Biomedical subjects

M Okawa

Publications and source records attributed to M Okawa.

At least 37 records · Page 2Linked to original sources

PubMed2000

Dynamical quark effects on light quark masses

Light quark masses are calculated in lattice QCD with two degenerate flavors of dynamical quarks. The calculations are made with improved actions with lattice spacing a = 0.22-0.11 fm. In the continuum limit we find m(M&Smacr;)(ud)(2 GeV) = 3.44(+0.14)(-0.22) MeV using the pi and rho meson masses as physical input, and m(M&Smacr;)(s)(2 GeV) = 88(+4)(-6) MeV or 90(+5)(-11) MeV with the K or straight phi meson mass as additional input. The quoted errors represent statistical and systematic combined, the latter including those from continuum and chiral extrapolations, and from renormalization factors. Compared to quenched results, two flavors of dynamical quarks reduce quark masses by about 25%.

Journal Article↗

PubMed2000

Altered phase relation between sleep timing and core body temperature rhythm in delayed sleep phase syndrome and non-24-hour sleep-wake syndrome in humans.

Changes in the phase relation between sleep timing and the circadian pacemaker are suspected to have an etiological significance in circadian rhythm sleep disorders. Simultaneous recordings of rest-activity and rectal temperature in seven sighted delayed sleep phase syndrome (DSPS) patients, seven sighted non-24-h sleep-wake syndrome (non-24) patients, and 14 healthy controls were made for 10-14 days continuously in the subjects' homes. We found that sleep length and the interval from the body temperature (BT) trough to sleep offset were significantly longer in both non-24 and DSPS patients than in the controls, and that the interval between sleep onset and the BT trough was significantly less in the non-24 patients than in the DSPS patients and the controls. We postulate these alterations in phase relation to be associated with phase changes of the circadian pacemaker via different illumination timings.

Adult↗

PubMed2000

Poor compensatory function for sleep loss as a pathogenic factor in patients with delayed sleep phase syndrome.

OBJECTIVE: Delayed sleep phase syndrome (DSPS) is a condition in which the patient is unable to reset or phase-advance his/her sleep timing properly after transient sleep delay and consequently shows persistent sleep phase delay. Prior studies suggested that DSPS is associated with a phase delay in the circadian pacemaker, but there was no evidence to explain the patient's inability to reset sleep phase. SUBJECTS AND METHODS: We used an ultra-short sleep-wake schedule together with simultaneous measurement of dim light melatonin rhythm after 24-hour sleep deprivation to allow the differential observation of diurnal sleep propensity fluctuation both from circadian and homeostatic aspects in 11 patients with DSPS (17-37 years; 8 men, 3 women) and 15 healthy controls (19-32 years; 8 men, 7 women). SETTING: NA. PATIENTS OR PARTICIPANTS: NA. INTERVENTIONS: NA. RESULTS: DSPS patients showed less ability to compensate for previous sleep loss during their circadian day and first hours of their circadian nighttime determined by dim light melatonin onset compared with controls, while controls compensated for previous sleep loss at most circadian times. Though shapes of dim light melatonin rhythm did not differ between the groups, phase angle between melatonin and sleep propensity rhythms was wider in DSPS patients than in controls. CONCLUSIONS: These findings suggest that poor compensatory function for sleep loss predisposes DSPS patients to failure to reset their sleep phase. Our results provide implications for understanding not only the pathophysiology of DSPS but also the biological basis for why some people can change their sleep schedule easily according to personal or social demands while others cannot.

Adolescent↗

PubMed2000

Menstrual changes in sleep, rectal temperature and melatonin rhythms in a subject with premenstrual syndrome.

We studied a sighted woman with premenstrual syndrome who showed menstrual changes in circadian rhythms. She showed alternative phase shifts in the sleep rhythm in the menstrual cycle: progressive phase advances in the follicular phase and phase delays in the luteal phase. Rectal temperature rhythm also showed similar menstrual changes, but the phase advance and delay started a few days earlier than changes in sleep-wake rhythm so that the two rhythms were dissociated around ovulation and menstruation. These results suggest that her circadian rhythms in sleep and temperature are under the control of ovarian steroid hormones and that these two rhythms have different sensitivity to the hormones.

Adult↗

PubMed2000

Diurnal preference, sleep habits, circadian sleep propensity and melatonin rhythm in healthy human subjects.

