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Biomedical subjects

T Ichijo

Publications and source records attributed to T Ichijo.

At least 19 recordsLinked to original sources
PubMed1995

The effect of interleukin-1 beta on the efferent activity of the vagus nerve to the thymus.

The effects of intravenous (i.v.) administration of recombinant human interleukin-1 beta (rhIL-1 beta) and human interleukin-1 beta-fraction (hfrIL-1 beta) on the activity of vagal efferent fibers innervating the thymus were observed in urethane-anesthetized rats. An i.v. injection of 10 ng rhIL-1 beta or hfrIL-1 beta caused a similar degree of increase in the efferent activity, which lasted longer than 2 h. The least effective dose was 1 ng and dose-dependent responses were observed after i.v. injection of rhIL-1 beta at doses of 1 ng, 10 ng and 100 ng. The IL-1 beta-induced activation of efferent activity of the vagal branch to the thymus implicates their involvement in the neural modulation of the thymic function.

Animals↗
PubMed1995

Intracerebroventricular injection of prostaglandin E2 increases splenic sympathetic nerve activity in rats.

The effects of central administration of prostaglandin E2 (PGE2) and its selective agonists on splenic sympathetic nerve activity (SNA) were investigated in urethan- and alpha-chloralose-anesthetized rats. An intra-third-cerebroventricular (13V) injection of PGE2 (0.1-10 nmol/kg) increased splenic SNA in a dose-dependent manner. An I3V injection of an EP1 agonist, 17-phenyl-omega-trinor PGE2 (1-30 nmol/kg), also resulted in a dose-dependent increase in splenic SNA, with a time course similar to that of PGE2-induced responses. In contrast, EP2 agonists, butaprost (10-100 nmol/kg I3V) and 11-deoxy-PGE1 (10-100 nmol/kg I3V), had no effect on splenic SNA. An I3V injection of M & B-28767 (an EP3/EP1 agonist, EP3 >> EP1) increased splenic SNA only at high doses (10-100 nmol/kg). Pretreatment with an EP1 antagonist, SC-19220 (200 and 500 nmol/kg), completely blocked the responses of splenic SNA to PGE2 (0.1 nmol/kg) and M & B-28767 (10 nmol/kg), respectively. These findings indicate that brain PGE2 increases splenic SNA through its action on EP1 receptors.

Animals↗
PubMed1994

Central interleukin-1 beta enhances splenic sympathetic nerve activity in rats.

The central administration of immune cytokines such as interleukin-1 (IL-1) and interferon-alpha (IFN-alpha) results in the suppression of peripheral cellular immunity, which depends, at least partly, on the sympathetic nervous activity. An intrathird cerebroventricular (I3V) infusion of recombinant human IL-1 beta (rhIL-1 beta) (1-5 ng/rat) elicited a dose-dependent increase in the electrical activity of the splenic sympathetic nerve in urethane and alpha-chloralose anesthetized rats. The effect of rhIL-1 beta (1 ng/rat) was completely blocked by pretreatment with an IL-1 receptor antagonist (1 microgram/rat, I3V 10 min before rhIL-1 beta), sodium salicylate (1 microgram/rat), or alpha-melanocyte stimulating hormone (alpha-MSH) (400 ng/rat). Furthermore, an antagonist of corticotropin-releasing factor (CRF), alpha-helical CRF9-41 (2 micrograms/rat), completely abolished the rhIL-1 beta-induced increase in the splenic nerve activity, although an I3V infusion of CRF (1 microgram/rat) excited it. These results suggest that IL-1 beta in the brain activates splenic sympathetic activity by its receptor-mediated and prostaglandin-dependent action that is sensitive to alpha-MSH, depending on CRF system. Our findings, together with the previous results, suggest that the splenic sympathetic nerve represents one of the communication channels from the brain to the immune system.

Analysis of Variance↗
PubMed1992

Observations on the structural features and characteristics of biological apatite crystals. 2. Observation on the ultrastructure of human enamel crystals.

In 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.

Dental Enamel↗
PubMed1991

Assessment of age-dependent changes in circadian blood pressure rhythm in patients with essential hypertension.

The effects of age on the circadian blood pressure rhythm of patients with untreated essential hypertension (n = 133, World Health Organization stage I or II) were compared with those of normotensive subjects (n = 91). Subjects were classified into three groups by age: young (less than 40 years old), adult (40-59 years old) and old (greater than or equal to 60 years old). Blood pressure was monitored every 5 min for 24 h, using a finger volume oscillometric device under fixed external conditions. The single cosinor method was used to evaluate circadian rhythm. There was no difference in the amplitude of circadian systolic or diastolic blood pressure rhythm among the different normotensive and essentially hypertensive age groups although a wide distribution of amplitude was noted within each group. The distribution of amplitude was wider in the hypertensive than in the normotensive groups. The amplitude of circadian blood pressure rhythm was independent of the mesor level. On the other hand, the amplitude of circadian heart rate rhythm decreased with increasing age both in normotensive subjects (P less than 0.05, young versus adult or old) and hypertensive patients (P less than 0.01, young and old versus adult). The acrophase of circadian systolic blood pressure rhythm in young hypertensives was greater than that in adult or old hypertensives (P less than 0.05, for both). Such age-dependent changes were not observed in the normotensive groups. Consequently, the acrophase of circadian systolic or diastolic blood pressure rhythm in young hypertensives was larger than that in young normotensives (P less than 0.05, for both systolic and diastolic blood pressure).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Dental anthropological study of Mongoloid in China].

