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Biomedical subjects

T Miyazaki

Publications and source records attributed to T Miyazaki.

At least 361 records · Page 20Linked to original sources
PubMed1995

Activation of Stat5 by interleukin 2 requires a carboxyl-terminal region of the interleukin 2 receptor beta chain but is not essential for the proliferative signal transmission.

The high-affinity interleukin 2 (IL-2) receptor (IL-2R) consists of three subunits: the IL-2R alpha, IL-2R beta c, and IL-2R gamma c chains. Two members of the Janus kinase family, Jak1 and Jak3, are associated with IL-2R beta c and IL-2R gamma c, respectively, and they are activated upon IL-2 stimulation. The cytokine-mediated Jak kinase activation usually results in the activation of a family of latent transcription factors termed Stat (signal transducer and activator of transcription) proteins. Recently, the IL-2-induced Stat protein was purified from human lymphocytes and found to be the homologue of sheep Stat5/mammary gland factor. We demonstrate that the human Stat5 is activated by IL-2 and that Jak3 is required for the efficient activation. The cytoplasmic region of the IL-2R beta c chain required for activation of Stat5 is mapped within the carboxyl-terminal 147 amino acids. On the other hand, this region is not essential for IL-2-induced cell proliferation.

3T3 Cells↗
PubMed1995

Three distinct IL-2 signaling pathways mediated by bcl-2, c-myc, and lck cooperate in hematopoietic cell proliferation.

Two interleukin-2 receptor-dependent signaling pathways have thus far been identified: the c-fos/c-jun induction pathway mediated by src family protein-tyrosine kinases and the c-myc induction pathway. Here, we provide evidence for the existence of a third, rapamycin-sensitive pathway, which results in the induction of another proto-oncogene, bcl-2. In the hematopoietic cell line BAF-B03, the expression of any two of lckF505 (an active form of p56lck), Bcl-2, or c-Myc is sufficient to promote transit of the cell cycle, regardless of the activation state of the third pathway. We also provide evidence that epidermal growth factor receptor signaling may act through the same pathway that involves p56lck. These studies demonstrate a novel approach to dissecting signaling pathways regulating cellular proliferation.

Animals↗
PubMed1995

Epidural pressure measurements. Relationship between epidural pressure and posture in patients with lumbar spinal stenosis.

STUDY DESIGN: The relationship between epidural pressure and lumbar posture was assessed in patients with lumbar spinal stenosis. OBJECTIVES: This study was performed to assess the relationship between epidural pressure and lumbar posture in patients with lumbar spinal stenosis. METHODS: The study was performed on 10 patients who had cauda equina symptoms at the L4-L5 level. The catheter transducer was inserted into the epidural space through L5-S1 interlaminar space and placed at the L4-L5 disc level. This transducer was connected with an amplifier and a recorder. Epidural pressure was continuously measured in various postures. RESULTS: Local epidural pressure at the stenotic level was low in lying and sitting postures, and high in standing postures. Pressure was increased with extension, but decreased with flexion. The highest pressure was 116.7 +/- 38.4 mm Hg in standing with extension. CONCLUSION: Epidural pressure was significantly related to posture. These pressure changes correlated with the development of cauda equina symptoms. The increase of epidural pressure by posture may induce compression of the cauda equina. These pressure changes may explain the postural dependency in eliciting symptoms.

Aged↗
PubMed1995

CNS myelinogenesis in vitro: time course and pattern of rat oligodendrocyte development.

