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Biomedical subjects

N Ueno

Publications and source records attributed to N Ueno.

At least 127 records · Page 7Linked to original sources
PubMed1997

Interaction between soluble type I receptor for bone morphogenetic protein and bone morphogenetic protein-4.

Bone morphogenetic proteins (BMPs) are multifunctional proteins that comprise the largest subfamily of the transforming growth factor-beta. These proteins bind to types I and II serine/threonine kinase receptors. Ligand-induced heteromeric dimerization of these receptors is the key event in initiation of biological responses. We report here large-scale expression and purification of extracellular domain of the type I receptor for BMP-2/4, using a silkworm expression system. This soluble form of BMP receptor (sBMPR) was in monomer form in solution and bound to BMP-4 but not to activin or transforming growth factor-beta1. Surface plasmon resonance studies showed that kinetic parameters of sBMPR for BMP-4 consisted of a relatively rapid association rate constant (ka = 3.81 +/- 0.19 x 10(4) s-1 M-1) and an extremely slow dissociation rate constant (kd = 3.69 +/- 0.26 x 10(-4) s-1). From these two kinetic parameters, affinity was determined to be similar to that of the intact membrane-associated receptor expressed on COS cells. sBMPR inhibited the alkaline phosphatase activity in BMP responsive cell lines such as mouse osteoblastic cell MC3T3-E1 and bone marrow stromal cell ST2. These data indicate that the extracellular domain of type I receptor for BMP-2 and BMP-4 is sufficient for high-affinity binding to its ligands and should prove useful in understanding the role of BMP-2/4 in vivo, because a suitable high-affinity anti-BMP antibody has yet to be developed.

Amino Acid Sequence↗
PubMed1997

Mesoderm induction by BMP-4 and -7 heterodimers.

Bone morphogenetic proteins (BMPs) are peptide growth factors belonging to the TGF-beta superfamily. A large number of these ligands, including BMP-2, -4 and -7 is expressed during early embryogenesis in the vertebrate embryo. In this study, we demonstrate that BMP-7 has ventralizing activity both in ectodermal explants as well as in whole embryos. As it was the case for BMP-2 and BMP-4, BMP-7 is a very poor inducer when provided as a homodimer protein. Because of this weak mesoderm inducing activity, it has been suggested that mesoderm induction by BMPs might represent an artifact of overexpression. We provide evidence demonstrating that unlike the homodimers of BMP-4 or BMP-7, the purified recombinant heterodimer of Xenopus BMP-4 and BMP-7 (BMP-4/7) has a potent mesoderm inducing activity at physiological concentrations. These results provide the first evidence for an embryonic function of BMP-4/7 heterodimers in the vertebrate embryo.

Animals↗
PubMed1997

Identification of a novel Drosophila protein kinase highly homologous to protein kinase N (PKN).

We identified a novel Drosophila gene, Dpkn (Drosophila protein kinase related to PKN), encoding a putative protein serine/threonine kinase. Although the cDNA obtained was incomplete at its 5'-terminal region, the deduced amino acid sequence of its kinase domain exhibits a high degree of similarity to protein kinase N (PKN), which has a kinase domain related to protein kinase C (PKC) and leucine zipper-like sequences in the amino terminal region. Expression of Dpkn was observed throughout Drosophila development, although its expression level decreased at later stages of embryogenesis. The expression of Dpkn is first detected in the newly formed mesodermal cell layer and is then restricted to the developing somatic musculature, indicating a possible role of Dpkn in the development of somatic muscles in Drosophila.

Amino Acid Sequence↗
PubMed1997

Color Doppler ultrasonography in the diagnosis of cavernous transformation of the portal vein.

