Tube Extension Research Articles

초소형 튜브와 튜브판의 링 프로젝션 용접 공정개발 및 강도 평가

Abstract Microminiature heat exchanger has been applied to the gas turbine in order to increase energy efficiency. During the production of microminiature heat exchanger, however, it is very difficult to weld tube to tubesheet. In this study, therefore, welding process of resistance ring projection was used, and weld tensile tests were performed. Sound weld joint was obtained as a result of applying resistance ring projection welding to microminiature heat exchanger to tubesheet. Cold weld occurred at under 1600A. Even though tensile strength was increased with increasing current, splash occurred and tensile strength decreased at 2000A due to the excessive current. Therefore it was determine that the optimal current is 1900A. As result of tensile tests based on ASME code for tube to tubesheet weldment, rupture position was weldment due to Fs (Fractured section) of nugget, which was smaller than tube thickness (t), and it was proven as a partial strength welding because of the average joint efficiency fr = 0.90. Key Words : Microminiature heat exchanger, Ring projection welding, Tube, Tubesheet, Electrode tip angle, Tensile strength, Tube extension, Welding current

J021 Regulation of cardiac progenitor cells during development

Cardiac progenitor cells of the second heart field (SHF) contribute to the poles of the elongating embryonic heart. Failure or perturbation of SHF development leads to congenital heart defects. Recent studies have demonstrated the existence, in the postnatal heart, of resident cardiac progenitor cells that specifically express the transcription factor Islet1, a SHF marker, and that have the potential to differentiate into cardiomyocytes, smooth muscle and endothelial cells. Interestingly, several evidences suggest that these residual progenitor cells arise from the SHF. Through analysis of a transgene integration site position effect we have identified the transcriptional repressor Hes1 as a novel regulator of SHF development. Hes1, a target gene of the Notch signaling pathway, is expressed SHF progenitor cells. Analysis of E15.5 Hes1-/- embryos reveals outflow tract alignment defects (ventricular septal defects and overriding aorta). At earlier developmental stages, Hes1-/- embryos display SHF proliferation defects, cardiac neural crest cells reduction and fail to completely extend the outflow tract. Thus these data reveal a role for Hes1, and potentially Notch signaling, in SHF development. Given the importance of Isl1 as a marker of resident progenitor cells in the later heart we are analysing the role of known and novel regulators of the SHF (Hes1, Fgf10 and Tbx1) in the regulation of myocardial progenitor cell fate and in the definition of the critical niche occupied by residual cardiac progenitor cells in the forming and definitive heart. In Fgf10-/- mice, outflow tract alignment occurs normally. However, Fgf10-/- hearts are highly dysmorphic. We thus hypothesize that Fgf10 deletion may affect the proliferative capacities of SHF progenitors in order to maintain the residual progenitor cells pool in the fetal heart. Initial results have revealed that whereas Fgf10-/- hearts undergo heart tube extension normally, proliferation is impaired. Together, our results identify Hes1 as a novel regulator of SHF progenitor cell deployment and reveal a potential role of Fgf10 in regulating cardiac progenitor cell fate and cardiac growth during the fetal period. This study will increase our understanding of the molecular mechanisms governing the maintenance and differentiation of cardiac progenitor cells.

Combined Proteomic and Cytological Analysis of Ca2+-Calmodulin Regulation inPicea meyeriPollen Tube Growth

Ca2+-calmodulin (Ca2+-CaM) is a critical molecule that mediates cellular functions by interacting with various metabolic and signaling pathways. However, the protein expression patterns and accompanying serial cytological responses in Ca2+-CaM signaling deficiency remain enigmatic. Here, we provide a global analysis of the cytological responses and significant alterations in protein expression profiles after trifluoperazine treatment in Picea meyeri, which abrogates Ca2+-CaM signaling. Ninety-three differentially displayed proteins were identified by comparative proteomics at different development stages and were assigned to different functional categories closely related to tip growth machinery. The inhibition of Ca2+-CaM signaling rapidly induced an increase in extracellular Ca2+ influx, resulting in dramatically increased cytosolic Ca2+ concentrations and ultrastructural abnormalities in organelles as the primary responses. Secondary and tertiary alterations included actin filament depolymerization, disrupted patterns of endocytosis and exocytosis, and cell wall remodeling, ultimately resulting in perturbed pollen tube extension. In parallel with these cytological events, time-course experiments revealed that most differentially expressed proteins showed time-dependent quantitative changes (i.e. some signaling proteins and proteins involved in organelle functions and energy production changed first, followed by alterations in proteins related to cytoskeletal organization, secretory pathways, and polysaccharide synthesis). Taken together, Ca2+-CaM dysfunction induced serial cytological responses and temporal changes in protein expression profiles, indicating the pivotal role of Ca2+-CaM in the regulation of tip growth machinery.

