Effect of pyridoxal 5-phosphate on the activity of GOT isozyme in plasma from patients with Duchenne muscular dystrophy

GOT isozyme (soluble GOT, s-GOT and mitochondrial GOT, m-GOT) activities with and without reactivation by the co-enzyme pyridoxal 5-phosphate (PALP) in plasma from 42 patients with Duchenne muscular dystrophy (DMD), and 11 normal controls were investigated. The magnitude of the enzyme activities in patients at the early stage of DMD greatly exceeded those of controls. As the disease progressed, the levels gradually declined, but late stage values were still higher than the control values except s-GOT with PALP. At the mid stage as well as the late stage, the increase in m-GOT activity was approximately to double the unstimulated activity, indicating that, in these patients, as much as half the m-GOT in the circulation was in the inactive apoenzyme form, whereas s-GOT showed negligible increase following PALP addition at any stage.

Toxicity of heavy metals and insecticides on slime mold Physarum polycephalum

Toxicity of heavy metals and insecticides on the slime mold Physarum polycephalum was investigated in order to examine and estimate with ease the toxicity of environmental and occupational contaminants and also to study the effects of various agents on the cell membrane. Changes in survival time and in membrane potential of the slime mold were measured using a double chamber method. The results obtained suggest that their toxicity for the slime mold is accompanied by some change in the cell membrane, and that studies on toxicity for various chemical substances in the slime mold can be used as a screening method.

The effects of phenylephrine in various ionic environments on the circular muscle of mid-pregnant rat myometrium

In 12-15-day pregnant rat myometrium, spikes of the longitudinal muscle were discharged spontaneously in burst, while the circular muscle had predominantly a plateau potential. In the longitudinal muscle, phenylephrine (10(-7) g/ml) slightly decreased the duration of the burst discharge and suppressed the contraction by beta-adrenoreceptor stimulation. In the circular muscle, phenylephrine (10(-7) g/ml) prolonged the duration of the plateau potential leading to an increase in tension without changing the amplitude of plateau, membrane potential and membrane conductance by alpha-adrenoreceptor stimulation. The effects of phenylephrine on the circular muscle in various ionic environments were observed. In K-free solution, spike generation ceased but phenylephrine depolarized the membrane, generated the prepotential with spikes and prolonged plateau duration. In low-Ca solution, spontaneous spike generation ceased and electrically evoked spikes showed short plateau duration. Phenylephrine restored the membrane activity and prolonged the plateau duration. Excess Ca showed either prolonged (less than 5mM) or reduced (greater than 8mM) the plateau duration, but phenylephrine consistently prolonged plateau duration. When Cl was replaced with either Br or benzene sulphonate, the former prolonged plateau duration and increased the excitability, whereas the latter reduced plateau duration and suppressed the spontaneous activity. Phenylephrine prolonged plateau duration in both Cl-deficient solutions. When NaCl was replaced by choline-Cl, leaving 15.7 mM Na remaining in NaHCO3 buffer, phenylephrine action completely ceased. The ionic mechanism involved in phenylephrine action is discussed.

Effect of ions and drugs on the plateau potential in the circular muscle of pregnant rat myometrium

Effect of Na, Ca, anions and isoprenaline on the plateau potential in circular muscle of 11- to 13-day pregnant rat myometrium were investigated using the double sucrose gap method. During the plateau potential, which amounted about 15-20 mV and lasted for 10-20 sec, the membrane conductance increased initially, then decreased. The amplitude and duration of the plateau potential increased by raising the external Ca concentration to between 0.3 and 3 mM, and decreased when the concentration was increased more. The plateau was prolonged in low Na solutin (54 mM). When 154 mM Cl was replaced with Br the plateau was prolonged, however, the plateau was nearly suppressed when Cl was replaced with benzene sulphonate or isethionate. Isoprenaline increased membrane conductance and depressed the plateau. It was concluded that a decrease in K conductance was largely responsible for the plateau potential, and an inward Ca current may have contributed to its formation.

Comparative investigations of alpha- and beta-effects on the longitudinal and circular muscles of the pregnant rat myometrium

Comparative effects of noradrenaline (10(-8)-10(-6) g/ml) and isoprenaline (10(-10)-10(-6) g/ml) on electrical and contractile activity were investigated in longitudinal and circular muscle strips of rat myometrium (13-19 days pregnant). When recorded with an intracellular microelectrode, spike potentials of longitudinal muscle discharged spontaneously in bursts. Treatment with either noradrenaline or isoprenaline hyperpolarized the membrane and increased membrane conductance, causing the cessation of spontaneous activity. Slow potential was dominant in the circular muscle, and it became prolonged after treatment with noradrenaline, leading to an increase in tension. Isoprenaline reduced the duration of the slow potential and depressed the contraction. The minimal concentration of isoprenaline needed to suppress the spontaneous activity in circular muscle was much higher than in longitudinal muscle. The excitatory effect of noradrenaline on circular muscle was antagonized by treatment with phentolamine, and the inhibitory effect of catecholamines on both longitudinal and circular muscles by propranolol. alpha-Adrenoceptor appears predominant in circular muscle, while beta-adrenoceptor in longitudinal muscle in rat myometrium during late-pregnancy.