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EVIDENCE FOR NITRIC OXIDE-GENERATOR CELLS IN THE BRAIN
Get PDFNitric oxide (NO) is a free radical that has been recently recognized as a neuronal messenger molecule. In order to understand the way in which NO functions in the central nervous system (CNS), it is important to identify the NO-generator and NO-target cells in the brain. I measured firstly the distribution of NO synthase in the brain, which catalyzes L arginine to form NO, by the measurement of citrulline formation that is also synthesized from L-arginine together with NO in equal molar bass. In the brain of adult rat, the most potent activity of NOS was apparent in the cerebellum, next in the olfacto1y bulb and medium in the cerebrum. Further, in the presence of NADPH and Ca2+, NOS activity was detected in the neuron cultures derived from the cerebrum of fetal rat. Astrocytes, one type of glia, prepared also from the cerebrum of fetal rat, appeared to have a small but significant NOS activity. As astrocytes possess a high amount of cytosolic guanylate cyclase that is known to be activated by NO, the changes in the intracellular cGMP levels in the astrocytes were measured as another index of NO formation. The treatment of astrocytes with NOS inhibitor caused the suppression of the intracellular cGMP levels. These results indicate that NO is definitely produced by astrocytes. In addition, in the blood vessel system of the brain, although NOS has been thought to be localized in the endothelial cells of only larger vessels, NOS activity was also observed in the microvessel endothelial cells of the cerebrum of both adult and fetal pig. These data suggest that neuronal cells may be the major site of NO generation in the brain, and that the NOS is a constitutive type. The data also suggest that astrocytes can also express constitutive NOS, although the potency is not so large. Microvessel endothelial cells of the brain are also one of the sources of NO. The NO produced by these cells increases the cGMP levels in the astrocytes and may affect some physiological and/or pathophysiological events in the brain.journal articl
OBSERVATIONS ON STRUCTURAL FEATURES AND CHARACTERISTICS OF BIOLOGICAL APATITE CRYSTALS: 6. OBSERVATION ON LATTICE IMPERFECTION OF HUMAN TOOTH AND BONE CRYSTALS Ⅰ.
Get PDFIn a series of studies to investigate the basic structural features and characteristics of the biological apatite crystals, using an electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals at near atomic resolution and showed the configuration of the hydroxyapatite structure through the cross and longitudinal sections of the crystals.
Subsequently, based on the results of the observations by the authors of the ultrastructu1 e of the tooth and bone, using the same approach, we have been able to directly examine the images of the lattice imperfections in the human enamel, dentin, and bone crystals, such as the point defect structures and dislocations in the crystals.
In this report, we describe the image of the point defect structures and line defect structures obtained, using the same approach from the sections of the human enamel, dentin, and bone crystals. The materials used for this study were the noncarious enamel and dentin from the freshly extracted human erupted lower first molars, and bone tissue obtained from the alveolar compact bone. The small cubes of the material were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine method s. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800 H and H-9000 types of transmission electron microscopes operated at 200 kV and 300 kV. Each crystal was observed at the initial magnification of 300,000-500,000 times and at the final magnification of 10,000,000 times and over.
We sincerely believe that the electron micrographs shown in this report are the first to show the images of the lattice imperfections in the human enamel, dentin, and bone crystals, such as the point defect and line defect structures, at near atomic resolution.journal articl
HETEROGENEITY OF PORPHYROMONAS GINGIVALIS STRAINS ON FIMBRILLIN GENE LOCUS BY RESTRICTION FRAGMENT LENGTH POLYMORPHISM ANALYSIS
Get PDFThe adherence of Porphyromonas gingivalis (P. gingivalis) to the periodontal tissue may be an initial step in the pathogenesis of periodontal disease, and fimbriae is believed to play an important role in such processes. However, the heterogeneity of the size, sequence and antigenic reactivity of the fimbriae have been reported. The aim of the present study was to investigate the heterogeneity of P. gingivalis strains on the fimbrillin gene locus by RFLPs analysis.
Fourty-seven P. gingivalis strains including 5 reference strains were used in this study. The plasmid (pUC13Bg 12.l) with the insert of fimA381 was modified with bisulfite and used as the probe. The genomic DNAs from P. gingivalis were digested with the restriction endonuclease Sac I and Pst I, electrophoresed, transferred and hybridized with the DNA probe.
All Sac I digests generated one major band and the band size was almost the same (ca 2.5-kb), except strain W50. The Pst I digests showed one or two major bands and could be divided into 9 groups based on the band patterns. Moreover, isolates from one patient showed different band patterns
By RFLPs analysis, genetic heterogeneity seems to exist within the fimbrillin gene locus of P. gingivalis strains. Such genetic heterogeneity may reflect the previously repo1ted difference of P. gingivalis fimbriae and moreover a single patient could be infected with more than one genotype of P. gingivalis.journal articl
STUDY ON MORPHOLOGY OF MANDIBULAR CORPUS AND RAMUS INFLUENCING THE ERUPTION OF MANDIBULAR FIRST PERMANENT MOLAR
Get PDFThe mandibular first permanent molar has been reported to be the first permanent tooth to erupt. However, according to the recent reports, a considerable increase in the number of children has been observed with the eruption of the mandibular first permanent molar after the eruption of the mandibular central incisor.
