Biomedical subjects

K Oyama

Publications and source records attributed to K Oyama.

At least 91 records · Page 5Linked to original sources

PubMed1996

[A case report of total cavopulmonary connection following total cavopulmonary shunt].

A 20-year-old man underwent total cavopulmonary shunt for univentricular heart type A (A.L.L.) with hemiazygos connection six years ago. Four years later, his condition deteriorated with easy fatigue and cyanosis. Cardiac catheterization showed recanalization of ligated SVC. Chest CT showed tight adhesion between the chest wall and the ascending aorta. We approached the heart through left anterolateral thoracotomy in order to avoid injury of the aorta and the ventricle during redo median sternotomy. Total cavopulmonary connection with intraatrial conduit was performed under circulatory arrest and retrograde cardioplegia without aortic cross clamp. His postoperative course was satisfactory. Left thoracotomy was useful for total cavopulmonary connection following total cavopulmonary shunt associated with postoperative adhesion.

Adult↗

PubMed1995

Effects of transient global ischemia and a monoamine oxidase inhibitor ifenprodil on rat brain monoamine metabolism.

Ifenprodil, a cerebral vasodilator and non-competitive glutamate antagonist, is also an anti-ischaemic agent; it has been shown to inhibit both forms of MAO in rat brain and lung (with slightly greater potency towards MAO-A), but it does not inhibit SSAO. The effects of ifenprodil on rat brain regional levels of monoamines and their principal metabolites following transient global ischaemia have been investigated 1 h after reperfusion. Among the three most ischaemically vulnerable brain regions (striatum, hippocampus and cortex), striatal DA, DOPAC, HVA, 5-HT and 5-HIAA levels were the most markedly increased. Simultaneous treatment with ifenprodil during reperfusion reversed the increases in the striatum, except for HVA, to the level similar to those of sham-operated controls. In contrast to the striatum, ifenprodil failed to reverse the increases seen in the cortex and hippocampus.

Animals↗

PubMed1995

Pathogenicity of bacteria using a simulated root canal system.

The purpose of this study was to investigate the reliability of an implantation test using Teflon-simulated root canals for evaluating the pathogenicity of root canal bacteria. Models including suspensions of lyophilized strains (Actinomyces israelii, Streptococcus faecalis, and Porphyromonas asaccharolyticus) were implanted in rat subcutaneous tissue for 1 wk, and histological changes were observed. Severe inflammation occurred around the models. Among them, P. asaccharolyticus induced the severest inflammatory response. Further study using P. asaccharolyticus was conducted to compare the implantation test's ability to evaluate pathogenicity with that of an injection test at 1, 2, or 4 wk. Tissue injected with a bacterial suspension showed no clear response through the experimental periods, whereas tissue around implantation sites showed a severe response at 1 wk. However, the inflammatory response subsided at later stages. Consequently, further improvement is needed to investigate pathogenicity for long periods.

Actinomyces↗

PubMed1995

Effect of corticosteroids on free and sulfoconjugated catecholamines at birth in premature newborn sheep.

We previously demonstrated that prenatal corticosteroids attenuated the expected exponential increase in circulating catecholamines at birth. The present studies were undertaken to determine if alteration in sulfoconjugation could account for this attenuation. Catheterized fetal lambs received saline (n = 6) or corticosteroids (n = 8) intravenously for 60 h. The lambs were delivered by cesarean section at 130 +/- 1 days gestation. Ventilatory and cardiovascular responses and plasma catecholamine concentrations were measured for 2 h after birth. Although plasma free catecholamines levels were higher in controls than in corticosteroid-treated fetuses, the sulfoconjugated levels were similar in the two groups. Thus the corticosteroid-treated fetuses had a higher proportion of plasma sulfoconjugated catecholamines consistent with the possibility that sulfoconjugation was augmented during intrauterine life. After birth, the corticosteroid-treated animals showed an attenuated increase in plasma free catecholamine levels compared with controls but a similar increase in sulfoconjugated catecholamine levels to the control animals. The proportion of plasma sulfoconjugated catecholamines was higher in the corticosteroid-treated animals; however, the increase in sulfoconjugated catecholamines was insufficient to account for the attenuated overall increase in total catecholamines in the corticosteroid-treated animals.

