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Biomedical subjects

M Stöhr

Publications and source records attributed to M Stöhr.

At least 73 records · Page 4Linked to original sources
PubMed1982

Rapid detection of mutagen induced micronucleated erythrocytes by flow cytometry.

The micronucleus test is a cytogenetic method for the screening of mutagens and carcinogens which exhibit clastogenic mechanisms of action. After application of clastogenic agents chromosomal fragments or even whole chromosomes can remain as conspicuous structures (micronuclei) in a small fraction of anucleated polychromatic erythrocytes which can be visually scored using a microscope following staining with May-Grünwald-Giemsa solutions. These time-consuming, painstaking, and tedious manual evaluations are often sources of unreliability and uncertainty. Here, a fluorescence technique is presented which applies DNA and protein fluorochromes to discriminate normal anucleated erythrocytes from micronucleated erythrocytes using a fluorescence microscope. This method is particularly tailored to be applied to flow cytometric instrumentation. Data obtained manually and automatically in flow show a strong linear correlation with high significance (r = 0.96) as far as the percentage of micronucleated erythrocytes as an indicator for the mutagenicity of a given drug is concerned. These results have been obtained by means of the established clastogens cyclophosphamide and mitomycin C.

Animals↗
PubMed1982

[Spinal and subcortical somatosensory evoked potentials after stimulation of the tibial nerve].

Evoked potentials in response to unilateral stimulation of the posterior tibial nerve at the ankle were recorded above the spinous processes L5, L1, C2, and at Cz' in 30 normal subjects. The "cauda-potential" recorded above L5 consists of two small negative peaks with a mean latency of 18 and 22.5 ms respectively, whereas the "cord-potential" recorded above L1 exhibited a peak latency of 21.2 ms and on average a three-times larger amplitude than the first of the two "cauda-potentials" (Fig. 1). Leads from the spinous process C2 revealed a sharp negative peak with a mean peak latency of 28.8 ms (N 30). Scalp recordings with a midfrontal (Fz-) reference inconsistently showed 1-2 small waves (P31, N33) prior to the primary cortical response (P40). Recordings with an ear- or non-cephalic reference consistently showed a large positive deflection (P30) which corresponded in latency with the simultaneously recorded cervical response (N30) and was followed by a distinct negative potential (N33) (Fig. 2a and b). Average latencies and amplitudes of the different spinal and subcortical evoked potentials (Tables 1 and 2), as well as the diagnostically more important interpeak-intervals, amplitude relations, and side-differences of latencies and amplitudes (Tables 3 and 4) were calculated. The diagnostic significance of these parameters will be shown in selected cases with spinal cord pathology.

Adolescent↗
PubMed1982

Spinal somatosensory evoked potentials in cervical cord lesions.

Short-latency somatosensory evoked potentials (SEPs) to median and ulnar nerve stimulation were studied in 17 patients with cervical cord lesions of different sites and origins. Spinal cord lesions involving the 6th and 7th cervical segment led to an attenuation or loss of the cervical response after stimulation of the median nerve, whereas lesions at C8/D1 only affected the cervical response evoked by ulnar nerve stimulation. The third component of the neck-SEP (N13) was exclusively involved in some cases. More extensive lesions additionally abolished the second component (N11). Spinal cord lesions above the 6th cervical segment caused some dissociation of the simultaneously recorded responses at C7 and C2, with preserved responses at C7 and disturbed or absent evoked potentials at C2.

Adult↗
PubMed1982

An open and double-blind cross-over study on the efficacy of clomipramine (Anafranil) in patients with painful mono- and polyneuropathies.

