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Tubular Structures (tubular + structure)

Distribution by Scientific Domains

Medical Sciences	34%
Chemistry	20%
Life Sciences	17%
Polymers and Materials Science	14%
Physics and Astronomy	5%
Earth and Environmental Science	5%

Selected Abstracts

An Ultrasonic Profiling Method for the Inspection of Tubular Structures

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2007
Francisco Gomez
These graphs not only show the inner contour of the pipe but also integrate the intensity of the echoes employed to create the profile. The enhanced profile is generated by superimposing the peak intensity from the returning echoes at the calculated x, y, and z coordinates where it reflected from the pipe wall. The proposed method is capable of showing anomalous conditions, inside pipes filled with liquid, with dimensions smaller than the theoretical lateral and axial resolution of the transducer, in contrast to traditional methods where these kinds of defects are not disclosed. The proposed inspection method and its capabilities were validated through the realization of simulations and experiments. The presented approach was particularly developed with the aim of scanning internal sections of pipes filled with liquid using rotary ultrasonic sonars, but it is expected that this research could be expanded to the inspection of other submerged structures, such as water tanks, or pressurized vessels. [source]

Nanodiamond Tipped and Coated Conical Carbon Tubular Structures,

CHEMICAL VAPOR DEPOSITION, Issue 7-8 2008
Boris Chernomordik
Abstract Studies of diamond nucleation and growth on conical carbon tubular structures show that the nucleation preferentially occurs at the tips, but only occurs on the sidewalls when they are pretreated with diamond or other powder dispersions, forming a nanodiamond coating. The high-resolution transmission electron microscopy (HRTEM) studies reveal that the diamond nucleation on the sidewalls may proceed through the formation of diamond nuclei within the walls at subsurface damage sites caused during pretreatment. In the case of experiments with low atomic hydrogen conditions, carbon onion structures are observed on the sidewalls but only with pretreatments. [source]

Isomeric Squaraine-Based [2]Pseudorotaxanes and [2]Rotaxanes: Synthesis, Optical Properties, and Their Tubular Structures in the Solid State

CHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2010
Min Xue
Abstract On the basis of formation of [2]pseudorotaxane complexes between triptycene-derived tetralactam macrocycles 1,a and 1,b and squaraine dyes, construction of squaraine-based [2]rotaxanes through clipping reactions were studied in detail. As a result, when two symmetrical squaraines 2,d and 2,e were utilized as templates, two pairs of isomeric [2]rotaxanes 3,a,b and 4,a,b as diastereomers were obtained, owing to the two possible linking modes of triptycene derivatives. It was also found, interestingly, that when a nonsymmetrical dye 2,g was involved, there existed simultaneously three isomers of [2]rotaxanes in one reaction due to the different directions of the guest threading. The 1H,NMR and 2D NOESY NMR spectra were used to distinguish the isomers, and the yield of [2]rotaxane 5,a with the benzyl group in the wider rim of the host 1,a was found to be higher than that of another isomer 5,b with an opposite direction of the guest, which indicated the partial selection of the threading direction. The X-ray structures of 3,b and 4,a showed that, except for the standard hydrogen bonds between the amide protons of the hosts and the carbonyl oxygen atoms of the guests, multiple ,,,,, stacking and CH,,,, interactions between triptycene subunits and aromatic rings of the guests also participated in the complexation. Crystallographic studies also revealed that the [2]rotaxane molecules 3,b and 4,a further self-assembled into tubular structures in the solid state with the squaraine dyes inside the channels. In the case of 4,a, all the nonsymmetrical macrocyclic molecules pointed in one direction, which suggests the formation of oriented tubular structures. Moreover, it was also found that the squaraines encapsulated in the triptycene-derived macrocycles were protected from chemical attack, and subsequently have potential applications in imaging probes and other biomedical areas. [source]

Poroma with sebaceous differentiation: Report of three cases

AUSTRALASIAN JOURNAL OF DERMATOLOGY, Issue 2 2010
Yuta Kurashige
ABSTRACT We herein report three cases of poroma, which showed sebaceous differentiation. The patients were two men and one woman, and the involved sites were the thigh, head and back. In all three cases, histopathological examination revealed anastomosing nests consisting of poroid cells proliferating into the dermis. Tubular structures lined by eosinophilic cuticular cells were scattered in the tumour nests. Furthermore, aggregations of mature sebocytes with vacuolated cytoplasm were also observed forming clusters, or intermingled with the poroma cells. Focal calcification was found within the nests in two cases. Sebaceous component were recognized in the presented three cases among the 62 cases (4.8%) examined in our department within the past 10 years. We also include a review of the 31 reported cases of poroma with sebaceous differentiation. None of them occurred in acral regions, where typical eccrine poromas predominate. The majority of cases were benign. This review indicates that some poromas may show sebaceous differentiation and be of apocrine lineage. [source]

