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Biomedical subjects

Tetsuo Shimizu

Publications and source records attributed to Tetsuo Shimizu.

At least 19 recordsLinked to original sources
PubMed2005

Measuring the thermal conductivity of a single carbon nanotube.

Although the thermal properties of millimeter-sized carbon nanotube mats and packed carbon nanofibers have been readily measured, measurements for a single nanotube are extremely difficult. Here, we report a novel method that can reliably measure the thermal conductivity of a single carbon nanotube using a suspended sample-attached T-type nanosensor. Our experimental results show that the thermal conductivity of a carbon nanotube at room temperature increases as its diameter decreases, and exceeds 2000 W/mK for a diameter of 9.8 nm. The temperature dependence of the thermal conductivity for a carbon nanotube with a diameter of 16.1 nm appears to have an asymptote near 320 K. The present method is, in principle, applicable to any kind of a single nanofiber, nanowire, and even single-walled carbon nanotube.

Journal Article↗
PubMed2005

Large-scale separation of metallic and semiconducting single-walled carbon nanotubes.

In the applications of single-walled carbon nanotubes (SWNTs), it is extremely important to separate semiconducting and metallic SWNTs. Although several methods have been reported for the separation, only low yields have been achieved at great expense. We show a separation method involving a dispersion-centrifugation process in a tetrahydrofuran solution of amine, which makes metallic SWNTs highly concentrated to 87% in a simple way.

Journal Article↗
PubMed2005

A three-factor model of the MADRS in major depressive disorder.

Major Depressive Disorder (MDD) may be composed of some symptom clusters with distinct neurochemical disturbances, suggesting the importance of the factor analysis of depressive symptoms; however, the results of previous studies using the Montgomery-Asberg Depression Rating Scale (MADRS) have been inconsistent. In the present study, factor analysis of the MADRS was performed in 132 Japanese patients (range 23-74 years, mean 47.6 years) with MDD without any psychiatric comorbidity. The principal component analysis with Varimax rotation identified three factors, accounting for 61% of the total variance: The first factor, labeled dysphoria, included pessimistic thoughts, suicidal thoughts, and reported sadness; the second factor, labeled retardation, included lassitude, inability to feel, apparent sadness, and concentration difficulties; and the third factor, labeled vegetative symptoms, included reduced sleep, reduced appetite, and inner tension. The score of the vegetative factor showed a significant positive correlation with age and was significantly higher in females than in males. This study suggests that the symptoms of MDD, as assessed by the MADRS, cluster into three factors (dysphoria, retardation, and vegetative symptoms).

Adult↗
PubMed2005

Suicide patterns and characteristics in Akita, Japan.

Akita Prefecture currently has the highest rate of suicide in Japan. Given this alarming statistic, investigation of the underlying causes of suicide and identification of strategies for suicide prevention are imperative. Members of the Akita Prefectural Medical Association (APMA) see most of the individuals who commit suicides in Akita Prefecture, so data from the APMA would prove advantageous in any investigation of suicides. In this study, members of the APMA who had attended to individuals who had committed suicide were asked to complete a questionnaire about the case to determine the factors underlying suicide in Akita Prefecture. From 1 July 2001 to 30 June 2002, a total of 138 cases (102 males, 36 females) of suicide were reported. Most suicide cases were of 50-69 year olds. Many cases involved relatively lethal methods (such as hanging). Most suicides were performed at home and at a time when the rest of the family was asleep or absent. The most common complaint appeared to be economic-related problems. Depressive disorder was the most common psychiatric disorder, and many cases displayed high depressive trait scores. The present results do not exclude the possibility that economic-related problems are playing a major role in recent increases in suicide numbers. However, strategies for dealing with depression as well as economic-related problems are considered important.

Adolescent↗
PubMed2005

Passive body heating ameliorates sleep disturbances in patients with vascular dementia without circadian phase-shifting.

