bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasmid Capture by the
Bacillus thuringiensis
Conjugative Plasmid pXO16
Authors: Timmery Sophie , Modrie Pauline , Minet Olivier , Mahillon Jacques
Published: January 2009

Conjugation, mobilization, and retromobilization are three related mechanisms of horizontal gene transfer in bacteria. They have been extensively studied in gram-negative species, where retromobilization, the capture of DNA from a recipient by a donor cell, was shown to result from two successive steps: the transfer of the conjugative plasmid from the donor to the recipient followed by the retrotransfer of the mobilizable plasmid to the donor. This successive model was established for gram-negative bacteria but was lacking experimental data from the gram-positive counterparts. In the present work, the mobilization and retromobilization abilities of the conjugative plasmid pXO16 from
Bacillus thuringiensis
subsp.
israelensis
were studied using the mobilizable plasmids pUB110 and pE194 and the “nonmobilizable” element pC194 lacking the
mob
and
oriT
features (all from
Staphylococcus aureus
). Experimental data suggested a successive model, since different retromobilization frequencies were observed between the small plasmids. More importantly, retromobilization was shown to be delayed by 50 and 150 min for pUB110 and pE194, respectively, compared to pXO16 conjugation. Natural liquid foods (cow milk, soy milk, and rice milk) were used to evaluate the putative ecological impact of these transfers. In cow and soy milk, conjugation, mobilization, and retromobilization were shown to occur at frequencies of 8.0 × 10
−1
, 1.0 × 10
−2
, and 1.2 × 10
−4
transconjugants per recipient, respectively. These data are comparable to those obtained with LB medium and about 10-fold lower than in the case of rice milk. Taken together, these results emphasize the potential role of plasmid capture played by
B. thuringiensis
in natural environments.
Pathway of γ-Aminobutyrate Metabolism in
Rhizobium leguminosarum
3841 and Its Role in Symbiosis
Authors: Prell Jurgen , Bourdès Alexandre , Karunakaran Ramakrishnan , Lopez-Gomez Miguel , Poole Philip
Published: January 2009

Pea plants incubated in
15
N
2
rapidly accumulated labeled γ-aminobutyrate (GABA) in the plant cytosol and in bacteroids of
Rhizobium leguminosarum
bv. viciae 3841. Two pathways of GABA metabolism were identified in
R. leguminosarum
3841. In the first, glutamate is formed by GABA aminotransferase (GabT), transferring the amino group from GABA to 2-oxoglutarate. In the second, alanine is formed by two ω-aminotransferases (OpaA and OpaB), transferring the amino group from GABA to pyruvate. While the
gabT
mutant and the
gabT opaA
double mutant grew on GABA as a nitrogen source, the final triple mutant did not. The semialdehyde released from GABA by transamination is oxidized by succinate semialdehyde dehydrogenase (GabD). Five of six potential GabD proteins in
R. leguminosarum
bv. viciae 3841 (GabD1, -D2, -D3, -D4, and -D5) were shown by expression analysis to have this activity. However, only mutations of GabD1, GabD2, and GabD4 were required to prevent utilization of GABA as the sole nitrogen source in culture. The specific enzyme activities of GabT, Opa, and GabD were highly elevated in bacteroids relative to cultured bacteria. This was due to elevated expression of
gabT
,
opaA
,
gabD1
, and
gabD2
in nodules. Strains mutated in aminotransferase and succinate semialdehyde dehydrogenases (
gabT
,
opaA
, or
opaB
and
gabD1
,
gabD2
, or
gabD4
, respectively) that cannot use GABA in culture still fixed nitrogen on plants. While GABA catabolism alone is not essential for N
2
fixation in bacteroids, it may have a role in energy generation and in bypassing the decarboxylating arm of the tricarboxylic acid cycle.
An RNA Hairpin Sequesters the Ribosome Binding Site of the Homing Endonuclease
mobE
Gene
Authors: Gibb Ewan A. , Edgell David R.
Published: January 2009

Previous transcript mapping of the bacteriophage Aeh1
nrd
operon revealed a predicted RNA hairpin upstream of the homing endonuclease
mobE
gene. We enzymatically mapped the hairpin, showing that the
mobE
ribosome binding site is sequestered. Cloning of the hairpin upstream of
lacZ
resulted in reduced β-galactosidase activity, consistent with translational regulation.
Prescribing placebos ethically: the appeal of negatively informed consent
Authors: Shaw D M
Published: January 2009

Kihlbom has recently argued that a system of seeking negatively informed consent might be preferable in some cases to the ubiquitous informed consent model. Although this theory is perhaps not powerful enough to supplant informed consent in most settings, it lends strength to Evans’ and Hungin’s proposal that it can be ethical to prescribe placebos rather than “active” drugs. This paper presents an argument for using negatively informed consent for the specific purpose of authorising the use of placebos in clinical contexts.
Late Quaternary paleoproductivity history on the Vancouver Island margin, western Canada: a multiproxy geochemical studyThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.
Authors: Chang Alice S. , Pedersen Thomas F. , Hendy Ingrid L.
Published: January 2009

