Inhibition of mobilization of acetylcholine: the weak link in neuromuscular transmission during partial neuromuscular block with d-tubocurarine

The authors have demonstrated earlier, by direct measurement of acetylcholine (ACh), that d-tubocurarine (d-Tc) and other nondepolarizing muscle relaxants decrease the release of ACh from the indirectly stimulated mouse hemidiaphragm preparation. It was the purpose of the present study to determine whether the decrease of the stimulated release of ACh and the increase in the intensity of the partial neuromuscular block observed at higher stimulation rates is caused by the inhibition of mobilization of ACh from reserve depots to release sites or by inhibition of the release process itself. To attain our objective, the authors have investigated the influence of the progressive increase of the rate of stimulation from 0.1 to 1, 2, 3, and 5 Hz on the force of contraction on the in vitro phrenic nerve-hemidiaphragm and in vivo sciatic nerve-tibialis anterior preparation in the absence of drugs and after about 20% neuromuscular block produced by d-Tc or by Mg2+. The latter is known to inhibit the Ca2+ dependent release of ACh. In the absence of drugs increasing the stimulation rate increased the force of contraction, in vivo and in vitro, during both indirect and direct stimulation. In the phrenic nerve-hemidiaphragm preparation the increase was significant at 1, 2, 3, and 5 Hz (P less than 0.001) with both types of stimulation. In the sciatic nerve-tibialis anterior preparation the force of contraction was only higher at 3 and 5 Hz (P less than 0.01). The similar magnitude of the increase of the force of contraction during direct and indirect stimulation indicates that it is caused by facilitation of the contraction of the muscle fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of atracurium and laudanosine on the release of 3H-noradrenaline

We examined the effects of atracurium and its breakdown product, laudanosine, on resting and stimulation-evoked release of 3H-noradrenaline (3H-NA) from sympathetic axon terminals of isolated right atria of guinea pigs. Both atracurium 1-100 mumol litre-1 and laudanosine 1-50 mumol litre-1 enhanced the release of 3H-NA evoked by field stimulation (2 Hz, 24 stimuli), but did not affect resting release. When the production of laudanosine from atracurium was inhibited by maintaining the atracurium solution at 4 degrees C, atracurium did not enhance the release of 3H-NA as occurred when it was kept at 37 degrees C. However, atracurium antagonized the inhibitory effect of oxotremorine on release of 3H-NA, whereas laudanosine did not. These data suggest that atracurium possesses an antimuscarinic effect. Its metabolite, laudanosine, in concentrations which would be expected following prolonged administration of atracurium, produced a marked increase in release of 3H-NA. This effect of laudanosine may explain some of the unwanted effects seen following administration of atracurium.

In vitro comparison of the neuromuscular antinicotinic and intestinal antimuscarinic effects of different nondepolarizing muscle relaxants

The postsynaptic antimuscarinic properties of different nondepolarizing muscle relaxants were compared with their postsynaptic antinicotinic effect. d-Tubocurarine, pipecuronium and vecuronium were the most selective antagonists on postsynaptic nicotinic receptors. Gallamine, diadonium and Duador (RGH-4201) had relatively greater effect on postsynaptic muscarinic receptors. Therefore, much less side effect is expected to occur when pipecuronium, d-tubocurarine or vecuronium are used.

Species variation in the site and mechanism of the neuromuscular effects of diadonium in rodents

The unusually wide, 80-fold species variation observed by others (1,2) in the neuromuscular (NM) potency of diadonium, a nondepolarizing muscle relaxant (MR), between cat and man suggested that the site and mechanism of its NM effect may vary in different species. To obtain information on this question, the NM potency of diadonium and the reversibility of its NM effect by neostigmine and/or 4-aminopyridine (4AP) was investigated on the in vitro phrenic nerve--hemidiaphragm preparations of rats, mice and guinea pigs. The concentration of diadonium that caused 90% NM block (IC90) was much greater in guinea pigs, 1.74 +/- 0.02 and 1.28 +/- 0.01 mu, when the preparations were stimulated with single stimuli at 0.1 Hz or with 0.1 s trains of 50 Hz tetani every 10 s, respectively, than in rats (IC90 = 62.4 +/- 0.89 and 52.1 +/- 1.00 microM) or mice (IC90 = 51.9 +/- 0.98 and 44.4 +/- 0.22 microM). In guinea pigs, the NM blocking effect of diadonium could be antagonized by neostigmine. This indicates that in this species the NM blocking effect of diadonium is primarily caused by inhibition of the interaction of acetylcholine (ACh), released by the nerve impulse, with the cholinergic receptors (cholinoceptors) of the postjunctional membrane (p.j.m.). By contrast, in rats and mice diadonium was not antagonized by neostigmine but was reversed by 4-aminopyridine. This suggests that in these species, in contrast to other nondepolarizing MR, diadonium does not inhibit NM transmission postsynaptically, but by inhibiting the positive nicotinic feedback mechanism of mobilization of ACh from reserve depots to release sites, causes a presynaptic NM block.(ABSTRACT TRUNCATED AT 250 WORDS)

