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Biomedical subjects

C J Maxwell

Publications and source records attributed to C J Maxwell.

At least 19 recordsLinked to original sources
PubMed2002

The influence of promoter and of electrode material on the cyclic voltammetry of Pisum sativum plastocyanin.

The reversible cyclic voltammetry of pea plastocyanin (Pisum sativum) was studied with a wide range of electrodes: edge-oriented pyrolytic graphite (PGE), glassy carbon (GCE), gold (Au) and platinum (Pt) electrodes. Plastocyanin was coated onto the electrode surface by exploiting the electrostatic interaction between the negatively charged protein and a wide range of positively charged promoters. The effect of the redox response with an extended range of promoters, including poly-L-lysine, polymyxin B, neomycin, tobramycin, geneticin, spermine and spermidine, were included in this study. The resulting cyclic voltammograms reveal that the observed midpoint potential for plastocyanin can be shifted significantly depending on the choice of promoter. The stability of the negatively charged plastocyanin-promoter layer on an electrode was gauged by the rate of bulk diffusion of the protein from the immobilised film into the solution. Reversible cyclic voltammograms were obtained using edge-oriented pyrolytic graphite (PGE) and glassy carbon electrodes (GCE) with all promoters; however, platinum and gold electrodes were unable to sustain a defined redox response. The combination of pyrolytic graphite electrode/poly-L-lysine/plastocyanin was found to be the most stable combination, with a redox response which remained well defined in solution for more than 1 h at pH 7.0. The midpoint potentials obtained in this manner differed between the two graphite electrodes PGE and GCE using poly-L-lysine as the promoter. This effect was in addition to the expected pH dependence of the midpoint potential for plastocyanin and the results indicated that the pK(a) for plastocyanin on PGE was 4.94 compared to that on GCE of 4.66. It is concluded that both the electrode material and the nature of the promoter can influence the position of the redox potentials for proteins measured in vitro. This study extends the range of biogenic promoters used in combination with electrode materials. Thus, we can begin to develop a more comprehensive understanding of electrode-protein interactions and draw conclusions as to metalloprotein function, in vivo. To support these studies, we have sought information as to the nature of the electrode/promoter/protein interaction using scanning tunneling microscopy (STM) to study both the promoter and the plastocyanin protein on a gold surface.

Biogenic Amines↗
PubMed2001

A randomized controlled trial of a community-based consultation service to prevent falls.

BACKGROUND: Multifaceted programs that combine assessment with interventions have been shown to reduce subsequent falls in some clinical trials. We tested this approach to see whether it would be effective if offered as a consultation service using existing health care resources. METHODS: The subjects of this randomized controlled trial had to be aged 65 years or more and had to have fallen within the previous 3 months. They were randomly assigned to receive either usual care or the intervention, which consisted of in-home assessment in conjunction with the development of an individualized treatment plan, including an exercise program for those deemed likely to benefit. The primary outcomes were the proportion of participants who fell and the rate of falling during the following year. Visits to the emergency department and admissions to hospital were secondary outcomes. RESULTS: One hundred and sixty-three subjects were randomly assigned to either the control or the intervention group, and 152 provided data about their falls. There were no significant differences between the control and intervention groups in the cumulative number of falls (311 v. 241, p = 0.34), having one or more falls (79.2% v. 72.0%, p = 0.30) or in the mean number of falls (4.0 v. 3.2, p = 0.43). Analysis of secondary outcomes (health care use) also showed no significant differences between the intervention group and the control group. In the Cox regression analysis, there was no significant difference between the groups in the proportion of subjects having one or more falls (p = 0.55), but there was a significantly (p < 0.001) longer time between falls in the intervention group. In a post hoc subgroup analysis, subjects with more than 2 falls in the 3 months preceding study entry who had been assigned to the intervention group were less likely to fall (p = 0.046) and had a significantly longer time between falls (p < 0.001), when compared with the group who received usual care. INTERPRETATION: The intervention did not decrease significantly the cumulative number of falls, the likelihood of participants having at least one fall over the next year or the mean number of falls. It did increase significantly the time between falls in a survival analysis when age, sex and history of falling were used as covariates.

