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H Kawakita

Publications and source records attributed to H Kawakita.

At least 19 recordsLinked to original sources
PubMed2005

Subaru telescope observations of Deep Impact.

The impact cratering process on a comet is controversial but holds the key for interpreting observations of the Deep Impact collision with comet 9P/Tempel 1. Mid-infrared data from the Cooled Mid-Infrared Camera and Spectrometer (COMICS) of the Subaru Telescope indicate that the large-scale dust plume ejected by the impact contained a large mass (approximately 10(6) kilograms) of dust and formed two wings approximately +/-45 degrees from the symmetric center, both consistent with gravity as the primary control on the impact and its immediate aftermath. The dust distribution in the inner part of the plume, however, is inconsistent with a pure gravity control and implies that evaporation and expansion of volatiles accelerated dust.

Cosmic Dust↗
PubMed2005

Deep Impact: observations from a worldwide Earth-based campaign.

On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.

Cosmic Dust↗
PubMed2002

Two novel strains of Wolbachia coexisting in both species of mulberry leafhoppers.

Wolbachia is an intracellular symbiont that causes reproductive disorders in many insects. Its presence in the leafhoppers Hishimonoides sellatiformis and Hishimonus sellatus, vectors of mulberry dwarf-Phytoplasma, was confirmed by the PCR analysis of 16S rDNA, ftsZ and wsp. Sequencing of cloned PCR products revealed that two Wolbachia strains coexist in both leafhoppers. The phylogenetic analysis of wsp revealed that these strains belong in novel positions in the B-group of Wolbachia. These strains were detected by PCR and/or PCR-RFLP in all of the tested non-genital organs including salivary glands, as well as in the tested genital organs of Hishimonoides sellatiformis. In addition, Wolbachia-like organisms were observed by electron microscopy in all PCR-positive organs. We discuss the possible horizontal transmission of Wolbachia via mulberry trees.

Animals↗
PubMed2001

The spin temperature of NH3 in Comet C/1999S4 (LINEAR).

A high-dispersion spectrum of Comet C/1999S4 (LINEAR) was obtained in the optical region with the high-dispersion spectrograph on the Subaru telescope when the comet was 0.863 astronomical units from the Sun before its disintegration. We obtained high signal-to-noise ratio emission lines of the cometary NH2 bands from which an ortho-to-para ratio (OPR) of 3.33 +/- 0.07 was derived on the basis of a fluorescence excitation model. Assuming that cometary NH2 mainly originates from ammonia through photodissociation, the derived OPR of NH2 molecules should reflect that of ammonia, which provides information on the environment of molecular formation or condensation and of the thermal history of cometary ices. Assuming that the OPR of ammonia in comets was unchanged in the nucleus, the derived spin temperature of ammonia (28 +/- 2 kelvin) suggests that a formation region of the cometary ammonia ice was between the orbit of Saturn and that of Uranus in the solar nebula.

Ammonia↗
PubMed1999

Medical check of competitive canoeists.

We gave a sports injury questionnaire survey to 821 active canoeists, members of the Japan Canoe Association (JCA), and performed a medical check of 63 top competitive JCA canoeists, including physical and laboratory tests and radiographic examinations of the chest, spine, shoulder, elbow, and wrist joints. Completed questionnaires were returned by 417 canoeists, whose reported racing styles were: kayak, 324; Canadian canoe, 71; slalom, 13; and not specified, 9. Of the 417 respondents, 94 canoeists (22. 5%) reported that they experienced lumbago; 20.9% experienced shoulder pain; 3.8%, elbow pain; and 10.8%, wrist pain. On medical examinations, lumbago was found to be mainly of myofascial origin or due to spondylolysis. Impingement syndrome was also observed in 4 canoeists with shoulder problems. The competitive canoeists had low blood pressure, and some had bradycardia. On laboratory examinations, serum hemoglobulin, hematocrit, high-density lipoprotein cholesterol (HDL-CHO), creatine phosphokinase (CK), and creatine (CRTN) in the top competitive canoeists showed high values in comparison with those of an age-matched control group. However, low serum total cholesterol (TP) values were observed in the top competitive canoeists.