After 24-h sleep deprivation, 33 healthy young subjects entered the 10/20 min ultra-short sleep-wake schedule for 26 h. Melatonin rhythm was hourly assessed simultaneously. Results indicated that morning preference was significantly correlated with habitual sleep onset (r=-0.41, P=0.04), habitual sleep offset (r=-0.52, P=0.002), melatonin peak time (r=-0.36, P=0.04), and sleep propensity onset time (r=-0.36, P=0.04). The intervals between habitual sleep mid-point and melatonin peak time and between habitual sleep mid-point and sleep propensity onset time were significantly longer in morning-preference subjects than in evening-preference subjects (P<0.05). These findings suggest that the variance of diurnal preference may be related to differences in phase relations between habitual sleep timing and the circadian pacemaker.

Adult↗

PubMed2000

Sleep loss and daytime sleepiness in the general adult population of Japan.

There are few epidemiological studies on sleep loss and daytime sleepiness in the general adult population of Japan. A total of 4000 adult people, aged 20 and over, were randomly drawn from five areas of Japan, and 3030 individuals were interviewed and completed a questionnaire including information about sleep duration and sleep problems. Overall, 29% slept less than 6 h at night, 23% reported having insufficient sleep, and 6% took sleep enhancing medications. The prevalence rates were 21% for symptoms of insomnia and 15% for excessive daytime sleepiness. Symptoms of insomnia were more prevalent in the elderly, whereas young people were more likely to report short sleep duration, subjective insufficient sleep and excessive daytime sleepiness. A multiple logistic regression model revealed that excessive daytime sleepiness had significant associations with young people, short sleep duration, insomnia symptoms, subjective insufficient sleep and sleep enhancing medication use. Short sleep duration was the strongest predictor of excessive daytime sleepiness. The findings indicate that sleep loss and excessive daytime sleepiness in the Japanese adult population are common, and comparable to those reported in Western countries. Excessive daytime sleepiness in the general adult population seems more likely to be attributed to short sleep duration.

Adult↗

PubMed2000

Genetic polymorphisms of human melatonin 1b receptor gene in circadian rhythm sleep disorders and controls.

Recent studies suggest that melatonin 1b (Mel1b) receptor, as well as melatonin 1a (Mel1a) receptor, is involved in the modulation of circadian rhythms in mammals. Mutational analysis was performed in the entire coding region of the human Mel1b receptor gene using genomic DNA from sleep disorder subjects. We have identified two missense mutations, G24E and L66F. However, neither is likely to be associated with sleep disorders in our study population. One of the subjects with non-24-h sleep-wake syndrome carries missense mutations in both the Mel1a and Mel1b receptor genes.

Adult↗

PubMed2000

Prevalence and correlates of self-reported sleep problems among Chinese adolescents.

STUDY OBJECTIVES: This study examined the prevalence and correlates of sleep problems in Chinese adolescents. DESIGN AND SETTING: An epidemiological questionnaire survey was carried out in five high schools in Shandong Province of Mainland China. PARTICIPANTS: A total of 1365 adolescents between the ages of 12 and 18 years comprising 823 boys and 542 girls. MEASUREMENTS AND INTERVENTIONS: The participants completed a self-administered questionnaire regarding sleep duration, sleep problems, stressful life events, lifestyles, and personal and family characteristics. RESULTS: Mean sleep duration at night was 7.64 hours (SD = 0.86) and decreased with increasing age. Of the sample, 16.9% (95% CI = 13.2-20.5%) reported insomnia symptoms including difficulty initiating sleep (10.8%), difficulty maintaining sleep (6.3%), and early morning awakening (2.1%). Nightmares were reported more frequently by girls (chi2=20.09, p<0.001). Only 2.3% of the sample had ever taken hypnotic medication during the past month. Almost 22% of the subjects went to bed later than 12:00 PM at least once a week. Multiple logistic regression analysis showed that greater age, being at senior high school, doing no habitual physical exercise, poor physical health, self-selection of diet, longer distance from home to school, and life stress experienced during the past 12 months were significantly associated with an increased risk of insomnia. CONCLUSIONS: Self-reported sleep problems in Chinese adolescents are common and associated with multiple factors. These findings suggest the need for comprehensive programs to prevent sleep problems in adolescents.

Adolescent↗

PubMed2000

An epidemiological study of insomnia among the Japanese general population.

The study examined the prevalence and correlates of insomnia in a representative sample (n=3030) from the general population of Japan. Using a structured questionnaire, we found that the overall prevalence of insomnia during the preceding month was 21.4%, including difficulty initiating sleep (DIS: 8.3%), difficulty maintaining sleep (DMS: 15.0%), and early morning awakening (EMA: 8.0%). Multiple logistic regression analysis showed that older age, being unemployed, lack of habitual exercise, poor perceived health, psychological stress, and being unable to cope with stress were associated with an increased prevalence of insomnia. These findings indicate that the prevalence of insomnia in the general population of Japan is comparable to that reported in Western countries, and that insomnia is associated with multiple psychosocial factors.

