Tomio Morohashi

Defects in mandibular bone area, enamel iron content and dentine formation following gastrectomy in rats

Fourteen 5-week-old male Sprague-Dawley rats were equally divided into two groups, sham-operated and gastrectomized. Tetracycline and calcein were given to label dentine. Four weeks after surgery, blood was collected for measurement of serum iron, calcium and parathyroid hormone (PTH) and the mandibles and maxillae were then removed. Sagittal sections of the maxilla or cross-sections of the mandible were prepared and examined. Backscattered electron images of the maxilla were taken and the iron content at the neck of incisors was measured by energy-dispersive X-ray. The dentine apposition rate in maxillary incisors was measured by fluorescence microscopy. Serum iron was significantly decreased, while PTH was significantly elevated without any change in the serum calcium in gastrectomized rats. Gastrectomy caused a gross loss of iron content in superficial enamel. The dentine apposition rate was significantly reduced by 30%. Both cortical and cancellous bone in the mandibula were significantly reduced. However, the total bone area in gastrectomized rats was similar to that in sham-operated rats. These results suggest that bone resorption was enhanced and dentine formation was reduced after gastrectomy.

Fructooligosaccharides prevent disorders of the femoral neck following gastrectomy in growing rats

Gastrectomy-evoked osteopenia in the femoral metaphysis of rats can be prevented by the consumption of fructooligosaccharides (FOS). We examined the effect of FOS on the femoral neck. Twenty-eight 5-week-old male Sprague-Dawley rats were divided into two groups, sham-operated (SH) and gastrectomized (GX). One week after each operation, the rats were fed diets containing 0.5% calcium with or without 7.5% FOS for 4 weeks. After dietary treatment, the middle of the femoral neck was cross sectioned. Backscattered electron images of the sections were then taken to calculate the following morphometric parameters: (1) percent trabecular bone volume (%TBV), (2) percent cortical bone volume (%CBV), and (3) percent bone marrow cavity (%MV); all were determined relative to the entire scan area (SC). Calcium, phosphorus, and magnesium (weight percent) were then measured on the cortical bone by energy-dispersive X-ray analysis. Total bone volume (%BV = %TBV + %CBV) and %CBV were almost identical among the groups, except in GX rats. In GX rats, these variables were significantly (approximately 20% and 30%, respectively; P ≪ 0.01) less than those in SH rats, whereas there were no changes in the other groups over the entire scan area. The calcium concentration close to the periosteal surface of cortical bone was markedly reduced by gastrectomy. This reduction was completely prevented by FOS consumption. These results suggest that FOS consumption prevents gastrectomy-evoked osteopenia regarding both volume and calcium concentration of the femoral neck.

The effects of stable strontium on calcium metabolism.: II. Effects of 1α-hydroxyvitamin D3 in strontium-fed rats, and inhibitory effect of strontium on bone resorptionin vitro

It has been postulated that the effect of strontium on bone metabolism due to the reduced plasma 1,25-dihydroxyvitamin D3 level following the inhibition of 1α-hydroxylation by strontium. The effects of strontium were examined on intestinal calcium absorption when rats were received synthetic 1α-hydroxyvitamin D3. Four groups of rats at the age of 36 days were fed a semi-synthetic vitamin D-deficient diet for 4 weeks containing 1% strontium and vitamin D3 (Sr-D group), 1% strontium and 1α-hydroxyvitamin D3 (Sr-α group), vitamin D3 (Co-D group), or 1α-hydroxyvitamin D3 (Co- α group), respectively. At the age of 60 days, calcium and strontium balance studies were conducted to determine intestinal calcium absorption over a 3-day period, and 1,25-dihydroxyvitamin D level was then measured. Serum 1,25-dihydroxyvitamin D in Sr-D group was undetectable, and intestinal calcium absorption significantly decreased. Replacement of vitamin D3 with 1α-hydroxyvitamin D3 recovered serum 1,25-dihydroxyvitamin D to the level in Co-D group. However, this substitution in Sr-α group failed to increase intestinal calcium absorption. We also examined the direct of strontium on bone resorption using45Ca pre-labeled mouse calvaria. Strontium was injected every day until sacrifice, and percent45Ca release from cultured calvariae was measured. Bone resorption was inhibited by strontium dose-dependently in groups which had and had not received parathyroid hormone in culture. These results suggest that strontium inhibits intestinal calcium absorption and has a direct inhibitory effect on bone resorption.

The effects of stable strontium on calcium metabolism: I. Kinetic analysis of calcium metabolism in strontium-fed rats

Stable strontium has been shown to inhibit the synthesis of 1α,25-dihydroxyvitamin D3(1,25(OH)2D3). In the present study, the effects of stable strontium on calcium metabolism were studied in growing rats. The rats were divided into control, 0.5%-Sr and 1.0%-Sr groups. After dietary treatment for 4 weeks, both intestinal calcium absorption (Vna) and the calcium absorption ratio (β) were suppressed dose-dependently by strontium. In contrast, while intestinal strontium absorption (sVna) was higher in the 1.0%-Sr group than that in the 0.5%-Sr group, there was no change in the strontium absorption ratio in the intestine (sβ). Although bone formation (Vo+) and bone resorption (Vo−) were both decreased in the strontium groups, no change was observed in the serum calcitonin and parathyroid hormone concentrations in the 1.0%-Sr group. Furthermore, a large amount of strontium deposited in newly formed bone. These results suggest that 1) the decrease of intestinal calcium absorption is due to either the reduction of 1,25(OH)2D3 synthesis or the competitive antagonistic action between calcium and strontium in the intestine, and 2) accumulation of a large amount of strontium in bone might directly inhibit bone formation and resorption.

Fructooligosaccharides consumption inhibits the loss of iron from the incisor enamel surface in gastrectomized rat

We examine the effects of fructooligosaccharides (FOS) on the reduction in the incisor iron content in gastrectomized rat. Twenty-eight 5-wk-old male Sprague-Dawley rats were divided into two groups: sham operated (bSH) and gastrectomized (bGX). After 4 wk each group was divided into two subgroups according to the presence or absence of 7.5% FOS in the synthetic diet (SH, SH+FOS, GX, and GX+FOS). At 10 wk wafter surgery, the maxilla was prepared to examine the iron content of the incisor enamel surface at four points. These points corresponded to the iron content at 6,7,8, and 10 wk, respectively. Blood was collected to determine serum iron levels at 4 and 10 wk. The serum iron level significantly decreased at 4 and 10 wk the GX group. At 10 wk, the level in the GX+FOS group significantly increased but did not reaach that in the SH group. The iron content of the enamel surface time-dependently increased and no significant differences were seen between SH and GX+FOS at 8 and 10 wk. These results suggest that FOS consumption impaired the loss of enamel content following gastrectomy, and this effect preceded the effect on the serum iron level.