Search PubMed⌕ Search

Biomedical subjects

J Heller

Publications and source records attributed to J Heller.

At least 19 recordsLinked to original sources
PubMed1995

Preliminary effects of in vitro lipid exposure on absorbable poly(ortho ester) films.

Bioabsorbable films show promise in preventing postoperative interfacial tissue adhesion. Absorbable polymers in film form are generally more sensitive to chemical environments, due to their large surface area to volume ratio. The in vivo environment contains lipids such as cholesterol, triglycerides, and phospholipids, which are known to affect the degradation of permanent and absorbable polymeric biomaterials. Preliminary investigations of in vitro lipid exposure of bioabsorbable poly(ortho ester) (POE) films for implant use are described. POE has been studied previously for use in controlled drug delivery and fracture fixation. Six-week in vitro exposure of 65:35 POE films to a cholesterol emulsion (1 g/L) showed no apparent difference in hydrolytic degradation rates of mechanical properties or mass loss compared to deionized water exposed films. Decreases of 28 and 6% in inherent viscosity were observed after 5 weeks for cholesterol and deionized water exposed films, respectively, suggesting cholesterol may have some effect. Further examination of the data, due to sample variation, revealed that clear, uniform films showed only minor changes in mass loss and mechanical properties after 6 weeks in either of the in vitro media. But slightly cloudy films possessing microscopic bubbles showed accelerated degradation in both media, indicating the effect of cholesterol was inconclusive due to sample variation. Control of the microbubble formation process could have utility in controlling hydrolytic degradation of POE films.

Biocompatible Materials↗
PubMed1995

[Effect of light intensity on binocular distance perception].

Empirical investigations of perceived binocular distance often use an experimental setting in which real point-like light sources are presented in a completely dark surround. The results obtained, however, may be a consequence of the joint influence of binocular and monocular depth cues. Here, for the first time, the effect of (monocular) illumination cues on the locus of perceived equidistance is experimentally investigated by manipulating the luminous intensity of the stimuli. In a computer-controlled setup, small light-emitting diodes were presented in complete darkness. Five subjects judged the perceived distance of stimuli, which appeared in four directions and at five levels of luminous intensity, with respect to a fixed standard. Adaptive methods were used to determine perceived equidistance. Although the results show a significant effect of illumination cues, their influence on the locus of perceived equidistance turned out to be far less than previously supposed. For three subjects it was practically negligible.

Adult↗
PubMed1993

Relative utilization of reptiles and rodents as hosts by immature Ixodes scapularis (Acari: Ixodidae) in the coastal plain of North Carolina, USA.

The interaction of immature black-legged ticks, Ixodes scapularis, with reptiles and rodents was investigated in various woodland habitats in the coastal plain of North Carolina. Reptiles were sampled from April 1 to September 30, 1991. No ticks were found on 95 specimens representing 16 species of snakes. Ticks were found on 54 (36.7%) of 147 lizards. I. scapularis was the only tick recovered from lizards. Some lizards were collected in drift fence traps each month of the study except August. Capture rates averaged one lizard per 16 trap-days. Larvae and nymphs of I. scapularis were removed from the southeastern five-lined skink (Eumeces inexpectatus), the ground skink (Scincella lateralis), the broad-headed skink (E. laticeps) and the eastern glass lizard (Ophisaurus ventralis), but ticks were not found on three other lizard species. Tick infestation rates and loads for parasitized species are presented. Ticks were almost exclusively attached at the base or in the axils of forelimbs of skinks and in the lateral grooves of eastern glass lizards. Rodents were live-trapped at sites where lizards were sampled and at other sites from 1 July, 1990 to 30 January, 1992. Capture rates averaged one rodent per 47 trap-nights. Ticks were found on 23 (17.8%) of 129 animals inspected. Five species of rodents were examined but only four species were found to be tick-infested. In contrast to lizards, few I. scapularis were collected. Rodents, principally the white-footed mouse (Peromyscus leucopus) and cotton mouse (P. gossypinus) were most frequently infested with immature American dog ticks, Dermacentor variabilis, during winter and early spring months. Burdens of D. variabilis on these rodents averaged 0.3 ticks per rodent. Effects of the diversion of ticks from feeding on Peromyscus mice on the transmission of the Lyme disease spirochete are discussed.

