Histological and functional aspects of different regions of the rabbit vagina

Relatively little data is available on regional differences in both morphological and functional studies of vaginal smooth muscle in the rabbit. Histological and in vitro strip studies were performed upon the vaginal walls of 10-week-old New Zealand White rabbits discriminately according to location (upper, middle or lower) and the type of muscle arrangement (longitudinal or circular). The contraction and relaxation responses of the vaginal smooth muscle were assessed. The upper and middle third of the vagina were histologically characterized by an abundance of smooth muscle, while the lower third was composed of numerous sinusoids scattered among smooth muscle bundles. The peak amplitudes of 60 mM KCl-induced contraction per tissue strip weight were regionally different (upper>middle>lower). Contractile responses induced by adrenergic agonists (epinephrine, norepinephrine, phenylephrine and isopreterenol) showed regional differences, and were mainly of a tonic nature in lower part and strong phasic in middle and upper vagina. Electrical field stimulation induced a prominent relaxation response in the lower third of the vagina precontracted with phenylephrine (5 microM). This relaxation response was partially inhibited by N-omega-nitro-L-arginine methyl ester (NAME, 43.3+/-6.9%, s.e.), a nitric oxide synthase inhibitor, and D-vasoactive intestinal peptide (VIP) (11.3+/-4.4%), a VIP receptor antagonist. The type of muscle arrangement did not affect the results. Our results demonstrated that rabbit vagina has regional difference, not only histologically but also functionally. The contractile response was induced in all regions of the rabbit vagina by sympathetic agonists, while the prominent nerve-mediated relaxation was identified in the lower third portion of the rabbit vagina. The nature of relaxation and contractile function of vagina awaits future investigation.     

Ion-channel currents of smooth muscle cells isolated from the prostate of guinea-pig

OBJECTIVE: To characterize the voltage-activated ion-channel currents in guinea-pig prostate smooth muscle cells (GPSMCs). MATERIALS AND METHODS: GPSMCs were isolated using collagenase, and used in a whole-cell patch clamp study. RESULTS: When GPSMCs were dialysed with a CsCl solution all the outward K+ currents were blocked and the step-like depolarization (holding voltage -70 mV) of the cell membrane evoked inward currents that were completely blocked by nifedipine (1 micromol/L). With KCl solution, step depolarizations showed outward K+ currents composed of fast, transient outward current (Ito) and outward currents that did not inactivate. Ito was resistant to a high concentration of tetraethylammonium (TEA, 5 mmol/L) but was blocked by 4-aminopyridine (5 mmol/L). The half-activation and half-inactivation voltages of Ito were 6 mV and -58 mV, respectively. With low Ca2+ buffer (0.1 mmol/L EGTA) in the solution, there were spontaneous transient outward currents (STOCs) at depolarized membrane voltages (0 mV). STOCs were blocked by TEA (1 mmol/L) or iberiotoxin (10 nmol/L) but were insensitive to apamin (100 nmol/L). CONCLUSION: This voltage-clamp study showed that GPSMCs have l-type Ca2+ channels and more than two types of K+ channels. The voltage- and time-dependent changes of these ion channels and their interactions might be important in forming action potentials and regulating contractility.     

Calcium-activated cationic channel in rat sensory neurons

Ion channels in sensory neurons are molecular sensors that detect external stimuli and transduce them to neuronal signals. Although Ca2+-activated nonselective cation (CAN) channels were found in many cell types, CAN channels in mammalian sensory neurons are not yet identified. In the present study, we describe an ion channel that is activated by intracellular Ca2+ in cultured rat sensory neurons. Half-maximal concentration of Ca2+ in activating the CAN channel was approximately 780 micro m. The current-voltage relationship of this channel was linear with a unit conductance of 28.8 +/- 0.4 pS at -60 mV in symmetrical 140 mm Na+ solution. The CAN channel was permeable to monovalent cations such as Na+, K+, Cs+, and Li+, but poorly permeable to Ca2+. The CAN channel in mammalian sensory neurons was reversibly blocked by intracellular adenine nucleotides, such as ATP, ADP, and AMP. Interestingly, single-channel currents activated by Ca2+ were blocked by fenamates, such as flufenamic acid, a class of nonsteroidal anti-inflammatory drugs. Thus, these results suggest that CAN channels in mammalian sensory neurons would participate in modulating nociceptive neural transmission in response to ever-changing intracellular Ca2+ in the local microenvironment.     

