Involvement of phosphoinositide turnover in ouabain inotropism.

We examined whether ouabain activities phospholipases and reinforces contraction force of papillary muscles through resultant second messengers. 2-Nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC), the inhibitor of phospholipase C (PLC), abolished the ouabain inotropy in rabbit papillary muscles. Calphostin C, the specific inhibitor of protein kinase C (PKC), also depressed the ouabain inotropy. 12-O-Tetradecanoylphorbor-13-acetate (TPA), the specific activator of PKC, enhanced the beat-to-beat phasic contractility at low concentrations. Radioenzymatic assay revealed that ouabain treatment doubled diacylglycerol (DG) content in excised papillary muscles. We concluded that ouabain activates PLC, and the resultant second messenger, DG, augments the cardiac contraction force through activation of PKC.

DNA homology between Candida albicans strains: evidence to justify the synonymous status of C. stellatoidea.

Genetic relatedness between strains of C. albicans and C. stellatoidea was studied by measuring G + C content and overall sequence homology. G + C contents determined by high-performance liquid chromatography were 32.6 to 34.2% for 26 strains of C. albicans and 33.0 to 33.9% for eight strains of C. stellatoidea. DNA-DNA hybridization with two C. albicans and two C. stellatoidea probes revealed that all 34 test strains formed a single cluster in which the extents of hybridization with the heterologous probes ranged between 77.9 and 105.6% of those with the homologous probes. These results give support to the unification of C. albicans and C. stellatoidea into a single species.

Adansonian study of Candida albicans: intraspecific homogeneity excepting C. stellatoidea strains.

Fifty-six strains of Candida albicans (40 fresh human isolates, 10 laboratory strains, and 6 Candida stellatoidea strains), seven strains of other Candida species, and one strain of Saccharomyces cerevisiae were examined for a total of 182 biochemical and physiological characters. As 121 characters proved positive or negative in all of the strains, analysis of similarity values (simple matching coefficients) derived from the remaining 61 characters revealed that C. albicans strains could be discriminated from other species with similarity values of 70% or lower, and that the cluster of C. albicans strains with internal similarity values above 70% could be divided into two subclusters representing classical C. albicans and C. stellatoidea, with intergroup similarity of 70 to 85% and intragroup similarities of 85% or higher. No discernible difference was noted between isolates from pathological specimens and those from healthy individuals.

Respiration of medically important Candida species and Saccharomyces cerevisiae in relation to glucose effect.

Strains of medically important Candida species (C. albicans, C. tropicalis, C. parapsilosis and C. [Torulopsis] glabrata) and Saccharomyces cerevisiae were examined for a glucose effect on respiratory activity. Reduced O2-consuming ability and a relative decrease in cytochrome type c, as determined by polarography and spectrophotometry, respectively, were observed in glucose-grown S. cerevisiae cells in contrast with acetate- or ethanol-grown cells. In glucose-grown cells of C. glabrata, O2 consumption was also reduced without any change in the cytochrome pattern compared to acetate-grown cells, while no such decrease was detected in any of the other strains of Candida species tested. These results suggest that the medically important Candida species, except for C. glabrata, can be categorized as members of the glucose-insensitive yeast type with respect to respiration.

Evidence for a glucose effect on N-acetylglucosamine catabolism in Candida albicans.

Two strains of Candida albicans were examined for a glucose effect on the catabolism of N-acetylglucosamine. It was shown that the induction of N-acetylglucosamine uptake capacity was almost completely blocked by glucose at 0.5% (w/v), whereas that of N-acetylglucosamine kinase was partially repressed.

Circus movement tachycardia induced by a single premature stimulus on the ventricular sheet--evaluation of the leading circle hypothesis in the canine ventricular muscle.

