Role of guanine nucleotide-binding protein in the regulation by adenosine of cardiac potassium conductance and force of contraction. Evaluation with pertussis toxin

In atrial cardiac preparations adenosine exerts a receptor-mediated negative inotropic effect due to an increased potassium conductance. Pretreatment of guinea pigs with pertussis toxin abolished the negative inotropic and action potential shortening effect of adenosine and the adenosine analogue (-)-N6-phenylisopropyladenosine (PIA). As pertussis toxin specifically inactivates guanine nucleotide-binding proteins involved in the signal transfer from receptor binding to specific cell functions, it is concluded that a guanine nucleotide-binding protein is involved in the regulation of the receptor-mediated change in potassium conductance and force of contraction.

Evidence for adenosine receptor-mediated isoprenaline-antagonistic effects of the adenosine analogs PIA and NECA on force of contraction in guinea-pig atrial and ventricular cardiac preparations

The effects of the adenosine agonists (-)-N6-phenylisopropyladenosine (PIA) and 5'-N-ethylcarboxamideadenosine (NECA) on force of contraction, adenylate cyclase activity and normal as well as slow action potentials were studied in guinea-pig isolated atrial (left auricles) and ventricular preparations (papillary muscles). In auricles PIA and NECA exerted concentration-dependent negative inotropic effects with similar potencies (mean EC50:0.05 mumol l-1 for PIA and 0.03 mumol l-1 for NECA). Similar results were obtained in the presence of isoprenaline. In papillary muscles PIA and NECA alone had no effect on force of contraction but produced negative inotropic effects in the presence of isoprenaline (mean EC50:0.19 mumol l-1 for PIA and 0.10 mumol l-1 for NECA). In both preparations, the negative inotropic effects of PIA and NECA in the presence of isoprenaline were antagonized by the adenosine receptor antagonist 8-phenyltheophylline. In both preparations, PIA and NECA did not affect adenylate cyclase activity, both in the absence and presence of isoprenaline. In auricles the negative inotropic effects of both nucleosides were accompanied by a shortening of the action potential. This effect was also observed in the presence of isoprenaline. In papillary muscles the adenosine analogs did not detectably alter the shape of the normal action potential. Ca2+-dependent slow action potentials elicited in potassium-depolarized preparations also remained unaltered in the presence of PIA or NECA alone. However, the isoprenaline-induced enhancement of the maximal rate of depolarization of slow action potentials was attenuated by PIA or NECA.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional evidence for the existence of adenosine receptors in the human heart

Adenosine added to isolated electrically driven preparations of human ventricular heart muscle antagonized the positive inotropic effect of isoprenaline (mean EC50 19 mumol 1(-1), n = 9). Similar effects were observed with the adenosine receptor agonist (-)-N6-phenylisopropyladenosine (mean EC50 0.5 mumol 1(-1), n = 7). These data provide functional evidence for the existence of adenosine receptors in the human myocardium which may modulate the force of contraction during beta-adrenergic stimulation and thus could be involved in the autoregulation of myocardial contractility.

Positive inotropic effect of Bay K 8644: cAMP-independence and lack of inhibitory effect of adenosine

The aim of the present study was to characterize the positive inotropic effect of the Ca2+ channel activator Bay K 8644. In isolated guinea-pig papillary muscles we investigated whether adenosine and the R site adenosine receptor agonist (-)-N6-phenylisopropyladenosine (PIA) were able to antagonize the positive inotropic effect of Bay K 8644. The effect of Bay K 8644 and adenosine or PIA on myocardial cAMP content was also measured. The influence of adenosine and PIA on the positive inotropic effect of the beta-adrenoceptor agonist isoprenaline and of the phosphodiesterase inhibitor amrinone was studied for comparison. Adenosine and PIA antagonized the positive inotropic effects of isoprenaline and amrinone in a concentration-dependent manner. In contrast, adenosine or PIA did not affect the positive inotropic effect of Bay K 8644. The positive inotropic effect of Bay K 8644 was not accompanied by a change in the cAMP content of the papillary muscles. Additionally applied adenosine or PIA also failed to affect the cAMP content. It is concluded that an increased myocardial cAMP content is not involved in the positive inotropic effect of Bay K 8644. Moreover, the results support the view that adenosine and PIA only antagonize the positive inotropic effects of drugs known to increase myocardial cAMP content and that an increased myocardial cAMP content is a prerequisite for the manifestation of a negative inotropic effect of the nucleosides in ventricular cardiac muscle.

