Evaluation of new geological reference materials for uranium-series measurements: Chinese Geological Standard Glasses (CGSG) and macusanite obsidian.

Recent advances in high-resolution, rapid, in situ microanalytical techniques present numerous opportunities for the analytical community, provided accurately characterized reference materials are available. Here, we present multicollector thermal ionization mass spectrometry (MC-TIMS) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) uranium and thorium concentration and isotopic data obtained by isotope dilution for a suite of newly available Chinese Geological Standard Glasses (CGSG) designed for microanalysis. These glasses exhibit a range of compositions including basalt, syenite, andesite, and a soil. Uranium concentrations for these glasses range from ∼2 to 14 µg g(-1), Th/U weight ratios range from ∼4 to 6, (234)U/(238)U activity ratios range from 0.93 to 1.02, and (230)Th/(238)U activity ratios range from 0.98 to 1.12. Uranium and thorium concentration and isotopic data are also presented for a rhyolitic obsidian from Macusani, SE Peru (macusanite). This glass can also be used as a rhyolitic reference material, has a very low Th/U weight ratio (around 0.077), and is approximately in (238)U-(234)U-(230)Th secular equilibrium. The U-Th concentration data agree with but are significantly more precise than those previously measured. U-Th concentration and isotopic data agree within estimated errors for the two measurement techniques, providing validation of the two methods. The large (238)U-(234)U-(230)Th disequilibria for some of the glasses, along with the wide range in their chemical compositions and Th/U ratios should provide useful reference points for the U-series analytical community.

Patients' beliefs: do they affect tuberculosis control? A study in a rural district of South Africa.

SETTING: A rural district of South Africa. OBJECTIVES: To describe the beliefs and experiences about tuberculosis of patients and community members and to suggest how these affect presentation to health services and treatment adherence. DESIGN: A descriptive study using structured interviews with individual patients, and focus group interviews with patients and community groups. RESULTS: There is a strong belief in this community that tuberculosis is the result of breaking cultural rules that demand abstinence from sex after the death of a family member and after a woman has a spontaneous abortion. People believe that the resulting disease can only be treated by traditional healers. This delays presentation to hospitals or clinics. There is also a belief in a 'western' type TB that can spread from sufferers or is due to environmental pollution or to smoking or alcohol excesses. A number of factors were cited that influenced adherence to treatment. These included the stigma of TB, the belief that there should be abstinence from sex while on treatment, difficulties accessing health services, long waits and unacceptable health worker attitudes. CONCLUSIONS: With the increasing rates of tuberculosis in South Africa, strenuous measures are needed to implement a good control programme that will increase the cure rate of tuberculosis patients. The results of this study suggest the need for health workers to learn about local beliefs that may influence presentation and adherence, and for traditional and western health workers to collaborate.

Environmental and human monitoring of Americium-241 utilizing extraction chromatography and alpha-spectrometry.

Recent developments in extraction chromatography have simplified the separation of americium from complex matrices in preparation for alpha-spectroscopy relative to traditional methods. Here we present results of procedures developed/adapted for water, air, and bioassay samples with less than 1 g of inorganic residue. Prior analytical methods required the use of a complex, multistage procedure for separation of americium from these matrices. The newer, simplified procedure requires only a single 2 mL extraction chromatographic separation for isolation of Am and lanthanides from other components of the sample. This method has been implemented on an extensive variety of "real" environmental and bioassay samples from the Los Alamos area, and consistently reliable and accurate results with appropriate detection limits have been obtained. The new method increases analytical throughput by a factor of approximately 2 and decreases environmental hazards from acid and mixed-waste generation relative to the prior technique. Analytical accuracy, reproducibility, and reliability are also significantly improved over the more complex and laborious method used previously.

Measurement and application of uranium isotopes for human and environmental monitoring.

