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Biomedical subjects

S Isono

Publications and source records attributed to S Isono.

At least 55 records · Page 3Linked to original sources
PubMed1993

Site of pharyngeal narrowing predicts outcome of surgery for obstructive sleep apnea.

Uvulopalatopharyngoplasty (UPPP), an operation that enlarges the pharyngeal airway at the level of the soft palate, improves respiratory status during sleep in only 50% of patients with obstructive sleep apnea (OSA). This poor outcome suggests that narrowing of the pharyngeal airway at nonpalatal sites contributes to the obstructive process in many patients with OSA. We have used a novel endoscopic method to identify regions of the passive pharyngeal airway most susceptible to narrowing or complete closure. In order to test the hypothesis that narrowing of the passive airway at the nasopharynx predicts a favorable surgical outcome, we have preoperatively assessed the local mechanics of the passive pharyngeal airway in 18 patients with OSA undergoing UPPP. The patient population was prospectively divided into two groups: an exclusively nasopharyngeal (ENP) group, consisting of patients exhibiting narrowing only in the nasopharynx, and a not exclusively nasopharyngeal (NENP) group, consisting of patients having at least one site of narrowing outside the nasopharynx. The frequency of respiratory disturbances and arousals and the cumulative time in apnea-hypopnea were significantly reduced after surgery for the ENP group, but not for the NENP group. Improvement rate for the ENP group (86%) exceeded that for the NENP group (18%) (p < 0.01). These differences became even greater when selection criteria for the ENP group were made more restrictive (i.e., restricted to the velopharynx) or more liberal (i.e., including secondary narrowing of the oropharynx). Our results show that evaluation of passive pharyngeal mechanics identifies patients with OSA likely to improve after UPPP.

Adult↗
PubMed1993

Pharyngeal narrowing and closing pressures in patients with obstructive sleep apnea.

Based on previous studies, we hypothesized that the pharynx collapses at multiple sites in most patients with obstructive sleep apnea (OSA). The purpose of this study was to document, in a population of apneic subjects, the site(s) of narrowing and closing pressure of the hypotonic pharynx. We endoscopically examined the pharynx in 45 OSA patients during sleep while they received nasal continuous positive airway pressure (CPAP), which produces hypotonia of pharyngeal muscles. Intrapharyngeal images and pressures were obtained at the end of expiration during single-breath tests (SBT). The fractional narrowing (FN) of each pharyngeal segment (nasopharynx, oropharynx, and hypopharynx) was calculated as the relative change in area when nasal airway pressure was reduced from a pressure that held the pharynx fully distended to the pressure at which the airway closed. The frequency distribution of FN for the nasopharynx was skewed toward larger values, and the frequency was relatively evenly distributed for the oropharynx and hypopharynx. A site having FN greater than 0.75 was defined as a site of primary narrowing, and a site showing FN 0.25 to 0.75 was defined as a site of secondary narrowing. The nasopharynx was a site of primary narrowing in 80% of patients, and two or more sites of narrowing were commonly observed (82%). Four categories of combined narrowing were identified: (1) primary narrowing only at the nasopharynx (18%); (2) primary narrowing at the nasopharynx plus other sites of secondary narrowing (40%); (3) primary narrowing at the nasopharynx plus other sites of primary narrowing (22%); and (4) other patterns (20%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Cloning and nucleotide sequencing of the genes, rpIU and rpmA, for ribosomal proteins L21 and L27 of Escherichia coli.

The rpIU and rpmA genes that encode ribosomal proteins (r-proteins) L21 and L27 of Escherichia coli K-12 have been isolated from the ordered clone bank of this bacterium. They were found to be located at coordinates 3,351.7-3,352.3 kb on the physical map of E. coli. The nucleotide sequence of the cloned genes and their flanking regions indicated that the two r-protein genes compose an operon. Upstream of the two genes there is an open reading frame (ORF) in the opposite direction. The deduced polypeptide encoded by this ORF has a molecular weight of 35,215 and shows a significant degree of sequence similarity to the enzyme that is involved in the carotenoid biosynthesis and encoded by the crtE gene of carotenogenic bacteria and to prenyltransferases found in various organisms.