82 patients with chronic pain resulting from mononeuropathy were treated with psychotropic drugs in an open therapeutic study. In this study we found that treatment with a combination of clomipramine (Anafranil) and small doses of neuroleptics was significantly superior to therapy with neuroleptics alone. In a subsequent double-blind study, it was attempted for the first time to determine the efficacy of clomipramine compared to that of acetylsalicylic acid in 48 patients with painful mono- and polyneuropathies. The test was carried out in a cross-over trial with two sequence groups. We evaluated assessments of pain by both patients and doctors, and were able to prove statistically that clomipramine possesses a significantly greater efficacy compared to that of acetylsalicylic acid. By taking into account recent anatomical, biochemical and pharmacological studies, it can be concluded that clomipramine probably has-in addition to the action on peripheral receptors-a direct effect upon pain modulation systems. It seems possible that clomipramine activates serotonin-containing neurons of the endorphin-mediated analgesia system that control pain transmission in the CNS.

Antipsychotic Agents↗
PubMed1982

Automated cytology. The state of the art.

Analytical cytology is the science of automatically analyzing morphologic, biochemical, biophysical, and functional aspects of cells by machine. Two basic techniques are used: image cytometry, in which microscopic objects on a slide or in a photograph are analyzed; and flow cytometry, in which biologic particles in aqueous suspensions are forced to pass through a measuring device. The latter technique has the added power of sorting particles according to type for further study. Currently, analytic cytology is being studied for use in the following areas: WBC differentiation, cell-cycle kinetics, prescreening for uterine cancer, screening of high-risk groups, monitoring of tumor therapy, and microbial and chromosome analysis. In all these areas, analytic cytology has the potential to improve existing techniques and to make results more uniform; likewise, its sensitivity, accuracy, and speed may well allow a breadth and depth of analysis not presently allowed by human study.

Automation↗
PubMed1981

Somatosensory evoked potentials following trigeminal nerve stimulation in trigeminal neuralgia.

The examination of somatosensory evoked potentials following trigeminal nerve stimulation in 20 subjects with idiopathic trigeminal neuralgia revealed a pathological increase in latency of the first positive component on the involved side in 7 (41%) of the 17 patients without antecedent surgical treatment. The mean difference in latency between the two sides was 1.3 msec (2p greater than or equal to 0.005). These results are indicative of microtraumatization of the trigeminal nerve in the posterior fossa by blood vessels, for example, leading to local demyelinization. The method seems to be of diagnostic value in selecting patients for more decompression by posterior fossa operations.

Adult↗
PubMed1981

[Morbus Gerstmann-Sträussler-Scheinker. The Sch. family-a report of three cases (author's transl)].

The clinical symptoms from three cases and histological findings from two patients suffering from morbus Gerstmann-Sträussler-Scheinker (M-GSS) are reported. This disease belongs to the group of subacute spongiform encephalopathies. It is extremely rare and so far has only been observed in 52 members of four large families, in which the symptoms begin between the age of 33 and 50 and lead to death in 4-5 years. In the family reported here, cerebellar symptoms including myoclonia and later dementia, bulbar, and pyramidal symptoms were typical; two patients also had deterioration of vision and hearing. CSF and other biochemical data were normal. The EEGs showed progressive general slowing without periodic dysrhythmia. Evoked potential gave no evidence of demyelinization. The disease may safely be distinguished from morbus Creutzfeldt-Jakob (M-CJ) and Alzheimer's disease by histology, which reveals kuru plaques in most cases and invariably multicentric plaques as well as cortical spongiform changes of varying degree with loss of nerve cells and glial proliferation; however, only minor degenerative alterations in the cortical vessels are seen. The transmission to monkeys and histological similarities to M-CJ and kuru suggest a slow virus related to that causing scrapie. Alternatively, the genetically determined susceptibility of the patient may decide the type of reaction to the slow virus. The disposition to M-GSS is autosomally dominant.

Adult↗
PubMed1981

Modification of the recovery-cycle of human median nerve by ischemia.

