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S Nishizawa

Publications and source records attributed to S Nishizawa.

At least 19 recordsLinked to original sources
PubMed2002

Neural activity of the globus pallidus interna and its anatomical relations to the optic tract in Parkinson's disease.

BACKGROUND: To reveal landmarks for placing the globus pallidus interna (GPi) target on MR images, visual evoked potentials (VEPs) of the optic tract (OT) and neural activities of the GPi were studied retrospectively. METHODS: The dorsal and lateral border of the OT were determined by VEPs of the OT, and neural activity in the pallidal region was recorded with a semimicro-electrode in 20 patients. The Unified Parkinson's Disease Rating Scale (UPDRS) was used to assess the condition of each patient before and 6 months and 12 months after surgery. FINDINGS: The location of trajectories relative to the lateral border of the OT were 3 mm medial (-3) in 6, 2 mm medial (-2) in 7, 1 mm medial (-1) in 8, at the lateral border (0) in 6, 1 mm lateral (+1) in 5, 2 mm lateral (+2) in 6, and 3 mm lateral (+3) in 5. The mean amplitudes along trajectories -3 and -2 mm were significantly higher than the others (post-hoc, p<0.01). In dorsoventral relations, the amplitudes from 5.1 mm to 6.8 mm of the medial trajectories (-3 to 0 mm) were significantly higher than others (post-hoc, p<0.01). The lesions placed medial to the lateral border of the OT located just above the lateral border of the OT on postoperative MR images (n=12) and brought better surgical benefits of total motor score, rigidity and bradykinesia than those placed lateral to the OT (n=8). INTERPRETATION: Our data indicate that hyperactive cells of the GPi are located medial to the lateral border of the OT and at least 5.1 mm above its dorsal surface, and this corresponds to the area just above the lateral border of the OT on MR images.

Aged↗
PubMed2001

Double-injection FDG method to measure cerebral glucose metabolism twice in a single procedure.

UNLABELLED: [18F]fluorodeoxyglucose (FDG) and positron emission tomography (PET) may be used to examine changes in cerebral glucose metabolism in two physiological conditions. We proposed and evaluated a double injection-single session FDG method with biological constraints for this purpose. METHODS: Simulated brain time-radioactivity curves (TACs) generated by using a plasma TAC from an actual study and physiological combinations of input values in a kinetic model were analyzed to evaluate the accuracy of the proposed method. The reproducibility of the estimated values obtained by this method was tested in five normal volunteers who were studied with a dynamic PET scan and two injections of FDG in a single session while fasting. RESULTS: The simulation study showed that the estimated values obtained by the proposed method agreed well with the input values. In the human study, plasma glucose levels were 5.3 +/- 0.2 and 5.0 +/- 0.2 mM in the first and second measurements, respectively. The difference between the plasma glucose measurements was small but statistically significant (p < 0.05). Although no systematic deviations were noted in K*1 or rCMRglc, there were small deviations in K* (less than 10%) and LC (less than 5%) with a statistical significance (p < 0.01). CONCLUSION: The deviation between the measurements in K* and LC seemed to relate to the difference in the plasma glucose level. The double-injection FDG method with biological constraints can be used to estimate rCMRglc and LC sequentially in a single PET scanning session.

Blood Glucose↗
PubMed2001

Assessment of cerebral hemodynamics before and after revascularization in patients with occlusive cerebrovascular disease by means of quantitative IMP-SPECT with double-injection protocol.

