Search PubMed⌕ Search

Biomedical subjects

A W Roberts

Publications and source records attributed to A W Roberts.

At least 19 recordsLinked to original sources
PubMed2006

The hyper-CVAD-rituximab chemotherapy programme followed by high-dose busulfan, melphalan and autologous stem cell transplantation produces excellent event-free survival in patients with previously untreated mantle cell lymphoma.

The hyper-CVAD + rituximab (R) programme consists of fractionated cyclophosphamide, vincristine, doxorubicin and dexamethasone + R alternating with high-dose methotrexate + cytarabine (HD MTX/ARA-C) + R. This regimen, when used as initial therapy for patients under 65 years of age with previously untreated mantle cell lymphoma (MCL), results in remission rates of > 85% with a median event-free survival (EFS) of > 50 months, but with a pattern of continuous relapse out to 60 months. We performed a study of hyper-CVAD + R, followed by consolidative peripheral blood progenitor cells autograft [autologous stem cell transplant (AuSCT)] with high-dose busulfan and melphalan (Bu/Mel) conditioning, in patients with responsive disease. Thirteen patients with a median age of 54 (range = 33-61) were treated. Complete remission (CR) was achieved in 12 patients (92%) after hyper-CVAD + R and 12 completed AuSCT after Bu/Mel conditioning. One patient died during the autograft and another declined AuSCT after achieving a CR with hyper-CVAD + R. With a median follow-up from diagnosis of 36 months (range = 16-53 months), the observed 36 months overall survival and EFS are both 92% for the whole cohort. These data confirm the excellent CR rates achieved by the use of hyper-CVAD + R in patients with MCL and suggest that consolidation with Bu/Mel and AuSCT may improve durable disease control when compared to published outcomes of hyper-CVAD + R alone.

Adult↗
PubMed2004

Roles of microtubules and cellulose microfibril assembly in the localization of secondary-cell-wall deposition in developing tracheary elements.

The roles of cellulose microfibrils and cortical microtubules in establishing and maintaining the pattern of secondary-cell-wall deposition in tracheary elements were investigated with direct dyes to inhibit cellulose microfibril assembly and amiprophosmethyl to inhibit microtubule polymerization. When direct dyes were added to xylogenic cultures of Zinnia elegans L. mesophyll cells just before the onset of differentiation, the secondary cell wall was initially secreted as bands composed of discrete masses of stained material, consistent with immobilized sites of cellulose synthesis. The masses coalesced, forming truncated, sinuous or smeared thickenings, as secondary cell wall deposition continued. The absence of ordered cellulose microfibrils was confirmed by polarization microscopy and a lack of fluorescence dichroism as determined by laser scanning microscopy. Indirect immunofluorescence showed that cortical microtubules initially subtended the masses of dye-altered secondary cell wall material but soon became disorganized and disappeared. Although most of the secondary cell wall was deposited in the absence of subtending cortical microtubules in dye-treated cells, secretion remained confined to discrete regions of the plasma membrane. Examination of non-dye-treated cultures following application of microtubule inhibitors during various stages of secondary-cell-wall deposition revealed that the pattern became fixed at an early stage such that deposition remained localized in the absence of cortical microtubules. These observations indicate that cortical microtubules are required to establish, but not to maintain, patterned secondary-cell-wall deposition. Furthermore, cellulose microfibrils play a role in maintaining microtubule arrays and the integrity of the secondary-cell-wall bands during deposition.

Asteraceae↗
PubMed2004

A pilot study of targeted itraconazole prophylaxis in patients with graft-versus-host disease at high risk of invasive mould infections following allogeneic stem cell transplantation.

Patients with severe graft-versus-host disease (GVHD) requiring intensive immunosuppression are at high risk of invasive mould infections (IMI). Prophylaxis with an active, oral antifungal agents with reliable absorption in this context is desirable. A total of 44 patients at high risk of post-engraftment IMI received itraconazole solution 2.5 mg/kg b.d. as prophylaxis. Two of the first nine patients, in whom bioavailability was compromised due to significant vomiting and/or diarrhoea, died of probable or proven invasive aspergillus. None of the subsequent 35 patients, some of whom had severe gut GVHD and who received liposomal amphotericin B prophylaxis until itraconazole was reliably tolerated and absorbed, developed IMI. The overall incidence of IMI was substantially lower than in historical controls. Itraconazole was generally well tolerated, with five patients (11%) ceasing the drug due to intolerance or disturbed liver function. Targeted prophylaxis with oral or parenteral antifungal agents in high-risk allograft recipients appears to be effective in reducing the incidence of IMI.

