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Biomedical subjects

W Wesemann

Publications and source records attributed to W Wesemann.

At least 19 recordsLinked to original sources
PubMed1993

Immobilization and light-dark cycle-induced modulation of serotonin metabolism in rat brain and of lymphocyte subpopulations: in vivo voltammetric and FACS analyses.

The effect of immobilization and light-dark cycle on the serotoninergic system of the n. raphe dorsalis and on the distribution of blood lymphocyte subpopulations was studied in the rat. As was shown by in vivo voltammetry, 10 min immobilization enhanced serotonin metabolism with a maximum 15 min after immobilization. The distribution of the blood lymphocytes into subpopulations was also affected: pan-T and T helper lymphocytes were reduced during immobilization and reached minimum values after 20 min recovery. The circadian rhythms of serotonin metabolism and the distribution of pan-T and T helper cells exhibited a slight phase shift if compared with each other.

Animals↗
PubMed1992

The effect of adrenergic drugs on serotonin metabolism in the nucleus raphe dorsalis of the rat, studied by in vivo voltammetry.

The serotonin (5-HT) and norepinephrine (NE) system participate in the control of behavioural functions. The experiments were aimed at the question whether the NE system of the locus coeruleus interferes with the 5-HT activity of the nucleus raphe dorsalis and of which receptors are possibly involved. The alpha 1- and beta-adrenoceptor agonists methoxamine and isoproterenol, as well as a high dose (600 micrograms/kg i.p.) of the alpha 2-adrenoceptor agonist clonidine, increased extraneuronal 5-hydroxyindoleacetic acid (5-HIAA) levels in the nucleus raphe dorsalis as measured by in vivo voltammetry. In contrast, a low dose (60 micrograms/kg i.p.) of clonidine and the alpha 1-, alpha 2- and beta-adrenoceptor antagonists, prazosin, piperoxane, and atenolol, reduced the 5-HIAA concentration. In the locus coeruleus, the origin of NE projections to the nucleus raphe dorsalis, clonidine decreased whereas piperoxane enhanced extracellular 3,4-dihydroxyphenylacetic acid (DOPAC), an index of NE metabolism in the locus coeruleus. The results suggest that 5-HT neurotransmission in the nucleus raphe dorsalis is stimulated by the NE system of the locus coeruleus and that adrenoceptor drugs may affect 5-HT neuronal activity in addition to NE neurotransmission.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Serotonin-norepinephrine interactions: a voltammetric study on the effect of serotonin receptor stimulation followed in the N. raphe dorsalis and the Locus coeruleus of the rat.

In vivo voltammetry with carbon fibre electrodes was used to study the effect of the serotoninergic (5-HT) neuronal system on the noradrenergic (NE) system in the Locus coeruleus of the rat. The voltammetric DOPAC signal in the Locus coeruleus, used as a measure of NE neuronal activity, was increased after systemic application of the 5-HT1B agonist CGS-12066B, the 5-HT2 antagonist ritanserin, and, to a lesser extent, by ipsapirone, a 5-HT1A agonist. The findings suggest that the NE neuronal system of the Locus coeruleus is stimulated by 5-HT1A and 5-HT1B receptor activation and inhibited by 5-HT2 receptors. Likewise the 5-HT releaser and uptake inhibitor fenfluramine increased the DOPAC level in the Locus coeruleus. In contrast to the 5-HT1 agonists, which reduced 5-hydroxyindoleacetic acid (5-HIAA) in the Nucleus raphe dorsalis, ritanserin increased the 5-HIAA signal in this nucleus. This finding could help to explain the action of ritanserin as sleep-modulating substance.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Enhanced release of cytokines, interleukin-2 receptors, and neopterin after long-distance running.

This study was designed to examine cytokine production in a group of 22 well-trained runners covering a distance of 20 km within 2 hr. After running, all participants displayed a marked granulocytosis for 7 hr. Plasma neopterin levels increased 1 hr after exercise for 24 hr. Except for interleukin-6 (IL-6), cytokines were not reliably detected in plasma but were present in urine. Already before exercise, cytokines were detected in the urine of runners when compared to sedentary controls. Directly after running, interferon-gamma and tumor necrosis factor-alpha were further elevated but rapidly declined to preexercise levels. Interleukin-1 beta and interleukin-6 increased at a slower rate after exercise but secretion into urine persisted longer until 12 and 7 hr, respectively. Interleukin-2 (IL-2) was not detected but soluble IL-2 receptors appeared in the urine directly after running. Enhanced cytokine levels were accompanied by an only low creatinin kinase increase, indicating little muscle damage. These data show that long-distance running elevates cytokine production which supports the concept that regular, but not excessive, physical exercise may be beneficial by maintaining a stimulated immune system.

