Biomedical subjects

J Iwamoto

Publications and source records attributed to J Iwamoto.

At least 55 records · Page 3Linked to original sources

PubMed1997

Transient corneal edema induced by nitric oxide synthase inhibition.

The aim of the study is to identify nitric oxide synthase (NOS) in the rabbit cornea and further investigate the physiological role of nitric oxide in the rabbit cornea. For histological identification, an immunohistochemical technique using anti-NOS monoclonal antibodies was employed. For the physiological study, we measured the corneal thickness in vivo as an indicator of corneal edema by ultrasonic pachymetry. The measurements were repeated before and after ipsilateral injections of N(G)-nitro-L-arginine methyl ester (L-NAME) or N(G)-nitro-D-arginine methyl ester (D-NAME) or 6-anilino-5,8-quinolinedione (LY-83583) with contralateral injection of vehicle (balanced salt solution) into the anterior chamber of the rabbit. We also monitored intraocular pressure (IOP) by pneumatonometry. Endothelial NOS (eNOS) immunoreactivity was demonstrated both in the corneal epithelium and the endothelium. The corneal thickness significantly increased after L-NAME or LY-83583 without significant rise of IOP, whereas no change was detected after vehicle or D-NAME. These results suggest that NO is spontaneously produced in the corneal endothelium and the NO/cyclic GMP pathway is involved in maintainance of corneal thickness.

Aminoquinolines↗

PubMed1996

Measurement of nitric oxide in human nasal airway.

The nasal output of nitric oxide (NO) is known to be high, but there have been varying reports of the exact level. We attempted to establish a quantitative measurement of nasal NO, and looked for a possible relationship with nasal resistance, at rest and during exercise. Nasal airway ventilation was performed by using an air pump at a constant flow rate, whilst the soft palate was elevated voluntarily. In a preliminary study, the flow rate for sampling was changed and concentrations of NO were measured. After determination of flow rate, rhinomanometry for nasal resistance and measurement of nasal NO by chemiluminescence were carried out before and after moderate exercise. The concentration of NO ([NO]) exhibited a hyperbolic relationship with flow rate of ventilation (V'E), indicating [NO] x V'E = net nitric oxide output (V'NO) = constant. Hence, nasal NO was expressed quantitatively as V'NO (nL.min-1). For 1 L.min-1 of ventilation, [NO] varied between 2 and 500 parts per billion (ppb) (mean = 323 ppb). The average nasal V'NO in 12 healthy male subjects was 323 +/- 91 nL.min-1 (mean +/- SD). After exercise on a treadmill (10 degrees, 5 km.h-1) for 4 min, nasal V'NO decreased to 229 +/- 63 nL.min-1. At rest, expiratory and inspiratory nasal resistance was 0.27 +/- 0.04 and 0.27 +/- 0.06 Pa.s.cm-3, respectively. After exercise, expiratory and inspiratory nasal resistance decreased to 0.17 +/- 0.04 and 0.16 +/- 0.04 Pa.s.cm-3, respectively. These data indicate that nasal NO can be measured quantitatively as V'NO and might be involved in the control of nasal resistance.

Adult↗

PubMed1994

Effect of graded exercise on nitric oxide in expired air in humans.

This study was performed to determine the influence of graded dynamic exercise and of voluntary hyperventilation on both the concentration ([NO]) and the amount of nitric oxide per unit time (VNO) in exhaled air. Young human subjects (n = 8) of varying fitness levels having peak O2 consumption (VO2) values ranging between 25.7 and 50.9 ml/min/kg were studied during graded levels of treadmill exercise. Expired [NO] determined by chemiluminescence was 26.3 +/- 6.7 SE parts per billion (ppb) at rest ranging between 11 and 66 ppb. Although variable, [NO] was maintained as work rate increased. VNO rose significantly in most subjects from a mean resting value of 12.3 +/- 3.5 nmol/min. VNO correlated linearly and significantly with ventilation (VE) and CO2 output in 6 of 8 subjects, with VO2 in 4 of 8 subjects, and with heart rate in 5 of 8 subjects. Increases of VNO per unit increase of VE were significantly higher in subjects having higher peak VO2 levels. Voluntary hyperventilation (two-fold of the control VE) for 1 min in 6 subjects decreased expired [NO] from 9.5 (+/- 2.5) to 4.8 (+/- 2.8) ppb and VNO was unchanged, while hyperventilation at 3 x control VE increased VNO by 50% and [NO] decreased to 4.7 +/- 1.8 ppb. VNO appeared to be related to VO2 during hyperventilation. The results suggest that VNO can be correlated with ventilation and heart rate during exercise and with VO2 during both exercise and hyperventilation. [NO] is influenced by the flow rate of the expired air whereas VNO is influenced by NO clearance at the alveolus.