[Asthma, eosinophilia and systemic vasculitis: Churg-Strauss syndrome]

In two female patients asthma, marked eosinophilia and symptoms of systemic vasculitis could be classified clinically or histologically as allergic angiitis and granulomatosis (Churg-Strauss syndrome). The course in one patient went back over 20 years, characterized by an asymptomatic interval of 16 years. It is to be assumed that the disease is more frequent than it is diagnosed. It has to be thought of when, in addition to asthma and eosinophilia, there is evidence of involvement of other organs.

[The theory of thermoluminescence]

The interaction of stimulating radiation with matter produces defects which can be divided into two groups: 1. electronic defects, 2. ionic defects. The formation of defects is essentially determined by electronic processes and elastic impacts. The supply of energy in the form of heat makes possible a thermal stimulation the probability of which is characterized by a Boltzmann factor. Whereas the classical explications are based on thermodynamic or statistical considerations, the quantum mechanical calculation relates to non-radiative transitions from traps. For the radiating recombination a selective rule is valid which guarantees the conservation of energy and impulse. The phenomenological description of thermoluminescence makes use of the kinetic processes in the non-stationary case and allows in simple models the determination of trap parameters, such as activation energy or pre-exponential factor. The simple models can be extended by introducing thermally separated trap levels. If the kinetic balance equations are solved exactly with the aid of an analogic computer, the simulated Glow curves show a good correspondence with experimental curves.

[Various aspects of psychopharmacotherapy in advanced age]

The author describes possibilities to treat acute states of confusion, states of agitation as well as twilight states, the paranoid-hallucinatory syndrome, the depressive syndrome and organically caused sleep disturbances by psychotropic drugs.

Adenosine inhibition of catecholamine-induced increase in force of contraction in guinea-pig atrial and ventricular heart preparations. Evidence against a cyclic AMP- and cyclic GMP-dependent effect

The antagonism between adenosine and isoprenaline on force of contraction, cyclic AMP (cAMP) and cyclic GMP (cGMP) content, adenylate cyclase activity and transmembrane action potential in isolated electrically driven atrial and ventricular muscle preparations from guinea-pig hearts was investigated. In atrial preparations adenosine added 5 min after isoprenaline decreased force of contraction. Adenosine abolished completely the positive inotropic effect of isoprenaline. Similarly, adenosine prevented the positive inotropic effect of isoprenaline when both substances were added simultaneously. In ventricular preparations adenosine also decreased the isoprenaline-induced increase in force of contraction. The effect was much smaller than it was in the atria. Adenosine reduced the isoprenaline-induced increase in force of contraction only by about 60%. Adenosine did not at all influence the positive inotropic effect of isoprenaline when both substances were added simultaneously. In both preparations the isoprenaline-induced increase in cAMP content of the intact contracting preparations was not diminished by adenosine. cGMP content remained unchanged too. Adenosine inhibited adenylate cyclase activity in broken cell preparations from both tissues. In atrial preparations the decrease in force of contraction of adenosine in the presence of isoprenaline was accompanied by a shortening of the action potential duration. In ventricular preparations adenosine failed to shorten the action potential. In conclusion, the effects of adenosine to inhibit the stimulatory action of isoprenaline on myocardial force of contraction are not due to changes in the cAMP and/or cGMP content. Instead, adenosine may inhibit a step beyond an increased cAMP level, e.g., may exert an inhibition of protein kinases. However, in the atria, but not in the ventricles, an additional direct effect of adenosine on transmembrane ion currents, most likely an increase in potassium conductance, probably is of even greater importance.

[Various psychiatric disorders in the aged]

The author describes the organic psychosyndrome, the dementia syndrome, the depressive syndrome as well as the paranoiac and hallucinatory syndromes.

Data compression in digital angiography using the Fourier transform

While digital techniques in radiology develop rapidly, problems arise with archival storage and communication of image data. This paper reports on experiments concerning data reduction of digital image sequences of the heart and the brain. The time-intensity curves corresponding to every picture element are subjected to the Fourier transform and reconstructed from a number of coefficients smaller than the original number of images. The reconstruction error is assessed by visual inspection and by determining the mean-square deviation of the original and the reconstructed curve. It is shown that compression factors between 5 and 10 may be achieved without loss of diagnostic information. It is furthermore demonstrated that storage of the images in the form of Fourier coefficients leads to advantages in fast retrieval, enhancement of morphology, and possibility of further quantitative analysis.

[Computer angiography in renal transplants (author's transl)]

The results of computed angiography in 12 patients with renal transplants are described. In five patients with normal function of the transplant and normal appearances on a conventional angiogram, under-perfusion averaging 36% was demonstrated. In two out of three patients with a stenosis at the anastomosis, the effect of the stenosis on function could be shown. In two patients with acute rejection of the graft and hypoxia of the tubules, the differential diagnosis could be clarified by means of computer angiography. Computer angiography can therefore be regarded as a valuable addition to conventional angiography for the differentiation between tubular hypoxia and acute rejection and for underperfusion of a renal transplant.

