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Biomedical subjects

H Sakuma

Publications and source records attributed to H Sakuma.

At least 37 records · Page 2Linked to original sources
PubMed2001

Arterial hyperintensity on fast fluid-attenuated inversion recovery images: a subtle finding for hyperacute stroke undetected by diffusion-weighted MR imaging.

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging is generally acknowledged to be more sensitive in detecting acute stroke than is conventional MR imaging. Our purpose in the present study was to evaluate the utility of fast fluid-attenuated inversion recovery (FLAIR) MR imaging compared with that of diffusion-weighted MR imaging for the diagnosis of hyperacute stroke. METHODS: We reviewed patient records and cerebral MR images from all patients in a 13-month period from whom diffusion-weighted and fast-FLAIR imaging were obtained within 6 hours after symptom onset (n = 11). Special attention was paid to the presence or absence of arterial hyperintensity on FLAIR images and abnormally high-signal regions on diffusion-weighted images in the affected vascular territories. RESULTS: Arterial hyperintensity was found in eight of 11 patients, all of whom had embolic or thrombotic infarctions with middle cerebral arterial (MCA) distribution. Arterial hyperintensity was negative in the remaining three patients; the vascular territories were the posterior circulation region in two of these patients and the MCA region in one, and the types of infarction in these same patients were lacunar in two and embolic in one. Regions with high-signal diffusion abnormalities relevant to the patients' symptoms were found in 10 of 11 patients. One patient showed no diffusion abnormalities but the presence of arterial hyperintensity in the affected MCA territory on the initial MR examination, and manifested embolic infarction along with arterial hyperintensity on the initial FLAIR image. CONCLUSION: Although diffusion-weighted MR imaging is highly sensitive to stroke, diffusion-weighted MR imaging alone may not rule out a possible infarction. Arterial hyperintensity on FLAIR images can precede diffusion abnormalities and may provide a clue to the early detection of impending infarction.

Aged↗
PubMed2001

[Efficacy of anticonvulsants on acute encephalitis with refractory, repetitive partial seizures (AERRPS)].

The first purpose of this study is to propose a new clinical entity, acute encephalitis with refractory, repetitive partial seizures (AERRPS), which satisfy the following five criteria: 1. a prolonged acute phase of more than 2 weeks; 2. partial seizures of the same seminology persisting from the acute phase to the convalescence; 3. seizures frequently evolving into convulsive status especially during the acute phase; 4. marked intractableness of seizures; 5. exclusion of related disorders such as known viral encephalitis or metabolic disorders. The second purpose is to evaluate the efficacy of therapeutic agents on AERRPS. We reviewed 21 cases reported previously, as well as one patient seen by us. Based on the data, we recommend that patients with AERRPS should be under a high dose intravenous barbiturate during the acute phase, followed by a high dose of phenobarbital or phenytoin in the convalescence. Clonazepam, zonisamide, and potassium bromide were sometimes effective during the recovery phase.

Acute Disease↗
PubMed2000

Cloning and chromosomal mapping of human glucuronyltransferase involved in biosynthesis of the HNK-1 carbohydrate epitope.

The HNK-1 carbohydrate is expressed on various cell adhesion molecules in the nervous system and is suggested to play a role in cell-cell and cell-substrate interactions. Here we describe the isolation of a cDNA encoding human glucuronyltransferase (GlcAT-P), which is a key enzyme in the biosynthesis of the HNK-1 carbohydrate. The primary structure deduced from the cDNA sequence predicted a type II transmembrane protein of 334 amino acids. Human GlcAT-P was 98.2% identical with rat GlcAT-P in amino acid sequence, the exception being the length of the cytoplasmic tail. Northern blot analysis indicated that human GlcAT-P is expressed mainly in the brain. There is a single copy of the human GlcAT-P gene (HGMW-approved symbol B3GAT1), and it was mapped to chromosome 11q25.

Amino Acid Sequence↗
PubMed2000

Effect of pertussis toxin on insulin-induced signal transduction in rat adipocytes and soleus muscles.