Expression patterns of epiplakin1 in pancreas, pancreatic cancer and regenerating pancreas

GENES TO CELLS, Issue 7 2008
Tetsu Yoshida
Epiplakin1 (Eppk1) is a plakin family gene with its function remains largely unknown, although the plakin genes are known to function in interconnecting cytoskeletal filaments and anchoring them at plasma membrane-associated adhesive junction. Here we analyzed the expression patterns of Eppk1 in the developing and adult pancreas in the mice. In the embryonic pancreas, Eppk1+/Pdx1+ and Eppk1+/Sox9+ pancreatic progenitor cells were observed in early pancreatic epithelium. Since Pdx1 expression overlapped with that of Sox9 at this stage, these multipotent progenitor cells are Eppk1+/Pdx1+/Sox9+ cells. Then Eppk1 expression becomes confined to Ngn3+ or Sox9+ endocrine progenitor cells, and p48+ exocrine progenitor cells, and then restricted to the duct cells and a cells at birth. In the adult pancreas, Eppk1 is expressed in centroacinar cells (CACs) and in duct cells. Eppk1 is observed in pancreatic intraepithelial neoplasia (PanIN), previously identified as pancreatic ductal adenocarcinoma (PDAC) precursor lesions. In addition, the expansion of Eppk1-positive cells occurs in a caerulein-induced acute pancreatitis, an acinar cell regeneration model. Furthermore, in the partial pancreatectomy (Px) regeneration model using mice, Eppk1 is expressed in "ducts in foci", a tubular structure transiently induced. These results suggest that Eppk1 serves as a useful marker for detecting pancreatic progenitor cells in developing and regenerating pancreas. [source]

Waveguide Modulator by Energy Remote Relay from Binary Organic Crystalline Microtubes

ADVANCED MATERIALS, Issue 41 2009
Qing Liao
Uniform crystalline binary microtubes in which perylene molecules are dispersed in a crystalline TPI matrix are fabricated. The perylene component plays a crucial role as an etching-assistant in the formation of the hollow tubular structure. The annular cavity of the microtubes enables them to act as waveguide modulators, in which wavelength redistribution occurs because of a remote energy relay process. [source]

Single-Crystalline Scroll-Type Nanotube Arrays of Copper Hydroxide Synthesized at Room Temperature,

ADVANCED MATERIALS, Issue 10 2003
W. Zhang
A novel nanolayer-rolled tubular structure of Cu(OH)2 has been grown in solution at ambient temperature and pressure. Significantly, the Cu(OH)2 nanotubes are phase-pure single crystallites and are arrayed uniformly on copper substrates (see Figure). The reaction conditions for the fabrication of the nanotube arrays are examined and possible growth mechanisms are discussed. [source]

Theoretical study of the interaction between sodium ion and a cyclopeptidic tubular structure

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007
Francesco Ferrante
Abstract DFT calculations have been carried out to describe the pathway of a sodium ion along the stacking direction of a tubular structure set up by five cyclopeptidic units, which can be considered a suitable model of a hollow tubular structure of indefinite length. A lattice of points inside the tubular structure is defined and the DFT interaction energy values with a sodium ion are obtained. The data allow predicting a zigzag path of the ion inside the hosting structure. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source]

Biomechanics of the rostrum and the role of facial sutures

JOURNAL OF MORPHOLOGY, Issue 1 2003
Katherine L. Rafferty
Abstract The rostrum is a large diameter, thin-walled tubular structure that receives loads from the teeth. The rostrum can be conceptualized both as a rigid structure and as an assemblage of several bones that interface at sutures. Using miniature pigs, we measured in vivo strains in rostral bones and sutures to gain a better understanding of how the rostrum behaves biomechanically. Strains in the premaxillary and nasal bones were low but the adjacent maxillary-premaxillary, internasal, and intermaxillary suture strains were larger by an order of magnitude. While this finding emphasizes the composite nature of the rostrum, we also found evidence in the maxillary and nasal bones for rigid structural behavior. Namely, maxillary strain is consistent with a short beam model under shear deformation from molar loading. Strain in the nasal bones is only partially supported by a long beam model; rather, a complex pattern of dorsal bending of the rostrum from incisor contact and lateral compression is suggested. Torsion of the maxilla is ruled out due to the bilateral occlusion of pigs and the similar working and balancing side strains, although it may be important in mammals with a unilateral bite. Torsional loading does appear important in the premaxillae, which demonstrate working and balancing side changes in strain orientation. These differences are attributed to asymmetrical incisor contact occurring at the end of the power stroke. J. Morphol. 257:33,44, 2003. © 2003 Wiley-Liss, Inc. [source]

