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Biomedical subjects

S Yokono

Publications and source records attributed to S Yokono.

At least 55 records · Page 3Linked to original sources
PubMed1991

The effects of age and anesthetic solubility on anesthetic-induced opisthotonus in mice.

In our previous report which indicated volatile anesthetics-induced opisthotonus in mice, we hypothesized that opisthotonus might relate with the rapidity of anesthetic induction, i.e., the blood/gas partition coefficient of the agent. To confirm this, we determined the incidence of opisthotonus induced by four different halogenated ethers (2.0% sevoflurane, 1.3% isoflurane, 2.0% enflurane, and 0.5% methoxyflurane) and 1.0% halothane, a haloalkane, in male ddN mice. The effect of age on opisthotonus was also evaluated by using young (10 +/- 2 weeks), middle-aged (6 +/- 1 mouths), and elderly (12 +/- 1 months) groups of male ddN mice. In each age group, the incidence of opisthotonus occurred in the following order: sevoflurane > isoflurane > enflurane > methoxyflurane > halothane. This partly supports our hypothesis as far as halogenated ethers are concerned. Halothane rarely produced opisthotonus. In the sevoflurane, isoflurane, and methoxyflurane groups, incidence was lower in middle-aged than in young or elderly mice, while incidence increased with age in the enflurane group.

Journal Article↗
PubMed1991

Subanesthetic concentrations of volatile anesthetics may enhance acquired avoidance training in ddN mice.

The effects of halothane, enflurane, and isoflurane on avoidance training were assessed in male ddN mice. Animals were trained to escape an aversive unconditioned stimulus (electric foot shock) within 3 s after being exposed to a conditioned stimulus (light and buzzer). Immediately after training (first session), the animals were exposed to halothane, enflurane, or isoflurane for 120 min and were then tested again on the avoidance task (second session) 30 min after cessation of the exposure. The performance ratios [B/A] (i.e., A is the score in the first session, and B the score in the second) were compared between the anesthetic groups and their respective control groups. Performance ratios in the control animals ([B/A]c) did not reach 100% except for those corresponding to the 0.5 and 1.0 MAC (minimal alveolar anesthetic concentration) halothane groups. Four of the nine performance ratios in the anesthetic groups ([B/A]a) exceeded 1.0. [B/A]a exceeded [B/A]c by 18.7% in the 0.25 MAC halothane group (P less than 0.05), by 13.5% in the 0.31 MAC enflurane group (i.e., not significant), and by 17.3% in the 0.29 MAC isoflurane group (P less than 0.01). [B/A]a/[B/A]c decreased dose-dependently for each anesthetic group. These results suggest that low concentrations of halothane, enflurane, and isoflurane may enhance the performance of ddN mice in acquired avoidance training performed 30 min after anesthetic exposure.

Anesthesia, Inhalation↗
PubMed1991

[A case of hysterical conversion manifested by pain in face and head].

We report a case of hysterical conversion, which was initially diagnosed as trigeminal neuralgia. The pain in the face and head which the patient complained seemed to be consistent with symptoms of trigeminal neuralgia. But it could not be relieved by repeated peripheral nerve blocks and even by Gasserian blocks. Failure to relieve pain by such blocks and concomitant hemifacial spasm with closure of the eye appeared to afford indication of microvascular decompression surgery. Injection of edrophonium before operation, for the purpose of differential diagnosis of myasthenic ptosis, made the patient free from all symptoms, i.e. facial pain, spasm, and ptosis. The diagnosis of hysterical conversion was made on this irrational episode. When we looked back the total clinical course, it was revealed that the patient's complaints and symptoms had been rather atypical, too various, and not anatomical. We also confirmed that various other episodes of this patient which had not received our attention during treatment were psychological features of hysteria, but we could not make his psychological stress clear, which had been in the background of hysterical conversion.

Conversion Disorder↗
PubMed1990

[Relationship between three phase bone scintigram and prognosis after sympathetic blockade in reflex sympathetic dystrophy of the hand].

We attempted to correlate the changes in three phase bone scintigram (TPBS) with prognosis after sympathetic blockade in reflex sympathetic dystrophy (RSD) of the hand. Subjects were 12 patients of RSD in acute or dystrophic stage, who all had increased images on TPBS. Either intravenous regional sympathectomy with guanethidine or stellate ganglion block was performed repeatedly. We compared TPBS obtained just before and after this series of sympathetic blocks and evaluated the eventual recovery of function of the hand. In 8 patients, blood flow (phase 1) image of TPBS decreased after the blockade. Of these patients, those who showed almost normalized tracer activity not only on flow image but on blood pool (phase 2) and delayed (phase 3) image, returned to normal. But others with normalized blood flow and still increased activity in blood pool and delayed image, remained with mild contracture of the hand. These results suggest that normalization of blood pool and delayed image on TPBS is a predictor of subsequent recovery after sympathetic blockade in RSD.