Amino Acid Sequence↗
PubMed1992

Efficient large-scale sequencing of the Escherichia coli genome: implementation of a transposon- and PCR-based strategy for the analysis of ordered lambda phage clones.

We have developed a strategy for efficient sequence analysis of the genome of E. coli K-12 using insertions of a Tn5-derived mini-transposon into overlapping ordered lambda phage clones to provide universal primer-binding sites, and PCR amplification of DNA segments adjacent to the insertions. Transposon-containing clones were selected by blue plaque formation on a dnaBamber lacZamber E. coli strain. Insertion points every 0.5-1 kb were identified by 'analytical PCR' and segments between the transposon inserts and phage arms were amplified by 'preparative PCR' using one biotinylated and one non-biotinylated primer. Single strands of amplified DNA fragments were coupled to Streptoavidin-coated paramagnetic beads (Dynabeads M280) through their biotin tails, purified magnetically, and used as templates for fluorescence-based automatic nucleotide sequencing.

Bacteriophage lambda↗
PubMed1992

Lack of the mechanoreceptor influences on ventilatory control during halothane anesthesia in humans.

Mechanical influences independent of chemoreceptor function on ventilatory control were studied in halothane-anesthetized, artificially ventilated patients using the technique reported by Altose et al. (Respir Physiol 66: 171-180, 1986). Contribution of mechanical factor was indirectly assessed by comparing the values of arterial carbon dioxide tension at which the subjects started breathing efforts during CO(2) loading induced by the following two methods. 1) Partial rebreathing of expired gas and 2) Mechanical hypoventilation (successive decrease in inflation volume). These two maneuvers resulted in a similar rate of increase in end-expiratory carbon dioxide tension. However, contrary to the observation made by Altose et al. in awake volunteers, we found comparable values of ventilatory recruitment threshold for Pa(CO)(2). Thus, we speculate that halothane anesthesia and/or loss of consciousness impair transmission of afferent information from the lung and/or chest wall musculature. Such effects may be responsible for the depression of load compensatory mechanism during anesthesia.

Journal Article↗
PubMed1992

Differential effects of vecuronium on diaphragm and geniohyoid muscle in anaesthetized dogs.

We have examined the sensitivity of the geniohyoid, an upper airway dilating muscle, to vecuronium in 12 anaesthetized dogs undergoing mechanical ventilation of the lungs and compared it with that of the diaphragm. Dogs were allocated randomly to two groups: pentobarbitone alone (group 1, n = 7); pentobarbitone combined with 0.2 MAC (0.44%) of enflurane anaesthesia (group 2, n = 5). Supramaximal single twitch stimulations (0.1 Hz) were applied to the phrenic nerves in the upper thorax and the geniohyoid branches of the hypoglossal nerves at the neck. The evoked responses were assessed by the transdiaphragmatic pressure (Pdi) and the isometric force of the geniohyoid muscles (Tgh) until complete recovery of these variables after i.v. administration of vecuronium 0.02 mg kg-1. In both groups, the magnitude of the depression of twitch response was greater and time required to reach control amplitude was longer in the geniohyoid than the diaphragm. The depression of Tgh was significantly greater in group 2 than in group 1, whereas no change was observed in Pdi between the two groups. We conclude that the geniohyoid is more sensitive to vecuronium than the diaphragm and the differential effects of vecuronium are facilitated by a low concentration of enflurane.

Anesthesia, Inhalation↗
PubMed1992

Genetic and biochemical analysis of ribosomal proteins of minocycline-susceptible and -resistant Mycobacterium smegmatis.

