Biomedical subjects

M Kanai

Publications and source records attributed to M Kanai.

At least 37 records · Page 2Linked to original sources

PubMed2001

Complications of hepatectomy for hilar cholangiocarcinoma.

We retrospectively reviewed postoperative complications in 105 patients with hilar cholangiocarcinoma who underwent hepatectomy at Nagoya University Hospital from January 1990 through March 1999. Of the 105 subjects, 97 (92.4%) underwent resection of two or more Healey's segments of the liver. Combined portal vein resection was performed in 33 (31.4%) patients and pancreatoduodenectomy in 10 (9.5%). Twenty (19.0%) patients had no postoperative complications, another 39 (37.1%) patients had minor complication(s) only, and the remaining 46 (43.8%) developed major complication(s). The morbidity rate reached as high as 81.0%. Major complications required relaparotomy in 11 (10.5%) patients. Of the 46 patients with major complication(s) 36 recovered; the remaining 10 patients died of liver failure with other organ failure(s) or of intraabdominal bleeding 12, 14, 18, 21, 57, 75, 75, 87, 93, or 134 days after surgery. Thus the 30-day mortality was 3.8% and the overall mortality 9.5%. Pleural effusion was the most frequent complication found in 66 (62.9%) patients, followed by wound sepsis in 39 (37.1%), and then liver failure in 29 (27.6%). Liver failure developed in 16.7% of 48 patients with less than 50% liver resection and in 36.8% of 57 patients with 50% or more resection (P < 0.05). Other organ failures, including renal, respiratory, gastrointestinal, and hematologic failures, developed as a sign of multiple organ failure following liver failure in most patients or preceding liver failure in a few patients. None of the six patients with four or more organ failures survived. Hepatectomy for hilar cholangiocarcinoma is risky owing to impaired hepatic functional reserve in jaundiced patients and the technical difficulty associated with hepatobiliary resection. Our goal is to reduce mortality to less than 5% while keeping a high resectability rate (above 80%).

Adult↗

PubMed2001

Five-year survivors after aggressive surgery for stage IV gallbladder cancer.

PURPOSE: To describe 5-year survivors after radical surgery for stage IV gallbladder cancer and to determine the characteristics leading to potential long-term survival. METHODS: Of 59 patients undergoing radical resection for stage IV disease between 1979 and 1994, 6 patients who have survived for more than 5 years were followed up. RESULTS: Three patients had developed obstructive jaundice due to involvement of the hepatic hilum, but the other three had not. The jaundiced patients had remarkable tumor spread over the bile duct and right hepatic artery within the hepatoduodenal ligament. However, the proper and left hepatic arteries and the portal trunk and its left branch were free from tumor involvement. The nonjaundiced patients had N1 or N2 lymph node metastasis. However, none underwent bile duct resection or pancreatoduodenectomy to establish radical lymphadenectomy. CONCLUSIONS: Selected patients with stage IV gallbladder cancer may be candidates for 5-year survival when the primary tumor is fairly localized even if it forms a large mass and involves neighboring organs including the hepatic duct, lymph node metastasis is limited to N1 and N2 except for the celiac and superior mesenteric nodes and is less infiltrative, and distant metastasis including that in the paraaortic area is absent.

Adult↗

PubMed2001

Serum-free coculture system for ex vivo expansion of human cord blood primitive progenitors and SCID mouse-reconstituting cells using human bone marrow primary stromal cells.

