principles to reason that the liver should remove virtually all of a well metabolized VOC, such as TCE, as long as concentrations in the portal blood were not high enough to saturate metabolism. To test this hypothesis, groups of unanesthetized male Sprague-Dawley rats received intravenous injections of 0.1, 1.0, or 2.5 mg TCE/kg as an aqueous emulsion. Other rats were gavaged with 0.0001, 0.001, 0.01, 0.1, 1, 2.5, 5, or 10 mg TCE/kg b.wt. Serial microblood samples were taken via an indwelling carotid artery cannula, to generate blood TCE versus time profiles. Headspace solid-phase microextraction gas chromatography with negative chemical ionization mass spectrometry (limit of quantitation = 25 pg/ml) was used to quantify TCE. TCE was undetectable in rats given 0.0001 mg/kg, but it exhibited linear kinetics from 0.1 to 5.0 mg/kg. Bioavailability was consistent over this dosage range, ranging from 12.5 to 16.4%. The presence of these limited amounts of TCE in the arterial blood disprove the aforementioned hypothesis, yet demonstrate that first-pass hepatic and pulmonary elimination in the rat afford its extrahepatic organs protection from potential adverse effects by the majority of the low levels of TCE absorbed from drinking water.

The Opportunity Rover's Athena science investigation at Meridiani Planum, Mars.

The Mars Exploration Rover Opportunity has investigated the landing site in Eagle crater and the nearby plains within Meridiani Planum. The soils consist of fine-grained basaltic sand and a surface lag of hematite-rich spherules, spherule fragments, and other granules. Wind ripples are common. Underlying the thin soil layer, and exposed within small impact craters and troughs, are flat-lying sedimentary rocks. These rocks are finely laminated, are rich in sulfur, and contain abundant sulfate salts. Small-scale cross-lamination in some locations provides evidence for deposition in flowing liquid water. We interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water, followed by evaporation, exposure, and desiccation. Hematite-rich spherules are embedded in the rock and eroding from them. We interpret these spherules to be concretions formed by postdepositional diagenesis, again involving liquid water.

Chemistry of rocks and soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer.

The Alpha Particle X-ray Spectrometer on the Opportunity rover determined major and minor elements of soils and rocks in Meridiani Planum. Chemical compositions differentiate between basaltic rocks, evaporite-rich rocks, basaltic soils, and hematite-rich soils. Although soils are compositionally similar to those at previous landing sites, differences in iron and some minor element concentrations signify the addition of local components. Rocky outcrops are rich in sulfur and variably enriched in bromine relative to chlorine. The interaction with water in the past is indicated by the chemical features in rocks and soils at this site.

The Spirit Rover's Athena science investigation at Gusev Crater, Mars.

The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.

Chemistry of rocks and soils in Gusev Crater from the alpha particle x-ray spectrometer.

The alpha particle x-ray spectrometer on the Spirit rover determined major and minor elements of soils and rocks in Gusev crater in order to unravel the crustal evolution of planet Mars. The composition of soils is similar to those at previous landing sites, as a result of global mixing and distribution by dust storms. Rocks (fresh surfaces exposed by the rock abrasion tool) resemble volcanic rocks of primitive basaltic composition with low intrinsic potassium contents. High abundance of bromine (up to 170 parts per million) in rocks may indicate the alteration of surfaces formed during a past period of aqueous activity in Gusev crater.

No difference in electroencephalographic power spectra or sensory-evoked potentials in patients anaesthetized with desflurane or sevoflurane.

BACKGROUND AND OBJECTIVE: Hitherto, neither desflurane nor sevoflurane, with similar physicochemical properties, have been compared with regard to their effects on the central nervous system. We compared the effects of desflurane and sevoflurane on electrical cortical activity and sensory transmission at two anaesthetic concentrations in patients undergoing hysterectomy. METHODS: The 1 and 2 MAC in nitrous oxide/oxygen (55%/45%) of desflurane or sevoflurane were administered while electroencephalographic power spectra and the somatosensory-evoked potentials were measured and correlated with cardiovascular effects. RESULTS: Both volatile agents induced a concentration-related increase of power in the slow delta-band and a concomitant decrease of power in the fast beta-domain. There was a close correlation with regard to the decrease in beta-power and heart rate (r2 = 0.988) and systolic blood pressure (r2 = 0.952) following both agents. Desflurane and sevoflurane had little effect on the early N20-peak, but affected the late N100-peak. There was a concentration-related increase in latency and a depression of amplitude height. Changes were not significantly different between both agents. CONCLUSIONS: Both desflurane and sevoflurane possess a similar profile with regard to their hypnotic effects and a similar outline in depressing propagation within the sensory nervous system. Cortical nervous effects are mirrored closely in heart rate and systolic blood pressure.

