PubMed Health⌕ Search

Biomedical subjects

H W Müller

Publications and source records attributed to H W Müller.

At least 109 records · Page 6Linked to original sources
PubMed1993

Expression of decorin mRNA in the nervous system of rat.

A rat cDNA clone (pCD67) isolated from a cDNA library of regenerating sciatic nerve by differential hybridization screening revealed 75% homology on the nucleic acid level and 81% homology (including conservative amino acid changes) to the deduced amino acid sequence of the core protein of human dermatan/chondroitin sulfate proteoglycan decorin (PGII, PG40, PG-S2). Two transcripts of 1.3 and 1.75 KB very similar in size to the two decorin mRNA species previously identified in connective tissue were detected by Northern blotting in both normal and injured sciatic nerve and in the mature and embryonic rat brain. The steady-state level of the decorin 1.3 KB mRNA was very much higher in peripheral nerve than in the central nervous system or in other non-neural tissues (skeletal muscle, heart, colon, kidney). In situ hybridization experiments indicated that decorin mRNA is expressed by Schwann cells and vascular cells in peripheral nerve. In the spinal cord the ventral horn motor neurons and other neurons in gray matter showed specific hybridization signals. Furthermore, in situ hybridization indicated decorin expression in Purkinje neurons and cells of the molecular layer in cerebellum, and in neurons of the primary olfactory cortex and brainstem (pons). Our data clearly demonstrate decorin mRNA expression in distinct neural cell populations, suggesting yet unknown functions of this proteoglycan in the peripheral and central nervous system.

Amino Acid Sequence↗
PubMed1992

Expression of inherent neuronal shape characteristics after transient sensitivity to epigenetic factors.

We investigated effects of different substrates and culture media on the early morphological differentiation of rat neocortical neurons in culture. In particular, we examined the effects of homotypic astrocytes, the adhesive glycoprotein laminin and the polycationic substrate poly-L-lysine, as well as diffusible astrocyte-derived conditioned medium factors and serum on (1) soma area, (2) total neuron area and (3) primary neurite number. To assess variations in morphological reactions of neurons with a defined neurotransmitter phenotype, we analyzed the differentiation of GABAergic neurons. The morphology of young neocortical neurons was dramatically affected by both substrate and culture medium. Replacement of the astrocytic monolayer or the astrocyte-conditioned medium by other substrates or non-conditioned medium, respectively, was accompanied by (1) spreading and flattening of neuronal somata, (2) a marked decrease in total neuron area and (3) an increase in the number of primary neurites. The various morphological parameters studied exhibited different sensitivities to changes of these external factors. Moreover, the influences of epigenetic factors on the generation of primary neurites depended on the transmitter phenotype of the neuron. The induced morphological alterations were transient. At the end of the first week in culture, the surviving neurons underwent substantial remodeling of their morphology leading to an expression of in vivo shape characteristics. These observations suggest that despite an early, transient sensitivity to environmental influences, the neuronal differentiation with respect to the morphological parameters studied in culture is to a large degree determined by intrinsic factors.

Animals↗
PubMed1992

An improved graphical method for pattern recognition from spike trains of spontaneously active neurons.

Spontaneous activity and rhythmical oscillations are common features of large neuronal networks in mammals. Detection of repetitive spike patterns or pacemaker activity during electrophysiological recording of spontaneous action potentials from single neurons can be difficult if a "noisy" background is present. This paper describes an improved method for an online spike train analysis based on joint interval histograms (JIH, Rodiek et al. 1962). By means of higher ordered JIH the discrimination of spike patterns with repetitive bursting activity or oscillations is possible even when randomly distributed action potentials appear. Examples of simulated spike trains and those recorded from cultured hippocampal neurons are presented.

Animals↗
PubMed1992

Peripheral myelin protein-22 gene maps in the duplication in chromosome 17p11.2 associated with Charcot-Marie-Tooth 1A.

Charcot-Marie-Tooth disease 1A (CMT1A) is a hereditary demyelinating peripheral neuropathy, associated with a DNA duplication on chromosome 17p11.2. A related disorder in the mouse, trembler (Tr), maps to mouse chromosome 11 which has syntenic homology to human chromosome 17p. Recently, the peripheral myelin protein-22 (pmp-22) gene was identified as the likely Tr locus. We have constructed a partial yeast artificial chromosome contig spanning the CMT1A gene region and mapped the PMP-22 gene to the duplicated region. These observations further implicate PMP-22 as a candidate gene for CMT1A, and suggest that over-expression of this gene may be one mechanism that produces the CMT1A phenotype.

