Cumulation of neomycin and its residual potentiation of tubocurarine in the cat

Cumulation and interaction of neuromuscular blocking effects of neomycin and tubocurarine were determined on responses of the tibialis anterior muscle of the anaesthetized cat to indirect stimulation. Neuromuscular block produced by neomycin was cumulative despite rapid and apparent full recovery of twitch tension and an interval of 3 h between dose-response studies. Ed50 of neomycin on twitch tension decreased (P less than 0.05) from 22 +/- 4 mg kg-1 to 12 +/- 3 mg kg-1 after 3 h; marked post-tetanic exhaustion was observed after the antibiotic. Neuromuscular block (80-90%) with neomycin 25-30 mg kg-1 followed by full recovery and 3-h interval decreased (P less than 0.05) the ED50 of tubocurarine on twitch tension from 0.2 +/- 0.02 mg kg-1 to 0.13 +/- 0.03 mg kg-1. Tubocurarine exhibited no cumulative effects at intervals of 2 h and did not significantly affect the response of twitch and tetanic tension to neomycin after an interval of 2 h. It is concluded that neomycin increases the sensitivity of neuromuscular transmission to tubocurarine despite apparently normal responses to indirect stimulation and that the post-tetanic exhaustion observed with neomycin alone may explain apnoea reported in patients with the antibiotic.

High-performance liquid chromatographic measurement of cloprednol in human plasma

A rapid and specific high-performance liquid chromatographic method for the quantitative determination of cloprednol in human plasma is described. Samples were extracted using methylene chloride-ether (40:60) and then purified further by solvent and pH partitioning techniques. Cloprednol was analyzed using normal-phase chromatography and UV detection at 254 nm. The final recovery after losses during the cleanup procedure for cloprednol from human plasma was 80.8%. The lowest concentration that could be measured with confidence was 8 ng/ml.

Heterogeneity of human thymocytes and a malignant T-lymphoblast cell line, MOLT-3

The purpose of this paper was to study the heterogeneity of human thymocytes and leukemic cells of the T-cell line MOLT-3 by velocity sedimentation. Analysis of the subpopulations of thymocytes demonstrated that they represent a heterogeneous population of cells with respect to their size, proliferative activity, and presence and quantities of terminal deoxynucleotidyl transferase and human thymus leukemia-associated antigen, a thymic isozyme of adenosine deaminase (HThy-L/ADA). Only a minor subpopulation of thymocytes (large cells) was in active cycle. The highest level of HThy-L/ADA was associated with the main subpopulation of thymocytes sedimenting at 3 to 4 mm/hr while low amounts of the HThy-L/ADA antigen (enzyme) were found in the minor fractions of the small and large cells. The distribution of terminal deoxynucleotidyl transferase-positive cells indicated that most, but not all, thymocytes contain the enzyme. Analysis of the T-cell line MOLT-3 showed that these cells could be separated into subpopulations with different biochemical and biological properties. More than one subpopulation of cells was capable of DNA synthesis. In contrast to the thymocytes, all fractions of MOLT-3 cells contained high amounts of HThy-L/ADA. The proportion of terminal deoxynucleotidyl transferase-positive cells as a function of sedimentation velocity was also quite constant although there was a slight but reproducible drop in the percentage of these cells in the slowly sedimenting fractions. The percentage of cells with receptors for sheep erythrocytes also remained high in fractions separated on the basis of size, although a consistently higher percentage was found in smaller cells. These studies indicated that thymus cells as well as the malignant T-cell line MOLT-3 can be separated on the basis of sedimentation velocity into subpopulations with different biological and biochemical properties. The data also indicated that the heterogeneity of MOLT-3 line cannot be explained solely on the basis of volume changes due to cell cycle, suggesting that they may represent heterogeneous populations of cells.

Rapid infusion of phenytoin sodium loading doses

The use of rapid intravenous infusions of phenytoin sodium to achieve prompt plasma therapeutic concentrations of phenytoin was studied in adult epileptic patients. Six adult patients who experienced recent tonic-clonic seizures were selected for study. Four of them had not been treated with phenytoin before the study; two were on chronic phenytoin therapy but had subtherapeutic serum levels. A leading dose of phenytoin sodium (15 mg/kg in 100 ml of 0.9% sodium chloride injection) was infused at 30-50 mg/min. Blood samples were drawn before phenytoin administration, every five minutes during the infusion, and at 1, 2, 4, 8, 12, 18, and 24 hours after completion of the infusion. Adverse effects were monitored during the infusion. Pharmacokinetic variables were calculated. Patients received from 750 to 1500 mg phenytoin sodium (mean +/- S.D. = 1040.8 +/- 297.3 mg). From 5 to 30 minutes were required to reach therapeutic (10-20 micrograms/ml) serum phenytoin concentrations; concentrations peaked at 31.1 +/- 10.0 micrograms/ml. Four of the six patients had therapeutic serum concentrations at 18 hours after completion of the infusion. Adverse effects were minimal and not severe; no cardiotoxicities were noted. Phenytoin half-life was 31.2 +/- 8.4 hours, total plasma clearance was 47.2 +/- 10.7 ml/kg/hr, and volume of distribution was 1.96 +/- 0.46 liters/kg. It is concluded that rapid intravenous infusion of phenytoin appears to be a reasonably safe and effective method of rapidly reaching therapeutic phenytoin concentrations.

