Evidence against solar influence on nuclear decay constants.

The hypothesis that proximity to the Sun causes variation of decay constants at permille level has been tested and disproved. Repeated activity measurements of mono-radionuclide sources were performed over periods from 200 days up to four decades at 14 laboratories across the globe. Residuals from the exponential nuclear decay curves were inspected for annual oscillations. Systematic deviations from a purely exponential decay curve differ from one data set to another and are attributable to instabilities in the instrumentation and measurement conditions. The most stable activity measurements of alpha, beta-minus, electron capture, and beta-plus decaying sources set an upper limit of 0.0006% to 0.008% to the amplitude of annual oscillations in the decay rate. Oscillations in phase with Earth's orbital distance to the Sun could not be observed within a 10-6 to 10-5 range of precision. There are also no apparent modulations over periods of weeks or months. Consequently, there is no indication of a natural impediment against sub-permille accuracy in half-life determinations, renormalisation of activity to a distant reference date, application of nuclear dating for archaeology, geo- and cosmochronology, nor in establishing the SI unit becquerel and seeking international equivalence of activity standards.

Wildfire-related smoke inhalation worsens cardiovascular risk in sleep disrupted rats.

Introduction: As a lifestyle factor, poor sleep status is associated with increased cardiovascular morbidity and mortality and may be influenced by environmental stressors, including air pollution. Methods: To determine whether exposure to air pollution modified cardiovascular effects of sleep disruption, we evaluated the effects of single or repeated (twice/wk for 4 wks) inhalation exposure to eucalyptus wood smoke (ES; 964 µg/m3 for 1 h), a key wildland fire air pollution source, on mild sleep loss in the form of gentle handling in rats. Blood pressure (BP) radiotelemetry and echocardiography were evaluated along with assessments of lung and systemic inflammation, cardiac and hypothalamic gene expression, and heart rate variability (HRV), a measure of cardiac autonomic tone. Results and Discussion: GH alone disrupted sleep, as evidenced by active period-like locomotor activity, and increases in BP, heart rate (HR), and hypothalamic expression of the circadian gene Per2. A single bout of sleep disruption and ES, but neither alone, increased HR and BP as rats transitioned into their active period, a period aligned with a critical early morning window for stroke risk in humans. These responses were immediately preceded by reduced HRV, indicating increased cardiac sympathetic tone. In addition, only sleep disrupted rats exposed to ES had increased HR and BP during the final sleep disruption period. These rats also had increased cardiac output and cardiac expression of genes related to adrenergic function, and regulation of vasoconstriction and systemic blood pressure one day after final ES exposure. There was little evidence of lung or systemic inflammation, except for increases in serum LDL cholesterol and alanine aminotransferase. These results suggest that inhaled air pollution increases sleep perturbation-related cardiovascular risk, potentially in part by increased sympathetic activity.

Primary standardisation of technetium-99m by liquid scintillation coincidence counting.

Technetium-99m was standardised by the 4π(LS)ce-γ coincidence extrapolation method. Sensitivity of the 4π(LS) channel to two types of radiation, namely conversion electrons and γ-rays, resulted in incorrect activity values being obtained when this was not adequately accounted for. Measurements were more robust when the LS detection efficiency was optimised, and when a γ-window setting was used that monitored the combined LS efficiency for conversion electrons and γ-rays. The primary standard was internationally compared through participation in the BIPM.RI(II)-K4.Tc99m key comparison.

Development of the Australian Standard for Germanium-68 by two Liquid Scintillation Counting methods.

In response to the increasing application of 68Ge/68Ga and 68Ga in nuclear medicine, an international comparison of activity measurement of 68Ge in equilibrium with 68Ga was organised. ANSTO standardised the comparison solution by the 4π(LS)ß+-γ coincidence extrapolation and TDCR efficiency calculation methods, with excellent agreement between the two results. The primary standard was transferred to the ANSTO Secondary Standard Ionisation Chamber. Internationally traceable Australian Certified Reference Materials (ACRMs) of 68Ge/68Ga can now be prepared in various measurement geometries applied in nuclear medicine.

