Effects of hypothermia on ionic movement in the guinea pig cochlea

Anesthetized and immobilized guinea pigs were subjected to hypothermia. During cooling, the cochlear microphonics and endocochlear potential decreased and K+ concentrations in both endolymph and perilymph were not significantly affected. The rate constant for K+ turnover to endolymph was determined by uptake of 43K into the endolymph when the perilymphatic space was perfused with artificial perilymph containing 43K. The rate constant for K+ decreased significantly in hypothermic guinea pigs when compared with that in normal guinea pigs. The K+ conductance of the endolymph-perilymph barrier, estimated from the rate constant, showed a marked decrease in hypothermic guinea pigs and was comparable with the K+ conductance, calculated from the rate of change of the endolymph K+ concentrations relative to the K+ electrochemical potential difference, recorded during permanent anoxia. These results suggest that hypothermia not only suppresses the active K+ transport system but also decreases the K+ permeability of the endolymph-perilymph barrier.

Comparison between the effects of continuous and impact noise on cochlear potentials in guinea pigs

Cochlear microphonics (CM), action potentials (AP), and endocochlear potential (EP) were recorded from anesthetized, immobilized guinea pigs during potential (EP) were recorded from anesthetized, immobilized guinea pigs during and following 20 min periods of noise exposure. Changes in cochlear potentials were compared in guinea pigs exposed to continuous broadband noise or mechanically generated impact noise of equal energy content. Over a range of continuous noise levels from 95 to 105 dB SPL it was found that continuous noise produced less suppression of CM and a greater suppression of AP than did impact noise of equal energy. A reduction of EP did not accompany CM suppression with either type of noise exposure. Suppression of CM and AP was also compared in guinea pigs with chronically implanted round window electrodes. In these preparations, AP was suppressed to a similar extent by impact and continuous noise of equal energy, but CM was suppressed to a significantly greater extent by impact noise. The data from both series of experiments indicate that the suppression of cochlear responses is not predicted by an "equal energy" rule when impact and continuous noise are compared.

Comparative effects of three calcium antagonists, diltiazem, verapamil and nifedipine, on the sinoatrial and atrioventricular nodes. Experimental and clinical studies

Diltiazem, verapamil and nifedipine suppress sinoatrial (SA) nodal function in the excised rabbit heart. Clinically, however, their suppressive effect on the SA node is modified considerably by the reflex increase in sympathetic tone as a result of the fall in blood pressure caused by the vasodilating action of the calcium antagonists. Diltiazem, verapamil and nifedipine suppress atrioventricular (AV) nodal conduction and prolong refractory periods in the excised rabbit AV node. Clinically, diltiazem and verapamil exert a similar suppressive effect on the AV node and are useful for treating and preventing AV nodal reentrant tachycardia. Nifedipine, in clinically practical doses, has no antiarrhythmic properties, probably because of reflex activation of the sympathetic system secondary to its hypotensive effect, which is greater than that of the other two calcium antagonists. Diltiazem and verapamil may sometimes worsen AV conduction, especially in patients with conduction disturbances. Nifedipine, on the other hand, can be used as a coronary vasodilator with the least untoward effect on AV conduction.

Myasthenia gravis: relation between jitter in single-fiber EMG and antibody to acetylcholine receptor

In 39 patients with myasthenia gravis, we measured jitter in the extensor digitorum communis muscle, using single-fiber electrode (SFEMG) and the serum titer of antiacetylcholine receptor antibody. Clinical severity was correlated more closely with jitter, especially the percentage of abnormal jitter pairs with blocking than with antibody titer. In patients who responded fairly well clinically after certain treatments, both the SFEMG abnormalities and antibody titer tended to improve in parallel with clinical improvement. After the plasma exchange, there was a time lag between the recovery from the defective neuromuscular transmission and the rapid decrease in antibody titer. The percentage of abnormal jitter pairs with blocking and the mean jitter value reflect defective neuromuscular transmission in generalized myasthenia gravis.

