Biomedical subjects

G Anderson

Publications and source records attributed to G Anderson.

At least 127 records · Page 7Linked to original sources

PubMed1996

Cervical cancer screening: are the 1989 recommendations still valid? National Workshop on Screening for Cancer of the Cervix.

Although screening for cervical cancer has been shown to be effective in reducing the morbidity and mortality associated with this disease, and despite many attempts to encourage the development of provincial programs, as of 1995 no province had a comprehensive screening program for cervical cancer. Participants at the Interchange '95 workshop, held in Ottawa in November 1995, reviewed the recommendations of the 1989 National Workshop on Screening for Cancer of the Cervix and identified factors that have impeded their implementation. Participants discussed the need for comprehensive information systems, quality control and strategies to increase recruitment of unscreened and underscreened women. They concluded that the formation of a Cervical Cancer Prevention Network involving key stakeholders will facilitate the development and implementation of provincial programs to ensure optimal screening. They agreed that, in the interim, recommendations for practising physicians should remain as they were following the 1989 workshop.

Canada↗

PubMed1996

Intracellular signaling pathways involved in the induction of apoptosis in immature thymic T lymphocytes.

We describe a novel technique for studying the signaling pathways that control thymocyte negative selection which maintains the essential interactions between thymocytes and thymic stromal cells. Bisected lobes from newborn mouse thymus are maintained in organ culture for up to 36 h, and the thymocytes analyzed by flow cytometry. Inclusion of [3H]inositol during culture allows measurements of phosphatidylinositol 4,5-biphosphate (PtdIns(4,5)P2) hydrolysis and inositol phosphate accumulation. Using this technique we have compared the thymocyte responses induced by anti-CD3, anti-Fas, Con A, and beta-adrenergic stimulation. We show that PtdIns(4,5)P2 hydrolysis precedes anti-CD3-induced thymocyte apoptosis, but not the apoptosis induced by anti-Fas. In contrast, Con A stimulates PtdIns(4,5)P2 hydrolysis, but does not induce thymocyte apoptosis. Anti-CD3, anti-Fas, and Con A all fail to change thymic cAMP levels, but beta-adrenergic stimulation causes a large increase in intracellular cAMP, and agents that elevate cAMP induce thymocyte apoptosis. Inhibition of protein synthesis (with cycloheximide or emetine) prevents the apoptosis induced by anti-CD3 and elevated cAMP, but not that induced by anti-Fas, whereas protease inhibition (with 3,4-dichloroisocoumarin or N(alpha)-tosyl-phenylalanine chloromethyl ketone) prevents the apoptosis caused by all of the effective stimuli. These results offer three important conclusions. First, activation of a variety of different signaling pathways can bring about thymocyte apoptosis. Second, ligation of the thymocyte TCR/CD3 complex provokes PtdIns(4,5)P2 hydrolysis, but signaling through this pathway alone does not necessarily lead to apoptosis. Third, by whichever signaling pathway the response is initiated, the activity of one or more protease enzymes appears to form an essential component in the final common pathway leading to apoptosis.

Adrenergic beta-Agonists↗

PubMed1996

Elevated cerebrospinal fluid corticotropin-releasing factor in Tourette's syndrome: comparison to obsessive compulsive disorder and normal controls.

Stress- and anxiety-related fluctuations in tic severity are cardinal features of Tourette's syndrome (TS), and there is evidence for involvement of noradrenergic mechanisms in the pathophysiology and treatment of the disorder. To examine further the pathobiology of this enhanced vulnerability to stress and anxiety, we measured central activity of corticotropin-releasing factor (CRF) in patients with TS and the related condition, obsessive compulsive disorder (OCD). Lumbar cerebrospinal fluid (CSF) was obtained in a standardized fashion for measurement of CRF from 21 medication-free outpatients with TS, 20 with OCD, and 29 healthy controls. The TS patients had significantly higher levels of CSF CRF than both the normal controls and the OCD patients. However, there was no difference in CSF CRF between the OCD patients and the normal controls. Group differences in CSF CRF were unrelated to current clinical ratings of depression, anxiety, tics, and obsessive compulsive behaviors. Although the functional significance of this finding remains to be elucidated, these results are consistent with the hypothesis that stress-related neurobiological mechanisms may play a role in the pathobiology of TS.