Why students choose a primary care or nonprimary care career. The Specialty Choice Study Group.

PURPOSE: To analyze the factors influencing students to choose residency training in primary care (internal medicine, family medicine, and pediatrics) or nonprimary care specialties and study the combined effect of reported responses on their choice. MATERIALS AND METHODS: A 12-item questionnaire using a 7-point Likert scale was mailed to the 1,164 graduating seniors from 9 medical schools in 1991. Responses ranged from 1, very negative influence, to 7, very positive influence. Four indicated no influence. The overall response rate was 69%. Univariate analysis of factors associated with specialty choice was done with the Mantel-Haenzsel chi-square test. Odds ratios were calculated for each significant variable without controlling for other variables. Factors found to have univariate significance were then tested for combined significance with logistic regression analysis. The regression was performed on a randomly chosen training sample, and validated on a test sample. RESULTS: Forty-five percent of respondents chose an internship and planned residency training in a primary care specialty. Factors that remained positively associated with choosing a primary care specialty when controlling for other factors were desire to provide comprehensive care, to keep options open, and to undertake ambulatory care. Desire for monetary reward was negatively associated with choice of a primary care specialty. CONCLUSIONS: Positive educational experiences in the ambulatory setting should be enhanced, and disparity in remuneration among disciplines reduced.

The treatment of urinary incontinence with electrical stimulation in nursing home patients: a pilot study.

OBJECTIVES: To test the effectiveness of electrical stimulation in the treatment of urinary incontinence in female nursing home patients. SETTING: A community long term care facility. PARTICIPANTS: Nine unselected female nursing home patients with urinary incontinence. All patients were moderately to severely cognitively impaired. By bedside cystometry, six patients had involuntary detrusor contractions while two had inconclusive results. INTERVENTION: Participants were treated with electrical stimulation for 8 weeks using the Microgyn II device. A current with a frequency of 20 hertz and a pulse width of 1 millisecond was delivered repeatedly for 2 seconds on, 4 seconds off for 15 seconds twice a week. MEASUREMENTS: The number of every-2-hour wet episodes during a 48-hour period (Wet) was recorded by a blinded observer at baseline and after 4 and 8 weeks of treatment. We evaluated the overall effect of electrical stimulation by averaging the Wet at 4 and 8 weeks for each patient and comparing it to Wet at baseline. MAIN RESULTS: The mean +/- standard deviation of intensity of electrical stimulation was 12 +/- 5 milliamps. Mean Wet at baseline was 11.8 +/- 4.2. For all patients mean Wet increased by 2.3 +/- 3.2, P = 0.07. Analysis of patients with documented involuntary detrusor contractions showed a mean increase in Wet of 2.6 +/- 3.6, P = 0.16. The volume of fluid at which an involuntary contraction occurred during cystometry showed a mean increase of 48.3 +/- 52.6 mL, P = 0.07 after 8 weeks of treatment. CONCLUSIONS: Electrical stimulation is well tolerated in elderly nursing home patients. However, it was ineffective in improving urinary incontinence. In fact, there was a tendency for the treatment to worsen the incontinence.

Effects of short-term administration of glucocorticoids on bone metabolism in healthy elderly men.

OBJECTIVE: To determine the effects of short-term glucocorticoid administration in healthy elderly men on bone GLA protein (BGP) levels, as well as levels of calcium, phosphorus, immunoreactive parathyroid hormone (PTH), and alkaline phosphatase. DESIGN: Subjects served as own control before and after prednisone treatment. SETTING: Male subjects were recruited by telephone from the Duke University Aging Center Volunteer Registry and the Department of Veterans Affairs Medical Center Gerofit Program (a supervised exercise program). PARTICIPANTS: Healthy males age greater than 60 years with no history of diabetes mellitus, glucose intolerance, or prior glucocorticoid use. Subjects could not be taking diuretic agents and could not have osteoporosis. The seven subjects mean age +/- std dev was 68.6 +/- 5.3 years. INTERVENTIONS: Prednisone 40 mg orally for 5 days. Fasting serum was obtained at baseline, on days 7 through 11, 13, 15, and 17. Assays of BGP, calcium, phosphorus, PTH, and alkaline phosphatase were performed. MAIN OUTCOME MEASURES: Changes in serum BGP levels was the primary outcome measure. Changes in serum calcium, phosphorus, PTH, and alkaline phosphatase levels were secondary outcome measures. RESULTS: Treatment caused reduction in BGP levels within 24 hours of first dose of prednisone, with levels dropping an average of 78% during the 5 days of treatment (P = 0.004). Within 24 hours of stopping treatment, BGP was no different from baseline. Other variables did not change with treatment. CONCLUSION: Glucocorticoid treatment suppresses BGP production in healthy elderly men in the same fashion as it does in younger healthy men.