OBJECTIVE: To improve diagnostic accuracy, we studied the use of color Doppler ultrasound (CDUS) in patients with cavernous transformation of the portal vein (CTPV). SUBJECTS AND METHODS: In 18 patients, the usefulness of CDUS was compared with that of B-mode US for visualizing and diagnosing CTPV. Sensitivity for detecting CTPV on B-mode US, CT, and CDUS was also compared in 14 patients who underwent angiography which showed typical findings of CTPV. In addition, we classified each patient based on the morphologic appearance in the ultrasound examination and correlated those findings with the etiology. RESULTS: CDUS proved to be superior to B-mode US in identifying collateral channels and was highly sensitive for detecting CTPV in 17 (94%) of the 18 patients. In comparison with angiography performed in 14 patients, B-mode US detected CTPV in 9 (64%) patients, contrast-enhanced CT in 7 (50%), and CDUS in 13 (93%), indicating that CDUS was the most reliable diagnostic tool. It was also possible to assess the etiology of CTPV using a combination of color Doppler findings. Detection of arterial flow patterns within the portal vein thrombus correlated with malignant findings on histologic examination, whereas benign thrombi showed no flow signals. CONCLUSION: CDUS proved to be a reliable and useful modality for diagnosing CTPV and evaluating the etiology of this entity.

Adult↗
PubMed1997

Possibility of differentiating small hyperechoic liver tumours using contrast-enhanced colour Doppler ultrasonography: a preliminary study.

We performed a preliminary study to investigate the possibility of differentiating small hyperechoic liver tumours, including hepatocellular carcinomas (HCCs), haemangiomas and focal fatty lesions, by administering a galactose-based contrast agent (SH/TA-508 (Levovist)) during colour Doppler ultrasonography (US). Ten patients (age range: 48-81 years) with small liver tumours (four HCCs, four hemangiomas and two focal fatty lesions) of less than 20 mm in diameter presented with hyperechoic masses with no intratumoural colour signals on conventional colour Doppler US. All patients subsequently underwent colour Doppler US with this contrast agent. Colour Doppler images of the tumours were assessed before and after the intravenous injection of 8 ml of the contrast agent at a concentration of 400 mg/ml. Prior to injection of the contrast agent, no intratumoural colour signals were observed in any cases. After injection, intratumoural colour signals appeared in all HCCs and in two haemangiomas with tumour-margin enhancement. The enhanced colour signals appeared to be related to cardiac contraction in the HCCs, but not in the haemangiomas. In the remaining two haemangiomas, only tumour-margin enhancement was observed. In the focal fatty lesions, neither intratumoural nor tumour-margin enhancement was observed. These results, although preliminary, suggest that the detection of colour Doppler signals is improved by using a contrast agent and the differences between enhanced colour signals from HCCs and haemangiomas may help differentiate hyperechoic HCCs from other hyperechoic tumours, including haemangiomas and focal fatty lesions.

Aged↗
PubMed1997

Conservation of BMP signaling in zebrafish mesoderm patterning.

To investigate the conservation of mechanisms for mesodermal patterning between zebrafish and Xenopus, we isolated two cDNA clones encoding bone morphogenetic protein (BMP)-related proteins from a zebrafish cDNA library. Based on their predicted amino acid sequences, these two clones were designated as zbmp-2 and zbmp-4. Whole-mount in situ hybridization analysis revealed that in gastrula embryo, both genes were localized in the ventral part of the embryo, consistent with the proposed function of Xenopus BMP-4 in ventral mesoderm specification. zbmp-4 expression, however, was also seen in the embryonic shield, the most dorsal mesodermal structure. To examine the ability of zbmp-2 to ventralize mesoderm, we injected synthetic mRNA into zebrafish embryos and found that overexpression of this gene eliminated dorsal structures including notochord at both morphological and molecular level. In contrast, expression of ventral marker gene eve1 was expanded to the dorsal side. These effects are analogous to the ventralization of embryos caused by ectopic xBMP-4 expression. Taken together, one may conclude that the developmental mechanisms for mesodermal patterning regulated by BMPs are evolutionarily conserved between amphibians and teleosts.

Amino Acid Sequence↗
PubMed1997

Diagnosing extrahepatic bile duct stones using intraductal ultrasonography: a case series.

