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Biomedical subjects

H Barker

Publications and source records attributed to H Barker.

At least 19 recordsLinked to original sources
PubMed2001

Umbravirus gene expression helps potato leafroll virus to invade mesophyll tissues and to be transmitted mechanically between plants.

Potato leafroll virus (PLRV) was mechanically transmissible when inocula also contained the umbravirus Pea enation mosaic virus-2 (PEMV-2). In plants infected with PLRV and PEMV-2, PLRV accumulated in clusters of mesophyll cells in both inoculated and systemically infected leaves. No transmissions were obtained by coinoculation with Potato virus Y, Potato virus X (PVX), Tobacco mosaic virus, or Cucumber mosaic virus (CMV), although PLRV was transmissible from mixtures with CMV(ORF4) (a recombinant that contained the movement protein (MP) gene of the umbravirus Groundnut rosette virus (GRV) in place of the CMV MP gene). In contrast, neither a recombinant PVX that expressed GRV MP nor a mutant of CMV(ORF4), in which the CMV 2b gene was untranslatable, was able to help PLRV transmission. Possibly both a cell-to-cell movement function and counterdefense mechanisms such as those that block posttranscriptional gene silencing are involved in movement of PLRV within plants and its mechanical transmission between plants.

Arachis↗
PubMed2001

A review of host major-gene resistance to potato viruses X, Y, A and V in potato: genes, genetics and mapped locations.

In view of modern developments in the technologies available for breeding potatoes for resistance to virus diseases, it is timely to review the host major genes that confer resistance, in Solanum species, to potato viruses X, Y, A and V (the viruses for which the resistance genes have been most extensively studied). Over the course of 60 years, many such genes in Solanum species have been characterized: a comprehensive list is presented. Inheritance studies are reviewed, including linkage studies and molecular mapping, and the positions of resistance genes mapped so far are listed. It is apparent from recent research that disease resistance genes are often clustered in particular regions of the chromosomes; the significance of these resistance gene clusters is discussed. The information presented will be useful for potato breeding, and for genetic and mapping studies and gene cloning.

Chromosome Mapping↗
PubMed2001

Breeding virus resistant potatoes (Solanum tuberosum): a review of traditional and molecular approaches.

Tetraploid cultivated potato (Solanum tuberosum) is the World's fourth most important crop and has been subjected to much breeding effort, including the incorporation of resistance to viruses. Several new approaches, ideas and technologies have emerged recently that could affect the future direction of virus resistance breeding. Thus, there are new opportunities to harness molecular techniques in the form of linked molecular markers to speed up and simplify selection of host resistance genes. The practical application of pathogen-derived transgenic resistance has arrived with the first release of GM potatoes engineered for virus resistance in the USA. Recently, a cloned host virus resistance gene from potato has been shown to be effective when inserted into a potato cultivar lacking the gene. These and other developments offer great opportunities for improving virus resistance, and it is timely to consider these advances and consider the future direction of resistance breeding in potato. We review the sources of available resistance, conventional breeding methods, marker-assisted selection, somaclonal variation, pathogen-derived and other transgenic resistance, and transformation with cloned host genes. The relative merits of the different methods are discussed, and the likely direction of future developments is considered.

Animals↗
PubMed2000

D-dimer assay for deep vein thrombosis: its role with colour Doppler sonography.

AIM: To evaluate the role of a negative D-dimer assay in the initial management of patients with clinically suspected deep venous thrombosis (DVT), using colour Doppler ultrasound as the primary diagnostic technique. MATERIALS AND METHODS: A double-blind prospective trial was performed on 143 patients with clinically suspected DVT. All patients underwent a D-dimer assay prior to anticoagulant therapy. DVT was confirmed or excluded by diagnostic colour Doppler ultrasound within 24 h of presentation. RESULTS: In nearly one-third of the cases (31.8%), Doppler ultrasound was positive. The D-dimer assay demonstrated a sensitivity of 97.7% with only one false-negative, but the specificity was low at 48.9% with 45 false-positive results. The positive predictive value for D-dimer assay was 48.8%, whilst the important negative predictive value was 98%. CONCLUSION: If D-dimer was used to screen for DVT, and patients with negative results were not imaged, then the imaging workload could be reduced by 35%. In this study one small calf vein thrombus would have been missed by adopting this practice.Bradley, M. (2000). Clinical Radiology 55, 525-527.

Adolescent↗
PubMed2000

Potato mop-top virus RNA can move long distance in the absence of coat protein: evidence from resistant, transgenic plants.