The purpose of this study is to investigate whether there is any morphological difference in the mandible including the mandibular corpus and the ramus between the subjects with the mandibular first permanent molar erupting prior to the mandibular central incisor (Group A) and the subjects with the mandibular central incisor erupting prior to the mandibular first permanent molar (Group B). Lateral, posteroanterior, 45-degree oblique cephalometric radiographs and dental plaster models were used as the materials.
Based on the data statistically analyzed, the results are summarized as follows:
1.No significant differences were found in the conventional angular lateral cephalometric measurements between the two groups.
2.No significant difference was found in the mandibular length between the two groups.
3.Significant differences were found in the mandibular corpus and the ramus between the two groups. In other words, the children in Group A have a narrower ramus, longer corpus and a larger eruption space for the mandibular first permanent molar than the children in Group B.
These results indicate that even though there was no significant difference in the anteroposterior dimension of the mandible between the two groups, the internal proportion of the mandible represented as the ratio between the corpus and ramus was significantly different. This may suggest that the different proportional constituents of the mandible have a close relationship with the eruption timing of the mandibular first permanent molar.journal articl
OBSERVATIONS OF STRUCTURAL FEATURES AND CHARACTERISTICS OF BIOLOGICAL APATITE CRYSTALS: 3. OBSERVATION ON ULTRASTRUCTURE OF HUMAN DENTIN CRYSTALS
Get PDFIn a series of studies to investigate the structural features of the biological crystals, using electron microscope, we examined the ultrastructure of the human dentin crystals at near atomic resolution through the cross and longitudinal sections of the crystals
The materials used for this study were the deep layer of the non-carious coronal dentin from freshly extracted human erupted permanent molars. The small cubes of the dentin were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut wth a diamond knife without decalcification. The sections were examined with the HITACH H-700 type of transmission electron microscope operated at 200kV. Each crystal was observed at the initial magnification of 300,000 times and at the final magnification of 10,000,000 times and over.
Using this approach, the authors have been able to show the configuration of the hydroxyapatite structure in the cross and longitudinal sections of the dentin crystals deposited within and between the collagen fibrils (intrafibrillar and interfibrillar crystal) in the intertubular dentin and observe the basic hexagonal pattern of the unit cell viewed down the c axis.
The authors sincerely believe that the electron micrograph shown in this report is the first atomic image to be obtained from a hydroxyapatite crystal from the human dentin, using the sections.journal articl
JOINT EPIDEMIOLOGICAL LONGITUDINAL DENTAL SURVEY IN NIGERIA, ESPECIALLY IN COMPARISON WITH THAT OF JAPANESE
Get PDFSince 1980 we carried out a longitudinal dental survey in Ile-Ife, as a joint study with the dental school of Ife University, Nigeria, being supported by A Grant under The Monbusho International Scientific Research Program for ten years. One thousand one hundred seventy-one children and adults were examined in the 1991 survey. The data were compared with the data in the previous survey and Japanese survey. Results were as follows: 1) Caries prevalence rate and the average number of DMFT were still very low, especially showing that both the caries prevalence and the average number of DMFT decreased in the rural areas because the attrition proceeded faster than the caries, 2) Nigerian deciduous and permanent dentition were larger than in the Japanese in all items measured , 3) the condylar head was transform ed from the round shape to the ultra-flat shape with age, 4) there was a fewer incidence of severe periodontal diseases despite of the marked deposition of calculus, 5) with respect to Nigerian foods, there was no difference between the rainy and dry seasons in both the urban and rural communities, 6) the weaning period of the baby is decided by their mother, taking care of the health of the baby, almost all babies at one year to two years and a few at three years and 7) the menu for the breakfast, lunch and supper of the baby was made considering the nutritional aspect of the baby.journal articl
OBSERVATIONS ON STRUCTURAL FEATURES AND CHARACTERISTICS OF BIOLOGICAL APATITE CRYSTALS: 7. OBSERVATION ON LATTICE IMPERFECTION OF HUMAN TOOTH AND BONE CRYSTALS II.
Get PDFIn a series of studies to investigate the structural features of the biological crystal, such as the tooth and bone, using an electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals at near atomic resolution and showed the configuration of the hydroxyapatite structure through the cross and longitudinal sections of the enamel, dentin, and bone crystals.
Subsequently, based on the results of our observations of the ultrastructure of the tooth and bone crystals, we attempted to clarify the essential structural features and characteristics of the lattice imperfections in the hydroxyapatite structure composing of the human enamel, dentin, and bone crystals from the morphological viewpoint.
