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Biomedical subjects

A Togari

Publications and source records attributed to A Togari.

At least 55 records · Page 3Linked to original sources
PubMed1993

In vivo and in vitro study of the effects of chlorpromazine on tooth mineralization in rats and mice.

The effects of chlorpromazine (CPZ) on tooth mineralization were examined using incisor dentine in adult rats and cultured tooth germs of mandibular first molars dissected from mouse embryos. CPZ (10, 50 and 250 mg/kg, s.c.) substantially inhibited dentine mineralization as evaluated by contact microradiographs. Plasma calcium and phosphorus concentrations were not decreased by CPZ (10 and 50 mg/kg). Physicochemical effects were not involved in the action of CPZ on the mineralization. In vitro experiments showed that CPZ (1 and 10 microM) inhibited mineralization and alkaline phosphatase (ALP) activity in the tooth germs. As CPZ has the properties of a calmodulin antagonist, the calmodulin antagonists W-7 and W-5 were also examined. Both inhibited mineralization and ALP activity in tooth germs; W-5 had less effect than W-7. These in vivo and in vitro findings suggest that CPZ inhibited cell-mediated mineralization in dentine without affecting the calcium-regulating system and physicochemical mineral deposition. In addition, calmodulin could be involved in cell-mediated mineralization.

Alkaline Phosphatase↗
PubMed1993

Alteration of in vitro bone metabolism and tooth formation by zinc.

1. The effects of zinc on bone metabolism and tooth formation was examined in organ cultures of calvaria and tooth germ, and in cell cultures of osteoblast-like cells, MC3T3-E1. 2. Treatment of calvaria with zinc (10, 100 microM) for 4 days both increased alkaline phosphatase (ALP) activity in bone and reduced the secretion of N-acetyl beta-glucosaminidase from bone, without affecting bone mineral or collagen content. The increase in ALP activity produced by zinc (10 microM) was inhibited neither by actinomycin D (5 micrograms/ml) nor by cycloheximide (0.5 micrograms/ml). 3. Treatment of MC3T3-E1 cells with zinc (50, 100 microM) for 25 days also increased ALP activity, but reduced calcium content in cells and in the matrix layer. 4. These results indicate that zinc increases ALP activity in osteoblasts without affecting de novo enzyme synthesis, and that it inhibits bone mineralization, in accordance with the inhibition of osteoclastic activity. 5. Treatment of tooth germ with zinc (100 microM) for 7 days also produced an increase in ALP activity and inhibition of mineralization. These results indicate that the increased ALP activity produced by zinc is a common phenomenon in hard tissues, and, further, that zinc inhibits mineralization during tissue formation.

Acetylglucosaminidase↗
PubMed1993

Comparison of body height and mandibular length between Caucasian and Japanese children.

This study compared pubertal growth of Japanese males and females with that of Caucasian children matched by age and gender. Total body height and mandibular length were compared between the two groups. Total body height showed that Caucasian males were taller than Japanese males from the ages of 10 to 15 years (p< 0.01-0.05). The annual maximum growth of Caucasian females peaked at the age of twelve, but Japanese females had a "spurtless" growth pattern, peaking one year earlier than Caucasian females. Total mandibular length, calculated at the age of 10, was about 3 mm greater in Japanese males and 5 mm greater in Japanese females than in Caucasians. At the age 15, the mandibles of Japanese males and females were about 7 mm and 9 mm longer than those of Caucasians, respectively. Adolescent mandibular growth spurt occurred, on the average, at the age of 13 in both Caucasian and Japanese males. Both female groups showed mandibular growth peaks at the age of 12.

Adolescent↗
PubMed1992

Multiple mRNA forms of human GTP cyclohydrolase I.