Microsurgical bisection of porcine morulae and blastocysts to produce monozygotic twin pregnancy

Porcine morulae were bisected by a glass needle after softening of zonae pellucidae by pronase followed by a treatment with 0.05% trypsin/0.02% EDTA for decreasing intercellular junction of blastomeres. Transfer of 49 half-morulae to three recipients resulted in one pregnancy. The blastocysts were bisected symmetrically so as to leave a cellular bridge between the sister half-embryos after the softening of zonae followed by or without the trypsin/EDTA treatment. Transfer of 47 monozygotic (MZ) pairs of half-blastocysts to nine recipients resulted in four pregnancies. A litter of nine fetuses was obtained from seven MZ pairs of half-blastocysts, demonstrating that at least two pairs of MZ twin fetuses were produced. It is thought that the procedure for bisecting blastocysts developed in this study is one of the potential methods of producing porcine MZ twins.

[Effect of laudanosine on catecholamine release in dogs]

It is well established that a large dose of atracurium (more than twice ED95) produces significant release of histamine in the blood accompanying hypotension but recovery to control level within a few minutes after the administration of atracurium. We speculated that laudanosine, a metabolite of atracurium may play an important role in preventing this cardiovascular disaster due to histamine release. From this concept, we investigated the effect of laudanosine on the release of epinephrine and norepinephrine in dogs, anesthetized with halothane, nitrous oxide and oxygen. Two different doses of laudanosine (1 microgram.kg-1 and 10 micrograms.kg-1) were selected and serum catecholamine levels were measured with HPLC in six dogs. Intravenous injection of 1.0 microgram.kg-1 laudanosine increased NE level from 0.11 +/- 0.03ng.ml-1 to 0.13 +/- 0.04ng.ml-1 at 3 minutes after the injection. Blood pressure, heart rate, pulmonary arterial pressure, pulmonary wedge pressure and central venous pressure did not change significantly. The intravenous injection of 10 micrograms.kg-1 laudanosine increased NE level from 0.09 +/- 0.02ng.ml-1 to 0.14 +/- 0.02ng.ml-1 at 1 minutes after the injection, but there was no remarkable cardiovascular effect. From this study we conclude that the intravenous injection of laudanosine increased serum NE level, but there was no significant hemodynamic change in the dogs.

[Plasma histamine release following the intravenous administration of atracurium in man]

The purpose of this study was to measure plasma histamine concentration following the intravenous bolus injection of atracurium in surgical patients and to clarify any correlation of resultant cardiovascular change with plasma histamine release. Twelve elective surgical patients of ASA-I were studied after the approved informed consent. Twenty of blood samples were collected for the assay of plasma histamine at 1 minute before as the control and 1, 3, 5, and 10 minutes after the administration of atracurium 0.6mg.kg-1 or 1.2mg.kg-1 intravenously. Plasma histamine was measured by utilization of the modified single isotope radioenzymatic assay. Blood pressure, heart rate, EKG and cutaneous signs were observed continuously during the study. Intravenous bolus administration of 0.6mg.kg-1 and 1.2mg.kg-1 atracurium which is larger than 2 times of ED95 demonstrated significant changes in heart rate, blood pressure and histamine release. A significant increase in plasma histamine, a decrease in blood pressure and an increase in heart rate occurred at 1 to 3 minutes after the injection of atracurium. Plasma histamine release and cardiovascular changes had strong correlation with the intravenous dose of atracurium.