BACKGROUND AND STUDY AIMS: Intraductal ultrasonography (IDUS), a new ultrasonographic diagnostic procedure, was used to assess the presence of extrahepatic bile duct stones. PATIENTS AND METHODS: The IDUS apparatus consisted of a 6-French high-frequency (20 MHz) probe. Prior to clinical application, in-vitro studies were conducted in a water tank. Clinically, IDUS was successful in 31 patients after endoscopic retrograde cholangiography. Interpretations of IDUS images were evaluated in comparison with cholangiographic and fluoroscopic findings. RESULTS: Experimental testing demonstrated that stones or fragments were typically visualized as strong, high-echo images with acoustic shadowing; air bubbles were seen as fan-shaped high-echo areas or comet-shaped high-echo areas; and sludge was visualized as soft, easily changing, high-echo structures. Extrahepatic bile duct stones were visualized by IDUS in 30 of 31 patients (96.8%), while fluoroscopy and cholangiography identified 19 (61.3%) and 25 (80.6%), respectively. Accurate differentiation between stones and air bubbles was also possible. CONCLUSION: IDUS could be a useful modality in the diagnosis of extrahepatic bile duct stones.

Adult↗
PubMed1997

Limitations of intraductal ultrasonography in differentiating between bile duct cancer in stage T1 and stage T2: in-vitro and in-vivo studies.

BACKGROUND AND STUDY AIMS: We investigated whether intraductal ultrasonography (IDUS) could distinguish between stage T1 and T2 bile duct cancer. MATERIALS AND METHODS: In-vitro study. Resected bile duct specimens (n = 8) were immersed in a water tank and were pierced with straight pins to clarify the normal layer structure. Ultrasonosgraphic images (20MHz) of the positions of pin echoes were compared to the positions of pin holes as seen on histologic analysis of the specimens. In-vivo study. A thin-caliber high-frequency (6 Fr, 20 MHz) ultrasonic probe was inserted into the bile duct via a transhepatic route or a transpapillary route in 26 patients with bile duct cancer who underwent surgical resection. RESULTS: In-vitro study. The inner hypoechoic layer on the IDUS image corresponded not only to the fibromuscular layer but also to a part of fibrous layer of the perimuscular loose connective tissue on histologic analysis, especially in the cases with moderate to severe bile duct wall fibrosis. The outer hyperechoic layer corresponded to the subserosal fat tissue. In-vivo study. In four of six patients with tumor limited to the inside hypoechoic layer on IDUS images, the histologic findings showed tumor invasion to the fibrous layer of the perimuscular loose connective tissue. Due to this limitation, accuracy of IDUS in T-staging was only 20/26 (77 %). CONCLUSIONS: IDUS cannot reliably distinguish bile duct cancer in stage T1 from that in stage T2.

Adult↗
PubMed1997

The role of endoscopic balloon sphincteroplasty in patients with gallbladder and bile duct stones.

We clarified the significance of endoscopic balloon sphincteroplasty (EBS) in the therapeutic treatment of biliary tract stones in the present era of laparoscopic cholecystectomy (LC). Patients with cholecysto-choledocholithiasis (n = 33) were treated by EBS. After endoscopic retrograde cholangiography (ERC), a balloon catheter (8 mm in diameter and 3 cm in width) was inserted into the bile duct using a guidewire, and positioned at the sphincter of Oddi. After inflating the balloon catheter, bile duct stones were removed by mechanical lithotripsy, a basket catheter, or a balloon catheter. In all patients, bile duct stones were removed by EBS without endoscopic sphincterotomy. No complication occurred except for 2 cases of mild pancreatitis, which was resolved within 48 hours. Twenty-four patients underwent LC before or after EBS. The remaining 9 patients did not undergo LC due to a poor-risk status for general anesthesia. None of them, however, experienced cholecystitis or colicky attacks after EBS. The combination of EBS and LC is an excellent method for treating cholecysto-choledocholithiasis.

Aged↗
PubMed1997

High altitude-induced changes in alpha1-adrenergic receptors and Ins(1,4,5)P3 responses in cerebral arteries.