Adult↗

PubMed1994

Methemoglobin production by nitric oxide in fresh sheep blood.

As nitric oxide (NO) inhalation is used therapeutically, we studied the production of methemoglobin (metHb) by NO in fresh adult sheep blood. NO solutions were prepared by bubbling a 10% NO-90% N2 gas mixture in phosphate-buffered saline (pH = 7.41 at 20 degrees C) for at least 60 min. Fresh blood samples were obtained from catheterized femoral arteries or veins just prior to mixing with NO solution. Measurements of metHb were made at times 0, 30 sec, 2 min and 5 min after mixing of NO-containing buffer and blood using a Radiometer OSM-3 hemoximeter. Mixing was performed using two syringes connected via a stopcock. The reaction of NO with blood occurred rapidly after mixing since data values for each of the time points after 30 sec were unchanged for all mixtures. The mixing volume ratio of NO-containing buffer to blood was either 1:1 (protocol A) for comparisons of arterial vs venous blood, or the ratios were randomized (protocol B) to investigate effects of Hb oxygenation. Protocol A elicited only slight increases of metHb in arterial and venous blood which did not differ significantly. In protocol B, an increase of metHb was associated with a relative decline of deoxyhemoglobin (deoxyHb). A higher molar ratio of NO/deoxyHb yielded greater amounts of metHb. Therefore, in fresh sheep blood, deoxyHb is converted to metHb in the presence of NO. This reaction is not affected by the presence of oxyhemoglobin.

Animals↗

PubMed1994

[Perceived health of persons and their practice of health promoting activities].

The perceived health of persons and their practice of health promoting activities were surveyed using a self-rating questionnaire with 49 items assessing level of health, practice of health promoting activities, life styles, health education, and participation in health screening for general health conditions and cancers. The questionnaires were mailed to 2,500 residents of a city, aged from 30 to 69 years old, randomly selected according to the composition ratios of the populations in the city. Persons from 2,333 subjects (1,057 male and 1,276 female) were effectively collected, representing about 1% of the city's population. General health was good in about 85% of the subjects, with decreases observed with age. Practice of activities for health promotion was wide-spread among the subjects. These activities included regularity, diet, nutrition, smoking and drinking control, physical exercise, sleep, and rest. The subjects expressed strong fear of cancers and concerns about deterioration in physical fitness. Their target life style was one with adequate sleep and rest, regularity in eating, good nutrition, and avoidance of overwork. Health screening participation rates were low at approximately 28% because of their perceived good health, and busy daily life and work. It appears that the perceived health of citizens may not always correlated with the practice of health promoting activities.

Adult↗

PubMed1993

Nitric oxide inhibition varies with hemoglobin saturation.

Endothelium-derived nitric oxide (NO) appears to be involved in the regulation of pulmonary vascular tone by O2. We hypothesized that the ability of blood to inhibit the vasodilation caused by NO would vary inversely with the saturation of hemoglobin by O2. To test this hypothesis, we used the pulmonary circulation of the unanesthetized fetal lamb as a bioassay for NO-induced vasodilation. Two to 3 days before the experiment, the main pulmonary artery, left atrium, carotid artery, and trachea of the fetus were catheterized and an ultrasonic blood flow transducer was placed around the proximal portion of the left pulmonary artery. On the day of the experiment, NO solution was prepared by bubbling 10% NO-90% N2 gas mixture in saline. This solution was injected into the fluid-filled potential air spaces of the fetal lungs via the trachea. At the highest dose (0.8 mumol), NO increased pulmonary blood flow fourfold and decreased pulmonary vascular resistance similarly. The dose-response curve for NO was similar to those obtained from isolated pulmonary blood vessels and gas-ventilated animals. Mixing NO solution with maternal arterial blood before injection decreased the effect of NO, and mixing it with venous blood virtually eliminated the effect. The decrease in fetal pulmonary vascular resistance caused by NO was inhibited by blood in inverse proportion to the saturation of hemoglobin with O2 in the blood (R2 = 0.93, P < or = 0.0001), confirming our hypothesis.