Adult↗
PubMed1992

Circadian and seasonal rhythms of 5-HT receptor subtypes, membrane anisotropy and 5-HT release in hippocampus and cortex of the rat.

Specific serotonin binding (5-HT1, 5-HT1A, and 5-HT2 subtypes) and membrane anisotropy were measured at 2 h intervals over a 24 h period in the hippocampus and cortex of Wistar WU rats, housed under a 12 h light-dark cycle, with lights on at 07.00. All experiments were performed both in March and December. In the hippocampus significant circadian rhythms could be ascertained for 5-HT1 binding sites in March and December while for 5-HT1A (subtype of 5-HT1) binding sites the circadian rhythm was only significant in March. The membrane anisotropy also showed significant variations only in March. Circadian rhythms were also found in the cortex for 5-HT1 (December) and 5-HT2 (March and December) binding sites as well as for the membrane anisotropy (December). A correlation was found between membrane anisotropy and 5-HT1 and 5-HT2 binding sites in hippocampus and cortex, respectively. A circadian rhythmicity was also observed for serotonin release as measured by in vivo voltammetry in both brain areas. The results obtained on the diurnal variations of serotonin receptor subtypes and serotonin release and the probable inverse relationship of these two parameters may be relevant in understanding the coupling of pre- and postsynaptic activity.

Analysis of Variance↗
PubMed1992

Contrast dependence of the oscillatory motion threshold across the visual field.

Observer sensitivity to oscillatory step displacements of sine-wave gratings was investigated at various loci in the visual field (0-30 degrees) as a function of contrast. Detection thresholds at 10 Hz and high grating contrasts were approximately 11-15 arcsec in the fovea and 37-47 arcsec at 30 degrees eccentricity. At any given contrast, threshold displacement increases linearly with eccentricity. The data provide evidence against an interpretation based on cortical magnification, because the slope and the scale-free x intercept of the eccentricity function vary strongly with contrast. While foveal thresholds for high-contrast gratings are in the range of the hyperacuities, the oscillatory motion threshold falls off an order of magnitude more slowly than the traditional hyperacuities. Rather than conceiving of the oscillatory motion threshold as a spatial acuity limited by cortical magnification, we suggest an alternative approach that is based on a form of contrast discrimination. Oscillatory motion can be decomposed into the sum of a modulating counterphase grating and a static masking grating, both of which are in spatial quadrature (i.e., 90 degrees out of phase). At low grating contrast, oscillatory motion can be detected when the counterphase component exceeds a constant contrast value. Above a critical contrast value of the static component Cscrit, threshold rises as a power function of contrast with a slope near 1.0. The critical contrast value Cscrit increases linearly with eccentricity, indicating that oscillating gratings observed with the peripheral visual field are less easily masked compared with foveally fixated gratings.

Contrast Sensitivity↗
PubMed1992

Therapy of Morbus Parkinson and radical-induced neurotoxicity in the rat--in vivo voltammetric studies.

In vivo pulse voltammetry was used to study the effect of anti-parkinsonian drugs and of neurotoxins in rat striatum. It could be demonstrated that besides the well-known changes of total dopamine (DA) concentrations the applied drugs affected also the extraneuronal DA metabolism in the living rat. In addition, neurotoxin-treated rats can be used as a model to study some aspects of the Parkinson syndrome.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1991

The lack of receptors for atrial natriuretic peptides on human monocytes prevents a rise of cGMP and induction of tumor necrosis factor-alpha synthesis.

Freshly harvested human monocytes were shown to produce tumor necrosis factor-alpha (TNF-alpha) in response to exogenously added or sodium nitroprusside-generated cGMP. In contrast, atrial natriuretic peptide (ANP) that acts by elevating cGMP in a variety of cells, was incapable of inducing TNF-alpha synthesis. This failure was due to a lack of ANP receptors and thus, to the inability of ANP to raise cGMP in human monocytes.

