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Biomedical subjects

H Nagata

Publications and source records attributed to H Nagata.

At least 145 records · Page 8Linked to original sources
PubMed1996

A modified maze procedure performed only on the left atrium for chronic atrial fibrillation associated with mitral valve disease: report of a case.

We describe herein the successful treatment of a patient with chronic atrial fibrillation (AF) associated with mitral valve stenosis and regurgitation, achieved by performing a modified maze procedure on the left atrium alone. The patient was a 51-year-old man who had suffered from intractable AF for 17 years, causing multiple cerebral emboli and palpitations. He had undergone open mitral commissurotomy and balloon commissurotomy 15 and 7 years ago, respectively. On admission, an echocardiogram revealed mitral valve restenosis and thrombosis in the left atrial appendage. Prosthetic valvular replacement was performed following isolation of all pulmonary veins with cryoablation to the posterior wall of the left atrium and excision of the left atrial appendage. Postoperatively, the AF disappeared and echocardiogram demonstrated a left atrial kick in the mitral valvular inflow without any evidence of thrombosis in the left atrium. Thus, we believe that our modified "left side only" maze procedure is a simple and efficient method for the treatment of chronic AF with mitral valve disease.

Atrial Fibrillation↗
PubMed1996

Differences in hemostasis among sclerosing agents in endoscopic injection sclerotherapy.

Endoscopic injection sclerotherapy is useful in stopping bleeding from esophageal varices. We compared the in vivo effects of sclerosants on thrombogenesis, hemostasis, and endothelial injury. We injected aethoxysclerol (AS) of ethanolamine oleate (EO) into the small veins of the rat intestine. The maximum thrombogenic index with AS was 30.7 and with EO was 9.2. The venous flow stopped sooner with EO than with AS. The thrombi caused by EO were mixed with red blood cells. Heparin pretreatment decreased the thrombogenic index with AS by 96.7%, but not that with EO. The area of the fluorescein-albumin conjugate that permeated from veins with AS was larger than that with EO. The fluorescent intensity with AS was lower than that with EO. We thus conclude that: (1) the size of thrombi is not necessarily proportional to the hemostatic efficacy; (2) change in a patient's coagulation may affect the potential of sclerosants; (3) the excellent hemostatic efficacy of EO is based on localized injury to the endothelium and the involvement of red blood cells aggregation; and (4) in vivo microscopy is useful in determining the rational selection of sclerosants.

Animals↗
PubMed1996

Simple left atrial procedure for chronic atrial fibrillation associated with mitral valve disease.

BACKGROUND: A computerized 48-channel mapping system was used to investigate the characteristics of an atrial epicardial electrogram during chronic atrial fibrillation (AF) in patients with solitary mitral valve disease. We have devised a simple left atrial procedure to eliminate the chronic AF during a mitral valve operation. METHODS: Using this mapping system, we performed intraoperative atrial mapping in 11 patients with chronic AF associated with mitral valve disease. The AF duration ranged from 0.4 to 15 years (mean, 8.0 +/- 4.5 years). A simple surgical ablation of the AF on the left atrium only was performed during the mitral valve operations. RESULTS: The mean AF cycle length of the atria ranged from 129 to 169 milliseconds in the right atrium and from 114 to 139 milliseconds in the left atrium. The mean AF cycle length of the left atrium was shorter than that of the right atrium. Regular and repetitive activation was found in the left atria of 7 of 11 patients. The AF disappeared in all patients immediately after the operation, and 10 of these patients continued to have a sinus rhythm postoperatively (AF-free rate, 91%). CONCLUSIONS: Computerized intraoperative mapping revealed a shorter mean AF cycle length in the left atrium. A simple left atrial procedure was effective in eliminating chronic AF associated with solitary mitral valve disease.

Adult↗
PubMed1996

Soft-X-ray damage to biological samples.

X-ray damage to biological samples was investigated in the wavelength region of 2.7-5 nm, which overlaps the so-called 'water-window', the wavelength range of 2.4-4.3 nm usually used in X-ray microscopy. Yeast cells and myofibrils were chosen as representatives of whole cell samples and motile protein systems, respectively. The samples were exposed to X-rays using an apparatus composed mainly of a laser-plasma X-ray source, a Wolter mirror condenser, and a sample cell. The yeast cells lost their dye exclusion ability when the X-ray flux was higher than 1 x 10(6) photons micron-2, while the myofibrils lost contractility when the X-ray flux was higher than 4 x 10(5) photons micron-2. These X-ray fluxes are lower than the flux required for the X-ray microscope observation of biological samples at a resolution higher than that of light microscopes.

