Comparison of inhibitory neuromuscular transmission in the Cynomolgus monkey IAS and rectum: special emphasis on differences in purinergic transmission.

KEY POINTS: Inhibitory neuromuscular transmission (NMT) was compared in the internal anal sphincter (IAS) and rectum of the Cynomolgus monkey, an animal with high gene sequence identity to humans. Nitrergic NMT was present in both muscles while purinergic NMT was limited to the rectum and VIPergic NMT to the IAS. The profile for monkey IAS more closely resembles humans than rodents. In both muscles, SK3 channels were localized to PDGFRα+ cells that were closely associated with nNOS+ /VIP+ nerves. Gene expression levels of P2RY subtypes were the same in IAS and rectum while KCNN expression levels were very similar. SK3 channel activation and inhibition caused faster/greater changes in contractile activity in rectum than IAS. P2Y1 receptor activation inhibited contraction in rectum while increasing contraction in IAS. The absence of purinergic NMT in the IAS may be due to poor coupling between P2Y1 receptors and SK3 channels on PDGFRα+ cells. ABSTRACT: Inhibitory neuromuscular transmission (NMT) was compared in the internal anal sphincter (IAS) and rectum of the Cynomolgus monkey, an animal with a high gene sequence identity to humans. Electrical field stimulation produced nitric oxide synthase (NOS)-dependent contractile inhibition in both muscles whereas P2Y1-dependent purinergic NMT was restricted to rectum. An additional NOS-independent, α-chymotrypsin-sensitive component was identified in the IAS consistent with vasoactive intestinal peptide-ergic (VIPergic) NMT. Microelectrode recordings revealed slow NOS-dependent inhibitory junction potentials (IJPs) in both muscles and fast P2Y1-dependent IJPs in rectum. The basis for the difference in purinergic NMT was investigated. PDGFRα+ /SK3+ cells were closely aligned with nNOS+ /VIP+ neurons in both muscles. Gene expression of P2RY was the same in IAS and rectum (P2RY1>>P2RY2-14) while KCNN3 expression was 32% greater in rectum. The SK channel inhibitor apamin doubled contractile activity in rectum while having minimal effect in the IAS. Contractile inhibition elicited with the SK channel agonist CyPPA was five times faster in rectum than in the IAS. The P2Y1 receptor agonist MRS2365 inhibited contraction in rectum but increased contraction in the IAS. In conclusion, both the IAS and the rectum have nitrergic NMT whereas purinergic NMT is limited to rectum and VIPergic NMT to the IAS. The profile in monkey IAS more closely resembles that of humans than rodents. The lack of purinergic NMT in the IAS cannot be attributed to the absence of PDGFRα+ cells, P2Y1 receptors or SK3 channels. Rather, it appears to be due to poor coupling between P2Y1 receptors and SK3 channels on PDGFRα+ cells.

Effect of a novel BKCa opener on BKCa currents and contractility of the rabbit corpus cavernosum.

Large-conductance Ca(2+)-activated K(+) (BKCa) channels are thought to play a key role in the regulation of corpus cavernosum smooth muscle (CCSM) excitability. Few BKCa channel openers have been accepted for clinical development. The effect of the novel BKCa channel opener GoSlo-SR5-130 on electrical activity in isolated rabbit CCSM cells and mechanical activity in strips of rabbit CCSM was examined. Single-channel currents were observed in inside-out patches. These channels were sensitive to Ca(2+), blocked by penitrem A, and had a conductance of 291 ± 20 pS (n = 7). In the presence of GoSlo-SR5-130, the number of open BKCa channels increased. Using voltage-ramp protocols, GoSlo-SR5-130 caused currents to activate at more negative potentials in a concentration-dependent manner, shifting the half-maximal activation voltage potential to the left on the voltage axis. Therefore, BKCa channels were open within the physiological range of membrane potentials in the presence of GoSlo-SR5-130. GoSlo-SR5-130 also resulted in an increase in the activity of spontaneous transient outward currents in myocytes isolated from CCSM, and this effect was reversed by iberiotoxin. In current-clamp mode, GoSlo-SR5-130 hyperpolarized the cell membrane. Isometric tension recording of strips of rabbit corpus cavernosum showed that GoSlo-SR5-130 inhibited spontaneous contractions in a concentration-dependent manner. This effect was reversed in the presence of iberiotoxin, suggesting that GoSlo-SR5-130 exerts its effect through BKCa channels. These findings suggest that GoSlo-SR5-130 is an effective tool for the study of BKCa channels and that these channels can modulate CCSM activity and are possible targets for the treatment of erectile dysfunction.

Eosinophil peroxidase induces the expression and function of acid-sensing ion channel-3 in allergic rhinitis: in vitro evidence in cultured epithelial cells.

BACKGROUND: Acid-sensing ion channels (ASIC) are a family of acid-activated ligand-gated cation channels. As tissue acidosis is a feature of inflammatory conditions, such as allergic rhinitis (AR), we investigated the expression and function of these channels in AR. OBJECTIVES: The aim of the study was to assess expression and function of ASIC channels in the nasal mucosa of control and AR subjects. METHODS: Immunohistochemical localization of ASIC receptors and functional responses to lactic acid application were investigated. In vitro studies on cultured epithelial cells were performed to assess underlying mechanisms of ASIC function. RESULTS: Lactic acid at pH 7.03 induced a significant rise in nasal fluid secretion that was inhibited by pre-treatment with the ASIC inhibitor amiloride in AR subjects (n = 19). Quantitative PCR on cDNA isolated from nasal biopsies from control and AR subjects demonstrated that ASIC-1 was equally expressed in both populations, but ASIC-3 was significantly more highly expressed in AR (P < 0.02). Immunohistochemistry confirmed significantly higher ASIC-3 protein expression on nasal epithelial cells in AR patients than controls (P < 0.01). Immunoreactivity for EPO+ eosinophils in both nasal epithelium and submucosa was more prominent in AR compared with controls. A mechanism of induction of ASIC-3 expression relevant to AR was suggested by the finding that eosinophil peroxidase (EPO), acting via ERK1/2, induced the expression of ASIC-3 in epithelial cells. Furthermore, using a quantitative functional measure of epithelial cell secretory function in vitro, EPO increased the air-surface liquid depth via an ASIC-dependent chloride secretory pathway. CONCLUSIONS: This data suggests a possible mechanism for the observed association of eosinophils and rhinorrhoea in AR and is manifested through enhanced ASIC-3 expression.

