The present study was designed to examine the effects of aerobic exercise on the change of alpha wave component in electroencephalogram (EEG) and plasma β-endorphin. Exercise consisted of 30-min cycling on an ergometer with the load adjusted to elicit a heart rate rise of 50% between resting and predicted maximal value. The EEG signals and blood samples were obtained before and after 30-min exercise. The EEG signal was digitized at a sampling frequency of 64 Hz and analyzed by means of computer-aided decomposition algorithm and frequency power spectral analyses, respectively. The blood samples were immediately centrifuged for 15-min for quantitative analysis of β-endorphin by means of radioimmunoassay method. Results indicated that β-endorphin was significatly (p<.05) greater after exercise as compared to that of the resting contorol. It was also found that the larger the changes in β-endorphin following exercise, the higher the appearance rate of alpha wave in EEG. There was a positive and significant correlation (r=563, p<0.05) between the increase in alpha wave component and that of the plasma β-endorphin. These results suggest that traquilizer effects of aerobic exercise could be explained, at least in part, by the increase of alpha wave component and plasma β-endorphin which in turn bring about the relaxation effects upon the central nervous system.

The purpose of the present study was to develop a new method that enables individualized determination of the optimal exercise intensity for health promotion. Our study was based on the following observations : (1) physical activity at ventilatory threshold (VT) has been useful for enhancing physical fitness and even improving medical conditions such as heart failure, hypertension and diabetes, (2) exercise intensity at VT is characterized by suppressed vagal activity, and (3) vagal activity can be evaluated by analyzing heart rate variability (HRV) . In the first study we defined a criteria for determining the exercise intensity corresponding to VT using HRV analysis (heart rate variability threshold, THRV) . In 16 normal subjects, a time series of ECG RR interval were recorded and the means of the sum of the squared differences in successive RR intervals (MSSDs) were calcu-lated during a ramp exercise test with a cycle ergometer. Based on the values of MSSD and the dif-ferences in successive MSSDs (ΔMSSD) at the intensity of VT, we defined the criteria of THRV as follows : MSSD<25 msec²and ΔMSSD<6 msec². Another exercise test with a cycle ergo-meter was performed to evaluate the relationship between THRV and VT in 63 normal subjects. Heart rate (HR) and oxygen uptake (VO₂/wt) at THRV were 111.8±13.2 beats/min and 15.2±4.4 ml/kg/min, and HR and VO₂/wt at VT were 116.2±11.6beats/min and 16.5±3.7ml/kg/min, respectively. There was a significant correlation between THRV and VT (HR : r=0.82, p<0.001, VO₂/wt : r=0.88, p< 0.001) . Thus, THRV and VT provided almost identical exercise intensities. As a result, we propose that, similar to VT, THRV can be used as an indicator of the optimal exercise intensity suitable for health promotion in normal subjects.

The present study was designed to examine the effects of aerobic exercise on the change of alpha wave component in electroencephalogram (EEG) and plasma β-endorphin. Exercise consisted of 30-min cycling on an ergometer with the load adjusted to elicit a heart rate rise of 50% between resting and predicted maximal value. The EEG signals and blood samples were obtained before and after 30-min exercise. The EEG signal was digitized at a sampling frequency of 64 Hz and analyzed by means of computer-aided decomposition algorithm and frequency power spectral analyses, respectively. The blood samples were immediately centrifuged for 15-min for quantitative analysis of β-endorphin by means of radioimmunoassay method. Results indicated that β-endorphin was significatly (p<.05) greater after exercise as compared to that of the resting contorol. It was also found that the larger the changes in β-endorphin following exercise, the higher the appearance rate of alpha wave in EEG. There was a positive and significant correlation (r=563, p<0.05) between the increase in alpha wave component and that of the plasma β-endorphin. These results suggest that traquilizer effects of aerobic exercise could be explained, at least in part, by the increase of alpha wave component and plasma β-endorphin which in turn bring about the relaxation effects upon the central nervous system.

Background: Vietnam is located in the endemic region of hepatitis B virus (HBV) infection, but no data of occult HBV infection was reported at present. Objectives: To investigate the prevalence of occult HBV infection in different ethnics of people and generations. Subjects and method: 80 voluteers with HbsAg negative from five different ethnics: Kinh, Tay, Mong, Giay and Dao in a Chino \ufffd?Vietnamses border province (Lao Cai) were enrolled in the study. After HBV-DNA was extracted, nested PCR of S gene and of Core-promoter/Pre-core region were used to detect HBV-DNA. Specifying nucleotide sequence was confirmed by direct sequencing. Results:The prevalence of occult HBV infection in population study was very high 73/80 (91,3%) by nested PCR of Core-promoter/Pre-core, significantly more sensitive than nested PCR of S gene (26,3%) (p<0,0001). The prevalence of occult HBV infection was notdifferent between ethnics of people or between children, adults. Conclusion: Occult HBV infection in Vietnamese is very common; however, nationwide further studies should be carried out to confirm this preliminary results and evaluate the impact of occult HBV infection in Vietnam.
Hepatitis B virus ; Hepatitis B Surface Antigens ;

To examine the potential risk of hepatitis B virus (HBV) spread in Indonesia by migrant workers, based on the molecular characteristics of HBV strains. Methods: Sera collected from migrant workers traveling to their destination countries (pre-migrant workers) and those returning to Indonesia (post-migrant workers) were screened for HBsAg by ELISA, followed by HBV DNA detection by PCR and (sub) genotype/subtype determination according to surface region and whole genome sequencing. Results: Of 87 pre-migrant workers, 15 (17.24%) were HBsAgpositive, whereas 15 (12.10%) of 124 post-migrant workers were HBsAg seropositive. HBV genotype analysis based on the S region showed that HBV-B3/adw2 was predominant (96.15%, 25/26) whereas 3.85% (1/26) of isolates were HBV-C3/adrq+. Whole genome sequencing of selected strains and phylogenetic tree analysis identified subgenotype B7 in three samples previously categorized as subgenotype B3 based on S region analysis, supporting a recent argument that subgenotypes B5/B7/B8/B9 could be considered as a quasi-subgenotype of B3. Conclusions: A high prevalence of HBsAg carriers was detected among migrant workers from Lombok Island, with no significant difference in prevalence between before and after returning to Indonesia. All strains were classified into genotypes common in Indonesia, and the results suggested that migrant workers are not a risk factor for HBV transmission into Indonesia.