Studies on the mechanisms underlying beta-adrenoceptor-mediated relaxation of rat abdominal aorta.

Mechanisms underlying beta-adrenoceptor (beta-AR)-mediated vascular relaxation were studied in the isolated rat abdominal aorta. In the endothelium-denuded helical preparations, a non-selective beta-AR agonist isoprenaline elicited a concentration-dependent relaxation. In the absence of beta-AR antagonists, isoprenaline-induced relaxation was not practically affected by an adenylyl cyclase inhibitor SQ 22,536 (300 microM), but was strongly diminished by high-KCl (80 mM). Isoprenaline-induced relaxation in the presence of SQ 22,536 was significantly diminished by iberiotoxin (IbTx, 0.1 microM), but was not affected by 4-aminopyridine (4-AP, 3 mM). Isoprenaline-induced relaxation was not also affected by SQ 22,536 (300 microM) even in the presence of CGP20712A (a beta(1)-selective antagonist) and ICI-118,551 (a beta(2)-selective antagonist) (0.1 microM for each), but was strongly diminished by high-KCl. By contrast, SQ 22,536-resistant, isoprenaline-induced relaxation in the presence of CGP20712A plus ICI-118,551 was not affected by IbTx (0.1 microM), but was inhibited significantly by 4-AP (3 mM). These results suggest that in rat abdominal aortic smooth muscle: 1) both beta(1)-/beta(2)-AR- and beta(3)-AR-mediated relaxations substantially involve cAMP-independent mechanisms; 2) beta(1)-/beta(2)-AR-mediated, cAMP-independent relaxant mechanisms are partly attributed to the large-conductance, Ca (2+)-sensitive K(+) (MaxiK, BK) channel whereas beta(3)-AR-mediated relaxant mechanisms are attributed to K(v) channel.     

Leukemia Cutis in Three Children: Clinical and Immunohistochemical Studies

Abstract: We report 3 children with leukemia cutis observed at the initial diagnosis of systemic leukemia. Leukemia subtypes in the three children were congenital monocytic, acute undifferentiated, and acute monocytic, respectively. The patients were girls age 10 days, 14 years, and 11 months, respectively, at diagnosis. We describe the clinical features of the cases and the results of immunohistochemical studies on paraffin-embedded skin biopsy specimens. The skin lesions were tumors and areas of reddish purple erythema in the first child, pigmented erythema in the second, and bright red erythema in the third. In the first two patients skin lesion biopsy specimens had dense leukemic infiltrates in the dermis with reactive T lymphocytes scattered among them. In the third patient, the infiltrating cells were almost all reactive T lymphocytes, with a few leukemic cells. A relationship between the leukemic-reactive cell ratio and the prognosis was suggested; dense leukemic cell infiltrates may be associated with a poor prognosis.     

Lidocaine Increases Intracellular Sodium Concentration through Voltage-dependent Sodium Channels in an Identified Lymnaea Neuron

Background: The local anesthetic lidocaine affects neuronal excitability in the central nervous system; however, the mechanisms of such action remain unclear. The intracellular sodium concentration ([Na+]i) and sodium currents (INa) are related to membrane potential and excitability. Using an identifiable respiratory pacemaker neuron from Lymnaea stagnalis, the authors sought to determine whether lidocaine changes [Na+]i and membrane potential and whether INa is related to these changes.

Methods: Intracellular recording and sodium imaging were used simultaneously to measure membrane potentials and [Na+]i, respectively. Measurements for [Na+]i were made in normal, high-Na+, and Na+-free salines, with membrane hyperpolarization, and with tetrodotoxin pretreatment trials. Furthermore, changes of INa were measured by whole cell patch clamp configuration.

Results: Lidocaine increased [Na+]i in a dose-dependent manner concurrent with a depolarization of the membrane potential. In the presence of high-Na+ saline, [Na+]i increased and the membrane potential was depolarized; the addition of lidocaine further increased [Na+]i, and the membrane potential was further depolarized. In Na+-free saline or in the presence of tetrodotoxin, lidocaine did not change [Na+]i. Similarly, hyperpolarization of the membrane by current injections also prevented the lidocaine-induced increase of [Na+]i. In the patch clamp configuration, membrane depolarization by lidocaine led to an inward sodium influx. A persistent reduction in membrane potential, resulting from lidocaine, brings the cell within the window current of INa where sodium channel activation occurs.     

