Biomedical subjects

Yuko Morikawa

Publications and source records attributed to Yuko Morikawa.

At least 19 recordsLinked to original sources

PubMed2006

Prognosis and prognostic factors in patients with hypertrophic cardiomyopathy in Japan: results from a nationwide study.

OBJECTIVE: To investigate prognosis and prognostic factors in patients with hypertrophic cardiomyopathy (HCM) in Japan. DESIGN: A nationwide epidemiological study. SETTING: Hospitals selected randomly from among all hospitals in Japan. PATIENTS: Clinical and epidemiological information for 2155 patients with HCM were collected in 1999. MAIN OUTCOME MEASURES: Patients were classified on the basis of baseline prognostic factors. Survival rates up to 5 years were calculated by Cox's proportional hazard model for 1605 patients. RESULTS: During the follow-up period, 241 deaths were recorded. The crude 5-year survival rate for the entire cohort was 86% (95% CI 84 to 88), and annual mortality ranged from 2.2% to 3.0%. A higher cardiothoracic ratio on chest x ray (HR 1.61; 95% CI 1.26 to 2.05, with 1 SD (6.2%) increase), a lower left ventricular ejection fraction (HR 1.42; 95% CI 1.20 to 1.69, with 1 SD (13%) decrease) and the presence of left bundle branch block (HR 3.14; 95% CI 1.28 to 7.71) were independently associated with a poorer prognosis, whereas the presence of apical hypertrophy at baseline (HR 0.58; 95%CI 0.36 to 0.92) predicted a better chance of survival. CONCLUSIONS: The nationwide survey of patients with hypertrophic cardiomyopathy yielded important information on its prognosis and prognostic factors. These observations afford, for the first time, a measure of risk stratification in patients with HCM in Japan.

Adult↗

PubMed2006

Development of a rapid and convenient method for the quantification of HIV-1 budding.

In cells, the expression of Gag protein, one of the major structural proteins of retroviruses, is sufficient for budding virus-like particles (VLPs) from the cell surface. We have previously reported that spheroplasts of Saccharomyces cerevisiae expressing HIV-1 Gag proteins from an episomal plasmid constitutively released a large amount of VLPs into culture media; however, commercially available ELISA kits which detect mature capsid of HIV-1 could not detect uncleaved 55-kDa Gag proteins released from budding yeast. We therefore developed a method to quantitate VLP levels released from budding yeast by using fusion protein from HIV-1 Gag and Firefly Luciferase. This system is useful for screening cellular factor(s) involved in retrovirus budding from S. cerevisiae.

Gene Products, gag↗

PubMed2006

Psychosocial work characteristics and sickness absence in Japanese employees.

OBJECTIVES: This study was undertaken to examine the association between sickness absence in Japanese employees and job demand/control and occupational class as psychosocial work characteristics. METHODS: The study was cross-sectional in design with data collected from 20,464 male and 3,617 female employees, whose mean age was 40.9 years (SD +/- 9.1 years) and 36.9 years (SD +/- 10.8 years), respectively. The participants were asked to write the total number of sick leaves they had taken during the past year, and a comparison was made between the group with more than 6 days of sickness absence and the group with 0-6 days as a reference group. Job demands, job control, and worksite support from supervisors and colleagues were analyzed by the Job Content Questionnaire, and likewise by the Generic Job Stress Questionnaire of the National Institute for Occupational Safety and Health. RESULTS: Both low job control and low support at the worksite were associated with a high frequency of sickness absence. But there was no clear relationship between job demands and sickness absence. The lowest sickness absence rate was found in male managers and the highest in male and female laborers. CONCLUSION: This is the first report of a large-scale survey of Japanese employees to show a high frequency of sickness absence associated with increased work stress and a socioeconomically low occupational class.

Adult↗

PubMed2006

G-protein beta 3 subunit polymorphism C1429T and low-density lipoprotein receptor-related protein 5 polymorphism A1330V are risk factors for hypercholesterolemia in Japanese males--a prospective study over 5 years.

