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Biomedical subjects

J Wenzel

Publications and source records attributed to J Wenzel.

At least 55 records · Page 3Linked to original sources
PubMed1990

Nitrogen partial pressures in man after decompression from simulated scuba dives.

In five subjects arterial and central venous nitrogen partial pressures (PN2) were measured after decompression from a chamber dive following a decompression schedule for scuba diving. The simulated dives consisted of exposure at rest to air at 6 bar for 30 min. corresponding to a depth of 50 m. Afterwards the subjects were decompressed with decompression stops at 2.5, 2.2, 1.9, 1.6 and 1.3 bar with a total decompression time of 73 min. Immediately after decompression and every 40 min. until the 240th min. arterial and central venous blood samples were analyzed for PN2 using a manometric Van Slyke apparatus. Venous PN2 remained elevated until 160 min. after decompression indicating still incomplete nitrogen wash-out at least two hours after decompression had been accomplished. Bubble formation is discussed as a cause for prolonged nitrogen elimination. Our data confirm that nitrogen elimination is prolonged after decompression from simulated dives at rest.

Arteries↗
PubMed1990

Effects of morphine on gamma-aminobutyric acid turnover in the basal ganglia. Possible correlation with its biphasic action on motility.

Morphine (15 mg/kg i.p.) produces a biphasic action on motility: hypokinesia and muscular rigidity ("catatonia"), followed by a hyperkinesia in association with some stereotyped behaviour. In the present studies, alterations in GABA (gamma-aminobutyric acid) turnover were studied in possible correlation with changes in motility. As a criterion of GABA turnover its accumulation after inhibition of GABA transaminase by gamma-acetylene GABA (GAG) was measured. During the first, depressory phase only, GABA turnover was increased in the substantia nigra. In contrast, GABA turnover was continuously enhanced during both phases of morphine's action in the nucleus accumbens. No significant alterations were observed in striatum or globus pallidus. These findings seem to be consistent with the assumption of at least a short- and a long-lasting action of morphine on the basal ganglia.

Alkynes↗
PubMed1990

[The individual variability of pyramidal neurons in the neocortex of the rat].

In Golgi-Kopsch impregnated pyramid neurons of the neocortex (regio precentralis agranularis and area striata) of adult rats the individual variability was investigated. As parameters served the dendritic lengths, spine numbers and spine densities along the dendritic orders (basal and apical), within single dendritic fields, the apical and basal parts of the dendritic tree and of the whole neuron. The statistical tests gave the following results: Pyramid neurons in the regio precentralis agranularis are more variable than pyramid neurons in the area striata. Within the area striata the lamina III-pyramid neurons are more invariable than the lamina V-pyramid neurons. The basal dendrites are statistically more invariable than the apical dendrites. The dendritic lengths are less variable than the spine values. In general, the variability is different in particular subdivisions of the neurons analyzed as well as for the parameter chosen. The variability of neuronal structures depends from genetical factors and from a functional training. The knowledges about this variability are still insufficient. They are of considerable importance for the planning of experiments followed by statistical analyses.

Animals↗
PubMed1990

Development of enolase isoenzymes in various regions of the human brain.

Various brain regions from 4 fetuses (21st to 28th gestational week) and from a 3-month-old infant were investigated for the total enolase activity and their isoenzyme distribution. In the brain tissue from a 3-month-old infant, the activity of the so-called neuron-specific enolase amounted to about 50% of the total enolase activity. In various brain regions different developmental patterns emerged for nonneuronal (NNE) and neuron-specific enolase (NSE). By the 21st gestational week the medulla, pons and thalamus had already reached a relatively high NSE activity (about 60-90% of that of the 3-month values), whereas the cortex regions had 10-30% only. It is concluded that in phylogenetically old regions, the switch from NNE to NSE-subunits appears before the 21st gestational week, in the phylogenetically young regions between the 21st and 28th gestational week.

Brain↗
PubMed1990

Nitrogen partial pressures in man after decompression from simulated scuba dives at rest and during exercise.

In 5 subjects arterial and central venous nitrogen partial pressures (PN2) were measured after decompression from a chamber dive following a decompression schedule for scuba diving. The simulated dives consisted of exposure to air at 6 bar for 30 min corresponding to a depth of 50 m. Afterward the subjects were decompressed with decompression stops at 2.5, 2.2, 1.9, 1.6, and 1.3 bar with a total decompression time of 67 min. In 3 of the subjects the measurements were repeated after they had exercised (workload 75 W) during bottom time. Immediately after decompression and every 40 min until Minute 240 arterial and central venous blood samples were analyzed for PN2 using a manometric Van Slyke apparatus. Venous PN2 remained elevated until 160 min after decompression, indicating still incomplete nitrogen washout for at least 2 h after decompression had been accomplished. We did not find any difference in PN2 values after decompression from dives at rest and after exercise. Applying a computer program based on a wide range of theoretical tissue half-times nitrogen elimination proved to be consistent with Haldanian theories when using our decompression profile. Our data confirm that nitrogen elimination is prolonged after decompression from simulated dives at rest and after exercise.

