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Biomedical subjects

J McDonald

Publications and source records attributed to J McDonald.

At least 19 recordsLinked to original sources
PubMed2002

Search for nu(mu)-->nu(e) and nu(mu)-->nu(e) oscillations at NuTeV.

Limits on nu(mu)-->nu(e) and nu(mu)-->nu(e) oscillations are extracted using the NuTeV detector with sign-selected nu(mu) and nu(mu) beams. In nu(mu) mode, for the case of sin(2)2alpha = 1, Delta(m)(2)>2.6 eV(2) is excluded, and for Delta(m)(2)>>1000 eV(2), sin(2)2alpha>1.1 x 10(-3). The NuTeV data exclude the high Delta(m)(2) end of nu(mu)-->nu(e) oscillation parameters favored by the LSND experiment without the need to assume that the oscillation parameters for nu and nu are the same. We present the most stringent experimental limits for nu(mu)(nu(mu))-->nu(e)(nu(e)) oscillations in the large Delta(m)(2) region.

Journal Article↗
PubMed2002

Precise determination of electroweak parameters in neutrino-nucleon scattering.

The NuTeV Collaboration has extracted the electroweak parameter sin(2)theta(W) from the measurement of the ratios of neutral current to charged current nu and (-)nu cross sections. Our value, sin(2)theta((on-shell))(W) = 0.2277 +/- 0.0013(stat) +/- 0.0009(syst), is 3 standard deviations above the standard model prediction. We also present a model independent analysis of the same data in terms of neutral-current quark couplings.

Journal Article↗
PubMed2001

Search for the lepton family number violating process nu(mu)e(-) --> mu(-)nu(e).

The NuTeV experiment at Fermilab has used a sign-selected neutrino beam to perform a search for the lepton number violating process nu(mu)e(-)-->mu(-)nu(e), and to measure the cross section of the standard model inverse muon decay process nu(mu)e(-)-->mu(-)nu(e). NuTeV measures the inverse muon decay asymptotic cross-section slope sigma/E to be (13.8 +/- 1.2 +/- 1.4) x 10(-42) cm(2)/GeV. The experiment also observes no evidence for lepton number violation and places one of the most restrictive limits on the cross-section ratio sigma(nu(mu)e(-)-->mu(-)nu(e))/sigma(nu(mu)e(-)-->mu(-)nu(e)) < or = 1.7% at 90% C.L. for V-A couplings and < or = 0.6% for scalar couplings.

Journal Article↗
PubMed2001

Observation of an anomalous number of dimuon events in a high energy neutrino beam.

A search for long-lived neutral particles ( N0's) with masses above 2.2 GeV/c(2) that decay into at least one muon has been performed using an instrumented decay channel at the NuTeV experiment at Fermilab. Data were examined for particles decaying into the final states mumu, mu(e), and mu(pi). Three mumu events were observed over an expected standard model background of 0.069+/-0.010 events; no events were observed in the other modes.

Journal Article↗
PubMed2001

Lower respiratory tract infections in Inuit infants on Baffin Island.

BACKGROUND: It has long been suspected that Canadian Inuit children suffer from frequent severe lower respiratory tract infections (LRTIs), but the causes and risk factors have not been documented. This study assessed the infectious causes and other epidemiologic factors that may contribute to the severity of LRTI in young Inuit children on Baffin Island. METHODS: A prospective case study was carried out at the Baffin Regional Hospital in Iqaluit, Nunavut, of infants less than 6 months of age, who were admitted to hospital between October 1997 and June 1998 with a diagnosis of LRTI. Immunofluorescent antibody testing was used to identify respiratory viruses, and enzyme immunoassay (EIA) and polymerase chain reaction (PCR) were used to test for Chlamydia trachomatis. Demographic and risk factor data were obtained through a questionnaire. RESULTS: The annualized incidence rate of admission to hospital for bronchiolitis at Baffin Regional Hospital was 484 per 1000 infants who were less than 6 months of age; 12% of the infants were intubated. Probable pathogens were identified for 18 of the 27 cases considered in our study. A single agent was identified for 14 infants: 8 had respiratory syncytial virus, 2 adenovirus, 1 rhinovirus, 1 influenza A, 1 parainfluenza 3 and 1 had cytomegalovirus. For 4 infants, 2 infectious agents were identified: these were enterovirus and Bordetella pertussis, adenovirus and enterovirus, cytomegalovirus and respiratory syncytial virus, and respiratory syncytial virus and adenovirus. C. trachomatis was not identified by either EIA or PCR. All infants were exposed to maternal smoking in utero, second-hand smoke at home and generally lived in crowded conditions. INTERPRETATION: Inuit infants in the Baffin Region suffer from an extremely high rate of hospital admissions for LRTI. The high frequency and severity of these infections calls for serious public health attention.

