Effect of glazing on the flexural strength of lithium disilicate glass ceramics / 대한치과재료학회지

The purpose of this study was to investigate the relationship between glazing treatment and flexural strength of dental lithium disilicate glass ceramics. Three commercial lithium disilicate glass ceramic blocks were cut to size and polished with abrasive papers and diamond pastes. The specimens were prepared in accordance to the manufacturer's instruction for the crystallization process and divided into three groups. The first group was over-glazed with glazing paste and liquid. The second group was self-glazed at a normal over-glazing temperature without glazing paste and liquid. The third group was an untreated control group. The three-point flexural test was carried out using the universal testing machine. The broken specimens were examined by SEM/EDS. The over-glazed group showed lowest flexural strength. There was no statistically significant difference between self-glazed group and untreated group with respect to flexural strength. The bubbles and cracks were found in the glaze layer of over-glazed group. As the tensile stress was concentrated at the bottom of glaze layer during the flexural test, it was evident that the bubbles played a role in initiation and propagation of cracks. A mixed layer formed between glaze layer and glass ceramic during the over-glazing process could have negative effects on the flexural strength of entire specimen.

Specific Expression of Aplysia Phosphodiesterase 4 in Bag Cells Revealed by in situ Hybridization Analysis

Phosphodiesterases (PDEs) play a key role in the regulation of cyclic adenosine monophosphate (cAMP), which in turn mediates various cellular functions including learning and memory. We previously cloned and characterized three PDE4 isoforms (ApPDE4) from Aplysia kurodai. Using reverse transcription polymerase chain reaction (RT-PCR), we found that ApPDE4 isoforms are primarily expressed in the central nervous system. However, the detailed distribution of ApPDE4 mRNA in Aplysia individual ganglions was not evident. In this study, to determine the distribution of ApPDE4 mRNAs in Aplysia ganglions, we performed in situ hybridization (ISH) using a probe targeting ApPDE4, including the PDE catalytic domain. Interestingly, we found the strongest ISH-positive signals in the symmetrical bag cell clusters of the abdominal ganglion. The R2, R14, L7, L2 and L11 neurons in the abdominal ganglion, LP1 neuron in pleural ganglion, and metacerebral (MCC) neurons were ISH-positive. Mechanosensory neurons of the sensory cluster were also stained on the ventral aspect of the right and left pleural ganglia. Taken together, we found the detailed distribution of ApPDE4 mRNA in Aplysia ganglion and support their roles in serotonin (5-HT)-induced synaptic facilitation of Aplysia mechanosensory neurons.

Short-term Outcomes of Hand-Assisted Laparoscopic Surgery vs. Open Surgery on Right Colon Cancer: A Case-Controlled Study

PURPOSE: This study was designed to evaluate short-term clinical outcomes by comparing hand-assisted laparoscopic surgery with open surgery for right colon cancer. METHODS: Sixteen patients who underwent a hand-assisted laparoscopic right hemicolectomy (HAL-RHC group) and 33 patients who underwent a conventional open right hemicolectomy (open group) during the same period were enrolled in this study with a case-controlled design. RESULTS: The operation time was 217 minutes in the HAL-RHC group and 213 minutes in the open group (P = 0.389). The numbers of retrieved lymph nodes were similar between the two groups (31 in the HAL-RHC group and 36 in the open group, P = 0.737). Also, there were no significant difference in the incidence of immediate postoperative leukocytosis, the administration of additional pain killers, and the postoperative recovery parameters. First flatus was shown on postoperative days 3.5 in the HAL-RHC group and 3.4 in the open group (P = 0.486). Drinking water and soft diet were started on postoperative days 4.8 and 5.9, respectively, in the HAL-RHC group and similarly 4.6 and 5.6 in the open group (P = 0.402 and P = 0.551). The duration of hospital stay was shorter in the HAL-RHC group than in the open group (10.3 days vs. 13.5 days, P = 0.048). No significant difference in the complication rates was shown between the two groups, and no postoperative mortality was encountered in either group. CONCLUSION: The patients with right colon cancer in the HAL-RHC group had similar pathologic and postoperative recovery parameters to those of the patients in the open group. The patients in the HAL-RHC group had shorter hospital stays than those in the open group. Therefore, hand-assisted laparoscopic right hemicolectomy for right-sided colon cancer is feasible.