The effect of age on driving skills.

OBJECTIVE: To assess the effect of age on driving skills independent of the limitations related to disease or dementia. DESIGN: Prospective comparison of driving skills across three age groups. SETTING: A university-based research study of student and university-affiliated volunteers. PARTICIPANTS: Healthy elderly (age 65+), teen-age (age 18-19), and young adult drivers (age 25-35). Twenty subjects in each age group were recruited after meeting entry criteria for the study. MAIN OUTCOME MEASURES: Total error count and score on the Miller Road Test, a standardized road test developed by the Division of Bus and Traffic Safety in North Carolina. RESULTS: The elderly were found to have fewer errors than either of the two younger groups of drivers (P = 0.0013). Specific driving skills were judged to be either superior or unchanged in the elderly subjects in comparison to their younger counterparts. CONCLUSIONS: Road test skills appear to be well preserved in the healthy elderly population. More road test studies are needed on elderly individuals with mental and physical impairments to determine if road tests can play a role in identifying the driver at high risk for a crash.

Diabetes: 'tight control' in a comprehensive treatment plan.

Two out of every five older Americans have abnormal glucose homeostasis. Approximately 1 in 5 has diabetes mellitus, but one-half of these persons are undiagnosed. Treatment of diabetes in older adults is usually managed by primary care physicians. A regular exercise program is the cornerstone of management, even in frail patients. Diet, weight loss, and regular patient education are also important. Age should not limit attempts at tight glucose control in older patients who are cognitively intact and otherwise reasonable candidates. The key to successful management is to follow through with a treatment plan that deals with all of the factors that influence glucose metabolism.

Hepatitis C seroprevalence in bone marrow transplant recipients and haemophiliacs.

AIM: To determine the prevalence of antibodies to hepatitis C (anti-HCV) in patients who have undergone bone marrow transplantation in Wellington, prior to the introduction of hepatitis C screening, and to contrast these results with the prevalence of anti-HCV in the Wellington haemophiliac population. METHOD: Serum specimens were obtained from 30 patients who had undergone bone marrow transplantation for the treatment of haematological disorders, and from 29 haemophiliacs. Specimens were analysed using a second generation HCV immunoassay. RESULTS: Exposure to blood products was high in bone marrow transplant recipients with subjects receiving red cells or platelets from an average of 53 donors (range 15-100, SD 23.2) during their transplant procedure. Despite the high usage of blood products, only one of the 30 patients tested was positive for hepatitis C on the basis of second-generation antibody testing. Confirmatory testing in this patient, (anti-HCV immunoblot assay) was negative. In contrast, 26 of 29 (89%) haemophiliac patients tested were positive for anti-HCV. CONCLUSION: Although the infective risk of blood products cannot be underestimated, the risk of patients contracting hepatitis C from multiple single-unit transfusions, prior to the introduction of screening for hepatitis C was low. This contrasts with the high risk of hepatitis C seroconversion in patients exposed to pooled plasma products.

Criteria mapping for the fractured permanent incisor.

Since hospital dental departments currently are regulated by the same quality assurance guidelines as other hospital departments, the Joint Commission on Accreditation of Healthcare Organizations now requires that dental departments review and evaluate the quality of care they deliver. Criteria mapping is an audit method that builds logic and decision making into this review process. This method was field tested on patients having fractures of anterior teeth. Statistically significant results were produced using the criteria map developed by this study; both evaluators scored the same in 98.6% of the criteria reviewed.