Accidental Falls↗
PubMed2001

Predictors of mammography use among Canadian women aged 50-69: findings from the 1996/97 National Population Health Survey.

BACKGROUND: Screening mammography, although recommended every 2 years for women aged 50-69, is thought to be underused among select groups of Canadian women. METHODS: We used data from the 1996/97 National Population Health Survey to describe current patterns in mammography use (including reasons for not having a mammogram within the 2 years before the survey and future screening intentions) in Canada and to determine factors associated with nonparticipation and time-inappropriate use (mammogram 2 or more years before the survey) among women aged 50-69. RESULTS: Among respondents aged 50-69, 79.1% (95% confidence interval [CI] 76.9%-81.2%) reported ever having had a mammogram, and 53.6% (95% CI 51.4%-55.9%) had had a recent (time-appropriate) mammogram (within the 2 years before the survey). Only 0.6% (95% CI 0.3%-0.9%) of recently screened women reported problems of access, and few reported personal or health system barriers as reasons for not obtaining a recent mammogram. Over 50% of the women who had not had a recent mammogram reported that they did not think it was necessary, and only 28.2% (95% CI 23.8%-32.7%) of those who had never had a mammogram planned to have one within the 2 years following the survey. The rate of time-appropriate mammography varied significantly by province, from 41.1% (95% CI 29.3%-52.9%) in Newfoundland to 69.4% (95% CI 61.3%-77.6%) in British Columbia. Significant predictors of never having had a mammogram included higher age, residence in a rural area, Asia as place of birth, no involvement in volunteer groups, no regular physician or recent medical consultations (including recent blood pressure check), current smoking, infrequent physical activity and no hormone replacement therapy. INTERPRETATION: Despite increases in mammography screening rates since the 1994/95 National Population Health Survey, current estimates indicate that almost 50% of women aged 50-69 have not had a time-appropriate mammogram. Our findings confirm continued low mammography participation rates among older women and those in rural areas, select ethnic groups and women with negative health care and lifestyle characteristics.

Age Factors↗
PubMed2000

Alcohol as a risk factor for HIV transmission among American Indian and Alaska Native drug users.

Quantitative alcohol interviews conducted as part of the National Institute on Drug Abuse (NIDA) Native American Supplement revealed very high rates of alcohol use among American Indian and Alaska Native active crack and injection drug users (IDUs). Of 147 respondents who completed the alcohol questionnaire, 100& percent had drunk alcohol within the past month, almost 42& percent reported that they drank every day, and 50& percent drank until they were drunk one-half of the time or more. Injection drug users (IDUs) demonstrated the highest frequency and quantity of alcohol use in the past 30 days. A significant positive association was also found between crack and alcohol use in the past 48 hours (c(2)=5.30, p<.05). Finally, those claiming more episodes of using alcohol before or during sex, reported significantly more events of unprotected sexual intercourse. Qualitative data from all four sites corroborated these quantitative findings. Many individuals also reported episodes of blacking out while drinking, and learned later that they had had unprotected sex with complete strangers or individuals they would not otherwise accept as partners. Implications of these findings for HIV/AIDS prevention efforts are addressed.

Adolescent↗
PubMed1999

Calcium-channel blockers and cognitive function in elderly people: results from the Canadian Study of Health and Aging.