Adult↗

PubMed2000

Quenched light hadron spectrum

We present results of a large-scale simulation for the flavor nonsinglet light hadron spectrum in quenched lattice QCD with the Wilson quark action. Hadron masses are calculated at four values of lattice spacing in the range a approximately 0.1-0.05 fm on lattices with a physical extent of 3 fm at five quark masses corresponding to m(pi)/m(rho) approximately 0.75-0.4. The calculated spectrum in the continuum limit shows a systematic deviation from experiment, though the magnitude of deviation is contained within 11%. Results for decay constants and light quark masses are also reported.

Journal Article↗

PubMed2000

Life events, locus of control, and behavioral problems among Chinese adolescents.

This study examined associations of life events and locus of control with behavioral problems among 1,365 Chinese adolescents by using the Youth Self-Report (YSR), Adolescent Self-Rating Life Events Checklist (ASLEC), and the Nowicki-Strickland Locus of Control Scale for Children. Results indicated that the overall prevalence of behavioral and emotional problems was 10.7% (95% CI = 9.9-11.5%). Logistic-regression analyses showed that a total of 13 negative life events mainly coming from academic domain and interpersonal relationships, high life-stress score, and high external locus score significantly increased the risk for behavioral problems. Life stress and locus of control significantly interacted with behavioral problems. These findings support the linkage between stressful life events and psychopathology in a general population of adolescents from mainland China, and demonstrate the stress-moderating effects of locus of control on psychopathology as well.

Adolescent↗

PubMed2000

Effects of small dose of brotizolam on P300.

Nine healthy men (mean age, 22.2 years) participated in two experimental sessions cross-overed randomly in a double blind manner; one with a placebo and the other with 0.125 mg of brotizolam (BTZ) administered in the morning. Resting electroencephalogram and event-related potential under oddball paradigm was recorded before and 1, 2, 4, 6 and 8 h after the administration. Mean 30-msec bin amplitude from 240 msec to 450 msec after the stimulus was compared between placebo and drug sessions in order to observe P300. Brotizolam reduced the amplitude of P300 at 6 h after administration. It was noted that the effects of BTZ were most marked at Fz.

Adult↗

PubMed2000

Melatonin treatment for circadian rhythm sleep disorders.

This study investigated the effects of melatonin administration on circadian rhythm sleep disorders, and aimed to clarify clinical characteristics of melatonin responders. The subjects were 46 patients with circadian rhythm sleep disorders: 30 Delayed Sleep Phase Syndrome (DSPS) and 16 non-24 h sleep-wake syndrome (non-24). Patients took 0.3-1.0 mg of melatonin 5, 3 and 1 h before habitual bedtime. Seventeen patients responded to melatonin (12 DSPS, five non-24). Comparison of clinical background between responders and non-responders revealed that the responders were characterized by short total sleep time and later onset age of clinical symptoms.

Administration, Oral↗

PubMed2000

Differential diagnosis of obstructive sleep apnea syndrome patients and snorers using cephalograms.

Severe snoring is thought by many to be an early stage of obstructive sleep apnea syndrome (OSAS), but the anatomical relation between snoring and OSAS, if any, has remained unclear. To compare the morphology of the airway between snorers and OSAS patients for possible similarities, we conducted a cephalometric analysis of Japanese OSAS patients (n=10), habitual snorers (n=10), and non-snoring controls (n=50). There was no significant difference in SNB (the angle formed by the sella, nasion and point B) between OSAS patients and the control subjects. Obstructive sleep apnea syndrome patients tended to have an anteriorly positioned maxilla, and an anteroposterior misalignment between the maxilla and mandible. There was also a tendency toward skeletal openbite. Both OSAS patients and snorers had large tongues and large soft palates, thus causing constriction of the airway with resultant smaller airway diameter and smaller airway surface area. Significant differences between OSAS patients and snorers were found in thickness and length of soft palate surface area, and thickness, length, and position of the hyoid bone. These results suggest that cephalographic measurements may be of considerable use in determining the seriousness of a patient's condition.

Adult↗

PubMed2000

Age-dependent expression of abdominal symptoms in patients with Yersinia enterocolitica infection.

