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Biomedical subjects

B Duffy

Publications and source records attributed to B Duffy.

At least 19 recordsLinked to original sources
PubMed2001

Activation of human dendritic cells by porcine aortic endothelial cells: transactivation of naïve T cells through costimulation and cytokine generation.

BACKGROUND: Dendritic cells (DC) are the most potent antigen-presenting cells in the immune system. To define the role of human DC in human anti-porcine immune responses, we defined the interaction of human DC with porcine aortic endothelial cells (PAEC). METHODS: To determine the immune responses, both monocyte-derived and peripheral blood DC were cultured with porcine and human endothelial cells. We analyzed the role of CD11a, CD11b, and CD54 in a cell-to-cell adhesion assay using antibodies against these molecules. The expression pattern of costimulatory molecules (CD40, CD80, CD86), adhesion molecules (CD54), and intracellular cytokines (interleukin-12p70 and tumor necrosis factor [TNF]-alpha) in DC after interaction with endothelial cells was determined by immunofluorescence. RESULTS: Human DC significantly adhered to PAEC (38-40%), and this adhesion was augmented (>50%) upon treatment with either recombinant swine interferon-gamma or recombinant human TNF-alpha. Addition of human DC to PAEC was blocked by pretreatment of DC with antibodies specific to human leukocyte function-associated antigen-1 or CD54. Adhesion of DC to PAEC also resulted in the activation of DC, which was manifested by up-regulation of costimulatory molecules (CD40, CD80, CD86), adhesion molecules (CD54), and HLA-DR. PAEC-activated human DC provided proliferative signals to the naïve autologous CD4+ T cells and synthesized interleukin-12p70 and TNF-alpha. However, activated DCs failed to lyse PAEC in such interaction. CONCLUSION: Human DC effectively adhered to PAEC and were activated by xenoantigen, resulting in highly efficient antigen presentation and proliferation of CD4+ T cells. Further, this interaction of human DC to PAEC is regulated by the participation of costimulatory and adherence molecules and cytokines.

Animals↗
PubMed2001

Defective apoptosis in lymphocytes and the role of IL-2 in autoimmune hematologic cytopenias.

Fas-mediated signaling is important for lymphocyte elimination. We investigated lymphocytes for Fas-signaling defects in 20 pediatric patients with chronic hematologic autoimmunity. In 5 of 20 (25%), there was profound resistance to exogenous FasL-mediated lysis, Fas mAb, and anti-CD3. FasL function, though variable, was not significantly different from that of simultaneously evaluated controls. Only 1 patient had a Fas mutation and manifestations of autoimmune lymphoproliferative syndrome. In contrast, lymphocytes from his clinically normal mother with the same mutation were normally sensitive to FasL. In 3 patients, normal Fas-mediated lysis was restored with rhIL-2. IL-2 had no effect in the other 2 patients. Activation and proliferation functions of IL-2 were normal in all 5. We conclude that altered Fas signaling, independent of Fas mutations, can precipitate hematologic autoimmunity. IL-2 can rescue some lymphocytes from this defect. In IL-2 refractory cases, a persistently defective response to IL-2 continues to confer a lymphocyte survival advantage. Hence, altered Fas pathway signaling with or without defective IL-2 responses should be considered in the etiology of hematologic autoimmunity.

Adolescent↗
PubMed2001

Characterization of spontaneous gacS and gacA regulatory mutants of Pseudomonas fluorescens biocontrol strain CHAO.

In Pseudomonasfluorescens strain CHAO, the response regulator gene gacA controls expression of extracellular enzymes and antifungal secondary metabolites, which are important for this strain's biocontrol activity in the plant rhizosphere. Two Tn5 insertion mutants of strain CHA0 that had the same pleiotropic phenotype as gacA mutants were complemented by the gacS sensor kinase gene of P. syringae pv. syringae as well as that of P. fluorescens strain Pf-5, indicating that both transposon insertions had occurred in the gacS gene of strain CHA0. This conclusion was supported by Southern hybridisation using a gacS probe from strain Pf-5. Overexpression of the wild-type gacA gene partially compensated for the gacS mutation, however, the overexpressed gacA gene was not stably maintained, suggesting that this is deleterious to the bacterium. Strain CHA0 grown to stationary phase in nutrient-rich liquid media for several days accumulated spontaneous pleiotropic mutants to levels representing 1.25% of the population; all mutants lacked key antifungal metabolites and extracellular protease. Half of 44 spontaneous mutants tested were complemented by gacS, the other half were restored by gacA. Independent point and deletion mutations arose at different sites in the gacA gene. In competition experiments with mixtures of the wild type and a gacA mutant incubated in nutrient-rich broth, the mutant population temporarily increased as the wild type decreased. In conclusion, loss of gacA function can confer a selective advantage on strain CHA0 under laboratory conditions.

