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Biomedical subjects

Y Takei

Publications and source records attributed to Y Takei.

At least 271 records · Page 15Linked to original sources
PubMed1992

Motion sickness and equilibrium ataxia.

In order to know the relationship between motion sickness and equilibrium ataxia, we performed Graybiel's ataxia test battery on 10 normal subjects: 1) before donning goggles which reversed the optical image horizontally and vertically; 2) while wearing the goggles and walking; and 3) after walking as long as possible up to 90 min. Horizontal reversal of vision resulted in a statistically significant decrease in the score for all the closed-eyes tests and one open-eyes test performed during walking and after walking, respectively. In contrast, walking while wearing vertical reversing goggles produced a significant but very small change for one of the closed-eyes tests alone. The present study indicates that failure to detect spatial orientation, which evokes autonomic nervous symptoms as an alarm sign, produces equilibrium ataxia by impairing the top-down regulation of body balance, and that vertically reversed vision does not impair spatial orientation needed to maintain upright posture or to execute locomotion.

Adult↗
PubMed1992

[Structure and function of ventricular natriuretic peptide (VNP)].

Ventricular natriuretic peptide (VNP) appears to be a new member of the ANP family, as judged by its uniquely long C-terminal 'tail' sequence and by its cDNA sequence. The eel VNP causes the entire spectra of actions known to be characteristic of the ANP family, and its vascular and renal effects are more potent than other eel natriuretic peptides in both eels and rats. Since VNP is a hormone originating from ventricles, it is possible that VNP is secreted more quickly and profoundly than atrium-originated ANP, in response to an increase in afterload or stenosis of the coronary artery, resulting in recovery of ventricular function. Therefore, identification of VNP in mammals is awaited for the development of a new drug which counteracts against heart failure.

Amino Acid Sequence↗
PubMed1991

Ethanol-induced disturbance of hepatic microcirculation and hepatic hypoxia.

The hypothesis was tested whether ingestion of ethanol might disturb the hepatic microcirculation with resulting hepatic hypoxia. Infusion of ethanol increased the portal pressure concentration-dependently in rat livers perfused with Krebs-Henseleit buffer at a constant flow rate (Emax = 11.5 cm H2O, EC50 = 90 mM). This increase in portal pressure was due to hepatic vasoconstriction, since it diminished in the presence of sodium nitroprusside, a direct acting vasodilator. The regional hepatic tissue hemoglobin concentration after perfusion with added erythrocyte suspension (hematocrit 1%), measured by tissue-reflectance spectrophotometry, was significantly diminished by the infusion of ethanol, indicating the impairment of the microcirculation of the superficial layer of the liver. When the absorption spectrum of the liver was examined by reflectance spectrophotometry, infusion of ethanol caused a parallel reduction of all the mitochondrial respiratory cytochromes in a concentration-dependent fashion, concomitant with the increase of portal pressure, indicating a marked reduction of oxygen concentration in superficial liver tissue. The reduction of the respiratory cytochromes was also associated with the decrease in oxygen consumption of the liver, indicating that the hepatic hypoxia was due to the reduction of oxygen delivery to hepatocytes rather than the increased oxygen consumption of the liver. The reduction of the respiratory cytochromes was correlated with the increase in portal pressure and was inhibited by sodium nitroprusside. These data indicate that the ethanol-induced hepatic vasoconstriction disturbs hepatic microcirculation, resulting in hepatic hypoxia and reduction of mitochondrial respiratory cytochromes.

Animals↗
PubMed1991

A novel natriuretic peptide isolated from eel cardiac ventricles.

A new natriuretic peptide, which exhibits the entire spectrum of actions known to be characteristic of atrial and brain natriuretic peptides (ANP and BNP), was isolated from eel cardiac ventricles and has been named ventricular natriuretic peptide (VNP). The primary structure of eel VNP is characterized by its uniquely long C-terminal 'tail' that extends from the second half-cystine. Thus, eel VNP appears to be a novel natriuretic peptide of a type not found in mammals. With respect to natriuretic (rat) and vasodepressor (rat and eel) activities, eel VNP is much more potent than human ANP in eels and almost equipotent in rats. Strong tachyphylaxis is observed for the vasodepressor effect in both rats and eels, whereas it is not observed for the natriuretic effect in rats.

