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Biomedical subjects

M Okazawa

Publications and source records attributed to M Okazawa.

At least 19 recordsLinked to original sources
PubMed2000

Mechanical properties of the tracheal mucosal membrane in the rabbit. I. steady-state stiffness as a function of age.

Airway responsiveness is exaggerated in infancy and declines with maturation. These age-related differences (R.S. Tepper, T. Du, A. Styhler, M. Ludwig, and J.G. Martin. Am. J. Respir. Crit. Care Med. 151: 836-840, 1995; R.S. Tepper, S.J. Gunst, C.M. Doerschuk, Y. Shen, and W. Bray. J. Appl. Physiol. 78: 505-512, 1995; R.S. Tepper, J. Stevens, and H. Eigen. Am. J. Respir. Crit. Care Med. 149: 678-681, 1994) could be due to changes in the smooth muscle, the lung, and/or the airway wall. Folding of the mucosal membrane can provide an elastic load (R.K. Lambert, J. Appl. Physiol. 71: 666-673, 1991), which impedes smooth muscle shortening. We hypothesized that increased stiffness of the mucosal membrane occurs during aging, causing an increased mechanical load on airway smooth muscle and a decrease in airway responsiveness. Forty female New Zealand White rabbits between 0.75 and 35 mo of age were studied. Rectangular mucosal membrane strips oriented both longitudinally and circumferentially to the long axis of the trachea were dissected, and the stress-strain relationships of each strip were tested. The results showed that the membrane was stiffer in the longitudinal than in the circumferential direction of the airway. However, there was no significant change with age in either orientation. We conclude that the mechanical properties of the airway mucosal membrane did not change during maturation and were not likely to influence age-related changes in airway responsiveness.

Aging↗
PubMed2000

Mechanical properties of the tracheal mucosal membrane in the rabbit. II. Morphometric analysis.

Folding of the airway mucosal membrane provides a mechanical load that impedes airway smooth muscle contraction. Mechanical testing of rabbit tracheal mucosal membrane showed that the membrane is stiffer in the longitudinal than in the circumferential direction of the airway. To explain this difference in the mechanical properties, we studied the morphological structure of the rabbit tracheal mucosal membrane in both longitudinal and circumferential directions. The collagen fibers were found to form a random meshwork, which would not account for differences in stiffness in the longitudinal and circumferential directions. The volume fraction of the elastic fibers was measured using a point-counting technique. The orientation of the elastic fibers in the tissue samples was measured using a new method based on simple geometry and probability. The results showed that the volume fraction of the elastic fibers in the rabbit tracheal mucosal membrane was approximately 5% and that the elastic fibers were mainly oriented in the longitudinal direction. Age had no statistically significant effect on either the volume fraction or the orientation of the elastic fibers. Linear correlations were found between the steady-state stiffness and the quantity of the elastic fibers oriented in the direction of testing.

Animals↗
PubMed1999

Activation of three types of voltage-independent Ca2+ channel in A7r5 cells by endothelin-1 as revealed by a novel Ca2+ channel blocker LOE 908.

1. We have shown that in addition to voltage-operated Ca2+ channel (VOC), endothelin-1 (ET-1) activates two types of Ca2+-permeable nonselective cation channel (NSCC) in A7r5 cells: its lower concentrations (< or = 1 nM; lower [ET-1]) activate only an SK&F 96365-resistant channel (NSCC-1), whereas its higher concentrations (> or = 10 nM; higher [ET-1]) activate an SK&F 96365-sensitive channel (NSCC-2) as well. 2. We now characterized the effects of a blocker of Ca2+ entry channel LOE 908 on NSCCs and store-operated Ca2+ channel (SOCC) in A7r5 cells, and using two drugs, clarified the involvement of these channels in the ET-1-induced increase in the intracellular free Ca2+ concentrations ([Ca2+]i). Whole-cell recordings and [Ca2+]i monitoring with fluo-3 were used. 3. LOE 908 up to 10 microM had no effect on increases in [Ca2+]i induced by thapsigargin or ionomycin, but SK&F 96365 abolished them. 4. In the cells clamped at -60 mV, both lower and higher [ET-1] induced inward currents with linear iv relationships and the reversal potentials of -15.0 mV. Thapsigargin induced no currents. 5. In the presence of nifedipine, lower [ET-1] induced a sustained increase in [Ca2+]i, whereas higher [ET-1] induced a transient peak and a sustained increase. The sustained increases by lower and higher [ET-1] were abolished by removal of extracellular Ca2+, and they were suppressed by LOE 908 to 0 and 35%, respectively, with the LOE 908-resistant part being abolished by SK&F 96365. 6. These results show that LOE 908 is a blocker of NSCCs without effect on SOCC, and that the increase in [Ca2+]i at lower [ET-1] results from Ca2+ entry through NSCC-1 in addition to VOC, whereas the increase at higher [ET-1] involves NSCC-1, NSCC-2 and SOCC in addition to VOC.

