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Biomedical subjects

K Okada

Publications and source records attributed to K Okada.

At least 181 records · Page 10Linked to original sources
PubMed2000

Influence of preparation conditions on the microstructure and bioactivity of alpha-CaSiO(3) ceramics: formation of hydroxyapatite in simulated body fluid.

Two different reagents, NaOH and NH(4)OH, were used to precipitate CaSiO(3) precursor powders from ethanol solutions of Ca(NO(3))(2). 4H(2)O and Si(OC(2)H(5))(4). The resultant powders of different Ca/Si ratio and residual Na(2)O content exhibited significant differences in the microtexture of the resulting sintered alpha-CaSiO(3) ceramics. The microtexture of the ceramics from the NaOH system (CS-Na) contained smaller grain sizes and a thicker glassy phase at the grain boundaries than those produced using NH(4)OH (CS-NH). The CS-Na ceramics were soaked in a simulated body fluid (SBF) at 36.5 degrees C for 2 h and 1, 5, 6, 10, 21, and 30 days while the CS-NH ceramics were soaked for 1, 5, 7, 15, 20, and 25 days using the same conditions. Hydroxyapatite (HAp) formed on the surfaces of both samples but at different formation rates due to differences in the microstructure. The CS-Na ceramics showed faster HAp formation because their smaller alpha-CaSiO(3) grains dissolved more readily, allowing the calcium concentration in the SBF quickly to approach the appropriate condition for nucleation of HAp. In addition, the thicker glassy phase at the grain boundaries facilitated a faster formation of silanol on the surface of the amorphous SiO(2) interlayer, a reaction that is considered to be a prerequisite for HAp formation. The formation of the HAp layer on the CS-Na ceramics therefore was very fast (12 microm/day), and their surfaces were covered completely within 5 days. A layer thickness of about 110 microm was achieved in 30 days, in contrast with the CS-NH ceramics, which took about 25 days to be fully covered with a 60-microm layer of HAp.

Body Fluids↗
PubMed2000

Matrix metalloproteinase-1 expression by interaction between monocytes and vascular endothelial cells.

There is accumulating evidence of complicated interactions among vascular cells, i.e. endothelial cells, smooth muscle cells and monocytes/macrophages, in the regulation of vascular function and remodeling. We have investigated the mechanisms responsible for matrix metalloproteinase (MMP)-1 expression by interactions between monocytes and vascular endothelial cells. THP-1 cells (human monocytic cell line) and human umbilical vein endothelial cells (HUVECs) were cocultured. MMP-1 levels in the culture medium were measured by enzyme-linked immunosorbent assays. Collagenolytic activity in the culture medium was measured by fluorescence labeled-collagen digestion. Immunohistochemistry using an anti-MMP antibody was carried out to determine which types of cell produce MMP-1. The addition of THP-1 cells to HUVECs for 48 h induced increases in MMP-1 levels and collagenolytic activity, which were 5- and 2-fold relative to those of HUVECs alone, respectively. A separate coculture experiment revealed that direct contact of THP-1 cells and HUVECs contributed to enhanced MMP-1 production in the cocolture. Immunohistochemical analysis revealed that both types of cell produce MMP-1 in the coculture. Neutralizing anti-interleukin-1 beta and tumor necrosis factor- alpha antibodies inhibited MMP-1 production by the coculture. The Src kinase and MEK inhibitors significantly inhibited MMP-1 production by the coculture. Coculture of THP-1 cells and HUVECs induced significant increases in Src and mitogen activated protein (MAP) kinase activities. Enhanced MMP-1 expression induced by monocyte-endothelial cell interactions may play an important role in the pathogenesis of atherosclerosis and plaque rupture.

Arteriosclerosis↗
PubMed2000

Passive and active recognition of one's own face.