A minocycline (MINO)-resistant mutant was isolated from Mycobacterium smegmatis strain Rabinowitschi. Polypeptide synthesis in the cell-free system prepared from the mutant was resistant to minocycline (MINO) because of alterated 30S ribosomal subunits. Upon two-dimensional gel electrophoresis, two proteins of 30S subunit were found to be altered. MINO resistance phenotype was transferred by mating to the recipient strain P-53. MINO resistance phenotype of a recombinant thus obtained was transferred by a different mating system to the recipient strain Jucho, once again. Ribosomal proteins of each of the donors, recipients and recombinants were analyzed and compared on 2-dimensional (2D) electrophoresis. Approximately 50 ribosomal proteins were observed in 70S ribosomes. Some proteins were differently electrophoresed in different strains. The 30S ribosomal subunits contained at least 19 proteins and 50S ribosomal subunits contained at least 23 proteins. Some proteins were easily washed off during dissociation of subunits in sucrose gradients. At least one protein (designated F) in both subunits was observed at the same position. One protein designated C in 30S subunits could be co-transferred to the recipient cells together with resistance phenotype at the frequency of 100% in the 30 recombinants examined so far. The other protein designated D in 30S subunits could be transferred at the frequency of 86-88%. Three other proteins in 50S subunits could be co-transferred to the recipient strain at a lower frequency. Minocycline resistance, therefore, could be mapped close to genes encoding the structure of ribosomal proteins in M. smegmatis.

Bacterial Proteins↗
PubMed1992

Effect of sevoflurane on diaphragmatic contractility in dogs.

The effect of sevoflurane on diaphragmatic contractility was investigated in 12 anesthetized, mechanically ventilated dogs with the thorax opened. Animals were divided into two groups of six each: the sevoflurane and time control groups. We assessed contractility by the transdiaphragmatic pressure (Pdi) during supramaximal stimulation of the phrenic nerve at frequencies of 0.5, 10, 20, 50, and 100 Hz under quasiisometric conditions. The integrated electrical activity (Edi) of the crural and costal parts of the diaphragm (Edi cru, Edi cost) was also measured. In the sevoflurane group, diaphragmatic contractility was determined during three levels of anesthesia, specifically 0, 1.0, and 1.5 minimum alveolar anesthetic concentration (MAC). Measurements were made at the start of the stimulation (initial) and at the end of the 2-s period (2-s). Increasing the depth of sevoflurane anesthesia did not cause any significant differences in Pdi and Edi at 0.5-, 10-, and 20-Hz stimulation. By contrast, at 50- and 100-Hz stimulation, initial Pdi during 1.0 and 1.5 MAC sevoflurane exposure decreased significantly compared with the 0 MAC value (P less than 0.05). In addition, there was a statistical difference in 2-s Pdi between 1.0 and 1.5 MAC at 100-Hz stimulation (P less than 0.05). The Edi cru showed similar changes in Pdi at both measurements, whereas there was no remarkable change in Edi cost. There was no significant change either in Pdi or in Edi with respect to time in the time control group. We conclude from these results that sevoflurane impairs diaphragmatic contractility through its inhibitory effect on neuromuscular transmission, predominantly of the crural part.

Anesthetics↗
PubMed1991

Cloning, characterization, and physical location of the rplY gene which encodes ribosomal protein L25 in Escherichia coli K12.

The rplY gene of Escherichia coli K12 encoding ribosomal protein L25 was cloned from the ordered clone bank and located at coordinate 2,291 kb on the physical map of E. coli. Determination of the nucleotide sequence indicated that the coding region contains 285 nucleotide pairs including a translational initiator and terminator. The amino acid sequence of the protein deduced from the nucleotide sequence matched completely the sequence determined for ribosomal protein L25. The coding region was found to be preceded by a typical promoter-like sequence and was followed by a DNA region capable of forming a secondary structure characteristic of a transcriptional terminator. Thus, the gene was concluded to constitute a transcriptional unit (operon). A preliminary analysis by Northern blot supported this conclusion. The codon usage pattern of the rplY gene is characteristic of the ribosomal protein genes in E. coli.

