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Biomedical subjects

H Miki

Publications and source records attributed to H Miki.

At least 127 records · Page 7Linked to original sources
PubMed1998

Usefulness of heavily T2-weighted magnetic resonance imaging in patients with cerebellopontine angle tumors.

OBJECTIVE: Heavily T2-weighted magnetic resonance imaging (MRI) has been reported to be useful for the diagnosis of lesions of the inner ear or its central connections. We evaluated the usefulness of heavily T2-weighted MRI in 18 patients with cerebellopontine angle tumors. METHODS: The lesions were acoustic neuromas in 14 patients and meningiomas in 4 patients. The findings of heavily T2-weighted MRI were compared with those of three-dimensional T1-weighted gradient field echo MRI. RESULTS: An accurate description of the situation of the tumor in the internal auditory canal (IAC) was possible, because the inner ear was clearly shown on the heavily T2-weighted magnetic resonance images. We could therefore detect the acoustic neuromas located at the fundus of the IAC and the meningiomas growing into the IAC. The residual tumor in the IAC can be shown postoperatively. It was difficult to demonstrate these findings using three-dimensional T1-weighted gradient field echo MRI because of the poor presentation of the petrous bone structures. The lower cranial nerves and the VIIth and VIIIth cranial nerves were more clearly demonstrated by heavily T2-weighted MRI than by three-dimensional T1-weighted gradient field echo MRI. Using heavily T2-weighted MRI, the VIIth and VIIIth cranial nerves of the lesion side were demonstrated in half of the patients with acoustic neuromas smaller than 2.5 cm. CONCLUSION: We conclude that heavily T2-weighted MRI is useful to detect the relationship among the tumor, the IAC, the inner ear, and the surrounding cranial nerves.

Adult↗
PubMed1998

Xanthan lyase of Bacillus sp. strain GL1 liberates pyruvylated mannose from xanthan side chains.

When the bacterium Bacillus sp. strain GL1 was grown in a medium containing xanthan as the carbon source, the viscosity of the medium decreased in association with growth, showing that the bacterium had xanthan-depolymerizing enzymes. One of the xanthan-depolymerizing enzymes (xanthan lyase) was present in the medium and was found to be induced by xanthan. The xanthan lyase purified from the culture fluid was a monomer with a molecular mass of 75 kDa, and was most active at pH 5.5 and 50 degrees C. The enzyme was highly specific for xanthan and produced pyruvylated mannose. The result indicates that the enzyme cleaved the linkage between the terminal pyruvylated mannosyl and glucuronyl residues in the side chain of xanthan.

Bacillus↗
PubMed1998

Failed hip prostheses in hemodialysis patients. Amyloid deposition at the bone-implant interface in 4 cases.

4 hemodialysis patients with failed bipolar hip prostheses underwent 6 revision arthroplasties. Their average age was 55 years, the average duration of hemodialysis was 14 years and the average interval from the primary arthroplasty to revision was 7 years. The interface membranes revealed amyloid deposits in all specimens. There were few polyethylene wear particles, and cement debris or foreign body reactions were rare. It appears that amyloid may cause osteolysis and early prosthetic loosening.

Adult↗
PubMed1998

[Asymptomatic pancreatic islet cell tumor (glucagonoma): case report].

A case of asymptomatic pancreatic islet cell tumor (glucagonoma) is reported. A 36-year-old woman undergoing a ultrasonic scan was found to have two masses in the body and tail of the pancreas measuring 5 cm and 4 cm in diameter, respectively. Investigations of serum peptide hormones revealed an elevated glucagon level of 27,500 pg/ml (normal < 100 pg/ml), suggesting the possibility of an islet cell tumor (glucagonoma). The patient, however, was asymptomatic although high levels of glucagon were present. The patient underwent distal pancreatectomy to remove the lesions in the body and tail of the pancreas. Histological findings revealed islet cell tumors of the pancreas, and immuno histochemical staining of the tumor cells demonstrated a positive reaction for chromogranin and glucagon.

Adult↗
PubMed1997

A novel ligand for an SH3 domain of the adaptor protein Nck bears an SH2 domain and nuclear signaling motifs.

