Mechanism of Relaxation Via TASK-2 Channels in Uterine Circular Muscle of Mouse

Plasma pH can be altered during pregnancy and at labor. Membrane excitability of smooth muscle including uterine muscle is suppressed by the activation of K+ channels. Because contractility of uterine muscle is regulated by extracellular pH and humoral factors, K+ conductance could be connected to factors regulating uterine contractility during pregnancy. Here, we showed that TASK-2 inhibitors such as quinidine, lidocaine, and extracellular acidosis produced contraction in uterine circular muscle of mouse. Furthermore, contractility was significantly increased in pregnant uterine circular muscle than that of non-pregnant muscle. These patterns were not changed even in the presence of tetraetylammonium (TEA) and 4-aminopyridine (4-AP). Finally, TASK-2 inhibitors induced strong myometrial contraction even in the presence of L-methionine, a known inhibitor of stretchactivated channels in myometrium. When compared to non-pregnant myometrium, pregnant myometrium showed increased immunohistochemical expression of TASK-2. Therefore, TASK-2, seems to play a key role during regulation of myometrial contractility in the pregnancy and provides new insight into preventing preterm delivery.

Expression of Nitric Oxide Synthase Isoforms after Endothelial Denudation of the Rat Carotid Artery

BACKGROUND AND OBJECTIVES: The nitric oxide synthase (NOS) system may be involved in the healing process following arterial injury. The expressions of eNOS or iNOS have been observed separately following endothelial denudation of rat carotid arteries. However, the expressions of nitric oxide synthase isoforms (eNOS, iNOS and nNOS) have not been observed simultaneously. MATERIALS AND METHODS: Using balloon catheter denudation of the rat carotid artery, as a model for arterial injury and restenosis, we have evaluated the time course of the expressions of eNOS, iNOS and nNOS simultaneously using immunohistochemistry and RT-PCR. RESULTS: From the immunohistochemistry, the iNOS protein was shown to be rapidly induced following injury (day 1) and was later seen to be relocalized to the neointima (day 5). Two weeks following injury the iNOS expression had declined. After 4 weeks the iNOS expression had disappeared completely. The eNOS protein was not detected until three days post injury. Two weeks following injury the eNOS expression was observed at the "pseudoendothelial" surface forming intimal smooth muscle cells. By week 4 the eNOS expression was detected on the morphological endothelium. The nNOS expression was detected at the media one day following injury and for the subsequent two weeks, but it was not detected at the neointima at all. RT-PCR demonstrated that iNOS mRNA was faintly expressed 1 day following endothelial denudation. The expression level of the iNOS mRNA was highest at 5 days, but gradually decreased until 2 weeks following injury. CONCLUSION: These results suggest that endothelial disruption may induce the expressions of iNOS and nNOS, and the re-expression of eNOS may reduce these expressions. The expressions of iNOS and nNOS could be a homeostatic mechanism that compensates for the loss of endothelium.

Role of Calcineurin-Dependent Signaling Pathway on the Left Ventricular Hypertrophy Induced by Pressure Overload

BACKGROUND AND OBJECTIVES: Calcineurin-dependent transcriptional pathway has recently been implicated in cardiac hypertrophy. Whether calcineurin inhibition can prevent the development of pressure-overload left ventricular hypertrophy (LVH) is still controversial. To elucidate this issue, the effects of calcineurin inhibitors on the prevention of pressure-overload LVH were examined in mice. MATERIALS AND METHODS: Pressure overload was induced by transverse aortic contriction (TAC) in 57 ICR mice. Three different doses of CsA (TAC/CsA group, n=21) and FK506 (TAC/FK group, n=20) were administered subcutaneously from -2 to 14 days after surgery and 16 mice were treated with vehicle (TAC group). Another 60 mice were sham-operated and treated with CsA (CsA group, n=19), FK506 (FK group, n=18) or vehicle (Control group, n=23). RESULTS: Two weeks after TAC, the LV weight-to-body weight (LVW/BW) ratio was not significantly different among the Control, CsA and FK groups although it was greater in the TAC group (4.55+/-0.69 mg/g) than in the Control(2.78+/-0.70 mg/g) and other sham-operated groups (p<0.00005). Low-dose CsA (5 mg/kg/day) or FK506 (0.6 mg/kg/day) injection following TAC did not decrease the LVW/BW ratio. However, intermediate-dose and high-dose CsA (25 and 50 mg/kg/day) or FK506 (2 and 6 mg/kg/day) treatment prevented pressure-overload induced LVH and the degree of LVH inhibition was dose-dependent. Interstitial and/or perivascular fibrosis was remarkably decreased by the administration of intermediate and high doses of calcineurin inhibitors for 2 weeks following TAC. CONCLUSION: Taken together, calcineurin inhibitors, CsA and FK506, attenuated pressure-overload LVH response in a dose-dependent fashion. This data indicates that a calcineurin-dependent signaling pathway is crucial in the development of pressure-overload LVH.

