Effect of insulin in combination with selenium on blood glucose and PI3K-mediated GLUT4 expression in skeletal muscle of streptozotocin-induced diabetic rats.

OBJECTIVES: We evaluated the effect of low doses of insulin (1 U/kg/day) and selenium (180 microg/kg/day) in combination on general physiological parameters, and on PI3K and GLUT4 levels in skeletal muscle of streptozotocin (STZ)-induced diabetic rats. MATERIALS AND METHODS: Diabetic rats were treated with insulin, selenium, and insulin and selenium in combination for four weeks. The levels of blood glucose and hemoglobin A1c were estimated, and the levels of P13K and GLUT4 in skeletal muscle were examined by immunoblotting and immunohistochemistry. RESULTS: Insulin in combination with selenium could significantly lower blood glucose and HbAlc levels, and restore the disturbances in PI3K and GLUT4 levels in skeletal muscle. Treatment with insulin was only partially effective in the restoration of diabetic alterations. CONCLUSION: We conclude that there was cooperation between insulin and selenium, and that treatment of diabetic rats with combined doses of insulin and selenium was effective in the normalization of blood glucose and correction of altered PI3K and GLUT4 distribution in skeletal muscle of diabetic rats.

Progress in cell membrane chromatography.

Cell membrane chromatography (CMC) was first established by He et al. in 1996. A bioaffinity chromatography technique, CMC has since proven to be an important method for studying drug-receptor interactions and screening active compounds from medicinal herbs. This paper briefly reviews the characteristics of the cell membrane stationary phase (CMSP), the CMC analytical system, and its applications.

Gross and microscopic anatomy of the human intrinsic cardiac nervous system.

BACKGROUND: The extent and locations of intrinsic cardiac ganglia on the human heart were investigated to facilitate studying their function. METHODS: The locations and number of major intrinsic cardiac ganglia were determined in six human hearts by means of microdissection following methylene blue staining. Light and electron microscopic analyses were performed on right atrial and cranial medial ventricular ganglia obtained from 12 other human hearts. RESULTS: Gross anatomy: Collections of ganglia associated with nerves, i.e., ganglionated plexuses, were observed consistently in five atrial and five ventricular regions. Occasional ganglia were located in other atrial and ventricular regions. Atrial ganglionated plexuses were identified on 1) the superior surface of the right atrium, 2) the superior surface of the left atrium, 3) the posterior surface of the right atrium, 4) the posterior medial surface of the left atrium (the latter two fuse medially where they extend anteriorly into the interatrial septum), and 5) the inferior and lateral aspect of the posterior left atrium. Ventricular ganglionated plexuses were located in fat 1) surrounding the aortic root, 2) at the origins of the right and left coronary arteries (the latter extending to the origins of the left anterior descending and circumflex coronary arteries), 3) at the origin of the posterior descending coronary artery, 4) adjacent to the origin of the right acute marginal coronary artery, and 5) at the origin of the left obtuse marginal coronary artery. Microscopic anatomy: Ganglia ranged in size from those containing a few neurons to large ganglia measuring up to 0.5 x 1 mm. The human heart is estimated to contain more than 14,000 neurons. Neuronal somata varied in size and shape. Many axon terminals in intrinsic cardiac ganglia contained large numbers of small, clear, round vesicles that formed asymmetrical axodendritic synapses, whereas a few axons contained large, dense-cored vesicles. CONCLUSIONS: The human intrinsic cardiac nervous system is distributed more extensively than was considered previously, most of its ganglia being located on the posterior surfaces of the atria and superior aspect of the ventricles. Each ganglion therein contains a variety of neurons that are associated with complex synaptology.

Cardiac responses activated by nicotine in canine ganglial plexus between aorta and pulmonary artery.

In order to study the location and function of nicotine-sensitive neurons of cardiac ganglial plexuses, microdissections of collections of fat pads were carried out, and nicotine (100 micrograms) was injected into the ganglial plexus between aorta and pulmonary artery (A-PGP) in 30 anesthetized open-chest dogs. There were numerous ganglia or neurons in A-PGP. Either positive or negative inotropic and chronotropic responses were elicited following injections of nicotine into A-PGP. Control injections of 0.1 ml saline into A-PGP and injections of nicotine (100 or 200 micrograms) into right marginal ganglial plexus did not elicit any cardiac responses. After acute decentralization, nicotine (100 micrograms) was again injected into the same locus of A-PGP. Some positive and negative responses could still be induced, but their frequencies were reduced. These suggest that nicotine can directly activate the efferent parasympathetic and sympathetic neurons and indirectly activate them by stimulating the afferent neurons existing on the surface of dog heart.

Gross and microscopic anatomy of the canine intrinsic cardiac nervous system.

