Effects of ryanodine on cardiac contraction, excitation-contraction coupling and "Treppe" in the conscious dog

The effects of ryanodine on left ventricular (LV) function and hemodynamics were studied in 16 conscious dogs, chronically instrumented for measurements of LV pressures and dimensions. Systemic infusion of ryanodine (0.5-4 micrograms/kg i.v.) resulted in a dose-dependent depression of cardiac contraction. For example, ryanodine, 4 micrograms/kg i.v., decreased LV fractional shortening by 30.5 +/- 4.1%, LV dP/dt by 41.5 +/- 4.0% and Vcfc by 37.8 +/- 4.1%, while increasing the isovolumic relaxation time constant, tau, from 23.1 +/- 1.4 to 34.1 +/- 3.6 ms without a major effect on preload or afterload. Ryanodine also depressed (P < 0.05) the plateau phase of the mechanical restitution and post-extrasystolic potentiation responses, indicating a direct effect on excitation-contraction coupling. The heart rate dependent positive staircase ("Treppe") was significantly enhanced (P < 0.05) after ryanodine infusion, i.e. LV dP/dt rose by 43.1 +/- 4.7% with an increase in heart rate from 150 to 240 beats/min in the presence of ryanodine 4 micrograms/kg, but by only 7.5 +/- 2.1% without ryanodine. The more pronounced "Treppe" in the conscious dog under the condition of impaired SR calcium release caused by ryanodine, supports the concept that the classical Bowditch "Treppe" reflects either a state of myocardial depression due to alteration in SR calcium handling, or enhanced availability of trans-sarcolemmal Ca2+ influx. This finding may help to understand the discrepancy in the importance of the "Treppe" between conscious animals and more isolated preparations.

Renoprotective effect of enalapril in uninephrectomized spontaneously hypertensive rats with neonatal streptozotocin-induced diabetes

We compared the renoprotective effect between angiotensin-converting enzyme inhibitor, enalapril, and a dihydropyridine-type calcium channel blocker, nicardipine, in a severe form of renal injury in rats. Two-day-old spontaneously hypertensive rats (SHR) were injected with streptozotocin or vehicle as control. UNX was performed at 3 weeks of age, and enalapril or nicardipine was administered in drinking water from 7 weeks of age. Uninephrectomy (UNX) markedly exacerbated hypertension and renal injury in the nondiabetic and diabetic SHR. Enalapril and nicardipine comparably reduced blood pressure in UNX diabetic SHR. However, serum creatinine was significantly elevated in the nicardipine-treated group as compared with the enalapril-treated group at 24 weeks of age (nicardipine-treated group, 67 +/- 4 microM; enalapril-treated group, 49 +/- 3 microM; P < 0.01; untreated group 57 +/- 4 microM). Furthermore, the incidence of glomerular sclerosis was similar between untreated and nicardipine-treated groups, whereas it tended to be reduced in the enalapril-treated group. In a separate experiment of diabetic SHR without UNX, enalapril therapy significantly ameliorated hyperglycemia and albuminuria (P < 0.01). This study showed that a renoprotective effect was seen in enalapril but not in nicardipine in UNX diabetic SHR despite the comparable reduction of blood pressure. This suggests that enalapril may be more effective than nicardipine in delaying the progression of a severe form of diabetic nephropathy.

Effects of maternal diabetes on blood pressure and glucose tolerance in offspring of spontaneously hypertensive rats: relation to birth weight

1. We studied the effects of maternal diabetes on blood pressure and glucose tolerance in the adult female offspring of spontaneously hypertensive rats. 2. Female spontaneously hypertensive rats were rendered diabetic by neonatal streptozotocin treatment, and then were mated with untreated male spontaneously hypertensive rats. Moderately severe hyperglycaemia was maintained during the gestation. 3. The birth weight was significantly lower in the female offspring of the diabetic dams than in the female offspring of the non-diabetic dams. The systolic blood pressure was significantly higher in the offspring from the diabetic dams than that from the control dams at 6 months of age (192 +/- 4 mmHg versus 213 +/- 4 mmHg, P < 0.01). The heart weight was also significantly increased in the offspring of the diabetic dams. Both the blood pressure and heart weight were inversely related to the birth weight. On the other hand, glucose tolerance was unaffected by maternal diabetes. 4. Maternal diabetes aggravated the severity of hypertension in the adult female offspring of spontaneously hypertensive rats. This suggests the importance of the metabolic environment during fetal growth for the development of hypertension.