Multiproxy analysis of a 38 m long sediment core recovered from the Vancouver Island margin (48.97°N, 127.04°W, water depth 1243 m) has yielded a millennial-scale history of upwelling and export production over the last ∼50 ka. Higher concentrations of marine organic carbon, opal, and trace Mo suggest that production was higher, and sedimentary pore waters more anoxic, during the warm Holocene, Bølling–Allerød, and interstadial events between 31 and 44 ka BP. Relatively lower production and higher inputs of terrigenous organic matter occurred during the last glacial (14.7–31 ka BP; Cordilleran ice sheet proximal to coring site at ∼19.5 ka BP) and from 44–50.4 ka BP. Enrichments in sedimentary δ15N during interstadial events are interpreted to reflect episodic delivery and upwelling of isotopically heavy nitrate to the surface waters and subsequent vectoring to the seafloor via settling planktonic detritus. Similar patterns are seen in southern California and other areas along the western margin of North America, implying that heavier nitrate generated by denitrification in the Eastern Tropical North Pacific has in the past been carried northward in the California Undercurrent at least as far as central Vancouver Island. This inference is consistent with modern hydrographic observations in the region. Comparison of the coherent Vancouver Island, Oregon, California, and northwest Mexico margin records with late Pleistocene climate history in Greenland reinforces the conclusion that a tight physical and biogeochemical coupling has existed for at least 50 ka between the North Atlantic and North American margin waters, including those off Vancouver Island.
Radial expansion of cylindrical cavities in sandy soils: application to pressuremeter tests
Authors: Coutinho António Gabriel F. de Sousa
Published: January 2009

A solution for radial expansion of cylindrical cavities in sandy soils is presented. This solution is based on a rigid–plastic model that is not perfectly plastic and is valid even for large deformations (finite strains). Its application to the pressuremeter test is made by using the principle of similitude between cylindrical cavities together with a numerical–graphical technique for solving Palmer's equation, already published by the author. Two examples are presented. The computations are made by the ANABELA II program. It is found that this solution makes it possible to obtain the curve of the friction angles mobilized at each step of the test deformation. The importance of knowing the volumetric deformations associated with the shear is demonstrated as well as the differences in the curves of the angles of friction that are mobilized when finite or infinitesimal strains are used. Finally, the value of the friction angle mobilized at the critical voids ratio is discussed. An attempt is made to compute its value using the theory presented. Key words: radial expansion, cylindrical cavities, sandy soils, rigid-plastic model, not perfectly plastic model, finite strains, infinitesimal strains, mobilized friction angles, volumetric deformations, friction angle mobilized at critical voids ratio.
How the Continents Deform: The Evidence From Tectonic Geodesy
Authors: Thatcher Wayne
Published: January 2009

Space geodesy now provides quantitative maps of the surface velocity field within tectonically active regions, supplying constraints on the spatial distribution of deformation, the forces that drive it, and the brittle and ductile properties of continental lithosphere. Deformation is usefully described as relative motions among elastic blocks and is block-like because major faults are weaker than adjacent intact crust. Despite similarities, continental block kinematics differs from global plate tectonics: blocks are much smaller, typically ∼100–1000 km in size; departures from block rigidity are sometimes measurable; and blocks evolve over ∼1–10 Ma timescales, particularly near their often geometrically irregular boundaries. Quantitatively relating deformation to the forces that drive it requires simplifying assumptions about the strength distribution in the lithosphere. If brittle/elastic crust is strongest, interactions among blocks control the deformation. If ductile lithosphere is the stronger, its flow properties determine the surface deformation, and a continuum approach is preferable.
Interleukin-1β contributes via nitric oxide to the upregulation and functional activity of the zinc transporter Zip14 (Slc39a14) in murine hepatocytes
Authors: Lichten Louis A. , Liuzzi Juan P. , Cousins Robert J.
Published: January 2009

Zinc metabolism during chronic disease is dysregulated by inflammatory cytokines. Experiments with IL-6 knockout mice show that LPS regulates expression of the zinc transporter, Zip14, by a mechanism that is partially independent of IL-6. The LPS-induced model of sepsis may occur by a mechanism signaled by nitric oxide (NO) as a secondary messenger. To address the hypothesis that NO can modulate Zip14 expression, we treated primary hepatocytes from wild-type mice with the NO donor S-nitroso N-acetyl penicillamine (SNAP). After treatment with SNAP, steady-state Zip14 mRNA levels displayed a maximal increase after 8 h and a concomitant increase in the transcriptional activity of the gene. Chromatin immunoprecipitation documented the kinetics of activator protein (AP)-1 and RNA polymerase II association with the Zip14 promoter after NO exposure, indicating a role of AP-1 in transcription of Zip14. We then stimulated the primary murine hepatocytes with IL-1β, an LPS-induced proinflammatory cytokine and a potent activator of inducible NO synthase (iNOS) and NO production. In support of our hypothesis, IL-1β treatment led to a threefold increase in Zip14 mRNA and enhanced zinc transport, as measured with a zinc fluorophore, in wild-type but not iNOS−/−hepatocytes. These data suggest that signaling pathways activated by NO are factors in the upregulation of Zip14, which in turn mediates hepatic zinc accumulation and hypozincemia during inflammation and sepsis.
Hypertensive state, independent of hypertrophy, exhibits an attenuated decrease in systolic function on cardiac κ-opioid receptor stimulation
Authors: Bolte Craig , Newman Gilbert , Schultz Jo El J.
Published: January 2009

