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H Nakase

Publications and source records attributed to H Nakase.

At least 91 records · Page 5Linked to original sources
PubMed1998

Local cerebral blood flow autoregulation following "asymptomatic" cerebral venous occlusion in the rat.

OBJECT: Maintenance of cerebral blood flow (CBF) autoregulation in the brain is of major importance for patient outcome in various clinical conditions. The authors assessed local autoregulation after "asymptomatic" cortical vein occlusion. METHODS: In Wistar rats, a single cortical vein was occluded photochemically by using rose bengal and fiberoptic illumination. In rats with bilateral carotid artery occlusion, mean arterial blood pressure (MABP) was lowered in 5-mm Hg increments down to 40 mm Hg by using hypobaric hypotension. Local CBF at each pressure level was assessed by performing laser Doppler (LD) scanning at 25 (5 x 5) locations within bilateral cranial windows. In this manner, the lower limit of autoregulation (LLA) was detected. The LLA was 60 mm Hg in both right and left hemispheres in Group A (five rats), in which the animals received illumination without rose bengal and had no venous occlusion. Of the 11 rats that underwent vein occlusion, three developed severe reductions in local CBF and/or a growing venous thrombus and were distinguished as Group C (symptomatic; three rats); from previous work we know that those animals are bound to experience venous infarction. The remaining rats formed Group B (asymptomatic; eight rats). In this group the LLA remained at 60 mm Hg in the left hemisphere without occlusion, whereas, in the right cortex with the occluded vein, the LLA was found to be 65 mm Hg. Below a carotid stump pressure of 25 mm Hg regional CBF in the affected hemisphere dropped more abruptly to a possibly ischemic range than that in the opposite normal hemisphere. CONCLUSIONS: The results of the present study suggest that cerebral venous circulation disorders are manifested via additional pathways, that is, from a partially impaired local autoregulation in the vicinity of the occluded vein, even under conditions in which the vein occlusion itself does not cause brain damage. Care should be taken in the control of blood pressure in patients with this pathological condition.

Analysis of Variance↗
PubMed1997

An experimental model of intraoperative venous injury in the rat.

Intraoperative obliteration of cerebral veins occasionally causes unexpected severe complications, especially in elderly patients. However, very title information is available on the pathophysiology of cerebral venous circulation disturbance. Occlusion of cortical veins in rats by a photochemical thrombotic technique is a less invasive, clinically relevant and reproducible model that is suitable for the study of venous circulation disturbance. In the present study, 54 male Wistar rats were used. We examined changes of the cerebral venous flow pattern by fluorescence anglography and brain damage histologically in a one- or two-(cortical) vein occlusion model using a photochemical thrombotic technique. Approximately 30% (9 of 27) of animals in the single-vein occlusion group and 90% (15 of 17) of those in the two-vein occlusion group had microcirculation perturbation, which results very soon in the formation of venous thrombus accompanied by severe venous infarction. In addition, infarction size in the two-vein occlusion group (9.7 +/- 3.2%) was significantly larger than in the single-vein group (2.9 +/- 1.3%) (unpaired T-test, P < 0.01).In conclusion, the photochemical dye technique of attaining cerebral venous occlusion is a worth while addition to the study of circulation perturbations of the brain.

Journal Article↗
PubMed1997

Increased hypoxic tolerance by chemical inhibition of oxidative phosphorylation: "chemical preconditioning".

A short ischemic episode preceding sustained ischemia is known to increase tolerance against ischemic cell death. We report early-onset long-lasting neuroprotection against in vitro hypoxia by preceding selective chemical inhibition of oxidative phosphorylation: "chemical preconditioning." The amplitude of CA1 population spikes (psap) in hippocampal slices prepared from control animals (control slices) was 31 +/- 27% (mean +/- SD) upon 45-min recovery from 15-min in vitro hypoxia. In slices prepared from animals treated in vivo with 20 mg/kg 3-nitropropionate (3-np) 1-24 h prior to slice preparation (preconditioned slices), psap improved to 90 +/- 15% (p < 0.01). Posthypoxic oxygen free radicals were reduced to 65 +/- 10% (mean +/- SD) of control in preconditioned slices (p < 0.05). Posthypoxic neuronal density improved from 52 +/- 15% (mean +/- SD) in control slices to 97 +/- 23% in preconditioned slices (p < 0.001). Glibenclamide, an antagonist at KATP-channels, partly reversed increased hypoxic tolerance. We conclude that chemical preconditioning induces early-onset long-lasting tolerance against in vitro hypoxia. Ultimately, this strategy may be applicable as a neuroprotective strategy in humans.