UNLABELLED: The purpose of this study was to validate a double-injection (DI) method with N-isopropyl-[123I]p-iodoamphetamine (IMP) to measure regional cerebral blood flow (rCBF) twice in a single session of dynamic SPECT and to elucidate a possible role of this method to identify patients with occlusive disease of major cerebral arteries, who might benefit from cerebral revascularization procedures (CR). MATERIALS AND METHODS: Fourteen patients with occlusion or severe stenosis of the internal carotid or middle cerebral artery were studied before and after CR to assess hemodynamic changes after revascularization treatment. We quantitatively measured rCBF before and after acetazolamide (ACZ) challenge along with cerebrovascular reserve capacity (CVR) with two injections of IMP in a single session of dynamic SPECT scans (DI method). The reliability and reproducibility of the DI method were validated by means of a simulation study and in eight patients who were examined without ACZ challenge to measure baseline rCBF twice. RESULTS: The analysis of simulated noisy data with realistic noise levels showed that the errors of the estimates for the first and the second rCBF and for the increase in rCBF were 2.6%, 8.1% and 10.4%, respectively. In the 8 patients examined by the DI method to measure baseline rCBF twice, the mean and the SD of percentage differences between the two consecutive measurements in rCBF were -1.3% and 5.5%, respectively. Eight out of 14 patients with occlusive disease had at least one region with a CVR less than 10%. They showed a significant increase in resting rCBF after CR, not only in the ipsilateral hemisphere (from 26.1 +/- 6.4 to 33.4 +/- 4.7) but also in the contralateral one (from 28.3 +/- 7.0 to 34.7 +/- 4.7) with a recovery of the ipsilateral CVR from 9.3 +/- 17.2 to 41.2 +/- 20.1%. The remaining six patients with good-moderate CVR did not show an increase in rCBF after CR (from 28.0 +/- 2.7 to 28.3 +/- 3.4). The three of them with a moderate CVR (10-25%) before CR showed normalization of CVR after CR. CONCLUSION: Patients with decreased rCBF and reduced CVR benefited from CR in terms of an increase in rCBF and recovery of CVR. The quantitative double-injection IMP-SPECT has the ability to identify those patients who may benefit from CR.

Aged↗
PubMed2001

Acute effects of stereotactic radiosurgery on the kinetics of glucose metabolism in metastatic brain tumors: FDG PET study.

UNLABELLED: Hyperacute changes in the expression of glycolysis-associate gene products as well as FDG uptake in tumor cells after high-dose irradiation reflect response of the cells to noxious intervention and may be a potential indicator of the outcome of treatment. To understand acute effects on the kinetics of glucose metabolism of tumors in vivo after high-dose irradiation, we analyzed dynamic FDG PET data in patients with metastatic brain tumors receiving stereotactic radiosurgery. MATERIALS AND METHODS: We studied 5 patients with metastatic brain tumors by means of dynamic FDG PET before and 4 hours after stereotactic radiosurgery. Rate constants of glucose metabolism (K1*- k3*) were determined in a total of 13 tumors by a non-linear least squares fitting method for dynamic PET and arterial blood sampling data. Rate constants after radiosurgery were compared with those before radiosurgery. Changes in the rate constants induced by the therapy were also correlated with changes in tumor size evaluated by CT and/or MRI 6 months later. RESULTS: Four hours after radiosurgery, the phosphorylation rate indicated by k3* was significantly higher (0.080 +/- 0.058) than that before radiosurgery (0.049 +/- 0.023) (p < 0.05, paired t test), but there was no significant change in the membrane transport rates indicated by K1* and k2*. Although increases in the net influx rate constant K* (= K1*k3*/(k2* + k3*)) were correlated with increases in k3*, K* after radiosurgery (0.027 +/- 0.011) was not significantly different from that before the therapy (0.024 +/- 0.012). The reduction in the tumor size was correlated with k3* after radiosurgery. CONCLUSION: Acceleration of the phosphorylation process was demonstrated in vivo in metastatic brain tumors as early as 4 hours after stereotactic radiosurgery, as shown experimentally in vitro in a previous report. The phenomenon may be a sensitive indicator of cell damage.

Aged↗
PubMed2001

Coexistence of thyrotropin-producing pituitary adenoma with papillary adenocarcinoma of the thyroid--a case report and surgical strategy.

We report a very rare case of thyrotropin (thyroxin stimulating hormone, TSH)-producing pituitary adenoma coexisting with a papillary adenocarcinoma of the thyroid. A 45-year-old woman presented with hyperhidrosis and a nodule in the left thyroid that was first noticed one year earlier. An endocrinological examination showed elevated serum levels of free triiodothyronine (T3) and free throxin (T4) without inhibition of TSH, suggesting the presence of syndromes of inappropriate secretion of TSH. A specimen obtained by needle aspiration of the thyroid nodule revealed the presence of papillary adenocarcinoma. Magnetic resonance images demonstrated a pituitary macroadenoma. The patient was diagnosed as having a TSH-producing pituitary adenoma coexisting with a papillary adenocarcinoma of the thyroid. The patient underwent a total thyroidectomy with resection of the neighboring lymph nodes. Two weeks after this surgery, the pituitary adenoma was totally removed via a pterional approach. Histological and immunohistochemical examinations of the surgical specimens confirmed the lesion as a papillary adenocarcinoma of the thyroid and a TSH-producing pituitary adenoma. Serum TSH levels decreased to undetectable levels immediately after the surgery for the pituitary adenoma. Prolonged stimulation of the thyroid gland by TSH may be involved in the growth of thyroid carcinoma. In cases with a TSH-producing pituitary adenoma, the possible coexistence of thyroid carcinoma should be carefully ruled out. In such cases, a total thyroidectomy followed by TSH level normalization should be performed. Incomplete removal of the thyroid might enable the carcinoma to re-grow if TSH level can not be normalized after the pituitary adenomectomy.

