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Biomedical subjects

L A Wolfe

Publications and source records attributed to L A Wolfe.

At least 37 records · Page 2Linked to original sources
PubMed1995

Electrocardiographic and echocardiographic characteristics of female athletes.

This study examined electrocardiographic and echocardiographic characteristics of endurance- and resistance-trained female athletes. The subjects were 10 varsity caliber endurance-trained athletes, 10 resistance-trained athletes, and 10 nonathletes. Data collection included anthropometric measurements, VO2max, standard 12-lead ECGs and left ventricular dimensions measured by M-mode and two-dimensional echocardiography. For endurance-trained athletes, absolute left ventricular end-diastolic volume and values normalized for lean body mass were significantly greater than in nonathletes. An interstudy comparison of female vs male endurance-trained athletes from the same population also revealed significantly lower values for M-mode left ventricular mass expressed per kilogram of lean body mass in the former. Absolute and normalized wall thicknesses were not significantly greater in resistance-trained athletes compared to the other two groups. Wall thickness indexed for lean body mass was similar for the three groups. Sinus bradycardia was observed in all endurance athletes and in four resistance-trained athletes. ECG criteria were unreliable for the prediction of left ventricular enlargement. It appears that both female resistance- and endurance-trained athletes exhibit a lesser degree of enlargement of left ventricular wall thickness and mass than male athletes. A close relationship between skeletal and cardiac muscularity in resistance-trained athletes of both genders also was supported.

Adult↗
PubMed1994

Effects of pregnancy and chronic exercise on respiratory responses to graded exercise.

Effects of cycle ergometer conditioning (heart rate 143 +/- 2 beats/min, 25 min/session, 3 sessions/wk) during the second and third trimesters of pregnancy were studied in 18 healthy previously sedentary women. A nonexercising control group (n = 9) was also studied. Graded exercise tests were conducted for both groups at approximately 17, 27, and 37 wk of gestation and at 20 wk postpartum. Both groups exhibited augmented ventilatory responses to exercise throughout pregnancy. Significant aerobic conditioning effects observed in the exercised group between entry and third trimester of pregnancy testing included a 17% increase in oxygen pulse at peak exercise, reduction in the respiratory exchange ratio during standard submaximal exercise, and an increase in work rate at the onset of blood lactate accumulation. Onset of blood lactate accumulation did not change significantly in the control group. Respiratory exchange ratio at peak exercise was higher in postpartum tests compared with those conducted in late gestation in both groups. Peak postexercise lactate levels were also significantly lower in second and third trimesters of pregnancy testing compared with postpartum in the control group. This effect appeared to be prevented by physical conditioning in the exercised group. The study results support the hypothesis that moderate aerobic conditioning increases maximal aerobic power and the capacity for sustained submaximal exercise. Chronic exercise also appeared to help to preserve anaerobic working capacity in late gestation.

Adult↗
PubMed1994

Effects of acute and chronic maternal exercise on fetal heart rate.

Maternal-fetal effects of cycle ergometer conditioning (heart rate of 145 beats/min at 25 min/day for 3 days/wk) were studied during the second and third pregnancy trimesters. Subjects were 22 previously sedentary women and 16 nonexercising pregnant control women. Fetal heart rate (FHR) characteristics were studied before, during, and after 15 min of upright cycling at a maternal heart rate target of 145 beats/min at the end of both the second and third trimesters. Despite higher cycling power outputs in the exercised group, mean FHR responses were similar in both groups and conformed to 1) gradual increase in FHR baseline during exercise, 2) normal variability, and 3) normal reactivity. Fetal bradycardia was observed during (n = 1) and after (n = 2) exercise in three isolated tests. The timing of these events suggested that the likelihood of significant fetal hypoxia is highest in the immediate postexercise period. These results also support the hypothesis that physically conditioned women can perform at higher exercise power outputs than sedentary women without inducing fetal hypoxic stress. Further study is recommended to examine possible fetal and placental adaptations to maternal aerobic conditioning.

Adult↗
PubMed1993

Stress analysis of endosseous implants using the Boundary Integral Equation (BIE) method.