Amino Acid Sequence↗
PubMed1991

Isolation of high-molecular-weight C-type natriuretic peptide from the heart of a cartilaginous fish (European dogfish, Scyliorhinus canicula).

A high-molecular-weight form of C-type natriuretic peptide (CNP) was isolated from both cardiac atria and ventricles of European dogfish, Scyliorhinus canicula, and its primary structure was determined. The peptide consists of 115 amino acid residues, in which the C-terminal 22 residues show high homology to CNPs identified to date. This is the first direct evidence for the presence of natriuretic peptide in the cartilaginous fish, and for the presence of CNP in an organ other than the brain.

Amino Acid Sequence↗
PubMed1991

Methyl palmitate prevents Kupffer cell activation and improves survival after orthotopic liver transplantation in the rat.

The purpose of this study was to determine whether prevention of Kupffer cell activation following orthotopic liver transplantation improves postoperative survival. First, particle phagocytosis by Kupffer cells was monitored continuously from the uptake of colloidal carbon by the perfused liver. Unstored livers took up carbon at rates of around 150 mg/g per hour, whereas storage for 24 h in Euro-Collins solution nearly doubled values to about 290 mg/g per hour. Treatment of rats with methyl palmitate, an inhibitor of phagocytosis by Kupffer cells, reduced carbon uptake to about one-third to one-half of control values in unstored and stored livers, respectively. Oxygen uptake, which was increased about 25% in stored and unstored livers by infusion of colloidal carbon, was only increased 5%-10% in both groups following treatment with methyl palmitate, suggesting that Kupffer cell activation was prevented by methyl palmitate. In livers transplanted after storage for 6 h in Euro-Collins solution (nonsurvival conditions), control rats survived only about 12 h, while treatment with methyl palmitate increased survival time significantly--more than threefold--to about 40 h. These data are consistent with the hypothesis that activation of Kupffer cells following cold ischemic storage and reperfusion is an early event involved in liver graft failure.

Animals↗
PubMed1991

Two-dimensional computer color graphics of gastric mucosal blood distribution in normal subjects and ulcer patients.

The mucosal blood volume in 20 to 24 different regions of stomach was estimated by reflectance spectrophotometry during endoscopy, and an image showing mucosal blood distribution was made by two-dimensional computer color graphics with the aid of a personal computer. In 55 normal controls, the estimated mucosal blood volume (EMBV) was greater in the corpus mucosa than in the antral mucosa, and less in the lesser curvature than in the greater curvature. The volume in the anterior and posterior walls was almost the same. In 15 patients with active gastric ulcers in the angular region, the EMBV was decreased in all regions in the stomach. In 37 patients with healing ulcers, the EMBV increased, resuming the same levels as in normal controls. However, the EMBV around the ulcer increased remarkably at this stage. In 35 patients with ulcers in the scarring stage, the distribution of the EMBV was similar to that in the normal controls. These hemodynamic changes were shown clearly in a color display with the aid of a personal computer. This method could offer new possibilities in endoscopic research.

Adult↗
PubMed1991

Leukocyte adhesion and cell death following orthotopic liver transplantation in the rat.