Nck is a small protein composed of Src homology regions (SH) 2 and 3, paralleling the adaptors c-Crk and Grb2/Ash, but its function remains enigmatic. To clarify Nck signaling, a human brain cDNA library was searched for targets of the SH3 moiety of Nck. A novel molecule detected therefrom (referred to as Nck-, Ash- and phospholipase Cgamma-binding protein 4) contained proline-rich sequences and, through the function of one of them, interacted with the middle SH3 domain of Nck. A NAP4 fusion peptide exhibited an affinity for Nck, Ash and phospholipase Cgamma in whole cell lysates. NAP4 also had an SH2 domain, which could bind to activated EGF receptor. These intermolecular interactions imply the intricacy of Nck-mediated signaling around the receptor protein-tyrosine kinases. In addition, NAP4 bore a putative nuclear localization signal and a Q-run/P-run composite, both characteristic of nuclear proteins, and might therefore relate to the presence of Nck in the cellular nucleus.

3T3 Cells↗
PubMed1997

Identification of N-WASP homologs in human and rat brain.

We recently identified Neural Wiskott-Aldrich Syndrome Protein (N-WASP) from bovine brain. An expression analysis using bovine cDNA revealed that N-WASP plays critical roles in the regulation of the cortical actin cytoskeleton. Here, we report the molecular cloning of N-WASP homologs from human and rat brain cDNA libraries. The predicted amino acid sequences of human and rat N-WASP show 96% and 95% identity to bovine N-WASP, respectively, suggesting the functional importance of the molecule. Antibody raised against recombinant rat N-WASP recognizes a 65-kDa protein that exists ubiquitously in whole brain, including cerebrum, cerebellum, interbrain, and medulla oblongata. N-WASP was shown to be concentrated at the nerve terminal region. The gene locus of human N-WASP was also determined at 7q31.3 by fluorescence in-situ hybridization (FISH) analysis.

Amino Acid Sequence↗
PubMed1997

Three-dimensional imaging for presentation of the causative vessels in patients with hemifacial spasm and trigeminal neuralgia.

BACKGROUND: In patients with hemifacial spasm and trigeminal neuralgia, preoperative detection of the relationship between the blood vessels and the cranial nerves involved is essential. METHODS: We studied the causative vessels in 20 patients with hemifacial spasm and six patients with trigeminal neuralgia by means of magnetic resonance (MR) imaging with spoiled gradient recalled acquisition in the steady state (SPGR), MR angiography, and three-dimensional (3-D) imaging reconstructed from the data of SPGR MR imaging by the surface rendering method at a workstation. RESULTS: In all patients, the preoperative SPGR MR images demonstrated that the causative vessels compressed or were in contact with the root exit or root entry zone (REZ) of the facial or trigeminal nerve. These causative vessels were identified by inspection of the MR angiographic and 3-D images. The 3-D images provided clear information as to the anatomic relationship between the causative vessels and the REZ of these nerves. These findings were corroborated by the intraoperative findings. The symptoms were completely relieved after surgery in 18 of the patients with hemifacial spasm and in all six patients with trigeminal neuralgia. In all patients, sufficient decompression was depicted on the postoperative SPGR MR images at the causative vessels and the REZ of the nerve. CONCLUSION: SPGR MR images, MR angiography, and 3-D images are useful for the identification of the causative vessels in patients with hemifacial spasm or trigeminal neuralgia. The 3-D images are particularly useful for the simulation planning of the operative procedure.

Adult↗
PubMed1997

Involvement of prostaglandin E2 in rabbit corneal injury by anterior segment ischaemia.

The involvement of prostaglandins (PGs) in the development of anterior segment ischaemia after occlusion of the bilateral long posterior ciliary arteries was investigated in rabbit eyes. In this experimental ischaemia, the tissue weight and protein content in the peripheral cornea and the protein content in the aqueous humour increased on the first postoperative day. Topically applied cyclooxygenase inhibitor diclofenac (0.1%) reduced corneal inflammation and further suppressed the elevation in the tissue weight and protein content in the peripheral cornea on day 1 after ischaemia, but did not affect the changes in the aqueous humour. Subconjunctivally administered PGE1 and PGE2 induced corneal oedema and increased corneal protein content in diclofenac-treated and ischaemia-induced eyes, but PGD2, PGF2alpha, and the stable PGI2 analogue cicaprost did not evoke any change. In fact, PGE2 content was markedly increased in the aqueous humour on day 1 after ischaemia, and diclofenac suppressed the increase. In addition, CPT-cAMP increased the corneal tissue weight and protein content in organ culture. These observations suggest that PGE2 may play an important role in developing corneal oedema at the initial stage of ischaemic damage, possibly through the cAMP-mediated pathway.

