Geographic variation in inpatient medical expenditure among older adults aged 75 years and above in Japan: a three-level multilevel analysis of nationwide data

Introduction

In Japan, a country at the forefront of population ageing, significant geographic variation has been observed in inpatient medical expenditures for older adults aged 75 and above (IMEP75), both at the small- and large-area levels. However, our understanding of how different levels of administrative (geographic) units contribute to the overall geographic disparities remains incomplete. Thus, this study aimed to assess the degree to which geographic variation in IMEP75 can be attributed to municipality-, secondary medical area (SMA)-, and prefecture-level characteristics, and identify key factors associated with IMEP75.

Methods

Using nationwide aggregate health insurance claims data of municipalities for the period of April 2018 to March 2019, we conducted a multilevel linear regression analysis with three levels: municipalities, SMA, and prefectures. The contribution of municipality-, SMA-, and prefecture-level correlates to the overall geographic variation in IMEP75 was evaluated using the proportional change in variance across six constructed models. The effects of individual factors on IMEP75 in the multilevel models were assessed by estimating beta coefficients with their 95% confidence intervals.

Results

We analysed data of 1,888 municipalities, 344 SMAs, and 47 prefectures. The availability of healthcare resources at the SMA-level and broader regions to which prefectures belonged together explained 57.3% of the overall geographic variance in IMEP75, whereas the effects of factors influencing healthcare demands at the municipality-level were relatively minor, contributing an additional explanatory power of 2.5%. Factors related to long-term and end-of-life care needs and provision such as the proportion of older adults certified as needing long-term care, long-term care benefit expenditure per recipient, and the availability of hospital beds for psychiatric and chronic care and end-of-life care support at home were associated with IMEP75.

Conclusion

To ameliorate the geographic variation in IMEP75 in Japan, the reallocation of healthcare resources across SMAs should be considered, and drivers of broader regional disparities need to be further explored. Moreover, healthcare systems for older adults must integrate an infrastructure of efficient long-term care and end-of-life care delivery outside hospitals to alleviate the burden on inpatient care.

Association between Internet use and depressive symptoms among older adults in two regions of Myanmar: a cross-sectional study

BACKGROUND

Internet use has both positive and negative effects on mental health. However, few studies have examined the association between internet use and mental health among older adults in developing countries. This study aimed to investigate the association between Internet use and depressive symptoms among older adults in two regions of Myanmar.

METHODS

Data based on a visit to 1,200 older adults in urban and rural Myanmar were obtained through stratified random sampling using the cross-sectional baseline survey of the longitudinal study titled "Healthy and Active Aging in Myanmar." Our analysis included 1,186 participants. The dependent variable was depressive symptoms, and the 15-item version of the Geriatric Depression Scale (GDS) was used as a continuous variable; the higher the score, the more likely a person was to be depressed. Internet use (one of the questions about household property ownership) was used as an independent variable. After confirming the absence of multicollinearity, we adjusted for age, gender, educational background, activities of daily living, residential area, and frequency of meeting friends, and stratified by subjective economic status (above or below average). We also examined the interaction between internet use and subjective economic status. A linear regression analysis was performed.

RESULTS

Among the 1,186 participants included in the analysis (women: 59.5%; median age: 68 years old), 202 (17.0%) were Internet users (95% Confidential Interval [CI]: 0.15, 0.19), and they had significantly lower GDS scores than the participants who did not use the Internet (B: -1.59, 95% CI: -2.04, -1.13).GDS showed a negative association with Internet use even in the multivariate analysis (B: -0.95, 95% CI: -1.41, -0.50). However, the interaction term for GDS between Internet use and subjective economic status was not significantly associated (B: 0.43, 95% CI: -1.11, 1.98).

CONCLUSIONS

Internet use and depressive symptoms were associated especially among the older adults. However, there were no significant interaction between Internet use and subjective economic status for GDS.

Associations between socioeconomic status and adherence to hypertension treatment among older adults in urban and rural areas in Myanmar: a cross-sectional study using baseline data from the JAGES in Myanmar prospective cohort study

OBJECTIVES

This study aims to investigate whether there is a differential association between socioeconomic status (SES) and adherence to hypertension medication among older adults in rural and urban areas in Myanmar and assess what type of SES is associated with a difference.

DESIGN

Cross-sectional study using baseline data from the Japan Gerontological Evaluation Study in Myanmar prospective cohort study. A multistage random sampling method was applied in each region.

SETTING

An urban and a rural area in Myanmar.