In response to high-altitude long-term hypoxemia, the cerebral arteries of fetal and adult sheep show decreased contractile responses to norepinephrine (NE) and other agonists. To test the hypothesis that hypoxia-induced developmental and vessel specific cerebral artery contractility changes are mediated, in part, by changes in alpha1-adrenergic receptor (alpha1-AR) density and/or NE-induced inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] responses, we performed the following study. In common carotid (Com) and main branch cerebral (MBC) arteries from normoxic adult ewes and near-term fetuses and those acclimatized to high altitude (3,820 m), we quantified alpha1-AR density (maximal binding in fmol/mg protein) and affinity (dissociation constant in nM) with the alpha1-AR antagonist [3H]prazosin. In addition, we quantified NE-induced Ins(1,4,5)P3 responses in these arteries. With long-term hypoxemia, alpha1-AR density in fetal and adult Com decreased 75% (from 113 +/- 18 to 28 +/- 5 fmol/mg protein) and 66% (from 54 +/- 3 to 18 +/- 4 fmol/mg protein), respectively, from normoxic control values. alpha1-AR density of the fetal and adult MBC decreased 76% (from 47 +/- 4 to 11 +/- 1 fmol/mg protein) and 61% (from 23 +/- 3 to 9 +/- 3 fmol/mg protein), respectively, from controls. In hypoxemic adult Com, the NE-induced Ins(1,4,5)P3 response decreased 51% (from 309 +/- 38 to 151 +/- 24%) from the control value. In fetal and adult MBC, long-term hypoxemia was associated with decreases of 35% (from 345 +/- 40 to 225 +/- 30%) and 44% (from 355 +/- 55 to 199 +/- 16%), respectively, from control values. We conclude that in the adult Com and MBC vessels, acclimatization to high-altitude, long-term hypoxemia was associated with significant decreases in both alpha1-AR density values and Ins(1,4,5)P3 responses to NE. Similarly, in the fetal MBC arteries, high-altitude hypoxemia was associated with marked attenuation of both alpha1-AR density and NE-induced Ins(1,4,5)P3 responses. The magnitude of decreases in NE-induced Ins(1,4,5)P3 responses in these vessels correlated fairly well with the decreases in alpha1-AR density. These findings suggest that changes in noradrenergic receptor-second messenger coupling may play a role in altered cerebrovascular tone in association with high-altitude acclimatization and other forms of long-term hypoxia in both fetus and adult.

Acclimatization↗
PubMed1997

Copper-ion-catalyzed vitreous liquefaction in vivo.

To investigate copper-ion (Cu2+)-catalyzed vitreous liquefaction in vivo, Cu2+ solution (10 mumol) was injected into the vitreous cavity of rabbits. At 24 h after the injection, the gel and liquid vitreous were weighed, and the percent of vitreous liquefaction was calculated. Cu2+ injection resulted in liquefaction of 58% of the vitreous, although control eyes had 12% liquefaction (p < 0.1). The vitreous liquefaction was more pronounced in the presence of exogenous ascorbic acid. However, the addition of mannitol, a hydroxyl-radical-specific scavenger, significantly suppressed the Cu(2+)-catalyzed vitreous liquefaction. The free radicals generated by the Cu(2+)-catalyzed oxidation system may cause vitreous liquefaction in vivo.

Animals↗
PubMed1997

Mesodermal subdivision along the mediolateral axis in chicken controlled by different concentrations of BMP-4.

Molecular mechanisms by which the mesoderm is subdivided along the mediolateral axis in early chicken embryos have been studied. When the presomitic mesoderm (medial mesoderm) was transplanted into the lateral plate, the graft was transformed into lateral plate tissue, indicating that the primitive somite was not fully committed and that the lateral plate has a cue for mesodermal lateralization. Since the lateral plate expresses a high level of BMP-4 mRNA, a member of the TGF-beta family, we hypothesized that it is the molecule responsible for the lateralization of the somite. To test this, we transplanted COS cells producing BMP-4 into the presomitic region. Those cells locally prevented the presomitic cells from differentiating into somites, converting them instead into lateral plate mesoderm, which was revealed by expression of cytokeratin mRNA, a marker for the lateral plate. The effect was dependent on the level of effective BMP-4: with a high level of BMP-4, the somite was transformed completely to lateral plate; with a low level, the somite formed but was occupied by the lateral somitic component expressing cSim 1, a marker for the lateral somite. These results suggest that different thresholds of effective BMP-4 determine distinct subtypes of the mesoderm as a lateralizer during early development.

Animals↗
PubMed1997

Xenopus msx1 mediates epidermal induction and neural inhibition by BMP4.

