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B Seddon

Publications and source records attributed to B Seddon.

At least 19 recordsLinked to original sources
PubMed2003

Molecular detection and beta-glucuronidase expression of gus-marked Bacillus subtilis L-form bacteria in developing Chinese cabbage seedlings.

AIM: To detect L-form bacteria in developing Chinese cabbage seedlings. METHODS AND RESULTS: Stable Bacillus subtilis L-forms were genetically modified to express the gus gene (encoding beta-glucuronidase). Germinated seeds of Chinese cabbage were soaked in mannitol based suspensions of the L-form bacteria or with mannitol alone and after washing were grown in aseptic conditions on plant growth medium. Histochemical staining of beta-glucuronidase activity (X-gluc) and Polymerase Chain Reaction (PCR) detection of the gus gene were achieved in the L-form associated seedlings. beta-Glucuronidase was localized in discrete spots, mainly in the roots with staining, and was also observed in the cotyledons and base of stems. Correlation was observed between PCR detection of the gus gene and histochemical staining with detection in similar tissues. Stable L-form bacteria were non-culturable after their association with plant material. CONCLUSIONS: The gus reporter gene system with its associated histological staining for enzyme activity was used successfully for detecting B. subtilis L-form bacteria in plant material. SIGNIFICANCE AND IMPACT OF THE STUDY: These molecular marked L-forms should provide a specific and sensitive technique for detecting L-form bacteria in planta and offer a method for further understanding the L-form/plant association.

Bacillus subtilis↗
PubMed2001

Sensory adaptation in naive peripheral CD4 T cells.

T cell receptor interactions with peptide/major histocompatibility complex (pMHC) ligands control the selection of T cells in the thymus as well as their homeostasis in peripheral lymphoid organs. Here we show that pMHC contact modulates the expression of CD5 by naive CD4 T cells in a process that requires the continued expression of p56(lck). Reduced CD5 levels in T cells deprived of pMHC contact are predictive of elevated Ca(2)+ responses to subsequent TCR engagement by anti-CD3 or nominal antigen. Adaptation to peripheral pMHC contact may be important for regulating naive CD4 T cell responsiveness.

Adaptation, Physiological↗
PubMed2001

Mode of antagonism of Brevibacillus brevis against Botrytis cinerea in vitro.

AIMS: To assess the activity of Brevibacillus brevis (formerly Bacillus brevis) Nagano and the antibiotic it produces, gramicidin S, against the plant pathogen Botrytis cinerea. METHODS AND RESULTS: Germination and growth of Bot. cinerea were assessed in the presence of B. brevis or gramicidin S in liquid media, on solid media and on leaf sections of Chinese cabbage. Germination was 10-fold more sensitive to gramicidin S than growth. Inhibition of Bot. cinerea was greater in liquid media compared with on solid media. Activity of gramicidin S against Bot. cinerea on leaf sections was much lower than in vitro. In vitro inhibition of Bot. cinerea by B. brevis Nagano was similar to equivalent levels of gramicidin. CONCLUSIONS: Antibiosis, via gramicidin S, is the mode of antagonism exhibited by B. brevis Nagano against Bot. cinerea in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: The mode of antagonism of B. brevis against Bot. cinerea was elucidated. The differing activity of gramicidin S against Bot. Cinerea in vitro and on leaf sections indicates one mechanism by which biocontrol activity may differ between laboratory and field conditions.

Antibiosis↗
PubMed2001

Selective media for the specific isolation and enumeration of Botrytis cinerea conidia.

AIMS: To develop selective media for the enumeration of Botrytis cinerea. METHODS AND RESULTS: Two new media, Botrytis Selective Medium (BSM) and Botrytis Spore Trap Medium (BSTM), were developed and compared with currently available media for the enumeration of B. cinerea conidia from the environment. The new Botrytis media proved advantageous over previous media because they were easier to prepare, had greater selectivity and allowed enumeration when a greater number of colony-forming units were present on individual plates. CONCLUSION: BSM and BSTM were shown to be suitable selective media for the enumeration of B. cinerea conidia from the environment. SIGNIFICANCE AND IMPACT OF THE STUDY: The media developed can be used to monitor the population of the pathogen B. cinerea and will allow detailed studies within the crop environments.