OBJECTIVE: In an attempt to maintain and expand human stem cells, many investigators have used xenogeneic, especially murine, stromal cells and fetal calf serum. Because of the possible transmission of infectious diseases, however, the safety of the delivery of grafts expanded in culture using xenogeneic cells and serum has been debated. Using primary human marrow stromal cells, we established a novel serum-free culture system to expand human primitive progenitors and transplantable stem cells. MATERIALS AND METHODS: Cord blood CD34(+) cells were cultured on a monolayer of human primary marrow stromal cells in the presence of thrombopoietin (TPO), flt3/flk2 ligand (FL), and/or stem cell factor (SCF) under serum-free conditions. After 2 or 4 weeks of culture, cells were examined for clonogenic progenitors and severe combined immunodeficient disorder (SCID) mouse-reconstituting cells (SRC). RESULTS: In the presence of TPO, FL, and SCF, marrow stromal cells supported more than a 100- and 1,000-fold expansion of CD34(+) cells and colony-forming units in culture after 2 and 4 weeks of incubation, respectively. In addition, cobblestone area-forming cells were expanded more than 18- and 60-fold after 2 and 4 weeks of culture, respectively. Furthermore, SRC assay demonstrated augmented engraftment by cultured cells. CONCLUSION: This ex vivo expansion system should prove valuable in clinical settings in which stromal cells are available from recipients or stem cell donors.

Acute Disease↗

PubMed2001

TGF-alpha inhibits apoptosis of murine gastric pit cells through an NF-kappaB-dependent pathway.

BACKGROUND AND AIMS: Recently, some growth factors have been shown to play roles not only as growth factors but also as cell-surviving factors. Transforming growth factor (TGF)-alpha is expressed in normal gastric mucosa. In this study, we investigated the cell-surviving effect of TGF-alpha on gastric mucosal cells and its signaling mechanism. METHODS: We used a gastric mucosal cell line, GSM06, and gastric cancer cell line, AGS. Apoptosis was induced by serum depletion or exposure to sodium butyrate. Analysis of apoptosis was performed by DNA ladder assay, measuring the DNA fragmentation ratio (Burton method), and 4',6-diamidino-2-phenylindole staining. RESULTS: TGF-alpha protected gastric mucosal cells against apoptosis induced by serum depletion or sodium butyrate in a dose-dependent manner. This antiapoptotic effect of TGF-alpha was blocked by the pretreatment with reagents that can potentially inhibit NF-kappaB activation, whereas neither MEK inhibitor PD098059 nor PI-3-kinase inhibitor wortmannin abolished this effect. Electrophoretic mobility shift assay showed nuclear factor kappaB (NF-kappaB) activation by TGF-alpha stimulation. TGF-alpha also enhanced the expression of Bcl-2 family proteins in an NF-kappaB-dependent manner. CONCLUSIONS: TGF-alpha plays an antiapoptotic role in gastric mucosal cells via the NF-kappaB-dependent pathway.

Animals↗

PubMed2001

BAPS prize-1999: Lung growth induced by prenatal tracheal occlusion and its modifying factors: a study in the rat model of congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: Prenatal tracheal occlusion (TO) has been shown to accelerate lung growth in animal models and models of pulmonary hypoplasia. However, these models may not mimic early events in human congenital diaphragmatic hernia (CDH). The authors previously have developed a model of TO in the rat. The purpose of this study was to apply this technique to characterize TO-induced lung growth in the early onset nitrofen-induced model of CDH, and to address the clinically important questions of the effect of timing of TO and maternal infusion of terbutaline on TO-induced lung growth. METHODS: Left-sided CDH was induced in the fetuses of time-dated pregnant Sprague-Dawley rats by feeding 100 mg of nitrofen on day 9 of gestation. TO was performed via maternal laparotomy and hysterotomy at 19 days' gestation. At harvest (21.5 days' gestation), lungs from nitrofen-exposed fetuses without CDH (non-CDH), with CDH (CDH), and with CDH and TO (CDH-TO) were compared by analysis of wet and dry weight, DNA and protein content, and stereologic morphometry. A second study was performed to assess relative lung growth achieved by equal intervals of TO after "early" (19 days) versus "late" (20 days) gestational TO. Finally, the effect of maternal infusion of terbutaline, a commonly used tocolytic for fetal surgery, on TO-induced lung growth was analyzed. RESULTS: Analysis of lung growth showed consistent and significant lung growth in CDH-TO lungs. Lung growth after TO was proliferative and characterized by an increase in parenchymal volume as manifest by increased total saccular number and surface area and radial saccular count. Although visceral reduction was partially achieved, herniated liver was reduced incompletely. The majority of lung growth occurred during the latter half of the TO period. Early gestational age at TO and maternal terbutaline administration adversely influenced lung growth in CDH-TO fetuses. CONCLUSIONS: Prenatal TO induces dramatic lung growth in the early onset, nitrofen-induced rat model of CDH. TO is more effective later in gestation presumably because of the advanced stage of lung development and lung fluid production. This effect could be counterbalanced by the use of beta-mimetic tocolytic, which inhibits fetal lung fluid production late in gestation. Multiple factors including fetal lung fluid production and absorption, pharmacologic agents, space-occupying herniated viscera, and timing and duration of TO may be important clinical variables. The development of the rat model should facilitate further studies into the cellular and molecular mechanisms responsible for TO-induced lung growth.