Animals↗
PubMed1996

Role of endothelin-1 in repeated electrical stimulation-induced microcirculatory disturbance and mucosal damage in rat stomach.

The aim of the present study was to clarify the involvement of endogenous endothelin in the pathogenesis of gastric mucosal damage. The rat stomach was exposed and repeated electrical stimulation (RES) was applied to the small arterial wall close to the lesser curvature. Significant mucosal haemorrhagic lesions (ulcer and erosion) were noted within 30 min after RES. Intravital microscopic observations revealed that an arteriolar constriction occurred in the submucosal layer of the rat stomach approximately 5 min after the completion of RES. Following the arteriolar constriction, the mucosal blood flow of the rat stomach, which was monitored by using a laser Doppler velocimeter, decreased to approximately 30% of the control value. The plasma immunoreactive endothelin-1 level in the regional blood of the stomach was significantly increased immediately after RES preceding the decrease in mucosal blood flow. Immunohistochemical studies revealed that endothelin-1 and big-endothelin-1 were detectable in the arteriolar endothelium around the muscularis mucosa, supporting the involvement of endothelin-1 in RES-induced mucosal ischaemia. In addition, BQ-123, a specific antagonist of the endothelin A (ETA) receptor, attenuated the reduction of blood flow and the development of haemorrhagic lesions observed in gastric mucosa subjected to RES. The results of the present study suggest that an excessive production of endothelin-1 in the arteriolar endothelium leads to microvascular derangements accompanied by haemorrhagic alterations of the gastric mucosa.

Animals↗
PubMed1996

Expression of functional Porphyromonas gingivalis fimbrillin polypeptide domains on the surface of Streptococcus gordonii.

Genetically engineering bacteria to express surface proteins which can antagonize the colonization of other microorganisms is a promising strategy for altering bacterial environments. The fimbriae of Porphyromonas gingivalis play an important role in the pathogenesis of periodontal diseases. A structural subunit of the P. gingivalis fimbriae, fimbrillin, has been shown to be an important virulence factor, which likely promotes adherence of the bacterium to saliva-coated oral surfaces and induces host responses. Immunization of gnotobiotic rats with synthetic peptides based on the predicted amino acid sequence of fimbrillin has also been shown to elicit a specific immune response and protection against P. gingivalis-associated periodontal destruction. In this study we engineered the human oral commensal organism Streptococcus gordonii to surface express subdomains of the fimbrillin polypeptide fused to the anchor region of streptococcal M6 protein. The resulting recombinant S. gordonii strains expressing P. gingivalis fimbrillin bound saliva-coated hydroxyapatite in a concentration-dependent manner and inhibited binding of P. gingivalis to saliva-coated hydroxyapatite. Moreover, the recombinant S. gordonii strains were capable of eliciting a P. gingivalis fimbrillin-specific immune response in rabbits. These results show that functional and immunologically reactive P. gingivalis fimbrillin polypeptides can be expressed on the surface of S. gordonii. The recombinant fimbrillin-expressing S. gordonii strains may provide an effective vaccine or a vehicle for replacement therapy against P. gingivalis. These experiments demonstrated the feasibility of expressing biologically active agents (antigens or adhesin molecules) by genetically engineered streptococci. Such genetically engineered organisms can be utilized to modulate the microenvironment of the oral cavity.

Animals↗
PubMed1996

Adenosine A2-receptor mediates ethanol-induced arteriolar dilation in rat stomach.

Topical application of ethanol to the gastrointestinal mucosa induces vasodilation. Using an in vivo microscopy technique, we studied the effect of topical ethanol on the submucosal microvessels that control mucosal blood flow in the rat stomach and identified vasoactive substances and receptors that mediate the ethanol vasoaction. Topical ethanol (1-20%) dilated submucosal arterioles dose dependently, but did not change venular diameters. An inhibitor of alcohol dehydrogenase, 1 mM 4-methylpyrazole, did not alter the ethanol vasoaction. Ethanol-induced arteriolar dilation was eliminated by adenosine deaminase, but other vasodilator inhibitors such as atropine, pyrilamine, indomethacin, human calcitonin gene-related peptide-(8-37), and N omega-nitro-L-arginine methyl ester did not prevent it. Ethanol-induced arteriolar dilation was inhibited by an adenosine A2-receptor antagonist, but not by an A1-receptor antagonist, whereas an A2-agonist, but not an A1-agonist, dose dependently dilated arterioles. Exogenous adenosine (10(-5)-10(-3) M) dilated arterioles to a similar extent as ethanol. This response was inhibited by an A2-antagonist. We conclude that nonmetabolized ethanol increases gastric mucosal blood flow via A2-receptors in submucosal arterioles.