Adolescent↗
PubMed1995

Transcranial magnetic stimulation of the motor cortex in cervical spondylosis and spinal canal stenosis.

STUDY DESIGN: This study investigated the clinical usefulness of motor evoked potentials and a silent period after motor evoked potentials produced by transcranial magnetic stimulation of the brain. OBJECTIVE: The results were correlated with the clinical state of the patients with myelopathy, whereas no abnormality of the conduction time was observed in the patients with spinal canal stenosis. SUMMARY OF BACKGROUND DATA: Magnetic stimulation has been widely used for examination of the descending excitatory motor pathways in the central nervous system, but little attention has been paid to cervical spondylosis and spinal canal stenosis. METHODS: Motor evoked potentials were examined in 35 normal subjects, 67 patients with cervical spondylotic myelopathy, and 24 patients with spinal canal stenosis. Motor evoked potentials were evoked by transcranial brain stimulation during relaxation and during maximum voluntary contraction of the target muscle. RESULTS: The central motor conduction time was found to correlate with the clinical state of the myelopathy patients, whereas no abnormality of the conduction time was observed in the patients with spinal canal stenosis. During maximum voluntary contraction of the target muscle, a silent period was always observed after the motor evoked potentials in the normal subjects, and its duration was markedly shortened in the myelopathy patients. CONCLUSIONS: In cervical myelopathy patients, the central motor conduction time was correlated with clinical evaluation and the silent period was significantly shortened. These findings about duration of the central motor conduction time and the silent period might be a useful parameter of spinal pathology.

Adult↗
PubMed1995

[Electrophysiological and MRI study on poor outcome after surgery for cervical myelopathy].

Occasionally, the outcome from laminoplasty for cervical spondylosis is disappointing despite an adequate operation. Before surgery, it is difficult to diagnose the pathological extent of the involvement of the spinal cord. The purpose of this study is to determine the efficacy of magnetic resonance imaging (MRI) and of the motor evoked potentials (MEPs) for the indication of the surgery and prognosis. Retrospectively, we investigated the MEPs and the MRI image of 31 patients in surgery for cervical myelopathy, involving 21 cases with cervical spondylosis and 10 cases with ossification of the posterior longitudinal ligamentum, and compared the findings from those with a poor outcome (n = 31) with the findings from those with a good outcome (n = 32). The MEPs from the thenar muscle and the tibialis anterior were evoked by transcranial magnetic brain stimulation. In the poor-outcome patients, the spinal canal was narrow and lumbar spinal canal stenosis was seen in 5 cases which required lumbar laminectomy. Before operation, the MEPs from the thenar muscle could not be evoked in 5 cases while there was a remarkably prolonged central motor conduction time in the other 26 cases. MRI revealed the deformed spinal cord in the involved area, and the signal intensity of the involved spinal cord in the T2 weighted image was remarkable high. The signal intensity ratio was significantly higher in the poor-outcome patients than in the good-outcome patients. This study suggested that a high signal intensity in the T2 weighted image and a prolonged conduction time or absence of MEPs largely corresponded to the clinical and other investigative features of myelopathy responsible for a poor outcome.

Aged↗
PubMed1995

[MEPs by transcranical magnetic stimulation in experimental acute spinal cord injury].

