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Biomedical subjects

L A Turner

Publications and source records attributed to L A Turner.

At least 37 records · Page 2Linked to original sources
PubMed1994

Differential effects of halothane and isoflurane on contractile force and calcium transients in cardiac Purkinje fibers.

BACKGROUND: Halothane and isoflurane have been shown to differentially effect mechanisms of contraction in working myocardial fibers. The aim of this study was to compare effects of halothane and isoflurane on contractile force (CF) and Ca2+ transients in canine cardiac Purkinje fiber preparations. METHODS: Fiber preparations (n = 29) were superfused with Krebs-Ringer solution and stimulated at 40-60 pulses/min at 30 degrees C in the absence and presence of 0.55% and 1.01% isoflurane or 0.27% and 0.78% halothane. Isometric tension (CF), and intracellular Ca2+ transients (luminescence, L) were measured after microinjecting the Ca2+ sensitive photoprotein aequorin into Purkinje fibers. Peak CF and peak L, rate of rise (slope) of CF and L, time to attain peak CF and L, and duration of CF and L at half-peak CF and L, were measured at 5 mM extracellular CaCl2. Changes in peak CF and peak L also were measured during incremental increases in CaCl2 from 3.6 to 9.0 mM. RESULTS: Both anesthetics depressed peak CF and peak L and the rate of increase in peak CF and L in a concentration-dependent fashion, and effects of halothane were greater than those of isoflurane. Time to attain peak L and duration of L at half-peak L was decreased or unchanged by isoflurane and was increased by halothane, whereas time to attain peak CF and duration of CF at half-peak CF was shortened by both. The change in peak CF response as a function of the change in peak L with increasing extracellular CaCl2 was attenuated similarly by both halothane and isoflurane. CONCLUSIONS: Halothane depresses peak CF and Ca2+ transients and prolongs Ca2+ transients more than does isoflurane at equivalent minimum alveolar concentration in Purkinje fibers. This suggests Ca2+ concentration is differentially altered by anesthetics in this tissue. Peak CF at equivalent peak Ca2+ transients, however, appears to be attenuated similarly by both anesthetics. These differences in anesthetic effect are qualitatively similar to those found in cardiac tissue of other species. These findings add to our understanding of effects of volatile anesthetics on contractile properties and myoplasmic Ca2+ in cardiac Purkinje fibers.

Animals↗
PubMed1994

Effect of strategy and attribution training on strategy maintenance and transfer.

Effects of rehearsal strategy and attribution training on strategy use and transfer were investigated with 12-year-old students who had mild or moderate mental retardation. Students were randomly assigned to four groups that received either rehearsal strategy training, attribution training, combined rehearsal and attribution training, or no training. Both rehearsal strategy groups outperformed the others at maintenance. However, at transfer, only the combined strategy and attribution group performed better than the attribution and control groups. For students with mental retardation, strategy transfer was enhanced by the addition of attributional training.

Child↗
PubMed1993

Factors predictive of follow-up clinic attendance and developmental outcome in a regional cohort of very low birth weight infants.

This population-based, retrospective cohort study of very low birth weight infants was undertaken to: 1) identify factors associated with nonattendance for follow-up, 2) estimate the prevalence of cerebral palsy at age > or = 18 months, and 3) model the prognostic association between prenatal and perinatal risk markers and cerebral palsy. The sample included 496 surviving very low birth weight infants born in 32 hospitals in Southwest Ontario between January 1982 and December 1986. Multivariate analyses were performed using the proportional odds regression model. Loss to follow-up was more likely among those with mothers < 20 years of age, those with unmarried mothers, and those not born in a tertiary center. Loss to follow-up was less likely for those with neonatal anemia and those of lower birth weight. Motor development of the 369 children who were followed at least 18 months was classified into one of three categories: normal, suspect, or cerebral palsy. Multivariate analysis revealed that factors predictive of poorer outcome were intraventricular hemorrhage, unmarried mother, male sex, recurrent apnea, and hydrocephalus. The finding that unmarried status was associated with loss to follow-up and was also an important predictor of cerebral palsy suggests that it is important for follow-up clinics to identify ways of assisting this population to remain in contact with the clinic.

Adult↗
PubMed1993

Health work force planning in the 90s, Part II: Enough in the right place at the right time?