To isolate full length cDNA clones encoding human GTP cyclohydrolase I, the first and rate-limiting enzyme in tetrahydrobiopterin biosynthesis, a cDNA library generated from human liver was screened by plaque hybridization. Analysis of the clones, hybridized with rat cDNA fragment, by restriction mapping and partial sequencing showed the existence of three kinds of cDNAs. All three cDNAs were identical in their central and 5' regions. They were, however, found to diverge at 3' ends. Furthermore, the three species of mRNAs corresponding to the three cDNAs were detected in human liver by reverse transcription-polymerase chain reaction (RT-PCR) analysis. These results indicate that, in humans, GTP cyclohydrolase I molecules are encoded by at least three distinct mRNAs.

Amino Acid Sequence↗
PubMed1991

Effects of retinoic acid on bone formation and resorption in cultured mouse calvaria.

1. The effects of retinoids on bone metabolism were examined in newborn mouse calvaria. 2. Incubation of calvaria with 0.01-1 microM retinoic acid for 4 days decreased their alkaline phosphatase (ALP) activity, mineral content and collagen content in a concentration-dependent fashion. 3. With treatment for 2 days, retinoic acid (1 microM) decreased the ALP activity and collagen content, but not the mineral content. 4. All these inhibitory effects were observed in calvaria from 0-day-old mice, but no inhibition of ALP activity was observed in calvaria from 14-day-old mice. 5. 1-Hydroxyethylidene-1,1-bisphosphonate (HEBP, 1 mM), which inhibits bone resorption, prevented the effect of retinoic acid (1 microM) on the bone mineral content, but not the effects on ALP and collagen (synthesized by osteoblasts). HEBP (1 mM) alone had no effect on the calvarial mineral and collagen contents. 6. These findings indicate that retinoic acid both stimulates bone resorption and inhibits osteoblastic activity by different mechanisms, and that stimulation of bone resorption by retinoic acid is inhibited by HEBP.

Alkaline Phosphatase↗
PubMed1991

Effect of HEBP (1-hydroxyethylidene-1,1-bisphosphonate) on experimental osteoporosis induced by ovariectomy in rats.

The present study was undertaken to test whether long term administration of HEBP could prevent the progress of bone loss induced by ovariectomy in rats. Administration of HEBP was started from day 111 after ovariectomy. The animals received subcutaneous injections of HEBP, at a dose of 0, 2, 4, or 8 mg/kg, every other day for 92 days. Tibiae, femora and incisor teeth were investigated by chemical analyses and by contact microradiography. Effects on calcium, phosphorus, and alkaline phosphatase activity in the plasma were also examined. Progress in the loss of bone density and ash content caused by ovariectomy was prevented by the administration of 2 mg/kg HEBP for 92 days and was partially prevented by the administration of 4 mg/kg. At a dose of 8 mg/kg, however, HEBP did not prevent the bone loss but, rather, potentiated it. These chemical findings were qualitatively confirmed by contact microradiography. A dose-dependent inhibition was observed in the mineralization of incisor dentin. These results suggest that HEBP, at least at low dose levels in which the inhibition of mineralization is not predominant, has a potency to prevent the progress of bone loss induced by ovariectomy. At higher doses, however, this compound seems not to be effective, because of the severe inhibition of mineralization.

Animals↗
PubMed1990

Dietary calcium deprivation increased the levels of plasma catecholamines and catecholamine-synthesizing enzymes of adrenal glands in rats.

Rats on calcium-deficient diets developed hypocalcemia, hyperparathyroidism and hypertension and showed an increase in plasma catecholamines. Adrenal gland catecholamines were decreased while tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) were found to be increased, as compared to controls. In contrast, no significant differences were found between controls and parathyroidectomized rats in plasma catecholamines, and catecholamines, TH and DBH of the adrenal gland. These findings seem to indicate that the genesis of hypertension in rats on a low calcium diet is secondary to hyperparathyroidism caused by a low calcium diet. Furthermore, some relation between catecholamines and parathyroid hormone seems to exist in the regulation of blood pressure in rats.