Animals↗

PubMed2001

Fetal tracheal occlusion in the rat model of nitrofen-induced congenital diaphragmatic hernia: tracheal occlusion reverses the arterial structural abnormality.

BACKGROUND/PURPOSE: The high mortality rate of congenital diaphragmatic hernia (CDH) is ascribed generally to pulmonary hypoplasia and persistent pulmonary hypertension characterized by associated pulmonary arterial structural changes. Prenatal tracheal occlusion (TO) accelerates lung growth, but the effect of TO on pulmonary arterial structure in CDH has not been well defined. The authors hypothesized that TO could reverse the pulmonary arterial structural changes observed in CDH. To address this hypothesis, we utilized the nitrofen-induced rat model of CDH to examine the effect of TO on pulmonary arterial morphology of CDH lungs. METHODS: Left-sided CDH was induced by administering 100 mg of nitrofen to pregnant Sprague-Dawley rats on day 9 of gestation. TO was performed on day 19, and the fetuses were harvested on day 21.5 of gestation. After the ductus arteriosus was ligated, the pulmonary arteries were injected with a barium-gelatin mixture, and the lungs were inflation fixed. Coronal sections of the lungs were stained with elastin van Gieson. External diameter (ED), internal diameter (ID), and medial and adventitial wall thickness of the pulmonary arteries were measured using a computer image analyzer, and the percent medial thickness (%MT) and adventitial thickness (%AT) were calculated. The lungs from nitrofen-exposed fetuses with left-sided CDH (CDH group), trachea-occluded left-sided CDH (CDH+TO group), non-CDH (non-CDH group), and normal fetuses (normal group) were compared. RESULTS: The %MT was significantly increased in all sizes of arteries in CDH compared with non-CDH and normal groups (P < .01). Compared with the CDH group, the CDH+TO group had significantly reduced %MT in all sizes of arteries (P < .01), to values comparable or less than the non-CDH and normal groups. The %AT of the CDH group was significantly increased in larger arteries compared with non-CDH and normal control groups (P < .01). CDH+TO had significantly decreased %AT compared with CDH in both larger (P < .01), and smaller arteries (P < .05) and that was comparable with the non-CDH and normal control groups. CONCLUSIONS: TO in hypoplastic CDH lung can reverse the pulmonary arterial structural changes that are seen in the nitrofen-induced fetal rat model of CDH. These data suggest that TO may reduce pulmonary vascular reactivity, and the risk of postnatal persistent pulmonary hypertension observed in human neonates with severe CDH. J Pediatr Surg 36:839-845.

Analysis of Variance↗

PubMed2001

Percutaneous cholangioscopic bilioenterostomy for unreconstructed segmental bile duct after hepatobiliary resection for hilar cholangiocarcinoma.

During a major hepatectomy, inadvertent ligation of the major segmental bile-duct branch of the liver remnant is a serious complication. We experienced this serious complication of inadvertent ligation of the bile-duct branch, which should be anastomosed to the jejunal loop, during a left hepatic trisegmentectomy with total caudate lobectomy for a hilar cholangiocarcinoma. A percutaneous transhepatic bilioenteric connection was then created, modifying an endoscopic ureteroneocystostomy technique, between the ligated segmental bile duct and the jejunal loop. In this procedure, we used two cholangioscopes; one was introduced through the percutaneous transhepatic drainage route, the other was introduced through an enterostomy which was made during the surgery for postoperative enteral feeding; we also used a transjugular intrahepatic portosystemic shunt (TIPS) kit under fluoroscopic guidance. We present here our technique of percutaneous transhepatic bilioenterostomy.