The efficacy of motor evoked potentials (MEPs) induced by magnetic brain stimulation was investigated experimentally for assessing acute spinal cord injury. Twenty-five rabbits were employed for the acute spinal cord injury model. Following laminectomy under intravenous and intraperitoneal anesthesia, the spinal cord at the level of the fifth lumbar vertebra wsa injured by Allen's weight drop method. MEPs from the tibialis anterior muscle (M-MEP) were recorded using bipolar electrodes: prior to the injury; immediately after the injury; at 30 min, 1 hour, 3 hours, and at 5 hours after the injury. MEPs from the spinal cord (S-MEP) were recorded proximal to and distal from the injury site using epidural tube electrodes. Subjects were divided into two groups; complete and incomplete paralysis, according to the degree of motor dysfunction at 1 week after the injury. All the 13 subjects with incomplete paralysis had shown immediately after the trauma a prolongation in the M-MEP latency, with a polyphasic wave form seen in 5 of them. In 3 cases, the amplitude of the M-MEPs was decreased without any change in wave form. In others, there was some variation in the change of wave form, but there was no relationship found between the change of wave form and the degree of motor dysfunction in this group. Histopathologically, infiltration of the inflammatory cells and diffuse hemorrhaging were seen in the gray matter of the injured spinal cord in the incomplete paralysis group. In 7 of the 10 cases with complete paralysis, the M-MEP disappeared within 3 hours. Histopathologically, large areas of the nerve cells disappeared from the gray matter in this group. The S-MEP disappeared immediately after trauma in the group with complete paralysis as well as in those with incomplete paralysis. This study indicated that MEPs taken immediately after a trauma may predict the severity of a spinal cord injury and were useful for evaluating the prognosis of motor function during the acute phase of a spinal cord injury.

Acute Disease↗
PubMed1991

Enhanced rectal and nasal absorption of human epidermal growth factor by combined use of the absorption promoter and the synthetic polymer in rats.

Previously, the presence of sodium carboxymethylcellulose (CMC Na) in addition to an absorption promoter, sodium caprate (C10 Na), in the dosing solution was found to be necessary for the enhancement of the rectal absorption of human epidermal growth factor (hEGF). In the present study, other synthetic polymers and absorption promoters were examined for their ability to enhance the rectal and nasal absorption of hEGF in rats. The effect of polymers in combined use with 100 mM C10 Na on the rectal absorption of hEGF was in the following order: 1% methylcellulose 1% hydroxypropylmethylcellulose 0.1% polyacrylic acid 1% CMC Na. Other absorption promoters such as N-lauroyl-alanine (C12-A) and dihydroxy-bile salts also enhanced the rectal absorption of hEGF in combined use with CMC Na. In order to confirm the increased rectal absorption of hEGF, the disappearance of hEGF from the rectal loop was examined. When hEGF in a 1% CMC Na solution (200 ug/kg) was administered in the rectal loop, the disappearance percent of hEGF during 60 min was 13.9% of the dose, although hEGF was not detected in the plasma. The presence of promoters such as 10 mM C10 Na or 15 mM C12-A in 1% CMC Na increased the disappearance percent to about 50% in a dosing range of hEGF from 100 to 500 ug/kg. On the other hand, a markedly enhanced nasal absorption of hEGF by 100 mM C10 Na was observed even in the absence of any polymer in a dising solution. However, addition of CMC Na into the dosing solution accelerated the rate of nasal absorption of hEGF in early phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1990

Ciliated cells in the human gastric mucosa. Evidence of metaplastic change.

In the gastric mucosa of Japanese patients, ciliated cells were found in association with intestinal metaplasia. The cells occurred frequently in the pyloric mucosa of nearly half of the cases examined but rarely in the cardiac mucosa of total 12 cases, but never adjacent to the chief cells of gastric glands. The ciliated cells were always found in the basal part of cardiac and pyloric glands, but never in the surface or in the foveolar epithelium. Furthermore, ciliated cells containing a few small mucus granules and simultaneously possessing numerous cilia and basal bodies were noted. Ciliated cells in the gastric mucosa have been found mainly in elderly Japanese patients, but were also observed exceptionally in one Chinese, two Swedes and one American. These ciliated cells are not present in the normal human gastric and intestinal mucosa, and therefore a new term, "ciliated metaplasia", is proposed for their occurrence.