Transthoracic visualization of pulmonary thrombus that mimicked left atrial thrombus. A case report

A forty-five-year-old woman with an unusual case of primary pulmonary hypertension is presented. She showed a progressive dilatation of the pulmonary arteries and pulmonary thrombus over twenty-one years. Transthoracic echocardiography showed the presence of pulmonary arterial thrombus that mimicked left atrial thrombus. However, when the transducer was rotated clockwise to obtain the short-axis view, a thrombus was observed in the right pulmonary artery with spontaneous echo contrast. Although the visualization of pulmonary arterial thrombus by echocardiography has been quite limited, it would be worthwhile since patients with primary pulmonary hypertension may have enlarged pulmonary arteries, as observed in the present case.

Pharmacokinetic study of trimethadione and its metabolite in blood, liver and brain by microdialysis in conscious, unrestrained rats

A microdialysis method has been developed in the past two decades to determine levels of drug and endogenous compounds in several organs under physiological conditions. In this study, we determined the pharmacokinetics of the model drug, trimethadione (TMO), and its only metabolite, dimethadione (DMO), in liver, blood and brain by the microdialysis method in freely-moving rats. Sampling times were extended up to 24 hours. The construction of a newly developed microdialysis probe for liver and blood is described. The elimination patterns of TMO in liver, blood and brain dialyzates were almost identical and the calculated t1/2 was approximately 3 hr in each sample. However, in brain, tmax was delayed compared with the others while the relative concentration of DMO (AUC0-24h) was lower in brain compared with liver and blood. These studies suggest that this concurrent and successive microdialysis sampling method will not only be a useful tool for pharmacokinetic and drug metabolism studies in the organs of small animals but will also decrease the number of experimental animals needed for a study.

Posterior hypothalamic control of rabbit tracheal tension and involvement of central histaminergic neurons

The hypothalamus is involved in the control of the cardiovascular system, but airway tone is less well defined. In the posterior hypothalamus, histaminergic neuronal cell bodies are located. Effects of electrical stimulation in the posterior hypothalamus on tracheal tension and the cardiovascular system were examined in anesthetized, paralyzed and artificially ventilated rabbits. Tracheal tension was determined from pressure exerted on a balloon inserted in the trachea and measured by a pressure transducer. Electrical stimulation of the posterior hypothalamus caused tracheal tension to decrease, arterial blood pressure to increase, and mild tachycardia followed by bradycardia. The tracheal tension decrease induced by posterior hypothalamic stimulation was not affected by atropine nor by transection of either the superior laryngeal nerve or the vagus nerve, but was depressed by adrenoceptor blockade. Tracheal tension decrease was also reduced by pyrilamine, a histamine H1-receptor antagonist, administered into the fourth ventricle, but was not affected by cimetidine, a histamine H2-receptor antagonist. The stimulation sites where these effects were evoked were interspersed among the loci of histamine immunoreactive cell bodies previously reported. Results suggest that posterior hypothalamic neurons decrease tracheal tension through the sympathetic nervous system, and involve the histaminergic neurons in this route.

Left ventricular performance during exercise testing in patients with silent and symptomatic myocardial ischemia

We compared cardiohemodynamic response to dynamic exercise in 32 patients with exercise-induced silent or symptomatic myocardial ischemia. All patients had coronary artery disease without prior myocardial infarction and left ventricular hypertrophy. Patients underwent supine leg-exercise testing and received right heart catheterization. All patients exhibited ischemic ST-segment depression on electrocardiogram during exercise testing. They were classified retrospectively into two groups according to the absence (n = 10, group 1) or presence (n = 22, group 2) of chest pain induced by exercise. There was no significant difference between groups in the magnitude of peak ST-segment depression. Pulmonary artery wedge pressure at peak exercise was significantly lower (p < 0.01), and the cardiac index was significantly higher (p < 0.01), in group 1 versus group 2. Our results indicate that exercise-induced left ventricular dysfunction is less severe in patients with silent myocardial ischemia than in those with symptomatic ischemia.

