Yoshihiro Izawa

Bone disorders in spontaneously hypertensive rat

SummaryThe bones of adult (26 weeks old) spontaneously hypertensive rats (SHR) were examined chemically and histologically by comparing them with those of the corresponding normotensive Wistar-Kyoto (WKY) rats. The mean cortical thickness, the mean ash weight per unit bone volume, and the ash as percentage of dry weight of femur were significantly lower in SHR than in WKY. Besides, the percent cortical area measured on tibial cross-section was also reduced in SHR compared with WKY. These findings strongly suggest that the development of osteoporotic bone disorders exists in adult spontaneously hypertensive rats.

Immobilization osteoporosis and active vitamin D: effect of active vitamin D analogs on the development of immobilization osteoporosis in rats.

SummaryThe therapeutic effects of vitamin D analogs, 1,24(R)-dihydroxycholecalciferol [1,24(R)(OH)2D3], 1,24(S)-dihydroxycholecalciferol [1,24(S)(OH)2D3], and 1,25-dihydroxycholecalciferol [1,25(OH)2D3] on immobilization osteoporosis were studied in rats. The right hind limb was immobilized through application of a plaster cast following the section of the sciatic nerve. The left hind limb was intact. Vitamin D analogs were orally administered for 6 weeks at dose levels of 0.02 and 0.10µg/kg/day, respectively. The mean lengths of the immobilized femurs were not significantly different from those of the intact femurs in all the experimental groups. In the immobilized femur of animals treated with 1,24(R)(OH)2D3, 0.10µg/kg, dry and ash weights were heavier and calcium and phosphorus contents greater than those in the nontreated group. Furthermore, the amount of calcified bone mass and the cortical thickness of the femurs of the immobilized limb in 1,24(R)(OH)2D3-treated animals were greater than those in the nontreated animals. Treatment with 1,25(OH)2D3 at 0.10µg/kg caused an increase of the bone mass in both immobilized and intact femurs when compared with those of the control group.It was concluded that the administration of 1,24(R)(OH)2D3 diminished the effect of immobilization in the development of osteoporosis without any side effects.

Effects of Malnutrition on Development of Experimental Pressure Sores

Using food‐deprived rabbits we investigated the effects of nutritional deficiency on the development of pressure sores. The body weight of these animals was decreased significantly from normal. Organ weights of liver, heart, spleen, kidney, and testis were significantly decreased from normal as well. Protein deficiency in these animals was indicated by serum tests, as well as by histologic features of liver and testis and ultrastructural findings on fibroblasts. We produced lesions in malnourished as well as normal rabbits by exposing their skin to a balloon‐produced compressive force of 120 ± 10 mmHg for 4 hours. Biopsies were taken 1, 2, and 3 days after the pressure application. Histologic findings at each time were as follows: At day one, the degree of ischemic skin destruction in the malnourished animals was more severe than that in the normal ones, and thrombi were occasionally seen in the malnourished cases. At day two, proliferation of fibroblasts and macrophage infiltration were evidenced in the normal animals, whereas signs of collagen fiber degeneration as well as microthrombi were seen in the malnourished ones. At three days, epidermal cells covered the lesions in the case of normal animals; however, massive necrosis of the epidermis was still recognized in the malnourished rabbits. Thus, the healing process of pressure sores was strongly suppressed in the malnourished animals. This suppression was attributed to the reduction in fibroblast proliferation, capillary formation, macrophage infiltration, and also to the low level of epidermal cell proliferation.

Neuronal and Muscular Inclusions in Rats with Hindlimb Dysfunction after Treating with Difluorobenzhydrylpiperadine

Rats showing an ataxic gait induced by 20 wk of treatment with 0, 30, or 60 mg/kg of difluorobenzhydrylpiperadine (DFBP), a detriazinyl metabolite of almitrine, were examined by light microscopy and transmission electron microscopy. Vacuolar degeneration associated with lamellar inclusions was observed in musculus soleus and m. interossei of the hindlimbs in DFBP-treated rats. The inclusions were also produced within sensory neurons, satellite and Schwann cells, and vascular endothelial cells of thoracic and lumbar dorsal root ganglia as well as muscle spindles of affected muscles. Membrane-bound vacuoles containing electron-dense granules were seen in the peripheral nerves. This study demonstrated neuronal and muscular toxicity of DFBP in rats.

Lipidosis of the dorsal root ganglia in rats treated with an almitrine metabolite

Toxic effects of a detriazinyl metabolite of almitrine (DTMA) were evaluated in rats and on cultured rat macrophages. In rats daily treated with DTMA for 16 weeks, spastic gaits with heel-lifting appeared, and lamellated and/or crystalloid bodies formed in sensory neurons, satellite cells, Schwann cells, and vascular endothelial cells of the dorsal root ganglia. The lysosomal lamellated bodies, which were not induced by almitrine, were produced also in cultured rat macrophages exposed to over 1 ξ 10−5 M DTMA.