Opioids/opiates are commonly administered to alleviate pain, unload the heart, or decrease breathlessness in patients with advanced heart failure. As such, it is important to evaluate whether the myocardial opioidergic system is altered in cardiac disease. A hamster model of spontaneous hypertension was investigated before the development of hypertension (1 mo of age) and in the hypertensive state (10 mo of age) to evaluate the effect of prolonged hypertension on myocardial opioidergic activity. Plasma β-endorphin was decreased before the development of hypertension and in the hypertensive state ( P < 0.05). There was no change in cardiac β-endorphin content at either time point. No differences were detected in cardiac or plasma dynorphin A, Met-enkephalin, or Leu-enkephalin, or in cardiac peptide expression of κ- or δ-opioid receptors. μ-Opioid receptor was not detected in either model. To determine how hypertension affects myocardial opioid signaling, the ex vivo work-performing heart was used to assess the cardiac response to opioid administration in healthy hearts and those subjected to chronic hypertension. Agonists selective for the κ- and δ-opioid receptors, but not μ-opioid receptors, induced a concentration-dependent decrease in cardiac function. The decrease in left ventricular systolic pressure on administration of the κ-opioid receptor-selective agonist, U50488H, was attenuated in hearts from hamsters subjected to chronic, untreated hypertension ( P < 0.05) compared with control. These results show that peripheral and myocardial opioid expression and signaling are altered in hypertension.
Prolonged NO treatment decreases α-adrenoreceptor agonist responsiveness in porcine pulmonary artery due to persistent soluble guanylyl cyclase activation
Authors: Perkins William J. , Kost Susan , Danielson Mark
Published: January 2009

A cultured porcine pulmonary artery (PA) model was used to examine the effects of prolonged nitric oxide (NO) treatment on the response of this vessel to acutely applied NO and to the α-adrenoreceptor agonist phenylephrine. Two-hour treatment with the NO donor ( Z)-1-[ N-(2-aminoethyl)- N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NO) decreased both NO and phenylephrine responsiveness. Twenty-four-hour treatment with DETA-NO resulted in a further reduction in NO responsiveness but no further reduction in phenylephrine responsiveness. Acute addition of soluble guanylyl cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo[4,3- a]quinoxalin-1-one (ODQ) had no effect on phenylephrine responsiveness in PA not treated with DETA-NO. ODQ treatment fully restored phenylephrine responsiveness in PA treated with DETA-NO. sGCβ1subunit protein levels in PA tissue homogenate were 48.6 ± 6.9, 51.6 ± 3.5, and 41.3 ± 2.8 ng/mg total protein for freshly prepared and 2-h and 24-h NO-treated PA, respectively. Steady-state tissue cGMP was not significantly different in control versus NO-treated PA. sGC specific activity in the absence of added NO was measured in PA homogenate and was 0.29 ± 0.02, 1.38 ± 0.12, and 0.53 ± 0.08 μmol cGMP·min−1·mg sGC−1, in freshly prepared and 2-h and 24-h NO treated PA, respectively. Ten-minute Hb treatment completely normalized sGC basal activity in homogenates prepared from DETA-NO-treated PA, which was 0.23 ± 0.02, 0.18 ± 0.03, and 0.25 ± 0.04 μmol cGMP·min−1·mg sGC−1, in freshly prepared and 2-h and 24-h NO-treated PA, respectively. The kinetics of the Hb reversal of NO-mediated sGC persistent activation do not support sGC covalent modification as the activation mechanism. We conclude that prolonged NO exposure results in a persistently increased sGC specific activity, which accounts for the observed α-adrenoreceptor agonist hyporesponsiveness.
Crosstalk between chromatin structure, nuclear compartmentalization, and telomere biology
Authors: Gonzalez-Suarez I. , Gonzalo S.
Published: January 2009

Telomeres are heterochromatic structures essential for the maintenance of genomic stability and the proliferative potential of human somatic cells. A minimal length of telomeric DNA repeats and proper binding of specialized proteins are required for the maintenance of telomere structure and function. Activation of telomere length maintenance mechanisms is considered a hallmark of cancer, while attrition of telomeres is a known contributor to the phenotypes associated with the aging process. However, the molecular mechanisms responsible for telomere homeostasis are not completely understood. Compelling data indicates that the epigenetic status of telomeric and subtelomeric chromatin also plays a role in the regulation of telomere biology. In addition, genomic regions are not randomly distributed within the nucleus, but rather compartmentalized into spatial and temporal domains whose functional implications for the cell are only beginning to be unraveled. Recent studies indicate that alterations in some of the mechanisms responsible for nuclear organization associate with defects in chromatin structure. These observations suggest a link between these two processes, raising the question of whether nuclear compartmentalization of telomeres might also impact on telomere biology.
Cellular senescence, telomere recombination and maintenance
Authors: Yang Q.
Published: January 2009

Cellular senescence can be activated by various types of stressful stimuli, including telomere shortening, oncogenic or tumor suppressor signals, and DNA damage. Progressive telomere shortening in successive cell divisions induces senescence due to the loss of terminal sequences during DNA replication. Maintenance of the telomere sequences at human chromosome ends is essential for immortalized cells to escape from the normal limitations of the proliferation capacity. In this article, the molecular and functional details of telomere maintenance and cellular senescence are reviewed, including the signals that trigger senescence, telomere capping, and the telomere length maintenance mechanisms.
Telomeric repeats far from the ends: mechanisms of origin and role in evolution
Authors: Ruiz-Herrera A. , Nergadze S.G. , Santagostino M. , Giulotto E.
Published: January 2009

