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Biomedical subjects

T Mashimo

Publications and source records attributed to T Mashimo.

At least 37 records · Page 2Linked to original sources
PubMed2001

Performance of heated humidifiers with a heated wire according to ventilatory settings.

Delivering warm, humidified gas to patients is important during mechanical ventilation. Heated humidifiers are effective and popular. The humidifying efficiency is influenced not only by performance and settings of the devices but the settings of ventilator. We compared the efficiency of humidifying devices with a heated wire and servo-controlled function under a variety of ventilator settings. A bench study was done with a TTL model lung. The study took place in the laboratory of the University Hospital, Osaka, Japan. Four devices (MR290 with MR730, MR310 with MR730; both Fisher & Paykel, ConchaTherm IV; Hudson RCI, and HummaxII; METRAN) were tested. Hummax II has been developed recently, and it consists of a heated wire and polyethylene microporous hollow fiber. Both wire and fiber were put inside of an inspiratory circuit, and water vapor is delivered throughout the circuit. The Servo 300 was connected to the TTL with a standard ventilator circuit. The ventilator settings were as follows; minute ventilation (V(E)) 5, 10, and 15 L/min, a respiratory rate of 10 breaths/min, I:E ratio 1:1, 1:2, and 1:4, and no applied PEEP. Humidifying devices were set to maintain the temperature of airway opening at 32 degrees C and 37 degrees C. The greater V(E) the lower the humidity with all devices except Hummax II. Hummax II delivered 100% relative humidity at all ventilator and humidifier settings. When airway temperature control of the devices was set at 32 degrees C, the ConchaTherm IV did not deliver 30 mg/L of vapor, which is the value recommended by American National Standards at all V(E) settings. At 10 and 15 L/min of V(E) settings MR310 with MR730 did not deliver recommended vapor, either. In conclusion, airway temperature setting of the humidifying devices influenced the humidity of inspiratory gas greatly. Ventilatory settings also influenced the humidity of inspiratory gas. The Hummax II delivered sufficient water vapor under a variety of minute ventilation.

Equipment Design↗
PubMed2001

Practical issues in bispectral analysis of electroencephalographic signals.

IMPLICATIONS: The aim of this report was to confirm the methodology of bispectral analysis of electroencephalogram. In developing a software for real-time bispectral analysis, we encountered several practical problems in bispectrum calculation. We settled those and concluded that 3 min of monitoring are required to obtain reliable and reproducible bicoherence values.

Algorithms↗
PubMed2001

[Anesthesia for a patient with cardiac sarcoidosis].

Anesthesia for a 49-year-old man with cardiac sarcoidosis is reported. Preoperative cardiac examination showed left ventricular dysfunction (ejection fraction = 27%) and myocardial conduction defects. In addition, his previous history included atrial fibrillation and cerebral infarction. Transesophageal echocardiography showed thrombus in the left appendage. Anesthesia was induced with fentanyl and diazepam and maintained with fentanyl and isoflurane. Perioperative hemodynamic monitoring included direct arterial pressure, central venous and pulmonary artery pressure and continuous cardiac output. In addition, transesophageal echocardiography was useful for watching thrombus in the left appendage. His hemodynamic condition was stable and no neurological complication was noted after anesthesia.

Anesthesia, General↗
PubMed2001

[Pathogenesis of complex regional pain syndrome (CRPS)].

Neuropathic pain results from injury to neural structures within the peripheral or central nervous systems. Such injury promotes spontaneous and ectopic firing of nerves as well as reorganization of the nervous system. Neuropathic pain persists chronically. Patients who suffer from neuropathic pain exhibit persistent or paroxysmal pain without apparent immediate cause or pain hypersensitivity after tissue damage. This hypersensitivity is manifest as hyperalgesia and allodynia. Complex regional pain syndrome, CRPS is a category of neuropathic pain and is further divided into type I(reflex sympathetic dystrophy: RSD) and type II(causalgia). CRPS is characterized by localized autonomic dysregulation in the affected area with vasomotor and/or sudomotor changes, edema, colour difference, sweating abnormality, and atrophy.

Brain↗
PubMed2000

The quantitative analysis of three action modes of volatile anesthetics on purple membrane.