COMPARATIVE MORPHOLOGY AND MOLECULAR PHYLOGENETIC ANALYSIS OF THREE NEW SPECIES OF THE GENUS KARENIA (DINOPHYCEAE) FROM NEW ZEALAND,

JOURNAL OF PHYCOLOGY, Issue 1 2004
Allison J. Haywood
Three new dinoflagellate species, Karenia papilionacea sp. nov., Karenia selliformis sp. nov., and Karenia bidigitata sp. nov., were compared with the toxic species Karenia mikimotoi (Miyake & Kominami ex Oda) G. Hansen & Moestrup, Karenia brevis (Davis) G. Hansen & Moestrup, and Karenia brevisulcata (Chang) G. Hansen & Moestrup using the same fixative. Distinguishing morphological characters for the genus Karenia included a smooth theca and a linear apical groove. The new species can be distinguished on the basis of morphological characters of vegetative cells that include the location and shape of the nucleus; the relative excavation of the hypotheca; the characteristics of apical and sulcal groove extensions on the epitheca; the cellular shape, size, and symmetry; the degree of dorsoventral compression; and the presence of an apical protrusion or carina. Species with pronounced dorsoventral compression swim in a distinctive fluttering motion. An intercingular tubular structure traversing the proximal and distal ends of the cingulum is common to the species of Karenia, Karlodinium micrum (Leadbeater & Dodge) J. Larsen, Gymnodinium pulchellum J. Larsen, and Gyrodinium corsicum Paulmier. Molecular phylogenetic analyses of rDNA sequence alignments show that the new species are phylogenetically distinct but closely related to K. mikimotoi and K. brevis. [source]

Sculpturing a fibular flap: Combined horizontal/vertical osteotomy and ostectomy for reconstruction of complex craniofacial defects with one flap

MICROSURGERY, Issue 8 2005
Ayhan Okumus M.D.
A fibular flap has great versatility in reconstructive procedures. Osteomies and ostectomies enable the flap to be used for variable defects. We used combined horizontal/vertical osteotomy and ostectomy for reconstruction of complex craniofacial defects with one flap in two patients. Vertical osteotomy transforms the tubular structure of a fibula into a flat bone that can be used for reconstruction of wider defects with less vertical height. Neither vertical osteotomy nor ostectomy had negative effects on viability and bony healing of the segments in our patients. We think that the fibular flap, thanks to its versatility, can be used for reconstruction of complex orbito-zygomatic and orbito-cranial defects successfully. © 2005 Wiley-Liss, Inc. Microsurgery 25:589,595, 2005. [source]

Polycystins: what polycystic kidney disease tells us about sperm

MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2004
Abraham L. Kierszenbaum
Abstract Experimental evidence indicates that the membrane-associated proteins polycystin-1 and polycystin-2 operate as a receptor-calcium channel complex that regulates signaling pathways essential for modulation of renal tubulogenesis. Polycystic kidney disease is characterized by defective renal tubular structure and results from mutations in either PKD1 or PKD2 genes. Recent data suggest that polycystin-1 and polycystin-2 might localize to primary cilium in principal cells of renal collecting tubules and are thought to act as mechanosensors of fluid flow and contents. Ciliary bending by fluid flow or mechanical stimulation induce Ca2+ release from intracellular stores, presumably to modulate ion influx in response to tubular fluid flow. Polycystins are also emerging as playing a significant role in sperm development and function. Drosophila polycystin-2 is associated with the head and tail of mature sperm. Targeted disruption of the PKD2 homolog results in nearly complete male sterility without disrupting spermatogenesis. Mutant sperm are motile but are unable to reach the female storage organs (seminal receptacles and spermathecae). The sea urchin polycystin-1-equivalent suPC2 colocalizes with the polycystin-1 homolog REJ3 to the plasma membrane over the acrosomal vesicle. This localization site suggests that the suPC2-REJ3 complex may function as a cation channel mediating acrosome reaction when sperm contact the jelly layer surrounding the egg at fertilization. Future studies leading to the identification of specific ligands for polycystins, including the signaling pathways, might define the puzzling relationship between renal tubular morphogenesis and sperm development and function. Mol. Reprod. Dev. 67: 385,388, 2004. © 2004 Wiley-Liss, Inc. [source]

