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Biomedical subjects

T Mashimo

Publications and source records attributed to T Mashimo.

At least 163 records · Page 9Linked to original sources
PubMed1984

Effects of volatile anesthetics on light-induced proton uptake of rhodopsin in bovine rod outer segment disk membrane.

The effects of volatile anesthetics upon the function of bovine rhodopsin were estimated from the measurements of light-induced proton uptake. The light-induced pH changes were measured at both 20 degrees C and 37 degrees C with suspensions to which volatile anesthetics were added in the liquid form. Each anesthetic depressed the light-induced proton uptake concentration-dependently. The anesthetic-induced depression was greater at 37 degrees C than at 20 degrees C. For each anesthetic the concentration needed to depress the proton uptake by 10% was roughly identical to that used clinically. Anesthetics also were added to the suspensions in the gaseous form with air. The light-induced proton uptake was decreased in proportion to the partial pressure of the anesthetic. The partial pressures of halothane and methoxyflurane that depressed the proton uptake by 10% at 37 degrees C were 2.0 x 10(-7) and 1.1 x 10(-2) atm., respectively. From these facts it is suggested that volatile anesthetics affect the light-induced conformational changes of rhodopsin molecule during the metarhodopsin I to metarhodopsin II transition and cause inhibition of the light-induced proton uptake of rhodopsin in the rod outer segment disk membrane.

Anesthetics↗
PubMed1983

Effect of inhalational anesthetics on the opioid receptors in the rat brain.

Effects of inhalational anesthetics, methoxyflurane and halothane, on the binding of various opioid ligands were studied. The binding affinity of 3H-methionine enkephalin (delta) was reduced by both anesthetics in the same manner, but the receptor density was not significantly affected. Methoxyflurane decreased the binding affinity but increased the receptor density of 3H-dihydromorphine (mu), while halothane had little effects on both affinity and density. Methoxyflurane also decreased binding affinities of 3H-ethylketocyclazocine (kappa) and 3H-SKF-10047 (sigma), but halothane did not decrease significantly. These effects of the anesthetics were completely disappeared by unsealing and ventilation.

Animals↗
PubMed1983

[The maternal and fetal acid-base status during general or spinal anesthesia for elective cesarean section in the left tilt position].

Thirty one healthy parturients received spinal or general anesthesia for elective cesarean section. Maternal blood pressures, maternal and fetal acid-base values, induction to delivery intervals (I-DI) and Apgar scores were determined. On spinal anesthesia, acute hydration by 6% hydroxyethyl starch solution and intramuscular injection of ephedrine were enforced prior to the block and in the left tilt position (17 degrees) oxygen inhalation immediately after the block was begun (group OII: 16 cases). As to general anesthesia, the same left tilt position was applied before the anesthesia by thiopental-0.5% halothane with-50% nitrous oxide in oxygen (group G: 15 cases). No significant decrease in maternal blood pressure was noticed, and maternal and the fetal acid-base status and Apgar scores were excellent in both groups. A positive correlation between umbilical venous pH values and 1 or 5 minutes Apgar scores was confirmed in group OII, and a negative correlation between 1 minute Apgar scores and I-DI was noticed in group G. Fetal acid-base values were not correlated with I-DI in either group, and it was postulated that placental or fetal circulation was sufficiently maintained. Biochemical status and clinical conditions in mothers and their infants are very favorable in well-conducted general or spinal anesthesia for elective cesarean section.

Acid-Base Equilibrium↗
PubMed1982

Anesthetics expand partial molal volume of lipid-free protein dissolved in water: electrostriction hypothesis.

The present study was undertaken to critically examine whether the dilating action of inhalation anesthetics is specific to lipid membranes. Delipidated crystalline bovine serum albumin was used as a model and the density of a salt-free aqueous solution was measured by a high-precision oscillation densimeter. The partial molal volumes of albumin at infinite dilution were 50,326, 51,019 and 51,698 cm3 . mol-1, respectively at 293, 308 and 323 degrees K. From the difference between the present value and the volume of dry albumin, the number of electrostricted water molecules at the surface of albumin in aqueous solution at 293.15 degrees K is estimated to be about 720. Addition of diethylether to the albumin solution increased the partial molal volume of albumin, dose-dependently. At 57.88 mmolal, diethylether expanded the partial molal volume of albumin at 293 degrees K by 295 cm3 . mol-1 or 0.59%. This volume expansion does not include the space occupied by the anesthetic molecules in albumin. If the expansion can be assumed to be caused mainly by melting of electrostricted water molecules, about 110 water molecules were released from the protein surface. The partial molal volume of diethylether was increased when bound to albumin. The increase indicates that the contact between diethylether and water is partially destroyed and that high pressure squeezes out anesthetic molecules from the protein.

Anesthetics↗
PubMed1979

Hydrophilic region of lecithin membranes studied by bromothymol blue and effects of an inhalation anesthetic, enflurane.

A pH-indicator dye, bromothymol blue, was used to probe the hydrophilic surface of dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine bilayer vesicles. The apparent pK of the surface-adsorbed dye was larger than the bulk pK value. The contribution of the choline positive charge on the dissociation constant of the dye adsorbed on the vesicle surface was estimated by screening the charge interaction with 2 M KCl. The effective surface potentials interacting with the dye were thus estimated to be 33.2, 45.6, and 46.8 mV, respectively, for the dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine vesicles. From the differences between the obtained effective potentials and the calculated surface potentials of the charge-determining plane of the choline head, the distances between the prototropic part of the dye and the choline charge-determining plane were estimated to be 10.5, 8.0, and 7.8 A, respectively. These values were obtained at 25 degrees C; the dimyristoylphosphatidylcholine membrane was in the liquid-crystalline phase and the other two were in the solid gel phase. Addition of an inhalation anesthetic, enflurane, decreased the distance in the dimyristoylphosphatidylcholine vesicles and increased the distance in the dipalmitoyl- and distearoylphosphatidylcholine vesicles. The increase of precessional motion of choline head by the inhalation anesthetic is apparently responsible for the changes.

Bromthymol Blue↗
PubMedDate not supplied

Carboxyhemoglobin and methemoglobin levels in banked blood.

Carboxyhemoglobin and methemoglobin levels in 312 units of banked blood and their relationship to the duration of storage were determined. The carboxyhemoglobin level decreased as the storage time increased, and its mean was 1.4% +/- 2.0% (SD) with a range from 0% to 9.6%. Methemoglobin increased during storage, showing a mean level of 1.6% +/- 0.4% and a range from 0.5% to 4.2%. In a separate study, blood drawn from six volunteers who had smoked two cigarettes each was stored as banked blood for 21 days. The mean initial level of carboxyhemoglobin was 4.4% +/- 1.6%, and the mean half-life of carboxyhemoglobin was approximately 47 days. Methemoglobin increased from an initial 1.3% +/- 0.2% to 2.4% +/- 0.6% at the end of storage. The use of banked blood containing high levels of these abnormal hemoglobins could be a potential risk in critically ill patients.

Aged↗