Atrial Natriuretic Factor↗
PubMed1991

Theory of eccentric photorefraction (photoretinoscopy): astigmatic eyes.

An optical analysis of eccentric photorefraction (photoretinoscopy) of astigmatic eyes is presented. The size and the angular tilt of the dark crescent appearing in the subject's pupil are derived as a function of five variables: the ametropia of the eye (Dsph, Dcyl, axis), the eccentricity of the flash, e, and the distance of the camera from the subject's eye, dc. A simplified solution and a solution of the inverse problem, which enable one to calculate the degree of ametropia from the size and the tilt of the crescent, are also presented. If the crescent is smaller than the pupil, both the size and the tilt of the dark crescent are independent of the pupil size. The angular tilt of the crescent is also independent of the eccentricity. Characteristic changes of the crescent as a function of the cylinder axis are illustrated for compound and mixed astigmatisms. The validity of the theoretical predictions was experimentally verified on a model eye.

Astigmatism↗
PubMed1991

A study of brain dopamine sulfate levels in relation to free dopamine and homovanillic acid in Parkinson's disease.

High performance liquid chromatography with electrochemical detection was used for determining dopamine sulfate in human brain tissues. Dopamine sulfate was examined in the striatum and frontal cortex of human brain. The concentrations of dopamine sulfate in these regions are extremely low in comparison to free dopamine, and to dopamine sulfoconjugates in the cerebrospinal fluid, plasma and urine. Data obtained with this technique in human post mortem brain specimens indicate that the analysis of tissues and body fluids for dopamine conjugates is useful for profiling metabolic dopamine activity in controls and neurodegenerative disorders like Parkinson's disease.

Brain↗
PubMed1990

[Comparison of the Lithander (Kolt test) pediatric visual acuity test with the standardized Landolt ring test].

The visual acuity values obtained with the four test figures of Lithander's "Kolt-test" have been compared with Landolt ring acuity under standardized conditions which meet the requirements of DIN 58,220 and ISO/DIS 8596/7. For a given test figure size, the Kolt-test optotypes turned out to be somewhat easier legible than the Landolt ring. On average, visual acuity measured with the Kolt-test exceeded Landolt ring acuity by 0.08 log (angle of resolution) units. Thus, according to DIN and ISO criteria, the legibility of the Kolt-test is not equivalent to the standard Landolt ring. Equal acuity values could be obtained by increasing the observation distance proposed by the manufacturer of the Kolt-test by 19%. The legibility of the four optotypes differs on adult subjects: "circle" is more difficult, "cross" is easier legible than "square" and "triangle". Confusion of Kolt-test figures is basically restricted to two pairs of two optotypes ("cross" - "triangle", "square" - "circle").

Adult↗
PubMed1989

Effects of two isomeric 1-aminoadamantanes on the membrane anisotropy and on alpha- and gamma-motoneurones excitability.

The structure-activity relationship of two isomeric 1-aminoadamantanes, 1-C-ethylaminoadamantane (D 174) and 1-amino-3-ethyladamantane (D 175), on membrane anisotropy and the excitability of neurons was studied in the CNS of the rat and in the decerebrated cat. Mass spectrometric analysis showed that after a single, 40 mg/kg dose, D 174 and D 175 were unevenly distributed within the CNS of the rat, moreover the distribution pattern of the two substances was different. As measured by fluorescence depolarization in controls the membrane anisotropy was found to be higher in the older parts as compared with the younger parts of the CNS. After i.p. application of 40 mg/kg the membrane anisotropy was reduced in the cortex by D 174, whereas D 174 and D 175 increased the rigidity in striatal membranes. If cortical membranes were incubated with the substances, the fluidizing effect of D 174 was more prominent than that of D 175. In the decerebrated cat only D 174 in a dose of 5 mg/kg i.p. raised the discharge of spinal alpha-motoneurones significantly. The results suggest that the membrane architecture is more affected by D 174 as compared with D 175 which is reflected by a greater effect on membrane anisotropy as well as on the activity of spinal alpha-motoneurones.

Adamantane↗
PubMed1989

Measurement of spatial contrast sensitivity with the swept contrast VEP.

