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At least 721 records · Page 40Linked to original sources
PubMed2006

Electrocrystallization of Phase I, CuTCNQ (TCNQ = 7,7,8,8-Tetracyanoquinodimethane), on indium tin oxide and boron-doped diamond electrodes.

The electrochemical reduction of TCNQ to TCNQ*- in acetonitrile in the presence of [Cu(MeCN)4]+ has been undertaken at boron-doped diamond (BDD) and indium tin oxide (ITO) electrodes. The nucleation and growth process at BDD is similar to that reported previously at metal electrodes. At an ITO electrode, the electrocrystallization of more strongly adhered, larger, branched, needle-shaped phase I CuTCNQ crystals is detected under potential step conditions and also when the potential is cycled over the potential range of 0.7 to -0.1 V versus Ag/AgCl (3 M KCl). Video imaging can be used at optically transparent ITO electrodes to monitor the growth stage of the very large branched crystals formed during the course of electrochemical experiments. Both in situ video imaging and ex situ X-ray diffraction and scanning electron microscopy (SEM) data are consistent with the nucleation of CuTCNQ taking place at a discrete number of preferred sites on the ITO surface. At BDD electrodes, ex situ optical images show that the preferential growth of CuTCNQ occurs at the more highly conducting boron-rich areas of the electrode, within which there are preferred sites for CuTCNQ formation.

Boron↗
PubMed2003

Does conversion and prevention of atrial fibrillation enhance survival in patients with left ventricular dysfunction? Evidence from the Danish Investigations of Arrhythmia and Mortality ON Dofetilide/(DIAMOND) study.

BACKGROUND: Atrial fibrillation is a common arrhythmia in patients with left ventricular dysfunction associated with increased morbidity and mortality. The present study investigated the potential of dofetilide to restore and maintain sinus rhythm in patients with left ventricular dysfunction, which might reduce mortality and hospitalizations. METHODS AND RESULTS: In the Danish Investigations of Arrhythmia and Mortality ON Dofetilide (DIAMOND) studies, 506 patients were in atrial fibrillation (AF) or atrial flutter (AFl) at baseline. Over the course of study, cardioversion occurred in 148 (59%) dofetilide- and 86 (34%) placebo-treated patients. In these patients, the probability of maintaining sinus rhythm for 1 year was 79% with dofetilide versus 42% with placebo ( P < 0.001). Dofetilide had no effect on all-cause mortality, but restoration and maintenance of sinusrhythm (independent of study treatment) was associated with a significant reduction in mortality (risk ratio [RR], 0.44; 95% CI, 0.30 to 0.64; P < 0.0001). In addition, dofetilide therapy was associated with a significantly lower risk ratio versus placebo for either all-cause (RR, 0.70; 95% CI, 0.56 to 0.89; P < or = 0.005) or congestive heart failure (RR, 0.69; 95% CI, 0.51 to 0.93; P < or = 0.02) rehospitalization. CONCLUSIONS: Dofetilide is safe and increases the probability of obtaining and maintaining sinus rhythm in patients with structural heart disease. The present study suggests that restoration of sinus rhythm--on placebo or dofetilide--is associated with improved survival.

Anti-Arrhythmia Agents↗
PubMed2003

Shwachman-Diamond syndrome with late-onset neutropenia and fatal acute myeloid leukaemia without maturation: a case report.

We report on a male patient affected by Shwachman Diamond syndrome (SDS) who presented an unusual delayed neutropenia and then developed a poorly differentiated acute myeloid leukaemia (M0-AML) with trilineage myelodysplasia in adulthood. Conventional cytogenetics revealed complex karyotypic changes (monosomies 20, 21, 22, additional 15p). The patient was treated with conventional chemotherapy but never reached complete remission of leukaemia and died 18 months after diagnosis. SDS is an inherited bone marrow failure syndrome with a high propensity to leukaemic transformation. Since neutropenia may be intermittent or with delayed onset, and leukaemic transformation may not occur until adulthood, full blood count should be regularly monitored in such patients.

Acute Disease↗
PubMed2001

Nanostructure. Epitaxial diamond polytypes on silicon.

Carbon is unique in the variety of configurations it can adopt with itself and other elements. Here we show how ion beams can be used to nanostructure various diamond polytypes, epitaxially aligning them to a silicon substrate. The ready controllability of ion beams, which are already used to manufacture submicrometre-scale devices, means that our findings should enable new carbon and non-carbon materials to be nanostructured for a host of applications.

Journal Article↗
PubMed2001

History of trace gases in presolar diamonds inferred from ion-implantation experiments.

