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Biomedical subjects

I Ezawa

Publications and source records attributed to I Ezawa.

At least 37 records · Page 2Linked to original sources
PubMed1995

The effect of ovariectomy on bone metabolism in rats.

It is well known that the ovariectomized rat is a good model for osteoporosis. Recently, it has been possible to measure the bone mineral density (BMD) of small animals accurately using dual energy X-ray absorptiometry (DXA). Therefore, in this study the change in the BMD in the different bone structures was examined in in vivo using aged and growing rats. The BMD of the lumbar spine and the tibial proximal metaphysis, which are mainly trabecular bone, in ovariectomized aged and growing rats with ovariectomized was significantly lower than those of the control (sham) group. However, the BMD of the tibial diaphysis, which is mainly cortical bone, showed no change nor had a tendency to decrease in the early stages of the experiment. These results suggest that it is important to take into account the age and the bone site in order to evaluate the experiment, which uses the rat model with ovariectomized osteoporosis.

Absorptiometry, Photon↗
PubMed1995

Dietary maltitol increases calcium content and breaking force of femoral bone in ovariectomized rats.

Maltitol is a disaccharide alcohol generated by hydrogenation of maltose and exhibiting resistance to intestinal disaccharidases. We demonstrated previously that maltitol stimulates transepithelial transport of calcium in the ileum, accompanied by an elevation of intestinal calcium absorption as well as calcium retention in the body. In this study, we examined whether the maltitol-induced increase in intestinal calcium absorption leads to an alteration of the physical properties of bones in rats subjected to ovariectomy. We used this study as a simulation model for postmenopausal females who are at risk for osteoporosis. Following the intake of a low-calcium diet for 28 d ovariectomized rats were fed diets containing either 10% maltose (control) or 10% maltitol, together with increased amounts of calcium (0.3% in Experiment 1 and 1.2% in Experiment 2) for 21 d. Balance studies performed during the final 5-d (Experiment 1) or 2-d (Experiment 2) period of the experiments showed that maltitol increased intestinal calcium absorption and retention. The breaking force of femoral bones was significantly elevated (by 5-7%) in animals fed the maltitol diet compared with that in rats fed the maltose diet. The calcium content in the femoral bones as well as the mineral bone density of the tibial metaphysis was also elevated in rats fed the maltitol diet. These results indicate that maltitol stimulates the intestinal absorption of dietary calcium leading to an increase in calcium content in the bone, and coinciding with the elevation of the breaking strength of the bone in ovariectomized rats.

Analysis of Variance↗
PubMed1995

Bioavailability of calcium from calcium carbonate, DL-calcium lactate, L-calcium lactate and powdered oyster shell calcium in vitamin D-deficient or -replete rats.

The bioavailability of calcium from various calcium sources in humans and animals has been the subject of investigation for many years and there is considerable controversy as to the relative bioavailability of different calcium salts. Most of the studies have used a calcium balance technique which has numerous problems in terms of performance and interpretation. Using a method for evaluating the efficacy of calcium from calcium salts used for plasma calcium metabolism and bone mineralization, we examined the bioavailability of calcium from four commercially available calcium salts, namely calcium carbonate, DL-calcium lactate, L-calcium lactate and powdered oyster shell-calcium in vitamin D-deficient or -replete rats. Among the calcium salts, the differences in bioavailability were small and not statistically significant as tested by analysis of variance in both groups of rats. Thus, we conclude that calcium is utilized to the same extent from calcium carbonate, DL-calcium lactate, L-calcium lactate and powered oyster shell-calcium in both vitamin D-deficient and -replete rats.

Animals↗
PubMed1995

Voluntary exercise increases osteogenetic activity in rat bones.

The purpose of this study was to investigate the effect of voluntary exercise on osteoinductive activity in rat bone. Sprague-Dawley male and female rats were allowed to exercise freely by running on a treadmill or kept as controls without exercise for 53 days. Decalcified humeral diaphyses from experimental and control rats were implanted intraperitoneally into host rats and harvested after 33 days. A significant increase in bone formation was confirmed in the implanted bone matrices from the running group in comparison with those from control animals by soft X-ray photography and determination of alkaline phosphatase activity and mineral content. Alkaline phosphatase activity in bone and serum was increased by exercise in both male and female animals. The results suggest that osteoinductive activity in the bone was probably due to increased levels of bone morphogenetic protein following voluntary exercise.