Bacterial Proteins↗
PubMed2001

The human Y chromosome derives largely from a single autosomal region added to the sex chromosomes 80-130 million years ago.

Mapping of human X-borne genes in distantly related mammals has defined a conserved region shared by the X chromosome in all three extant mammalian groups, plus a region that was recently added to the eutherian X but is still autosomal in marsupials and monotremes. Using comparative mapping of human Y-borne genes, we now directly show that the eutherian Y is also composed of a conserved and an added region which contains most of the ubiquitously expressed Y-borne genes. Little of the ancient conserved region remains, and the human Y chromosome is largely derived from the added region.

Animals↗
PubMed2000

Autoinduction of 2,4-diacetylphloroglucinol biosynthesis in the biocontrol agent Pseudomonas fluorescens CHA0 and repression by the bacterial metabolites salicylate and pyoluteorin.

The antimicrobial metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) contributes to the capacity of Pseudomonas fluorescens strain CHA0 to control plant diseases caused by soilborne pathogens. A 2, 4-DAPG-negative Tn5 insertion mutant of strain CHA0 was isolated, and the nucleotide sequence of the 4-kb genomic DNA region adjacent to the Tn5 insertion site was determined. Four open reading frames were identified, two of which were homologous to phlA, the first gene of the 2,4-DAPG biosynthetic operon, and to the phlF gene encoding a pathway-specific transcriptional repressor. The Tn5 insertion was located in an open reading frame, tentatively named phlH, which is not related to known phl genes. In wild-type CHA0, 2, 4-DAPG production paralleled expression of a phlA'-'lacZ translational fusion, reaching a maximum in the late exponential growth phase. Thereafter, the compound appeared to be degraded to monoacetylphloroglucinol by the bacterium. 2,4-DAPG was identified as the active compound in extracts from culture supernatants of strain CHA0 specifically inducing phlA'-'lacZ expression about sixfold during exponential growth. Induction by exogenous 2,4-DAPG was most conspicuous in a phlA mutant, which was unable to produce 2, 4-DAPG. In a phlF mutant, 2,4-DAPG production was enhanced severalfold and phlA'-'lacZ was expressed at a level corresponding to that in the wild type with 2,4-DAPG added. The phlF mutant was insensitive to 2,4-DAPG addition. A transcriptional phlA-lacZ fusion was used to demonstrate that the repressor PhlF acts at the level of transcription. Expression of phlA'-'lacZ and 2,4-DAPG synthesis in strain CHA0 was strongly repressed by the bacterial extracellular metabolites salicylate and pyoluteorin as well as by fusaric acid, a toxin produced by the pythopathogenic fungus Fusarium. In the phlF mutant, these compounds did not affect phlA'-'lacZ expression and 2, 4-DAPG production. PhlF-mediated induction by 2,4-DAPG and repression by salicylate of phlA'-'lacZ expression was confirmed by using Escherichia coli as a heterologous host. In conclusion, our results show that autoinduction of 2,4-DAPG biosynthesis can be countered by certain bacterial (and fungal) metabolites. This mechanism, which depends on phlF function, may help P. fluorescens to produce homeostatically balanced amounts of extracellular metabolites.

Anti-Bacterial Agents↗
PubMed1999

Intercellular adhesion molecule-1/leukocyte function associated antigen-1 blockade inhibits alloantigen specific human T cell effector functions without inducing anergy.

