Search PubMed⌕ Search

Biomedical subjects

N Fujiwara

Publications and source records attributed to N Fujiwara.

At least 163 records · Page 9Linked to original sources
PubMed1989

Morphogenesis of mineralized tissues induced by neonatal mouse molar pulp isografts in the spleen.

Tooth pulps dissociated intact with EDTA were isografted for up to 40 days, and examined by light and electron microscopy for hard tissue morphodifferentiation. Grafts formed tubular dentine and osteodentine. Tubular dentine, penetrated regularly by elongated odontoblast processes, resembled normal dentine and was formed when the original odontoblasts continued normal matrix secretion. Osteodentine was formed by spindle-shaped cells with large round nuclei which presumably were transformed pulp cells, and incorporated the same elements as found in cells of non-tubular dentine. Occasionally, odontoblasts were contiguous with both the regular dentine and the osteodentine. Thus in EDTA-dissociated pulps transplanted to the spleen, the original odontoblasts produce tubular dentine and other pulp cell differentiate to form osteodentine.

Animals↗
PubMed1989

In vitro effects of calcitonin and/or parathyroid hormone on odontogenesis of mouse embryonic molars.

Mandibular first molars of mouse embryos were cultivated for examination of the effects of calcitonin (CT) and/or parathyroid hormone (PTH) on the odontogenesis of the molars, and for determination of whether and how CT, which is a PTH antagonist, has an influence on the effect of PTH on odontogenesis. On the second day, the inner enamel epithelium in the control group had already differentiated into pre-ameloblasts. Typical odontoblasts had secreted a layer of predentin. On the fourth day of culture, the pre-ameloblasts achieved terminal differentiation into secretory ameloblasts, and enamel and dentin had already been deposited. PTH (1 unit/mL) inhibited the odontogenesis of the cultured molars during the designated culture periods (two and four days), while CT (0.5 unit/mL) stimulated odontogenesis. On the second day, the development of the molars in the CT + PTH group showed an intermediate stage between the control and PTH-treated explants, but on day 4 it corresponded to that of the controls. Moreover, when the molars exposed to PTH for two days were untreated and treated with CT for an additional two days, the former produced a small quantity of enamel matrix, while the latter formed a large amount of the matrix. These histological findings were also supported by a morphometric analysis of the enamel matrix in the cultured molars. The present results suggest that CT stimulates, but PTH suppresses, the odontogenesis of the mouse embryonic molars, and that CT is an antagonist to the inhibitory effect of PTH on odontogenesis.

Amelogenesis↗
PubMed1989

Synthesis of 1-(5'-O-benzoyl-3'-deoxy-beta-D-glycero-pentofuran-2'-ulosyl)uracil and its alpha-anomer by [1,2]-hydride shift.

In contrast with direct tosylation of 5'-O-benzoyl- (1d) or 5'-O-pivaloyl-1-beta-D-lyxofuranosyl-uracil (1e) with TsCl/pyridine, tosylation of the 2', 3'-O-dibutylstannylene derivatives (4d,e) of these compounds proved to give the 3'-O-tosyl derivatives 2d, e selectively. Coversion of 2d as a model to 1-(5'-O-benzoyl-3'-deoxy-beta-D-glycero-pentofuran-2'-ulosyl )uracil (5-beta) by base-induced [1,2]-hydride shift was examined under various reaction conditions, and the alpha/beta ratio of the product mixture (5-alpha, beta) determined by 1H NMR spectroscopy in each case. The BzOLi/DMF combination has proved to be most profitable for obtaining 5-beta.

Stereoisomerism↗
PubMed1989

Hypoxia in brain slices.

