A 27-year-old female with short stature and mild hearing loss was diagnosed as having focal-segmental glomerulosclerosis by renal biopsy at our hospital. One year later she developed progressive renal dysfunction and cardiac failure and was admitted again to our hospital for evaluation. Though her only neurological disorder was mild hearing loss, her short stature and elevated lactate and pyruvate values in cerebrospinal fluid suggested mitochondrial cytopathy. A muscle biopsy specimen of the left biceps brachii, using modified Gomori trichrome stain, showed a typical image of ragged-red fibers, and an increased number of giant mitochondria with paracrystalline inclusions were visible by electron microscopy. Mitochondrial DNA from the skeletal muscle showed an A-to-G transition at 3243 of transfer RNA^Leu(UUR), the common point mutation for mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes. These data confirmed the diagnosis of atypical mitochondrial cytopathy with renal and heart involvement. Mitochondrial cytopathies are often associated with hypertrophic cardiomyopathy but rarely with renal disease. Among the few reported cases with associated renal disease, most included renal tubular disorders; few cases with focal glomerular sclerosis are known. The present case of atypical mitochondrial cytopathy was characterized by a unique clinical course and rare complications with focal-segmental glomerulosclerosis.

ABSTRACT-There is no data about whether botulinum neurotoxin inhibits the parasympathetic ganglionic neurotransmission in the heart, although botulinum toxin as a clinical drug inhibits the release of acetylcholine at the neuromuscular junction. Therefore, we investigated whether botulinum toxin (type A) injected into the sinoatrial (SA) fat pad inhibits decreases in heart rate induced by stimulation of the preganglionic parasympathetic nerves in the heart of the anesthetized dog. Stimulation of the parasympathetic nerves in the SA fat pad (SAP stimulation) prolonged the atrial interval but not the atrioventricular (AV) interval, and cervical vagus nerve stimulation (CV stimulation) prolonged both atrial and AV intervals. After botulinum toxin (20 or 25 mouse units) was injected into the SA fat pad, it gradually inhibited the prolongation of the atrial interval evoked by SAP and CV stimulations but not the prolongation of the AV interval evoked by CV stimulation. Conditioning successive stimulation of the cervical vagus nerves accelerated the inhibition by botulinum toxin of the chronotropic response to CV stimulation. These results indicate that selective injection of botulinum toxin into the SA fat pad blocks bradycardia mediated by parasympathetic ganglionic activation in the dog heart.

Some parasympathetic ganglionic cells are located in the epicardial fat pad between the medial superior vena cava and the aortic root (SVC-Ao fat pad) of the dog. We investigated whether the ganglionic cells in the SVC-Ao fat pad control the right atrial contractile force, sinus cycle length (SCL), and atrioventricular (AV) conduction in the autonomically decentralized heart of the anesthetized dog. Stimulation of both sides of the cervical vagal complexes (CVS) decreased right atrial contractile force, increased SCL, and prolonged AV interval. Stimulation of the rate-related parasympathetic nerves to the sinoatrial (SA) node (SAPS) increased SCL and decreased atrial contractile force. Stimulation of the AV conduction-related parasympathetic nerves to the AV node prolonged AV interval. Trimethaphan, a ganglionic nicotinic receptor blocker, injected into the SVC-Ao fat pad attenuated the negative inotropic, chronotropic, and dromotropic responses to CVS by 33 approximately 37%. On the other hand, lidocaine, a sodium channel blocker, injected into the SVC-Ao fat pad almost totally inhibited the inotropic and chronotropic responses to CVS and partly inhibited the dromotropic one. Lidocaine or trimethaphan injected into the SAPS locus abolished the inotropic responses to SAPS, but it partly attenuated those to CVS, although these treatments abolished the chronotropic responses to SAPS or CVS. These results suggest that parasympathetic ganglionic cells in the SVC-Ao fat pad, differing from those in SA and AV fat pads, nonselectively control the atrial contractile force, SCL, and AV conduction partially in the dog heart.

Effects of a Na+/Ca2+ exchanger inhibitor, KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl] isothiourea methanesulfonate), on the sinoatrial nodal pacemaker activity, atrial contractility and ventricular contractility were investigated in the isolated and blood-perfused right atrium and left ventricle of the dog. KB-R7943 (0.03- 3 micromol) induced negative inotropic effects and negative followed by positive chronotropic effects in the right atrium and negative inotropic effects in the left ventricle. Neither atropine nor hexamethonium affected the cardiac responses to KB-R7943. Propranolol attenuated the positive chronotropic response to KB-R7943 but imipramine did not. Tetrodotoxin potentiated the positive chronotropic response to KB-R7943 in 6 of 11 isolated atria. When NaCl infusion increased atrial contractile force and atrial rate, KB-R7943-induced negative inotropic and chronotropic responses were attenuated in a dose-dependent manner. CaCl2 infusion potentiated the negative chronotropic response to KB-R7943 but did not affect the inotropic response significantly. On the other hand, ouabain (17 nmol) attenuated the negative inotropic response, but not chronotropic response, to KB-R7943. These results suggest that KB-R7943-induced cardiac effects relate to the Na+ activity, probably mediated through the Na+/Ca2+ exchanger, and the Na+/Ca2+ exchanger modifies the pacemaker activity and myocardial contractility in the dog heart.

The results suggest that activation of parasympathetic elements not located in the SA fat pad attenuates the increase in heart rate and the shift in pacemaker location evoked by sympathetic activation. The sympathetic and parasympathetic effects interact at presynaptic and postsynaptic sites in the dog heart.