The focus of this discussion has been on achieving a distribution of health care professionals that meets the objective of making health services available to the total population. The need for a systematic approach to planning, not only for the health care work force, but for the system in general, has been recognized as the highest priority for the health care systems of industrialized countries for over a decade. Overall, the goal of health care work force planning the world over is "to provide the right type of education and training for the right number and type of people needed to render effectively and safely the right types of service when and where required by the population." What is needed is a readiness to evaluate existing service delivery models, to retain those found to be effective and efficient, and to re-direct resources from outdated or ineffective strategies into new approaches found to better meet this goal. We need to envision the health care work force as a whole; work toward making it as efficient as possible, and thereby maintain our national commitment to universal health care.

Canada↗
PubMed1993

Work force planning in the 90s, Part I: Efficiency, economy and political will--the need for a new approach.

Critical to health services management in today's economic climate is efficient utilization of our costly and sometimes limited supply of health care professionals. This two-part article gives an overview of current issues in health care work force planning in Canada. In Part I, the problems of estimating current supply are discussed. Needs-based and demand-based forecasting are contrasted. Comprehensive needs-based planning is recommended and changes needed in order to move toward this type of planning are discussed. In Part II, the maldistribution of health care professionals and various corrective measures within the context of needs-based comprehensive planning are discussed.

Canada↗
PubMed1993

Antibodies to hydrocortisone in reagent red cells causing positive antibody screening tests.

When a patient's serum contains a temperature-independent antibody reacting with all antibody screening and antibody identification panel cells but with few or no units of blood used for crossmatching, one should suspect an antibody against a constituent of the suspension medium of the reagent blood cells. This observation is confirmed by negative reactions with a) washed reagent cells or b) another manufacturer's cells that do not contain the same additives. Two patients are described with antibodies to hydrocortisone that are present in one manufacturer's antibody screening cells and identification panels. The hydrocortisone was added by the manufacturer to prevent hemolysis of the reagent red cells. The patient's antibodies were IgM, complement independent, and nonneutralizable by prior incubation with hydrocortisone. The addition of hydrocortisone to other manufacturers' reagents converted previously negative reactions to the same level of positivity as was seen with the reagent from the index manufacturer. Antibodies to reagent constituents can cause delays in finding compatible blood. It is suggested that manufacturers delete irrelevant additives or those of questionable necessity from their reagents.

Aged↗
PubMed1993

Transient negative dromotropic effects of catecholamines on canine Purkinje fibers exposed to halothane and isoflurane.

The time-dependent effects of catecholamines in combination with volatile anesthetics on conduction velocity of canine Purkinje fibers were investigated to evaluate a controversial older hypothesis that the arrhythmogenic interaction between epinephrine and halothane may involve abnormal conduction. Two groups of 12 in vitro preparations were stimulated at 150 beats/min. In the first group, 5 microM epinephrine by itself did not alter conduction velocity over a 10-min period from a control mean value of 1.97 +/- 0.08 m/s. However, 5 microM epinephrine, in the presence of either 0.4 mM halothane or 0.4 mM isoflurane, reduced conduction velocity (P < or = 0.01) by about 10-15% within 3-5 min, with recovery toward control by 10 min. The mean conduction velocity at the 4th minute of exposure, in the presence of halothane and epinephrine (1.65 +/- 0.11 m/s), was lower (P < or = 0.01) than that obtained in the presence of isoflurane and epinephrine (1.74 +/- 0.07 m/s). In the second group, both 5 microM norepinephrine and 5 microM epinephrine, in the presence of either anesthetic, depressed conduction velocity (P < or = 0.01) with a similar time course. The reduction of conduction velocity with norepinephrine was less (P < or = 0.01) than that with epinephrine, and again the decreases of conduction velocity were larger (P < or = 0.01) with 0.4 mM halothane than 0.4 mM isoflurane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

The effects of halothane and isoflurane on slowly inactivating sodium current in canine cardiac Purkinje cells.