Errors in diagnosis and margin determination of soft-tissue sarcomas initially treated at non-tertiary centers.

One hundred four patients with soft-tissue sarcoma referred to our institution who were initially managed at an outside medical center were retrospectively reviewed. The accuracy of histologic diagnosis and adequacy of tumor resection performed at these centers was evaluated. Review of the original pathologic specimens was performed. Thirty-seven percent of the histologic diagnoses were changed, and 82% of cases with excisional or wide resections had positive margins. The incidence of errors in diagnosis and inadequate tumor resection suggest that biopsy and histologic analysis of sarcomas should be performed by physicians experienced in their management.

PBPK modeling of the metabolic interactions of carbon tetrachloride and tetrachloroethylene in B6C3F1 mice.

Potential exists for widespread human exposure to low levels of carbon tetrachloride (CT) and tetrachloroethylene (TET). These halocarbons are metabolized by the cytochrome P450 system. CT is known to inhibit its own metabolism (suicide inhibition) and to cause liver injury by generation of metabolically derived free radicals. The objective of this research was to use develop a physiologically based pharmacokinetic (PBPK) model to forcast the metabolic interactions between orally administered CT and TET in male B6C3F1 mice. Trichloroacetic acid (TCA), a stable metabolite of TET, was used as a biomarker to assess inhibition of the cytochrome P450 system by CT. Metabolic constants utilized for CT were 1.0mg/kg/h for Vmaxc_CT and 0.3 for Km_CT (mg/l). Values for TET (based in TCA production), were 6.0mg/kg/h for Vmaxc_TET was 3.0mg/l for Km_TET. The rate of loss of metabolic capacity for CT (suicide inhibition) was describe as: Vmaxloss ( mg / h )=- Kd ( RAM × RAM ) , where Kd (h/kg) is a second-order rate constant, and RAM (mg/h) is the Michaelis-Menten description of the rate of metabolism of CT. For model simplicity, CT was assumed to damage the primary enzymes responsible for metabolism of CT (CYP2E1) and TET (CYP2B2) in an equal fashion. Thus, the calculated fractional loss of TET metabolic capacity was assumed to be equivalent to the calculated loss in metabolic capacity of CT. Use of a Kd value of 400h/kg successfully described serum TCA levels in mice dosed orally with 5-100mg/kg of CT. We report, for the first time, suicide inhibition at a very low dose of CT (1mg/kg). The PBPK model under-predicted the degree of metabolic inhibition in mice administered 1mg/kg of CT. This PBPK model is one of only a few physiological models available to predict the metabolic interactions of chemical mixtures involving suicide inhibition. The success of this PBPK model demonstrates that PBPK models are useful tools for examining the nature of metabolic interactions of chemical mixtures, including suicide inhibition. Further research is required to compare the inhibitory effects of inhaled CT vapors with CT administered by oral bolus dosing and determine the interaction threshold for CT-induced metabolic inhibition.

[(18)F]FMISO and [(18)F]FDG PET imaging in soft tissue sarcomas: correlation of hypoxia, metabolism and VEGF expression.

Hypoxia imparts resistance to radiotherapy and chemotherapy and also promotes a variety of changes in tumor biology through inducible promoters. The purpose of this study was to evaluate the use of positron emission tomography (PET) imaging with fluorine-18 fluoromisonidazole (FMISO) in soft tissue sarcomas (STS) as a measure of hypoxia and to compare the results with those obtained using [(18)F]fluorodeoxyglucose (FDG) and other known biologic correlates. FDG evaluates energy metabolism in tumors while FMISO uptake is proportional to tissue hypoxia. FMISO uptake was compared with FDG uptake. Vascular endothelial growth factor (VEGF) expression was also compared with FMISO uptake. Nineteen patients with STS underwent PET scanning with quantitative determination of FMISO and FDG uptake prior to therapy (neo-adjuvant chemotherapy or surgery alone). Ten patients receiving neo-adjuvant chemotherapy were also imaged after chemotherapy but prior to surgical resection. Standardized uptake value (SUV) was used to describe FDG uptake; regional tissue to blood ratio (>or=1.2 was considered significant) was used for FMISO uptake. Significant hypoxia was found in 76% of tumors imaged prior to therapy. No correlation was identified between pretherapy hypoxic volume (HV) and tumor grade ( r=0.15) or tumor volume ( r=0.03). The correlation of HV with VEGF expression was 0.39. Individual tumors showed marked heterogeneity in regional VEGF expression. The mean pixel-by-pixel correlation between FMISO and FDG uptake was 0.49 (range 0.09-0.79) pretreatment and 0.32 (range -0.46-0.72) after treatment. Most tumors showed evidence of reduced uptake of both FMISO and FDG following chemotherapy. FMISO PET demonstrates areas of significant and heterogeneous hypoxia in soft tissue sarcomas. The significant discrepancy between FDG and FMISO uptake seen in this study indicates that regional hypoxia and glucose metabolism do not always correlate. Similarly, we did not find any relationship between the hypoxic volume and the tumor volume or VEGF expression. Identification of hypoxia and development of a more complete biologic profile of STS will serve to guide more rational, individualized cancer treatment approaches.

