Search PubMed⌕ Search

Biomedical subjects

C Tashiro

Publications and source records attributed to C Tashiro.

90 records · Page 5Linked 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↗
PubMed1977

Depression of phase-transition temperature in a model cell membrane by local anesthetics.

Disordering, fluidizing and dilating effects of anesthetics upon cell membranes are well recognized. The fluidization can be precisely measured with phospholipid membranes. When phospholipids are dispersed in water, they form globules of bilayer structure. These model membranes undergo transition between crystalline (ordered and less fluid) and liquid crystalline (less ordered and fluid) phases according to the temperature, the degree of packing of each molecule, and the chemical environment. The phase transition occurs in a cooperative fashion and the turbidity of the dispersion changes abruptly, clear in liquid crystalline phase and turbid in crystalline phase. The present study was undertaken to quantitate the fluidizing effects of local anesthetics on dipalmitoyl lecithin (DPL) bilayer dispersion by measuring the turbidity change. Tetracaine, bupivacaine, lidocaine, and procaine were studied. They all depressed the phase-transition temperature. The binding of the drugs to the model membrane followed unsaturable kinetics, and the pH titration curve showed that only uncharged molecules were active. The freezing point depression was analyzed according to the Van't Hoff model. From this model, the partition coefficients of the uncharged molecules between DPL and water were estimated: lidocaine 76, procaine 159, bupivacaine 812, and tetracaine 1,405. The concentration of local anesthetics in the DPL phase needed to decrease the phase-transition temperature 1 degree C showed a constant value of 0.132 M. The concentration of local anesthetics in the DPL phase is a function of pH, partition coefficient, and volume ratio between the DPL and aqueous phases. The normalized values of the fluidizing action of these drugs at physiologic conditions correlated well with their nerve-blocking potencies. The present results indicate that the uncharged molecules fluidize the lecithin membrane by unsaturable nonspecific binding. The possible effect of the charged molecules upon the fluidity of natural membranes remains to be established.

Anesthetics, Local↗
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↗
PubMedDate not supplied

Effect of preanesthetic rectal famotidine on pH and volume of gastric contents in pediatric outpatients.

STUDY OBJECTIVE: To determine the feasibility and effects of preanesthetic rectal famotidine on gastric fluid pH and volume in pediatric patients. DESIGN: Randomized, prospective, double-blind, controlled study. SETTING: Operating room at a medical center. PATIENTS: Eighty patients undergoing minor surgery under general anesthesia randomly allocated to one of two groups. INTERVENTIONS: Thirty-four patients in Group 1 were given 0.5 mg/kg of diazepam rectally 30 to 120 minutes before anesthesia induction. Thirty-eight patients in Group 2 received 1 mg/kg of famotidine, a new histamine (H2) blocker, and 0.5 mg/kg of diazepam through the same route. Six patients in Group 1 and two patients in Group 2 were excluded from the study due to gastrointestinal (GI) disorders. MEASUREMENTS AND MAIN RESULTS: Patients with gastric pH less than 2.5 or volume of gastric contents greater than 0.4 ml/kg were considered to be at risk for pulmonary aspiration. Thirty-five (92%) of the Group 2 patients had gastric contents with pH greater than 2.5 and gastric volume less than or equal to 0.4 ml/kg. Only 13 (38%) of the patients in Group 1 had similar gastric pH and volume. Rectal administration did not cause the children pain, and no anorectal problems of famotidine were detected. CONCLUSIONS: Famotidine 1.0 mg/kg administered rectally 30 minutes prior to general anesthesia appears to result in a satisfactory increase in gastric pH.

Administration, Rectal↗