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Biomedical subjects

A M O'Connor

Publications and source records attributed to A M O'Connor.

At least 19 recordsLinked to original sources
PubMed1995

Brain glucose uptake and unawareness of hypoglycemia in patients with insulin-dependent diabetes mellitus.

BACKGROUND: In patients with insulin-dependent diabetes mellitus (IDDM) whose treatment results in nearly normal mean plasma glucose concentrations, an unawareness of hypoglycemia can develop, and such patients are at increased risk for seizures and coma. We tested the hypothesis that during hypoglycemia, these patients would have normal glucose uptake in the brain and that consequently no sympathoadrenal activation would begin, resulting in an unawareness of hypoglycemia. METHODS: We measured glucose uptake in the brain at plasma glucose concentrations of 105 and 54 mg per deciliter (5.8 and 3.0 mmol per liter) in 24 patients with IDDM, stratified into three groups according to their glycosylated hemoglobin values (mean [+/- SD] values, 7.2 +/- 0.5, 8.5 +/- 0.4, and 10.2 +/- 1.3 percent) and compared the values for brain glucose uptake with those measured in 15 normal subjects at plasma glucose concentrations of 85 and 55 mg per deciliter (4.2 and 3.1 mmol per liter). We also recorded the subjects' hypoglycemic-symptom scores and measured their plasma concentrations of counterregulatory hormones. RESULTS: There was no significant change in the uptake of glucose in the brain (calculated as the uptake during hypoglycemia minus the uptake during normoglycemia) among the patients with IDDM who had the lowest glycosylated hemoglobin values (+0.6 +/- 2.0 mg [3.3 +/- 11.1 mumol] per 100 g of brain tissue per minute, P = 0.39). Conversely, glucose uptake in the brain fell in both the group with intermediate values (a decrease of 1.3 +/- 1.0 mg [7.2 +/- 5.6 mumol] per 100 g per minute, P = 0.009) and the group with the highest values (a decrease of 1.8 +/- 1.6 mg [10.0 +/- 9.0 mumol] per 100 g per minute, P = 0.01), as it did in the normal subjects (a decrease of 1.6 +/- 1.8 mg [9.0 +/- 10.1 mumol] per 100 g per minute, P = 0.003). The responses of plasma epinephrine and pancreatic polypeptide and the frequency of symptoms of hypoglycemia were lowest in the group with the lowest glycosylated hemoglobin values. CONCLUSIONS: During hypoglycemia, patients with IDDM who have nearly normal glycosylated hemoglobin values have normal glucose uptake in the brain, which preserves cerebral metabolism, reduces the responses of counterregulatory hormones, and causes an unawareness of hypoglycemia.

Adult↗
PubMed1995

Speech and language disorders in patients with high grade glioma and its influence on prognosis.

One hundred and sixteen patients with high grade glioma were entered into a prospective phase two study and treated with accelerated radiotherapy from 1988 to 1993. In this cohort of patients we analysed speech deficit as a subdivision of global functional status in terms of incidence, category and prognosis for survival. Forty three patients (37%) had a speech deficit at presentation. Eighty percent of these had a component of expressive dysphasia, associated with considerable degree of awareness and distress. The overall median survival was 9.5 months. On univariate analysis, median survival in patients with speech difficulties (6 months) was worse than patients with normal speech (10.5 months) (log rang p = 0.005). Multivariate analysis established independent significance from age, Karnofsky Performance Status (KPS), gender, histological grade, extent of surgery and seizures. This paper highlights the importance of assessing individual categories of functional disability which in patients with high grade glioma include mobility, cognitive function and communication. Each of these factors may seriously affect an individual's activities of daily living, hence quality of life and separate analysis has a number of clinical implications. Firstly, with over a third of patients suffering speech difficulties, adequate speech therapy facilities should be freely available to score the degree of deficit, devise coping strategies and institute communication therapy. Secondly, an understanding of prognostic factors aids the critical analysis of phase two studies and the design and stratification of future prospective trials which should include an analysis of speech deficit. Thirdly, separating individual patients into good and bad prognostic groups can assist strategic management decisions.

Adult↗
PubMed1995

Reliability and validity of measures used to elicit health expectations, values, tradeoffs and intentions to be immunized for hepatitis B.

