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Biomedical subjects

Y Okamoto

Publications and source records attributed to Y Okamoto.

At least 289 records · Page 16Linked to original sources
PubMed1997

Adenosine-sensitive atrial reentrant tachycardia originating from the atrioventricular nodal transitional area.

INTRODUCTION: Atrial tachycardia shows wide variations in its electrophysiologic properties and sites of origin. We report an atrial tachycardia with ECG manifestations and electrophysiologic characteristics similar to an atypical form of AV nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS: This supraventricular tachycardia was observed in 11 patients. It was initiated by atrial extrastimulation with an inverse relationship between the coupling interval of an extrastimulus and the postextrastimulus interval. Its induction was not related to a jump in the AH interval, and its perpetuation was independent of conduction block in AV node. Ventricular pacing during tachycardia demonstrated AV dissociation without affecting the atrial cycle length. A very small dose of adenosine triphosphate (mean 3.9 +/- 1.2 mg) could terminate the tachycardia. The earliest atrial activation during tachycardia was recorded at the low anteroseptal right atrium with a different intra-atrial activation sequence from that recorded during ventricular pacing, where the tachycardia was successfully ablated in 9 of 10 attempted patients. Bidirectional AV nodal conduction remained unaffected after successful ablation. CONCLUSION: There may be an entity of adenosine-sensitive atrial tachycardia probably due to focal reentry within the AV node or its transitional tissues without involvement of the AV nodal pathways. This tachycardia can be ablated without disturbing AV nodal conduction from the right atrial septum.

Adenosine↗
PubMed1997

Pulmonary endothelial thiazine uptake: separation of cell surface reduction from intracellular reoxidation.

The objective of this study was to further evaluate the hypothesis that the accumulation of thiazine dyes, such as methylene blue, by cultured bovine pulmonary arterial endothelial cells involves reduction on the cell surface, followed by diffusion of the lipophilic reduced form of the dye into the cells and intracellular reoxidation to the relatively membrane-impermeant hydrophilic form. The specific question addressed was whether inhibition of methylene blue uptake by cyanide and azide is via inhibition of extracellular reduction or inhibition of intracellular reoxidation. We used the cell membrane-impermeant ferricyanide ion as a secondary electron acceptor to measure the extracellular reduction of methylene blue independently from its uptake by the cells. In addition, toluidine blue O, incorporated into an acrylamide polymer so that it could not permeate the cells in either its reduced or oxidized forms, was used to examine the effects of cyanide and azide on the extracellular reduction. Microscopic observations of the effect of the inhibitors on the intracellular accumulation of methylene blue were also made. The results indicate that the reduction and intracellular sequestration are separate processes and that, in doses that inhibited intracellular reoxidation, and therefore uptake and sequestration, neither cyanide nor azide had an inhibitory effect on extracellular reduction. The intracellular distribution of the observable oxidized form of the dye was consistent with oxidation of the reduced dye within subcellular organelles. The demonstration that extracellular reduction and intracellular sequestration are separate events is consistent with the hypothesized sequence of events.

Acrylic Resins↗
PubMed1997

A simple quantitative measurement of mRNA of human beta-actin by reverse transcription competitive PCR with a compact digital camera.

Reverse transcription (RT) competitive polymerase chain reaction (PCR) is a sensitive and useful technique for the absolute quantitation of mRNA level. We developed a competitive PCR method with a compact digital camera DC 40 (Eastman Kodak Company, NY, U.S.A.) for the measurement of human beta-actin cDNA (mRNA), a reference gene in an analysis for target gene expression. The devised method, compared with currently used methods, was easy, safe, sensitive, and highly reproducible to assay an infinitesimal level of cDNA (mRNA).

Actins↗
PubMed1997

Synthesis and antitumor activity of fused quinoline derivatives. IV. Novel 11-aminoindolo[3,2-b]quinolines.

Indolo[3,2-b]quinoline derivatives (1) having various amine moieties were prepared and their antitumor activities against P388 leukemia in mice were evaluated, for the purpose of gaining an insight into the role of the amine moiety in the antitumor activity and searching for an effective amine moiety. Introduction of a methylene group between the phenyl group and amino or methanesulfonamido group resulted in decrease or loss of activity.