Acetamides↗
PubMed1999

Pharmacological characterization of Ca2+ entry channels in endothelin-1-induced contraction of rat aorta using LOE 908 and SK&F 96365.

We have recently shown that endothelin-1 (ET-1) activates two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and store-operated Ca2+ channel (SOCC). These channels can be pharmacologically discriminated using Ca2+ channel blockers such as SK&F 96365 and LOE 908. Here we characterized Ca2+ entry channels involved in ET-1-induced contractions of rat thoracic aortic rings and increases in the intracellular free Ca2+ concentration ([Ca2+]i) of single smooth muscle cells using these blockers. LOE 908 or a blocker of voltage-operated Ca2+ channel nifedipine had no effect on the contractions and increases in [Ca2+]i induced by thapsigargin or ionomycin, whereas SK&F 96365 abolished them. The contractions and increases in [Ca2+]i induced by ET-1 depended on extracellular Ca2+ but were resistant to nifedipine. The responses to lower concentrations (< or =0.1 nM) of ET-1 were abolished by either SK&F 96365 or LOE 908. The responses to higher concentrations (> or = 1 nM) were abolished by SK&F 96365, but were partially resistant to LOE 908. SK&F 96365 inhibited the LOE 908-resistant contractions induced by higher concentrations of ET-1 with IC50 values similar to those for contractions induced by thapsigargin or ionomycin. These results show that the contractions and increases in [Ca2+]i of rat aortic smooth muscles at lower concentrations of ET-1 involve only one Ca2+ entry channel which is sensitive to SK&F 96365 and LOE 908 (NSCC-2), whereas those at higher concentrations of ET-1 involve another Ca2+ entry channel which is sensitive to SK&F 96365 but resistant to LOE 908 (SOCC) in addition to the former channel.

Acetamides↗
PubMed1999

Mechanical properties of lung parenchyma during bronchoconstriction.

Interdependence between airways and the lung parenchyma is thought to be a major mechanism preventing excessive airway narrowing during bronchoconstriction. Because the elastance of the lung increases during bronchoconstriction, the lung's tethering force could also increase, further attenuating bronchoconstriction. We hypothesized that the bulk (kappa) and shear moduli (mu) of the lung increase similarly during bronchoconstriction. To test this hypothesis, we excised rabbit lungs and measured the lung volume, pulmonary elastance, kappa, and mu at transpulmonary pressures of 4, 6, 8, 12, and 16 cmH2O using pressure-volume curves, slow oscillations of the lung, and an indentation test. Bronchoconstriction was induced by nebulizing carbachol by using small tidal-volume ventilation to prevent hyperinflation. The measurement of kappa and mu was repeated after carbachol treatment. After carbachol treatment, the increase in kappa was significantly greater than that in mu. The estimated value for mu was approximately 0.5 x transpulmonary pressure both before and after carbachol treatment. These data suggest that the tethering effect of the lung parenchyma, which serves to attenuate bronchoconstriction, is not significantly increased during carbachol administration unless there is hyperinflation.

Air Pressure↗
PubMed1999

Ca2+ entry channels in rat thoracic aortic smooth muscle cells activated by endothelin-1.

The contraction of the rat aorta induced by endothelin-1 (ET-1) requires entry of extracellular Ca2+, but involvement of voltage-operated Ca2+ channel is minor. Using whole-cell recordings of patch-clamp and monitoring of the intracellular free Ca2+ concentration ([Ca2+]i), we characterized Ca2+ entry channels in A7r5 cells activated by ET-1. ET-1 activates three types of voltage-independent Ca2+ entry channels: two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and a store-operated Ca2+ channel (SOCC). Furthermore, it was found that these channels can be pharmacologically discriminated using Ca2+ channel blockers such as SK&F 96365 and LOE 908. NSCC-1 is resistant to SK&F 96365, but sensitive to LOE 908, whereas NSCC-2 is sensitive to both SK&F 96365 and LOE 908. SOCC is sensitive to SK&F 96365, but resistant to LOE 908. Using these channel blockers, we analyzed Ca2+ entry channels involved in the ET-1-induced contractions of rat thoracic aorta and increases in [Ca2+]i of single smooth muscle cells. The responses to lower concentrations of ET-1 (< or = 0.1 nM) were abolished by either SK&F 96365 or LOE 908 alone. In contrast, the responses to higher concentrations of ET-1 (> or = 1 nM) were suppressed by SK&F 96365 or LOE 908 to about 10% and 35% of controls, respectively, and abolished by combined treatment with SK&F 96365 and LOE 908. These results show that the responses of rat aorta to lower concentrations of ET-1 involve only one Ca2+ channel that is sensitive to SK&F 96365 and LOE 908 (NSCC-2), whereas those to higher concentrations of ET-1 involve NSCC-1, NSCC-2 and SOCC, contributing 10%, 55% and 35%, respectively, to total Ca2+ entry.

