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Biomedical subjects

M Stöhr

Publications and source records attributed to M Stöhr.

At least 55 records · Page 3Linked to original sources
PubMed1985

[Generators of somatosensory evoked potentials following stimulation of nerves of the arm].

The cervical evoked potentials recorded above the 7th spinous process represent activity from the dorsal roots (N 11a) and the dorsal horn (N 13a), respectively. The upper neck responses are attributed to ascending activity in the dorsal column (N 11b) and the activation of the cuneate nucleus (N 13b). Scalp-leads from the contralateral sensory hand area using an Fz-reference consistently exhibit a sequence of components with successively more rostrally located generator sites: P 15 in or near the thalamus, N 20/P 25 in the primary sensory cortex and the following components in the parietal association fields (area 5 and 7).

Afferent Pathways↗
PubMed1984

Suggestive evidence that the highly metastatic variant ESb of the T-cell lymphoma Eb is derived from spontaneous fusion with a host macrophage.

Two lines of evidence are reported which suggest that the highly metastatic variant ESb of the T-cell lymphoma Eb is derived from spontaneous fusion with a host macrophage. Firstly, ESb cells are shown to express the macrophage differentiation antigen Mac-1 which was not found on Eb cells or on any other tumor cells tested except the macrophage tumor line Pu5. Secondly, the progression from low to high metastatic capacity could be reproduced in vitro following hybridization of thioguanine-resistant Eb cells (EbTGR) with syngeneic bone-marrow-derived macrophages. Two HAT medium-selected hybrid tumor lines (Eb-F1 and Eb-F2) could be established. They were found to express cell surface markers of both parental lines: T lymphoid differentiation antigens from T-lymphoma and macrophage antigens (Mac-1, class II MHC antigens) from the normal cell fusion partner. The antigens were identified on the hybrids and subclones thereof by means of monoclonal antibodies and 3 different detection assays: cytofluorography, complement-dependent cytotoxicity and immunoprecipitation followed by gel electrophoresis. Animals inoculated s.c. with the parental line EbTGR developed local tumors but not metastases and survived for more than 40 days. In contrast, animals inoculated similarly with Eb-F1 or Eb-F2 cells quickly developed metastases in visceral organs and died as early as 10-14 days following inoculation. In many but not all respects, the in vitro-derived T-lymphoma-macrophage hybrids resembled the spontaneous in vivo-derived variant ESb. These findings, together with the presence of Mac-1 antigen on ESb cells, suggest (1) that ESb variant cells may be derived from spontaneous fusion with a host cell, most likely a macrophage and (2) that somatic cell fusion may be an important mechanism of genetic rearrangements leading to metastatic variants. The new highly metastatic tumor lines which were developed under well-defined in vitro conditions, and their subclones, may become very useful tools for studying the contribution of specific genetic traits and of membrane-related structures to various steps of the metastatic process.

Animals↗
PubMed1984

Accessory nerve stimulation in the assessment of myasthenia gravis.

Repetitive nerve stimulation (5/second) was done at the median nerve at the wrist and at the accessory nerve just behind the sternocleidomastoid muscle before and 20 seconds to 5 minutes after tetanic nerve stimulation (1 minute). Since the degree of the neuromuscular block depends on the body temperature these investigations were done successively at skin temperatures of 32 degrees C and 36 degrees C. A comparison of the results obtained revealed the highest rate of pathologic decrement with posttetanic accessory nerve stimulation (32 degrees C = 77%, 36 degrees C = 87%), whereas with posttetanic median nerve stimulation pathological results were obtained in a significantly lower proportion (32 degrees C = 50%, 36 degrees C = 60%). The advantages of the stimulation of the accessory nerve for the detection of partial neuromuscular block are: 1. The superficially located accessory nerve allows for supramaximal stimulation with rather low stimulus intensities (6-20 mA). 2. Since the accessory nerve is mainly a motor nerve, the stimulation is less painful than the stimulation of a mixed nerve. 3. Stimulation of a proximal nerve is more sensitive for detecting a defect in neuromuscular transmission than stimulation of a distal nerve. 4. There is no risk of a pneumothorax and of a traumatic nerve lesion as there is with stimulation of the brachial plexus by needle electrodes.