Alprostadil↗
PubMed1997

Relationship between prognostic score and thyrotropin receptor (TSH-R) in papillary thyroid carcinoma: immunohistochemical detection of TSH-R.

We have demonstrated the expression of thyrotropin receptor (TSH-R) in thyroid neoplasms (13 adenomas, 21 papillary carcinomas, two follicular carcinomas) and adjacent normal thyroid using the monoclonal antibody against human TSH-R and have also demonstrated a relationship between prognostic scores and the expression of TSH-R. Among the adenomas, eight showed an intensity similar to that of normal thyroid and five showed a higher intensity than normal. Two tumours exhibited heterogeneous distribution of TSH-R. Among the papillary carcinomas, seven showed similar intensity to normal tissue and four showed higher intensity and ten showed weaker intensity. Eight tumours showed heterogeneous distribution of the stain. Among the follicular carcinomas, one showed similar intensity to normal tissue and the other exhibited weaker intensity. Both cases showed homogeneous distribution of TSH-R. The adenomas never showed a weaker intensity than normal thyroid, but various intensities of TSH-R occurred in differentiated carcinomas. There was no significant relationship between the clinical data and the signal intensity in the adenomas. Among the papillary carcinomas, however, the group with weaker intensity had significantly poorer prognostic scores than the other two groups. Thus, we assume that low TSH-R may be expressed by the clinically high-risk group of patients with papillary thyroid carcinoma.

Adenocarcinoma, Follicular↗
PubMed1997

Does recurrent acute pancreatitis lead to chronic pancreatitis? Sequential morphological and biochemical studies.

The pathogenesis of chronic pancreatitis (CP) has been debated as to whether it is a de novo process or the consequence of acute pancreatitis (AP). We investigated whether recurrent AP in rats leads to CP, by sequential morphological and biochemical studies. Thirty male Wistar rats were fed a choline-deficient diet with intraperitoneal ethionine injections twice daily at a dose of 60 mg/100 g body weight twice weekly, and six rats were killed at 4, 6, and 8 weeks; the remaining 12 rats, followed without further treatment, were killed at 12 and 16 weeks. The pancreata from study and control groups were examined by histology, immunohistochemistry, and bio- and immunoassays. Histologically, moderate to severe intra- and perilobular fibrosis and other CP-like lesions appeared maximally at 8 weeks. Immunohistochemically, the earliest extracellular matrix change was strong fibronectin staining at 4 weeks, with a progressive increase to 8 weeks. Collagens I and III came to show strong, and collagen IV moderate, interstitial staining at 6-8 weeks. These morphological changes, however, returned to nearly normal at 16 weeks. Prolyl hydroxylase was significantly elevated at 4 and 6 weeks and normalized after 8 weeks, with no significant change in collagenase. In conclusion, our results suggest that even severe CP-like lesions induced by recurrent AP are reversible in the absence of persistently elevated prolyl hydroxylase and/or suppressed collagenase. The mechanism regulating these changes remains to be studied further.

Acute Disease↗
PubMed1997

Morphologic characteristics of N-methyl-N-nitrosourea-induced retinal degeneration in C57BL mice.

Morphologic characteristics of retinal degeneration induced by a single systemic administration of N-methyl-N-nitrosourea (MNU) in mice was investigated. The aim was to characterize the MNU-induced retinal lesions in mice and compare them with human retinitis pigmentosa. A dose of 60 mg/kg body weight MNU, injected intraperitoneally into male and female C57BL mice, evoked progressive retinal degeneration in all treated mice, while control mice remained normal. An early change was photoreceptor apoptosis followed by infiltration of macrophages and swelling of the pigment epithelial cells with phagosomal inclusions for apoptotic photoreceptor cell removal. Loss of the majority of photoreceptor cells occurred within a week. Then, Feulgen-positive corpuscles, indicative of an aggregation of degenerative photoreceptor elements, vitread the outer limiting membrane were surrounded by Müller cell processes, and the duplication of the pigment epithelial cells sclerad the outer limiting membrane were seen 2 and 3 weeks after the treatment. Finally, the Feulgen-positive corpuscles disappeared and Müller cell processes were in direct contact with the continuous lining of the single layer of pigment epithelial cells. As in retinitis pigmentosa in humans, the primary event was loss of photoreceptor cells by apoptosis, but the migration of the pigment epithelial cells within the retina was not seen in the present model.