We examined the relationship between the C825T, C1429T, and A-350G variants in the G-protein beta 3 subunit (GNB3) gene, the A1330V and Q89R variants in the low-density lipoprotein receptor-related protein 5 (LRP5) gene, and the risk of hypercholesterolemia in a prospective study in Japanese workers. This study included observations over a 5-year period from 1997 to 2002 on 936 males and 662 females who were not hypercholesterolemic on entry. Hypercholesterolemia was defined as a serum total cholesterol level of 240 mg/dL or higher. Pooled logistic regression analyses were performed using either of the gene variants with age, body mass index, smoking, alcohol consumption, and habitual exercise as the covariates. The risk of the development of hypercholesterolemia was 2.27 times higher in males with the TT genotype of GNB3/C1429T than in males with the CC genotype (95% confidence interval, 1.04-4.94), after adjustment for the effects of other potential covariates. Simultaneously, the risk was 1.49 times higher in males with the AV genotype of LRP5/A1330V than in males with the AA genotype (95% confidence interval, 1.04-2.12) after adjustment for the effects of other potential covariates. This study indicates the GNB3/C1429T and LRP5/A1330V are independent risk factors for hypercholesterolemia in Japanese males and suggests that targeting these polymorphisms may be beneficial when attempting to prevent hypercholesterolemia in the general Japanese male population.

Adult↗

PubMed2006

Low-density lipoprotein receptor-related protein 5 variant Q89R is associated with hypertension in Japanese females.

We examined the influence of the Q89R variant in low-density lipoprotein receptor-related protein 5 on hypertension in a large Japanese cohort. We used multivariate logistic regression analysis to adjust for the effects of other factors known to influence hypertension such as age, body mass index, blood chemistry and lifestyle. Our cohort consisted of 1444 males and 1161 females selected from 3834 male and 2591 female workers in a single company. Hypertension was defined as systolic blood pressure 140 mmHg and/or diastolic blood pressure 90 mmHg or the use of antihypertensive medication. Because the RR genotype was so rare (three normotensive males and three normotensive females), they were excluded from analyses. Genotype distributions for Q89R in hypertensive females (QR = 14, QQ = 60) were significantly different (p = 0.033) from normotensive females (QR = 113, QQ = 971). In contrast, those in hypertensive males (QR = 26, QQ = 230) and in normotensive males (QR = 145, QQ = 1040) were similar. Allele distributions were not significantly different in either gender. In females, multivariate logistic regression showed that the QR genotype was associated with hypertension with odds ratio of 2.1 compared to the QQ genotype. This study indicates that the Q89R polymorphism is an independent factor for hypertension in Japanese females.

Adult↗

PubMed2006

G-protein beta3 subunit gene variant (C825T) is unlikely to have a significant influence on serum total cholesterol level in Japanese workers.

We investigated the association between hypercholesterolemia or serum total cholesterol level and the C825T polymorphism in the G-protein ss3 subunit gene in Japanese workers using multivariate analysis to control possible confounding factors. The study subjects were 1,452 males and 1,169 females selected from 3,834 males and 2,591 females. Hypercholesterolemia was classified as either a total serum cholesterol $5.7 mmol/L (220 mg/dL) or taking lipid-lowering medication. The statistical power of the study was estimated as 99.9% based on total cholesterol levels of previous significant studies in Caucasians and Japanese. The genotype distributions in males with hypercholesterolemia (CC = 78, CT = 154, TT = 78) and females (CC = 60, CT = 137, TT = 52) were not significantly different from normal males (CC = 280, CT = 595, TT = 267) or females (CC = 234, CT = 501, TT = 185). Allele distributions also were not significantly different in either sex. Logistic regression analysis of hypercholesterolemia data and analysis of variance, t-test and multiple regression of serum total cholesterol data demonstrated no significant relationship with the C825T genotype. Despite sufficient statistical power, this study did not demonstrate a significant influence of C825T on hypercholesterolemia or serum total cholesterol level. The targeting of this polymorphism therefore is unlikely to be beneficial in preventing hypercholesterolemia in the general Japanese population.

Alleles↗

PubMed2006

Gender differences in the association between anthropometric indices of obesity and blood pressure in Japanese.

To investigate which of four anthropometric variables of obesity has the strongest association with blood pressure (BP), and to investigate whether there are gender differences in these relationships in Asian adults, we evaluated the associations of four anthropometric variables, body mass index (BMI), waist circumference, waist-to-hip ratio and waist-to-height ratio, with BP and the prevalence of hypertension in a cross-sectional study. A total of 4,557 employees of a metal-products factory in Toyama, Japan (2,935 men and 1,622 women, aged 35 to 59 years) were included in the study. Waist circumference in men and BMI in women had the strongest associations with BP. As for the age-adjusted rate ratio (RR) of the prevalence of hypertension for one standard deviation increase in each anthropometric variable, RR was the highest for waist circumference in men (RR, 1.44; 95% confidence interval [CI], 1.31-1.58), and for BMI in women (RR, 1.61; 95% CI, 1.38-1.88). The associations of waist circumference in men and BMI in women remained significant after adjustment for each of the other variables. The associations of waist-to-height ratio with BP and the prevalence of hypertension were a little weaker than those of waist circumference for both men and women. In conclusion, among four anthropometric variables of obesity--i.e., BMI, waist circumference, waist-to-hip ratio, and waist-to-height ratio-waist circumference had the strongest association with BP and the prevalence of hypertension in men and BMI had the strongest association with BP and hypertension in women. Waist circumference in men and BMI in women should be given more importance in the screening of and guidelines on hypertension in Asians.