Facial identity recognition has been studied mainly with explicit discrimination requirement and faces of social figures in previous human brain imaging studies. We performed a PET activation study with normal volunteers in facial identity recognition tasks using the subject's own face as visual stimulus. Three tasks were designed so that the activation of the visual representation of the face and the effect of sustained attention to the representation could be separately examined: a control-face recognition task (C), a passive own-face recognition task (no explicit discrimination was required) (P), and an active own-face recognition task (explicit discrimination was required) (A). Increased skin conductance responses during recognition of own face were seen in both task P and task A, suggesting the occurrence of psychophysiological changes during recognition of one's own face. The left fusiform gyrus, the right supramarginal gyrus, the left putamen, and the right hypothalamus were activated in tasks P and A compared with task C. The left fusiform gyrus and the right supramarginal gyrus are considered to be involved in the representation of one's own face. The activation in the right supramarginal gyrus may be associated with the representation of one's own face as a part of one's own body. The prefrontal cortices, the right anterior cingulate, the right presupplementary motor area, and the left insula were specifically activated during task A compared with tasks C and P, indicating that these regions may be involved in the sustained attention to the representation of one's own face.

Adult↗
PubMed2000

Correlation between human personality and neural activity in cerebral cortex.

Personality traits are a variance of behavioral patterns among individuals and may reflect a variance of brain activity, but their neurobiological explanation is still a matter of debate. Cloninger proposed three dimensions of personality traits, each of which has strong correlation with activity in a specific central monoaminergic system. Although this theory has been supported by physiological and genetic studies, it is still unclear how these personality parameters are correlated with the activity of the cortical networks which control human behavior. Here we measured the regional cerebral blood flow (rCBF) at rest in 30 normal volunteers who completed the personality inventory of Cloninger. Voxel-by-voxel analysis was employed to identify cortical regions where the rCBF showed significant correlation with any of the three personality parameters. Statistically significant correlation was observed in several paralimbic and neocortical regions and was consistent with the assumed monoaminergic influence on neural activity and the distribution of its projections, in each personality dimension. The results suggest that activity in a variety of cortical regions is associated with human personality traits and lend support to Cloninger's theory concerning central monoaminergic influence on human personality traits.

Adult↗
PubMed2000

A case of primary squamous cell carcinoma of the breast with rapid progression.

Primary squamous cell carcinoma of the breast is a rare disease for which no definite treatment or prognosis has been established. This report describes our experience with one case of primary squamous cell carcinoma of the breast that ended in death after rapid progression. The patient was a 58 year old woman who visited our hospital complaining of a growing tumor and pain in the right breast. Ultrasonographically the tumor consisted of solid tumor and a large cyst. Squamous cell carcinoma was diagnosed by fine-needle aspiration cytology. Neoadjuvant CEF was given, but the tumor continued to grow, so CEF was discontinued after one course and modified radical mastectomy was performed subsequently. There was no evidence of metastasis to lymph nodes. About 5 months post operatively CT of the head and chest X-ray demonstrated metastatic lesions in the brain and lungs. Resection of the cerebral tumor was performed. About 1 month after the operation, however, a new metastatic brain tumor was found and the patient later died.

Breast Neoplasms↗
PubMed2000

Evaluation of motor- and sensory-evoked potentials for spinal cord monitoring during thoracoabdominal aortic aneurysm surgery.

OBJECTIVE: To assess the utility of spinal cord monitorings for prediction of spinal cord ischemia, we investigated the role of both motor evoked potentials and sensory evoked potentials during thoracoabdominal aortic aneurysm surgeries. METHODS: We monitored two kinds of sensory evoked potentials; descending evoked spinal cord potentials from the lumbar enlargement after cervical spinal cord stimulation and segmental evoked spinal cord potentials at the lumbar enlargement elicited by peroneal nerve stimulation, and motor evoked potentials from the lumbar enlargement elicited by direct subcranial stimulation in 9 thoracoabdomonal aortic aneurysm surgeries. RESULTS: Postoperative paraplegia occurred in one case in which the patients died during the perioperative period. One case showed transient paraparesis, but recovered following rehabilitatation. These cases showed a decrease in the amplitude of descending evoked spinal cord potentials and motor evoked potentials. CONCLUSION: The recovery of the amplitude of the motor evoked potentials and the descending evoked spinal cord potentials after declamping correlated with the neurologic outcome.