Adenosine Triphosphate↗
PubMed1997

Orbital varix diagnosed by color Doppler flow imaging--case report.

A 66-year-old male presented with an angiographically occult orbital varix. Angiography and phlebography failed to demonstrate the lesion. Computed tomography angiography showed the varix, but not the vascular flow. Color Doppler flow imaging clearly demonstrated the well-defined varix with slow flow velocity, as well as the precise anatomical location. We recommend color Doppler flow imaging as one of the differential diagnostic tools for intraorbital vascular lesions.

Aged↗
PubMed1997

In situ characterization of islets in diabetes with a mitochondrial DNA mutation at nucleotide position 3243.

Changes in the pancreas of diabetic patients with the A-to-G mitochondrial DNA (mtDNA) mutation at nucleotide position 3243 base pair (bp) have not previously been described. The clinical phenotypes of diabetes associated with the mtDNA 3243 mutation range from NIDDM to IDDM. We sought the presence of the mutation and studied volume of beta-, alpha-, and delta-cells, mitochondrial enzyme activity, and presence of apoptosis in diabetic pancreases obtained at autopsy. Pancreases were obtained from 16 patients with IDDM, from 18 patients with NIDDM, and from 11 nondiabetic patients. Mitochondrial enzyme activity was determined for cytochrome c oxidase (COX), the subunits of which are partially encoded by mtDNA, and for succinate dehydrogenase (SDH), the subunits of which are solely encoded by nuclear DNA. The volumes of islet beta-, alpha-, and delta-cells were estimated by computerized morphometry. Pancreatic cells were examined for apoptosis by an in situ end-labeling procedure. The mtDNA 3243 mutation was detected in 1 of 16 (6%) pancreases from the IDDM patients; none of the pancreases from 18 NIDDM patients and 11 nondiabetic patients had the mutation. The single patient with the mtDNA 3243 mutation was a 56-year-old woman with IDDM, aged 39 years at diabetes onset, whose mother was diagnosed with NIDDM. The patient had a history of secondary failure of oral hypoglycemic agents and had a marked decrease in the number of beta-cells. The islet beta-cells and non-beta-cells of the patient showed extremely decreased COX enzyme activity. The islet cells in the patient showed a high activity when examined for SDH. Some pancreatic exocrine cells also showed decreased COX activity with high SDH activity. In IDDM, NIDDM, and nondiabetic patients without the mtDNA 3243 mutation, only weak staining for SDH of the islet cells showed. The percentage of heteroplasmy of the mtDNA 3243 mutation in pancreatic micropunched islet specimens was 63 +/- 5% (mean +/- SD) in the islets, 32 +/- 3% in the exocrine pancreas, and 8 +/- 1% in peripheral polymorphonuclear cells. Apoptotic cells were not observed in the IDDM pancreas in the patient with the mtDNA 3243 mutation. The fact that higher levels of mutated mtDNA at 3243 bp were found in affected islets rather than in other tissue suggests that the distribution of the mutant may determine the effect on islet function. A characteristic decrease in the mitochondrial enzyme with COX activity and accelerated SDH activity of the affected islets may provide new insights into the pathogenesis of mitochondrial diabetes.

Adult↗
PubMed1997

Microcirculation after cerebral venous occlusions as assessed by laser Doppler scanning.