Rapid elevation of liver hydroxyproline content following a single administration of various chemical carcinogens to rats

The liver hydroxyproline content increased 14 days following a single administration of various chemical carcinogens, 2-N-fluorenylacetamide (FAA), 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB), diethylnitrosamine (DEN), dimethylnitrosamine (DMN), and thioacetamide, to rats. The rapid elevation of hydroxyproline following FAA administration, which did not induce liver cell necrosis, was accompanied by an increase in liver collagenase activity. These findings are of interest in relation to the regulatory mechanism of liver fibrogenesis.

Heterogeneity of presynaptic muscarinic receptors involved in modulation of transmitter release

In order to extend the characterization of muscarinic receptors at presynaptic sites their inhibitory effect on the stimulation-evoked release of [3H]noradrenaline and [3H]acetylcholine from different axon terminals was studied and the dissociation constants and potencies of different antagonists were estimated, in guinea-pig and rat. While oxotremorine reduced the release of [3H]acetylcholine and [3H]-noradrenaline in a concentration-dependent manner from different release sites (Auerbach plexus, noradrenergic neurons in the right atrium, cerebral cortex), McN-A 343, an M1 receptor agonist, enhanced their release evoked by field stimulation. When the inhibitory effect of oxotremorine on transmitter release was studied, pancuronium, pirenzepine and atropine were competitive antagonists of presynaptic muscarinic receptors located on the noradrenergic axon terminals of the atrium. While atropine and pirenzepine inhibited the muscarinic receptors of cholinergic axon terminals in the Auerbach plexus, pancuronium and gallamine had a very low affinity. Significant differences were found in the affinity constants of antagonists for muscarinic receptors located in the cholinergic axon terminals of Auerbach plexus and cerebral cortex, and noradrenergic axon terminals of the atrium. While atropine and pirenzepine exerted similar effects on these presynaptic sites, pancuronium, gallamine and (11-(2-[diethylamino)-methyl)-1-piperidinyl)acetyl)-5, 11-dihydro-6(1-pyrido(2,3-b)(1,4)-benzodiazepin-6-on) were much more effective on muscarinic receptors controlling acetylcholine release from the cerebral cortex and noradrenaline release from the heart. There was more than 100-fold (2.0 pA2 units) difference in affinities of these antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of presynaptic muscarinic receptors located on different tissue preparations

Three different tissue preparations were used to demonstrate the heterogeneity of presynaptic muscarinic receptors that modulate neurotransmitter release. The presynaptic antimuscarinic potency of several muscarinic antagonists was characterized with the enhancement of the neurotransmitter release evoked by electrical stimulation on the guinea-pig ileum Auerbach plexus, the guinea-pig atrium and the rat brain cortex. Presynaptic muscarinic receptors located on the Auerbach plexus proved to be different of those present on the cortical cholinergic interneurons and on the sympathetic plexus of the guinea-pig atrium.

The effect of digoxin on contractility and fatigue of isolated guinea pig and rat hemidiaphragms

Digoxin could improve diaphragm contractility and fatigability if inhibition of sodium-potassium adenosine triphosphatase enhances calcium influx from extracellular sources, or it could impair contractility and worsen fatigue if it impairs maintenance of the membrane potential. We studied the effects of digoxin on isometric force production, fatigue, and recovery in isolated, directly stimulated, guinea pig and rat diaphragms. Digoxin had no effect on maximal twitch or tetanic tensions compared with control diaphragms in either rat (2 ng/ml to 20 micrograms/ml) or guinea pig (2 ng/ml to 2 micrograms/ml) hemidiaphragms. Digoxin worsened high frequency fatigue and impaired recovery from fatigue in guinea pigs (200 ng/ml to 2 micrograms/ml) but not in rat (2 micrograms/ml) hemidiaphragms. We conclude that digoxin has no effect on diaphragm contractility. Hypopolarization of the membrane potential is the likely cause for the increased fatigability. The difference in responsiveness between species is likely due to insensitivity of rat sodium-potassium adenosine triphosphatase to digoxin.