Adrenal Cortex Hormones↗

PubMed1995

Early endovascular treatment for ruptured basilar bifurcation aneurysm--case report.

A 69-year-old male presented with sudden onset of headache. Computed tomography of the head demonstrated diffuse subarachnoid hemorrhage. Angiography showed a saccular basilar bifurcation aneurysm. Endovascular coil occlusion of the aneurysm on the same day enabled complete obliteration of the aneurysm. He did not develop vasospasm and returned home 4 months later. Early endovascular occlusion of the aneurysmal sac is an alternative method for the management of ruptured basilar bifurcation aneurysms.

Aged↗

PubMed1994

The effects of corticosteroids and thyrotropin-releasing hormone on newborn adaptation and sympathoadrenal mechanisms in preterm sheep.

OBJECTIVES: We examined the effect of prenatal corticosteroids and thyrotropin-releasing hormone on postnatal adaptation and sympathoadrenal function in preterm lambs. STUDY DESIGN: Catheterized fetal lambs received saline solution (n = 6), corticosteroids alone (n = 8), or corticosteroids plus thyrotropin-releasing hormone (n = 6) for 60 hours. The lambs were delivered by cesarean section at a gestational age of 130 +/- 1 days. Ventilatory, cardiovascular, and metabolic responses and plasma catecholamine concentrations were measured for 2 hours after birth. Statistical analysis was performed by use of independent t tests or analysis of variance. RESULTS: Ventilatory function and cardiac contractility were significantly improved in both corticosteroid and corticosteroid plus thyrotropin-releasing hormone animals. Lambs treated with corticosteroid plus thyrotropin-releasing hormone had significantly higher aortic pressure and left ventricular blood pressure than either of the other groups. The postnatal norepinephrine and epinephrine surge was blunted in response to corticosteroid and corticosteroid plus thyrotropin-releasing hormone treatment. There were no differences in metabolic responses among the three groups. CONCLUSIONS: In premature lambs prenatal exposure to corticosteroids and thyrotropin-releasing hormone improves postnatal cardiovascular adaptation more than corticosteroids alone.

Adaptation, Physiological↗

PubMed1994

Bone turnover and calcium metabolism during 20 days bed rest in young healthy males and females.

Bone is a dynamic tissue that functions not only as a mechanical support, but also as a major component of the metabolic and endocrine systems maintaining mineral homeostasis. It has been shown that immobilization induces decalcification of bone. To evaluate the effect of immobilization on bone mineral density and calcium metabolism, we investigated 9 young healthy males and females during 20 days bed rest. Three methods for measuring bone mineral density were performed to quantify whole body and regional bone changes: 1) dual energy X-ray absorptiometry, 2) quantitative computed tomography, and 3) multiple scanning X-ray photodensitometry, respectively. Bone mineral density showed a rapid decreasing tendency, especially in both lumbar and metacarpal bones (mean +/- SE: 4.6 +/- 0.6% and 3.6 +/- 0.4%, respectively). Urinary daily excretion of deoxypyridinoline, a sensitive marker of bone matrix resorption, tended to increase by day 10, and to decline by day 20 (mean +/- SE: 42.2 +/- 1.4, 27.6 +/- 2.2 nmol day-1, respectively). However, neither alkaline phosphatase nor tartrate-resistant acid phosphatase, both markers of osteoclast and mature osteoblast function, changed. These results showed that in the early stage of immobilization, bone matrix might be resorbed without any activation of osteoclasts, resulting in rapid decalcification of vertebral and cortical bones without any discernible changes in anatomical structure.

Absorptiometry, Photon↗

PubMed1994

[The accuracy and clinical issue of preoperative diagnosis of gastric cancer].