Oligodendrocyte precursor cells that develop into myelin-forming cells of the central nervous system (CNS) were cultured from newborn rat brain to study how they proliferate and differentiate in normal conditioning medium, and their cell development was characterized by scanning electron microscopy (SEM) observation and immunocytochemical studies. We have identified A2B5-negative pre-O2A progenitor cells (so-called "type-1" oligodendrocytes) in the secondary cultures on the astrocyte feeder layer. These cells are very small (diameter: 3.5 microns), round, and glossy, and develop into the process-bearing O2A progenitor cells (called "type-2" oligodendrocytes), which also express myelin basic protein (MBP) both in the cell body and in their cell processes. Finally, they develop into mature oligodendrocytes (called "type-3" oligodendrocytes). After MBP expression is elicited in these cells and MBP accumulates in the cell process in the area in contact with the axon, these cells are capable of forming the myelin sheath. Therefore, we examined the mechanism of myelin-sheath formation of "type-3" oligodendrocytes using video time-lapse movies, and demonstrated that these cells initially sent out processes to search for axons several times before the onset of myelination. Then thick filopodia extended towards the axon, and at the same time, the axonal part of neuron moved forward. Finally the ruffling lamellipodial parts wrapped up the axon similarly to a transverse wave with the secured thick filopodial process on the axon acting as scaffolding. These results suggest that our experimental systems are useful in studying normal oligodendrocyte development and their cellular biochemistry, as well as investigating the mechanism of myelin formation by oligodendrocytes.

Animals↗
PubMed1995

Glycine induces two distinct membrane currents in neonatal rat sympathetic preganglionic neurones in vitro.

1. The effects of glycine (Gly) on neonatal (12- to 16-day-old) rat sympathetic preganglionic neurones (SPNs) in transverse (500 microns) thoracolumbar spinal cord slices were studied by whole-cell patch-clamp techniques. 2. Gly elicited three types of membrane currents when applied to SPNs by pressure ejection (100 mM; 20-180 ms pulse duration): (1) an outward current (20/94 cells); (2) an inward current (30/94); and (3) a biphasic response (44/94) consisting of an outward followed by an inward current. 3. The Gly-induced outward current (IGly,(out)) had a mean reversal potential of -67 mV, was reversed in a low (5.7 mM) chloride Krebs solution, and was reversibly eliminated by strychnine (0.1-1 microM). 4. The Gly-induced inward current (IGly,(in)) had a mean reversal potential of -41 mV, was reduced in a Na(+)-free and increased in a high (15 mM) K+ solution; strychnine at the high concentration of 1 microM reduced the response by an average of 53%. 5. The electrophysiological and pharmacological characteristics of the biphasic response suggest that it was a combined response of outward and inward currents. 6. The results show that Gly elicits two distinct membrane currents, a Cl(-)-dependent outward current and a cationic inward current, which are mediated by strychnine-sensitive and strychnine-resistant Gly receptors. Functionally, activation of both types of Gly receptors reduces neuronal excitability and attenuates synaptic transmission.

Adrenergic Fibers↗
PubMed1995

Serum pyridinolines as specific markers of bone resorption in hemodialyzed patients.

Serum levels of hydroxylysyl pyridinoline and lysyl pyridinoline were quantified in uremic patients undergoing maintenance hemodialysis and in healthy subjects. Pre-hemodialysis serum levels of hydroxylysyl pyridinoline and lysyl pyridinoline in the hemodialyzed patients were significantly higher than those in healthy subjects. Serum levels of hydroxylysyl pyridinoline and lysyl pyridinoline decreased significantly after hemodialysis with reduction rates of about 40%. Pre-hemodialysis serum levels of hydroxylysyl pyridinoline and lysyl pyridinoline correlated significantly with intact parathyroid hormone, osteocalcin and bone-specific alkaline phosphatase. Lysyl pyridinoline showed better correlations with these parameters than hydroxylysyl pyridinoline. Parathyroidectomy markedly decreased serum levels of hydroxylysyl pyridinoline and lysyl pyridinoline. These results indicate that serum pyridinolines, especially lysyl pyridinoline, may be used as specific biochemical markers of bone resorption in hemodialyzed patients.

Acid Phosphatase↗
PubMed1995

C-type natriuretic peptide inhibits intimal thickening after vascular injury.