Aged↗
PubMed2000

Osteoblastoma-like osteosarcoma.

We report an osteoblastoma-like osteosarcoma in the right proximal fibula in a 22-year-old woman. Radiographs showed an irregular osteolytic lesion from the metaphysis to the epiphysis in the proximal fibula with partial destruction of cortical bone. Tissue from a biopsy indicated a typical osteoblastoma. Curettage and bone graft was performed. One year after the surgery, local recurrence occurred, and a wide excision was performed. Histological examination of the en-bloc surgical specimen revealed the tumor had permeated through the host bony trabeculae, although the nuclear atypia was not marked. Immunohistochemical expression of MIB-1 was detected in 9.0% of cells.

Adult↗
PubMed2000

Cystic fibrous dysplasia mimicking giant cell tumor: MRI appearance.

We report the case of a 43-year-old man who presented with an osteolytic and expansive lesion in the left distal femur mimicking a giant cell tumor. Magnetic resonance imaging (MRI) showed that most of the lesion was cystic, and histological examination revealed fibrous dysplasia with marked cystic degeneration. Radiographic findings of cystic fibrous dysplasia in the end of a long bone may be similar to those of a giant cell tumor, and a biopsy is essential for the final diagnosis.

Adult↗
PubMed2000

Recurrent idiopathic iridocyclitis after autologous peripheral blood stem-cell transplantation followed by G-CSF administration for acute lymphoblastic leukemia.

We describe a patient who experienced a recurrence of idiopathic iridocyclitis on day 12 after autologous peripheral blood stem-cell transplantation (auto-PBSCT) followed by G-CSF administration for acute lymphoblastic leukemia (ALL). Autologous SCT has been reported to be effective and safe in achieving dose intensification of chemotherapeutic drugs for the treatment of hematopoietic malignancies, but its therapeutic effect on autoimmune diseases is not definite. The findings from the present case suggest that auto-PBSCT followed by G-CSF administration for patients with a history of some kind of autoimmune disorders may induce exacerbation or recurrence of its symptoms after hematopoietic recovery.

Combined Modality Therapy↗
PubMed2000

MRI findings of small subcortical "lacunar-like" infarction resulting from large vessel disease.

Small subcortical infarctions resulting from large-vessel disease are often observed. It is important to distinguish these from pure lacunar infarction resulting from small-vessel disease because the investigations and examinations differ. We investigated the differences on brain magnetic resonance imaging (MRI) between small subcortical "lacunar-like" infarcts resulting from large-vessel disease and pure lacunar infarcts. Thirteen subjects with small lacunar-like infarcts (size < 2 cm), resulting from large-vessel disease, and 30 subjects with lacunar infarcts (< 2 cm), without large-vessel disease were studied. We measured infarction size using a 1.5-T MRI device and evaluated silent subcortical hyperintensity lesions using the modified Scheltens' score. Large-vessel lesion was confirmed by conventional angiography, duplex carotid scan, and magnetic resonance angiography. There was no difference in the mean age of the two groups. Cerebrovascular risk factors and atherosclerotic complications were also comparable for the two groups. Progressive stroke was more common in the lacunar-like infarction group than in the lacunar infarction group (P = 0.004). Scores for periventricular hyperintensity, white matter hyperintensity, basal ganglia hyperintensity, and total subcortical hyperintensity scores were significantly higher in the lacunar infarction group than in the lacunar-like infarction group. The difference in basal ganglia hyperintensity scores was remarkable (P = 0.001). The enlargement of the perivascular space was also significantly greater in the lacunar infarction group than in the lacunar-like infarction group. These findings seem to reflect differences in the pathogenesis of infarction between the two groups. Silent subcortical hyperintensity lesions and enlargement of perivascular space are useful for between distinguishing small lacunar-like infarct resulting from large-vessel disease and pure lacunar infarction. This may have significant implications for the management of patients with lacunar-sized infarctions. It suggests that the pathogenesis of lacunar-sized infarction is variable.

Aged↗
PubMed2000

A decreased serum concentration of nitrite/nitrate correlates with an increased plasma concentration of lactate during and after major surgery.

