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Biomedical subjects

John Barrett

Publications and source records attributed to John Barrett.

At least 37 records · Page 2Linked to original sources
PubMed2004

Binding of hematin by a new class of glutathione transferase from the blood-feeding parasitic nematode Haemonchus contortus.

The phase II detoxification system glutathione transferase (GST) is associated with the establishment of parasitic nematode infections within the gastrointestinal environment of the mammalian host. We report the functional analysis of a GST from an important worldwide parasitic nematode of small ruminants, Haemonchus contortus. This GST shows limited activity with a range of classical GST substrates but effectively binds hematin. The high-affinity binding site for hematin was not present in the GST showing the most identity, CE07055 from the free-living nematode Caenorhabditis elegans. This finding suggests that the high-affinity binding of hematin may represent a parasite adaptation to blood or tissue feeding from the host.

Animals↗
PubMed2004

Nonmyeloablative allogeneic immunotherapy for solid tumors.

Over the past decade, considerable advances have been made in the field of allogeneic hematopoietic stem cell transplantation. Recognition that transplanted donor immune cells can cure patients with leukemia has led to the development of nonmyeloablative or "low-intensity" conditioning regimens, which have expanded the application of allogeneic transplantation to a growing number of hematological malignancies. The improved safety and preliminary success of this transplant approach have justified applying allogeneic immunotherapy to patients with treatment-refractory solid tumors.

Animals↗
PubMed2004

The ultrasound screen for penetrating truncal trauma.

A prospective blinded pilot study was performed at an urban level 1 trauma center to evaluate the efficacy of ultrasound in ruling out penetrating visceral truncal injury. For 8 months, 49 nonconsecutive patients who presented with truncal gunshot and stab wounds were evaluated by a 10-MHz ultrasound tranducer probe. The deepest muscle bundle and the fascia enveloping it was examined by ultrasound. These images were compared to the equivalent contralateral unaffected side of the patient. All the patients then underwent standard testing to evaluate for potential intracavitary injury. Forty-nine patients with a mean age of 28 years (SD, 8.8) were evaluated by ultrasound. A total of 58 injuries were evaluated of which 37 were stab wounds and 21 were gunshot wounds. Thoracoabdominal and back and flank injuries were the most commonly evaluated injuries. There were 20 true positives, 20 false positives, and 18 true negatives, each with approximately twice as many stab as gunshot wounds. There were no false negatives. The sensitivity and negative predictive value of ultrasound in determining clinically significant truncal visceral injury in penetrating truncal trauma is 100 per cent. The specificity and positive predictive value are both approximately 50 per cent. Ultrasonic examination of the injured abdominal wall layers in truncal penetrating trauma is an excellent screening tool. Simple comparative assessment with the unaffected contralateral side allows a highly sensitive method of decreasing the number of potentially morbid, time consuming, and expensive tests that are currently employed to rule out visceral injury.

Adult↗
PubMed2003

Modification of the ionizing radiation response in living cells by an scFv against the DNA-dependent protein kinase.

The non-homologous end joining pathway uses pre-existing proteins to repair DNA double-strand breaks induced by ionizing radiation. Here we describe manipulation of this pathway in living cells using a newly developed tool. We generated a single chain antibody variable fragment (scFv) that binds to the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), a key enzyme in the pathway. In contrast to existing pharmacologic inhibitors, the scFv binds a newly defined regulatory site outside the kinase catalytic domain. Although the scFv inhibits kinase activity only modestly, it completely blocks DNA end joining in a cell-free system. Microinjection of the scFv sensitizes human cells to radiation, as measured by a reduction in efficiency of colony formation and induction of apoptosis at an otherwise sublethal dose of 1.5 Gy. The scFv blocks non-homologous end joining in situ at a step subsequent to histone gamma-H2AX focus formation but preceding gamma-H2AX dephosphorylation. Blockage occurs in cells exposed to as little as 0.1 Gy, indicating that DNA-PKcs is essential for double-strand break repair even at low radiation doses. The ability to modify the radiation response in situ in living cells provides a link between biochemical, genetic and cytologic approaches to the study of double-strand break repair intermediates.

Apoptosis↗
PubMed2003

Proteomic analysis of the larval stage of the parasite Echinococcus granulosus: causative agent of cystic hydatid disease.

