Biomedical subjects

J Midorikawa

Publications and source records attributed to J Midorikawa.

9 recordsLinked to original sources

PubMed2001

Continuous observation of superoxide generation in an in-situ ischemia-reperfusion rat lung model.

To investigate the time course of superoxide generation in ischemia-reperfusion in the in-vivo rat lung, the present study used an enhanced chemiluminescence method with 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo[1, 2-alpha]pyrazin-3-one (MCLA) as a specific probe. The right pulmonary artery was occluded for 120 min, followed by 90-min reperfusion. Chemiluminescence induced by MCLA was continuously monitored by a photomultiplier exposed to the right lung. Chemiluminescence increased gradually in 30 min of reperfusion and remained elevated throughout reperfusion. The ratio of the luminescence count during reperfusion to the preischemic value increased to 2.20+/-0.31 (mean+/-SEM) (p<0.02 vs preischemic level), 2.50+/-0.39 (p<0.005), and 2.69+/-0.44 (p<0.005), at 30, 60, and 90 min of reperfusion, respectively. Bolus administration of superoxide dismutase during the reperfusion period significantly attenuated the chemiluminescence by 45.0+/-6.7% (p<0.01). The present results suggest that increasing oxygen radical formation leading to ischemia-reperfusion lung injury may occur even after a short period of occlusion of the pulmonary artery alone in vivo.

Animals↗

PubMed1997

Lack of ventilatory threshold in patients with chronic obstructive pulmonary disease.

We investigated whether the ventilatory threshold (VET) could be detected in 25 patients with severe chronic obstructive pulmonary disease (COPD). Exercise on a treadmill was performed until symptom-limited maximum oxygen uptake (VO2SL) was obtained. VET was absent in 14 patients (56%, VET(-) group) and present in the others (44%, VET(+) group). Basal pulmonary functions and dyspnea index (VE,SL/MVV) were not different between the two groups. Endurance time and exercise tolerance (VO2SL/bw) were significantly less in VET(-) than in VET(+). In the former group, PaO2 and pH at maximal exercise decreased and PaCO2 increased significantly, but HCO3- did not change compared with the corresponding values before exercise. In the latter group, PaCO2 at maximal exercise increased significantly, and pH and HCO3- decreased significantly compared with the values before exercise, but PaO2 did not. The changes in PaO2 and PaCO2 were not different between the two groups, but changes in pH and HCO3- in VET(+) were greater than those in VET(-). These results suggest that the absence of VET in some COPD patients indicates a lower exercise capacity without producing metabolic acidosis. This may be caused by rapidly developing dyspnea.

Aged↗

PubMed1995

Hypoglossal nerve stimulation affects the pressure-volume behavior of the upper airway.

To determine the effects of electrical hypoglossal nerve and submental stimulation on upper airway collapsibility, we examined the pressure-volume (P-V) relationships during bilateral supramaximal stimulation of the distal cut hypoglossal nerve ends over a range of frequencies from zero to 100 Hz in the sealed upper airway of 10 anesthetized supine dogs. Animals were artificially ventilated with 50% O2 and maintained under relative hyperoxia and hypocapnia during the study to eliminate the ventilatory drive output. Sealed upper airway pressures were obtained during random injections of different volumes of air from zero to 50 ml with and without hypoglossal nerve stimulation, and the upper airway P-V curves were obtained. The characteristics of the P-V curves were as follows: (1) the upper airway compliance defined as the slope of the regression of P-V curves fell from 4.07 +/- 0.33 ml/cm H2O without stimulation to 3.02 +/- 0.30 ml/cm H2O with stimulation at 50 Hz and plateaued at frequencies greater than 50 Hz, and (2) the volume at a given pressure during stimulation was larger than that without stimulation. The effects of submental stimulation on upper airway collapsibility were similar to those of hypoglossal nerve stimulation. These results suggest that the increase of upper airway muscle tone by hypoglossal nerve or submental stimulation stiffens the upper airway and that increases in muscle tone expand the upper airway.

Animals↗

PubMed1994

Effect of pilocarpine on propranolol-induced bronchoconstriction in asthma.

To investigate whether increased release of acetylcholine may be involved in propranolol-induced bronchoconstriction (PIB), the inhibitory effect of pilocarpine (Pilo), an agonist of M2-muscarinic receptors that in 11 stable asthmatic subjects. The bronchial responsiveness to Pilo was also measured in terms of Dmin, defined as the cumulative dose at the point where respiratory resistance (Rrs) began to increase. In PIB, the maximum increase in Rrs (Rrs max) after stopping inhalation for 1 min was measured. Atropine reversed PIB. After pilocarpine pretreatment at a dose equal to Dmin, Rrs max divided by baseline Rrs decreased significantly from 206.6 +/- 61.1 to 163.0 +/- 42.6% (mean +/- SD) (p = 0.001). The ratio of PIB (Rrs max/baseline Rrs) with Pilo to PIB without Pilo correlated inversely according to the pretreatment dose (Dmin) of Pilo (p < 0.05). These results suggest increased release of acetylcholine in PIB and that M2-muscarinic receptors are at least in part functioning in stable asthmatic airways.

Acetylcholine↗

PubMed1994

Effects of prostaglandin E2 inhalation on hypercapnic response in normal subjects.