Alkaline Phosphatase↗
PubMed1994

The effect of voluntary exercise on bone mineral density and skeletal muscles in the rat model at ovariectomized and sham stages.

The changes of bone mineral density (BMD) and skeletal muscles were evaluated in the rat model at either sham or ovariectomized stages to attempt to make clear the effect of voluntary running exercise on bone metabolism. In comparison with the control groups within the ovariectomized (OVX) and the sham groups, in the running groups, (1) the urinary phosphorus (P) and creatinine (Cr) excretions showed an increase concurrently with the increase in the running distance; (2) the weight of the quadriceps femoris was significantly higher; and (3) the BMD of appendicular and axial bones was significantly greater. These results suggest that voluntary running exercise could effect the BMD, the weight of the skeletal muscles, and the acceleration of energy metabolism.

Animals↗
PubMed1994

WBN/Kob rat: a new model of spontaneous diabetes, osteopenia and systemic hemosiderin deposition.

A long-term investigation of bone mineral metabolism in a newly developed strain, the WBN/Kob rat, which spontaneously develops diabetes, possibly due in part to hemosiderin deposition, was conducted. WBN/Kob rats used in this study developed diabetes after 9 months of age. Bone mass peaked at 6 months or 8 months of age, and femoral breaking strength was maximal at 8 months of age, declining rapidly after the development of diabetes. In contrast, both the bone mass and the mechanical strength increased up to 14 months of age in controls. The serum osteocalcin (BGP) levels were lower at 4 months of age and serum 1.25(OH)2D levels were significantly lower throughout the study in WBN/Kob rats than in controls. These results suggest that abnormal bone and mineral metabolism is present in WBN/Kob rats before the onset of diabetes, and that bone strength and BMD decrease simultaneously with the development of diabetes. This strain can serve as a useful model, not only of hemosiderosis and diabetes, but also of osteopenia.

Absorptiometry, Photon↗
PubMed1994

Evaluation of the effect of soybean milk and soybean milk peptide on bone metabolism in the rat model with ovariectomized osteoporosis.

We have reported that soybean milk is an excellent source for increasing bone mineral density (BMD) and mechanical bone strength. However, it is not known what kind of components in soybean milk affect bone metabolism. Consequently, the purpose of this study is to find the effective components in soybean milk on bone metabolism. It might be some peptide in soybean milk. Therefore, in this study the soybean milk was separated into two different preparations according to molecular weight: a high-molecular-weight soybean milk, and a low-molecular-weight soybean milk. Then, the effect of the peptides in soybean milk on bone metabolism was examined. After producing the experimental osteoporotic model rats, they were divided into four groups. The BMD and the mechanical bone strength of the three experimental groups, whose diet contained a soybean milk, a high-molecular soybean milk, or a low-molecular soybean milk (soybean milk peptide) were significantly higher than those of the control group. Moreover, the intestinal Ca absorption for the three experimental groups was significantly increased. From these results, the peptides in the soybean milk are effective for the acceleration of the intestinal Ca absorption. It is possible to assume that the mechanism for increasing the BMD and the mechanical strength in the three experimental groups was due to increasing the intestinal Ca absorption by alimenting the soybean milk, the high-molecular soybean milk or the low-molecular soybean milk.

Animals↗
PubMed1994

The effect of tochu bark on bone metabolism in the rat model with ovariectomized osteoporosis.

In this study, Tochu bark extract was examined to find out whether it is effective in preventing bone loss after menopause. Six-week-old Sprague-Dawley female rats were ovariectomized (OVX) or were sham-operated (sham). The rats in the OVX and the sham groups were fed a low-calcium diet (Ca 0.01%, P 0.3%) for 33 days. Thereafter, the rats in the OVX group were subdivided into two groups: a control group and a Tochu group. The diet for the Tochu group contained 2% Tochu bark extract (Ca 0.3%, P 0.3%). The diet for the control group and the sham group was the control diet; it contained 0.3% Ca and 0.3% P. The rats in each group were fed each experimental diet for the next 31 days. The bone mineral density (BMD) and the breaking strength of the control group were lower than those of the sham group. However, the BMD and the bone strength had improved in the Tochu group. These results suggest that the Tochu bark extraction could be effective in the prevention of osteoporosis. Moreover, in the Tochu group, intestinal Ca absorption increased. This means the Tochu bark extract accelerated the intestinal Ca absorption. This could possibly affect the increase of the BMD and the bone strength. Moreover, the muscle weight of the Tochu group was higher than that of the control group. These results suggest that Tochu bark extract is also effective for the improvement of the bone and the muscle metabolism in sedentary people with back pains and/or joint pains.