We evaluated measures eliciting health expectations, health values, health tradeoffs and intentions to take hepatitis B (HepB) vaccine among health science and technology students. We tested 23 students two weeks apart and then surveyed a cross-section of 373 students in 6 health disciplines. In a subsequent prospective study, 863 students were tested, invited to be immunized, and followed to observe who presented for immunization. The test-retest reliability coefficients exceeded 0.80 for all but the health value measures. All but the health values measures discriminated between those with strong and weak intentions to be immunized. Expectation measures discriminated among disciplines with different risks of exposure to blood and body fluids. The intention, health tradeoff and expectation measures discriminated between those who did and did not present themselves for immunization. We conclude that all but the health values measures met acceptable standards of reliability and validity. Health value tradeoff measures are more discriminating than health value measures.

Allied Health Personnel↗
PubMed1995

Human gastrin and vasoactive intestinal polypeptide responses to endurance running in relation to training status and fluid ingested.

1. Plasma concentrations of gastrin, glucose, vasoactive intestinal polypeptide and non-esterified fatty acid were analysed in six male endurance runners and six male hockey players before, during and 15 min after 90 min treadmill running at 65% maximum oxygen uptake under two conditions: no fluid ingestion (trial A) and ingestion of 8% maltodextrin solution (trial B). 2. Exercise resulted in significantly elevated plasma gastrin concentrations compared with resting values in both groups after trial A (endurance runners, 69.4 ng/l; hockey players 71.4 ng/l) and trial B (endurance runners, 105.5 ng/l; hockey players, 83.2 ng/l). The gastrin response was not significantly different between the trials. 3. Plasma vasoactive intestinal polypeptide levels increased significantly beyond resting levels for both groups during trial A (endurance runners, 76.1 +/- 53.7 ng/l; hockey players 155.6 +/- 41.9 ng/l) and trial B (endurance runners 47.5 +/- 21.3 ng/l; hockey players 132.9 +/- 43.9 ng/l). The vasoactive intestinal polypeptide response to trial B was significantly attenuated compared with trial A. 4. There were no significant differences between endurance runners and hockey players for plasma gastrin, although hockey players produced significantly elevated concentrations of plasma vasoactive intestinal polypeptide after both trials compared with endurance runners. 5. Plasma glucose levels throughout trial B were significantly greater than after trial A irrespective of the group. Plasma glucose concentrations were not significantly different between endurance runners and hockey players. 6. Plasma non-esterified fatty acid concentrations rose significantly for both groups throughout exercise. Trial B resulted in an attenuated non-esterified fatty acid response compared with trial A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Circulating gastrointestinal hormone changes in marathon running.

The purpose of this study was to observe the effect of marathon running on the release of gastrointestinal hormones and whether these might be related to gastrointestinal disturbances in marathon runners. Vasoactive intestinal polypeptide, gastrin, secretin, pancreatic polypeptide, neurokinin A, pancreastatin, insulin and glucagon-like peptide 1 were measured before, immediately upon finishing and 30 min after the race. Twenty-six competitors of the 1992 Belfast Marathon volunteered for this study. They had a mean age of 37 years and a mean finishing time of 239 min. Eight of the subjects complained of gastrointestinal distress during the race. The circulating concentration of all the GI hormones measured, except insulin were significantly elevated after the race. There was no significant change in glucose levels at the finish of the race. Statistical analysis revealed no direct relationship between the large increases in hormone levels and the occurrence of GI symptoms. These results show that GI hormone concentrations are affected by marathon running. Mechanisms of release and possible roles are discussed.

Adult↗
PubMed1995

Appropriateness of adjuvant systemic therapy for axillary node-negative breast cancer: a physician opinion survey.