The effects of hypoxia on hippocampal CA1 neurones in tissue slices of the rat brain were studied in vitro by intracellular recording. In response to superfusion of a hypoxic medium equilibrated with 95%N2-5% CO2, a majority of the neurones showed a transient depolarization followed by a hyperpolarization of 5-15 mV in amplitude and 4-12 min in duration. The hyperpolarization was, in turn, followed by a slow depolarization which within 20 min of hypoxic exposure reached a plateau level of about 25 mV above the prehypoxic resting potential. Both the initial hyperpolarization and subsequent depolarization were associated with a reduction in membrane resistance. The hyperpolarization reversed in polarity at a membrane potential of -83 mV. There was an almost linear relationship between amplitude of the hyperpolarization and membrane potential. The hyperpolarization was markedly enhanced in potassium-free media and was depressed in high-potassium solution. Superfusion of ouabain (5-7 microM)-containing medium in normoxic conditions produced hyperpolarizing and depolarizing responses similar to those elicited by hypoxic exposure. The slow depolarization was also mimicked by elevation of the extracellular potassium concentration to 10-20 mM. Evoked i.p.s.p.s were abolished within 4 min of hypoxic exposure while evoked e.p.s. p.s were maintained for about 20 min of hypoxic superfusion. Soma spikes of the neurones elicited by a depolarizing pulse were also well preserved. Their threshold was, however, raised, concomitant with a decrease in the peak amplitude. In a minority of the neurones the slow depolarization was suddenly followed by a rapid depolarization, after which the neurones showed no functional recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[The metabolism of glucose monitored by 13C-NMR in the gerbil brain in vivo-natural course and application to the ischemic model].

Glucose metabolism is altered in various pathologic conditions in the brain, i. e. ischemia, epilepsy and hypoglycemia. Therefore, analysis of glucose metabolism in pathologic conditions needs careful investigation of that in steady state. 13C-NMR method allows continuous sequential monitoring of changes in metabolism of glucose in vivo. The natural abundance of 13C is quite low (1.1%) and by administering 13C labelled in various skeleton in glucose, it is possible to monitor the metabolites in vivo. In this study, 13C glucose labelled in 1-position of carbon was employed to investigate the metabolic pathways in the control and transient ischemic gerbil brain with reperfusion. Male mongolian gerbils weighing 60-80 g were employed in this study. The gerbils were anesthetized by intraperitoneal administration of pentobarbital. The right skull was exposed and a surface coli was placed directly above the skull bone. After the operation, the animals were fastened to the NMR probe vertically. 500 mg/kg of [1-13C] glucose was injected via femoral catheter. 13C-NMR spectra were serially obtained before and after injection with GX-270 NMR spectrometer (JEOL, Tokyo, Japan, 6.34 T). In other series of experiments, 30 minutes of cerebral ischemia were induced after 15 minutes of glucose injection by the bilateral common carotid artery occlusion. In the normal gerbil brain, after administration of [1-13C] glucose (500 mg/kg), alpha and beta-anomers of [1-13C] glucose peak appeared abruptly and reached its peak level at 7.5-15 min acquisition period. The C2 peak representing glutamate and/or glutamine appeared later. The C3 and C4 peak started to appear even later at 30-40 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Influence of 1,25-dihydroxyvitamin D3 on cell proliferation during odontogenesis of the mouse embryonic molars in vitro.

Mandibular first molars from 17-day-old mouse embryos were cultured for 2 and 4 days in alpha-MEM supplemented with 10% newborn bovine serum containing 0.02% ethanol or 0.1, 1.0 or 10 ng/ml 1,25-(OH)2D3. After embedding, every 6th section was stained and mitotic features of inner dental epithelium (IDE) and dental papilla cells (DP) were counted under a light microscope. On the 2nd day, no significant differences were observed in the IDE and DP mitotic indexes among the control, ethanol, and the three vitamin D groups. On the 4th day, the indexes for all groups decreased. But the IDE indexes for all vitamin D groups were significantly different from those for the control (P less than 0.01) and ethanol (P less than 0.05) groups, whereas the DP index was significant (P less than 0.05) only in the 10 ng/ml vitamin D group. The present results suggest that vitamin D3 may have an influence on cell proliferation of IDE and DP in mouse embryonic molars in vitro.