Animals↗
PubMed1992

The influence of weight reduction and exercise regimes upon the personality profiles of overweight males.

In the present study, the MMPI was used to detect personality changes in 53 overweight, yet otherwise healthy, males who were participating in either a weight reduction or an aerobic exercise conditioning program. Analysis of pre- and post-intervention scores revealed that only the participants in the aerobic conditioning group demonstrated the predicted desirable psychological changes. More specifically, this group displayed significant clinically desirable changes on the Hs, PD, and HEA scores. Similar to the weight loss participants, a demographically matched nonintervention comparison group showed none of these desirable changes and actually yielded a significant increase on the D scale. However, when compared to this "normal" group, both intervention programs showed statistically significant differences on at least two MMPI scales.

Age Factors↗
PubMed1992

The effect of lipase on the release of naltrexone from triglyceride-coated cellulose acetate phthalate microspheres.

The ultimate objective of this work is to develop a device that can be triggered by morphine to release naltrexone. In this device, naltrexone is dispersed in cellulose acetate phthalate microspheres which are then spray-coated with a trilaurin protective coating. The microspheres are contained within a macroporous cylinder which also contains a reversibly inactivated lipase. This enzyme in its inactive state is unable to remove the protective coating but in its active state is able to do so. Inactivation is achieved by the covalent attachment of morphine followed by complexation with a morphine antibody. Triggering is accomplished by the displacement of the lipase-morphine conjugate from the antibody. In this phase we have investigated the effect of lipase on the release of naltrexone from trilaurin-coated microspheres and found that the coated microspheres are stable in a pH 7.4 phosphate buffer at 37 degrees C for at least 1 month, but release 80% of the incorporated naltrexone in one hour when 100 mg of capsules in 5 mL buffer are exposed to 25 micrograms of lipase.

Biocompatible Materials↗
PubMed1991

[Conversion of the intensity of loading from the bicycle ergometer to a treadmill and to field training in women].

When evaluating the standard of functional fitness, state of training or work capacity of subjects, when diagnosing loads, when assessing training of healthy subjects and sportsmen and locomotor rehabilitation of patients usually two types of ergometers are used--a pedalling ergometer and a treadmill. Each of these ergometers has its specific properties, advantages and shortcomings. For the practical use of results of functional examination in the laboratory, where the majority of our diagnostic departments possesses only a pedalling ergometer it is necessary to convert the load intensity from the bicycle to a treadmill and to the field where physical training is usually implemented. Based on our measurements in groups women with different grades of training, differing as to age, it is possible to elaborate a general equation which relates the load intensity on the pedalling ergometer P/W.kg-1 and the speed of running on the treadmill with a zero gradient v/km.h-1 in the form v = 3,695.P-1,419. This relationship can be used with an error of cca 12% in the zone of submaximal load intensities (up to 90% of the maximal load intensity). For P lower than 3.9 W.kg-1 this equation can be used for direct conversion to flat ground. For higher load intensities there is the relationship v = 3,156.P + 0.446 which has the same error of 12% as for even ground.

Adolescent↗
PubMed1991

[Energy requirements in women during pedalling on a bicycle ergometer].

The bicycle ergometer is the most frequently used equipment for loading tests for the purpose of functional diagnosis and for the purpose of locomotor rehabilitation. The energy required to meet this locomotor activity is within a wide range of load intensities which depends linearily on the intensity of pedalling. The steepness of this linear relationship which characterizes the degree of adaptation of the organism to this type of locomotor activity is the smaller the more the investigated subjects are adapted to the load. In general it depends on the degree of training, age, sex, strength, pedalling frequency, on the load protocol and on the biomechanical conditions during pedalling (e.g. the height of the saddle). Based on our measurements in a group of untrained women of different age and in trained women of different age it can be demonstrated that all individual relations between energy characterized by means of VO2 and the intensity of the load - P is within the zone where the upper borderline is formed by the equation VO2(ml) = 11.00.P (W) + 403 and the lower borderline by VO2(ml) = 9.90.P (W) + 252. The basic relationship, independent on the degree of training, age and strength, valid in the zone of pedalling frequencies of 60-80 rot. min-1 and in the zone of load intensities of 75-325 W has the shape of VO2(ml) = 10.60.P(W) + 269. The maximum error of assessment of VO2 by means of the load intensity is 9% or less.