An improved method is described utilizing extraction chromatography, anion exchange, and alpha spectroscopy for measurement of uranium isotopes in human and environmental surveillance studies. These methods provide a sensitivity of approximately 0.7 mBq per isotope per sample and are generally accurate within the precision of the measurements. The extraction chromatography methods greatly simplify separation of uranium from iron in silicate matrices and provide increased sample throughput and data quality for water, soil, and air filter samples. For bioassay samples, the coprecipitation/anion exchange/alpha spectrometric methods provide rapid throughput and sufficient sensitivity to meet new analytical performance standards in human monitoring studies. In addition, the 234U:238U data can be used as a fingerprint of natural vs. anthropogenic sources of uranium. For 1995 data from our laboratory, a large percentage (79-94% by matrix) of samples appear to be of natural 234U:238U isotopic composition. For all matrices, samples with higher uranium concentration generally have more depleted isotopic composition (smaller 234U:238U). A small percentage of soil (11%), air filter (3%), urine (3%), and water (3%) samples have depleted isotopic signatures at the 95% confidence interval, indicating anthropogenic contributions of uranium to these samples.

Achromobacter xylosoxidans bacteremia: report of four cases and review of the literature.

Seventy-seven cases of bacteremia due to Achromobacter xylosoxidans were reviewed, and susceptibility studies were performed on 11 clinical isolates of A. xylosoxidans. Nosocomial bacteremia was noted in 54 of 77 patients (70%), and 28 (36%) had infection associated with an outbreak or acquired from a discrete point source. The most common underlying illnesses were malignancies (30%) and cardiac disease (21%); immunosuppression affected 27%. The most common clinical syndromes were primary and catheter-associated bacteremia (19% each) and pneumonia (16%). The case-fatality rate was 30%; only 3% of patients with primary or catheter-associated bacteremia died, but 65% of patients with meningitis, endocarditis, and pneumonia died. The case-fatality rate in neonates was 80%. Susceptibility studies showed that all strains were resistant to aminoglycosides, most were resistant to quinolones, and all were susceptible to broad-spectrum penicillins, imipenem, ceftazidime, and trimethoprim-sulfamethoxazole. Two-disk approximation and time-kill studies showed synergy or additive effects for the combination of gentamicin and piperacillin against most strains.

Eating attitudes and behaviors of pre- and postpubertal females: clues to the etiology of eating disorders.

Eating disorders are most likely to occur in females in early adolescence. In the hope of identifying the nature of the changes occurring across puberty which may predispose adolescents to eating disorders three groups, 30 prepubertal girls, 28 postpubertal girls, and 28 adult women matched on height and weight to the postpubertal group were compared for meal pattern characteristics and food intake regulation, as well as changes in eating attitudes and behaviors. They completed a set of psychometrics measuring their eating attitudes, body image, and disposition and also maintained 7-day diaries of everything they ingested, time of ingestion, and subjective and social conditions. Neither the overall intakes nor the meal sizes significantly differed between age groups. The prepubertal females ate the most relative to body weight, ate with more other people present and earlier in the day. They were relatively happy, calm, slightly hungry, unrestrained, satisfied with their bodies and depression was associated with lower intake. The postpubertal group, on the other hand, were relatively restrained, ate faster, and ate only 76.5% of the recommended amount. They had a more negative body image, greater dissatisfaction with their bodies, and greater restraint of eating than the prepubertal group, and depression was associated with higher intake. These changes may leave the young woman extremely vulnerable and under the appropriate conditions or with the appropriate personality type may lead to the development of an eating disorder.

Mechanisms of magma generation beneath hawaii and mid-ocean ridges: uranium/thorium and samarium/neodymium isotopic evidence.

Measurements of uranium/thorium and samarium/neodymium isotopes and concentrations in a suite of Hawaiian basalts show that uranium/thorium fractionation varies systematically with samarium/neodymium fractionation and major-element composition; these correlations can be understood in terms of simple batch melting models with a garnet-bearing peridotite magma source and melt fractions of 0.25 to 6.5 percent. Midocean ridge basalts shows a systematic but much different relation between uranium/thorium fractionation and samarium/neodymium fractionation, which, although broadly consistent with melting of a garnet-bearing peridotite source, requires a more complex melting model.

MRI of sarcoid spondylodiskitis.

We report the MR appearance of a rare case of sarcoidosis of the spine presenting as spondylodiskitis. Vertebral and disk signal changes were typical for diskitis. In the appropriate clinical setting the differential diagnosis of diskitis should include sarcoidosis.

Variable efficacy of calcium carbonate tablets.

Orally administered calcium carbonate tablets are commonly prescribed as a calcium supplement and for their phosphate-binding effects in renal failure patients. Two cases are reported in which a commercially available brand of calcium carbonate tablets appeared to be ineffective. Formal investigation of the bioavailability of this product revealed it to have impaired disintegration and dissolution and a lack of clinical efficacy. Recommendations that will enable physicians to avoid prescribing and pharmacists to avoid dispensing ineffective calcium carbonate tablets are proposed.

