Amiloride inhibition of responses of rat single chorda tympani fibers to chemical and electrical tongue stimulations

Amiloride inhibition of single fiber responses of the rat chorda tympani to ionic chemical and electrical tongue stimulations was studied. Amiloride reduced responses to both chemical and electrical stimulations with NaCl or LiCl in most of the single fibers. However, the magnitude of reduction of the response by amiloride varied among the fibers and was greater for chemical than electrical stimulation with NaCl in each fiber. Thirty-two single fibers were divided into two groups, such as 18 high (HAS) and 14 low amiloride-sensitive (LAS) fibers. Percent responses (control, 100%) of the former group to chemical stimulus with NaCl after amiloride ranged from 1.1 to 42.5%, while those of the latter from 72.8 to 108.0%. In HAS fibers, amiloride also reduced responses to KCl and CaCl2, but to a smaller degree than those to NaCl and LiCl. Fifteen out of 18 HAS fibers more strongly responded to a chemical stimulus with 0.1 M NaCl than 0.01 M HCl, while the opposite was true for 13 out of 14 LAS fibers, although the threshold concentration for NaCl was rather lower in LAS fibers than in HAS fibers. These results suggest that there exist at least two different receptor mechanisms for NaCl or LiCl which are amiloride-sensitive and -insensitive, and the observed differences in relative specificities to ionic taste stimuli and sensitivities to amiloride among rat chorda tympani fibers are possibly due to a disproportional distribution of these two receptors.     

Inhibition of inward rectifier K+ currents by angiotensin II in rat atrial myocytes: lack of effects in cells from spontaneously hypertensive rats.

We examined the effects of angiotensin II (Ang II) on inward rectifier K+ currents (IK1) in rat atrial myocytes. [125I]Ang II-binding assays revealed the presence of both Ang II type 1 (AT1) and type 2 (AT2) receptors in atrial membrane preparations. Ang II inhibited IK1 in isolated atrial myocytes with an IC50 of 46 nmol/l. This inhibition was abolished by the AT, antagonist RNH6270 but not at all by the AT2 antagonist PD123319. Treatment of cells with pertussis toxin or a synthetic decapeptide corresponding to the carboxyl-terminus of Gialpha-3 abolished the inhibition by Ang II, indicating the role of a Gi-dependent signaling pathway. Accordingly, Ang II failed to inhibit IK1 in the presence of forskolin, dibutyryl-cAMP or protein kinase A catalytic subunits. In spite of the increased binding capacities for [125I]Ang II, Ang II failed to affect IKI in cells from spontaneously hypertensive rats (SHR). AT, immunoprecipitation from atrial extracts revealed decreased amounts of Gialpha-2 and Gialpha-3 proteins associated with this receptor in SHR as compared with controls. The reduced coupling of AT, with Gialpha. proteins may underlie the unresponsiveness of atrial IK1 to Ang II in SHR cells.     

Newborn infant with maternal anti-SSA antibody-induced complete heart block accompanying cardiomyopathy.

Newborn case of maternal anti-SSA antibody-induced congenital complete heart block (CCHB) accompanying cardiomyopathy is presented. Unexpectedly, she died of ventricular tachycardia, not bradycardia, 6 days after birth. Autopsy revealed left ventricular cardiomyopathy with endocardial fibroelastosis. Thus, when evaluating fetal cardiac performance in cases of maternal anti-SSA antibody-induced CCHB, it is necessary to pay attention to myocardial attributes such as endocardial hyperplasia.     

Heterogeneity of human bone

Matched samples of bone from the lumbar spine and tibia were obtained at autopsy from three adult males who had no known evidence of metabolic bone disease at the time of their demise. The soluble noncollagenous bone proteins were quantitatively extracted from these samples and assayed for the relative content of two bone-associated proteins, osteocalcin and osteonectin. When compared to trabecular bone, cortical bone had higher levels of osteocalcin and much lower levels of osteonectin. When concentration is expressed per gram of dried bone, the osteocalcin excess in cortical bone ranged from 30- to 32-fold, and the osteonectin excess in trabecular bone ranged from 21- to 47-fold. These differences were significant (P less than 0.01) using analysis of variance. We conclude that the human skeleton is not homogeneous with regard to these biochemical markers and that cortical and trabecular bone are biochemically quite distinct. This implies that these two types of bone may be subject to distinct regulatory mechanisms and that global assessments of skeletal function and bone quality based upon soluble markers should be applied with caution. The data also imply that a differential assessment of skeletal performance may be possible using biochemical serum markers.     

Monitoring the protective effects of minocycline treatment with radiolabeled annexin V in an experimental model of focal cerebral ischemia.