Adolescent↗
PubMed2004

Guidelines for the use of antifungal agents in the treatment of invasive Candida and mould infections.

ABSTRACT Treatment of invasive fungal infections is increasingly complex. Amphotericin B deoxycholate has long been the mainstay of treatment. However, there has been increasing recognition of both the propensity for nephro-toxicity in haematology, transplant and intensive care patients as well as its adverse impact on morbidity and mortality. This has coincided with the availabilty of newer, and in certain settings, more effective antifungal agents. Although the newer agents clearly cause less nephrotoxicity than amphotericin B, drug interactions, hepatic effects and unique side-effects need to be considered. The spectrum of the newer triazoles and echinocandins varies, highlighting the importance of accurate identification of the causative organism where possible. Consensus Australian guidelines have been developed to assist clinicians with treatment choices by reviewing the current evidence for the efficacy, the toxicity and the cost of these agents.

Antifungal Agents↗
PubMed2002

A phase I dose-escalation study of etoposide continuous infusion added to busulphan/cyclophosphamide as conditioning prior to autologous or allogeneic stem cell transplantation.

Relapse of the primary disease remains the predominant cause of death following bone marrow transplantation for high-risk haematological malignancies. Improved supportive care and patient selection have resulted significant improvements in toxicity with standard conditioning regimens. Further dose intensification to reduce the risk of relapse may therefore be feasible. We determined the maximal tolerated dose (MTD) of a 5-day continuous infusion (CI) of etoposide when added to oral busulphan 16 mg/kg and intravenous cyclophosphamide 120 mg/kg (Bu/Cy) as conditioning in 44 autograft and 18 allograft recipients at high risk of relapse. The major toxicity of escalating doses of etoposide was oral and gastro-intestinal mucositis, reflected by a statistically significant increase in the requirement for total parenteral nutrition in both autografts and allograft recipients. Time to neutrophil and platelet recovery, opiate analgesia requirements, and duration of hospitalization were not affected by etoposide dose escalation. The MTD in autograft recipients was 300 mg/m(2)/day (1500 mg/m(2) total dose), and 100 mg/m(2)/day (500 mg/m(2) total dose) for allograft recipients. Mucositis and hepatotoxicity were more frequent in allograft recipients, suggesting that methotrexate may have contributed to the lower tolerable dose in these patients. As a consequence, further dose escalation may not be possible in heavily pre-treated patients undergoing allogeneic transplantation. Conversely, high dose CI etoposide can be added with relative safety to Bu/Cy in autograft recipients.

Adolescent↗
PubMed2002

Successful allogeneic stem cell transplant after invasive pulmonary zygomycosis.

We report the successful outcome of allogeneic stem cell transplant (SCT) in a patient with acute lymphoblastic leukaemia (ALL) and pulmonary zygomycosis diagnosed prior to transplant. The lesion was surgically excised and SCT proceeded with antifungal therapy, granulocyte transfusions and G-CSF support during the period of neutropenia.

Adult↗
PubMed2002

Failure of porcine reproductive and respiratory syndrome virus to replicate in porcine endothelial cell cultures.

Clinical, gross, and microscopic pathologic and immunohistochemical findings in pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV) suggest that PRRSV may replicate in endothelial cells. Endothelial cell cultures from porcine aorta and pulmonary artery were tested for susceptibility to various strains of PRRSV. Cultures were identified as endothelium by light microscopy and immunohistochemical staining for P-selectin and von Willebrand factor. Five strains of PRRSV, i.e., the National Veterinary Services Laboratories, Ames, IA PRRSV strain 130-PDV and 4 field strains isolated from pneumonic lungs, failed to replicate in these porcine large-vessel endothelial cell cultures.