PARTICIPANTS

A total of 1200 older adults over 60 years old in Myanmar were randomly selected in 2018 (600 each from rural and urban areas). Of them, 573 had hypertension and were eligible for the analysis (urban: 317, rural: 256).

OUTCOME

Adherence to hypertension medication (yes/no) is the outcome of interest. Three types of SES (wealth, education and current employment status) were the independent variables.

RESULTS

We found that 21.5% of urban residents and 48.4% of rural residents were non-adherent in the study population. Poisson regression modelling stratified by area was performed to estimate the prevalence ratios (PRs) of not following treatment instructions. Demographic information and complications of hypertension were adjusted for in all models as possible confounders. In terms of SES, middle level of wealth compared with low level was significantly associated with poor adherence (PR 2.68, 95% CI 1.28 to 5.59) in the urban area, but education and employment status did not show similar associations. Lower education compared with middle/high school or higher was significantly associated with poor adherence in the rural area (no school: PR 3.22, 1.37-7.58; monastic: 3.42, 1.16-5.07; primary school: 2.41, 1.18-4.95), but wealth and income did not show similar associations.

CONCLUSIONS

SES and adherence to hypertension medication were differently associated among older adults in rural and urban areas in Myanmar. To ensure healthcare access to hypertension treatment for every citizen, the differential association between SES and adherence in urban/rural areas needs to be recognised.

Association between Happiness and Economic Status among Older Adults in Two Myanmar Regions

Few studies have examined whether objective or subjective economic status (ES) has a greater association with the happiness of older adults, despite concerns regarding the growing economic cost of morbidity and their functional dependence in developing countries with aging populations. Thus, this study examined whether objective/subjective ES was associated with happiness in older adults in two Myanmar regions. A multistage random sampling procedure and face-to-face interviews were conducted in the urban and rural areas of Myanmar. The happiness of 1200 participants aged >60 years was evaluated using a single happiness score ranging from 0 (very unhappy) to 10 (very happy). The wealth index, used as an objective ES, was calculated from 17 household asset items, such as radio, washing machines, and television. Subjective ES was assessed by asking “Which of the following best describes your current financial situation in light of general economic conditions?” Responses ranged from “very difficult” to “very comfortable”. Both low objective and subjective ES were negatively associated with happiness, after adjusting for confounding variables and stratification by region (urban and rural areas). Although objective and subjective ES had similar associations with happiness in urban areas, subjective ES had a stronger association in rural areas.

Association between depressive symptoms and objective/subjective socioeconomic status among older adults of two regions in Myanmar

Low objective socioeconomic status (SES) has been correlated with poor physical and mental health among older adults. Some studies suggest that subjective SES is also important for ensuring sound physical and mental health among older adults. However, few studies have been conducted on the impact of both objective and subjective SES on mental health among older adults. This study examines whether objective or subjective SES is associated with depressive symptoms in older adults in Myanmar. This cross-sectional study, conducted between September and December, 2018, used a multistage sampling method to recruit participants from two regions of Myanmar, for face-to-face interviews. The Geriatric Depression Scale (GDS) was used to evaluate the depressive symptoms. Participants were classified as having no depressive symptom (GDS score <5) and having depressive symptoms (GDS score ≥5). Objective and subjective SES were assessed using the wealth index and asking participants a multiple-choice question about their current financial situation, respectively. The relationship between objective/subjective SES and depressive symptoms was examined using a multivariable logistic regression analysis. The mean age of the 1,186 participants aged 60 years and above was 69.7 (SD: 7.3), and 706 (59.5%) were female. Among them, 265 (22.3%) had depressive symptoms. After adjusting for objective SES and other covariates, only low subjective SES was positively associated with depressive symptoms (adjusted odds ratio, AOR: 4.18, 95% confidence interval, CI: 2.98-5.87). This association was stronger among participants in the rural areas (urban areas, AOR: 2.10, 95% CI: 1.08-4.05; rural areas, AOR: 5.65, 95% CI: 3.69-8.64). Subjective SES has a stronger association with depressive symptoms than objective SES, among older adults of the two regions in Myanmar, especially in the rural areas. Interventions for depression in older adults should consider regional differences in the context of subjective SES by reducing socioeconomic disparities among the communities.

Health and Economic Burden of Injurious Falls Into Irrigation Canals in Japan: A Retrospective Cohort Study

BACKGROUND

Falls into small water bodies can cause drowning and trauma. Such falls, especially into irrigation canals, and the subsequent trauma are common in Japan. However, few studies have investigated their characteristics, costs, and prognosis.