Adolescent↗

PubMed1996

A cost-effectiveness evaluation of 3 antimicrobial regimens for the prevention of infective complications after abdominal surgery.

OBJECTIVE: To measure the cost and effectiveness of 3 established antimicrobial regimens for the prevention of infective complications after abdominal surgery. DESIGN: A prospective randomized trial was performed involving a total of 1070 patients undergoing abdominal surgery. SETTING AND PATIENTS: All patients having upper gastrointestinal tract, colorectal, appendiceal, or biliary surgery at a major teaching hospital in Melbourne, Australia, were considered for entry into the study. INTERVENTIONS: Patients were randomized prior to surgery to receive a single dose of cefotaxime sodium (1 g), ticarcillin plus clavulanic acid (3.1 g), or ceftriaxone sodium, (1 g). All drugs were given intravenously at the start of anesthesia. MAIN OUTCOME MEASURES: Rates of major wound infections, minor wound infections, other wound problems, and other infective complications. The acquisition and administrative costs of the drugs used and the costs of the infective complications were measured. RESULTS: A Total of 1070 patients were entered into the study. Major wound infections occurred in 21 patients (2.0%). Twenty-five patients (2.3%) developed a minor wound infection. Other infective complications developed in 107 patients. There were significantly fewer minor wound infections in the ceftriaxone-treated group as compared with the other 2 groups. There was no differences in the frequency of major wound infections, other wound problems, or other infective complications. The acquisition costs of cefotaxime and ticarcillin plus clavulanic acid were less than those of ceftriaxone. The estimated cost of treating the infective complications in the group of patients who received ticarcillin plus clavulanic acid ($128,039) was greater than the cost associated with the groups being treated with cefotaxime ($91,243) or ceftriaxone ($96,095). CONCLUSIONS: The study indicates that each of the 3 regimens was associated with highly satisfactory control of postoperative infective complications after abdominal surgery. On the basis of the estimated costs of infective complications, cefotaxime and ceftriaxone appear equally effective for the prevention of infective complications after abdominal surgery. Acquisition costs for cefotaxime were lower and it is recommended as the preferred agent on this basis.

Anti-Bacterial Agents↗

PubMed1996

Attenuation of vasospasm and capillary no-reflow by ischemic preconditioning in skeletal muscle.

Vasospasm and capillary no-reflow are common complications following replantation and free flap transfer. The purpose of the present study was to clarify whether vasospasm and capillary no-reflow which are induced by prolonged warm ischemia/reperfusion can be attenuated by ischemic preconditioning in the vascular isolated cremaster muscle model. Male Sprague-Dawley rats were anesthetized with pentobarbital. Arteriole diameter and capillary perfusion were measured utilizing intravital microscopy. In the control group, the cremasters sustained 4-hour warm global ischemia followed by 60-minute reperfusion. In the ischemic preconditioning group, the cremasters were subjected to one cycle of 45-minute ischemia followed by 15-minute reperfusion prior to 4-hour warm global ischemia followed by 60-minute reperfusion. The results from this experiment showed that ischemic preconditioning significantly attenuated ischemia/reperfusion-induced vasospasm and capillary no-reflow which occur early during reperfusion after prolonged warm ischemia in skeletal muscle. The mechanism of this phenomenon remains to be elucidated.

Animals↗

PubMed1996

The stability and persistence of mutualisms embedded in community interactions.