A new model of diabetic pregnancy with genetic hypertension: pregnancy in spontaneously hypertensive rats with neonatal streptozotocin-induced diabetes

OBJECTIVE

We designed this study to develop a new animal model of high-risk pregnancy complicated by hypertension and diabetes mellitus.

STUDY DESIGN

Female spontaneously hypertensive rats were injected intraperitoneally with 75 mg/kg streptozotocin or vehicle as control at 2 days of age. They were mated with untreated male spontaneously hypertensive rats at 4 to 5 months of age.

RESULTS

Hyperglycemia, defined as > 20 mmol/L plasma glucose level, was maintained during pregnancy in streptozotocin-treated spontaneously hypertensive rats, and systolic blood pressure was significantly higher in the streptozotocin-treated group than in controls before delivery (p < 0.01). Furthermore, urinary albumin excretion was significantly increased in the streptozotocin-treated group during and after pregnancy compared with the prepregnant level (p < 0.05), whereas in controls it remained unchanged. The incidence of low birth weight was significantly higher in male neonates from streptozotocin-treated mothers than those from control mothers (p < 0.05).

CONCLUSION

Neonatally streptozotocin-treated spontaneously hypertensive rats may be useful for studying the combined effect of hypertension and diabetes mellitus during pregnancy.

Differential effects of dobutamine and a phosphodiesterase inhibitor on early diastolic filling in patients with congestive heart failure

OBJECTIVES

This study was designed to compare the influence of beta-adrenergic stimulation (dobutamine) and a selective phosphodiesterase inhibitor (MS-857) on left ventricular diastolic performance and Doppler transmitral flow velocity patterns in patients with congestive heart failure and to elucidate the mechanisms for changes in early diastolic filling induced by each agent.

BACKGROUND

Both beta-adrenergic agonists and phosphodiesterase inhibitors act through the cyclic adenosine monophosphate pathway. However, it is controversial whether they have similar effects on diastolic performance. No previous studies have investigated the effects of these agents on Doppler-derived measurements of diastolic filling. We hypothesized that they would have different effects on early diastolic filling in patients with congestive heart failure.

METHODS

Twenty patients with chronic congestive heart failure resulting from idiopathic dilated cardiomyopathy were randomized to receive intravenous infusion of dobutamine (5 micrograms/kg body weight per min, n = 10) or oral administration of MS-857 (15 mg, n = 10). Transmitral flow velocity patterns were obtained with simultaneous recordings of pressure-volume loops using a conductance catheter with a micromanometer tip before and after drug administration.

RESULTS

Left ventricular filling pressure was reduced by both agents. Dobutamine decreased the time constant of isovolumetric relaxation and increased the difference between pulmonary artery wedge pressure at the peak of the v wave and left ventricular minimal pressure (10 +/- 3 to 12 +/- 4 mm Hg, p < 0.01) and peak early filling velocity (47 +/- 7 to 56 +/- 11 cm/s, p < 0.01). The diastolic pressure-volume relation showed a leftward shift in all patients. In contrast, MS-857 did not affect the time constant but maintained the pressure difference (9 +/- 3 to 8 +/- 3 mm Hg, p = NS) and peak early filling velocity (50 +/- 7 to 49 +/- 12 cm/s, p = NS). The diastolic pressure-volume relation after MS-857 showed a downward shift in most patients.

CONCLUSIONS

These results indicate that beta-adrenergic stimulation and phosphodiesterase inhibitors have different effects on early diastolic filling through different mechanisms in patients with congestive heart failure.

Effect of maternal diabetes on longevity in offspring of spontaneously hypertensive rats

We studied the effect of maternal diabetes induced by neonatal streptozotocin treatment on the longevity of the male offspring in spontaneously hypertensive rats (SHR). Maternal diabetes significantly decreased the survival in the offspring as compared with the control (p < 0.01). Mean age at death was 14.9 +/- 0.6 months in the offspring from the diabetic dams and 17.9 +/- 1.1 months in that from the control. The life span was significantly correlated with the birth weight (rs = 0.55, p = 0.009). These findings suggest that a diabetic pregnancy may accelerate an age-related degenerative process of the offspring in SHR.