Contrast response functions (CRFs) for the VEP were obtained with a Discrete Fourier Transform (DFT) technique employing swept contrast gratings. VEP CRFs in infants were found to have a form similar to those observed in adults, being linear functions of log contrast over a range of near-threshold contrasts. CRFs with low and high contrast lobes were present in infants, as they are in adults. Contrast thresholds were estimated by extrapolation of the CRF to zero microvolts. The effects of additive EEG noise and of the DFT data window on the shape of the measured CRF are considered. For large signals, the measured CRF is nearly independent of the additive noise, but at small signal values additive noise introduces a small bias towards larger amplitudes. The VEP signal-plus-noise distribution was modeled as a family of Rice distributions in order to evaluate the effects of bias on the estimates of threshold. The amount of bias depends inversely upon the slope of the CRF. The amount of bias introduced by a smoothing window also depends upon slope of the CRF as well as the sweep rate. The combined effects of additive noise and window bias were such that the total bias was nearly independent of CRF slope. Sweep VEP contrast thresholds were shown empirically to be unaffected by changes in the range of contrast swept.

Adult↗
PubMed1989

Correlation of membrane anisotropy with function in subpopulations of human blood platelets.

Human blood platelets were fractionated on a discontinuous Percoll gradient into high density (HD), intermediate (ID), and low density (LD) platelets. The subpopulations were characterized with regard to [14C]serotonin uptake and release, cAMP content, aggregation, and membrane anisotropy, which is inversely related to membrane fluidity. Membrane anisotropy, which was high in LD platelets, was found to decrease with increasing density (LD greater than ID greater than HD). LD platelets showed significant lower cAMP levels and [14C]serotonin uptake than the total platelet population (TPP) and ID and HD platelets. Upon ADP and serotonin stimulation the cAMP content was reduced in all platelet populations with the exception of HD platelets in which cAMP was unchanged. Upon thrombin stimulation the cAMP content was reduced only in TPP and LD platelet population and it was increased in HD platelet population. Thrombin activation changed the anisotropy only in LD platelets. Thrombin at a concentration of 0.001 U/ml reduced whereas 0.01 and 0.05 U thrombin/ml increased the membrane anisotropy significantly. As compared with TPP and the other subpopulations, LD platelets were most sensitive upon ADP and thrombin stimulated [14C]serotonin release as well as upon ADP, serotonin and thrombin induced aggregation. The findings suggest that the differing functional abilities of the platelet subpopulations are correlated to the various membrane anisotropies observed in these fractions.

Adenosine Diphosphate↗
PubMed1989

Absolute ocular fundus dimensions measured by multiple-beam interference fringes.

Multiple-beam interference fringes have been projected onto the retina to serve as a size reference for fundus photography. The absolute fringe spacing is determined by measurable parameters. The interference fringes are extremely narrow so that fringe maxima and fundus structures can be perceived equally well, and a high precision of measurement is achieved. The method has been applied to a model eye of varying ametropia (within +/- 7 diopters). The reproducibility of measurement is within 0.5%. In vivo measurements on human eyes demonstrate the clinical applicability.

Fundus Oculi↗
PubMed1988

Effects of daytime noise load on the sleep-wake cycle and endocrine patterns in man. III. 24 hours secretion of free and sulfate conjugated catecholamines.

This study was designed to re-examine the circadian profiles of dopamine, noradrenaline and adrenaline in the plasma and to investigate the influence of daytime noise stress on these profiles. Twelve subjects participated in two experimental series of 60 h; during one they were exposed to 85 dB(A) industrial noise from 9:00 to 21:00 h. Blood samples were taken for a period of 24 h at 20 min intervals and the plasma levels of the free and the sulfoconjugated catecholaminergic compounds were simultaneously measured. A significant (p less than 0.001) circadian rhythm was found for free noradrenaline, free adrenaline and conjugated dopamine. Noise stress significantly increased (p less than 0.001) free adrenaline levels during the first 6 h of exposure and lowered (p less than 0.001) free noradrenaline values during the whole time of exposure; dopamine did not respond. It was concluded that strong noise load has effects on the sympatho-adrenomedullary system but the actual release pattern of each catecholaminergic metabolite is controlled by separate determinants.

Adult↗