In addition to their location at terminal positions, telomeric-like repeats are also present at internal sites of the chromosomes (intrachromosomal or interstitial telomeric sequences, ITSs). According to their sequence organization and genomic location, two different kinds of ITSs can be identified: (1) heterochromatic ITSs (het-ITSs), large (up to hundreds of kb) stretches of telomeric-like DNA localized mainly at centromeres, and (2) short ITSs (s-ITSs), short stretches of telomeric hexamers distributed at internal sites of the chromosomes. Het-ITSs have been only described in some vertebrate species and they probably represent the remnants of evolutionary chromosomal rearrangements. On the contrary, s-ITSs are probably present in all mammalian genomes although they have been described in detail only in some completely sequenced genomes. Sequence database analysis revealed the presence of 83, 79, 244 and 250 such s-ITSs in the human, chimpanzee, mouse and rat genomes, respectively. Analysis of the flanking sequences suggested that s-ITSs were inserted during the repair of DNA double-strand breaks that occurred in the course of evolution. An extensive comparative analysis of the s-ITS loci and their orthologous ‘empty’ loci confirmed this hypothesis and suggested that the repair event involved the direct action of telomerase. Whereas het-ITSs seem to be intrinsically prone to breakage, the instability of s-ITSs is more controversial. This observation is consistent with the hypothesis that s-ITSs are probably not themselves prone to breakage but represent ‘scars’ of ancient breakage that may have occurred within fragile regions. This study will review the current knowledge on these two types of ITS, their molecular organization, how they arose during evolution, their implications for chromosomal instability and their potential applications as phylogenetic/forensic markers.
Studying telomere replication by Q-CO-FISH: the effect of telomestatin, a potent G-quadruplex ligand
Authors: Arnoult N. , Shin-Ya K. , Londoño-Vallejo J.A.
Published: January 2009

Telomere replication is a critical process for preserving genome integrity. The telomere replication fork proceeds unidirectionally from the last subtelomeric origin towards the end of the chromosome, replicating the 5′–3′ G-rich strand by lagging mechanisms and the complementary C-rich strand by leading mechanisms. It has been proposed that the G-rich nature of telomeres may favor the formation of secondary structures such as G-quadruplexes during replication and that specific mechanisms must prevent this to allow the fork to progress unimpeded. The potential of G-quadruplex formation by telomeric sequences has been clearly demonstrated in vitro but it is not known whether these structures form in vivo. We tested the effect of a potent and specific G-quadruplex ligand, telomestatin (TMS), on telomere replication using a novel quantitative approach applied to CO-FISH. We show that TMS, although it penetrates and persists within cells, does not affect telomere replication after short or long-term treatments of mouse embryonic fibroblasts. It does however affect the hybridization efficiency of FISH telomeric probes that recognize the G-rich strand. Our work illustrates the use of a novel technique to measure telomere replication efficiency and suggests that G-quadruplex ligands do not affect telomere replication in a non tumoral context.
A possible role for telomerase RNA and telomere length in global mitotic recombination
Authors: Bouffler S.D. , Finnon P. , Blasco M.A. , Ainsbury E.
Published: January 2009

Telomeres are specialised structures at the ends of mammalian chromosomes with many unique properties. Recombinational events at telomeres are more frequent than in the remainder of the genome by several orders of magnitude. This study examined the influence of telomerase status and telomere length on genome-wide recombination assessed by genomic sister chromatid exchange (G-SCE). Telomerase deficiency per se appears to increase G-SCE frequencies in splenocytes but as telomeres shorten through subsequent generations of mTerc–/– mice this increase is progressively lost. Telomerase status and telomere length also influences the induction of G-SCE by UV light. Even when mitotic recombination is affected by PARP deficiency, mTerc and telomere length interact to further affect G-SCE frequencies. Taken together the data presented here demonstrate that telomerase status and telomere length can affect recombination frequencies genome-wide.
Mechanisms of telomeric instability
Authors: Baird D.M.
Published: January 2009

Telomeres are the nucleoprotein structures that cap the ends of linear chromosomes. The length of telomeric DNA is an important determinant of function; with short telomeres triggering either replicative senescence or, in the absence of a functional DNA damage response, telomere fusion. Telomere fusion can trigger cycles of anaphase-bridging, breakage and fusion that can lead to genomic arrangements, of the type that are frequently found in cancer. Telomere erosion as a function of ongoing cell division results in the gradual loss of sequences from the terminus; this is superimposed by additional mutational mechanisms that generate large-scale, apparently sporadic, telomeric deletions. These events occur in normal human cells, irrespective of telomerase activity, and because they create telomeres that are capable of fusion, they represent a significant cell-intrinsic mutational mechanism. Here I review some of the potential mechanisms that may result in sporadic telomeric deletion.
The number of dysfunctional telomeres in a cell: one amplifies; more than one translocate
Authors: Tusell L. , Soler D. , Agostini M. , Pampalona J. , Genescà A.
Published: January 2009