In this paper we argue that two-species models of mutualism may be oversimplifications of the real world that lead to erroneous predictions. We present a four-species model of a pollination mutualism embedded in other types of community interactions. Conclusions derived from two-species models about the destabilizing effect of mutualisms are misleading when applied to the present scenario; although the mutualisms are locally destabilizing, the effect is more than canceled by an increased chance of feasibility. The crucial difference is the interaction of the mutualists with other species in a larger web. Furthermore, community persistence (without unrealistic population explosion), arguably a superior ecological criterion, is greatly enhanced by the presence of mutualisms. Therefore, we predict that mutualisms should be common in the real world, a prediction matching empirial findings and in contrast to the predictions from local stability analysis of basic two-species models. This method of stabilizing a mutualism appears superior in some ways to the often-used method of introducing density dependence in the strength of the mutualism, because it permits obligate mutualisms to exist even at low densities, again matching empirical findings. Lastly, this study is an example of how complex model assemblages can behave qualitatively differently from analogous simpler ones.

Animals↗

PubMed1996

Distribution of prescription drug exposures in the elderly: description and implications.

Using data from a comprehensive prescription drug benefit program in British Columbia, we studied the distribution of prescription drug expenditures and exposures in the community-dwelling elderly over a 1-year period. Overall, 84% of the population was exposed to at least one prescription drug. The 11% of individuals with the highest level of use accounted for 50% of total drug expenditures. Individuals 65 to 74 years of age were exposed to a median of 2.2 different drugs during the year compared to a median of 3.8 for those 75 years of age and over. Twenty-four percent of the 65- to 74-year-old population were exposed to six or more different drugs during a 1-year period compared to 37% of the 75 years and over population. Central nervous system and cardiovascular drugs were most commonly responsible for multiple drug exposures. Forty-eight percent of the individuals exposed to six or more different drugs received prescriptions from three or more different physicians. In British Columbia, 98% of the elderly receiving six or more different drugs received at least one prescription from a general practitioner or a family practitioner.

Aged↗

PubMed1996

Approached to monitoring the results of long-term disease prevention trials: examples from the Women's Health Initiative.

We contrast monitoring therapeutic trials with monitoring prevention trails. We argue that in monitoring prevention trials one should place more emphasis on formally defined global measures of health, not simply on a single targeted disease, particularly when an intervention may reduce the incidence of some diseases but increase the incidence of others. We describe one approach, illustrated by the Women's Health Initiative. For each of several sets of hypothetical interim results ("scenarios"), members of the Data and Safety Monitoring Committee (DSMC) were asked whether they would continue or stop the trial. In parallel with this exercise, various statistical methods of monitoring that are based on (1) the primary targeted disease, (2) a combination of various disease outcomes, or (3) a mixture of both were applied to these scenarios. One objective was to find a statistical approach that mirrors the majority view of the DSMC. A second objective was to stimulate discussion among DSMC members in preparation for their task of monitoring the trial as the real data become available. We found that no single method fully matched the majority vote of the DSMC. However, a mixed approach requiring the primary outcome to be significant and the global index to be "supportive," with separate monitoring of adverse effects, corresponded with the majority vote quite well. This approach maintains the emphasis on the primary hypothesis while assuring that broader safety and ethical issues of multiple diseases are incorporated.

Bayes Theorem↗

PubMed1996

Involvement of LFA-1/ICAM-2 adhesive interactions and PKC in activation-induced cell death following SEB rechallenge.

Ligation of T-cell receptor (TCR) causes mature T cells to proliferate or, on re-exposure to antigen, can cause them to die by activation-induced cell death (AICD). In proliferative responses, costimulatory and adhesive interactions are required and activation of protein kinase C (PKC) has been shown to be essential. Whether or not interactions involving costimulatory signals and PKC have a role in facilitating AICD remains unclear. Here we have examined the role of CD28/B7 and leucocyte function associated antigen-1 (LFA-1)/intracellular adhesion molecule (ICAM) mediated interactions in AICD triggered by staphylococcal enterotoxin B (SEB) in murine lymph node T cells. We show that, after a primary proliferative response to SEB, LFA-1/ICAM-2 adhesive interactions can play a part in AICD following SEB rechallenge, while B7 and ICAM-1 mediated interactions are not essential for this process. In addition, using a highly selective PKC inhibitor, Ro31.8425, we show that PKC activation is essential for the regulation of AICD by SEB rechallenge.