Amino Acid Sequence↗
PubMed1991

Diaphragmatic function during sevoflurane anaesthesia in dogs.

The effect of increasing the concentration of sevoflurane anaesthesia on diaphragmatic function was investigated in six mechanically ventilated dogs. Diaphragmatic function was assessed by measuring the transdiaphragmatic pressure (Pdi) generated during bilateral supramaximal stimulation of the cervical phrenic nerves at frequencies of 0.5, 10, 20, 50, and 100 Hz under quasi-isometric conditions. Measurements were performed at 1, 1.5 and 2 MAC concentrations after maintaining stable conditions for one hour. The Pdi-stimulus frequency relationship was compared at each anaesthetic concentration. The sequence of changing anaesthetic depth was altered in random fashion among animals. The Pdi amplitude generated by single twitch (0.5 Hz) was unchanged at the three concentrations. In addition, no change in Pdi during 10, 20, 50 Hz stimulation was noted at any of the three levels of anaesthesia. By contrast, Pdi with 100 Hz stimulation during 2 MAC sevoflurane exposure (28.1 +/- 5.0 cmH2O) decreased below Pdi levels seen at 1 and 1.5 MAC (35.3 +/- 4.3 cmH2O and 31.5 +/- 4.3 cmH2O, respectively) (P less than 0.05). From these results, we conclude that sevoflurane impairs diaphragmatic function in deep anaesthesia.

Abdomen↗
PubMed1991

Enflurane suppresses phrenic nerve-diaphragm transmission in vivo.

We examined the effects of enflurane on the diaphragmatic function in 15 pentobarbital-anesthetized, mechanically ventilated dogs. They were divided into three groups of five animals each, according to the administered concentration of enflurane. The diaphragmatic function was assessed from transdiaphragmatic pressure (Pdi) and integrated diaphragmatic electromyography (Edi) developed at functional residual capacity against an occluded airway during bilateral supramaximal phrenic nerve stimulation at 0.5, 10, 20, 50 and 100 Hz under quasiisometric condition. After a control measurement, enflurane was administered at a constant end-expired concentration (0, 0.5 and 1 MAC) and the measurement was repeated after 1 hour of exposure. The Pdi amplitude generated by single twitch (0.5 Hz) and during 10, 20 and 50 Hz stimulation was unchanged between the groups. No change in Pdi during 100 Hz stimulation was noted during 0 and 0.5 MAC exposure, while it was reduced by 1 MAC of enflurane. When the values of Pdi were expressed as % of maximum Pdi (%Pdi,max) that developed during control measurement and analyzed in terms of %Pdi,max-stimulus frequency relationship, a significant decrease in %Pdi,max was noted for 100 Hz stimulation in 0.5 and 1 MAC groups compared to the control. Similarly, Edi during 100 Hz stimulation obtained in 0.5 and 1 MAC groups was markedly depressed compared to the control. Edi during 50 Hz stimulation was also decreased at 1 MAC. Relative changes in Edi following enflurane administration were greater than the corresponding changes of Pdi. These results demonstrate that enflurane impairs diaphragmatic function through its inhibitory effects on neuromuscular transmission.

Journal Article↗
PubMed1991

Effects of partial paralysis on the swallowing reflex in conscious humans.

