Home About us Contact
|
Home About us Contact | ||
|
|
||
Short Segment (short + segment)
Selected AbstractsZircon sensitive high mass-resolution ion microprobe U,Pb and fission-track ages for gabbros and sheeted dykes of the Taitao ophiolite, Southern Chile, and their tectonic implicationsISLAND ARC, Issue 1 2006Ryo Anma Abstract The Late Miocene,Pliocene Taitao ophiolite is composed of a complete sequence of classic oceanic lithosphere and is exposed approximately 50 km southeast of the Chile triple junction, where the Chile Ridge subducts beneath the South American Plate. Gabbros and ultramafic rocks are folded into a complex pattern, but only evidence for block rotation has been reported in the overriding sheeted dyke complex. In the present study, sensitive high mass-resolution ion microprobe U,Pb and fission-track dating methods were applied to zircon crystals separated from gabbros and sheeted dykes. Two sets of radiometric ages of gabbros range between 5.9 ± 0.4 and 5.6 ± 0.1 Ma. These ages coincide within their error ranges and imply rapid intrusion and cooling of gabbros. The U,Pb age of a dacite dyke intruded into the sheeted dyke complex was determined to be 5.2 ± 0.2 Ma. These data indicate that the magmas of the Taitao ophiolite were formed during the 6 Ma Chile Ridge collision event and emplaced in a shorter period than previously thought. A short segment of the Chile Mid-oceanic Ridge must have been emplaced during the 6 Ma event. [source] Tracheal agenesis: management of the first 10 months of lifePEDIATRIC ANESTHESIA, Issue 9 2004S. Baroncini-Cornea MD Summary Tracheal agenesis is a potentially lethal congenital anomaly, appearing only at birth. We describe a newborn preterm infant who presented with immediate respiratory distress and no audible cry. There was almost complete tracheal agenesis with a very short segment of distal trachea (only two tracheal rings) arising from the anterior wall of the esophagus, before dividing into the mainstem bronchi. The anomaly was unsuspected prenatally, as the scan showed pyloric atresia and complex congenital cardiac disease. Despite the patient's difficult course, with correction of the rare-associated malformations (cardiac and gastrointestinal tract anomalies), the fact that the child is lively and neurologically normal for her age, requires that we now consider the patency of the airway and the possibility of surgical correction, in accordance with a good quality of life. [source] Specialized intestinal metaplasia in patients with gastro-oesophageal reflux diseaseBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 1 2000E. Carton Background: There is an increasing awareness that short (less than 3 cm) segments of Barrett's epithelium and macroscopically normal cardia epithelium may harbour specialized intestinal metaplasia (SIM), a premalignant phenotype. The prevalence of SIM was studied prospectively in an unselected population of patients attending for endoscopy, and the association of SIM with symptoms, lifestyle, medication, endoscopic oesophagitis and carditis was investigated. Methods: Two hundred consecutive patients underwent endoscopy. Biopsies taken from just below the squamocolumnar junction were stained for SIM, and were analysed for carditis and Helicobacter pylori infection. A detailed questionnaire of symptoms, tobacco consumption and the use of proton pump inhibitors was completed. Results: Forty-two patients (21 per cent) had SIM: 19 (15 per cent) of 126 in an endoscopically normal oesophagus, 15 (24 per cent) of 63 in a short segment of Barrett's epithelium and eight of 11 in classical Barrett's oesophagus. There was a significant association between SIM and carditis (P < 0·0001) and endoscopic oesophagitis (P = 0·03). Conclusion: SIM is prevalent in patients undergoing endoscopy, does not correlate with symptoms or H. pylori infection, but is significantly associated with endoscopic and pathological markers of gastro-oesophageal reflux. © 2000 British Journal of Surgery Society Ltd [source] Structures and Stabilities of Small DNA Dumbbells with Watson,Crick and Hoogsteen Base PairsCHEMBIOCHEM, Issue 7 2003Nuria Escaja Dr. Abstract The structures and stabilities of cyclic DNA octamers of different sequences have been studied by NMR and CD spectroscopy and by restrained molecular dynamics. At low oligonucleotide concentrations, some of these molecules form stable monomeric structures consisting of a short stem of two base pairs connected by two mini-loops of two residues. To our knowledge, these dumbbell-like structures are the smallest observed to date. The relative stabilities of these cyclic dumbbells have been established by studying their melting transitions. Dumbbells made up purely of GC stems are more stable than those consisting purely of AT base pairs. The order of the base pairs closing the loops also has an important effect on the stabilities of these structures. The NMR data indicate that there are significant differences between the solution structures of dumbbells with G,C base pairs in the stem compared to those with A,T base pairs. In the case of dumbbells with G,C base pairs, the residues in the stem form a short segment of a BDNA helix stabilized by two Watson,Crick base pairs. In contrast, in the case of d,pCATTCATT,, the stem is formed by two A,T base pairs with the glycosidic angles of the adenine bases in a syn conformation, most probably forming Hoogsteen base pairs. Although the conformations of the loop residues are not very well defined, the thymine residues at the first position of the loop are observed to fold back into the minor groove of the stem. [source] Identification of mosquito bloodmeals using mitochondrial cytochrome oxidase subunit I and cytochrome b gene sequencesMEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2008J. S. TOWNZEN Abstract Primer pairs were designed and protocols developed to selectively amplify segments of vertebrate mitochondrial cytochrome oxidase subunit 1 (COI) and cytochrome b (Cyt b) mtDNA from the bloodmeals of mosquitoes (Diptera: Culicidae). The protocols use two pairs of nested COI primers and one pair of Cyt b primers to amplify short segments of DNA. Resultant sequences are then compared with sequences in GenBank, using the BLAST function, for putative host identification. Vertebrate DNA was amplified from 88% of our sample of 162 wild-caught, blood-fed mosquitoes from Oregon, U.S.A. and GenBank BLAST searches putatively identified 98% of the amplified sequences, including one amphibian, seven mammalian and 14 avian species. Criteria and caveats for putative identification of bloodmeals are discussed. [source] Syndromes of disordered chromatin remodelingCLINICAL GENETICS, Issue 2 2003J Ausió Syndromes of disordered ,chromatin remodeling' are unique in medicine because they arise from a general deregulation of DNA transcription caused by mutations in genes encoding enzymes which mediate changes in chromatin structure. Chromatin is the packaged form of DNA in the eukaryotic cell. It consists almost entirely of repeating units, called nucleosomes, in which short segments of DNA are wrapped tightly around a disk-like structure comprising two subunits of each of the histone proteins H2A, H2B, H3 and H4. Histone proteins are covalently modified by a number of different adducts (i.e. acetylation and phosphorylation) that regulate the tightness of the DNA,histone interactions. Mutations in genes encoding enzymes that mediate chromatin structure can result in a loss of proper regulation of chromatin structure, which in turn can result in deregulation of gene transcription and inappropriate protein expression. In this review we present examples of representative genetic diseases that arise as a consequence of disordered chromatin remodeling. These include: ,-thalassemia/mental retardation syndrome, X-linked (ATR,X); Rett syndrome (RS); immunodeficiency-centromeric instability,facial anomalies syndrome (ICF); Rubinstein,Taybi syndrome (RSTS); and Coffin,Lowry syndrome (CLS). [source] | |||||||||||||