Animals↗
PubMed1997

Biological activity of purpurogallin.

Purpurogallin showed antibacterial activity toward gram-positive bacteria. Strong activity against methicillin-resistant Staphylococcus aureus [minimal inhibitory concentration (MIC) against methicillin of 1600 micrograms/ml] was found, with MIC of 11.0 micrograms/ml. Purpurogallin inhibited the growth of all tested plants and decreased the chlorophyll content in the cotyledons of Brassica campestris subsp. rapa. It showed potent inhibitory activity against prolyl endopeptidase (the 50% inhibitory concentration was 1.6 x 10(-5) M), unlike its analogues, hinokitiol and tropolone.

Anti-Bacterial Agents↗
PubMed1997

Simple i.v. inoculation of HIV-1 to Thy/Liv SCID-hu mice induce reproducible HIV infection with narrowing of medulla in human thymic implant.

Human fetal thymus/liver engrafted SCID mice were constructed and studied for its susceptibility to HIVBRU infection by i.v. inoculation which seemed to represent an appropriate route of HIV infection in vivo. By the i.v. inoculation of HIV, the medulla in the engrafted thymus narrowed significantly when compared with that of the human thymic implant from virus-uninoculated mice. Further, immunohistochemical staining indicated the presence of HIV antigen predominantly in thymic epithelial cells in medulla of the engrafted thymus. Polymerase chain reaction (PCR) assays resulted in amplifications of HIV genome in the implanted grafts as well as in lymph nodes and PBMC. The virus infections to the implants were confirmed biologically by coculturing with PHA-stimulated human PBMC and the graft cells from the HIV-inoculated SCID-hu mice. Thus, the i.v. inoculation of HIV into Thy/Liv SCID-hu mice induce narrowing of medulla of the engrafted thymus and may become an efficient and useful tool for screening candidate anti-HIV agents.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Successful laparoscopy assisted ovariohysterectomy in two dogs with pyometra.

Two dogs with pyometra were treated by laparoscopy assisted ovariohysterectomy. Hemostasis of the mesovarium was achieved with an ultrasonic scalpel and hemoclips. Both ovaries and the uterus were exposed via a 10-mm caudal port that was enlarged to 3 cm and the uterine cervix was excised after ligation of the uterine arteries. These cases were the first report on ovariohysterectomy for pyometra by laparoscopy assisted surgery in the veterinary field.

Animals↗
PubMed1997

Detection of interleukin 6-producing cells among various organs in normal mice with an improved enzyme-linked immunospot (ELISPOT) assay.

The enzyme-linked immunospot (ELISPOT) assay is an efficient technique for the enumeration of single cells secreting antibodies or cytokines. To assess mice interleukin 6 (IL-6)-secreting cells at a single cell level, a highly sensitive ELISPOT assay with 5-bromo-4-chloro-3-indolylphosphate p-toluidine salt and nitroblue tetrazolium chloride (BCIP/NBT) as a gel-substrate has been developed. The IL-6 specific ELISPOT assay thus developed with an ordinary plastic ELISA plate is as efficient as the previous IL-6 specific ELISPOT assay system which uses a nitrocellulose coated plate, and is much more economic and convenient. We demonstrated with this newly devised ELISPOT assay that the ratio of IL-6 producing cells in the resident peritoneal exuded cells was highest in normal BALB/c mice, and a few IL-6 secreting cells were detected in all organs we tested, namely the spleen, bone marrow, Peyer's patch, axillary lymph node and thymus.

Animals↗
PubMed1997

The ventricular gradient and altered ventricular activation patterns.

The ventricular gradient vector was determined in normal persons and in cases with left and right bundle branch block (BBB) by means of the best fit method from body surface potential mapping data. Similar measurements were also made in cases with artificial ventricular pacing and the G vector during sinus rhythm was compared with that of the paced beats. Results indicated that the magnitude of the G vector in cases with BBB was smaller than in normal persons. The directional change in the G vector was found to be along the direction of the QRS change in the majority of cases with left BBB. In right BBB, the direction of the G change was variable but the angle between the QRS change was less than 90 degrees on average. Following right ventricular pacing a small increase of the G magnitude was observed acutely, which was opposite in direction to the QRS change. Possible mechanisms are discussed. The G changes in left and right BBB are considered to be based on certain chronic processes, different from those involved in the acute immediate effect of altered activation.