Outcomes of Early Liver Transplantation in a Hospital That Is Starting to Perform Liver Transplantation / 대한이식학회지

BACKGROUND: In Korea, the number of liver transplantation (LT) center is still changing. Many more centers are performing liver transplantations than that during the past decades. But several centers have stopped liver transplantation, while some centers have newly started performing liver transplantation. We present our initial experience in a newly built center as an example for any center that is considering performing LT. METHODS: A total of 33 consecutive adult LTs that were performed from June 2006 to October 2009 were analyzed by comparing the first 11 living donor liver transplants (LDLTs) performed with the help of an outside experienced team (group 2) with the second 11 LDLTs (group 3) and the 11 deceased donor liver transplantations (DDLTs) cases (group 1) that were independently performed in our center. RESULTS: There was no operative mortality for the donors and there were two operative mortalities for the recipients. During a mean follow-up of 27.1 months (range: 2 days~61 months), there were two cases of late mortality for the recipients. There were no re-operations and no major complications for the donors. The warm ischemic time was significantly longer in group 1 than that in groups 2 and 3. Otherwise, there was no significant difference in the operative outcomes among the three groups. CONCLUSIONS: Thorough preparation and the valuable assistance of an experienced liver transplantation team at the beginning can facilitate a more rapid learning curve and bring about good outcomes even in a small, newly established institution.

Effects of Family History on the Occurrence of Atopic Dermatitis in Infants / 소아알레르기및호흡기학회지

PURPOSE: The prevalence of atopic dermatitis (AD) has been increased in Korea. We aim to investigate the risk factors for development of AD in infants, especially those factors related to the family history. METHODS: The data from 542 infants in our prospective birth cohort study were analyzed. The data from their parent were collected by questionnaires and skin prick tests. They were regularly followed up at 1 year of age when the presence of AD and allergen sensitization was determined. Various factors such as sex, cesarean section delivery, duration of breast feeding, presence of siblings, vaccination, antibiotic use and pet keeping were also assessed. RESULTS: AD developed in 109 infants (20.4%). In univariate analysis, the presence of either maternal or paternal allergic diseases increased the risk for development of AD in their infants. Multivariate logistic analysis, however, showed that only the presence of maternal allergic diseases correlated with the development of AD (P=0.018). While AD developed in 14.7% in infants of parents with no allergic history, the incidences of AD in infants with a single parent allergy history and in those with 2 parent allergy history were 27.0% and 41.7%, respectively. Their adjusted relative risks (95% confidence intervals) were 1.85 (1.24-2.89) and 2.93 (1.68-4.96), respectively. CONCLUSION: Parental allergic diseases, especially maternal allergic diseases, are possible risk factors for development of AD in Korean infants.

Relaxant Effect of Spermidine on Acethylcholine and High K+-induced Gastric Contractions of Guinea-Pig

In our previous study, we found that spermine and putrescine inhibited spontaneous and acetylcholine (ACh)-induced contractions of guinea-pig stomach via inhibition of L-type voltage- dependent calcium current (VDCCL). In this study, we also studied the effect of spermidine on mechanical contractions and calcium channel current (IBa), and then compared its effects to those by spermine and putrescine. Spermidine inhibited spontaneous contraction of the gastric smooth muscle in a concentration-dependent manner (IC50=1.1+/-0.11 mM). Relationship between inhibition of contraction and calcium current by spermidine was studied using 50 mM high K+-induced contraction: Spermidine (5 mM) significantly reduced high K+(50 mM)-induced contraction to 37+/-4.7% of the control (p<0.05), and inhibitory effect of spermidine on IBa was also observed at a wide range of test potential in current/voltage (I/V) relationship. Pre- and post-application of spermidine (5 mM) also significantly inhibited carbachol (CCh) and ACh-induced initial and phasic contractions. Finally, caffeine (10 mM)-induced contraction which is activated by Ca2+-induced Ca2+release (CICR),` was also inhibited by pretreatment of spermidine (5 mM). These findings suggest that spermidine inhibits spontaneous and CCh-induced contraction via inhibition of VDCCL and Ca2+releasing mechanism in guinea-pig stomach.