We quantitatively assessed the spectroscopic changes of purple membrane in relation to the concentrations of a volatile anesthetic. As reported previously, volatile anesthetics show three modes of action on purple membrane. By using an anesthetic for which the concentration in solution could be determined spectroscopically and by applying modified analytical methods regarding the M-intermediate lifetime, we were able to clarify the quantitative relation between anesthetic concentration and each mode of action, a relation which in the past has only been described qualitatively. We also determined through the measurement of transient pH changes with pyranine that the proton pump efficiency per photochemical cycle in an action mode induced with low concentrations of anesthetic does not change from that of the native state. Moreover, we dynamically obtained the individual M-bacteriorhodopsin difference spectrum of each state at room temperature using our flash photolysis system equipped with a wavelength-tunable dye laser. These results demonstrated again that we should clearly distinguish different action modes of anesthetics according to their concentrations.

Anesthetics↗
PubMed2000

The alpha and gamma subunit-dependent effects of local anesthetics on recombinant GABA(A) receptors.

Although convulsions due to local anesthetic systemic toxicity are thought to be due to inhibition of GABA(A) receptor-linked currents in the central nervous system, the mechanism of action remains unclear. We therefore examined the effects of local anesthetics on gamma-aminobutyric acid (GABA)-induced currents using recombinant GABA(A) receptors with specific combinations of subunits. Murine GABA(A) receptors were expressed by injection of cRNAs encoding each subunit into Xenopus oocytes. The effects of local anesthetics (lidocaine, bupivacaine, procaine and tetracaine) on GABA-induced currents of receptors expressing different subunit combinations (alpha1beta2, alpha1beta2gamma2s, alpha4beta2gamma2s and beta2) were examined via the two electrode voltage clamp method. At alpha1beta2, alpha1beta2gamma2s and alpha4beta2gamma2s GABA(A) receptors, all local anesthetics inhibited GABA-induced currents in a dose-dependent manner. The presence of the gamma2s subunit resulted in a greater inhibition by all local anesthetics, but the presence of the alpha4 subunit resulted in less inhibition. At beta2 homomeric receptors, local anesthetics directly induced an outward current similar to that of picrotoxin. These data indicated that (1) the alpha and gamma subunits of GABA(A) receptors modulated the inhibitory effects of local anesthetics on GABA(A) function, and (2) local anesthetics can activate the beta2 subunit and may block the GABA(A) receptor channel pore.

Anesthetics, Local↗
PubMed2000

Activation of the tumor metastasis suppressor gene, KAI1, by etoposide is mediated by p53 and c-Jun genes.

KAI1 is a metastasis suppressor gene which is capable of inhibiting the processes of tumor metastasis without affecting tumorigenicity per se. We found that etoposide, a topoisomerase II inhibitor, is able to activate the expression of the KAI1 gene in a dose-dependent manner in human prostate cancer cell lines, ALVA, DU145, and PC-3 as well as in human lung carcinoma cell A549. The activation of the KAI1 gene was mainly mediated by the c-Jun gene in the PC-3 and DU145 cell lines, while it was mediated by both p53 and c-Jun genes in the A549 cell line. These results suggest that the augmentation of the KAI1 gene expression is independently controlled by p53 and c-Jun at the transcriptional level in the human cancer cell lines. Furthermore, treatment of these cell lines with etoposide resulted in significant reduction of cellular invasion measured by the Matrigel invasion chamber. Because etoposide has been shown to be effective on advanced prostate cancer when used in combination with other regimens, our results provide further rationale to use this drug as an antimetastatic agent.

5' Untranslated Regions↗
PubMed2000

The influence of the timing of administration of thiopentone sodium on nitric oxide-mediated neurotoxicity in vitro.

Thiopentone sodium is a highly useful pharmacological agent that provides a neuroprotection against cerebral ischaemia. Since not all patients can receive thiopentone sodium before cerebral ischaemia occurs, we investigated the influence of timing of thiopentone sodium administration on the neurotoxicity induced by nitric oxide (NO) using Shibuta's established model of primary brain cultures. Cortical neurones prepared from 16-day gestational rat foetuses were used after 13-14 days in culture. The cells were exposed to an NO-donor, NOC-5 at 30 microM. Thiopentone sodium administered at 30 and 10 min before or 5, 10 and 15 min after exposure to NOC-5, but not thereafter, significantly attenuated NO-induced neurotoxicity compared with controls. The survival rate of the neurones in which thiopentone sodium was administered at 15 min after exposure to NOC-5 was 55.7+/-2.4%, compared to a 10.0+/-1.6% survival rate in neurones when thiopentone sodium was administered at 30 min after exposure to NOC-5. These findings demonstrate that thiopentone sodium, which protects cerebral cortical neurones against NO-mediated cytotoxicity, should be given as soon as possible in case ischaemic or hypoxic neuronal damage is predicted.