Singapore's experience of SARS

The coronavirus that causes severe acute respiratory syndrome (SARS) is transmitted mainly via respiratory droplets. Typical presenting symptoms are akin to those of ordinary pneumonia. Young patients start with fever, chills, malaise, headache, or myalgia; cough and dyspnoea follow. Older persons and those taking corticosteroids may have neither fever nor respiratory symptoms. Exceptional suspicion is needed to identify SARS early in the illness. During an outbreak, even patients with low suspicion of SARS should be promptly isolated, and all contacts quarantined. Health workers need training in the use of appropriate barriers against droplets and other body fluids. Any fever cluster in patients or carers requires immediate action: discharges, visits, and transfers between wards and hospitals should be stopped. Halting hospital admissions and ten-day quarantine of suspected cases create wide buffer zones. To counter a possible resurgence of SARS, a system of prepared isolation and quarantine facilities is important.     

Results of Caldwell-Luc after failed endoscopic middle meatus antrostomy in patients with chronic sinusitis

OBJECTIVES/HYPOTHESIS: The Caldwell-Luc operation for treatment of medically refractory chronic maxillary sinusitis has largely been replaced by functional endoscopic sinus surgery. Despite this change, the Caldwell-Luc procedure still has well documented indications including treatment of both failed endoscopic middle meatus antrostomy and irreversible mucosal changes. The purpose of the study was to review the authors' experience and results of Caldwell-Luc procedure after failed endoscopic middle meatus antrostomy in patients clinically deemed to have irreversible mucosal changes. STUDY DESIGN: Retrospective review of preoperative and postoperative results of patients who underwent Caldwell-Luc procedure for refractory chronic maxillary sinusitis after failed endoscopic middle meatus antrostomy. METHODS: The preoperative and postoperative clinical course of patients treated with Caldwell-Luc procedure performed by a single surgeon between 1996 and 2001 were reviewed. Only patients with a history of chronic sinusitis after failed maximal medical therapy, no prior Caldwell-Luc procedure, prior endoscopic middle meatus antrostomy, and at least 6 months of follow-up were included. Outcome measurements including documented endoscopic examinations and the need for repeat surgery, and postoperative computed tomography scan results were evaluated to assess treatment success. RESULTS: The study involved 11 men and 26 women who underwent 50 Caldwell-Luc procedures. Caldwell-Luc procedure was performed bilaterally in 13 patients. The average number of prior endoscopic middle meatus antrostomies before Caldwell-Luc procedure was 2. Of all patients, 92% responded to surgical treatment as demonstrated by an endoscopic examination or computed tomography scan revealing a disease-free maxillary sinus. Repeat Caldwell-Luc procedure was required in 8.0% (n = 3) because of continued sinusitis. Two of the three cases with repeat Caldwell-Luc procedures demonstrated clinical improvement during follow-up. Average follow-up was 23.5 months. CONCLUSION: Caldwell-Luc procedure seems to be highly effective in the management of medically refractory chronic sinusitis after failed endoscopic middle meatus antrostomy. Caldwell-Luc procedure should remain in the otolaryngologist's surgical repertoire for these selected cases.     

Hydrodissection for complete removal of a ranula

Hydrodissection has been used in various surgical fields to facilitate excision in both routine and difficult cases. This procedure involves the injection under pressure of saline and lidocaine with 1:100,000 epinephrine into the dissection plane. Removing a ranula without rupturing it can be a tedious and time-consuming process. Therefore, we used hydrodissection to assist us in performing these procedures. To review our experience with the treatment of ranulas, we performed a retrospective study of 38 patients who had undergone hydrodissection for ranula removal between January 1996 and December 2002 at our academic tertiary care hospital. Compared with other removal techniques, we found that hydrodissection was associated with less bleeding, fewer incidents of neural and soft-tissue damage, and a lower recurrence rate. In addition to reporting our study results, we also describe our hydrodissection technique, which is relatively simple, effective, and convenient for otolaryngologists.     