Animals↗
PubMed1996

Role of substance P in the vascular response of nasal mucosa in nasal allergy.

The effects of topically administered substance P (SP) on nasal blood flow and nasal airway resistance (NAR) were evaluated in 11 subjects with perennial nasal allergy. The change in NAR induced by SP was compared with those induced by nasal challenge with histamine, leukotriene D4 (LTD4), and antigen. In doses > or = 16 nmol, SP caused a significant increase of nasal blood flow within 5 minutes that lasted for less than 20 minutes. In doses > or = 16 nmol, SP caused a dose-dependent, short-lasting, significant increase in NAR. The magnitude of the increase in NAR was LTD4 > SP > histamine when compared on a molar basis. Our results may suggest that SP released from C fiber terminals is partially involved in an early nasal vascular response after antigen challenge by acting on adjacent vascular smooth muscle to cause a transient vasodilatation of both resistance and capacitance vessels only while sensory stimulation persists in subjects with nasal allergy.

Adolescent↗
PubMed1996

Relationship between intracoronary thrombolysis and fibrino-coagulation--special reference to TAT/PIC and FPA/PIC.

To clarify the relationship between the results of intracoronary thrombolytic therapy (ICT) and fibrino-coagulation in patients with acute myocardial infarction (AMI), the thrombin-antithrombin III complex (TAT) and fibrinopeptide A (FPA), as indices of accelerated coagulation, and the plasmin- alpha 2-plasmin inhibitor complex (PIC), as an index of accelerated fibrinolysis in peripheral blood, were measured just before and after heparin injection (5,000 U), and immediately after ICT. Twenty-four patients with AMI were divided into 2 groups according to the results of ICT; successful ICT (group S) and unsuccessful ICT (group F). As a control group (group C), 14 age-matched normal volunteers were also studied. The levels of TAT and FPA before ICT were significantly higher in groups S and F than in group C (p < 0.01). The TAT level before ICT in group F was higher than that in group S (p = 0.07), however, the TAT, FPA and PIC levels showed no significant differences between groups S and F at each sampling time. TAT/PIC before ICT was significantly higher in group F than in group S (F: 0.026 +/- 0.020 vs S: 0.008 +/- 0.004, p < 0.05), whereas there was no remarkable difference in FPA/PIC between groups S and F. These results indicate that hyper-coagulation had occurred in the AMI cases and that coagulation had been more accelerated in group F. TAT/PIC might be an index of the equilibrium of the fibrino-coagulating system. Therefore, TAT/PIC measurement before thrombolytic therapy may be more useful than TAT measurement alone for evaluating recanalization in ICT.

Aged↗
PubMed1996

[Efficacy of left atrial only procedure for the treatment of chronic atrial fibrillation associated with mitral valve disease].

We supposed that chronic atrial fibrillation originated as a result of discontinuity of the refractory period of the dilated left atrium in the mitral valvular disease. We then performed left atrial only procedures to treat the chronic atrial fibrillation (AF) associated with mitral valve disease. These procedures were the left atrial isolation and the modified left sided maze procedure, consisting of isolation of all pulmonary veins and cryoablation to the posterior wall of the left atrium, in addition to excision of the left atrial appendage. Twenty-eight patients underwent these procedures over the past thirty months. Patient ages and the duration of AF ranged from 37 to 71 years and from 0.5 to 26 years, with an average of 8.3 years, respectively. Chronic AF disappeared in twenty-four patients (86%) at discharge. Three patients with severe tricuspid insufficiency had sustained AF and one patient had atrial flutter postoperatively. Three patients showed sick sinus syndrome postoperatively and two of these required a DDD pacemaker. Severe tricuspid regurgitation (p < 0.020) was the factor in recurrence of AF. Left atrial only procedures were effective in the treatment of chronic AF associated with mitral valvular disease.

Adult↗
PubMed1996

[Effects of lactation and lifestyles including food intake on bone density of lactating women].