Adrenal Glands↗
PubMed1990

Acute effect of parathyroid hormone-(1-34) fragment on blood pressure in rats fed a low calcium diet.

1. Acute effects of human PTH-(1-34) fragment on blood pressure were examined in rats fed a low or normal calcium diet. 2. Plasma biochemistry showed that a low calcium diet evoked hyperparathyroidism as well as hypocalcemia in rats. 3. Subcutaneous administration of human PTH-(1-34) caused a significant decrease in tail-cuff systolic blood pressure in rats fed a normal calcium diet, but not in rats fed a low calcium diet. 4. Intravenous administration of human PTH-(1-34) reduced the arterial blood pressure in rats, dose-dependently. The reduction of blood pressure was more pronounced in rats fed a normal calcium diet than that in the rats fed a low calcium diet. 5. It is suggested that the hypotensive action of human PTH-(1-34) was more pronounced in the rats fed a normal diet than in the rats fed a low calcium diet, and that PTH has different cardiovascular consequences under chronic hyperparathyroidism and/or hypocalcemia.

Animals↗
PubMed1990

Atmospheric nuclear weapon test history as characterized by the deposition of 14C in human teeth.

The 14C concentration in the collagen of human teeth was retrospectively investigated to determine whether its incorporation was related to atmospheric testing of nuclear weapons. Teeth were extracted for dental therapy from July 1987 to February 1988 from patients who were residents in Japan. Tooth collagen was extracted with HCl and converted to amorphous C by heating in a vacuum line. Specimens for 14C analysis were prepared by mixing the amorphous C with silver powder. The 14C concentration was measured by mass spectrometer. The 14C concentration in tooth collagen rapidly increased in 1961 after the bomb tests, peaked around 1967-1968, and then gradually decreased. The collagen of human teeth maintains the 14C concentration at the age of root completion for life. The results of this study indicate that the history of environmental contamination from atmospheric nuclear weapon's tests has been characterized by deposition of 14C in the tooth collagen 14C of human beings.

Adolescent↗
PubMed1990

[Comparisons of effects of vitamin D3 metabolites on mineralization: utilization of incisor dentin in parathyroidectomized rats].

The rat incisor is continuously growing throughout the animal's life recording the state of mineralization within its dentin at all times. Therefore, it was assumed that the incisor dentin was suitable material for studying the effects of various drugs on such mineralization. The present study set out to examine the effects of vitamin D3 metabolites on the remineralization of dentin and the serum calcium level in parathyroidectomized (PTX) rats. Male Wistar rats weighing about 200-250 g were parathyroidectomized. Each rat was given daily 12 g of a synthetic diet containing 0.1% Ca and 0.4% P (normal P) or 0.06% P (P deficient) without vitamin D. Exp. I: Three groups of rats given a normal P diet were orally administered vehicle, 25 (OH) D3 (50 IU/rat) or 1,25 (OH)2D3 (5 IU/rat) for 5 days from the 28th day after PTX, respectively. Exp. II: Two groups of rats given a normal P diet or a P deficient diet were further divided into 4 sub-groups and intramuscularly administered 0, 5,000, 10,000 or 20,000 IU of vitamin D3 on the 9th day after PTX, respectively. The active vitamin D3, 1,25 (OH)2D3 restored the mineralization of the dentin which had been suppressed following PTX, and elevated the serum calcium level to about 9 mg/dl. However, the 25 (OH) D3 neither restored the mineralization of the dentin nor elevated the serum calcium level in the PTX rats. At doses below 1,000 IU, vitamin D3 could not restore the mineralization of the dentin. However, at massive doses above 5,000 IU, the mineralization was restored in proportion to the dose. The serum calcium levels also increased in proportion to the dose. It is assumed that the increase of the serum calcium level was mainly due to the enhancement of calcium absorption from the intestine by vitamin D3. Both remineralization of the incisor dentin and increase of the serum calcium level were more marked in groups of rats given a P deficient diet than in those given a normal P diet. In all cases in the present experiments, the degree of mineralization of the dentin seemed to correspond with the degree of elevation of the serum calcium levels. These results suggest that the remineralization of the dentin in the PTX rats was attributable to the effect of the vitamin D3 metabolites on serum calcium regulation. Relative biological activities of 1,25 (OH)2D3, 25 (OH) D3 and vitamin D3 on the remineralization of dentin were estimated to be 1, less than 0.02 and less than 0.001, respectively.