Nicotine induces a long QT phenotype in Kcnq1-deficient mouse hearts

We have previously shown that targeted disruption of the mouse Kcnq1 gene produces a long QT phenotype in vivo that requires extracardiac factors for manifestation (Casimiro et al., 2001). In the present study, we explore the hypothesis that autonomic neuroeffector transmission represents the "extra cardiac" stimulus that induces a long QT phenotype in mouse hearts lacking Kcnq1. Using the isolated perfused (Langendorff) mouse heart preparation, we challenged wild-type (Kcnq1+/+) and mutant (Kcnq1-/-) mouse hearts with nicotine, an autonomic stimulant. ECGs were recorded continuously, and QT intervals were compared at baseline and peak nicotine-induced heart rates. No significant differences in QT or any other ECG parameters were observed in Kcnq1+/+ versus Kcnq1-/- hearts at baseline. In the presence of nicotine, however, the JT, QT, and rate-corrected QT (QTc) intervals were significantly prolonged in Kcnq1-/- hearts relative to Kcnq1+/+ hearts (e.g., QTc = 92 +/- 11 ms versus 66 +/- 2 ms, respectively, p < 0.01). Similar findings were obtained when the hearts were challenged with either epinephrine or isoproterenol (0.1 microM each), thereby suggesting that sympathetic stimulation drives the long QT phenotype in Kcnq1-deficient hearts. This idea is supported by in vivo ECG data obtained from unrestrained conscious mice using radiotelemetry recording techniques. Again, no significant ECG differences were observed in Kcnq1-/- versus Kcnq1+/+ mice at baseline, but handling/injection stress led to significant QTc increases in Kcnq1-/- mice relative to wild-type controls (11 +/- 3 versus -1 +/- 1%, respectively, p < 0.05). These data suggest that sympathetic stimulation induces a long QT phenotype in Kcnq1-deficient mouse hearts.     

A meta-analysis of the effects of various interventions in preventing endotracheal suction-induced hypoxemia

The purpose of this study was to clarify the effects of interventions that were applied to prevent endotracheal suction-induced hypoxia by meta-analysis. To obtain a sample for this meta-analysis, a computerized search was performed through MEDLINE in addition to tracking down additional references cited in bibliographies of past reports. Finally thirty research reports were examined. In terms of the application time of oxygenation, insufflation and preoxygenation were the most prevalently used in the studies. Regarding the methods of oxygenation, the most prevalent technique for oxygenation was hyperoxygenation in combination with hyperinflation. Hyperoxygenation and hyperinflation were most frequently induced by FiO2 of 1 and a 150% tidal volume of three to six breaths, respectively. Suctioning was commonly sustained for <15 seconds using pressures of -80 to -120 mmHg and with size 14 French catheters. Insufflation was less effective than the other methods examined in the present study. From this study, it can be concluded that the interventions that were applied to prevent endotracheal suction-induced hypoxia, regardless of their application times or methods, reduced suction-induced hypoxia significantly.     

Effect of parenteral glutamine supplementation on plasma amino acid concentrations in extremely low-birth-weight infants

BACKGROUND: Glutamine is one of the most abundant amino acids in both plasma and human milk and may be conditionally essential in premature infants. However, glutamine is not provided by standard intravenous amino acid solutions. OBJECTIVE: We assessed the effect of parenteral glutamine supplementation on plasma amino acid concentrations in extremely low-birth-weight infants receiving parenteral nutrition (PN). DESIGN: A total of 141 infants with birth weights of 401-1000 g were randomly assigned to receive a standard intravenous amino acid solution that did not contain glutamine or an isonitrogenous amino acid solution with 20% of the total amino acids as glutamine. Blood samples were obtained just before initiation of study PN and again after the infants had received study PN (mean intake: 2.3 +/- 1.0 g amino acids x kg(-1) x d(-1)) for approximately 10 d. RESULTS: Infants randomly assigned to receive glutamine had mean plasma glutamine concentrations that increased significantly and were approximately 30% higher than those in the control group in response to PN (425 +/- 182 and 332 +/- 148 micromol/L for the glutamine and control groups, respectively). There was no significant difference between the 2 groups in the relative change in plasma glutamate concentration between the baseline and PN samples. In both groups, there were significant decreases in plasma phenylalanine and tyrosine between the baseline and PN samples; the decrease in tyrosine was greater in the group that received glutamine. CONCLUSIONS: In extremely low-birth-weight infants, parenteral glutamine supplementation can increase plasma glutamine concentrations without apparent biochemical risk. Currently available amino acid solutions are likely to be suboptimal in their supply of phenylalanine, tyrosine, or both for these infants.