Recently we have found that C-type natriuretic peptide (CNP) inhibits proliferation of cultured rat vascular smooth muscle cells through an elevation of cGMP. We have now tested whether administration of CNP inhibits the development of intimal lesions induced by air-drying injury in rat common carotid arteries in vivo. CNP treatment (1 microgram/kg per min, iv infusion) for either 14 or 5 days resulted in 70% or 60% reduction, respectively, of intimal cross-section area 14 days after injury as compared with control rats. We also found that CNP potently stimulated cGMP production in injured carotid arteries with intimal thickening, but not in intact ones. These results indicate that GC-B, CNP specific receptor/guanylyl cyclase, is expressed at the sites of vascular injury, and that CNP might be efficacious in the prevention of restenosis caused by intimal thickening following coronary angioplasty.

Animals↗
PubMed1995

Detection of (1-3)-beta-D-glucan in a rat model of aspergillosis.

The G test containing factor G, fractioned from the Limulus lysate, was used to detect (1-3)-beta-D-glucan in a rat model of aspergillosis. Aspergillus fumigatus strain MF-13, 1 x 10(4) conidia, were inoculated transtracheally into rats treated with cortisone acetate (100 mg/kg) and fed a low-protein (8%) diet. Increased serum (1-3)-beta-D-glucan was found on the sixth day after inoculation in concentrations of 370 +/- 178 pg/ml (mean +/- SD) in untreated controls, and 154 +/- 43 pg/ml in rats treated with 0.5 mg/kg of amphotericin B. On day 11 (1-3)-beta-D-glucan concentrations were 2,590 +/- 2,940 pg/ml and 448 +/- 442 pg/ml, respectively. The elevation in levels of (1-3)-beta-D-glucan increased in correlation with the elevation of galactomannan antigen titers; (1-3)-beta-D-glucan is thus measurable during experimental aspergillosis in rats.

Amphotericin B↗
PubMed1995

(1-->3)-beta-D-glucan in culture fluid of fungi activates factor G, a limulus coagulation factor.

Two well-known polysaccharides, (1-->3)-beta-D-glucan and mannan, are major structural components of the fungus cell wall. The G test is a direct method to measure (1-->3)-beta-D-glucan using a (1-->3)-beta-D-glucan-sensitive component, factor G, fractionated from the limulus lysate. The concentration of (1-->3)-beta-D-glucan in culture supernatants of Candida albicans increased to 1,390.0 pg/ml at 24 hours. The concentration of mannan also increased parallel with fungal growth. However, after digestion of supernatants with endo-(1-->3)-beta-D-glucanase, the reactivity to factor G disappeared, although titers of antimannan monoclonal antibody-based latex agglutination were unchanged. Our study demonstrated that cell suspensions of both C. albicans and Cryptoccocus neoformans activated the limulus factor G, and that not only the conidia form but also the filamentous form of Aspergillus fumigatus reacted with factor G. Various Candida spp. (C. paraspilosis, C. glabrata, C. tropicalis, C. krusei), Saccharomyces cerevisiae, Rhodotorula rubra, Trichosporon beigelii, and A. fumigatus released soluble (1-->3)-beta-D-glucan into their culture supernatants, but C. neoformans and Cunninghamella bertholletiae showed only a small reaction to the G test during their culture. Our results indicate that the G test is a good method for serodiagnosis of deep mycosis and also as a screening tool for contamination of medical devices, drugs, and experimental materials with (1 --> 3)-beta-D-glucan.

Agglutination↗
PubMed1995

Binding properties of fibrinogen receptor GPIIb-IIIa purified from human erythroleukemia cells.

Large amounts (2.3 mg) of an inactive form of the glycoprotein GPIIb-IIIa were obtained in highly purified form from 7-liter cultures of human erythroleukemia (HEL) cells. The purified GPIIb-IIIa was converted to an activated form after its immobilization to 96-well plastic plates. The binding of fibrinogen to the activated GPIIb-IIIa was investigated using 24 kinds of RGD peptides and showed that the IC50 values of these peptides correlated with those obtained with activated platelets. These findings indicated that the binding properties of the activated GPIIb-IIIa from HEL cells are quite similar to those of the platelets.

Amino Acid Sequence↗
PubMed1995

Cadherin-11 expressed in association with mesenchymal morphogenesis in the head, somite, and limb bud of early mouse embryos.