It has been reported that pertussis toxin (PTX) suppresses the function of trimeric guanine nucleotide binding protein (G-protein). We examined the effect of PTX on insulin-induced glucose uptake, diacylglycerol (DG)-protein kinase C (PKC) signalling, phosphatidylinositol (PI) 3-kinase and PKC zeta activation and insulin-induced tyrosine phosphorylation of Gialpha to clarify the role of G-protein for insulin-mediated signal transduction mechanism in rat adipocytes and soleus muscles. Isolated adipocytes and soleus muscles were preincubated with 0.01 approximately 1 ng/ml PTX for 2 hours, followed by stimulation with 10-100 nM insulin or 1 microM tetradecanoyl phorbol-13-acetate (TPA). Pretreatment with PTX resulted in dose-responsive decreases in insulin-stimulated [3H]2-deoxyglucose (DOG) uptake, and unchanged TPA-stimulated [3H]2-DOG uptake, without affecting basal [3H]2-DOG uptake. In adipocytes, insulin-induced DG-PKC signalling, PI 3-kinase activation and PKC zeta translocation from cytosol to the membrane were suppressed when treated with PTX, despite no changes in [125I]insulin-specific binding and insulin receptor tyrosine kinase activity. Moreover, to elucidate insulin-stimulated tyrosine phosphorylation of 40 kDa alpha-subunit of G-protein (Gialpha-2), adipocytes were stimulated with 10 nM insulin for 10 minutes, homogenized, immunoprecipitated with anti-phosphotyrosine antibody, and immunoblotted with anti-Gialpha-2 antibody. Insulin-induced tyrosine phosphorylation of Gialpha-2 was found by immunoblot analysis with anti-Gialpha-2 antibody. These results suggest that G-protein regulates DG-PKC signalling by binding of Gialpha-2 with GTP and PI 3-kinase-PKC zeta signalling by releasing of Gbetagamma via dissociation of trimeric G-protein after insulin receptor tyrosine phosphorylation in insulin-sensitive tissues.

Adipocytes↗
PubMed2000

Quantitative analysis of paradoxical inward rib cage movement during sleep in children.

Paradoxical inward rib cage movement in children is quantified by the labored breathing index (LBI) on the respiratory inductive plethysmography. Labored breathing index during rapid eye movement sleep (REMS) in 59 children without obvious sleep disordered breathing (SDB) declined with age, and decreased to the mature low level at 35 months of age. The LBI was also found to reflect well the severity of SDB. Paradoxical inward rib cage movement, which was quantified by LBI, is concluded to be an important finding in diagnosing SDB in child patients.

Adolescent↗
PubMed2000

Assessment of coronary flow reserve using fast velocity-encoded cine MR imaging: validation study using positron emission tomography.

OBJECTIVE: Previous studies using intravascular Doppler sonography and positron emission tomography (PET) have shown that the hemodynamic significance of coronary artery stenosis can be evaluated by measuring coronary flow reserve. The purpose of this study was to assess whether MR imaging measurements of coronary flow reserve in the left anterior descending artery are comparable with those obtained with PET in the corresponding territory. SUBJECTS AND METHODS: MR imaging and PET flow measurements were obtained in 10 healthy volunteers. Blood flow velocity in the left anterior descending artery was measured with breath-hold velocity-encoded cine MR imaging before and after IV administration of dipyridamole. The coronary flow velocity reserve measured by MR imaging was compared with the myocardial perfusion reserve in the anterior myocardium quantified on using PET and (15)O-labeled water. RESULTS: The average flow velocity reserve in the left anterior descending artery measured on MR imaging was 2.44+/-1.14 in healthy volunteers, which was comparable with the myocardial perfusion reserve measured by PET (2.52+/-0.84). MR imaging and PET measurements of the coronary flow reserve showed a significant correlation (r = 0.79, p<0.01). CONCLUSION: MR imaging measurement of the flow velocity reserve in the proximal left anterior descending artery correlates well with the myocardial perfusion reserve obtained with PET and (15)O-labeled water.

Adult↗
PubMed2000

Temporal bone pathology in Wegener's granulomatosis.

This study aimed to demonstrate the temporal bone histopathology of two cases of Wegener's granulomatosis in which the initial symptoms were profound hearing loss and facial nerve palsy respectively. The first case, a woman of 44, suffered profound hearing loss which was remarkably improved by steroid and cyclophosphamide treatment for a time, and which seemed to be caused by invasion from granulation tissue filled in the tympanic cavity. The second case was a 61-year-old woman presenting with the facial nerve palsy. The bony canal of the horizontal portion of the facial nerve was destroyed due to granulation tissue which filled in the tympanic cavity, and granulomatous involvement was observed in the facial nerve. Wegener's granulomatosis can involve the middle ear and/or inner ear, causing hearing loss of conductive, mixed or sensorineural type. Pathogenesis of facial nerve palsy seems to be related to Wegener's granulomatous involvement of facial nerve, because the facial nerve palsy also resolved by using steroid and cyclophosphamide.

Adult↗
PubMed2000

Probable involvement of the 5-hydroxytryptamine(4) receptor in methotrexate-induced delayed emesis in dogs.

