Search PubMed⌕ Search

Biomedical subjects

C Braun

Publications and source records attributed to C Braun.

At least 109 records · Page 6Linked to original sources
PubMed1995

Peripheral myelin protein-22 is expressed in rat and mouse brain and spinal cord motoneurons.

Peripheral myelin protein PMP-22 is expressed by Schwann cells and is a constituent of peripheral nervous system (PNS) myelin. Two PMP-22 transcripts, SR13 and CD25, differing in their 5' non-coding sequences have been described. SR13 is present both in the PNS and in non-neural tissue, whereas CD25 mRNA is almost exclusively expressed in Schwann cells. PMP-22 mRNA is also present in the central nervous system (CNS), but at much lower levels than in the PNS. We have investigated the regional distribution of PMP-22 mRNA in the rat and mouse CNS by the reverse transcriptase-polymerase chain reaction method, using oligonucleotide primers specific for the SR13 or CD25 transcripts. SR13 mRNA was detected in all the CNS regions analysed, whereas the CD25 message was present only in the brainstem and the spinal cord. Localization of the PMP-22 transcripts, determined by in situ hybridization in 21 day-old animals, showed selective expression in the motor nuclei. The PMP-22 signal was very weak in the nuclei of the oculomotor and trochlear nerves and absent in the nucleus of the abducens nerve. A strong PMP-22 signal was observed in the motor nuclei of the trigeminal, facial, ambigus, vagus, hypoglossal and accessory spinal nerves and in the ventral horn of the spinal cord. The PMP-22-positive cells were identified as motoneurons on the basis of topographic and morphological criteria, as well as immunolabelling with neuron-specific antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Nitric oxide reductase from Pseudomonas stutzeri. Primary structure and gene organization of a novel bacterial cytochrome bc complex.

Nitric oxide (NO) reductase is an integral membrane component of the anaerobic respiratory chain of Pseudomonas stutzeri that transforms nitrate to dinitrogen (denitrification). The enzyme catalyzes the reduction of NO to nitrous oxide. The structural genes for the NO reductase complex, norC and norB, were sequenced and their organization established by primer extension and Northern blot analysis. The norCB genes encoding the cytochrome c and cytochrome b subunits of the enzyme are contiguous and transcribed as a single 2.0-kb transcript. The promoter region has a canonical recognition motif for the transcriptional activator protein Fnr, centered at -40.5 nucleotides from the initiation site of transcription. No similarity of the derived gene products to known cytochromes of b- or c-type was found in a data bank search. Post-translational processing of the two subunits was limited to the removal of the terminal methionine to leave an N-terminal serine in either subunit. The mature cytochrome c subunit (16508Da, 145 residues) is predicted to be a bitopic protein with a single membrane anchor. The mature cytochrome b subunit (53006Da, 473 residues) is a putatively polytopic, strongly hydrophobic membrane-bound protein with 12 potential transmembrane segments. Several histidine and proline residues were identified with potentially structural and/or functional importance. Mutational inactivation of NO reductase by deletion of norB or the norCB genes affected strongly the in vivo activity of respiratory nitrite reductase (cytochrome cd1), but to a much lesser extent the expression level of this enzyme. In turn, mutational inactivation of the structural gene for cytochrome cd1, nirS, or loss of in vivo nitrite reduction by mutation of the nirT gene, encoding a presumed tetraheme cytochrome, lowered the expression level of NO reductase to 5-20%, but hardly its catalytic activity. The cellular concentration of NO reductase increased again on restoration of nitrite reduction in the nirS::Tn5 mutant MK202 by complementation with nirS or with the heterologous nirK gene, encoding the Cu-containing nitrite reductase from Pseudomonas aureofaciens. Thus, NO may be required as an inducer for its own reductase. Our results show that the nitrite-reducing system and the NO-reducing system are not operating independently from each other but are interlaced by activity modulation and regulation of enzyme synthesis.

Amino Acid Sequence↗
PubMed1994

Veratridine triggers exocytosis in Paramecium cells by activating somatic Ca channels.

Paramecium tetraurelia wild-type (7S) cells respond to 2.5 mM veratridine by immediate trichocyst exocytosis, provided [Ca2+]o (extracellular Ca2+ concentration) is between about 10(-4) to 10(-3) M as in the culture medium. Exocytosis was analyzed by light scattering, light and electron microscopy following quenched-flow/freeze-fracture analysis. Defined time-dependent stages occurred, i.e., from focal (10 nm) membrane fusion to resealing, all within 1 sec. Veratridine triggers exocytosis also with deciliated 7S cells and with pawn mutants (without functional ciliary Ca channels). Both chelation of Ca2+o or increasing [Ca2+]o to 10(-2) M inhibit exocytotic membrane fusion. Veratridine does not release Ca2+ from isolated storage compartments and it is inefficient when microinjected. Substitution of Na+o for N-methylglucamine does not inhibit the trigger effect of veratridine which also cannot be mimicked by aconitine or batrachotoxin. We conclude that, in Paramecium cells, veratridine activates Ca channels (sensitive to high [Ca2+]o) in the somatic, i.e., nonciliary cell membrane and that a Ca2+ influx triggers exocytotic membrane fusion. The type of Ca channels involved remains to be established.