Ultrastructure of sperm ,tail stump' defect in wild boar

ANDROLOGIA, Issue 1 2009
M. L. Fischman
Summary Sperm ,tail stump' defect was found in ejaculates of a wild boar maintained in captivity. It was in good physical condition, the testes and genital tract were found to be of normal size and consistency. There was no evidence of macroscopic abnormalities at the clinical analysis and at necropsy. The volume and concentration of the semen samples obtained by electroejaculation were lower than normal. The slides examined contained a high level of abnormal spermatozoa (52.7%). The most frequent morphological finding was a droplet-like form attached to the base of the head or a very short stump. The non-stumped spermatozoa had no normal tail but a shortened one. Analysing the histological structure with light microscopy, no ring of spermatozoa was observed lining the lumen of the seminiferous tubules and the characteristically cellular structure was not conserved. The ultrastructural examination evidenced a disorganisation of the normal tubular structure of the flagellum, with lost of regular pattern of the axial bundle of fibrils and the mitochondrial helix. The origin of this abnormality is unknown. [source]

Environmental sex determination, external sex differentiation and structure of the androgenic gland in the Pacific white shrimp Litopenaeus vannamei (Boone)

AQUACULTURE RESEARCH, Issue 15 2006
Rafael Campos-Ramos
Abstract Environmental effects on sex determination in Litopenaeus vannamei were studied by rearing day 1 postlarvae at three temperatures, under three photoperiods, at high density and by starving. None of the environmental conditions affected sex determination or differential development of gender in this species. From day 50, the development of the endopodite of the first pair of pleopods revealed the first external differentiation, showing a triangular structure with three setae in females, whereas a tubular structure remained in males. Juvenile shrimp sex differentiation took place from days 50,90, independent of size, only if postlarvae reached a development threshold of 150 mg of body weight and 20 mm of body length previously. Histology and scanning electron microscopy of the vas deferens revealed that the androgenic gland (AG) is a single 2-mm cord attached in the subterminal ejaculatory region, just before the distal vas deferens narrows. The AG is composed of large oval cells containing vacuolated cytoplasm, and each cell has a prominent rounded nucleus, similar to all descriptions of the AG in Malacostracans, so we assume that it should have the same function in sex differentiation. [source]

The fine needle aspiration biopsy diagnostic criteria of proliferative breast lesions: A retrospective statistical analysis of criteria for papillomas and radial scar lesions

DIAGNOSTIC CYTOPATHOLOGY, Issue 7 2007
Andrew Field F.R.C.P.A.
Abstract This study aimed to analyze statistically the accuracy of fine needle aspiration biopsy cytological criteria in diagnosing epithelial hyperplasia with atypia (EHA), papillary lesions (PAP), and radial scar/complex sclerosing lesions (RS/CSL). The 42 criteria studied were extracted from a literature review and those developed and used in our department. Cytological cases with diagnoses of EHA, PAP, and RS/CSL for the period of 1997,2001 were correlated with relevant histological follow-up and the positive predictive power of these diagnoses have been presented in an earlier publication. Some 77 cases with definite, specific histological diagnoses of atypia or a more severe lesion, PAP and RS/CSL, were reviewed and scored using 55 cytological criteria. As the group of EHA and RS/CSL yielded a smaller number of cases, these were grouped together in the statistical analysis and compared to PAP. The cytological features, which were most diagnostic for PAP, were stellate (Odds ratio 1.75) and meshwork (Odds ratio 3.29) tissue fragments, while the presence of tubular structures was inversely proportional to the histological outcome of PAP. True papillary fragments were uncommon and not statistically significant in diagnosing PAP of the breast. Diagn. Cytopathol. 2007;35:386,397. © 2007 Wiley-Liss, Inc. [source]

CHARACTERISTIC INTRADUCTAL ULTRASONOGRAPHIC FEATURES OF PORTAL BILIOPATHY

DIGESTIVE ENDOSCOPY, Issue 4 2008
Tsukasa Ikeura
The term ,portal biliopathy' is used to describe cholangiographic abnormalities seen in patients with extrahepatic portal vein obstruction. Portal biliopathy is mainly composed of extrinsic compression of the bile duct caused by enlarged venous collaterals. Herein we report a case of asymptomatic portal biliopathy caused by idiopathic extrahepatic portal vein obstruction. In the present case, intraductal ultrasonography showed normal anatomic layers of the distal common bile duct wall, surrounded by numerous tubular structures which were suspected to be collateral vessels. We suggest that intraductal ultrasonography may be a helpful imaging procedure for detection of this pathological condition. [source]