Diamond grains are the most abundant presolar grains found in primitive meteorites. They formed before the Solar System, and therefore provide a record of nuclear and chemical processes in stars and in the interstellar medium. Their origins are inferred from the unusual isotopic compositions of trace elements-mainly xenon-which suggest that they came from supernovae. But the exact nature of the sources has been enigmatic, as has the method by which noble gases were incorporated into the grains. One observation is that different isotopic components are released at different temperatures when the grains are heated, and it has been suggested that these components have different origins. Here we report results of a laboratory study that shows that ion implantation (previously suggested on other grounds) is a viable mechanism for trapping noble gases. Moreover, we find that ion implantation of a single isotopic composition can produce both low- and high-temperature release peaks from the same grains. We conclude that both isotopically normal and anomalous gases may have been implanted by multiple events separated in space and/or time, with thermal processing producing an apparent enrichment of the anomalous component in the high-temperature release peak. The previous assumption that the low- and high-temperature components were not correlated may therefore have led to an overestimate of the abundance of anomalous argon and krypton, while obscuring an enhancement of the light-in addition to the heavy-krypton isotopes.

Journal Article↗
PubMed1999

The gene encoding ribosomal protein S19 is mutated in Diamond-Blackfan anaemia.

Diamond-Blackfan anaemia (DBA) is a constitutional erythroblastopenia characterized by absent or decreased erythroid precursors. The disease, previously mapped to human chromosome 19q13, is frequently associated with a variety of malformations. To identify the gene involved in DBA, we cloned the chromosome 19q13 breakpoint in a patient with a reciprocal X;19 chromosome translocation. The breakpoint occurred in the gene encoding ribosomal protein S19. Furthermore, we identified mutations in RPS19 in 10 of 40 unrelated DBA patients, including nonsense, frameshift, splice site and missense mutations, as well as two intragenic deletions. These mutations are associated with clinical features that suggest a function for RPS19 in erythropoiesis and embryogenesis.

Amino Acid Sequence↗
PubMed2003

Extreme crustal oxygen isotope signatures preserved in coesite in diamond.

The anomalously high and low oxygen isotope values observed in eclogite xenoliths from the upper mantle beneath cratons have been interpreted as indicating that the parent rock of the eclogites experienced alteration on the ancient sea floor. Recognition of this genetic lineage has provided the foundation for a model of the evolution of the continents whereby imbricated slabs of oceanic lithosphere underpin and promote stabilization of early cratons. Early crustal growth is thought to have been enhanced by the addition of slab-derived magmas, leaving an eclogite residuum in the upper mantle beneath the cratons. But the oxygen isotope anomalies observed in eclogite xenoliths are small relative to those in altered ocean-floor basalt and intermediate-stage subduction-zone eclogites, and this has hindered acceptance of the hypothesis that the eclogite xenoliths represent subducted and metamorphosed ocean-floor basalts. We present here the oxygen isotope composition of eclogitic mineral inclusions, analysed in situ in diamonds using an ion microprobe/secondary ion mass spectrometer. The oxygen isotope values of coesite (a polymorph of SiO2) inclusions are substantially higher than previously reported for xenoliths from the subcratonic mantle, but are typical of subduction-zone meta-basalts, and accordingly provide strong support for the link between altered ocean-floor basalts and mantle eclogite xenoliths.

Journal Article↗
PubMed1997

Diamond-Blackfan anaemia: genetic homogeneity for a gene on chromosome 19q13 restricted to 1.8 Mb.

Diamond-Blackfan anaemia (DBA; MIM#205900) is a rare disorder manifested as a pure red-cell aplasia in the neonatal period or in infancy. The clinical hallmark of DBA is a selective decrease in erythroid precursors and anaemia. Other lineages are usually normal and the peripheral white blood cell count is normal. In approximately one-third of cases, the disease is associated with a wide variety of congenital anomalies and malformations. Most cases are sporadic, but 10-20% of them follow a recessive or a dominant inheritance pattern. A female with DBA and a chromosomal translocation involving chromosome 19q was recently identified. We undertook a linkage analysis with chromosome 19 markers in multiplex DBA families of Swedish, French, Dutch, Arabic and Italian origin. Significant linkage to chromosome 19q13 was established for dominant and recessive inherited DBA with a peak lod score at D19S197 (Zmax = 7.08, theta = 0.00). Within this region, a submicroscopic de novo deletion of 3.3 Mb was identified in a patient with DBA. The deletion coincides with the translocation break-point and, together with key recombinations, restricts the DBA gene to a 1.8-Mb region. The results suggest that, despite its clinical heterogeneity, DBA is genetically homogeneous for a gene in 19q13.