Research on cerebral venous circulation disturbances (CVCDs) has been limited partly by the paucity of animal models that produce consistent venous infarction. Occlusion of two adjacent cortical veins in rats by means of a photochemical thrombotic technique provides a minimally invasive, clinically relevant, and reproducible model suited to study the pathophysiology of CVCDs. In this study, the effects of venous occlusion on regional cortical blood flow and the brain damage that ensues were evaluated. Cortical vein occlusion was induced by photoactivation of rose bengal via 100-microm fiberoptic illumination. The cerebral venous flow pattern was examined using fluorescence angiography until 90 minutes after venous occlusion, and regional cerebral blood flow (rCBF) was determined at 48 locations by using laser Doppler scanning. Histological damage was assessed 48 hours after vein occlusion. Occlusion of two cortical veins (Group T; seven animals) was compared with single-vein occlusion and its ensuing brain damage (Group S; five animals) and with sham-operated control (five animals). An rCBF reduction occurred 30 minutes after occlusion in Group T and was more extensive than the decrease in Group S after 60 minutes. Observation frequency histograms based on local CBF data obtained in Group T demonstrated that local CBF at some sites decreased to a level below the ischemic threshold within 90 minutes. Six of the seven rats in Group T had a growing venous thrombus with extravasation of fluorescein. The resulting infarction was significantly larger in Group T (9.8 +/- 4.5% of the hemispheric area) than in Group S (only 3 +/- 1.5% of the hemispheric area). In conclusion, microcirculation perturbations occur early after venous occlusion and result in the formation of a venous thrombus accompanied by local ischemia and severe venous infarction. The extent of vein occlusion determines the resulting brain damage. Based on the results of this study, the authors conclude that CVCDs may be attenuated by prevention of venous thrombus progression together with the use of protective measures against the consequences of ischemia.

Animals↗
PubMed1996

Expression of vascular permeability factor/vascular endothelial growth factor in human hepatocellular carcinoma.

Vascular permeability factor (VPF)/vascular endothelial growth factor (VEGF) is unique in its ability to promote vascular permeability and endothelial cell growth, and its role in tumor development has received considerable attention. In this report, we describe the elevation of VPF/VEGF transcript expression in human hepatocellular carcinoma. Surgical samples of 23 patients with hepatocellular carcinoma were studied using reverse transcription-PCR analysis. The oligonucleotide primers were designed to amplify all four known splicing variants that could be expressed in the samples studied. Sixteen cases showed VPF/VEGF transcript expression in the tumor (16/23, 69.6%), whereas only 9 of the 23 patients showed it in the corresponding nontumoral part. There was no difference between the pattern of expression of VPF/VEGF isoforms in tumoral and nontumoral tissues. VPF/VEGF mRNA expression in the liver tumors was associated with fibrous capsule formation and septal formation (P < 0.05 respectively, Fisher's exact P test). In situ hybridization confirmed the presence of VPF/VEGF mRNA expression in tumor cells and less intensely in hepatocytes of nontumoral liver. We also found that VPF/VEGF expression in the tumor cell was increased in the area adjacent to necrotic regions (presumably hypoxic regions). As a regulator of vascular permeability and endothelial cell growth factor, VPF/VEGF may play an important role in the development of hepatocellular carcinoma.

Adult↗
PubMed1996

Local cerebral blood flow in a rat cortical vein occlusion model.

The symptoms following sinus and vein occlusion observed in patients and experimental animals display a considerable variability that so far remains largely unexplained. In a rat cortical vein occlusion model using a photochemical thrombotic technique, we examined changes in the cerebral venous flow pattern by fluorescence angiography and regional cerebral blood flow (rCBF) and cerebral blood volume fraction (CBVF) by a modern laser Doppler "scanning" technique. Brain damage was assessed histologically. Fluorescence angiographic findings fell into two groups: group A, rats with an altered venous flow pattern after occlusion (n = 12), and group B, rats with interruption of blood flow and/or a growing venous thrombus (n = 5). In addition, sham-operated animals made up group C (n = 5). Extravasation of fluorescein, a massive decrease in rCBF, a short-lasting increase in CBVF, and regional brain damage were typical for group B. In addition, cortical CBF mapping revealed a transient hyperperfusion zone with hyperemia surrounding a hypoperfused ischemic core in group B. A circulation perturbation following venous occlusion appeared near those occluded cerebral veins without sufficient collateral flow. Furthermore, the venous thrombus continued to grow, accompanied by local critical ischemia and severe brain damage. Conversely, 71% of the animals (12 of 17) tolerated occlusion of a solitary vein without major flow disturbances or histological evidence of damage to the CNS (group A).

Animals↗
PubMed1996

Alterations of regional cerebral blood flow and oxygen saturation in a rat sinus-vein thrombosis model.

