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Biomedical subjects

K Hashiba

Publications and source records attributed to K Hashiba.

At least 55 records · Page 3Linked to original sources
PubMed1992

The influence of advancing age on the electrophysiological changes of the atrial muscle induced by programmed atrial stimulation.

The influence of advancing age on the electrophysiological changes of the atrial muscle induced by programmed atrial stimulation, such as fragmented atrial activity (FAA), interatrial conduction delay (ICD), and repetitive atrial firing (RAF), was investigated in 42 patients with neither documented episodes of paroxysmal atrial fibrillation nor sick sinus syndrome. The induction rates of FAA, ICD, and RAF were not affected by age. The zones of FAA, ICD and RAF, did not show any correlation with age. However, the longest coupling interval giving rise to FAA (longest CI-FAA) or ICD (longest CI-ICD) showed a significant correlation with age (longest CI-FAA; r = 0.428, p less than 0.01, longest CI-ICD; r = 0.398, p less than 0.01). Although the longest coupling interval giving rise to RAF did not show a direct correlation with age (r = 0.267), it was significantly longer in patients over 60 years of age than in those under 60 (p less than 0.05). These results suggest that aging affects the electrophysiological properties of the atrial muscle, which can help to explain why atrial fibrillation is seem more frequently in the elderly.

Adult↗
PubMed1992

Production of active and inactive renin by adrenal explant cultures and the existence of a prorenin activating enzyme in the adrenal gland.

We previously demonstrated high levels of inactive renin (IR) in nephrectomized rat plasma which provided evidence for extra-renal sources of IR. However, the sources of IR were unknown. This study examined whether the adrenal gland is capable of producing active renin (AR) and IR, using explants of adrenal capsules (glomerulosa portions) from control and nephrectomized (Nepex) rats. Explants from both control and Nepex rats produced large quantities of IR and small quantities of AR. The productions of both IR and AR in Nepex rats were significantly greater than in control rats. High potassium culture medium markedly increased IR and slightly, but significantly, enhanced AR in both control and Nepex rats. On the other hand, sodium had little effect on either IR or AR. A renin-angiotensin system has been reported in the adrenal gland. Recently, a prorenin activating enzyme was demonstrated in the kidney and the aortic wall. The next study was performed to demonstrate the existence of a prorenin activating enzyme in the adrenal gland, using inactive renin from culture medium from Nepex rat explants as the substrate. A 26 KD component in adrenal zona glomerulosa tissues isolated by Sephacryl S-200 column chromatography, converted IR to AR in IR rich medium. The pH optimum for prorenin activation by the enzyme was 6.5. Inhibitor studies indicate that this enzyme is a serine protease. These data suggest that (1) the adrenal gland is an extra-renal source of inactive renin and (2) a prorenin activating enzyme exists in the adrenal gland.

Adrenal Glands↗
PubMed1992

Interactive effects of verapamil and sympathetic nerve stimulation on the sinus and AV nodes in the canine hearts.

The interactive effects of verapamil and sympathetic nerve stimulation on the sinus and atrioventricular (AV) nodes were studied in 33 bilaterally stellectomized and vagotomized dogs. Sinus cycle length (SCL) and AV nodal conduction time (AH) at a constant drive cycle length (600 msec) were recorded. Sympathetic nerve stimulation (SNS) was performed for 40 sec by electrical stimulation of the right stellate ganglion. Several doses of verapamil (0.5-2.0 microgram/ml, 1.0 ml) were injected directly into the sinus and AV node arteries at 20 sec of SNS. In addition, SNS was repeated at two different intensities after verapamil administration. Verapamil significantly increased the SCL and the AH in a dose dependent fashion, which was reduced by SNS. The reductions of SCL and AH by the SNS were attenuated in the presence of verapamil when the stimulation intensity was weak, but not when the stimulation intensity was strong. It is concluded that verapamil and sympathetic nerve activity interact antagonistically on the sinus node automaticity and AV nodal conduction.

Animals↗
PubMed1991

Effects of standing on the induction of paroxysmal supraventricular tachycardia.