Toxicologic studies of the hormonal form of vitamin D3: Acute and subacute toxicity of 1α-hydroxycholecalciferol

Abstract Toxicologic examination of 1α-hydroxycholecalciferol (1α-HCC) revealed its acute toxicity to be high, and the sex variation in sensitivity of the rat to be slightly different. In subacute toxicity studies in rats, body weight gain was extremely inhibited in the animals which received 12.5, 25 and 50 μg/kg. Urinalysis revealed higher calcium concentration in the urine of experimental groups while excretion of urinary phosphate was reduced in the rats receiving 12.5, 25 and 50 μg/kg. Proteinuria was seen in rats of 12.5 μg/kg and higher dose groups. Blood cell counts showed moderate leukocytosis in the higher dose groups than in the 12.5 μg/kg group. Laboratory tests in blood indicated that plasma calcium concentration, total protein, total cholesterol, and blood urea nitrogen in the 12.5-μg/kg and higher dose groups were elevated significantly. Though scattered histological changes were seen in the kidney, heart, aorta, testes, thymus, lung, liver, thyroid, and intestinal mucosa. The main action of 1α-HCC was recognized in the necrosis of the intima of the arteriole in the heart, in digestive tracts and in voluntary muscles, resulting from the degeneration and fibrosis of muscles. However, all those lesions which were caused by the administration of 1α-HCC were fully reversible after 50 days in the recovery group. In rats, oral administration of 2.5 μg/kg of 1α-HCC for 30 days was considered to be a nontoxic dose under the conditions of this experiment.

Disorders of bone metabolism caused by small bowel resection in rats

SummaryDisorders of bone metabolism caused by resection of three quarters of the small bowel in rats were investigated biochemically and histomorphologically. Metabolic bone disorders developing 90 days after in 75%-distal-small-bowel resected rats were characterized by reduction in ash content of the femur and by the disappearance of the trabecular bone in tibial metaphysis. Biochemical studies showed significant decrease in serum Ca and 1,25-dihydroxyvitamin D concentrations in 75% distal small bowel resected rats. These data suggest that 75% distal small bowel resection impairs intestinal absorption of calcium and results in a negative calcium balance, which may contribute to the development of bone metabolic disorder in rats. On the other hand, 75% proximal small bowel resection causes no obvious metabolic bone disorders in rats, possibly because of the adaptation by the remaining part of the intestine.

Toxicological aspects of feprazone, a new nonsteroidal anti-inflammatory drug

Abstract The subacute and chronic toxicities of oral feprazone were studied in rats and beagle dogs. Administration of more than 150 mg/kg/day of feprazone to rats for 1 month induced retardation of growth and liver enlargement. In addition, treatment with 600 mg/kg/day of feprazone caused death, gastrointestinal ulcers, decreased hemoglobin concentration, and leucocytosis. Treatment of rats with 540 mg/kg/day of feprazone for 6 months had similar effects to those described above except that it did not cause death or gastrointestinal ulcers. Toxic nephropathy, nontoxic goiter, hepatomegaly, and increase of ovarian weight were observed in rats given more than 60 or 180 mg/kg/day of feprazone for 6 months. Injection of 1080 mg/kg/day of feprazone into dogs, caused one of six animals to become moribund on Day 18 and one to die on Day 7. The dogs surviving after administration of 360 and 1080 mg/kg/day of feprazone for 1 month showed anemia, leucocytosis, and elevations of phenolsulfonphthalein retention and serum alkaline phosphatase (ALP) activity. Similar effects were observed in dogs surviving after treatment with 150 or 375 mg/kg/day of feprazone for 12 months; in addition, increased ALP activity was observed even at a dose of 60 mg/kg/day. Liver enlargement was observed in dogs treated with all doses of feprazone for 1 or 12 months, and cytoplasmic inclusion bodies were observed in liver cells of dogs given more than 120 mg/kg/day of feprazone for 1 month.

Effect of 1α-hydroxyvitamin D3 on bone metabolic disorders in gastrectomized rats

The effect of 1α-hydroxyvitamin D3 (1α(OH)D3) on the metabolic bone disorders developed in gastrectomized rats were investigated biochemically and histomorphologically. 1α(OH)D3 was suspended in 0.2 % Triton-X-100 aqueous solution after dissolving in a very small amount of ethanol, was given orally to the rats for 10 weeks. The sham operated animals and the gastrectomy control animals received the vehicle alone. Gastrectomy was followed by the development of the metabolic bone disorders after 10 weeks of observation. This was characterized by reduction in ash content of the femur and histologically by a disappearance of the trabecular bone in tibial metaphysis. Decrease Ca absorption from the intestines was demonstrated by a radiotracer technique. Biochemical studies showed significant decreases in serum 25(OH)D concentration in gastrectomized rats. These findings suggest that gastrectomy partially impairs intestinal absorption of calcium and results in a negative calcium balance, which may contribute to the development of bone metabolic disorders in rats. The administration of 1α(OH)D3 increased dose-dependently serum calcium and Ca absorption from the intestine and prevented the development of bone metabolic disorders histomorphologically.

Bone metabolic disorders caused by small bowel resection, and the influence of 1α-hydroxyvitamin D3 on the rats

Metabolic bone disorders caused by resection of the distal three quarters of the small bowel and the effects of 1α-hydroxyvitamin D3 (1α(OH)D3) on the rats were investigated biochemically and histomorphologically. 1α(OH)D3 was administered orally to the rats for 13 weeks. A group of “ sham operation” animals and the 75%-distal-small-bowel-resected control animals received only the vehicle. Bone changes developed 13 weeks after the partial bowel resection. The disorder was characterized by reductions in ash content of the femur and by the disappearance of the trabecular bone in tibial metaphysis.Decreased Ca absorption from the intestines was demonstrated by a radiotracer technique, and biochemical studies showed significant decreases in serum Ca and 1,25(OH)2D concentrations in the bowel-resected rats.These findings suggest that 75% distal small bowel resection impairs intestinal absorption of calcium and results in a negative calcium balance, which may contribute to the development of bone metabolic disorder in rats. This disorder was demonstrated as high bone turnover via urinalysis and by a radiotracer technique.Administration of 1α(OH)D3 increased dose-dependent Ca absorption from the intestine and the serum Ca, normalized the bone turnover rate and prevented the development of bone metabolic disorder.