Animals↗
PubMed2001

Placental defects and embryonic lethality in mice lacking suppressor of cytokine signaling 3.

Mice lacking suppressor of cytokine signaling 3 (SOCS3) exhibited embryonic lethality with death occurring between days 11 and 13 of gestation. At this stage, SOCS3(-/-) embryos were slightly smaller than wild type but appeared otherwise normal, and histological analysis failed to detect any anatomical abnormalities responsible for the lethal phenotype. Rather, in all SOCS3(-/-) embryos examined, defects were evident in placental development that would account for their developmental arrest and death. The placental spongiotrophoblast layer was significantly reduced and accompanied by increased numbers of giant trophoblast cells. Delayed branching of the chorioallantois was evident, and, although embryonic blood vessels were present in the labyrinthine layer of SOCS3(-/-) placentas, the network of embryonic vessels and maternal sinuses was poorly developed. Yolk sac erythropoiesis was normal, and, although the SOCS3(-/-) fetal liver was small at day 12.5 of gestation (E12.5), normal frequencies of erythroblasts and hematopoietic progenitor cells, including blast forming unit-erythroid (BFU-E) and, colony forming unit-erythroid (CFU-E) were present at both E11.5 and E12.5. Colony formation for both BFU-E and CFU-E from SOCS3(-/-) mice displayed wild-type quantitative responsiveness to erythropoietin (EPO), in the presence or absence of IL-3 or stem cell factor (SCF). These data suggest that SOCS3 is required for placental development but dispensable for normal hematopoiesis in the mouse embryo.

Animals↗
PubMed2001

Rac and Cdc42 GTPases control hematopoietic stem cell shape, adhesion, migration, and mobilization.

Critical to homeostasis of blood cell production by hematopoietic stem/progenitor (HSC/P) cells is the regulation of HSC/P retention within the bone marrow microenvironment and migration between the bone marrow and the blood. Key extracellular regulatory elements for this process have been defined (cell-cell adhesion, growth factors, chemokines), but the mechanism by which HSC/P cells reconcile multiple external signals has not been elucidated. Rac and related small GTPases are candidates for this role and were studied in HSC/P deficient in Rac2, a hematopoietic cell-specific family member. Rac2 appears to be critical for HSC/P adhesion both in vitro and in vivo, whereas a compensatory increase in Cdc42 activation regulates HSC/P migration. This genetic analysis provides physiological evidence of cross-talk between GTPase proteins and suggests that a balance of these two GTPases controls HSC/P adhesion and mobilization in vivo.

Animals↗
PubMed2001

Poly(rC) binding proteins mediate poliovirus mRNA stability.

The 5'-terminal 88 nt of poliovirus RNA fold into a cloverleaf RNA structure and form ribonucleoprotein complexes with poly(rC) binding proteins (PCBPs; AV Gamarnik, R Andino, RNA, 1997, 3:882-892; TB Parsley, JS Towner, LB Blyn, E Ehrenfeld, BL Semler, RNA, 1997, 3:1124-1134). To determine the functional role of these ribonucleoprotein complexes in poliovirus replication, HeLa S10 translation-replication reactions were used to quantitatively assay poliovirus mRNA stability, poliovirus mRNA translation, and poliovirus negative-strand RNA synthesis. Ribohomopoly(C) RNA competitor rendered wild-type poliovirus mRNA unstable in these reactions. A 5'-terminal 7-methylguanosine cap prevented the degradation of wild-type poliovirus mRNA in the presence of ribohomopoly(C) competitor. Ribohomopoly(A), -(G), and -(U) did not adversely affect poliovirus mRNA stability. Ribohomopoly(C) competitor RNA inhibited the translation of poliovirus mRNA but did not inhibit poliovirus negative-strand RNA synthesis when poliovirus replication proteins were provided in trans using a chimeric helper mRNA possessing the hepatitis C virus IRES. A C24A mutation prevented UV crosslinking of PCBPs to 5' cloverleaf RNA and rendered poliovirus mRNA unstable. A 5'-terminal 7-methylguanosine cap blocked the degradation of C24A mutant poliovirus mRNA. The C24A mutation did not inhibit the translation of poliovirus mRNA nor diminish viral negative-strand RNA synthesis relative to wild-type RNA. These data support the conclusion that poly(rC) binding protein(s) mediate the stability of poliovirus mRNA by binding to the 5'-terminal cloverleaf structure of poliovirus mRNA. Because of the general conservation of 5' cloverleaf RNA sequences among picornaviruses, including C24 in loop b of the cloverleaf, we suggest that viral mRNA stability of polioviruses, coxsackieviruses, echoviruses, and rhinoviruses is mediated by interactions between PCBPs and 5' cloverleaf RNA.

