Biomedical subjects

I Ezawa

Publications and source records attributed to I Ezawa.

At least 19 recordsLinked to original sources

PubMed1998

Activation of dihydropyridine sensitive Ca2+ channels in rat hippocampal neurons in culture by parathyroid hormone.

We examined the effects of parathyroid hormone (PTH) on rat hippocampal neurons in culture to determine whether it caused a similar intracellular calcium concentration ([Ca2+]i) increase in these cells to that seen with renal epithelial cells and found that PTH induced the effect in about 30% of the neurons. The effects appeared gradually during continuous administration of full-length PTH(1-84) or its active fragment, PTH(1-34), but not of an inactive fragment, PTH(39-84). However, the active fragment of the PTH-related peptide (PTHrP(1-34)) had little effect on [Ca2+]i during 60 min of administration. The PTH effect was inhibited by nifedipine, an L-type Ca2+ channel antagonist, and facilitated by S-(-)-BAY K 8644, an L-type Ca2+ channel agonist. Our findings suggest that PTH is one of the causal factors for the age-related increase in the density of voltage gated Ca2+ channels in hippocampal neurons.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1998

The maltitol-induced increase in intestinal calcium transport increases the calcium content and breaking force of femoral bone in weanling rats.

Maltitol is a disaccharide alcohol that is produced by hydrogenation of maltose and exhibits resistance to intestinal disaccharidases. We demonstrated previously that maltitol stimulated transepithelial diffusional calcium transfer 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 the diffusional transfer of intestinal calcium absorption leads to an alteration of the physical properties of bones in the weanling rats which exhibit the maximal level of intestinal active calcium absorption. Rat pups were removed from dams at 24 d of age and were fed the diets containing either maltose (control) or maltitol and a requisite amount of calcium (0.52%) for 21 d. Balance studies performed during the final 5-d period showed that maltitol-fed rats had greater calcium retention and calcium absorption. The breaking force of femoral bones was 13% greater in the rats fed the maltitol diet than in controls. The calcium content and dry weight of both femurs and tibias, as well as the bone mineral density of tibias, were elevated in the rats fed the maltitol diet. In a separate experiment, gastric intubation of maltitol-containing diet increased the serum calcium concentration in the portal vein at 2 and 4 h compared to controls. These results indicate that the maltitol-induced increase in the intestinal calcium absorption through paracellular pathway leads to enhancement of the calcium content and the breaking strength in the bone of weanling rats.

Absorptiometry, Photon↗

PubMed1998

Modulation of bone mass and turnover in growing rats by voluntary weight-bearing exercise and glucose supplementation.

Female Sprague-Dawley rats, 9 weeks of age, were assigned to four groups: Group 0 (n = 8) was dissected for base-line control, and the other three groups were fed for 3 mo: Group 1 (n = 9), sedentary controls; Group 2 (n = 6), running rats housed in a cage with a treadmill and pair-fed with Group 1; and Group 3 (n = 7), running rats, pair-fed and allowed free access to additional glucose. The distances of voluntary running did not significantly differ between Groups 2 and 3. Menstrual cycles in these rats were apparently maintained as observed from daily running distances. The amount of glucose taken by rats in Group 3 was 3.5 +/- 0.4 (mean and SE) g/d. Body weight (BW) at the end of the experiment for Groups 1, 2, and 3 were 295.0 +/- 7.9, 211.7 +/- 5.4 (p < 0.001 vs. Group 1), and 259.0 +/- 3.5 g (p < 0.01 vs. Group 2), respectively. The parameters of bone mass such as ash weights of the femur and bone mineral content of the lumbar spine and the tibia in Groups 1 and 2 did not differ, but the values were significantly greater in Group 3 than in Group 2. However, these parameter values corrected for BW were significantly greater in Group 2 than in Group 1 and did not significantly differ between Groups 2 and 3. The parameters of bone formation, such as serum bone alkaline phosphatase activity levels and trabecular bone formation rates corrected for BW, were significantly greater in Group 2 than in Group 1 but did not differ between Group 2 and 3. However, the parameters of bone resorption, such as serum tartrate resistant acid-phosphatase levels, were significantly less in Group 3 than in Group 2. These results suggest that voluntary running augments the age-dependent increase in bone mass by modulating the bone turnover when an adequate energy source is supplied under conditions of normal menstruation, and an adequate supply of energy could be necessary to enhance the age-dependent increase in bone mass.

Acid Phosphatase↗

PubMed1998

[Nutritional therapy].

Osteoporosis is one of the life style related diseases. Therefore, from the viewpoint of prevention, daily diet and nutrient intake are important. An adequate intake of calcium together with nutrient balance plays an essential role in maintaining and promoting health and preventing osteoporosis. Moreover, prior to nutritional therapy, it is essential to understand the current nutritional status and dietary habits of the individual.

Adolescent↗

PubMed1997

Effect of long-term alcohol administration on bone metabolism in rats.