BACKGROUND AND PURPOSE: The pathophysiology of sinus-vein thrombosis (SVT) in patients and experimental animals is still poorly understood. This study was designed to examine and further elucidate the pathophysiological sequence of events, especially the relationship between local and regional blood flow and hemoglobin oxygen saturation (HbSO2) detected at identical locations. The use of both parameters as outcome indicators should be compared. METHODS: SVT was induced by ligation of the superior sagittal sinus (SSS) and slow injection of kaolin-cephalin suspension into the SSS in rats. Regional cerebral blood flow (rCBF) was assessed by laser-Doppler flowmetry together with regional HbSO2, which was measured by a microspectrophotometric technique at 48 identical locations for 90 minutes after SVT using a scanning technique. Fluorescence angiography was performed before and 30 and 90 minutes after SVT induction. After 48 hours the animals were killed for histology. RESULTS: The fluorescence angiographic findings could divide animals into three groups: (1) group A, with a solitary SSS thrombus (n=8); (2) group B, with a thrombosis of SSS and cortical veins (n=10); (3) group C, animals that had undergone sham operation (n=5). Decreases of rCBF and HbSO2 and brain damage were seen in group B but not in group A. The reduction of local HbSO2 preceded the flow decrease after sagittal sinus ligation but before thrombosis. Blood pressure in group A was found to be significantly higher after SVT than in groups B and C. CONCLUSIONS: The brain with acute extension of thrombus from the SSS into cortical veins experiences a critically reduced supply of blood and oxygen. CBF, local HbSO2, and repeated angiography can be helpful monitors for the early detection of critical conditions after SVT. Local HbSO2 has a greater sensitivity to predict outcome than lCBF. Moreover, therapies directed to improve perfusion pressure or reduce vascular resistance may open further therapeutic windows during SVT progression.

Animals↗
PubMed1996

Dural arteriovenous fistula of the posterior fossa developing after surgical occlusion of the sigmoid sinus. Report of five cases.

In this article, the authors present five cases of dural arteriovenous fistula (AVF) that developed in the transverse-sigmoid sinus 2 to 6 years after sacrifice of the sigmoid sinus because of tumor involvement. The original tumor was meningioma in two patients and neurinoma, glomus jugulare tumor, and ameloblastoma in one patient each. The involved sigmoid sinus was resected along with the tumor and ligated at the normal edge; all that remained of the sigmoid sinus was a small stump on the retrosigmoid portion. Serial angiography performed before and after tumor surgery revealed no abnormal arteriovenous communications or dural AVF in any of the cases. Although many reports have suggested that sinus thrombosis is a precipitating factor in the pathogenesis of dural AVFs, this has been difficult to verify because of the small number of cases in which serial angiography was performed before the development of a dural AVF. In all of the cases presented in this article, surgical resection of a dural AVF and histological examination were performed. Subintimal fibrous thickening was marked, and the sinus wall was found to contain many dural vessels. Organized thrombosis with neovascularization was seen in only two patients. These cases demonstrate that subintimal fibrous thickening a hypertrophied sinus wall secondary to increased intrasinus pressure or sinus thrombosis occurring after sinus occlusion can provoke the development of a dural AVF within the course of a lifetime. Maintenance of intrasinus blood flow may be very important to prevent this late postoperative complication.

Arteriovenous Fistula↗
PubMed1996

Endoscopic variceal ligation versus endoscopic injection sclerotherapy: comparison of hepatic and renal function.

OBJECTIVES: The aim of the present study was to compare the safety of endoscopic variceal ligation (EVL) and endoscopic injection sclerotherapy (EIS) in terms of liver and kidney functions in patients with liver cirrhosis. METHODS: Forty-four patients admitted to Takatsuki General Hospital between February 1991 and March 1993 with esophageal varices due to liver cirrhosis were randomly assigned to receive either EVL or EIS. Serum levels of AST, ALT, total bilirubin (T-bil), direct bilirubin (D-bil), prothrombin time (PT), hepaplastin test (HPT), antithrombin III (ATIII), creatinine (Cr), and blood urea nitrogen (BUN) were measured before and 24 h, 3 days, 7 days, and 14 days after both forms of therapy. RESULTS: Significant elevations of serum T-bil, serum D-bil, and serum ALT and AST levels were observed in the EIS group but not in the EVL group. No significant increases of serum PT, HPT, ATIII, BUN, or Cr levels were observed after treatment in either group. CONCLUSION: EVL should be considered a first choice therapy for eradicating esophageal varices.

Endoscopy↗
PubMed1995

An intra-arterial electrode for intracranial electro-encephalogram recordings.

