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Biomedical subjects

Y Miake

Publications and source records attributed to Y Miake.

28 records · Page 2Linked to original sources
PubMed1990

Effect of solution composition on morphological and structural features of carbonated calcium apatites.

The composition of enamel mineral corresponds to that of a calcium carbonato-apatite. For insight to be gained into the precipitation of carbonato-apatites having specific properties (crystal size, morphology, and carbonate incorporation into the crystal lattice), apatites were prepared at 80 degrees C in aqueous systems having various CO3 concentrations and pH values of around 7.5 or 10.5 (+/- 0.5). The various preparations had a wide range (0.005 to 0.19) of CO3/Ca molar ratios that bracket the ratios found in porcine enamel mineral at various developmental stages. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction analyses showed that the calcium apatites precipitating at neutral pH incorporated the carbonate into both the hydroxyl and phosphate ion sites in their lattices (A,B-types), whereas the preparations made at the alkaline pH (high OH-(-)CO3(2-)-competition) or in the presence of fluoride (F-(-)CO3(2-) competition) yielded only the B-type carbonato-apatite. It was also ascertained that the size and morphology of the carbonato-apatites, assessed by specific surface area determination and high-resolution electron microscopy, were highly dependent on the driving force for precipitation and the presence of regulators (CO3(2-) and F-) in solution. In neutral media, early precipitates were thin-ribbon in appearance, but grew into crystals having flattened-hexagonal cross-sections. In the presence of fluoride or in alkaline media, acicular apatite crystals, precipitated initially, grew into large rod-like carbonato-apatites having a symmetric-hexagonal cross-section. In both neutral and alkaline solutions, carbonate inhibited the growth of apatite crystals along their c axis, leading to the formation of bulkier crystals. The formation of carbonato-apatites at the neutral pH and their properties are consistent with observations made on enamel minerals formed in the early developmental stages.

Apatites↗
PubMed1985

Unusual collagen aggregates induced in rat incisor dentin after vinblastine administration.

Young male Wistar rats weighing 100 g were injected intravenously with 0.2 mg of vinblastine sulfate (VBL). At 24, 27, and 36 hours and 2, 4, and 6 days after introduction of the drug, the rats were fixed by means of perfusion and the upper incisors were removed for electron microscopy. Many secretion granules had accumulated in the young odontoblasts 24 hours after VBL administration. Newly formed predentin located between odontoblasts contained small amounts of an unusual collagen aggregate characterized by a fine, symmetrically striated structure, and paired, dense bands, which were present at both ends. After 27 hours, following the disappearance of the secretion granules in the odontoblasts, unusual collagen aggregates had increased in amount. Two days after administration, the predentin layer, which was close to the odontoblasts, was composed largely of unusual collagen aggregates. During dentinogenesis, the layer of unusual collagen aggregates gradually shifted into the dentin, where, 4 days after VBL administration, it was, to a large degree, located. Mineralization of the unusual collagen aggregates began with the deposition of fine, filamentous crystals that later grew into needle-shaped crystals 40 A thick. These findings suggest that unusual collagen aggregates are produced as a result of the secreting function of odontoblasts and are mineralized, as are normal collagen fibrils in dentin.

Animals↗
PubMed1982

Electron microscopic study on the effects of vinblastine on young odontoblasts in rat incisor.

Young Wistar male rats were injected intravenously with 2 mg/kg of vinblastine sulfate. After three, six, 12, 24 and 48 hours, the upper incisors were dissected out of the animals, and their young odontoblasts were observed in an electron microscope. Three to six hours after the injection, the regular polarity of the nuclei and the cytoplasmic organelles were dramatically changed following a decrease in the number of microtubules. Disturbance in protein synthesis was suggested at this stage by unusual shapes and the arrangement of the rough endoplasmic reticulum and loss of the polysomal arrangement of the ribosomes attached to the reticulum. After more than 12 hours, accumulation of secretion granules and the occurrence of bodies, containing a few strands of collagen-like fibrils, were frequently seen in various portions of the cells, indicating retarded export of the secretion substance. Occurrence of a number of unusually short fibrils in predentin was another prominent feature noticed in later stages. The fibrils were about 3000A long by 2000A or 600A wide, and many of the 2000A wide fibrils were characterized by a banded structure which resembled the previously reported SLS collagen. The 600A wide fibrils were usually banded with about 600A periodicity.

Animals↗
PubMedDate not supplied

Maternal stress induces synaptic loss and developmental disabilities of offspring.

Mild prenatal stress affects the serotonergic system in the hippocampus of rat offspring. Pregnant rats were daily exposed to mild stress treatments (consisting of crowding and saline injection) during days 15 to 21 of pregnancy. Their offspring were assessed by a series of biochemical, histological and behavioral tests. On 35 days after birth, 5-hydroxytryptamine (5-HT) level was decreased by 17% (P < 0.05), whereas 5-hydroxyindolacetic acid (5-HIAA) level was increased by 18% (P < 0.05) in the offspring of prenatally stressed rats. The metabolic rate (5-HIAA/5-HT) was increased by 49% (P < 0.01). Synaptic density in the hippocampus of prenatally stressed offspring was also decreased by 32% (P < 0.0001) on postnatal day 35. There was no significant group difference in the spatial learning acquisition test of the Morris water maze; however, in the reversal task, prenatally stressed 5-week old rats spent more time than control animals searching for the platform of the pool. Escape latency in the cued test showed no significant difference. Together with data in our previous studies, that have shown 5-HT to facilitate synapse formation and maintenance in the central nervous system, synaptic loss is suggested to occur in relation to changes of 5-HT system in the hippocampus of prenatally stressed offspring. This may be associated with reported changes in behavior and learning ability in prenatally stressed offspring.

Animals↗