Accessory Nerve↗
PubMed1984

[Effect of hemodialysis on somatosensory evoked potentials in uremia patients].

Spinal and cortical potentials in response to unilateral stimulation of the median nerve of the wrist were recorded in 13 uremic patients, 1 h prior to and 1 h after dialysis. A comparison of the data from these patients with those of a control group revealed a slowing of impulse conduction in the peripheral nerve only, whereas the central part of the somatosensory system was not affected. Amplitudes of the evoked potentials tended to increase after dialysis. This could be due to a decrease of descending inhibition or a transitory change of the resting membrane potential caused by the elimination of dialyzable substances.

Adult↗
PubMed1984

Spinal and cortical evoked potentials following stimulation of the posterior tibial nerve in the diagnosis and localization of spinal cord diseases.

Evoked potentials from unilateral stimulation of the posterior tibial nerve at the ankle were recorded over the spinous processes L5, L1, C2 and Cz' in 30 normal subjects (Table Ia, b and c), 11 patients with multiple sclerosis (Table II) and 8 patients with a proven space-occupying spinal cord lesion (Table III). Delayed sensory conduction of both absolute latencies and side to side differences of P40 was seen in 91% of MS patients. Additional recording of spinal evoked potentials over L5, L1 and C2 did not significantly increase the percentage of abnormal responses. The spinal cord evoked responses therefore have their diagnostic importance in localizing the demyelinating process to the spinal or supraspinal section of the sensory pathway and in excluding peripherally delayed impulse conduction. The absolute latencies were within normal limits or only slightly delayed in the spinal tumor group. The interpeak latencies between the lumbar and the cervical or cortical responses showed less variability as compared to the absolute ones and revealed slight delays in some cases. Diagnostically more important seems the amplitude quotient between the cortical and the lumbar evoked potentials (P40/S response) which was below the normal range in two thirds of the tumor group patients.

Adolescent↗
PubMed1984

Inheritance of immunogenicity and metastatic potential in murine cell hybrids from the T-lymphoma ESb08 and normal spleen lymphocytes.

T-lymphoma cells were fused with normal lymphoid cells to examine the segregation of tumorigenicity and metastatic capacity in the hybrids. In independent fusions the immunogenic ESb08 T-lymphoma line fused successfully with normal syngeneic spleen cells (from DBA/2 and CD1 mice) enriched either with T-cells or B-cells. Ten times fewer hybrids were obtained with B-cells compared to the number obtained with T-cells, and marker assays showed that both types of fusions preferentially generated T-T hybridomas. Some of the hybrids resembled their tumor parent in their ability to form primary and secondary tumors only in irradiated DBA/2 mice, whereas other hybrids lost the high ESb08 immunogenicity, were equally tumorigenic, and in some cases metastatic, in nonirradiated mice. DNA distributions of the original hybrid lines ranged from a hexaploid DNA content (expected for complete hybrids derived from a tetraploid line and normal diploid cells) to a tetraploid DNA content, confirming the reported chromosome instability of T-T hybrids. No correlation was noted between the initial DNA content and tumorigenicity, but in the case of complete hybrids, reduction in the ploidy levels always was observed in the cells of primary and metastatic lesions. One chromosomally stable and highly malignant hybrid (C2), which was analyzed for segregation of chromosomes and for drug-resistance markers, showed preferential loss of chromosomes from the normal T-cell fusion partner. The decreased immunogenicity of this hybrid could not be related to any detectable loss of chromosomes from the ESb08 tumor parent.

Animals↗
PubMed1983

Isopycnic density-gradient centrifugation: a separation parameter which improves flow cytometric measurements on heterogeneous tumors.

The analytic and prognostic value of flow cytometric measurements can generally be improved by preseparation of cells. The present data demonstrate clearly the distinct character of bands obtained in density-gradient separation. Density-gradient centrifugation in Percoll after extensive Ca2+ + Mg2+ elimination helps to resolve more detail in flow cytometric measurements (e.g., additional DNA stem lines in human tumors) and can be used in studies of tumor heterogeneity. The significance of investigations of tumor heterogeneity is demonstrated by the different reactivity of subpopulations of the experimental murine tumor S 180 to vincristine.

Animals↗
PubMed1983

Cell type-specific binding of Ricinus lectin to murine cerebellar cell surfaces in vitro.