Fitness for service assessment of coolant channels of Indian PHWRs

A typical coolant channel assembly of pressurised heavy water reactors mainly consists of pressure tube, calandria tube, garter spring spacers, all made of zirconium alloys and end fittings made of SS 403. The pressure tube is rolled at both its ends to the end fittings and is located concentrically inside the calandria tube with the help of garter spring spacers. Pressure tube houses the fuel bundles, which are cooled by means of pressurised heavy water. It, thus, operates under the environment of high pressure and temperature (typically 10 MPa and 573 K), and fast neutron flux (typically 3 × 10 17 n/m 2 s, E > 1 MeV neutrons). Under this operating environment, the material of the pressure tube undergoes degradation over a period of time, and eventually needs to be assessed for fitness for continued operation, without jeopardising the safety of the reactor. The other components of the coolant channel assembly, which are inaccessible for any in-service inspection, are assessed for their fitness, whenever a pressure tube is removed for either surveillance purpose or any other reasons. This paper, while describing the latest developments taking place to address the issue of fitness for service of the Zr–2.5 wt% Nb pressure tubes, also dwells briefly upon the developments taken place, to address the issues of life management and extension of zircaloy-2 pressure tubes in the earlier generation of Indian pressurised heavy water reactors.

Mineralization of vestimentiferan tubes at methane seeps on the Congo deep-sea fan

Vestimentiferan tube worms are prominent members of modern methane seep communities and are totally reliant as adults on symbiotic sulphide-oxidizing bacteria for their nutrition. The sulphide is produced in the sediment by a biochemical reaction called the anaerobic oxidation of methane (AOM). A well-studied species from the Gulf of Mexico shows that seep vestimentiferans ‘mine’ sulphide from the sediment using root-like, thin walled, permeable posterior tube extensions, which can also be used to pump sulphate and possibly hydrogen ions from the soft tissue back into the sediment to increase the local rate of AOM. The ‘root-balls’ of exhumed seep vestimentiferans are intimately associated with carbonate nodules, which are a result of AOM. We have studied vestimentiferan specimens and associated carbonates from seeps at the Kouilou pockmark field on the Congo deep-sea fan and find that some of the posterior ‘root’ tubes of living specimens are enclosed with carbonate indurated sediment and other, empty examples are partially or completely replaced by the carbonate mineral aragonite. This replacement occurs from the outside of the tube wall inwards and leaves fine-scale relict textures of the original organic tube wall. The process of mineralization is unknown, but is likely a result of post-mortem microbial decay of the tube wall proteins by microorganisms or the precipitation from locally high flux of AOM derived carbonate ions. The aragonite-replaced tubes from the Kouilou pockmarks show similar features to carbonate tubes in ancient seep deposits and make it more likely that many of these fossil tubes are those of vestimentiferans. These observations have implications for the supposed origination of this group, based on molecular divergence estimates.

Measuring Intra-Abdominal Pressure outside the ICU: Validation of a Simple Bedside Method

Intra-abdominal pressure measurement is essential to the diagnosis of patients with intraabdominal hypertension or abdominal compartment syndrome. The most common method for measuring intra-abdominal pressure (IAP) is the intravesicular or "bladder" technique, which requires electronic monitoring technology not available on the typical surgical ward. Herein we describe and validate a simple, rapid screening method for bedside IAP measurement using the patient's indwelling urinary catheter and a readily available intravenous tubing extension. Validation of this technique across the clinically important IAP diagnostic spectrum demonstrated acceptable bias (1.6 mm Hg; 95% confidence interval 1.4-1.8) with limits of agreement of 0.36 to 2.8. This demonstrates good agreement between the two IAP methods and validates the bedside technique as a simple, cost-effective, and reproducible method for screening IAP measurements outside of the critical care setting.