Influence of left ventricular hypertrophy on left ventricular function during dynamic exercise in the presence or absence of coronary artery disease

OBJECTIVES

We investigated the influence of left ventricular hypertrophy in the presence or absence of coronary artery disease on hemodynamic characteristics during exercise in subjects without previous myocardial infarction.

BACKGROUND

Left ventricular hypertrophy has been found to increase the vulnerability of the myocardium to the development of ischemia. However, the independent influences of left ventricular hypertrophy and coronary artery disease have not been assessed in humans.

METHODS

Symptom-limited supine leg exercise tests were performed by 78 patients. They were classified into the following subgroups: no coronary artery disease or left ventricular hypertrophy (group I, n = 30), left ventricular hypertrophy only (group II, n = 12), coronary artery disease only (group III, n = 20) and both left ventricular hypertrophy and coronary artery disease (group IV, n = 16). Mean left ventricular mass index was 105, 158, 109 and 159 g/m2 in groups I to IV, respectively.

RESULTS

Pulmonary artery wedge pressure increased from 6 +/- 3 (mean +/- SD) mm Hg at rest to 10 +/- 5 mm Hg at peak exercise in group I, from 8 +/- 2 to 18 +/- 8 mm Hg in group II (p < 0.05 vs. group I), from 6 +/- 3 to 23 +/- 6 mm Hg in group III (p < 0.01 vs. group I) and from 8 +/- 4 to 30 +/- 7 mm Hg in group IV (p < 0.01 vs. group I; p < 0.01 vs. group II; p < 0.05 vs. group III). Multiple regression analysis showed that the number of diseased coronary vessels and left ventricular mass index were independent predictors of peak pulmonary artery wedge pressure (F = 59.2 and 19.1, respectively; multiple correlation coefficient r = 0.74, p < 0.0001).

CONCLUSIONS

Left ventricular hypertrophy and coronary artery disease independently increased left ventricular filling pressure during supine leg exercise. Severe left ventricular dysfunction was induced by exercise when both conditions were present.

Left ventricular function in asthmatic children chronically treated with theophylline evaluated by exercise Doppler echocardiography

To evaluate the chronic effects of theophylline on cardiac function, M-mode and pulsed Doppler derived variables were measured at rest and the suprasternal continuous wave Doppler measurement of ascending aortic flow was used during treadmill exercise testing. Subjects consisted of 13 children with stable asthma (mean 11.7 +/- 2.2 years) who were treated with theophylline for at least one year and 16 age-matched, untreated normal volunteers. In the resting state, the chronic administration of theophylline seemed to produce a slight increase in percent fractional shortening, outflow peak velocity and atrial contribution to ventricular filling in the asthmatic children as compared to normals, but these changes were not statistically significant. The asthmatic children showed significantly lower values than the controls in exercise induced changes in the peak velocity, stroke index and cardiac index, but not in the heart rate. Therefore, chronic administration of theophylline appears to have a minimal effect on resting cardiac function, but a possibly deleterious effect on the cardiac response to exercise testing.

Circadian blood pressure variation in non-insulin-dependent diabetes mellitus with nephropathy

We studied a circadian blood pressure variation in relation to the progression of diabetic nephropathy in patients with non-insulin-dependent diabetes mellitus (NIDDM). Age, duration of diabetes, body mass index and glycemic control did not differ among the groups of patients with normo-, micro- and macroalbuminuria. None of the patients received antihypertensive drugs. There were no differences in renal and autonomic functions between normo- and microalbuminuric groups, but these functions were impaired in the macroalbuminuric group. The rise in blood pressure was more apparent in 24-h ambulatory blood pressure (AMBP), especially during night-time, as compared with casual blood pressure. Such blood pressure rise was in accordance with the progression of nephropathy. However, pulse rate did not differ among the three groups. The nocturnal fall in blood pressure was blunted in the micro- and macroalbuminuria groups, but evident in the normoalbuminuric group. In the latter, daytime systolic blood pressure (SBP) was significantly higher than night-time SBP (123 +/- 5 mmHg vs. 113 +/- 3 mmHg, P = 0.002). In contrast, in the former two groups of patients, there were no significant differences in SBP between daytime and night-time (134 +/- 9 mmHg vs. 134 +/- 9 mmHg, ns, for microalbuminuria and 159 +/- 8 mmHg vs. 165 +/- 7 mmHg, ns, for macroalbuminuria). Urinary albumin excretion was significantly correlated with night-time SBP (r = 0.48, P = 0.015), but not with daytime SBP (r = 0.30, ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Early detection of successful coronary reperfusion based on serum myoglobin concentration: comparison with serum creatine kinase isoenzyme MB activity