Retroperitoneal feeding tube for peritoneal dialysis patients.

Treatment of the cachetic, hypoalbuminemic, peritoneal dialysis patient represents a vexing patient management problem. In the past, when the cause of inanition was intractable vomiting secondary to gastroparesis, the solution was to create a transperitoneal percutaneous enterogastrostomy. This endoscopic procedure bypassed the nonfunctioning stomach and allowed for adequate nutrition. When hypoalbuminemia is present, the patient is predisposed to the possible complications of peritoneal sepsis, dialysis fluid leak, and wound dehiscence. The authors report a unique, enteric feeding tube that is a solution to the problem of continuing adequate, complication-free dialysis in a cachetic, hypoalbuminemic peritoneal dialysis patient with no available site for either temporary or permanent hemodialysis vascular access. The procedure does not violate the peritoneal cavity and has proven to be effective, acceptable to the patient, apparently safe, and easy for both staff and patient use.

Reversibility of deficient sleep entrained growth hormone secretion in a boy with achondroplasia and obstructive sleep apnea.

Obstructive sleep apnea may lead to disordered sleep architecture and impair the physiologic slow wave sleep related growth hormone release. Obstructive sleep apnea occurs with craniofacial syndromes and in children with airway narrowing, pharyngeal hypoplasia, tonsillar adenoidal hypertrophy, micrognathia and achondroplasia. To examine the relationship between disordered sleep and growth hormone release we studied a 9 year old male with achondroplasia, growth failure (3 cm/year) and obstructive sleep apnea. Polysomnography data and a 20 min sampling for sleep entrained growth hormone showed before therapeutic tracheostomy numerous apneic episodes, absent slow wave sleep and abnormal low growth hormone secretion during sleep. Normalized slow wave sleep entrained growth hormone secretion after tracheostomy led to a sustained increase in growth rate. Normal growth rate (greater than 5 cm/year) continues 2 years after tracheostomy. We conclude that obstructive sleep apnea may impair sleep related growth hormone release. Obstructive sleep apnea may be a useful model for other diseases in which growth failure and sleep disturbances are linked.

Heparin free dialysis: comparative data and results in high risk patients.

Heparin free hemodialysis was compared to systemic heparinization, intermittent saline flushes and constant saline infusions in eight, stable chronic patients dialyzing on hollow-fiber artificial kidneys (HFAK) at blood flows of 250 to 300 ml/min. No significant differences in small molecule clearance, fluid removal or dialyzer clotting were noted. Since this data showed that heparin free hemodialysis without supplemental saline was feasible in a group of stable, chronic dialysis patients, we then prospectively studied twenty-nine patients judged to be at increased risk of hemorrhage from heparinization during 100 heparin-free dialyses. The incidences of severe and moderate dialyzer clotting were 7% and 20%, respectively. Seventeen of 27 treatments in which moderate or severe clotting occurred had identifiable factors thought to predispose to dialyzer clotting such as low blood flows, poor vascular-access function, severe hypotension and intradialytic blood transfusions. Although higher hematocrit values were associated with greater degrees of dialyser clotting, stepwise discriminant analysis employing blood flow, blood pressure, hematocrit and transfusion administration could not develop an accurate predictor or combination of predictors of clotting. No patient experienced de novo or increased bleeding and problems with inadequate dialysis were not observed. Since this method of heparin free dialysis is as safe and effective as previously reported strategies and requires no specialized equipment or procedures, it is a reasonable initial strategy for dialyzing high risk patients.

Thrombotic complications of indwelling central catheters used for chronic hemodialysis.

A new double-lumen silicone-rubber dialysis catheter, designed to be placed surgically in central veins, is now available. There is little published data concerning the long-term use of this catheter for hemodialysis, but a review of the literature suggests that pericatheter thrombus formation with or without occlusion of major veins has been a complication of chronic central venous catheterization with a variety of catheters, in both dialysis and nondialysis settings. We had this catheter placed in four diabetic patients who had severe problems related to maintenance of adequate vascular access. Two of the four patients underwent venography within 3 months of catheter placement because of impaired catheter function and were found to have thrombi on the outside of their catheters. These thrombi could not be dissolved with fibrinolytic agents, and the catheters were removed surgically without incident. The other two patients have no radiologic evidence of thrombus formation 4 and 7 months, respectively, after catheter placement. We suggest that proper selection of patients for this type of vascular access should be the subject of future studies and that patients with malfunctioning catheters undergo venography to rule out the presence of significant catheter related thrombosis.