Garnet-filled trails associated with carbonaceous matter mimicking microbial filaments in Archean basalt

GEOBIOLOGY, Issue 4 2009
K. LEPOT
The study of the earliest traces of life on Earth can be complicated by abiotically formed biomorphs. We report here the finding of clustered micrometer-sized filaments of iron- and calcium-rich garnets associated with carbonaceous matter in an agate amygdale from a 2.7-billion-year-old basalt of the Maddina Formation, Western Australia. The distribution of carbonaceous matter and the mineral phases composing the filaments were analyzed using a combination of confocal laser scanning microscopy, laser-Raman micro-spectroscopy, focused ion beam sectioning and transmission electron microscopy. The results allow consideration of possible biogenic and abiotic processes that produced the filamentous structures. The filaments have a range of sizes, morphologies and distributions similar to those of certain modern iron-mineralized filamentous bacteria and some ancient filamentous structures interpreted as microfossils. They also share a high morphological similarity with tubular structures produced by microbial boring activity. However, the microstructures and the distribution of carbonaceous matter are more suggestive of an abiotic origin for the filaments. They are characteristic features of trails produced by the displacement of inclusions associated with local dissolution of their silica matrix. Organic compounds found in kerogen or bitumen inclusions may have contributed significantly to the dissolution of the quartz (or silica gel) matrix driving filamentous growth. Discriminating the products of such abiotic organic-mediated processes from filamentous microfossils or microbial borings is important to the interpretation of the scarce Precambrian fossil record and requires investigation down to the nanoscale. [source]

Notch2 signaling promotes biliary epithelial cell fate specification and tubulogenesis during bile duct development in mice,

HEPATOLOGY, Issue 3 2009
Jan S. Tchorz
Intrahepatic bile duct (IHBD) development begins with the differentiation of hepatoblasts into a single continuous biliary epithelial cell (BEC) layer, called the ductal plate. During ductal plate remodeling, tubular structures arise at distinct sites of the ductal plate, forming bile ducts that dilate into the biliary tree. Alagille syndrome patients, who suffer from bile duct paucity, carry Jagged1 and Notch2 mutations, indicating that Notch2 signaling is important for IHBD development. To clarify the role of Notch2 in BEC differentiation, tubulogenesis, and BEC survival, we developed a mouse model for conditional expression of activated Notch2 in the liver. We show that expression of the intracellular domain of Notch2 (Notch2ICD) differentiates hepatoblasts into BECs, which form additional bile ducts in periportal regions and ectopic ducts in lobular regions. Additional ducts in periportal regions are maintained into adulthood and connect to the biliary tight junction network, resulting in an increased number of bile ducts per portal tract. Remarkably, Notch2ICD-expressing ductal plate remnants were not eliminated during postnatal development, implicating Notch2 signaling in BEC survival. Ectopic ducts in lobular regions did not persist into adulthood, indicating that local signals in the portal environment are important for maintaining bile ducts. Conclusion: Notch2 signaling regulates BEC differentiation, the induction of tubulogenesis during IHBD development, and BEC survival. (HEPATOLOGY 2009.) [source]

Anatomy of the lactating human breast redefined with ultrasound imaging

JOURNAL OF ANATOMY, Issue 6 2005
D. T. Ramsay
Abstract The aim of this study was to use ultrasound imaging to re-investigate the anatomy of the lactating breast. The breasts of 21 fully lactating women (1,6 months post partum) were scanned using an ACUSON XP10 (5,10 MHz linear array probe). The number of main ducts was measured, ductal morphology was determined, and the distribution of glandular and adipose tissue was recorded. Milk ducts appeared as hypoechoic tubular structures with echogenic walls that often contained echoes. Ducts were easily compressed and did not display typical sinuses. All ducts branched within the areolar radius, the first branch occurring 8.0 ± 5.5 mm from the nipple. Duct diameter was 1.9 ± 0.6 mm, 2.0 ± 90.7 mm and the number of main ducts was 9.6 ± 2.9, 9.2 ± 2.9, for left and right breast, respectively. Milk ducts are superficial, easily compressible and echoes within the duct represent fat globules in breastmilk. The low number and size of the ducts, the rapid branching under the areola and the absence of sinuses suggest that ducts transport breastmilk, rather than store it. The distribution of adipose and glandular tissue showed wide variation between women but not between breasts within women. The proportion of glandular and fat tissue and the number and size of ducts were not related to milk production. This study highlights inconsistencies in anatomical literature that impact on breast physiology, breastfeeding management and ultrasound assessment. [source]

