Biomedical subjects

M Pohl

Publications and source records attributed to M Pohl.

At least 55 records · Page 3Linked to original sources

PubMed1997

Enkephalinergic and dynorphinergic neurons in the spinal cord and dorsal root ganglia of the polyarthritic rat - in vivo release and cDNA hybridization studies.

Complex and contradictory data have been reported regarding the changes in spinal opioidergic systems associated with chronic inflammatory pain in the rat. In an attempt to solve these discrepancies, the in vivo release of met-enkephalin and dynorphin and the expression of the corresponding propeptide genes were investigated at the spinal level in arthritic rats and paired controls. A dramatic increase in the concentration of prodynorphin mRNA (+300-550%) and a less pronounced elevation of that of dynorphin-like material (+40-50%) were found in the dorsal part of cervical and lumbar segments of the spinal cord in rats rendered arthritic by an intradermal injection of Freund's adjuvant four weeks prior to these measurements. In addition, the spinal release of dynorphin-like material (assessed through an intrathecal perfusion procedure in halothane-anaesthetized animals) was approximately twice as high in arthritic rats as in controls. In spite of significant elevations in the levels of both met-enkephalin (+30-70%) and proenkephalin A mRNA (+40-50%) in the dorsal part of cervical and lumbar segments, the spinal release of met-enkephalin-like material was decreased (-50%) in arthritic rats as compared to paired controls. Proenkephalin A mRNA (but not prodynorphin mRNA) could be measured in dorsal root ganglia, and its levels were dramatically reduced in ganglia at the lumbar segments in arthritic rats. Such parallel reductions in the spinal release of met-enkephalin-like material and the levels of proenkephalin A mRNA in dorsal root ganglia of arthritic rats support the idea that the activity of primary afferent enkephalinergic fibres decreases markedly during chronic inflammatory pain.

Animals↗

PubMed1997

Silent period following transcranial magnetic stimulation: a study of intra- and inter-examiner reliability.

Transcranial magnetic stimulation-evoked silent period (SP) has been attributed largely to the activity of intracortical inhibitory systems and recent reports provided evidence that it is a useful indicator of central motor disturbances. We studied the intra- and inter-examiner reliability of SP measurements in 28 healthy subjects. In 15 subjects SP measurements were performed by one single examiner and repeated by the same examiner 3 days and 7 days later, showing a high degree of intra-examiner reliability over time. In another subgroup consisting of 13 volunteers SP measurements were performed on the same subject by three different examiners, demonstrating a higher level of variability. In both subgroups we found a high interindividual variability ranging from 44-258 ms and a considerably lower side-to-side difference within subjects. Our results suggest that longitudinal assessments of the SP in patients with central motor involvement should optimally be performed by a single examiner. Regarding the wide range of possible SP durations in healthy subjects the intraindividual side-to-side symmetry seems to be the most valuable parameter.

Adult↗

PubMed1997

Ultrasound studies of the intestinal wall in patients with cystic fibrosis.

BACKGROUND: In 1994, first published reports described cystic fibrosis patients who experienced a then unknown complication-ileocecal and colonic stenoses with submucosal proliferation requiring surgical intervention. To investigate a suspected correlation between increased intestinal wall diameter and high doses of pancreatic enzymes, we carried out a prospective study in our CF-outpatient clinic. METHODS: By ultrasound analysis we measured the intestinal wall diameter in 201 patients. One hundred ninety-three patients treated with pancreatic enzymes had pancreatic insufficiency. Eight patients showed normal pancreatic function, seven of them had never been treated with pancreatic enzymes. The control group included 12 healthy children. Measuring points were the distal ileum, cecum, ascending, and descending colon. Measurements were made by the longitudinal and cross sectional cut. The following aspects of the patients' history were recorded (a) current type of pancreatic enzyme medication; (b) total dosage per day (with reference to lipase units); (c) duration of therapy with standard-strength pancreatic enzyme (SSPE) preparations (< or = 10,000 lipase units per capsule) and HSPE preparations (> or = 20,000 lipase units per capsule); (d) gastrointestinal complication (distal intestinal obstruction syndrome, meconium ileus, abdominal surgery, intussusception), diabetes mellitus, and hepatobiliary complications. RESULTS: The intestinal wall diameter in patients receiving HSPE therapy was greater (with prominent submucosal layer) than that in patients receiving SSPE therapy or in patients with pancreatic sufficiency. Healthy subjects had the smallest intestinal wall diameter. There was no correlation between patient history and increased intestinal wall thickness. CONCLUSIONS: Ultrasound detects characteristic ileocecal wall lesions in the majority of cystic fibrosis patients on pancreatic enzymes. These lesions may lead to significantly increased ileocecal wall thickness, which is correlated but not restricted to HSPE.