Effects of Polyamines on Contractility of Guinea-Pig Gastric Smooth Muscle

This study was designed to investigate the effects of polyamines on mechanical contraction and voltage-dependent calcium current (VDCC) of guinea-pig gastric smooth muscle. Mechanical contraction and calcium channel current (I(Ba)) were recorded by isometric tension recording and whole-cell patch clamp technique. Spermine, spermidine and putrescine inhibited spontaneous contraction of the gastric smooth muscle in a concentration-dependent manner. Spermine (2 mM) reduced high K+ (50 mM)-induced contraction to 16+/-6.4% of the control (n=9), and significantly inhibited I(Ba) in a reversible manner (p<0.05; IC50=0.8 mM). Pre- and post-treatment of tissue with spermine (2-5 mM, n=10) also inhibited acetylcholine (10 micrometer)-induced phasic contraction to 5+/-6.4% of the control. Inhibitory effect of spermine on I(Ba) was observed at a wide range of test potentials of current/voltage (I/V) relationship (p<0.05), and steady-state activation of I(Ba) was shifted to the right by spermine (p<0.05). Spermidine and putrescine (1 mM each) also inhibited I(Ba) to 51+/-5.7% and 81+/-5.3% of the control, respectively. And putrescine (1 mM) inhibited I(Ba) at whole tested potentials (p<0.05) without significant change of kinetics (p<0.05). Finally, 5 mM putrescine also inhibited high K+ -induced contraction to 53+/-7.1% of the control (n=4). These findings suggest that polyamines inhibit contractions of guinea-pig gastric smooth muscle via inhibition of VDCC.

Sodium-activated Potassium Current in Guinea pig Gastric Myocytes

This study was designed to identify and characterize Na+ -activated K+ current (I(K(Na))) in guinea pig gastric myocytes under whole-cell patch clamp. After whole-cell configuration was established under 110 mM intracellular Na+ concentration ([Na+]i) at holding potential of -60 mV, a large inward current was produced by external 60 mM K+([K+] degree). This inward current was not affected by removal of external Ca2+. K+ channel blockers had little effects on the current (p>0.05). Only TEA (5 mM) inhibited steady-state current to 68+/-2.7% of the control (p<0.05). In the presence of K+ channel blocker cocktail (mixture of Ba2+, glibenclamide, 4-AP, apamin, quinidine and TEA), a large inward current was activated. However, the amplitude of the steadystate current produced under [K+]degree (140 mM) was significantly smaller when Na+ in pipette solution was replaced with K+ - and Li+ in the presence of K+ channel blocker cocktail than under 110 mM [Na+]i. In the presence of K+ channel blocker cocktail under low Cl- pipette solution, this current was still activated and seemed K+ -selective, since reversal potentials (E(rev)) of various concentrations of [K+]degree-induced current in current/voltage (I/V) relationship were nearly identical to expected values. R-56865 (10-20 microgram), a blocker of IK(Na), completely and reversibly inhibited this current. The characteristics of the current coincide with those of IK(Na) of other cells. Our results indicate the presence of IK(Na) in guinea pig gastric myocytes.

Sinus Node Function after Extended Transseptal Approach for Mitral Valve Surgery: 164 Clinical Cases / 대한흉부외과학회지

BACKGROUND: Extended transseptal approach can provide an excellent view of the mitral valve but the safety of this approach is controversial because this incision requires transection of the sinus node artery, which in most cases and can result postoperative arrhythmia. The purpose of this study was to evaluate perioperative and longterm conduction disturbances and the cardiac rhythms of patients who underwent an extended transseptal approach for mitral valve surgery. MATERIAL AND METHOD: Postoperative cardiac rhythms were analyzed in the 164 consecutive patients who received mitral valve replacements with a extended transseptal approach between March 1992 and July 2003. RESULT: Of the 84 patients in normal sinus rhythm, 34 (39%) had developed transient junctional rhythm and atrial fibrillation after operation, lasting less than 72 hours in most of cases. No intractable arrhythmias occurred. Most of these arrhythmia were not detected at the time of discharge and only 8 patients (9%) had atrial fibrillation at discharge. Postoperative PR intervals increased for 1 week, then decreased within 2 weeks postoperatively, and returned to normal range by 6 months postoperatively. During the postoperative period, 4 of the 78 patients with preoperative atrial fibrillation developed normal sinus thythm. CONCLUSION: The postoperative arrhythmias were temporary and showed no significant complications after extended transseptal approach for the mitral valve surgery.