[Quantification and visualization of oxygen partial pressure in vivo by 19F NMR imaging of perfluorocarbons]. / Quantification and visualization of oxygen partial pressure in vivo by 19F NMR imaging of perfluorocarbons.

Due to the high solubility of molecular oxygen in perfluorocabons (PFC), this class of fluorinated compounds has gained wide-spread interest for its biomedical application as temporary blood substitutes and as radiosensitizers. Since the observation that the NMR spin-lattice relaxation times (T1) of some 19F PFC resonances are sensitive to oxygen tension (pO2), this paramagnetic effect has been used to non-invasively probe pO2 in vivo. In this study, combined 19F/1H NMR image data of Copenhagen rats after PFC application were evaluated with the software package MATLAB. The analysis of the 19F NMR data resulted in image matrices with calculated T1 values in each pixel. By using a calibration curve, the corresponding pO2 values were computed. Color overlays of pO2 contour lines on T1-weighted 1H images show a good anatomical-functional correspondence.

Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits.

Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at -42 degrees latitude to about 40 grams per square centimeter at -77 degrees. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 +/- 15% of the layer by weight.

Acute, subacute, and subchronic oral toxicity studies of 1,1-dichloroethane in rats: application to risk evaluation.

1,1-Dichloroethane (DCE) is a solvent that is often found as a contaminant of drinking water and a pollutant at hazardous waste sites. Information on its short- and long-term toxicity is so limited that the U.S. EPA and ATSDR have not established oral reference doses or minimal risk levels for the volatile organic chemical (VOC). The acute oral LD(50) in male Sprague-Dawley (S-D) rats was estimated in the present study to be 8.2 g/kg of body weight (bw). Deaths appeared to be due to CNS depression and respiratory failure. In an acute/subacute experiment, male S-D rats were given 0, 1, 2, 4, or 8 g DCE/kg in corn oil by gavage for 1, 5, or 10 consecutive days. The animals were housed in metabolism cages for collection of urine and sacrificed for blood and tissue sampling 24 h after their last dose. There were decreases in body weight gain and relative liver weight at all dosage levels, as well as increased renal nonprotein sulfhydryl levels at 2 and 4 g/kg after 5 and 10 days. Elevated serum enzyme levels, histopathological changes, and abnormal urinalyses were not manifest. For the subchronic study, adult male S-D rats were gavaged with 0.5, 1, 2, or 4 g DCE/kg 5 times weekly for up to 13 weeks. Animals receiving 4 g/kg exhibited pronounced CNS depression, with more than one-half dying by week 11. The 2-g/kg rats exhibited moderate CNS depression. One 2-g/kg rat died during week 6. There were very few manifestations of organ damage in animals that succumbed or in survivors at any dosage level. Decreases in bw gain and transient increases in enzymuria were noted at 2 and 4 g/kg. Serum enzyme levels and blood urea nitrogen were not elevated, nor were glycosuria or proteinuria present. Chemically induced histological changes were not seen in the liver, kidney, lung, brain, adrenal, spleen, stomach, epididymis, or testis. Hepatic microsomal cytochrome P450 experiments revealed that single, high oral doses of DCE did not alter total P450 levels, but did induce CYP2E1 levels and activity and inhibit CYP1A1 activity. These effects were reversible and regressed with repeated DCE exposure. There was no apparent progression of organ damage during the 13-week subchronic study, nor appearance of adverse effects not seen in the short-term exposures. One g/kg orally (po) was found to be the acute, subacute, and subchronic LOAEL for DCE, under the conditions of this investigation. In each instance, 0.5 g/kg was the NOAEL.