The usefulness of serum myoglobin (Mb) concentration for early detection of successful reperfusion was compared with that of creatine kinase isoenzyme MB (CKMB) activity in 49 patients with acute myocardial infarction. To determine accurately the time of reperfusion, we performed coronary angiography every 5 minutes during reperfusion therapy. Reperfusion was obtained in 32 patients (reperfused group) but not in 17 patients (nonreperfused group) until 60 minutes after the initiation of reperfusion therapy. Blood samples were taken before and 15, 30, and 60 minutes after the angiographic confirmation of reperfusion in the reperfused group. In the nonreperfused group, samples were taken before and 15, 30, and 60 minutes after the initiation of treatment. We calculated the Mb ratio (value after reperfusion or treatment initiation to value before) and CKMB ratio (value after to value before). When values > 2.4 for the Mb ratio or > 2.0 for the CKMB ratio were used as the criteria for reperfusion within 60 minutes after initiation of treatment, the sensitivities were 91% and 56% at 15 minutes after reperfusion, 97% and 84% at 30 minutes, and 100% and 100% at 60 minutes, respectively. For each ratio the specificity of detection was 100% at all times evaluated. Thus the Mb ratio accurately detected the success of reperfusion as early as 15 minutes after reperfusion and may be more useful than the CKMB ratio for detecting the success of reperfusion within 30 minutes.

Hemodynamic effects of the calcium channel blocker pranidipine on exercise-induced angina

Hemodynamic effects of a newly developed calcium channel blocker, pranidipine, on dynamic exercise-induced angina were investigated. Ten patients with stable effort angina pectoris underwent symptom-limited bicycle ergometer exercise testings before and after a single oral administration of pranidipine, and effects of pranidipine on systemic, cardiac and coronary hemo-dynamics induced by dynamic exercise were evaluated invasively. Pranidipine administration reduced systemic vascular resistance (from 1,764 +/- 109 to 1,115 +/- 60 dynes.sec/cm5; p < 0.01 at test, and from 1,120 +/- 102 to 795 +/- 62 dynes.sec/cm5; p < 0.05 at peak exercise) and mean arterial pressure (from 93 +/- 5 to 76 +/- 3 mmHg; p < 0.01 at test, and from 85 +/- 7 to 72 +/- 6 mmHg; p < 0.05 at peak exercise) with the increase in heart rate and cardiac index throughout exercise. Pranidipine also decreased coronary vascular resistance from 1.29 +/- 0.21 to 0.89 +/- 0.17 mmHg/ml/min (p < 0.05) at resting condition. At peak exercise, rate-pressure product and myocardial oxygen consumption decreased (from 237 +/- 21 to 215 +/- 18 x 10(2); p < 0.05, and from 31.3 +/- 7.5 to 21.7 +/- 3.9 ml/min; p < 0.05, respectively), while coronary vascular resistance did not change significantly. Furthermore, pranidipine mitigated ST-segment depression and elevation of pulmonary artery wedge pressure at peak exercise (from 0.20 +/- 0.03 to 0.13 +/- 0.02 mV; p < 0.01, and from 25 +/- 3 to 11 +/- 2 mmHg; p < 0.01, respectively). These results suggest that the major therapeutic effects of pranidipine for dynamic exercise-induced angina would be to reduce myocardial oxygen demand by improving peripheral circulation and reducing preload and afterload.(ABSTRACT TRUNCATED AT 250 WORDS)

Susceptibility to neonatal streptozotocin-induced diabetes in spontaneously hypertensive rats