Squamous cell apocrine hidradenoma

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 10 2007
Jorge Angulo
Apocrine hidradenoma is a benign adnexal neoplasm with apocrine differentiation. The neoplasm is composed of four different types of epithelial cells, including pale or clear cells, polygonal cells, mucinous cells and squamous cells, with variable proportions of them from case to case. In most examples of this neoplasm, clear or the polygonal cells are predominant, whereas the other types of neoplastic cells are less abundant. We report two cases of apocrine hidradenoma mostly composed of squamous cells. Histopathologic examination showed that the neoplasms were composed of both solid and cystic areas. The solid aggregations of neoplastic cells were composed of a peripheral layer of basaloid polygonal cells, whereas squamous cells forming the bulk of the aggregations. These squamous cells showed large eosinophilic cytoplasm and vesicular nuclei with prominent nucleoli. In one case, small foci of mucinous cells could also be seen in some aggregations of neoplastic cells, mostly around ductal structures. In both the cases, some of the tubular structures lined by epithelial cells showed evidence of decapitation secretion in their luminal border. The neoplastic stroma consisted of sclerotic collagen bundles when compared with adjacent normal dermis, and artefactual clefts separated the neoplasms from the surrounding tissue. The rare cases described in this report are exceptional because most of the neoplastic cells showed squamous appearance and for that reason we think that squamous cell apocrine hidradenoma is the most appropriate name for these neoplasms. [source]

Lipomatous mixed tumor with follicular differentiation of the skin

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 5 2006
Satomi Kasashima
A very rare case of cutaneous mixed tumor with numerous adipose tissue and hair follicular structures in a 67-year-old Japanese male was reported. A well-circumscribed tumor was in the subcutaneous tissue of the cheek and far from the parotid gland. Histologically, the tumor consisted of an admixture of the adipose tissue, fibromyxoid tissue with spindle cells, and branching tubular structures. Outer layers of ductal epithelial cells and single spindle cells were often in a transition, likely as typical mixed tumor. Branching ducts connected with keratinous cysts, strands of trichoblastic basophilic cells and clear cell nests. There was a gradual transition, between small-sized adipocytes and vacuolated spindle cells. No chondroid stroma was seen. To our knowledge, this tumor is the first case of a lipomatous mixed tumor with hair follicular differentiation. The case indicates an additional wide spectrum of histologic appearances of cutaneous mixed tumor. [source]

Dysplasia and carcinoma development in a repeated dextran sulfate sodium-induced colitis model

JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 10 2002
Isao Okayasu
Abstract Background: As an important mechanism underlying the increased risk of colorectal carcinoma development in patients with long-standing ulcerative colitis, promotion as a result of the regenerative process has been proposed. In the present study, a dysplasia-carcinoma sequence in a novel repeated colitis model in mice is documented. Methods: Repeated colitis was induced by nine administration cycles of 3% dextran sulfate sodium (DSS; molecular weight, 54 000): each administration cycle comprised 3% DSS for 7 days followed by distilled water for the subsequent 14 days, to give conditions similar to the clinically observed active and remission phases in humans. Results: Multiple colorectal tumors (nine low- and four high-grade dysplasias and two carcinomas) developed in 25 mice. These neoplastic lesions consisted of tubular structures, presenting as various types of elevated, flat and depressed tumor, similar to those in ulcerative colitis patients. A time-course study with assessment of the severity of colitis and in vivo bromodeoxyuridine uptake during a single 3% DSS administration cycle revealed a high level of regenerative activity in the colitis-affected mucosal epithelia. Conclusion: Thus, with the present repeated colitis model, regeneration and neoplastic lesions were apparent, the biological features of which provide evidence of a colorectal dysplasia,invasive carcinoma sequence in ulcerative colitis. [source]