Transgenic expression of a translatable version of the Potato mop-top virus (PMTV) coat protein (CP) gene (encoded by RNA 3) in Nicotiana benthamiana prevented production of symptoms and infective virus particles. RNAs 1 and 2 accumulated in inoculated and systemic leaves but, apart from small amounts of CP transgene RNA transcript, no genomic-length RNA 3 was found. Crude leaf extracts from inoculated plants were not infective. However, when RNA extracts from such transgenic plants were inoculated to nontransgenic N. benthamiana and N. clevelandii, RNA 1 and RNA 2 replicated in systemic leaves of both species in the absence of RNA 3 and virus particles, but symptoms did not develop. We suggest that the triple-gene block proteins of PMTV (encoded by RNA 2) represent a class of long-distance RNA movement factors.

Blotting, Northern↗
PubMed1999

Rapid production of single-chain Fv fragments in plants using a potato virus X episomal vector.

We have used a plant virus episomal vector, based on potato virus X (PVX) to transiently express a single-chain Fv (scFv) and its diabody derivative in plants. The scFv was directed against a continuous epitope (cryptotope) on the coat protein of potato virus V. A cloned, full-length PVX vector sequence, containing the scFv gene, was used to direct in vitro transcription and the resulting RNA was used to inoculate Nicotiana clevelandii plants. Within a few days, plants developed characteristic symptoms and immunoblot analysis showed that accumulation of scFv protein coincided with accumulation of PVX. Targeting of the scFv to the apoplast greatly increased protein accumulation compared with cytosolic scFv and produced more severe symptoms on infected plants. ELISA demonstrated that the scFv and diabody extracted from infected plants showed the same antigen-binding specificity as that of the parental monoclonal antibody. The PVX vector is a convenient, rapid, low-cost in planta expression system that can also be used for assessment of scFv production and function prior to stable plant transformation.

Amino Acid Sequence↗
PubMed1999

Cost-effectiveness of brief psychodynamic-interpersonal therapy in high utilizers of psychiatric services.

BACKGROUND: It is known that a small number of patients with mental health problems have chronic disorders and account for a disproportionate amount of mental health costs. This randomized controlled trial evaluated the cost-effectiveness of psychodynamic-interpersonal therapy vs treatment as usual in patients with mental health problems who were unresponsive to usual treatment. METHOD: Subjects (N = 110) with nonpsychotic disorders unresponsive to 6 months of routine specialist mental health treatment were enrolled in a randomized controlled trial. Sixty-three percent were women, the mean age was 41.4 years, the median duration of illness was 5 years, 68% were unemployed or receiving state benefits because of illness, and 75.5% had a depressive illness. Intervention patients received 8 weekly sessions of psychodynamic-interpersonal psychotherapy. Control patients received usual care from their psychiatrist. Outcome measures included ratings of psychological distress and health status and a detailed economic evaluation. Analysis was conducted on an intent-to-treat basis. RESULTS: Subjects randomized to psychotherapy had a significantly greater improvement than controls in psychological distress and social functioning 6 months after the trial. Baseline treatment costs were similar for both groups. Subjects who received psychotherapy showed significant reductions in the cost of health care utilization in the 6 months after treatment compared with controls. The extra cost of psychotherapy was recouped within 6 months through reductions in health care use. CONCLUSION: These preliminary findings suggest that brief psychodynamic-interpersonal therapy may be cost-effective relative to usual care for patients with enduring nonpsychotic symptoms who are not helped by conventional psychiatric treatment.

Adult↗
PubMed1998

Isolation and characterization of alpha-tubulin genes from Septoria tritici and Rhynchosporium secalis, and comparative analysis of fungal alpha-tubulin sequences.

The alpha-tubulin genes from Septoria tritici and Rhynchosporium secalis have been cloned and sequenced. The predicted amino acid sequence and intron structure showed strong homology with other known filamentous fungal alpha-tubulins. Comparison of sixteen fungal alpha-tubulin sequences based on amino acid sequence homology and intron structure identified five groups of proteins. Group 1 consists of filamentous fungi, including S. tritici and R. secalis, the dimorphic fungus Histoplasma capsulatum, and Pneumocystis carinii. Group 2 includes two divergent isoforms from Neurospora crassa and Aspergillus nidulans. Group 3 includes the yeast Saccharomyces cerevisiae and the dimorphic fungus Candida albicans. Group 4 contains the single yeast Schizosaccharomyces pombe. Group 5 includes the only Basidiomycete, Schizophyllum commune. This analysis supports the classification of P carinii as a primitive Ascomycete. The presence of an additional glycine residue between the second and third amino acid found only in Group 2 proteins may indicate a functionally distinct fungal isotype. Implications in terms of structure-function relationships for alpha-tubulin molecules are discussed.