Adenocarcinoma, Papillary↗
PubMed2001

Post-traumatic high flow priapism: demonstrable findings of penile enhanced computed tomography.

Post-traumatic high flow priapism is a rare disease. A review of English published reports revealed 63 cases. Enhanced computed tomography (CT) of the penis has not previously been used as a diagnostic method for post-traumatic high flow priapism. We present a case of post-traumatic high flow priapism diagnosed with enhanced CT of the penis. Additionally, diagnostic modalities for post-traumatic high flow priapism are discussed with review of published work.

Adult↗
PubMed2001

Prevention of postoperative complications in skull base surgery for nasal or paranasal sinus carcinoma invading the skull base.

With recent technical advances in skull base surgery, radical resection of a nasal or paranasal sinus carcinoma invading the skull base can now be achieved. To assure a satisfactory surgical result, it is essential to prevent postoperative infection. In our series of 14 cases, serious postoperative infections occurred in the earliest 10 cases, and only 2 of these patients are still alive. The vascularised abdominal muscle flap for skull base reconstruction was fixed with fibrin glue, but was not adequate to fill the dead space, resulting in cerebrospinal fluid leakage and subsequent meningitis. Once the infection occurred, a free bone flap became the focus of infection. Based on these earlier experiences, we used a ROC fastener system to completely fill the dead space with an abdominal muscle flap, and bone flap was primarily craniectomised in the four most recent cases. With this technique, there were no postoperative infections.

Abdominal Muscles↗
PubMed2001

Incidentally identified syringomyelia associated with Chiari I malformations: is early interventional surgery necessary?

OBJECTIVE: The purpose of this study was to analyze clinical data and magnetic resonance imaging (MRI) findings for patients with asymptomatic, incidentally identified syringomyelia associated with Chiari I malformations who were monitored for more than 10 years, and to clarify the natural history of these lesions. METHODS: The clinical records of nine patients who had not been surgically treated and were regularly subjected to neurological and MRI examinations were analyzed. In MRI studies, the axial diameter of the syrinx at the widest level, the longitudinal extent of the syrinx, and the extent of tonsillar herniation into the spinal canal were analyzed. As a control, MRI findings for 11 patients with symptomatic syringomyelia associated with Chiari I malformations who had been surgically treated were also analyzed, and these MRI parameters were statistically compared between the asymptomatic and symptomatic groups. RESULTS: One patient underwent surgery, because of neurological changes, 7 years after the first visit. None of the remaining patients demonstrated any neurological change during the follow-up period (11.2+/-0.7 yr), and all of them have been faring well without surgery. No statistically significant differences in MRI findings between the asymptomatic and symptomatic groups were observed. CONCLUSION: The long-term clinical courses of patients with asymptomatic, incidentally identified syringomyelia associated with Chiari I malformations were observed to be benign. MRI parameters did not provide predictable values to recommend interventional surgery. Unless changes in neurological or MRI findings are detected, early interventional surgery is not necessary.

Adolescent↗
PubMed2001

The optimal stimulation site for chronic stimulation of the subthalamic nucleus in Parkinson's disease.

To determine the optimal stimulation site within the subthalamic nucleus (STN), monopolar stimulation of four electrode contacts and the resulting effects on parkinsonian symptoms were evaluated in 10 consecutive patients. The UPDRS score for rigidity and akinesia improved significantly after stimulation at each of the contacts, compared to the pre-evaluation state (Fisher's test, p < 0.05). The most significant improvement was obtained after stimulation at contact-2 (rigidity: 74.4 +/- 20.4%, akinesia: 53.7 +/- 14.3%) (Fisher's test, p < 0.001). Contact-2 was located at the dorsal border of the STN at a mean distance of 0.3 +/- 0.7 mm. DBS at the dorsal border of the STN, where the stimulation affects the neurons as well as their axonal fibers, produces the greatest clinical improvement in parkinsonian symptoms.