Animals↗
PubMed1994

Cross-sectional and longitudinal studies on the effect of water exercise in controlling bone loss in Japanese postmenopausal women.

The effects of water exercise, as a form of daily physical activity (water exercise in a warm water pool), on bone loss in healthy Japanese postmenopausal women have been cross-sectionally and longitudinally investigated from the viewpoint of preventing osteoporosis. In the cross-sectional study, the bone mineral density (BMD) of the lumbar spine (Z-score (%)) in the Veterans group (N = 27), who had been exercising for 35.2 months on average, was significantly higher than that in the Newcomers (N = 40), who had only begun to exercise 3 or 4 weeks before, and that in the Non-exercisers (N = 30), serving as a control group. The rate of change in the BMD of the lumbar spine was -0.92%/year in the Non-exercisers (N = 30), +1.55%/year in the Veterans (N = 20), and +2.16%/year in the Newcomers (N = 15), based on BMD Z-scores. In the Exercisers groups, it was found that the rate of change in the BMD showed a slight increase rather than a decrease irrespective of the duration of menopause. On the other hand, in the Non-exercisers group, the rate of change in the BMD decreased slightly. The results of questionnaires showed that the subjects' general awareness of health and fitness in daily life was enhanced after starting the water exercise program. These results suggest that consistently participating in water exercise is an important factor in preventing bone loss, and moreover, appears not only to indirectly improve awareness of daily physical activity but also to promote health and improve daily life.

Aged↗
PubMed1994

The nutritional evaluation of globin on maintenance of bone metabolism in ovariectomized osteoporotic rats.

In our previous study, globin was found to be an effective dietary source for increasing bone mineral density (BMD) and mechanical strength. In this study, the bioavailability of the globin preparation was examined to clarify the mechanism of increase in bone density and strength. Six-week-old Sprague-Dawley female rats were ovariectomized and were fed on a low Ca diet for 30 days to produce the experimental osteoporotic rats. Thereafter they were divided into two groups. The BMD and the mechanical strength of bone of the rat group, whose diet was supplemented with globin, were significantly higher than those of the control group. The levels of the serum calcitonin and the bone-type alkaline phosphatase (Alp) activity in serum and bone were also higher, and the tartrate-resistant acid phosphatase (Tr-Acp) activity in serum and bone was lower in the globin group. Moreover, the bone morphogenetic protein activity in bone in the globin group was found to be greater. From these results, it is concluded that alimentary globin is effective for the acceleration of bone formation and the prevention of bone resorption.

Acid Phosphatase↗
PubMed1994

[A diet and nutritional therapy of osteoporosis].

Calcium intake, in particular, has never been sufficient in Japan, according to the national nutrition survey conducted by the Ministry of Health and Welfare. Based on this fact, adequate intake of calcium from normal daily diet would be difficult. From the viewpoint of prevention, daily diet and nutrient intake are important. Especially, adequate intake of calcium is one of the important means to prevent osteoporosis. On the other hand, there are a great deal of studies about development of calcium supplements. Calcium supplementing might take after meal, if calcium intake from diet is inadequate. Proper calcium intake together with nutrient balance should be maintain for the prevention of osteoporosis.

Calcium, Dietary↗
PubMed1993

The effect of casein phosphopeptides on calcium utilization in young ovariectomized rats.