Aconitine↗
PubMed1994

Mortality of Dutch workers exposed to carbon disulfide.

Epidemiological studies carried out in Great Britain, Scandinavia and the United States indicate that workers exposed to carbon disulfide are at an increased risk for cardiovascular disease (CVD) mortality, and in particular for ischemic heart disease (IHD) mortality. In the epidemiological study reported here a retrospective cohort design was used. The total study population consisted of 3322 workers from a Dutch viscose textile plant who had all been employed for at least half a year between 1 January 1947 and 1 January 1980. Only production and maintenance workers were selected for the study. A group of 1434 workers who had been exposed to carbon disulfide was identified from the files available at the plant. The remaining 1888 workers who had not been exposed to carbon disulfide were used as a reference group. The total study population was followed for mortality until 1 January 1988. For the 762 workers who had died before that date, the causes of death were checked at the Central Bureau of Statistics. The results show a slightly but significantly increased risk for CVD mortality (CVD-specific SMR of 115), despite the observation of the so-called healthy worker effect and the statistical uncertainties inherent to this type of study. The results are in accordance with those reported by other investigators. The results indicate that exposure to relatively low levels of carbon disulfide increases the risk of CVD mortality.

Carbon Disulfide↗
PubMed1994

A test of brain electrical source analysis (BESA): a simulation study.

The present report summarizes the results of a simulation study on the accuracy of Scherg's implementation of spatio-temporal analysis (BESA) for estimating the parameters (wave shape, location, orientation) of the intracranial sources of event-related brain potentials (ERPs) recorded from the scalp. In view of the subjective factors that might influence a solution, 10 subjects, ranging from those with much experience with ERPs and extensive background in the use of BESA to those with little experience with BESA and/or no knowledge of ERPs, independently analyzed a set of simulated somatosensory ERP data. The simulation contained wave forms from 32 electrode sites generated by a combination of 10 dipole sources. The primary question was how faithfully the different subjects would depict the source wave shapes, locations and orientations. Based on the 9 subjects who were familiar with ERPs, the grand-average cross-correlation coefficient between subjects' estimated and actual source wave shapes was 0.89 (standard deviation (S.D.) = 0.17). The grand-average location error, based upon a head diameter of 17 cm, was 1.4 cm (S.D. = 1.0 cm). The grand-average orientation error was 24.4 degrees (S.D. = 20 degrees).

Brain↗
PubMed1994

Neurophysiological differences between perception and imagery.

The present study was designed to examine brain activity underlying mental imagery is conceptualized as behavior guided by internal representation only, the activity of the prefrontal lobes was assumed to be a measure of differentiation of imagery from perception. Twenty-one subjects were requested to observe and imagine a swinging pendulum and to touch and imagine a coshball in separate trials. The EEG was recorded from 15 standard electrode sites and analyzed with (1) traditional alpha power and (2) an estimation of dimensional complexity (a measure derived from nonlinear dynamics). Both EEG measures revealed expected object-related differences during perception as well as during imagery. The visual pendulum showed relative to the tactile coshball increased dimensional complexity and less alpha power at parietal and frontal sites. However, only the EEG dimension supported the main hypothesis: Imagery resulted in increased prefrontal dimensional complexity in comparison to perception independent of the modality of the image. In contrast, for alpha power the difference between imagery and perception was due to stimulus modality.

Adolescent↗
PubMed1994

Emotional qualities of odors and their influence on the startle reflex in humans.

Recent human and animal research suggests that the startle reflex might serve as a psychophysiological indicator of the emotional valence of foreground stimulation. The present experiment was designed to evaluate the emotional effects of positive and negative odorant stimuli. We examined the effects of continuous hydrogen sulphide (H2S) and vanillin stimulation on the magnitude of the acoustic startle reflex (measured at the M. orbicularis oculi) and on ratings of subjective valence in 16 healthy subjects. In accordance with the view that odors have emotional qualities, we found that H2S, a presumed negative foreground stimulus, significantly enhanced the startle-reflex amplitude relative to neutral air stimulation, whereas vanillin, a positive foreground stimulus, tended to reduce the reflex amplitude compared with neutral air stimulation. Both odorant stimuli were rated as equally intense by the subjects, and heart rate and electrodermal activity were not affected differentially by the two odorants.