Adult↗

PubMed2006

G-protein beta3 subunit gene variant is unlikely to have a significant influence on serum uric acid level in Japanese workers.

The C825T variant of the G-protein beta3 subunit (GNB3) gene has attracted renewed attention as a candidate gene for obesity, hypertension and hyperuricemia. The main role of G-protein is to translate signals from the cell surface into a cellular response. The 825T allele is associated with a splice variant of GNB3 protein and enhanced G-protein activation. We examined the relationship between this variant and the risk of hyperuricemia in Japanese workers. The study subjects were 1,452 men and 1,169 women selected from 3,834 men and 2,591 women in 1997. On the basis of common clinical criteria, hyperuricemia I was defined as serum uric acid >or= 7.0 mg/dl in men and 6.0 mg/dl in women or taking antihyperuricemic medication. The hyperuricemia I group consisted of 186 men and 20 women and its control of 1,266 men and 1,149 women. Hyperuricemia II was defined as serum uric acid > 5.7 mg/dl (median) in men and 3.9 mg/dl (median) in women or taking antihyperuricemic medication. The hyperuricemic II group consisted of 684 men and 570 women and its control of 768 men and 599 women. To replicate previous significant results in young Caucasian men, we selected these criteria because the authors of the study in young Caucasian men adopted the median in their subjects as a cut-off. The statistical power was estimated as 99% based on the significant results in Caucasians. Genotype and allele distributions in men and women with hyperuricemia I and II were not significantly different from those in the corresponding control groups. Logistic regression analysis on hyperuricemia I and II, and multiple regression on serum uric acid level demonstrated no significant effect of the C825T genotype. Despite the sufficient statistical power, this study could not demonstrate the significant influence of C825T on hyperuricemia or serum uric acid. The targeting of this polymorphism is unlikely to be beneficial in the prevention of hyperuricemia in the general Japanese population.

Cross-Sectional Studies↗

PubMed2006

[Study of animal viruses in yeast].

Yeast is often considered to be a model eukaryotic organism, in a manner analogous to E. coli as a model prokaryotic organism. Yeast has been extensively characterized and the genomes completely sequenced. Despite the small genome size, yeast displays most of features of higher eukaryotes. The facts that most of cellular machinery is conserved among different eukaryotes and that the powerful technologies of genetics and molecular biology are available have made yeast model eukaryotic cells in biological and biomedical sciences including virology. Cumulative data indicate that yeast can be a host for animal viruses. I briefly describe yeast gene expression and review viral replication in yeast. Great discovery include complete replication of animal viruses and production of virus-like particle vaccines in yeast. Current studies on yeast focus on identification of host factors and machinery used for viral replication. The studies are based on traditional yeast genetics and genome-wide identification using a complete set of yeast deletion strains.

Animals↗

PubMed2006

The -1438A/G polymorphism in the 5-hydroxytryptamine receptor 2A gene is related to hyperuricemia, increased gamma-glutamyl transpeptidase and decreased high-density lipoprotein cholesterol level in the Japanese population: a prospective cohort study over 5 years.