Adolescent↗
PubMed1991

Chronic exposure to a benzodiazepine partial agonist does not alter GABAA receptor function in cultured neurons.

The benzodiazepine partial agonist Ro16-6028 does not lead to GABAA receptor downregulation in vivo. To assess effects of this compound in vitro, cultured neurons were exposed to Ro16-6028, 1 and 10 microM. GABA-dependent chloride uptake was unaffected at either dose of Ro16-6028 from 2 to 10 days, in contrast to decreased function observed with clonazepam, 1 microM, at 10 days, Ro16-6028 exposure did not alter GABA-independent chloride uptake, total neuronal protein, or cellular protein synthesis.

Animals↗
PubMed1991

[Anaerobic "all-out" stress tests: selection of the type and duration of stress].

In the diagnosis of prerequisite conditions for short-term highly intensive activity, performed under conditions of oxygen deficit anaerobic loading tests are used. Contrary to tests of constant performance, "all-out" tests follow up changes of performance in the course of time, i. e. they record the maximal anaerobic performance as well as the decline of performance in the course of the test. In a group of 17 subjects three types of loads were compared (bicycle ergometry, a test repeated jumps and running) and two periods of anaerobic tests--45 s and 120 s. The results achieved in different tests--total work, maximum performance, decline of performance, post-load lactate concentration in blood--differed depending on the type of load and duration of the test. Correlation analysis did not reveal a close relationship between the results of different anaerobic tests, there was however a relationship between the maximum performance and the total work at the level of general physical fitness. The longer variant of the test--120 s--did not prove more suitable, neither from the aspect of the assumed markedly higher lactate cumulation in blood nor from the aspect of maximum performance, as compared with the 45 s test. A close relationship was revealed between the results of the 45 s and 120 s jumping and running test but not between the results of bicycle ergometry. The post-load lactate concentration cannot be considered a highly reliable indicator of the level of the anaerobic energy metabolism in the working muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

X-ray photoelectron spectroscopy analysis of the surface chemical structure of some biodegradable poly(orthoesters).

The surface analysis of some biodegradable poly(orthoesters) has been undertaken using X-ray photoelectron spectroscopy (XPS). There is very good agreement between the experimental and theoretical surface compositions. All the carbon environments of the poly(orthoesters) are detected within the high-resolution C1s peak envelopes and again, good agreement is observed between the theoretical and experimental proportions of each carbon environment. The data confirm the high surface purity of these polymers and demonstrate the potential for the use of XPS in future studies of the solid state in-situ degradation of poly(orthoesters).

Biocompatible Materials↗
PubMed1991

Compliance with a low calorie diet for two weeks and concurrent and subsequent mood changes.

One hundred people intending to use the Cambridge Diet for a 2 to 3-week period were asked about their weight, dieting, eating behaviours and demographic factors and completed the Profile of Mood States, Multiple Affect Adjective Checklist, Beck Depression Inventory, Locus of Control Scale, Dutch Eating Behaviour Questionnaire and Dieting Motivation Questionnaire. They were also asked to complete the Multiple Affect Adjective Checklist and the Profile of Mood States daily for a period of 14 days and on a further two occasions at weekly intervals. Complete follow-up data was collected on 47 of the original participants. In these people, a slight decrease in depression occurred during the diet. Approximately one fifth of the people who attempted to use the diet for a two-week period succeeded in complying with it fully. None of the factors assessed reliably predicted compliance with the diet.

Adult↗
PubMed1991

Persistent elevation in GABAA receptor subunit mRNAs following social stress.

Stress is associated with alterations in GABA/benzodiazepine binding and function. We evaluated effects of social stress on GABAA receptor subunit (alpha 1 and gamma 2) mRNAs by Northern hybridization. In cortex, no change was observed in either subunit mRNA immediately after stress, but a 4 hours mRNAs for both subunits were increased. These changes persisted for 72 hours after stress, and returned to baseline levels at 7 days. No changes in mRNAs were observed in sham-treated mice. No changes in either subunit mRNA were observed in stressed or sham-treated mice in cerebellum or hippocampus. In undefeated resident mice, mRNAs for both subunits in cortex were unaffected at 24 hours after the stress episode. Social stress is associated with increases in GABAA receptor alpha 1 and gamma 2 subunit mRNAs in cortex.