Chromosomal instability is increasingly appreciated as a key component of tumorigenesis in humans. A combination of abnormal telomere shortening and cell-cycle checkpoint deficiency has been proposed as the initial lesions causing destabilizing chromatin bridges in proliferative cells. We examined the participation of the different types of end-to-end fusions in generating instable karyotypes in non-transformed human breast epithelial cells. We concluded that short dysfunctional telomeres represent an initiating substrate for post-replicative rejoining of sister chromatids and are likely to make an important contribution to the formation of chromosomal rearrangements and the amplification of chromosome arm segments in breast epithelial cells. We propose that there is a chronological order in the participation of the different types of end-to-end fusions in the generation of chromosomal instability. Thus, intrachromosomal post-replicative joining would proceed mainly in the early stages after overcoming growth arrest, when telomere dysfunction is limited and affects only one chromosome end in a cell. The absence of a second substrate for end joining will conduct the cell with the uncapped chromosome to replicate its DNA and fuse the uncapped sister chromatids after replication. Later, since telomeres shorten progressively with each DNA replication round, the uncapping will affect many more chromosome ends, and fusions between the uncapped ends from different chromosomes will be produced. While the fusion of sister chromatids will produce chromosome segment amplification and terminal deletions in the daughter cells, interchromosomal fusion will produce unbalanced rearrangements other than chromosome segment amplifications.
BRCA1 knock-down causes telomere dysfunction in mammary epithelial cells
Authors: Cabuy E. , Newton C. , Slijepcevic P.
Published: January 2009

A breast cancer predisposing gene, BRCA1, is a major suppressor of chromosomal instability and its dysfunction affects multiple pathways involved in DNA damage response. There is increasing evidence that the mechanisms involved in maintenance of telomeres, specialized structures at chromosome ends, are linked with DNA damage response. We therefore investigated whether BRCA1 dysfunction affects telomere maintenance. To achieve this we knocked-down BRCA1 in two mammary epithelial cell lines using RNA interference. Subsequent analysis by immunofluorescence, RT-PCR and Western blotting revealed that a short interfering RNA oligonucleotide used was able to knock-down BRCA1 efficiently. This knock-down did not have any effect on telomerase enzyme activity and telomere length. However, BRCA1 knock-down correlated with the increase in chromatin bridges in anaphase cells which usually reflect telomere dysfunction. Therefore, this study suggests that BRCA1 knockdown in mammary epithelial cells causes telomere dysfunction.
Increased genomic alteration complexity and telomere shortening in B-CLL cells resistant to radiation-induced apoptosis
Authors: Salin H. , Ricoul M. , Morat L. , Sabatier L.
Published: January 2009

B-cell chronic lymphocytic leukemia (B-CLL) results in an accumulation of mature CD5+/CD23+ B cells due to an uncharacterized defect in apoptotic cell death. B-CLL is not characterized by a unique recurrent genomic alteration but rather by genomic instability giving rise frequently to several chromosomal aberrations. Besides we reported that ∼15% of B-CLL patients present malignant B-cells resistant to irradiation-induced apoptosis, contrary to ∼85% of patients and normal human lymphocytes. Telomere length shortening is observed in radioresistant B-CLL cells. Using fluorescence in situ hybridization (FISH) and multicolour FISH, we tested whether specific chromosomal aberrations might be associated with the radioresistance of a subset of B-CLL cells and whether they are correlated with telomere shortening. In a cohort of 30 B-CLL patients, all of the radioresistant B-CLL cell samples exhibited homozygous or heterozygous deletion of 13q14.3 in contrast to 52% of the radiosensitive samples. In addition to the 13q14.3 deletion, ten out of the 11 radioresistant B-cell samples had another clonal genomic alteration such as trisomy 12, deletion 17p13.1, mutation of the p53 gene or translocations in contrast to only three out of 19 radiosensitive samples. Telomere fusions and non-reciprocal translocations, hallmarks of telomere dysfunction, are not increased in radioresistant B-CLL cells. These findings suggest (i) that the 13q14.3 deletion accompanied by another chromosomal aberration is associated with radioresistance of B-CLL cells and (ii) that telomere shortening is not causative of increased clonal chromosomal aberrations in radioresistant B-CLL cells.
Genomic imbalances in key ion channel genes and telomere shortening in sudden cardiac death victims
Authors: Banerjee B. , Peiris D.N. , Koo S.H. , Chui P. , Lee E.J.D. , Hande M.P.
Published: January 2009

Sudden cardiac death (SCD) can be caused by a number of reasons. Previous works have identified the genetic causes, such as alterations in the DNA sequence, for many of these diseases. We hypothesize that some patients may show genomic imbalances and changes in the gene copy number leading to genetic instability. To clarify this, we analysed DNA samples from SCD victims using comparative genomic hybridization (CGH), a molecular cytogenetic technique that permits the genome-wide screening of chromosomal imbalances, and telomere length measurement. DNA derived from peripheral blood and heart tissue of 14 SCD cases and six apparently healthy control individuals were subjected to CGH analysis. Telomere length measurements were done by the Southern blotting method. Eight out of 14 SCD cases exhibited changes in DNA/gene copy number. CGH analysis showed variation in the gene copy number of some of the genes associated with potassium (KCNAB1, KCNH2, and KCNA4) and calcium (RyR2, ATP2A2) ions which are involved in maintaining the ionic balance of the heart. Alterations in TERC and TERT genes were also detected in SCD victims. In nine SCD victims shorter telomeres were detected. This might have resulted from excessive cellular proliferation and/or oxidative stress in these individuals. Copy number changes observed and telomere shortening detected in SCD cases would possibly explain at least some of the causes of SCD at early ages in humans. Identification of biomarkers of SCD is of great importance and thus the present study will facilitate the identification of some of the biomarkers.
Distribution of (TTAGGG)n telomeric sequences in karyotypes of the Xenopus species complex
Authors: Nanda I. , Fugate M. , Steinlein C. , Schmid M.
Published: January 2009

