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Biomedical subjects

Y Katayama

Publications and source records attributed to Y Katayama.

At least 19 recordsLinked to original sources
PubMed2007

Rapid microglial activation induced by traumatic brain injury is independent of blood brain barrier disruption.

Following CNS injury, microglia respond and transform into reactive species exhibiting characteristic morphological changes that have been termed "activated" or "ameboid" microglia. In an attempt to establish that microglial reactions induced immediately after injury are caused by intrinsic mechanisms rather than infiltration of blood and its constituents, oxygenized Ringer's solution was perfused into the cerebral circulation of rats so that the circulating blood could be eliminated prior to injury induction. Under artificial respiration, a catheter was inserted from the cardiac apex into the ascending aorta, and oxygenized Ringer's solution was immediately perfused with a pulsatile blood pump, resulting in wash out of the circulating blood from the brain within 1 min. Subsequently, a cortical contusion was induced in the unilateral parietal cortex using a controlled cortical impact (CCI) device. At 5 min following the injury, the brain was fixed by perfusion of fixative through the catheter and removed. Coronal vibratome sections were then processed for CR3 immunohistochemistry to examine the microglial activation. It appeared that microglial activation with both morphological transformation and an increase in CR3 immunoreactivity was induced throughout the hemisphere ipsilateral to the injury side exclusively, even in rats with elimination of circulating blood. The microglial reactions did not differ substantially from those observed in the control rats with extensive BBB disruption. The present results thus provide direct evidence that the microglial activation induced immediately after injury is independent of infiltration of circulating blood induced by concurrent BBB disruption.

Animals↗
PubMed2006

Pressure-induced site-selective disordering of Ge2Sb2Te5: a new insight into phase-change optical recording.

We demonstrate that , the material of choice in phase-change optical recording (such as DVD-RAM), can be rendered amorphous by the application of hydrostatic pressure. It is argued that this structural change is due to a very strong second-nearest-neighbor Te-Te interaction that determines the long-range order in the metastable cubic phase of and also to the presence of vacancies. This newly discovered phenomenon suggests that pressure is an important factor for the formation of the amorphous phase which opens new insight into the mechanism of phase-change optical recording.

Journal Article↗
PubMed2006

Effects of obesity phenotype on fat metabolism in obese men during endurance exercise.

OBJECTIVE: The effects of obesity phenotype on fat metabolism during endurance exercise are unclear. This study aimed to investigate in obese men whether body fat distribution would influence plasma fat availability and oxidation during endurance exercise. DESIGN: Fourteen sedentary men (body mass index (BMI) > 25 kg/m2) were divided into two groups by visceral fat (VF) area: VF obese (VF-Ob) (n = 7, age; 52.0 +/- 2.5 (s.e.) years) and abdominal subcutaneous fat obese (SF-Ob) (n = 7, age; 57.3 +/- 2.8 (s.e.) years). All participants performed stationary cycling exercise for 60 min at 50% of peak oxygen uptake. MEASUREMENTS: Blood and respiratory gas samples were taken for analysis of hormone, metabolite and substrate oxidation in each participant at rest and during exercise. RESULTS: There is a significant group x time interaction in the plasma concentration of free fatty acid (FFA) (P < 0.05) and glycerol (P < 0.05) during the exercise bout. In addition, total plasma concentration of FFA (area under the curve) was 59.2% higher in VF-Ob compared with SF-Ob men during endurance exercise (1.99 +/- 0.24 and 1.25 +/- 0.13 mEq/l/min, respectively; P < 0.05). Total plasma concentration of glycerol (area under the curve) was 102.3% higher in VF-Ob than SF-Ob men during the exercise (69.6 +/- 12.5 and 34.4 +/- 5.1 mg/dl/min, respectively; P < 0.05). However, fat oxidation was not different throughout the exercise between VF-Ob and SF-Ob men (176.5 +/- 25.7 and 183.0 +/- 12.8 kcal/60 min, respectively). CONCLUSION: During moderate endurance exercise, plasma fat availability may be higher in men with VF obesity compared to men with SF obesity. However, total fat oxidation is similar between obesity phenotype.