Binding, Competitive↗
PubMed2001

Acute left ventricular failure following melphalan and fludarabine conditioning.

Cardiotoxicity has rarely been reported as a complication of melphalan or fludarabine administration as single agents. Recently, melphalan and fludarabine have been used in combination as non-myeloablative conditioning chemotherapy prior to allogeneic stem cell transplantation. We have observed the development of severe left ventricular failure in three of 21 patients treated with this combination. Cardiotoxicity in this context has not previously been reported and has implications for the assessment, monitoring and treatment of patients undergoing pre-transplant conditioning with melphalan and fludarabine.

Acute Disease↗
PubMed2001

Poliovirus 5'-terminal cloverleaf RNA is required in cis for VPg uridylylation and the initiation of negative-strand RNA synthesis.

Chimeric poliovirus RNAs, possessing the 5' nontranslated region (NTR) of hepatitis C virus in place of the 5' NTR of poliovirus, were used to examine the role of the poliovirus 5' NTR in viral replication. The chimeric viral RNAs were incubated in cell-free reaction mixtures capable of supporting the sequential translation and replication of poliovirus RNA. Using preinitiation RNA replication complexes formed in these reactions, we demonstrated that the 3' NTR of poliovirus RNA was insufficient, by itself, to recruit the viral replication proteins required for negative-strand RNA synthesis. The 5'-terminal cloverleaf of poliovirus RNA was required in cis to form functional preinitiation RNA replication complexes capable of uridylylating VPg and initiating the synthesis of negative-strand RNA. These results are consistent with a model in which the 5'-terminal cloverleaf and 3' NTRs of poliovirus RNA interact via temporally dynamic ribonucleoprotein complexes to coordinately mediate and regulate the sequential translation and replication of poliovirus RNA.

5' Untranslated Regions↗
PubMed2000

Role of the guanosine triphosphatase Rac2 in T helper 1 cell differentiation.

T helper 1 (TH1) cells mediate cellular immunity, whereas TH2 cells potentiate antiparasite and humoral immunity. We used a complementary DNA subtraction method, representational display analysis, to show that the small guanosine triphosphatase Rac2 is expressed selectively in murine TH1 cells. Rac induces the interferon-gamma (IFN-gamma) promoter through cooperative activation of the nuclear factor kappa B and p38 mitogen-activated protein kinase pathways. Tetracycline-regulated transgenic mice expressing constitutively active Rac2 in T cells exhibited enhanced IFN-gamma production. Dominant-negative Rac inhibited IFN-gamma production in murine T cells. Moreover, T cells from Rac2-/- mice showed decreased IFN-gamma production under TH1 conditions in vitro. Thus, Rac2 activates TH1-specific signaling and IFN-gamma gene expression.

Animals↗
PubMed2000

Identification of a genetic locus modulating splenomegaly induced by granulocyte colony-stimulating factor in mice.

Clinically detectable splenomegaly and splenic rupture are uncommon but potentially life-threatening consequences of G-CSF administration. Increased spleen size in mice injected with G-CSF is a complex genetic trait amenable to investigation in experimental inter-strain crosses by quantitative trait analysis. A quantitative trait locus (QTL) with highly significant linkage (LOD 7.9) for splenomegaly was identified within a 22 centimorgan (cM) region on chromosome 1. Inheritance of a C57BL/6 haplotype in this region was associated with a greater spleen weight. The relevance of this locus was confirmed by analysing the responses of mice congenic for the distal 12 cM of this region (C57BL/6 and C57BL/6.SJL-Ptprc(a) Pep3(b)). Consistent with the QTL effect, mice lacking C57BL/6 alleles in this region had reduced splenomegaly induced by G-CSF. Intriguingly, peripheral blood neutrophilia and progenitor cell mobilisation responses to G-CSF were also significantly influenced.