Acetamides↗
PubMed1999

[A study of the long-term effectiveness of an outpatient pulmonary rehabilitation program].

Pulmonary rehabilitation is one of the most important components of comprehensive care for patients with significant disability due to chronic respiratory failure. Because pulmonary rehabilitation has not been popular in Japan, the long-term effectiveness of pulmonary rehabilitation has rarely been reported. We therefore examined the long-term effectiveness of an outpatient pulmonary rehabilitation program for patients with chronic respiratory failure. Our program was composed of a once-a-week introduction program for 2 months and a support program that was continued every 4 weeks as long as possible. Thirty stable patients with chronic respiratory failure were enrolled in the program; 21 patients (COPD: 15, lung complications of tuberculosis: 6) completed the 9-week introduction program and the ensuing 6-month support program. Good compliance with the home training regimen was maintained during the period. The introduction program significantly alleviated dyspnea (Fletcher's grade: 3.3 to 3.0, p < 0.01) and improved the data for activity (Spector's score: 5.3 to 5.8, p < 0.01) and 6-minute walking distance (319 to 384 m, p < 0.01). These benefits were sustained during the 6-month support program. We concluded that outpatient pulmonary rehabilitation can alleviate dyspnea and improve the activity and exercise tolerance of patients with chronic respiratory failure, and that the effectiveness of training can be well maintained with a minimal support program.

Activities of Daily Living↗
PubMed1998

Endothelin-induced apoptosis of A375 human melanoma cells.

Endothelin-1 (ET-1) inhibited serum-dependent growth of asynchronized A375 human melanoma cells, and the growth inhibitory effect was markedly enhanced when ET-1 was applied to the cells synchronized at G1/S boundary by double thymidine blocks. Flow cytometric analysis revealed that ET-1 did not inhibit the cell cycle progression after the release of the block but caused a significant increase of the hypodiploid cell population that is characteristic of apoptotic cell death. ET-1-induced apoptosis was confirmed by the appearance of chromatin condensation on nuclear staining and DNA fragmentation on gel electrophoresis. The increase in the hypodiploid cell peak was manifest within 16 h of exposure to 5 nM ET-1. Within the same time range, ET-1 caused actin reorganization and drastic morphological changes of the surviving cells from epithelioid to an elongated bipolar shape. These phenotypical changes were preceded by ET-1-induced increase and nuclear accumulation of the tumor suppressor protein p53. All of these effects of ET-1 were mediated by ETB via a pertussis toxin-sensitive G protein. Flow cytometric analysis with fluorescent dye-labeled ET-1 revealed up-regulation of ETB expressed by the cells in G1/early S phases, and overexpression of the receptor protein by cDNA microinjection conferred the responsiveness (both apoptosis and morphological changes) to ET-1 irrespective of the position of the cell in the cell cycle. These results indicated the presence of ETB-mediated signaling pathways to apoptotic cell machinery and cytoskeletal organization. Furthermore, the densities of ETB expressed by individual A375 melanoma cells appeared to be regulated by a cell cycle-dependent mechanism, and the receptor density can be a limiting factor to control the apoptotic and cytoskeletal responses of the cells to ET-1. Although the molecular mechanisms remain to be elucidated, these findings added a new dimension to the diverse biological activities of ETs and also indicated a novel mechanism to control the responsiveness of the cell to the peptides.

Cell Division↗
PubMed1997

Bromodeoxyuridine-induced expression of endothelin A in A375 human melanoma cells.

