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Biomedical subjects

J Koenig

Publications and source records attributed to J Koenig.

At least 55 records · Page 3Linked to original sources
PubMed1993

Effect of sera from myasthenia gravis patients and of alpha-bungarotoxin on acetylcholinesterase during in vitro neuromuscular synaptogenesis.

Myasthenia gravis (MG) is mediated by circulating antibodies directed against acetylcholine receptor (AChR) but the antibody titre is poorly correlated with the clinical severity of the disease. We analysed acetylcholinesterase (AChE) activity, molecular forms and distribution during in vitro synaptogenesis, in the presence of sera from MG patient. We observed that the formation of AChE patches is inhibited in proportion to the anti-AChR antibody titre, whatever the clinical severity of the disease. The total activity and the proportion of the different molecular forms were unchanged suggesting that AChE level and distribution are controlled by independent mechanisms. To clarify the relationship between the mechanisms of AChE concentration during synaptogenesis and AChR concentration, we compared the effect of MG sera (receptors are internalised and degraded) and of the acetylcholine antagonist alpha-bungarotoxin (non-functional receptors are still present in the muscular membrane). In the presence of alpha-bungarotoxin, the number of AChR clusters, and AChE activity and concentration were equivalent to control values. The comparison of the results obtained with antibodies and alpha-bungarotoxin suggests that the presence and/or concentration of AChR is a necessary condition for normal concentration of AChE during synaptogenesis.

Acetylcholinesterase↗
PubMed1993

[Effect of the mutation muscular dysgenesis on the mitochondrial metabolism of fibroblasts in vitro].

Muscular dysgenesis is a lethal mutation characterized by an absence of striated muscle contraction. This abnormality of function caused by a defect in excitation-contraction coupling is due to the lack of the alpha 1 subunit from the dihydropyridine receptor in the transverse tubule membrane. A phenotypical reversion is obtained in vitro by addition of normal cells, as fibroblasts, in dysgenic muscle culture. Perisynaptic fibroblasts from denervated muscle have been shown to synthetize molecules which are usually concentrated at the synapses suggesting that signal arising after denervation may influence fibroblasts synthesis ability. We show here that the energetic metabolism level from dysgenic fibroblast is lower than that from normal fibroblasts. The synthesis or the release of muscular signals that are involved in fibroblast differentiation could be disturbed in mdg/mdg myotubes.

Electron Transport↗
PubMed1991

The effect of tetanus toxin on in vitro synaptogenesis.

Cultures of spinal cord neurons and cocultures of rat embryo neurons and muscle cells have been studied in the presence of tetanus toxin (TT) at a concentration of 40 micrograms/ml of medium. TT strongly stimulated neurite outgrowth, notably branching from the cell bodies. In addition it induced a marked, overall increase in acetylcholine receptor (AChR), but inhibited focalisation of AChR and acetylcholinesterase (AChE) at the synaptic sites. TT seems to act on neurite emergence, on the neuronal factor(s) controlling AChE and AChR concentrations, and on the factor(s) modulating degradation and/or synthesis of AChR.

Acetylcholinesterase↗
PubMed1991

Fura-2 imaging of spontaneous and electrically induced oscillations of intracellular free Ca2+ in rat myotubes.

Rat myotubes have a resting [Ca2+]i of about 82 nM. Myotubes 3-5 days old (quiescent myotubes) display electrically induced and spontaneous transients in the intracellular concentration of free Ca2+ ions ([Ca2+]i) uncoupled to any detectable contraction. By contrast, 1- to 2-day-old myotubes are insensitive to electrical stimuli and, after 6 days in culture, stimulated myotubes always show [Ca2+]i transients and twitch contractions. The spatial distribution of [Ca2+]i variations in quiescent myotubes is heterogeneous, local increases in [Ca2+]i being mainly observed near the periphery of the cell. The small effect of different external Ca2+ concentrations and of Cd2+ on the amplitude of the [Ca2+]i oscillation indicates that the main source of Ca2+ may be the sarcoplasmic reticulum. This conclusion is supported by the close similarity between electrically induced and caffeine-induced [Ca2+]i maps. These findings suggest that, at an early stage of myotube ontogenesis, a part of the excitation/contraction coupling, as membrane ionic channels, voltage sensors and Ca2+ release and reuptake mechanisms, is functional but, apparently, still uncoupled to the contractile machinery.