Animals↗

PubMed1993

[Difference in perceived health between blue- and white-collar workers of a manufacturing factory by a self-administered questionnaire].

In order to examine the differences in which blue- and white-collar workers perceive their own health status, a survey using self-administered questionnaire was conducted. The subjects were 1,428 male workers in a tire manufacturing factory, consisting of 1,185 blue-collar workers and 243 white-collar workers. Most of the blue-collar workers were engaged in shift work consisting of three shifts/d. The questionnaire included 32 items concerning health habits, life and job satisfaction, mental stress, and type A behavior. The following findings were obtained. Good daily health habits were related to age. Older workers had better health habits than the younger ones both in white- and blue-collar workers. The white-collar workers were more satisfied with their life and jobs, and also showed type A behaviors at a higher rate. As for fatigue and dissatisfaction association with shift work, the workers' complaints increased in the order of day shift, evening shift and midnight shift. The older workers had fewer complaints than the younger ones. These results suggested that health management and education will be more effective if the working conditions and the background of each worker are taken into consideration.

Adult↗

PubMed1992

Methylene blue inhibits hypoxic cerebral vasodilation in awake sheep.

Cerebral vasodilation in hypoxia may involve endothelium-derived relaxing factor-nitric oxide. Methylene blue (MB), an in vitro inhibitor of soluble guanylate cyclase, was injected intravenously into six adult ewes instrumented chronically with left ventricular, aortic, and sagittal sinus catheters. In normoxia, MB (0.5 mg/kg) did not alter cerebral blood flow (CBF, measured with 15-microns radiolabeled microspheres), cerebral O2 uptake, mean arterial pressure (MAP), heart rate, cerebral lactate release, or cerebral O2 extraction fraction (OEF). After 1 h of normobaric poikilocapnic hypoxia (arterial PO2 40 Torr, arterial O2 saturation 50%), CBF increased from 51 +/- 5.8 to 142 +/- 18.8 ml.min-1 x 100 g-1, cerebral O2 uptake from 3.5 +/- 0.25 to 4.7 +/- 0.41 ml.min-1 x 100 g-1, cerebral lactate release from 2 +/- 10 to 100 +/- 50 mumol.min- x 100 g-1, and heart rate from 107 +/- 5 to 155 +/- 9 beats/min (P < 0.01). MAP and OEF were unchanged from 91 +/- 3 mmHg and 48 +/- 4%, respectively. In hypoxia, 30 min after MB (0.5 mg/kg), CBF declined to 79.3 +/- 11.7 ml.min-1 x 100 g-1 (P < 0.01), brain O2 uptake (4.3 +/- 0.9 ml.min-1 x 100 g-1) and heart rate (133 +/- 9 beats/min) remained elevated, cerebral lactate release became negative (-155 +/- 60 mumol.min-1 x 100 g-1, P < 0.01), OEF increased to 57 +/- 3% (P < 0.01), and MAP (93 +/- 5 mmHg) was unchanged. The sheep became behaviorally depressed, probably because of global cerebral ischemia. These results may be related to interference with a guanylate cyclase-dependent mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

N omega-nitro-L-arginine influences cerebral metabolism in awake sheep.