Air Pollution, Indoor↗
PubMed2001

An evaluation of the use of proton pump inhibitors.

OBJECTIVES: To review whether Proton Pump Inhibitors (PPIs) are prescribed for appropriate indications and to assess the quality of information being supplied to GPs on discharge. METHOD: Prospective study of 85 patients consecutively admitted on, or initiated on, PPIs comparing prescribing patterns with the health authority consensus statement on PPIs and reviewing the quality of information provided to GPs on discharge. RESULTS: 39 patients were admitted on PPIs; 30% had absolute indications for prescribing, 3% had possible indications for prescribing and 67% were for indications other than those in the consensus statement. 46 patients had PPIs initiated as inpatients; 39% had absolute indications for prescribing, 10% had possible indications for prescribing and 51% were for indications other than those in the consensus statement. 10% of patients admitted on PPIs had therapy reviewed prior to discharge, whilst 60% of patients initiated on PPIs during admission were reviewed prior to discharge. Information provided to GPs on discharge usually included dosage and frequency. 18% of discharge letters indicated the intended duration of therapy and 7% suggested a review date. For those initiated on PPIs as inpatients 51% of discharge letters gave an indication. CONCLUSION: Frequent review of therapy and improved communications between primary and secondary care are vital to rationalise the use of PPIs and to reduce expenditure.

Drug Prescriptions↗
PubMed2001

End-stage renal disease in liver transplants.

Renal dysfunction is one of the most significant problems following orthotopic liver transplantation (OLTx). Since the major risk factor for delayed renal dysfunction following OLTx is presumed to be cyclosporine (CsA) nephrotoxicity, it has been suggested that CsA is the most probably cause of end-stage renal disease (ESRD) in this population of patients. To test this hypothesis the records of OLTx patients in our center who developed ESRD requiring dialysis were reviewed. There were 132 consecutive adult patients with end-stage liver disease (ESLD) who received 146 OLTxs between 1990 and 2000. Five patients (3.4%) developed ESRD requiring dialysis. Four of the five patients developed nephrotic range proteinuria prior to reaching ESRD. Renal biopsy in four patients showed focal segmental glomerulosclerosis, diabetic nephropathy, membranous nephropathy and cyclosporine toxicity. The underlying hepatic and metabolic disease may have played a role in the genesis of glomerular diseases in these OLTx patients. Perhaps if more renal biopsies are performed in OLTx patients with chronic renal failure, we might discover that, although CsA/tacrolimus therapy is a definite risk factor for post-transplantation chronic renal failure, other disease processes may also play a significant role.

Aged↗
PubMed2001

Morphologic features of the rheumatic mitral regurgitant valve by three-dimensional echocardiography.

BACKGROUND: Rheumatic fever remains a significant worldwide cause of mitral regurgitation (MR). We describe morphologic features of the rheumatic MR valve by quantitative 3-dimensional (3D) echocardiography. METHODS: Eight healthy subjects and 16 patients with less than moderate (n = 7) or more than or equal to moderate (n = 9) rheumatic MR underwent 3D echocardiography by use of freehand transthoracic scanning. Left ventricular (LV) borders, mitral chordae, papillary muscles and annuli were traced at end-diastole (ED) and end-systole (ES) with LV surfaces and mitral annulus reconstructed in 3D. Regional LV function was quantified by myocardial thickening. Regional LV shape was assessed by alignment of diseased ED endocardial surfaces to a reference normal surface. RESULTS: In the diseased group, LVs were more spheric and had regional shape abnormality in the area of anterior papillary muscle attachment. LV volumes, ejection fraction, and regional function in the areas of papillary attachment were not different. Mitral annular length and area were increased and correlated with LVED volume but were no different in height, sphericity, or beat-to-beat deformity. Chordal and papillary muscle lengths were not reduced. The interchordal angle (between the anterior and posterior chordae) was more acute in MR. CONCLUSION: Alterations in LV geometry and mitral apparatus morphologic features contribute to rheumatic regurgitant disease. Consequent changes include malalignment of the papillary muscles and a narrowed interchordal angle that is opposite to the widening seen in MR from dilated cardiomyopathy. We hypothesize that leaflet involvement with retraction causes increased tension on the chordae, a reduction in the interchordal angle, and a consequent coaptation defect.