Variations in excitability have been shown to follow single activation of sensory and motor axons in human peripheral nerve, with a sequence of refractoriness, supernormal and subnormal excitability ("recovery cycle"). Modifications of the recovery cycle of nerve excitability by ischemia have been investigated in the present study in sensory fibers of human median nerve. During ischemia, there is an initial fall in the nerve threshold to a brief electric pulse, followed by a progressive rise in threshold until the nerve becomes inexcitable. These ischemia-induced threshold changes interact with the impulse-induced variations in nerve excitability during the recovery period, leading to a characteristic alteration of the recovery cycle with a progressive reduction of the magnitude and duration of the supernormal period. Conduction velocity becomes progressively reduced, probably because of a slowed conduction of the action potential in the fastest conducting fibres, due to ischemic depolarization of the resting membrane potential. In the postischemic phase the magnitude and duration of supernormality are increased, probably because of the hyperpolarization of the resting membrane potential in this condition. Conduction velocity only returns to normal values after 12-25 min.

Action Potentials↗
PubMed1981

Activity-dependent variations in threshold and conduction velocity of human sensory fibers.

Activity-dependent changes in threshold with a sequential set of events (action potential, refractoriness, supernormal and subnormal period) can regularly be observed in sensory fibers of the human median nerve, the whole recovery cycle lasting for 120-200 ms in different subjects. Supernormality is probably due to an after-depolarization of the membrane potential and has its peak 5-8 ms after the conditioning pulse. The subsequent period of subnormal excitability results from a long-lasting hyperpolarization of the membrane and reaches its maximum 40-60 ms after the conditioning pulse. In contrast to some findings in slow-conducting fibers of different experimental animals, the fast-conducting fibers of the human median nerve do not reveal the phenomenon of supernormal conduction velocity.

Action Potentials↗
PubMed1981

[Diagnostic value of somatosensory evoked potentials (SEP) in lesions of the brachial plexus (author's transl)].

Simultaneous recording of SEP from the contralateral scalp, the lower neck (C 7) and Erb's point following median or ulnar nerve stimulation may be helpful in the localisation of lesions of the brachial plexus and associated spinal roots. In lesions proximal to the dorsal root ganglia, the potential recorded from Erb's point (EP), as well as the first component of the neck-SEP ("NSEP 1", "N 9") are normal, whereas the following components of the cervical response ("NSEP 2 + 3", "N 11 + N 13") are reduced or absent, depending on the severity of the functional impairment (Fig. 1). In lesions distal to the ganglia the EP-potential shows a significant reduction in amplitude as compared to the normal side. The neck- and scale-SEP are less attenuated or even normal in this condition, because of the phenomenon of synaptic amplification (Fig. 2). Combined lesions of the brachial plexus and cervical roots, which especially occur in traumatic injuries are characterized by an attenuation of the EP-potential and a relatively larger attenuation or an absence of the neck-SEP (N 13) (Fig. 3). SEP examination may therefore be valuable in estimating the degree of involvement distal and proximal to the dorsal root ganglia.

Brachial Plexus↗
PubMed1981

Early effects of the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate on the cell cycle traverse of asynchronous HeLa cells.

Within 24 hr after incubation of synchronous HeLa cell cultures with small nontoxic doses of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA; 10(-7) or 10(-8) M), a variety of transient alterations in the cell cycle traverse was detected by different techniques. The measurement of thymidine incorporation rates into DNA, of labeling and mitotic indices, and of flow cytometry revealed (a) an inhibition of cells in G1 shortly prior to their entering S phase, (b) a reduced rate of DNA synthesis and a delayed passage of cells through S phase which were in this phase on addition of TPA, (c) a delayed passage through G2 of a portion of cells which were somewhere in the first half of the S phase on addition of TPA, and (d) an instant but short-lasting blockage in G2 immediately before mitosis. The effects of TPA are reminiscent of published results on X-irradiated cell cultures. None of these effects was noticed with the hyperplasiogenic but nonpromoting phorbol ester 4-O-methyl-12-O-tetradecanoylphorbol-13-acetate (10(-6) M). The data were confirmed by experiments with synchronized HeLa cells as described in an accompanying paper.

Cell Cycle↗