Fluctuations in peripheral serum testosterone levels within a day, with age and by sexual stimulation in male beagle dogs bred indoors

Fluctuations in serum levels of testosterone (T) within a day, both with age and as a result of sexual stimulation, were examined in male beagle dogs. Eighty male dogs aged between 3 months and 16 years and bred in our laboratory were used under strictly controlled breeding conditions (temperature: 22 +/- 1 degree C, relative humidity: 55 +/- 5%, lighting time: 8:00 a.m.-8:00 p.m.). The level of T was measured by an RIA method. In order to examine the fluctuation in T level within a day, blood samples were obtained at 0:00, 6:00, 12:00 and 18:00 in each of five dogs aged 1.7 and 2.1 years. T levels fluctuated with a regular pattern that was lowest at 12:00, and increased to a peak at 18:00-6:00, thereafter decreasing until 12:00. In order to examine the change in T level with age, blood samples were obtained at 9:00, 12:00 and 16:00 from 70 dogs aged between 3 months and 16 years. The regular diurnal pattern of T level was usually seen, and the levels at 12:00 were always low and did not fluctuate at any age except for 6 months, and 13, 14 and 16 years. The T level at 9:00 increased to reach a peak at 4 years, whereas that at 16:00 did so at 2 years. T levels at 9:00 were significantly higher at 4-12 and 14 years than at 3 months, and were higher at 4 years than at 9 months.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of aminopyridines on Ca2+-dependent evoked release of acetylcholine from rat cortex slices

The release of acetylcholine (ACh) elicited by electrical stimulation was investigated in rat brain cortical slices preloaded with 3H-choline. Decreasing the [Ca2+]o from 2.5 to 0.3 mM caused a progressive reduction of the evoked release of ACh. 4-Aminopyridine (4AP) or LF14 [(1,1-dimethyl-3-(4-amino-3-pyridyl)], 4 x 10(-5) M doubled the evoked release of ACh when the [Ca2+]o was 2.5 mM and quadrupled it when it was 0.3 mM, to levels higher than those obtained with 2.5 mM [Ca2+]o alone. This indicates that both 4AP and LF14 decrease the Ca2+ requirements for the evoked release of ACh. The findings of this study indicate that LF14 may be suitable for the symptomatic treatment of senile dementia of Alzheimer's type, presumably caused by dysfunction of cholinergic transmission in the brain.

Interferon production under the control of heterologous inducible enhancers and promoters

In a search for a useful enhancer to control expression of interferon (IFN) gene in mammalian cells, mouse IFN-beta cDNA ligated 3' downstream to the enhancer-promoter of either mouse metallothionein-I (MT-I) or Drosophila heat shock protein (HSP) was introduced into various cultured cells by calcium-phosphate precipitation method, and the level of IFN transiently produced was compared. In the case of the MT-I enhancer-promoter, low levels of IFN were produced without induction (0-21 IU/ml) and the level increased 5-50 times by heavy metals. In contrast, the basal level of expression of the HSP enhancer-promoter was very low and its expression was increased several hundred to thousand times by heat shock or arsenite. Thus the HSP enhancer-promoter appears to be a potent inducible element with very low basal level and high inducibility.

Sexing of half-embryos produced by microsurgical bisection of mouse morulae and production of chimeric mouse of defined sex composition by aggregating two sexed half-embryos

Using the halved morulae of mice obtained with microsurgical technique, the following two experiments were performed. 1) Sexing of half-embryos by chromosomal analysis and transfer of the half-embryos after determining the sex of the other monozygotic half. One half of the bisected embryo was cultured in Colcemid solution (0.04 micrograms/ml) to be ensured for chromosomal preparation. More than 50% (152/270) of the blastulated embryos from the halves could be sexed by direct sex chromosome analysis. Thirty-nine of the half-embryos of which the co-twin halves were sexed, were transplanted in to the uterine horns of 18 pseudopregnant mice, and twelve became pregnant. The autopsies of them on Day 18 to 20 of pregnancy, revealed the presence of 16 fetuses. The morphological sex of these fetuses thus obtained coincided completely with the previous judgement based on the chromosomal sexing. 2) Production of chimeras of defined sex composition by aggregating two half-morulae of defined sex. Out of 147 pairs of half-morulae of two different strains (ICR and C3H/He), which were replaced in pairs into empty zona pellucidae, 107 (72.8%) were aggregated successfully and developed in vitro into full expanding blastocysts of typical form. Among the 107 aggregate blastocysts, 31 were sexed for both component embryos by chromosomal analysis on the co-twin half-embryos. When these 31 blastocysts were transferred, 11 living offspring including 4 chimeras were obtained. Transfer of 12 male-male and 5 female-female aggregate blastocysts resulted in 8 males and 1 female, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple method for monitoring muscular relaxation during continuous infusion of vecuronium