Tbx3 Is Required for Outflow Tract Development

Conotruncal and ventricular septal congenital heart anomalies result from defects in formation and division of the embryonic outflow tract. Cardiac remodeling during outflow tract and ventricular septation converts the tubular embryonic heart into a parallel circulatory system with an independent left ventricular outlet and right ventricular inlet. Tbx3 encodes a T-box-containing transcription factor expressed in the developing conduction system of the heart. Mutations in TBX3 cause ulnar-mammary syndrome. Here we show that mice lacking Tbx3 develop severe outflow tract defects, including connection of both the aorta and pulmonary trunk with the right ventricle, in addition to aortic arch artery anomalies and abnormal communication between the right atrium and left ventricle. Alignment defects are preceded by a delay in caudal displacement of the arterial pole of the heart during aortic arch artery formation. Embryonic anterior-posterior patterning and cardiac chamber development are unaffected in Tbx3 mutant embryos. However, the contribution of second heart field derived progenitor cells to the arterial pole of the heart is impaired. Tbx3 is expressed in pharyngeal epithelia and neural crest cells in the pharyngeal region, suggesting an indirect role in second heart field deployment. Loss of Tbx3 affects multiple signaling pathways regulating second heart field proliferation and outflow tract morphogenesis, including fibroblast growth factor signaling, leading to a failure of normal heart tube extension and consequent atrioventricular and ventriculoarterial alignment defects.

Nkx genes regulate heart tube extension and exert differential effects on ventricular and atrial cell number

Heart formation is a complex morphogenetic process, and perturbations in cardiac morphogenesis lead to congenital heart disease. NKX2-5 is a key causative gene associated with cardiac birth defects, presumably because of its essential roles during the early steps of cardiogenesis. Previous studies in model organisms implicate NKX2-5 homologs in numerous processes, including cardiac progenitor specification, progenitor proliferation, and chamber morphogenesis. By inhibiting function of the zebrafish NKX2-5 homologs, nkx2.5 and nkx2.7, we show that nkx genes are essential to establish the original dimensions of the linear heart tube. The nkx-deficient heart tube fails to elongate normally: its ventricular portion is atypically short and wide, and its atrial portion is disorganized and sprawling. This atrial phenotype is associated with a surplus of atrial cardiomyocytes, whereas ventricular cell number is normal at this stage. However, ventricular cell number is decreased in nkx-deficient embryos later in development, when cardiac chambers are emerging. Thus, we conclude that nkx genes regulate heart tube extension and exert differential effects on ventricular and atrial cell number. Our data suggest that morphogenetic errors could originate during early stages of heart tube assembly in patients with NKX2-5 mutations.

Activity of carboxylic acid amide (CAA) fungicides against Bremia lactucae

Four carboxylic acid amide (CAA) fungicides, mandipropamid (MPD), dimethomorph (DMM), benthiavalicarb (BENT) and iprovalicarb (IPRO) were examined for their effects on various developmental stages of Bremia lactucae, the causal agent of downy mildew in lettuce, in vitro and in planta. Spore germination in vitro or on leaf surfaces was inhibited by all CAA fungicides (technical or formulated). MPD was more effective in suppressing germination than DMM or BENT, whereas IPRO was least effective. CAA induced no disruption of F-actin microfilament organisation in germinating spores of B. lactucae. CAA applied to germinating spores in vitro prevented further extension of the germ tubes. When applied to germinated spores on the leaf surface they prevented penetration. Preventive application of CAA to intact plants inhibited infection. MPD was more effective in suppressing infection than DMM or BENT, whereas IPRO was least effective. Curative application was effective at ≤3 h post-inoculation (hpi) but not at ≥18 hpi. CAA (except IPRO) applied to upper leaf surfaces inhibited spore germination on the lower surface and hence reduced infection. CAA suppressed sporulation of B. lactucae on floating leaf discs and when sprayed onto infected plants two days before onset of sporulation. BENT and DMM were more effective in suppressing sporulation than MPD or IPRO. Epidemics of downy mildew in shade-house grown lettuce were suppressed by CAA. A single spray applied to five-leaf plants before transplanting controlled the disease for 50 days. The results suggest that CAA are effective inhibitors of spore germination and therefore should be used as preventive agents against downy mildew of lettuce caused by B. lactucae.