PURPOSE: To examine variations in physicians' recommendations for systemic adjuvant therapy in the treatment of women with node-negative breast cancer (NNBC) and to determine factors used in making specific recommendations. MATERIALS AND METHODS: A questionnaire was sent by mail to all 149 Ontario physicians who actively treated breast cancer in 1993. The questionnaire described 48 clinical scenarios of women with NNBC, which included all possible combinations of the following factors: menopausal status, tumor size, hormone receptor status, histologic and nuclear grade, and lymphatic and/or vascular invasion. Respondents rated the appropriateness of administering tamoxifen, combination chemotherapy, or both tamoxifen and combination chemotherapy on a nine-point scale from extremely inappropriate to extremely appropriate. Respondent agreement and disagreement were tabulated for each scenario, and factors associated with specific treatment ratings were analyzed by logistic regression. RESULTS: The response rate was 87%. Agreement for the appropriateness of specific therapies was most evident where clinical trials have demonstrated efficacy, whereas disagreement was observed in scenarios in which support for a specific treatment is not available in the current literature. Relevant tumor- and patient-specific factors were used in decision-making; personal characteristics of the respondents had no statistically significant impact on appropriateness ratings. CONCLUSION: The physicians surveyed had good knowledge of NNBC prognostic factors, but had a range of opinion on optimal therapy for many clinical scenarios, which reflects current knowledge of the benefits of adjuvant therapy for NNBC.

Adult↗
PubMed1994

Adaptation in brain glucose uptake following recurrent hypoglycemia.

Brain glucose metabolism is impaired during hypoglycemia, but, if sustained, brain metabolism reverts to normal in animal models--data in man are lacking. We tested the hypothesis that adaptations occur to allow maintenance of normal rates of brain glucose uptake (BGU) following recurrent hypoglycemia in man. Twelve normal humans were studied over 4 days. On the initial day, arterial plasma glucose concentrations were decreased from 4.72 to 2.50 mmol/liter in five 0.56 mmol/liter steps. Cerebral blood flow, brain arteriovenous glucose difference, BGU, and cognitive function were quantitated at each step. BGU was initially impaired at the 3.61 mmol/liter glucose step (P = 0.04) and was antedated by increments in epinephrine that began at 4.16 mmol/liter (P = 0.03). The onset of hypoglycemic symptoms occurred during the 3.61 mmol/liter glucose step (P = 0.02), whereas tests of cognitive function generally deteriorated at the 3.05 mmol/liter step (P < 0.05). During the next 56 hr, mean glucose concentrations were kept at 2.9 +/- 0.1 mmol/liter and reached normal only during meals. The stepped clamp protocol was repeated beginning at 4.16 mmol/liter on the last day. No decrement in BGU was observed at any step; cognitive function was preserved until significantly lower glucose concentrations on the final day relative to the first (P = 0.04). Subjects remained asymptomatic of hypoglycemia until they reached a glucose concentration of 2.50 mmol/liter (P < 0.001 vs. day 1), while initial increments in all counterregulatory hormones were forestalled to lower glucose steps than on day 1. Therefore, adaptations occur that allow normal BGU and cerebral function to be maintained during recurrent systemic hypoglycemia. Counterregulatory events that should result in symptoms of hypoglycemia and increments in endogenous glucose production are prevented until extremely subnormal glucose concentrations.

Acclimatization↗
PubMed1992

Low-cost hepatitis B vaccine improves uptake among self-paying health-care students.

Advisory committees recommend hepatitis B (HBV) immunization for professional and student health-care workers. However, the currently licensed vaccines are expensive, and previous surveys have shown that few students (14%) have been immunized in Canada. A low-cost immunization program was offered to health-care students in order to determine whether the effectiveness of HBV immunization could be improved by substantially reducing the vaccine cost to recipients. The immunogenicity, side effects, and 3-dose completion rate of a low-cost Korean HBV vaccine were compared with a similar U.S.-made vaccine. A total of 922 postsecondary students enrolled in 6 health-care disciplines in Ottawa, Canada were surveyed for hepatitis-B immunization status. Nonimmunized students were subsequently offered HBV vaccine at total cost of $15 (Canadian), randomly allocated to receive 3 intramuscular doses of either Korean or U.S.-made plasma-derived HBV vaccine in a double-blind fashion, surveyed about side effects, and tested for hepatitis B surface antibody seroconversion. Only 12% of the 922 surveyed students had been previously immunized when vaccine was obtainable only at high cost. However, 66% of those not immunized participated in the vaccine trial and paid the $15 fee. Hepatitis-B surface antibody seroconversion (greater than or equal to 10 sample ratio units by radioimmunoassay) occurred in 291/311 (93.6%) and 299/310 (96.5%) of recipients of 3 doses of the Korean and U.S. vaccines, respectively (P = 0.10). There were no meaningful differences in vaccine adverse effects, and 92.6% of recipients of either vaccine completed 3 doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Effects of framing and level of probability on patients' preferences for cancer chemotherapy.