BACKGROUND: Concern has been raised about the potential for adverse cognitive effects associated with the use of calcium-channel blockers (CCBs) in older people. This study was undertaken to examine prospectively the association between the use of these and other antihypertensive drugs and cognitive function. METHODS: The authors examined data from the Canadian Study of Health and Aging (CSHA), a population-based, prospective 5-year investigation of the epidemiology of dementia and other health problems in Canadians 65 years of age and older. The risk of cognitive decline, as indicated by a decline in performance on the Modified Mini-Mental State (3MS) examination over the 5-year period, was assessed in relation to the use of antihypertensive and diuretic drugs by 205 subjects with a history of hypertension and no evidence of dementia at baseline. RESULTS: The proportion of subjects whose cognitive performance declined over the study period was significantly higher in the group using CCBs than in the group using other antihypertensive agents (75% v. 59%). The adjusted odds ratio (OR) for a significant decline in cognitive performance (defined as a decrease in 3MS score of 10 points or more) was 2.28 (95% confidence interval [CI] 1.12-4.66) for subjects using CCBs. The adjusted ORs (and 95% CIs) for cognitive decline in subjects using selected antihypertensive agents or diuretics relative to those exposed to beta-blockers were as follows: angiotensin-converting-enzyme inhibitor, OR 1.36 (95% CI 0.41-4.55); diuretic or other antihypertensive drug, OR 1.45 (95% CI 0.51-4.14); dihydropyridine CCB (nifedipine), OR 1.94 (95% CI 0.52-7.27) and non-dihydropyridine CCB (diltiazem or verapamil), OR 3.72 (95% CI 1.22-11.36). INTERPRETATION: Older people taking CCBs were significantly more likely than those using other agents to experience cognitive decline. These findings are consistent with the results of previous cross-sectional research and emphasize the need for further trials to examine the associations between CCB use, blood pressure and cognitive impairment in elderly patients.

Age Factors↗
PubMed1999

Differences between males and females in risk of NSAID-related severe gastrointestinal events.

PURPOSE: NSAID use has long been established as a risk factor for severe gastrointestinal (GI) events. It is also known that age and gender affect the risk of such events independently of nonsteroidal antiinflammatory drug (NSAID) use. The objective of the present study is to distinguish between gender as an independent risk factor for severe GI events, and the differences between males and females in risk of NSAID-related severe GI events. METHODS: The study design was a nested case-control study. During the study period, 1029 cases were hospitalized with GI bleeds and/or perforations and 14 481 controls without such GI events were selected. Exposure consisted of the number of NSAID prescriptions dispensed by a pharmacy, prior to the data of hospitalization for cases and a corresponding date for controls. RESULTS: Males have a risk of serious GI events 1.4 times greater than females, independent of NSAID use. However, females have the greater increase in risk of NSAID-related GI events, e.g. at four prescriptions women have an odds ratio (OR) of 7.4 (p<0.05), while men have a corresponding OR of 3.2 (p<0.05). The increasing risk of severe GI events with number of NSAID prescriptions was considerably greater for females than for males, indicating effect-modification. In a stratified analysis by age and gender, it was clear that gender was the greater influence. Various metabolic and epidemiological potential explanations are discussed. CONCLUSIONS: Age and gender are separate risk factors for GI complications as related to NSAID use. Although implied in other studies, the effect of gender on the risk of NSAID-related GI events is clearly stated in this study.

Journal Article↗
PubMed1999

Nitroaromatic munition compounds: environmental effects and screening values.