The Boundary Integral Equation (BIE) method for modelling mathematically an endosseous implant within its bony surroundings is described in this study. The results are compared to those calculated by Finite Element Analysis (FEA), and the following conclusions drawn: both FEA and BIE are able to provide stress analyses of the dental implant situation and give similar numerical values of stresses and strains at the implant-bone interfaces. The BIE method does not produce a pictorial representation of the calculated stresses in the form of stress contours, as this is not applicable to boundary investigations. It is easier to alter the outline of the implant with line elements than with solid elements; therefore slight alterations in the outline form of an implant are easy to investigate with regard to their resultant interfacial stress levels. The BIE method is simpler to use than FEA, but little software is commercially available. The aim of the study was to determine whether future developments in this field could be useful in the stress analysis of endosseous implants.

Dental Implantation, Endosseous↗
PubMed1993

Aerobic exercise in pregnancy: an update.

The endocrine effects of pregnancy cause striking changes in maternal metabolism, cardiovascular regulation, acid-base balance, and thermoregulation at rest and during standard submaximal exercise. The apparent purpose of these changes is to accommodate fetal needs in addition to those of the exercising woman. A significant body of evidence supports the hypothesis that healthy women can perform acute exercise of moderate intensity and duration without jeopardizing fetal well-being. Compiled studies also suggest that maximal oxygen uptake (VO2max, L.min-1) and the work rate at the onset of blood lactate accumulation (OBLA) are not significantly altered during the course of a normal pregnancy. However, some evidence suggests that maximal anaerobic power may be reduced. More information is needed on maternal cardiorespiratory function, carbohydrate metabolism, and acid-base balance at exercise intensities above OBLA and on fetal adaptability to strenuous maternal exercise. Recent studies support the view that moderate fitness conditioning can augment maternal metabolic and cardiopulmonary capacities without altering fetal development or pregnancy outcome. Implications of recent scientific studies for the design of aerobic exercise programs for pregnant women are discussed.

Exercise↗
PubMed1993

Recent advances in understanding maternal and fetal responses to exercise.

In the past decade, physical health fitness has become increasingly more important in the lives of women of child-bearing age. Many have made regular, and sometimes vigorous commitments to exercise programs. In 1985, the American College of Obstetricians and Gynecologists (ACOG) developed a set of guidelines for women who plan to exercise during pregnancy. Recommendations were based on available, but somewhat limited, scientific data and common sense. Since that time, researchers have learned a significant amount of new information about how a pregnant woman and her fetus respond to aerobic activity. The objective of this communication is to review recent investigations in this area. Specific topics include a) maternal responses to exercise, b) fetal responses to maternal exercise, c) animal research models, and d) pregnancy and physical conditioning. Our objectives are to present information that will a) stimulate new and innovative research designs for exercise and pregnancy studies, and b) add significantly to our knowledge and ability to develop safe and effective exercise programs for women who wish to remain physically active throughout a normal-term pregnancy.

Animals↗
PubMed1992

Biocompatibility tests on a novel glass-ceramic system.

The aim of this study was to look at the bone bonding potential of six formulations of a novel glass-ceramic system. Cylinders of the ceramics were implanted in rabbit tibiae for 4 and 7 weeks. Histological tests, both quantitative and qualitative, as well as push-out tests, were carried out during the bonding assessment. Bone growth was quite prolific, even at 4 weeks, as evidenced by growth up to and along the implant surfaces. The interfacial shear strengths compared well with other biomaterials in use as endosseous implants. Therefore it seems pertinent to pursue further long-term experimentation with this material.

Animals↗
PubMed1992

Relationships between cardiac dimensions, anthropometric characteristics and maximal aerobic power (VO2max) in young men.