OBJECTIVE

Our aim was to clarify the characteristics, prognosis, and economic burden of trauma due to falls into irrigation canals in Kurashiki City, Japan.

METHODS

This 4-year, single-center, retrospective cohort study was conducted at a Japanese tertiary care hospital between January 1, 2013 and December 31, 2016. We enrolled patients who had fallen into irrigation canals constructed more than 300 years ago, and transported to our hospital by ambulance. The study outcomes included the characteristics, prognosis, and health care costs of such trauma.

RESULTS

We enrolled 266 patients with a median age of 66 years (range 19-64 years). Most patients fell into irrigation canals while walking (49.3%), riding a bicycle (35.0%), or driving or riding in a car (7.1%). Extremities were the most frequently affected body parts, and the head and chest were less frequently affected. Four patients (1.5%) died in the emergency department (ED), and 121 (45.5%) were hospitalized (109 in our hospital and 12 transferred to other hospitals). The total costs of ED and hospital stays were 777,625 US dollars (266 patients) and 712,059 US dollars (109 patients hospitalized in our hospital), respectively.

CONCLUSIONS

Trauma due to falls into irrigation canals can be severe and even fatal, and the related costs are high. Our study highlights the importance of implementing appropriate measures to prevent falls into irrigation canals and of promoting awareness among citizens.

Involvement of bone morphogenic protein-2 (BMP-2) in the pathological ossification process of the spinal ligament

OBJECTIVE

To investigate the function of bone morphogenic protein-2 (BMP-2) in the ossification of the spinal ligament (OSL).

METHODS

Total RNA was prepared from the cultured spinal ligament cells from patients with OSL and analysed by reverse transcription-polymerase chain reaction using specific primers for BMP-2. BMP-2 mRNA expression in ligament tissues was examined by in situ hybridization. Spinal ligament cells from patients without OSL were treated with BMP-2 and examined for alkaline phosphatase activity.

RESULTS

Expression of the BMP-2 gene was detected in cultured spinal ligament cells. In ligament tissues, BMP-2 mRNA was present in the chondrocyte-like cells in the fibrocartilage zone. Exogenous BMP-2 increased alkaline phosphatase activity in spinal ligament cells from patients without OSL.

CONCLUSION

The BMP-2 gene is expressed in the spinal ligaments of OSL patients, and exogenous BMP-2 stimulates osteogenic differentiation of spinal ligament cells. The expression of BMP-2 in the spinal ligaments could be a clue in elucidating how heterotrophic osteogenesis develops in ligament tissue.

Possible involvement of vitamin D receptor gene polymorphism in male patients with ossification of spinal ligaments

Ossification of spinal ligaments (OSL) is a common form of myelopathy characterized by heterotopic bone formation in the spinal ligaments, predominantly in men. Although the etiology of OSL is not fully understood, previous studies have strongly suggested the involvement of genetic factors in this disease. To investigate the possible involvement of vitamin D receptor (VDR) gene polymorphism in Japanese male patients with OSL, we analyzed: (a) the VDR genotype defined by BsmI polymorphism in patients with obvious OSL and controls; and (b) the effect of 1,25-dihydroxyvitamin D3 on alkaline phosphatase (ALP) activity of spinal ligament cells derived from patients without OSL. With regard to the VDR genotype, of the patients with OSL (n = 27), none had the BB genotype (0%), one had the Bb genotype (4%), and 26 had the bb genotype (96%). In the control group (n = 97) three had the BB genotype (3%), 18 had the Bb genotype (19%), and 76 had the bb genotype (78%). As a result, the B allele frequency in patients with OSL (2%) was significantly lower than in controls (12%). 1,25-Dihydroxyvitamin D3, at concentrations of 10-9 and 10-8 M, significantly increased ALP activity of the ligament cells (n = 8), suggesting that 1,25-dihydroxyvitamin D3 is able to promote osteogenic differentiation of normal ligament cells. Among the Japanese, sensitivity to vitamin D has been reported to vary between the alleles of the VDR; i.e., bone mineral density (BMD) in patients without the B allele is increased by vitamin D treatment, whereas patients with the B allele do not show such an increase in BMD. The present investigation is a small preliminary study, but the findings suggest, for the first time, that the B allele of the VDR acts as an inhibitor in the pathogenesis of human male OSL.

