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J Koenig

Publications and source records attributed to J Koenig.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1987

The theophylline method of the Abbott "Vision" analyzer evaluated.

We evaluated the analytical performance of the Abbott "Vision" analyzer for theophylline measurement. The within-day precision (CV) was 1.8% and 3.1% at theophylline concentrations of 15.2 and 25.2 mg/L, respectively; between-day precision was 3.5% and 4.8% at 14.9 and 24.4 mg/L, respectively. Bilirubin (143 mg/L) and triglyceride (7.4 g/L) did not interfere, but hemoglobin caused lower values for apparent theophylline, the magnitude of the decrease being proportional to the hemoglobin concentration. At the cutoff concentration of 1 g/L programmed into the instrument by the manufacturer, hemoglobin reduced the theophylline value by less than 10%. Results by the Vision method (y) compared well with those by the "TDX" procedure (x): r = 0.98, y = 0.978x - 0.270 mg/L. The Vision method gave comparable theophylline values for serum, plasma, and whole-blood samples. We also validated analytically and clinically that capillary blood samples collected by finger stick can be used interchangeably with blood samples collected by venipuncture for monitoring theophylline therapy.

Autoanalysis↗
PubMed1986

Presynaptic or postsynaptic origin of acetylcholinesterase at neuromuscular junctions? An immunological study in heterologous nerve-muscle cultures.

Numerous studies have shown that the acetylcholine receptor (AChR) is inserted in the plasma membrane of the muscle fiber, and that it is focalized at the site of neuromuscular junctions, as an effect of neural influence. In contrast, acetylcholinesterase (AChE) may be presynaptic or anchored in the basal lamina, as well as postsynaptic at neuromuscular junctions. We investigated the origin of the junctional enzyme, particularly the collagen-tailed asymmetric A12 forms, by studying the AChE contents of heterologous rat and chicken neuromuscular cocultures by immunohistochemical and biochemical methods. We found that the overall content of AChE, in the neuromuscular cocultures, including the A12 form, was essentially identical to the sum of the contents of separate myotube and motoneuron cultures. The sedimentation coefficients of the rat and chicken asymmetric forms are sufficiently different to clearly differentiate these enzymes in sucrose gradients: 16 S for rat, 20 S for chicken A12 AChE. Sedimentation analyses of AChE in cocultures thus showed that the A12 form was of muscular origin. In the case of aneural cultures of myotubes, histochemical staining of AChE activity or immunohistochemical staining with specific antibodies showed only very scarce, faint concentrations of enzyme. Some patches of acetylcholine receptor (AChR) were, however, visible in these cultures. Neuromuscular contacts are readily established in cocultures of myotubes with embryonic motoneurons from spinal cords. In the presence of motoneurons, the myotubes presented a larger number of AChR patches. The most remarkable feature of neuromuscular cocultures was the presence of numerous intense AChE patches which always coincided with AChR clusters. By specifically staining nerve terminals with tetanus toxin, we could show an excellent correlation between neuromuscular contacts and the presence of AChE-AChR patches. We found that the AChE patches in heterologous cocultures could be stained exclusively by the anti-myotube AChE antiserum. The focalized enzyme is therefore exclusively, or very predominantly, provided by the myotube.

Acetylcholinesterase↗
PubMed1986

Infection of cultured rat myotubes and neurons from the spinal cord by rabies virus.

Rabies virus multiplication was investigated in cultured primary rat myotubes and neurons. The susceptibility of these two cell types to fixed rabies challenge virus strain (CVS) was monitored by fluorescence and virus titration. Differentiated rat myotubes were susceptible to rabies virus infection, and showed an increasing accumulation of viral material from day one to day four. However, these cells did not release infective viral particles, nor did they accumulate infectious virions in the cytoplasm. In contrast, infected neurons released large amounts of infectious particles. Electron microscopy observation of infected myotubes showed minor alterations and the presence of typical viral inclusions in the cytoplasm without mature virions assembling viral membranes. Competition binding experiments show that alpha-bungarotoxin inhibits rabies virus infection from 10(-5) to 10(-7) M, whereas lower toxin concentrations failed to have any effect. These data do not confirm the hypothesis of a fixed rabies virus amplification step at the site of the viral entry. On the other hand, the high susceptibility of peripheral neurons to rabies virus infection is an argument for the direct uptake of virions by these cells. The restrictive viral multiplication in the myotubes is an alternative explanation for the local persistence of rabies virus at the site of inoculation.

Animals↗
PubMed1985

Effects of dextran on five biuret-based procedures for total protein in serum.

We evaluated the effect of dextran on values for total protein in serum as measured by the biuret method with five widely used automated instruments: the American Monitor Parallel; the Du Pont aca II; the Roche Cobas-Bio; the Kodak Ektachem 400; and the Beckman Astra 8. Dextran concentrations as great as 25 or 30 g/L had relatively little or no influence on total protein measurements by the latter three instruments. Dextran concentrations exceeding 6 g/L caused falsely low results with the aca, whereas the Parallel gave falsely high results when the dextran concentration exceeded 2 g/L. The aca total protein procedure could be protected from the interference by dextran concentrations up to 30 g/L by injecting 0.4-0.8 mL of ethylene glycol directly into the reagent pack before sampling. However, we could not eliminate the interference with the Parallel procedure by any simple means; we thus recommend that it not be used for measuring total protein in serum samples from patients who are being treated with dextran.

Adult↗
PubMed1985

Inaccurate values for direct bilirubin with some commonly used direct bilirubin procedures.