Although most clinicians agree that patients should be informed about treatment alternatives, little is known about the way patients perceive probabilistic information about treatment outcomes and how it influences the choices they make. The purpose of this study was to examine the influence of level and framing of probability on preferences for cancer treatment alternatives in which tradeoffs between quantity and quality of life are made. 129 healthy volunteers and 154 cancer patients indicated their preferences for a toxic treatment over a non-toxic treatment at varying survival probabilities. Subjects responded to questions in one of three randomly assigned conditions: (1) a positive frame in which the probability of survival was given; (2) a negative frame in which the probability of dying was given; and (3) a mixed frame in which the probability of surviving and dying were both given. The cancer patients' preferences for the more effective toxic treatment was significantly stronger than the healthy volunteers. Both groups were significantly influenced by the level of probability that was presented. Preferences for the toxic treatment were weaker when the chance of survival dropped below 50%. This weakening preference below 50% survival was enhanced for subjects who responded in the negative frame. A negative frame or probability level below 0.5 would seem to stimulate a "dying mode" type of value system in which quality of life becomes more salient in decision making than quantity of life. The implications in eliciting informed consent from patients are discussed.

Adolescent↗
PubMed1988

Lactational responses to dietary magnesium, potassium, and sodium during winter in Florida.

Forty-eight midlactation Holstein cows were used to evaluate dietary treatments arranged as a 4 x 2 x 2 factorial: .26, .38, .48, or .60% Mg, .24 or .62% Na, and 1.14 or 1.59% K. Supplemental Mg, K, and Na were supplied by feed-grade magnesium phosphate, potassium bicarbonate, or sodium chloride. All dietary treatments were equal in Ca and P. There were no effects of dietary Na or K on feed intake or milk production. Feed intakes were equal with .26, .38, and .48% Mg but declined 4.9% with .60% Mg. Milk yields responded curvilinearly to dietary Mg. Similarly, 4% FCM yields responded curvilinearly, increasing 7% with .48% Mg compared with .26% Mg then declining with .60% Mg. Milk fat percentages were unaffected by dietary Mg concentration, but milk fat yields responded curvilinearly. Milk protein percentages declined linearly as dietary Mg increased. Plasma Mg concentrations increased linearly from 2.52 to 2.68 mg/dl as dietary Mg increased. Renal fractional excretions of Ca responded curvilinearly as dietary Mg increased and decreased as dietary K increased. Results of this experiment suggested that current recommendations for dietary Mg do not maximize lactational performance. A companion laboratory experiment showed that feed-grade magnesium phosphate had less alkalizing capacity than two MgO sources.

Animals↗
PubMed1987

Eliciting preferences for alternative drug therapies in oncology: influence of treatment outcome description, elicitation technique and treatment experience on preferences.

Several methodologic issues arise in eliciting preferences for therapy. Examples are the selection of appropriate descriptions of treatment outcomes and of elicitation techniques. Of particular importance is the correspondence of patients' anticipated preferences for treatment to actual preferences once they have experienced treatment. Treatment outcome descriptions and elicitation techniques were compared for a hypothetical drug decision problem involving trade-offs between quality and quantity of life. Preferences of 54 cancer patients were elicited before, and 6 weeks following initiation of chemotherapy treatment. Patients' preferences were not influenced by the way information about side effects was presented, nor the stated probability of survival at high and moderate levels. A riskless rating technique produced different preferences from those of a risky treatment choice method. Although patients experienced significant toxicity following initiation of treatment, their preferences remained stable on retest. The results raise questions about the extent to which patients are willing, at the time of decision making, to trade off survival rate for improved quality of life.

Antineoplastic Agents↗
PubMed1985

Eliciting preferences for alternative cancer drug treatments. The influence of framing, medium, and rater variables.