Ascomycota↗
PubMed2000

Long-term survival but impaired homeostatic proliferation of Naïve T cells in the absence of p56lck.

Interactions between the T cell receptor (TCR) and major histocompatibility complex antigens are essential for the survival and homeostasis of peripheral T lymphocytes. However, little is known about the TCR signaling events that result from these interactions. The peripheral T cell pool of p56lck (lck)-deficient mice was reconstituted by the expression of an inducible lck transgene. Continued survival of peripheral naïve T cells was observed for long periods after switching off the transgene. Adoptive transfer of T cells from these mice into T lymphopoienic hosts confirmed that T cell survival was independent of lck but revealed its essential role in TCR-driven homeostatic proliferation of naïve T cells in response to the T cell-deficient host environment. These data suggest that survival and homeostatic expansion depend on different signals.

Animals↗
PubMed2000

The third function of the thymus.

Nonresponsiveness of mammalian T cells to self-antigens is not totally accounted for in terms of clonal deletion, T-cell anergy and T-cell ignorance: studies have shown that the T-cell repertoire of healthy individuals contains cells with the potential to cause autoimmune disease. This article describes a T-cell-mediated mechanism that prevents the realization of this potential and indicates how its failure can lead to the development of autoimmunity.

Animals↗
PubMed2000

Target volume definition in conformal radiotherapy for prostate cancer: quality assurance in the MRC RT-01 trial.

BACKGROUND AND PURPOSE: Prior to randomization of patients into the UK Medical Research Council multicentre randomized trial (RT-01) of conformal radiotherapy (CFRT) in prostate cancer, clinicians at participating centres were required to complete a quality assurance (QA) clinical planning exercise to enable an investigation of inter-observer variability in gross target volume (GTV) and normal structure outlining. MATERIALS AND METHODS: Thirteen participating centres and two investigators completed the clinical planning exercise of three practice planning cases. Clinicians were asked to draw outlines of the GTV, rectum and bladder on hard-copy computerized tomography (CT) films of the pelvis, which were transferred onto the Cadplan computer planning system by a single investigator. Centre, inferior and superior CT levels of GTV, rectum and bladder were noted, and volume calculations performed. Planning target volumes (PTV) were generated using automatic volume expansion of GTVs by a 1 cm margin. Anterior, right and left lateral beam eye views (BEV) of the PTVs were generated. Using a common central point, the BEV PTVs were superimposed for each beam direction of each case. Radial PTV variation was investigated by measurement of a novel parameter, termed the radial line measurement variation (RLMV). RESULTS: GTV central slice and length were defined with reasonable consistency. The RLMV analysis showed that the main part of the prostate gland, bladder and inferior rectum were outlined with good consistency among clinicians. However, the outlining of the prostatic apex, superior aspect of the prostate projecting into the bladder, seminal vesicles, the base of seminal vesicles and superior rectum were more variable. CONCLUSION: This exercise has demonstrated adequate consistency of GTV definition. The RLMV method of analysis indicates particular regions of clinician uncertainty. Appropriate feedback has been given to all participating clinicians, and the final RT-01 trial protocol has been modified to accommodate these findings.

Humans↗
PubMed2000

Inducible expression of a p56Lck transgene reveals a central role for Lck in the differentiation of CD4 SP thymocytes.