We describe the preparation of Echinococcus granulosus metacestode protein extracts for two-dimensional electrophoresis (2-DE). Protoscoleces and hydatid fluid were prepared by precipitation using trichloroacetic acid (TCA) to remove nonprotein contaminants. Compared to the untreated control, TCA precipitation improved the 2-DE gel profile of the protoscoleces proteins. Comparison of 2-DE gels from insoluble and soluble fractions of the protoscoleces protein extract showed that most proteins are insoluble after lysis by sonication. Host serum proteins, especially albumin and globulins, caused horizontal streaking problems on the hydatid fluid 2-DE gels due to their high content in this sample. Even after the preparation of a hydatid fluid parasite enriched fraction, the high amount of bovine serum albumin and globulins made parasite-specific proteins difficult to detect by 2-DE. Despite the absence of an E. granulosus genome sequencing or expressed sequence tag (EST) projects, it was possible to identify 15 prominent protein spots from a whole protein protoscoleces 2-DE gel by peptide mass fingerprinting. These include actins, tropomyosin, paramyosin, thioredoxin reductase, antigen P-29, cyclophilin, and the heat shock proteins hsp70 and hsp20. This work demonstrates that 2-DE and PMF are important tools to identify proteins from the hydatid fluid and protoscoleces and for the comparative analysis of cysts from different hosts or between active and resting cysts.

Animals↗
PubMed2003

Allogeneic stem cell transplantation for chronic myeloid leukemia.

Allogeneic stem cell transplantation (SCT) plays a central role in chronic myeloid leukemia (CML) because it remains the only treatment with proven curative potential. For this reason, SCT has been more frequently performed in CML than in any other disease. The susceptibility of CML to the graft-versus-leukemia (GVL) effect and our ability to monitor minimal residual disease are particular features that place this disease at the forefront of GVL research. This review describes the mechanism of cure of CML by SCT, current results of transplantation, factors determining outcome, management of relapsed or persistent disease, and recent treatment advances.

Graft vs Leukemia Effect↗
PubMed2003

Design, synthesis, and evaluation of radiolabeled integrin alpha v beta 3 receptor antagonists for tumor imaging and radiotherapy.

The goal of this research is the development of tumor imaging and radiotherapeutic agents based on targeting of the integrin alpha(v)beta(3) (vitronectin receptor). Macrocyclic chelator DOTA has been conjugated to peptidomimetic vitronectin receptor antagonist SH066 to give TA138. TA138 and (89)Y-TA138 retain antagonist properties and high affinity for integrin alpha(v)beta(3) (IC(50) = 12 and 18 nM, respectively), and good selectivity versus integrin alpha(IIb)beta(3) (IC(50) > 10,000 nM). TA138 forms stable complexes with (111)In and (90)Y in > 95% RCP. (111)In-TA138 demonstrates high tumor uptake in the c-neu Oncomouse (Charles River Laboratories [Charles River, Canada]) mammary adenocarcinoma model (9.39% ID/g at 2 hours PI) and low background activity. Blood clearance is rapid and excretion is renal. Tumors are visible as early as 0.5 hours PI. Radiotherapy studies in the c-neu Oncomouse model demonstrated a slowing of tumor growth at a dose of 15 mCi/m(2), and a regression of tumors at a dose of 90 mCi/m(2).

Adenocarcinoma↗
PubMed2003

Detection of intra-abdominal injury using diagnostic peritoneal lavage after shotgun wound to the abdomen.

BACKGROUND: The utility of diagnostic peritoneal lavage (DPL) as a diagnostic tool specifically for shotgun wound to the abdomen (SGWA) is unknown. This prospective study was undertaken to determine the sensitivity, specificity, and accuracy of DPL for the detection of intra-abdominal injuries following SGWA. METHODS: DPL was performed on all patients sustaining SGWA who lacked a clear indication for laparotomy. Patients exceeding 10,000 red blood cells (RBC)/mm were taken for exploratory laparotomy. A prospective database was kept with information on wound location, DPL result, findings upon laparotomy and outcome. RESULTS: Thirty-two DPLs were performed at our urban Level I trauma center for SGWA. Of these, 8 patients had a positive DPL. Upon laparotomy, 7 patients were found to have intra-abdominal injuries, 6 of which required surgical intervention. One patient had no peritoneal penetration or intra-abdominal injury. Of the 24 patients that had a negative DPL, 1 subsequently developed indications for laparotomy and was found to have operative injuries. For predicting intra-abdominal injuries DPL has a sensitivity, specificity and accuracy of 87.5%, 95.8% and 93.8%, respectively. CONCLUSION: For patients presenting with SGWA who do not present with indications for immediate laparotomy, DPL is a reliable indicator of intra-abdominal injury and need for operative intervention.

Abdominal Injuries↗
PubMed2003

The PHD/LAP-domain protein M153R of myxomavirus is a ubiquitin ligase that induces the rapid internalization and lysosomal destruction of CD4.