To evaluate the effects of standing on induction of paroxysmal supraventricular tachycardia, electrophysiologic studies were performed in both the supine and standing positions in 22 patients with atrioventricular (AV) reciprocating tachycardia and in 11 with AV node reentrant tachycardia. AV reciprocating tachycardia was induced in 9 of the 22 patients with AV reciprocating tachycardia when they were in the supine position and in 17 when standing. The effective refractory period of the AV node markedly shortened, from 275 +/- 72 to 203 +/- 30 ms (n = 16, p less than 0.005) after standing. The effective refractory period of the accessory pathway shortened slightly, from 293 +/- 75 to 278 +/- 77 ms (n = 8, p less than 0.005), after standing. AV node reentrant tachycardia was induced in 3 of the 11 patients with AV node reentrant tachycardia when they were in the supine position and in 6 when standing. The effective refractory periods of the slow pathway and fast pathway shortened markedly, from 293 +/- 72 to 216 +/- 40 ms (n = 6, p less than 0.025) and from 416 +/- 85 to 277 +/- 50 ms (n = 10, p less than 0.005), respectively, after standing. Plasma norepinephrine levels increased during standing both in patients with AV reciprocating and in those with AV node reentrant tachycardia (n = 11, p less than 0.005, n = 8, p less than 0.005, respectively). In conclusion, standing, which is associated with increased sympathetic tone, changed the electrophysiologic properties of the reentrant circuits, facilitating induction of AV reciprocating tachycardia and AV node reentrant tachycardia.

Blood Pressure↗
PubMed1991

Prolonged and fractionated right atrial electrograms during sinus rhythm in patients with paroxysmal atrial fibrillation and sick sinus node syndrome.

Intraatrial catheter mapping of the right atrium was performed during sinus rhythm in 92 patients: Group I = 43 control patients without paroxysmal atrial fibrillation or sick sinus node syndrome; Group II = 31 patients with paroxysmal atrial fibrillation but without sick sinus node syndrome; and Group III = 18 patients with both paroxysmal atrial fibrillation and sick sinus node syndrome. Atrial electrograms were recorded at 12 sites in the right atrium. The duration and number of fragmented deflections of the atrial electrograms were quantitatively measured. The mean duration and number of fragmented deflections of the 516 atrial electrograms in Group I were 74 +/- 11 ms and 3.9 +/- 1.3, respectively. The criteria for an abnormal atrial electrogram were defined as a duration of greater than or equal to 100 ms or eight or more fragmented deflections, or both. Abnormal atrial electrograms were observed in 10 patients (23.3%) in Group I, 21 patients (67.7%) in Group II and 15 patients (83.3%) in Group III (Group II versus Group I, p less than 0.001; Group III versus Group I, p less than 0.001). The mean number of abnormal electrograms per patient with an abnormal electrogram was 1.3 +/- 0.7 in Group I, 2.5 +/- 1.9 in Group II and 3.5 +/- 2.5 in Group III (Group I versus Group II, p less than 0.01; Group II versus Group III, p less than 0.05). A prolonged and fractionated atrial electrogram characteristic of paroxysmal atrial fibrillation can be closely related to the vulnerability of the atrial muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Arrhythmogenic properties of the ventricular myocardium in cardiomyopathic Syrian hamster, BIO 14.6 strain.

STUDY OBJECTIVE: Incidence of spontaneous cardiac arrhythmias and inducibility of ventricular arrhythmias in the cardiomyopathic hamster, BIO 14.6 strain, were examined. DESIGN: A 3 min electrocardiogram (ECG) was recorded weekly to 50 weeks of age. Programmed ventricular stimulation was then performed with single and double ventricular premature stimuli during both sinus rhythm and ventricular pacing, and with brief bursts of ventricular pacing to induce ventricular arrhythmias. EXPERIMENTAL MATERIAL: 19 male cardiomyopathic and 10 age matched normal hamsters from 16 to 50 weeks were used for recording the 3 min ECG; 11 cardiomyopathic and 10 normal hamsters aged 50 to 55 weeks were used for the induction of ventricular arrhythmias. MEASUREMENTS AND MAIN RESULTS: Spontaneous and sporadic ventricular premature contractions were documented in 8.3% of 218 ECGs from the cardiomyopathic hamsters between the ages of 30 and 46 weeks, whereas no ventricular arrhythmia was recorded in normal hamsters throughout the entire follow up period. Non-sustained ventricular tachycardia (NSVT) was induced in 7/11 cardiomyopathic hamsters by single ventricular premature stimulus. Either NSVT or ventricular fibrillation was induced in all cardiomyopathic hamsters with a significantly prolonged intraventricular conduction delay and refractory period. In contrast, neither NSVT nor ventricular fibrillation was induced in normal hamsters. CONCLUSION: This study provides the first evidence of the high arrhythmogenicity of the ventricles in cardiomyopathic hamsters.