Animals↗
PubMed1988

Changes in spontaneous firing patterns of rat hippocampal neurones induced by volatile anaesthetics.

1. The effects of the volatile anaesthetics, halothane, isoflurane and enflurane, on rat hippocampal CA1 and CA3 neurones in in vitro preparations were studied by intracellular recording methods. 2. The three anaesthetics, at concentrations similar to those used clinically (0.2-1.2 mM), initially increased and then subsequently decreased the spontaneous firing of CA1 neurones without affecting the resting membrane properties or the EPSPs evoked by focal stimuli. 3. The anaesthetics at these concentrations depressed both the fast after-hyperpolarization of the soma spike and the post-tetanic hyperpolarization induced by repetitive stimulation. They also decreased the IPSPs evoked by focal stimuli. 4. The threshold for spike generation was gradually elevated by as much as 4-6 mV during application of the anaesthetics at these concentrations. The subthreshold potential oscillations (which are likely to be associated with periodic alterations in non-inactivating Ca2+ and Na+ currents) were enhanced in the low concentrations (0.2-0.5 mM), but were depressed in the high concentrations (0.8-1.2 mM). 5. The results suggest that the transient increase in the firing frequency was caused by a depression of both the spike after-hyperpolarization and the post-tetanic hyperpolarization, and that the reduction of spontaneous firing was mainly due to an elevated threshold for spike generation. 6. The three anaesthetics altered the pattern of spontaneous spike-firing in CA3 neurones from solitary spiking to burst firing without affecting the resting membrane properties. 7. The effects of the anaesthetics on the active membrane properties and the postsynaptic potentials in CA3 neurones were similar to the effects in CA1 neurones. 8. In the majority of CA3 neurones, soma spikes elicited by depolarizing current pulses were followed by a Ca2+-dependent after-depolarization, which was in turn followed by a prolonged after-hyperpolarization (post-burst hyperpolarization). The anaesthetics facilitated the after-depolarizing potential, while they depressed the post-burst hyperpolarization. Combination of the two effects would give rise to the highly stereotyped burst (about 1 Hz in frequency) in the presence of the volatile anaesthetics.

Action Potentials↗
PubMed1987

Effects of pentobarbital and ketamine on brain injury-induced anti-ischemic activity.

Survival rates following incomplete brain ischemia induced during pentobarbital anesthesia were significantly higher in mice with a minor brain injury, inflicted one week before, than in those given a sham operation. Improvement of the survival rates in mice with brain injury, however, became insignificant when brain ischemia was imposed during ketamine anesthesia, suggesting that the actions of certain factors or protective mechanisms against brain ischemia, developed by brain injury, are antagonized by ketamine and/or potentiated by barbiturate anesthesia.

Anesthesia↗
PubMed1987

The development of mandibular molar tooth germs isografted in the mouse spleen.

Tooth germs taken from 13-day-old embryonic mice and isografted in the spleen of adult mice were examined by light and electron microscopy. Well-organized tooth structures from the early cap stage to fully developed and mineralized mature teeth were obtained up to day 60 after transplantation. Germs on day 2 were similar to those prior to the onset of grafting but reached the late cap stage of development on day 4. On day 6, enamel and dentine formation were initiated and inner enamel epithelium and dental papilla cells were polarized. On days 10-15, enamel-matrix secretion was completed and almost all ameloblasts had become resorptive enamel epithelium. India ink injected from the recipient caudal vein accumulated to the capillaries within the pulp throughout the newly-formed vessels. On day 20, defined root formation had begun but occasionally irregular and cellular osteodentine was formed in root areas. On day 30, transplants were covered with reduced enamel epithelium and acellular cementum was formed at the root areas together with rudimentary periodontal ligament fibres. Cellular cementum became thicker up to day 40. There was little evidence of cellular infiltration from recipient tissue up to day 60. The spleen seems to be a suitable site for transplantation of tooth germs.

Animals↗