Cerebral vasodilation in hypoxia may involve endothelium-derived relaxing factor-nitric oxide (NO). An inhibitor of NO formation, N omega-nitro-L-arginine (LNA, 100 micrograms/kg i.v.), was given to conscious sheep (n = 6) during normoxia and again in hypocapnic hypoxia (arterial PO2 approximately 38 Torr). Blood samples were obtained from the aorta and sagittal sinus, and cerebral blood flow (CBF) was measured with 15-microns radiolabeled microspheres. During normoxia, LNA elevated (P < 0.05) mean arterial pressure from 82 +/- 3 to 88 +/- 2 (SE) mmHg and cerebral perfusion pressure (CPP) from 72 +/- 3 to 79 +/- 3 mmHg, CBF was unchanged, and cerebral lactate release (CLR) rose temporarily from 0.0 +/- 1.9 to 13.3 +/- 8.7 mumol.min-1 x 100 g-1 (P < 0.05). The glucose-O2 index declined (P < 0.05) from 1.67 +/- 0.16 to 1.03 +/- 0.4 mumol.min-1 x 100 g-1. Hypoxia increased CBF from 59.9 +/- 5.4 to 122.5 +/- 17.5 ml.min-1 x 100 g-1 and the glucose-O2 index from 1.75 +/- 0.43 to 2.49 +/- 0.52 mumol.min-1 x 100 g-1 and decreased brain CO2 output, brain respiratory quotient, and CPP (all P < 0.05), while cerebral O2 uptake, CLR, and CPP were unchanged. LNA given during hypoxia decreased CBF to 77.7 +/- 11.8 ml.min-1 x 100 g-1 and cerebral O2 uptake from 154 +/- 22 to 105.2 +/- 12.4 mumol.min-1 x 100 g-1 and further elevated mean arterial pressure to 98 +/- 2 mmHg (all P < 0.05), CLR was unchanged, and, surprisingly, brain CO2 output and respiratory quotient were reduced dramatically to negative values (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

[A 4 degrees C-1 min method of cold water immersion test for peripheral circulatory function in fingers].

To assess the validity of a new simplified cold water immersion test (4 degrees C-1 min method) for peripheral circulatory function, comparison was made with the conventional method (10 degrees C-10 min method). These two different methods of cold immersion test were applied to 23 patients with vibration disease and 24 healthy men. Observation was made on finger skin temperature by a thermistor and complaints in the hand by a 5-step self-reported scale method every minute during the test. The patterns of recovery of skin temperature after cold immersion in each group were similar in both methods. Pain in the hand in the 4 degrees C-1 min method was less than that in the 10 degrees C-10 min method. The recovery rate at 5 min in the patients with Raynaud's phenomenon was lower than that in those without Raynaud's phenomenon in the 4 degrees C-1 min method (p < 0.01). However, no significant differences were noted in 10 degrees C-10 min method. The results suggest that the new method is feasible in detecting the response of vasodilation after immersion. In the recovery rate at 5 min after immersion, near values of the sensitivity and specificity were observed between 50% cut-off values in the 4 degrees C-1 min method and 30% value in the 10 degrees C-10 min method. Thus, the 4 degrees C-1 min method is considered to be more useful to evaluate the physiological response after cold immersion than the 10 degrees C-10 min method.

Adult↗

PubMed1991

Intracranial pressures and O2 extraction in conscious sheep during 72 h of hypoxia.

High-altitude cerebral edema may occur within several days after a rapid ascent to altitude. However, the mechanisms that produce this potentially lethal condition are unclear. This experiment assessed systemic arterial and intracranial pressures (n = 22) and cerebral blood flow per unit cerebral O2 consumption (Qc/cVo2) and cerebral O2 extraction fraction (cEo2) (n = 9) in conscious sheep before and during 72 h of normobaric hypoxia (arterial O2 tension approximately 40 mmHg, oxygen saturation in arterial blood approximately 50%). Qc/cVo2 and cEo2 were calculated from systemic arterial and cerebral venous O2 contents. Wet-to-dry brain weight ratios were calculated during normoxia (n = 4) or after 72 h of hypoxia (n = 5) in additional sheep. Intracranial pressures did not change during hypoxia (+ 1.3 to +1.8 mmHg, P = 1.0); however, estimated intracranial capillary hydrostatic pressure may have increased 1-20 mmHg depending on the arterial-to-downstream resistance ratio. During the 72 h of hypoxia, Qc/cVO2 doubled (P = 0.02) and cEo2 tended to decrease (5% absolute, P = 1.0). Regional wet-to-dry brain weight ratios after 72 h of hypoxia were 4-13% greater than their respective ratios during normoxia (0.001 less than P less than or equal to 0.05); indirect evidence suggests that this increased brain water content was extravascular. The sheep may be an appropriate model for the further study of high-altitude cerebral edema.