BACKGROUND: The aim of the present study was to determine the relationship between the expression of abdominal symptoms and the age of patients with Yersinia enterocolitica infections. METHODS: Twenty-four patients with positive fecal cultures of Yersinia enterocolitica participated in the present study. The abdominal symptoms were taken from medical records. Statistical analysis was performed by Mann-Whitney U-test. RESULTS: Patients with diarrhea were younger than those without diarrhea (P = 0.014). Older children had abdominal pain or irritability more frequently than younger children (P = 0.004). CONCLUSIONS: In Yersinia enterocolitica infections, younger children are predisposed to diarrhea and older children are predisposed to abdominal pain.

Abdominal Pain↗

PubMed2000

Supplementary administration of artificial bright light and melatonin as potent treatment for disorganized circadian rest-activity and dysfunctional autonomic and neuroendocrine systems in institutionalized demented elderly persons.

Increased daytime napping, early morning awakening, frequent nocturnal sleep interruptions, and lowered amplitude and phase advance of the circadian sleep-wake rhythm are characteristic features of sleep-waking and chronobiological changes associated with aging. Especially in elderly patients with dementia, severely fragmented sleep-waking patterns are observed frequently and are associated with disorganized circadian rhythm of various physiological functions. Functional and/or organic deterioration of the suprachiasmatic nucleus (SCN), decreased exposure to time cues such as insufficient social interaction and reduced environmental light, lowered sensitivity of sensory organs to time cues, and reduced ability of peripheral effector organs to express circadian rhythms may cause these chronobiological changes. In many cases of dementia, the usual treatments for insomnia do not work well, and the development of an effective therapy is an important concern for health care practitioner and researchers. Recent therapeutical trials of supplementary administration of artificial bright light and the pineal hormone melatonin, a potent synchronizer for mammalian circadian rhythm, have indicated that these treatments are useful tools for demented elderly insomniacs. Both bright light and melatonin simultaneously ameliorate disorganized thermoregulatory and neuroendocrine systems associated with disrupted sleep-waking times, suggesting a new, potent therapeutic means for insomnia in the demented elderly. Future studies should address the most effective therapeutic design and the most suitable types of symptoms for treatment and investigate the use of these tools in preventive applications in persons in early stages of dementia.

Aged↗

PubMed2000

Behavioral and emotional problems in Chinese children of divorced parents.

OBJECTIVE: This study examined the behavioral problems in Chinese children of divorced parents. METHOD: A total of 58 children of divorce and 116 gender-, age-, and school class-matched controls were ascertained from a general population sample of children aged 6 through 15 years. Parents completed the Child Behavior Checklist (CBCL), and teachers completed the Teacher's Report Form (TRF) and Conners Hyperkinesis Index. RESULTS: Parent-reported problem scores on the CBCL total scale and each subscale, and prevalence of all CBCL syndromes except for Somatic Complaints, were significantly higher in children of divorce than in controls. Teacher-reported problem scores on the TRF total scale and Social and Attention Problems and prevalence of Attention Problems were significantly different for the 2 groups of children. Social competence was rated significantly lower in children of divorce than in controls. Discriminant function analysis showed that behavioral problems in children of divorce were characterized by aggressive behavior, withdrawal, and social problems. CONCLUSIONS: The findings emanating from China provide the first evidence of the link between parental divorce and children's psychopathology and clarify the psychopathological dimensions in Chinese children of divorced parents.

Adolescent↗

PubMed2000

Attaining nocturnal urinary control, nocturnal enuresis, and behavioral problems in Chinese children aged 6 through 16 years.

OBJECTIVE: To estimate the prevalence of nocturnal enuresis and to examine associations between nocturnal urinary control or enuresis and behavioral problems in Chinese children. METHOD: A community sample of 3,600 children aged 6 through 16 years was drawn from Shandong Province of China in 1997; 3,344 (93%) returned completed questionnaires. The Child Behavior Checklist and Teacher's Report Form were used to measure children's behavioral problems. RESULTS: The proportion of children attaining nocturnal urinary control before age 2 was 7.7%; by age 3, this had increased to 53.1%, and by age 5 to 93%. The overall prevalence of nocturnal enuresis was 4.3%, with a significantly higher prevalence in boys than girls. There was no significant decrease in the prevalence of enuresis between 6 and 16 years of age. Multiple logistic regression analyses showed that attaining nocturnal urinary control after age 4 and current enuresis were significantly associated with an increased risk of behavioral, emotional, and academic problems. CONCLUSIONS: Chinese children attain nocturnal urinary control earlier than Western children. The prevalence of nocturnal enuresis is low but fairly stable in children between 6 and 16 years. The findings support the link between nocturnal enuresis and psychopathology in children and adolescents.

Adolescent↗