Adult↗
PubMed2002

Mutations in SBDS are associated with Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome (SDS; OMIM 260400) is an autosomal recessive disorder with clinical features that include pancreatic exocrine insufficiency, hematological dysfunction and skeletal abnormalities. Here, we report identification of disease-associated mutations in an uncharacterized gene, SBDS, in the interval of 1.9 cM at 7q11 previously shown to be associated with the disease. We report that SBDS has a 1.6-kb transcript and encodes a predicted protein of 250 amino acids. A pseudogene copy (SBDSP) with 97% nucleotide sequence identity resides in a locally duplicated genomic segment of 305 kb. We found recurring mutations resulting from gene conversion in 89% of unrelated individuals with SDS (141 of 158), with 60% (95 of 158) carrying two converted alleles. Converted segments consistently included at least one of two pseudogene-like sequence changes that result in protein truncation. SDBS is a member of a highly conserved protein family of unknown function with putative orthologs in diverse species including archaea and eukaryotes. Archaeal orthologs are located within highly conserved operons that include homologs of RNA-processing genes, suggesting that SDS may be caused by a deficiency in an aspect of RNA metabolism that is essential for development of the exocrine pancreas, hematopoiesis and chrondrogenesis.

Alleles↗
PubMed1997

Cord blood stem cell transplantation for Diamond-Blackfan anemia.

Bone marrow transplantation has been successfully employed in the treatment of Diamond-Blackfan anemia (DBA). Transplantation with bone marrow stem cells involves, however, considerable treatment-related toxicity, partially in the form of GVHD. Through the use of cord blood stem cells it may be possible to reduce the risk for both acute and chronic GVHD, although possibly in the face of an increased risk for non-engraftment. We report the successful treatment of a boy with DBA by cord blood stem transplantation from an HLA-identical sibling.

Fanconi Anemia↗
PubMed1998

Bone marrow transplantation in Shwachman-Diamond syndrome: report of two cases and review of the literature.

Patients with Shwachman-Diamond syndrome (SDS) have an increased frequency of myelodysplasia and leukemic transformation. We described two patients who received allogeneic stem cell transplantation and developed multiple complications, including seizure, hyperglycemia and renal tubular acidosis. A review of the literature showed that patients with SDS appeared to have an increased incidence of various transplant-associated problems. These patients frequently have underlying organ dysfunction and should be managed with extreme caution when treated with allogeneic stem cell transplantation.

Bone Marrow Transplantation↗
PubMed1999

Failure of allogeneic bone marrow transplantation to correct Diamond-Blackfan anaemia despite haemopoietic stem cell engraftment.

We report the case of a 10-year-old boy with congenital pure red cell aplasia (Diamond-Blackfan anaemia) who received an allogeneic bone marrow transplant (BMT) from his HLA-identical sister. The transplant was complicated by moderate veno-occlusive disease (VOD). Despite cytogenetic evidence of complete donor haemopoietic stem cell engraftment there was selective failure of red cell engraftment and he remains red cell transfusion-dependent. This is the first case of a stem cell transplant failing to correct the defect in this condition despite engraftment.

Bone Marrow Transplantation↗
PubMed2000

Epstein-Barr virus-associated lymphoproliferative disease after a cord blood transplant for Diamond-Blackfan anemia.

A 7-year-old boy with Diamond-Blackfan anemia (DBA) developed lymphoproliferative disease (LPD) after a cord blood transplant (CBT). 3.1 x 107/kg mononuclear cells from an HLA one-locus mismatched CB were transplanted after conditioning with total body irradiation (8 Gy), cyclophosphamide (200 mg/kg) and antithymocyte globulin (10 mg/kg). Complete engraftment occurred on day 33 post transplant. Despite the resolution of grade II graft-versus-host disease (GVHD), he died of lymphoma on day 130 post transplant. The tumor was of donor origin, indicating clonal proliferation of Epstein-Barr virus (EBV)-infected B cells. This is the first report of EBV-LPD after CBT. Post-transplant LPD can be a serious EBV-associated complication of CB grafts. Bone Marrow Transplantation (2000) 25, 209-212.