A decrease in the production of nitric oxide (NO) due to surgical stress has been reported. We investigated whether this decrease in NO production was related to cytokine induction and/or other clinical parameters. We therefore measured the concentrations of serum nitrite/nitrate (a stable end product of NO), serum interleukin (IL)-6, and standard clinical parameters in 13 patients undergoing major upper abdominal and thoracoabdominal surgery at preanesthesia (PRE), 2h after a surgical incision (2H), at the end of surgery (END), and on the morning of postoperative days 1 (POD 1) and 3 (POD 3). The serum concentration of nitrite/nitrate was thus found to have significantly decreased at END, POD 1, and POD 3 compared with PRE. In addition, the serum nitrite/nitrate concentration correlated negatively with the plasma lactate level, and no relationship was observed between the serum nitrite/nitrate level and either the serum IL-6 level or any other clinical parameters. Our findings thus suggest that the decrease in the serum nitrite/nitrate level might therefore be related to tissue hypoperfusion both during and after major surgery.

Aged↗
PubMed2000

N-methylation ability for azaheterocyclic amines is higher in Parkinson's disease: nicotinamide loading test.

The discovery of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) leads to the hypothesis that Parkinson's disease (PD) is may be initiated or precipitated by endogenous toxins by the mechanism similar to that of MPTP in genetically-predisposed individuals. The higher cerebrospinal fluid levels of N-methylated azaheterocyclic amines, such as beta-carboline and tetrahydroisoquinoline, have been found in parkinsonian patients compared with age-matched controls. To estimate the N-methylation ability for azaheterocyclic amines in parkinsonian patient, nicotinamide was dosed with 100 mg to 26 parkinsonians and 20 controls consisted of 16 other neurogenic disease patients and 4 healthy volunteers. The urine was collected for 4 h, and then analyzed urinary its metabolites by an improved HPLC method. Nicotinamide has a pyridine ring in its structure and may be metabolized through the pathways similar to those for the endogenous neurotoxins. The urinary excretions of nicotinamide metabolites were significantly affected by aging. The excretion of N1-methylnicotinamide decreased along with aging both in PD patients and controls. In younger (65 years old or younger) PD patients, the excretion amount of N1-methylnicotinamide was significantly higher than that in younger controls. The decline rate of N1-methylnicotinamide excretion in parkinsonians was significantly greater than that in controls; the rate is more than 2-fold higher in parkinsonian patients. The age-associated decrease in 1-methyl-2-pyridone-5-carboxyamide excretion was observed only in parkinsonian patients, but not in controls. The total excreted amount of N-methylated metabolites (N1-methylnicotinamide plus 1-methyl-2-pyridone-5-carboxyamide) was also observed the age-related decline in both groups. The urinary excretions of nicotinamide and nicotinamide-N-oxide were not influenced by aging. These results would indicate that the excess N-methylation ability for azaheterocyclic amines before the onset had been implicated in PD. On the other hand, the present results suggested that the contribution of aberrant cytochrome P450 or aldehyde oxidase activity acting on the pyridine ring, that could act as detoxification routes of endogenous neurotoxins, would be small in the etiology of PD.

Aged↗
PubMed2000

Selective intercostal arterial perfusion during thoracoabdominal aortic aneurysm surgery.

BACKGROUND: This clinical study evaluated changes in motor evoked potentials (MEP) elicited by direct cerebral cortical stimulation and evoked spinal cord potentials (ESCPs) elicited by direct spinal cord stimulation during selective intercostal arterial perfusion for thoracoabdominal aortic aneurysm (TAAA) repair. We also determined the efficacy of this perfusion method for prevention of paraplegia. METHODS: Two kinds of ESCPs and MEPs were monitored during the prosthetic replacement step for TAAA surgeries. We performed selective intercostal arterial perfusion from the T7 intercostal artery to the L1 intercostal artery through a small piece of Dacron graft while monitoring spinal cord potentials in five cases of TAAA. RESULTS: The MEP amplitude decreased after clamping the aorta but quickly recovered after selective perfusion of intercostal arteries. Other spinal cord potentials did not change during the reconstruction of intercostal arteries. Postoperative paraplegia or parapalesis did not occur in any of the patients. CONCLUSIONS: Monitoring of MEPs during selective intercostal arterial perfusion was a useful adjunct to prevent postoperative paraplegia in TAAA surgery.

