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Biomedical subjects

A Bischoff

Publications and source records attributed to A Bischoff.

At least 19 recordsLinked to original sources
PubMed1992

Automated detection of radiation-induced chromosome aberrations following fluorescence in situ hybridization.

The cytogenetic detection of rare chromosome aberrations induced by ionizing radiation requires the evaluation of large numbers of cells. In this report, an image analysis program based on thresholding of grey level histograms is described for a rapid automated detection of chromosome translocations in metaphase spreads from human lymphocytes following irradiation and chromosome in situ suppression (CISS) fluorescence in situ hybridization (FISH). To classify a metaphase spread as "normal", "aberrant", or "excluded", a minimum medium time of less than two seconds was required on a general purpose Personal Computer. Using appropriately stained specimen, for the false classification rate an upper limit of about 10% was estimated. The upper limit for the rate of "excluded" cells was estimated to be about 11% (99% confidence ranges). FISH-procedures allow to score chromosome aberrations also in the interphase nucleus. To apply simple threshold algorithms for segmentation of the FISH-stained nuclear areas, it is required that the grey level contrast is sufficiently high. The preliminary results presented here on the image analysis of human lymphocyte nuclei suggest the feasibility of such an approach.

Chromosomes↗
PubMed1991

Response of the medullary respiratory network of the cat to hypoxia.

1. The effect of systemic hypoxia was tested in anaesthetized, immobilized, thoracotomized and artificially ventilated cats with peripheral chemoreceptor afferents either intact or cut. Extracellular recordings from different types of medullary respiratory neurones and intracellular recordings from stage 2 expiratory neurones were made to determine the hypoxia-induced changes in neuronal discharge patterns and postsynaptic activity as an index for the disturbances of synaptic interaction within the network. 2. The general effect of systemic hypoxia was an initial augmentation of respiratory activity followed by a secondary depression. In chemoreceptor-denervated animals, secondary depression led to central apnoea. 3. The effects of systemic hypoxia were comparable with those of cerebral ischaemia following occlusion of carotid and vertebral arteries. 4. In chemoreceptor-denervated animals, all types of medullary respiratory neurones ceased spontaneous action potential discharge during hypoxia. 5. Reversal of inhibitory postsynaptic potentials (IPSPs) and/or blockade of IPSPs was seen after 2-3 min of hypoxia. 6. During hypoxia, the membrane potential of stage 2 expiratory neurones showed a slight depolarization to -45 to -55 mV and then remained stable. 7. The neurone input resistance increased initially and then decreased significantly during central apnoea. 8. Rhythmogenesis of respiration was greatly disturbed. This was due to blockade of IPSPs and, in some animals, to more complex disturbances of phase switching from inspiration to expiration. 9. Central apnoea occurred while respiratory neurones were still excitable as shown by stimulus-evoked orthodromic and antidromic action potentials. 10. The results indicate that the medullary respiratory network is directly affected by energy depletion. There is indication for a neurohumoral mechanism which blocks synaptic interaction between respiratory neurones in chemoreceptor-intact animals.

Action Potentials↗
PubMed1991

Respiratory neuronal activity during apnea and other breathing patterns induced by laryngeal stimulation.

Respiration cycles through three distinct phases (inspiration, postinspiration, and expiration) each having corresponding medullary cells that are excited during one phase and inhibited during the other two. Laryngeal stimulation is known to induce apnea in newborn animals, but the cellular mechanisms underlying this effect are not known. Intracellular recording of ventral respiratory group neurons was accomplished in intact anesthetized, paralyzed, and mechanically ventilated piglets. Apnea was induced by insufflation of the larynx with ammonia-saturated air, smoke, or water. Laryngeal insufflation induced phrenic nerve apnea, stimulation of postinspiratory neurons, and stable membrane potentials in inspiratory and expiratory cells consistent with postinspiratory inhibition. Usually the membrane potential of each neuronal type cycled through an expiratory level before onset of the first recovery breath. Variants of the apnea response, probably reflecting the aspiration reflex or sniffing, sneezing, coughing, and swallowing, were also observed. These latter patterns showed oscillation between inspiration and postinspiration without an apparent intervening stage II expiratory phase. However, stage II expiratory activity always preceded onset of the first ramp inspiration after such a pattern. These findings suggest that activation of postinspiratory mechanisms causes profound alterations in the respiratory pattern and that stage II expiration importantly modulates recovery of ramp inspiratory activity. The mechanism of this latter effect may be inhibition of early inspiratory neurons with consequent postinhibitory rebound.

Animals↗
PubMed1991

[Outpatient dental surgery under anesthesiological monitoring. Investigation with 1022 patients at risk].

The aim of the study was to explore retrospectively the risks of ambulatory treatment under local anaesthesia during dental operations of elderly patients. Anaesthetic care was divided into control and therapeutical measures. Among the previous disorders the hypertension and its sequelae proved to be the main risk factors. The need of anaesthetic intervention doubled, when the time of operation exceeded 30 min. Due to good interdisciplinary cooperation, 99.3% of the operations took their proper course.

Adolescent↗
PubMed1989

Intracellular recordings of respiratory neurons in the lateral medulla of piglets.

Membrane potentials of respiratory neurons in the ventral respiratory group were recorded using intracellular techniques in the medulla of newborn piglets. Three types of neurons were demonstrated: inspiratory neurons with an augmenting pattern of spike activity during inspiration; postinspiratory neurons with a short decrementing firing pattern that started immediately after inspiration ended; and stage II expiratory neurons with an augmenting spiking pattern that began shortly after inspiratory termination and ended before onset of the next inspiration. When not firing, the membrane potential trajectories of each cell type revealed two complementary patterns of relative inhibition. This latter finding suggests arrival of inhibitory synaptic potentials during these periods. These findings suggest that the respiratory control mechanisms of the newborn piglet are organized in a three-phased manner similar to that of adult cats.