Animals↗

PubMed1991

Renal, hormonal, and fluid shift responses to ANP during head-out water immersion in awake dogs.

Renal responses to low doses of atrial natriuretic peptide (ANP) may be potentiated during water immersion-induced central hypervolemia. To test this hypothesis, ANP was infused in awake dogs in doses of 0, 5, and 25 ng.kg-1.min-1 either when the dogs were in air or during head-out water immersion (WI) under thermoneutral conditions (37 degrees C). In general, there were greater diuretic (V) and natriuretic responses (UNaV) at the same level of plasma ANP in WI, with the slopes (or sensitivities) of V and UNaV in relation to plasma ANP levels being significantly increased during WI. Plasma renin activity decreased only during WI and was significantly correlated with both V and UNaV only during WI. Plasma and urinary arginine vasopressin levels were unchanged during WI. Infusion of ANP prevented the usual decline of hematocrit that occurs during WI. These results support the view that the renal sensitivity to ANP is augmented during the plasma volume expansion of WI. In addition, ANP may attenuate the transcapillary fluid shift that occurs during WI.

Animals↗

PubMed1991

Cerebral metabolic and pressure-flow responses during sustained hypoxia in awake sheep.

Conscious sheep (n = 6), exposed to 3.5 h of normobaric hypoxia (arterial PO2 = 40 Torr) while allowed varying arterial PCO2, showed striking early increments of cerebral blood flow (CBF; +200-250%, by radiolabeled microspheres) and decrements of cerebral vascular resistance (CVR) in association with an early temporary elevation of cerebral O2 consumption (CMRO2; +25-60%). After 2 h, CMRO2 returned to normoxic levels, while CBF declined to a lower but still elevated level (+150%). CBF/CMRO2 increased twofold, while cerebral fractional extraction of O2 was unchanged. Mean arterial pressure was unchanged, but cerebral venous pressure rose (+11 mmHg) in a stable fashion such that cerebral perfusion pressure declined by 13%. Cerebral venous hematocrit and hemoglobin concentration were both elevated (+2.2-2.7% Hct units; +1.0-1.3 g/dl, respectively) above the corresponding arterial values between 150 and 210 min of hypoxia, suggesting venous hemoconcentration in possible association with a transcapillary fluid shift. CBF, and especially CVR, were well correlated with arterial O2 content.

Acid-Base Equilibrium↗

PubMed1990

Cardiovascular, renal, and endocrine responses in male quadriplegics during head-out water immersion.

The present study was undertaken to determine the relative influence of the action of the central nervous system on the mechanism of water-immersion-induced diuresis by comparing physiological responses of quadriplegic (QP) and normal subjects. After overnight fasting seven male QP subjects with complete cervical cord transections (C5-C8) and six normal men were tested before, during, and after 3 h of head-out immersion (HOI) in thermoneutral water (34.5-35.0 degrees C). The reversible increase in urine flow and the total urine volume (309 +/- 53 ml in 3 h) in QP subjects were comparable with that of the normal subjects (318 +/- 96 ml in 3 h). While osmolal excretion was increased in QP subjects, its magnitude was less when compared with that of normal subjects. Instead, the increased urine flow in QP subjects was characterized by increased glomerular filtration rate (GFR) and free water clearance, in contrast to a predominantly osmotic diuresis with no changes in GFR in the normal subjects. The HOI elevated (P less than 0.05) systolic pressure only in QP subjects, whereas the increase in cardiac output was the same in both groups. While plasma renin activity and aldosterone responses to HOI in QP subjects were comparable with those of normal individuals, plasma atrial natriuretic factor (ANF) in QP subjects was twofold higher (P less than 0.05) during HOI, and the approximately threefold increase in ANF (P less than 0.05) in QP subjects due to HOI was the same as that of normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Changes in insulation of body tissue and wet suits during underwater exercise at various atmospheric pressures.