It is known that the ventilatory response to carbon dioxide (CO2) is increased in asthmatics with airway obstruction. Increased vagal afferent activity as well as increased airway resistance have been postulated as the causative mechanisms. However, whether increased vagal afferent activity without bronchoconstriction increases the ventilatory response to CO2 has not been investigated in humans. We examined the effects of prostaglandin E2 (PGE2) inhalation, which is known to stimulate vagal afferent receptors in the lung without an increase in airway resistance, on the respiratory response to CO2 in seven healthy male subjects. Either physiologic saline or PGE2 (100 micrograms/ml) was inhaled through a Bird nebulizer for 3 min. Twenty minutes after each inhalation, the responses of minute ventilation (VE) and occlusion pressure (P0.1) to hyperoxic hypercapnia were measured. Both the relationships between VE and P0.1 to an increase in tension of end-tidal CO2 (PETCO2) were analyzed by linear regression. Although the mean value of respiratory resistance after PGE2 (3.0 cm H2O/L/s +/- 0.4) did not differ significantly from that after saline (3.1 cm H2O/L/s +/- 0.4), inhaled PGE2 significantly increased the hypercapnic response. This result suggests that the increased vagal afferent activity per se plays an important role in increasing the hypercapnic ventilatory response in humans.

Administration, Inhalation↗

PubMed1993

Upper airway muscle activity during sustained hypoxia in awake humans.

To examine the effects of sustained hypoxia on upper airway and chest wall muscle activity in humans, we measured genioglossus muscle (GG) activity, inspiratory intercostal muscle (IIM) activity, and ventilation during sustained hypoxia in 17 normal subjects and 17 patients with obstructive sleep apnea (OSA). The trial of sustained hypoxia was performed as follows: after an equilibration period of 3 min, isocapnic hypoxia (arterial O2 saturation = 80 +/- 2%) was maintained for 20 min. GG EMG was measured with a fine-wire electrode inserted percutaneously, and IIM EMG was measured with surface electrodes. Ventilatory response to sustained hypoxia was initially increased and subsequently decreased. Stable phasic GG activity during spontaneous tidal breathing was observed in 6 normal subjects and 10 patients with OSA. Responses of GG and IIM activities to sustained hypoxia showed a biphasic response qualitatively similar to the ventilatory response in these 16 subjects. The absolute value of the subsequent decline in GG activity was similar to that of the initial increase, whereas the subsequent decline in IIM activity was smaller than that of the initial increase. Percent GG activity was significantly lower than both percent IIM activity and percent minute ventilation during the decline and plateau phases. There were no significant differences in ventilatory and EMG responses between the normal subjects and the patients with OSA. We conclude that, during wakefulness, upper airway muscle activity declined to a greater extent than inspiratory pump muscle activity during sustained hypoxia.

Adult↗

PubMed1992

[Bronchial asthma].

In the first study, to clarify whether increased vagal afferent activity contributes to the increase in ventilatory response to CO2 in patients with asthma, we examined the effects of prostaglandin E2 (PGE2) inhalation on the respiratory response to CO2 in seven normal subjects. After PGE2 inhalation, the ventilatory and occlusion pressure responses to CO2 increased significantly compared with those after saline inhalation, with no increase in respiratory resistance. These results suggest that increase in vagal afferent activity may play a role in the increased hypercapnic response during acute exacerbations of asthma. In the second study, to clarify the reduced respiratory chemosensitivity associated with asthma-related deaths, we examined the hypercapnic and hypoxic ventilatory responses in five patients with near-fatal asthma who were given artificial ventilation and/or became unconsciousness during an acute exacerbation of asthma. Hypoxic ventilatory response was significantly lower in these subjects than in patients with uncomplicated asthma and normal subjects, suggesting that lowered hypoxic ventilatory response may be related to death from asthma.

Asthma↗

PubMed1990

[Sideroblastic anemia associated with adenine phosphoribosyltransferase deficiency].

We report a case of acquired idiopathic sideroblastic anemia associated with adenine phosphoribosyltransferase (APRT) deficiency. A 72-year-old male had been troubled with urolithiasis since his teens. In 1984, he was referred to us because of chronic renal failure and anemia. He was diagnosed as having sideroblastic anemia and required red cells transfusion regularly. In June 1989, he was admitted to our hospital because of cerebral infarction. Peripheral blood analysis showed pancytopenia. Bone marrow aspiration revealed hypercellularity with 36.2% erythroblasts, and 18.5% ringed sideroblasts of all nucleated cells. According to the FAB classification, a diagnosis of refractory anemia with ring sideroblasts was made. As his urinary stone consisted of 2, 8-dihydroxyadenine by analysis of infrared spectrum, genetic and enzymatic studies were performed. These studies indicated APRT deficiency. He died of pneumonia accompanied with progressive renal failure on August 9, 1989.

Adenine Phosphoribosyltransferase↗

PubMed1989

Signet cell carcinoma of the stomach in a patient with acquired immunodeficiency syndrome: a case report.

A case of signet cell carcinoma associated with AIDS is presented. A 50-year old Japanese man with hemophilia A was suffering from human immunodeficiency virus (HIV) infection, the result of multiple injections of clotting factor concentrates. A diagnosis of signet cell carcinoma of the stomach was reached upon endoscopic and histological examinations. Opportunistic infections of esophageal candidiasis and candida septicemia occurred. The patient died of repeated gastrointestinal bleeding and cachexia. Although there is a possibility of the patient having a coincidential carcinoma along with AIDS, the HIV infection, perhaps, had a role in causing signet cell cercinoma.

Acquired Immunodeficiency Syndrome↗