Reversal of dantrolene sodium-induced depression of skeletal muscle in the cat

Dantrolene sodium, a muscle relaxant, does not have a clinically useful antagonist. The present study was undertaken to test the efficacies of germine monoacetate, 4-aminopyridine, neostigmine, and calcium chloride as possible agents for the reversal of the direct skeletal muscle depression produced by dantrolene sodium in the cat anesthetized with alpha-chloralose. Depression of the indirectly elicited twitch responses (0.1 Hz) of the tibialis anterior muscle by 25, 50, 75 and 84 per cent was produced by dantrolene, 0.16, 0.36, 0.88 and 1.13 mg/kg respectively; spontaneous recovery of twitch tension during the subsequent 30 min was negligible. After the 30-min observation period had elapsed, one of the reversal agents under study was given (iv) in divided doses at intervals of 10 min (five cats for each agent). Germine monoacetate (2 X 0.5 mg/kg) immediately reversed the dantrolene-induced twitch depression, with an over-shoot that persisted for an hour. 4-Aminopyridine (4 X 0.5 mg/kg) caused a steady but incomplete reversal to 17 per cent depression, 30 min after the last dose. Neostigmine (4 X 0.04 mg/kg) caused an immediate, but transient, reversal of the twitch depression, with overshoot. Calcium chloride (4 X 10 mg/kg) was without effect. It is concluded that germine monoacetate is the drug of choice for reversal of the muscle depression produced by dantrolene sodium in the cat.

Anesthetic management of the pediatric patient with multiple congenital anomalies including severe hemifacial hypertrophy

An anesthesia induction technique not widely utilized is described for a pediatric patient presenting with severe hemifacial hypertrophy, severe mental retardation, as well as a seizure disorder and other congenital anomalies. The anatomically and/or pathologically altered airway as well as other anomalies increase the risks of anesthesia.

The action of dantrolene on transmitter mobilization at the rat neuromuscular junction

Dantrolene sodium (20 microM) was found to decrease transmitter mobilization and the apparent available store of acetylcholine at frequencies of nerve stimulation of 50 and 100 Hz at the neuromuscular junction of the rat hemidiaphragm preparation treated with 2 microM (+)-tubocurarine. This effect of dantrolene sodium was not as marked at frequencies of nerve stimulation of 25 Hz or less, also no significant effect of the drug was observed on the amplitude of endplate potentials (EPPS) at any frequency of nerve stimulation. No effect of dantrolene sodium (20 microM) on mean miniature EPP amplitude or frequency was observed. It is suggested that the action of dantrolene sodium on mean EPP quantal content may be due to an action on stores of bound calcium within the motor nerve terminal. This effect of the drug is unlikely to be of physiological consequence in vivo, since it was only observed at high frequencies of nerve stimulation and did not cause a significant reduction of EPP amplitude during trains of stimuli.

Levels of cyclic nucleotides in autotransplanted 7, 12-dimethylbenz[a]anthracene-induced rat mammary tumors during their growth and regression

Previous studies indicated that autotransplanted 7, 12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumors were hormone-dependent and, if derived from a single primary tumor, many of their metabolic parameters varied little. Therefore, these tumors transplanted in multiple sites provided an opportunity for serial sampling of individual tumors for repeated biochemical evaluations. In the present study, primary mammary tumors induced by DMBA in female noninbred Sprague-Dawley rats were autotransplanted at six sites. When these grafts grew to an average size of 6 cm, the hosts were ovariectomized. Eighteen days later when all tumors were apparently regressing, a silastic tubing 2 cm long containing crystalline estradiol was implanted sc into each host for 14 days. Individual tumors were serially removed from each host before ovariectomy, after ovariectomy, and after estrogen replacement. Levels of cyclic AMP (cAMP) and cyclic GMP (cGMP) in these tumors were measured by radioimmunoassay. Results indicated that tumor regression was associated with an elevation of cAMP levels and that tumor growth was accompanied by a decline in cAMP. The level of cGMP did not correlate with either tumor growth or regression. Therefore, the concept that cAMP is a biologic regulator for tissue proliferation and regression may be applied to the present model of autotransplanted, DMBA-induced rat mammary tumors.