Animals↗
PubMed1990

Neurite outgrowth and proliferation of non-neuronal cells on cryostat sections of adult muscle.

Rat spinal cord cells were cultured on cryostat sections of innervated and denervated muscle. Neurite outgrowth was greater on sections of denervated muscle, which therefore appeared to act on in vivo nerve regeneration. It seems that muscle sections were able to release into the culture medium factors that increase proliferation of fibroblasts. The muscle therefore appeared able to modulate its interaction with its environment by acting on different types of cells.

Animals↗
PubMed1990

A quantitative assessment of respiratory patterns and their effects on dentofacial development.

The purpose of this study was to assess the effects of quantitatively determined breathing patterns on dentofacial development in growing children. Forty-nine subjects ranging in age from 10 to 16 years participated in the breathing pattern assessment portion of this project. Oral, nasal, and total airflow were measured at separate times by means of a head-out body plethysmograph technique and the values were compared with the subjects' and parents' subjective perceptions of their breathing modes. These breathing pattern measurements also were compared to nasal airway resistance and nasal power. Temporal variation and cyclic respiration, which may play important roles in quantitative evaluations of childrens' breathing patterns, also were addressed. In addition, objective assessments of possible associations between dentofacial structure and respiration were made on 45 of these children. Most subjects' exhibited was either an oronasal or a completely nasal respiratory pattern. However, significant variation in breathing measures was evident among a number of subjects whose breathing was measured twice on the same day and on different days. No significant correlations were found between objectively measured and subjectively determined impressions of respiratory patterns. In addition, there was no association between nasal airway resistance or nasal power and plethysmograph recordings of percent of mouth breathing. Comparisons of measured breathing modes and dentofacial characteristics revealed a weak tendency among mouth breathers toward a Class II skeletal pattern and retroclination of maxillary and mandibular incisors. In contrast, subjective perception of mouth breathing was associated with increased anterior facial height and greater mandibular plane angles. Nasal power and resistance were not correlated with either dental or skeletal variables. This study presents evidence that determination of respiratory pattern is a complex issue for which methods must be refined and performed longitudinally.

Adolescent↗
PubMed1990

Acetylcholinesterase in cocultures of rat myotubes and spinal cord neurons: effects of collagenase and cis-hydroxyproline on molecular forms, intra- and extracellular distribution, and formation of patches at neuromuscular contacts.

Cultures of rat myotubes from 18-day-old embryos produce both globular (G) and asymmetric (A) forms of acetylcholinesterase (AChE; EC 3.1.1.7), mostly G1, G4, and A12 and a small proportion of A8. We show that all forms are partly intracellular and partly exposed to the extracellular medium; the A forms and their intra- and extracellular distribution are not modified when myotubes are grown in the presence of spinal cord neurons. In these cocultures, however, AChE patches may be detected immunohistochemically at sites of neuromuscular contacts. These patches represent a very minor proportion of AChE activity. We found that collagenase removes AChE patches but not the acetylcholine receptor clusters with which they coincide. This digestion specifically decreases the level of the A12 form. cis-Hydroxyproline, an inhibitor of collagen synthesis, reduces the level of G1 and blocks the synthesis of A forms.

Acetylcholinesterase↗
PubMed1989

In vitro synaptic maturation.

Cocultures of spinal cord neurons and muscle cells taken from rat embryos were used for in vitro reproduction of embryonic synapses. This system did not display the synaptic maturation characteristics of postnatal development: decreased multiple innervation and the presence of a developed subneural apparatus. Studies on cultures consisting of 3 cell types (muscle cells, nerve cells, Schwann cells), or on co-cultures (muscle cells, nerve cells), in the presence or absence of a monoclonal antibody directed against an antigen from Schwann cells, have shown that Schwann cells participate in synaptic maturation and in the elimination of superfluous synapses. The synapses were visualised for optical microscopy by co-localisation of acetylcholinesterase (AChE) spots and acetylcholine receptor (AChR) clusters.

Animals↗
PubMed1989

In vitro evidence for a neurite growth-promoting activity in Trembler mouse serum.

