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Biomedical subjects

J Koenig

Publications and source records attributed to J Koenig.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1980

Role of central nervous system neurotransmitters in mediating the effects of morphine on growth hormone- and prolactin-secretion in the rat.

Unanesthetized adult male rats with indwelling right atrial cannulae were used in the majority of experiments. Morphine (MOR, 3.0 mg/kg) caused a large but transient increase in both GH and PRL levels, which could be prevented with naloxone. Disruption of central noradrenergic function with diethyldithiocarbamate (400 mg/kg) or phenoxybenzamine (15 mg/kg) abolished the GH-releasing effect of MOR, without interfering with the PRL secretory response. Depletion of brain serotonin stores with p-chlorophenylalanine (300 mg/kg) or 5,7-dihydroxytryptamine or administration of serotonin receptor blocker, cyproheptadine (2.5 mg/kg), did not diminish the GH respnse to MOR but it inhibited, or in the case of 5,7-DHT treatment abolished the activation of PRL secretion. Additionally, metergoline (0.1 and 1.0 mg/kg), another serotonin receptor blocker, caused an inhibition of the GH-releasing action of MOR; however, this inhibition was reversed by pretreatment with spiroperidol (0.1 mg/kg). Metergoline also markedly diminished the MOR-induced elevation of PRL. Inhibition of catecholamine synthesis with alpha-methyl-p-tyrosine (alpha-MT, 250 mg/kg) blunted the effect of MOR on GH; however, dopamine receptor blockers, spiroperidol (0.01 and 0.1 mg/kg) or (+)butaclamol (0.3 and 1.3 mg/kg), were without any influence. alpha-MT or spiroperidol did not alter the effect of MOR on PRL secretion, but the higher dose of (+)butaclamol suppressed it. It is concluded that the GH-releasing action of MOR requires unimpaired functioning of the central noradrenergic system, while the serotonergic and dopaminergic systems appear to play no significant role in it. In contrast, serotonergic systems seem to be essential for the activation of PRL secretion, whereas the noradrenergic system is not involved. It remains uncertain whether morphine activtes PRL secretion also through inhibition of dopaminergic activity. We favor the view that the dopaminergic component participates in the PRL activation by MOR, but that its contribution to the overall effect is rather small.

Animals↗
PubMed1978

[Formation of the neuromuscular junction in cultures of rat embryonic cells].

The morphological evidence of the primary nerve muscle contacts are described. They consist of areas of cholinesterase activity (detected histochemically) localized on the myotube membranes and of mutiple clusters of ACh receptors whose 125I-alpha-bungarotoxin binding sites are revealed by radio-autography. After the stage of the primary nerve muscle contacts, some of which seem transient, characteristic neuromuscular junctions appear. These neuromuscular junctions which possess subneural infoldings are similar to the end-plates of the Rat in vivo.

Animals↗
PubMed1978

[Molecular forms of acetylcholinesterase in the slow muscle and the fast muscle of the chicken].

Five molecular forms of AChE are present in the slow (ALD) and twitch (PLD) muscles of the chick. These forms have 4 S, 7 S, 11 S, 15 S and 20 S sedimentation coefficient in sucrose gradient. The heaviest forms, the 20 S and 15 S of AChE are absent in uninnervated muscles and present in innervated muscles. In innervated muscles, the 20 S and 15 S AChE are present in both nerve-free segments and end-plates zones. The 20 S and 15 S which are not specifically associated with the end-plate zones in the chick could be considered as a biochemical "marker" of neuromuscular interactions.

Acetylcholinesterase↗
PubMed1976

[Influence of some nutritional factors on the canthaxanthine pigmentation of the rainbow trout].

The present investigation was made to approve nutritionnal factors which affect the utilisation of food canthaxanthin by hatchery trout. Rainbow trout were obtained from a commercial trout farm, kept in running water and feeding in experimental pellets for 4 to 8 weeks. Five diets were tested (1-standard [7.5 u.i/g], 2-low protein content, 3-High lipid content, 4-non supplemented with vitamin A, 5-High vitamin A content [23 U.I./g]). All diets containing 250 mg of canthaxanthin per kilo of food, the fish were fed at the rate of approximately 2.5 p. 100 of their body weight per day. The estimation of canthaxanthin from fish tissues was accomplished as follows: the tissues were gomogeneized and extracted with several volumes of solvents. The solution containing all the pigment was evaporated. The purification of the canthaxanthin was obtained by column silica gel chromatography. The pigment was eluated with ethyl-ether as solvent. Quantitative assay of total carotenoïd was effected by spectre photometric estimation of optical density at 480 nm of this fraction dissolved in benzene. The carotenoïd composition of this fraction was studied by silica-gel thin layer chromatography. In these conditions:--it was shown by spectral studies that the canthaxanthins present in the diet are essentially those deposed in the flesh of the trout fed;--a series of experiment were made to examine the effect of composition of artificially composed feeds for pigmentation of the rainbow trout. The pigment deposition was found to correlate with the amount of lipids present in these diet. In this condition, the pigment is more dispersed with lipids present and the pigment absorption may be facilitated and later be deposed. 8 weeks alimentation are needed to observe the effect of these nutritionnal factor;--when the diet is non supplemented with vitamin A, the same quantity of canthaxanthin mixed with this food gives trout redder flesh than the standard diet. On an other hand, an antagonist effect of diet with high vitamin A content is demonstrated on the amount of the pigment deposed in the flesh of trout;--no effect of protein content of the diet was found in these experiments;--no effect of ratio calorie/protein of the diets with the intensity of deposed pigment in the flesh rainbow trout;--a correlation between neutral lipids of the tissue and the pigment deposed in the flesh of the trout fed with canthaxanthin was confirmed.

Animal Nutritional Physiological Phenomena↗