This prospective cohort study in Japanese workers examined the relationship between the -1438A/G polymorphism in the 5-hydroxytryptamine receptor 2A gene and the development of positive findings for various life-style-related disorders. This study over the 5-year period, 1997-2002, included observations of several disorders in cohorts ranging between 560-1023 for males and 477-735 for females who had negative findings for each disorder at baseline. The criteria for development of the disorders were: hypertension, systolic blood pressure > or =140 mmHg or dia-stolic blood pressure > or =90 mmHg or taking antihypertensive medication; overweight, body mass index (BMI) > or =25 kg/m(2); obesity, BMI > or =30 kg/m(2); new onset of cerebral stroke; metabolic abnormalities, glycosylated hemoglobin A1c >6.0%, total cholesterol > or =240 mg/dl, high-density lipoprotein cholesterol <40 mg/dl, uric acid >7.0 mg/dl, gamma-glutamyl transpeptidase > or =60 IU/l in males and > or =30 IU/l in females. Pooled logistic regression analyses were performed using the -1438A/G genotype and other potential factors as covariates. The odds ratios to AA genotype were significant for uric acid (GG, 0.52; AG, 0.59), obesity (AG, 0.24) in males and for high-density lipoprotein cholesterol (GG, 0.11; AG, 0.36), gamma-glutamyl transpeptidase (GG, 0.53; AG, 0.62) and total cholesterol (GG, 1.84) in females. The present study is the first prospective cohort investigation to demonstrate that the -1438G allele has a protective effect against the development of a range of cardiovascular and metabolic disorders. This study indicates that the -1438A/G polymorphism is an independent factor for various disorders in the general Japanese population and suggests that targeting of this polymorphism may be beneficial for preventing these disorders in Japan.

Adult↗

PubMed2006

[Effectiveness of lifestyle modification programs for control of blood pressure: a non-randomized controlled trial in Komatsu, Japan].

PURPOSE: A non-randomized controlled trial was conducted to evaluate the effectiveness of three lifestyle modification programs to reduce blood pressure: individual counseling only; counseling using group dynamics; and individual support using mail. METHODS: We enrolled men and women ages 20-69 with a systolic blood pressure (SBP) of 130-159 mmHg and/or a diastolic blood pressure of 85-99 mmHg (high-normal or mild hypertension). Participants were assigned to one of 4 groups: individual counseling (n = 134); group counseling (n = 79); mailing support (n = 127); and controls (with usual care) (n = 178). The three intervention programs included behavioral support for each person's lifestyle problems once a month for 6 months. Sex and age adjusted net blood pressure change (and 95% confidence intervals [CIs]) compared with the control group was calculated for each of the intervention groups. RESULTS: Net SBP change was the largest for the group counseling group: sex and age adjusted net SBP change was -6.5 mmHg (95% CI: -10.0, -3.0). Net SBP change for the mailing support group was also significant (-4.3 mmHg [95% CI: -7.3, -1.3]). Net SBP change for the individual counseling group was -2.5 mmHg (95% CI: -5.5, 0.5). Looking at the results separately by sex, net SBP reduction was also largest in women of the group counseling group, whereas improvement in men was similar among 3 groups (approximately 4 mmHg). Body weights were reduced by about 1 kg in all 3 groups. CONCLUSIONS: Lifestyle modification programs using group dynamics or using individual support by mail, in addition to individual behavioral support, appear to be effective for blood pressure reduction. Group counseling may be more effective in women.

Adult↗

PubMed2005

Low-density lipoprotein receptor-related protein 5 variant A1330V is a determinant of blood pressure in Japanese males.

We examined the influence of the A1330V variant in the low-density lipoprotein receptor-related protein 5 gene on blood pressure in a large cohort of Japanese workers. This study used analysis of covariance in a multivariate general linear model to adjust for other potential factors such as age, body mass index, blood chemistry and lifestyle. The target subjects were 1440 males and 1169 females selected from 3834 male and 2591 female workers in a single company. Hypertension was defined as systolic blood pressure >or=140 mm Hg and/or diastolic blood pressure >or=90 mm Hg or the use of antihypertensive medications. Genotype distributions for A1330V in hypertensive males (AA=139(54.5%), AV=101(39.6%), VV=15(5.9%)) and females (AA=48(63.2%), AV=24(31.6%), VV=4(5.3%)) were not significantly different from normotensive males (AA=594(50.1%), AV=488(41.2%), VV=103(8.7%)) and females (AA=568(52.0%), AV=441(40.3%), VV=84(7.7%)). Allele distributions were not significantly different in either sex. In males, analysis of covariance showed that the VV genotype was associated with a 2.5 mm Hg lower diastolic blood pressure and a 2.3 mm Hg lower mean blood pressure than the AA genotype. This study indicates that the 1330V allele is an independent factor for lower diastolic and mean blood pressure in Japanese males.

Adult↗

PubMed2005

Urinary cadmium and mortality among inhabitants of a cadmium-polluted area in Japan.

