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Biomedical subjects

K Hibino

Publications and source records attributed to K Hibino.

At least 19 recordsLinked to original sources
PubMed2006

Anisotropy and corotation of galactic cosmic rays.

The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.

Journal Article↗
PubMed2004

Observation by an air-shower array in Tibet of the multi-TeV cosmic-ray anisotropy due to terrestrial orbital motion around the Sun.

We report on the solar diurnal variation of the galactic cosmic-ray intensity observed by the Tibet III air shower array during the period from 1999 to 2003. In the higher-energy event samples (12 and 6.2 TeV), the variations are fairly consistent with the Compton-Getting anisotropy due to the terrestrial orbital motion around the Sun, while the variation in the lower-energy event sample (4.0 TeV) is inconsistent with this anisotropy. This suggests an additional anisotropy superposed at the multi-TeV energies, e.g., the solar modulation effect. This is the highest-precision measurement of the Compton-Getting anisotropy ever made.

Journal Article↗
PubMed2000

Spatial differences and seasonal changes of net carbonate accumulation on some coral reefs of the Ryukyu Islands, Japan.

This study sought to understand short-term spatial changes in accretion and erosion on (experimental) carbonate blocks on three coral reefs of the Ryukyu Islands, Japan. The principal objectives were to differentiate net accretion/erosion according to season, location, depth and substrate-type. At all locations the summer season showed more positive net weight changes and higher coralline algal coverage than the winter season. Windward reefs revealed higher net accretion and higher coralline algal coverage than leeward reefs. Massive (Holocene) Porites blocks showed highest net loss, followed by Pleistocene carbonate and (Holocene) Acropora blocks. High population densities of Echinometra mathaei (de Blainville) were recorded on reefs adjacent to large human populations and overall net carbonate loss significantly correlated to densities of E. mathaei type A.

Journal Article↗
PubMed2000

EMG activities of two heads of the human lateral pterygoid muscle in relation to mandibular condyle movement and biting force.

Electromyographic (EMG) activities of the superior (SUP) and inferior heads (INF) of the lateral pterygoid muscle (LPT) were recorded in humans during voluntary stepwise changes in biting force and jaw position that were adopted to exclude the effects of acceleration and velocity of jaw movements on the muscle activity. The SUP behaved like a jaw-closing muscle and showed characteristic activity in relation to the biting force. It showed a considerable amount of background activity (5-32% of the maximum) even in the intercuspal position without teeth clenching and reached a nearly maximum activity at relatively lower biting-force levels than the jaw-closing muscles during increment of the biting force. Stretch reflexes were found in the SUP, the function of which could be to stabilize the condyle against the biting force that pulls the condyle posteriorly. This notion was verified by examining the biomechanics on the temporomandibular joint. The complex movements of the mandibular condyle in a sagittal plane were decomposed into displacement in the anteroposterior direction (Ac) and angle of rotation (RAc) around a kinesiological specific point on the condyle. In relation to Ac, each head of the LPT showed quite a similar behavior to each other in all types of jaw movements across all subjects. Working ranges of the muscle activities were almost constant (Ac <3 mm for the SUP and Ac >3 mm for the INF). The amount of EMG activity of the SUP changed in inverse proportion to Ac showing a hyperbola-like relation, whereas that of the INF changed rather linearly. The EMG amplitude of the SUP showed a quasilinear inverse relation with RAc in the hinge movement during which the condyle rotated with no movement in the anteroposterior direction. This finding suggests that the SUP controls the angular relationship between the articular disk and the condyle. On the other hand, the position of the disk in relation to the maxilla, not to the condyle, is controlled indirectly by the INF because the disk is attached to the condyle by tendinous ligaments.

Adult↗
PubMed2000

Midgut malrotation in adulthood.

A 29-year-old man was admitted to our hospital with a history of recurrent right upper quadrant abdominal pain and vomiting. These symptoms appeared intermittently for 7 years. Various examinations revealed a diagnosis of midgut malrotation. Laparotomy was performed and revealed reverse rotation of the duodenum with paraduodenal hernia and a normal rotating colon. This case suggests that recurrent abdominal complaints in an adult should arouse suspicion of midgut malrotation.

Abdominal Pain↗
PubMed1999

Observation of Multi-TeV Gamma Rays from the Crab Nebula using the Tibet Air Shower Array.

The Tibet experiment, operating at Yangbajing (4300 m above sea level), is the lowest energy air shower array, and the new high-density array constructed in 1996 is sensitive to gamma-ray air showers at energies as low as 3 TeV. With this new array, the Crab Nebula was observed in multi-TeV gamma-rays and a signal was detected at the 5.5 sigma level. We also obtained the energy spectrum of gamma-rays in the energy region above 3 TeV which partially overlaps those observed with imaging atmospheric Cerenkov telescopes. The Crab spectrum observed in this energy region can be represented by the power-law fit dJ&parl0;E&parr0;&solm0;dE=&parl0;4.61+/-0.90&parr0;x10-12&parl0;E&solm0;3 TeV&parr0;-2.62+/-0.17 cm-2 s-1 TeV-1. This is the first observation of gamma-ray signals from point sources with a conventional air shower array using scintillation detectors.

Journal Article↗
PubMed1994

[Hemodynamic TIA associated with severe anemia--a case report].