Animals↗
PubMed1991

Influence of sympathetic nerve activity on ventricular arrhythmogenicity in the dog with chronic hypokalemia.

To examine the influence of sympathetic nerve activity on ventricular arrhythmogenicity in the dog with chronic hypokalemia, an electrophysiologic study was performed before and after bilateral stellectomy (BS) in 10 dogs with chronic hypokalemia (2.8 +/- 0.1 mEq/L), which was created by feeding a low-potassium diet and by administering furosemide over a four-week period, and the results were compared with those obtained from 10 dogs with normokalemia (4.7 +/- 0.3 mEq/L) from being fed an ordinary diet over a four-week period. Before BS the incidence of electrically induced ventricular arrhythmias was higher in the hypokalemic than in the normokalemic dogs. After BS it was decreased considerably in the hypokalemic but not in the normokalemic dogs. Heterogeneity of effective refractory period (delta ERP), which was determined as the difference between the longest and shortest effective refractory periods in three sites of the right and left ventricles, was greater in the hypokalemic than in the normokalemic dogs before BS. The delta ERP decreased slightly in the two groups both before and after BS. There was, however, no significant difference in delta ERP in the two groups both before and after BS. Ventricular fibrillation threshold (VFT) was significantly lower in the hypokalemic dogs than in the normokalemic dogs before BS (p less than 0.005). VFT was elevated in the two groups after BS. Percent increase in VFT after BS was significantly greater in the hypokalemic than in the normokalemic dogs. In conclusion, sympathetic nerve activity may play an important role in the increase in ventricular arrhythmogenicity in the presence of chronic hypokalemia.

Animals↗
PubMed1991

Changes in sodium-22 turnover and total body potassium in two-kidney, one-clip renovascular hypertension.

Changes in sodium-22 turnover and total body potassium (TBK) were studied during acute (within 2 weeks after clipping) and chronic (12-14 weeks after clipping) phases in two-kidney, one-clip (2k, 1c) hypertensive rabbits by using a whole body counter. Sodium-22 injected intravenously was eliminated more rapidly in hypertensive rabbits than in controls. The biological half-life (BHL) of sodium-22 was shorter in hypertensive rabbits during both acute (p less than 0.05) and chronic phases (p less than 0.001). A significant negative correlation was obtained between the BHL of sodium-22 and blood pressure (r = -0.588, p less than 0.05) in hypertensive rabbits. TBK decreased significantly at the chronic phase in hypertensive rabbits (p less than 0.05), while TBK showed no significant change in controls. Serum sodium and potassium did not change during the observation period. Increased plasma aldosterone concentration was observed during the acute phase in hypertensive rabbits. These results suggested that sodium retention was not a major factor in the acute and chronic phases of 2k, 1c hypertension in rabbits and that pressure natriuresis could explain, at least in part, the lack of sodium retention. Furthermore, there appears to be a derangement in the intracellular potassium metabolism which may be associated with the maintenance rather than the development of hypertension.

Aldosterone↗
PubMed1991

Conduction properties of the antegrade fast and slow AV nodal pathways associated with AV nodal reentrant tachycardia.

To elucidate differences in conduction properties among the normal atrioventricular (AV) node and the antegrade fast and slow dual AV nodal pathways (DAVNPW), AV nodal conduction curves were analyzed quantitatively in 38 patients. Eighteen patients had antegrade DAVNPW with AV nodal reentrant tachycardia (AVNRT) (dual pathways group) and the remaining 20 had smooth AV nodal conduction curves, without evidence of AV nodal dysfunction (control group). The effective refractory period (ERP) of the antegrade fast pathway was longer than that of the normal AV node (at both basic cycle lengths of 700 and 500 msec, p less than 0.01). Although the atrial premature beats were delayed by a longer ERP in the fast pathway, there was no significant difference in the degree of prolongation of AV nodal conduction time related to shortening of the coupling interval (i.e., ratio of A2H2 increment to A1A2 decrement) between these two pathways. On the other hand, the ERP of the antegrade slow pathway was similar to that of the normal AV node. The degree of prolongation of AV nodal conduction time (relative to the shortening of the coupling interval) was greater in the antegrade slow pathway than in the normal AV node. In conclusion, these findings suggest that in DAVNPW with AVNRT: (1) the antegrade fast pathway is similar to the AV node and its conduction properties are unlikely to be better than those of the normal AV node and (2) the antegrade slow pathway has quantitatively poorer conduction properties than the normal AV node, since it has a greater degree of decremental conduction.