Interleukin-10 gene transfer improves the survival rate of mice inoculated with Escherichia coli

OBJECTIVE

To determine whether administration of recombinant adenovirus vectors encoding the interleukin (IL)-10 protein (AxCAmIL-10) decreases the mortality of septic mice.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research laboratory.

SUBJECTS

Adult male C57B/6 mice.

INTERVENTIONS

Untreated mice and those injected intraperitoneally with 1 x 10(9) pfu of AxCAmIL-10 were used as control 1 and 2, respectively. Double-capsules without Escherichia coli were intraperitoneally embedded in another group (control 3). Mice embedded with capsules containing E. coli were divided into the following groups: simultaneous administration of 0.5 mL of saline (group 1), and administration of AxCAmIL-10 3 hrs before embedding (group 2) or 1 hr after embedding (group 3). Histopathologic changes together with expression concentrations of IL-10 and tumor necrosis factor (TNF) in various organs and plasma were examined 18 hrs after each treatment. Observation periods were 5-8 days. Survival rates were compared between these groups.

MEASUREMENTS AND MAIN RESULTS

The plasma IL-10 concentrations were increased in control 2, group 2, and group 3 but not in control 1, control 3, or group 1, indicating successful adenovirus gene transfer. Plasma TNF values were significantly reduced in groups 2 and 3 as compared with group 1, with no significant differences in endotoxin concentrations. Survival rates were significantly better in groups 2 and 3 than in group 1 (p < .05).

CONCLUSION

These findings suggested that IL-10 has a favorable effect on survival of septic mice via inhibition of TNF production or endotoxin stimulation.

Hyperleptinemia in female patients with ossification of spinal ligaments

In order to examine the involvement of leptin in the ossification of spinal ligaments (OSL), the present study examined (i) serum levels of leptin and insulin in OSL patients and controls, (ii) serum leptin levels in children of OSL females with severe obesity, (iii) the expression of leptin receptor mRNA in human spinal ligaments, and (iv) effects of leptin on cultured human ligament cells. In the OSL females, serum leptin levels were significantly higher than those of the control females, and the levels were positively correlated to the serum insulin levels, while in the control females, there was a tendency of inverse correlation. The daughters of OSL females with severe obesity also had high serum leptin levels, although they had not developed OSL. The expression of leptin receptor mRNA was confirmed in the ligaments, but leptin did not influence the alkaline phosphatase activity nor procollagen type I carboxyl-terminal peptide content of the ligament cells. These findings suggest that leptin is involved genetically and indirectly with the pathogenesis of OSL in female patients.

Porcine luteinizing hormone isoform(s): relationship between their molecular structures, and renotropic versus gonadotropic activities

We recently demonstrated the renotropic activity in ovine LH isoform(s). In this study we purified porcine (p) LH isoforms and analyzed their structures and bioactivities. Purified pLH preparation (G-100 fraction 3) was dissociated into alpha- and beta-subunits, followed by isolation with reverse phase HPLC. Six components were isolated and analyzed for their amino acid compositions and amino-terminal amino acid sequences. alpha-Subunits were found to have heterogeneous N-terminal sequences, which started at Phe-1, Gly-4, Phe-6, or Thr-7. This N-terminal heterogeneity and the presence of the initial 6 amino acids has not been reported previously to the best of our knowledge. Moreover, the first 10 residues, Phe-Pro-Asp-Gly-Glu-Phe-Thr-Met-Gln-Gly, were identical with those of the ovine LH alpha subunit. At least 3 different beta-subunits were identified as heterogeneous in their carboxyl-terminal amino acids. The pLH preparation (G-100-fraction 3) was then chromatographed by an isoelectrofocusing (IEF) column. Four IEF fractions were obtained. Their amino acid structures appeared to be identical, as judged by the identical elution profiles on reverse phase HPLC, but their carbohydrate compositions were slightly different, especially in N-acetylgalactosamine in alpha-subunits. Thus, fractionation on IEF depended on the heterogeneity in carbohydrate structures. Each IEF fraction had different potencies in terms of its gonadotropic activity (in vitro) and renotropic activity (in vivo and in vitro). The discrepancy was observed not only between gonadotropic activity and renotropic activity, but also between in vivo and in vitro renotropic activity. This study identified the structural heterogeneity of pLH isoforms and demonstrated their biological heterogeneity. We concluded that the carbohydrate structure of the pLH isoform is important for expressing its biological heterogeneity (gonadotropic and renotropic activity.