We discussed the accuracy and clinical issue of preoperative diagnosis for 764 patients with gastric cancer from 1987 to 1990. The accuracy of diagnosis, location, tumor size, wall invasion, involved lymph node were 81.8, 80.5, 62.2, 82.5% respectively. The clinicopathological characteristics of the regions which we missed preoperative diagnosis are infiltrating type and scirrhous type in diagnosis of tumor size, and large tumor in diagnosis of wall invasion. Especially in the case of early gastric cancer, we missed diagnosis of wall invasion of the regions with clinicopathological characteristics as follows: depressed type, undifferentiated type and ulceration in lesions. Now it is difficult to diagnosis wall invasion before surgery, so we have to be careful to determine the indication of endoscopic resection or limited operation for early gastric cancer, especially with clinicopathologic characteristics stated as above.

Diagnosis, Differential↗

PubMed1993

Smooth pursuit eye movement dysfunction as a biological marker for prediction of disease courses of schizophrenia: a preliminary report.

We investigated the relationship between a smooth pursuit eye movement (SPEM) dysfunction and long-term disease courses of schizophrenia. Many schizophrenic patients without the SPEM dysfunction tended to show an acute onset of illness, undulating courses and relatively good outcomes. On the other hand, patients with cogwheel-like SPEM dysfunction tended to show a chronic onset, simple courses, relatively severe outcomes and negative symptoms.

Adult↗

PubMed1993

Effects of corticosteroids in preterm sheep on adaptation and sympathoadrenal mechanisms at birth.

This study investigates the effects of prenatal corticosteroid administration on newborn sympathoadrenal mechanisms involved in postnatal adaptation. Randomly assigned preterm (122-125 days) fetal sheep were treated with hydrocortisone or saline for 60 h and delivered by cesarean section. We examined postnatal physiological adaptation, sympathoadrenal responses, cardiac beta-receptor density, and the receptor-cyclase system. We observed increased ventilatory, cardiovascular, and metabolic responses function in the corticosteroid-treated animals despite a marked attenuation in the anticipated surge of plasma catecholamine concentrations and a decrease in epinephrine secretion rate, which is normally seen at birth. Myocardial beta-adrenergic receptor density and affinity states were comparable in both groups. Basal and agonist-mediated adenylyl cyclase activity in myocardial tissue was increased in the corticosteroid-treated animals. We speculate that the increase in myocardial adenylyl cyclase activity may be accompanied by similar changes in other organ systems and that this could account for the augmentation in respiratory, cardiovascular, and metabolic responses in the corticosteroid-treated animals.

Acclimatization↗

PubMed1993

Plasma epinephrine appearance and clearance rates in fetal and newborn sheep.

Newborn plasma catecholamine levels are elevated compared to fetal life. Whether this reflects increased catecholamine secretion after birth or decreased clearance is not known. To determine the plasma appearance and clearance rates for catecholamines during the transition to postnatal life, we compared plasma epinephrine appearance and clearance rates in fetal sheep before birth and in newborns after delivery. Plasma epinephrine appearance and clearance rates were measured by radiotracer analysis in eight fetuses at 127 +/- 1 days of gestation and, after cesarean delivery, at 130 +/- 1 days of gestation. There was no difference in plasma epinephrine appearance rate during the fetal (26 +/- 4 ng.kg-1 x min-1) or newborn studies (31 +/- 5 ng.kg-1 x min-1). The fetal plasma epinephrine clearance rate (131 +/- 13 ml.kg-1 x min-1) was significantly higher than newborn plasma epinephrine clearance rate (40 +/- 3 ml.kg-1 x min-1). Thus fetal plasma epinephrine appearance rate is not different from appearance rate in the immediate newborn period when catecholamine levels are higher than during most other physiological circumstances. The increase in circulating catecholamine levels at birth is due in part to a significant decrease in clearance rate. It is likely that removal of the placental contribution to whole body clearance accounts for much of the difference observed in fetal and newborn clearance rates.

Animals↗

PubMed1993

Cutaneous late-phase reaction to environmental antigen in patients with atopic dermatitis.