Nerve conduits and growth factor delivery in peripheral nerve repair

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2007
Lukas A. Pfister
Abstract Peripheral nerves possess the capacity of self-regeneration after traumatic injury. Transected peripheral nerves can be bridged by direct surgical coaptation of the two nerve stumps or by interposing autografts or biological (veins) or synthetic nerve conduits (NC). NC are tubular structures that guide the regenerating axons to the distal nerve stump. Early synthetic NC have primarily been made of silicone because of the relative flexibility and biocompatibility of this material and because medical-grade silicone tubes were readily available in various dimensions. Nowadays, NC are preferably made of biodegradable materials such as collagen, aliphatic polyesters, or polyurethanes. Although NC assist in guiding regenerating nerves, satisfactory functional restoration of severed nerves may further require exogenous growth factors. Therefore, authors have proposed NC with integrated delivery systems for growth factors or growth factor,producing cells. This article reviews the most important designs of NC with integrated delivery systems for localized release of growth factors. The various systems discussed comprise NC with growth factors being released from various types of matrices, from transplanted cells (Schwann cells or mesenchymal stem cells), or through genetic modification of cells naturally present at the site of injured tissue. Acellular delivery systems for growth factors include the NC wall itself, biodegradable microspheres seeded onto the internal surface of the NC wall, or matrices that are filled into the lumen of the NC and immobilize the growth factors through physical-chemical interactions or specific ligand-receptor interactions. A very promising and elegant system appears to be longitudinally aligned fibers inserted in the lumen of a NC that deliver the growth factors and provide additional guidance for Schwann cells and axons. This review also attempts to appreciate the most promising approaches and emphasize the importance of growth factor delivery kinetics. [source]

Multistep filling of porous silicon with conductive polymer by electropolymerization

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009
Kazuhiro Fukami
Abstract The filling of porous silicon with polypyrrole by electropolymerization was investigated. The filling with polypyrrole proceeded preferentially along the porous silicon wall, leading to the formation of tubular structures. By repeating the porosification, the pore filling and the additional porosification, through-tubes of polypyrrole were formed in macropores. The technique to form through-tube was also applied to medium-sized pores. A double layer with polypyrrole was produced by the repetition of porosification and pore filling twice. The immobilization of glucose oxidase was performed by electropolymerization in an aqueous solution containing glucose oxidase and pyrrole. Glucose oxidase was immobilized physically in the polypyrrole film. In the double layer, the sensitivity of glucose oxidase was measured by electrochemical oxidation of hydrogen peroxide, which was produced by the enzymatic reaction of glucose oxidase to gluconolactone. When glucose oxidase was immobilized in the upper layer, glucose was detected sensitively. On the other hand, when glucose oxidase was immobilized in the lower layer, the sensing current showed a slow and a low response. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Mechanical properties of auxetic tubular truss-like structures

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2008
F. Scarpa
Abstract The mechanical properties of cellular tubular structures made of centresymmetric cells are evaluated using analytical and numerical simulations. A theoretical model based on bending stiffness of the single ribs composing the unit cell of the tubes is developed, providing estimations for the Poisson's ratios and uniaxial stiffness of the tubular grid-like structures, as well as their Eulerian buckling load. Full 3D Finite Element models in linear elastic regime are used to validate the theoretical results. A continuum nonlinear tube bending model is also presented to show the dependence of the curvature-bending moment versus the Poisson's ratio of the core. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The rotational molding of a thermotropic liquid crystalline polymer

POLYMER ENGINEERING & SCIENCE, Issue 3 2005
Eric Scribben
Thermotropic liquid crystalline polymers (TLCPs) exhibit a number of mechanical and physical properties such as excellent chemical resistance, low permeability, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance, which make them desirable as a rotationally molded storage vessel. However, there are no reports in the technical literature of the successful rotational molding of TLCPs. In this article, conditions are identified that lead to the successful rotational molding of a TLCP, Vectra B 950. First, a technique was developed to produce particles suitable for rotational molding because TLCPs cannot be ground into a free-flowing powder. Second, because the viscosity at low shear rates can be detrimental to the sintering process, coalescence experiments with isolated particles were carried out to determine the thermal and environmental conditions at which sintering should occur. These conditions were then applied to static sintering experiments to determine whether coalescence and densification of the bulk powder would occur. Finally, the powders were successfully rotationally molded into tubular structures in a single axis, lab-scale device. The density of the molded structure was essentially equivalent to the material density and the tensile strength and modulus were approximately 18 MPa and 2 GPa, respectively. POLYM. ENG. SCI., 45:410,423, 2005. © 2005 Society of Plastics Engineers [source]

Angioarchitecture of the Branchial Arterial System of Carp (Cyprinus carpio L.)