BACKGROUND: Intercellular adhesion molecule (ICAM-1) is important in leukocyte adhesion-dependent events and some data suggest that ICAM-1 provides T cell costimulation. We anlayzed the role of the ICAM-1 and leukocyte function associated antigen-1 (LFA-1) interaction in human T cell alloreactivity in vitro. METHODS: Allo-antigen-induced T cell proliferation and cytotoxic T lymphocyte lytic activity were assessed by mixed lymphocyte reaction assay and 51 Chromium release assay, respectively. Immunostaining and flow cytometry were used to assess the expression of receptors on activated T cells. RESULTS: Alloantigen-induced T cell proliferation and cytotoxic T lymphocyte activity were markedly inhibited by antibodies to ICAM-1 and LFA-1. These antibodies had to be present at the time of initial T cell receptor/antigen engagement to inhibit proliferation. Neither IL-2 nor IL-4 were involved in the observed inhibition by antibodies. Inhibition was not associated with altered cell surface expression of receptors such as CD3, CD4, ICAM-1, LFA-1, CD25, and HLA-DR however, these antibodies did impede the ability of generation of functionally active T cells. Interestingly, these antibodies inhibited soluble, but not immobilized OKT3-induced proliferation of peripheral blood leukocytes. Antibody-mediated inhibition of proliferation failed to impair the ability of T cells to subsequently proliferate in response to stimulation by the original or third party alloantigen or mobilize [Ca++]i in response to CD3 or LFA-1 receptor ligation. CONCLUSIONS: These data demonstrate that blockade of ICAM-1/LFA-1 binding at the time of allorecognition potently blocks initial T cell effector functions that could be due to lack of effective T cell/APC engagement.

Adult↗
PubMed1999

Cisapride and caesarean section: their role in babies with gastroschisis.

OBJECTIVE: The objective of this study was to compare the neonatal postoperative course and morbidity for patients with gastroschisis who received cisapride with those who did not receive cisapride. STUDY DESIGN: Data were obtained by review of the medical records of all the patients with gastroschisis who were admitted to Sydney Children's Hospital between January 1984 and December 1995. Data were compared between 15 babies who received cisapride with 27 who did not. The mode of delivery and outcome of babies in whom gastroschisis was diagnosed antenatally was compared with those who were diagnosed at birth. RESULTS: Duration to the commencement of feeds, attainment of full feeds and the length of hospital stay were not statistically different between these two groups, with or without cisapride (p = > or = 0.1). There were more elective Caesarean sections in the antenatally diagnosed group compared to those detected at birth and the outcome of these two groups showed no statistically significant difference. CONCLUSIONS: Our study identified no benefit from cisapride therapy in babies with gastroschisis and also there was no benefit from elective Caesarean section for babies with antenatal diagnosis of gastroschisis.

Australia↗
PubMed1998

Transition metals as protease inhibitors.

An alternative approach to the development of clinically useful protease inhibitors was investigated. The approach utilized coordination chemistry of transition metal ions rather than substrate analogs to block active sites of these enzymes. In the case of serine proteases it was found that aqueous Ti(IV) is a potent inhibitor of the trypsin subclass, but not the chymotrypsin subclass. The direct binding of Ti(IV) to trypsin was made possible by the presence of a free carboxyl group at the bottom of the substrate binding pocket of the enzyme, and the five-coordinate geometry of TiO(SO4)(H2O). Although initial binding of Ti(IV) was reversible, it was followed in time by irreversible inhibition. Direct binding of octahedral or tetrahedral metal ion complexes was prevented by the inability of the enzyme active sites to promote formation of a five-coordinate transition state of the metal ion required for reaction. These studies demonstrate the ability of direct metal ion binding as a way to enhance blocking of enzyme active sites as compared with that of traditional organic inhibitors. Application of these findings was investigated by measuring the affect Ti(IV) had on growth of Escherichia coli, Salmonella typhimurium, and Pseudomonas aeruginosa. Five-coordinate titanyl sulfate completely inhibited the growth of these organisms. This suggests that five-coordinate titanyl sulfate, which is easier and less expensive to manufacture than conventional antibiotics, may be useful in controlling endemic infections of E. coli and S. typhimurium.

Binding Sites↗
PubMed1998

Analysis of graft-versus-host disease (GVHD) and graft rejection using MHC class I-deficient mice.

