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Biomedical subjects

J Katayama

Publications and source records attributed to J Katayama.

At least 37 records · Page 2Linked to original sources
PubMed1996

Cloning and nucleotide sequence of the mphB gene for macrolide 2'-phosphotransferase II in Escherichia coli.

Macrolide 2'-phosphotransferase II [MPH(2')II] inactivates macrolide antibiotics. The mphB gene for MPH(2')II was cloned from Escherichia coli and sequenced. Analysis of the nucleotide sequence indicated that mphB encoded a protein of 302 amino acids with a molecular mass of 34483 Da. The carboxy terminal region of the deduced protein contained a sequence that resembled a conserved functional domain in aminoglycoside phosphotransferases.

Amino Acid Sequence↗
PubMed1996

Two components of metabotropic glutamate responses in acutely dissociated CA3 pyramidal neurons of the rat.

The excitatory and inhibitory actions of metabotropic glutamate receptor (mGluR) agonists were investigated in acutely dissociated rat hippocampal CA3 pyramidal neurons, using the conventional whole-cell and nystatin-perforated patch recording configurations under the voltage-clamp condition. With the conventional whole-cell recording, glutamate (Glu) and quisqualic acid (QA) induced only ionotropic inward currents accompanied by increased membrane conductance at a holding potential (VH) of -45 mV. The response was reversibly blocked in the presence of D-2-amino-5-phosphonopentanoic acid (D-AP5) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the antagonists of N-methyl-D-aspartate (NMDA) receptor and non-NMDA receptor, respectively. With nystatin-perforated patch recording, mGlu responses insensitive to both D-AP5 and CNQX were observed. Fifty-five % of the cells responded by a slow inward current accompanied by conductance decrease (ImGlui) at a VH of -44 mV. One % of the neurons showed an outward current with conductance increase (ImGluo), and 34% of the neurons showed ImGluo followed by ImGlui. The onset of ImGluo occurred approximately 900 ms after the response to 30 mM K+. The time to peak of ImGluo were 32- to 79-times longer than those of ionotropic responses. ImGlui appeared at lower concentrations than ionotropic Glu responses, whereas ImGluo appeared at similar concentrations as ionotropic responses. The rank order of affinity was QA > Glu > (+/-)-1-aminocyclopentane-trans-1, 3-dicarboxylic acid (tACPD) for both ImGlui and ImGluo. Half-maximal effective concentrations (EC50) and the threshold concentrations for the three agonists were four- to tenfold lower for ImGlui than for ImGluo. The current-voltage relationship showed that the reversal potentials of ImGlui and ImGluo shifted 55 and 59 mV, respectively, for a tenfold change in extracellular K+ concentration, indicating that K+ is the charge carrier of both mGlu responses. During ImGlui, both the leakage current and muscarine-sensitive voltage-dependent K+ current (M current) were suppressed. ImGluo induced by 10(-4) M tACPD was abolished by 3.10(-7) M charybdotoxin and 10(-6) M ryanodine. These results show that there are two components of mGlu responses in CA3 pyramidal neurons and that ImGlui and ImGluo show different pharmacological properties.

Animals↗
PubMed1996

P300, probability, and the three-tone paradigm.

The effects of stimulus probability on P300 from a 3-tone paradigm were examined in two experiments. Experiment 1 manipulated the probability of the non-target tone as 0.10, 0.45, or 0.80, while the target tone probability was always 0.10. Experiment 2 manipulated the probability of 3 tones as 0.10, 0.30, or 0.60, with one of the infrequent tones assigned as the target in each condition. Subjects were required to press a button in response to the target stimulus in both experiments. The results indicated that the P300 to the target and the non-target were both affected by the probability of the eliciting stimulus, such that component amplitude was inversely related to probability; no reliable P300 latency effects were found. Target tones elicited larger P300 amplitude than the non-target tones at the same probability. The findings suggest that probability effects on P300 amplitude are independent of responding to a specific target stimulus and are discussed with reference to the clinical utility of the 3-tone paradigm.

Acoustic Stimulation↗
PubMed1996

[Functional imaging of the sensorimotor cortex using an ultra-fast MR imaging method].