COPI Vesicle Transport Is a Common Requirement for Tube Expansion in Drosophila

BackgroundTube expansion defects like stenoses and atresias cause devastating human diseases. Luminal expansion during organogenesis begins to be elucidated in several systems but we still lack a mechanistic view of the process in many organs. The Drosophila tracheal respiratory system provides an amenable model to study tube size regulation. In the trachea, COPII anterograde transport of luminal proteins is required for extracellular matrix assembly and the concurrent tube expansion.Principal FindingsWe identified and analyzed Drosophila COPI retrograde transport mutants with narrow tracheal tubes. γCOP mutants fail to efficiently secrete luminal components and assemble the luminal chitinous matrix during tracheal tube expansion. Likewise, tube extension is defective in salivary glands, where it also coincides with a failure in the luminal deposition and assembly of a distinct, transient intraluminal matrix. Drosophila γCOP colocalizes with cis-Golgi markers and in γCOP mutant embryos the ER and Golgi structures are severely disrupted. Analysis of γCOP and Sar1 double mutants suggests that bidirectional ER-Golgi traffic maintains the ER and Golgi compartments and is required for secretion and assembly of luminal matrixes during tube expansion.Conclusions/SignificanceOur results demonstrate the function of COPI components in organ morphogenesis and highlight the common role of apical secretion and assembly of transient organotypic matrices in tube expansion. Intraluminal matrices have been detected in the notochord of ascidians and zebrafish COPI mutants show defects in notochord expansion. Thus, the programmed deposition and growth of distinct luminal molds may provide distending forces during tube expansion in diverse organs.

Effects of epicuticular wax fromDigitaria sanguinalisandFestuca arundinaceaon infection byCurvularia eragrostidis

Epicuticular wax is a plant’s initial defence system to various foreign invasions, including invasion by fungi. In this study, we investigated the effect of epicuticular wax of Digitaria sanguinalis and Festuca arundinacea on invasion by the fungus Curvularia eragrostidis and the difference in components of epicuticular waxes between the two plants. The epicuticular wax of D. sanguinalis (host) significantly enhanced the growth of germ tubes of C. eragrostidis conidia, but had no effect on appressorium formation. However, the epicuticular wax of F. arundinacea (non-host) inhibited the extension of germ tubes and the differentiation of appressoria. Analysis using gas chromatography-mass spectrometry indicated that the constituents of these two epicuticular waxes were remarkably different. Among the 24 and 21 compounds found in the wax of D. sanguinalis and F. arundinacea, respectively, only four were the same. (Z, Z)-9,12-Octadecadien-1-ol constituted 54.3% of the total wax of D. sanguinalis, while 9-tricosene accounted for 49.8% of the total waxes of F. arundinacea. Furthermore, an extracellular esterase preparation from C. eragrostidis conidia could completely degrade the epicuticular wax of D. sanguinalis after 4 h incubation at 25°TC, but only partially degrade the wax from F. arundinacea. These results suggest that the components of the wax and their chemical characteristics are important in determining how effectively these plants are able to combat invasion of C. eragrostidis.

Root inoculation with a forest soil streptomycete leads to locally and systemically increased resistance against phytopathogens in Norway spruce

Soil streptomycetes are commonly antagonistic against plant pathogens. However, interactions involving increased defense responses in the host plant, leading to suppression of plant disease development, have not yet been detailed. Here, the mechanisms were studied of disease suppression by Streptomyces sp. GB 4-2 against Heterobasidion root and butt rot in Norway spruce (Picea abies) seedlings. GB 4-2 promoted mycelial growth of the phytopathogenic fungus, germination rate of fungal spores, extension of germ tubes and early colonization of outer cortical layers of the plant root. Reduced colonization of the inner cortical cell layers was accompanied by the induction of cell wall appositions, and increased xylem formation in the vascular cylinder emerged after bacterium-fungus coinoculation. Bacterial treatment led to decreased water content in roots and needles and increased photosynthetic yield (F(v)/F(m)) and peroxidase activities in needles. The infection of needles by Botrytis cinerea was reduced by bacterial pretreatment. Complex interactions of GB 4-2 with Norway spruce and Heterobasidion abietinum were discovered. The bacterium promoted the growth of the phytopathogenic fungus but induced plant defense responses. Host responses indicate that GB 4-2 induces both local and systemic defense responses in Norway spruce.