The genomes of several poxviruses contain open reading frames with homology to the K3 and K5 genes of Kaposi's sarcoma-associated herpesvirus (KSHV) and the K3 gene of murine gammaherpesvirus 68, which target major histocompatibility complex class I (MHC-I) as well as costimulatory molecules for proteasomal or lysosomal degradation. The homologous gene product of myxomavirus (MV), M153R, was recently shown to reduce the cell surface expression of MHC-I. In addition, normal MHC-I surface expression was observed in cells infected with MV lacking M153R (J. L. Guerin, J. Gelfi, S. Boullier, M. Delverdier, F. A. Bellanger, S. Bertagnoli, I. Drexler, G. Sutter, and F. Messud-Petit, J. Virol. 76:2912-2923, 2002). Here, we show that M153R also downregulates the T-cell coreceptor CD4 and we study the molecular mechanism by which M153R achieves the downregulation of CD4 and MHC-I. Upon M153R expression, CD4 was rapidly internalized and degraded in lysosomes, whereas deletion of M153R from the genome of MV restored CD4 expression. The downregulation of both CD4 and MHC-I was dependent on the presence of lysine residues in their cytoplasmic tails. Increased ubiquitination of CD4 was observed upon coexpression with M153R in the presence of inhibitors of lysosomal acidification. Surface expression of CD4 was restored upon overexpression of Hrs, a ubiquitin interaction motif-containing protein that sorts ubiquitinated proteins into endosomes. Moreover, the purified PHD/LAP zinc finger of M153R catalyzed the formation of multiubiquitin adducts in vitro. Our data suggest that M153R acts as a membrane-bound ubiquitin ligase that conjugates ubiquitin to the cytoplasmic domain of substrate glycoproteins, with ubiquitin serving as a lysosomal targeting signal. Since a similar mechanism was recently proposed for KSHV K5, it seems that members of the unrelated families of gamma-2 herpesviruses and poxviruses share a common immune evasion mechanism that targets host cell immune receptors.

Amino Acid Sequence↗
PubMed2003

Emerging therapeutic strategies for myelodysplastic syndrome.

Increasing understanding of the pathophysiology of myelodysplastic syndromes (MDS) and a greater appreciation of the large impact that marrow failure has on the symptomatology and outcome of MDS have led to new treatment approaches. We describe recent developments of methods to manage marrow failure, suppress the MDS clone, and widen the applicability of curative treatment with allogeneic stem cell transplants.

Antineoplastic Agents↗
PubMed2002

Trans-mediastinal gunshot wounds: are "stable" patients really stable?

Gunshot wounds that traverse the mediastinum frequently cause serious injury to the cardiac, vascular, pulmonary, and digestive structures contained within. Most patients present with unstable vital signs signifying the need for emergency operation. An occasional patient will present with stable vital signs. Work-ups for such a patient may range from surgical exploration to radiographic and endoscopic testing to mere observation. We report our experience with diagnostic work-up of the stable patient with a transmediastinal gunshot wound. All stable patients who present to our urban level I trauma center following a transmediastinal gunshot wound undergo diagnostic work-up consisting of chest radiograph, cardiac ultrasound, angiography, esophagoscopy, barium swallow, and bronchoscopy. The work-up is dependent on the trajectory of the missile. Information on these patients is kept in a prospective database maintained by the trauma attending physicians. This database was analyzed and comparisons were made using Student's t-test and the Fisher exact c2 as appropriate. Over a 68-month period, 50 stable patients were admitted following a transmediastinal gunshot wound. All of these patients had a chest radiograph followed by one or more of the above tests. 8 patients (16%) were found to have a mediastinal injury (4 cardiac, 3 vascular, and 1 tracheo-esophageal) requiring urgent operation (group 1). The remaining 42 patients (84%) did not have a mediastinal injury (group 2). There was no difference between groups with respect to blood pressure, pulse, respiratory rate, pH, base deficit, or initial chest tube output. There was one death in each group, and three complications in group 2. Patients may appear stable following a transmediastinal gunshot wound, even when they have life-threatening injuries. There is no difference in vital signs, blood gas, or hemothorax to indicate which patients have serious injuries. We advocate continued aggressive work-up of these patients to avoid missing an injury with disastrous consequences.

Adult↗
PubMed2002

Activity of STI571 in chronic myelomonocytic leukemia with a platelet-derived growth factor beta receptor fusion oncogene.