Ultrasonic bone densities were measured in 131 lactating women, aged 21 to 42 years, at 6-590 days postpartum. STIFFNESS Calculated from the combined value of speed of sound and broadband ultrasound attenuation at the calcaneus was used as an index of bone density. The relationships of STIFFNESS with period of lactation, current and past consumption of cow's milk, various food intake frequency, history of participating in sports, daily physical activity, using calcium drugs and sun exposure were examined using stepwise multiple regression analysis, including age and weight as independent variables. 1) The mean (SD) of STIFFNESS was 79.8 (11.9). Thirty-three women (25% of subjects) showed STIFFNESS less than 70. 2) Period of lactation showed a significant negative effect on STIFFNESS (p < 0.05). However, no such effect appeared for women with cow's milk intake of less than 100 ml per day. This result suggests a protection of calcium levels in bone. 3) Current daily cow's milk intake showed significant positive effect on STIFFNESS (p < 0.05). For women lactating less than 150 days, this relation between cow's milk intake and STIFFNESS was clear (r = 0.44, p < 0.01). 4) Significant relation between STIFFNESS and food intake frequencies was found in milk and milk products only among various foods. This result indicates that cow's milk and milk products are important sources of calcium during lactation.

Adult↗
PubMed1996

Identification of a polymorphism in the transmembrane domain of the protooncogene c-kit in healthy subjects.

c-Kit is the receptor for stem cell factor (SCF) and is found on hematopoietic stem cells, mast cells, melanocytes, and germ cells. Aggregation of c-Kit by SCF regulates cell proliferation, differentiation, and survival. In the process of examining c-Kit, a polymorphism in the transmembrane domain of the protooncogene c-Kit was identified. This polymorphism consisted of an A-to-C transversion at nucleotide (nt) 1642, and was deduced to substitute leucine for methionine at codon 541. The frequency of the allele with 'C' at nt 1642 was 0.09 in 64 unrelated subjects. Analysis of a two-generation family with the polymorphism suggested that this polymorphism did not result in disease. This is the first report of a polymorphism in the transmembrane domain of c-Kit, and may be of value in understanding and following the function of c-Kit in normal subjects and in those with other abnormalities of c-Kit.

Adult↗
PubMed1995

Activation of protein kinase C by oxidized diacylglycerols.

The effects of 1,2-diacylglycerol hydroperoxide (DAG-OOH), its alcohol (DAG-OH), "unoxidized" 1,2-diacylglycerol (DAG), 1,2-dioleoylglycerol (DOG), and phorbol 12-myristate acetate (PMA) on the activity of protein kinase C (PKC) isolated from rat brain were examined in the presence and absence of phosphatidylserine (PS) and calcium ion. Both DAG-OOH and DAG-OH stimulated the activity of PKC dose- and time-dependently. The ability of additives for PKC activation increased in the order of DOG, DAG << DAG-OOH, DAG-OH < PMA. DAG-OOH and DAG-OH activated PKC even in the absence of PS and calcium ion as PMA does. If DAG-OOH and DAG-OH are released from the oxidized biomembranes by the action of phospholipase C, these components may act like PMA and serve to activate the PKC-dependent signal transduction system.

Animals↗
PubMed1995

Binding of hemoglobin by Porphyromonas gingivalis.

In this study, we investigated whether Porphyromonas gingivalis can bind hemoglobin as an initial step in the acquisition of heme from hemoglobin. The binding of human hemoglobin by P. gingivalis cells was determined using [3H]hemoglobin. Hemoglobin binding occurred rapidly, reversibly and specifically. A Scatchard analysis of the binding data generated a linear plot, indicating a single population of binding proteins. The apparent Kd was 1.0 +/- 0.19 x 10(-6) M and there were 3.2 +/- 0.76 x 10(4) binding sites per cell. Hemoglobin binding was inhibited by unlabeled human hemoglobin but not by hemin and protoporphyrin IX. The binding was only partially inhibited by human serum albumin, transferrin, lactoferrin, catalase and cytochrome c. These results suggest that the ligand recognized by the binding protein may not be the heme moiety. The binding of hemoglobin considerably increased when the organisms were grown under hemin-limited conditions. Hemoglobin bound to outer membrane proteins extracted from P. gingivalis cells on a dot blot binding assay and binding ability was lost after heating bacterial proteins. These results suggest that P. gingivalis cells interact with human hemoglobin through specific binding sites on their surfaces as a preliminary step in iron acquisition.

Bacterial Outer Membrane Proteins↗