Available data on the occurrence, transport, transformation, and toxicity of eight nitroaromatic munition compounds and their degradation products, TNT, TNB, DNB, DNA, 2-ADNT, RDX, HMX, and tetryl were used to identify potential fate in the environment and to calculate screening benchmarks or safe environmental levels for aquatic and terrestrial organisms. Results of monitoring studies revealed that some of these compounds persist at sites where they were produced or processed. Most of the compounds are present in soil, sediment, and surface water or groundwater at military sites. Soil adsorption coefficients indicate that these chemicals are only moderately adsorbed to soil and may leach to groundwater. Most of these compounds are transformed by abiotic or biotic mechanisms in environmental media. Primary transformation mechanisms involve photolysis (TNT, RDX, HMX, tetryl), hydrolysis (tetryl), and microbial degradation (TNT, TNB, DNB, DNA, 2-ADNT, and HMX). Microbial degradation for both nitro and nitramine aromatic compounds involves rapid reduction of nitro groups to amino groups, but further metabolism is slow. With the exception of DNB, complete mineralization did not usually occur under the conditions of the studies. RDX was resistant to microbial degradation. Available ecotoxicological data on acute and chronic studies with freshwater fish and invertebrates were summarized, and water quality criteria or ecotoxicological screening benchmarks were developed. Depending on the available data, criteria/benchmarks were calculated according to USEPA Tier I or Tier II guidelines. The munitions chemicals are moderately to highly toxic to freshwater organisms, with chronic screening values < 1 mg/L. For some chemicals, these low values are caused by inherent toxicity; in other cases, they result from the conservative methods used in the absence of data. For nonionic organic munitions chemicals, sediment quality benchmarks were calculated (based on Kow values and the final chronic value) according to USEPA guidelines. Available data indicate that none of the compounds is expected to bioconcentrate. In the same manner in which reference doses for humans are based on studies with laboratory animals, reference doses or screening benchmarks for wildlife may also be calculated by extrapolation among mammalian species. Chronic NOAELs for the compounds of interest were determined from available laboratory studies. Endpoints selected for wildlife species were those that diminish population growth or survival. Equivalent NOAELs for wildlife were calculated by scaling the test data on the basis of differences in body weight. Data on food and water intake for seven selected wildlife species--short-tailed shrew, white-footed mouse, meadow vole, cottontail rabbit, mink, red fox, and whitetail deer--were used to calculate NOAELs for oral intake. In the case of TNB, a comparison of toxicity data from studies conducted with both the white-footed mouse and the laboratory rat indicates that the white-footed mouse may be more resistant to the toxic effects of chemicals than the laboratory rat and may further indicate the lesser sensitivity of wildlife species to chemical insult. Chronic NOAEL values for the test species based on the laboratory studies indicate that, by the oral route of exposure, TNB and RDX are not highly toxic to mammalian species. However, as seen with TNB, values are less conservative when chronic studies are available or when studies were conducted with wildlife species. Insufficient data were located to calculate NOAELs for avian species. In the absence of criteria or guidelines for terrestrial plants, invertebrates, and soil heterotrophic processes, LOECs were used as screening benchmarks for effect levels in the environment. In most cases, too few data were available to derive a screening benchmark or to have a high degree of confidence in the benchmarks that were derived. (ABSTRACT TRUNCATED)

Animals↗
PubMed1997

A prospective study of falls after benzodiazepine use: a comparison of new and repeat use.

Although research has consistently demonstrated an increased risk for falls and fall-related fractures among persons receiving benzodiazepine (BZD) medications, the association between new as compared with chronic use and fall-related morbidity among different age groups is less clear. The objectives of this prospective cohort study were to examine the associations between BZD sedative and tranquillizer use and fall-related hospitalizations within 28 days of the fill date, and to explore variations in risks among new (after the first prescription) and chronic (after the third prescription) BZD users of different ages. Data were derived from the Saskatchewan Health linked databases for the years 1979-1986. Fall rates increased with age (especially beyond 70 years) and were highest among those receiving BZD sedatives and tranquillizers compared with controls for both new and chronic users. After adjusting for age, sex and selected health and social factors, a significantly increased risk of fall-related hospitalization was found among new BZD sedative (OR=2.8) and tranquillizer (OR=2.0) users compared with controls, and this risk was only slightly reduced among chronic BZD sedative (OR=2.4) and tranquillizer (OR=1.6) users. These risk estimates were consistent across age, with the exception that chronic BZD tranquillizer use remained significant only among those aged 70 years and older.

Journal Article↗
PubMed1997

Calculation of soil-water and benthic sediment partition coefficients for mercury.

To accurately model mercury transport to water bodies, an assessment of this pollutant's behavior in the watershed is critical. Partition coefficients, defined as an estimate of the ratio of the pollutant concentration sorbed onto soil/sediment particles to the pollutant concentration dissolved in pore water at equilibrium, is an important term in multimedia models. In this paper, partition coefficients are calculated for two broad species of mercury: inorganic mercuric mercury (Hg-II) and methylmercury (MHg). Although there is considerable variability in the calculated values, the approximate mean values for the soil-water partition coefficients range from 3.3 x 10(3) to 6.0 x 10(4) L/kg for Hg-II and 2.0 x 10(1) to 6.7 x 10(3) L/kg for MHg. For the benthic sediment partition coefficients, the values range from 5.7 x 10(3) to 9.9 x 10(5) L/kg for Hg-II, and 6.5 x 10(2) to 1.1 x 10(5) L/kg for MHg.