UNLABELLED: The aim of this study was to assess changes in brain activity during a motor task and variable sensory stimulation using echo planar imaging, which represents the fastest clinically usefull imaging technique available. MATERIALS AND METHODS: The subjects of this study were 11 healthy-volunteers, 4 males and 11 females, with an average of 26.4 years. The subjects were instructed to tap the fingers of one hand as the motor task. Compressed air was applied 5 times a second as "simple" sensory stimulation. Simple figures were drawn on the subjects palm as "complex" sensory stimulation. In all cases, functional imaging was performed by T2*-weighted echo planar imaging (TE = 53 msec, TR = 3000 msec, flip angle = 90 degrees, matrix 64 x 64, FOV = 205 mm, slice thickness = 8 mm) alternately at rest and during the task (intervals: 30 sec). A total of 60 images was collected in 3 minutes. Images obtained by subtracting images at rest and during the task were analyzed. RESULTS AND DISCUSSION: Almost all subjects showed a transient signal increase in the contralateral paracentral region during simple sensory stimulation. Continuous signal increases in the contra- and/or ipsi-lateral para-central region were observed during complex sensory stimulation. Some exhibited signal increases in the parietal or frontal association cortex, but they disappeared when subject's attention was distracted during stimulation. All subjects displayed signal increases in the contralateral para-central region during the motor task. Some of them exhibited signal increases in the medial frontal area (supplementary motor area) and ipsilateral para-central region. These results suggest that the signal increases of functional MRI reflect not only simple reactions to stimulation but higher cerebral function as well.

Adult↗
PubMed1995

Effect of rat thyroid proliferative lesion development by intermittent treatment with sulfadimethoxine.

To determine whether production of thyroid proliferative lesions would be enhanced by intermittent rather than continuous treatment with a goitrogen, male F344 rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN, 2800 mg/kg body weight, single s.c. injection) were given water containing 0.1% sulfadimethoxine (SM) for 20 weeks (group 1) or 0.1% SM for the first 8 weeks followed by 2 cycles consisting of 2 weeks withdrawal and 4 weeks retreatment with 0.1% SM (group 2). Control rats (group 3) were untreated for 20 weeks after the DHPN initiation. Serum T3 and T4 levels were significantly decreased in groups 1 and 2 compared to group 3. Serum thyroid stimulating hormone level was significantly increased in all treated groups compared to group 3. The numbers of follicular cell hyperplasias were significantly increased in group 2 compared to group 1. BrdU labeling indices for follicular cells and hyperplasias were also significantly elevated in group 2 compared to group 1. Electron microscopic examination of thyrotrophs in the anterior pituitary in groups 1 and 2 revealed dilated rough ER cisternae with intracisternal dense granules. The number of intracytoplasmic secretory granules in group 2 was moderately decreased compared to group 1. Therefore, the results of the present study suggest that it may be possible to enhance production of thyroid neoplastic lesions by intermittent treatment.

Animals↗
PubMed1993

The measurement of intracellular sodium ion concentration in the horizontal cells of the stingray retina.

Membrane potentials, and intracellular concentrations of sodium ions in the horizontal cells of the stingray retina were measured directly by means of ion-selective microelectrodes. The electrodes used were of the double-barreled type and bis[(12-crown-4)methyl]methyldodecylmalonate was used as the ion-selective resin. The average intracellular concentration of Na+ ions in the horizontal cells and the extracellular concentration of Na+ ions near the horizontal cells were 123 mM and 351 mM, respectively (n = 27). The equilibrium potential was estimated to be +27.3 mV. Although each value of the equilibrium potential was scattered over a wide range, they were always positive regardless of the membrane potential. This was the first direct measurement of the sodium ion-concentration for the retinal horizontal cells. The results support the idea that the origin of the dark depolarization of the stingray horizontal cell is caused by the glutamate-induced high-sodium conductance of the membrane.

Animals↗
PubMed1992

Negative brain potentials elicited by an unexpected color patch or word.

The purpose of this study was to examine whether a physical stimulus that deviates from a semantic context can elicit the N400 component of event-related brain potentials (ERPs). ERPs were recorded while 12 students judged the veracity of a simple statement (e.g., red/is not/blue) presented with the order of subject (S), object (O), and verb (V), which is normal in Japanese grammar. In one condition, S was a color patch and O was a word representing the color, while in the other condition, S was a color name and O was a patch. In both conditions, a late additional negative potential was elicited by the O stimulus when it was mismatched with S. In addition, the negativities elicited by the incongruous color patch and word had the same morphology and scalp distribution. The results indicate that not only a word but a physical stimulus which deviates from a semantic context can elicit the N400 component.