Expression of endothelin (ET) receptor subtypes was examined in an experimental model of A375 human melanoma cell differentiation using the pyrimidine analog bromodeoxyuridine (BUdR). BUdR (10 microM)-treated cells had an increased surface area and an increased dendricity, were contact-inhibited and lacked tumorigenecity in athymic nude mice. The untreated A375 cells exclusively expressed ETB and BUdR-induced phenotypical changes were accompanied by induction of ETA expression as evidenced by northern blotting, [125I]ET-1 binding assay and [Ca2+]i measurement. Thus, BUdR-induced differentiation of A375 melanoma cells may provide a model system to study the receptor subtype switch in melanocyte development.

Animals↗
PubMed1997

Fast Fourier transform analysis of dynamic data: sine wave stress-strain analysis of biological tissue.

We propose an improvement to the dynamic oscillation method using as an example the measurement of the tensile stiffness of the rabbit tracheal mucosal membrane. A sine wave oscillation technique was used to study the tissue mechanical properties. A mathematical model was developed using fast Fourier analysis. After mathematically eliminating the machine response, this analysis reveals the tissue frequency response over a wide range of frequencies. This study addresses the advantages of using Fourier analysis to interpret dynamic properties of biological tissue and provides a complete description of how to obtain the pure tissue response.

Animals↗
PubMed1997

Eosinophilic leukocyte accumulation during vagally induced bronchoconstriction.

Eosinophilic leukocytes (eosinophils) are important effector cells in allergic inflammatory diseases such as asthma, in which significant accumulation of these cells is observed in the bronchial mucosa. However, there is little information about the relationships between bronchoconstriction and accumulation of eosinophils. We hypothesized that eosinophils are retained in the bronchial vasculature in the inner airway wall during bronchoconstriction because of deformation of the mucosal membrane. To test this hypothesis we induced unilateral bronchoconstriction in open chest guinea pigs by stimulating the right vagus nerve and compared the accumulation of eosinophils in the airway wall of the constricted and contralateral unconstricted lungs using histologic specimens. Results show that the density of eosinophils (number of cells/wall area) significantly increased in the inner wall and decreased in the adventitia of the constricted airways compared with the contralateral unconstricted airways. There was a positive relationship between the amount of smooth muscle shortening and the eosinophil density in the inner wall. On the other hand, this relationship was significantly negative in the adventitia. Atropine completely inhibited the eosinophil accumulation in the inner wall. These data suggest that eosinophils can accumulate in the airway inner wall during bronchoconstriction because of geometrical factors.

Animals↗
PubMed1996

Airway wall dimensions during carbachol-induced bronchoconstriction in rabbits.

Airway wall area is an important determinant of airway narrowing. We hypothesized that in cross-sectioned peripheral airways, the wall area internal to the outer smooth muscle border (inner wall area) would decrease and the airway wall area external to the outer smooth muscle layer (adventitial area) would increase during bronchoconstriction because of the relocation of blood and/or fluid between these compartments. To test this hypothesis, we used anesthetized open-chest rabbits and measured airway wall dimensions and smooth muscle shortening of membranous airways after carbachol-induced bronchoconstriction using morphometric techniques. Acute (3-min) and sustained (40-min) bronchoconstriction was induced by aerosol nebulization of carbachol and compared with saline treatment. After physiological measurements, the heart base was snared, and the lung and heart were excised en bloc and frozen by using liquid nitrogen while a transpulmonary pressure of 2 cmH2O was maintained. The lung was processed for light-microscopic examination by using a freeze substitution technique. Results show that adventitial area was significantly decreased after sustained but not acute bronchonconstriction. The mechanism of this change, which contradicts our hypothesis, is unclear. However, the decrease of adventitial area could increase rather than decrease the effect of lung parenchymal tethering and attenuate airway narrowing.

Administration, Inhalation↗
PubMed1996

Human airway narrowing measured using high resolution computed tomography.

Exaggerated airway narrowing in response to bronchoconstricting stimuli is a characteristic feature of asthmatic subjects. It is unknown whether the site of airway narrowing differs in asthmatic subjects from that observed in normal subjects. Increased airway wall thickness has been suggested as a contributing cause for airway hyperresponsiveness in asthma, based on histologic measurements. We measured airway wall thickness and the site and magnitude of airway narrowing in response to inhaled methacholine in normal subjects and in patients with mild to moderate asthma using high resolution computed tomography (HRCT). After a comparable decrease in FEV1, there were no differences in the site or magnitude of airway narrowing for any category of airway size in asthmatic subjects and normals. However, the results show that the smaller airways of the asthmatic subjects are significantly thickened and that the airway wall area does not change after bronchoconstriction whereas it decreases in normal subjects. We conclude that airway wall thickening and the lack of a change in airway wall dimensions following bronchoconstricting stimuli could contribute to exaggerated airway narrowing in asthma.

