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Biomedical subjects

I Yoneda

Publications and source records attributed to I Yoneda.

At least 19 recordsLinked to original sources
PubMed2003

Microbial contamination of dialysate and its prevention in haemodialysis units.

At the haemodialysis centres of nine hospitals in Japan, microbial contamination of treated water (reverse osmosis method), acid and bicarbonate concentrates, and dialysate was investigated. Among these fluids used in haemodialysis, the dialysate was most frequently contaminated and had the highest concentration of bacteria. Of 40 dialysate samples analysed, 42.5% showed a bacterial count of more than 2000cfu/mL, which was above the Association for the Advancement of Medical Instrumentation (AAMI) standard. However, among the 40 samples from 20 dialysis machines, all six dialysate samples from three dialysis machines that used an ultrafiltration membrane in the circuit before the entrance of the dialysate into the dialyser, showed a bacterial count of < or =10 cfu/mL. In addition, when an ultrafiltration membrane was used in the circuit before the entrance of the dialysate into the dialyser for four dialysis machines showing dialysate samples contaminated with 10(4)-10(5)cfu/mL the bacterial count in dialysate samples from these machines became zero. Because dialysis machines are susceptible to microbial contamination, it is necessary to take measures such as placing an ultrafiltration membrane into the circuit before the entrance of dialysate into the dialyser.

Colony Count, Microbial↗
PubMed2000

Time of useful consciousness determination in aircrew members with reference to prior altitude chamber experience and age.

BACKGROUND: Hypoxia tolerance has been evaluated by the secondary responses to oxyhemoglobin deoxygenation: the time of useful consciousness (TUC), subjective symptoms, ventilatory responses, and cardiovascular changes. It is not clear whether the deoxygenation rate per se reflects hypoxia tolerance or how it relates to the former parameters. METHODS: In Study 1, we monitored arterial oxygen saturation (SaO2) by pulse oximetry in the nonsmoking subjects experiencing hypoxia at the simulated altitude of 25,000 ft. Male subjects were divided into two groups: junior (< or =39 yr, n = 108) and senior (> or =40 yr, n = 44). The duration from mask-off to mask-on (TUC), the duration from mask-off to the time of SaO2 of 90%(T90), the duration from 90% to 70% of SaO2(T70), and the SaO2 value at mask-on (bottom SaO2) were compared between the two groups. (In a separate, but related study, 10 medical variables were analyzed by stepwise regression to investigate the contributing factors to hypoxia tolerance in 77 other subjects, including 11 female subjects.) In study 2, 12 subjective hypoxic symptoms at 25,000 ft were compared between junior (n = 369) and senior (n = 160) groups. RESULTS: TUC was significantly longer in the junior group, but T70 was longer and bottom SaO2 was higher in the senior group. Age was adopted as a contributing variable in three out of six dependent parameters. Subjective symptoms were in the similar rank order for both groups. CONCLUSION: Pulse oximetry reconfirmed that age is a major influencing factor for acute hypoxia tolerance. This may be due not only to the physiological effect but also to the training experience to recognize hypoxic deterioration more quickly.

Adult↗
PubMed1999

A simple method to control tracheal cuff pressure in anaesthesia and in air evacuation.

The pressure within latex balloons remains constant despite the balloons being inflated to more than 40 times their initial volume. We used this property to enable improved tracheal cuff pressure control. A latex balloon with an initial volume of 5 ml was connected via a vinyl duct attached with a roller clamp and three-way stopcock to a standard tracheal tube cuff. The 5 ml latex balloon was then inflated with 250 ml of air. The pressure within the tracheal tube cuff was monitored throughout anaesthesia with the inflated latex balloon acting as a pressure controller. Throat symptoms were recorded on the first four postoperative days. The controller kept the tracheal tube cuff pressures constant, and reduced the incidence of postoperative throat symptoms. Variations in cuff pressures with and without the controller were investigated in an altitude chamber to simulate flight. In the altitude chamber, cuff pressure reached over 200 cmH2O at 10 000 feet without the controller, whereas such variations were practically eliminated when the controller was used.

Adult↗
PubMed1999

EEG topographical analysis of spatial disorientation.