Adult↗
PubMed1992

Intracellular and extracellular chloride ions in the horizontal cells of the stingray retina.

Intracellular and extracellular concentrations of chloride ([Cl-]i, [Cl-]o) ions in the horizontal cells of the stingray retina were studied by means of ion-selective microelectrodes. The electrodes used were of the double-barreled type and Corning's #477315 resin was used as the exchanger. The average [Cl-]o and [Cl-]i in the L-type cells were 320 and 130 mM, respectively (n = 37), and the equilibrium potential (ECl) was calculated as -23.3 mV. In some cases, dark membrane potentials were more positive than the ECl. With white light stimulus, the membrane hyperpolarized to a more negative level than ECl. Based on the experiments described above, the hypothesis that the hyperpolarizing response of horizontal cells is due to the permeability change of the membrane to chloride ion was excluded in the stingray retina.

Animals↗
PubMed1991

Negative brain potentials reflect the subjective distance between standard and deviant tones.

The purpose of this study was to examine the effects on event-related brain potentials (ERPs) of occasionally presented deviants in a sequence of tones. The sequence consisted of a series of frequent standard C5 tones from the diatonic musical scale, in which three deviants (F #5, C6, and F #6) and a target (C4) were occasionally embedded. Twenty subjects were asked to detect the target. The deviants elicited frontal N2. The amplitude of the N2 was smaller for C6 than for the other two deviants, whereas peak latencies increased as a function of the frequency distance between the deviant and the standard. The smaller N2 to C6 than that to the other deviants was considered to reflect closer subjective distance due to the octave relationship between C6 and the standard C5.

Adult↗
PubMed1987

Sentence verification and event-related brain potentials.

The purpose of this study was to examine whether the decision process affected scalp recorded event-related brain potentials (ERPs). ERPs were recorded while 10 subjects evaluated the veracity of four types of Japanese sentences; true-affirmative (TA), true-negative (TN), false-affirmative (FA), and false-negative (FN). Each sentence was presented visually, one word at a time in the following order: Subject (S); object (O); and verb (V). This order of words, which is normal in Japanese grammar, allowed the ERP waveforms associated with semantic mismatch between the S and O occurring in the middle of the sentence to be separated from those elicited by the decision concerning the sentence's truth or falsity occurring at the end of the sentence. Semantic mismatch was associated with a negative component (N310) following the O-word. In addition, P3s were elicited by sentence final words. Affirmative sentences elicited larger P3s than did negative sentences, and true sentences elicited earlier P3s than did false sentences. P3s were smaller in amplitude when they followed a mismatch between the S and O words. The result suggested that by using Japanese sentences, it may be possible to examine sentence-level rather than word-level processes.

Adult↗
PubMed1985

[A report of five cases of multiple cancer with hematologic malignancies].

Five patients with multiple cancers that included hematologic malignancies are described. The incidence of multiple cancers in hematologic malignancies has been 8.8% in the past two and a half years at our hospital. The combinations were: 1) primary bilateral breast cancers and acute monocytic leukemia; 2) breast cancer, malignant lymphoma and gastric cancer; 3) malignant lymphoma and gastric cancer; 4) malignant lymphoma and prostate cancer, and 5) colon cancer and multiple myeloma. Our experience suggests an increasing incidence of multiple cancer in hematologic malignancies.

Aged↗
PubMed1982

Wegener's granulomatosis: successful treatment with high-dose cyclophosphamide.

A 30-year-old male taxi driver developed extensive purpuric necrotic lesions all over his body. He had a consolidated shadow in the right upper lung field, proteinuria with microscopic hematuria, and granulomatous change in the nasal mucosa. The standard regimen of prednisolone alone or in combination with cyclophosphamide showed only a limited effect on the lesion. However, weekly intravenous injections of a high dose of cyclophosphamide (500 mg/week) in combination with 60 mg/day of prednisolone exhibited dramatical suppression of the disease activity.

Adult↗