Scintigraphic evaluation of regional pulmonary circulation and ventilation abnormalities in mitral valvular disease and congestive heart failure

Regional pulmonary mean transit time, MTT (RV-Lung) was measured by radionuclide angiography using 99mTc-pertechnetate or 99mTc-HSA. In 8 normal subjects, MTT (RV-Lung) in upper (U) and lower (L) lung fields averaged 2.48 and 2.81 sec, respectively. In MS and CHF groups, MTT (RV-Lung) in L was markedly prolonged (5.04 and 5.10 sec, respectively) and after appropriate medical or surgical treatment, MTT in L markedly reduced. Pulmonary ventilation perfusion scintigraphy with 133Xe was performed in 18 patients with MS. Both Vu/L and Ou/L increased in accordance with the severity of disease, however, Vu/L had never exceeded unity. The estimation of regional MTT in the lung field is to be useful way in evaluating the severity of pulmonary circulatory disturbance in MS or in congestive heart failure.

Effects of verapamil on accessory pathway properties and induction of circus movement tachycardia in patients with the Wolf-Parkinson-White syndrome

The electrophysiological effects of 0.2 mg/kg of intravenously administered verapamil (mean plasma level, 51.3 ng/ml) were evaluated using intracardiac recordings and electrical stimulation in 10 patients with the concealed or manifest Wolff-Parkinson-White syndrome. Verapamil produced a minimal effect on both the antegrade and retrograde effective refractory periods of the accessory pathway and the retrograde conduction time over the accessory pathway, but significantly lengthened the intranodal conduction time as well as the effective and functional refractory periods of the atrioventricular (AV) node. Reproducible sustained circus movement tachycardia was initiated in 8 patients before administration of verapamil and in 2 after verapamil. The sustained tachycardia could no longer be initiated in 6 patients because of an increase in AV nodal refractoriness. In 4 patients, atrial echoes were induced at longer premature beat intervals due to a greater AV conduction delay of the atrial impulse. The cycle length of the tachycardia was lengthened in 2 patients, reflecting an increase in the A-H interval after verapamil administration. In conclusion, these results show that verapamil has no apparent effect on either antegrade or retrograde accessory pathway properties and suggest that verapamil does indeed prevent sustained circus movement tachycardia by increasing the AV nodal refractoriness in some patients with the Wolff-Parkinson-White syndrome.

Cardiomyopathy and other chronic toxic effects induced in rabbits by doxorubicin and possible prevention by coenzyme Q10

Cumulative dose-dependent toxic effects, particularly cardiomyopathy, induced by doxorubicin and the possible prevention by coenzyme Q10 (CoQ10) were studied in rabbits. In rabbits given doxorubicin alone, there was considerable body weight loss, alopecia, pancytopenia, significant increase in serum creatine phosphokinase and LDH, and ECG changes characterized by tachycardia, flat and inverted T wave, the premature ventricular contractions. In rabbits given doxorubicin plus CoQ10, the only change was pancytopenia. In rabbits treated with doxorubicin alone, the most prominent histologic changes were observed in mitochondria of myocytes, and these changes were characterized by loss of outer membrane, disarrangement of cristae, and formation of numerous concentric lamellae. In addition to mitochondrial changes, there were numerous vacuolizations and extensive depositions of both electron-dense and membranous laminated bodies in the sarcoplasm and disarrangement of Z-band and filamentous changes of myofibrils. Numerous vacuolizations in the capillary endothelial cytoplasm in the myocardium were also conspicuous. On the other hand, few significant morphologic changes were seen in the nuclei of myocytes. There were few ECG and histopathologic changes in rabbits treated with both doxorubicin and CoQ10. These findings suggest that the cardiomyopathy of doxorubicin may be prevented or is at least inhibited by CoQ10. The mechanisms of both doxorubicin-induced cardiomyopathy and its prevention by CoQ10 are discussed.