Action Potentials↗
PubMed1988

Effect of propranolol on early postischemia arrhythmias and noradrenaline and potassium release of ischemic myocardium in anesthetized pigs.

In anesthetized open-chest pigs, DL- or D-propranolol (1 mg/kg i.v.) was administered 15 min prior to ligation of the left anterior descending coronary artery (LAD) about halfway from its origin. Sequential myocardial tissue samples were obtained before and after LAD occlusion. The samples were analyzed histofluorimetrically to determine the density of catecholamine containing neurons (quantified morphometrically), and radioenzymatically for total tissue noradrenaline content. The extracellular K+ concentration was measured using K+-sensitive polyvinyl chloride (PVC)-membrane electrodes on the surface of the ischemic myocardium. Under control conditions, ventricular arrhythmias (VA) occurred in a typical 1a and 1b phase. Pretreatment with propranolol diminished the number of VA generated in the 1b phase but not those in the 1a phase; however, these differences were statistically not significant. Neither pretreatment with DL- nor D-propranolol influenced the time course or probability of development of ventricular fibrillation (VF). Coronary artery occlusion led to a significant reduction in noradrenaline concentration of the ischemic myocardium in control animals (from an initial concentration of 526 +/- 65 ng/g w/w to 368 +/- 75 ng/g w/w) within the first 5 min of ischemia, whereas noradrenaline concentration remained nearly unchanged in drug-treated animals (from 838 +/- 86 to 811 +/- 61 ng/g w/w in the DL group and from 701 +/- 36 to 709 +/- 31 ng/g w/w in animals that received D-propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1987

[Metoclopramide, methylprednisolone and flunitrazepam in cytostatic-induced vomiting].

The antiemetic efficacy of a combination of high-dose metoclopramide, methylprednisolone and flunitrazepam was tested in an open pilot study in 30 tumor patients undergoing strongly emetic chemotherapy. 26 of 30 patients (87%) were partially or completely protected from nausea and vomiting. In 11 of 12 patients receiving the strongly emetogenic cytostatic agent cisplatin in a dose of greater than or equal to 50 mg/m2, the gastrointestinal side effects were partially or completely abolished. The antiemetic efficacy of the combination was maintained during subsequent courses of chemotherapy. All patients experienced somnolence after administration of flunitrazepam. Only 2 of 30 patients had a shortlived extrapyramidal reaction. The combination of high-dose metoclopramide, methylprednisolone and flunitrazepam is an effective antiemetic treatment and should be considered as first-line antiemetic treatment in patients receiving strongly emetic cancer chemotherapy.

Adolescent↗
PubMed1979

Recurrent familial neuropathy with liability to pressure palsies: reports of two cases and ultrastructural nerve study.

Electrophysiological, histological and ultrastructural studies on two patients (one family) with familial neuropathy and a liability to pressure palsies are reported. There was slowing of nerve conduction velocities and increase of distal latencies of clinically affected and clinically non-affected nerves. These alterations were confirmed by biopsy of the sural nerive which had the characterized signs of the disease. Pathogenetically there seems to be an endogeneous metabolic defect of the Schwann cell to synthetize a normal myelin sheath, which is responsible for the particular susceptibility to mechanical damage.

Adolescent↗
PubMed1979

Morphological observations in the nervous system of prenatal mucopolysaccharidosis II (M. Hunter).

Light and electron microscopic finding in the nervous system of a 23-week-old fetus are reported, in which MPS II was diagnosed prenatally. The degrees of myelination and neuronal differentiation were similar as in a normal fetus of the same age. A storage of mucopolysaccharides in typical vacuolar inclusion bodies was present throughout the peripheral and central nervous system, mainly in cells of mesenchymal origin. "Zebra" bodies and granulo-membranous bodies, which are thought to represent secondard ganglioside accumulation were only found in the well developed neurons of the spinal cord and spinal ganglia, but not in the poorly developed neurons of the cerebellar and cerebral cortex. Mucopolysaccharide storage in endothelial cells of cerebral bood vessels precedes the appearance of lipid storgae in cerebral neurons.

Brain↗
PubMed1979

Neuropathy, amyloidosis, and monoclonal gammopathy.

Three cases of neuropathy with monoclonal gammopathy and amyloid deposits in peripheral nerves are described. They appeared to present a benign gammopathy because of the duration of the neuropathy in the absence of any clinical or biological sign of myeloma or macroglobulinaemia. The pathological abnormality found in the sural nerves of the three patients was characterised by a marked loss of myelinated and unmyelinated nerve fibres because of active axonal degeneration with Wallerian degeneration. The most striking feature in all three cases was the finding of deposits identified as an accumulation of microfibrils.

Aged↗
PubMed1979

Diabetic encephalopathy. Does it exist?

A case of a diabetic aged 65 years with an insidious progressive cerebral disorder with ataxia, tremor, general rigidity and mental deterioration is reported. Pathological examination revealed multiple small infarcts in the pons, the basal ganglia and medulla oblongata, corresponding to the lacunar state. The parenchymal lesions were associated with changes in the small arteries consistent with diabetic angiopathy. Since the patient was normotensive, the pathogenetic role of hemodynamic abnormalities in relation with diabetes is suggested.

Aged↗