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.

Constitutively active BMP type I receptors transduce BMP-2 signals without the ligand in C2C12 myoblasts

Bone morphogenetic protein-2 (BMP-2), a member of transforming growth factor-beta superfamily, inhibits the terminal differentiation of C2C12 myoblasts and changes their differentiation pathway into cells expressing osteoblast phenotypes such as alkaline phosphatase (ALP) activity and osteocalcin production (Katagiri et al., 1994, J. Cell Biol. 127, 1755-1766). Two type I receptors for BMP-2 (BMPR-IA and BMPR-IB) have been cloned, but the role of the respective receptors in signal transduction is not clear. In the present study, we examined the signal transduction of BMP-2 in C2C12 cells using constitutively activated mutant BMPR-IA and BMPR-IB. C2C12 cells expressed BMPR-IA and BMPR-II mRNAs, but not BMPR-IB mRNA at detectable levels in Northern blotting. When mutated BMPR-IA and BMPR-IB were transiently transfected into C2C12 cells, both BMPR-IA and BMPR-IB similarly induced ALP activity in the absence of BMP-2. We also established subclonal cell lines of C2C12 cells by stably transfecting mutated BMPR-IB. When the mutated BMPR-IB-transfected cells were cultured in medium with low serum (differentiation medium) without BMP-2, the cells differentiated into ALP-positive mononuclear cells and not into myosin heavy chain-positive myotubes. These mutated BMPR-IB-transfected cells expressed ALP activity and osteocalcin mRNA in a time-dependent manner, but neither muscle creatine kinase nor myogenin mRNAs. These results indicate that the mutated BMP-2 type I receptors can constitutively transduce BMP-2 signals in the absence of the ligand in C2C12 cells.

Regulation of epidermal induction by BMP2 and BMP7 signaling

The specification of neural fate in Xenopus embryos has been shown to be under regulation by negative factors. The secreted protein bone morphogenetic protein-4 (BMP4) has been identified as one of these factors: in the early gastrula ectoderm, BMP4 can both inhibit neural fate and induce epidermis. In this study, we show that two other Xenopus BMP genes, BMP2 and BMP7, are endowed with the same types of activities. First, we show that expression of a dominant negative form of the BMP2 ligand, which blocks normal processing of the wild-type ligand, causes neuralization of Xenopus ectoderm. Second, we have isolated the Xenopus BMP2/7 receptor (XALK2) and generated a constitutively active mutant that signals in a ligand-independent manner. We show that signals from the activated BMP2/7 receptor also inhibit neuralization and induce epidermis in dissociated ectoderm cells. Consistent with both findings we show that secreted BMP2 and BMP7 ligands can also mediate neural inhibition and epidermal induction. These results suggest that both BMP2 and BMP7 may be involved independently or together with BMP4 in the inhibition of the neural fate and the onset of the epidermal induction pathway in vivo. This further supports the idea that epidermal induction is due to the effects of multiple signals from heterogeneous BMP genes.

A kinase domain-truncated type I receptor blocks bone morphogenetic protein-2-induced signal transduction in C2C12 myoblasts

Members of the transforming growth factor (TGF)-beta superfamily bind the transmembrane serine/threonine kinase complex consisting of type I and type II receptors. Their intracellular signals are propagated via respective type I receptors. Bone morphogenetic protein (BMP)-2, a member of the TGF-beta superfamily, induces ectopic bone formation when implanted into muscular tissues. Two type I receptors (BMPR-IA and BMPR-IB) have been identified for BMP-2. We have reported that BMP-2 inhibits the terminal differentiation of C2C12 myoblasts and converts their differentiation pathway into that of osteoblast lineage cells (Katagiri, T., Yamaguchi, A., Komaki, M., Abe, E., Takahashi, N., Ikeda, T., Rosen, V., Wozney, J. M., Fujisawa-Sehara, A. and Suda, T. (1994) J. Cell Biol. 127, 1755-1766). In the present study, we examined the involvement of functional BMP-2 type I receptors in signal transduction in C2C12 cells, which expressed mRNA for BMPR-IA, but not for BMPR-IB in Northern blotting. TGF-beta type I receptor (TbetaR-I) mRNA was also expressed in C2C12 cells. Subclonal cell lines of C2C12 that stably expressed a kinase domain-truncated BMPR-IA (DeltaBMPR-IA) differentiated into myosin heavy chain-expressing myotubes but not into alkaline phosphatase (ALP)-positive cells, even in the presence of BMP-2. In contrast, the differentiation of the DeltaBMPR-IA-transfected C2C12 cells into myotubes was suppressed by TGF-beta1, as in the parental C2C12 cells. BMP-2 did not efficiently suppress the mRNA expression of muscle-specific genes such as muscle creatine kinase, MyoD, and myogenin, nor did it induce the expression of ALP mRNA in the DeltaBMPR-IA-transfected C2C12 cells. In contrast, TGF-beta1 inhibited mRNA expression of the muscle-specific genes in those cells. When wild-type BMPR-IA was transiently transfected into the DeltaBMPR-IA-transfected C2C12 cells, a number of ALP-positive cells appeared in the presence of BMP-2. Transfection of wild-type BMPR-IB or TbetaR-I failed to increase the number of ALP-positive cells. These results suggest that the BMP-2-induced signals, which inhibit myogenic differentiation and induce osteoblast differentiation, are transduced via BMPR-IA in C2C12 myoblasts.