The purpose of these experiments was to employ video microscopy to identify early pathological changes after orthotopic liver transplantation in the rat. Liver transplantation was performed using the cuff technique. Survival was greater than 90% when livers were stored for 1 hr in Ringer's solution prior to transplantation (survival conditions), whereas all rats died following storage of grafts for 4 hr in cold Euro-Collins solution (nonsurvival conditions). Postoperatively, each recipient animal was anesthetized, the abdomen was opened, and the liver was placed on the stage of an inverted fluorescence microscope equipped with a low-light ISIT video camera. Precautions were taken to prevent the liver surface from drying. The fluorescent dyes fluorescein sodium (1.0 mumol/kg), acridine orange (2.5 mumol/kg), and propidium iodide (1 mumol/kg) were injected intravenously to label hepatocytes, polymorphonuclear leukocytes, and the nuclei of irreversibly damaged cells, respectively. In livers from untransplanted rats, movement of labeled leukocytes through the hepatic sinusoids was smooth and rapid (velocity, 500-550 microns/sec) and margination (adhesion) of cells was minimal (less than 1%). After transplantation, however, velocity was diminished 2-3-fold, and margination was increased to 10% of leukocytes in survival groups and to 40% in nonsurvival groups 4 hr postoperatively. In the nonsurvival groups, irreversible cell death detected by propidium iodide fluorescence was minimal 15 min after transplantation--however, massive cell damage was detected 4 hr postoperatively. In addition, serum transaminases and necrosis were higher at 4 hr than 15 min postoperatively. Taken together, these data demonstrate that leukocyte margination increases following orthotopic liver transplantation and is followed rapidly by cell death. These events likely play a role in the mechanism of early graft failure following transplantation.

Animals↗
PubMed1991

Increase in survival of liver grafts after rinsing with warm Ringer's solution due to improvement of hepatic microcirculation.

Temperature increases membrane fluidity and decreases vascular resistance in isolated organs. Therefore, these studies were designed to determine if a rinse with warm buffer could increase survival time in the rat model of orthotopic liver transplantation by improving hepatic microcirculation. Brief periods of warm ischemia (3-8 min) did not damage the liver as indexed by minimal release of LDH. Survival of rats for 30 days was greater than 90% in this model when livers were stored for 1 hr in Ringer's solution; yet grafts stored for 8 hr in Euro-Collins solution and rinsed with 20 ml of cold (0-4 degrees C) Ringer's solution survived postoperatively only around 3 days. However, livers stored for 8 hr in Euro-Collins and rinsed with 20 ml of warm (37 degrees C) Ringer's survived longer than 30 days (i.e., permanently). Serum transaminase levels reached peak values around 6000 U/L one day postoperatively in the cold-rinsed group, and liver injury assessed histologically was substantial. Under these conditions, pulmonary infiltration of inflammatory cells was observed in about 23% of lung tissue examined and was associated with massive bleeding. Following a warm rinse, however, maximal SGOT levels and injury to both liver and lung were reduced significantly by 80-90% 24 hr postoperatively. Moreover, the warm rinse improved hepatic microcirculation. It accelerated blood flow into the liver approximately two-fold, as indexed by the half-time of changes in hemoglobin reflectance from the liver surface, improved the distribution of colloidal carbon in the organ observed macroscopically, and decreased vascular resistance by over 50%. These data support the hypothesis that a brief rinse of liver grafts with warm buffer markedly improves the hepatic microcirculation, leading to dramatic improvement in graft survival. This work demonstrates clearly that a brief warm rinse may be useful clinically in liver transplantation.

Animals↗
PubMed1991

Carolina rinse solution--a new strategy to increase survival time after orthotopic liver transplantation in the rat.

Recently, we described a new solution, Carolina rinse, that prevents nonparenchymal cell injury in vitro after reperfusion of livers stored in University of Wisconsin cold solution (Currin RT, Toole JG, Thurman RG, Lemasters JJ. Transplantation 1990; 50: 1076). The present study was designed to examine the effect of Carolina rinse on graft survival in vivo. Unlike UW cold storage solution, which is high in potassium, Carolina rinse contains extracellular inorganic ions at levels similar to blood, a calcium channel blocker and a radical scavenger. Carolina rinse also contains fructose and mildly acidotic pH to reduce hypoxic cell death. Livers from Lewis rats were explanted, stored in UW cold storage solution under nonsurvival conditions, and rinsed with either 15 ml of Ringer's, UW solution, Carolina rinse, or Carolina rinse saturated with nitrogen prior to completion of implantation surgery. In the Ringer's rinse group, only 4% of recipients survived 30 days postoperatively. In this group, SGOT levels reached maximal values of about 5000 U/L. Survival was also poor (25%) when grafts were rinsed with UW solution. In the Carolina rinse group, however, 9 of 16 rats (56%) survived indefinitely, and maximal postoperative SGOT levels were reduced 3-fold. Liver injury indexed histologically was also decreased about 3-fold by Carolina rinse compared with the control group rinsed with Ringer's solution. Carolina rinse diminished postoperative sinusoidal endothelial cell damage assessed by electron microscopy and reduced carbon particle phagocytosis due to Kupffer cells significantly. Moreover, Carolina rinse diminished graft swelling and improved postoperative hepatic microcirculation compared with the Ringer's rinse group. Taken together, these results indicate that Carolina rinse is a superior alternative to Ringer's solution in vivo to protect liver grafts from reperfusion injury when removing high-potassium-containing cold storage solutions clinically prior to implantation.