Incompatibility of R plasmids derived from Salmonella and Escherichia coli strains isolated simultaneously from a bovine fecal sample

Seven strains of Salmonella typhimurium were isolated from 2 fecal samples of calves, and the strains were resistant to ampicillin, chloramphenicol, kanamycin, nalidixic acid, streptomycin, sulfadimethoxine, and tetracycline. Also, 11 Escherichia coli strains were obtained from 1 of the 2 samples, and these strains possessed the identical drug resistance patterns as did the salmonellae. The thermosensitive R plasmids conferring sextuple drug resistance and mercury resistance from Salmonella strains were Fi- (no fertility inhibition) and belonged to incompatibility group H1, whereas conjugative 6 R plasmids isolated from 11 E coli strains were Fi+ (fertility inhibition) and belonged to incompatibility group FII. Thermosensitive R plasmids conferring sextuple drug (ampicillin, chloramphenicol, kanamycin, streptomycin, sulfadimethoxine, and tetracycline) have not been reported in Japan. Genetic relationship of R plasmids derived from the multiresistant strains of Salmonella and E coli was discussed on the basis of incompatibility properties of R plasmids.

Permeability to potassium of the endolymph-perilymph barrier and its possible relation to hair cell function

The endocochlear potential and potassium concentrations in endolymph and perilymph were simultaneously measured in the basal turn of the guinea pig cochlea with double-barreled K+ selective electrodes. The K+ conductance and K+ permeability coefficient of the endolymph-perilymph barrier were calculated from the rate of change of endolymph K+ concentration relative to the K+ electrochemical potential difference recorded during permanent anoxia. When anoxia was induced in guinea pigs treated with kanamycin, the rate of decline of the electrochemical potential difference for K+ between the endolymph and perilymph was reduced when compared to normal guinea pigs. In guinea pigs exposed to broad band noise at 115 dBA for periods from 11-15 days, the rate of decline of the electrochemical potential difference for K+ across the endolymph-perilymph barrier was reduced but not to the extent found in guinea pigs treated with kanamycin. The K+ conductance and K+ permeability coefficient of the endolymph-perilymph barrier showed substantial decreases in noise exposed and kanamycin treated guinea pigs, as compared to normal guinea pigs. The magnitude of decrease of K+ permeability of the endolymph-perilymph barrier by noise or kanamycin was correlated with suppression of the maximum output of the cochlear microphonic.

A histopathological study on pyloric ulcer

After the pyloric ulcer was defined as a peptic ulcer occurring at the pylorus or having its centre in the prepyloric region within 2 cm from the pylorus, its histopathological features were studied on 94 pyloric ulcers in 88 surgically resected stomachs. 72.3 per cent of these ulcers were less than 1.0 cm in diameter. The incidences of UI-II, III and IV ulcers were almost equal, and the majority of UI-II and UI-III ulcers were found in scarring stage in the specimens. These pyloric ulcers were classified into three types according to whether the centre of ulcer is situated above (Type-1), on (Type-2) or below (Type-3) the pylorus. Type-1 ulcers wre the most frequent, their incidence being 70.2 per cent. On histologic examination, it was observed that duodenal gland area extended over the pyloric antrum in 90 per cent of the specimens. Contrary to the mucosal rule of Oi for the genesis of peptic ulcer, pyloric ulcers were located in poric gland gland are in 30.9 per cent and on the glandular boundary in 57.4 per cent. Only in 11.76 per cent, the ulcer developed in duodenal gland area. In 68.2 per cent, pyloric ulcer was associated with other gastric or duodenal ulcers. The majority of these coexisting gastric ulcers occurred in the pyloric gland area adjacent to the antrofundic border, and all the duodenal ulcers in the proximal duodenum. Moderate or severe atrophic changes in gastric antral mucosa were found in a large number of the specimens with coexisting gastric ulcer, whereas the changes were less pronounced in those with pyloric ulcer alone.