Animals↗
PubMed1991

Dissociated cell culture of rat cerebral cortical neurons in serum-free, conditioned media: GABA-immunopositive neurons.

The gamma-aminobutyric acid (GABA)ergic properties of embryonic (E15d) rat cortical neurons were studied in dissociated serum-free culture by immunohistochemical methods. GABA-like immunoreactivity was found in a subpopulation of neurons from the first day onwards. The number of GABA-positive neurons reached mature values (10.5-12.6%) within the first week, while their morphological differentiation was not found to be fully completed until the 11th day of culture and was characterized by several discrete developmental stages. First, GABA-positive neurons gained their mature complement of neurites at 3 days in vitro (DIV). Three days later somal maturation became evident, followed at least by the maturation of the neuritic arbor. Double-labelling studies revealed the coexpression of GABA and tyrosine hydroxylase within the same cells. The similarities of relative number, morphology, time course of development and biochemistry of cultured GABAergic neurons compared with those in situ suggest that the applied culture system is a useful model to investigate several aspects of GABAergic neurotransmission at the cellular level.

Animals↗
PubMed1991

Axon-regulated expression of a Schwann cell transcript that is homologous to a 'growth arrest-specific' gene.

We have isolated a 1.8 kb cDNA (pCD25) clone that encodes a transcript that is differentially expressed during nerve regeneration. Nucleotide sequence comparison indicates 89.6% homology with the recently identified murine 'growth arrest-specific' gene gas3. The open reading frame of the CD25 transcript predicts a 17 kDa protein with four putative transmembrane regions. Steady-state levels of the CD25 mRNA are very much higher in sciatic nerve than in other tissues, and expression in sciatic nerve is confined to Schwann cells. Following nerve injury, the transcript levels rapidly declined in nerve segments distal to the site of lesion, but recovered upon nerve regeneration. In contrast, in distal stumps of permanently transected nerves, the mRNA level remained very low. Substantial amounts of the mRNA could be reinduced only upon anastomosis of these interrupted nerve stumps. Re-induction of the mRNA followed the elongation of regenerating axons through the distal nerve segment. Our data indicate that axons regulate expression of the CD25 mRNA in Schwann cells, and suggest that the CD25 protein functions during Schwann cell growth and differentiation.

Amino Acid Sequence↗
PubMed1991

Identification of meningeal cell released neurite promoting activities for embryonic hippocampal neurons.

Primary cultures of meningeal cells from embryonic rat cerebra secrete neurite growth-inducing components into serum-free culture medium. This conditioned medium (CM) was analyzed by FPLC and immunochemical and enzymatic treatments and tested for neurite promoting activity (NPA) in a quantitative bioassay using hippocampal neurons from embryonic rat. By immunoprecipitation or specific adsorption we identified laminin (LN)-proteoglycan complexes and fibronectin (FN), respectively, as the major neurite promoting components within meningeal cell CM. The LN-proteoglycan complexes and their NPA were sensitive to chondroitinase (chondroitin ABC lyase, EC 4.2.2.4) and to a smaller extent to heparitinase (heparitin sulfate lyase, EC 4.2.2.8). Minor fractions of the total NPA in CM correlated with free LN and a putative but not yet characterized FN-proteoglycan complex.

Animals↗
PubMed1991

Uptake of endoneurial lipoprotein into Schwann cells and sensory neurons is mediated by low density lipoprotein receptors and stimulated after axonal injury.

During Wallerian degeneration of rat sciatic nerve, the expression of apolipoprotein E increases and apolipoprotein E-containing endoneurial lipoproteins accumulate in the distal nerve segment. In established primary cultures dissociated from dorsal root ganglia, Schwann cells and sensory neurons internalized rhodamine-labeled lipoproteins isolated from crushed rat sciatic nerve as well as low density lipoprotein (LDL) from human serum. The uptake of endoneurial lipoproteins could be inhibited by an excess of LDL or at low temperature (4 degrees C). After transection of nerve fibers in dorsal root ganglia explant cultures, the uptake of lipoproteins was markedly stimulated in Schwann cells that were in close proximity to degenerating neurites. A specific monoclonal antibody directed to the bovine LDL receptor (clone C7) was shown to cross-react with LDL receptor preparations of rat endoneurial cells. LDL receptor immunoreactivity was expressed by cell bodies and processes of cultured Schwann cells, sensory neurons, and fibroblasts from dorsal root ganglia. Incubation of Schwann cells and neurons with the LDL receptor antibody strongly inhibited the uptake of endoneurial lipoproteins. Our results provide direct evidence for the important role of the LDL receptor-mediated pathway to internalize endoneurial lipoproteins into Schwann cells and peripheral neurons required for reuse of cholesterol and other lipids in myelin and plasma membrane biogenesis during nerve repair.