Intradermal testing with 7 environmental allergens was performed on 71 patients with atopic dermatitis (AD) with respiratory atopy (RAT) and 30 pure AD patients, and the cutaneous late-phase reaction (CLPR) was observed several to 48 h after challenge. CLPR was not seen in pure AD. In AD patients with RAT, CLPR was positive in 29 of 71 patients. No macroscopic eczematous lesions appeared. All CLPR-positive patients showed RAST scores of 2 or more. We assume that CLPR can be an exacerbating factor in AD with RAT, while it is not directly involved in pure AD.

Adolescent↗

PubMed1993

Combined assessment with myocardial contractility and an index related to ventricular afterload in patients with isolated severe mitral regurgitation undergoing valve replacement. A retrospective study.

The afterload to the left ventricle increases following valve replacement in chronic mitral regurgitation (MR), yet there has been no study taking into account left ventricular (LV) afterload. In 43 patients with isolated chronic MR undergoing mitral valve replacement (MVR), we calculated LV wall stress using preoperative LV end-diastolic dimensions and diastolic aortic pressure (predictive LV wall stress = pWS). This value would represent LV wall stress at the instant of aortic valve opening immediately after MVR, assuming that LV end-diastolic dimensions and the aortic pressure did not change after operation. We also calculated end-systolic wall stress/volume index (ESS/ESVI) ratio, an index of myocardial function. None of 15 patients with the ESS/ESVI ratio > 1.6 had postoperative mortality or morbidity, whereas among the 26 patients with the ESS/ESVI ratio < 1.6, 12 patients had mortality (3 patients) and/or morbidity requiring intraaortic balloon pumping or prolonged catecholamine support. Three patients who died had pWS > 200 kdynes/cm2. Including these 3, all 5 patients whose pWS > 200 had mortality or severe morbidity immediately after surgery. In contrast, among the 38 patients with lower pWS, none died and only 7 patients (18%) had morbidity. Thus, patients who had a low contractility index and a high predictive afterload value had high mortality and morbidity. We conclude that the prediction of postoperative mortality and morbidity is improved by combined assessment of myocardial function and the hypothetical postoperative LV afterload.

Catecholamines↗

PubMed1993

Adrenocortical carcinoma with a giant pericardial mass.

A patient with a history of adrenocortical carcinoma presented with massive pericardial effusion and a giant pericardial mass. Death resulted from cardiac tamponade. At autopsy a large necrotic mass was histologically similar to the original adrenocortical carcinoma. We present this case and review the literature on metastatic pericardial disease.

Adrenal Cortex Neoplasms↗

PubMed1992

Free and sulfoconjugated catecholamine responses at birth in newborn sheep.

There have been little data on catecholamine sulfoconjugation in developing animals or humans. We studied the differences in free and sulfoconjugated catecholamines at birth in newborn sheep. Baseline concentrations of sulfoconjugated norepinephrine and epinephrine were the predominant form of circulating catecholamine, representing 77 +/- 4 and 65 +/- 12% of total circulating catecholamines, respectively. At birth the free epinephrine concentration increased 10-fold (49 +/- 27 to 653 +/- 21 pg/ml, respectively), and plasma free norepinephrine concentration rose 4-fold (307 +/- 92 to 1,178 +/- 389 pg/ml). In contrast, there was only a transient twofold increase in the sulfoconjugated epinephrine. There was no increase in the sulfoconjugated form of norepinephrine. These data demonstrate that, while the near-term newborn sheep has a well-developed mechanism for sulfoconjugation of circulating catecholamines, this does not occur rapidly. During the logarithmic increases of circulating catecholamines at birth, there are not commensurate increases in the concentration of sulfoconjugated norepinephrine or epinephrine. Thus sulfoconjugation does not appear to represent a significant mechanism for inactivation of the high circulating levels of catecholamines seen at birth.

Aging↗

PubMed1992

Single umbilical artery ligation-induced fetal growth retardation: effect on postnatal adaptation.