Animals↗
PubMed1996

New evidence on benzodiazepine use and falls: the time factor.

The objectives of this prospective study were to calculate incidence rates for fall-related hospitalization, to compare the effect of risk factors among benzodiazepine (BZD) users and unexposed controls, and to examine variations in risks according to length of time following a BZD prescription. Data were derived from Saskatchewan Health linked data bases, leading to information on 468 hospitalizations for injury due to falls among a study population of 321422. Incidence rates per 10000 within 28 days of the prescription fill date were 26.2, 12.1 and 9.0 for BZD sedative users, BZD tranquillizer users and for unexposed controls, respectively. Incidence rates increased with age, and were higher for women than for men. Results from multivariate logistic regression models also showed a greater risk of falling for BZD users but the odds ratio was higher for men than for women. A history of treatment for alcohol abuse was a very strong risk factor for falls among both men (odds ratio, 10.7) and women (odds ratio, 4.3). The highest risk of serious injury due to falls was within 15 days of filling the prescription, with an odds ratio of 3.6 for BZD sedatives and 2.6 for BZD tranquillizers. Risk decreased with further increase of time after the BZD fill date. For the individual BZD, flurazepam and triazolam showed the highest increase in risk with odds ratios of 3.4 and 2.7, respectively, while oxazepam, lorazepam and diazepam showed odds ratios of 2.2, 2.0 and 1.8 (all odds ratios mentioned are statistically significant at p < 0.05).

Accidental Falls↗
PubMed1988

Severe Raynaud's phenomenon in a patient with antinuclear antibody-negative systemic lupus erythematosus.

There is a well-recognized subset of patients with clinical findings consistent with systemic lupus erythematosus (SLE) but with negative antinuclear antibodies (ANA). Most of these patients have significant cutaneous involvement with little central nervous system or renal pathology. The following case report describes such a patient whose presentation was suggestive of SLE but who was ANA negative despite repeated testing. Additionally, the patient was found to have severe Raynaud's phenomenon and cutaneous vasculitis. This case is noteworthy because of the prominence of vascular insufficiency as a presenting feature of ANA-negative SLE.

Adult↗
PubMed1986

Changes in the structural and functional properties of human eosinophils during experimental hookworm infection.

Normal volunteers were infected with hookworm larvae Necator americanus. Peripheral blood counts showed a mean of 524 +/- 29 eosinophils/mm3 of blood before infection and a mean of 3,008 +/- 456 eosinophils/mm3 of blood during infection (P less than .01). Absolute numbers of neutrophils did not change. Eosinophils and neutrophils from the infected period were compared with the noninfected state in each subject. The percentage of hypodense eosinophils increased from a mean of 34% +/- 13% to 80% +/- 7% during infection (P less than .05). Superoxide production of eosinophils increased from a mean of 56 +/- 9 to 97 +/- 12 nmol of O2-./10(6) cells per 60 min (P less than .05) during infection. Chemotaxis of eosinophils to Escherichia coli endotoxin-activated serum increased from a mean average distance migrated of 19 +/- 2 micron (P less than .05), whereas neutrophil responsiveness did not change. This is the first report of changes in eosinophil density and stimulation of eosinophil function in normal hosts experimentally infected with hookworm. The data indicate that hookworm infection preferentially increases eosinophil production and activity with little effect on neutrophils.

Chemotaxis, Leukocyte↗
PubMedDate not supplied

Regional variation in the use of medications by older Canadians--a persistent and incompletely understood phenomena.