In oncology there is increasing interest in the development of techniques to help patients choose between alternative therapies in ways that are consistent with their preferences. The purpose of this study was to examine some methodological problems associated with the elicitation of preferences. Preferences for alternative drug therapies were sought from 208 visitors to an open house at the Ontario Cancer Institute and from 216 university nursing students. Preferences were not significantly dependent on the sex, age or professional status of the respondents, nor on the medium used for elicitation of preferences (computer terminal versus pencil-and-paper questionnaire). In contrast, the importance of the way decision problems are framed was confirmed. Comparison of a positive frame (outcomes expressed as the probability of surviving) with a negative frame (outcomes expressed as the probability of dying) and a mixed frame (probabilities of surviving and dying were both given) pointed to the presence or absence of the word "survive" in the outcome description as the main source of framing bias. The framing effect was in the opposite direction to that hypothesized.

Adolescent↗
PubMed1983

Factors related to the early phase of rehabilitation following aortocoronary bypass surgery.

Physical and psychosocial functioning of 30 male patients prior to and 3 months following aortocoronary bypass surgery were compared. Relationships between rehabilitation outcome and selected physical, psychosocial, and health care system variables were examined. Although patients' perceptions of their health improved after surgery, there was little improvement in physical and psychosocial functioning, and vocational functioning declined. When the outcome variables were regressed on their possible explanatory variables, the variance in exercise tolerance and energy expenditure on household activities remained unexplained. Energy expenditure on postoperative leisure activities was related to fear of injury. Preoperative psychosocial functioning, depression, and postoperative perception of health explained postoperative psychosocial functioning. Postoperative perception of health dependent on the number of bypass grafts and spouse's/family's fear of patients' injury.

Activities of Daily Living↗
PubMedDate not supplied

Effectiveness of a pregnancy smoking cessation program.

OBJECTIVE: To evaluate two nursing approaches to promoting smoking cessation during initial antenatal visits. DESIGN: Experimental, with assignment to interventions using a random, alternate-day strategy and blind assessment of smoking at baseline, 1 month postintervention, 36 weeks' gestation, and 6 weeks postpartum. SETTING/PARTICIPANTS: 224 daily smokers, fewer than 31 weeks gestation, during first prenatal visit, at a teaching hospital antenatal clinic. INTERVENTIONS: An evening class providing guidance on a self-help program for 2 hours on a group basis or 20 minutes on an individual basis during the prenatal appointment. MAIN OUTCOME MEASURE: Smoking cessation, confirmed by urinary cotinine levels. RESULTS: All women assigned to the referral intervention received a referral, but none attended the classes. In contrast, 93% assigned to the immediate intervention received the intervention. The group receiving immediate intervention had two to three times higher rates of cessation at all follow-up periods, with significant differences at the 1-month follow-up. There were certain similarities between the groups. CONCLUSION: Cessation interventions should be administered during the first prenatal visit.

Adult↗
PubMedDate not supplied

Validation of a decisional conflict scale.

The study objective was to evaluate the psychometric properties of a decisional conflict scale (DCS) that elicits: 1) health-care consumers' uncertainty in making a health-related decision; 2) the factors contributing to the uncertainty; and 3) health-care consumers' perceived effective decision making. The DCS was developed in response to the lack of instruments available to evaluate health-care-consumer decision aids and to tailor decision-supporting interventions to particular consumer needs. The scale was evaluated with 909 individuals deciding about influenza immunization or breast cancer screening. A subsample of respondents was retested two weeks later. The test-retest reliability coefficient was 0.81. Internal consistency coefficients ranged from 0.78 to 0.92. The DCS discriminated significantly (p < 0.0002) between those who had strong intentions either to accept or to decline invitations to receive influenza vaccine or breast cancer screening and those whose intentions were uncertain. The scale also discriminated significantly (p < 0.0002) between those who accepted or rejected immunization and those who delayed their decisions to be immunized. There was a weak inverse correlation (r = -0.16, p < 0.05) between the DCS and knowledge test scores. The psychometric properties of the scale are acceptable. It is feasible and easy to administer. Evaluations of responsiveness to change and validation with more difficult decisions are warranted.

Aged↗