Adult↗
PubMed1997

Gender differences in effects of 20 days horizontal bed rest on muscle strength in young subjects.

Gender differences in the effect of 20 days bed rest (BR) on muscle strength were evaluated in voluntary 11 male and 7 female students. Maximum Isometric Voluntary Contractions (MVC) of 4 right arm muscles (RAM), 5 right leg muscles (RLM), and 2 body trunk muscles were measured with an isometric dynamometer, respectively. Muscle masses (MM) of right arm and leg and body trunk were determined by dual energy X-ray absorptiometry, respectively. The maximum cross sectional area (CSAmax) of right m. quadriceps femoris was measured by magnetic resonance imaging. Elbow flexion MVC in males and all MVC of RLM except knee flexion in both males and females were decreased (p<0.05), but elbow extension MVC in females was increased (p<0.05), while all of other MVC only tended to decrease. However, the decrements in leg MVC were not correlated to the leg MM, and also the decrement in knee extension was not correlated to the CSAmax of m. quadriceps. The reduction of MVC of antigravity muscles might be caused not only by a decrease in MM but also by other factors. The greater decrements of leg MVC during BR were the higher initial level in males, but the inverse was observed in females. However, this discrepancy between males and females cannot be explained in the present study.

Adolescent↗
PubMed1997

Effects of 20 days horizontal bed rest on maintaining upright standing posture in young persons.

The effects of 20 days horizontal bed rest (BR) on postural reflex were studied by measuring fluctuation of center of gravity in the body during two legs or one leg upright standing in 10 young volunteers. The fluctuation was decided as total moving distance of the center recorded during 60sec standing on a force plate. The stability was measured by the moved area. After BR, the moving distance increased during two legs standing with open eyes (p<0.05), but statistically unchanged with closed eyes. The moving area decreased during right one-leg standing with closed eyes (p<0.05), but unchanged during left one-leg standing. Despite with open eyes the increased distance suggested that postural reflexes to maintain upright position were probably decreased by increased unsuitable feedback informations from the visual receptor deconditioning during BR. The decreased area during right one-leg standing with closed eyes also suggested that the declined standing posture reflex was probably related to more rapidly lowered functions for maintaining standing position in the dominating leg than in the other.

Adult↗
PubMed1997

Effects of 20 days horizontal bed rest on kinesthesia during knee flexion and two-point discrimination in skin of young subjects.

Investigating the effect of 20 days bed rest (BR) on kinesthesia and two-point discrimination, 10 young volunteers participated in this study as subjects. Angle position sensation of right knee was measured in the prone position during flexion and extension monitored by a goniometer after two-point discrimination in skin was determined on the same lower leg. Flexed constant error was unchanged but directional constant error and absolute error were increased after BR (p<0.05). Two-point discrimination was unchanged after BR, which brought about a decline of the orientation of moving the joint indicated as over shooting of the angle during knee flexion, while it did not affect superficial sensation observed by two-point discrimination. Probably, an adjustment of deep sensation to the knee joint is lowered by the reduction in kinesthesia as well as the sensory disturbance during BR, which is independent on information from superficial sensation.

Adult↗
PubMed1997

Two distinct novel splice site mutations in a compound heterozygous patient with protein S deficiency.

Genetic analysis revealed two distinct novel splice site mutations in a compound heterozygous patient with protein S deficiency. The paternal mutation was a G-to-T transition at position-1 of the acceptor splice site of intron N (Mutation I), and the maternal mutation was a G-to-C transversion at position-1 of the donor splice site of intron C (Mutation II). Both splice site mutations decreased the mutated mRNA accumulation to the same extent, approximately 40% of the normal mRNA. However, the mutations were associated with different phenotypical expressions: the paternal mutant protein S was not detected in vivo, while the maternal mutant protein S was present in the plasma in reduced quantity. Because Mutation I caused a cryptic splicing in the mutated mRNA, resulting in a reading frameshift and premature termination, the predicted mutant protein S might be highly unstable. In contrast. Mutation II led to the substitution of Va146 by Leu, which might be much less deleterious for the synthesis, secretion and stability of the predicted mutant protein S. It was supposed that the different post-translational metabolisms produced the distinct phenotypical expressions of the mutations.