The chromosomal distribution of the conserved vertebrate telomeric (TTAGGG)n sequence was studied by fluorescence in situ hybridization (FISH) in four Xenopus species and the triploid Silurana tropicalis. As expected, hybridization signals were observed at the distal ends of every chromosome in all species. In addition, the hybridization pattern demonstrates varied organization of (TTAGGG)n sequences in the different karyotypes. In X. borealis and X. muelleri hybridization signals intensely labeled one end of a homologous chromosome pair that coincides with the sites containing ribosomal RNA gene clusters. The karyotype of X. clivii remarkably differs from other Xenopus karyotypes in displaying numerous interstitial telomeric sites (ITS). C-banding analysis shows that the non-telomeric sites appear to correspond to the interstitially located constitutive heterochromatin. This suggests that interstitial telomeric sites in X. clivii do not necessarily represent the relic of ancestral telomeres resulting from the fusion of chromosomes, but their occurrence is due to the fact that (TTAGGG)n repeat arrays may be a constituent of highly repetitive DNA.
Blood Coagulation and Cancer: Thrombosis and Survival, Clinical Relevance and Impact
Authors: Vestjens J.H.M.J. , Sassen S. , Prins M.H.
Published: January 2009

There is a strong association between deep venous thrombosis and cancer. In this review, we will discuss the increased incidence of cancer following an idiopathic venous thrombotic event (VTE) and the increased incidence of VTE and its recurrence in cancer patients. Furthermore, we will review the adverse impact VTE has on cancer patients’ morbidity and mortality. Finally, the potential influence of anticoagulation on survival of cancer patients is discussed. Although the data are encouraging, anticoagulation is still of limited value for routine clinical practice in anticancer treatment.
Tissue Factor and Cancer
Authors: Milsom Chloe , Rak Janusz
Published: January 2009

Tissue factor (TF), the key regulator of haemostasis and angiogenesis, is also involved in the pathology of several diseases, including cardiovascular, inflammatory and neoplastic conditions. In the latter, TF is upregulated by cancer cells, as well as by certain host cells, and it is the interactions between these distinct pools of TF-expressing cells that likely influence tumour progression in several ways. Furthermore, the release of TF microparticles into the circulation is thought to contribute to the systemic coagulopathies commonly observed in cancer patients. The direct regulation of TF by oncogenic events has provided a plausible explanation for the relatively common overexpression of TF in various cancers and its involvement in tumour growth, angiogenesis, metastasis and coagulopathy. However, this constitutive influence is modified by the tumour microenvironment, cellular interactions and host factors rendering TF expression patterns complex and heterogeneous. It appears that in many biological contexts TF plays a central role in disease progression and thereby potentially constitutes an attractive therapeutic target, especially in scenarios where the risk of bleeding can be avoided by selecting appropriate medications, refined dosing or by targeting the signalling component of TF activity. The efficacy and safety of such approaches still awaits clinical verification.
Microparticles and Cancer
Authors: Amin Chirag , Mackman Nigel , Key Nigel S.
Published: January 2009

Cancer is a prothrombotic state, with an increased prevalence of arterial and venous thromboemboli. Microparticles (MPs) are sub-micron-sized vesicles derived from activated or apoptotic cancer cells and/or host cells that may causally contribute to these clinical events, although the strength of the evidence thus far is inconclusive. We review the state-of-the-art understanding of the origin of circulating MPs, their role as a potentially important procoagulant entity in cancer, and their clinically documented association with malignancies. It is anticipated that if the functional importance of circulating MPs in clinically meaningful endpoints in cancer can be proven by appropriately designed and powered prospective studies, future investigation will focus on whether MPs can be targeted for therapeutic purposes.
The Plasminogen Activator System and Cancer
Authors: McMahon Brandon , Kwaan Hau C.
Published: January 2009

The fibrinolytic system, more appropriately referred to as the plasminogen activator system, controls not only the intravascular fibrin deposition but also participates in a wide variety of physiologic and pathologic processes. In cancer, the components of this system are involved in tumor growth, invasion and metastasis, through their effect on angiogenesis and cell migration. These components are found in most tumors and their expression signifies not only their function but also carries a prognostic value. Their expression is in turn modulated by cytokines and growth factors, many of which are up-regulated in cancer. Though both plasminogen activators, tPA and uPA, are expressed in tumor cells, uPA with its receptor (uPAR) is mostly involved in cellular functions, while tPA with its receptor annexin II on endothelial surface regulates intravascular fibrin deposition. Among the inhibitors of fibrinolysis, PAI-1 is a major player in the pathogenesis of many vascular diseases as well as in cancer. Therapeutic intervention, either using plasminogen activators or use of experimental inhibitor agents against PAI-1, has shown encouraging results in experimental tumors but not verified clinically. Information provided in this brief review is aimed to promote greater interest in the role of the plasminogen activator system in cancer.
Non-Anticoagulant Heparins and Inhibition of Cancer
Authors: Casu Benito , Vlodavsky Israel , Sanderson Ralph D.
Published: January 2009