Bile Duct Neoplasms↗

PubMed2001

Hepatocellular carcinoma with biliary tumor thrombi: aggressive operative approach after appropriate preoperative management.

BACKGROUND: The aim of this study was to clarify clinicopathologic characteristics of, and to evaluate an aggressive treatment strategy for, hepatocellular carcinoma with biliary tumor thrombi. METHODS: From 1980 to 1999, a total of 132 patients underwent hepatectomy for hepatocellular carcinoma. Of these, 17 patients had macroscopic biliary tumor thrombi and were retrospectively analyzed. RESULTS: The operative procedures included right hepatic trisegmentectomy (n = 1), right or left hepatic lobectomy (n = 11), and segmentectomy or subsegmentectomy (n = 5). In 13 patients, tumor thrombi extended beyond the hepatic confluence and was treated by thrombectomy through a choledochotomy in 8 patients and extrahepatic bile duct resection and reconstruction in 5 patients. The 3- and 5-year survival rates were 47% and 28%, respectively, with a median survival time of 2.3 years. These survival rates were similar to those achieved in 115 patients without biliary tumor thrombi. In a multivariate analysis, expansive growth type and solitary tumors were independent prognostic variables for favorable outcome after operation, whereas biliary tumor thrombi was not a significant prognostic factor. CONCLUSIONS: Surgery after appropriate preoperative management of hepatocellular carcinoma with biliary tumor thrombi yields results similar to those of patients without biliary involvement. Hepatectomy with thrombectomy through a choledochotomy appears to be as effective as a resection procedure.

Bile Duct Neoplasms↗

PubMed2001

Pancreaticobiliary arteriovenous malformation with common bile duct dilation in a patient with hemobilia.

Arteriovenous malformation of the pancreas is a very rare entity. We describe a case involving the head of the pancreas associated with progressive hemobilia bleeding from the lower part of the common bile duct. The patient was a 50-year-old man with acute epigastralgia. Endoscopic retrograde cholangiopancreatography revealed hemobilia and cystic dilation of the common bile duct. Angiography demonstrated increased blood volume in the head of the pancreas and early filling of the superior mesenteric and portal veins. Abdominal pain and progressive anemia caused by hemobilia required surgical treatment. Histologic examination of the resected specimen revealed marked proliferation of the blood vessels in the pericholedochal area and the exact point of bleeding from the pancreaticobiliary arteriovenous malformation.

Angiography↗

PubMed2001

Endovascular stent grafting for the treatment of blunt thoracic aortic injury.

OBJECTIVE: Recent advances of endovascular stent-grafting (ESG) provide a new therapeutic option with minimum surgical damage for blunt aortic injury (BAI) during its acute phase. To clarify the effectiveness of ESG for BAI, a prospective clinical study at a university hospital was conducted. METHODS: All patients with blunt thoracic injury underwent thoracic contrast-enhanced computed tomographic (CT) scan. Six patients age 48.8 +/- 19.8 years, with Injury Severity Scores of 35.8 +/- 8.1, and with BAI were treated according to our protocol. The stent-graft covered by woven Dacron was placed at the injury site. Endoleakage was then checked by aortography and CT scan was again performed once a day on days 7 through 14. RESULTS: All patients had injury of the aortic isthmus. ESG placement was performed within 8 hours after injury except in one (48 hours). The operating time was 159.5 +/- 21.1 minutes and bleeding volume was 105 +/- 26.6 mL. No endoleakage was found. Repeat CT scan revealed disappearance of hematoma. All patients except one had an event-free clinical course. One patient died because of rupture of the ascending aorta on day 6; however, autopsy revealed evidence of the healing process at the injury site sealed by ESG. CONCLUSION: An ESG is a valid therapeutic option with minimal surgical invasion for patients with acute-phase aortic injury.