Surgical Treatment of Superior Vena Cava Syndrome Caused by Hemodialysis Catheter: Report of 2 cases / 대한흉부외과학회지

The major etiology of superior vena cava (SVC) syndrome is malignancy. Radiologic endovascular intervention is the treatment of choice for patients with SVC syndrome due to malignant disease, which is unresponsive to radiation therapy and chemotherapy. However, it is not clear whether endovascular intervention can replace open surgery as the primary method of management of benign SVC syndrome. We report two cases of benign SVC syndrome resulting from dialysis catheters placed in the central veins. One patient underwent bypass surgery between innominate vein and right atrium by expanded polytetrafluoroethylene. Another patient had large thrombi in SVC and other central veins. We removed them under cardiopulmonary bypass to prevent pulmonary embolism, and SVC was repaired and augmented by autologous pericardium. Prompt symptomatic relief and angiographic improvements of collateral flow were achieved in both patients.

Intramural Bronchogenic Cyst of the Esophagus: A case report / 대한흉부외과학회지

Bronchogenic cysts are anomalous cystic lesions of foregut and usually located in the lung or mediastinum. Generally intramuscular cysts of the esophagus are considered as enterogenous foregut malformations. We report a young adult with an intramural bronchogenic cyst causing dysphagia and heartburn. It was located in the muscular layer of the esophagus and was removed without any damage to the mucosa. Histopathologic findings revealed that it was a bronchogenic cyst.

Regulation of L-type Calcium Channel Current by Somatostatin in Guinea-Pig Gastric Myocytes

To study the direct effect of somatostatin (SS) on calcium channel current (IBa) in guinea-pig gastric myocytes, IBa was recorded by using whole-cell patch clamp technique in single smooth muscle cells. Nicardipine (1microM), a L-type Ca2+ channel blocker, inhibited IBa by 98+/-1.9% (n=5), however IBa was decreased in a reversible manner by application of SS. The peak IBa at 0 mV were decreased to 95+/-1.1, 92+/-1.9, 82+/-4.0, 66+/-5.8, 10+/-2.9% at 10-10, 10-9, 10-8, 10-7, 10-5 M of SS, respectively (n=3~6; mean+/-SEM). The steady-state activation and inactivation curves of IBa as a function of membrane potentials were well fitted by a Boltzmann equation. Voltage of half-activation (V0.5) was -12+/-0.5 mV in control and -11+/-1.9 mV in SS treated groups (respectively, n=5). The same values of half-inactivation were -35+/-1.4 mV and -35+/-1.9 mV (respectively, n=5). There was no significant difference in activation and inactivation kinetics of IBa by SS. Inhibitory effect of SS on IBa was significantly reduced by either dialysis of intracellular solution with GDPbetaS, a non-hydrolysable G protein inhibitor, or pretreatment with pertussis toxin (PTX). SS also decreased contraction of guinea-pig gastric antral smooth muscle. In conclusion, SS decreases voltage-dependent L-type calcium channel current (VDCCL) via PTX- sensitive signaling pathways in guinea-pig antral circular myocytes.

A Clinical Study of Sepsis with Thrombocytopenia in Premature Infants / 소아과

PURPOSE: This study was performed to characterize sepsis with thrombocytopenia in premature infants to determine if thrombocytopenia is a prognostic factor in sepsis in premature infants. METHODS: We retrospectively analyzed the medical records of sepsis in premature infants admitted to the neonatal intensive care unit(N=41) at the Hallym University Sacred Heart Hospital from January 1999 to December 2002. The incidence, risk factors, symptoms, hematologic and bacteriologic findings were analyzed during episodes of sepsis. RESULTS: Of the 41 cases, 29(72%) were associated with thrombocytopenia. The ratio of male to female was 1.2 : 1. The vast majority(98%) were late-onset sepsis. The risk factors of the thrombocytopenic group were low birth weight and low gestational age. Major symptoms were poor activity (72%), apnea/tachypnea(52%), but were not significantly different between two groups. In the thrombocytopenic group(N=29), low total WBC count and high CRP level were discovered(P=0.03, P<0.01). The mean platelet count was 70.17(x103/mm3) at diagnosis of sepsis, and a mean platelet nadir was 43.10(x103/mm3). The severe thrombocytopenia(below 50x103/mm3) in the thrombocytopenic group was discovered in 69% and the duration of thrombocytopenia was about eight days. The majority of pathogens were gram-negative bacteria and candida. The thrombocytopenic group showed a pro longed length of stay and a high mortality rate. According to comparisons between the survived and expired groups, low birth weight, low gestational age, neutropenia and thrombocytopenia were significantly correlated with mortality(P<0.05). CONCLUSION: The sepsis with thrombocytopenia in premature infants showed late-onset sepsis and high morbidity and mortality, although differences were not significant statistically. Especially, low birth weight and low gestational aged infants should be cautiously treated and monitored.