Animals↗
PubMed1999

Deficiency of the hematopoietic cell-specific Rho family GTPase Rac2 is characterized by abnormalities in neutrophil function and host defense.

In mammals, the Rho family GTPase Rac2 is restricted in expression to hematopoietic cells, where it is coexpressed with Rac1. Rac2-deficient mice were created to define the physiological requirement for two near-identical Rac proteins in hematopoietic cells. rac2-/- neutrophils displayed significant defects in chemotaxis, in shear-dependent L-selectin-mediated capture on the endothelial substrate Glycam-1, and in both F-actin generation and p38 and, unexpectedly, p42/p44 MAP kinase activation induced by chemoattractants. Superoxide production by rac2-/- bone marrow neutrophils was significantly reduced compared to wild type, but it was normal in activated peritoneal exudate neutrophils. These defects were reflected in vivo by baseline neutrophilia, reduced inflammatory peritoneal exudate formation, and increased mortality when challenged with Aspergillus fumigatus. Rac2 is an essential regulator of multiple specialized neutrophil functions.

Actins↗
PubMed1998

Cytokine production and function in c-mpl-deficient mice: no physiologic role for interleukin-3 in residual megakaryocyte and platelet production.

Mice lacking thrombopoietin (TPO), or its receptor c-Mpl, display defective megakaryocyte and platelet development and deficiencies in progenitor cells of multiple hematopoietic lineages. The contribution of alternative cytokines to thrombopoiesis in the absence of TPO signalling was examined in mpl-/- mice. Analysis of serum and organ-conditioned media showed no evidence of a compensatory overproduction of megakaryocytopoietic cytokines. However, consistent with a potential role in vivo, when injected into mpl-/- mice, interleukin-6 (IL-6) and leukemia inhibitory factor (LIF) retained the capacity to elevate megakaryocytes and their progenitors in hematopoietic tissues and increase circulating platelet numbers. However, double mutant mice bred to carry genetic defects both in c-Mpl and IL-3 or the alpha chain of the IL-3 receptor, displayed no greater deficiencies in megakaryocytes or platelets than mpl-deficient animals, suggesting absence of a physiologic role for IL-3 in the residual megakaryocytopoiesis and platelet production in these mice.

Animals↗
PubMed1998

Hematopoietic stem cell deficiencies in mice lacking c-Mpl, the receptor for thrombopoietin.

Thrombopoietin (TPO) acts as a lineage-specific late-acting factor to stimulate megakaryocyte and platelet formation. However, analysis of mice lacking either the cytokine or its receptor, c-Mpl, also revealed deficiencies in progenitor cells of multiple hematopoietic lineages, suggesting that TPO signaling may play an important role in the regulation of the hematopoietic stem cell compartment. To investigate this hypothesis, we determined preprogenitor and colony forming unit-spleen (CFU-S) numbers and analyzed the long-term hematopoietic repopulating capacity of bone marrow cells from mpl-/- mice. mpl-/- mice had 4- to 12-fold fewer preprogenitor cells than wild-type mice. In irradiated normal recipients, mpl-/- bone marrow generated 8- to 10-fold fewer spleen colonies than wild-type marrow at both 8 and 12 days after transplantation. This defect was intrinsic to the transplanted hematopoietic cells, as the microenvironment of mpl-/- recipients supported similar CFU-S growth to that observed in wild-type recipients. In definitive assays of stem cell function, bone marrow cells from mpl-/- mice failed to compete effectively with normal cells for long-term reconstitution of the hematopoietic organs of irradiated recipients, even when transplanted in 10-fold excess. Serial transplantation studies further suggested that stem cell self-renewal also may be compromised in mpl-/- mice. These data imply that TPO, signaling through c-Mpl, plays a vital physiological role in the regulation of hematopoietic stem cell production and function.

Animals↗