Amino Acid Sequence↗
PubMed1998

Recovery of spermatogenesis following bone marrow transplantation.

Preparative regimens used in bone marrow transplantation usually result in impairment of male fertility. Although recovery of fertility is more likely after chemotherapy-based regimens, this is a rare occurrence after TBI containing regimens. We undertook a cross-sectional study of recovery of spermatogenesis in men who had undergone allogeneic and autologous marrow or peripheral stem cell transplant between 1984 and 1995. We identified six out of 42 patients eligible for analysis to have either recovered fertility or spermatogenesis. Seminal fluid analysis showed that four out of 25 patients recovered sperm counts. This has important implications for patient counselling, post-transplant follow-up and contraceptive advice.

Adult↗
PubMed1998

Fungal beta-tubulin, expressed as a fusion protein, binds benzimidazole and phenylcarbamate fungicides.

Benzimidazoles are important antitubulin agents used in veterinary medicine and plant disease control. Resistance is a practical problem correlated with single amino acid changes in beta-tubulin and is often linked to greater sensitivity to phenylcarbamates. This negative cross-resistance creates opportunities for durable antiresistance strategies. Attempts to understand the molecular basis of benzimidazole resistance have been hampered by the inability to purify tubulin from filamentous fungi. We have overcome some of these problems by expressing beta-tubulin as a fusion with a maltose binding protein. This fusion protein is soluble, and we confirm for the first time using a gel filtration assay that benzimidazoles indeed bind to beta-tubulin. This binding is reduced by the mutation Glu198-->Gly198, which also confers resistance. Binding of phenylcarbamates is the complete opposite, reflecting their biological activity and the negative cross-resistance. This suggests that the fungicide binding sites fold correctly in the fusion protein.

Base Sequence↗
PubMed1997

Clonal stability in late-relapsing childhood lymphoblastic leukaemia.

We report stability of a clonal immunoglobulin heavy chain (IgH) gene rearrangement in a case of childhood acute lymphoblastic leukaemia (ALL) relapsing 17 years after completion of first-line therapy. Clonal stability was shown by polymerase chain reaction amplification of the hypervariable CDRIII region of IgH gene. Identically sized products from the original diagnostic and the second presentation samples were obtained and direct sequencing confirmed complete sequence homology. Absence of clonal evolution together with recent reports of persistent minimal residual disease in patients in long-term complete remission, suggests that 'cure' of childhood ALL may be critically dependent on effective immune surveillance to keep such disease below clinically significant levels.

Adult↗
PubMed1997

Short and long distance spread of potato leafroll luteovirus: effects of host genes and transgenes conferring resistance to virus accumulation in potato.

Potato leafroll luteovirus (PLRV) movement through phloem of PLRV-resistant potato clones was examined in experiments in which stem pieces were grafted either between infected rootstocks and virus-free susceptible scions or between infected scions and virus-free susceptible rootstocks. These test plants permitted either upwards or downwards virus movement into the susceptible tissue. Resistant potato clones had either host gene-mediated resistance (H-MR) or transgene-mediated resistance (T-NR, conferred by transformation with the PLRV coat protein gene) to PLRV accumulation. The rate of PLRV movement was similar whether stem tissue was taken from H-MR, T-MR or susceptible potato clones. Virus movement through two graft unions began around 7 days after grafting and was generally complete by about 14 to 16 days. Virus movement occurred soon after acquiring functional phloem continuity across grafts as demonstrated by tracing with 6(5)-carboxyfluorescein, a phloem-mobile dye. Most of the delay in virus detection after grafting probably resulted from the time necessary to develop new phloem strands across graft unions; subsequent movement of PLRV was rapid suggesting a passive process. PLRV infection was largely excluded from external phloem bundles in stem tissue of clones with either H-MR or T-MR. This trait was less pronounced as tissue aged. The mechanism limiting PLRV invasion of external phloem bundles of the T-MR clones appears to be similar to that operating in the H-MR clones. Results are discussed in the context of a proposed model of PLRV movement.

Antigens, Viral↗
PubMed1996

Human T-cell lymphotropic virus type I infection in Barbados: results of a 20-year follow-up study.