The binding of several plant lectins, Concanavalin A (Con A), Lens culinaris A (LCA), wheat germ agglutinin (WGA), and Ricinus communis agglutinin 120 (RCA 120) to cell surfaces of developing mouse cerebellar cells was assayed by the use of fluorescein isothiocyanate (FITC)-conjugated compounds. Freshly dissociated, live single-cell suspensions from 6-day-old mouse cerebellum contain 93% ConA, 99% LCA, 98% WGA, and 59% RCA 120-positive cells with ring fluorescence. Of the RCA 120-positive cells, 4% express a high and 55% a lower or very low number of lectin receptors. Flow cytometric analysis of fluorescent lectin binding yields results qualitatively similar to those obtained by scoring positive and negative cells in the fluorescence microscope. In monolayer cultures of 6-day-old mouse cerebellum practically all cells express receptors for ConA, LCA, and WGA, whereas RCA 120 binding sites are absent from neurons with small cell bodies (granule, basket and stellate cells) and present in large number on neurons with large cell bodies (Purkinje and possibly Golgi Type-II cells) and fibroblasts. RCA 120 receptors are weakly expressed on astro- and oligodendroglia. Cell type-specific expression of RCA 120 receptors is constant throughout all ages studied (embryonic day 13 to postnatal day 9). At early embryonic ages the proportion of highly fluorescent neurons with large cell bodies is significantly increased.

Agglutination↗
PubMed1983

Brainstem auditory evoked potential abnormalities in vascular malformations of the posterior fossa.

Recent reports indicate that malformations of arteries and veins in the posterior fossa are a common cause of facial spasm and trigeminal neuralgia. More rarely they may also cause facial nerve paresis and hearing loss. When vascular malformations are present, brainstem auditory evoked potentials (BAEPs) sometimes show abnormalities similar to those usually recorded in patients with tumours in the cerebellopontine angle. In three patients with facial spasm, one with trigeminal neuralgia and one with facial paresis pathologically delayed absolute latencies and/or interpeak latencies of BAEPs associated with vascular malformations were found. It is concluded that those BAEP abnormalities associated with tumours in the posterior fossa may also be caused by vascular malformations. BAEPs are valuable aids to the diagnosis of such malformations.

Adult↗
PubMed1983

Combined recordings of compound nerve action potentials and spinal cord evoked potentials in differential diagnosis of spinal root lesions.

Three cases are presented to demonstrate the diagnostic value of sensory neurography in combination with somatosensory evoked potentials in the diagnosis of proximally located neuropathy and its differentiation to centrally located demyelinating processes. Simultaneous recording of cortical and spinal evoked potentials, as well as peripheral nerve action potentials, revealed in two cases (herpes zoster, Guillain-Barré syndrome) a site of lesion at the spinal roots suggesting radiculitis and in one case (tick bite) a site of lesion central to the source of lumbar evoked potentials suggesting myelitis. In all cases almost complete recovery of sensory conduction velocities suggests a complete repair myelination not previously described.

Adolescent↗
PubMed1983

The significance of somatosensory evoked potentials for localization of unilateral lesions within the cerebral hemispheres.

Thirty patients with unilateral lesions of the cerebral hemisphere and clinical signs of an affected somatosensory system (mainly disturbances of kinesthesia and stereoesthesia) were investigated. SEP recordings were abnormal in 27. The degree of sensory loss (especially kinesthesia) correlated well with the SEP abnormalities in 26. These SEP abnormalities could be segregated into 4 groups (types 1-4). A type 1 SEP with pathological evoked potentials from P15 on (but a normal P13/14 complex with ear- or extracephalic reference recordings) correlated with lesions of the thalamus, the internal capsule, and the centrum semiovale. A type 2 SEP characterized by loss or severe attenuation of N20 and the following components was found in patients with lesions of the postcentral gyrus. A variant (type 2a) showed isolated loss of N20, but preserved subsequent components and may be due to lesions restricted to area 3b. A third pattern of SEP abnormality is characterized by a preserved primary cortical response and loss of all the subsequent potentials. It is assumed to correlate with lesions of the parietal association cortex. In only 1 case was a type 4 SEP found, with pathological features from N3 (N55) on, caused by an ischemic stroke in area 39. Loss of all evoked responses after P13/14, including P15, suggests a lesion between thalamus and centrum semiovale. Lesions located close to the postcentral cortex lead to a loss of N20 and a variable cut off of the rising negativity following P15. Preservation of the primary cortical complex and distortion or loss of the later components point to a parietal lesion. Severe disturbances of kinesthesia and stereognosia in patients with a normal primary cortical complex and isolated abnormality of the following potentials suggests that the adjacent association cortex may be important for the perception of this complex somatosensory information. Thus the neuronal activity underlying the primary cortical response does not suffice for perception of motion and for stereoesthesia.