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.

Development of flexible ventriculoscope (Yamadori-type VII) and its application to experimental animals

We developed a new ventriculoscope (Yamadori-type VII), a 2.1 mm calibrated fiberscope with a monopolar coagulator, that can be inserted from the cisterna cerebellomedullaris into the third cerebral ventricle of experimental animals, like dogs. With the improved performance of the neuroendoscope compared to its prototype, Yamadori III, it was possible to inspect clearly and to produce electrocoagulative lesions accurately on any part of the intraventricular structures with minimal injury to nearby vital brain areas.

Assessment of right hepatic artery involvement in patients with biliary tract cancer using color Doppler ultrasonography

The accuracy of color Doppler ultrasonography (CDUS) in diagnosing right hepatic artery (RHA) involvement was preoperatively evaluated in 28 patients with biliary tract cancer. When a tumor partially or completely surrounded the RHA, the circumferential involvement was diagnosed as positive. With B-mode ultrasonography imaging alone in the 10 nonsurgical patients, the correspondence rates with angiography for the presence of invasion, absence of invasion, and overall were 33%, 0%, and 10%, respectively. However, CDUS allowed clearer visualization of the RHA than did B-mode imaging, and the correspondence rates of CDUS with angiography were 100%, 43%, and 60%, respectively. In the 13 surgical patients, the accuracy levels of B-mode imaging, CDUS, computed tomography, and angiography for the detection of RHA involvement were 46%, 77%, 58%, and 92%, respectively, when compared with surgical and histopathologic findings. Although the accuracy of CDUS was lower than that of angiography, it can be performed repeatedly and noninvasively. CDUS is expected to be useful for the initial assessment of RHA involvement.

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.

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.

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.

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.

Cross-linking of vitreous collagen and degradation of hyaluronic acid induced by bilirubin-sensitized photochemical reaction

To determine the mechanisms of vitreous liquefaction following vitreous hemorrhage, we investigated the effects of the free radicals produced by a bilirubin-sensitized photochemical reaction on collagen and hyaluronic acid (HA). Bovine vitreous collagen and HA were irradiated by visible light in the presence of bilirubin, which is produced from the degradation of hemoglobin, as a photosensitizer. Changes in molecular weight were monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the collagen, and high-performance liquid chromatography for the HA. We found that free radicals caused an increase in high-molecular-weight components and insolubilization of the vitreous collagen, and a decrease in the molecular weight of HA. The changed molecular properties of the vitreous collagen could be attributed to the extensive cross-linking of the molecules. This cross-linking and the degradation of HA, both induced by the bilirubin-sensitized photochemical reaction, may contribute to vitreous liquefaction following vitreous hemorrhage.

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.

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.

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.

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.

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.

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.

Effects of swimming training on brown-adipose-tissue activity in obese ob/ob mice: GDP binding and UCP m-RNA expression

Brown adipose tissue (BAT) of obese animals is generally in a relatively atrophied and thermogenically quiescent state. The aim of the current study was to investigate the effect of swimming training on BAT activity in lean and obese (ob/ob) mice. The trained mice underwent a 6-week endurance swimming training (1 h/day, 5 days/week) in water at 35-36 degrees C. The swimming training significantly increased BAT mass and its protein content in both the lean and obese mice, suggesting hypertrophy. After swimming training, the amounts of protein and guanosine 5'-diphosphate binding in the mitochondria recovered from BAT of both mice increased significantly as compared with the respective sedentary groups, whereas the uncoupling protein (UCP) content increased significantly only in lean mice. After swimming training, the level of UCP mRNA expression did not change substantially in lean mice but appeared to increase in obese mice. The results obtained here suggest that swimming training leads to an increase in the nonshivering thermogenesis of obese mice in addition to lean mice.