Effect of limited tryptic modification of a bacterial poly(3-hydroxybutyrate) depolymerase on its catalytic activity

The extracellular poly(3-hydroxybutyrate) depolymerase of Alcaligenes faecalis T1, which hydrolyzes both hydrophobic poly(3-hydroxybutyrate) and water-soluble oligomers of D(-)-3-hydroxybutyrate, lost its hydrolyzing activity toward the hydrophobic substrate on mile trypsin treatment, but retained its activity toward water-soluble oligomers. The molecular mass of the trypsin-treated enzyme was 44 kDa, as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, which was 6 kDa smaller than that of the native enzyme (50 kDa). The trypsin-treated enzyme seemed to be less hydrophobic than the native one, because it was rather weakly adsorbed to a hydrophobic butyl-Toyopearl column compared with the native enzyme, and showed no ability to bind to poly(3-hydroxybutyrate), to which the native enzyme tightly bound. These results suggest that, in addition to a catalytic site, the enzyme has a hydrophobic site, which is not essential for the hydrolysis of water-soluble oligomers, but is necessary for the hydrolysis of hydrophobic substrates, and this hydrophobic site is removed from the enzyme by the action of trypsin.

[Studies on the diuretic effect of haloperidol in adult rats]

An increase in urinary flow has been observed in rats during cataleptic response to haloperidol. The present experiment was carried out to study the mechanism of haloperidol-induced diuresis. Wistar-Imamichi adult female rats were injected i.p. with haloperidol in a dose of 0.1, 1 or 10 mg/kg, and the time course of changes in urine volume was observed. The dose-dependent diuretic effect of 1 or 10 mg/kg haloperidol was significant from 4 hr afterward, and the haloperidol-induced diuresis was prevented by pretreatment with phenoxybenzamine, prazosin or yohimbine. Chlorpromazine but not spiperone and pimozide induced a significant increase in urine volume, though the effect of chlorpromazine was less marked as compared with that of haloperidol. Clonidine in a dose of 0.125-1.0 mg/kg enhanced urine flow markedly from 30 min, and the same alpha-adrenergic blockers were also effective in blocking the diuretic effect of clonidine. Urinary osmolarity in 1 mg/kg haloperidol- and 0.125 mg/kg clonidine-treated rats decreased significantly, whereas only clonidine stimulated urinary Na and K excretion. Plasma osmolarity and negative free water clearance did not change in both haloperidol- and clonidine-treated rats. The present results suggest that the haloperidol-induced diuretic effect could be due to the central alpha-adrenoceptor blocking action of haloperidol.

Degradation of poly(3-hydroxybutyrate) by poly(3-hydroxybutyrate) depolymerase from Alcaligenes faecalis T1

The extracellular poly(3-hydroxybutyrate) depolymerase purified from Alcaligenes faecalis T1 has two disulfide bonds, one of which appears to be necessary for the full enzyme activity. This depolymerase hydrolyzed not only hydrophobic poly(3-hydroxybutyrate) but also water-soluble trimer and larger oligomers of D-(-)-3-hydroxybutyrate, regardless of their solubilities in water. Kinetic analyses with oligomers of various sizes indicated that the substrate cleaving site of the enzyme consisted of four subsites with individual affinities for monomer units of the substrate. Analyses of the hydrolytic products of oligomers, which had labeled D-(-)-3-hydroxybutyrate at the hydroxy terminus, showed that the enzyme cleaved only the second ester linkage from the hydroxy terminus of the trimer and tetramer, and acted as an endo-type hydrolase toward the pentamer and higher oligomers. The enzyme appeared to have a hydrophobic site which interacted with poly(3-hydroxybutyrate) and determined the affinity of the enzyme toward the hydrophobic substrate.

Purification and properties of extracellular poly(3-hydroxybutyrate) depolymerases from Pseudomonas lemoignei

Extracellular poly(3-hydroxybutyrate) depolymerase was purified from the culture medium of Peudomonas lemoignei and separated into four isozymes (A1, A2, B1 and B2) by CM-Sepharose CL-6B chromatography. The molecular weights of A1 and A2 and those of B1 and B2 were estimated to be 54 000 and 58 000, respectively, by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The isoelectric points of A1, A2, B1 and B2 were found to be approximately pH 9.7, 10.0, 10.0 and 10.6, respectively, by isoelectric focusing. All four enzymes hydrolyzed poly(3-hydroxybutyrate) and oligomeric esters of D-(-)-3-hydroxybutyrate, but showed no activity toward the dimeric ester. Analysis of hydrolytic products of the oligomeric esters with A1 and B2 suggested that the enzymes hydrolyzed mainly the second and third ester bonds from the free hydroxy terminus at different frequencies, depending upon the chain length of the substrates.