Animals↗

PubMed1996

Half-life of nitric oxide in aqueous solutions with and without haemoglobin.

Nitric oxide (NO) has been linked to many regulatory functions in mammalian cells. Studies of NO release are hampered by the short half-life of the molecule. In the blood, NO disappears within seconds because it binds avidly with haemoglobin (Hb). The relationship between Hb concentration and NO disappearance, however, has not been described. In this study we utilized an amperometric NO sensor (WPI, Sarasota, FL) to monitor continuously the disappearance of NO from an aqueous solution when Hb (free or as red blood cells) was added. The calibration and linearity of the NO sensor was checked frequently using a chemical reaction to generate a known concentration of NO. An aliquot of NO solution (prepared from authentic gas) was added to a glass beaker containing 20 ml saline to generate NO concentration of approximately 1200 nM. Under our experimental conditions (PO2 = 40 mmHg), NO concentration fell slowly over 20 min with a half-life of 445 s. However, when haemoglobin was added, NO disappeared rapidly in proportion to Hb concentration. The results suggest that rapid binding of NO to Hb occurs in a 4:1 ratio. The maximum rate constant of NO disappearance due to binding with Hb was 2 x 10(5) M-1 s-1. The 4:1 binding ratio between NO:Hb may be used as a tool to quantitate NO release in some biological assays. The study supports the notion that NO acts as an autocoid because it disappears rapidly in the presence of Hb and is not likely to act as a circulating humoral substance. The NO sensor was useful for monitoring of NO concentration in Hb free solutions, but its response time limits its use in blood.

Animals↗

PubMed1996

Parental presence during induction of anesthesia. A randomized controlled trial.

BACKGROUND: To determine whether parental presence during induction of anesthesia is an effective preoperative behavioral intervention, a randomized controlled trial with children undergoing outpatient surgery was conducted. METHODS: Eighty-four children were randomly assigned to a parent-present or parent-absent group. Using multiple behavioral and physiologic measures of anxiety, the effect of the intervention on the children and their parents was assessed. Predictors for the response to the intervention were examined using multivariate linear regression analysis. RESULTS: When the intervention group (parent-present) was compared to the control group (parent-absent), overall there were no significant differences in any of the behavioral or physiologic measures of anxiety tested during induction of anesthesia. Using the child's serum cortisol concentration as the outcome, parental presence, the child's age and baseline temperament, and trait anxiety of the parent, were identified as predictors of the child's anxiety during induction. Analysis of variance demonstrated that three groups showed diminished cortisol concentrations with parental presence: children older than 4 yr (P = 0.001), children whose parent had a low trait anxiety (P = 0.02), and children who had a low baseline level of activity as assessed by temperament (P = 0.05). CONCLUSIONS: Children who were older than 4 yr or those with a parent with a low trait anxiety or who had a low baseline level of activity/temperament benefited from parental presence during induction.

Anesthesia↗

PubMed1996

Patterns of dissociation in clinical and nonclinical samples.

Research has consistently found elevated mean dissociation scores in particular diagnostic groups. In this study, we explored whether mean dissociation scores for different diagnostic groups resulted from uniform distributions of scores within the group or were a function of the proportion of highly dissociative patients that the diagnostic group contained. A total of 1566 subjects who were psychiatric patients, neurological patients, normal adolescents, or normal adult subjects completed the Dissociative Experience Scale (DES). An analysis of the percentage of subjects with high DES scores in each diagnostic group indicated that the diagnostic group's mean DES scores were a function of the proportion of subjects within the group who were high dissociators. The results contradict a continuum model of dissociation but are consistent with the existence of distinct dissociative types.

Adolescent↗

PubMed1996

Cellular interactions in thymocyte development.