Adolescent↗
PubMed2001

Evidence-based health care and community nursing: issues and challenges.

This paper examines the implications of the movement towards evidence-based health care for community-based, primary health care nursing in Australia. While both aim to improve health status, we argue that they are antithetical in many respects. Community nurse practitioners draw upon primary health care principles and adopt a holistic, preventive, empowering approach to working with and in communities. By contrast, evidence-based approaches utilise systematic reviews of primarily quantitative research to inform decisions about health at three levels: public health, the health care system, and individual patients. In response to this challenge, community nurses must reiterate their philosophies and practice models. Moreover, it is imperative to produce verifiable evidence of the effectiveness of their approach while mounting a thorough critique of the evidence-based movement.

Australia↗
PubMed2001

Intravenous self-administration of heroin/cocaine combinations (speedball) using nose-poke or lever-press operant responding in mice.

Acquisition and dose-related self-administration of heroin (H)/cocaine (C) combinations in C57BL/6 x SJL mice were studied in nose-poke or lever-press operant responding procedures. C57BL/6 x SJL mice readily acquired self-administration in both operant procedures with a combination of doses known to be ineffective when each drug was used alone (H: 15 microg/kg and C: 150 microg/kg per injection). Similar numbers of infusions were obtained under conditions of fixed-ratio (FR) 3 versus 1 for the nose-poke and lever-press responses, respectively. Dose-effect curves for heroin:cocaine combinations revealed a pattern corresponding to a leftward shift of the dose-response for intravenous cocaine self-administration. Curves were similar whether generated with 1 or 3 days of availability per dose, or including subjects that did not respond preferentially (> 70% responses) to the hole or lever associated with drug delivery, along with those that did. Motor activity induced by a combination of low doses for each drug was examined (H: 0.375 mg/kg and C: 3.75 mg/kg, i.p.). Under these conditions, the combination of both drugs induced an initial cocaine-like stimulation of horizontal activity, in contrast to the tendency of heroin to decrease activity. It is concluded that heroin:cocaine combinations used in the present study had reinforcing effects in C57BL/6 x SJL mice, and produced a cocaine-like effect in the early part of drug-induced activity sessions, followed by a locomotor profile corresponding to the average of both drugs.

Animals↗
PubMed2001

Office design and technology placement: fundamental foundations.

Build technology infrastructure on a solid foundation. Outline the technology vision, determine the budget, research products and vendors, plan a practical installation and support your investment with training. Reap the rewards of today's dental technologies by establishing your practice as high technology yet soft touch.

Capital Financing↗
PubMed2000

Naturally large cosmological neutrino asymmetries in the minimal supersymmetric standard model

A large neutrino asymmetry could have significant observable consequences for nucleosynthesis and the cosmic microwave background. If the baryon asymmetry originates via the Affleck-Dine mechanism along a d = 4 flat direction of the scalar potential in the minimal supersymmetric standard model and if the lepton asymmetry originates via Affleck-Dine leptogenesis along a d = 6 direction, corresponding to the lowest dimension directions conserving R parity, then the ratio n(L)/n(B) is naturally in the range 10(8)-10(9). As a result, a potentially observable neutrino asymmetry is correlated with a baryon asymmetry of the order of 10(-10).

Journal Article↗
PubMed2000

Efficacy and acceptability of testosterone implants, alone or in combination with a 5alpha-reductase inhibitor, for male hormonal contraception.