Animals↗
PubMed2000

Localization of a novel tumor metastasis suppressor region on the short arm of human chromosome 2.

Much of the lethality of malignant neoplasms is attributable directly to their ability to develop secondary growths in organs at a distance from the primary tumor mass, whereas few patients die from their primary neoplasm. Little is known about the molecular mechanism of tumor metastasis, however, which is controlled by a variety of positive and negative factors. In the search for metastasis suppressor genes, we have used the microcell-mediated chromosome transfer method and a rat prostate tumor model in SCID mice. When human chromosome 2 was introduced into the highly metastatic rat prostatic tumor cell, AT6.1, the metastatic ability of this cell was significantly (>99%) decreased in animals. An STS-based PCR analysis for 8 hybrid clones indicates that the suppressor activity is located in the p25-22 region of the chromosome. Furthermore, the AT6.1 cell with human chromosome 2 showed a reduced ability to invade Matrigel, suggesting that the suppressor activity is involved in the step of tumor invasion during the progression of prostate cancer. We have also examined the status of the suppressor region on chromosome 2 in human prostate cancer specimens and found that this region was often lost in high-grade tumors. These results suggest that the putative suppressor gene on chromosome 2 is functionally involved in the progression of human prostate cancer. Genes Chromosomes Cancer 28:285-293, 2000.

Aged↗
PubMed2000

Direct inhibition of microtubule-based kinesin motility by local anesthetics.

Local anesthetics are known to inhibit neuronal fast anterograde axoplasmic transport (FAAT) in a reversible and dose-dependent manner, but the precise mechanism has not been determined. FAAT is powered by kinesin superfamily proteins, which transport membranous organelles, vesicles, or protein complexes along microtubules. We investigated the direct effect of local anesthetics on kinesin, using both in vitro motility and single-molecule motility assays. In the modified in vitro motility assay, local anesthetics immediately and reversibly stopped the kinesin-based microtubule movement in an all-or-none fashion without lowering kinesin ATPase activity. QX-314, a permanently charged derivative of lidocaine, exerted an effect similar to that of lidocaine, suggesting that the effect of anesthetics is due to the charged form of the anesthetics. In the single-molecule motility assay, the local anesthetic tetracaine inhibited the motility of individual kinesin molecules in a dose-dependent manner. The concentrations of the anesthetics that inhibited the motility of kinesin correlated well with those blocking FAAT. We conclude that the charged form of local anesthetics directly and reversibly inhibits kinesin motility in a dose-dependent manner, and it is the major cause of the inhibition of FAAT by local anesthetics.

Adenosine Triphosphatases↗
PubMed2000

Intrathecal lithium reduces neuropathic pain responses in a rat model of peripheral neuropathy.

We tested the ability of lithium (Li(+)) to block heat hyperalgesia, cold allodynia, mechanical allodynia and mechanical hyperalgesia in rats experimentally subjected to painful peripheral neuropathy. Chronic constrictive injury (CCI) to the sciatic nerve induced persistent hyperalgesia and allodynia. Intrathecal injection of Li(+) (2.5-40 micromol) into the region of lumbar enlargement dose-dependently reduced heat hyperalgesia, cold allodynia and mechanical allodynia for 2-6 h after injection, but had no effect on mechanical hyperalgesia. Li(+) had no significant effect on responses from control and sham-operated animals. Intrathecal injection of myo-inositol (2.5 mg) significantly reversed both the anti-hyperalgesic and anti-allodynic effect of Li(+). These findings suggest that intrathecal Li(+) suppresses neuropathic pain response in CCI rats through the intracellular phosphatidylinositol (PI) second messenger system in spinal cord neurons. Lithium (Li(+)) has already found widespread clinical application; these results suggest that its therapeutic utility may be extended to include treatment of neuropathic pain syndromes resulting from peripheral nerve injury.

Animals↗
PubMed2000

Infrared transmission of electronic information via LAN in the operating room.