Adolescent↗
PubMed1991

Effects of sympathetic and parasympathetic stimulation on the induction of atrial flutter in dogs with aseptic pericarditis.

To study the effects of sympathetic stimulation (SS) and vagal stimulation (VS) on the induction of atrial flutter (AF) and its cycle length, aseptic pericarditis was produced surgically in 17 adult mongrel dogs. Programmed atrial stimulation was used to induce AF and to determine the effective refractory periods (ERP) and maximum conduction delay (maxCD) of the atrium. These tests were performed before and during stimulation of the right cervical vagus nerve and the right stellate ganglion. Results showed: (1) AF could be induced in animals with short ERP and large maxCD before SS; (2) ERP was significantly shortened, maxCD was significantly increased by VS; (3) During SS, ERP was slightly shortened, but there were no changes in maxCD and the induction rate of AF; (4) The cycle length of AF was shortened by SS, however, the cycle length of AF was shortened more notably by VS than by SS. From these findings, a shortening of the ERP and an increase in maxCD appear to be related to an increased AF induction rate by VS.

Animals↗
PubMed1991

[The relationship between the aortic pulse wave velocity and osteoporosis in elderly women].

The relationship between arteriosclerosis and osteoporosis (OP) was assessed in 20 elderly women. The aortic pulse wave velocity (PWV) was used as the index of arteriosclerosis and bone mineral content (BM) of the vertebral body, which was measured by quantitative computed tomography, was used as an index of OP. PWV and BM showed a significant correlation with aging (PWV and age: r = 0.466, p less than 0.05, BM and age: r = -0.487, p less than 0.05). In the group in which the serum alkaline phosphatase (ALP) was higher than 180 IU/l (n = 11), there was a significant inverse correlation between PWV and BM (r = -0.728, p less than 0.02). On the other hand, there was no correlation between PWV and BM in the group in which ALP was lower than 180 IU/l (n = 9). These results suggest that in cases with OP and high levels of ALP, calcium (Ca) seems to be released from the bone system and transferred to the wall of the aorta. The mechanism and pathogenesis of this Ca transference is unknown and should be investigated.

Aged↗
PubMed1991

Effect of the adrenal inhibitor trilostane on the morphology of the adrenocortical cells of Dahl salt-sensitive and Dahl salt-resistant rats.

The effects of trilostane on the adrenal cortex of Dahl salt-sensitive (DS) and Dahl salt-resistant (DR) rats were investigated morphometrically, histochemically, ultrastructurally and biochemically. The statistical analysis indicated that trilostane induced a significant increase in the adrenal weight and the surface area of cells and nuclei in the zona fasciculata (ZF) of the adrenal cortex of DS and DR rats (P less than O.OI). DS rats treated with trilostane revealed marked accumulation of large amounts of lipid droplets and a decrease in the activity of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in the ZF. Ultrastructurally, the mitochondria of the ZF in DS rats treated with trilostane revealed swelling of matrix with a loss of cristae and occasional interruption of the membranes of mitochondria. Some of them had a continuity with lipid vacuoles or SER, presenting a characteristic 'feather'-like appearance. Other characteristic findings in DS rats treated with trilostane were a marked villous proliferation of plasma membranes with numerous dense bodies, occasional coated pits, and pinocytic vesicles in the outer portion of the ZF. In DS and DR rats the plasma level of ACTH increased, and corticosterone decreased significantly (P less than O.OI) after treatment with trilostane. These morphological alterations were considered to be an expression of the inhibitory effects of trilostane on the adrenal steroidogenesis in DS and DR rats, more especially in DS rats. Simultaneously there were confirmed morphological alterations in the cells of the ZF, reflecting the feedback stimulation of endogenous ACTH. The cells of the ZF of DS rats were more responsive to suppression by trilostane than those of DR rats.

3-Hydroxysteroid Dehydrogenases↗
PubMed1991

Relationship between blood pressure and left ventricular mass in male patients with essential hypertension.