Adult↗
PubMed1989

Morphine-induced alterations of local cerebral glucose utilization in the basal ganglia of rats.

The actions of various doses of morphine on the local cerebral glucose utilization (LCGU) were studied by means of the autoradiographic [14C]2-deoxyglucose technique. Morphine (1-15 mg/kg i.p.) decreased LCGU in most areas of the basal ganglia (caudate nucleus, globus pallidus, nucleus accumbens), but not in the substantia nigra pars compacta. LCGU was also decreased in limbic nuclei, such as septum, hippocampus and amygdala, and in most thalamic areas. In most cortical regions, a decrease was found as well. Findings in some efferent nuclei seemed of particular interest, namely in the substantia nigra pars reticulata, anteroventral and lateral nucleus of the thalamus and the subthalamic nucleus, where decreases in LCGU were found after administration of 7.5 mg/kg or sometimes lower doses, but not after 15 mg/kg of morphine. The decreases seem to reflect a general depressory effect of morphine on neuronal activity which is known from electrophysiological studies. Part of these effects might be, in addition, due to an activation of dopaminergic neurons, since dopamine mainly acts as an inhibitory neurotransmitter. This dopaminergic activation leads to characteristic behavioral effects after lower doses of morphine. The largest dose used (15 mg/kg) produces muscular rigidity, probably by a direct action on the striatum. This effect antagonizes and masks the dopaminomimetic effects. The results suggest that it also antagonizes the functional alterations in some efferent nuclei of the basal ganglia manifest after lower doses of morphine. Local injections of morphine (15 micrograms) led to decreases of LCGU in the various parts of the striatum, but to increases in lateral and anteroventral thalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Toxicity of different endodontic antiseptics].

The median lethal dose (LD 50) of endodontic antiseptics sodium hypochlorite, chloramine and chlorhexidine digluconate was determined in experiment on albino mice using the method described by Litchfield and Wilcoxon. Sodium hypochlorite and chloramine have shown a twice stronger toxic effect than chlorhexidine digluconate. The difference was significant.

Animals↗
PubMed1988

[Quantitative histological studies of lamina V and lamina III pyramidal neurons in the motor cortex of the rat. The question of laterality].

Laterality of several brain functions has been demonstrated in the human brain cortex as well as in several animal species indicating an evolutionary genesis of the brain's asymmetry. To get some morphological data, we investigated Golgi impregnated pyramidal neurons in lamina III of regio precentralis agranularis of the major cortex from adult rats. The spine number and density and the length of the dendrites forming a basal or apical single dendritic field (SDF = EDF) of these neurons were estimated. The statistical significance of the data was proved by comparing the neuronal parameters obtained from the right or left hemisphere of the same animal (individual laterality), as well as by testing the mean values from right or left cortex of several animals (species laterality). However, in both cases no statistical significance could be obtained. From these results two conclusions should be drawn: Firstly, the parameters in a single dendritic field of cortical pyramidal neurons of both brain sides are statistically equivalent and not asymmetrical developed. Secondly, the single dendritic field of cortical pyramidal neurons can not serve as a morphological counterpart for functional asymmetries in the rat brain. Here, further interdisciplinary research is necessary.

Animals↗
PubMed1987

[Vesicle population of synapses in the hippocampus of the rat following early postnatal deprivation and administration of pyridostigmine].