Adenosine↗
PubMed1991

Endothelin-1-like immunoreactivity in human urine.

By using a radioimmunoassay specific for endothelin-1 (ET-1), we studied whether ET-1-like immunoreactivity (LI) is present in human urine. Significant amounts of ET-1-LI were present in human urine, and the daily urinary excretion of ET-1-LI in 30 normal subjects was 67.6 +/- 35.5 ng/day. The mean urinary excretion of ET-1-LI determined in spot urine was 82.8 +/- 38.2 pg/mg creatinine (n = 30), while the mean plasma concentrations of ET-1-LI in the same individuals were 1.1 +/- 0.5 pg/ml. There was no significant correlation between urinary ET-1-LI excretion and its plasma levels. Reverse-phase high-pressure liquid chromatography of human urine extract revealed a major ET-1-LI component coeluting with standard ET-1. The present study demonstrates the presence of ET-1-LI excreted in human urine, although its exact source and physiological significance in renal tissues remain to be determined.

Adult↗
PubMed1991

Spatial gaze stability under active high-frequency head oscillation after acoustic neuroma surgery.

Spatial gaze stability under active high-frequency head oscillations was investigated in 31 patients after acoustic neuroma surgery. Whereas gaze stability upon rotation to the intact side was excellent during the entire time course after surgery, rotation to the affected side produced marked gaze disturbance at frequencies higher than 1.0 Hz, and did not recover even several years after surgery. The maximal oscillation frequency decreased in the patient group. Oscillopsia, being found in 20% of the patients, showed little correlation with gain value or maximal oscillation frequency. Long-lasting disturbances of active head oscillation, gaze stability and perception after unilateral labyrinthine loss may indicate persistent asymmetry of spatial orientation during high-frequency head movements.

Adult↗
PubMed1991

Age-related change in human gastric mucosal energy metabolism.

Many investigators have reported a decrease in mucosal blood flow resulting in impairment of gastric mucosal energy metabolism in animal experiments. Recently, endoscopic studies using reflectance spectrophotometry and laser Doppler flowmetry have indicated that gastric mucosal blood flow in humans decreases with age. However, changes in energy metabolism in human gastric mucosa with age remains obscure. In this study, we measured adenine nucleotides in biopsy samples from human gastric mucosa, using high-performance liquid chromatography, and investigated changes in energy metabolism with age in subjects proven normal endoscopically. Energy charge (EC = (ATP + 1/2 ADP)/ATP + ADP + AMP) in the gastric antral and body mucosa showed decrease with age. When the subjects were divided into two groups, less than and more than 65 years old, the EC level was significantly lower in the latter than the former in both antral and body mucosa (0.65 +/- 0.06 versus 0.74 +/- 0.03 in the antrum, 0.73 +/- 0.04 versus 0.79 +/- 0.04 in the body) and significantly less in the antral mucosa than in body mucosa in both groups. The adenosine triphosphate (ATP) level in the older group showed a significant decrease (6.48 +/- 1.14 versus 9.63 +/- 1.92 in the antrum, 8.59 +/- 1.64 versus 10.60 +/- 2.13 in the body) compared with those less than 65 years old. In the antral mucosa of the older group the adenosine diphosphate (ADP) level was also significantly lower than that in the group less than 65. In conclusion, in the elderly, the energy metabolism in human gastric mucosa is impaired, and this may weaken their defensive mechanism.