Acoustic Stimulation↗
PubMed1994

Congenital rubella syndrome despite repeated vaccination of the mother: a coincidence of vaccine failure with failure to vaccinate.

Congenital rubella syndrome occurred in a boy born to a mother who had been properly vaccinated three times before conception, but developed only low titers of rubella antibody. The non-vaccinated father most likely infected the mother on a home visit during the third to fifth weeks of gestation. He served in the army and fell ill during an outbreak of a rubella-like disease in his military unit. The mother subsequently developed a slight rash, but rubella IgM antibodies were lacking and rubella infection was not suspected. This incidence demonstrates the necessity of vaccinating all children, including boys and young men, in order to reduce the number of infections and prevent further cases of congenital rubella syndrome.

Adult↗
PubMed1994

Classical conditioning of pain responses.

Classical conditioning is involved in the acquisition of chronic pain. The present study investigated whether experimental pain responses can be conditioned using auditory stimuli in a differential trace conditioning paradigm. 16 healthy subjects served as paid volunteers. The UCS was an intracutaneous electrical stimulus applied to the left middle-finger (10 ms duration). Tones of 1000 and 1400 Hz (both 80 dB SPL, 50 ms) were used as CS+ and CS-, respectively. A trace conditioning paradigm was used with an 800 ms interval between CS and UCS. Somatosensory event related potentials (SEP) and auditory event related potentials (AEP) were recorded from 29 electrode sites. Subjective pain reports were measured with an adjective list that allowed a detailed description of subjects' sensations elicited by painful and auditory stimuli. Data revealed significant differences of the subjective sensations between the CS+ and CS-, but no differences in the amplitudes and latencies of the P50, N100, P200, and P300 AEP components. No changes in the topographical organization of the CS+ and CS- were found. A significant differential negativity in the brain sites responsible for processing the UCS was obtained, which is attributed to the anticipation of the UCS after CS+ presentation.

Acoustic Stimulation↗
PubMed1993

Syntheses of 2-deoxy-2-fluoro mono- and oligo-saccharide glycosides from glycals and evaluation as glycosidase inhibitors.

Several fluorinated oligosaccharides, including 2-deoxy-2-fluoro derivatives of cellobiose, maltose, and maltotriose were synthesized by the action of fluorine or acetyl hypofluorite on the corresponding glycal peracetates. Temperature effects on the stereoselectivities of these reactions were examined. Addition of acetyl hypofluorite to several 2-substituted glycals in the gluco or galacto series gave 2,2-disubstituted arabino- or lyxo-hexose derivatives; 3,4,6-tri-O-acetyl-2-fluoro-D-glucal or the analogous galactal yielded 2-deoxy-2,2-difluoro arabino- or lyxo-hexose peracetates, whereas 2-acetoxy-3,4,6-tri-O-acetyl-D-glucal or the analogous galactal gave 2(R)-2-acetoxy-2-fluoro-arabino- or lyxo-hexose peracetates, respectively. 2-Acetamido-3,4,6-tri-O-acetyl-D-glucal gave 2(R)-2-acetamido-2-acetoxy-3,4,6-tri-O-acetyl-alpha-D-arabino-hexopyrano syl fluoride. 2,4-Dinitrophenyl 2-deoxy-2-fluoro-beta-cellobioside was an inactivator of the exoglucanase from Cellulomonas fimi while 2-deoxy-2-fluoro-alpha-maltosyl and alpha-maltotriosyl fluorides were slow substrates of human pancreatic alpha-amylase and rabbit muscle glycogen debranching enzyme, respectively.

Acetates↗
PubMed1993

Simultaneous high-performance liquid chromatographic determination of both the cleavage pattern and the stereochemical outcome of the hydrolysis reactions catalyzed by various glycosidases.

A high-performance liquid chromatographic method for the simultaneous determination of both the stereochemical outcome and the cleavage pattern of enzymatic action on unmodified sugar substrates is described. Three different enzymes were investigated by this method. Human pancreatic alpha-amylase hydrolyzed maltopentaose with retention of anomeric configuration, with the cleavage position being two glucose units from the reducing end. Cellulomonas fimi endoglucanase D hydrolyzed cellopentaose with retention of anomeric configuration and predominantly two glucose units from the reducing end. beta-D-Xylosidase from Butyrivibrio fibrisolvens hydrolyzed o-nitrophenyl beta-D-xylopyranoside with inversion of anomeric configuration.