OBJECTIVE: This study investigated the sleep-promoting, thermoregulatory, and circadian phase-shifting actions of passive body heating (PBH) in elderly insomniac patients (IPs) with mild-to-moderate vascular dementia. METHODS: Thirteen elderly IPs with vascular dementia (mean age 76.9 years; male/female ratio 2/11) were subjected to a PBH trial session. This session comprised a 3-day baseline period, 2-day PBH period, and 1-day post-PBH period. In the PBH period, the subjects received PBH (immersion in hot water about 40.0 degrees C to mid-thorax level) for 30 minutes beginning 2 hours before bedtime. Sleep-waking, estimated by actigraph, core body temperature (cBT), and heart rate variability were continuously monitored. Dim-light melatonin-onset time (DLMO) was determined in the baseline and post-PBH periods. RESULTS: PBH significantly improved subjects' sleep quality; sleep latency decreased; sleep efficiency increased; and wake time after sleep onset decreased. These trends were more prominent in the latter half of the sleep time. PBH induced a rapid cBT elevation of approximately 0.80 degrees C, on average, followed by enhanced heat loss (DeltacBT: difference in cBT between just after the PBH and bedtime), lasting 1.5 hours before sleep. There was a significantly positive correlation between DeltacBT and sleep latency. PBH induced no significant phase shift in DLMO. Heart-rate variability data showed that PBH induced parasympathomimetic action during sleep time in the subjects. CONCLUSION: PBH may have a sleep-promoting effect by intervening in the thermoregulatory and autonomic systems in elderly IPs with vascular dementia.

Aged↗
PubMed2005

[Comparison of intrapleural OK-432 and cisplatin for malignant pleural effusion in lung cancer patients].

Malignant pleural effusion is typical of complications in advanced lung cancer patients, most of whom complain of dyspnea. The standard treatment for symptomatic pleural effusion is intrapleural administration of a chemical agent. In Japan, OK-432, a streptococcal preparation, and cisplatin (CDDP) have been among the most frequently used chemical agents. There have been very few reports on the efficacy of chemical agents for malignant pleural effusion. We compared therapeutic efficacy and toxicity of intrapleural OK-432 with CDDP in a case-control study. The subjects consisted of 32 lung cancer patients with malignant pleural effusion who were admitted to our hospital between January 2000 and June 2004. The therapeutic efficacy was assessed from duration of chest drainage after intrapleural administration, response rate, time to progression of malignant pleural effusion, and survival time. No statistically significant difference was observed for therapeutic efficacy. Although the OK-432-treated group had only grade 1 fever, chest pain, nausea, the CDDP-treated group had a grade 2 increase in creatinine and grade 3 nausea. Intrapleural OK-432 seemed to be better tolerated in the treatment of malignant pleural effusion than intrapleural CDDP.

Aged↗
PubMed2005

[The improvement of the enforcement rate of the standard regimen (A) of tuberculosis chemotherapy by the introduction of common database system for tuberculosis].

OBJECTIVE: The purpose of this study was to improve the enforcement rate of the standard regimen (A) of tuberculosis chemotherapy. SUBJECTIVE AND METHODS: We introduced the common database system for tuberculosis in three national hospitals in Hokkaido. From January 2002 to December 2003, we collected the anonymous informations of the patients with tuberculosis at the start of treatment, at the discharge and at the end of treatment. Then, we reported the enforcement rate of the standard regimen (A) as a clinical indicator periodically to three hospitals. RESULTS: Four hundred and twenty-nine patients were registered. In patients below 80 years old, the enforcement rate of the standard regimen (A) was 48.5% in 2002. The enforcement rate rose significantly to 62.7% (p = 0.0126) in 2003. In elder smear-positive patients (> or =75) and in elder smear-negative patients (> or =70), the enforcement rate was low (29.1% and 25.0%, respectively). Furthermore in young smear-negative patients (< or =29), the enforcement rate was low (28.0%). As the extent of their disease was minimal, they were treated with other regimens. In patients treated with the standard regimen (A), there were no significant differences in the frequency of adverse effects between elder patients ( 70) and other patients (< or =69). There were also no significant differences in the frequency of changing the regimen between them. Median admission period of 2002 was 114 days. In 2003, it was shortened significantly to 110 days (p = 0.0487). CONCLUSION: By the introduction of the common database system for tuberculosis, the enforcement rate of the standard regimen (A) was improved. Low enforcement rate in young smear-negative patients in an important problem to be improved in the future. The clinical indicator based on the common database system between hospitals, is useful to clarify the problems, and then to improve the quality of medical performance.

Adult↗
PubMed2004

Remarkable effect of milnacipran, a serotonin-noradrenalin reuptake inhibitor (SNRI), on depressive symptoms in patients with Parkinson's disease who have insufficient response to selective serotonin reuptake inhibitors (SSRIs): two case reports.

The authors present here two cases of Parkinson's disease with depression refractory to SSRIs treatment, who experienced a complete remission after replacing the ongoing SSRIs with a serotonin-noradrenalin reuptake inhibitor (SNRI), milnacipran. The case reports suggest that milnacipran may be one of the treatment options for depression in patients with Parkinson's disease who had inadequate response to SSRIs. Further studies are warranted to confirm this observation.