Adolescent↗

PubMed1997

Ureteral xanthine calculus and aberrant umbilical artery causing ureteral obstruction.

A 30-month-old girl presented with gastrointestinal symptoms and a febrile urinary tract infection. Sonographic and radiographic imaging demonstrated left hydronephrosis due to a radiolucent ureteral stone. Surgical exploration identified an aberrant, patent left umbilical artery causing ureteral obstruction. Stone and urine analyses revealed hereditary xanthinuria that had not previously been recognized in this child and her family.

Child, Preschool↗

PubMed1997

Protein design on pyruvate decarboxylase (PDC) by site-directed mutagenesis. Application to mechanistical investigations, and tailoring PDC for the use in organic synthesis.

Pyruvate decarboxylases (E.C. 4.1.1.1) from various organisms have been studied for many years, mainly with respect to the mechanism of the non-oxidative decarboxylation reaction. Although the C-C-bond-forming properties of these enzymes are known and have been applied for many years in biotransformations for the synthesis of chiral alpha-hydroxy ketones, only little is known about the factors influencing the carboligase side-reaction. The present review surveys recent efforts in the study of site-directed mutagenesis on PDCs, which are discussed against a background of the structural and kinetical investigations. It also includes recent studies on tailoring the PDCs of Zymomonas mobilis for the syntheses of (R)-phenylacetyl carbinol (PAC), a pre-step in the synthesis of L-ephedrine, by protein design techniques.

Amino Acid Sequence↗

PubMed1996

In vitro testing of artificial heart valves: comparison between Newtonian and non-Newtonian fluids.

The in vitro testing of artificial heart valves is often performed with simple fluids like glycerol solutions. Blood, however, is a non-Newtonian fluid with a complex viscoelastic behavior, and different flow fields in comparable geometries may result. Therefore, we used different polymer solutions (Polyacrylamid, Xanthan gum) with blood-like rheological properties as well as various Newtonian fluids (water, glycerol solutions) in our heart valve test device. Hydrodynamic parameters of Björk-Shiley heart valves with a tissue annulus diameter (TAD) of 21-29 mm were investigated under aortic flow conditions. Major results can be summarized as follows. The mean systolic pressure differences depend on the model fluids tested. Closing time and closing volume are not influenced by the rheological behavior of fluids. These parameters depend on TAD and the pressure differences across the valve. In contrast, rheological behavior has a pronounced influence upon leakage flow and leakage volume, respectively. Results show furthermore that the apparent viscosity data as a function of shear rate are not sufficient to characterize the rheological fluid behavior relevant to hydrodynamic parameters of the heart valves investigated. Therefore, similarity in the yield curves of non-Newtonian test fluids mimicing blood is only a pre-requisite for a suitable test fluid. More information about the viscous and elastic component of the fluid viscosity is required, especially in geometries where a complex flow field exists as in the case of leakage flow.

Acrylic Resins↗

PubMed1996

Genetic homogeneity of autoimmune polyglandular disease type I.