BACKGROUND: We have previously reported on regional variability in medication consumption by older Canadians. In this study, we used longitudinal data to determine whether regional differences in commonly consumed medications persisted and to explore potential explanatory factors for observed differences. METHODS: We utilized data from the second phase of the Canadian Study of Health and Aging to assess the number, types, and variability of medications used between regions. Linear and logistic regressions (LRs) were used to predict the number of medications and the use of specific agents where significant regional variability was found to exist. RESULTS: There were significant regional differences in the number of medications consumed and in the prevalence of use of acetaminophen (p < 0.002), benzodiazepines (p < 0.020), nitrates (p = 0.040), and complementary and alternative medicines (CAMs; p < 0.020). The proportion of subjects using acetaminophen was highest in British Columbia (44.6%) and lowest in Quebec (27.3%). Benzodiazepine and nitrate consumption was highest in Quebec (35.9 and 19%, respectively) and lowest in the Praires (18.2%) and Atlantic Canada (6.6%). CAM use was highest in British Columbia (47.1%) and lowest in the Atlantic region (26.8%). Similar inter-regional differences had been found 5 years previously. There were no significant regional differences in the prevalence of hypertension, myocardial infarction, diabetes, arthritis/rheumatism, or depression. Region remained a significant explanatory variable for the number of medications and nitrate, benzodiazepine, and CAM use in our multivariate models. CONCLUSIONS: Regional differences in medication use persisted over the course of this longitudinal study. Much of the variability remains unexplained. The reasons for regional differences in consumption of drugs and their clinical significance should be addressed.

Acetaminophen↗
PubMedDate not supplied

Concerning the role of aluminum in causing dementia.

Topics outlined in an earlier paper by Eichhorn are expanded, with particular emphasis on the implications of the associations between aluminum (Al) concentrations and various indications of mental impairment. These associations represent the main thrust of the evidence that Al is a contributory cause for some forms of dementia. Of particular interest are the more recently observed associations between Al concentrations in drinking (finished) water and various indications of mental impairment, and the relevance of other water quality variables such as silica, fluoride, and pH. Various unresolved questions are also identified.

Aluminum↗
PubMedDate not supplied

The prevalence and correlates of influenza vaccination among a home care population.

OBJECTIVE: To estimate the prevalence and correlates of influenza vaccination in a Home Care population. METHODS: This was a cross-sectional investigation involving linkage of three population-based databases from a rural Alberta Regional Health Authority, i.e., the Regional immunization and the Regional home oxygen information systems to the Regional home care information system. The sample comprised 649 persons who had been admitted or discharged from the Regional Home Care Program in the period Oct. 1-Dec. 31, 1998. An anonymous data file was released to the investigators. We estimated the proportion ever vaccinated against influenza, the proportion vaccinated in the period Oct. 1-Dec. 31, 1998 ("currently vaccinated"); and explored sociodemographic and program correlates of current vaccination. RESULTS: 67% had ever been vaccinated against influenza; 60.7% were currently vaccinated. Factors associated with current vaccination (multivariate analysis) include older age, being married, not receiving nursing services, district of residence and program status. CONCLUSIONS: Influenza vaccination rates were suboptimal. The correlates of vaccination suggest systems-level impediments to influenza vaccination.

Aged↗
PubMedDate not supplied

Factors important in promoting cervical cancer screening among Canadian women: findings from the 1996-97 National Population Health Survey (NPHS).

Although routine Pap screening represents an effective tool in the early detection of cervical cancer, it remains underused by some Canadian women. This study examines selected sociodemographic, health, lifestyle, and system barriers to Pap test participation among 33,817 women aged 18+ years in the cross-sectional 1996-97 National Population Health Survey (NPHS). Among women 18 years and over, 87% reported ever having had a Pap test while 72% reported a recent (< 3 years) test. A report of ever and recent use was most common among women 25-34 (92% and 86.9%, respectively). Only 0.6% of recently screened women reported access problems. Among those without a recent test, most (53%) reported that they did not think it was necessary. Pap test use varied little across provinces and was less common among older and single women, those with lower education, a spoken language other than English, a birth place outside Canada and negative health and lifestyle characteristics.

Adolescent↗