Animals↗
PubMed1997

Effect of magnesium on parathyroid cells: evidence for two sensing receptors or two intracellular pathways?

It currently remains controversial as to the intracellular mechanisms coupled to the inhibition of parathyroid hormone (PTH) secretion that are modulated by extracellular divalent cations. To study mechanisms responsible for regulation of PTH release by cations, we investigated the effect of Mg2+ on cytosolic Ca2+ levels ([Ca2+]i) and PTH secretion in single isolated bovine parathyroid cells. Addition of 9.0 mM Mg2+ evoked a spike of [Ca2+]i in approximately 80% of cells in the presence of extracellular Ca2+. Mg2+ decreased steady-state [Ca2+]i, which represented inhibition of influx of extracellular Ca2+ in 13-78% of cells. The percentage of cells that had a decline in steady-state [Ca2+]i after exposure to Mg2+ was dependent on the extracellular Ca2+ concentration. The effect of Mg2+ on intracellular Ca2+ response was dose dependent. Extracellular Mg2+ inhibited PTH secretion in cells that showed decline in steady-state [Ca2+]i, although cells that showed a spike after addition of Mg2+ secreted more PTH than cells that did not show a spike. The spike of [Ca2+]i and decline in steady-state [Ca2+]i that occur in response to extracellular Mg2+ may be caused independently by two distinct mechanisms that differentially regulate secretion of PTH.

Animals↗
PubMed1997

Intracranial vascular stenosis and occlusion: MR angiographic findings.

PURPOSE: To investigate whether obtaining axial source images from three-dimensional Fourier transform (3DFT) time-of-flight MR angiography improves the detection of intracranial vascular stenosis and occlusion if added to maximum-intensity projection (MIP) images. METHODS: The angiograms of 103 patients who had MR angiography for evaluation of possible intracranial vascular disease were reviewed retrospectively in a quantitative and nonquantitative fashion. Diameters of vessels on MR angiograms were measured quantitatively by two reviewers using a magnifying loupe and compared with the results from conventional angiograms. Degrees of stenoocclusive disease were categorized into five classes; an artery with stenosis of 50% or greater was considered to be diseased. Another five observers also reviewed the MIP images with and without source images in a blinded fashion by means of nonquantitative visual inspection. RESULTS: In all, 23 stenoocclusive lesions of 50% or greater were available for review. In the quantitative analysis, with MIP images alone, 14 (78%) of 18 moderate and severe stenoses and four (80%) of five occlusions were identified correctly. The addition of the source images increased the sensitivity to 100% for moderate and severe stenoses and to 100% for occluded vessels. In the visual inspection study, however, no statistically significant differences were found between interpretations of MIP images alone and those of MIP images in combination with source images. CONCLUSION: In the quantitative study, interpretation of source images rather than MIP images reduced the tendency to overestimate stenosis seen with MR angiography and improved the sensitivity for detecting stenosis of 50% or greater. There was a discrepancy between the quantitative study and visual inspection. Experienced observers had a tendency to underestimate the degree of stenosis.

Adult↗
PubMed1997

['Ischemic tolerance' in ischemia-reperfusion injury in the optic nerve in rats].

Brief ischemia caused by high intraocular pressure induced tolerance to subsequent ischemia-reperfusion injury in rats. Male Wistar rats were subjected to 15 minutes of ischemia. This ischemic injury did not show distinct axonal damage in the optic nerve in electron microscopy. 1, 2, 4, 7, and 14 days after the first 15 min ischemia, the rats were subjected to a second ischemia for 45 minutes (ischemic tolerance). After 1 week, the rats were perfusion fixed and the optic nerves were processed for light and electron microscopy. Samples of the axonal density in the central optic nerve 2 mm behind the lamina cribrosa were observed and counted an electron micrographs. In axonal morpometric findings, 2 days and more after brief ischemia, the damage was lessened more than after 45 minutes ischemia (control) and the difference was significant. This 'ischemic tolerance' induced by brief ischemia might be considered the same stress as brain ischemia-reperfusion injury.

