Genetic markers in Welsh gypsies

Data are presented on polymorphic genetic markers of 84 Welsh gypsies, members of an inbred population characterised by a high incidence of phenylketonuria and other recessively inherited diseases. Sixteen polymorphic loci were studied: the ABO blood group distribution was comparable to that of the surrounding population, the B gene frequency being 7-5%, a lower frequency than most earlier studies in gypsies. The haptoglobin 1 gene frequency (23-7%) was very different from that of the British population, resembling the frequency found in India and some previously reported gypsy groups. The data on Welsh gypsies for the various loci are discussed in relation to the known evidence for a number of European gypsy populations, and in relation to the genetic structure of these populations. It is concluded that genetic divergence has occurred in the European gypsies, and that this may have been accentuated by the dispersal, isolation, and inbreeding which have occurred during the present century.

The effect on atrial and ventricular intracellular potentials, and other pharmacological actions of L9146, a non-halogenated benzo(b)thiophene related to amiodarone

L9146 was synthesised in the hope of eliminating the unwanted side-effects of amiodarone which has been shown to be effective in the control of atrial fibrillation, flutter, and in pre-excitation syndromes such as Wolff-Parkinson-White syndrome. L9146 has pharmacological and electrophysiological effects similar to those of amiodarone. It is an antagonist of both alpha and beta adrenoceptor-mediated cardiovascular effects of a noncompetitive type. It lowers vascular resistance briefly, and causes a longer lasting bradycardia. It moderately reduces the maximum rate of depolarisation (MRD), conduction velocity, and totally suppresses ventricular pacemakers activated by high doses of isoprenaline. In addition, L9146 greatly prolongs action potential duration (APD) in atrial and ventricular muscle. In normal ventricular conducting tissue the action potential duration (APD) is shorter in the bundle of His than in the false tendons, and shorter still in the ventricular muscle. L9146 lengthened APD throughout, but particularly in the proximal portion, and even more in the muscle, so that APD became uniform. The decrement of conduction of premature action potentials was increased to the point at which slowly conducting premature AP's were eliminated altogether.

Proceedings of the physiological society [proceedings]

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Climate and painful crisis of sickle-cell disease in Jamaica

In a 10-year retrospective study a close correlation was found between low temperatures and hospital admissions for severe painful crises of sickle-cell disease.

The effects of prolonged beta-adrenoceptor blockade on heart weight and cardiac intracellular potentials in rabbits

Estimates were made in vivo in rabbits of the relative beta-receptor blocking potency and duration of action of propranolol and practolol. In further experiments groups of litter mates were injected twice daily with approximately equi-active amounts of propranolol or practolol, or with saline, for several weeks. The heart weights of the treated animals were significantly lower than those of the controls, the water contents were higher, and the dry weight differences were highly significant; -16.8% after 2 mg/kg bd propranolol for six weeks and -33.8% after 10 mg/kg practolol. (The treated animals grew less rapidly than the controls; when corrected for body weight these figures were -11.9% and -20.4%, respectively.) In the practolol group, but not the propranolol group, the duration of the atrial intracellular potentials was prolonged. There was no evidence that the prolonged treatment with either drug had a negative inotropic effect, or reduced positive inotropic responses to isoprenaline.

Further studies regarding the structure activity relationships of beta-adrenoceptor antagonists

1. The ortho (M66,527) and para (M66,368) analogues of 1-t-butylamino-3-(methoxyphenoxy)-2-propanol and para substituted tertiary butylphenoxy-1-N-isopropylamine-3 propanol-2 oxalate acid (L8429) were tested in dogs for their beta-adrenoceptor blocking activity.2. M66,527, which contains a methoxy group in the ortho position of the benzene ring, was found to be comparable to propranolol in blocking cardiac and peripheral vascular responses to isoprenaline. Like propranolol, M66,527 was more potent on peripheral receptors.3. Transference of the methoxy group to the para position (M66,368) reduced the overall potency; however, this compound was found to be relatively cardioselective in that it was 2 to 3.6 times more active in blocking cardiac responses to isoprenaline.4. The cardioselective properties of the short chain para methoxy substituent were less than those reported for compounds with longer para substitutions (i.e. practolol, para oxprenolol and para alprenolol).5. L8429, with a tertiary butyl group in the para position, was a weak beta-adrenoceptor antagonist without cardioselective properties. A longer, less bulky n-butyl group may provide for a more potent and selective antagonist.6. The results support the view that the size and site of the substituent on the benzene ring may be of importance in determining the cardioselective potency of beta-adrenoceptor antagonists.

The effects on cardiac muscle and nerve of a fluorinated decahydroquinoline derivative, L7810, rapidly absorbed after oral administration

1. L7810 (4-carbamoyloxy-1-(4-(4-fluorophenyl)-4-oxobutyl) decahydroquinoline, has a local anaesthetic action on frog nerve 1.75 times that of procaine.2. L7810 protected anaesthetized guinea-pigs against ouabain-induced ventricular fibrillation and increased the lethal dose of ouabain.3. L7810 reduced the rate of rise of intracellularly recorded action potentials in rabbit isolated atria; the resting potential was not affected, but the duration of the action potential was prolonged.4. Unlike most drugs with local anaesthetic properties L7810 did not depress contractions in isolated atria but increased them.5. L7810 reduced the spontaneous frequency, maximum follow frequency and conduction velocity of rabbit isolated atria.6. L7810 had no blocking action on the chronotropic or positive inotropic actions of isoprenaline on isolated atrial muscle.7. In anaesthetized dogs L7810 caused a small dose-related bradycardia, and a large dose-related decrease in peripheral vascular resistance. There was no blockade of the effects of isoprenaline on heart rate or peripheral blood flow.