Animals↗
PubMed1991

Blunt injuries to the extracranial cerebral vessels associated with spine fractures.

Injury of the extracranial carotid or vertebral artery with associated spine fractures is a rare but documented entity. In this article, four cases are examined in which patients suffered axial fractures after motor vehicle accidents and subsequently were found to have pathology in one or more of the extracranial arteries. Misdiagnosis is a common complication because symptoms from this are often attributable to closed head injury. Early detection and treatment, however, are essential. As many as 40% of the cases reported have permanent neurologic deficit. Although cerebral angiography remains the diagnostic gold standard, other modalities (eg, transcranial doppler and magnetic resonance angiography) continue to be examined. The treatment of these lesions remains controversial. A variety of surgical procedures may be applicable depending on the time between the injury and the onset of symptoms, the location of the vascular injury, and the rapidity of diagnosis. Anticoagulation therapy appears to play a large role in the management of patients with injury of the extracranial carotid or vertebral artery.

Adult↗
PubMed1991

Ventilatory threshold and work efficiency on a bicycle and paddling ergometer in top canoeists.

The purpose of this investigation was to determine the effect of increasing specific (paddling ergometer) and non-specific (bicycle ergometer) work load on the parameters at the ventilatory threshold (VT) and on work efficiency (WE) during increasing exercise ergometry. When highly trained male canoeists were given an unspecific exercise load, the values of %VO2max at VT were close to the values characteristic for an untrained population (72.3 +/- 5.3% VO2max). When the same subjects were given a specific work load, they produced values typical for highly trained athletes (83.4 +/- 2.5% VO2max). Non-specific exercise produced WE values close to those of untrained subjects on the bicycle ergometer (23.3 +/- 2.1%), and when loading is specific, the groups of working muscles are smaller, producing lower WE values (14.7 +/- 3.5%). It was concluded that the responses to submaximal exercise intensities in the case of nonspecific loading suggests caution in the interpretation of physiological variables which may be sensitive to training status. The assessment of VT and WE as supplementary characteristics during laboratory measurements, enables us, along with other parameters, to ascertain not only the effectiveness of the training process used, but also the specificity of a loading apparatus.

Adaptation, Physiological↗
PubMed1991

Exercise intensity conversion from a bicycle ergometer to a treadmill.

In the evaluation of the general functional fitness and/or work capacity of subjects for the purpose of exercise diagnostics, physical fitness enhancement in untrained healthy subjects or sportsmen and exercise rehabilitation of patients, two types of ergometers are generally used: a bicycle ergometer and a treadmill. To facilitate the conversion of results of functional examinations made in the laboratory to field conditions, where, as a rule, physical activity is performed, the intensity of exercise assessed on the bicycle ergometer must be converted to that on a treadmill and vice versa. Measurements on a bicycle ergometer and treadmill in differently trained groups of men can be supplemented with data from the literature to develop a general equation which relates exercise intensity on the bicycle ergometer P (W.kg-1) and running speed on the treadmill v (km.h-1) as v = 3.544.P +/- 0.625. In the submaximal range of exercise intensities (20-80% of maximal aerobic power) this relationship is independent on the training status, age, body weight, strength and speed capacity of the subjects examined. The above equation may be used in the submaximal exercise intensity range with a maximum error of about 12% or less.

Adaptation, Physiological↗
PubMed1991

The lack of cardiac hypertrophy in newborn Prague hypertensive rats.

Newborn rats of four different strains with spontaneous hypertension show heart enlargement mainly due to cardiac hyperplasia. To determine whether this anomaly is common in all genetically hypertensive rats, we have compared newborns of Prague hypertensive rats (PHR) with their respective normotensive controls (PNR). The heart ventricles, kidneys and livers of newborn animals were analyzed for their weight, protein and DNA content. The total heart weight and the heart/body weight ratio were significantly lower in PHR than in PNR. On the other hand, there were no differences in total or relative kidney weight and in total liver weight. The relative protein content was significantly lower in kidney and liver of PHR but there were no differences between hypertensive and normotensive animals in relative DNA content of all organs studied. Our results suggest a possible dissociation of genes which determine organ weights from those responsible for blood pressure determination.

Animals↗