The purpose of this study was to evaluate the craniofacial and occlusal characteristics of the inhabitants in China. The material consisted of cephalograms, pantomograms, dental casts and anthropological measurements taken from 517 inhabitants: 416 Han Chinese in Beijing, Shanghai, Guangzhou and Changchun and 101 Mongolians in Hohhot. The data were compared among the above five regions and also with the Japanese data. The findings were summarized as follows: I. Craniofacial characteristics; a) The Han Chinese and the Mongolians showed brachycephaly. b) The inhabitants in Guangzhou showed a tendency of bimaxillary protrusion with a smaller facial height, and the inhabitants in Changchun showed a larger gonial angle with a larger facial height than those of the other regions. c) The Mongolians had a larger value of the saddle angle and of the bi-gonial breadth. d) Compared with the Japanese, their craniofacial complex was characterized by a larger facial angle, smaller mandibular plane angle and a smaller gonial angle. II. Occlusal characteristics; a) The inhabitants in China had a similar tendency in the dental arch form and in the dental trait frequency. b) The inhabitants in Beijing had a larger mesiodistal crown-diameter of the anterior teeth than those in the other regions. c) Compared with the Japanese, their teeth were characterized by a smaller mesiodistal crown-diameter (especially on the upper first molar), higher frequency of shovel-shape and lower frequency of Carabelli's tuberculum.

Adolescent↗
PubMed1991

Ultrastructural observation on matrix fibers in the condylar cartilage of the adult rat mandible.

In this study, ultrastructural and immunohistochemical studies were performed on the adult rat (15 weeks old) mandibular condyle, with particular attention to the matrix fibers in the condylar cartilage. The fibrous zone had thick collagen fibrils which formed fibril bundles. These collagen fibrils consisted mainly of Type I collagen. From the proliferative zone to the mature zone, the density of the collagen fibrils became higher. In the hypertrophic zone, thick collagen fibrils were formed around the chondrocytes. Immunohistochemical study indicated that these collagen fibrils consisted mainly of Type I collagen. Therefore, it was confirmed that the hypertrophic chondrocytes in this tissue had one of the osteoblastic phenotypes.

Animals↗
PubMed1990

Observations on the structural features and characteristics of biological apatite crystals. 1. Observation on the shape and arrangement of the cross sectioned enamel crystals.

In a series of studies to investigate the structural features of biological crystals, using transmission electron microscope, the observations have been made on the shape and arrangement of the cross-sectioned crystal obtained from cross sections through the body of adult human enamel rod, in the surface layer, and in the middle and deep layers. The shapes of the cross sectioned crystals in the surface layer of the enamel are generally different from those in the middle and deep layers. In the surface layer of the enamel, the cross sectioned crystals show a considerable variation in shape and size, and have an irregular shape. The crystals are densely packed. Each crystal is adjacent to the neighboring one, and usually, the arrangement of crystals have an appearance rather like a "stone wall". In contrast, the cross sectioned enamel crystals in the middle and deep layer, are somewhat small than those in the surface layer, and have greater gaps between the crystals. In the middle and deep layers of the enamel, it is rare for the shapes of the crystals to be irregular, therefore, they retain their original shape, most of which are long and hexagonal.

Dental Enamel↗
PubMed1989

[Dental anthropological study of the Central American Indians].

The purpose of this study was to evaluate the dento-craniofacial morphology and the occlusal characteristics in the Central American Indians from the dental-anthropological point of view. The sample consisted of cephalograms, pantomograms, dental casts, photos and records (anthropometric measurements and oral examinations) which were taken from 210 modern Central American Indians and 212 ancient Central American Indians. The results were summarized as follows: 1. Craniofacial morphology: The modern Central American Indians showed; (1) smaller facial height and shorter depth of the cranial base and jaws than those of the Caucasians. (2) posterior position of peri-orbital structures, and smaller values of anterior facial height in comparison with the Japanese, which were similar to the Peruvian Indians. (3) shorter depth of the jaws and prominence of the chin than the ancient Central American Indians. 2. Dental arch form and tooth size: The modern Central American Indians had; (1) wider dental arches than the Caucasians, while sharing similar values with the Peruvian Indians and the Japanese. (2) smaller incisors, larger premolars and molars in the mesio-distal crown diameter compared with the Caucasians. (3) smaller teeth in the mesio-distal crown diameter than the ancient Central American Indians. 3. Occlusal conditions: The modern Central American Indians showed a good mesio-distal relationship between the upper and lower first molars in 70 percent.

Adolescent↗
PubMed1983

The ultrastructure and hardness of the transparent layer of human carious dentin.

The ultrastructure of the transparent layer of carious dentin was investigated in relation to hardness. This layer was the deeper part of the intermediately-softened inner carious dentin. Intratubular deposition of fine crystals was initially observed at the uppermost layer of normal dentin, increased in the subtransparent layer, and gradually shifted to deposition of rhomboid-shaped crystals in the transparent layer. Crystals were not seen in the tubules in the overlying discolored layer. Softening, due to demineralization of the intertubular and peritubular dentin, started at the bottom of the subtransparent layer and increased in the outward direction.

Crystallization↗
PubMed1982

Digital processing methods for structural analysis of an electron micrograph.

Digital processing method using the scanning-densitometer with microcomputer provides a useful description system. It draws attention to the usefulness of local lattice averaging in clarifying images of periodic structures in crystals as well as crystalloids and para crystalline arrays in biological specimens. Digital processing of lattice images in crystal structures from the selected diffraction spots is successfully developed to the structural analysis of evaporated gold, graphitized carbon and human tooth enamel of hydroxyapatite. Furthermore, known microbody crystalloids in enzyme and icosahedral capsids in virus are confirmed and clarified by the procedure of selecting diffraction spectra transformed from the information taken with high resolution electron micrographs. The processed results can provide significant improvements in structural analysis of an electron micrograph.

Crystallography↗