Cross-sectional study of changes in the ocular components in school children.

Ocular dioptric component measurements were taken as part of a study of clinical optometric examination results and refractive errors in school children. A cross-sectional analysis of the ocular components used linear regression analysis to assess changes in the components with age. Vitreous depth increased. The slope of corneal power with age was not significantly different from zero. Calculated crystalline-lens equivalent power decreased with age. Anterior chamber depth increased, crystalline-lens thickness decreased, and total axial length increased. From the standpoint of effect on refractive error, the major component changes are an increase in vitreous depth, which by itself would produce a shift in the direction of myopia, and decrease in crystalline-lens power, which by itself would produce a change in the direction of hyperopia.

Variation and correlation of clinical tests of accommodative function in a sample of school-age children.

Accommodative facility, lag of accommodation, accommodative response, and relative accommodation were measured in 244 school-age (7.9 to 15.9 years of age) children. The tests studied included monocular estimate method (MEM) dynamic retinoscopy, Nott dynamic retinoscopy, low neutral dynamic retinoscopy, the binocular cross cylinder test, lens accommodative rock (facility), distance (near-far) accommodative rock, negative relative accommodation (NRA), and positive relative accommodation (PRA). The mean, standard deviation, and range of test findings of each test are presented. Coefficients of correlation among the various tests are presented.

Variation and correlation of standard clinical phoropter tests of phorias, vergence ranges, and relative accommodation in a sample of school-age children.

This paper presents a study of standard clinical phoropter tests of dissociated phorias, fusional vergence ranges, and relative accommodation ranges in 244 school-age (7.9 to 15.9 years of age) children. The tests studied included von Graefe phorias and base-in and base-out fusional vergence ranges at both distance and near, as well as negative relative accommodation (NRA) and positive relative accommodation (PRA) tests. Coefficients of correlation among the various tests are presented. Means and correlations were similar to those previously reported for adult populations. Distributions of distance lateral phorias and some distance fusional vergence parameters were leptokurtic.

Clinical findings before the onset of myopia in youth. I. Ocular optical components.

PURPOSE: A study was conducted to identify variables that were different in children who were emmetropic and became myopic and in children who remained emmetropic. METHODS: A cohort of initially emmetropic children had eye and vision examinations at 6-month intervals for a period of 3 years. Ocular optical components were measured by keratometry and ultrasonography. Crystalline lens power was calculated using Bennett's formulas. RESULTS: There was a tendency for keratometer power of both principal meridians to be greater in the became-myopic group than in the remained-emmetropic group. Axial length to corneal radius (AL/CR) ratio was significantly greater in the became-myopic group than in the remained-emmetropic group. The variable with the highest sensitivity and specificity was the AL/CR ratio using the horizontal meridian corneal radius. CONCLUSIONS: Greater corneal powers and greater AL/CR ratios are risk factors for youth onset myopia.

Clinical findings before the onset of myopia in youth: 3. Heterophoria.

BACKGROUND: Some contemporary theories of the etiology of youth onset myopia suggest differences in accommodation and convergence function. Previous studies have related esophoria to various aspects of myopia development. This paper examines whether differences in phorias exist before the onset of myopia. METHODS: A cohort of initially emmetropic children had eye and vision examinations at 6-month intervals for a period of 3 years. Dissociated phorias were measured by the von Graefe method. These prospective data were analyzed by: (1) comparing phorias in children who became myopic to those in children who remained emmetropic; (2) determination of sensitivity and specificity of phorias to distinguish between children who became myopic and those who did not; and (3) determining the change in phorias with time. These same analyses were also performed as additional analyses of some previously published retrospective private practice data. RESULTS: Distance phorias were not significantly different in the became-myopic and remained-emmetropic group by the Mann Whitney U test in either the private practice data or the prospective data. The near phoria was more convergent in the became-myopic group than in the remained-emmetropic group in the private practice data (p < 0.02 by Mann Whitney U test). In the prospective data there were proportionately more children who became myopic outside the near phoria range of 3 delta exo to 1 delta eso (p < 0.05 by chi 2 test). In both data sets the near phoria showed an eso shift with time in the children who became myopic, beginning before and continuing after the onset of myopia. The children in the remained-emmetropic groups did not show eso shifts in near phoria. CONCLUSIONS: A near phoria which is not close to orthophoria appears to be a risk factor for youth onset myopia, but sensitivity and specificity were not as high as those for other variables such as corneal power, axial length to corneal radius ratio, positive relative accommodation (PRA), and midpoint of the near fusional vergence range. The onset of myopia is associated with an eso (convergent) shift in the near phoria.