Adult↗

PubMed2001

Warning from Nagano: increase of vulvar hematoma and/or lacerated injury caused by snowboarding.

BACKGROUND: On the basis of the number of women snowboarders whose vulvar injuries we have recently treated, we believe that the cases of vulvar hematoma and lacerated injuries caused by snowboarding have been increasing. To analyze the causal relation between snowboarding and vulvar injuries, we investigated how women were injured during snowboarding. METHODS: During the last three ski-ing seasons at the five hospitals near the ski resorts in Nagano Prefecture, Japan, the clinical charts of all patients with vulvar injuries during snowboarding were reviewed for the number of patients treated, the condition of the patients at diagnosis, and the characteristics of vulvar injuries. All patients were also asked by phone about how their vulvar injury was caused during snowboarding. RESULTS: The number of patients with vulvar injuries during the last three seasons was 16, 14, and 35, respectively. The types of vulvar injuries included hematoma in 33 (51%) patients, hematoma with lacerated injury in 17 (26%), and lacerated injury in the remaining 15 (23%). Of the 65 patients, 45 (69%) needed surgical treatment. Characteristically, 54 (88%) patients were injured when they tumbled onto the binding of the snowboard at the same time that one foot was left off the board and the binding was not turned down but left erect. CONCLUSION: It is important for women snowboarders to realize that in snowboarding there are dangers that may cause vulvar injuries. The prevention of such injuries requires that the binding should be turned down when the foot is left off the board and that snowboarders should try not to tumble onto the board.

Adolescent↗

PubMed2001

The Japan Home-health Apparatus Industrial Association: investigation of home-use electronic sphygmomanometers.

The Japanese Home-health Apparatus Industrial Association is an official independent organization comprising ten departments. That concerned with home electronic sphygmomanometers, which has seven participants from different Japanese manufacturers, has already undertaken and is currently involved in various activities related to voluntary standards for performance validation and quality assurance. Because Japanese companies form a large proportion of manufacturers, these activities are important in terms of autonomic regulation. Although many improvements have been made to home electronic sphygmomanometers, some problems still remain unresolved, especially in terms of measurement reliability and easy operation by lay people. Another aspect of the department's work relates to making proposals on major validation standards, such as those of the Association for the Advancement of Medical Instrumentation, the British Hypertension Society and Comité Européen de Normalisation (CEN). Clinical validation should be discussed in order to define a more accurate standard method of measurement using auscultation and more appropriate criteria that are unaffected by primary blood pressure variation.

Blood Pressure Determination↗

PubMed2001

Fetal lung growth after short-term tracheal occlusion is linearly related to intratracheal pressure.

Prenatal tracheal occlusion (TO) has been shown to accelerate fetal lung growth, yet the mechanism is poorly understood. The goal of this study was to determine the relationship between fetal intratracheal pressure (Pitr) and fetal lung growth after TO. Fetal lambs underwent placement of an intratracheal catheter and a reference catheter at 115--120 days gestation (term, 145 days). Fetal Pitr was continuously controlled at three levels (high, 8 mmHg; moderate, 4 mmHg; low, 1 mmHg) by a servo-regulated pump. The animals were killed after 4 days, and the parameters of lung growth were compared. Lung volume (136.0 +/- 16.7, 94.9 +/- 9.7, 55.5 +/- 12.4 ml/kg), lung-to-body weight ratio (6.31 +/- 0.70, 4.89 +/- 0.38, 3.39 +/- 0.22%), whole right lung dry weight (3.01 +/- 0.29, 2.53 +/- 0.15, 2.07 +/- 0.24 g/kg), right lung DNA (130.0 +/- 11.3, 116.7 +/- 8.6, 97.5 +/- 10.9 mg/kg), and protein contents (1,865.5 +/- 92.5, 1,657.6 +/- 106.8, 1,312.0 +/- 142.5 mg/kg) in high, moderate, and low groups, respectively, all increased in the moderate compared with the low group and increased further in the high compared with the moderate group. Morphometry confirmed a stepwise increase in the volume of respiratory region and alveolar surface area. We conclude that lung growth in the first 4 days after TO is closely correlated with fetal Pitr, offering additional evidence that an increase in lung expansion is one of the major factors responsible for TO-induced lung growth.