Echocardiographic dimensions, anthropometric data and maximal oxygen uptake (VO2max) were studied in 26 healthy sedentary male controls (mean age, 22.0 yrs) and 15 male endurance athletes (mean age, 20.3 yrs). Athletes displayed significantly greater mean values for left ventricular internal dimension at end-diastole (LVIDd), end-diastolic volume (LVEDV) and left ventricular mass (LVM). Statistically significant positive correlations were observed within the sedentary control group between left ventricular end-diastolic dimensions (LVIDd, mm and/or LVEDV, cm3) and body height (cm), body weight (kg), chest circumference (cm) and body surface area (m2). Left ventricular mass (LVM, g) correlated significantly with lean body mass (kg). Ectomorphic somatotype rating (Ecto) correlated negatively with LVEDV and LVM. Finally, VO2max (l/min) correlated significantly with LVIDd, LVEDV and LVM. Multiple linear regression analysis indicated that the degree of endomorphy (Endo), LVIDd (mm/m2) and chest circumference accounted for 89% of the variance in VO2max (ml/kg/min) within the athlete group. Endo, Ecto and LVIDd (mm/m2) accounted for 86% of the variance in VO2max (ml/kg/min) in the control group. This study supports the hypothesis that maximal aerobic power can be predicted from cardiac and anthropometric measurements.

Adult↗
PubMed1992

Cardiac responses of young women to conditioning for a 10 kilometer race.

Seven previously sedentary women (mean age, 19 yrs) participated in an 11-week running program (4-5 sessions/week) in preparation for a 10 km race. Training intensity was 80-85% of maximum heart rate reserve. Exercise duration began at 20 minutes/session and was lengthened 5 minutes/session every 2 weeks. A control group consisting of 4 women was also evaluated. Maximal oxygen uptake (VO2max, ml/kg/min) increased 11% in the trained group and decreased 6% in the control group during the study (p less than 0.05). Oxygen uptake, cardiac output (Q), and stroke volume (SV) increased significantly (p less than 0.05) in the trained group during each of 3 levels of steady state cycle ergometer exercise (heart rate targets: 115, 135 and 155 beats/min, respectively). Arteriovenous oxygen difference (a-V02 diff) was not increased significantly after training. Resting left ventricular dimensions and performance evaluated by echocardiography also did not change significantly after training. It was concluded that short-term conditioning in this population results in an increased exercise Q without concomitant increases in left ventricular dimensions or arteriovenous oxygen difference.

Adult↗
PubMed1992

Microscopy of bone cells, bone tissue, and bone healing around implants.

Newer methods of scanning microscopy using both light and electrons are particularly relevant to the study of bone cells, bone matrix organization, matrix mineralization, bone modeling and remodeling, and the adaptation of cells and matrix to implants. Most of such studies are conducted on retrieved implants, at least after the death of the related tissue. Because the retention of the tissue-implant relationship in such preserved tissue is crucial for critical evaluation of the implant, methods based on the study of flat surfaces of embedded tissue blocks are very important. Using electrons, the backscattered electrons in a scanning electron microscope can be employed to evaluate mean atomic number (density) and cathodoluminescence can identify polymers and fluorescent labels. Using light, confocal microscopical techniques permit the examination of layers deep to the block face. Confocal reflected and fluorescence methods allow the study of cell behavior upon both transparent and opaque substrates in the laboratory. Examples of the above are presented and interpretation problems discussed. Current experiments are aimed at enabling the study of bone wound healing and bone adaptation to implanted materials in vivo, through the implantation of optical quality windows and/or newly conceived and designed microscopical objective lenses.

Animals↗
PubMed1991

Microculture screening assay for primary in vitro evaluation of drugs against Pneumocystis carinii.