The effects of halothane (0.45 and 0.9 mM, equivalent to 0.7 and 1.5 vol%, respectively) and isoflurane (0.56 and 1.23 mM, equivalent to 0.9 and 2.0 vol%) on slowly inactivating Na+ current were examined by whole-cell voltage-clamp techniques. This approach allows evaluation of the role of anesthetic inhibition of inward Na+ current on the action potentials of canine Purkinje fibers isolated from the false tendons. Cells were superfused with Tyrode's solution containing nifedipine and Ni2+ to block Ca2+ channel currents and internally dialyzed with Cs+ to block outward K+ currents. Veratridine (0.5 microM) was used throughout the experiments to enhance the slow Na+ current. Na+ current was elicited by depolarizing pulses from a holding potential of -100 mV to stepwise (10 mV increments) more positive membrane potentials and measured at 200 ms after initiation of the voltage pulse before, during, and after exposure to anesthetics. Slowly inactivating Na+ current showed threshold activation at -80 mV and peak activation around -55 to -40 mV. This current was abolished by 5 microM tetrodotoxin, showing the characteristic feature of Na+ channel current. Halothane and isoflurane depressed the amplitude of slowly inactivating Na+ current in a concentration-dependent manner and did not shift the current-voltage relationship for slow Na+ current activation. There was no significant difference between the sensitivities of slow Na+ current to halothane or isoflurane at equianesthetic concentrations. Inhibition of slow inward Na+ current may contribute to the marked decrease of action potential duration produced by volatile anesthetics in false tendon Purkinje fibers but does not account for the larger decreases of duration produced by isoflurane than halothane.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1993

Actions of halothane and isoflurane on Purkinje fibers in the infarcted canine heart: conduction, regional refractoriness, and reentry.

The actions of halothane (HAL) and isoflurane (ISO) on conduction and regional refractoriness were studied in infarcted canine hearts to compare their effects on reentry in vitro. In two anesthetic groups of 8 hearts, high and low dose effects were assessed using action potentials recorded from Purkinje fibers located in the nonischemic and ischemic regions. An extrastimulus technique was used to determine the relationship between delay of conduction of premature impulses into the more refractory ischemic region and induction of reentrant responses. At high doses (HAL 0.60 mM and ISO 0.64 mM, approximately 2.3 minimum alveolar anesthetic concentration [MAC]) both anesthetics decreased (P < or = 0.05) the effective refractory period for direct intracellular stimulation of nonischemic fibers (local ERP, initial control: 294 +/- 8 ms); the decrease with HAL (-29 +/- 6 ms) was smaller (P < or = 0.05) than with ISO (-50 +/- 7 ms). HAL and ISO also decreased (P < or = 0.05) the coupling interval of the earliest premature impulse which conducted into the infarct (system effective refractory period [SERP], control: 301 +/- 7 ms) by -31 +/- 11 and -44 +/- 8 ms, respectively. In contrast, the functional refractory period (FRP) in the ischemic region (control:354 +/- 4 ms) was increased by HAL (26 +/- 8 ms; P < or = 0.05) but decreased by ISO (-14 +/- 4 ms, P < or = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Actions of volatile anesthetics on ischemic and nonischemic Purkinje fibers in the canine heart: regional action potential characteristics.

The effects of halothane, isoflurane, and enflurane on proximal (false tendon) and distal (apical) Purkinje fibers were measured in vitro in infarcted canine hearts to assess their effects on action potentials of fibers located within the nonischemic and ischemic regions, respectively. High- and low-dose anesthetic effects were evaluated in three groups of eight preparations and compared to changes occurring at identical times in eight infarcted control preparations. Under control conditions in all groups, the action potential duration at 90% repolarization (APD90, mean +/- SEM) of ischemic distal fibers (396 +/- 9 ms) was longer (P < or = 0.01) than that of nonischemic proximal fibers (344 +/- 5 ms) and the ischemic fibers exhibited (P < or = 0.05) reduced maximum diastolic potential, amplitude, and Vmax relative to nonischemic fibers. Halothane (0.25 and 0.6 mM), isoflurane (0.4 and 0.8 mM), and enflurane (0.8 and 1.6 mM) produced dose-dependent decreases of nonischemic fiber APD90 with less decrease (P < or = 0.01) of ischemic fiber APD90 and thereby accentuated (P < or = 0.05) regional differences of APD90 at high dose. The decreases of nonischemic fiber APD90 were greater (P < or = 0.01) for 0.8 mM (2.9 minimum alveolar anesthetic concentration [MAC]) isoflurane (-95 +/- 5 ms) and 1.6 mM (2.5 MAC) enflurane (-79 +/- 12 ms) than for 0.6 mM (2.2 MAC) halothane (-41 +/- 3 ms). Isoflurane increased the pathologic difference (ischemic > nonischemic) between the repolarization times (APD90) of Purkinje fibers in the infarcted heart more (P < or = 0.05) than halothane.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1992

Twelve-month comparison of two treatments for erectile dysfunction: self-injection versus external vacuum devices.