The purpose of this study was to investigate the effects of different degrees of alcohol ingestion on bone strength and mineral density. Three different groups of growing female rats were administered different doses of an alcohol-water solution for a period of 6 months. These three groups were divided into: 1) the control group, which was only given water; 2) the moderate group, which was given 5% ethanol solution for only 2 h per day; and 3) the excess group, which was given only 5% ethanol solution for 163 days. This ethanol consumption induced no detrimental effect on biochemical parameters including liver function. The moderate group showed significantly higher (p < 0.05) levels of proximal metaphysis as compared to the control group, while there was no difference between the excess group and the control group. Similarly, in comparison to the control group, the moderate group exhibited a significant increase (p < 0.001) in bone mechanical strength, while the excess group showed either the same or decreased bone stiffness. These results indicate that alcohol intake has both beneficial and hindering effects on the skeleton, depending on the concentration and frequency of ethanol intake.

Absorptiometry, Photon↗

PubMed1997

Effects of ovariectomy on intestinal alkaline phosphatase expression in rats.

The aim of this study was to investigate the effects of ovariectomy (OVX) on intestinal alkaline phosphatase (ALP) activity in rats. The calcium (Ca) and phosphorus (P) contents and the mechanical strength of bone were decreased significantly by OVX. Two kinds of mRNAs of rat intestinal ALP (RTIN-1 and RTIN-2) were detected by reverse transcription-polymerase chain reaction (RT-PCR). In OVX rats, the level of RTIN-2 mRNA was lowered significantly, while that of RTIN-1 mRNA did not change. This result was compatible with the results of enzymatic activity. This finding suggests the possibility that OVX affects bone metabolism not only directly but also in an indirect way through an intestinal Ca and/or P metabolism via regulation of intestinal RTIN-2 ALP expression.

Alkaline Phosphatase↗

PubMed1997

Effects of physical characteristics and dietary habits on bone mineral density in adolescent girls.

In the health management of bone, of most importance is how to spend the period until peak bone mass, that is appropriate self management for bone health. Therefore, we evaluated the effects of physical characteristics and dietary habits on the bone mineral density (BMD) of the second metacarpal bone (sigma GS/D: BMD) by the digital image processing method (DIP) in 197 healthy adolescent girls (Japanese students at a junior high school, aged 12-15 y), an important period of physical and bone growth. Concerning the physical characteristics of the subjects according to age group, body height in each age group was higher than the standard values for Japanese according to age, but body weights in the 14-year-old and 15-year-old groups were significantly lower than the standard values for Japanese. Compared with the standard BMD values for Japanese according to age, BMD in the subjects was high in the 12-year-old, 13-year-old and 14-year-old groups but low in the 15-year-old group (-7.3%). Concerning the nutritional state, energy, calcium (Ca), and iron intakes were insufficient in every age group. BMD relative to the standard BMD value for Japanese (standard value was regarded as 0%) was evaluated according to the ingestion frequency of Ca-rich foods. The relative BMD value (%) increased with the ingestion frequency of Ca-rich foods. These results suggest that maintenance of an appropriate physique and adequate intake of nutrients such as Ca are important for bone growth during adolescence. Active promotion of educational guidance mainly on the effects of diet on bone health in adolescents in necessary.

Adolescent↗

PubMed1996

Expression of mRNA encoding intestinal type alkaline phosphatase in rat liver and its increase by fat-feeding.

The presence of types of alkaline phosphatase (ALP) other than the tissue non-specific type enzyme in rat liver and its increase by fat feeding are known. In order to examine expression of intestinal type ALP in liver, specific oligonucleotide primers corresponding to two types of mRNAs of rat intestinal ALP (RTIN-1 and -2) were designed and amplified by means of the reverse transcriptase-polymerase chain reaction (RT-PCR). It was found that RTIN-1 mRNA was expressed only in the intestine but not in the liver, while RTIN-2 mRNA was expressed both in the intestine and in the liver. By fat feeding, expression of RTIN-1 mRNA increased in the intestine and that of RTIN-2 mRNA increased both in the intestine and in the liver. Thus, it was concluded that rat liver expressed one of the intestinal type ALP (RTIN-2) which was enhanced by fat feeding.

Alkaline Phosphatase↗

PubMed1996

Ovariectomy decreases osteogenetic activity in rat bone.

The purpose of this study was to investigate the effect of ovariectomy on osteoinductive activity in the bone in rat. Homograft implantation of decalcified humeral diaphysis from ovariectomized or sham-operated rats was performed and harvested after several time periods. A significant decrease in bone induction was found in terms of soft X-ray photography, alkaline phosphatase activity, mineral content and expression of osteocalcin (BGP; bone gla-protein) in the implants from the ovariectomized group in comparison to those from the sham-operated animals. This result suggested that the level of osteoinductive activity, probably due to bone morphogenetic protein, decreased in ovariectomized animals.

Alkaline Phosphatase↗

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↗