The effect of casein phosphopeptides (CPPs) on Ca utilization in ovariectomized (OVX) rats was studied. A mixture of CPPs corresponding to the amino acid sequences 1-25 and 1-28 in the beta-casein was isolated from the tryptic digest of beta-casein (beta CPP). After being fed a low Ca diet for 30 days, OVX rats were fed experimental diets of which the Ca level was 0.1%, 0.3% or 0.5% with or without 0.15% beta CPP for 28 days. During days 1-3 of the Ca refeeding period, rats fed beta CPP with 0.5% Ca showed a higher Ca absorption than control rats not supplemented with beta CPP. During days 7-9 and 26-28, there were no significant differences in Ca and P balances between the beta CPP group and the control group for each dietary Ca level. Femoral Ca and P contents from rats fed beta CPP tended to be higher than those from control rats. These results suggest that beta CPP supplementation could have an effect on Ca absorption at a certain degree of Ca deficiency.

Absorption↗
PubMed1992

The effect of milk and skim milk intake on serum lipids and apoproteins in postmenopausal females.

The effects of milk and skim milk intake on serum lipids, apoprotein levels and fatty acid composition were investigated in postmenopausal females. After a 25-day intake of 200 ml/day of whole milk, the milk group had increased HDL and LDL cholesterol levels, with a slight decrease in the proportion of 18:0 fatty acids in the phospholipid fraction. The skim milk group, which had consumed 20 g/day of skim milk for 25 days, showed no changes. After intake of 400 ml/day of whole milk for 29 days, LDL, HDL and total cholesterol concentrations were even more increased and the VLDL-phospholipid concentration was decreased, with significant increases in apoA-I, apoA-II and apoB concentrations. In the skim milk group, consuming 40 g of skim milk per day for 29 days, total cholesterol, atherogenic index, HDL-triglyceride concentrations were decreased and HDL-phospholipid, apoA-I and apoA-II concentrations were increased. Daily skim milk consumption, which is effective in preventing osteoporosis, and careful selection of foods should be recommended for Japanese postmenopausal women who consume more than 200 ml/day of whole milk.

Aged↗
PubMed1992

The effect of spiny lobster shell powder on bone metabolism in ovariectomized osteoporotic model rats.

Calcium has been found to be indispensable in the prevention of osteoporosis. Recently, there has been a great deal of research into the best way to consume calcium. In this study, the effect of "powdered lobster shell" on bone metabolism was examined in ovariectomized osteoporotic model rats. This powder has a good flavor and taste, and contains high quantities of calcium. Six-week-old SD-strain female rats were ovariectomized and were fed a low Ca diet (0.01% Ca and 0.3% P) for 32 days. Thereafter, the rats were divided into two groups; the control group was fed a control diet (0.3% Ca and 0.3% P) and an experimental group, the lobster group, was fed a lobster shell powder diet (0.3% Ca and 0.3% P) ad libitum for 30 days. The results were as follows: in comparison with the control group, the lobster group had significant increases in (1) bone mineral density [BMD (DEXA Hologic's QDR-1000] of lumbar spines and tibial proximal metaphyses, which are mainly trabecular bones, and BMD of tibial diaphyses, which is a mainly cortical bone, (2) the breaking force and energy of femur. These results suggests the lobster shell powder could be a valuable source of dietary calcium in increasing BMD, breaking force and energy in osteoporotic model rats.

Animals↗
PubMed1991

The effect of milk and skim milk intake on serum lipids and apoproteins in young females.

The effect of milk and skim milk intake on serum lipid and apoprotein levels was investigated in young females with consideration of each subject's menstrual period. When milk and dairy products were not allowed, the serum cholesterol concentration tended to decrease in high density lipoprotein (HDL) and very low density lipoprotein (VLDL), the triglyceride concentration tended to increase in HDL and low density lipoprotein (LDL), the phospholipid concentration showed no change, and the apoB, apoC-III and apoE significantly decreased. In the milk group, VLDL cholesterol and phospholipid concentrations were increased with a significant increase in the apoB concentration after intake of 200 ml/day of milk for one menstrual period, and these levels did not change when the milk intake was doubled. VLDL phospholipid increased and apoE decreased after the intake of 20 g/day of skim milk, and LDL cholesterol and HDL phospholipid concentrations tended to decrease when the skim milk intake was doubled.

Adult↗
PubMed1988

Effect of 24,25-dihydroxyvitamin D3 on 1,25-dihydroxyvitamin D3 metabolism in calcium-deficient rats.