The T lymphocyte-specific protein tyrosine kinase p56lck (Lck) is an essential component of the TCR-mediated signal transduction complex. Lck knockout mice have reduced numbers of double-positive thymocytes and very few mature single-positive cells, particularly of the CD4 lineage. Here we demonstrate the ability of a tetracycline-based tissue-specific inducible Lck transgene to restore expansion of early thymocytes and maturation of single-positive cells in Lckneg mice upon induction with doxycycline. Restoration of Lck expression is particularly important for positive selection to the CD4+ lineage but has a lesser impact on selection to the CD8+ lineage, suggesting activation of Lck is an important component of the signals involved in lineage choice during thymic differentiation.

Animals↗
PubMed2000

Selective medium based on tyrosine metabolism for the isolation and enumeration of Brevibacillus brevis (Bacillus brevis).

AIMS: To develop a selective medium for the enumeration of Brevibacillus brevis Nagano spores from soil and plant material. METHODS AND RESULTS: Tyrosine agar was developed as a selective medium and compared with nutrient agar for the enumeration of B. brevis Nagano spores from sterile and non-sterile plant and soil extracts. Brevibacillus brevis Nagano colonies could be easily identified only on tyrosine agar due to their clear halo and distinct colony morphology. Identification was confirmed by thin layer chromatography of the antibiotic, gramicidin S, produced by this strain. CONCLUSIONS: Tyrosine agar was shown to be a suitable selective medium for the enumeration of B. brevis Nagano. SIGNIFICANCE AND IMPACT OF THE STUDY: The medium developed, tyrosine agar, can be used to monitor the population of the biological control agent, B. brevis Nagano, and will allow detailed studies within the crop environment.

Bacillus↗
PubMed2000

The physiological role of regulatory T cells in the prevention of autoimmunity: generation, specificity and mode of action.

Until recently, the traditional view was that tolerance to self antigens was maintained by a combination of physical deletion, in the thymus, and functional deletion, in the periphery, of autoreactive T cells. There is now, however, abundant evidence that the normal T cell repertoire contains overtly autoreactive T cells whose pathogenic potential is held in check by the activity of a distinct subset of peripheral T cells, the so-called regulatory or suppressor T cells. This article examines data from one model of rodent autoimmunity, where autoimmune pathology develops following thymectomy and irradiation of normal laboratory rats, which characterize the development and function of these so-called regulatory T cells.

Animals↗
PubMed1999

Peripheral autoantigen induces regulatory T cells that prevent autoimmunity.

Previous studies have shown that autoimmune thyroiditis can be induced in normal laboratory rats after thymectomy and split dose gamma-irradiation. Development of disease can be prevented by reconstitution of PVG rats shortly after their final irradiation with either peripheral CD4(+)CD45RC- T cells or CD4(+)CD8(-) thymocytes from syngeneic donors. Although the activity of both populations is known to depend on the activities of endogenously produced interleukin 4 and transforming growth factor beta, implying a common mechanism, the issue of antigen specificity of the cells involved has not yet been addressed. In this study, we show that the regulatory T cells that prevent autoimmune thyroiditis are generated in vivo only when the relevant autoantigen is also present. Peripheral CD4(+) T cells, from rats whose thyroids were ablated in utero by treatment with 131I, were unable to prevent disease development upon adoptive transfer into thymectomized and irradiated recipients. This regulatory deficit is specific for thyroid autoimmunity, since CD4(+) T cells from 131I-treated PVG.RT1(u) rats were as effective as those from normal donors at preventing diabetes in thymectomized and irradiated PVG.RT1(u) rats. Significantly, in contrast to the peripheral CD4(+) T cells, CD4(+)CD8(-) thymocytes from 131I-treated PVG donors were still able to prevent thyroiditis upon adoptive transfer. Taken together, these data indicate that it is the peripheral autoantigen itself that stimulates the generation of the appropriate regulatory cells from thymic emigrant precursors.

Animals↗
PubMed1999

Regulatory T cells in the control of autoimmunity: the essential role of transforming growth factor beta and interleukin 4 in the prevention of autoimmune thyroiditis in rats by peripheral CD4(+)CD45RC- cells and CD4(+)CD8(-) thymocytes.