Teaching catheterization to children.

Children can learn to perform self-catheterization as early as their preschool years with the aid of newly developed teaching techniques. Clean self-catheterization is widely accepted and allows the child to remain dry, without infection, and independent in the management of the lower urinary tract.

Brain tissue oxygen pressure, carbon dioxide pressure and pH during ischemia.

In this case we evaluated brain tissue pO2, pCO2 and pH during ischemia and arterial oxygen desaturation (hypoxia). In both situations brain pO2 decreased. During ischemia, tissue pCO2 increased while pH decreased; but both pCO2 and pH were stable during hypoxia. These results suggest that brain tissue pO2, pCO2 and pH measures provide information on tissue perfusion and oxygen availability during ischemia and hypoxia.

Cerebral interstitial tissue oxygen tension, pH, HCO3, CO2.

BACKGROUND: There are many techniques for monitoring the injured brain following trauma, subarachnoid hemorrhage, or surgery. It is thought that the major determinants for recovery of injured cerebral tissue are oxygen, glucose delivery, and the clearance of metabolites. These factors, at optimal levels, are probably responsible for the regaining of neuronal functions. These parameters are in turn dependent on the tissue's blood flow and metabolism. METHODS: We have been using a single, compact, polyethylene sensor, the Paratrend 7 for the measurement of cerebral oxygen tension, CO2, pH, and temperature. This sensor is designed for continuous blood gas analysis to aid in monitoring neurosurgical patients, both during surgery and in the intensive care unit. RESULTS: Using the Paratrend 7 sensor, we found the normal range of values to be: PO2 33 +/- 11 mm Hg; PCO2 48 +/- 7 mm Hg; pH 7.19 +/- 0.11. Critical measurements are considered to be tissue PO2 < 10 mm Hg; PCO2 > 60 mm Hg, and pH < 6.8. We have had no complications with this device; the risks are similar to those of placing a parenchymal intracranial pressure monitor. CONCLUSIONS: We believe that assessment of interstitial cerebral oxygen saturation can be of great value both intraoperatively and postoperatively. In our experience, the Paratrend 7 system is an effective method of measuring tissue cerebral oxygen tension, along with carbon dioxide levels, pH, and temperature.

Role of a perivascular ultrasonic micro-flow probe in aneurysm surgery.

There are various intraoperative monitoring devices available today for helping the neurosurgeons the progress of the intracranial aneurysm surgery. Till now the intraoperative ultrasonic blood flow probes has been used only in vascular, cardiac, and transplant surgery. In the University of Illinois at Chicago we have been able to use the same technology in various neurovascular surgeries. We describe the use of the ultrasonic perivascular blood flow probes in patients operated for clipping of intracranial aneurysm. The use of this perivascular micro-flow probe and its importance in cerebral aneurysm will be discussed.

Teaching self-catheterization skills to children with neurogenic bladder complications.

We examined the effects of simulation training on the acquisition of self-catheterization skills in 2 female children with spina bifida. Based on a task analysis, the children were taught to perform on a doll each of the components of preparation, and, using a mirror to locate the urinary meatus, to insert and remove the catheter and to clean-up. Before, during, and after training, the children's performance of the skills on the doll and on themselves was assessed. Results of a multiple baseline design across subjects and skill components showed that doll training facilitated the children's acquisition of self-catheterization skills.

Teaching intermittent self-catheterization to young children with myelodysplasia.

A new technique is described which enables children with neurogenic bladder secondary to myelodysplasia to learn self-catheterization prior to their school years. Inexpensive dolls, complete with male or female genitalia, and a specially designed mirror to magnify the female children's genitalia, were used with four children (three girls, one boy) with mental ages of five years. Each child successfully demonstrated self-catheterization within two days, and gradual progress toward complete independence has been promoted.

A phase I trial of a 5-day schedule of intravenous topotecan and etoposide in previously untreated patients with small-cell lung cancer.

A phase I dose-escalation study was undertaken to determine the maximum tolerated dose of the intravenous combination of topotecan and etoposide in previously untreated patients with small-cell lung cancer. Nineteen patients were treated with 30-min infusions of topotecan (0.5 mg/m(2)/day for cohort 1; 0.75 mg/m(2)/day for cohort 2) followed by 1-hour infusions of a fixed daily dose of etoposide (60 mg/m(2)/day) for 5 consecutive days every 3 weeks. Patient cohort 1 (n = 7) received a total of 41 courses of chemotherapy. Grade 4 neutropenia occurred after 17% of the courses of therapy, and there was 1 episode of dose-limiting toxicity in this patient cohort. In patient cohort 2 (n = 12), a total of 64 courses of chemotherapy were administered. Grade 3 or 4 neutropenia occurred following 41 and 37% of the courses of therapy, respectively. Grade 3 thrombocytopenia occurred following 19% of the courses of therapy, and there were 3 episodes of dose-limiting toxicity in this patient cohort. There were no toxic deaths, and all nonhematologic toxicity (except hair loss) was