This study directly compared two nonsurgical treatments for erectile dysfunction, self-injection of papaverine/phentolamine and external vacuum devices, in terms of usage rates, effectiveness, side effects, dropout rates, and impact on patient sexual and psychologic functioning. Both alternatives were regularly, successfully, and safely used by patients, though dropout rates were higher for self-injection. Both produced erections of improved quality, and effected sustained improvements in frequency of intercourse, orgasm, and sexual satisfaction. Spontaneous erections also improved with both treatments. General psychiatric symptomatology was decreased, and anxiety was improved. There were no differences between the two treatments in sexual or psychologic impact. Relative contraindications and esthetic considerations are presented.

Coitus↗
PubMed1992

Through the eyes of women: the sexual and psychological responses of women to their partner's treatment with self-injection or external vacuum therapy.

We prospectively delineated and contrasted the sexual, marital and psychological responses of women to their partner's use of 2 treatments for erectile dysfunction: 1) self-injection of papaverine and phentolamine, and 2) vacuum tumescence therapy. The women were assessed at 5 points during a 12-month period with psychometric questionnaires and clinical interviews. Statistical analysis indicated that the women responded equally well to both treatments. They demonstrated significant increases in frequency of intercourse, sexual arousal, coital orgasm and sexual satisfaction. No significant changes were noted on the psychometric questionnaires. The women reported feeling more at ease in their relationships and characterized sex as more leisurely, relaxed and assured. Negative responses focused on the lack of spontaneity and hesitation about initiating sex. Self-injection and vacuum pump therapy restore potency in men and secondarily facilitate improved sexual function in women.

Coitus↗
PubMed1992

Differential effects of halothane, enflurane, and isoflurane on Ca2+ transients and papillary muscle tension in guinea pigs.

These studies were designed to examine the effects of inhalational anesthetics on rapid changes in myocardial intracellular Ca2+ and Ca2+ sensitivity of the contractile apparatus. The effects of halothane, enflurane, and isoflurane on rapid changes in intracellular Ca2+ (Ca2+ transients as measured with bioluminescent protein aequorin) and contractile characteristics were compared in guinea pig right ventricular papillary muscles. In addition to examination of their potencies at equianesthetic concentrations, the effects of these agents on alterations in Ca2+ sensitivity at myofilaments were also investigated. The negative inotropic effects of halothane (0.65 and 1.15%) and enflurane (1.0 and 2.2%) were dose-dependent and closely related to a decrease in Ca2+ transients. In the presence of isoflurane (0.77 and 1.6%), the contractile force decreased in a dose-dependent manner, but the decrease was significantly less as compared to that with equianesthetic concentrations of halothane and enflurane. An additional feature observed in the presence of isoflurane was a dissociation between intracellular Ca2+ availability and contractile force. Although the magnitude of the Ca2+ transients did not change when the percentage of isoflurane was increased from 0.77 to 1.6, the contractile force decreased. Because of these findings, the effects of halothane (1.2%), enflurane (2.2%), and isoflurane (1.6%) on the relationship between intracellular Ca2+ and tension developed in the papillary muscle were examined in order to assess myofibrillar responsiveness to Ca2+. The results indicate that only isoflurane slightly but significantly shifted the Ca2+/isometric tension curve toward higher intracellular Ca2+ concentrations; no differences were observed in the absence and presence of equianesthetic concentrations of halothane and enflurane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

External vacuum devices in the treatment of erectile dysfunction: a one-year study of sexual and psychosocial impact.

This prospective study assessed the sexual and psychosocial effects of 12 months' use of an external vacuum device in the treatment of erectile dysfunction. Results showed that the external vacuum device produced erections sufficient for intercourse in 87% of the men in our sample. The dropout rate was only 20% over the 12-month period. Use of the external vacuum device was associated with improvements in men's and their partners' sexual functioning. These improvements included erections of better quality, increased partner arousal, and increased frequency of orgasm and sexual satisfaction for men and women. The external vacuum device was also associated with decreases in general psychiatric symptomatology for men. Similar improvements in psychological functioning were not found for partners. Side effects and factors in patient and partner acceptance of the external vacuum device are discussed.