Basal lamina components, such as heparan sulfate proteoglycan (HSPG) and laminin play an important role in neuritic outgrowth for CNS and PNS neurons in culture. The mutant mouse 'Trembler' is characterized by hypomyelinization and production of an excess of basal lamina layers around Schwann cells in peripheral nerves. In order to analyse whether or not the serum of the mutant animals contains neurite outgrowth-promoting factors, we cultured rat spinal cord neurons in the presence of Trembler serum. Under these conditions, the outgrowth of neurites was increased approx. 2 times as compared to control serum. Trembler serum induces neuritic outgrowth characterized both by an increase in number of primary neurites emerging from the nerve cell body as well as by an increase in peripheral branching of neurites. To characterize the factors implicated in this increase we added antibodies directed against HSPG or laminin to the mutant serum. As a result, the increase in neuritic outgrowth was reduced or abolished in both cases. Trembler effect on neurite growth disappeared when the number of the non-neuronal cells was reduced, suggesting that the mutant serum did not act directly on neurons but by the intermediary action of non-neuronal cells.

Animals↗
PubMed1989

Rescue of excitation-contraction coupling in dysgenic muscle by addition of fibroblasts in vitro.

Muscular dysgenesis (mdg) in mice causes the failure of excitation-contraction (E-C) coupling in skeletal muscle. Cultured dysgenic muscle fails to contract upon depolarization, lacks typical muscle ultrastructure, including normal triads, and lacks functional voltage-dependent slow calcium channels. We show that normal rodent fibroblasts and 3T3 fibroblasts "rescue" dysgenic myotubes, reestablishing contractions (i.e., E-C coupling), normal ultrastructure, and functional slow calcium channels. These results support the finding that the expression of the slow calcium channel is affected in the mdg mutation and that this protein is essential for E-C coupling. Additionally, fibroblast rescue provides a system for examining the mechanisms of heterotypic cellular influence on cell function.

Action Potentials↗
PubMed1989

Restoration of dysgenic murine (mdg) myotube contraction after addition of Schwann cells from normal mice in vitro.

Muscular dysgenesis in mutant mice is characterised by failure of excitation-contraction (E-C) coupling and consequent loss of skeletal muscle contraction. Contractile activity is restored in vitro by the addition of normal mice cells (11) (18) (7). In the present study we show a new model: contraction and ultrastructural organization of dysgenic myotubes are restored by coculture with Schwann cells from normal mice.

Animals↗
PubMed1988

Does the Schwann cell synthesize a molecule concentrated at the neuromuscular synapse?

The monoclonal antibody 6.17 binds to a molecule concentrated at the neuromuscular synapse. We tested it in various experimental conditions and all along the normal muscle development. It seems that the 6.17 corresponding antigen, suspected of Schwann cell origin, would be later localised in the synaptic space, but not in the basal lamina. Thus, the Schwann cell might participate to the synthesis of some synaptic molecules.

Animals↗
PubMed1988

Effect of myasthenic patient sera on the number and distribution of acetylcholine receptors in muscle and nerve-muscle cultures from rat. Correlations with clinical state.

We studied the functional activities (FA) of sera obtained from 83 myasthenic patients on rat muscle cultures. Using the same sets of cultures, two parameters were evaluated after exposure to sera: residual fraction (RF) of acetylcholine receptors (AChR) coupled to 125I-labelled alpha-bungarotoxin (alpha Bgt) (81 sera) and the number of rhodamine labelled clusters (56 sera). Two types of culture were assayed: muscle alone and nerve-muscle cocultures (12 cases). In all combinations (fluorescence, radiolabelling, muscle alone and nerve-muscle cocultures), we found a significant correlation between FA and antibody (Ab) titre, and no correlation between FA and clinical severity: only sera with a high or intermediate Ab titre were effective, whatever the clinical severity of disease. With active sera, AChR loss was about 50% whereas the disappearance of AChR clusters was quite complete, which suggests AChR redistribution induced by MG sera.

Animals↗
PubMed1988

[Is muscular acetylcholinesterase activity correlated with the intracellular concentration of free calcium?].

