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Biomedical subjects

J Heller

Publications and source records attributed to J Heller.

At least 145 records · Page 8Linked to original sources
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↗
PubMed1991

The effects of labetalol and prazosin on exercise haemodynamics in hypertensive patients.

The antihypertensive and haemodynamic effects of labetalol were compared with those of prazosin both at rest and during bicycle exercise in 38 moderate to moderately severe hypertensive patients (supine DBP 95 to 119 mmHg when untreated). Following a two week open placebo phase to establish baseline BP and baseline exercise performance, patients were randomly and double-blindedly assigned to receive labetalol or prazosin. Drug dose was titrated from 100 to 400 mg labetalol twice daily, or from one to 10 mg prazosin twice daily at weekly intervals until BP was controlled (supine DBP less than or equal to 90 mmHg with at least a 10 mmHg decrease from baseline). Eighteen labetalol and twenty prazosin patients achieved BP control and were subsequently reexercised to fatigue on a bicycle ergometer. The mean changes from baseline for heart rate and rate pressure product (heart rate x SBP) were reduced only in the labetalol group; the difference between the labetalol and prazosin groups was significant (P less than 0.01) both at rest and during exercise. This haemodynamic profile of labetalol may be important in selecting a vasodilating antihypertensive for patients with concomitant ischaemic heart disease.

Adult↗
PubMed1990

Augmentation of GABAA receptor function by chronic exposure to GABA-neutral and GABA-negative benzodiazepine ligands in cultured cortical neurons.

Chronic benzodiazepine agonist administration may lead to decreases in gamma-aminobutyric acidA (GABAA) receptor binding and function, but little information is available concerning chronic GABA-neutral or GABA-negative benzodiazepine exposure. We evaluated effects of chronic exposure to flumazenil (Ro15-1788) and FG 7142 (N-methyl-beta-carboline-3-carboxamide) on GABA-dependent chloride uptake in chick cerebral cortical neurons in primary culture. Acute flumazenil treatment (1 microM) had no effect on chloride uptake, but uptake was increased after 2 days of exposure. Similar increases were observed after 4 and 10 days. Flumazenil, 0.1 microM, had no effect after 10 days, and a 10 microM concentration had a similar effect as the 1 microM concentration. Acute FG 7142 (1 microM) decreased chloride uptake, but uptake was increased markedly after 2, 4, and 10 days of treatment. No effect was observed after treatment for 10 days with 0.1 microM, but a 10 microM concentration showed similar enhancement to the 1 microM concentration. Concurrent treatment with 0.3 microM flumazenil which did not affect chloride uptake and 1 microM FG 7142 for 10 days substantially attenuated the effects of FG 7142, suggesting that FG 7142 effects are mediated at the benzodiazepine site. Benzodiazepine receptor binding was increased in cultures treated for 10 days with 1 microM flumazenil or FG 7142, with an increase in receptor number in both cases but no change in apparent affinity. Neither flumazenil nor FG 7142 (1 microM for 10 days) altered GABA-independent chloride uptake, total cellular protein, protein synthesis or degradation, or neuronal survival. These results indicate that both chronic GABA-neutral and GABA-negative benzodiazepine exposures in cultured cortical neurons lead to increases in GABA-dependent chloride uptake and benzodiazepine binding. Effects of GABA-negative benzodiazepine exposure appear to be greater than those observed with GABA-neutral benzodiazepine exposure.

Animals↗
PubMed1990

[Energy requirements in women during running on a treadmill and running over terrain].

Running is the most frequently used training method of promoting aerobic efficiency, functional capacity and fitness as well as weight reduction. The energy demand on running expressed indirectly in terms of oxygen consumption correlated with 1 kg body weight (VO2.kg-1) can be established on the basis of the running speed (v) using different nomograms and graphs. These relations are linear within the range of submaximum exertion of training intensity, approximately within the range of 20-90% of maximum oxygen consumption. The relationship between VO2.kg-1 and the running speed generally depends on the sex, age, amount of training practice and on the inherent speed capabilities. Based on the measurements of women of different training practice and age, supplemented with data drawn from literature, the authors established an "average" relationship, independent of age, record of training practice and the speed norm valid for the running carpet in the form of VO2.kg-1 = 2.804. v (km.h-1) + 8.922. The error in determining VO2.kg-1 within the range of the speed of 8-18 km.h-1 is approximately 8% or less. Similarly, using nomograms which facilitate the transfer of the running speed on the running carpet to the outdoor speed, the authors found a general equation for a flat terrain in the form of VO2.kg-1 = 3.359. v + 3.308 which can be used for the speed range of 8-16 km.h-1 with the same error as the one obtained indoors. The above relations can be used for estimating the reactions of the organism to indoor or outdoor exertion with the aim of establishing suitable training exertion intensity.