Recent advances in technology have brought many kinds of monitoring devices into the operating room (OR). The information gathered by monitors can be channeled to the operating ward information system via a local area network (LAN). Connecting patients to monitors and monitors to the LAN, however, requires a large number of cables. This wiring is generally inconvenient and particularly troublesome if the layout of the OR is rearranged. From this point of view, wireless transmission seems ideally suited to clinical settings. Currently, two modes of wireless connectivity are available: radio-frequency (RF) waves or infrared (IR) waves. Some reports suggest that RF transmission is likely to cause electromagnetic interference (EMI) in medical devices such as cardiac pacemakers or infusion pumps. The risk of malfunctioning life-sustaining devices and the catastrophic consequences this would have on seriously ill patients rules out the use of RF. Here, we report an IR system using IR modems for LAN connectivity in the OR. In this study, we focused on the possible detrimental effects of EMI during wireless connectivity. In our trial, we found no evidence of EMI of IR modems with any of the medical devices we tested. Furthermore, IR modems showed similar performance to a wired system even in an electrically noisy environment. We conclude that IR wireless connectivity can be safely and effectively used in ORs.

Hospital Information Systems↗
PubMed2000

Administration of human chorionic gonadotropin with a controlled-release function to immature rats for application in male infertility therapy.

Biodegradable poly(DL-lactic acid) (PLA) devices with controlled release of human chorionic gonadotropin (hCG) were fabricated in a 2-mm cylinder form by the meltpressing technique. The devices fabricated were inserted subcutaneously in the backs of immature rats. It was found that the serum level of testosterone (T) remained constant at approximately 0.7 ng/ml for an experimental period of 14 days, resulting in greater Leydig cell production of testosterone. This was also suggested from the results of immunohistochemical observation of the testis and weight changes of prostates, such as the ventral prostates and seminal vesicle.

Absorbable Implants↗
PubMed2000

Supraspinal, not spinal, alpha(2) adrenoceptors are involved in the anesthetic-sparing and hemodynamic-stabilizing effects of systemic clonidine in rats.

UNLABELLED: Clonidine, an alpha(2) agonist, reduces the anesthetic requirement and attenuates harmful hemodynamic responses to noxious stimuli. We examined the responsible sites of action in the central nervous system for the minimum alveolar anesthetic concentration (MAC) and MAC blocking adrenergic response (MAC-BAR) reducing effects of systemically administered clonidine in halothane-anesthetized rats. The MAC for halothane was determined by the tail clamp method, and MAC-BAR was defined as the MAC which attenuated hemodynamic responses within 10% after the tail clamp. We examined the effect of IV clonidine in the presence of rauwolscine, an alpha(2) antagonist given through IV, intrathecal (IT), intracisternal (IC), or intracerebroventrical (ICV) routes. IV clonidine reduced MAC and MAC-BAR dose-dependently. IV and ICV rauwolscine antagonized the MAC-reducing effect of clonidine, whereas IC and IT rauwolscine did not. In comparison, IV, ICV, and IC rauwolscine antagonized the MAC-BAR-reducing effect of clonidine; IT rauwolscine had no effect. Our data demonstrate that the alpha(2) adrenoceptors in the regions above mesencephalon and both the regions above mesencephalon and the lower brainstem are responsible for the MAC and MAC-BAR-reducing effect of systemic clonidine in rats, respectively. However, the spinal alpha(2) adrenoceptors were not involved in these effects of clonidine. IMPLICATIONS: In the regions above mesencephalon, alpha(2) adrenoceptors were the most responsible for the minimum alveolar concentration-reducing effect and both the lower brainstem and regions above mesencephalon were involved in the minimum alveolar concentration blocking adrenergic response-reducing effect of clonidine. The spinal alpha(2) adrenoceptors did not significantly contribute to these effects of clonidine.

Adrenergic alpha-Agonists↗
PubMed2000

Pulmonary disposition of propofol in surgical patients.