The ability to swallow may be affected by administration of a small dose of muscle relaxant. To test the hypothesis that a subparalyzing dose of a muscle relaxant can impair swallowing, effects of partial paralysis produced by pancuronium on the swallowing reflex were investigated in eight conscious subjects. The swallowing reflex was induced by a bolus injection or a continuous infusion of distilled water into the mesopharynx. The swallowing function was assessed by electromyogram of suprahyoid muscles (EMGSH), mesopharyngeal pressure (Pmeso), and hypopharyngeal pressure (Phypo). Peripheral muscle activity was simultaneously determined by train of four ratio (TOFR) of hypothenar muscles to electrical stimulation of ulnar nerve and by hand grip strength (HGS). Following control measurements, measurements during partial paralysis and after recovery from partial paralysis were performed after intravenous administration of pancuronium 0.02 mg/kg. Partial paralysis significantly depressed EMGSH (bolus injection 44.1 +/- 10.0%, continuous infusion 55.9 +/- 10.2% of control value, P less than 0.01). Pmeso also significantly decreased (bolus injection 64.9 +/- 6.7 to 47.8 +/- 5.8 mmHg, P less than 0.01; continuous infusion 63.4 +/- 7.7 to 52.5 +/- 5.8 mmHg, P less than 0.05). The TOFR of peripheral muscles decreased to 81.4 +/- 6.7% of control value (P less than 0.01), and HGS was reduced from 44.6 +/- 1.9 to 39.4 +/- 2.0 kg (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Breathing pattern and occlusion pressure waveform in humans anesthetized with halothane or sevoflurane.

To examine the ventilatory effects of sevoflurane, breathing pattern, airway occlusion pressure waveform, and the mechanical variables of the respiratory system were determined in seven subjects anesthetized with sevoflurane and in an additional seven subjects anesthetized with halothane. All patients breathed 1 MAC of anesthetic using oxygen as the carrier gas, and the measurements were performed in the absence of surgical stimulation. The durations of inspiration and expiration were significantly longer during sevoflurane than during halothane administration. Tidal volumes were larger in the sevoflurane group than in the halothane group. Occlusion pressure waveforms were also markedly different between the two groups. Occlusion pressure during the initial 300-400 ms tended to be less in the sevoflurane-anesthetized than in the halothane-anesthetized subjects. There was no evidence of an active Hering-Breuer reflex with either anesthetic. Mechanical variables of the respiratory system were essentially identical between the two anesthetics. We conclude that (a) the ventilatory effects of halothane and sevoflurane are different, (b) the difference in the respiratory timing and depth of breathing originates from the action of the anesthetics on the central respiratory neural network, and (c) the different shape of the tracheal occlusion pressure may be largely due to the different effects of halothane and sevoflurane on the muscles of the rib cage.

Airway Resistance↗
PubMed1990

Enflurane impairs canine diaphragmatic contractility in vivo.

We examined the effect of enflurane on diaphragmatic contractility in six anesthetized mechanically ventilated dogs. The diaphragmatic force was assessed from transdiaphragmatic pressure (Pdi) developed at functional residual capacity against an occluded airway during cervical phrenic nerve stimulation. Pdi-stimulus frequency relationship was compared at three levels of anesthesia, namely 1, 1.5, and 2 MAC (minimum alveolar concentration) of enflurane. The sequence of changing anesthetic concentration was randomized between animals. Pdi at 50 and 100 Hz stimulation was significantly decreased with increasing MAC while Pdi at 10 Hz stimulation was not affected by the depth of anesthesia. Pdi of 20 Hz stimulation was significantly decreased at 2 MAC as compared to those at 1 and 1.5 MAC. We conclude that enflurane decreases contractility of the diaphragm mainly through impairment of the neuromuscular transmission and/or membrane excitability. Part of its effects is, however, probably related to the impairment of excitation-contraction coupling, as suggested by the depression of Pdi at 2 MAC in response to 20 Hz stimulation.

Journal Article↗
PubMed1990

Breathing pattern and respiratory mechanics in sevoflurane-anesthetized humans.