Autoimmune polyglandular disease type I (APECED) is an autosomal recessive autoimmune disease (MIM 240300) characterized by hypoparathyroidism, primary adrenocortical failure, and chronic mucocutaneous candidiasis. The disease is highly prevalent in two isolated populations, the Finnish population and the Iranian Jewish one. Sporadic cases have been identified in many other countries, including almost all European countries. The APECED locus has previously been assigned to chromosome 21q22.3 by linkage analyses in 14 Finnish families. Locus heterogeneity is a highly relevant question in this disease affecting multiple tissues and with great phenotypic diversity. To solve this matter, we performed linkage and haplotype analyses on APECED families rising from different populations. Six microsatellite markers on the critical chromosomal region of 2.6 cM on 21q22.3 were analyzed. Pairwise linkage analyses revealed significant LOD scores for all these markers, maximum LOD score being 10.23. The obtained haplotype data and the geographic distribution of the great-grandparents of the Finnish APECED patients suggest the presence of one major, relatively old mutation responsible for approximately 90% of the Finnish cases. Similar evidence for one founder mutation was also found in analyses of Iranian Jewish APECED haplotypes. These haplotypes, however, differed totally from the Finnish ones. The linkage analyses in 21 non-Finnish APECED families originating from several European countries provided independent evidence for linkage to the same chromosomal region on 21q22.3 and revealed no evidence for locus heterogeneity. The haplotype analyses of APECED chromosomes suggest that in different populations APECED is due to a spectrum of mutations in a still unknown gene on chromosome 21.

Alleles↗

PubMed1996

The two orphan Na+/Cl(-)-dependent transporters Rxt1 and V-7-3-2 have an overlapping expression pattern in the rat central nervous system.

The messenger RNA expression patterns of two orphan Na+/Cl(-)-dependent transporters, Rxt1 and V-7-3-2, were compared in the adult rat CNS by in situ hybridization histochemistry. The sites of synthesis of both orphan transporters were found to largely overlap. The highest concentrations of Rxt1 and V-7-3-2 mRNAs were present in the olfactory bulb, cerebral cortex, hippocampus, habenular and pontine nuclei, and cerebellum. Low levels of orphan transporters mRNAs were observed in the basal ganglia (caudate-putamen, nucleus accumbens, globus pallidus), septum nuclei, substantia nigra, colliculi and brainstem. Only few regions were found to express only one of these two orphan transporters: Rxt1 mRNA in the thalamic area and the hilus of the dentate gyrus. V-7-3-2 mRNA in motoneurons of the most ventral zone of the spinal cord. Rxt1 mRNA was generally more abundant than V-7-3-2 mRNA, except in few areas (piriform cortex, horizontal limb of the diagonal band, medial habenular nucleus, pyramidal and granular cell layers in the hippocampus) where the levels of both mRNAs were similar. The overall parallelism between both distributions was further confirmed at the cellular level on emulsion-coated sections, especially in the hippocampus where pyramidal and granular neurons very probably synthesize both Rxt1 and V-7-3-2. These data provide a further demonstration of the synthesis of the orphan transporters Rxt1 and V-7-3-2 exclusively in neurons whose locations suggest that they might correspond to glutamatergic neurons and subsets of GABAergic neurons.

Amino Acid Sequence↗

PubMed1995

The replacement of Trp392 by alanine influences the decarboxylase/carboligase activity and stability of pyruvate decarboxylase from Zymomonas mobilis.

The bulky tryptophan residue 392 located in the deep cleft leading to the active center of pyruvate decarboxylase (PDC) from Zymomonas mobilis was changed to alanine which is found in the equivalent position of PDC from yeast. The mutation reduced the decarboxylase activity towards pyruvate by a factor of two (60-70 U/mg), whereas the Km (1.1 mM in Mes/KOH buffer) remains unchanged compared with the wild-type enzyme. The apparent Km for thiamine diphosphate (thiamin-P2) in the presence of 5 mM MgSO4 was increased by a factor of 10 (84 microM in Mes/KOH buffer) and the tetrameric mutant protein was less stable, as indicated by urea denaturation experiments. The mutation enhanced the carboligase activity of the enzyme towards benzaldehyde by a factor of four. The resulting alpha-hydroxyketone was identified as (R)-phenylacetylcarbinol.

Acetone↗

PubMed1995

In situ hybridization evidence for the synthesis of 5-HT1B receptor in serotoninergic neurons of anterior raphe nuclei in the rat brain.