Analysis of Variance↗
PubMed2006

Cerebral blood oxygenation changes induced by bypass blood flow in moyamoya disease and non-moyamoya cerebral ischaemic disease.

BACKGROUND: Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis has been used to prevent stroke in patients with moyamoya disease (MD) and non-moyamoya ischaemic disease (non-MD). However, little is yet known regarding the difference between these groups of patients in the extent to which the bypass contributes to maintaining adequate cerebral blood oxygenation (CBO), or the temporal changes after surgery. In the present study, we evaluated the CBO changes induced by bypass blood flow in patients with MD and non-MD during the peri-operative periods employing optical spectroscopy. METHODS: We investigated 13 patients who underwent STA-MCA anastomosis, including 5 MD and 8 non-MD patients. We evaluated the effects of STA blood flow on the CBO in the MCA territory on the anastomosis side, employing visual light spectroscopy during surgery and near infrared spectroscopy (NIRS) at one week after surgery. FINDINGS: In 4 MD patients and one non-MD patient, the STA blood flow increased the oxyhaemoglobin and cortical oxygen saturation (CoSO2), indicating that the bypass supplied blood flow to the ischaemic brain; the CBO changes were observed more frequently in MD than in non-MD patients (p<0.02). The pre-anastomosis CoSO2 (65.4+/-5.4%) in MD was significantly lower than that (72.8+/-7.6%) in non-MD (p<0.05). Postoperative NIRS demonstrated that the bypass began to supply blood flow to the brain in 5 non-MD patients whose bypass did not supply blood flow during surgery. CONCLUSIONS: Although MD has vessels of small diameter as compared to non-MD, the bypass begins to supply blood flow to the ischaemic brain earlier in MD than in non-MD after anastomosis. The fact that the CoSO2 in MD was lower than that in non-MD suggested that the perfusion pressure in MD was lower than that in non-MD, and this might account for the difference in the bypass blood supply after anastomosis between MD and non-MD. Our data suggest that, even if the bypass does not supply blood to the brain during surgery in non-MD, the bypass blood flow gradually increases after surgery.

Adolescent↗
PubMed2006

Surgical management of early massive edema caused by cerebral contusion in head trauma patients.

Early massive edema caused by severe cerebral contusion results in elevation of intracranial pressure (ICP) and clinical deterioration within 24-72 hours post-trauma. Previous studies indicate that cells in the central area of the contusion undergo shrinkage, disintegration, and homogenization, whereas cellular swelling is predominant in the peripheral area, suggesting that early massive edema is attributable to high osmolality within necrotic brain tissue and may generate an osmotic potential across central and peripheral areas. We analyzed the effects of surgical excision of necrotic brain tissue in 182 patients with cerebral contusion registered with Japan Neurotrauma Data Bank; 121 patients (66%; Group I) were treated conservatively, and 61 (34%; Group II) were treated surgically. Most Group II cases (90%) underwent complete excision of necrotic brain tissue and evacuation of clots. Group I demonstrated higher mortality at 6 months post-trauma compared to Group II (48%) vs. 23%; p = 0.0001; n = 182). Striking differences were observed in patients scoring 9 or more on Glasgow Coma Scale at admission (56% vs. 17%); p = 0.017; n = 45) and demonstrated "talk-and-deteriorate" (64% vs. 22%: p = 0.026; n = 29), supporting our hypothesis that early massive edema is caused by cerebral contusion accompanied by necrotic brain tissue, indicating that surgical excision of necrotic brain tissue provides satisfactory control of progressive elevation in ICP and clinical deterioration in many cases.

Adolescent↗
PubMed2006

Acute hemispheric swelling associated with thin subdural hematomas: pathophysiology of repetitive head injury in sports.