Pneumocystis carinii inoculated into 96-well filtration plate assemblies was shown to synthesize radiolabeled folates de novo from [para-3H]aminobenzoic acid ([3H]pABA). At the end of each incubation with [3H]pABA, a vacuum manifold was used to remove the medium and wash P. carinii. The membrane at the base of each well was dried and punched out, and the level of 3H retained was determined by direct scintillation counting. High-pressure liquid chromatography analysis of duplicate filters confirmed that direct counting of 3H retained on membranes (after correction for unmetabolized [3H]pABA) was an accurate reflection of total [3H]pABA incorporation by P. carinii. Greater than 95% of the 3H recovered was shown to be present as polyglutamated species. After digestion with rat plasma folic acid gamma-glutamyl hydrolase, para-aminobenzoylglutamate, N10-formyltetrahydrofolate, and tetrahydrofolate were identified as the major 3H-labeled components. para-Aminobenzoylglutamate was presumed to have arisen from folylpolyglutamates synthesized by P. carinii and was therefore included in the calculation of total [3H]pABA incorporation. P. carinii incorporation of [3H]pABA under optimal conditions was used as a selective measure of in vitro viability against which the inhibitory effects of some antipneumocystis agents (pentamidine, sulfamethoxazole, 566C80, and piritrexim) were quantitated. The concentrations of pentamidine, sulfamethoxazole, 566C80, and piritrexim required for 50% inhibition in this assay were 7.3, 0.1, 1.4, and approximately 100 microM, respectively. The results suggest that this 96-well [3H]pABA incorporation assay has considerable potential for objective in vitro drug screening against P. carinii.

4-Aminobenzoic Acid↗
PubMed1991

The 'athletic heart syndrome'. A critical review.

Cardiological findings in athletes are often similar to those observed in clinical cases. Electrocardiographic and cardiac imaging abnormalities as well as physical findings may be the same in both of these groups. Bradycardia and rhythm disturbances are the most common abnormalities in athletes. Most athletes with abnormal electrocardiograms are asymptomatic and numerous investigators have failed to detect heart disease in association with such electrocardiograms. In contrast to cardiac dysfunction observed in clinical cases, enhanced or normal ventricular systolic and diastolic function have been reported in athletes. In endurance athletes, this is associated with very high values for maximal aerobic power (VO2max). Absolute and body size-normalised cardiac dimensions in most athletes do not approach values from chronic disease states, and may not exceed echocardiographic normal limits. In addition, pathological and physiological enlargement appear to be biochemically and functionally different. Myosin ATPase enzyme expression and calcium metabolism are different in rats with pathologically or physiologically induced enlargement. The reported biochemical differences underlie systolic and diastolic dysfunction in pathological enlargement. Conversely, trained rodents and humans have demonstrated enhanced systolic and diastolic function. It is important to note that cardiac enlargement observed in athletes is the result of normal adaptation to physical conditioning and/or hereditary influences. Conversely, pathological changes result from disease processes which can lead in turn to reduced function, morbidity and mortality. Since the mid 1970s echocardiography has been used to compare cardiac dimensions in male endurance- and resistance-trained athletes. A sport-specific profile of eccentric and concentric enlargement has been documented in endurance and resistance athletes, respectively. Subsequent studies of athletes have examined factors such as age, sex and degree of competitive success to determine their contribution to these sport-specific cardiac profiles. Unique athletic subgroups have also been analysed and have included ballet dancers, rowers, basketball players and triathletes. However, there is a paucity of data on cardiac dimensions in female athletes. Finally, physical conditioning studies have also examined echocardiographic dimensions before and after endurance and resistance training. Significant enlargement of internal dimensions, wall thickness or left ventricular mass have been reported but such increases are relatively small and by no means universal. Several conflicting explanations for enlarged cardiac dimensions appear in the literature. Chronic volume and pressure haemodynamic overloading during physical conditioning has been proposed to explain eccentric and concentric cardiac enlargement in endurance- and resistance-trained athletes respectively. However, twin studies suggest that hereditary factors may be important determinants of cardiac dimensions and/or the degree of cardiac adaptability to physical conditioning.(ABSTRACT TRUNCATED AT 400 WORDS)

Body Mass Index↗
PubMed1990

Fluorescence in the tandem scanning microscope.

Our studies have shown that the fluorescence mode can be used to good effect in both tandem scanning microscopes (TSM: direct view confocal microscopes) as well as confocal scanning laser microscopes (CSLM). Applications are presented which show that the two great advantages of TSM are real-time viewing and real colour, which allow faster use and interpretation. CSLM are complementary, not competitive, being currently more sophisticated for low-level fluorescence work. This is equally possible with available TSM, but requires further development using CCD cameras and image-processing systems.