Adrenergic Uptake Inhibitors↗
PubMed2004

Similar profiles in human period1 gene expression in peripheral mononuclear and polymorphonuclear cells.

Increasing amounts of data have indicated the physiological significance of circadian clock gene regulation in various peripheral cells. In the present study, we examined expression of the human homolog of period1 (hPer1) in peripheral mononuclear cells (MNCs) and polymorphonuclear neutrophils (PMNs) in seven healthy young male volunteers (mean age, 21.0 years; range, 19-24 years) under modified constant routine conditions. The expression of hPer1 as determined by real-time PCR with gene-specific hybriprobes in MNCs and PMNs showed significant daily variations with similar acrophases and peak transcription in the subjective morning. The acrophases in hPer1 expression rhythms in MNCs and PMNs were found to correlate positively with that of the serum melatonin secretion rhythms, which is a reliable phase marker of the suprachiasmatic nucleus (SCN), the circadian master clock. The present findings indicate that clock gene activity could be preserved across different peripheral blood cell types and support the assumption that peripheral clocks are entrained by the SCN.

Adult↗
PubMed2004

Diazepam reduces both arterial blood pressure and muscle sympathetic nerve activity in human.

It is known that benzodiazepines have a hypotensive effect, but the mechanism has not been well elucidated yet. To clarify whether this effect is due to central or peripheral mechanism, we administered 5 mg of diazepam or saline intravenously to healthy volunteers and assessed the change in blood pressure, heart rate, muscle sympathetic nerve activity and heart rate variability. After diazepam administration, systolic and mean blood pressure decreased significantly. Muscle sympathetic nerve activity was also significantly reduced but heart rate did not change, whereas the variables of spectral analysis of heart rate variability did not show significant change. We concluded that the hypotensive effect of diazepam in human is mainly due to the central mechanism.

Action Potentials↗
PubMed2004

Enhanced heat loss and age-related hypersensitivity to diazepam.

Whether elderly people suffer from age-related changes in pharmacokinetics and/or pharmacodynamics with administration of benzodiazepines is still a matter of controversy. We investigated the course of brain function and thermoregulation after oral administration of a standard benzodiazepine, diazepam (DZP), in 8 healthy young men (mean age, 19.8 years; range, 18 to 23 years) and 8 healthy middle-aged and older men (mean age, 60.9 years; range, 53 to 71 years). Placebo or DZP was administered in a single-blind crossover manner to the young men (placebo, 5-mg, 10-mg DZP) and to the older men (placebo, 5-mg DZP), and plasma DZP concentration, choice reaction time, proximal body temperature, and distal body temperature were monitored with high time resolution under a modified constant routine condition to exclude masking effects. Whereas there was no evidence of age-related alterations in pharmacokinetics between the 2 groups, the older subjects, in comparison to the young subjects, showed a more delayed choice reaction time in response to the same plasma DZP level, suggesting that hypersensitivity is related to increased age. DZP at 5 mg in the older subjects induced acute and transient hypothermia to the same degree as that induced by DZP at 10 mg in the young subjects. The distal-proximal body temperature gradient (difference between distal body temperature and proximal body temperature), an indicator of blood flow in distal skin regions, showed strong positive correlation with the delay in choice reaction time in both groups. These findings suggest that hypersensitivity to benzodiazepine in older persons may be due, at least in part, to age-related changes in thermoregulation, especially in the heat loss process.

Adolescent↗
PubMed2004

Positive association between T-182C polymorphism in the norepinephrine transporter gene and susceptibility to major depressive disorder in a japanese population.

Norepinephrinergic neurotransmission in the central nervous system appears to have a major impact on the symptomatology in major depressive disorder and the human norepinephrine transporter (NET) gene is one of the key candidates for genetic studies in major depressive disorder. The authors established a new allele-specific PCR-based genotyping procedure and examined whether the NET T-182C polymorphism was associated with the susceptibility to major depressive disorder in a Japanese population. This study included 145 patients with major depressive disorder (according to DSM-IV) and 164 healthy volunteers. There was a significant difference in the genotype distribution between major depressive disorder patients and healthy volunteers (p = 0.02), and the C/C genotype was associated with lesser susceptibility to major depressive disorder. The NET T-182C polymorphism may be in part related to the pathophysiology of major depressive disorder in a Japanese population.

Adult↗