Adult↗
PubMed1989

400 MHz two-dimensional nuclear Overhauser spectroscopy on anesthetic interaction with lipid bilayer.

Interaction between a volatile anesthetic, methoxyflurane, and dipalmitoylphosphatidylcholine (DPPC) vesicle membrane was analyzed by nuclear Overhauser effect (NOE) difference spectroscopy and two-dimensional nuclear Overhauser spectroscopy (NOESY). The NOE difference spectra were obtained by selectively irradiating methoxy protons (hydrophobic end) of the anesthetic: a negative nuclear Overhauser effect of -2.94% was observed with the choline methyl protons of DPPC. The NOESY spectra revealed a cross-peak between the anesthetic methoxy protons and the choline methyl protons. A dipole-dipole interaction exists between the hydrophobic end of the anesthetic and the hydrophilic head group of DPPC. No other cross-peaks were observed. The anesthetic orients itself at the membrane/water interface by interacting with the hydrophilic surface of the DPPC membrane, leaving the hydrophilic end of the anesthetic molecule in the aqueous phase. The preferred residence site of dipolar volatile anesthetics is the membrane/water interface.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

The central nervous stimulating effect of four different halogenated ether anesthetics and halothane in mice.

Although enflurane is a convulsive anesthetic, its structural isomer, isoflurane, is believed not to be. We reported previously that, unexpectedly, isoflurane more frequently produced opisthotonus in young mice, especially during the induction period, than enflurane. In the present study, we examined the incidences of opisthotonus induced by four halogenated ether anesthetics and halothane to evaluate their CNS stimulating actions. As experimental animals, we used young male mice, with another two aged groups of male mice to clarify the relationship of the incidence of opisthotonus to aging. The percentage incidence of opisthotonus was 93% for sevoflurane, 81% for isoflurane, 64% for enflurane, 17% for methoxyflurane and 2% for halothane. These results suggest that the halogenated ether anesthetic, which is rapidly uptaken by the CNS during induction, is more likely to produce CNS stimulation, subsequently leading to opisthotonus. There was no age related susceptibility difference to anesthetic-induced opisthotonus, except for enflurane, in which the incidence of opisthotonus was higher in the aged group.

Journal Article↗
PubMed1982

Hydrogen bonding and anesthetic potency.

Hydrogen bond strengths in terms of the proton chemical shifts of five potent inhalation anesthetics containing acidic hydrogen were measured in cyclohexane and in methanol using the proton magnetic resonance spectroscopic method. The purpose of this study is to quantitatively compare the relative polar character of potent anesthetics. The hydrogen bond shift (delta ppm) of each anesthetic is the difference in the chemical shifts of the infinitely diluted unassociated anesthetic in cyclohexane and that of the infinitely diluted hydrogen bonded anesthetic in methanol. It was found that the hydrogen bond shifts (in delta ppm) are as follows: methoxyflurane, 0.72; chloroform, 0.75; halothane, 1.06; isoflurane, 1.38; enflurane, 1.44. There is a good correlation between the hydrogen bond shifts and the clinical potencies (minimum alveolar concentration in man). The conclusion from this study is that the acidic halogenated inhalation anesthetics are more potent if they form weaker hydrogen bonds.

Anesthetics↗
PubMed1981

Interfacial preference of anesthetic action upon the phase transition of phospholipid bilayers and partition equilibrium of inhalation anesthetics between membrane and deuterium oxide.

The half-height linewidth (v 1/2) of the 1H-NMR spectra of dipalmitoylphosphatidylcholine vesicles changes abruptly at the phase transition temperature. In the absence of inhalation anesthetics, proton signals from the choline head group (hydrophilic interface) and acyl-chain tails (lipid core) change at the same temperature of 39.6 degrees C. The present study compared the effect of four inhalation anesthetics, i.e., methoxyflurane, chloroform, halothane and enflurane, upon the ligand-induced phase transition of phosphatidylcholine vesicle membranes at 37 degrees C. The anesthetics showed differential action upon the phase transition of the phospholipid vesicle membranes between the lipid core and the hydrophilic interface. The concentrations of anesthetics which induced the phase transition of the lipid core were about 2-fold greater than those required for the phase transition of the interfacial choline head groups. From the area under the proton signals of inhalation anesthetics in the NMR spectra, the maximum solubilities of methoxyflurane, chloroform and halothane in 2H2O at 37 degrees C were determined to be 0.671 . 10(-4), 2.637 . 10(-4) and 1.398 . 10(-4) (expressed as mole fractions), or 3.35, 13.17 and 6.98 mmol/1000 g 2H2O, respectively. The solubilities of the anesthetic vapor in 2H2O expressed as mole fractions according to Henry's law ere 9.586 . 10(-4), 6.432 . 10(-4) and 2.311 10(-4)/atm (1.013 . 10(5) Pa) partial pressure, respectively. The presence of phospholipid vesicles in 2H2O increased the solubility of the inhalation anesthetics. From difference between solubility in 2H2O and a dipalmitoylphosphatidylcholine vesicle suspension, the partition coefficients of methoxyflurane, chloroform and halothane between the phospholipid vesicle membranes and 2H2O were estimated. These values, calculated from the mole fractions, were 3364, 1660 and 3850, respectively at 37 degrees C.

Anesthetics↗