Predetermination of dose requirement of pancuronium

The neuromuscular sensitivity of 71 patients (A.S.A. class I or II) was tested by scoring on a scale from 1 to 6 the ability to lift the upper eyelid 2 minutes after pretreatment with 1 mg of pancuronium. Subsequently, each patient also received an additional "intubation dose" pancuronium (in milligrams) equal to the eye-opening test score (group I), or either 1 mg (group II) or 2 mg (group III) in excess. The resultant depression of the neurally evoked muscle response of the little finger was quantified by another score (the response score) which allowed for assessment of neuromuscular block beyond the limit of 100% depression of the twitch. The criteria for the response score, in the response score, in the order of increasing magnitude of block, were: (1) visible twitch responses to all 4 of the train-of-four stimulation remained; (2) part of the train-of-four twitches was eliminated; (3) all twitches were eliminated; (4) tetanus was eliminated; (5) post-tetanic twitch following a 5-second 50 Hz tetanus was also eliminated; and (6) not even the post-tetanic twitch became elicitable again in 30 minutes. It was found that 1 mg of pancuronium depressed the eye-opening score to 4.0 +/- 0.2, from 5.1 +/- 0.1 (mean +/- SEM, p < 0.01). Following the additional "intubation dose" of pancuronium, patients in group I had an average response score of 2.2 +/- 0.3, those in group II a score of 3.4 +/- 0.2, and those in group III, a score of 4.8 +/- 0.6. Each additional 1 mg of pancuronium (increasing from group I to III) linearly increased the average response score. In terms of frequency response, patients in group I had more than a 50% change of being scored 1, while those in group II had a greater than 50% chance of being scored 3, 4, or 5, and those in group III had more than a 50% chance of being scored 6. It is concluded that sensitivity to pancuronium can be quantified by the ptotic response to a 1-mg test dose of pancuronium, and that a sensitivity-adjusted additional "intubation dose" of pancuronium can be predetermined in individual patients.

The association of diabetes insipidus with hypoparathyroidism. Addison's disease and mucocutaneous candidiasis

A case of central diabetes insipidus is reported in association with idiopathic hypoparathyroidism, adrenal failure and mucocutaneous candidiasis. The diabetes insipidus was recognised at the same time as the discovery of aldosterone and cortisol deficiency, and occurred several years after the initial onset of mucocutaneous candidiasis and hypocalcaemia. Control of the diabetes insipidus was achieved initially with nasal aqueous lysine vasopressin and later with desmopressin. The development of diabetes insipidus may be a further aspect of endocrine secretory failure associated with idiopathic hypoparathyroidism.

Thalifaurine and dehydrodiscretine, new quaternary protoberberines from Thalictrum fauriei

Two new quaternary protoberberines, thalifaurine and dehydrodiscretine, were isolated from the ethanolic extract of Thalictrum fauriei Hayata. Based on spectral analysis and correlation with compounds of known structure, thalifaurine was shown to be 3-hydroxy-2-methoxy-10,11-methylenedioxyberbinium chloride and dehydrodiscretine was established as 3-hydroxy-2,20,11-trimethoxyberbinium chloride. The structural assignment was confirmed by synthesis of both compounds. Magnoflorine also was isolated and identified.

Energy-linked quinacrine fluorescence changes in submitochondrial particles from skeletal muscle mitochondria. Evidence for intramembrane H+ transfer as a primary reaction of energy coupling

Submitochondrial particles obtained from skeletal muscle are open membrane fragments which show energy coupling yet cannot sustain transmembrane ion gradients. An energy-linked decrease in fluorescence emission of the fluorescent probe quinacrine is observed with skeletal muscle particles which is enhanced by the anion SCN-. This is essentially the same reaction observed with beef heart submitochondrial particles, in which the reaction is known to be a monitor of intramembrane H+ transfer. The results with skeletal muscle particles show that this intramembrane H+ transfer occurs in the absence of any electrochemical potential across the membrane. Further, it occurs independently of the direction of H+ exchange with the suspendingly medium, since energization of skeletal muscle submitochondrial particles is known to give H+ efflux into the medium, while energization of beef heart particles gives H+ uptake from the medium. We conclude that a primary reaction of energy coupling is intramembrane H+ transfer linked to electron transport but shielded from the suspending medium. Movements of H+ between membrane and medium are secondary reactions derived from the primary one, possibly linked by a series of intramembrane conformational changes comprising a sequential membrane Bohr effect.

Fish poisoning with particular reference to ciguatera

An historical review of the literature concerning a type of fish poisoning found in the tropics, characteristic of perfectly fresh fish. The clinical features are briefly mentioned, and the aetiology discussed. A new epidemiological model is reported and appropriate preventative health-care measures are suggested.