Delayed emesis in cancer patients undergoing chemotherapy remains a significant problem. The pathogenesis of delayed emesis is still obscure. It was recently demonstrated that methotrexate (MTX), an anticancer drug, evoked delayed emesis in dogs in a manner similar to its actions in humans. We evaluated the antiemetic activity of FK1052, a potent antagonist for both the 5-hydroxytryptamine (HT)(3) and 5-HT(4) receptors, on delayed emesis induced by MTX in beagle dogs. Animal behavior was recorded for 3 days using a video camera. Delayed emesis lasting up to 72 h was observed in dogs treated with MTX (2.5 mg/kg i.v.), but acute emesis did not occur. The following antiemetics, at the dose that prevents cisplatin-induced acute emesis in dogs, were administered i.v. as multiple injections every 12 h during days 2 to 3. FK1052 (1 and 3.2 mg/kg) significantly reduced the emetic episodes caused by MTX, whereas ondansetron (1 mg/kg), a selective 5-HT(3) receptor antagonist, was not effective. The emetic episodes induced by MTX were also inhibited by another 5-HT(3/4) receptor antagonist, tropisetron (1 mg/kg). CP-122,721 (0. 1 mg/kg), a potent selective tachykinin NK(1) receptor antagonist, significantly reduced the emetic responses to MTX. Copper sulfate-induced emesis in dogs was also prevented by FK1052, tropisetron, and CP-122,721 but not by ondansetron. FK1052, tropisetron, and ondansetron had negligible affinity for the NK(1) receptor at 1 microM. These results suggest that the 5-HT(4) receptor may be in part involved in the production of delayed emesis induced by MTX in dogs and that FK1052 may be a useful drug against both acute and delayed emesis induced by cancer chemotherapy.

Animals↗
PubMed2000

HRG4 (UNC119) mutation found in cone-rod dystrophy causes retinal degeneration in a transgenic model.

PURPOSE: To investigate the function and pathogenicity of HRG4, a photoreceptor synaptic protein homologous to the Caenorhabditis elegans neuroprotein UNC119. METHODS: HRG4 was screened for mutations in patients with various retinopathies, and a transgenic mouse model was constructed and analyzed based on a mutation found. RESULTS: A heterozygous premature termination codon mutation was found in a 57-year-old woman with late-onset cone-rod dystrophy. In some transgenic mice carrying the identical mutation, age-dependent fundus lesions developed accompanied by electroretinographic changes consistent with defects in photoreceptor synaptic transmission (depressed b-wave, normal c-wave), and retinal degeneration occurred with marked synaptic and possible transsynaptic degeneration. CONCLUSIONS: HRG4, the only synaptic protein known to be highly enriched in photoreceptor ribbon synapses, is now shown to be pathogenic when mutated.

Adaptor Proteins, Signal Transducing↗
PubMed2000

[A patient of infantile polymyositis triggered by respiratory syncytium virus infection].

An 11-month-old boy developed acute polymyositis about 1 week after respiratory syncytium virus (RSV) pneumonia. He was admitted to our hospital because of interstitial pneumonia. RSV infection was confirmed by the presence of its antigen in his nasal discharge. Two weeks later, his chest X-ray findings improved and RSV antigen became negative, but severe generalized muscle weakness developed, causing respiratory failure. Muscle biopsy demonstrated inflammatory cellular infiltration with occasional fiber necrosis. Intravenous steroid pulse therapy was remarkably effective resulting in complete recovery of his muscle power. In this patient polymyositis was preceded with RSV infection, suggesting a close relationship between polymyositis and RSV infection. Although many patients of viral myositis have been reported to be associated with coxsackie B, HCV and HTLV-1 viruses, our patient is the first infantile polymyositis secondary to RSV infection.

Acute Disease↗
PubMed1999

Assessment of myocardial function and perfusion in a canine model of non-occlusive coronary artery stenosis using fast magnetic resonance imaging.

Magnetic resonance (MR) functional and perfusion imaging were employed in a canine model of coronary artery stenosis (n = 6) for the quantification of functional and perfusion deficits before and after dipyridamole administration. Left anterior descending and circumflex (LCX) coronary blood flow were measured continuously after placing Doppler flowmeters. Inversion recovery gradient echo images during the transit of MR contrast medium gadolinium-benzyloxypropionictetraacetate dimeglumine (Gd-BOPTA/Dimeg) and fast breath-hold cine MR images were acquired at baseline, during LCX stenosis in basal state, and during LCX stenosis with vasodilation (dipyridamole 0.5 mg/kg). The extent of the functional defect and perfusion defect was expressed as percent of left ventricle (LV) circumference. During stenosis (LCX flow: 62.6 +/- 5.6% of baseline) the extent of the functional defect was slightly larger than the perfusion defect (11.0 +/- 1.8% versus 6.3 +/- 1.70% of LV circumference, respectively; P < 0.01). During vasodilation the extent of the functional defect was considerably smaller than the perfusion defect (25.3 +/- 2.5% versus 35.3 +/- 3.5%; P < 0.01). Thus, the sizes of ischemic regions displayed by MR perfusion defect and functional defect differ from each other.

Animals↗
PubMed1999

Assessment of coronary flow reserve with fast cine phase contrast magnetic resonance imaging: comparison with measurement by Doppler guide wire.