Brain Mapping↗
PubMed2001

Identification of differentially expressed genes in rat hippocampus after transient global cerebral ischemia using subtractive cDNA cloning based on polymerase chain reaction.

BACKGROUND AND PURPOSE: The purpose of this study is to identify new molecules that play important roles in the phenomena that occur in the hippocampus after transient global cerebral ischemia, as clues to better understanding of the mechanisms. METHODS: A subtractive cDNA library was established by suppression subtractive hybridization of rat hippocampal tissues after transient global cerebral ischemia. With differential screening of the library, upregulated fragments were identified. The mRNA expression levels of selected genes were measured with semiquantitative reverse transcriptase polymerase chain reaction (PCR). RESULTS: Among more than 100 isolated fragments, approximately half were determined to be identical to known sequences. The rest showed high homology to known sequences, and only 2 did not exhibit homology to any known sequences. The expression of 5 genes identified in this study increased in 24 hours after ischemia to a level twice as high as that in sham-operated controls. These included furin, prosaposin, synaptotagmin IV, heat shock protein 105, and the neutral and basic amino acid transporter (NBAT). The increases in the mRNA expression levels of the genes except NBAT, as revealed by semiquantitative reverse transcription PCR, were statistically significant at both 6 and 24 hours after ischemia. CONCLUSIONS: Genes isolated are thought to be associated with production of proteins necessary for degeneration, neuroprotection, and reconstruction of neurons. How the expression of these genes relates to functional changes after ischemia remains to be determined. PCR-based subtractive cDNA cloning is demonstrated to be a useful tool for analyzing in vivo gene expression in animal ischemia models.

Amino Acid Transport Systems, Basic↗
PubMed2001

Diagnostic and surgical strategies for intractable spontaneous intracranial hypotension. Case report.

The authors present the case of a 55-year-old man suffering from intractable spontaneous intracranial hypotension, in whom conservative treatment with 19 weeks of bed rest was not effective. In this period the patient twice underwent surgery for bilateral chronic subdural hematoma, a complication of spontaneous intracranial hypotension. Conventional radionuclide cisternography, magnetic resonance imaging, and computerized tomography myelography did not demonstrate cerebrospinal fluid (CSF) leakage. Repeated radionuclide cisternography with the patient in an upright position revealed leakage of the tracer at upper cervical levels. Computerized tomography myelography with breath holding also showed CSF leakage of the contrast medium bilaterally at upper cervical levels. The patient underwent surgery, and bilateral C-2 and C-3 spinal nerve root pouches were sealed off from the subarachnoid space with oxidized cellulose cotton and fibrin glue. Epiarachnoid spaces around the root sleeves were also sealed to ensure complete resolution of the CSF leakage. After the surgery, the patient was completely free of the disease. In the case of intractable persistent spontaneous intracranial hypotension, surgical treatment is preferable to long-term conservative management. To identify CSF leakage, radionuclide cisternography with the patient in the upright position is useful. When obvious leakage is encountered, surgical sealing of the lesion should be performed via a subarachnoid approach.

Cerebral Ventricles↗
PubMed2000

Naming of animals and tools: a functional magnetic resonance imaging study of categorical differences in the human brain areas commonly used for naming visually presented objects.

To investigate the neural substrates for naming objects and their category-dependency, we performed functional magnetic resonance imaging (fMRI) with naming of animals and tools. Naming objects, irrespective of their category, activated left frontal to bilateral parietal regions and occipital to posterior temporal regions. Within these areas, naming animals caused more activation of the primary visual cortex bilaterally and the ventral occipital cortex to the inferior temporal area on the right side. Naming tools caused more activation of the posterior part of the left middle temporal area, the rostral part of the left inferior parietal lobule, and the left inferior frontal cortex. These findings suggest that the neural network for naming objects has discrete category-dependent nodes through which pertinent conceptual knowledge may be mediated.

Adult↗
PubMed2000

Selective potassium ion recognition by benzo-15-crown-5 fluoroionophore/gamma-cyclodextrin complex sensors in water.