Newborn male Wistar rats were subjected to early postnatal social and nutritional deprivation by separation of the pups from their mother animals from Day 3 to Day 14 for 16 hours daily. One group of the deprived animals was treated by daily injections of pyridostigmine (1 microgram/0.05 ml saline from Day 1 to Day 4, 5 micrograms/0.05 ml saline from Day 5 to Day 14). At the age of 14 days or 6 months, 5 deprived, 5 deprived and pyridostigmine treated rats and 5 controls were investigated. In the stratum radiatum of the hippocampal CA 1-region the vesicle population of axospinodendritic synapses was examined for quantitative ultrastructural changes using electron microscopic and morphometric methods. The vesicle density (number of vesicles/micron 2 terminal area) was determined in the whole presynaptic terminal as well as in distinct zones in the presynaptic terminal. 14 days of deprivation did not change the vesicle density in the whole presynaptic terminal, but did change the distribution of the vesicles. In 14 days old deprived rats the vesicle density was found to be decreased by about 10% in the presynaptic area bordering the synaptic contact zone (area 1), and it was increased by about 7% in the more distant area of the presynaptic terminal (area 2). Deprivation and simultaneous pyridostigmine treatment resulted in an elevated vesicle density in the whole presynaptic terminal by about 25%, in area 1 by about 8%, and in area 2 by about 30%. At the age of 6 months, the early postnatally deprived rats showed an increase in the vesicle density by about 8% in all areas of the presynaptic terminal when compared with the controls. Simultaneous pyridostigmine treatment led to a reduced vesicle density in the whole presynaptic terminal by about 5%, in area 1 by about 9%, and in area 2 by about 4%. The findings obtained following deprivation are interpreted as being the expression of an insufficient requirement of synaptic mechanisms caused by a lack of sensoric inputs during the early postnatal period. The results obtained in the neonatally pyridostigmine treated rats suggest permanent changes in the neurotransmitter metabolism following treatment with the psychotrophic drug. This may reflect a mechanism to compensate the effect of deprivation by neonatal pyridostigmine administration.

Animals↗
PubMed1986

[Effect of early postnatal social and nutritional deprivation and simultaneous treatment with pyridostigmine on synaptogenesis in the hippocampus of the rat. Electron microscopy, morphometric and stereologic studies].

During the first two weeks of life newborn male Wistar rats were subjected to social and nutritional deprivation. One group of the deprived animals was treated by daily injections of pyridostigmine (1 microgram/0.05 ml saline from Day 1 to Day 4, 5 micrograms/0.05 ml saline from Day 5 to Day 14). At the age of 14 days or 6 months, 5 deprived, 5 deprived and pyridostigmine treated animals and 5 controls were sacrificed by perfusion. The stratum radiatum of the hippocampal CA1-region was investigated for quantitative ultrastructural changes using electron microscopic, morphometric and stereologic methods. The following results were obtained: The number of synapses per unit area or per unit volume brain tissue (hippocampus) was found to be reduced by about 10% in 14 days old deprived as well as in deprived and pyridostigmine treated rats in comparison to the controls. At the age of 6 months both groups of the experimental animals showed an increase in the density of synapses by about 20% when compared to the controls. The proportion of axo-spinodendritic synapses in the total number of synapses (axo-dendritic and axo-spinodendritic synapses) was decreased on Day 14 and was increased at the age of 6 months in the neonatally deprived rats. Following additional pyridostigmine treatment, both in the juvenile and in the adult rats the ratio of axo-spinodendritic to axo-dendritic synapses was approximated to that of the controls. The calculation of the volume of all presynaptic terminals or all postsynaptic spines per unit volume brain tissue (volume density) revealed a decrease by about 6% (terminals) or 5% (spines) on Day 14 after deprivation and an increase by about 8% (terminals) or 14% (spines) following simultaneous pyridostigmine administration. At the age of 6 months the presynaptic terminals in early postnatally deprived rats showed a higher volume density by about 14%. In the deprived and pyridostigmine treated animals volume density enhancements were obtained for the terminals (by about 7%) and for the spines (by about 25%). The volume and surface of an individual presynaptic terminal were unchanged in 14 days old as well as in 6 months old deprived rats in comparison to the controls. Deprivation and simultaneous pyridostigmine treatment led to an increase in the volume (by about 25%) and the surface (by about 12%) of the terminals on Day 14. However, at the age of 6 months the volume and surface were reduced by about 14% or 12% when compared to the controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Effect of early and late postnatal hypoxia on subcellular synaptosomal fractions from cerebral cortex of rats. I. An electron-microscopical and biochemical study.

Synaptosomal fractions of brain cortex of rats exposed to moderate intermittent hypobaric hypoxic conditions during the first or second decade of the postnatal life were investigated electron microscopically one day or up to one week after the hypoxia experiment. Mitochondria and synaptosomes with impaired morphology were observed to occur more frequently in fractions obtained from hypoxic animals. Synaptosomes showed lesions of the outer membrane and loss of the synaptoplasmatic content, or condensation of the synaptosomal content with increasing electron density, deformation of the synaptosomes in size and shape, disappearance of structural details, degeneration of intrasynaptosomal mitochondria in form of strong condensation and, finally, formation of intrasynaptosomal vacuoles with dense core inclusions. The mitochondrial reaction was characterized by two antagonistic configurations: condensation of the matrix with secondary enlargement of the intracistal spaces and of the outer compartment and, finally, the decay of the matrix condensate in several crumbs. On the other hand, swelling of the matrix with strong enlargement of the whole mitochondrium, later defects in the outer membrane and the degeneration into empty mitochondrial ghosts, appearing in the upper fractions. Some characteristic marker enzymes were tested in the fractions. The results hint at an elevated vulnerability of synaptosomes obtained from animals exposed to postnatal hypoxia, as indicated by the lowered quotient of LDH activities after and before addition of Triton X-100. Furthermore, there are clues to a decrease in the number of synaptic connections within the cortex of hypoxia exposed animals, as is concluded from the diminished AChE activity in the subcellular fractions of these animals. However, no different effect of early or late postnatal hypoxia exposition was evident in the biochemical parameters.