Adenine Nucleotides↗
PubMed1991

[Control of gaze and locomotion by spatial orientation].

We reported a new theory for daily vestibular functions which advocates top-down regulation of posture and gaze by supposing the coordinates in the brain. The hypothesis consists of three principles; first, the vestibular system is primarily a sensory system to detect spatial orientation; second, multisensory integrations reconstruct three-dimensional coordinates in the brain, which ascertain spatial orientation; third, daily behaviours like gazing or walking are controlled in a feed-forward manner by programming on the coordinates in the brain. The hypothesis was useful to understand strategic differences between active and passive movements, to distinct gaze control from ocular reflexes, to apply the rules of gaze control to posture control, and to clarify the mechanism to produce motion sickness.

Fixation, Ocular↗
PubMed1991

[The motion sickness under reversing goggles (1st report)].

We observed locomotion and motion sickness in 10 normal adults wearing reversing goggles while moving outdoors. Horizontal reversal of the visual field produced moderate to severe ataxia and motion sickness in all subjects except one. There was marked variability in the sensitivity among different subjects. In contrast, vertical reversal produced no symptoms. Confusion of information relation to spatial orientation possibly caused both the motion sickness and abnormal locomotion. Horizontal reversal of visual information produces disorientation because visual information is equal in importance to that from the semicircular canals. In the case of vertical reversal of visual information, orientation may be assured by gravity. The present study suggests that motion sickness is a biological signal alerting the organism to loss of spatial orientation rather than a mere autonomic symptom produced by mismatched sensory information. It appears that motion sickness is accompanied by dysequilibrium and abnormality of locomotion.

Adult↗
PubMed1991

[Evaluation of usefulness of Tc-99m-GSA liver scintigraphy in chronic liver diseases].

Liver scintigraphy was performed using a newly developed radiopharmaceutical, Tc-99m-DTPA-Galactosyl-Human-Serum-Albumin (Tc-99m-GSA), which binds specifically to the receptors on the hepatic cell surface, in 15 patients with chronic liver diseases. The scintigraphy was evaluated qualitatively and quantitatively, and the results were compared with those obtained from the Tc-99m-PMT or Tc-99m-sn-phytate scintigraphy, and the liver function tests. The Tc-99m-GSA scintigraphy showed clear liver images in chronic hepatitis. However, in liver cirrhosis, the liver images was not clear and the cardiac images still existed 40 minutes after administration of Tc-99m-GSA, suggesting that the image quality of the Tc-99m-GSA scintigrams may be inferior to that of Tc-99m-sn-phytate or Tc-99m-PMT in some cases of severe liver dysfunction. The time-activity curves of the heart and liver were analyzed by non-linear regression analysis. The clearance rate from plasma (Kd) were obtained from the time-activity curve of the heart, and the hepatic uptake rate (Ku), hepatic excretion rate (Ke) and peak time of hepatic uptake-excretion curve (PT) were obtained from the time-activity curve of the liver. Kd, Ku and PT values were more significantly decreased or prolonged in the patients with liver cirrhosis than those in the patients with chronic hepatitis. Kd, Ku and PT values had positive correlations with the result of the serum liver function tests, ICG-R15 and ICG-K. Ku and PT values had also correlations with the histological degrees of hepatic fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Ethanol-induced focal cell necrosis via microcirculatory disturbance in the perfused rat liver.

In the perfused rat liver, infusion of ethanol induced an initial increase in portal pressure which is an indicator of vasoconstriction and a subsequent increase in lactic dehydrogenase (LDH) release, which is an indicator of cell damage in a dose-dependent fashion. Simultaneous infusion of sodium nitroprusside, a potent vasodilator, (100 microM) inhibited the increases in portal pressure and LDH release. Focal hepatocellular necrosis evidenced by trypan-blue stained cell nuclei were localized in midzonal and pericentral area of the liver lobules at 60 min after ethanol load. These ethanol-induced microcirculatory disturbance might be involved in the pathogenesis of alcoholic liver disease.

Animals↗