Low-molecular-weight heparins (LMWH) appear to prolong survival of patients with cancer. Such a beneficial effect is thought to be associated with interruption of molecular mechanisms involving the heparan sulfate (HS) chains of cell surface and extracellular matrix proteoglycans (HSPGs), growth factors and their receptors, heparanase, and selectins. The beneficial effects of heparin species could also be associated with their ability to release tissue factor pathway inhibitor from endothelium. The utility of heparin and LMWH as anticancer drugs is limited due to their anticoagulant properties. Non-anticoagulant heparins can be obtained either by removing chains containing the antithrombin-binding sequence, or by inactivating critical functional groups or units of this sequence. The non-anticoagulant heparins most extensively studied are regioselectively desulfated heparins and ‘glycol-split’ heparins. Some modified heparins of both types are potent inhibitors of heparanase. A number of them also attenuate metastasis in experimental models. With cancer cells overexpressing selectins, heparin-mediated inhibition of tumor cells-platelets aggregation and tumor cell interaction with the vascular endothelium appears to be the prevalent mechanism of attenuation of early stages of metastasis. The structural requirements for inhibition of growth factors, heparanase, and selectins by heparin derivatives are somewhat different for the different activities. An N-acetylated, glycol-split heparin provides an example of application of a non-anticoagulant heparin that inhibits cancer in animal models without unwanted side effects. Delivery of this compound to mice bearing established myeloma tumors dramatically blocked tumor growth and progression.
Clinical Studies with Anticoagulants to Improve Survival in Cancer Patients
Authors: Gerotziafas Grigoris T. , Papageorgiou Chryssoula , Hatmi Mohamed , Samama Meyer-Michel , Elalamy Ismail
Published: January 2009

Cancer is linked with hypercoagulability and risk of thrombosis and this close association was recognized by Armand Trousseau in 1865. The relation between cancer and blood coagulation is reciprocal: cancer induces a hypercoagulable state and predisposes to thrombosis and activation of platelets, blood coagulation and fibrinolysis interfere with tumor cell biology, tumor growth, angiogenesis and metastatic process. In the present article, we analyze the clinical trials which assessed the influence of anticoagulant treatment on the survival of patients with cancer. The available data show that low-molecular-weight heparins (LMWHs) tend to be more effective and safer than vitamin K antagonists (VKA) in improving survival in patients with cancer. The beneficial effect of anticoagulation with either LMWHs or VKA is not universal for all patients with cancer. There are some histological types of cancers which, at early stages, appear to be more sensitive than others to the effect of anticoagulant treatment. The available clinical trials, although limited, are encouraging for the beneficial effect of anticoagulant treatment on the survival of cancer patients. More clinical trials are needed, targeting groups of patients homogenous regarding the type of cancer, the stage of the disease and life expectancy. The forthcoming clinical trials have to address some issues regarding the optimal dose, the timing and the duration of treatment with LMWH in relation to chemotherapy or other anticancer therapies.
Endoscopic Ablation of Barrett’s Esophagus Using the Halo® System
Authors: Fleischer David E. , Sharma Virender K.
Published: January 2009

There is increasing interest in the endoscopic treatment of Barrett’s esophagus. Endoscopic treatment has been utilized for many years, but in the past, no specific method has emerged as an appealing treatment option with appropriate safety, efficacy and ease of treatment for both patients and physicians. Recently there has been a growing literature related to the endoscopic ablation of Barrett’s esophagus using radiofrequency ablation (RFA) (Halo® system). In order to discuss when RFA is indicated for Barrett’s, one needs to know: (1) What is the ‘histology’ of the Barrett’s? Does the patient have intestinal metaplasia, low-grade dysplasia, high-grade dysplasia or intramucosal carcinoma? (2) What are the endoscopic options to be considered as opposed to RFA? What are the advantages and disadvantages of each? (3) What additional variables need to be examined?
Endoscopic Resection of Early Esophageal and Gastric Neoplasias
Authors: Pohl Juergen , Pech Oliver , May Andrea , Manner Hendrik , Ell Christian
Published: January 2009

The advent of endoscopic resection (ER) techniques has enabled gastroenterologists to remove premalignant or neoplastic lesions throughout the gastrointestinal tract. This review discusses the indications and the several techniques of ER in early carcinomas of the esophagus and stomach. Before ER is performed an accurate evaluation of patients and careful staging of lesions is mandatory. After ER of the neoplasia histological assessment of the entire specimen with detailed histological analysis of layer infiltration is crucial. First long-term follow-up studies of large numbers of patients confirm the excellent effectiveness of ER for well-differentiated mucosal lesions without lymphangitic invasions.
Laparoscopic Fundoplication for GERD: Are We There Yet?
Authors: Garcia-Gallont Rudolf
Published: January 2009

Although proton pump inhibitor treatment remains the first-line treatment for gastroesophageal reflux disease (GERD), the panorama of an indefinitely prolonged medical treatment faces patients and physicians with the need to look for an equivalent, more definitive therapy. Facing global results, after many series have demonstrated the safety of the laparoscopic antireflux surgery procedure in experienced hands, with a low incidence of intra- and postoperative morbidity and a short postoperative hospital stay (averaging 2 days), the immediate benefit as well as the long-term alleviation of symptoms (very good: 82%, good: 92%) seem to justify the place of surgical fundoplication in the therapeutic armamentarium for GERD as a valid alternative to medical treatment. Careful patient selection for surgery, a complete and thorough preoperative workup, an intervention in experienced hands, and a patient well informed about the pros and cons of both medical and surgical therapy are mandatory.
Therapeutic Balloon-Assisted Enteroscopy
Authors: Aktas Huseyin , Mensink Peter B.F.
Published: January 2009