Interactions between stromal cells and thymocytes play a crucial role in T cell development. The thymic stroma is complex and consists of epithelial cells derived from the pharyngeal region during development, together with macrophages and dendritic cells of bone marrow origin. In addition, fibroblasts and matrix molecules permeate the whole framework. It is now apparent that these individual stromal components play specialized roles at different stages of T cell differentiation. Thus, at the early CD4-8- stage of development, T cell precursors require fibroblast as well as epithelial cell interactions. Later, at the CD4+8+ stage, as well as providing low avidity TCR/MHC-peptide interactions, thymic epithelial cells have been shown to possess unique properties essential for positive selection. Dendritic cells, on the other hand, are probably efficient mediators of negative selection, but they may not be solely responsible for this activity. Alongside the functional roles of stromal cells, considerable progress is being made in unraveling the nature of the signaling pathways involved in T cell development. Identification of the pre-T cell receptor (pre-TCR) and associated signaling molecules marks an important advance in understanding the mechanisms that control gene rearrangement and allelic exclusion. In addition, a better understanding of the signaling pathways that lead to positive selection on the one hand and negative selection on the other is beginning to emerge. Many issues remain unresolved, and some are discussed in this review. What, for example, is the nature of the chemotactic factor(s) that attract stem cells to the thymus? What is the molecular basis of the essential interactions between early thymocytes and fibroblasts, and early thymocytes and epithelial cells? What is special about cortical epithelial cells in supporting positive selection? These and other issues are ripe for analysis and can now be approached using a combination of modern molecular and cellular techniques.

Animals↗

PubMed1996

Childhood physical and sexual abuse in patients with anxiety disorders and in a community sample.

OBJECTIVE: The authors investigated whether histories of childhood physical or sexual abuse were reported more frequently in a clinical sample of patients with anxiety disorders than in a matched community comparison sample. METHOD: A standardized interview with an extensive series of trauma probes was administered to 125 patients with DSM-IV anxiety disorders (panic disorder, social phobia, or obsessive-compulsive disorder) and to 125 age- and gender-matched subjects drawn from a random community sample. RESULTS: Childhood physical abuse was higher among both men (15.5%) and women (33.3%) with anxiety disorders than among comparison subjects (8.1%). Childhood sexual abuse was higher among women with anxiety disorders (45.1%) than among comparison women (15.4%) and was higher among women with panic disorder (60.0%) than among women with other anxiety disorders (30.8%). CONCLUSIONS: These findings confirm the association between anxiety disorders and reported childhood physical and sexual abuse and extend earlier findings by pointing to a particular association between sexual abuse and panic disorder in women.

Adolescent↗

PubMed1996

Mini ecosystem in space--preliminary experiment on board STS-77.

An enclosed ecosystem which is stable on Earth will behave differently when brought into space. Micro-gravity and radiation will affect the dynamics of material circulation or the activities of small creatures of the ecosystem. One series of space experiments aiming to address such issues was planned in the United States (It is termed as ABS--Autonomous Biological System) and Japanese group has been involved with cooperating with the analysis of the flight samples. Before the ecosystem will be on board Russian Space Station "Mir" later 1996 for 3 months, a preliminary flight was carried out in May 1996 on Space Shuttle (STS-77) for 10 days flight. It was the first of such experiments to fly one whole ecosystem in space.

Animals↗

PubMed1996

Trends in the utilization of noninvasive cardiac diagnostic tests in Ontario from fiscal year 1989/90 to 1992/93.