Animals↗

PubMed2001

Multifunctional asymmetric catalysis.

Two types of general and practical enantioselective catalysts, namely, bimetallic complexes and Lewis acid-Lewis base bifunctional catalysts were developed based on the concept of multifunctional catalysis. In the first part of this review, the first example of a catalytic enatioselective nitro-Mannich reaction as well as a direct catalytic enantioselective aldol reaction of 2-hydroxyacetophenone using bimetallic complexes is discussed. The new complex, composed of ytterbium, potassium, and BINOL in a ratio of 1:1:3, promoted the nitro-Mannich reaction of nitromethane with up to 91% ee. On the other hand, second generation ALB catalyzed an enantioselective and diastereoselective nitro-Mannich reaction of nitroalkanes in up to 83% ee with a diastereomeric ratio up to 7:1. Moreover, the reaction of aldehydes with 2-hydroxyacetophenone in the presence of LLB, KHMDS, and H2O selectively gave the corresponding anti-alpha,beta-dihydroxy ketones in up to 95% ee and, in the presence of the catalyst prepared from linked-BINOL and 2 eq of Et2Zn, selectively afforded the syn-alpha,beta-dihydroxy ketones in up to 86% ee. In the second part, the development of new catalysts displaying a Lewis acidity and a Lewis basicity is described. The Lewis acid of the catalyst activates aldehydes, imines, acyl quinoliniums, and ketones. At the same time, the Lewis base activates the nucleophile (TMSCN). Catalysts of this type produced a highly enantioselective cyanation of these electrophiles. Application of the catalytic enantioselective cyanosilylation of aldehydes to a total synthesis of epothilones is also described.

Catalysis↗

PubMed2001

[Development and application of enantioselective Lewis acid-Lewis base bifunctional catalyst].

The design, synthesis, and application of a new bifunctional enantioselective catalyst containing both Lewis acidity and Lewis basicity are described. Recent developments of chiral quaternary stereocenter synthesis through catalytic enantioselective Reissert-type reaction and cyanosilylation of ketones forming the S-enantiomer are chiefly reviewed. The catalysts are composed of a Lewis acid metal (aluminum, titanium, or lanthanide) and a Lewis base (the oxygen atom of a phosphine oxide), of which positions are defined by 2,2'-binaphthol (BINOL) or a carbohydrate scaffold. Utilizing these catalysts, we have developed a variety of enantioselective cyanation reactions, such as cyanosilylation of aldehydes and ketones, Strecker-type reaction, and Reissert-type reaction. These reactions showed a broad substrate generality. Investigations toward the elucidation of the reaction mechanism, involving kinetic studies, comparison of the results by control catalysts, and absolute configurations of the products, revealed that these reactions are catalyzed by a dual activation of a substrate and trimethylsilyl cyanide (TMSCN) by the Lewis acid and the Lewis base of these catalysts. Catalytic enantioselective synthesis of several drug lead compounds, such as anti-cancer epothilones, potent N-methyl-D-aspartate (NMDA) receptor antagonists, phenytoin analogs, salsolinol carboxylic acid, and anti-cancer camptothecin was achieved, using these reactions as key steps.

Acids↗

PubMed2001

Clinical significance of preheparin serum lipoprotein lipase mass in coronary vasospasm.