Previous studies have shown that induction of autoimmune diabetes by adult thymectomy and split dose irradiation of PVG.RT1(u) rats can be prevented by their reconstitution with peripheral CD4(+)CD45RC-TCR-alpha/beta+RT6(+) cells and CD4(+)CD8(-) thymocytes from normal syngeneic donors. These data provide evidence for the role of regulatory T cells in the prevention of a tissue-specific autoimmune disease but the mode of action of these cells has not been reported previously. In this study, autoimmune thyroiditis was induced in PVG.RT1(c) rats using a similar protocol of thymectomy and irradiation. Although a cell-mediated mechanism has been implicated in the pathogenesis of diabetes in PVG.RT1(u) rats, development of thyroiditis is independent of CD8(+) T cells and is characterized by high titers of immunoglobulin (Ig)G1 antithyroglobulin antibodies, indicating a major humoral component in the pathogenesis of disease. As with autoimmune diabetes in PVG. RT1(u) rats, development of thyroiditis was prevented by the transfer of CD4(+)CD45RC- and CD4(+)CD8(-) thymocytes from normal donors but not by CD4(+)CD45RC+ peripheral T cells. We now show that transforming growth factor (TGF)-beta and interleukin (IL)-4 both play essential roles in the mechanism of this protection since administration of monoclonal antibodies that block the biological activity of either of these cytokines abrogates the protective effect of the donor cells in the recipient rats. The prevention of both diabetes and thyroiditis by CD4(+)CD45RC- peripheral cells and CD4(+)CD8(-) thymocytes therefore does not support the view that the mechanism of regulation involves a switch from a T helper cell type 1 (Th1) to a Th2-like response, but rather relies upon a specific suppression of the autoimmune responses involving TGF-beta and IL-4. The observation that the same two cytokines were implicated in the protective mechanism, whether thymocytes or peripheral cells were used to prevent autoimmunity, strongly suggests that the regulatory cells from both sources act in the same way and that the thymocytes are programmed in the periphery for their protective role. The implications of this result with respect to immunological homeostasis are discussed.

Animals↗
PubMed1998

Deaggregated homologous immunoglobulin-peptide conjugates induce peptide-specific T cell nonresponsiveness in vivo.

Previous studies have proven the efficacy of intravenous injection of deaggregated protein as a means of inducing tolerance. In the present study, the immunodominant peptide 70-86 of myelin basic protein (MBP) was covalently linked to either mouse Ig or Lewis rat IgG. Lewis rats immunized with MBP in complete Freund's adjuvant were completely protected from development of experimental allergic encephalomyelitis (EAE) by their injection with as little as 40 microg of peptide conjugate on days 0 and 10 after immunization. Peptide-specific proliferative and cytokine responses by T cells from treated rats in vitro were severely depressed compared with controls, while responses to whole MBP were unaffected. Significantly, injections of 100 microg of peptide conjugate on days 0 and 4 after adoptive transfer of peptide-specific T lines protected rats from passive EAE while a single injection of 100 microg of conjugate at the onset of active EAE prevented any further disease progression. Both results suggest that primed effector cells as well as naive T cells are prone to tolerance induction by this means. The ability to intervene in ongoing immune responses with such specificity may be useful therapeutically in control of autoimmunity or allergic responses to environmental antigens.

Animals↗
PubMed1998

Bacillus isolates from the spermosphere of peas and dwarf French beans with antifungal activity against Botrytis cinerea and Pythium species.