BACKGROUND: A three-dimensional description of the distribution and organization of the canine intrinsic cardiac nervous system was developed in order to characterize its full extent physiologically. METHODS: The anatomy of the canine intrinsic cardiac nervous system was investigated in 67 mongrel dogs by means of visualization following methylene blue staining as well as by light and electron microscopic analyses. RESULTS: Collections of ganglia associated with nerves, i.e., ganglionated plexuses, were identified in specific locations in epicardial fat and cardiac tissue. Distinct epicardial ganglionated plexuses were consistently observed in four atrial and three ventricular regions, with occasional neurons being located throughout atrial and ventricular tissues. One ganglionated plexus extended from the ventral to dorsal surfaces of the right atrium. Another ganglionated plexus, with three components, was identified in fat on the left atrial ventral surface. A ganglionated plexus was located on the mid-dorsal surface of the two atria, extending ventrally in the interatrial septum. A fourth atrial ganglionated plexus was located at the origin of the inferior vena cava extending to the dorsal caudal surface of the two atria. On the cranial surface of the ventricles a ganglionated plexus that surrounded the aortic root was identified. This plexus extended to the right and left main coronary arteries and origins of the ventral descending and circumflex coronary arteries. Two other ventricular ganglionated plexuses were identified adjacent to the origins of the right and left marginal coronary arteries. Intrinsic cardiac ganglia ranged in size from ones comprising one or a few neurons along the course of a nerve to ones as large as 1 x 3 mm estimated to contain a few hundred neurons. Intrinsic cardiac neuronal somata varied in size and shape, up to 36% containing multiple nucleoli. Electron microscopic examination demonstrated typical autonomic neurons and satellite cells in intrinsic cardiac ganglia. Many of their axon profiles contained large numbers of clear, round, and dense-core vesicles. Asymmetrical axodendritic synapses were common. CONCLUSIONS: The canine intrinsic cardiac nervous system contains a variety of neurons interconnected via plexuses of nerves, the distribution of which is wider than previously assumed.

Differential cardiac responses induced by nicotine sensitive canine atrial and ventricular neurones.

OBJECTIVE: The aim was to study the locations and functions of atrial and ventricular nicotine sensitive neurones. METHODS: In anaesthetised open chest dogs, cardiovascular effects elicited by nicotine (100 micrograms in 0.1 ml 0.9% saline), administered at specific loci of in situ atrial and ventricular ganglionated plexi, were studied before and after decentralisation. RESULTS: Cardiovascular responses were elicited when 41% of atrial and 36% of ventricular ganglionated plexus loci were studied. Subsequently, ganglia were identified adjacent to active sites. When cardiovascular responses were elicited, either tachycardia or bradycardia was induced, depending on the locus investigated. When tachycardia occurred, atrial and/or ventricular forces were augmented. When bradycardia occurred, atrial forces were suppressed. Ventricular fibrillation was induced in two animals when ventricular ganglionated plexus loci were investigated. Cardiovascular responses were not elicited when up to 2000 micrograms of nicotine were administered adjacent to intrinsic cardiac axons, indicating that responses were not primarily due to axonal effects. Control injections of saline (0.1 ml) into active loci did not elicit cardiovascular responses. Following acute decentralisation, responses initiated by nicotine were attenuated or eliminated. Depressor responses were no longer elicited following atropine administration, nor augmentor ones following propranolol administration. CONCLUSIONS: (1) The canine heart contains nicotine sensitive neurones which can induce either augmentor or depressor cardiac effects. (2) Nicotine sensitive atrial neurones modify primarily, but not exclusively, atrial tissues, whereas ventricular ones modify primarily, but not exclusively, ventricular tissues. (3) Nicotine sensitive intrinsic cardiac neurones can interact with central neurones to modulate the heart.

Cardiac responses induced by bradykinin activation of canine ganglial plexus between aorta and pulmonary artery.

To study the function of bradykinin-sensitive cardiac neurons, bradykinin (50 micrograms) was injected into the ganglial plexus between aorta and pulmonary artery (A-PGP) in 33 anesthetized open-chest dogs. Either positive or negative inotropic and chronotropic responses were elicited. Control injections of 0.1 ml saline into A-PGP and injections of bradykinin (50 or 100 micrograms) into the right marginal ganglial plexus did not elicit any cardiac response. After acute decentralization, bradykinin (50 micrograms) was again injected into the same locus of A-PGP. Some positive responses were still induced, while negative ones were completely abolished. These data suggested that bradykinin can directly activate the efferent neurons associated with sympathomimetic activation, and indirectly activate them by stimulation of afferent neurons.

Dietary sodium intake and left ventricular hypertrophy in normotensive rats.

In three different normotensive rat strains, we evaluated the effects of a large range of dietary sodium (101, 342, and 1,370 mumol Na+/g) on cardiac structure in relation to age of the rats and to changes in central hemodynamics and cardiac sympathetic neuronal activity. In young, 4-wk-old Wistar-Kyoto rats (WKY) an increase in dietary sodium induced a dose-related increase in left ventricular (LV) weight (+10 and +24% after 4 wk of 342 or 1,370 mumol Na+/g diets, respectively). Young Wistar rats also developed LV hypertrophy (+14%) on a high sodium intake, but this was less than that seen in WKY. In more mature Wistar and WKY rats, the extent of this trophic response to high sodium intake diminished. In contrast to young Wistar and WKY rats, Dahl salt-resistant rats did not show a trophic response with initiation of high sodium intake at 4 wk of age. The cardiac trophic response to dietary sodium was not associated with changes in central hemodynamics (i.e., filling pressures, cardiac output, and blood pressure). Norepinephrine turnover rate of the left ventricle tended to decrease in response to high dietary sodium intake. We conclude that food sodium can significantly increase LV weight depending on the strain and age of the rats and that this trophic response occurs independent of cardiac volume or pressure overload.

