Effects of calcium antagonist, 6-(N, N-diethylamino) hexyl-3, 4, 5-trimethoxybenzoate, on digitalis-induced arrhythmias and cardiac contractions

6-(N, N-Diethylamino) hexyl-3, 4, 5-trimethylbenzoate (TMB-6) and lidocaine were equipotent (1 mg/kg) in the conversion of ectopic rhythms to normal rhythms in digoxin-toxic dogs. However, TMB-6 had fewer side effects on heart rates and dp/dt than lidocaine. TMB-6 inhibited the contractile force of electrically stimulated dog and guinea-pig atria and ventricles at concentrations ranging from 2.5 X 10(-5) to 1.7 X 10(-4) M. Elevation of extracellular Ca++ concentrations from 2.7 to 5.4 mM produced a significant increase in the ID50 of TMB-6 in atria (from 2.5 X 10(-5) to 5.0 X 10(-5) M in dogs and from 7.2 X 10(-5) to 1.0 X 10(-4) M in guinea pigs). TMB-6 (7.3 X 10(-5) to 2.4 X 10(-4) M) depressed the amplitude of Ca++-dependent action potentials in depolarized dog cardiac Purkinje fibers. These results are discussed with regard to the antagonism of TMB-6 on Ca++ availability in the myocardium which leads to the conversion of cardiac arrhythmias.     

Protein hydration in solution: experimental observation by x-ray and neutron scattering

The structure of the protein-solvent interface is the subject of controversy in theoretical studies and requires direct experimental characterization. Three proteins with known atomic resolution crystal structure (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 of E. coli ribonucleotide reductase) were investigated in parallel by x-ray and neutron scattering in H2O and D2O solutions. The analysis of the protein-solvent interface is based on the significantly different contrasts for the protein and for the hydration shell. The results point to the existence of a first hydration shell with an average density approximately 10% larger than that of the bulk solvent in the conditions studied. Comparisons with the results of other studies suggest that this may be a general property of aqueous interfaces.     

The effect of atropine on insulin stimulated gastric secretion and gastrin release

A 28-years-old patient with a palpable mass of two fist's size in the upper abdomen rapidly developed an obstructive jaundice. A pancreatic tumor was suspected and therefore ERCP was carried out. Unusual alterations caused by metastatic lesions of a post mortem diagnosed testicular teratoma narrowing and invading the common bile duct and displacing the main pancreatic duct were visualized.     

Differentiation for aggregation in the cellular slime moulds: the emergence of autonomously signalling cells in Dictyostelium discoideum

The results of experiments on small populations of Dictyostelium discoideum, directed towards the measurement of the development in time of the competence of the cells to signal autonomously, are reported. This competence is quantified by X3, the intrinsic probability that a given cell may turn autonomous. The data show an early exponential growth in time of X3, followed by saturation. The saturation value depends on the population size suggesting that the differentiation is a co-operative phenomenon. The differentiation of autonomous cells starts roughly 7 h after the removal of food and saturates within 21 h.     

Construction,operation and evaluation of a rapid-response potentiostat

Factors involved in construction and utilization of an inexpesive, rapid-response potentiostat with 50 mA current capabilities are discussed. The potentiostat can be used with ancillary units, eg function generators, for a variety of rapid pertubation approaches, eg cyclic voltammetry at scan rates to 4000 V/s or greater, potential-step chronoamperometry with data acquisition after 40 μs or less, pulse polarography at millisecond or shorter discharge times, and phase-selective ac polarography at frequencies to at least 15 kHz. Examination of the Fe(III/II) couple reversibility in oxalate media, the adsorption of adenine, and the dimerization of the NAD free radical are described.