Adult↗
PubMed2000

Endovascular stent-grafting through the aortic arch: an alternative approach for distal arch aortic aneurysm.

BACKGROUND: Endovascular stent-grafting is an innovative procedure; we have developed a novel approach to treat distal arch aortic aneurysm through a small incision in the aortic arch. METHODS: Eight patients with thoracic aortic aneurysms were treated with an endovascular stent-graft that was introduced into the thoracic aorta through a small incision in the aortic arch. Of these patients, 7 had distal arch aortic aneurysms, and 1 had chronic aortic dissection of Stanford type B. Four of these patients had received concomitant coronary artery bypass grafting, and 1 patient had undergone tricuspid valvular annuloplasty. The stent-graft was introduced into the distal arch aorta and descending aorta through a small incision in the aortic arch, under selective cerebral perfusion and hypothermic circulatory arrest. RESULTS: The selective cerebral perfusion time ranged from 52 to 86 minutes (mean, 68 minutes) and the operating time from 289 to 422 minutes (mean, 318 minutes). There was no endoluminal leakage into the aneurysm. Seven patients survived and were discharged, but 1 patient suffered a cerebral infarction and died during the follow-up period. CONCLUSIONS: Placing an endovascular stent-graft through the aortic arch is an acceptable alternative treatment for distal arch aortic aneurysms.

Aged↗
PubMed2000

Effect of hyperthermia on the viability and the fibrinolytic potential of human cancer cell lines.

The effects of heat treatment on the viability and fibrinolytic potential of four cultured human carcinoma cell lines, fibrosarcoma cells (HT-1080), lung adenocarcinoma cells with highly metastatic potential (HAL-8), melanoma cells (Bowes) and osteosarcoma cells (NY), determined by measuring their levels of urokinase-type plasminogen activator (u-PA) and its specific receptor (u-PAR), were investigated by comparing them with those of human umbilical vein endothelial cells (HUVECs). HUVECs incubated at 43 degrees C for 120 min exhibited no decrease in viability but exhibited an increase in both u-PA and u-PAR. HT-1080 and HAL-8 showed a moderately high heat-resistance (viability, 60-90%) that correlated with the reduction of u-PAR but not u-PA. On the other hand, Bowes and NY cells, with poor heat-resistance (viability, 20-50%), exhibited stronger cell-associated u-PA activity when they survived at 43 degrees C for 120 min. Since the u-PA/u-PAR system is directly involved in the invasiveness and metastatic potential of carcinoma cells, hyperthermia would alter the biological activity of these carcinoma cells.

Adenocarcinoma↗
PubMed2000

Reduced interleukin-1 responsiveness in immune system and central nervous system of inbred polydipsic (STR/N) mice.

Inbred polydipsic mice (STR/N strain) have primary polydipsia. The previous studies found abnormalities in the central nervous system (CNS), especially in the hypothalamus and circumventricular organ. As a part of pursuing to find the cause of the polydipsia, we investigated immunological characteristics of STR/N mice, using the ICR strain of mice as control. Their thymic subset cells showed that CD4+CD8+ double positive cells were increased, CD4+ single positive cells were decreased and CD5 expression was deficient, compared to ICR mice. T cell proliferative response and interleukin (IL)-2 production caused by IL-1beta stimulation were reduced in STR/N mice than those in the ICR mice. In in vivo studies the degree of thymic atrophy and the increases in serum level of ACTH and corticosterone induced by intraperitoneal IL-1beta injection were much less in STR/N mice than those in controls. Furthermore, adipsic response also induced by IL-1beta injection was greatly reduced compared to their control mice. All these results suggest that the responsiveness to IL-1 is impaired both in the immune system and the CNS of STR/N mice.

Adrenocorticotropic Hormone↗