Evaluation of traumatic atlantooccipital dislocations.

The diagnosis of traumatic atlantooccipital dislocation (AOD) from the cross-table lateral radiograph is difficult because of problems in demonstrating the complex anatomy of this area and the intricate radiographic methods used to diagnose AOD. Although CT or polytomography seem to be the most accurate diagnostic methods, it is often the lateral radiograph from which the diagnosis and further decisions are made. To determine both the best radiographic method for diagnosing AOD from the lateral radiograph and the role of CT and tomography in the diagnosis of AOD, the literature was reviewed concerning how the diagnosis of AOD has been obtained. In addition, the Wholey dens-basion line, the Powers ratio, the Dublin method of diagnosing AOD, and measurement of the atlantooccipital joint width were applied to 12 cases of traumatic AOD; and the Wholey dens-basion line and the Powers ratio were determined in 100 normal adults and 50 normal children. An alternative plain radiographic method for diagnosing AOD was developed, called the X-line method. This was the most accurate of the methods tested, correctly diagnosing AOD in 75% of cases. The Wholey dens-basion line and direct measurement of the atlantooccipital joint width were each correct in 50% of cases, the Powers ratio in 33% of cases, and the Dublin method in only 25% of cases. Ultimately, either CT or polytomography should provide the definitive diagnosis. In this regard high-resolution CT with reformatted coronal and sagittal images generated from 2-mm thin axial slices appeared to have the most promise as the first study of choice.

Magnetic resonance imaging of the sella turcica and parasellar region. A clinical-radiographic evaluation with computed tomography.

Thirty-one magnetic resonance (MR) scans and computed tomography (CT) scans were obtained on 25 patients in whom lesions involving the sella turcica or parasellar region were clinically suspected. Surgical pathologic studies were available in 19 cases. Twenty-two of the MR scans were of diagnostic value equivalent to that of the corresponding CT studies. In two small meningiomas, an empty sella, and a sphenoid-middle fossa tumor, MR technology failed to delineate the pathologic process adequately. In the remaining five patients, MR either more convincingly demonstrated the pathologic anatomy or yielded diagnostic information not present in the CT study. In view of the absence of ionizing radiation, high degree of tissue contrast and spatial resolution, and multiplanar capability, magnetic resonance scanning will probably become the initial imaging modality of choice in patients suspected of harboring sellar and parasellar tumors.

Comparison of coaxial and side-by-side double lumen subclavian catheters with the single lumen catheter.

Subclavian catheters are increasingly being used for vascular access. Many double lumen catheters (DLCs) have been designed to alleviate the need for a single-needle machine. Clinical studies comparing the safety of various DLCs with single lumen catheters (SLCs) are scarce. This study compares our experience with Sh-SLCs (Single-Shiley), Vas-DLCs (Coaxial-Vascath), and Qu-DLCs (Side-by-Side, Quinton). Similar aseptic insertion and handling techniques were used. The catheters were filled with heparin at the end of dialysis (HD) and no interdialytic infusions were given. Fifty-two Sh-SLCs were inserted in 46 patients for 253 HDs, 71 Vas-DLCs in 47 patients for 185 HDs, and 51 Qu-DLCs in 38 patients for 215 HDs. HDs/catheter were 4.9, 2.6, and 4.2, the percent incidence of septicemia was 2%, 7%, and 0%, and the catheter failure was 11%, 48%, and 16% for Sh-SLCs, Vas-DLCs, and Qu-DLCs, respectively (P less than 0.05 Vas-DLC v Sh-SLC and Qu-DLC). The poor flow problems were more frequent on the left side with Vas-DLCs (16/31) and Qu-DLCs (7/17), but not with Sh-SLCs (2/25). Other major complications were not noted. These results suggest that infections and mechanical problems may be more frequent with Vas-DLCs than Sh-SLCs and Qu-DLCs. Use of Qu-DLCs is a safe and may be preferred since a single-needle machine is not required. Insertion of a DLC on the right side may be preferred due to higher mechanical problems on the left side.