The regional distribution of the mRNA encoding the serotonin 5-HT1B receptor was studied in the central nervous system of the rat by in situ hybridization histochemistry and Northern blot analysis. A 180 base pair probe, corresponding to a highly selective portion of the third intracellular loop of the rat 5-HT1B receptor, was used. In most regions, a single 5 kb message was found by Northern blot analysis. However, two additional bands (2.5 and 4 kb) were detected in the striatum. The rank order of 5-HT1B mRNA abundance was striatum >> septum = ventral tegmentum > or = colliculi = hypothalamus = hippocampus > brain stem > or = cerebellum > or = dorsal horn of the spinal cord > cerebral cortex > or = ventral horn of the spinal cord > olfactory tubercle. This distribution was confirmed by in situ hybridization, which further revealed that the 5-HT1B mRNA was present in dorsal root ganglia, the layer IV of the cerebral cortex, the Purkinje cell layer of the cerebellum, the pyramidal neurons in the CA1 area of the hippocampus, and the dorsal and median raphe nuclei. In situ hybridization was also performed in nomifensine (10 mg/kg/i.p.)-pretreated rats whose serotoninergic neurons were extensively and selectively lesioned by microinjection of 5,7-dihydroxytryptamine (8 micrograms/1 microliter) directly into the anteroventral vicinity of anterior raphe nuclei 3 weeks before sacrifice. In lesioned rats, 5-HT1B mRNA was present in the same areas and at the same levels as in control rats, except in the dorsal and median raphe nuclei, where a marked decrease (-75%) in its local concentration was observed. These data provide the first demonstration of the synthesis of 5-HT1B receptor within serotoninergic neurons, as expected of their presynaptic autoreceptor function at the level of serotoninergic terminals.

5,7-Dihydroxytryptamine↗

PubMed1995

Chromosomal localization of opioid peptide and receptor genes in the mouse.

Opiate receptors are the primary targets for the drugs of abuse morphine and heroin. In this study, we completed the localization on mouse chromosomes of the genes encoding mu (Oprm) and kappa (Oprk) receptors, as well as the genes for the opioid propeptides proenkephalin (Penk) and prodynorphin (Pdyn). The genetic mapping was performed using a panel of DNA samples from an interspecific cross [C3H/HeJ-gld and (C3H/HeJ-gld x Mus spretus)F1] that has been characterized for more than 800 markers throughout the genome. The genes are localized on mouse Chr 1 (Oprk, 10 cM from the centromere), Chr 2 (Pdyn, 75 cM from the centromere), Chr 4 (Penk, 1 cM from the centromere) and Chr 10 (Oprm, 10 cM from the centromere). Interestingly, the gene for the mu receptor is located in the same region as a Quantitative Trait Locus for high morphine consumption, thus raising the possibility of its direct role in drug abuse mechanisms.

Animals↗

PubMed1995

Reversible renin mediated massive proteinuria successfully treated by nephrectomy.

We report on a patient with severe hypertension and nephrotic range proteinuria, which were renin mediated in origin. Aortography demonstrated occlusion of the right renal artery and renal vein renin measurements lateralized strongly to the right kidney. Removal of the right kidney led to amelioration of hypertension and proteinuria. Massive proteinuria in this setting is due to high levels of intrarenal angiotensin II and is reversible with deactivation of the renin-angiotensin system.

Aged↗

PubMed1995

[Differentiated evaluation of heart valve stenosis by expanded Bernoulli equation--in vitro studies of model stenoses].

A suitable measure for the hydrodynamic assessment of heart valve stenoses must be independent of flow and should correspond to the morphology of the stenoses. The "effective orifice area" according to Gorlin does not fulfil this requirement, generally, because it is constant only under special conditions. This suggests the development of a multidimensional stenosis model. The idea for doing so is based on hydrodynamic evaluation of different elementary stenosis types in comparison with a valve that behaves like Gorlin's theory. The Bernoulli equation can than be expanded definitely and one gets a set of unknown stenosis parameters corresponding to the elementary stenoses. The clinical relevance of these must be evaluated by morphological evidence and by similarity of the flow-pressure drop characteristics as compared to real heart valve stenoses. A suitable reference valve is the Björk-Shiley valve. This valve was combined with evident elastic and stiff obstacles to opening with the result of flow-pressure drop characteristics similar to biological valves written in terms of flow q: [formula: see text] where q and q2 are mean flow and mean square flow through the valve, respectively. Empirical results reported in the literature can be explained as special cases of the stenosis model as demonstrated by examples. The proposed equation can be interpreted in physically founded terms in contrast with an empirical one. It gives rise to a differentiated evaluation of heart valve stenosis by orifice area (c2), elastic properties of shape and material (c1) and pre-stress (c0) independent on flow. The model can be extended step by step as required.