The influence of cadmium (Cd) body burden on mortality remains controversial. Excess mortality and the dose-response relationship between mortality and urinary cadmium excretion were investigated in this study among environmentally exposed subjects. A 15-year follow-up study was carried out on 3119 inhabitants (1403 men and 1716 women) of the Cd-polluted Kakehashi River basin, whose urinary Cd concentration was examined in a 1981-1982 health impact survey. The mortality risk of high urinary Cd (> or = 10 microg/g Cr) subjects after adjustment for age using Cox's proportional hazard model was higher than that of moderate urinary Cd (< 10 microg/g Cr) subjects in both sexes. When the subjects were divided into five groups according to the amount of urinary Cd (<3, 3-5, 5-10, 10-20, > or = 20 microg/g Cr), the mortality risk was significantly increased among the subjects with urinary Cd > or = 3 microg/g Cr in proportion to the increases in the amount of urinary Cd concentration after adjustment for age, especially in women. Furthermore, special causes of death among high and moderate urinary Cd were investigated, and mortality risk ratio for heart failure, which is a cause of death often diagnosed in cases with a gradual deterioration culminating in death, was significantly increased in both sexes, compared with the moderate urinary Cd subjects. Also, in women the mortality risk for renal diseases in the high urinary Cd subjects was significantly higher than that in the moderate urinary Cd subjects. These results suggest that a causal association between Cd body burden and mortality exists among inhabitants environmentally exposed to Cd but that no special disease may be induced except renal diseases.

Aged↗

PubMed2005

Relationship of alcohol consumption to 7-year blood pressure change in Japanese men.

OBJECTIVE: To determine the association of alcohol consumption with years-long blood pressure (BP) change, as well as baseline BP, adjusted for potential confounders. DESIGN: A prospective cohort study. SETTING: A metal-products factory in Toyama, Japan. PARTICIPANTS: A total of 3900 men aged 20-59 years. MAIN OUTCOME MEASURES: BP was measured annually for 7 years after the baseline examination. The generalized estimating equation method was used to analyze the relationship of alcohol consumption to baseline BP and average annual BP change, adjusting for age, yearly weight, work-related factors, and lifestyle factors, including the frequency of intake of 22 food groups. RESULTS: The baseline systolic BP after multivariate adjustment was 3.9 and 5.0 mmHg higher in drinkers consuming 200-299 and > or = 300 g alcohol/week, respectively, than in non-drinkers (P < 0.001). The annual increase in systolic BP was 0.44 mmHg greater in drinkers consuming > or = 300 g/week than in non-drinkers after adjustment for age and weight change (P < 0.001), where the increase over 7 years was estimated to be 3.08 mmHg greater. Even after being adjusted for the frequency of intake of 22 food groups, drinkers consuming > or = 300 g/week showed a 0.33 mmHg greater annual increase in systolic BP than non-drinkers (P = 0.022). Baseline diastolic BP was significantly associated with alcohol consumption, but annual BP change was not. CONCLUSIONS: An alcohol intake > or = 300 g/week was associated with significantly greater annual BP increase, and baseline BP was significantly higher in drinkers consuming > or = 200 g/week. It is necessary to limit alcohol intake to less than 200 g/week to prevent hypertension.

Adult↗

PubMed2005

A cross-sectional study on the relationship of job stress with natural killer cell activity and natural killer cell subsets among healthy nurses.

The present study investigated the effects of job stress on cellular immune function, such as NK cell activity and NK cell subsets. The participants were 61 female nurses aged 23-59, who worked in a public psychiatric hospital in Ishikawa, Japan. Each subject completed the Nursing Job Stressor Scale (NJSS) and their NK cell activity and lymphocyte surface antigens (CD16+56+) were evaluated as immune system parameters. The NJSS has seven subscales: conflict with other nursing staff, nursing role conflict, conflict with physicians or autonomy, conflict with death or dying, quantitative work load, qualitative work load and conflict with patients. Factors influencing NK cell activity, and the proportion and cell counts of CD16+56+ lymphocytes were evaluated. Increase in quantitative work load significantly decreased NK cell activity. Conversely, no linear relationship was observed between qualitative work load and immunological variables, with the highest percentage of CD16+56+ lymphocytes observed among participants in the medium work load group. The other five NJSS subscales did not relate to immune parameters. In conclusion, the results suggest that perceived job strains, particularly quantitative work load, decreased NK cell function.

Adult↗

PubMed2005

Shift work and the risk of diabetes mellitus among Japanese male factory workers.