Therefore, using the same approach, we examined the images of the lattice imperfection of the normal human enamel, dentin, and bone crystals. In this report, following the previous ovservation of the lattice imperfection on the point defect structure and the dislocations appearing in the inner structure of the crystal, we describe the image of the face defect structure obtained by using the same approach from the sections of the human enamel, dentin, and bone crystals, such as the stacking fault, grain boundary , and others.
The materials used for this study were the human enamel, dentin, and bone crystals. The small cubes of the material were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800 H and H-9000 type transmission electron microscopes operated at 200 kV and 300 kV respectively. Each crystal was observed at an initial magnification of 300,000 times and at a final magnification of 10,000,000 times and over.
We sincerely believe that the electron micrographs shown in this report are the first to show the images of the lattice imperfections from the sections obtained from the hydroxyapatite crystal composing of the human enamel, dentin, and bone tissue, such as the grain boundary, stacking fault, and others, at near atomic resolution.journal articl
OBSERVATIONS ON STRUCTURAL FEATURES AND CHARACTERISTICS OF BIOLOGICAL APATITE CRYSTALS: 8. OBSERVATION ON FUSION OF HUMAN ENAMEL CRYSTALS
Get PDFIn a series of studies to investigate the basic structural features and characteristics of the biological apatite crystals, using a transmission electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals at near atomic resolution and showed the configuration of the hydroxyapatite structure through the cross and longitudinal sections of the crystals.
Subsequently, based on the results of the observations by the authors of the ultrastructure of the tooth and bone, using the same approach, we have been able to directly examine the images of the lattice imperfections in the human tooth and bone crystals, such as the point defect structure, line defect, and face defect, in the crystals.
In this report, we describe the images of the crystal fusion obtained by using the same approach from the sections of the human enamel crystals
The materials used for this study were the noncarious enamel from the freshly extracted human erupted lower first molars. The small cubes of the material were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800 H and H-9000 type transmission electron microscopes operated at 200 kV and 300 kV. Each crystal was observed at an initial magnification of 300,000 times and at a final magnification of 10,000,000 times and over.
We are, therefore, able to confirm that the fusion between the adjacent crystals can occur at some time during the life history of the human enamel.
We sincerely believe that the electron micrographs shown in this report are the first to show the ultrastructures of the crystal fusion in the human enamel crystals at near atomic resolution.journal articl
STRESS OF TOOTH AND PDL STRUCTURE CREATED BY BITE FORCE
Get PDFStress is created by the bite force and distributed along the tooth towards the PDL structure. It 1s of interest to investigate the complex tooth structure, consisting of enamel, dentine, pulp, and thin cementum layer and how it functions in stress distribution. This study was intended to analyze the role of the tooth and PDL structures in stress distribution, by using a three-dimensional finite element method. A mandibular first molar was constructed for the finite element model. The bite forces were measured by Pressensor, and these bite force values were programmed to load down upon the occlusal surface of the model. The results were expressed by stress contours and principal stress graphs. The stress was found to decrease as it distributed from the occlusal surface towards the cervical portion in the dentine and the pulp. In contrast, the stress, especially a compressive stress, increased gradually in the enamel layer in the lower half of the crown, in the same direction. It was apparent in displayed pattern of stress that the stress distributed outward towards the surrounding portion of the lower half of the crown. This resulted in a uniform magnitude of the principal stresses for all aspects of the mesial and distal roots. The stresses of both roots were generally compressive stress. When comparing the stress values of sampling points positioned between the root surfaces and the periphery of the PDL (the alveolar wall), all principal stresses for those of the PDL (periodontal ligament) were less than those of the root surfaces. These findings revealed that the PDL, the dentine, and the pulp functioned in cooperation in stress reduction; and the sequences of enamel, dentine, and pulp influenced the pattern of stress distribution. The different material properties of the tooth structure in sequence was considered a very important factor for stress reduction and for the pattern of stress distribution, especially in the root.journal articl
OBSERVATIONS ON THE STRUCTURAL FEATURES AND CHARACTERISTICS OF BIOLOGICAL APATITE CRYSTALS: 2. OBSERVATION ON THE ULTRASTRUCTURE OF HUMAN ENAMEL CRYSTALS
Get PDFIn a series of studies to investigate the structural features of biological crystals, using an electron microscope, we examined the ultrastructure of human enamel crystals at near atomic resolution through the cross and longitudinal sections of the crystals.
The materials used for this study were the middle layer of the noncarious enamel from freshly extracted human erupted permanent molars. The small cubes of the enamel were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with HITACHI H-500 and H-700 types of transmission electron microscopes operated at 125-200 kV. Each crystal was observed at the initial magnification of 300,000 times and at the final magnification of 10,000,000 times and over.
Using this approach, the authors have been able to show the configuration of the hydroxyapatite in the cross and longitudinal sections of the enamel crystals and observe the basic hexagonal pattern of the unit cell viewed down the c-axis. The authors sincerely believe that the electron micrograph shown in this report is the first atomic image to be obtained from a hydroxyapatite crystal from the human enamel, using the sections.journal articl