BACKGROUND: We examined EEG topography while subjects experienced spatial disorientation (SD) such as vection and somatogravic illusion (SGI). METHODS: Five healthy male subjects were exposed to a rotating image evoking vection (Experiment 1) and to a 0.58 G linear forward acceleration evoking SGI (Experiment 2). The data were analog-to-digital converted with an epoch length of 1 s and a sampling frequency of 256 Hz. Polynomial coefficient vectors were calculated for the following analyses of EEG under the illusion: a) objective evaluation of topographical difference by two-way MANOVA; b) visual inspection of the power spectra maps; and c) logarithmic deviation ratio topography (log DRT). RESULTS: MANOVA demonstrated significant differences in EEG topography in the high alpha band while the vection was evoked. No significant difference was revealed in any bands for SGI. Characteristic patterns common to all subjects were hardly identified on the power spectra maps. By log DRT under vection, a decrease of power was observed in the centro-parietal area on the left side in one subject, on the right in another subject, and in the mid-right frontal area in a third subject compared with the control with eyes open. As for SGI, log DRT revealed a decrease of power in the occipital area in most of the trials as the magnitude was reduced by a visible horizon. CONCLUSIONS: MANOVA revealed a significant change in EEG topography while the subjects felt vection. Log DRT reflected characteristic patterns under vection and SGI. Thus EEG topography may be useful for the study of SD.

Acceleration↗
PubMed1999

A case of 43-year-old fighter pilot with bronchial asthma.

A Japan Air Self-Defense Force (JASDF) fighter pilot with adult onset atopic bronchial asthma was successfully returned to flying status. This was against the common wisdom of most Japanese military flight surgeons. Bronchial asthma generally results in permanent disqualification from flying duties because of possible acute incapacitation during flight. This JASDF pilot was treated with inhaled medications, including beclomethasone, for 6 mo with suppression of all clinical symptoms. All medications were discontinued and the pilot was observed for another 7 mo before resumption of flying status. This aeromedical disposition was based on the thinking that his long asymptomatic period indicated bronchial inflammation was resolved, bronchial reactivity was improved, and thus the risk of exacerbation was reduced.

Adult↗
PubMed1998

Probable decompression sickness in a trainee with atopic dermatitis.

Hypobaric chamber training has a potential risk of inducing decompression sickness (DCS). A case of a patient with an atopic dermatitis who complained of paresthesia and numbness in his left arm and shoulder during the altitude exposure is presented here. His symptoms were severe enough for the attending medical officer to diagnose Type II DCS, but it turned out to be a probable case of simple skin bends requiring no treatment. The author can find no better explanation for this discrepancy than the contribution of dermatitis. The possibility of atopic dermatitis confounding the correct diagnosis of the severity of DCS is proposed.

Adult↗
PubMed1997

Comparisons of altitude tolerance and hypoxia symptoms between nonsmokers and habitual smokers.

BACKGROUND: Increased levels of carboxyhemoglobin (COHb) in smokers are blamed for inducing pre-hypoxic tendency classified as anemic hypoxia. If COHb can be simply converted to altitude, there should be significant differences between smokers and nonsmokers with respect to hypoxia tolerance. However, the studies of the effects of carbon monoxide and/or smoking habit on the physiological functions at altitude do not have consistent conclusions, and many pilots still have smoking habits. This study was designed to assess whether there is a definite significant difference for time of useful consciousness (TUC), subjective symptoms, or performance degradation between nonsmokers and smokers. METHODS: During the hypoxia experience of routine physiological training, TUC and 12 typical subjective symptoms were examined at the chamber altitude of 25,000 ft (7620 m) in 589 nonsmokers and 582 smokers in Study 1. The time until the deterioration of handwriting was assessed by 6 physiological training observers in 51 nonsmokers and 70 smokers in Study 2. The results were compared between the groups. RESULTS: Smokers revealed significantly fewer subjective symptoms in 5 out of 12 symptoms. There were no significant differences in TUC and the rate of handwriting deterioration between the groups. CONCLUSIONS: Paradoxically, smokers are slightly resistant to hypoxia with respect to emerging subjective symptoms. However, bluntness to hypoxia could postpone the detection of the possible hypoxic occurrence in pilots.