OBJECTIVES: This study investigated whether shift work is a risk factor for the development of diabetes mellitus. METHODS: The workers, 2860 men in a sash and zipper factory in the Toyama prefecture of Japan, were followed for 8 years, and the incidence rate of diabetes mellitus was determined. The cohort contained fixed daytime blue-collar workers, shift blue-collar workers, and white-collar workers. The workers were considered to have diabetes mellitus if, in their annual health examination, they had a glycated hemoglobin level of > or = 6.1 or if the diagnosis had been made by a hospital physician. The relative risks were estimated by Cox's proportional hazards regression model. RESULTS: Among the 2860 workers, there were 87 cases of new-onset diabetes mellitus, resulting in an incidence rate of 4.41 per 1000 person-years. The age-adjusted incidence was highest for the two-shift workers and lowest for the white-collar workers. The relative risk of diabetes mellitus for the two-shift workers and the three-shift workers compared with the fixed daytime workers was 1.73 and 1.33, respectively, after adjustment for all the confounding factors, but these values were not statistically significant. When the white-collar workers were used as a reference group, a significantly increased risk of diabetes mellitus was found for the two-shift workers (relative risk was 2.01 after adjustment for all confounding factors), but not for the three-shift workers or the fixed daytime blue-collar workers. CONCLUSIONS: The study suggests that shift work is a risk factor for the onset of diabetes mellitus and that there is a different risk associated with different shift schedules.

Adult↗

PubMed2004

Comparison of four blood pressure indexes for the prediction of 10-year stroke risk in middle-aged and older Asians.

Information has been sparse on the comparison of 4 blood pressure (BP) indexes (systolic BP [SBP], diastolic BP [DBP], pulse pressure [PP], and mean BP [MBP]) in relation to long-term stroke incidence, especially in middle-aged and older Asian people. A prospective cohort study was performed in 4989 Japanese (1523 men and 3466 women) aged 35 to 79 at baseline with 10 years of follow-up. End points included stroke incidence (total, ischemic, and hemorrhagic). Multivariate-adjusted hazard ratios with a 1-SD higher value for each BP index were determined by Cox proportional hazard analyses; Wald chi2 tests were used to compare the strength of relationships. Analyses were also done for each of 4 age-gender groups consisting of men and women aged 35 to 64 and 65 to 79 years. During follow-up, 132 participants developed stroke. Adjusted hazard ratios for all strokes were 1.68 for SBP, 1.72 for DBP, and 1.80 for MBP, which were higher than that for PP (1.34). SBP and DBP were related positively to stroke risk after adjustment of each other. PP was not the strongest predictor in any age-gender groups among 4 BP indexes. In men aged 65 to 79 years, SBP showed the strongest relationship to all stoke risk (hazard ratio 1.62) among 4 BP indexes. In women aged 65 to 79 years, hazard ratios for all strokes were 2.48 for MBP, 2.46 for DBP, 2.25 for SBP, and 1.57 for PP. The long-term incident stroke risk of high BP in Asians should be assessed by SBP and DBP together, or by MBP, not by PP.

Adult↗

PubMed2004

Human immunodeficiency virus type 1 Gag assembly through assembly intermediates.

Human immunodeficiency virus Gag protein self-assembles into spherical particles, and recent reports suggest the formation of assembly intermediates during the process. To understand the nature of such assembly intermediates along with the mechanism of Gag assembly, we employed expression in Escherichia coli and an in vitro assembly reaction. When E. coli expression was performed at 37 degrees C, Gag predominantly assembled to a high order of multimer, apparently equivalent to the virus-like particles obtained following Gag expression in eukaryotic cells, through the formation of low orders of multimer characterized with a discreet sedimentation value of 60 S. Electron microscopy confirmed the presence of spherical particles in the E. coli cells. In contrast, expression at 30 degrees C resulted in the production of only the 60 S form of Gag multimer, and crescent-shaped structures or small patches with double electron-dense layers were accumulated, but no complete particles. In vitro assembly reactions using purified Gag protein, when performed at 37 degrees C, also produced the high order of Gag multimers with some 60 S multimers, whereas the 30 degrees C reaction produced only the 60 S multimers. However, when the 60 S multimers were cross-linked so as not to allow conformational changes, in vitro assembly reactions at 37 degrees C did not produce any higher order of multimers. ATP depletion did not halt Gag assembly in the E. coli cells, and the addition of GroEL-GroES to in vitro reactions did not facilitate Gag assembly, indicating that conformational changes rather than protein refolding by chaperonins, induced at 37 degrees C, were solely responsible for the Gag assembly observed here. We suggest that Gag assembles to a capsid through the formation of the 60 S multimer, possibly a key intermediate of the assembly process, accompanied with conformational changes in Gag.

Capsid↗