Animals↗
PubMed1989

An in vitro analogue of immune dysfunction with altered immunoglobulin production in the aged.

The consequences of aging of the immune system include impaired T-lymphocyte responsiveness and aberrant immunoglobulin production. Although T cells from elderly individuals have a well-described defect in lymphoblastic transformation in response to some polyclonal mitogens, immunoglobulin abnormalities have lacked a clear in vitro model. Peripheral blood mononuclear cells from 13 young and 13 old healthy donors were cultured with phytohemagglutinin (PHA) or pokeweed mitogen (PWM). Old-donor-cell phytohemagglutinin (PHA), but not PWM, cultures had significantly lower lymphoblastic transformation compared with young donor cultures. IgG, IgA, and IgM production tended to be lower in old- versus young-donor PWM cell cultures. By contrast, despite lower lymphoblastic transformation in old-donor PHA cell cultures, immunoglobulin production was higher for old- versus young-donor cell cultures. No significant age differences were present in initial lymphocyte counts, percent B cells, T cells or monocytes, or helper/suppressor ratios to explain this enhancement in immunoglobulin production. PHA-stimulated mononuclear cell cultures in the aged demonstrate not only a defect in proliferation but also increased immunoglobulin production. This in vitro system may be useful to characterize further the pathogenesis of altered immunoglobulin production in the elderly.

Adult↗
PubMed1989

Prescription of aerobic exercise during pregnancy.

Available evidence supports the existence of both risks and benefits of aerobic conditioning during human pregnancy. During intensive exertion, maternal skeletal muscle and the fetus may compete for blood flow, oxygen delivery and essential fuel substrates. Hence, the most important hypothetical risks include acute fetal hypoxia, hyperthermia and malnutrition. If exercise is repeated on a chronic basis, teratogenic effects, fetal growth retardation or altered fetal development may result if maternal/fetal adaptive reserve is exceeded. A dose-response relationship for such effects has been demonstrated in laboratory animals, but specific findings may have limited applicability to voluntary exercise in pregnant women. Although further investigation is needed, the majority of published studies suggest that fitness-type conditioning does not jeopardise fetal well-being in healthy well-nourished women. Benefits of such exercise appear to include increases in maximal aerobic power (VO2max, L/min) and enhanced cardiopulmonary reserve. It has also been proposed that exercise prevents accumulation of excess body fat, promotes psychological well-being, helps to prevent gestational diabetes and low back pain and may facilitate labour. However, these benefits remain to be confirmed by objective scientific study. Due primarily to a lack of scientific data, existing medical guidelines for exercise during pregnancy are conservative and follow a common sense approach. Good agreement exists on the need for preparticipation medical screening and continuing surveillance to verify the existence of maternal/fetal adaptive reserve. Women are advised to select safe, non-ballistic exercise modalities and to avoid thermal or hyperbaric environmental stress during exercise. Exercise in the supine position is also prudent to avoid, particularly in late gestation. The usefulness of heart rate in prescribing and monitoring exercise intensity has been questioned, with use of conventional perception of exertion scales being the most logical alternative. Prediction of maximal aerobic power (VO2max) from submaximal work rate/heart rate relationships is also problematic during pregnancy. Other areas of debate include the advisability of initiating a new exercise programme during pregnancy, methods for prevention of fetal hyperthermia, the safety of weight-training/isometric exercise and optimal methods for training of pre/postnatal fitness instructors.

Exercise Therapy↗
PubMed1989

Bone response to a matched modulus endosseous implant material.

The aim of this study was to assess bone response to a novel matched modulus material using more rigid titanium as a control. Implants subjected to different loading conditions were retrieved from rabbit tibiae after various time intervals, and new bone growth was assessed by histomorphometric methods. Block face microscopy was employed for histologic purposes. From a statistical analysis of the histomorphometric results, it could be concluded that titanium implants encouraged the greatest overall amount of bone formation around them when they were unloaded, when they were loaded immediately, and after a healing period.

Animals↗