We compared five methods for the determination of total and direct bilirubins in serum samples from normal controls, subjects with Gilbert's syndrome, and serum pools containing about 50 and 150 mg of total bilirubin per liter. The Kodak Ektachem method and a diazotized sulfanilic acid method with 0.15 mmol/L sodium nitrite concentrations are the only methods that gave accurate direct bilirubin values, as judged by liquid-chromatographic results. The aca method that involved p-nitrobenzene diazonium tetrafluoroborate and another diazotized sulfanilic acid method with a higher concentration of sodium nitrite (0.8 mmol/L) yielded falsely high values for direct bilirubin, which could lead to clinical confusion. The more recently introduced diazotized sulfanilic acid method of the aca gave substantially better results than the p-nitrobenzene diazonium tetrafluoroborate method but was still inaccurate. Systematic investigation of these procedures revealed that the overestimation of direct bilirubin by the diazotized sulfanilic acid method was related to the amount of unconjugated bilirubin present and its ability to react as direct bilirubin in the presence of higher concentrations of sodium nitrite. Inherent properties of p-nitrobenzene diazonium tetrafluoroborate appeared to be responsible for inaccuracies in that method, which could not be corrected by varying reagent concentration or the reaction conditions.

Adult↗
PubMed1984

Single acetylcholine-activated channel currents in developing muscle cells.

The properties of single acetylcholine-activated ion channels in developing rat myoblasts and myotubes in tissue culture have been investigated using the gigaohm seal patch clamp technique. Two classes of ACh-activated channels were identified. The major class of channels (accounting for greater than 95% of all channel openings) has a conductance of 35 pS and a mean open time of 15 msec (at room temperature and -80 mV). The minor class of channels has a larger conductance (55 pS) and a briefer mean open time (2-3 msec). Functional ACh-activated channels are present in undifferentiated mononucleated myoblasts 1-2 days in culture, although the channel density on such cells is low. Over the next week in culture, as the myoblasts fuse to form multinucleate myotubes, there is a marked increase in channel density and an increase in the proportion of large conductance channels. No significant change, however, occurs in channel conductance or open time (within a given class of channels) during this period. At high concentrations of ACh, channels desensitize and channel openings occur in groups, similar to what has been previously described in adult muscle. The rate of channel opening within a group of openings increases with increasing agonist concentration while mean open time is independent of agonist concentration, as expected from simple models of drug action. During a group of openings, the channel is open for half the time (i.e., channel opening rate is equal to channel closing rate) at a concentration of approximately 6 micron ACh.

Acetylcholine↗
PubMed1984

Action of veratridine on acetylcholinesterase in cultures of rat muscle cells.

Studies on cultures of embryonic rat muscle cells have suggested that the presence of collagen-tailed forms may be correlated with spontaneous contractile activity: these forms disappear in the presence of tetrodotoxin which blocks the sodium channels involved in the propagation of action potentials. The effect of veratridine, a drug which maintains the sodium channels in the open state, was studied. It is shown here that in young cultures veratridine provoked a dramatic increase in total acetylcholinesterase activity and changed the distribution of the molecular forms of the enzyme, increasing the proportion and absolute amount of the A12 form. In order to elucidate the mechanism of action of this drug, the effects of various ions, ionophores, or other agents that modify the ionic permeabilities of membranes were also investigated.

Acetylcholinesterase↗
PubMed1984

Acute diquat intoxication. Interest of its repeated determination in urine and the evaluation of renal proximal tubule integrity.

A 33-year old farmer ingested approximately 300 ml of a 20% solution of diquat along with about 80 mg flunitrazepam. The patient presented neurological (coma grade I), digestive (oro-pharyngeal erosions, ileus), hepatic (cytolysis), hematological (thrombopenia) and renal (tubular dysfunction) signs. Plasma creatinine did not exceed 1.22 mg/dl (upper normal value), but retinol binding protein level in urine (a marker of renal tubular dysfunction) reached a value of 337 mg/d (normal values less than 300 micrograms/d). Its level returned to normal value 18 days after the ingestion. Four hours after the poisoning, diquat level in blood amounted to 10.4 mg/l, but its level was below the detection limit (0.2 mg/l) 6 hours later. In urine, however, diquat was detected until day 13. The following therapy was applied: ventilation (FiO2:0.21), gastro-intestinal lavage, hemoperfusion, anti-oxidants and prolonged forced diuresis. The patient made an uneventful recovery. intestinal washout must be applied with caution since an ileus is a classical complication of diquat poisoning. Hemoperfusion was found to be of little value. The interest of prolonged application of forced diuresis is suggested by the detection of diquat in urine for about 2 weeks along with the presence of biological signs of renal tubular dysfunction.

Adult↗
PubMed1984

Scanning electron microscopic study of nerve-muscle junctions in embryonic rat cell cultures.

The morphology of neuromuscular junctions between embryonic rat spinal cord and muscle cells grown in vitro has been studied by scanning electron microscopy (SEM). Histochemical detection of acetylcholinesterase (AChE) spots and autoradiographic detection of acetylcholine receptor protein (AChR) were performed in parallel. At the scanning EM level the contacts exhibit a marked polymorphism; the nervous endings may present as a bulbous swelling, or often as a plexiform network on the surface of the myotubes. Many neuromuscular contacts seem to occur 'passing by'; in other places, neurites processes slide along myotubes without any differentiated contacts. The muscle cell surface does not look substantially modified in the contact area. The distribution of the contacts between nerve and muscle cells is at the same time convergent and divergent.

Animals↗
PubMed1982

[In vitro study of the action of isaxonine on the growth of rat spinal cord neurons (author's transl)].

Dissociated spinal cord cells were cultured in appropriate culture medium. In these conditions the cell bodies tended to emit neurites and to interconnect. Grown with isaxonine, spinal cord neurons form larger aggregates, neurites number is higher, connection between cellular groups is more larger, and branching of neurites is more distal. Future research will try to verify the assumption of an increase in neuromuscular contacts under the influence of isaxonine.

Animals↗