Mechanisms of ventricular tachycardia induced by local application of a properly timed premature stimulus were studied with routine microelectrode technique and extracellular recordings on a ventricular sheet. Thinly sliced preparations obtained from subepicardial muscle of the canine ventricle were used as an approximation of a two-dimensional model. On these preparations, spontaneously sustained tachycardia easily induced by a single premature stimulus. Since delayed after-depolarizations were never evoked by frequent stimulations even in the K+-free and high-Ca++ media, these tachycardias seemed to be induced by re-entrant and circus movement mechanisms. To analyse the re-entrant mechanisms, action potentials generated by normal driving stimuli were recorded from multiple points (40 approximately 50 points) and the spreads of the depolarization and repolarization phases of the action potentials were mapped. The depolarizing wave front on the map always showed a circular or elliptical pattern. Whenever the pattern of spread of the repolarizing wave was similar to that of the depolarizing wave, sustained tachycardia was never brought about by any premature stimulus. On the other hand, when the map of the spread of the repolarizing wave was very complicated and mixed with that of the depolarizing wave, sustained tachycardia was frequently induced. From the above results, it is suggested that the nonuniform recovery of excitability plays a role in the generation of sustained tachycardia. Moreover, a portion of the unidirectional block of the premature impulse was determined by calculated using the conduction velocity of the premature impulse and the effective refractory period in each cell; then a route of re-entry for the premature impulse was simulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Germ tube-forming cells of Candida albicans are more susceptible to clotrimazole-induced killing than yeast cells.

Yeast and germ tube-forming cells of Candida albicans were compared with respect to their susceptibility to killing induced by the imidazole antifungal clotrimazole. Cultures consisting largely of germ tube-forming cells or exclusively yeast cells were prepared by incubating cells of a germ tube-proficient strain in a proline-containing phosphate buffer at 37 degrees C or 25 degrees C, respectively. When treated with clotrimazole at 37 degrees C, the cultures of germ tube cells lost colony-forming ability much more rapidly than those of yeast cells. However, this difference was diminished in the cells preincubated at 37 degrees C but prevented from forming germ tubes by 5 mM cysteine, a suppressor of germ tube formation. In another C. albicans isolate showing a very poor capacity to form germ tubes at 37 degrees C, such a difference in killing rate was much smaller than that for the germ tube-proficient strain. Furthermore, when an isogenic pair of strains, one proficient and the other deficient in germ tube formation, were compared with each other, germ tube-forming cultures of the former were found to be more sensitive than yeast cell cultures of the latter. It is inferred from these results that the germ tube-forming cell of C. albicans is more sensitive to clotrimazole-induced killing than the yeast cell.

Length-dependent changes of pacemaker frequency in the isolated rabbit sinoatrial node.

To correlate changes in pacemaker frequency with those of length and tension in mammalian atrial tissues, a strip of the sinoatrial (SA) nodal tissue (about 10 mm in length and 4 mm in width) isolated from the rabbit heart was subjected to constant-length and constant-load stretches, and the relation between the resulting pacemaker frequency changes and the segmental length changes of the preparation was examined by means of cinematographic recording of the preparation with carbon markers on its surface. The amount of stretch-induced length changes was larger in the perinodal tissue segments than in the SA nodal segments, indicating that the nodal area is less extensible than the perinodal area. The time course of stretch-induced length changes of one nodal segment (closer to the inferior vena cava) was found to roughly parallel that of pacemaker frequency changes, suggesting that the pacemaker frequency is primarily dependent on the length but not on the tension of the SA nodal area.

The effect of local blood flow on the healing of experimental intestinal anastomoses.

Using dogs, we experimentally produced devascularized areas in the small intestine and colon and took quantitative measurements of the submucosal local blood flow using the hydrogen clearance method.. In the area slightly toward the ischemic side of the devascularized margin, local blood flow is less on the mesenteric side in both the ileum and the colon, and microcirculation is better maintained in the colon that in the ileum. When the anastomosis was performed in the area in which the local blood flow on the mesenteric side was 60 per cent of the control value in the ileum or 70 per cent in the colon, recovery of the control value was achieved by the seventh postoperative day. When anastomosis was performed in the area in which the local blood flow on the mesenteric side was 15 per cent of the control value in the ileum and 22 per cent of the control value in the colon, the flow on the mesenteric side did not recover to the level of the control value by the seventh postoperative day, and anastomotic leakage occurred in some dogs. All anastomotic leakage occurred on the mesenteric side. The local blood flow rate at the point at which the last signal was detected by Doppler ultrasound flowmeter after moving Doppler probe from the devascularized margin toward the ischemic side was 57 per cent of the control value in the ileum and 54 per cent of that in the colon. Such levels of blood flow are considered sufficient for successful healing of tissue after an anastomosis.

