Mechanism of anticholinesterase activities of cardiotoxin, protamine and polylysine

Cardiotoxin, protamine and polylysine are potent inhibitors of various cholinesterases. CaCl2 and MgCl2 overcome the inhibition. The order of addition of the inhibitor and the protecting agent (MgCl2) influences the final degree of the inhibition observed. These findings suggest that cardiotoxin, protamine and polylysine inhibit cholinesterases by the ionic binding of their basic groups with the anionic sites of cholinesterase molecules.

N-Acetyl-beta-glucosaminidase activity in hydatidiform mole

The N-acetyl-beta-glucosaminidase activity in hydatidiform mole is two-fold higher than that in full-term placenta. Qualitatively, the enzymes from the two tissues are similar with respect to KM values and pH optima. Both enzymes also contain a new isoenzyme form detectable by polyacrylamide gel electrophoresis. However, the molar enzyme is more susceptible to heat denaturation, presumably due to the presence of a higher level of the heat-labile isoenzyme form A in this tissue. Data are also presented incicating that the placenta is not the source of the N-acetyl-beta-glucosaminidase activity in maternal serum.

Sacral chordoma. A rare cause of chronic pelvic and low-back pain

A case of sacral chordoma causing chronic, persistant low-back pain for 5 years is reported. This tumor was palpable on pelvic and rectal examination in the presacral area. Early excision is the treatment of choice for this slow growing tumor of primitive notochordal origin. Diagnosis is often late and incomplete surgical excision leads to local recurrence and eventual death. Knowledge of the existence of this rare condition, together with careful pelvic and rectal examination, are the importnat keys to diagnosis and possible curative treatment.

Is the contractile response to exogenous acetylcholine due to a presynaptic effect?

Whether the contractile response induced by exogenous acetylcholine (ACh) chiefly involved the pre- or post-synaptic junctional site of the motor endplate was studied by using the cat gastrocnemius nerve muscle preparation poisoned with beta-bungarotoxin (beta-BuTX), a toxin isolated from the venom of Bungarus multicinctus which acts presynaptically. 2 After neuromuscular transmission was completely blocked by beta-BuTX, the dose-response curve of the contractile response induced by close intra-arterial injection of ACh, was compared with that of the control. No appreciable difference was observed. 3 In contrast, the response to ACh was completely abolished when neuromuscular transmission was blocked by alpha-bungarotoxin, a toxin isolated from the same venom which acts postsynaptically. 4 It is concluded that postjunctional site of the motor end-plate is chiefly involved in the contractile response produced by exogenous ACh.

Fetal activity acceleration determination for the evaluation of fetal reserve

Fetal activity acceleration determination (FAD) was performed 462 times on a total of 410 patients for the evaluation of fetal reserve. Simultaneous oxytocin challenge test (OCT) was performed 324 times to evaluate the correlation between the two tests. In 308 instances, FAD was positive and OCT was either negative or probably negative. In 2 cases with inadequate FAD results the simultaneous OCT was suspicious and positive. In four instances of negative FAD the simultaneous OCT was positive. The correlation between the two tests was excellent. The outcome of all cases with positive FAD was also excellent. The result of the present study strongly suggests that the positive FAD indeed provides reassurance of fetal well-being. Only the inadequate or negative FAD requires the performance of an OCT for further evaluation of the fetal condition.

The porcine ovarian follicle: III. Development of chorionic gonadotropin receptors associated with increase in adenyl cyclase activity during follicle maturation

Specific binding of human chorionic gonadotropin (hCG), and the hCG-sensitive adenyl cyclase of granulosa cells from small (1-2 mm), medium (3-5 mm), and large (6-12 mm) porcine ovarian follicles have been studied. The number of hCG-binding sites per cell (n) increases during follicle maturation without a change in the binding affinity. The values for n were 300-400 for small, 1,000-1,600 for medium, and 8,200-10,000 for large-follicle cells. The dissociation constant is 2.4 X 10(-10)M for all cells. hCG-sensitive adenyl cyclase was demonstrated in porcine granulosa cells. The adenyl cyclase system of granulosa cells becomes increasingly responsive to hCG stimulation during follicle development. Maximal adenyl cyclase activation by hCG (1 mug/ml) was 240, 750, and 7,000 molecules of cyclic AMP formed/sec/cell, respectively, for small, medium, and large follicle cell. The concentration of hCG giving half-maximal stimulation (1.0 X 10(-9)M) was similar for both large and medium follicle cells. It is concluded that: 1) an increase in hCG receptor sites per cell occurs during maturation of the porcine ovarian follicle without change of binding affinity, and 2) the increase in the number of hCG receptors correlates well with hCG-sensitive adenyl cyclase activity during follicle development.

Mechanism of action of cobra cardiotoxin in the skeletal muscle

Cobra cardiotoxin (CTX) is a potent polypeptide in inducing irreversible contracture of the chick biventer cervicis muscle. this polypeptide is about 2000 times more potent than caffeine in inducing contracture of this muscle preparation but the rate of CTX contracture is slower. Studies on the interaction on CTX with divalent cations showed that low Ca0++ (10(-31-2 mM)-Krebs' enhanced markedly while ethylene glycol bis (beta-aminoethyl ether)-N,N'-tetraacetic acid-Krebs' or high Ca++ (12 mM) inhibited completely CTX contracture; 10 mM Mg++ enhanced but 20 mM Mg++ or 10 mM Zn++ inhibited CTX contracture. Neither Na+ nor tetrodotoxin affected CTX contracture. Comparison of CTX and caffeine contracture showed that ethylenediamine tetraacetic acid (1 mM) and Mn++ (5 mM) inhibited CTX contracture completely but inhibited caffeine contracture only partially; procaine did not inhibit CTX contracture but inhibited caffeine contracture competitively; by contrast, N-ethylmaleimide inhibited CTX but not caffeine contracture. Neither caffeine nor K+ contracture was inhibited by 12 mM Ca++. CTX could induce contracture in the depolarized muscle and the muscle with T-tubule destroyed or closed, whereas K+ failed to induce contracture in the latter. Caffeine contracture was inhibited in the muscle with a previous elicitation of CTX contracture. This antagonistic effect of CTX could be prevented by calcium. Moreover, CTX increased both 45Ca++ efflux and 45Ca++ uptake. Both Zn++ (0.6 mM) and Mg++ (10 mM) but not protamine and polylysine mimicked CTX to increase 45 Ca++ uptake. Zn++ (0.6mM) was also found to be effective in replacing Ca0++ to induce CTX contracture in 10(-6) M Ca0++. CTX increased Ca and Na but decreased K contents of the muscle. The binding of radioactive iodinated CTX was inhibited not only by unlabeled CTX but also by 10mM Ca++. All of these findings suggest that CTX may affect a membrane calcium binding site and may induce contracture by releasing the membrane calcium rather than by increasing Na+ permeability of the muscle membrane.