Aortic Valve↗

PubMed1994

Reversible dissociation and unfolding of pyruvate decarboxylase from Zymomonas mobilis.

The denaturation and renaturation process of pyruvate decarboxylase (PDC) from Zymomonas mobilis (ATCC 29191) has been investigated using guanidine hydrochloride and urea as denaturing agents. The quarternary structure of the homotetramer is strongly stabilized by the cofactors Mg2+ and thiamine diphosphate (TDP). The structural transitions were monitored by activity measurements, fluorescence spectroscopy, circular dichroism and gel-filtration chromatography. A three-step denaturation process, described as follows, is indicated by non-coincidental denaturation curves: (a) inactivation of the tetramer upon dissociation of cofactors (> 0.4 M guanidine hydrochloride, > 1 M urea); (b) dissociation of the tetramer into monomers (> 1 M guanidine hydrochloride, > 3 M urea); (c) complete unfolding of these (> 2.5 M guanidine hydrochloride, > 5 M urea). The refolding process initiated by rapid dilution of fully denatured protein in renaturation buffer involves the rapid reassociation of an inactive intermediate followed by the reconstitution of the active site.

Amino Acid Sequence↗

PubMed1994

Differential effects of the novel analgesic, S 12813-4, on the spinal release of substance P- and calcitonin gene-related peptide-like materials in the rat.

The possible inhibitory control by the novel analgesic S 12813-4 (3-(2-(4-phenylpiperazine-1-yl)-ethyl)-2-oxo-2,3- dihydrooxazolo(b)pyridine) of spinal neurones containing substance P (SP) and/or calcitonin gene-related peptide (CGRP) was assessed in vitro and in vivo in the rat. S 12813-4 (10 nM-0.1 mM) did not affect the spinal release of CGRP-like material (CGRPLM) but inhibited in a concentration dependent manner the K(+)-evoked overflow of SP-like material (SPLM) from slices of the dorsal half of the rat lumbar enlargement. The inhibitory effect of 10 microM S 12813-4 on SPLM release was not additive with that of Na (0.1 mM), and could be prevented by the alpha 2-adrenoceptor antagonist idazoxan (10 microM). Similarly, idazoxan (10 microM) suppressed the inhibition by intrathecally administered S 12813-4 (10 microM) of the spinal outflow of SPLM in halothane anaesthetized rats whose intrathecal space was perfused with an artificial cerebrospinal fluid. These data suggest that the analgesic effect of S 12813-4 might involve some alpha 2-adrenoreceptor-mediated control of SPLM release within the spinal cord. Whether this control concerns SP-containing primary afferent fibres (presynaptic inhibition) or SP-containing interneurones and/or bulbo-spinal SP-ergic pathways (postsynaptic inhibition) deserves further investigations.

Adrenergic alpha-Antagonists↗

PubMed1994

Characterization of an atypical member of the Na+/Cl(-)-dependent transporter family: chromosomal localization and distribution in GABAergic and glutamatergic neurons in the rat brain.

A 3.7-kb cDNA fragment, designated rat-XT1, was isolated from a rat whole-brain cDNA library. The nucleotide sequence of XT1 codes for a 727 amino acid protein with a calculated molecular mass of 81,139 Da and 12 putative transmembrane domains. This protein shares significant homology (28-32%) with the monoamine- (dopamine, norepinephrine, serotonin), amino acid- (taurine, proline, GABA, glycine), choline-, and betaine-, Na+/Cl(-)-dependent transporters. The homology is especially high within the first, second, sixth, and eighth transmembrane domains (45-75%). Thus, XT1 clearly belongs to the Na+/Cl(-)-dependent neurotransmitter transporter superfamily. However, XT1 may define a new subfamily of transporter because it differs structurally from other members of this family in that the extracellular loop linking transmembrane domains 7 and 8 and the C-terminal tail are significantly larger in size. Transient or stable expression of rat-XT1 failed to confer to the transfected cells the ability to transport actively any of the > 60 established or putative neurotransmitter substances assessed. Northern blot analyses of peripheral and neural tissues demonstrated that expression of the 8-kb XT1 mRNA is essentially restricted to the nervous system. In situ hybridization demonstrated a broad but discrete localization of XT1 message in the CNS, particularly in the cerebellum (Purkinje and granular cell layers), the hippocampus (pyramidal and granular cell layers), and the thalamus and throughout the cerebral cortex. This distribution parallels that of the neurotransmitters glutamate and aspartate; however, neither of these excitatory amino acids is a substrate for transport. One noticeable exception to the codistribution of the mRNA for rat-XT1 and these excitatory neurotransmitters is the cerebellar Purkinje cell layer, in which GABAergic neurons are localized. The gene encoding for XT1 is localized to the mouse chromosome 3 in the vicinity of the locus for the mouse neurological disorder spastic (spa).