Adult↗
PubMed1982

Effects of retinoic acid and tumor promoter 12-o-tetradecanoylphorbol-13-acetate (TPA) on the cell cycle of HeLa cells.

The influence of retinoic acid (RA) - a modifier of tumor promotion - on the cell cycle of HeLa cells, and its ability to interfere with the early irradiation-like effects induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) has been investigated by a variety of different techniques. These include measurement of thymidine incorporation and uptake, of labelling and mitotic indices, and of DNA histograms by flow cytometry. Within 24 h RA (2 X 10-5 M) alone caused a short-lasting inhibition of DNA synthesis; later a decrease of cells in S phase and a steady descending mitotic activity were observed. On combined treatment with RA and TPA (10-8 M), the latter seems to dominate RA in two instances: (1) the transient G2 blockage due to TPA is seen as the earliest effect; however, the cultures do not seem to recover as well if RA is also present; (2) the TPA-induced GI blockage appears to be effective but less pronounced in the presence of both chemicals. Where the third typical TPA-induced effect is concerned, however, both compounds seem to act to a comparable degree in the same time frame; namely by an initial inhibition of DNA synthesis which thus might be a point of critical interference if promoter and modifier age given together.

Cell Cycle↗
PubMed1982

Short-latency somatosensory evoked potentials to median nerve stimulation: components N 13--P 13, N 14--P 14, P 15, P 16 and P 18 with different recording methods.

Comparative recordings of short-latency somatosensory evoked potentials with midfrontal (Fz), ear and non-cephalic reference electrodes were obtained in 12 normal subjects to define the site of the generators of the different components and the spatial distribution and interference of the different components recorded at the neck and scalp. Such investigations provide the basis for identical investigations in patients with focal lesions of the central nervous system. The N 13 recorded from the neck (C2-Fz) and the inconsistently recorded component N 14 were quite similar in latency to the far-field potentials P 13 and P 14 recorded at the scalp (C3', C4'--ear or hand). The component P 15 was clearly visible only in scalp-Fz leads and occurred 0.2--0.9 ms (mean 0.5 ms) later than P 14 in ear or hand reference recordings. This is evidence against the identity of these two components proposed by others. In a larger group of 48 subjects, using an exclusive Fz-reference lead, normal values were established of the components P 15, P 16 and P 18, as well as their scalp distribution.

Adult↗
PubMed1982

Assignment of snRNA gene sequences to the large chromosomes of rat kangaroo and chinese hamster isolated by flow cytometric sorting.

Chromosomes from a rat kangaroo (Potorous tridactylus) cell line (PtK2) and from a Chinese hamster (Cricetulus griseus) cell line (CHV79) were isolated by means of fluorescence activated flow cytometric sorting. DAPI (4'-6-diamino-2-phenylindole) was used as the DNA specific fluorescent dye. The karyotype of the PtK2 cells which exhibits 13 chromosomes was separated into 6, and the 22 chromosomes of the CHV79 cells were resolved into 11 fractions. DNA extracted from these chromosomal fractions was used for restriction enzyme digestion and blotting on nitrocellulose filters. The blots were challenged with gene probes corresponding to ribosomal RNA (18S and 28S) and small nuclear RNA (U1-snRNA) genes. The rRNA genes were exclusively assigned to chromosomes containing the nucleolus organizing region (in PtK2: X chromosome; in CHV79: chromosomes 4, 5, 6, and 11). - Solely the largest chromosomes in both cell lines hybridized with U1-snRNA indicating that these gene sequences are located on those chromosomes only. Further possible genetic and biochemical applications of this experimental system are discussed.

Animals↗