An extracellular D(-)-3-hydroxybutyrate oligomer hydrolase from Alcaligenes faecalis

A strain of Alcaligenes faecalis secretes an extracellular D(-)-3-hydroxybutyrate oligomer hydrolase, in addition to poly(3-hydroxybutyrate) depolymerase, when it is grown in a medium containing poly(3-hydroxybutyrate) as the sole carbon source. The oligomer hydrolase (EC 3.1.1.22), which has been purified to electrophoretic homogeneity, has a molecular weight of 68 000, as estimated by Sephadex G-100 gel filtration, and of 74 000, by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The isoelectric point of the enzyme is approx. 6.0 and the pH optimum for the enzyme reaction is 8.5. The purified oligomer hydrolase has high affinity for oligomeric esters (apparent Km for the D(-)-3-hydroxybutyrate dimer = 32.8 microM; for the dodecamer = 1.3 microM), but does not attack poly(3-hydroxybutyrate) (average molecular weight, 32 500) at all. Analysis of hydrolysates of the oligomeric esters suggests that the enzyme hydrolyzes these substrates from the carboxyl terminus, releasing D(-)-3-hydroxybutyrate units one by one.

An extracellular poly(3-hydroxybutyrate) depolymerase from Alcaligenes faecalis

A strain of Alcaligenes faecalis T1, which was isolated from activated sludge, excreted an extracellular poly(3-hydroxybutyrate) depolymerase as it grew in a medium containing poly(3-hydroxybutyrate) as the sole carbon source. The molecular weight of the enzyme, purified from the culture medium to electrophoretic homogeneity, was 48 000 as determined by Sephadex G-100 filtration, and 50 000 by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate. The pH optimum for the enzyme reaction was 7.5. The purified enzyme depolymerized poly(3-hydroxybutyrate) purified from Zoogloea ramigera 1-16-M, but did not attack the bacterial native poly(3-hydroxybutyrate)-containing granules. Km values were 13.3 micrograms/ml (= 0.78 microM, based on an estimated average molecular weight of 17 000) for poly(3-hydroxybutyrate) and 5.4 mM for the trimeric ester of D(--)-3-hydroxybutyric acid. Analysis of hydrolytic products of poly(3-hydroxybutyrate), several oligomeric esters of D(--)-3-hydroxybutyric acid, and the methyl ester of the trimeric ester indicated that the enzyme hydrolyzed these substrates from the free hydroxyl terminus, releasing D(--)-3-hydroxybutyrate dimer units one at a time.

An NAD-linked acetoacetyl-CoA reductase from Zoogloea ramigera I-16-M

An NAD-linked acetoacetyl-CoA reductase of Zoolgoea ramigera I-16-M was purified to electrophoretic homogeneity. In contrast to the D(-)-3-hydroxybutyryl-CoA-specific NADP-linked acetoacetyl-CoA reductase from the same bacterium [Saito, T. et al (1977) Arch. Microbiol. 114, 211 - 217], the purified enzyme was strictly stereospecific to L(+)-3-hydroxybutyryl-CoA, and was active not only with NAD+ but also with NADP+, although NADP+ was less effective than NAD+ as coenzyme. The enzyme showed a pH optimum at 6.3 for the reduction of acetoacetyl-CoA and at 8.0 for the oxidation of L(+)-3-hydroxybutyryl-CoA. In the reduction reaction, Km values for acetoacetyl-Coa and NADH were 8.8 microM and 6.5 microM, respectively, and in the oxidation reaction, Km values for L(+)-3-hydroxybutyryl-CoA and DNA+ were 7.0 microM and 32 microM, respectively. Among various 3-hydroxyacyl-CoAs tested, L(+)-3-hydroxybutyryl-CoA and L(+)-3-hydroxyvaleryl-CoA were the most active substrates. Poly(3-hydroxybutyrate) synthesis from acetyl-CoA, by a system reconstituted from purified preparations of 3-oxothiolase, acetoacetyl-CoA reductase and poly(3-hydroxybutyrate) synthase, was observed when the NADP-linked but not the NAD-linked reductase was used. These findings indicate that the NAD-linked acetoacetyl-CoA reductase is not directly involved in the biosynthesis of poly(3-hydroxybutyrate).