INTRODUCTION: The most common head injury in sports is concussion, and repeated concussions occurring within a short period occasionally can be fatal. Acute subdural hematoma is the most common severe head injury and can be associated with severe neurologic disability and death in sports. We investigated severe brain damage resulting from repetitive head injury in sports, and evaluated the pathophysiology of sports-related repetitive injury. METHODS: We reviewed the literature containing detailed descriptions of repetitive severe sports-related head injury. In total, 18 cases were analyzed with regard to age, gender, type of sports, symptoms before second injury, and pathology of brain CT scans. RESULTS: The majority of cases involved young males aged 16 to 23 years old, who sustained a second head injury before symptoms from the first head injury had resolved. Ten of 15 cases did not suffer loss of consciousness at insult. Eight cases were confirmed on brain CT scans after the second injury, and all 8 cases revealed brain swelling associated with a thin subdural hematoma. CONCLUSIONS: Second impact syndrome is thought to occur because of loss of autoregulation of cerebral blood flow, leading to vascular engorgement, increased intracranial pressure, and eventual herniation. Our investigation suggests that the existence of subdural hematoma is a major cause of brain swelling following sports-related, repetitive head injury.

Adolescent↗
PubMed2006

Matrix metalloproteinase-9 is associated with blood-brain barrier opening and brain edema formation after cortical contusion in rats.

Matrix metalloproteinases (MMPs) are associated with blood-brain opening and may be involved in the pathophysiology of acute brain injury. Previous research demonstrated that knockout mice deficient in MMP-9 subjected to transient focal cerebral ischemia had reduced blood-brain barrier (BBB) disruption and attenuated cerebral infarction. In this study, we examined MMP-9 up-regulation, BBB disruption, and brain edema formation after cortical impact injury in rats. Cortical contusion was induced by controlled cortical impact. Animals were sacrificed at intervals after injury. MMP up-regulation was assessed by gelatin zymography, and BBB integrity was evaluated using Evans blue dye with a spectrophotometric assay. Brain water content was measured by comparing wet and dry weights of each hemisphere as an indicator of brain edema. Zymograms showed elevated MMP-9 as early as at 3 hours after injury, reaching a maximum at 18 hours. Peak levels of BBB disruption occurred 6 hours after injury. Brain edema became progressively more severe, peaking 24 hours after injury. Compared to control group, treatment with MMP-inhibitor GM6001 significantly reduced BBB disruption 6 hours and brain water content (85.9 +/- 0.5% vs. 82.6 +/- 0.3%; p < 0.05) 24 hours after injury. These findings suggest that MMP-9 may contribute to BBB disturbance and subsequent brain edema after traumatic brain injury.

Animals↗
PubMed2006

Preclinical evidence of Alzheimer changes in progressive mild cognitive impairment: a qualitative and quantitative SPECT study.

OBJECTIVES: Baseline brain single-photon emission computed tomography (SPECT) can predict mild cognitive impairment (MCI) patients at risk for progressive MCI (PMCI). METHODS: Twenty-eight subjects [12 MCI, 6 with probable Alzheimer's Disease (AD), and 10 normal subjects] underwent baseline brain SPECT and were clinically followed for a mean period of 36 months. RESULTS: Of 12 MCI patients, 6 progressed to PMCI and 6 remained stable. Baseline SPECT identified asymmetric perfusion reduction in the parahippocampus (-5%), lateral parietal (-8%), and posterior cingulate (-11%) cortices--reductions consistent with that of mild AD--in five of the six PMCI patients. Significant perfusion reduction was observed particularly in the frontal cortices of probable AD when compared with PMCI (P < 0.05). CONCLUSION: Baseline SPECT can identify brain perfusion abnormalities among patients with MCI for progression to PMCI. This imaging modality may aid in MCI treatment stratification.

Aged↗
PubMed2005

DBS therapy for the vegetative state and minimally conscious state.