Sodium-induced cardiac hypertrophy. Cardiac sympathetic activity versus volume load.

To investigate the possible contributions of cardiac volume overload and cardiac sympathetic hyperactivity in the effects of sodium on cardiac mass, we evaluated the effects of treatment with saline (1%) and deoxycorticosterone acetate + saline (DOCA/saline) for 10 days and 3 and 6 weeks on ventricular anatomy and intracardiac pressures. Sympathetic activity in the heart and other tissues was assessed at 10 days and 3 weeks by catecholamine turnover rates and tyrosine hydroxylase activity. Both saline and DOCA/saline produced concentric left ventricular (LV) hypertrophy. Right ventricular weight showed only small increases. Saline treatment did not affect LV end-systolic pressure, whereas DOCA/saline caused a moderate increase (to 159 mm Hg). Right atrial pressure was not affected by either treatment, whereas LV end-diastolic pressure increased but only after the development of LV hypertrophy. Both saline and DOCA/saline decreased LV norepinephrine concentration; only DOCA/saline decreased norepinephrine content per LV. However, neither treatment altered the norepinephrine turnover rate constant, the absolute turnover rate, or the tyrosine hydroxylase activity. The results demonstrate that increased saline intake or DOCA/saline produces concentric LV hypertrophy without any increase in blood pressure in the case of saline and with increases in LV filling pressure following rather than preceding the appearance of LV hypertrophy. The lack of an increase in LV norepinephrine turnover and tyrosine hydroxylase activity suggests that the hypertrophy is not mediated through increased cardiac neuronal sympathetic activity.

Cardiac responses elicited by peptides administered to canine intrinsic cardiac neurons.

In order to study the effects of peptides on intrinsic cardiac neurons, substance P, bradykinin, oxytocin, calcitonin gene related peptide, atrial natriuretic peptide and vasoactive intestinal peptide were administered into canine atrial or ventricular ganglionated plexi. When substance P was injected into right atrial or cranial medial ventricular ganglionated plexi heart rate, atrial force and ventricular intramyocardial pressures were augmented. No cardiac changes occurred when similar volumes of saline (i.e., peptide vehicle) were injected into these ganglionated plexi. When bradykinin was injected into atrial or ventricular ganglionated plexi heart rate, atrial force and ventricular force were augmented in approximately 50% and depressor responses were elicited in approximately 50% of these animals. When oxytocin was injected into right atrial ventral ganglionated plexi heart rate and atrial forces were reduced in five of ten dogs studied. No cardiac changes occurred when oxytocin was injected into left atrial or ventricular ganglionated plexi. No responses were elicited when calcitonin gene related peptide, atrial natriuretic peptide or vasoactive intestinal peptide was administered into atrial or ventricular ganglionated plexi. Following acute decentralization of the heart, no significant responses were elicited by repeat administrations of substance P, bradykinin or oxytocin, implying that connectivity with central nervous system neurons was necessary for consistent responses to be elicited. It is concluded that substance P, bradykinin and oxytocin can affect neurons on the heart such that cardiodynamics are modified, these different peptides eliciting different cardiac responses.

Arterial vasodilators, cardiac volume load, and cardiac hypertrophy in normotensive rats.

To assess a possible involvement of cardiac volume overload in the development of cardiac hypertrophy during chronic arterial vasodilator treatment, changes in indexes of cardiac volume load in relation to changes in cardiac anatomy were evaluated during treatment of normotensive rats with 120 mg/l hydralazine or 120 mg/l minoxidil, with drinking water. Long-term treatment with hydralazine, but not minoxidil, caused small decreases in systolic blood pressure; neither vasodilator affected heart rate with chronic treatment. Arterial vasodilator treatment for 2 wk or more resulted in increases in plasma and blood volumes by 10-20%. Both arterial vasodilators increased right atrial pressure and left ventricular end-diastolic pressure in the initial weeks of treatment. Only the minoxidil group showed a persistent increase in right atrial pressure throughout the treatment period. These hemodynamic changes were associated with increases in left ventricular (LV) internal diameter and right ventricular (RV) weight, and with minoxidil these changes were also associated with increased LV weight. LV wall thickness did not increase. Cardiac volume overload therefore indeed occurs during treatment with arterial vasodilators and may contribute to their effects on cardiac anatomy (i.e., development of RV hypertrophy and, in the case of minoxidil, also, eccentric LV hypertrophy), which are consistent with cardiac volume overload.