The effect of 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] on 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] metabolism was examined in rats fed on a low-calcium diet. These rats exhibit hypocalcaemia, high urinary cyclic AMP excretion, a markedly elevated serum 1,25(OH)2D concentration and low serum concentrations of both 24,25(OH)2D and 25(OH)D. When the rats are treated orally with 1, 5 or 10 micrograms of 24,25(OH)2D3/100 g every day, there is a dramatic decrease in serum 1,25(OH)2D concentration in a dose-dependent manner concomitant with an increase in serum 24,25(OH)2D concentration. Serum calcium concentration and urinary cyclic AMP excretion are not significantly affected by the 24,25(OH)2D3 treatment, which suggests that parathyroid function is not affected by the 24,25(OH)2D3 treatment. The 25(OH)D3 1 alpha-hydroxylase activity measured in kidney homogenates is markedly elevated in rats on a low-calcium diet but is not affected by any doses of 24,25(OH)2D3. In contrast, recovery of intravenously injected [3H]1,25(OH)2D3 in the serum is decreased in 24,25(OH)2D3-treated rats. Furthermore, when [3H]1,25(OH)2D3 is incubated in vitro with kidney or intestinal homogenates of 24,25(OH)2D3-treated rats there is a decrease in the recovery of radioactivity in the total lipid extract as well as in the 1,25(OH)2D3 fraction along with an increase in the recovery of radioactivity in the water-soluble phase. These results are consistent with the possibility that 24,25(OH)2D3 has an effect on 1,25(OH)2D3 metabolism, namely that of enhancing the degradation of 1,25(OH)2D3. However, because a considerable proportion of the injected 24,25(OH)2D3 is expected to be converted into 1,24,25(OH)3D3 by renal 1 alpha-hydroxylase in 24,25(OH)2D3-treated rats, at least a part of the decrease in serum 1,25(OH)2D concentration may be due to a competitive inhibition by 24,25(OH)2D3 of the synthesis of 1,25(OH)2D3 from 25(OH)D3. Thus the physiological importance of the role of 24,25(OH)2D3 in regulating the serum 1,25(OH)2D concentration as well as the mechanism and metabolic pathway of degradation of 1,25(OH)2D3 remain to be clarified.

24,25-Dihydroxyvitamin D 3↗
PubMed1987

Role of insulin in the stimulation of renal 25-hydroxyvitamin D3-1 alpha-hydroxylase by phosphorus deprivation in rats.

The increase in serum 1,25(OH)2D concentration in response to dietary phosphorus (P) depreviation is dependent on the presence of insulin in rats. The present study was undertaken to clarify whether insulin exerts its effects by affecting the renal production of 1,25(OH)2D. The 25(OH)D-1 alpha-hydroxylase activity in kidney homogenates was markedly stimulated by P deprivation in control rats (0.20 +/- 0.06 pmol/g tissue/min in the rats on a normal P diet v 1.3 +/- 0.15 pmol/g/min in the rats on a low P diet; 6.5-fold increase). In contrast, in streptozotocin-diabetic rats, the increase in the renal 1 alpha-hydroxylase activity in response to P deprivation (0.25 +/- 0.01 pmol/g/min; 3.6-fold increase) as well as the enzyme activity in the rats on a normal P diet (0.07 +/- 0.01 pmol/g/min) was markedly suppressed. Furthermore, all the changes in the renal 1 alpha-hydroxylase activity in insulin-deficient rats disappeared by insulin replacement (0.16 +/- 0.01 pmol/g/min in the rats on a normal P diet v 1.3 +/- 0.01 pmol/g/min in the rats on a low P diet; eightfold increase). These results demonstrate that the stimulation of 1 alpha-hydroxylase in response to dietary P deprivation is blunted by insulin deficiency and is fully restored by insulin replacement. It is suggested that insulin, in addition to its direct stimulatory effect on 1 alpha-hydroxylase, alters the responsiveness of renal 1 alpha-hydroxylase to P deprivation. These effects of insulin on 1 alpha-hydroxylase may be responsible for the change in serum 1,25(OH)2D concentration in response to dietary P deprivation, although the possibility cannot be ruled out that insulin also affects the metabolic clearance of 1,25(OH)2D.

Animals↗