Adult↗
PubMed1995

The role of SH and S-S groups in Bacillus cereus beta-amylase.

The properties of sulfhydryl (SH) and disulfide (S-S) groups in Bacillus cereus BQ10-S1 Spo III beta-amylase have been investigated to clarify their roles in the enzyme action. Two out of three cysteine residues in B. cereus beta-amylase were found to form an S-S bond, which was found to be located between Cys91 and Cys99 by the analysis of an S-S containing peptide. The replacement of the soybean beta-amylase model around L3 loop 1 revealed that the S-S bond is located at the root of this flexible loop that moves between open and closed forms during catalysis. The analysis of fluorescence labeled peptides revealed that the remaining free SH group was Cys331. Modification of Cys331 with N-ethylmaleimide or p-chloromercuribenzoic acid (PCMB) caused inactivation of the enzyme. The rate constants for the reactions were consistent with those of Cys343 in soybean enzyme. The binding affinity of the PCMB-modified enzyme to maltose was also decreased. These results indicate that the modification of Cys331, which exists as a free SH group in B. cereus beta-amylase caused inactivation by a similar mechanism to that in the case of Cys343 in soybean beta-amylase as assumed from the sequence homology. This cysteine residue has a common role in beta-amylases irrespective their origin.

Bacillus cereus↗
PubMed1994

Inhibition by SKF 525A and quinacrine of endogenous glibenclamide-sensitive K+ channels in follicle-enclosed Xenopus oocytes.

Effects of local anesthetics-related drugs, SKF 525A (proadifen, a cytochrome P450 inhibitor) and quinacrine (a phospholipase A2 inhibitor) on glibenclamide-sensitive K+ currents were investigated using native Xenopus oocytes. SKF 525A and quinacrine suppressed cromakalim-induced/glibenclamide-sensitive K+ currents with IC50 values of 9.8 microM and 4.4 microM, respectively. Inhibitors of either cytochrome P450 or phospholipase A2, which are structurally unrelated to local anesthetics, however, did not affect the K+ currents. Similar results were obtained for Y-26763-induced/glibenclamide-sensitive K+ currents. SKF 525A and quinacrine block the glibenclamide-sensitive K+ currents by a mechanism irrelevant to the inhibition of cytochrome P450 or phospholipase A2 in oocytes.

Animals↗
PubMed1994

Effect of atracurium, vecuronium, pancuronium and tubocurarine on renal sympathetic nerve activity in baroreceptor denervated dogs.

The mechanism of arterial hypotension induced by non-depolarizing neuromuscular blocking agents may be multifactorial and differ between drugs. The purpose of this study was to evaluate the effect of high-dose atracurium and equivalent doses of other non-depolarizing neuromuscular blocking agents on haemodynamic state and sympathetic nervous activity. In studies on 24 mongrel dogs anaesthetized with alpha-chloralose, the left kidney was exposed retroperitoneally and renal sympathetic nerve activity was recorded continuously after bilateral sino-aortic denervation and cervical vagi section. The dogs were allocated to four groups; atracurium 1.5 mg kg-1, tubocurarine 0.3 mg kg-1, pancuronium 0.3 mg kg-1 or vecuronium 0.3 mg kg-1 was administered to six dogs in each group. Histamine 1 micrograms kg-1 was given to two dogs in each group, 1 h before administration of neuromuscular blocking agents. We observed that atracurium and tubocurarine significantly decreased arterial pressure, heart rate and renal sympathetic nerve activity (P < 0.05), but pancuronium and vecuronium did not Histamine-induced arterial hypotension but did not affect heart rate or renal sympathetic nerve activity. As both arterial and cardiopulmonary baroreflex pathways were inactivated in these animals, we conclude that atracurium decreased arterial pressure by suppressing efferent sympathetic nerve activity in a manner similar to that of tubocurarine.

Animals↗
PubMed1994

Attenuation of arterial baroreflex control of renal sympathetic nerve activity during lidocaine infusion in alpha-chloralose-anesthetized dogs.