Acetylcholinesterase↗
PubMed1986

Effect of early and late postnatal hypoxia on subcellular synaptosomal fractions from cerebral cortex of rats. II. A quantitative ultrastructural study.

Synaptosomal subfractions were isolated by discontinuous sucrose gradient centrifugation from the P2-fraction of cerebral cortices of juvenile rats exposed to moderate intermittent hypobaric hypoxia from day 2-11 (early postnatal period) or from day 12-21 (late postnatal period) after birth. Ultrastructural investigations were carried out on fractions A and E of the preparation. Quantitative parameters of synaptosomes and mitochondria (volume density, numerical density, profile size frequency distribution) were estimated in a stereological analysis. Early postnatal hypoxia exposition strengthened the irreversible swelling of mitochondria. The effect on synaptosomes was less pronounced, very large synaptosomes showed significant condensation. Late postnatal hypoxia exposition resulted in strong condensation of synaptosomes in all size classes and similar reaction in mitochondria. Both hypoxia experiments produced an enhanced vulnerability of the synaptosomal membranes against the fractionation procedure and the appearance of monstrous large condensed synaptosomes. The results are discussed in view of hypothetical biochemical mechanisms underlying these changes.

Age Factors↗
PubMed1985

Accuracy of blood alcohol estimations obtained with a breath alcohol analyser in a casualty department.

The accuracy and reliability of a rapid blood alcohol estimation by means of a breath alcohol analyser has been evaluated under casualty department conditions in a series of 646 road-crash victims managed at the Dandenong and District Hospital. A higher correlation (r = 0.91) was found between the breath alcohol analyser readings in 633 casualties and those obtained by blood analysis in the police laboratory. In 13 unconscious casualties in whom a nasal breath test was performed, the correlation was lower (r = 0.76). In six casualties, the breath alcohol analyser readings showed lower alcohol concentrations than the legal limit of 0.05 g/100 mL (10.9 mmol/L), but blood analysis detected an illegal concentration. Further evaluation of the accuracy of the breath alcohol analyser in other casualty departments is necessary before it can be recommended as a screening device in States which have legislated for compulsory blood alcohol tests in adult road casualties.

Accidents, Traffic↗
PubMed1985

First report of bluetongue antibody in Chile.

A sample of 1,752 bovine sera collected from 99 herds throughout the Tenth Region, Chile, from March 8 to November 20, 1982, was analyzed for bluetongue (BT) antibodies using the immunodiffusion (ID) test. The prevalence of BT virus (BTV) antibody was 19.6%. Sixty-four (64.6%) herds showed at least 1 positive animal, which suggests an important antibody distribution in the area. The examination of 500 sera of sheep in 14 herds indicated the following results: 8/500 animals were positive in 5/14 of the herds.

Animals↗
PubMed1985

[Stimulation-induced changes in the ultrastructure of the synapses in the hippocampus by post-tetanic potentiation].

Within the frame of experimental brain research at present the phenomenon of potentiation (posttetanic potentiation, long-term potentiation) is considered to provide a possible mechanism of learning processes and memory formation on the synaptic level. Tetanic stimulation of the Nucleus septalis fimbrialis produces the posttetanic potentiation in synapses of the hippocampal CA 3-region, whereafter a long-lasting increase in the amplitude of evoked potentials can be recorded. By quantitative electron microscopical morphometry we investigated the morphological changes in synapses of the Stratum radiatum of the hippocampal CA 3-region of rabbits (1 hour following posttetanic stimulation). Tetanic stimulation of the Nucleus septalis fimbrialis induces an enlargement of the postsynaptic spine area significantly by 28% and a decrease of the mean area of presynaptic terminals by 24%. No changed number of synapses were found in comparison to the controls. Furthermore stimulation of the Nucleus septalis fimbrialis induces a transient decrease of synaptic vesicles in various zones of the presynaptic area, especially near the presynaptic membrane. These results demonstrate morphologically detectable changes as a consequence of synaptic activation. Therefore posttetanic potentiation is characterized by various morphologic changes reflecting probably an early phase of the learning process with transient effects on the ultrastructure of the synapses.

Animals↗