Three fluoroionophores Cn (n = 1, 3, 5), in which the crown ether unit and pyrenyl moiety are connected by a -(CH2)n- spacer, have been used to construct supramolecular Cn/gamma-cyclodextrin (gamma-CyD) complexes for alkali metal ion sensing in water. The Cn (n = 3, 5) are found to selectively form 2:1 complexes with K+ in the presence of gamma-CyD and exhibit the pyrene dimer emission in water. Equilibrium analysis of the C3/gamma-CyD complex reveals that the observed dimer emission arises from a 2:1:1 complex of C3 with K+ and gamma-CyD. In the absence of K+, the fluorescence lifetimes for the dimer species ((C3)2CyD and (C3)2(CyD)2) and the monomer species (C3CyD and C3(CyD)2) are 13-18 and 130-180 ns, respectively. Upon addition of 0.10 M KCI, a rising component corresponding to pyrene excimer formation is observed at the dimer emission region. For the C3/gamma-CyD complex, the apparent association constant for K+ of (3.8 +/- 1.3) x 10(9) M(-2) is only slightly affected by the presence of Na+. Although the C5/gamma-CyD complex shows high sensitivity for K+, the selectivity for K+ over Na+ is lower than that of the C3/gamma-CyD complex. In contrast, fluoroionophore C1 with the shortest methylene spacer exhibits no response for alkali metal cations in the presence of gamma-CyD. These results demonstrate that the response function of supramolecular Cn/gamma-CyD complexes is strongly affected by the methylene spacer length of Cn. The highest K+ selectivity is obtained for the C3/gamma-CyD complexes in water.

Journal Article↗
PubMed2000

The complete nucleotide sequence of the mitochondrial genome of sugar beet (Beta vulgaris L.) reveals a novel gene for tRNA(Cys)(GCA).

We determined the complete nucleotide sequence of the mitochondrial genome of an angiosperm, sugar beet (Beta vulgaris cv TK81-O). The 368 799 bp genome contains 29 protein, five rRNA and 25 tRNA genes, most of which are also shared by the mitochondrial genome of Arabidopsis thaliana, the only other completely sequenced angiosperm mitochondrial genome. However, four genes identified here (namely rps13, trnF-GAA, ccb577 and trnC2-GCA) are missing in Arabidopsis mitochondria. In addition, four genes found in Arabidopsis (ccb228, rpl2, rpl16 and trnY2-GUA) are entirely absent in sugar beet or present only in severely truncated form. Introns, duplicated sequences, additional reading frames and inserted foreign sequences (chloroplast, nuclear and plasmid DNA sequences) contribute significantly to the overall size of the sugar beet mitochondrial genome. Nevertheless, 55.6% of the genome has no obvious features of information. We identified a novel tRNA(Cys) gene (trnC2-GCA) which shows no sequence homology with any tRNA(Cys) genes reported so far in higher plants. Intriguingly, this tRNA gene is actually transcribed into a mature tRNA, whereas the native tRNA(Cys) gene (trnC1-GCA) is most likely a pseudogene.

Arabidopsis↗
PubMed2000

Protein kinase cdelta and alpha are involved in the development of vasospasm after subarachnoid hemorrhage.

We have previously shown the enhanced activity of protein kinase C in the membrane fraction of the canine vasospastic artery after subarachnoid hemorrhage, which increased with progression of angiographic vasospasm. This study examined identification of protein kinase C isoforms in the canine basilar artery, and the changes in expression and/or translocation of each isoform during the development of vasospasm. Vasospasm was produced by using the "two-hemorrhage" canine model in the basilar artery, and angiographic progression of vasospasm was assessed consecutively. Two isoforms, protein kinase Calpha and delta were identified in basilar arteries by Western blotting. Densitometric analysis showed that the expression of protein kinase Cdelta in the membrane fraction was significantly increased in the earlier stage, and protein kinase Calpha was increased later as vasospasm progressed. These results indicate that protein kinase Cdelta and alpha isoforms may play a significant role in the development and maintenance of vasospasm.

Actins↗
PubMed2000

Neural substrates for depth perception of the Necker cube; a functional magnetic resonance imaging study in human subjects.

We have studied the cerebral activity for the depth perception of the Necker cube by functional magnetic resonance imaging. Three types of line drawing figures were used as stimuli, the Necker cube, hidden line elimination cube and overlapping squares. Subjects were instructed to perceive both orientations of the depth of the Necker cube. They were instructed to shift their attention voluntarily during viewing overlapping squares to obtain a control for the attentional shift in perceiving the Necker cube. A hidden line elimination cube was used as a control for monocular stereopsis. The results showed a clear symmetrical activation in premotor and parietal areas during the Necker cube perception compared with other conditions. The present result suggests that a neural process similar to mental image manipulation occurs during depth perception of the Necker cube.

Brain Mapping↗