Adult↗
PubMed1997

[A case of Wilson-Mikity syndrome with marked and monoclonal elevation of IgM in blood].

Wilson-Mikity syndrome, a chronic respiratory insufficiency occurring in premature newborn infants, is known to show an elevation of serum IgM, but its etiology is obscure. We studied the immunological properties of IgM in a female infant of this syndrome, whose IgM in cord blood was very high level at 639.1 mg/dl with monoclonal elevation. The IgM bound to protein(s) in human umbilical venous endothelial cells and in human lung tissue. However, IgMs from this patient after recovery, from patient's mother and from another normal newborn did not bind to the proteins. Tissue-binding activity of the patient's IgM may be associated with tissue damages in this syndrome.

Female↗
PubMed1997

[Experience in treatment of patients with locally advanced or recurrent breast cancer: intraarterial infusion chemotherapy combined with radiotherapy].

For the purpose of local control and breast conservation, intraarterial infusion chemotherapy combined with radiotherapy has been indicated in patients with locally advanced breast cancer both in primary and recurrent cases. The present series, evaluated during the past 4 years, consisted of 15 patients 35-83 years of age, with invasive ductal carcinoma, including 10 with primary breast cancer (stage IIIb: 1; IV: 9) and 5 with postoperative recurrence (stage IIIb: 2, IV: 3). Intraarterial chemotherapy is started, basically infusing ADM 50 mg, MMC 10 mg and CDDP 50 mg into the internal thoracic and/or subclavian artery 1-3 times, followed by reduction surgery (quadrantectomy: 4, wide resection: 2) and radiotherapy to the breast, supraclavicular, parasternal and cervical regions according to tumor extent. Local response after arterial infusion was CR: 2, PR: 10, NC: 3 (response rate: 73%). The response rate of distant metastases after arterial infusion was 73%. Of 10 patients with primary breast cancer, recurrence was noted in 1. Breast conservation was successful in 8 of 10 patients. One of them, in stage IIIb, has survived for 4.5 years with no evidence of disease and with breast conservation. Five patients with postoperative recurrence showed CR with no recurrence after intraarterial chemotherapy and radiotherapy. Acute skin reaction occurred in 6 patients, and was especially frequent in patients with postoperative recurrence (4 of 5). According to these results, combined therapy affords breast conservation even in patients with locally advanced breast cancer, and improves patient's QOL in stage IV.

Adult↗
PubMed1997

[Development and clinical application of MR simulation system for radiotherapy planning: with reference to intracranial and head and neck regions].

To obtain the optimal radiation field, an MR simulation system (MRSS) has been developed. It basically depends upon the higher soft tissue contrast resolution of MRI than of CT. The system consists of an MR unit, an image processing work-station and a laser marking system. In brief, the procedures are as follows: [1] marking the reference point on the patient's skin out of the MR gantry, and automatic table shift to set the reference point at the center of the magnetic field (CMF); [2] MR imaging (T1W1: SE, TR:500 msec, TE: 20 msec); [3] transfer of MR data to a work-station through floppy disc; [4] postprocessing of MR data using a work-station to perform radiotherapy planning; delineation of ROI for irradiation, calculation of the contour of radiation field along with iso-center; [5] corresponding the reference point correspond with the base point of the laser marking system on the CT table; [6] reproducing the calculated iso-center on the patient's skin using the laser marking system. A phantom study of geographic distortion and the total accuracy of MRSS revealed that the former was less than 1 mm within a 90 mm distance between MR slices and CMF, while the latter showed maximal errors of 2 mm in field size and 3 mm in iso-center. This system was applied to 15 patients with intracranial or head and neck lesions, and all procedures were smoothly performed. In order to evaluate the usefulness of MRSS, 6 experienced radiation oncologists compared the difference between MRSS and a CT simulation system in setting the radiation field. The results were satisfactory in all cases, especially in cases in which the tumor extent was unclear on CT images. In spite of some limitations of MRI such as distortion of image and impossibility of iso-dose curve calculation, it was considered that this system could support radiotherapy planning for intracranial or head and neck regions.

Adult↗