Animals↗
PubMed1990

Electrophysiological properties of rat septal region neurons during development in culture.

We report on the development of membrane properties of septal region neurons from embryonic rats in serum-free culture during 1-25 days in vitro (DIV). Na(+)-dependent action potentials could be evoked within 1 day after plating and 3 different types of outward current were observed by means of the patch-clamp technique: IK, IA and IC. In some neurons the neurotransmitter GABA evoked a chloride current after 2 DIV. In addition a cationic current elicited by glutamate appeared after 4 DIV. Within 8-12 DIV virtually all neurons were sensitive to both GABA and glutamate. Spontaneous action potentials and postsynaptic potentials occurred after 7-10 DIV but cultured septal neurons did not generate any pacemaker-like activity.

Action Potentials↗
PubMed1990

Regeneration-associated high level expression of apolipoprotein D mRNA in endoneurial fibroblasts of peripheral nerve.

A cDNA clone containing the entire coding region of rat apolipoprotein D (Apo D) was isolated from a cDNA library of regenerating sciatic nerve by differential hybridization. Only small amounts of Apo D mRNA were detected in noninjured mature nerve. Moderately increased levels of Apo D transcripts were found in transected nerves, which were prevented from regeneration by ligation. In contrast, in regenerating crushed nerve, the steady-state level of Apo D mRNA transiently increased at least 40-fold above control levels at the time when axons from the proximal stump grow into the distal nerve segment. Using transverse sections and primary cell cultures from regenerating nerve, Apo D transcripts could be localized by in situ hybridization in endoneurial fibroblasts but not in Schwann cells, macrophages or perineurial and epineurial cells. Apo D protein (Mr 32.8 kd) was secreted and accumulated in the endoneurial extracellular space where it could be detected in lipoprotein fractions by immunoblotting using established antibodies to human Apo D. High level expression of Apo D mRNA seems to be a novel regeneration-associated molecular event of endoneurial fibroblasts indicating a function for Apo D and fibroblasts in nerve repair.

Amino Acid Sequence↗
PubMed1990

GABA and glutamate receptor development of cultured neurons from rat hippocampus, septal region, and neocortex.

The early development of functionally active GABA and glutamate receptors on neurons from hippocampus, septal region, and neocortex of embryonic rats were studied using primary dissociated serum-free cell cultures. The responses to GABA and glutamate, applied to individual neurons by pressure ejection, were tested at different developmental stages, starting at 1 day in vitro (DIV) until 3 weeks. In all three types of neuronal cultures, the GABAA-receptor developed prior to the glutamate receptors, and after 9 DIV most of the neurons were sensitive to both GABA and glutamate. N-methyl-D-aspartate (NMDA) and non-NMDA receptor subtypes of the glutamate receptors could be distinguished in hippocampal cultures. The development of GABA and glutamate receptors on septal region neurons appeared to be delayed as compared to hippocampal neurons. In neocortical cultures the majority of neurons was sensitive to GABA just after plating, whereas the sensitivity to glutamate was retarded. The differences in GABA and glutamate receptor development among these three neuronal cultures provide evidence that the appearance of transmitter receptors on cultured neurons is predominantly determined by intrinsic mechanisms rather than by environmental conditions. The proportion of spontaneously active networks in these cultures increased with a time course very similar to the rise in glutamate-sensitive neurons suggesting that functional active glutamate receptors may be involved in the generation of spontaneous activity.

Animals↗
PubMed1989

Astroglia-released neurite growth-inducing activity for embryonic hippocampal neurons is associated with laminin bound in a sulfated complex and free fibronectin.

Neurons from embryonic (E18) rat hippocampus were chosen to identify and characterize neurite growth-stimulating proteins accumulating in serum-free conditioned media (CM) obtained from primary or secondary cultures of cerebral astrocytes (less than 5% nonglial cells) using a quantitative cell culture bioassay. CM were fractionated by FPLC on an anion exchange column (Mono Q) and by gel filtration (Superose 6). Column fractions were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblotting and enzyme-linked immunosorbent assay (ELISA) using antibodies to laminin (LN) and fibronectin (FN). The neurite-promoting activity (NPA) was tested by incubating aliquots of the eluted fractions with poly-L-lysine precoated glass coverslips prior to addition of neurons suspended in chemically defined medium. We provide evidence that the NPA in astroglial CM could be assigned mainly to a negatively charged, highly sulfated LN complex consisting predominantly of the B-chains of LN and presumably a sulfated proteoglycan that was sensitive for chondroitinase and to a lower degree to heparinase degradation. In addition, a smaller proportion of the NPA was associated with uncomplexed LN and free FN. FN reached approximately 10 times the concentration of LN in astroglial CM. As revealed by immunofluorescence microscopy, both LN and FN are simultaneously expressed by cultured astrocytes; however, only the production of FN, measured by ELISA, increased during the time astrocytes were in culture, whereas the release of LN remained unchanged. We conclude that, besides the most active LN complex, FN bound to a polycationic matrix is able to induce neurite growth in hippocampal neurons in vitro.