OBJECTIVE: To describe pattern of utilization of noninvasive cardiac diagnostic test in Ontario. DESIGN: Retrospective analysis using Ontario Health Insurance Plan (OHIP) administrative data. SETTING: Ambulatory care settings in Ontario. MAIN OUTCOME MEASURES: First, the volume of services and expenditures on electrocardiograms (ECG), ambulatory ECG, radionuclide angiocardiograms (RNA), echocardiograms, exercise stress tests (EST), and myocardial perfusion scintigrams from 1989/90 to 1992/93; second, the number and specialty of physicians performing these tests. MAIN RESULTS: Ontario spent $119 million on noninvasive diagnostic cardiology test in 1992/93, representing 2.67% of total OHIP expenditures. Expenditures on these procedures grew by 49.3 % over the four-year period, exceeding the overall OHIP growth rate, and was most rapid for nuclear cardiology and echocardiography. Changing demographics accounted fpr only a minor portion of expenditure growth. Second, age-adjusted utilization rates for EST, myocardial perfusion scintigraphy and RNA were higher for men, but sex differences tended to diminish over time. Third, utilization rates differed markedly by geographic region, and variations were greatest for nuclear medicine studies. Geographic variations tended to be attenuated over time. There was also wide variation in the frequency with which physicians performed Doppler studies with two-dimensional echocardiography. CONCLUSIONS: The use of noninvasive cardiac diagnostic test has grown rapidly in recent years. This growth may have been influenced by practice guidelines, by greater diffusion of, and access to, newer technology and by more testing in women. Wide regional variations suggest that clearer practice guidelines are needed concerning the appropriate use of noninvasive cardiac diagnostic investigations.

Angiocardiography↗

PubMed1996

Pharmacology of the pulmonary diseases.

The management of patients with pulmonary diseases may pose a challenge to the dentist. A thorough understanding of the major respiratory diseases is paramount to the successful treatment of these individuals. Morbidity and mortality for COPD patients have increased over time. There has been a decline in the number of smokers in the United States, but it may take two or three decades before health care systems notice a decrease in associated health care visits. Smoking tobacco is the major cause of COPD. Health care providers need to inform patients about smoking cessation programs and motivate them toward that end. The most important factor in preventing COPD is helping patients stop smoking. Mainstays in the treatment of COPD include inhaled anticholinergics and supplemental oxygen, when indicated. For certain patients, beta2-agonists, mucolytics, anti-inflammatory agents, and antibiotics are indicated. Asthma morbidity and mortality continue to rise significantly despite scientific advances and improved understanding of the disease and ability to render effective treatment. The reasons for this are not entirely clear. Asthma treatment has been revolutionized over the past decade. If proper preventive environmental measures and medications are prescribed, and the patients are carefully educated and complaint, their prognosis is good, and their condition should rarely require emergency treatment or hospitalization. The management of TB in the dental office involves several aspects of the disease. The dentist should be able to refer properly a patient with signs and symptoms of disease or to follow up on inadequate treatment. The medications taken for TB do not usually modify the dental management of the patient. The complications of the medications may, however, affect some drugs the dentist could prescribe. The resurgence of TB in the United States mandates that every dentist understand this disease and its importance.

Anti-Asthmatic Agents↗

PubMed1996

The association between participant characteristics and serum concentrations of beta-carotene, retinol, retinyl palmitate, and alpha-tocopherol among participants in the Carotene and Retinol Efficacy Trial (CARET) for prevention of lung cancer.

As part of the multicenter Carotene and Retinol Efficacy Trial (CARET) lung cancer prevention study, we investigated the associations of baseline demographic, health history, and nutritional intake information and the prerandomization serum concentrations of beta-carotene, retinol, retinyl palmitate, and alpha-tocopherol in a random subset of 1182 smokers and asbestos-exposed workers. Dietary intake was estimated via a self-administered food frequency questionnaire using the recently updated United States Department of Agriculture/National Cancer Institute database. In multiple regression analyses, supplemental vitamin use was the strongest predictor of each of the four analytes. There was a statistically significant inverse relationship between smoking and beta-carotene concentrations. Lower serum beta-carotene was associated with current smoking, higher daily cigarettes smoked, and more pack-years. Serum beta-carotene concentrations were higher with increasing years since stopping cigarette use, which suggests a biological mechanism for the lower serum concentration of beta-carotene in smokers. We found weak inverse associations between alcohol intake and the serum concentrations of both beta-carotene and retinol. As in previous reports, dietary intakes as measured by a food frequency questionnaire can only moderately predict serum concentrations of beta-carotene, retinol, retinyl palmitate, and alpha-tocopherol.

Alcohol Drinking↗