A p21-Activated Kinase Is Required for Conidial Germination in Penicillium marneffei

Asexual spores (conidia) are the infectious propagules of many pathogenic fungi, and the capacity to sense the host environment and trigger conidial germination is a key pathogenicity determinant. Germination of conidia requires the de novo establishment of a polarised growth axis and consequent germ tube extension. The molecular mechanisms that control polarisation during germination are poorly understood. In the dimorphic human pathogenic fungus Penicillium marneffei, conidia germinate to produce one of two cell types that have very different fates in response to an environmental cue. At 25 °C, conidia germinate to produce the saprophytic cell type, septate, multinucleate hyphae that have the capacity to undergo asexual development. At 37 °C, conidia germinate to produce the pathogenic cell type, arthroconidiating hyphae that liberate uninucleate yeast cells. This study shows that the p21-activated kinase pakA is an essential component of the polarity establishment machinery during conidial germination and polarised growth of yeast cells at 37 °C but is not required for germination or polarised growth at 25 °C. Analysis shows that the heterotrimeric G protein α subunit GasC and the CDC42 orthologue CflA lie upstream of PakA for germination at both temperatures, while the Ras orthologue RasA only functions at 25 °C. These findings suggest that although some proteins that regulate the establishment of polarised growth in budding yeast are conserved in filamentous fungi, the circuitry and downstream effectors are differentially regulated to give rise to distinct cell types.

Survivorship and tube growth of reef‐building Serpula vermicularis (Polychaeta: Serpulidae) in two Scottish sea lochs

Abstract In the UK, reef formation by the tubicolous polychaete Serpula vermicularis L. has been recorded in only two sea lochs in Argyll, west Scotland. Serpula vermicularis aggregations are now confined to Loch Creran, those in Loch Sween having died out for unknown reasons. Survivorship and tube extension rates were measured in situ in order to compare habitat quality of the two sea lochs and to determine the feasibility of artificial restoration of Loch Sween reefs using stock translocated from Loch Creran. After labelling and measurement, clusters of inhabited tubes collected from Loch Creran were re‐planted at two sites in Loch Sween and two in Loch Creran in July 2004, and monitored at intervals before recovery and remeasurement in July 2005. In Loch Sween the tube clusters gradually disappeared over the monitoring period. Only remnants were left by May 2005 and no growth data were obtained. In Loch Creran 76% of the labelled tubes were relocated. Confirmed mortality over the year was 5.3% and mean tube extension rate was 33 mmy−1. There was no significant difference in tube growth between the two Loch Creran sites and inter‐individual differences accounted for most of the variability in the data. Individual tube extension declined significantly with worm body mass but mean extension showed no relationship to total worm biomass in each cluster. Annual tube extension rate in Loch Creran was low in comparison with literature data from other serpulids, suggesting that tube growth is strongly seasonal. The 10‐month persistence of some living worms in Loch Sween suggests that there is no physiological barrier to survival of stock translocated from Loch Creran but in situ video monitoring would be necessary to determine the cause of tube disappearance. Copyright © 2007 John Wiley & Sons, Ltd.

Significant depletions of the ionospheric plasma density at middle latitudes: A possible signature of equatorial spread F bubbles near the plasmapause