Testosterone (T) treatment suppresses serum gonadotropins and reduces sperm output sufficiently for contraceptive efficacy in approximately 70% of Caucasian men. In the remaining 30% of men, an increase in 5alpha-reductase activity may maintain testicular androgen activity, thus accounting for the failure of sperm suppression. The form of T therapy is a major consideration in the safety and acceptability of T-based contraception. As compared to T ester injections, T implants provide a more physiological serum T profile and fewer side effects, but have not yet been used in contraceptive efficacy studies. We have used T implants (800-1200 mg every 3 months) in 29 normal men for 3-16 months. T implants produced long-term suppression of sperm densities below 1 million/mL in approximately 70% of men without significant androgenic side effects. No pregnancies occurred in 214 months of exposure. In 16 men failing to suppress within 3 months of T 800 mg, no evidence of enhanced spermatogenic suppression was seen with the co-administration of the type 2 5alpha-reductase inhibitor, finasteride, for 3 months when compared to placebo. We conclude that: 1) T implants provide adequate spermatogenic suppression in approximately 70% of Caucasian men, a rate comparable to intramuscular T injections but with minimal side effects; and, 2) the inclusion of a type 2 5alpha-reductase inhibitor does not enhance spermatogenic suppression.

5-alpha Reductase Inhibitors↗
PubMed2000

Vitamin and mineral supplement use by older rural adults.

BACKGROUND: Vitamin and mineral supplement products are widely consumed by older adults. This study describes supplement product use in a multiethnic rural population, relates supplement usage to dietary nutrient intake, and determines predictors of supplement usage. METHODS: Data are from a population-based sample of 130 community-dwelling adults aged 70 years and older in two rural North Carolina counties. The sample was 34% African American, 36% European American, and 30% Native American. Interviewer-administered semiquantitative food frequency questionnaires were used to obtain data on usual diet and supplement use. In-home interviews allowed verification of supplement composition. Intakes from diet and supplement products were examined for vitamins A, E, B6, C, folate, iron, zinc, and calcium. RESULTS: Of those who participated in the study, 47% reported using one or more supplement products. African Americans were significantly less likely to take supplements than Native Americans or European Americans. Based on dietary intakes, 65% of the participants were deficient (<2/3 recommended dietary allowance [RDA]) for at least one nutrient. The use of supplement products for the eight nutrients investigated was not related to dietary nutrient deficiency. For all nutrients investigated, except iron and calcium, a greater proportion of those without dietary deficiency took a supplement product than those with deficiency. Using logistic regression, ethnicity (European American and Native American), and gender (women) were significant predictors of supplement use. CONCLUSIONS: These findings suggest that although both dietary deficiencies of vitamins and minerals and supplement use are relatively high in this population, there is no association between supplement use and deficient dietary intakes for the eight nutrients examined. Health care providers should be aware that nutritional counseling and guidance on appropriate supplement usage is needed in this population.

Black or African American↗
PubMed2000

Nutritional self-management of elderly widows in rural communities.

Studies of the nutritional status of older adults (by marital status) and of older women recently widowed suggest that widows are nutritionally vulnerable. Yet few studies have examined nutrition-related behaviors among widows to see why this is true. We conceptualize these behaviors as nutritional self-management strategies, encompassing behaviors related to obtaining food, consuming it, and maintaining food security. Data come from in-depth interviews conducted with 64 widowed women age 70+ in rural North Carolina (23 African American, 24 European American, 17 Native American). Transcripts were coded and analyzed using a systematic text-analysis procedure. Length of widowhood ranged from less than 1 year to 39 years. Themes identified in recent widows' interviews and corroborated in those widowed longer indicate that there are varied responses to widowhood. Some may have a positive impact on nutritional strategies (e.g., following own dietary needs), but most are likely to be negative (e.g., meal skipping, reduced home food production, less dietary variety). Rural communities need to develop ways to identify such widows and assist them in finding acceptable ways to meet nutritional needs.

Adult↗
PubMed2000

On their own: nutritional self-management strategies of rural widowers.

In-depth interviews conducted with 12 rural widowers participating in a population-based study of nutritional strategies of rural adults 70 years and older were analyzed to (a) identify factors that place widowers at risk for nutritional problems and (b) understand how rural residence is related to this risk. The nutritional strategies that successfully accomplished three groups of food-related tasks (food acquisition, food use, and maintaining food security) focused on one of three resource domains: self-care, informal support, and formal support. Resources that facilitated these nutritional strategies are identified, as are those conditions that led to nutritional strategies inadequate to ensure food acquisition, food use, and food security. These findings can be used to help identify rural elderly widowers who are at nutritional risk.

Adaptation, Psychological↗