Twenty-one cases of a vegetative state (VS) and 5 cases of a minimally conscious state (MCS) caused by various kinds of brain damage were evaluated neurologically and electrophysiologically at 3 months after brain injury. These cases were treated by deep brain stimulation (DBS) therapy, and followed up for over 10 years. The mesencephalic reticular formation was selected as a target in 2 cases of VS, and the CM-pf complex was selected as a target in the other 19 cases of VS and 5 cases of MCS. Eight of the 21 patients emerged from the VS, and became able to obey verbal commands. However, they remained in a bedridden state except for 1 case. Four of the 5 MCS patients emerged from the bedridden state, and were able to enjoy their life in their own home. DBS therapy may be useful for allowing patients to emerge from the VS, if the candidates are selected according to appropriate neurophysiological criteria. Also, a special neurorehabilitation system may be necessary for emergence from the bedridden state in the treatment of VS patients. Further, DBS therapy is useful in MCS patients to achieve consistent discernible behavioral evidence of consciousness, and emergence from the bedridden state.

Adolescent↗
PubMed2005

Experimental model for investigating hyponatremia after subarachnoid hemorrhage in rats.

Hyponatremia is a common complication in patients with aneurysmal subarachnoid hemorrhage (SAH). Such patient demonstrates excessive natriuresis and an increased risk of symptomatic cerebral vasospasm. However, the precise mechanisms underlying SAH induced hyponatremia remain unclear. In the present study, in order to establish an experimental model of hyponatremia following SAH, we induced SAH in rats, and evaluated the serum sodium (Na) levels, Na excretion and physiological parameters. Twenty-four male Wistar rats were used. SAH was induced by an endovascular puncture method. The mean arterial pressure (MAP), intracranial pressure (ICP), and cerebral blood flow (CBF) were monitored continuously. The urine was collected cumulatively for 12 hours after SAH, and the urine Na concentration was determined with a spectrophotometer. The serum Na levels were measured at 12 hrs, 2 and 4 days following the SAH induction. The mean (+/- standard deviation) baseline ICP was 3.5 +/- 2.6 mmHg, and increased to 67.4 +/- 17.6 mmHg immediately following induction of SAH. CBF decreased rapidly, and then gradually recovered to 70-80% of baseline. The urine volume and total Na excretion were significantly increased in comparison to those of the sham (P < 0.05). The serum Na level was significantly decreased at 4 days following SAH (P < 0.05). The present results demonstrated for the first time that rats with SAH exhibited excessive natriuresis. The endovascular puncture model is suitable for investigating hyponatremia that occurs concomitantly with natriuresis and diuresis after SAH.

Animals↗
PubMed2005

Vanishing pituitary mass revealed by timely magnetic resonance imaging: examples of spontaneous resolution of nonfunctioning pituitary adenoma.

Spontaneous necrosis of a pituitary adenoma is not rare but represents a very unlikely way of curing a nonfunctioning pituitary adenoma. We report two cases of nonfunctioning pituitary adenoma, one of them with a family history of pituitary adenoma, in whom spontaneous complete resolution occurred through the necrosis of previously well-delineated adenoma. Sequential magnetic resonance imaging (MRI) scans provided clear evidence of the event, resulting in an empty sella. In the present cases, the pituitary necrosis was entirely asymptomatic with the exception of an initial atypical headache in one case, and cured the patients as well as a surgical procedure would have done. This exceptional curative process, however, should certainly not be relied on and does not rule out the possibility of recurrence.

Adenoma↗
PubMed2005

Sentinel surveillance for international Shigella by a quarantine station in Japan.

The Japanese quarantine system monitors incoming passengers to detect imported pathogens at international airports. At one airport, we found that 74% of 13 315 travellers returning with diarrhoea had visited only one country before entering Japan. On the basis of our results, we hypothesized that the international distribution and potential source of bacterial strains could be inferred by analysing strains isolated from travellers returning to Japan. In order to demonstrate the potential for this system, we randomly selected five Shigella sonnei strains and examined their restriction fragment length polymorphism patterns. One set of strains appeared to be closely related, while three sets, isolated from travellers who visited different countries were possibly related. These results suggest that international distributions and potential sources of S. sonnei may be inferred by monitoring isolates from passengers arriving at a Japanese quarantine station.