Platelet-derived growth factor beta receptor (PDGFbetaR) fusion genes have been shown to be critical transforming oncogenes in a subset of patients with chronic myelomonocytic leukemia (CMML). The sensitivity of dysregulated tyrosine kinase oncogenes to the tyrosine kinase inhibitor STI571 (imatinib mesylate) makes it a potentially attractive treatment option in this subset of patients. We have recently cloned a novel member of the PDGFbetaR fusion oncogene family, rabaptin-5-PDGFbetaR. A patient with CMML carrying the rabaptin-5-PDGFbetaR fusion gene underwent allogeneic stem cell transplantation (SCT) and was monitored closely with a sensitive reverse transcriptase-polymerase chain assay to detect the novel fusion gene transcript. After achieving a molecular remission at 5 months after transplantation, 15 months after SCT the patient showed persistent and progressive evidence of molecular relapse. After demonstrating in vitro that cells transformed with this specific fusion oncogene are efficiently killed by STI571, the patient was started on STI571. The patient responded rapidly and entered molecular remission after 6 weeks of therapy, and he continues to be in remission 6 months later. These results suggest that STI571 may be an effective targeted therapy in patients with CMML related to PDGFbetaR fusion oncogenes.

Adult↗
PubMed2002

Changes in T-cell receptor VB repertoire in aplastic anemia: effects of different immunosuppressive regimens.

We studied the degree and the pattern of skewing of the variable region of beta-chain (VB) T-cell receptor (TCR) repertoire in aplastic anemia (AA) at initial presentation and after immunosuppression using a high-resolution analysis of the TCR VB complementarity-determining region 3 (CDR3). Age-matched healthy individuals and multitransfused patients with non-immune-mediated hematologic diseases were used as controls. In newly diagnosed AA, the average frequency of CDR3 size distribution deviation indicative of oligoclonal T-cell proliferation was increased (44% +/- 33% vs 9% +/- 9%; P =.0001); AA patients with human leukocyte antigen (HLA)-DR2 and those with expanded paroxysmal nocturnal hemoglobinuria clones showed more skewed VB repertoires. Nonrandom oligoclonal patterns were found for VB6, VB14-16, VB21, VB23, and VB24 subfamilies in more than 50%, and for VB15, VB21, and VB24 in more than 70% of AA patients with HLA-DR2. Patients received immunosuppression with antithymocyte globulin (ATG)/cyclosporine (CsA) or cyclophosphamide (CTX) with CsA in combination, and their VB repertoire was reanalyzed after treatment. Whereas no significant change in the degree of VB skewing in patients who had received ATG was seen, patients treated with CTX showed a much higher extent of oligoclonality within all VB families, consistent with a profound and long-lasting contraction of the T-cell repertoire. VB analysis did not correlate with the lymphocyte count prior to lymphocytotoxic therapy; however, after therapy the degree of VB skewing was highly reflective of the decrease in lymphocyte numbers, suggesting iatrogenic gaps in the VB repertoire rather than the emergence of clonal dominance. Our data indicate that multiple specific clones mediate the immune process in AA.

Adolescent↗
PubMed2002

Optimizing engraftment--source and dose of stem cells.

In recent years, the use of antibodies to measure CD34(+) cells and the availability of peripheral blood (PB) and umbilical cord blood (CB) as additional stem cell sources other than bone marrow (BM) has increased interest in determining the impact of stem cell source and dose on the outcome of allogeneic stem cell transplantation. In addition to differences in their stem cell content, transplants from the three sources differ in the composition and state of activation of immune cells. As a consequence, BM, CB, and PB transplants have different kinetics of hematological recovery, the most rapid engraftment being observed with PB and the slowest with CB. Stem cell source also incurs different risks for developing graft-versus-host disease (GVHD): PB transplants show a possible increase in acute and a definite increase in chronic GVHD compared with BM. CB transplants have a favorably low risk of GVHD even in mismatched transplants. Stem cell dose in an independent factor in transplants from any source, determining engraftment, transplant-related mortality and risk of leukemic relapse. These findings are of clinical importance-an understanding of the impact of stem cell source and dose is essential to obtain optimum conditions for a successful outcome after transplant.

Blood Cells↗
PubMed2002

Nonmyeloablative stem cell transplantation for solid tumors: expanding the application of allogeneic immunotherapy.

In the arena of tumor immunology, there is a growing perception that the graft-versus-leukemia (GVL) reaction that follows allogeneic stem cell transplantation represents the most potent form of cancer immunotherapy currently in clinical use. While allogeneic stem cell transplantation has become an accepted form of "immunotherapy" for the treatment of hematological malignancies, its efficacy in inducing antitumor effects against nonhematological cancers has, until recently, been largely unexplored. The investigational application of nonmyeloablative allogeneic stem cell transplantation (NST) in solid tumors represents the logical consequence of almost 50 years of experimental and clinical research into the immunological basis for the cure of hematological malignancies following allogeneic bone marrow transplant (BMT). Here we review the historical background, development, and preliminary clinical results of allogeneic stem cell transplantation as immunotherapy for solid tumors.

Animals↗