Since the introduction of the first balloon-based enteroscopic technique in 2001, therapeutic balloon-assisted enteroscopy (BAE) using either the single or double balloon enteroscopy technique (respectively SBE and DBE) has evolved rapidly. Argon plasma coagulation (APC), polypectomy, dilation therapy of strictures, and therapy of the pancreatico-biliary system in patients with surgical altered proximal intestinal anatomy: all have been successfully introduced to treat pathological findings in all segments of the small bowel. The clinical impact of treatment of vascular malformations, strictures caused by chronic inflammation (especially Crohn’s disease) and polypectomy therapy (especially in the Peutz-Jeghers syndrome) seems evident. The decrease of, often repeated, surgical therapy after successful therapeutic BAE in the latter 2 patient groups appears to be a big step forward in treatment. The development of newer enteroscopes, specialized equipment and improved sedation of patients adds positively to the clinical management of undergoing therapeutic BAE. The overall complication rate of therapeutic BAE seems acceptable, but is higher compared to therapeutic colonoscopy which needs further attention in future.
Endoscopic Balloon Dilation of Anastomotic Strictures Occurring after Laparoscopic Gastric Bypass for Morbid Obesity
Authors: Caro Luis , Sánchez Christian , Rodríguez Pablo , Bosch Jorge
Published: January 2009

Background: Gastrojejunal anastomotic stenosis of laparoscopic Roux-en-Y gastric bypass (LRYGB) for morbid obesity occurs in 3–25% of cases. The aim of this report was to evaluate the utility of endoscopic balloon dilation for the therapy of anastomotic strictures after LRYGB. Patients and Methods: 111 consecutive patients were treated with endoscopic dilation under sedation with propofol. Dilations were performed with through-the-scope over-the-wire balloons, with sizes ranging from 6 to 18 mm. The outcomes of the procedure were analyzed. Results: 200 endoscopic balloon dilations were performed in 111 patients. Repeated dilations were necessary in patients with complex stenosis. In 75% of the patients it was possible to dilate to 12 mm during the first session. Only in 2% of the cases was it impossible to introduce the endoscope through the stenosed anastomosis after dilation. On follow-up a repeat dilation was necessary in 26% of the cases. Minor complications occurred in 2.7% of patients (2 concealed perforations and 1 hematoma of the esophagus). These were treated conservatively. None of the patients required operation. Conclusions: Endoscopic balloon dilation is a safe and effective therapy for anastomotic strictures occurring after LRYGB.
ERCP with the Balloon-Assisted Enteroscopy Technique: A Systematic Review
Authors: Koornstra Jan J. , Fry Lucía , Mönkemüller Klaus
Published: January 2009

Background: Endoscopic retrograde cholangiopancreatography (ERCP) is generally difficult with conventional instruments in patients with surgically altered gastrointestinal anatomy. Balloon-assisted enteroscopy is a relatively new technique that allows for access to the papilla of Vater or a biliodigestive anastomosis in postsurgical reconstructions. Aim: To systematically review the utility of balloon-enteroscope-assisted ERCP for patients with altered gastrointestinal anatomy. Material and Methods: Systematic search of the literature on diagnostic and therapeutic interventions in the pancreaticobiliary system using balloon-assisted enteroscopy in patients with previous intestinal surgery indexed in of MEDLINE, Current Contents, PubMed, and references from relevant articles using the search terms ‘balloon’, ‘enteroscopy’, ‘endoscopy’, ‘ERCP’ and ‘cholangiography’. Only papers published as ‘full text’ in English were included. Results: In total, 16 relevant reports are available on balloon-assisted procedures performed in 63 patients with a variety of anatomical configurations. Double balloon procedures as well as single balloon techniques have been reported. Successful interventions in these patients include balloon dilation of stenotic biliodigestive anastomoses, sphincterotomy, extraction of bile stones and stent placement. No serious complications have yet been reported. Conclusions: Balloon-assisted enteroscopy is a safe and feasible technique to obtain biliary or pancreatic access in patients with surgically altered anatomical configurations. The diagnostic and therapeutic potential of balloon-assisted ERCP is large, and could be further improved if customized accessories become more widely available.
Interventional Endoscopic Ultrasound
Authors: Ramesh Jayapal , Varadarajulu Shyam
Published: January 2009

Endoscopic ultrasonography (EUS), since its development in the 1980s, has undergone a great deal of technological advancement in imaging, scopes with larger channels and accessories. This has given the endosonographer an immense reach in terms of accessing difficult areas with fewer complications. Currently, it is possible not only to obtain tissue for histological diagnosis but also to perform therapeutic procedures that hitherto would have needed surgery with its attendant morbidity. EUS has evolved over the years and EUS-guided fine needle aspiration for histological diagnosis has become standard practice. A wide array of interventional procedures are performed under EUS guidance including, celiac plexus neurolysis, drainage of pancreatic and pelvic fluid collections, drainage of obstructive biliary/pancreatic ducts, and implantation of fiducial markers/radioactive seeds into gastrointestinal tumors. Also, various experimental procedures are underway evaluating the role of EUS in radiofrequency ablation, vascular therapy, and natural orifice transluminal endoscopic surgery. In this review, we examine the various EUS-guided interventions currently undertaken and explore the potential of other emerging experimental techniques.