Aircraft↗
PubMed2005

Heavy alcohol intake, homocysteine and Type 2 diabetes.

Although moderate alcohol intake is associated with reduced risk of atherosclerotic disease in both the general population and in diabetic patients, a recent report suggests that heavy alcohol intake facilitates the development of atherosclerosis exclusively in diabetic individuals. We studied cross-sectionally the effects of the interaction between ethanol consumption category and the prevalence of diabetes on plasma total homocysteine (tHcy), a risk factor for atherosclerotic disease, in middle-aged men. Heavy drinking was associated with elevated tHcy levels only in diabetic subjects but not in non-diabetic subjects. Plasma tHcy of heavy drinkers (average ethanol consumption > 30 ml/day) was higher than that of abstainers in the diabetic subgroup (10.25 +/- 3.39 vs. 8.88 +/- 1.94 micromol/l, P < 0.05), whereas tHcy levels in heavy drinkers were comparable with that of abstainers in the non-diabetic subgroup (9.36 +/- 2.52 vs. 9.12 +/- 2.10 micromol/l, NS). In a two-factor anova, significant interaction was observed on the effects of ethanol consumption category and diabetes prevalence on tHcy levels (P < 0.01). Confounding factors including folate, vitamin B(12), creatinine, age or cigarette smoking did not contribute to the interaction. These findings may partly explain the reported association between heavy drinking and atherosclerosis in diabetic subjects.

Alcohol Drinking↗
PubMed2005

Function of sigma1 receptors in Parkinson's disease.

OBJECTIVE: The objective of this study was to investigate the mapping of sigma1 receptors in Parkinson's disease (PD) using [11C]SA4503 and positron emission tomography (PET), and to assess whether sigma1 receptors are involved in the damaged dopaminergic system in PD patients. MATERIALS AND METHODS: We studied seven normal volunteers and six PD patients. The low density of dopamine transporters and the normal or high density of dopamine receptors were confirmed in the putamen of all patients using [11C]CFT and [11C]RAC PET. A dynamic series of PET data acquisition was performed with arterial blood sampling. We computed the binding potential (BP) of [11C]SA4503. RESULTS: In PD patients, the BP was significantly lower on the more affected than the less affected side of the anterior putamen, although there was no significant difference with respect to the BP between patients and controls. CONCLUSIONS: Release of dopamine is reduced asymmetrically in the putamen of early PD. [11C]SA4503 PET is an indicator of presynaptic dopaminergic damage in PD.

Adult↗
PubMed2005

Reliability of MIBG myocardial scintigraphy in the diagnosis of Parkinson's disease.

AIM: To evaluate the reliability of [(123)I]meta-iodobenzylguanidine (MIBG) myocardial scintigraphy for diagnosing Parkinson's disease (PD). PATIENTS/METHODS: A series of 391 outpatients showing one or more parkinsonian-like symptoms was longitudinally followed up for accurate clinical diagnosis. MIBG scintigraphy was performed in the patients and 10 normal controls of similar age. The heart to mediastinum uptake ratio was calculated in each person, and the values were considered abnormal if they were greater than two standard deviations below the control mean. RESULTS: MIBG uptake was decreased in most patients with PD (87.7%), and was seen in all advanced cases with Hohen-Yahr stage III or more; the sensitivity and specificity of scintigraphy for detecting PD were 87.7% and 37.4%, respectively. Surprisingly, over half of the patients without PD (66.5%) also exhibited low uptake, resulting in considerable overlap in the ratios between PD and the other disorders. CONCLUSION: MIBG scintigraphy is a sensitive, but not specific, test for PD. Low MIBG uptake does not necessarily indicate PD, but is essential for diagnosing advanced PD.

3-Iodobenzylguanidine↗