A 62-year-old man developed recurrent TIAs presenting as mild unconsciousness, dysarthria and weakness of the right upper extremity lasting for 15 to 20 minutes. He was found to have severe iron deficiency anemia (hemoglobin: 5.5-5.9g/dl; hematocrit: 18.4-19.5%) which insidiously developed through the chronic bleeding from the gastric ulcer. He had slight hypertension (184/86mmHg), but no orthostatic hypotension. DSA and MR angiography showed severe stenosis at the origin of the bilateral internal carotid arteries and of the left vertebral artery. There was also hypoplasia of the right vertebral artery. Blood circulation detected by 123I-IMP-SPECT was markedly decreased in the whole brain and in the right hemisphere of the cerebellum. TIA was, however, completely disappeared following to the recovery of anemia. The present case suggested that the presence of severe anemia accelerated the occurrence of hemodynamic TIA (regional cerebral anemic hypoxia), which is probably the consequence of the reduced oxygen-transporting capacity of the blood.

Aged↗
PubMed1990

[Fundamental properties of the human lateral pterygoid muscle activity and quantitative observation in relation to vertical dimension and bite force].

The purpose of this study is to investigate the fundamental property of the superior head of the lateral pterygoid muscle (LPT) of the human beings. The experiments were performed on 6 subjects. Electromyographic activity of the superior head of LPT were simultaneously recorded with masseter, temporal and digastric muscle. The findings may be summarized as follows: 1. Superior head of LPT showed the maximum activity during closing and clenching. 2. Superior head of LPT showed remarkable tonic activity at rest position and notable activity during swallowing and passive retrusion. 3. Superior head of LPT activity was related to vertical dimension and bite force quantitatively, but such relationship was quite different from masseter and temporal muscle. 4. Jaw-jerk reflex was evoked by mechanical chin tap in the superior head of LPT, masseter and temporal muscle showing identical time course. 5. Periodontal excitatory reflex was evoked by mechanical tooth stimulation in the superior head of LPT and temporal muscle. From these findings it was concluded that superior head of LPT was qualitatively similar to but quantitatively distinct from jaw closing muscles such as masseter and temporal muscle.

Bite Force↗
PubMed1989

[Study of a particle counting method for index of masticatory efficiency].

The present report discusses our new simplified measuring method of masticatory efficiency by counting particles in the matter of making test materials and the standard equation for subjects with normal dentition. 1. Two kinds of hydrocolloid impression materials, reversible and irreversible, were used as the test materials. 2. For evaluating the shape of test materials, 12 subjects with normal dentition were tested and for calculating the standard equation, 108 subjects with normal dentition were tested. 3. Each subject was investigated by the simplified method of counting particles through a sieve system. The number of remaining particles on the mesh was calculated as a masticatory performance. 4. As indicated in a previous report by Dr. Ozawa about cubical test materials, columnar test materials are easier to make than the others and these were avairable for the present particle counting method for investigating masticatory efficiency. 5. We obtained the standard equation for both kinds of test material using 108 subjects with normal dentition. To simplify the measuring method, we selected the standard equation of a 5-mesh sieve with 10 strokes chewing for the index of masticatory efficiency. The standard equation of a 5-mesh sieve for both test materials are as follows; 1) Reversible hydrocolloid test material: Y = -1.605X+29.058 2) Irreversible hydrocolloid test material: Y = -1.116X+23.868 6. 5, 10-mesh sieve with 10 strokes chewing showed the smallest variation in the individual coefficient of variation with both kinds of test material.

Colloids↗
PubMed1988

Age-dependent effect of UV light in abnormal alpha neoprotein formation in the lens.

The aim of this study was to determine whether or not alpha neoprotein formation can occur in the lens in response to a photolytic process. Alpha crystallin from young calf and aged bovine lenses was irradiated for up to 22 hours with UV light. After cortical alpha crystallin had been irradiated, it completely preserved its quaternary antigenic determinants. In contrast, 24.3% of the bovine nuclear alpha crystallin completely lost their quaternary determinants as a result of irradiation. The latter population of molecules still preserved the association of A chains with B chains, suggesting the formation of abnormal proteins. The exposure to UV irradiation can cause the formation of alpha neoproteins from aged but not from young alpha crystallin. Comparison of photolytic rates based on spectroscopic and chromatographic parameters also show an age-related increase in the susceptibility of alpha crystallin to photolyze. It is suggested that this increase is due to the age-related formation of a photosensitizer in alpha crystallin.

Aging↗
PubMed1976

Hybridization of glyceraldehyde-3-phosphate dehydrogenase in borate.

Conditions for the hybridization of glyceraldehyde-3-phosphate dehydrogenase (GPD) [EC 1.2.1.12] in the presence of dilute borate were examined with horseshoe crab and rabbit GPDs. Hybridization was strongly dependent upon pH, borate concentration, and temperature. The optimum medium for hybridization was 10mM Tris-HCl-1 mM 2-mercaptoethanol-1mM EDTA containing 10-20 mM borate, pH 8.5-9.0. Hybridization was performed by incubation of two electrophoretically distinct GPDs at 30 degrees for 3-15 hr in the above medium at a protein concentration of 1-2 mg/ml. The time course of hybridization was analyzed under the optimized conditions. Symmetrical A2B2-type hybrid appeared only 5 min after incubation for 1 hr. Hybridization of GPDs from 7 different species was examined under the optimal conditions. Hybridization was detected with rabbit-horseshoe crab, yeast-rabbit, yeast-chicken, and chicken-horseshoe crab combinations. Subunit-subunit interaction, the mechanism of hybridization, and the structure of GPD are discussed based on the results obtained.

Animals↗