Effects on cardiac muscle of the -adrenoceptor blocking drugs INPEA and LB46 in relation to their local anaesthetic action on nerve

1. As a local anaesthetic on frog nerve, LB46 had 0.4 times the activity of procaine and 2 times that of INPEA.2. In reducing the maximum rate of depolarization (MRD) of intracellularly recorded cardiac action potentials, LB46 was 20 times more potent than INPEA.3. As an antagonist of the chronotropic effect on atrial muscle and of the inotropic effects on ventricular muscle of isoprenaline the pA(2) values for LB46 were 9.05+/-0.15 and 9.30+/-0.06 respectively, and for INPEA 6.00+/-0.16 and 6.10+/-0.12.4. LB46 was 8 times more active than racemic propranolol in blocking the effects of isoprenaline on isolated cardiac muscle, and since its direct action on the cardiac membrane was only 0.1 times that of propranolol, there was a net gain of 80 times in the specificity of LB46 for class 2 (antisympathetic) over class 1 (depression of MRD) antidysrhythmic actions.5. INPEA was 2.5 times less active as a beta-adrenoceptor blocking drug on cardiac muscle than (+)-propranolol, and 1,300 times less active than LB46.6. INPEA, but not LB46, prolonged the duration of both atrial and ventricular intracellular action potentials.

Effect of altering potassium concentration on the action of lidocaine and diphenylhydantoin on rabbit atrial and ventricular muscle

All previously studied antiarrhythmic drugs which also have local anaesthetic properties reduce the maximum rate of depolarization (MRD) of cardiac muscle. Recent evidence suggested that lidocaine and diphenylhydantoin (DPH) might have a different mode of action, because they did not reduce MRD except at high concentration. The latter evidence, however, was obtained from tissues nourished by solutions containing 2.7-3 m M potassium. In the present experiments, the effects of lidocaine and DPH were studied in solutions with 5.6 and 3 mM KCl. In the former, both drugs reduced MRD at concentrations similar to those found in the blood of treated patients, but in low [KCl] higher concentrations were necessary. It was concluded that there was no reason to suppose that the mode of action of lidocaine and DPH on the cardiac membrane is fundamentally different from that of quinidine, procaine, procainamide and other compounds which interfere directly with depolarization.

Local anaesthetic and anti-arrhythmic actions of alprenolol relative to its effect on intracellular potentials and other properties of isolated cardiac muscle

1. Alprenolol, a beta-adrenoceptor blocking drug reported to have the same potency as propranolol in vitro and in vivo, was found to be four times more active than procaine as a local anaesthetic on frog sciatic nerve.2. At doses of 0.125 mg/kg and above alprenolol protected anaesthetized guinea-pigs against ouabain-induced ventricular fibrillation.3. In isolated rabbit atria, resting potentials were unchanged, and the duration of the action potential was not prolonged, by concentrations of alprenolol up to 10.5 x 10(-6)M. The maximum rate of depolarization (MRD), however, was reduced by 30% at a concentration of 0.525 x 10(-6)M. This was 214 times less than the concentration which reduced the frog action potential height by 25%.4. The concentration of alprenolol required to produce more than 15% decrease in contraction or maximum driven frequency was 3.5 x 10(-6)M.5. As a test of the direct action of alprenolol on isolated cardiac muscle, MRD was also a more sensitive test than the measurement of electrical threshold or conduction velocity.

The effect of altered thyroid state on atrial intracellular potentials

1. A group of rabbits was made hypothyroid by thyroidectomy, and another group was injected daily with L-thyroxine. After an appropriate interval respective alterations in thyroid state were confirmed by measurement of heart weight and of plasma iodine, and the animals' atria were isolated for recording.2. Measurements were made of atrial contractions, conduction velocity, spontaneous heart rate and maximum driven frequency, and action potentials were recorded with intracellular micro-electrodes.3. The resting potential and action potential heights were not affected by differences of thyroid state.4. Atrial arrhythmias are common in hyperthyroidism, rare in myxoedema. The possibility that hypothyroidism might reduce the rate of rise of the action potential, as do anti-arrhythmic drugs, and hyperthyroidism increase it, was investigated. Although the rate of rise was slower in hypothyroid atria at some driving frequencies, this could not alone account for an anti-arrhythmic effect, because at frequencies near the spontaneous heart rate the rate of rise of the action potential was not reduced.5. The duration of the repolarization phase of the action potential was greatly prolonged in atria from thyroidectomized rabbits, and was shortened in hyperthyroid atria. These changes could account for a reduced probability of arrhythmias in hypothyroidism, and the converse in hyperthyroidism.