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005
N. Ito
The arterial system of the gills of carp and its histological structure were studied light and electron microscopically by making Mercox or Neoplane Latex corrosion cast preparations. Four pairs of afferent and efferent branchial arteries, and a pair of afferent and efferent pseudobranchial arteries were identified in the branchial arterial system. The 1st and 2nd afferent branchial arteries are given off directly from the ventral aorta, and the 3rd and 4th afferent arteries originate from their common trunk, which is branched off from the ventral aorta caudal to the origin of the former branchial arteries. Numerous afferent filamental arteries are connected to the lamellar blood capillary networks in the gill lamellae via afferent lamellar arterioles, and efferent filamental arteries followed the efferent lamellar arterioles are converged into four efferent branchial arteries that are connected to the dorsal aorta. To the pseudobranchia, afferent pseudobranchial arteries are connected with the ventral branches of the 1st efferent branchial arteries to provide arterial blood to the organ through the afferent mandibular arteries. Afferent pseudobranchial lamellar arterioles originating from the afferent pseudobranchial filamental arteries are connected with the blood capillary networks in the pseudobranchial lamellae, and blood in the capillary networks is drained into the efferent pseudobranchial filamental arteries via 2-4 pseudobranchial lamellar arterioles. Branches of the efferent pseudobranchial filamental arteries are connected with the arteries to the eyeballs and provide blood to choroid of the vascular tunic of them. Pseudobranchial cells surrounding lamellar capillaries in the pseudobranchia are furnished with abundant mitochondria and tubular structures, and the histological findings suggest the cells may share an ability to exchange physiological materials between the cells and the blood in the capillary networks of pseudobranchia. [source]

Metastatic sclerosing mesothelioma in a cow

AUSTRALIAN VETERINARY JOURNAL, Issue 7 2002
E BEYTUT
Metastatic sclerosing mesothelioma in a crossbred cow is described. Accumulation of fluid in the abdominal cavity and solitary or coalesced nodules on the peritoneum, hepatic capsule and visceral pleurae, were observed after slaughter. Histological examination of the nodules revealed that they were composed of tubular structures supported by massive connective tissue. The lumina of the tubules were lined by solitary neoplastic mesothelial cells, or occasionally small groups of such cells were observed in the lumen. Identification of the mesothelial character of the tumours was dependent upon the histopathological and cytological characteristics of the nodules and histochemical stainings. [source]

Immunohistochemical staining of cutaneous tumours with G-81, a monoclonal antibody to dermcidin

BRITISH JOURNAL OF DERMATOLOGY, Issue 1 2004
Y. Minami
Summary Background Recently, the novel antimicrobial peptide named dermcidin (DCD) was reported in human eccrine sweat glands. Objectives We investigated the expression of DCD in a variety of cutaneous tumours in order to assess the usefulness of the monoclonal antibody (G-81), which recognizes a fragment of DCD. Patients/methods We studied the immunoreactivity of the G-81 antibody on 197 cutaneous tumours. Results A total of 13 of 26 cutaneous mixed tumours showed substantial immunoreactivity. In contrast all the following cases were completely unreactive: (i) epithelial tumours (seborrhoeic keratosis, squamous cell carcinoma, Bowen's disease, actinic keratosis, genital Paget's disease); (ii) follicular tumours (basal cell carcinoma, trichilemmoma, trichoepithelioma, trichoblastoma, keratoacanthoma, proliferating trichilemmal tumour, pilomatricoma); (iii) melanocytic tumours (malignant melanoma, naevus cell naevus, Spitz naevus, blue naevus); (iv) neural tumours (schwannoma, neurofibroma, Merkel cell neoplasm); (v) mesenchymal tumours (soft fibroma, dermatofibroma, dermatofibrosarcoma protuberans, vascular leiomyoma, leiomyosarcoma, lipoma, juvenile xanthogranuloma, angiomyoma); and (vi) other sweat gland tumours (poroid neoplasms, syringoma, cylindroma, clear cell hidradenoma, spiradenoma, syringoid eccrine carcinoma, mucinous carcinoma, apocrine cystadenoma, syringocystadenoma papilliferum, apocrine adenocarcinoma). Twenty-six cutaneous mixed tumours were considered from histopathological findings to be the apocrine type, but 13 of 26 mixed tumours contained some DCD-immunopositive cells that possibly differentiate into eccrine secretory glands. Conclusions We found the expression of DCD in tubular structures of 50% of cutaneous mixed tumours with apocrine differentiation. These results suggest that a number of cutaneous mixed tumours show both eccrine and apocrine differentiation in the same neoplasm. [source]