There is considerable individual variation in the dose of vecuronium required for the maintenance of surgical relaxation. Therefore to provide uninterrupted relaxation without overdosage it is advisable to regulate the IV infusion of vecuronium on the basis of appropriate monitoring. Monitoring with mechanomyography (MMG) or electromyography requires costly equipment and is too complex for routine clinical use. Visual observation of the adductor pollicis muscle contracting against zero resistance is not suitable for the reliable assessment of the degree of neuromuscular (NM) block. For clinical purposes satisfactory monitoring can be achieved with the simple device (Myoscan) described. The reliability of the Myoscan was tested in 30 patients by simultaneous monitoring of the force of contraction of the adductor pollicis on one side with the Myoscan and on the contralateral side with the MMG. Retrospective analysis of the MMG indicated that the conduct of anaesthesia would have been virtually the same if it would have been based on MMG monitoring.

Production of normal piglets from microsurgically split morulae and blastocysts

The embryo splitting technique was applied to pig embryos, and the developmental ability of the split embryos was examined by means of in vitro culture and transfer. Morulae, early blastocysts and blastocysts were collected from Landrace x Large White F(1) gilts which had been mated to Duroc boars. The embryos were bisected with a fine glass or alloy (PtIr) needle after the softening of zonae pellucidae. The halved-embryos, which had either been placed in zonae pellucidae or not, were transferred to recipient gilts immediately after the micromanipulation (Experiment 1) or after cultivation for 15 to 20 h (Experiment 2). In Experiment 1, two fetuses were obtained from one of three recipients which had received 12 half-embryos. In Experiment 2, three of five recipients became pregnant, and in one recipient, seven piglets of a litter were obtained from 12 zona-free half-embryos produced from the original seven blastocysts. The results obtained indicate that a simple method not requiring the encasing of split embryos into zonae pellucidae is satisfactory to produce viable half-embryos.

Are fluorescent bodies of Y-spermatozoa detectable in common with mammalan species?

An attempt was made to detect the fluorescent bodies (F-body), using Quinacrine mustard (Q-M) staining in the spermatozoa from eight mammalian species (human, bull, boar, dog, rabbit, rat, mouse, and mastomys) as well as in the cock (used as negative control). Sperm suspension, prepared after rinsing by repeated centrifugation with phosphate buffered saline (PBS), was either stained with Q-M for 24 h or treated with protease and then stained with Q-M for 60 min. The final concentration of Q-M in the mixed staining sperm suspension was 0.025 mg/ml. The examination using a reflecting fluorescent microscope revealed that the F-body found in human sperm was also present in the sperm of all the mammals but not in the cock after 24 h of staining. The enzyme-treated specimens showed higher incidences of F-bodies than specimens stained for 24 h without enzymatic digestion. These findings strongly suggest that the F-body is commonly present in the spermatozoa of many mammalian species.

Follow-up study of 582 liver cirrhosis patients for 26 years in Japan

A long-term follow-up study of liver cirrhosis (LC) was performed in 582 patients diagnosed by peritoneoscopy and liver biopsy in the 26 years from 1958 to 1984. The etiology of LC consisted of hepatitis B virus (HBV) in 21%, alcoholic in 39% and cryptogenic in 39%. Fifty-nine percent of patients had died. Causes of death were hepatocellular carcinoma (HCC 44%), liver failure (30%), rupture of esophageal varices (14%), gastrointestinal bleeding (4%) and non-liver-related causes (8%). HCC accounted for increasing percentages (68%) since 1980. In all groups classified by the etiology, the causes of death had the same order in incidence. The age of onset of LC increased by 10 years from 42 to 52 years old and the age of death by 15 years from 43 to 58 in the 26-year period. The cumulative survival rate improved over the period. The 50% survival year was 7.9 in total patients, and 7.0, 8.5 and 10.0 in the three periods 1958-64, 1965-74 and 1975-84, respectively. It was 9.5, 6.3 and 9.8 in HBV, alcoholic and cryptogenic, respectively. LC patients survived 40-44% of the life expectancy of the general population in Japan in all age groups. Cox's multiregression life-table method selected three important prognostic factors from 7 parameters: a poor prognosis with a history of heavy alcohol consumption and old age at onset, and a better prognosis with recent onset.