Experimental study of cardiomyopathy induced by glucocorticoids.

Abnormal ECG changes were found in some patients who were treated glucocorticoid during long term. In experimental animals, chronic administration of glucocorticoid resulted abnormal ST and T changes of ECG, increased duration of action potential and induced electron microscopical changes of mitochondria. No significant changes were found in serum and myocardial potassium content.

Staining and relative determination of elemental contents by the laser microprobe.

An improved laser microprobe procedure is developed and applied to the measurement of calcium content in microareas of right and left subepicardial muscles. The staining of canine cardiac muscles by Methylene Blue solution (1% w/v) was found to improve sampling efficiency. Elemental content is proportional to T-1/gamma, where T is the transmittance of the characteristic emission line of the element of the photographic plate and gamma is its contrast. In the present system, the calcium content is analyzed using T-3.2. We find that the staining of samples and the determination of T-1/gamma are useful procedures in the application of laser microprobe to the study of elemental content in biologic microareas.

Change of P-Q intervals of the electrocardiogram in the rat hearts sensitized with the killed group A streptococci.

Prolongation of P-Q interval in the anesthetized rat was observed by repeated injection of killed group A streptococci. The prolongation was clearly recognized at about the 11th week after the first injection, but afterwards P-Q interval recovered to the normal level in spite of continuous injection of killed streptococci. His bundle electrogram recorded from isolated heart revealed the prolongation of A-H interval in the treated rat. Moreover, the transmembrane action potential in the atrioventricular nodal region of treated rat was slightly deteriorated, but the action potentials in the other cardiac muscles were not changed. It was deduced from the above results that P-Q prolongation was transiently brought about by the injection of killed group A streptocci and that deterioration of muscle in the atrioventricular nodal region might take a main part in the P-Q prolongation.

Persistent atrial standstill developed in a patient with rheumatic heart disease: electrophysiological and histological study.

A case with persistent atrial standstill is presented which developed from atrial fibrillation associated with rheumatic combined valvular heart disease. In addition to clinical and electrocardiographic findings, electrophysiological and histological studies by using microelectrode technique and electron microscopy, respectively, were carried out on specimens from the right atrial appendage resected at mitral valve surgery. Scattered but severe loss of myocardial cells in the atria and deterioration of the action potential of these poorly sustained myocardial cells were confirmed. The suggestive evidence is also shown that the deteriorated action potential observed by micro-electrode technique in this case may be composed of calcium current.

Electrophysiologic effects of propranolol on the human heart.

Effects of propranolol (10(-9) to 10(-4) Gm/ml) on various electrophysiologic properties of human papillary muscles obtained from patients undergoing corrective open heart surgery were studied to have an insight into the mechanism of its antiarrhythmic activity in man. Propranolol (10(-8) to 10(-6) Gm/ml) produced significant decreases in the action potential duration, effective refractory period and dv/dt of depolarization phase of action potential without significantly affecting the resting potential and amplitude of action potential. These effects were concentration dependent. High concentration (10(-4) Gm/ml) of propranolol not only produced greater decreases in the above parameters but also reduced the resting potential and amplitude of action potential. Although propranolol decreased both the action potential duration and effective refractory period, the shortening of the action potential duration was greater than the shortening of the effective refractory period. It shifted the membrane responsiveness curve to the right and down. It produced frequency dependent decreases in the dv/dt of phase 0 of action potential and the rate of repolarization. Propranolol also increased the threshold of stimulation. Propranolol produced electrophysiologic changes in the human myocardium qualitatively similar to those in canine myocardium. The probable mechanism of its antiarrhythmic activity in man has been discussed.

Experimental studies on the effect of glucocorticoids on cardiac muscle.

Abnormal electrocardiographic changes were found in some patients on long-term glucocorticoid treatment. In experimental animals, chronic glucocorticoid administration resulted in an increase of amplitude of the QRS complex and abnormal ST and T changes. Changes of action potential were somewhat different in the subendocardial and the subepicardial layers. Diffuse mitochondrial alterations were found, particularly in the subepicardial layer. In rabbits treated with glucocorticoids, no significant changes were found in either serum or myocardial potassium content. Slightly decreased Vmax was the observed hemodynamic change.