Adolescent↗
PubMed1990

[The effect of body constitution on work capacity evaluated by means of mechanical efficiency].

The utilizable sources of energy of the human organism are relatively restricted where by interindividual differences are not substantial, while differences in physical performance are extreme. The capacity to transform chemical energy into mechanical work, sometimes described also as the work capacity of the organism is evaluated by means of mechanical efficiency--ME. In men with varying amounts of training (incl. untrained ones), differing significantly as to the percentage of body fat (3.8-17.2%), assessed by measurement of ten skinfolds, the authors assessed ME on a treadmill. The highest ME values were recorded in trained sportsmen (endurance runners--32.4%), lowest in untrained middle-aged men (16.9%). The authors found a close negative correlation of ME and maximal oxygen consumption per kg body weight and values of body fat percentage. With the increasing percentage of body fat the values of ME decline, the prerequisites for effective transformation of chemical energy of the organism into mechanical work are reduced and the work capacity of the organism declines.

Adult↗
PubMed1990

Ultrastructure of the sperm and spermatogenesis in five South African species of the trochid genus Oxystele (Mollusca, Prosobranchia).

Sperm of Oxystele are of the primitive type, which is typical of molluscs using external fertilization. They comprise a head, which is composed of a barrel-shaped nucleus and large conical acrosome; a midpiece of five or six spherical mitochondria; and a tail, with a 9 + 2 arrangement of microtubules. The morphology of the sperm broadly resembles that of the sperm of other trochids as well as that of the sperm of the Pleurotomariidae, Haliotidae, and Fissurellidae but differs considerably from that of the Patellidae. Each of the five species examined was found to have a different sperm morphology. Our results support the suggestion of Heller and Dempster (in preparation) that Oxystele variegata Anton actually consists of two sympatric species. The morphological changes that occur during spermatogenesis are very similar in all species and resemble descriptions given for other molluscs with primitive sperm.

Animals↗
PubMed1990

Immunological differentiation between neuroborreliosis and multiple sclerosis.

Neuroborreliosis, a tick-borne spirochaetosis of the central nervous system, is diagnosed by the presence of intrathecally synthesized Borrelia burgdorferi-specific antibodies. Multiple sclerosis and neuroborreliosis can show similarities in clinical symptoms as well as lymphocytic cell reactions and oligoclonal bands in the isoelectric focusing of cerebrospinal fluid. To differentiate between multiple sclerosis and neuroborreliosis we tested intrathecally synthesized IgM and virus antibodies. The IgM indices were higher for most of the neuroborreliosis patients studied than for those with multiple sclerosis, and cell counts were also significantly higher in the acute stage of the disease. In 84% of multiple sclerosis patients we were able to demonstrate intrathecal antibody production against measles, rubella or mumps virus. Neuroborreliosis patients had no intrathecal virus antibody synthesis. The specification of oligoclonal bands resulting from isoelectric focusing of cerebrospinal fluid with an ELISA for B. burgdorferi can further substantiate the diagnosis of neuroborreliosis or help to rule it out in multiple sclerosis patients with positive borrelia-specific serology.

Adult↗
PubMed1990

The cause of a depressed glomerular filtration rate after an ischaemic insult: whole kidney and superficial nephron study in the dog.

Twenty-four hours after 90 min clamping of the left renal artery in dogs, the glomerular filtration rate (GFR) was decreased in the whole kidney (0.34 ml.min-1g KW-1 [KW = Kidney weight] vs 0.64 in contralateral unclamped kidney) just as in the single nephron (SNGFR, 19.7 vs 51.8 nl.min-1). Renal blood flow (RBF) did not change; single nephron glomerular blood flow (SNGBF) was decreased by 9% only. After injection of Lissamine green into the renal artery, brief diffuse tinting of the whole kidney surface was observed. Thereafter, patchy coloration - corresponding to passage of the dye through patient tubuli - took place in approximately one-quarter to one-third of the kidney surface. Micropuncture measurements were carried out in these areas. The values of hydraulic pressure in peritubular capillaries and proximal convolutions were not different from those found in controls; directly measured glomerular capillary pressure was decreased (48.7 vs 59.5 mmHg). The ultrafiltration coefficient(Kf) was significantly depressed (2.7 vs 3.8 mmHg.nl-1.min). Total kidney and arteriolar resistances remained unchanged but afferent resistance (RA) was elevated (11%) and efferent resistance (RE) was lowered (23%) compared with those of controls. Ninety-seven percent of proximally microinjected 3H-inulin was recovered from the control kidney but only 85% from the kidney rendered ischaemic. In conclusion, the typical findings at 24 h after 90 min ischaemia are low GFR and SNGFR with normal RBF and almost normal superficial SNGBF values. This phenomenon is mainly due to a decrease in Kf and a decrease in RE with a simultaneous increase in RA; back-leak through damaged tubuli seems to play only a minor role.

Animals↗