Adult↗
PubMed1995

Determinants of airway smooth muscle shortening in excised canine lobes.

There is marked heterogeneity of airway narrowing in intraparenchymal airways in response to bronchoconstricting stimuli. We hypothesized that this heterogeneity results from variations in the structure of the airway wall. Freshly excised dog lung lobes were inflated to transpulmonary pressures (PL) of between 5 and 15 cmH2O, and an aerosol containing a high concentration of carbachol was administered. The lobes were fixed and processed for light-microscopic examination and morphometric analysis of membranous airway dimensions. The relationships of smooth muscle shortening to PL and airway dimensions were analyzed using multiple linear regression. The results show that airway smooth muscle shortening was greater at lower PL and in airways with larger internal perimeter and a greater number of folds per internal perimeter and that it was less in airways with greater inner wall area. We conclude that the magnitude and variability of airway smooth muscle shortening and airway narrowing in response to maximal constricting stimuli are influenced by mechanical factors related to airway wall geometry.

Airway Resistance↗
PubMed1995

Effect of chronic antigen and beta 2 agonist exposure on airway remodeling in guinea pigs.

We recently reported that chronic exposure to fenoterol (FEN) in guinea pigs increases in vivo and in vitro airway responsiveness to a degree similar to that induced by chronic antigen (ovalbumin [OA]) exposure. We hypothesized that these changes were due to airway inflammation and airway remodeling. To trace newly recruited granulocytes as a marker of inflammation and to detect DNA replication in resident airway wall cells, the nucleotide 5'-bromo-2'-deoxyuridine (BrdU) was administered intermittently over the six-wk period of chronic FEN and/or OA exposure. Noncartilaginous airway dimensions were measured and the area fraction of BrdU-immunoreactive and total nuclei in adventitia, smooth muscle, and epithelium was determined by immunohistochemistry and point counting. The proliferation index was defined as the ratio of the two area fractions in each wall area. The adventitial areas of FEN- and OA-treated airways were respectively 62 and 88% greater than those of control airways (p < 0.05). The inner wall areas were not increased. The smooth muscle cell and epithelial cell proliferation index was increased after OA (smooth muscle index: control, 2.7 +/- 1.1% [SEM]; OA, 23.0 +/- 3.7%; p < 0.02) but not after FEN exposure, and there was an increased number of BrdU-immunoreactive granulocytes in the adventitia and epithelium after OA but not after FEN exposure. The increased in vivo airways responsiveness produced by chronic OA or FEN exposure may be attributable to adventitial thickening and increased in vitro muscle contractility, but the cellular mechanisms underlying these and other airway wall responses are different.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1994

Proposed nomenclature for quantifying subdivisions of the bronchial wall.

There is increasing interest in the structural components of the airway wall because of the airway remodeling that is observed in conditions such as asthma and chronic obstructive pulmonary disease and because of their contribution to changes in airway mechanics. This interest has stimulated several groups to make morphometric measurements on airway cross sections, and their results have been reported using a variety of nomenclature. We propose the adoption of a standard system of nomenclature that is based on accepted terms for subdivisions of the airway wall and has been agreed to by several groups working in this field.

Bronchi↗
PubMed1993

Airway smooth muscle shortening in excised canine lung lobes.

To estimate the importance of lung parenchymal airway interdependence in attenuating airway narrowing, airway smooth muscle shortening in response to nebulized carbachol was measured in excised canine lung lobes and compared with the calculated load applied by lung elastic recoil. Pulmonary resistance of matched right and left upper lobes of five dogs was measured in a pressure-compensated volume plethysmograph by forced oscillation (6 Hz) before and after administration of an aerosol of carbachol (250 mg/ml) or saline. Matched lobes were studied at transpulmonary pressures (PL) of 5, 7, 10, 12, and 15 cmH2O. The lungs were then fixed at that PL by pulmonary arterial perfusion with formaldehyde, and cross sections of multiple airways from each lobe (n = 275) were examined by use of morphometric techniques to measure luminal area and smooth muscle length. By use of the saline lobe as a control, percentage of muscle shortening and decrease in airway lumen area caused by carbachol could be calculated. Passive and active smooth muscle stresses in each airway were calculated from PL and the calculated change in peribronchial pressure for a given change in airway diameter. The increase in pulmonary resistance and average smooth muscle shortening after administration of carbachol was greater in lobes held at lower PL. There was marked variation in narrowing between airways within a lobe: smooth muscle shortening ranged between 0 and 65% but averaged < 45% at all levels of PL.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