Forty-one human T-cell lymphotropic virus type I (HTLV-1)-seropositive individuals were identified among 1,012 subjects with stored serum samples from a health and seroepidemiological survey conducted in Barbados in 1972. These 41 subjects plus 79 HTLV-1 seronegative household members were targeted in a follow-up study 20 years later. Sixteen seropositive subjects and 22 seronegative subjects were interviewed, examined, and phlebotomized. There were no changes in HTLV-1 serostatus between the 1972 and follow-up serum samples. Three (19%) of the seropositive subjects had HTLV-1-associated disorders: two with dermatitis and one with "smoldering" adult T-cell leukemia. Neurologic and immunologic function was similar in HTLV-1-seropositive and HTLV-1-seronegative subjects. HTLV-1 antibodies persist over many years, and the risk for seroconversion of household contacts is low.

Adolescent↗
PubMed1994

Release of gastric inhibitory polypeptide from cultured canine endocrine cells.

Canine intestinal duodenal and jejunal epithelial cell preparations enriched for endocrine cells were obtained by sequential collagenase digestion and centrifugal elutriation and maintained in culture for a 40-h period. Adherent cells contained a total cell content (TCC) of 11.5 +/- 2.5 ng (mean +/- SE) immunoreactive gastric inhibitory peptide (IRGIP)/well and 1.4 +/- 0.2 ng immunoreactive somatostatin (IRS)/well. Release experiments were performed by incubation of the cells with various stimuli over a 2-h period. Basal release of IRGIP in 5 mM glucose-5 mM K+ was 2.7 +/- 0.4% TCC. Incubation with concentrations of K+ > 20 mM or glucose > 15 mM significantly increased IRGIP release, as did the addition of a somatostatin immunoneutralizing antibody to the basal media. The addition of the Ca2+ ionophore, A-23187 (10 microM), or the adenylate cyclase activator, forskolin (100 microM), resulted in an IRGIP output greater than four times basal. Porcine gastrin-releasing peptide (GRP), at 1-100 nM, significantly stimulated IRGIP release in a concentration-dependent fashion. IRS release was increased significantly by 55 mM K+, 20 mM glucose, 10 microM A-23187, 100 nM GRP, or 100 microM forskolin.

Animals↗
PubMed1994

Experimental arthritis and uveitis in rats associated with Mycobacterium butyricum.

OBJECTIVE: To determine if the anterior uveitis associated with adjuvant arthritis (AA) in the rat can be passively transferred with arthritis to syngeneic recipients using spleen cells or T cell lines prepared from animals given complete Freund's adjuvant (CFA) and Mycobacterium butyricum (M. butyricum) in incomplete Freund's adjuvant (IFA). METHODS: Spleen cells from Lewis or Lewis SsN rats given IFA, CFA, type I collagen in IFA (CI-IFA), or type II collagen in IFA (CII-IFA) were administered to naive rats or rats treated with pertussis toxin or bacterial endotoxin. Three CD4+ T cell lines, propagated from CFA injected rats and maintained in vitro with M. butyricum (M-1), bovine proteoglycan (PR-1) or an extract of M. butyricum (MBE-1) were administered to naive or immunosuppressed rats. The arthritogenic and uveitogenic properties of these cell preparations and intradermal MBE-IFA, CII-IFA and intraperitoneal (ip) M. butyricum without adjuvant were evaluated. RESULTS: Uveitis was observed in 15/69 (22%) arthritic rats given CFA. Spleen cells prepared from CFA injected rats caused arthritis in 55 (82%) and uveitis in 2 (3%) of 67 cell recipients. Uveitis occurred in 2/6 cell recipients pretreated with bacterial endotoxin. Neither uveitis nor arthritis was observed in rats given IFA (0/6) or spleen cells prepared from rats given IFA (0/27), CI-IFA (0/6), or CII-IFA (0/28). CII-IFA produced polyarthritis in 5/6 rats, but no uveitis. CII-IFA induced arthritis associated uveitis in 1/15 animals receiving spleen cells from rats given CII-IFA, but not those given CI-IFA (0/3) or IFA (0/13). Uveitis was observed in one recipient of the M-1 T cell line and in 2 recipients of the PR-1 T cell line. Immunization with 400 micrograms of MBE-IFA induced uveitis but not arthritis in 3/11 animals. The MBE specific T cell line was neither arthritogenic nor uveitogenic. A high frequency (5/6) of uveitis accompanied arthritis in male Lewis rats given ip M. butyricum. Arthritis occurred in 4/10 female Lewis rats given ip M. butyricum and 2 arthritic animals also developed uveitis. CONCLUSION: Uveitis occurs infrequently in arthritic rats given spleen cells from CFA injected animals. The ip administration of M. butyricum constitutes a novel disease model in which the immunopathological relationships between arthritis and uveitis may be more reliably studied.

Animals↗