Blood Component Transfusion↗
PubMed2002

Successful allogeneic hematopoietic stem cell transplantation (HSCT) for Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome (SDS) is a rare genetic disorder characterized by pancreatic insufficiency, short stature, skeletal abnormalities and bone marrow dysfunction. Patients with SDS have varying degrees of marrow aplasia, which can be severe or progress to leukemic transformation. While allogeneic hematopoietic stem cell transplantation (HSCT) can be curative for the hematologic disturbances of SDS, a recent review of the literature reveals few survivors. Poor outcome with HSCT is often related to excessive cardiac and other organ toxicity from transplant preparative therapy. We describe two young children with SDS who developed aplastic anemia and subsequently underwent successful allografting using a non-cardiotoxic conditioning regimen. Case 1 received marrow from an HLA-identical sibling while case 2 received partially matched umbilical cord blood from an unrelated donor. Both patients are presently alive and well with sustained donor engraftment and excellent hematopoietic function at 36 and 22 months post-HSCT.

Abnormalities, Multiple↗
PubMed2002

Liver failure complicating non-alcoholic steatohepatitis following allogeneic bone marrow transplantation for Shwachman-Diamond syndrome.

Bone marrow transplantation is potentially curative therapy for the hematologic complications associated with Shwachman-Diamond syndrome (SDS). This syndrome is, however, also associated with significant pancreatic and hepatic dysfunction, which may complicate BMT. We report a case of liver failure due to non-alcoholic steatohepatitis (NASH) following BMT for SDS. This case illustrates the need for assessing liver dysfunction pre-BMT in these patients, in addition to highlighting the potential risk posed by pre-existing steatosis for the development of rapidly progressive hepatic failure following transplantation.

Adult↗
PubMed2002

Bone marrow transplantation in Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome is a rare autosomal recessive disorder characterized by exocrine pancreatic dysfunction, metaphyseal dysostosis and bone marrow dysfunction with a predilection towards severe hematologic complications. Allogeneic bone marrow transplantation has been used as a therapeutic approach for SDS patients with serious hematologic abnormalities with mixed results. There is some concern that these patients may be more susceptible to early (<100 days) transplant-related complications than other transplant groups. We report a patient who received a matched allogeneic transplant without developing serious early transplant-related complications, but eventually died from relapse of his disease. Although experience is limited, a review of the reported cases suggests patients with SDS may be transplanted without significant short-term morbidity and mortality.

Adult↗
PubMed2005

Hematopoietic stem cell transplantation for Shwachman-Diamond syndrome: experience of the French neutropenia registry.

Our objective was to study the outcome of allogeneic hematopoietic stem cell transplantation (HSCT) for Shwachman-Diamond Syndrome (SDS). Among 71 SDS patients included in the French Severe Chronic Neutropenia Registry, 10 received HSCT between 1987 and 2004 in five institutions. The indications were bone marrow failure in five cases, and myelodysplastic syndrome (MDS) or leukemia in five cases. The median follow-up of patients who survived without relapse is 6.9 years (3.1-16.8 years). The conditioning regimen consisted of a busulfan-cyclophosphamide combination (n=6) or total body irradiation plus chemotherapy (n=4). Six patients received stem cells from unrelated donors and four from identical siblings. Engraftment was complete in eight patients and unassessable in two patients. These latter two patients died of infections 32 and 36 days after HSCT, with grade IV graft-versus-host disease and multiorgan dysfunction. A third patient died from an acute respiratory distress syndrome 17 months after HSCT with progressive granulocytic sarcoma. One patient had an MDS relapse 4 months after HSCT and died 10 months later. The overall 5-year event-free survival rate is 60+/-15%. We conclude that HSCT is feasible for patients with SDS who develop bone marrow failure or malignant transformation.

Adolescent↗
PubMed2005

Successful unrelated umbilical cord blood transplantation in children with Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by pancreatic insufficiency and variable degrees of neutropenia. SDS patients are at risk of developing myelodysplasia, aplastic anemia, and leukemic transformation. The role and timing of allogeneic hematopoietic stem cell transplantation (HSCT) in SDS remain controversial. We report three SDS patients with severe aplasia transplanted using unrelated umbilical cord blood (UCB). Patients received melphalan (180 mg/m2), etoposide (1200 mg/m2), anti-thymocyte globulin (90 mg/kg), and total lymphoid irradiation (500 cGy); graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and prednisone. Myeloid engraftment occurred promptly with absolute neutrophil count >500 cells/mm3 on day 15 +/- 5 and all patients displayed 100% donor chimerism by 2 months post transplant. The major complication of transplant was GVHD, with all patients developing grade II or III acute GVHD, one progressing to chronic extensive GVHD. Patients are alive 309, 623, and 2029 days post transplant. Factors important in HSCT outcome for SDS may include transplantation at a young age, avoidance of cyclophosphamide, and adequate GVHD prophylaxis. Importantly, these cases also suggest that unrelated UCB, in the absence of a matched family member, is an excellent alternative stem cell source for SDS patients undergoing HSCT.

Abnormalities, Multiple↗