A range of isolation procedures including washing, sonication and incubation in nutrient broth were used separately and in combination to obtain potential bacterial antagonists to Botrytis cinerea and Pythium mamillatum from the testae and cotyledons of peas and dwarf French beans. Heat treatment was also used to bias this selection towards spore-forming bacteria. Ninety-two bacterial isolates were obtained, 72 of which were provisionally characterized as species of Bacillus. Four of these Bacillus isolates (B3, C1, D4 and J7) displayed distinct antagonism in vitro against Botrytis cinerea and P. mamillatum when screened using dual culture analysis. Further characterization of these antagonists using API 50CHB biochemical profiling identified isolate D4 as Bacillus polymyxa and isolates B3, C1 and J7 as strains of B. subtilis. In vitro screening techniques, using cell-free and heat-killed extracts of liquid cultures against Botrytis cinerea, demonstrated the production of antifungal compounds by these four Bacillus antagonists. With each isolate the antifungal activity was found not to be either exclusively spore-bound nor released entirely into the medium but present in both fractions. The antifungal compounds produced by these isolates were shown to be heat-stable. Their identification, production and release require further study for exploitation as biocontrol systems.

Antibiosis↗
PubMed1997

Homeostatic mechanisms in the control of autoimmunity.

The data in this article challenge the current paradigm that self tolerance among T cells can be fully accounted for in terms of intrathymic clonal deletion, anergy and T-cell 'indifference'. We show that autoreactive T cells are under the control of a dominant T-cell-mediated control mechanism and that the thymus is a particularly potent source of these protective cells. We further show that 'peripheral' self antigens implicated in autoimmune diseases are expressed intrathmically and we consider possible consequences of such expression. Finally we show that autoantigen-specific peripheral T cells can be programmed to prevent autoimmunity.

Adrenal Glands↗
PubMed1997

Clinical utility of abdominal CT scanning in patients with HIV disease.

AIM: To evaluate the yield of abdominal computed tomography (CT) in patients with human immunodeficiency virus (HIV) infection and to assess the influence of CT scanning on patient management and diagnosis. METHOD: A retrospective analysis of 216 abdominal CT scans, performed on 156 patients (147 men, nine women; age range 22-57 years), between March 1992 and October 1994 was undertaken. Clinical information, including the indication for performing the scan and the eventual diagnosis, was obtained from the case notes and the contribution of CT scanning to patient management assessed. RESULTS: Indications for CT fell into five main groups: investigation of pyrexia of unknown origin (PUO) (n = 82), staging and response to treatment of previously diagnosed neoplasms (n = 46), investigation of abdominal pain (n = 20), CT undertaken to clarify the results of other imaging investigations (n = 20) and miscellaneous indications (n = 48). An eventual diagnosis thought to account for the clinical presentation was made in 150 cases (68%), reflecting the high level of underlying pathology. CT contributed to patient management in a large proportion of cases (62%), but only led directly to a diagnosis in a minority (12%). CONCLUSION: With the exception of patients presenting with PUO, abdominal CT remains an important investigation in the management of patients with HIV infection. In patients presenting with PUO a thorough infection screen should be undertaken prior to CT scanning. Whilst frequently contributing to patient management, CT rarely leads directly to a diagnosis.

AIDS-Related Opportunistic Infections↗
PubMed1996

The thymus contains a high frequency of cells that prevent autoimmune diabetes on transfer into prediabetic recipients.

Rats of the PVG.RT1u strain develop autoimmune diabetes when thymectomized at 6 wk of age and are rendered relatively lymphopenic by a cumulative dose of 1,000 rads 137Cs gamma-irradiation given in four split doses. Previous studies have shown that the disease is prevented by the intravenous injection of 5 x 10(6) CD4+ CD45RC-TCR alpha beta+ RT6+ peripheral T cells from normal syngeneic donors. These cells have a memory phenotype and are presumably primed to some extrathymic antigen. However, we now report that the CD4+ CD8- population of mature thymocytes is a very potent source of cells, with the capacity to prevent diabetes in our lymphopenic animals. As few as 6 x 10(5) of these cells protect approximately 50% of recipients and the level of protection increases with cell dose. It appears that one characteristic of the intrathymic selection of the T cell repertoire is the generation of cells that regulate the autoimmune potential of peripheral T cells that have been neither clonally deleted intrathymically nor rendered irreversibly anergic in the periphery.

ADP Ribose Transferases↗