BACKGROUND: The lungs have been mentioned as a possible site contributing to the extrahepatic clearance of propofol. The objective of the present study was to clarify the pulmonary disposition of propofol directly in human lungs by investigating both the first-pass uptake and pulmonary extraction at pseudo-steady state. METHODS: Nine patients were enrolled in the first-pass uptake study. Propofol (5 mg) and indocyanine green (ICG; 15 mg) were simultaneously administered via a central venous catheter within 1 s, and sequential arterial blood samples were obtained from the radial artery at 1-s intervals up to 45 s. Eleven patients were included in the infusion study, and propofol was infused via the jugular vein at a rate of 50 microgram. kg-1. min-1. Blood samples were simultaneously collected from pulmonary and radial arteries up to 60 min. RESULTS: A pronounced difference in the dilution curves between propofol and ICG was observed, and 28.4 +/- 11.6% (mean +/- SD) of propofol was taken up during the single passage through the human lung. The mean pulmonary transit time of propofol (31.3 +/- 6.0 s) was significantly longer than that of ICG (22.4 +/- 2.7 s; P < 0.01), indicating that some of the propofol trapped by lungs returned to the circulation by back diffusion. In the constant infusion study, no significant differences were observed with the plasma concentrations of propofol between pulmonary and radial arteries except for that at 2 min. The area under the curve of pulmonary and radial arterial concentration curves to 60 min were 59.1 +/- 14.8 and 56.8 +/- 12.5 microg. ml-1. min-1, respectively. No significant difference was observed with the area under the curve, suggesting that metabolism was not involved in the pulmonary uptake in human lungs. CONCLUSIONS: Most of the propofol that undergoes pulmonary uptake during the first pass was released back to the circulation by back diffusion. Metabolism was not involved in the pulmonary uptake in human lungs.

Anesthesia, General↗
PubMed2000

Interaction of the effects between vitamin D receptor polymorphism and exercise training on bone metabolism.

Bone metabolism is strongly influenced by heredity and environmental factors. To investigate interaction of the effects between vitamin D receptor polymorphism by Fok I and resistance exercise training on bone metabolism, young male subjects with FF genotype (F, n = 10) and Ff or ff genotypes (f, n = 10) followed 1 mo of weight training, and changes in bone metabolism were compared. An additional 14 subjects served as a sedentary control. Biomarkers of bone formation, bone-specific alkaline phosphatase, and osteocalcin were significantly increased by training in both F and f groups. 1, 25-Dihydroxyvitamin D(3), known to upregulate bone formation, was also increased by the training in the f but not in the F group. Bone resorption assessed by cross-linked NH(2)-terminal telopeptide of type I collagen was significantly suppressed by the training, and the decrease in F was greater and longer lasting than that in f group. In conclusion, stimulation of bone formation and suppression of bone resorption occurred within 1 mo in young men. Despite a significant increase in 1,25-dihydroxyvitamin D(3) in the f group but not in the F group, the response of bone metabolism to the training in the F was similar to or greater than that in f group, suggesting a functional difference between vitamin D receptor genotypes f and F.

Adult↗
PubMed2000

Identification of quantitative trait loci for serum cholesterol levels in stroke-prone spontaneously hypertensive rats.

The stroke-prone spontaneously hypertensive rat (SHRSP) has been reported to show significantly lower levels of serum total cholesterol than the normotensive control strain Wistar-Kyoto rat (WKY). Because selective inbreeding was conducted for stroke proneness, this concomitantly inherited characteristic of SHRSP may play some pathophysiological role in stroke. We evaluated the genetic determinants of the cholesterol trait by estimating heritability and subsequently by undertaking a genome-wide screen with 161 genetic markers in F(2) progeny involving SHRSP and WKY (104 male and 106 female rats). Three quantitative trait loci (QTLs) were detected on rat chromosomes 5, 7, and 15. Markers from the linked region on chromosome 15 indicated significant evidence of linkage with a maximal log of the odds (LOD) score of 7.7, whereas those on chromosomes 5 and 7 cosegregated with the trait in a sex-specific manner (the QTL close to genetic marker D5 Mit5 reached an LOD score of 7.3 in males, and that close to D7 Mit10 reached an LOD score of 3.2 in females). The male-specific QTL on chromosome 5 appeared to overlap with previously reported QTLs for stroke-associated phenotypes, but an identical gene (or genes) appeared unlikely to control these and the cholesterol traits simultaneously. In the present study, serum cholesterol levels were shown to be highly genetically determined in SHRSP (the heritability estimates are 76% in males and 83% in females), and 3 QTLs with substantial effects were identified. Further work, however, is required to clarify whether the cholesterol trait is related to the etiology of stroke or has been retained by chance through the inbreeding process in SHRSP.

Alleles↗