Cadherin-11 (cad-11) is a novel member of the cadherin family of cell adhesion molecules, having recently been identified by means of the polymerase chain reaction. To study the function and expression of this molecule, we cloned mouse, cad-11 cDNA. Transfection of L cells with cDNA led them to acquire a typical cadherin-dependent cell-cell adhesiveness, and the L cells expressing cad-11 did not coaggregate with L cells expressing E-, P-, N-, or R-cadherin when they were mixed, indicating that this novel cadherin has a homophilic binding specificity, as found for other cadherins. To determine the developmental expression pattern of this molecule, we performed in situ hybridization analysis on early mouse embryos. Cad-11 first appeared in mesodermal layers only in the head and tail regions at the mid-to-late primitive streak stages. In the head, this appearance was followed by strong expression in mesenchymal tissues including branchial arches. In the trunk, the paraxial mesoderm initially did not express cad-11. However, as the somites formed, they expressed cad-11, and this expression was strictly correlated with their initial condensation and segregation from the presomitic mesoderm. The cad-11 expression in the somites was eventually restricted to sclerotome cells. As the limb buds developed, cad-11 appeared in the distal portion of the limb mesenchyme, and, at later stages, its expression was most evident at the peripheral mesenchyme. Cad-11 was thus expressed by restricted populations of mesenchymal cells in early embryos, although it was also expressed in parts of the neural tube, such as the optic vesicle and dorsal midline, and in part of the otic vesicle. As a step to investigate the role of cad-11 in mesenchymal cell adhesion, we dissociated the limb bud mesenchyme into single cells, pelleted them, and cultured them as aggregates. In these cultures, cad-11-positive cells clearly sorted out of the negative cell population, suggesting that cad-11 might be involved in selective association of mesenchymal cells. For comparison, we studied the expression of N-cadherin and found that the expressions of these two cadherins were differential, and complementary in some tissues. These results suggest that cad-11 is involved in specific associations of subsets of mesenchymal cells and also of some neural cells during early embryogenesis.

Amino Acid Sequence↗
PubMed1995

Chronic cholecystitis following hemobilia due to traumatic intrahepatic injury.

We report a patient who presented with colicky abdominal pain, hematemesis, and melena following a blunt abdominal injury sustained in an automobile accident. Serologic tests suggested liver dysfunction and computed tomography (CT) revealed dilatation of the intrahepatic bile duct. Duodenoscopy demonstrated hemobilia originating from the duodenal papilla of Vater. Angiography revealed a pseudoaneurysm of the hepatic artery and angiographic embolization sucessfully stopped the hemorrhaging. However, even following the angiographic embolization, the patient remained symptomatic and repeat CT demonstrated thickening of the gallbladder wall and a lesion resembling a blood clot. We strongly suspected cholecystitis and performed a laparoscopic cholecystectomy. Grossly, the resected specimen revealed wall thickening with a congested mucosa and three blood clots; histologically, these changes were consistent with a diagnosis of chronic cholecystitis. The clinical message of this paper is that patients should be observed for this usual complication of hemobilia after liver injury.

Adolescent↗
PubMed1995

Schmorl's nodes and low-back pain. Analysis of magnetic resonance imaging findings in symptomatic and asymptomatic individuals.

Magnetic resonance imaging (MRI) findings in cases with symptomatic and asymptomatic Schmorl's nodes have been analysed. In all symptomatic cases, the vertebral body marrow surrounding the Schmorl's node was seen as low signal intensity on T1-weighted images and as high signal intensity on T2-weighted images. It was confirmed by histological examination that the MRI findings indicated the presence of inflammation and oedema in the vertebral bone marrow. These MRI findings were not seen in asymptomatic individuals. Inflammatory changes in the vertebral body marrow induced by intraosseous fracture and biological reactions to intraspongious disc materials might cause pain. We postulate that after fracture healing and subsidence of inflammation, the Schmorl's nodes become asymptomatic, in analogy with old vertebral compression fractures. MRI is not only useful in detecting the recently developed Schmorl's nodes but also in differentiating between symptomatic and asymptomatic Schmorl's nodes.

Adolescent↗