Hypertonic saline alters electrical barrier of the airway epithelium.

OBJECTIVE: The effect of tonicity changes in nebulizer solutions and irrigations on nasal mucosa is not well known. The present study aims to determine the basic mechanism of hypertonic solution on airway epithelial barrier. STUDY DESIGN AND SETTING: We investigated the electrical potential difference (PD) that is influenced by both active transport and the transepithelial electrical resistance of the epithelial mucosa in the human nose in vivo. The short circuit current (SCC) revealed net ion transport across the epithelium in the guinea pig trachea in vitro. Finally, the size dependency of macromolecules across the tracheal mucosa was determined in vitro using FITC-labeled dextrans of different sizes. RESULTS: PD was significantly decreased after topical application of hypertonic solution both in human and in guinea pig nose. SCC was significantly decreased after application of hypertonic solution. The transport of these dextrans from the basolateral to the apical side was not increased significantly after apical application of hypertonic saline. CONCLUSIONS: Hypertonic saline enhances the electrical permeability of the airway epithelial mucosa but not transport of macromolecule in the short term.     

Comparison of Tympanic, Esophageal and Blood Temperatures during Mild Hypothermic Cardiopulmonary Bypass: A Study using an Infrared Emission Detection Tympanic Thermometer

Objective. Tympanic temperature can be obtained instantaneously using an infrared emission detection (IRED) thermometer. Its accuracy has been documented in a variety of clinical settings, but its performance at low body temperatures is still unknown. In this study we evaluated its performance during coronary artery revascularization surgery in which mild hypothermic cardiopulmonary bypass (CPB) was used. Methods. Thirty adult patients undergoing coronary artery bypass graft surgery were enrolled in the study. Tympanic temperature obtained using IRED thermometry (Tt1) was compared with core temperatures from the esophagus (Te), and venous blood of CPB (Tv) before, during, and after CPB. We also measured tympanic temperature using a thermocouple probe (Tt2) in 16 of the 30 patients in order to study the agreement between the two methods. Values for correlation coefficients and limits of agreement were computed to assess the degree of agreement among the temperatures obtained. Results. The highest agreement with Tv during CPB was obtained from Tt1 (r = 0.94, 0.41 ± 1.73, limits of agreement) and from Te (0.91, 0.36 ± 2.46). Tt1 also showed good agreement with Tt2 during surgery. Conclusions. Infrared tympanic thermometry is a reliable, alternative method to measure tympanic temperature and may be useful to assess core temperature in both normothermic and mild hypothermic conditions.     

Immunohistochemical localization of vitronectin, its receptor and beta-3 integrin in Alzheimer brain tissue.

The vitronectin receptor (VNR) is an integrin which consists of an alpha-subunit which can associate with multiple beta-subunits. A polyclonal antibody to this integrin weakly stained resting microglia in white matter of control brain and strongly stained reactive microglia in both gray and white matter of Alzheimer brain. This antibody, as well as a monoclonal antibody to beta 3, stained some platelets in capillaries of both control and Alzheimer tissue. When the antiserum was immunoabsorbed with a preparation enriched in the alpha-chain of the vitronectin receptor, it failed to stain microglial cells, but continued to stain platelets. When it was immunoabsorbed with a peripheral blood platelet preparation, all immunostaining was abolished. These results indicate that the vitronectin receptor of microglia is associated with a beta-chain different from beta 3, but that beta 3 is expressed by some platelets in brain capillaries. An antibody to vitronectin itself stained senile plaques and neurofibrillary tangles in Alzheimer entorhinal cortex, but only residual plasma in control tissue. Senile plaques positive for vitronectin had microglial cores strongly positive for the vitronectin receptor. The high levels of vitronectin receptor on reactive microglia in areas containing extracellular vitronectin suggest the possibility that vitronectin is serving an opsonizing function for microglial phagocytosis.