A new method for intracranial monitoring of brain electrical activity by means of an intra-arterial guide wire as electrode is described. We carried out intracranial electro-encephalography (EEG) using an insulated Seeker Lite-10 guide wire 18 times in 14 patients: ten times in 6 patients with cerebral arteriovenous malformation (AVM) before embolization, and another 8 times in 8 patients with epilepsy. In all cases, a 2-5 times stronger high voltage potential EEG compared with scalp EEG could be recorded. In 3 patients with complex partial epilepsy, intra-arterial (IA) EEG was recorded under subdural strip electrode monitoring, and IAEEG at the sphenoidal portion of the middle cerebral artery was compared with subdural electrode recordings. Frequent interictal spike discharges recorded with subdural electrodes in the lesional medial temporal lobe were simultaneously visible on IAEEG recording. This method is equivalent to that using a semi-invasive electrode, but ECoG recording can be performed at angiography. IAEEG is a method of electrode recording that has the possibility of clinical application.

Adolescent↗
PubMed1995

Monitoring of venous blood flow velocity during interhemispheric approach for deep seated lesions.

No precise intra-operative monitoring of venous blood flow has yet been developed for neurosurgical procedures. Preservation of the bridging veins is an important issue in order to minimize complications due to disturbances of venous blood flow during an interhemispheric approach. In the present study, venous blood flow velocity was measured in 11 anterior circulation aneurysms. The measurement was performed before brain retraction, during brain retraction and after completion of the procedure without brain retraction. In 6 cases, a bridging vein was dissected completely free from the dura up to its entry into the superior sagittal sinus (SSS group). In 5 cases, dura was cut parallel to the bridging vein so that the vein remained covered by the dura (dura group). Venous blood flow velocity was measured by microvascular Doppler sonography. The results show that venous blood flow can be better preserved during the retraction when the bridging vein remains covered with the dura than if the vein is dissected completely free from the dura.

Aged↗
PubMed1995

Use of local cerebral blood flow monitoring to predict brain damage after disturbance to the venous circulation: cortical vein occlusion model by photochemical dye.

A rat model of cortical vein occlusion by the photochemical thrombotic technique was used to evaluate whether monitoring the change in the local cerebral blood flow (LCBF) could predict brain damage after cortical vein occlusion. The cortical vein occlusion was attained by using the photochemical thrombotic technique, and the sequential LCBF was measured by using a laser Doppler flowmeter positioned over the middle frontal cortex between two adjacent dorsal veins for 120 minutes after the start of the irradiation to the cortical vein. Rats were assigned to one of three experimental groups. In Group A (n = 10), one dorsal cerebral vein was occluded; in Group B (n = 10), two adjacent dorsal cerebral veins were occluded; and in a sham-operated group (n = 5), the rats also underwent craniotomy and light exposure but received injections of saline rather than the rose bengal dye. After 24 hours, the rats were submitted to perfusion fixation and were examined histopathologically. After irradiation-induced cortical vein occlusion, a gradual and significant decrease of the LCBF was observed in both Group A (significantly different from the LCBF of the sham-operated group after 90 min, P < 0.05, and 120 min, P < 0.01) and Group B (significantly different from the LCBF of the sham-operated group at 30 min, P < 0.05, and at 60, 90, and 120 min, P < 0.01). Significant differences (P < 0.01) in the LCBF were also seen between the two experimental groups at 90 and 120 minutes after the start of the irradiation and the subsequent brain damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Myotonin protein kinase].

The mutation underlying myotonic dystrophy is the expansion of polymorphic CTG repeat in the 3'-noncoding region of the myotonin protein kinase (MtPK) gene mapping to chromosome 19q13.3. A full-length cDNA of human MtPK was cloned and expressed in COS-1 cells. MtPK is recovered from the COS cell extract as a 70 kDa protein, which coincides with the size deduced from the predicted amino acid sequence. Biochemical characteristics of MtPK expressed in COS cells and its expression are investigated.

Chromosomes, Human, Pair 19↗
PubMed1994

The "turn-over" technique for selective cerebral angiography.

In older patients with severe aortic atherosclerosis or pronounced tortuosity of the brachiocephalic vessels, selective catheterisation may be impossible. In order to overcome this difficulty we introduced a new "turn-over" technique. This involves introduction of a long guidewire through the catheter, advancing it and turning it over just above the aortic valves and finally introducing it into each major vessel, followed by the catheter. Selective catheterisation was completely achieved with the turn-over technique in 13 patients. Turning over the catheter just above the aortic valves and introducing it into the vessels was very easy.

Aged↗