Plasma density irregularities in the equatorial F region ionosphere are generally called equatorial spread F (ESF). Large‐scale plasma bubbles associated with ESF processes are generated in the bottomside F region and penetrate the F peak to the topside F region. It is still not fully understood how high ESF bubbles can reach. In this paper, we present the measurements of deep depletions of the ionospheric plasma density at 840‐km altitude with the Defense Meteorological Satellite Program (DMSP) satellites in the evening sector on 29 October 2003. The plasma depletions occurred after an interval of strong southward interplanetary magnetic field (IMF). A prominent feature of the observations is that the plasma depletions occurred at very high magnetic latitudes (MLAT), as well as at equatorial latitudes. The equatorial depletions were identified as plasma bubbles. The depletions at middle latitudes (20°–46° MLAT) were separated from the conventional ionospheric midlatitude trough and identified as the extension of ESF flux tubes into these latitudes. It implies that the plasma bubble, which caused the emptied flux tube at 46° MLAT, reached the altitude of 6800 km over the magnetic equator. The observations may represent the highest altitude/latitude of plasma bubbles that has ever been reported in the literature. For the plasma depletions at even higher latitudes (47°–49° MLAT) near the subauroral polarization stream (SAPS)/midlatitude trough, there are two candidate generation mechanisms. One is the extension of ESF flux tubes into these latitudes, implying that the plasma bubbles reached the altitude of 8400 km over the magnetic equator. Because the SAPS/midlatitude trough corresponds to the plasmapause at the plasmaspheric heights, the observations suggest that ESF plasma bubbles may have reached the plasmapause. Another mechanism is a field‐aligned, low‐density structure between the plasmasphere and ionosphere, and the plasma structure is generated through the strong electric field in the subauroral polarization stream region.

Congenital Cholesteatoma: Risk Factors for Residual Disease and Retraction Pockets—A Report on 117 Cases

To define predictors of residuals and retraction pockets (RP) in children operated on for congenital cholesteatoma (CC). Retrospective review (1996-2005), academic center. One hundred seventeen patients treated for CC corresponding to modified Derlacki's criteria were included (median age, 6.5 yr). No case of RP at time of diagnosis, with a mean follow-up of 2.5 years after last surgery. Clinical and surgical data influencing outcome. Multivariate analysis. Two groups were defined after CC removal: group I (12 cases), no second look required and no case of subsequent re-intervention; group II (105 cases), planned second look always performed (mean delay, 12.1 mo), no difference of sex ratio (M/F = 2). Group I patients were younger than in group II (3.3 vs. 5.9 yr, P < .001). All of them had a normal contralateral eardrum and a disclosure of CC by routine examination (vs. 19% in group II, P < .001). In group I, the mass occupied one or two anterior quadrants (41.6% and 58.4%, respectively) versus more than two quadrants in 46.6% in group II. Residuals and RP rates were 41% and 15%, respectively (only in group II). Predictors for residuals were atticotomy (odds ratio [OR] 2.9, 95% confidence interval [CI] 1.3-6.7) and destruction of stapes (OR 4.3, 95% CI 1.7-10.5). Predictors for RP were eustachian tube extension (OR 6.8, 95% CI 1.7-26.8) and nonreconstructed atticotomy (OR 5.9, 95% CI 1.1-30.9). Young children with small CC had no recurrences. Residuals were more frequent in case of atticotomy and stapes destruction. RP occurred especially in cases of eustachian tube extension and if cartilage tympanoplasty was not performed. Tympanic and canal wall reinforcement should be considered in extensive CC.

Building the Right Ventricle

See related article, pages 1000–1007 Abnormal development of the arterial pole of the heart underlies a significant fraction of congenital heart defects. Critical steps in arterial pole development are formation of the myocardial outflow tract (or conotruncal region) and its subsequent division into separate left and right ventricular outlets. Division of the cylindrical outflow tract is a complex morphogenetic process driven by cardiac neural crest cell influx and associated with rotation of the myocardial wall and cell death, ensuring alignment of the ascending aorta and pulmonary trunk with the left and right ventricles.1–3 The transient nature of the embryonic outflow tract raises existential but also clinically relevant questions as to the origin of this structure and its fate. In an article in this issue, Rana et al have addressed the latter in the developing chick heart with important inferences for the origin of the right ventricle.4 Using scanning confocal microscopy, Rana et al monitored the rise and fall of the myocardial outflow tract. After a 4-fold increase in length to reach a maximum extension the myocardial outflow tract shortens 5-fold. At the same time a nonmyocardial component appears, giving rise to the ascending aorta and pulmonary trunk. Rana et al focused on the retraction phase by following the fate of clusters of DiI labeled cells in ovo at 2 developmental timepoints and concluded that the proximal outflow tract gives rise to a large part of the right ventricular free wall. Although the concept of ventricularisation of the proximal outflow tract (or conal absorption) to form the right ventricular outlet is not new,5–7 the extent to which myocardium initially in the outflow tract contributes to the trabeculated part of the free ventricular wall …