Animals↗
PubMed1988

GABA activated chloride currents in cultured rat hippocampal and septal region neurons can be inhibited by curare and atropine.

In order to study the influence of curare and atropine on the gamma-aminobutyric acid (GABA)-evoked chloride current, we have investigated cultures of hippocampal and septal region neurons from embryonic rats (E18). The neurons were cultured under the trophic influence of spatially separated astrocytes in serum-free medium. By means of the patch clamp technique, the excitable cells displayed GABA induced chloride currents within 1-15 days in vitro. In both cultures picrotoxin or bicuculline as well as curare or atropine reversibly inhibited the chloride current in a dose dependent manner. We conclude that curare and atropine are not specifically anti-cholinergic for cultured central neurons. Our results provide evidence for common ligand binding properties shared by GABAA and acetylcholine (ACh) receptors supporting the recent concept of a receptor superfamily.

Animals↗
PubMed1988

Antibodies to calcium/phospholipid binding protein (calelectrin) recognize neurons, astrocytes and Schwann cells in the nervous system of rat.

We report on the identification of proteins Mr 32 kDa, 34 kDa, 68 kDa in rat brain or sciatic nerve which cross-react (by immunoblotting) with antibodies to purified Ca2+/phospholipid binding protein calelectrin from Torpedo marmorata. Immunocytochemical staining revealed that anti-calelectrin antibodies labeled cell bodies and processes of cortical neurons and astrocytes in the central nervous system (CNS). In sciatic nerve, calelectrin-like immunoreactivity was expressed in the cytoplasm of Schwann cells of adult as well as newborn rat. Additional staining occurred at periaxonal sites in mature nerve. The localization of calelectrin-related proteins in distinct cell types of the mammalian nervous system suggests a cell-specific role of this new group of proteins in Ca2+-mediated membrane processes involved in neural function.

Animals↗
PubMed1988

[Treatment of cruciate ligament lesion following knee trauma].

In the treatment of the capsular ligament lesions of the knee joint, the most important therapeutic measure is the reconstruction of the central pillar of the cruciate ligaments. 112 patients with ruptures of the cruciate ligaments and associated injuries have been operated from 1975 through 1985. 78 out of them can be checked-up. Most of the accidents are due to sports or professional activities. 76% of the patients are treated early, i.e. within the first six days from the accident. The rates of simple instabilities as well as of anteromedial rotation instabilities are 40% each, the remaining injuries are severe combined traumas to the knee. In many cases the articular structures are involved, too. The surgical procedure is described. In 89% of the cases, the articular stability is restored with very good or good success by reconstruction. A permanent instability is only observed in two patients. Taking into consideration the mobility and the subjective opinions of patients, 71% have very good or good results.

Adolescent↗
PubMed1987

Nonresident macrophages in peripheral nerve of rat: effect of silica on migration, myelin phagocytosis, and apolipoprotein E expression during Wallerian degeneration.

The selective toxicity of silica quartz dust to macrophages was used to assess the role of these cells in Wallerian degeneration and nerve repair. Left sciatic nerves of adult Wistar rats were crushed and one group of animals received repetitive intraperitoneal injections of silica (200 mg two times per week starting 1 day prior to injury), whereas the control group received saline. Unexpectedly, silica treatment did not impair the initial invasion of (hematogenous) macrophages into the degenerating distal nerve stump as revealed by histological and immunocytochemical methods. However, 4 weeks after the lesion three specific events in Wallerian degeneration were significantly inhibited in silica-treated animals: 1) inhibition of phagocytosis and degradation of myelin, 2) delay in disappearance of nonresident macrophages from regenerating nerve, 3) reduction of synthesis and/or secretion of apolipoprotein E in resting macrophages. On the other hand, axonal regrowth and remyelination were not affected by silica. These in situ experiments support and extend previous studies suggesting specific functions for nonresident macrophages in Wallerian degeneration of peripheral nerve.

Animals↗