The purpose of this study was to identify the relationship between sensitivity of arterial baroreflex and plasma concentrations of lidocaine. Using twelve mongrel dogs anesthetized with alpha-chloralose, the left kidney was exposed retroperitoneally, and renal sympathetic nerve activity was recorded continuously. Lidocaine was infused in four different doses: 2 mg.kg BW-1 bolus + 100 micrograms.BW-1 x min; 3 mg.kg BW-1 bolus + 200 micrograms.kg BW-1 x min; 6 mg.kg BW-1 bolus + 400 micrograms.kg BW-1 x min; and 12 mg.kg BW-1 + 800 micrograms.kg BW-1 x min. Baroreflex depressor and pressor tests using sodium nitroprusside (5-10 micrograms.kg-1) and phenylephrine (2-4 micrograms.kg-1) were performed before and at 10 min after beginning lidocaine infusion. Plasma lidocaine concentrations determined by high performance liquid chromatography revealed that the steady-state levels were maintained during the baroreflex tests. Baroreflex sensitivity was preserved at plasma concentrations of lidocaine below 5 micrograms.ml-1. However, cardiac and sympathetic baroreflex sensitivity were significantly attenuated (P < 0.01) when plasma lidocaine concentrations were well above human convulsion levels (10 micrograms.ml-1). The results indicate that hemodynamic derangement observed in the lidocaine-induced central nervous system toxicity is, at least in part, due to the attenuated arterial baroreflex.

Animals↗
PubMed1993

Effects of local anesthetics and related drugs on endogenous glibenclamide-sensitive K+ channels in Xenopus oocytes.

Effects of local anesthetics and structurally related drugs on the glibenclamide-sensitive K+ currents evoked by Y-26763 (a K+ channel opener) were investigated in native Xenopus oocytes. The K+ current induced by Y-26763 (100 microM) was reversibly suppressed by all six local anesthetics tested in a concentration-dependent manner with the rank order of potencies (IC50 in microM): bupivacaine (67) > dibucaine (136) > tetracaine (845) > lidocaine (1710) = mepivacaine (1945) > procaine (3112). (+)-Propranolol and mexiletine also suppressed Y-26763-induced K+ currents with IC50 values of 115 microM and 789 microM, respectively. These results suggest that a suppressive action on glibenclamide-sensitive K+ channels is the common property of local anesthetics.

Anesthetics, Local↗
PubMed1993

[Effect of intravenous lidocaine infusion on arterial baroreflex].

The purpose of the first study was to identify the relationship between reflex sympathetic nerve activity and plasma concentration of lidocaine. Lidocaine was infused in 4 different doses: 2 mg.kg-1 bolus + 100 micrograms.kg-1 x min-1, 3 mg.kg-1 bolus + 200 micrograms.kg-1 x min-1, 6 mg.kg-1 bolus + 400 micrograms.kg-1 x min-1 and 12 mg.kg-1 bolus + 800 micrograms.kg-1 x min-1. Baroreflex depressor and pressor tests using sodium nitroprusside (5-10 micrograms.kg-1) and phenylephrine (2-4 micrograms.kg-1) were performed before and at 10 min after the start of lidocaine infusion. Plasma lidocaine concentrations determined by HPLC revealed that its steady-state levels were maintained during the baroreflex tests. Baroreflex sensitivity was preserved at clinical concentrations of lidocaine (< 5 micrograms.ml-1). However, baroreflex was significantly attenuated when plasma lidocaine concentrations were above seizure levels (> 10 micrograms.ml-1). This result indicates that hemodynamic derangement observed in the lidocaine-induced CNS toxicity is, at least in part, due to the attenuated arterial baroreflex. In the second study, the author evaluated the effect of respiratory acidosis and alkalosis on the baroreflex with or without lidocaine infusion (2 mg.kg-1 + 100 micrograms.kg-1 x min-1). Respiratory acidosis (PaCO2: 65.6 +/- 3.4) enhanced the baroreflex significantly, but lidocaine infusion abolished this acidosis-induced enhancement. The author concludes that hypercarbia should be avoided in patients receiving intravenous lidocaine infusion.

Acidosis, Respiratory↗
PubMed1992

[Neuromuscular blocking effect of ORG9426, a new non-depolarizing muscle relaxant, and its recovery with various antagonists in vitro].