Animals↗
PubMed1989

Elevation of blood pressure in young rats fed a low calcium diet. Effects of nifedipine and captopril.

Hypertension was developed in 5-week-old male rats fed a low calcium diet, which evokes hypocalcemia and nutritional hyperparathyroidism, for 2 weeks. Blood pressure returned to normal after changing to a normal calcium diet. These changes of blood pressure were preceded by changes of calcium levels in plasma. In parathyroidectomized rats receiving a normal calcium diet, blood pressure did not rise, though the plasma calcium level decreased to a similar extent as in rats fed the low calcium diet. These findings seem to indicate that hyperparathyroidism, not hypocalcemia, is involved in the elevation of blood pressure in rats fed a low calcium diet. The elevated blood pressure was reduced by a calcium antagonist, nifedipine, but not by an inhibitor of angiotensin-converting enzyme, captopril. This may indicate that hypertension due to nutritional hyperparathyroidism responds to the calcium antagonist nifedipine and calcium supplementation, and is not dependent on renin.

Animals↗
PubMed1989

Bone disorder in cardiomyopathic hamsters.

Bones of cardiomyopathic hamsters (UM-X7.1 Syrian hamsters), at 5, 10 and 20 weeks of age, were compared chemically and histomorphologically with those of normal Syrian hamsters. Femurs of UM-X7.1 hamsters were significantly shorter than those of normal hamsters, and the mean dry weight, mean volume, mean ash weight per unit bone volume and mean ash as a percentage of dry weight of femurs were all significantly less in UM-X7.1 hamsters. The bone disorder preceded the myocardial calcium precipitation and myocardial hypertrophy in the cardiomyopathic hamsters. In addition, the percentage of cortical area measured on the cross-section of tibia and the appositional rate of bone minerals, determined by a tetracycline labelling technique, were also lower in the UM-X7.1 hamsters. These findings suggest that the bone disorder was associated with decreased bone formation in the UM-X7.1 Syrian hamsters.

Acid Phosphatase↗
PubMed1989

[Dynamic study of orthodontic wires for Edgewise appliance].

In this research, I conducted a dynamic assessment of both the orthodontic direct force of a round wire and the torque of a rectangular wire, which are used quite commonly for clinical orthodontic treatment. The results are summarized as follows. 1. Leveling .0175" multistranded wire and .016" Ni-Ti wire are orthodontic wires with great flexibility and are superior to others for clinical use at the early stage of leveling. However, if the wire is too firmly legated to the teeth with a flexure of more than 2.0 mm for the former, and more than 0.5 mm for the latter, there is the danger of excessively strengthening the orthodontic force. In the case of .016" stainless steel wire, it is highly possible to give an excessive orthodontic force if it is tied to all the teeth affected by crowding without a bending loop. 2. Torquing Because of their low torque, .017" x .025" multistranded wire and .017" x .025" Ni-Ti wire are suitable for controlling torque from the early stage of treatment. The careless use of .017" x .025" and .018" x .025" stainless steel wires must be avoided because of the possibility of producing an excessive torque on a local part.

Dental Stress Analysis↗
PubMed1989

[Comparisons of bioavailability of various calcium salts. Utilization incisor dentin in parathyroidectomized rats].