We studied the difference in the susceptibility to neonatal streptozotocin (STZ) diabetes between spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Two-day-old female SHR and WKY were injected intraperitoneally with 75.0 mg/kg of STZ or vehicle for control. Hyperglycemia developed in both strains at 4 days of age, but SHR were more hyperglycemic. Overt hyperglycemia developed in SHR with aging after a partial recovery from initial hyperglycemia at 10 days of age, whereas WKY did not develop significant hyperglycemia except shortly after STZ treatment. Percentage of insulin-positive B cells in total islet cells and pancreatic immunoreactive insulin (IRI) content were measured at 4 days, 10 days, 4 weeks, and 12 weeks of age. B cells per islet and pancreatic IRI content were significantly reduced in STZ-treated groups as compared with control in both SHR and WKY at 4 days of age, but later they increased significantly with aging in both strains. However, the reduction in pancreatic IRI content relative to control was significantly greater in SHR than in WKY from 4 days (-94.5 +/- 3.5%, -84.1 +/- 4.8%; p < 0.01) to 12 weeks (-97.1 +/- 2.1%, -28.0 +/- 2.5%; p < 0.05), and the reduction in B cells per islet was also greater in SHR at 4 weeks of age. These results indicated that the initial destruction of pancreatic B cells induced by STZ was greater, and the following regeneration was less in SHR than in WKY. The association of the susceptibility to neonatal STZ diabetes with the development of genetic hypertension in SHR remained to be elucidated.

Central mediation of tracheal pressure through H1 and H2 receptors after histamine administration to the fourth ventricle of anesthetized rabbit

Administration of 1.5, 5.0 and 15 nmol histamine (HA) into the fourth ventricle (IVth) decreased tracheal pressure (PT) dose-dependently in anesthetized rabbits. Maximum decrease of PT occurred 0.9 +/- 0.1 min (mean +/- S.E.M., n = 9) after administration of 15 nmol, and recovery occurred at 4.5 +/- 1.0 min (n = 9). The decrease of PT was blocked by the H1 receptor antagonist, pyrilamine administration into the IVth, or intravenous injection of the alpha-adrenoceptor antagonist, phentolamine. Recovery from the PT decrease was delayed by the H2 receptor antagonist, cimetidine. The results suggest that HA centrally decreases PT through H1 receptors, which action is mediated by the sympathetic nervous system, and this decrease may be modulated through H2 receptors.

Effect of aging on glucose tolerance in spontaneously hypertensive rats

We studied the age-related changes of glucose tolerance in female spontaneously hypertensive rats (SHR) that did not become obese with aging. Oral glucose tolerance test was performed in young (3 months), middle-aged (6 to 11 months), and aged (26 months) SHR. Fasting plasma glucose was significantly lower in aged SHR than in young SHR. The increase in plasma glucose after glucose administration over fasting level was significantly higher in aged SHR than in middle-aged SHR, but did not differ between young and aged rats. Pancreatic islet size and pancreatic immunoreactive insulin content were similar between young and aged SHR. The present study demonstrated that glucose tolerance did not deteriorate in SHR with aging, while genetic hypertension persisted. This suggests that the persistence of hypertension per se may not affect glucose tolerance in SHR.

Spontaneous remission of diabetes arrests progression of nephropathy in streptozotocin-treated spontaneously hypertensive rats

Although antihypertensive therapy retards the progression of diabetic nephropathy associated with hypertension, it is not known whether glycemic control reverses or arrests diabetic nephropathy under untreated hypertension. We previously reported that spontaneous remission of diabetes occurred in the neonatal streptozotocin (STZ) model of spontaneously hypertensive rats (SHR) after 28 weeks of age, whereas hypertension persisted. Thus, we studied diabetic nephropathy before and after the recovery from hyperglycemia in this model. Two-day-old male SHR were injected intraperitoneally with STZ or vehicle for control. Hypertension was developed and maintained in both STZ and control groups in a similar degree. Before the amelioration of hyperglycemia, urinary albumin excretion increased progressively in STZ-treated SHR as compared with control (24 weeks; 1.6 +/- 0.5 mg/day, 17.5 +/- 2.3 mg/day, P < 0.001), and renal and glomerular hypertrophies were seen with mesangial expansion in STZ-treated SHR. However, along the recovery from hyperglycemia, urinary albumin excretion did not increase in the STZ-treated group, while it consistently increased in the control group (52 weeks; 25.4 +/- 10.0 mg/day, 29.7 +/- 11.4 mg/day, not significant). Furthermore, there were no significant differences in renal weight, glomerular tuft area, and the incidence of glomerular sclerosis between the two groups at 52 weeks of age. This study suggests that glycemic control may be effective for diabetic nephropathy even in the coexistence of untreated hypertension.