Clinical findings before the onset of myopia in youth: 4. Parental history of myopia.

BACKGROUND: We conducted a study to compare variables in children who were initially emmetropic and became myopic to those in children who remained emmetropic. This paper examines parental history of myopia in the two groups of children. METHODS: A cohort of initially emmetropic children was given eye and vision examinations at 6-month intervals for 3 years. Data on parental history of myopia were obtained by questionnaire. RESULTS: A greater proportion of children in the became-myopic group had myopic parents compared to children in the remained-emmetropic group. The sensitivity for onset of myopia was 0.95 and specificity was 0.38 if at least one parent was myopic. A sensitivity of 0.36 and a specificity of 0.87 were found for both parents being myopic. There was a significant association between parental history of myopia and development of myopia in the children in the study (p < 0.01 by chi 2 for categorization of whether neither, one, or both parents were myopic for children in the became-myopic and remained-emmetropic groups). CONCLUSION: Parental history of myopia is a risk factor for the development of myopia.

Clinical findings before the onset of myopia in youth: 2. Zone of clear single binocular vision.

BACKGROUND: Many theories of myopia etiology suggest differences in accommodation and convergence in children who become myopic. Several studies have found differences in accommodation and convergence in myopes and emmetropes. Only one previous study examined accommodation and convergence before youth onset myopia. METHODS: A cohort of initially emmetropic children was given eye and vision examinations at 6-month intervals for 3 years. The data collected included fusional vergence ranges at 4 m and 40 cm, and relative accommodation findings with a target at 40 cm. These clinical accommodation and vergence test findings were compared in children who became myopic (became-myopic group) to children who did not (remained-emmetropic group). The mean test findings were used to construct a zone of clear single binocular vision (ZCSBV) for each group. RESULTS: The midpoint between the 40-cm fusional vergence range blur points was more convergent in the became-myopic group (+5.8 delta compared to +3.2 delta in the remained-emmetropic group; p < 0.004). The positive relative accommodation (PRA) finding was less in magnitude in the became-myopic group (-1.46 D) than in the remained-emmetropic group (-2.04 D), the difference being significant at he 0.02 level. CONCLUSIONS: The ZCSBV near blur point were more convergent in the children who became myopic as indicated by the more convergent position of the midpoint of the near fusional vergence range. The lower value for the PRA test in the became-myopic group duplicates the same result reported in a previous study for retrospective longitudinal private practice data.

The effect of oral deferoxamine on iron absorption in humans.

Acute iron overdose is a serious cause of morbidity and mortality, however, optimal gastric decontamination procedures in iron overdose are unclear. In order to determine the effectiveness of oral deferoxamine mesylate solution in humans to prevent the absorption of iron in acute exposures, the following prospective case control crossover study was designed. Seven informed adult human volunteers were given an oral dose of 5 mg/kg elemental iron alone in a control phase and again in an experimental phase followed by a single equimolar dose of oral buffered deferoxamine solution. Plasma iron concentrations were determined spectrophotometrically for eight hours following administration of iron alone and following doses of iron with deferoxamine. There was no significant difference in peak iron concentration, time to peak iron concentration or area-under-the-curve between the two groups. Based on our results, equimolar doses of oral deferoxamine do not appear to decrease the absorption of low doses of oral iron in humans.