Minocycline is an antibiotic now recognized to have antiapoptotic and antiinflammatory properties. Because of these properties, minocycline may be of benefit in reducing neuronal apoptosis from ischemia and subsequent postischemic inflammation if administered soon after a stroke. We now explore the feasibility of using (99m)Tc-annexin V, an in vivo marker of apoptosis, with SPECT to monitor the antiapoptotic effects of minocycline therapy. METHODS: CB6/F1 adult male mice underwent unilateral distal middle cerebral artery occlusion (dMCA) occlusion and were imaged and sacrificed at 1, 3, 7, or 30 d after injury. Animals were given minocycline (or vehicle) 30 min and 12 h after dMCA occlusion and then given 22.5 mg/kg twice daily for up to 7 d. Before imaging, behavioral tests were performed to evaluate the neurologic function. After imaging, brains were collected for histology and assessed for the degree of apoptosis and microglial activation. RESULTS: (99m)Tc-Annexin V uptake in injured hemispheres was significantly decreased 2- to 3-fold by minocycline at all time points. Minocyline reduced infarct size as seen histologically and improved behavioral indices as late as 30 d. Infarct volume as seen histologically correlated with radiolabeled annexin V uptake seen by SPECT. In situ fluorescent microscopy demonstrated that annexin V bound primarily to neurons at 1 and 3 d, with a shift toward microglia by 7 and 30 d. CONCLUSION: We found that minocycline significantly reduces neuronal apoptosis and infarct size and improves neurologic outcome in mice after acute focal cortical ischemia.     

Methylmercury causes diffuse damage to the somatosensory cortex: how to diagnose Minamata disease]

The first acute case of methylmercury (MeHg) poisoning by the consumption of fish arose in Minamata, Japan, in 1953. It was officially recognized and called Minamata disease (MD) in 1956. There are still arguments about the definition of MD in terms of its associated clinical symptoms and lesions even 50 years after the initial recognition of MD. Studies on this MD epidemic are reviewed along with its historical background. Since MeHg dispersed from Minamata to the Shiranui Sea, residents living around the sea had been exposed to low-dose MeHg through fish consumption for about 20 years (at least from 1950 to 1968). These chronic MeHg poisoning patients complained of paresthesia at the distal parts of their extremities and around the lips even 30 years after the cessation of exposure to MeHg of anthropogenic origin. The persisting somatosensory disorders after the discontinuation of exposure to MeHg were induced by diffuse damage to the somatosensory cortex, but not by damage to the peripheral nervous system, as previously believed. Based on these findings, symptoms and lesions in MeHg poisoning are reappraised.     

Improvement in Wound Healing by Epidermal Growth Factor (EGF) Ointment. I. Effect of Nafamostat,Gabexate, or Gelatin on Stabilization and Efficacy of EGF

The healing effect of human epidermal growth factor (hEGF) on open wounds was studied in rats. No improvement in wound healing was found by topical application of EGF alone to open wound sites. We found an ointment containing EGF and a protease inhibitor, nafamostat mesilate or gabexate mesilate, or gelatin accelerated the healing rate of open wounds. Significant increases in the dry weight of the wound site granulation tissue, uronic acid (as an index of acid mucopolysaccharide) and hydroxyproline (as an index of collagen) were observed by treatment with EGF ointment containing nafamostat compared with the controls. The effects of the protease inhibitor on wound healing were dose dependent. Nafamostat was more efficient than gabexate or gelatin on wound healing. The degradation of ¹²⁵I-EGF in wound tissue homogenate was significantly decreased in the presence of a protease inhibitor, such as nafamostat or gabexate, or gelatin. These findings indicate that the stabilization of EGF at the wound site is an important factor in permitting the expression of its healing effects and suggest that the ointment containing EGF and a stabilizing agent would be a suitable dosage form for acceleration of wound repair.     

Radiographic evaluation of periapical status and prevalence of endodontic treatment in an adult Japanese population.

OBJECTIVES: To determine the prevalence of periapical radiolucencies and endodontic treatment in an adult Japanese population. STUDY DESIGN: Periapical status and length of root fillings of 672 adult patients attending Okayama University Hospital of Dentistry were evaluated using full mouth intraoral radiographs. RESULTS: Overall, 87% of the subjects had root-filled teeth, and 70% exhibited an apical radiolucency. Of the 16,232 teeth examined, 21% had been root-filled, and, of these, 40% exhibited an apical radiolucency. Root-filled teeth that were overfilled or that were mandibular incisors had the highest prevalence of apical radiolucencies. CONCLUSIONS: The prevalence of root-filled teeth appears higher in this Japanese population than in Europe or America; however, the ratio of teeth with an apical radiolucency to root-filled teeth was within the range of that reported for other countries. Overfilled teeth and mandibular incisors are most likely to exhibit apical radiolucencies.     

Intraperitoneal high-dose cisplatinum chemotherapy (CDDP-ip) in patients with carcinomatous peritonitis

Immediately after CDDP-ip, the level of free Pt in ascites reached nearly 100 micrograms/ml, and the AUC (area under the curve) for ascites was 20-140 times greater than that for serum. The free Pt in serum following CDDP-ip administration was detected for several hours, and interestingly, the AUC for serum after ip therapy was 0.4-2.2 times greater than that after iv therapy. As a result, free Pt was found to act on cancer cells in the abdominal cavity directly at a high concentration. At the same time, the possibility of an antitumor effect from the vascular side of the tumor was also suggested. On the other hand, cases of ovarian cancer had various levels of peritoneal clearance (CLp), which depended on the severity of their carcinomatous peritonitis. The CLp had a great influence on the peak plasma concentration and on the AUC of free Pt in serum. In particular, the peak plasma concentration produced by CDDP-ip was 40-80% of the plasma concentration produced by CDDP-iv. These findings indicate that high-dose CDDP-ip is possibly effective and useful for advanced ovarian cancer, producing only very mild side effects.