A Clinical and Radiologic Study of Acute Focal Bacterial Nephritis in Children

PURPOSE: To raise awareness of the clinical importance of, and the need for proper management of acute focal bacterial nephritis(AFBN), we analyzed 22 AFBN patients and 22 other upper urinary tract infection patients by use of comparative studies. METHODS: From January 2000 to May 2002, 22 AFBN patients aged from 1 month to 12 months were selected. As a control group, 22 UTI patients with no radiologic abnormalities were selected and matched by age and sex. RESULTS: The incidence of AFBN was more common in boys than in girls. Since both groups had similar symptoms, it was difficult to diagnose AFBN by clinical presentations alone. ESR and CRP were significantly higher in AFBN patients. The most common causative organism was E. coli in both groups. On the sonographic findings, the most lesions were seen on the upper lobe of the kidney; more frequently, on left kidney. The lesions showed globular or wedge-shaped increased echogenecity. 99mTc-DMSA scan showed the complete coincidence of the location, size and shape in all cases compared to the findings of renal sonography. CONCLUSION: The roles of renal sonography and DMSA scan were very important, and ultrasonography was an excellent initial tool in diagnosing AFBN. Since the degree of infection in AFBN is more severe than other urinary tract infections and evollution into a renal abscess is possible, early diagnosis and appropriate antibiotics therapy is essential.

A Clinical Study of Acute Colonic Diverticulitis in Children

PURPOSE: Children with acute colonic diverticulitis(ACD), can be misdiagnosed with acute appendicitis. METHODS: We reviewed 15 cases of ACD during five years, from January 1998 to June 2002 retro spectively. RESULTS: Most patients(80%) with ACD in children presented with right lower quadrant pain. The primary diagnosis on admission was mostly acute appendicitis(87%), and all ACD in children occurred in the right colon. Fourteen patients were managed by conservative treatment including antibiotics. A follow-up study was performed in 15 patients. There were symptomatic recurrences in two patients, but no significant complication was noted. The frequency of ACD was 11.7 per 1000 acute appendicitis. CONCLUSION: ACD in children can mostly be cured by conservative treatment. It is prudent to choose the management through the diagnostic work up, including abdominal sonography and computed tomography, because there was no significant difference of clinical findings between ACD and acute appendicitis.

A Clinical Study of Acute Symptomatic Seizures in Children

PURPOSE: The present study was designated to sex, age, etiology of acute symptomatic seizures, which refer to the seizure caused by specific and transient pathophysiologic abnormalities in the central nervous system and other systems, and furthermore to analyze the incidence of acute symptomatic seizures before and during hospitalization. METHODS: The medical records of six hundred and ten convulsive children under fifteen years of age, who visited the Hallym University Sacred Heart Hospital from January 1999 to May 2001, were reviewed. One hundred and fourteen cases out of them were analyzed, and febrile seizures and unprovoked seizures were excluded. RESULTS: Among six hundred and ten children who had seizure during hospitalization, one hundred and fourteen(18.7%) had acute symptomatic seizures exclusive of febrile seizures and unprovoked seizures. The ratio of male to female was 1:2.1 and the peak age was three or less, accounting for 93.9%. Acute symptomatic seizures were caused by acute gastroenteritis(42.0%), metabolic/toxic disturbances(34.1%), cerebrovascular diseases(8.8%), CNS infections(8.0%), hypoxemia(4.4%), brain tumors(1.8%), and others(0.9 %). Remarkably, hypocalcemia and shaken baby syndrom were up to 82.1% of metabolic/ toxic distubances and 30.0% of cerebrovascular diseases, respectively. Among the one hundred and fourteen patients, 41.2% suffered from seizures before and during hospitalization and 11.4% did not before but did during hospitalization. CONCLUSION: Eighteen point seven percent of the cases of convulsions reviewed were classified into acute symptomatic seizures exclusive of febrile seizures and unprovoked seizures with the male to female ratio of 1:2.1 and high incidence age of three or less years. The leading causes of acute symtomatic seizures were acute gastroenteritis and hypocalcemia, comprising 70%. Shaken baby syrome and hyponatremia due to water intoxication can be prevented by public education about the danger, and central nervous system infection can be reduced by vaccine development and nationwide vaccination against the bacteria causing the central nervous system infection. In addition, appropriate prevention and management of seizure attacks are required for the patients with acute symptomatic seizures during hospitalization.