Epidermal fate in Xenopus ectoderm has been shown to be induced by a secreted growth factor, Bone Morphogenetic Protein 4 (BMP4). However, the molecular mechanism mediating this response is poorly understood. Here, we show that the expression of the homeobox gene, msx1, is an immediate early response to BMP4 in Xenopus embryos. The timing of expression and embryonic distribution of msx1 parallel those described for BMP4. Moreover, overexpression of msx1 in early Xenopus embryos leads to their ventralization as described for BMP4. Consistent with mediating a BMP type of signaling, overexpression of msx1 is sufficient to induce epidermis in dissociated ectoderm cells, which would otherwise form neural tissue. Finally, msx1 can also rescue neuralization imposed by a dominant negative BMP receptor (tBR) in ectodermal explants. We propose that Xenopus msx1 acts as a mediator of BMP signaling in epidermal induction and inhibition of neural differentiation.

Animals↗
PubMed1997

Functional analysis of an ascidian homologue of vertebrate Bmp-2/Bmp-4 suggests its role in the inhibition of neural fate specification.

The ascidian tadpole larva is thought to be close to a prototype of the ancestral chordate. The vertebrate body plan is established by a series of inductive cellular interactions, whereas ascidians show a highly determinate mode of development. Recent studies however, suggest some roles of cell-cell interaction during ascidian embryogenesis. To elucidate the signaling molecules responsible for the cellular interaction, we isolated HrBMPb, an ascidian homologue of the vertebrate bone morphogenetic protein (BMP) gene, from Halocynthia roretzi. The amino acid sequence of HrBMPb closely resembled those of vertebrate BMP-2 and BMP-4 and of Drosophila Decapentaplegic (DPP). In addition to the sequence similarity, HrBMPb overexpression induced the ventralization of Xenopus embryos, suggesting functional conservation. The zygotic expression of HrBMPb was first detected around gastrulation. HrBMPb expression was maintained in some cells at the lateral edges of the neural plate through gastrulation to neurulation, although that in the presumptive muscle cells was downregulated. HrBMPb was not expressed in the presumptive epidermis during gastrulation. When HrBMPb mRNA was injected into fertilized Halocynthia eggs, cells that normally give rise to the neural tissue differentiated into epidermis, causing a loss of anterior neural tissue in the larva. In addition, HrBMPb might function synergistically with HrBMPa, an ascidian homologue of BMPs-5 to 8. However, HrBMPb overexpression did not affect differentiation of the notochord and muscle cells. These results suggest that HrBMPb functions as a neural inhibitor and as an epidermal inducer but not as a ventralizing agent in ascidian development.

Amino Acid Sequence↗
PubMed1997

Color Doppler ultrasonography in the diagnosis of portal vein invasion in patients with pancreatic cancer.

We retrospectively evaluated the diagnostic usefulness of color Doppler ultrasonography for detecting portal vein invasion in 21 patients with pancreatic cancer who underwent surgical exploration (14 resection, seven inspection). Real-time gray scale ultrasonography, color Doppler ultrasonography, computed tomography, and angiography were performed in all patients to evaluate portal vein invasion, and the images were compared with the histopathologic or surgical inspection findings. On comparison between gray scale ultrasonographic and color Doppler ultrasonographic images, the tumor-vessel relations were visualized more clearly on color Doppler ultrasonography than on gray scale ultrasonography in 14 (22.2%) of 63 vessels. The sensitivity of color Doppler ultrasonography, computed tomography, and angiography for diagnosing portal invasion was 73.7%, 73.7%, and 73.6%, and the specificity was 95.1%, 95.5%, and 90.9%, respectively; the overall accuracy was 84.1%, 88.9% and 85.7%, respectively. A mosaic signal pattern was observed in 12 vessels and showed an accuracy of 86.4% for diagnosing portal vein invasion. In conclusion, compared with gray scale ultrasonography, color Doppler ultrasonography provided improved images of the tumor and portal vein. Furthermore, the accuracy of color Doppler evaluation of portal vein invasion appears to be equal to that of computed tomography and angiography. Therefore, color Doppler ultrasonography may play an important role as an initial examination for evaluating portal vein invasion.

Adult↗