Actinomycetales↗
PubMed1993

A calcium influx is neither strictly associated with nor necessary for exocytotic membrane fusion in Paramecium cells.

Exocytosis of trichocysts in Paramecium cells was generally believed to depend on extracellular Ca, since it is accompanied by a Ca influx and not seen in the absence of Ca. However, by short term removal of Ca we showed recently that only extrusion of secretory contents, but not membrane fusion after stimulation with aminoethyldextran (AED), depends on extracellular Ca. We have now extended these studies to longer times and shown that membrane fusion is stimulated by AED even after 1 min at low Ca (< or = 30 nM). At prolonged times membrane fusion was induced by sole removal of Ca. In the presence of AED, trichocyst contents were slowly extruded followed by resealing of the fused membranes, indicating independency of endocytotic membrane fusion from extracellular Ca (though we observed aberrant resealing). Later on, Ca removal is followed by cell death. By using videomicroscopy, we further provide the first evidence that exocytosis is not necessarily accompanied by an influx of Ca in the presence of the usual high concentrations (1 mM), since local exocytosis at the rear end of the cells is not followed by ciliary reversal which is triggered by Ca influx. We conclude that a Ca influx is neither regularly associated with, nor necessary for, induction of exocytotic membrane fusion in Paramecium cells. As a source for a possible alternative intracellular liberation of calcium during exocytosis, we analyzed the subplasmalemmal alveolar sac system by electron spectroscopic imaging and found indications for Ca redistributions shortly after stimulation.

Animals↗
PubMed1993

[Osteosynthesis using a buttress plate--a new principle for stabilizing scaphoid pseudarthroses].

Deformity with palmar bone resorption can be observed in 20-50% of scaphoid pseudarthroses. A palmar wedge-shaped defect develops after repositioning and debridement of the pseudarthrosis. In the present paper 16 cases in which operations with cancellous bone grafting and palmar buttress plate osteosynthesis in addition were performed are presented. In all but 1, the pseudarthrosis united. All patients were pain-free at follow-up examination a minimum of 9 months (mean 28 months) only slightly reduced. Grip strength and mobility were after operation. The persisting pseudarthrosis necessitated wrist arthrodesis because of radiocarpal arthrosis. Metal slackening with erosion and rupture of the flexor pollicis longus tendon occurred in 1 patient. Palmar buttress plating is a biomechanically consistent form of osteosynthesis. It neutralizes all relevant forces. This means that cancellous bone grafts are sufficient, whereas lag screw or tension band osteosyntheses need cortico-cancellous grafts to resist compression forces. Stability and better chances of healing of pure cancellous bone grafts are the main advantages of palmar buttress plating in scaphoid pseudarthroses.

Bone Plates↗
PubMed1992

Autogenously vascularised bone allografts. Experimental model of a new bone-muscle composite graft.

Conventional bone allografts carry a high incidence of complications such as infections and pseudarthroses due to immunological rejection and avascularity of grafts. In vascularised grafts healing and remodelling of bone is quicker and more complete. However, vascularised allografts need immunosuppression for prevention of rejection with vascular occlusion. Autogenously vascularised allografts are formed after implantation of bone in muscle of the recipient, allowing vascularisation from this muscle. A muscle-bone composite graft is thus obtained that can be transferred as a pedicled or free graft with microvascular anastomosis. In this study donors were DA and recipients Lewis rats. The bone grafts were implanted in the adductor muscles and transferred after 6 weeks into a femoral defect. A higher number of osteocytes were found in the autogenously vascularised group than in non-vascularised grafts. "Creeping substitution" was found in all cortical layers in vascularised grafts, whereas in conventional allografts bone resorption predominated. The experimental data suggest that in rat autogenously vascularised bone allografts show a remodelling pattern comparable with that of conventional vascularised bone autografts. The advantage of the autogenously vascularised bone allograft is that it allows transfer of a vascularised bone allograft together with its well-vascularised recipient bed without immunosuppressive treatment.

Animals↗
PubMed1992

[Techniques of continuous nerve block at the level of the wrist].

Functional treatment without pain is a condition for good results after operations at gliding structures (tendons) or periarticular structures. Good analgesia of the arm and hand is obtained with continuous axillary nerve blocks. Often there is concomitant paralysis and active motion is not possible. We therefore use continuous nerve blocks at the wrist. The technique of these blocks is described in the paper. We use a prefabricated catheter set to introduce the polyethylene catheter and to place it near the nerve as in single shot wrist block. This technique for continuous analgesia of the hand can be used for functional treatment after tenolyses, arthrolyses and stable osteosyntheses of fingers. Median, radial and ulnar nerves can be blocked all at the same time or alone.

Humans↗