The efficacy of radiotherapy as postoperative treatment for desmoid tumors.

PURPOSE: The purpose of this study was to determine if radiotherapy is a beneficial adjuvant treatment after desmoid tumor resection. METHODS AND MATERIALS: A retrospective analysis was performed on 54 patients who underwent surgery without prior radiation at our institution between 1982 and 1998 to remove a desmoid tumor. Thirty-five patients had adjuvant radiation therapy after surgery, and 19 patients had surgery alone without immediate postoperative radiation. Sixteen of the 35 patients who underwent immediate postoperative radiation treatment had at least one prior resection before reoperation at our institution. Recurrence was defined as radiographic increase in tumor size after treatment. Follow-up interval (mean 39 months) and duration of local control were measured from the date of surgery at our institution. Potential prognostic factors for time to tumor progression were analyzed. RESULTS: Adjuvant treatment with radiation was the only significant prognostic factor for local control. The five-year actuarial local control rate was 81% for the 35 patients who underwent radiation in addition to surgery, compared to 53% for the 19 patients who underwent surgery alone (p = 0.018). For the patients who did not receive adjuvant radiation, only younger age at the time of surgery was associated with increased risk of failure (p = 0.035). Gross or microscopic margin status and number of prior operations were not detected as prognostic for local failure. For patients who did receive postoperative radiation, only abdominal location was associated with increased risk of failure (p = 0.0097). CONCLUSION: Radiation treatment as an adjuvant to surgery improved local control over surgery alone. Multiple operations before adjuvant radiation did not decrease the probability of subsequent tumor control. Radiation should be considered as adjuvant therapy to surgery if repeated surgery for a recurrent tumor would be complicated by a significant risk of morbidity.

Acute, short-term, and subchronic oral toxicity of 1,1,1-trichloroethane in rats.

1,1,1-Trichloroethane (TRI) is a widely used solvent that has become a frequent contaminant of drinking water supplies in the U.S. There is very little information available on the potential for oral TRI to damage the liver or to alter its P450 metabolic capacity. Thus, a major objective of this investigation was to assess the acute, short-term, and subchronic hepatotoxicity of oral TRI. In the acute study, male Sprague-Dawley (S-D) rats were gavaged with 0, 0.5, 1, 2, or 4 g TRI/kg bw and killed 24 h later. No acute effects were apparent other than CNS depression. Other male S-D rats received 0, 0.5, 5, or 10 g TRI/kg po once daily for 5 consecutive days, rested for 2 days, and were dosed for 4 additional days. Groups of the animals were sacrificed for evaluation of hepatotoxicity 1, 5, and 12 days after initiation of the short-term experiment. This dosage regimen caused numerous fatalities at 5 and 10 g/kg, but no increases in serum enzymes or histopathological changes in the liver. For the subchronic study, male S-D rats were gavaged 5 times weekly with 0, 0.5, 2.5, or 5.0 g TRI/kg for 50 days. The 0 and 0.5 g/kg groups were dosed for 13 weeks. A substantial number of rats receiving 2.5 and 5.0 g/kg died, apparently due to effects of repeated, protracted CNS depression. There was evidence of slight hepatocytotoxicity at 10 g/kg, but no progression of injury nor appearance of adverse effects were seen during acute or short-term exposure. Ingestion of 0.5 g/kg over 13 weeks did not cause apparent CNS depression, body or organ weight changes, clinical chemistry abnormalities, histopathological changes in the liver, or fatalities. Additional experiments did reveal that 0.5 g/kg and higher doses induced hepatic microsomal cytochrome P450IIE1 (CYP2E1) in a dose- and time-dependent manner. Induction of CYP2E1 activity occurred sooner, but was of shorter duration than CYP2B1/2 induction. CYP1A1 activity was not enhanced. In summary, 0.5 g/kg po was the acute, short-term, and subchronic NOAEL for TRI, for effects other than transient CYP2E1 induction, under the conditions of this investigation. Oral TRI appears to have very limited capacity to induce P450s or to cause liver injury in male S-D rats, even when administered repeatedly by gavage in near-lethal or lethal dosages under conditions intended to maximize hepatic effects.

The elemental composition of asteroid 433 eros: results of the NEAR-shoemaker X-ray spectrometer

We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.