Cilia↗
PubMed1990

[In vivo wear test for posterior composites. 1. Development of wear test predicting composite wear in vivo].

A wear test method based on a new concept was developed for predicting the wear rate of posterior composite restorations in vivo. The concept based on the conclusions derived from our clinical tests on posterior composites that composite restorations would be deteriorated chemically and by repeated compressive stress as well as by abrasion by food passing during mastication. New wear tests were performed on several posterior restorative materials under various conditions to compare the effect of abrasion using the tooth-brush. The results of wear rate using the present test on specimens stored in a 0.1 N-NaOH solution (37 degrees C) for 6 days were parallel to those measured in clinical tests. However, the abrasion test results obtained using a tooth-brush on deteriorated specimens did not match the clinical data. These findings suggested that degradation or aging of specimens and repeated compressive stress are necessary for the wear test to simulate the wear of posterior composites in vivo.

Composite Resins↗
PubMed1989

Ultrastructure of metaplastic ciliated cells in human stomach.

Intestinal metaplasia of the gastric mucosa occurs commonly in aged Japanese patients and has been discussed in relation to the high incidence of gastric cancer in Japanese. Ciliated cells in the gastric mucosa have frequently been found in association with intestinal metaplasia in the pyloric gland and rarely in the cardiac gland in many Japanese patients, and exceptionally in one Chinese and in one Swedish patient. Electron microscopic examination of 12 Japanese patients has revealed that these structures are not metaplastic stereocilia, but true cilia. Ciliated cells have been found in the basal part of the gastric glands and never in the surface epithelium. The fine structure of the gastric cilia was almost the same as that of normal respiratory cilia. However, in the gastric cilia, most dynein arms were inconspicuous even after tannic acid fixation, indicating that ciliary beating of the gastric cilia is problematic. Abnormal cilia and basal bodies also were found. Ciliated cells have always occurred in association with intestinal metaplasia, therefore this phenomenon might be a type of metaplasia and is named "ciliated metaplasia" of the gastric mucosa.

Aged↗
PubMed1989

Ultrastructure of the mucus-negative vacuolated cells in the metaplastic pyloric gland of the human stomach.

Mucus-negative vacuolated cells, often with apical cilia, were found in the metaplastic pyloric gland of the human stomach. These vacuoles were not stained by various mucus stains, but contained neutral fat. Electron microscopic observation revealed that the ciliated cells had prominent autophagosomes in the supranuclear region and sometimes had large vacuoles. These vacuoles were limited by a unit membrane and had electron-lucent contents consisting of small amounts of lipid droplets and lamellar bodies. The non-mucus vacuolated cells might correspond to the mature ciliated cells in which cystic degeneration of the autophagosomes occurred after digestion by lysosomal enzymes.

Cilia↗
PubMed1989

Ciliated cells in the cardiac gland of the human stomach. Evidence of metaplastic change.

In a study on 12 Japanese patients, many ciliated cells were found in the human cardiac mucosa in association with intestinal metaplasia. Two cases were studied by electron microscopy, which revealed the presence of cilia and basal bodies in the apical portion of the mucosal cells. The ciliated cells sometimes contained prominent autophagosomes in the supranuclear region and abundant filaments in the cytoplasm, but neither mucus nor neuroendocrine granules were evident. Ciliated cells have commonly been found in human pyloric mucosa showing intestinal metaplastic changes in aged Japanese patients. In the cardiac mucosa, the incidence of ciliated cells was relatively low. Ultrastructural study revealed that the metaplastic gastric cilia were almost the same as those of respiratory cilia. The presence of ciliated cells in the adult human gastric mucosa was always associated with intestinal metaplasia; therefore our interpretation is that this is a type of metaplasia, for which we propose a new term, "ciliated metaplasia" of the stomach.

Aged↗