To clarify the independent changes of insulations of body tissues (Itissue) and wet suit (Isuit) in the wet-suited subject during underwater exercise, overall heat flow from the skin (Htissue) and wet suit (Hsuit) and esophageal (Tes), skin (Tsk), and wet suit temperatures were measured at 1, 2, and 2.5 atmospheres absolute (ATA) at critical water temperature (Tcw). The average Tcw in nine wet-suited men (23-38 yr) was 22.3 +/- 0.2, 26.3 +/- 0.2, and 28.0 +/- 0.4 degrees C (SE) at 1, 2, and 2.5 ATA, respectively. At Tcw of each pressure male volunteers wearing 5-mm neoprene wet suits completed three 2-h experiments while immersed up to the neck. During one experiment the subjects remained at rest, and in the other two they exercised on an underwater ergometer at two different intensities (2 and 3 met). Tes significantly declined (P less than 0.05) over 2 h from 37.1 to 36.5 degrees C during rest in each pressure. The 2-met exercise prevented Tes from falling in all pressures, and the 3-met exercise elevated Tes by 0.2-0.3 degrees C. There was no exercise-dependent difference in Isuit, but a pressure-dependent difference was remarkable. The Itissue at rest was identical for all pressures; however, it progressively decreased as a function of exercise intensity. It is concluded that overall Itissue is entirely determined by work intensity at Tcw, but not by atmospheric pressure. On the contrary, Isuit at Tcw is solely dependent on the pressure, but not on the work intensity.

Adult↗

PubMed1989

Renal sympathetic nerve activity and renal responses during head-up tilt in conscious dogs.

Renal sympathetic nerve activity (RSNA) was measured in conjunction with functional responses of the kidney during head-up tilt in eight conscious female dogs. A 40 degree head-up tilt resulted in a sustained increase in RSNA by 53 +/- 10% (P less than 0.05) relative to control level. Urine flow and osmolal and sodium excretions decreased significantly to a nadir of -55 +/- 4, -42 +/- 7, and -59 +/- 10%, respectively, whereas free water clearance and creatinine clearance did not change significantly during head-up tilt. The systemic arterial pressure (at kidney level) increased significantly from 110 +/- 4 to 129 +/- 6 mmHg, and central venous pressure decreased significantly from -0.7 +/- 0.5 to -7.6 +/- 0.6 mmHg. The chronic bilateral renal denervation, which was performed 2-4 wk before the experiment, abolished both the antidiuretic and antinatriuretic responses to heald-up tilt. These results indicate that an increase in RSNA plays a significant role in the decrease in urine flow and sodium excretion induced by 40 degree head-up tilt in conscious dogs.

Animals↗

PubMed1989

Ashimycins A and B, new streptomycin analogues.

Detailed analysis of the fermentation broth of Streptomyces griseus strain FT3-4 resulted in the identification of two new streptomycin analogues named ashimycins A and B. Their structures have been determined by NMR spectral analysis and chemical degradations.

Chemical Phenomena↗

PubMed1988

Renal and endocrine responses in the elderly during head-out water immersion.

After overnight food and fluid restriction, seven healthy old (62-74 yr) and eight young (21-28 yr) men were examined before, during, and after 3-h head-out immersion (HOI) in thermoneutral water (34.5 +/- 0.5 degrees C). On separate days, all subjects remained seated in air for 5 h to obtain the time control data. Although HOI induced a reversible increase in urine flow in all subjects, the response was faster and greater in magnitude in the elderly than in the young. Na excretion and osmolal clearance also followed a response pattern identical to that of urine flow; thus the HOI-induced diuresis was entirely osmotic. Endogenous creatinine clearance increased in the elderly at 2 h of HOI, suggesting an age-related modification in kidney hemodynamics. Although there was virtually the same cephalad blood shift (measured by impedance cardiography), mean arterial pressure significantly increased (P less than 0.05) during HOI in the elderly, which also indicated a different response of peripheral circulation to HOI in the elderly. Control level of plasma atrial natriuretic factor (ANF) was nearly twofold greater in the elderly compared with the young. The HOI induced a nearly fourfold increase in ANF in the elderly, whereas that for the young was threefold. Both plasma aldosterone and ADH responses to HOI were attenuated in the elderly compared with the young, which had no correlation with urine flow or Na excretion. It is concluded that the elderly release more ANF at a given cephalad volume expansion compared with the young, but the vasodilative reaction to ANF was attenuated in the elderly.

Adult↗