Animals↗
PubMed1997

Tyrosine kinase signaling regulates Wiskott-Aldrich syndrome protein function, which is essential for megakaryocyte differentiation.

Platelets are produced from megakaryocytes differentiated from megakaryoblasts, but the differentiation mechanism still remains unknown. Here, we demonstrate that a tyrosine kinase signaling regulates Wiskott-Aldrich syndrome protein (WASP), which is essential for megakaryocyte differentiation. MEG-01 megakaryoblastic cells differentiate into large multinucleated megakaryocyte-like cells characterized by microvesicle formation with a protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol 13-acetate. With parallel to the differentiation, WASP begins to accumulate at microvesicles with actin filaments and associates with tyrosine-phosphorylated Shc, the phosphorylation of which is induced. Moreover, a tyrosine kinase inhibitor, herbimycin A, blocked not only phosphorylation of Shc but also microvesicle formation without affecting cell enlargement and multinucleation, whereas a PKC inhibitor, H-7, completely inhibited all these processes. Because WASP also binds to Ash/Grb2 SH3 domains and the association of Ash/Grb2 and Shc is induced by 12-O-tetradecanoylphorbol 13-acetate treatment, a signaling pathway, PKC-tyrosine kinase-Shc-Ash/Grb2-WASP, is suggested for regulating megakaryocyte differentiation. In addition, WASP antisense oligonucleotide treatment abolishes both microvesicle formation and gathering of actin filaments. These data clearly show that WASP controls the assembly of actin filaments required for microvesicle formation downstream of PKC-tyrosine kinase.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1997

Chronic exertional compartment syndrome in lower legs: localization and follow-up with thallium-201 SPECT imaging.

UNLABELLED: The purpose of this study was to ascertain whether 201Tl SPECT imaging of the leg is useful in precise localization of the ischemic compartment involved in chronic exertional compartment syndrome (CECS). METHODS: Imaging and quantitative analyses of postexercise 201Tl SPECT leg examinations were retrospectively performed in nine patients with clinically diagnosed CECS and eight control subjects. Imaging and quantitative criteria for the ischemic compartment were decreased 201Tl perfusion less than the lower limits of normal, which were defined as 2 s.d. below the mean percentage uptake of the control subjects. The SPECT imaging results were compared with those of quantitative analysis, postoperative SPECT images and clinical diagnoses. RESULTS: Postexercise normal legs had nonuniform 201Tl distribution in both legs and in the four compartments. Lower limits of normal mean percentage 201Tl uptake were about 60% for the anterior compartment and about 50% for the other three compartments. Redistribution was observed in 67% of normal compartments in the control subjects. The SPECT images demonstrated 16 ischemic compartments in eight of the nine patients. The SPECT results were consistent with those of quantitative analysis. There were discrepancies between the clinical and SPECT diagnoses in six legs (33% of the 18 legs) of five patients. Postoperative SPECT demonstrated 201Tl perfusion was improved in all involved compartments for that fasciotomy was performed. CONCLUSION: Thallium-201 SPECT imaging of the legs can easily provide precise localization of the ischemic compartment, which is demonstrated as decreased 201Tl distribution on the stress image. This technique is promising for the screening and follow-up of CECS.

Adult↗
PubMed1997

[Functional MRI of higher brain function with gradient echo on clinical MR unit].

MR imaging of brain function has been successfully performed at 1.5 T clinical MR unit. In the early studies, functional MRI were performed with simple stimulation such as visual and motor. Recently, many investigators have attempted to demonstrate the specific brain localization of higher brain functions such as memory, imagination, language and so on. In this study, we attempted the functional MRI for motor and word imagination with gradient echo sequences on clinical MR unit. In our experiences, motor cortex was activated on motor imagination task and Broca area was activated on word imagination task, respectively. We demonstrated the higher brain functions were able to be demonstrated on clinical MR unit with gradient echo sequences.

Frontal Lobe↗