In the present study, we compared the bioavailability of various calcium salts in the diet such as calcium lactate, calcium carbonate and calcium phosphate by examining the effects of these calcium salts on serum calcium concentration and on the mineralization of incisor dentin in parathyroidectomized (PTXed) rats. Each rat was given daily 12 g of a low calcium (0.1% Ca) diet beginning from 3 days before the operation and continuing for 11 days after. Then the diet was changed to those containing various calcium salts (1.5% Ca). The serum calcium and phosphorous concentrations were examined every three days, just before feeding time and 6 hours after. The degree and site of the mineralization of incisor dentin were examined histologically by a time marking method using lead acetate. In the PTXed rats maintained on a low calcium diet, the serum calcium concentration decreased to about 4.5 mg/dl and the mineralization of incisor dentin was inhibited. On the 11th day, just before feeding on diets containing various calcium salts, the serum calcium concentrations were very similar for each group, but at 6 hours after feeding, concentration was 7.6 mg/dl in the calcium lactate group, 6.2 mg/dl in the calcium carbonate group and 4.8 mg/dl in the calcium phosphate group. On the 17th day following administration of the high calcium diets, the serum calcium concentrations were 9.8 mg/dl in the calcium lactate group, 8.4 mg/dl in the calcium carbonate group and 4.4 mg/dl in the calcium phosphate group. Mineralization of the incisor dentin was best in the calcium lactate group, moderate in the calcium carbonate group and poor in the calcium phosphate group. We also examined the effects of dietary phosphorus contents on serum calcium concentrations and on the mineralization of incisor dentin using PTXed rats. On the 17th day following the administration of diets (1.5% Ca, with calcium lactate) containing various amounts of phosphorus, the serum calcium concentrations in the calcium lactate group were 8.8 mg/dl (0.4% P), 6.9 mg/dl (0.8% P) and 4.2 mg/dl (1.6% P) respectively. Mineralization of incisor dentin was also inhibited in rats fed a high phosphorus diet. These results suggest that in PTXed rats, absorption of calcium from the intestines and mineralization of the incisor dentin is best by the administration of calcium lactate, moderate by calcium carbonate and poor by calcium phosphate, and that phosphorus in the diet inhibits calcium absorption from the intestines.

Animals↗
PubMed1989

[Apical root resorption of maxillary central incisors following orthodontic treatment].

This research shows the relationship between orthodontic treatment and apical root resorption. The latest edgewise appliance with a pre-adjusted bracket (Alexander method) was used in the present experimentation. Examination by roentgen cephalometry and intraoral radiography was performed before and after the maxillary central incisors had been moved orthodontically. The conclusion is that there was no significant difference among the grade 0, 1, 2 and 3 of apical root resorption in the change of long axis inclination of the maxillary central incisors. But there was a significant difference among the grade 0, 1, 2 and 3 of root resorption in the distance of the apical root movement. The most apical root resorption was observed when the apical root was moved lingually.

Humans↗
PubMed1987

Effect of spermine on tyrosine hydroxylase activity before and after phosphorylation by cyclic AMP-dependent protein kinase.

The effect of spermine on tyrosine hydroxylase (TH) activity purified from bovine adrenal medulla was examined before and after phosphorylation by the catalytic subunit of cyclic AMP-dependent protein kinase (A-kinase). Before phosphorylation, spermine (less than 1 mM) inhibited the enzymatic activity, and negative cooperative effect of spermine on TH (Hill coefficient = 0.7) was observed from the kinetic analysis concerning 6-methyl-5,6,7,8-tetrahydropterin (6MPH4). Spermine interacted noncompetitively toward tyrosine and the Ki for spermine was calculated to be 68 microM. Phosphorylation abolished the ability of spermine to inhibit TH activity in a negative cooperative manner against the pterin cofactor, and also increased four-fold the Ki value against the substrate. These results suggest that spermine may inhibit TH activity by interacting with the pterin binding site of the enzyme molecule in a manner of negative cooperativity, and that this inhibition is reversed by the conformational change of regulatory domain of TH after phosphorylation by A-kinase.

Allosteric Regulation↗