To assess whether prolonged intrauterine stress and resultant fetal growth retardation result in depletion of adrenal catecholamines and alter the adrenergic signal transduction system, we studied newborn sheep after single umbilical artery ligation (SUAL)-induced growth retardation. The animals were delivered at term, and postnatal cardiovascular, pulmonary, endocrine, and metabolic responses were measured. We also evaluated the status of myocardial and pulmonary beta-adrenergic receptor number and function. SUAL caused significant growth retardation but relative preservation of brain and adrenal gland weight and adrenal catecholamine content. Blood pressure, plasma free fatty acid, and glucose responses at birth were blunted in SUAL animals. The plasma epinephrine (Epi) and norepinephrine levels were comparable in both groups for the first 2 h of age. By 4 h, both plasma concentration and plasma appearance rate of Epi were reduced to 40% of control in SUAL animals (P less than 0.05). Neither beta-receptor density, affinity, nor adenylate cyclase activity were altered by SUAL in either cardiac or pulmonary membranes. These results suggest that, rather than overt depletion, there is relative sparing of initial adrenal medullary function that later waned. This response and preservation of the beta-adrenergic signal transduction system may represent partial compensation for the physiological stress induced by SUAL.

Adaptation, Physiological↗

PubMed1992

Prolonged beta-agonist infusion does not induce desensitization or down-regulation of beta-adrenergic receptors in newborn sheep.

In adult animals, prolonged beta-agonist exposure leads to down-regulation of beta-adrenergic receptors and desensitization. Prior evidence from our lab suggests that this may not occur in developing animals. To study this, we measured the response to graded epinephrine infusion [2.7, 5.5, 13.6, 27.3 mumol/(kg.min), (0.5, 1.0, 2.5, 5.0 micrograms/(kg.min)], myocardial beta-agonist receptor density, and components of the receptor-cyclase system in newborn lambs before (n = 6) and after (n = 5) 3 d of continuous isoproterenol administration (2 micrograms/kg/min). beta-Adrenergic receptors were measured by radioligand binding. Epinephrine dose-response curves were analyzed for the threshold and slope for changes in mean blood pressure, systolic blood pressure, and heart rate versus plasma epinephrine levels. Despite 3 d of continuous isoproterenol infusion, we observed no desensitization of the hemodynamic response to epinephrine. There was a reduction in receptor density when expressed per membrane protein [155.3 +/- 19.5 (controls) versus 73.2 +/- 3.8 fmol/mg protein (agonist exposed), p less than 0.05], but no alteration in receptor density when expressed per g cardiac wet weight [258.8 +/- 39.9 (controls) versus 406.8 +/- 74.0 fmol/g wet weight (agonist exposed)]. There was no alteration in agonist affinity or in adenylyl cyclase activity after adjustment for membrane protein recovery. Prolonged beta-agonist infusion in newborn lambs does not desensitize hemodynamic responses to infused epinephrine. We propose that receptor regulation in developing animals is fundamentally different than in adult animals.

Adrenergic beta-Agonists↗

PubMed1992

Prediction of surgical result of valve replacement for chronic isolated mitral regurgitation--the significance of preoperative estimation of postoperative left ventricular afterload.

Left ventricular (LV) afterload increases after mitral valve replacement, thus it would be useful to estimate postoperative LV afterload before surgery. We tested the usefulness of an index, wall stress, obtained from preoperative end-diastolic LV dimensions and diastolic blood pressure which would represent LV afterload after surgery. The data were compared with surgical mortality and morbidity. The wall stress ranged from 98 to 220 kdynes/cm2 and was 202 or higher in 3 patients who died. Five patients had wall stress above 200 kdynes/cm2. Among these, intra-aortic balloon pumping (IABP) was used in 4, and 3 died. Prolonged catecholamine support for greater than 10 days was given to all of the 4 patients, including two who died 14 and 23 days after surgery. Among 38 patients who had wall stress less than 200 kdynes/cm2, none died, IABP was performed in 3 patients, and prolonged catecholamine infusion was required in 5 patients. The incidence of mortality and morbidity were significantly higher in the high stress than in the low stress group (Chi-square analysis). Left ventricular end-diastolic index was larger in the high stress than in the low stress group (p less than 0.05). The mass/end-diastolic volume ratio was smaller in the high stress group than in the low stress group (P less than 0.05). In conclusion, this new index, predictive wall stress, is useful in selecting patients who would have high mortality and morbidity.

Cardiac Catheterization↗