Age-related changes in left and right ventricular filling velocity profiles and their relationship in normal subjects

To confirm age-related changes in left and right ventricular filling velocity profiles and to compare left and right ventricular filling parameters in normal subjects, we performed pulsed Doppler echocardiographic studies in 108 normal subjects (72 men and 36 women) aged 15 to 78 years. An age-related decrease in peak early velocity (E velocity), an increase in peak atrial velocity (A velocity), and augmented ratio of A velocity to E velocity (A/E) were observed in left ventricle (r = -0.71, 0.63, and 0.83, respectively). Similar age-related changes were found in right ventricle (r = -0.71, 0.54, and 0.78). Aging had a greater effect on the filling of the left ventricle than the right one (i.e., a steeper slope). The difference between left and right ventricular filling increased with advancing age. Left ventricular filling indexes exceeded those of the right ventricle. Significant correlations were observed between the right and left ventricular filling parameters (r = 0.58 to 0.90). A strong relation was noted in A/E (r = 0.90). There was no significant relation between age and left ventricular mass. The left ventricular mass appeared to have little effect on left and right ventricular filling in normal individuals. Thus in clinical studies the age-related decrease in early diastolic filling and the increased atrial filling in both left and right ventricles should be considered. The atrial contribution to ventricular filling may be more pronounced in the left ventricle than the right ventricle in older subjects.

Abnormal postexercise systolic blood pressure response is a good indicator of impaired left ventricular filling during supine cycle ergometer exercise in patients with coronary artery disease

To determine whether the postexercise systolic blood pressure (SBP) response is a useful marker of left ventricular filling abnormalities, supine leg exercise testing was conducted in 14 control subjects and 70 patients with coronary artery disease (CAD). An abnormal postexercise SBP response (the ratio of SBP after 3 min of recovery to the peak exercise SBP) was defined as 0.85 or more, which represented the cutoff point with the highest sensitivity and specificity for prediction of pulmonary artery wedge pressure (PAWP) of at least 20 mmHg at peak exercise in CAD patients. There was a significant difference between the SBP ratios of the two groups (Control, 0.72 +/- 0.05; CAD, 0.86 +/- 0.13; p < 0.01). There was no significant difference between the PAWP of the two groups at rest, but the PAWP at peak exercise was significantly higher in the CAD group (20.2 +/- 8.9 mmHg) than in the control group (11.5 +/- 4.0 mmHg)(p < 0.01). PAWP at peak exercise was > or = 20 mmHg in 35 (50%) of the 70 CAD subjects. The SBP ratio was significantly correlated with PAWP at peak exercise (r = 0.67, p < 0.01) in the CAD group, but not in the control group. An SBP ratio of > or = 0.85 showed a sensitivity of 80% and a specificity of 80% for predicting a peak exercise PAWP of > or = 20 mmHg in CAD patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A new diabetes model induced by neonatal alloxan treatment in rats

Rats treated with streptozotocin (STZ) during the neonatal period have been used as a model of non-insulin-dependent diabetes mellitus. The present study was designed to produce another diabetes model by substituting alloxan for STZ. Male Sprague-Dawley rats of 2, 4 or 6 days of age were injected intraperitoneally with 200 mg/kg of alloxan monohydrate after 16 h fast. Control rats received vehicle alone at 6 days of age. Non-fasting plasma glucose levels in alloxan-treated rats significantly increased after 8 weeks as compared with control, as the age of alloxan treatment advanced (6.6 +/- 0.2 (S.E.M.) mM in control, 8.3 +/- 0.3 mM in 2 days, P < 0.05, 9.8 +/- 0.9 mM in 4 days, P < 0.05, 17.1 +/- 3.5 mM in 6 days, P < 0.05). For the long-term observation, alloxan-treated rats were divided into mild and severe diabetes groups. Hyperglycemia persisted in both groups until 52 weeks (6.5 +/- 0.1 mM in control, 10.3 +/- 0.7 mM in mild diabetes group, 25.3 +/- 3.6 mM in severe group), but significant albuminuria developed only in severe diabetes group. The diabetogenicity of alloxan rapidly increased during the neonatal period, and the neonatal alloxan diabetes model may be useful for studying chronic diabetic complications.