Fast cine phase contrast magnetic resonance imaging (fast cine phase contrast MRI) can measure phasic coronary flow velocity in humans. The purpose of this study was to compare the coronary flow velocity reserves measured by MR IMAGING with those obtained by Doppler guide wire. Nineteen patients with ischemic or valvular heart disease were studied. Fast cine phase contrast MR images of the left anterior descending (LAD) artery were acquired during breath-hold time in the basal state and after administration of dipyridamole. Flow velocity in the LAD artery was also measured with Doppler guide wire before and after venous injection of dipyridamole in all subjects. Flow velocity in the coronary artery measured with MR IMAGING in the basal state (12.5 +/- 4.9 cm/sec) was significantly lower than that obtained with Doppler guide wire (32.4 +/- 12.1 cm/sec, P < 0.01). However, MR assessments of coronary flow velocity reserve showed a good linear correlation with those measured by Doppler guide wire (r = 0.91). In conclusion, fast cine phase contrast MR imaging is a useful technique, which can provide a noninvasive assessment of flow reserve ratios in patients with coronary artery disease. J. Magn. Reson. Imaging 1999;10:563-568.

Blood Flow Velocity↗
PubMed1999

MR measurement of coronary blood flow.

The functional significance of coronary arterial stenosis can be evaluated by measuring the pharmacological flow reserve. Magnetic resonance (MR) imaging has a unique potential for noninvasive measurement of coronary blood flow and flow reserve in the native coronary artery and bypass graft. Restenosis after coronary balloon angioplasty and stenting in the left anterior descending artery can be detected noninvasively with serial MR measurements of the coronary flow reserve. Further refinement of the MR pulse sequences to improve spatial and temporal resolutions may permit accurate quantification of blood flow volume and flow reserve in all major coronary arterial branches. MR assessments of blood flow volume and flow pattern allow noninvasive detection of significant stenosis in the coronary artery bypass graft as well. By integrating MR blood flow measurement in the coronary sinus and cine MR assessment of left ventricular myocardial mass, altered myocardial micro-circulation in patients with diffuse myocardial diseases, such as hypertrophic cardiomyopathy and cardiac transplant, has been documented. J. Magn. Reson. Imaging 1999;10:728-733.

Animals↗
PubMed1999

Malignant rhabdoid tumor of the colon: report of a case.

A malignant rhabdoid tumor of the colon is very rare and only three cases have been previously described. A 76-year-old man was admitted to the hospital complaining of epigastralgia. An elastic mass was palpable in the right upper abdomen. A barium enema and endoscopic examination showed a giant gyrate tumor arising from the cecum. Abdominal ultrasonography and a computed tomography scan revealed the tumor to be located in the colon associated with multiple liver metastases and gallbladder stones. A right colectomy and cholecystectomy were thus performed. The tumor was histologically composed of sheets of large round and polygonal nuclei with vesicular chromatin, and abundant acidophilic cytoplasm, often containing hyalin-like inclusion. The cytoplasm was positive for vimentin and neuron-specific enolase, and hyaline globules of the rhabdoid tumor cells stained positive for cytokeratin in some cells. Transmission electron microscopy showed characteristic rhabdoid cells with an aggregation of intermediate filaments. A histologic diagnosis of malignant rhabdoid tumor of the colon was made. The tumor demonstrated several unusual findings for malignant rhabdoid tumors including diploidy by a flow cytometric analysis, and positive nuclear immunohistochemical staining for p53 protein and Ki-67 antigen. We report herein the third known case of a pure colonic rhabdoid tumor.

Aged↗
PubMed1999

Fast magnetic resonance imaging of the heart.

Fast MR imaging techniques have multiple applications for evaluation of cardiac disease. Cine MRI and MR tagging have been shown to be highly accurate and reproducible in evaluating regional and global myocardial function. Segmented k-space cine MRI and echo-planar imaging (EPI) can considerably improve time efficiency and thereby the clinical utility of these techniques. Double IR fast spin-echo sequences enable breath-hold acquisition of T2 weighted MRI with good suppression of the blood signal. Myocardial perfusion can be assessed with fast dynamic MRI after administration of contrast media. Multi-shot EPI improves temporal resolution and also provides full coverage of the left ventricle. Substantial progress has been made in respiratory gated 3D coronary artery MR angiography with navigator echoes. The newer approaches for coronary arterial imaging including breath-hold three-dimensional segmented EPI and high resolution spiral MRI may further improve clinical usefulness of coronary MR angiography. Assessment of coronary blood flow and flow reserve with phase contrast MRI has the potential for the non-invasive evaluating of the presence and significance of stenosis in the native coronary artery and bypass grafts. Fast cardiac MRI may emerge as a cost effective modality for comprehensive assessments of both cardiac morphology, function, blood flow and perfusion.

Coronary Circulation↗