[Glycogen phosphorylase activity in infarct-affected and nonaffected parts of the human myocardium after death]

Distinct differences in activity of glycogen phosphorylase were not observed in various parts of an intact human myocardium. This enzymatic activity vas considerably decreased in the left ventricle of the myocardium impaired by infarction; with prolongation of the infarction period the enzymatic activity decreased further. Isozymes of glycogen phosphorylase I, II and III were liberated from ischemic myocardium according to their quantitative ratio in the heart. The glycogen phosphorylase activity, which was observed in blood serum of patients with acute myocardial infarction, was apparently liberated into blood due to the myocardium impairment. Evaluation of the enzymatic activity in blood serum of the patients might serve as an index of the necrosis degree.

[Measurement and differential demonstration of renal blood flow by computer angiography (author's transl)]

A new computer-aided x-ray technique is presented which, unlike conventional cine- or video-densitometry, allows a high-resolution quantitative display of the parameters of renal blood flow as so-called 'functional images'. The parameters include blood flow velocity and local perfusion of the kidney. This technique, which we call computer angiography, has decisive advantages; the functional images provide more, and more rapid, information on renal blood flow dynamics than can be obtained by the qualitative evaluation of a series of pictures. The clinical relevance of computer angiography is illustrated by a nephrotic syndrome, polycystic disease and a hypernephroma.

Relative stimulation of aspartate aminotransferase activity in human serum by pyridoxal 5'-phosphate in myocardial infarction

The relative stimulation of aspartate aminotransferase was investigated in human serum by saturation of apoaspartate aminotransferase with pyridoxal 5'-phosphate. This stimulation depended on the time-course after injury and the peak level was attained later than the maximum value of aspartate aminotransferase activity.

Mitochondrial adenosine triphosphatase from yeast, Saccharomyces cerevisiae. Purification, subunit structure and kinetics

1. A procedure for the purification of ATPase extracted by chloroform from baker's yeast (Saccharomyces cerevisiae) is reported. The yield based on submitochondrial particles was 55% and the purification was 100-fold. The isolated complex was homogenous as assessed by gel filtration, ion-exchange chromatography, sedimentation in sucrose gradient and in the analytical ultracentrifuge. The molecular weight determined by gel filtration was 400000 +/- 20000. Ultracentrifugation yielded s020,w = 12.50 +/- 0.13 S and the laser light scattering study gave a diffusion coeficient of D20w - 2.92 X 10(-7) cm2 s-1. The amino acid composition as well as absorption, fluorescence, and circular dichroism spectra, from which the helicity of 39% was evaluated, are given. 2. On polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, six components with molecular weights of 58500(alpha), 55000 (beta), 42000, 34000 (gamma), 10000(delta), and 8600 (epsilon) were observed with a stoichiometry of 3:3:1:1:1:1. The amino acid composition is given for alpha + beta and gamma as well as delta and epsilon components. 3. The maximum specific activity of the enzyme was 200 U/mg under the optimum conditions. The enzyme was inactivated by incubation at 0 degrees C and strongly inhibited by the antibiotic Dio-9 but not by oligomycin and N, N'-dicyclohexyl-carbodiimide. The effects of kinetic parameters and anions on the enzyme are reported. Two active sites for Mg-ATP with Km values of 0.045mM and 0.37mM and a single activie site for Mg-ITP with Km = 0.179mM were found. A study of the temperature dependence of the maximum activity revealed a straight line in the Arrhenius plots with an activation energy of 11.0 kcal/mol (= 46 kH/mol).

The assay of glycogen phosphorylase in human blood serum and its application to the diagnosis of myocardial infarction

Methods are described (a) for the estimation of glycogen phosphorylase activity (EC 2.4.1.1) in human blood serum based on the chemical determination of liberated orthophosphate or on the enzymic determination of glucose 1-phosphate in a coupled assay system and (b) for the electrophoretic separation of isophosphorylases I, II, and III in human. Glycogen phosphorylase activities ranging from 1.5 to 18 mU/ml were found in the serum of patients with acute myocardial infarction. In contrast, no glycogen phosphorylase activity was detected in the serum of healthy persons. The enzyme appears in the serum 4 hours after the onset of the infarction and reaches a maximum after 20 to 30 hours. Acrylamide gel electrophoresis of serum after a myocardial infarction revealed only muscle isophosphorylase I, the isoenzyme characteristic of the heart. No phosphorylase activity was detected in serum of patients with angina pectoris, endocarditis, and uncomplicative congestive heart failure. From these findings it appears that the new serum enzyme test may prove to be a valuable addition to presently existing methods for the early differential diagnosis of acute myocardial infarction.