Visualization of outflow tract development in the absence of Tbx1 using an FgF10 enhancer trap transgene

Tbx1, the major gene underlying del22q11.2 or DiGeorge syndrome in humans, is required for normal development and septation of the cardiac outflow tract. The fibroblast growth factor 10 gene (Fgf10) and an Fgf10 enhancer trap transgene are expressed in outflow tract myocardial progenitor cells of the anterior heart field. To visualize outflow tract development in the absence of Tbx1, we have analyzed the expression profile of the Fgf10 enhancer trap transgene during outflow tract development in Tbx1(-/-) embryos. Transgene expression confirms hypoplasia of the distal outflow tract in the absence of Tbx1, and altered expression in pharyngeal mesoderm reveals loss of specific bilateral subpopulations of outflow tract progenitor cells and disruption of the posterior boundary of the anterior heart field. Our results support the conclusion that Tbx1 controls deployment of Fgf10-expressing progenitor cells during heart tube extension. Furthermore, although normal Fgf10 levels are dependent on Tbx1, loss of Fgf10 alleles does not significantly modify the cardiac phenotype of Tbx1 heterozygous or homozygous mutant embryos.

Nonlinear viscoelastic membranes

The subject of nonlinear viscoelastic membranes is an important class of problems within nonlinear viscoelasticity that involves interesting and important applications, computational issues and applied mathematics. The viscoelastic materials discussed in this paper are described by nonlinear single integral constitutive equations. After presenting the general constitutive framework, two fundamental membrane problems are formulated: the inflation of a circular membrane and the extension and inflation of a circular tube. Both problems involve large axially symmetric deformations and lead to a system of nonlinear partial differential–Volterra integral equations. A numerical method of solution is presented that combines methods for solving nonlinear Volterra integral equations and nonlinear ordinary differential equations. Finally, some properties of the equations are discussed that are related to the possibility that there may exist a critical time when the solution develops multiple branches.

Endoscopic retrograde cholangiography in post–orthotopic liver transplant population with Roux-en-Y biliary reconstruction

Endoscopic retrograde cholangiography (ERC) is a well-established modality for diagnostic and therapeutic maneuvers in pancreaticobiliary disorders. However, it is technically more challenging in patients with postsurgical anatomy like Roux-en-Y anastomoses. Its effectiveness in post-orthotopic liver transplantation (OLT) patients with Roux-en-Y biliary reconstruction has not been reported. We sought to assess the efficacy and safety of ERC in this patient population. A total of 132 OLTs with Roux-en-Y biliary reconstruction were performed at our institution from June 1998 to August 2005. Data from consenting patients who underwent ERC were reviewed once they were identified through computerized medical index system. Of 132 OLT patients with Roux-en-Y biliary reconstruction, 31 patients (9 female and 22 male subjects ranging in age from 11 months to 70 years) underwent ERC. The indication for liver transplant was end-stage liver disease or occurrence of cholangiocarcinoma from primary sclerosing cholangitis in 28 patients and a case each of chronic hepatitis C, alcoholic liver disease, and metastatic islet cell carcinoma. A variable-stiffness pediatric colonoscope was used in most cases. ERC indications were both diagnostic and therapeutic and included the following: evaluation of increased liver biochemistries and fever in 12 patients, dilation of anastomotic biliary strictures in 10 patients, removal of fractured biliary tube or retained biliary stent in 6 patients, and in 1 patient each, biliary stone removal, management of bile leak, and jejunal tube extension placement for nutritional purpose. ERC was successful in 22 patients (71%). There were no postprocedural complications. Although ERC is technically more difficult and time-consuming in OLT patients with Roux-en-Y anastomoses, these data suggest that ERC is an effective and safe diagnostic and therapeutic modality with few or no complications when performed by experienced endoscopists. ERC was successful in most patients and allowed therapeutic interventions that obviated the need for percutaneous radiological intervention or surgery.