Neurotensin enhances gastric motility in antral circular muscle strip of guinea-pig

Many reports suggest that neurotensin (NT) in the gastrointestinal tract may play a possible role as a neurotransmitter, a circulating hormone, or a modulator of motor activity. NT exerts various actions in the intestine; it produces contractile and relaxant responses in intestinal smooth muscle. This study was designed to investigate the effect of NT on motility of antral circular muscle strips in guinea-pig stomach. To assess the role of Ca2+ influx in underlying mechanism, slow waves were simultaneously recorded with spontaneous contractions using conventional intracellular mircoelectrode technique. At the concentration of 10-7 M, where NT showed maximum response, NT enhanced the magnitude (863 +/- 198%, mean +/- SEM, n = 13) and the frequency (154 +/- 10.3%, n = 11) of spontaneous contractions. NT evoked a slight hyperpolarization of membrane potential, tall and steep slow waves with abortive spikes (278 +/- 50%, n = 4). These effects were not affected by atropine (2 micrometer), guanethidine (2 micrometer) and tetrodotoxin (0.2 micrometer). NT-induced contractile responses were abolished in Ca2+-free solution and reduced greatly to near abolition by 10 micrometer of verapamil or 0.2 mM of CdCl2. Verapamil attenuated the effects of NT on frequency and amplitude of the slow waves. Taken together, these results indicate that NT enhances contractility in guinea-pig gastric antral circular muscle and Ca2+ influx through the voltage-operated Ca2+ channel appears to play an important role in the NT-induced contractile mechanism.

Reoxygenation stimulates EDRF(s) release from endothelial cells of rabbit aorta

We have reported that hypoxia stimulates EDRF(s) release from endothelial cells and the release may be augmented by previous hypoxia. As a mechanism, it was hypothesized that reoxygenation can stimulate EDRF(s) release from endothelial cells and we tested the hypothesis via bioassay experiment. In the bioassay experiment, rabbit aorta with endothelium was used as EDRF donor vessel and rabbit carotid artery without endothelium as a bioassay test ring. The test ring was contracted by prostaglandin F2a (3 X 10-6 M) which was added to the solution perfusing through the aorta. Hypoxia was evoked by switching the solution aerated with 95% O2/5% CO2 mixed gas to one aerated with 95% N2/5% CO2 mixed gas Hypoxia/reoxygenation were interexchanged at intervals of 2 minutes (intermittent hypoxia). In some experiments, endothelial cells were exposed to 10-minute hypoxia (continuous hypoxia) and then exposed to reoxygenation and intermittent hypoxia. In other experiments, the duration of re oxygenation was extended from 2 minutes to 5 minutes. When the donor aorta was exposed to intermittent hypoxia, hypoxia stimulated EDRF(s) release from endothelial cells and the hypoxia-induced EDRF(s) release was augmented by previous hypoxia/reoxygenation. When the donor aorta was exposed to continuous hypoxia, there was no increase of hypoxia-induced EDRF(s) release during hypoxia. But, after the donor aorta was exposed to reoxygenation, hypoxia-induced EDRF(s) release was markedly increased. When the donor aorta was pretreated with nitro-L-arginine (10-5 M for 30 minutes), the initial hypoxia-induced EDRF(s) release was almost completely abolished, but the mechanism for EDRF(s) release by the reoxygenation and subsequent hypoxia still remained to be clarified. TEA also blocked incompletely hypoxia-induced and hypoxia/reoxygenation-induced EDRF(s) release EDRF(s) release by repetitive hypoxia and reoxygenation was completely blocked by the combined treatment with nitro-L-arginine and TEA. Cytochrome P450 blocker, SKF-525A, inhibited the EDRF(s) release reversibly and endothelin antgonists, BQ 123 and BQ 788, had no effect on the release of endothelium-derived vasoactive factors. Superoxide dismutase (SOD) and catalase inhibited the EDRF(s) release from endothelial cells. From these data, it could be concluded that reoxygenation stimulates EDRF(s) release and hypoxia/reoxygenation can release not only NO but also another EDRF from endothelial cells by the production of oxygen free radicals.