The role of the calcium ion Ca2+ as an agent of intracellular control in a variety of physiological processes is well established. In vertebrate skeletal muscle fibers, Ca2+ is involved in muscle contraction, modulation of membrane permeability and regulation of metabolic activity. Recently it was suggested that ion fluxes through membranes regulate the level of two cholinergic macromolecules, the acetylcholine receptor and the A12 form of acetylcholinesterase (AChE), the presumed synaptic form of the enzyme. Muscle cells paralysed by veratridine, which maintains the Na+ channel in the open state, showed an increase in total AChE and in the levels of the A12 form. The effect of veratridine on AChE was blocked in the presence of agents that block Ca2+ permeability suggesting that Ca2+ is involved in this effect. To understand whether the level of muscle AChE is related in some way to the level of free intracellular Ca2+, we analysed the variations of Ca2+ levels in rat muscle cells treated by agents which modify the ionic permeabilities. This level was determined by spectrofluorimetry using the fluorescent Ca2+ indicator: Quin 2. However no correlation between these parameters was observed in our experimental conditions.

Acetylcholinesterase↗
PubMed1987

Congenital fibrosarcoma.

Congenital fibrosarcoma is a rare fibrous tissue malignancy occurring most commonly in the extremities (71%), but presenting in axial locations as well (29%). Two of our five patients had lower extremity tumors and three had axial lesions located in the thoracolumbar region and anterior neck. Amputation was considered necessary to treat the extremity tumors. Two of the patients with axial lesions had incomplete resection, which raised the question of adjunctive therapy and prompted this review. Forty-seven additional cases of fibrosarcoma, present at birth or diagnosed within the first 3 months of life, were adequately described and documented in the literature giving a total of 52 cases. There was no sex predominance (male 26, female 20, unknown 6). Thirty-seven (71%) of the patients had extremity lesions. The local recurrence rate for extremity tumors was 32% with metastatic and mortality rates of 8% and 5%, respectively. Axial tumors (15 cases, 29%) had a local recurrence rate of 33%, which is similar to that for extremity lesions, but the metatstatic and mortality rates were 26% each indicating a more aggressive behavior for axial lesions. The overall mortality rate of 11.5% and metastatic rate of 13.5% for congenital fibrosarcoma, are not dissimilar to the figures quoted for older children. This pattern of tumor behavior, therefore, does not seem to warrant a different attitude because of the "congenital" occurrence of the tumor. Surgery must be considered the mainstay of therapy for fibrosarcoma, but there is a need for adjunctive therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗
PubMed1987

Primary muscle cells cultivated in medium conditioned by spinal cord cells show changes in messenger RNA as detected by translation in ovo accompanied by synthesis of extracellular matrix components.

Primary muscle cell cultures were prepared from rat embryos and maintained in normal (unconditioned) and spinal cord (conditioned) media. In order to relate translational regulation to the morphological changes associated with each culture condition, mRNA was isolated from both culture variants and subjected to in ovo translation. Xenopus oocytes were injected with mRNA and their incubation media checked for the presence of newly formed proteins coded by the mRNAs and secreted into the medium. Electrophoretograms indicated mRNA-dependent synthesis of several proteins in the molecular mass range of 30-260 kD. To further characterize these proteins, antisera directed against several extracellular matrix proteins were used for immunoprecipitation: antigens recognized by anti-heparan-sulfate-proteoglycan and anti-fibronectin were enhanced in conditioned cells, whereas laminin was found to be reduced.

Animals↗
PubMed1987

Heparan sulfate proteoglycan and laminin mediate two different types of neurite outgrowth.

Spinal cord neurons cultured in vitro have been shown to respond to changes in their environment by means of 2 different types of neurite outgrowth: (1) neurite elongation and (2) emergence and branching of newly formed neurites. Culture of spinal cord neurons with heparan sulfate proteoglycan (HSPG) medium resulted in a 3-fold increase in neurite elongation compared to the control. Extensive branching was seen when neurons were cultured in laminin-supplemented culture medium. HSPG-induced elongation and laminin-induced branching of neurites were blocked by specific anti-HSPG and antilaminin sera, respectively. Furthermore, laminin antibodies did not inhibit neurite elongation and HSPG antibodies did not block neurite branching. Conditioned medium from primary embryonic rat muscle cultures (MCM) mimicked the effects of both HSPG and laminin on neurite outgrowth. Immunoprecipitation with anti-HSPG and antilaminin antibodies demonstrated that MCM contains these 2 basal lamina components. Our observations suggest that HSPG and laminin might be highly effective molecules for promoting neurite outgrowth of rat spinal cord neurons in vitro.

Animals↗