Amino Acid Sequence↗

PubMed1994

Expression of preproenkephalin A gene and presence of Met-enkephalin in dorsal root ganglia of the adult rat.

The expression of the preproenkephalin A gene was investigated in adult rat dorsal root ganglia (DRG). A radioimmunoassayable Met-enkephalin (ME)-like material was detected in 0.1 M HCl extracts of rat DRG, representing approximately 60 pg of ME equivalents/mg of protein. Chromatographic analyses indicated that the major component of the ME-like material coeluted with authentic ME. In northern blot experiments on total RNA extracted from DRG, a cDNA probe corresponding to the entire coding region of rat preproenkephalin A mRNA yielded a single band of the expected size for this mRNA, i.e., 1.5 kb. Polymerase chain reaction (PCR) experiments were carried out with DRG, striatum, and liver cDNAs using two primers flanking the 1,371-1,771 base region of the preproenkephalin A gene. Thirty PCR cycles performed on both striatum and DRG cDNAs generated a single band of 400 bp, as expected, whereas only trace amounts of this product were detectable using liver cDNAs. Nucleotide sequencing of the PCR product obtained with DRG cDNAs revealed a 100% homology with the 1,371-1,771 sequence of the preproenkephalin A gene. In situ hybridization with a cRNA probe showed that about 3.5% of DRG cells expressed the preproenkephalin A transcript. However, most of these cells probably did not process proenkephalin to enkephalins, as thorough immunohistochemical investigations with anti-ME antibodies allowed the detection of only one in approximately 6,000 cells (in 30 sections of DRG) that exhibited ME-like immunoreactivity. Cells expressing preproenkephalin A mRNA were intermediate-sized neurons, suggesting that primary afferent ME-containing fibers belong to the A category and may participate in a local (spinal) inhibitory control of nociception.

Amino Acid Sequence↗

PubMed1994

Opioidergic control of the spinal release of neuropeptides. Possible significance for the analgesic effects of opioids.

Several neuropeptides play a key role in the transfer (substance P, calcitonin gene-related peptide, etc) and control (enkephalins, cholecystokinin, etc) of nociceptive messages from primary afferent fibres to spino-thalamic neurones in the dorsal horn of the spinal cord. This first relay in nociceptive pathways has been shown to be a major target for opioids such as analgesic drugs, and the effects of exogenous (mainly morphine) and endogenous opioids on the release of neuropeptides within the dorsal horn are reviewed here for a better understanding of the cellular mechanisms responsible for their antinociceptive action. Complex modulations of the in vitro (from tissue slices) and in vivo (in halothane-anaesthetized rats whose intrathecal space was perfused with an artificial cerebrospinal fluid) release of substance P and calcitonin gene-related peptide by opioids have been reported, depending on the opioid receptor (mu, delta, kappa, and their subtypes) stimulated by these compounds. In particular, the inhibition by delta agonists of substance P release from primary afferent fibres, and that by the concomitant stimulation of mu and kappa receptors of the release of calcitonin gene-related peptide are very probably involved in the analgesic action of specific opioids and morphine at the level of the spinal cord. Furthermore, the negative modulation (through presynaptic opioid autoreceptors) by delta and mu agonists of the spinal release of met-enkephalin, and the complex inhibitory/excitatory influence of delta, mu and kappa receptor ligands on the release of cholecystokinin within the dorsal horn very likely also contribute to the antinociceptive action of these drugs and morphine. The reviewed data strongly support the existence of functional interactions between mu and kappa receptors within the spinal cord, and their key role in the analgesic action of non specific opiates (acting on mu, delta and kappa receptors) such as morphine.

Analgesics, Opioid↗