In order to determine the respiratory effects of sevoflurane in humans, breathing pattern and mechanical behavior of respiratory system were investigated in ten subjects at anesthetic depth of 1 MAC (minimum alveolar concentration). Average tidal volume and breathing frequency amounted to 275 ml and 20.9 breaths per minute. Arterial carbon dioxide tension amounted to 45.6 mmHg. Duration of inspiration was 1.06s and that of expiration was 1.92s. Mean inspiratory flow rate amounted to 259 ml.s(-1). Average value of passive respiratory elastance determined by the method of Zin et al. amounted to 21.8 cmH(2)O. l(-1), while those of active respiratory elastance and resistance obtained by the method of Behrakis et al. were 28.0 cmH(2)O. l(-1) and 3.15 cmH(2)O. l(-1).s(-1), respectively. Values of these variables were compared to those reported in halothane and enflurane anesthesia and possible explanations of the differences between the anesthetics are discussed.

Journal Article↗
PubMed1990

Different effects of halothane and enflurane on diaphragmatic contractility in vivo.

We examined the effects of halothane and enflurane on diaphragmatic contractility in 12 anesthetized, mechanically ventilated dogs. The diaphragmatic force was assessed from transdiaphragmatic pressure (Pdi) developed at functional residual capacity against an occluded airway during cervical phrenic nerve stimulation. Animals were randomly assigned to two groups, a halothane group (n = 6) and an enflurane group (n = 6). The Pdi stimulus-frequency relationship was compared at anesthetic levels of 1, 1.5, and 2 MAC (minimum alveolar concentration) in each group. The sequence of changing anesthetic concentration was randomized. In addition, the Pdi-frequency relationship was also compared between 1 MAC of halothane and enflurane in 8 of 12 dogs. In animals anesthetized with enflurane, Pdi significantly decreased with 50- and 100-Hz stimulation in the presence of increasing MAC values, whereas Pdi at 10-Hz stimulation was not affected by the depth of anesthesia. Pdi with 20-Hz stimulation during 2 MAC enflurane also decreased significantly below Pdi levels seen at 1 and 1.5 MAC. By contrast, with halothane there was no difference in Pdi at any of the stimulation frequencies during any of the three levels of anesthesia. There was no statistical difference, however, between Pdi-frequency relationships during 1 MAC of halothane and enflurane in eight animals. From these results, we conclude that halothane does not impair diaphragmatic contractility any more than enflurane does, but enflurane decreases force generation of the diaphragm at high stimulation frequencies in a dose-related fashion. This depressant effect of enflurane occurs mainly through the impairment of neuromuscular transmission and/or membrane excitability.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Respiratory effects of expiratory flow-resistive loading in conscious and anesthetized humans.

The response of breathing patterns to increased expiratory resistance is not only of physiologic interest, with respect to the control of breathing, but also of clinical interest because of its clinical relevance to obstructive diseases such as asthma and emphysema. To elucidate the response of breathing patterns to increased expiratory resistance during anesthesia, the respiratory effects of expiratory flow-resistive loading on breathing patterns were studied in 15 conscious and 10 lightly anesthetized subjects. Inspiratory time, expiratory time, respiratory frequency, inspiratory duty cycle, tidal volume, minute ventilation, and mean inspiratory flow rate were determined from a respiratory inductive plethysmograph. End-tidal CO2 was continuously recorded. In awake subjects, respiratory frequency was reduced without change in tidal volume or mean inspiratory flow rate, and minute ventilation was significantly decreased; the synchrony between rib cage and abdomen wall motion was well maintained during the loads. In contrast, in anesthetized subjects, respiratory frequency was reduced with remarkable increases in tidal volume, mean inspiratory flow rate, and minute ventilation, whereas coordination between rib cage and abdomen compartments was disturbed. End-tidal CO2 did not change in conscious subjects, but it increased in anesthetized subjects during the loads. These results indicate that there are differences between conscious and anesthetized subjects in breathing patterns during expiratory loading, and suggest that the ability to coordinate rib cage-abdomen wall motion is easily disturbed during anesthesia in patients with expiratory flow limitation.

Adolescent↗