We evaluated the neuromuscular blocking effect of ORG9426, a new non-depolarizing muscle relaxant, and its recovery by means of washout or by antagonists in vitro, using phrenic nerve-hemidiaphragm preparations of rats. IC50 and IC90 of ORG9426 in single twitch were 10.62 +/- 0.58 microM and 15.75 +/- 0.95 microM; and those in train of four ratio were 9.04 +/- 0.38 microM and 11.87 +/- 0.42 microM, respectively. The potency of ORG9426 in vitro was compared with those of other non-depolarizing muscle relaxants. The order of potency among the non-depolarizing muscle relaxants was the following: d-tubocurarine greater than pipecuronium greater than pancuronium greater than vecuronium greater than ORG9426. There was no difference between ORG9426 and vecuronium in the recovery from block with washout, neostigmine, 4-aminopyridine, 3, 4-diaminopyridine, and edrophonium. In conclusion, the potency of ORG9426 is relatively low, and it can be easily antagonized by anti-cholinesterases and aminopyridines.

Aminopyridines↗
PubMed1991

Percutaneous absorption of elcatonin and hypocalcemic effect in rat.

The percutaneous absorption of elcatonin (EC), a hypocalcemic peptide, was investigated. A transdermal dosage form of EC was produced using a gel base, absorption enhancer and protease inhibitor, and applied to rats for 24 h. The combination of bile salt such as taurocholate and glycocholate, and n-octyl-beta-D-glucoside or n-octyl-beta-D-thioglucoside (OTG) exerted the potent enhancing effect on the absorption of EC, and a potent hypocalcemic effect was shown for 24 h or longer. The least level of plasma calcium was obtained 6 h or longer after application, suggesting the relatively rapid absorption of EC. The apparent bioavailability of EC in system 5 was 4.6%, this value being noteworthy in the percutaneous absorption of peptides. When the enhancing effect of taurocholate and OTG was separately measured, both agents acted additively on the absorption of EC. An EC ointment maintained the hypocalcemin effect after storage for 15 d at 40 degrees C. The transdermal dosage form has the potential to be an efficient drug delivery system for Paget's disease and osteoporosis.

Animals↗
PubMed1991

[A simple method of retrograde intubation].

A safe and simple method to facilitate retrograde intubation was presented. An epidural catheter was introduced into the oropharynx through a 16-G extracath sheath inserted through the cricothyroid membrane into the trachea. After passing the catheter beyond the distal end of the endotracheal tube, a knot was made. Intubation was done by pulling the catheter, which can be cut apart and pulled out afterwards. This method would make the damage or contamination of the cricothyroid membrane minimum and the trouble of losing the catheter could be abolished. We believe this way of intubation can be applied universally because it needs no special tool or device.

Aged↗
PubMed1991

[The effect of temperature on the action of several neuromuscular blocking agents in vitro].

The effects of lowered muscle temperature on the action of neuromuscular blocking drugs have been investigated so far from basic or clinical aspects, but the results of these studies are conflicting probably because of the differences of methods and/or species of the animals. The effects of hyperthermia on neuromuscular junction are not yet known. To clarify the effects of variations in temperature on the neuromuscular blockade produced by each of the 5 neuromuscular blocking agents in current use (vecuronium, pancuronium, pipecuronium, dTc, SCC), we used the rat phrenic nerve-hemidiaphragm preparation and compared the ED50 at each temperature with that at 37 degrees C. The temperatures examined were 17 degrees C, 27 degrees C, 32 degrees C, 37 degrees C, 40 degrees C, and 42 degrees C. As to vecuronium and pancuronium, potentiating effects were observed with both hypothermia and hyperthermia. In contrast, pipecuronium was not affected by the change of temperature from 27 degrees C to 42 degrees C. SCC was only potentiated at the temperatures of 27 degrees C and 17 degrees C, while dTc showed a biphasic phenomenon by hypothermia. The ED50's of dTc at 37 degrees C and 27 degrees C were twice as large as that of at 32 degrees C, but ED50 of 17 degrees C was significantly lower than that of 37 degrees C. Hyperthermia did not modify the neuromuscular blockade by dTc.

Animals↗