The present study investigated the clinical significance of preheparin serum lipoprotein lipase (LPL) mass in coronary vasospasm by examining its relationship with the acetylcholine-induced coronary artery response in patients without angiographically demonstrable atherosclerotic coronary artery disease (CAD). The subjects were 39 men who had suspected CAD and who underwent coronary angiography. Coronary vasospasm was defined as a marked luminal narrowing or total occlusion provoked by the intracoronary administration of acetylcholine. Preheparin LPL mass was lower (p<0.05) in 25 subjects in whom vasospasm was induced by the acetylcholine provocation test than in the 14 subjects with a negative response. As regards preheparin LPL mass, the subjects with multiple vessel spasm had significantly low concentrations (p<0.05) compared with single vessel spasm, although serum lipid levels were not significantly different. Multiple regression analysis revealed only preheparin LPL mass had a significant absolute t-value (2.016) among the coronary risk factors. Low preheparin LPL mass is interpreted as reflecting an impaired acetylcholine-induced coronary relaxation in coronary vasospasm and preheparin LPL mass may be useful as a marker of early stage coronary atherosclerosis that is not detectable by angiography.

Acetylcholine↗

PubMed2001

Alterations in autonomic nervous control of heart rate among tourists at 2700 and 3700 m above sea level.

OBJECTIVES: Many travelers who are not specially trained for activities at high altitude are at risk of physical problems, including cardiovascular disorders, when exposed to high-altitude environments. In the present study, we investigated how actual acute exposure to altitudes of 2700 and 3700 m affected the autonomic nervous control of heart rate in untrained office workers. METHODS: Physiological parameters (heart rate, respiratory rate, arterial blood oxygen saturation, and end-expiratory carbon dioxide tension) were measured at sea level, 2700 m, and 3700 m. The power of heart rate variability was quantified by determining the areas of the spectrum in 2 component widths: low frequency (LF; 0.04-0.15 Hz) and high frequency (HF; 0.15-0.5 Hz). The ratio of LF power to HF power (LF:HF), which is considered to be an index of cardiac sympathetic tone, was also assessed. RESULTS: Both HF and LF heart rate variability decreased according to the elevation of altitude. High- and low-frequency powers at 3700 m were significantly lower than those at sea level (P < .01 for HF, P < .05 for LF). The LF:HF ratio at 2700 m was not significantly different from that at sea level. However, it was significantly increased at 3700 m (P < .01). CONCLUSIONS: At 2700 and 3700 m, the activity of the autonomic nervous system measured by heart rate variability was decreased in untrained office workers. The sympathetic nervous system was dominant to the parasympathetic at 3700 m. These alterations in the autonomic nervous system might play some role in physical fitness at high altitudes.

Adult↗

PubMed2001

A glass capillary ultramicroelectrode with an electrokinetic sampling ability.

A glass capillary ultramicroelectrode (tip diameter approximately 1.2 microm) having an electrokinetic sampling ability is described. It is composed of a pulled glass capillary filled with an inner solution and three internal electrodes (Pt working and counter electrodes and an Ag/AgCl reference electrode). The voltammetric response of the capillary electrode is based on electrokinetic transport of analyte ions from the sample solution into the inner solution across the conical tip. It was found that the electrophoretic migration of analytes at the conical tip is faster than electroosmotic flow, enabling electrokinetic transport of analyte ions into the inner solution of the electrode. By using [Fe(CN)6]4- and (ferrocenylmethyl)trimethylammonium (FcTMA+) ions as model analytes, differential pulse voltammetric responses of the capillary electrode were investigated in terms of tip diameter of the capillary, sampling voltage, sampling time, detection limit and selectivity. The magnitude of the response depends on the size and charge of analyte ions. With a capillary electrode having a approximately 1.2-microm tip diameter, which minimizes non-selective diffusional entry of analytes, the response after 1 h sampling at +1.7 V is linearly related to [Fe(CN)6]4- concentration in the range of 0.50-5.0 mM with the detection limit of 30 microM. Application of a potential of the same sign as that of the analyte ion forces the analyte to move out from the electrode to the solution, enabling reuse of the same capillary electrode. The charge-selective detection of analytes with the capillary electrode is demonstrated for [Fe(CN)6]4- in the presence of FcTMA+.

Algorithms↗