Expression of Vascular Endothelial Growth Factor and iNOS in Pterygia

To evaluate the expression of vascular endothelial growth factor (VEGF) in pterygia and seek the reciprocal relationships between VEGF and nitric oxide (NO) in development of pterygia. Conjunctiva sampled during conjunc-tival transplantation of pterygial operation and pterygia were used in this study. OCT compound-fixed-cryopreserved tissues consisted normal conjunctiva and pterygia were used to study the expression of VEGF and iNOS with immunohistochemistry. For confirmation of NOS activity, NADPH-diaphorase staining was done. ELISA for detection of VEGF amounts was performed. The expression of VEGF and iNOS were revealed in the epithelium of pterygia, although there were not expressed in the epithelium of normal conjunctiva. The epithelium of pterygia was stained with NADPH-diaphorase. The results of ELISA showed the higher amount of VEGF inpterygia compared with conjunctiva. These findings suggest that VEGF and NO play an important role in fibrovascular development of pterygia.s

A Case of Bilateral Conjunctival Malignant Lymphoma Misdiagnosed as Allergic Conjunctivitis

Lymphoma originating in mucosal-associated lymphoid tissue (MALToma) is characterized by small B-cell lymphocytes of low-grade malignancy. They have salmon-colored multiple conjunctival masses and the bilateral occurrences are relatively rare. We evaluated a 32 year-old man with bilateral conjunctival mass lesions who was referred to our department with the diagnosis of allergic conjuctivitis. Histologic and immunocytochemical examination of the conjunctival biopsy revealed mucosal associated lymphoid tissue lymphoma. The patients was successfully treated with low-dose local radiotherapy.

Nitric Oxide-Mediated Neurotoxicity after Excimer Laser Photorefractive Keratectomy

The aim of this study was to evaluate neurotoxicity of Nitric oxide(NO) on cornea after excimer laser photorefractive keratectomy(PRK). PRK was performed on rabbit eyes. According to the time table, tear samples were collected with microcapillary tubes and corneal sensitivity was measured with a Cochet-Bonnet esthesiometer. No generation in the tear fluid was analyzed. To demonstrate NO Synthase(NOS), immunohistochemical localization was performed on frozen sections from rat eyeball tissue. Western blot analysis was used for detection of peroxynitrite, powerful oxidant of NO. NO generation was increased and reached to a maximum value(0.69+/-0.22micrometer/microgram) after 96 hours of PRK, as compared with in normal subjects(Mean: 0.30+/-0.08micrometer/microgram) and was not increased in the treated group with topical application of Ng-nitro-L-arginine methyl ester(L-NAME), a competitive inhibitor of constitutive NOS(cNOS) and inducible NOS(iNOS). Corneal sensitivity decreased below pretreatment levers after three postoperative days, but it was not observed in the L-NAME applied group. We have confirmed that a very strong iNOS and BNOS immunoreactivity was present in corneal keratocytes. Western blot analysis identifed the bands of nitrotyro-sine-proteins suggesting in vivo peroxynitrite toxicity. Our results suggested that NO generated from the enzyme after PRK decreased corneal sensitivity by damaging corneal sensory nerve through the NO and iths oxidant peroxitrite. Therefore topical application of a NOS inhibitor may be effective in maintaining corneal sensitivity.

Studies on the B Cell Proliferation and Differentiation Factors in Human B Cell System

We have studied the function of lymphokines on human tonsillar B cell prolifertion and differentiation. B cells were stimulated with Staphylococcus aureus Cowanl (SAC) or anti- bead. The followings showed the results of this study. 1) In B cell activation, SAC induced B cell DNA synthesis but anti-mubead did not. SAC could activate and proliferate B cells. Minimal number of B cells were required to proliferate effectively. 2) In B cell proliferation, SAC could proliferate B cell in the abscence of lymphokines. Exogenous IL-2 or IL-4 enhanced B cell proliferation. The roles of IL-2 were very important in B cell proliferation. The effect of IL-4 on the IL-2 induced B cell proliferation was inhibitory in SAC-B cells. IL-4 could enhance the proliferation of anti-mu bead activated B cells. 3) In B cell differentiation, IL-2 was a major factor to differentiate SAC activated B cells, but IL-4 did not. IL-6 had a synergistic effect on the differentiation. The results of this study showed that the different signal transduction mechanisms were involved in B cell proliferation and differentiation. The B cell resposes to lymphokine were different, and it is depend upon antigens or mitogens.