Different mechanisms for K+-induced relaxation in various arteries

(K+)o can be increased under a variety of conditions including subarachnoid hemorrhage. The increase of (K+)o in the range of 5 ~ 15 mM may affect tensions of blood vessels and cause relaxation of agonist-induced precontracted vascular smooth muscle (K+-induced relaxation). In this study, effect of the increase in extracellular K+ concentration on the agonist-induced contractions of various arteries including resistant arteries of rabbit was examined, using home-made Mulvany-type myograph. Extracellular K+ was increased in three different ways, from initial 1 to 3 mM, from initial 3 to 6 mM, or from initial 6 to 12 mM. In superior mesenteric arteries, the relaxation induced by extracellular K+ elevation from initial 6 to 12 mM was the most prominent among the relaxations induced by the elevations in three different ways. In cerebral arteries, the most prominent relaxation was produced by the elevation of extracellular K+ from initial 1 to 3 mM and a slight relaxation wasp rovoked by the elevation from initial 6 to 12 mM. In superior mesenteric arteries, K+-induced relaxation by the elevation from initial 6 to 12 mM was blocked by Ba2+ (30 muM) and the relaxation by the elevation from 1 to 3 mM or from 3 to 6 mM was not blocked by Ba2+. In cerebral arteries, however, K+-induced relaxation by the elevation from initial 3 to 6 mM was blocked by Ba2+, whereas the relaxation by the elevation from 1 to 3 mM was not blocked by Ba2+. Ouabain inhibited all of the relaxations induced by the extracellular K+ elevations in three different ways. In cerebral arteries, when extracellular K+ was increased to 14 mM with 2 or 3 mM increments, almost complete relaxation was induced at 1 or 3 mM of initial K+ concentration and slight relaxation occurred at 6 mM. TEA did not inhibit Ba2+/-sensitive relaxation at all and NMMA or endothelial removal did not inhibit K+-induced relaxation. Most conduit arteries such as aorta, carotid artery, and renal artery were not relaxed by the elevation of extracellular K+. Among conduit arteries, trunk of superior mesenteric artery and basilar artery were relaxed by the elevations of (K+)o. These data suggest that K+-induced relaxation has two independent components, Ba2+-sensitive and Ba2+-insensitive one and there are different mechanisms for K+-induced relaxation in various arteries.

Sensitivity of rabbit cerebral artery to serotonin is increased with the moderate increase of extracellular K+

(K+)O can be increased under a variety of conditions including subarachnoid hemorrhage. The increase of (K+)O in the range of 5~15 mM may affect tensions of blood vessels and can change their sensitivity to various vasoactive substances. Therefore, it was examined in the present study whether the sensitivity of cerebral arteries to vasoactive substances can be changed with the moderate increase of (K+)O, using Mulvany-type myograph and (Ca2+)c measurement. The contractions of basilar artery and branch of middle cerebral artery induced by histamine were not increased with the elevation of (K+)O from 6 mM to 9 mM or 12 mM. On the contrary, the contractions induced by serotonin were significantly increased with the elevation of (K+)O. The contractions were also significantly increased by the treatment with nitro-L-arginine (10-4 M for 20 minutes). In the nitro-L-arginine treated arteries, the contractions induced by serotonin were significantly increased with the elevation of (K+)O from 6 mM to 12 mM. K+-induced relaxation was evoked with the stepwise increment of extracellular K+ from 0 or 2 mM to 12 mM by 2 mM in basilar arterial rings, which were contracted by histamine. But (K+)O elevation from 4 or 6 mM to 12 mM by the stepwise increment evoked no significant relaxation. Basal tension of basilar artery was increased with (K+)O elevation from 6 mM to 12 mM by 2 mM steps or by the treatment with ouabain and the increase of basal tension was blocked by verapamil. The cytosolic free Ca2+ level was not increased by the single treatment with serotonin or with the elevation of (K+)O from 4 mM to 8 or 12 mM. In contrast to the single treatment, the Ca2+ level was increased by the combined treatment with serotonin and the elevation of (K+)O. The increase of free Ca2+ concentration was blocked by the treatment with verapamil. These data suggest that the sensitivity of cerebral artery to serotonin is increased with the moderate increase of (K+)O and the increased sensitivity to serotonin is due to the increased (Ca2+)i induced by extracellular Ca2+ influx.