Adaptation, Psychological↗
PubMed1991

Sexual, psychological, and marital impact of self-injection of papaverine and phentolamine: a long-term prospective study.

This prospective study assessed the long-term effects of self-injection of papaverine hydrochloride and phentolamine mesylate along several critical domains for 42 men and 26 partners. Over the course of one year, men were, on average, injecting themselves five times monthly, with 84% of these injections producing satisfactory erections. Treatment resulted in statistically significant improvements in quality of erection, sexual satisfaction, frequency of intercourse, and coital orgasm. The women also demonstrated significant improvement in sexual satisfaction, arousal, frequency of intercourse, and coital orgasm. Decreases in general psychiatric symptomatology were apparent for men but not for partners. The dropout rate was 57%. The common side effects of treatment were development of fibrotic nodules (26%), abnormal liver function values (30%), and bruising (19%). We conclude that self-injection should be considered among the accepted treatments for erectile dysfunction. It does appear to enhance the sexual lives of men and women when the treatment is efficacious and the couple is motivated to utilize it.

Adaptation, Psychological↗
PubMed1991

Halothane, enflurane and isoflurane on abnormal automaticity and triggered rhythmic activity of Purkinje fibers from 24-hour-old infarcted canine hearts.

The effects of inhalation anesthetics halothane, enflurane, and isoflurane on spontaneous impulse initiation (automaticity) and triggered sustained rhythmic activity were examined in Purkinje fibers derived from normal (n = 38) and 24-h-old infarcted canine hearts (n = 27) to further understanding of their influence on the cellular mechanisms underlying generation of cardiac arrhythmias. Purkinje fibers from normal or infarcted hearts were superfused with modified Krebs' solution (37 degrees C) with or without epinephrine (2 or 15 microM) and equilibrated with a 97% O2-3% CO2 gas mixture (control). Transmembrane action potentials were recorded using conventional microelectrode techniques, and Purkinje fibers were exposed to anesthetic concentrations equivalent to 2.0 MAC. Normal Purkinje fibers were not spontaneously active unless exposed to epinephrine. All anesthetics (enflurane greater than halothane, isoflurane; P less than 0.05) increased automaticity of normal Purkinje fibers exposed to either epinephrine concentration. Partially depolarized Purkinje fibers from infarcted hearts were either spontaneously active or were quiescent. For ischemic fibers that beat spontaneously, abnormal automaticity was sustained (duration greater than 300 s) or periodic (duration less than 300 s). Sustained abnormal automaticity was elicited by epinephrine (15 microM) in some quiescent partially depolarized fibers. None of the anesthetics affected the rate of sustained abnormal automaticity, regardless of whether the induction of such automaticity required epinephrine, nor did anesthetics significantly affect the duration of trains of periodic abnormal automaticity. Finally, quiescent, partially depolarized Purkinje fibers were tested for triggered rhythmic activity during pacing at a cycle length of 800 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1991

Opposing effects of diacetyl monoxime on contractility and calcium transients in isolated myocardium.

Isolated, perfused guinea pig hearts were used to determine the effects of diacetyl monoxime (DAM) on atrial rate, atrioventricular conduction time (AVCT), and left ventricular peak systolic pressure (LVSP). Contractile force and calcium transients were also monitored in isolated papillary muscles injected with aequorin in the absence and presence of ryanodine (RYA). In the isolated heart, 0.2-5 mM DAM caused significant dose-dependent decreases in LVSP (up to 51%) without change in atrial rate and AVCT. DAM (10 mM) produced a small slowing of atrial rate, no change in AVCT, and a 76% decrease in LVSP; 20 and 30 mM DAM further reduced LVSP, decreased atrial rate 38%, and produced AV dissociation. In isolated, paced papillary muscles, 2, 10, and 30 mM DAM decreased contractile force 27, 58, and 87%, respectively, while calcium transients increased by -9, 38, and 225%, respectively. All cardiac effects of DAM were readily reversible. RYA (1 microM) alone and with DAM (30 mM) decreased contractile force by 30 and 99%, respectively and decreased calcium transients by 59 and 74%, respectively. This study shows that low concentrations of DAM have little effect on electrical activity but greatly depress contractility and modify intracellular handling of calcium.

Animals↗