We performed retrospective study of the relationship between the severity and duration of hypertension and echocardiographically-detected left ventricular hypertrophy (echo-LVH) in patients with untreated essential hypertension. The subjects consisted of 92 untreated essential hypertensives who were observed for more than 5 years from the onset of diastolic hypertension (greater than or equal to 95 mmHg), and whose left ventricular (LV) mass index was measured at the end of the observation period. On the basis of the frequency of diastolic hypertension during the observation period, the population was categorized in 3 groups. In Group I (32 cases), diastolic hypertension was observed in more than 80% of blood pressures obtained throughout the entire observation period. In Group II (38 cases), diastolic hypertension was observed in 33 to 80% of the observation period. In Group III (22 cases), diastolic hypertension was observed in less than 33% of the observation period. The average diastolic blood pressure during the entire observation period in each group were 101.0, 96.0, and 90.7 mmHg in groups I, II, and III, respectively. The LV mass index was significantly higher in groups I (114.6 g/m2) and II (105.3 g/m2) than in group III (90.7 g/m2) (p less than 0.01). The prevalence of echo-LVH (more than 121 g/m2) was 34.4%, 18.4%, and 4.8% in groups I, II, and III, respectively. The average diastolic blood pressure in patients with echo-LVH (99.3 +/- 5.1 mmHg) was significantly higher than in patients without echo-LVH (95.7 +/- 4.7 mmHg). We concluded that the degree and duration of diastolic pressure elevation are closely correlated to the LV mass index.

Blood Pressure↗
PubMed1990

The influence of glycosylation on the fate of renin expressed in Xenopus oocytes.

It has been recently reported that, in Xenopus oocytes injected with the mRNA for human renin, this secretory renal glycoprotein acquires phosphomannosyl residues on its asparagine-linked oligosaccharide chains, remains intracellular and undergoes a proteolytic cleavage which removes the prosegment. To understand the influence of glycosylation on the fate of renin in Xenopus oocytes and whether it is specific for human renin, we have expressed human renin and mouse Ren1 renin, which are glycosylated at two and three selected asparagine residues, respectively, and mouse Ren2 renin, which is not glycosylated, in Xenopus oocytes. The majority of human and Ren1 renins remained intracellular and underwent proteolytic cleavage, whereas mouse Ren2 renin was secreted efficiently. When human and Ren1 renins were expressed in oocytes treated with tunicamycin, both were secreted efficiently. A mutant of human renin, which had amino-acid substitutions at both glycosylation sites, was also secreted efficiently, whereas that mutated at one of the two sites was not. These results indicate that the majority of all of the glycosylated renin molecules remain intracellular and undergo proteolytic cleavage, probably due to the acquisition of phosphomannosyl residues, and the human renin remains intracellular if it is only glycosylated at one of the two sites.

Amino Acid Sequence↗
PubMed1990

A processing enzyme for prorenin in mouse submandibular gland. Purification and characterization.

Renin is produced from an inactive precursor, prorenin, through proteolytic cleavage at paired basic amino acid residues. In this study, an enzyme which specifically cleaves mouse Ren 2 prorenin at the paired basic residues has been purified from mouse submandibular gland by CM-Toyopearl chromatography, antipain-Sepharose chromatography, and isoelectric focusing. This enzyme, named prorenin converting enzyme, consists of two polypeptide chains of 17 and 10 kDa. The enzyme has an isoelectric point of 9.5-9.8, and its pH optimum is between 7.5 and 8.5. It specifically cleaves the peptide bond on the carboxyl side of the Arg at the Lys-Arg pair of mouse Ren 2 prorenin to yield mature renin but does not cleave mouse Ren 1 and human prorenins. Studies on the effects of inhibitors indicate that this enzyme is a serine protease that differs from the enzymes processing other prohormones at paired basic amino acid residues.

Amino Acid Sequence↗
PubMed1990

Suppression of exercise-induced ventricular arrhythmias by propranolol and diltiazem in a woman without organic heart disease--a case report.

A thirty-five-year-old woman without organic heart disease who has exercise-induced ventricular arrhythmias suppressed by propranolol and diltiazem is reported. Treadmill exercise provoked reproducibly nonsustained ventricular tachycardia (NSVT) and salvos of ventricular premature contraction (VPC). QRS morphology of these ventricular arrhythmias showed left bundle branch block pattern and right axis deviation. Oral propranolol (20 mg) and diltiazem (90 mg) prevented exercise provocation of NSVT and VPC. However, oral mexiletine (200 mg) and procainamide (500 mg) could not prevent exercise provocation of these ventricular arrhythmias. No ventricular arrhythmias could be induced by any form of ventricular extrastimulations. Right ventricular pacing at a rate of 210 beats/minute provoked NSVT of which the QRS morphology was similar to that of exercise-induced NSVT. Triggered activity may be a possible electrophysiologic mechanism for exercise-induced ventricular arrhythmias in this patient, although other mechanisms such as reentry and enhanced automaticity could not be completely excluded.

Adult↗