GVHD is a major complication in allogeneic bone marrow transplantation (BMT). MHC class I mismatching increases GVHD, but in MHC-matched BMT minor histocompatibility antigens (mH) presented by MHC class I result in significant GVHD. To examine the modification of GVHD in the absence of cell surface MHC class I molecules, beta2-microglobulin-deficient mice (beta2m(-/-)) were used as allogeneic BMT recipients in MHC- and mH-mismatched transplants. Beta2m(-/-) mice accepted MHC class I-expressing BM grafts and developed significant GVHD. MHC (H-2)-mismatched recipients developed acute lethal GVHD. In contrast, animals transplanted across mH barriers developed indolent chronic disease that was eventually fatal. Engrafted splenic T cells in all beta2m(-/-) recipients were predominantly CD3+alphabetaTCR+CD4+ cells (15-20% of all splenocytes). In contrast, CD8+ cells engrafted in very small numbers (1-5%) irrespective of the degree of MHC mismatching. T cells proliferated against recipient strain antigens and recognized recipient strain targets in cytolytic assays. Cytolysis was blocked by anti-MHC class II but not anti-CD8 or anti-MHC class I monoclonal antibodies (MoAbs). Cytolytic CD4+ T cells induced and maintained GVHD in mH-mismatched beta2m(-/-) mice, supporting endogenous mH presentation solely by MHC class II. Conversely, haematopoietic beta2m(-/-) cells were unable to engraft in normal MHC-matched recipients, presumably due to natural killer (NK)-mediated rejection of class I-negative cells. Donor-derived lymphokine-activated killer cells (LAK) were unable to overcome graft rejection (GR) and support engraftment.

Animals↗
PubMed1998

Get ready--get-set--go teach! Analyzing patients as learners in home healthcare.

Teaching is an integral part of the home care nursing role and has assumed increasing importance as a cost-saving intervention. This article gives the home health nurse insight into the importance of thoroughly assessing the patient's learning style before developing and implementing the teaching plan.

Community Health Nursing↗
PubMed1997

Cowpox in British voles and mice.

Serosurveys indicate that bank voles, field voles and woodmice are probably reservoir hosts of cowpox virus in western Europe, although virus has not yet been isolated from these species. In this study, bank voles, field voles, woodmice and laboratory mice were shown to be susceptible to combined intradermal and subcutaneous inoculation with 3-20 plaque-forming units (pfu) of cowpox virus. Bank and field voles, but not laboratory mice, were also susceptible to combined oral and nasal inoculation with 50 pfu. Few clinical signs were seen and virus was generally recovered only from inoculation sites. Bank voles were not susceptible to injection of ectromelia virus (5000 pfu) into the skin (as described above). These results provide information on which further pathogenesis and transmission studies can be based, and support the view that the orthopoxvirus antibody detected in British wild voles and woodmice indicates infection with cowpox virus. However, further investigation of the pathogenesis of cowpox in these species is needed to understand better the epidemiology of the disease.

Administration, Intranasal↗
PubMed1997

Using a creative teaching process with adult patients.

Because the patient or caregiver must manage healthcare needs after the nurse has left the home, patient education is an important component to home health nursing (Rice, 1996). Fortunately, patient teaching is ideal for home healthcare. To make the most of the home learning environment with adult patients, the nurse must assess, design, develop, implement, and evaluate an individualized patient teaching plan. Throughout the ADDIE process, the nurse manipulates and integrates the home environment to maximize the possibility that the patient will accept, remember, and apply the information presented. Taking into account how adults learn, the nurse provides relevant problems and situations for the patient to practice newly acquired knowledge and skills. The instruction presents learners with alternatives to their current ways of thinking, behaving, and living (Brookfield, 1986). Given the information and the tools needed to regain a sense of control and experience life safely, within their abilities of medical illness or injury, informed adult patients are likely to experience fewer complications and enhanced self-esteem. For pertinent, timely, and personal healthcare instruction, there is no place quite like home.

Adult↗
PubMed1996

Cytolytic effector mechanisms of human CD4+ cytotoxic T lymphocytes.

To elucidate mechanisms by which human CD4+ cells mediated cytolytic activity, we studied the expression of cytolytic proteins and the effects of inhibitors and mAbs on T-cell clones. Of seven cytolytic CD4+ clones, three were specific for the HLA-DR17, while four recognized DR18. Anti-HLA-DR mAb and anti-CD4 mAb blocked lysis. In addition, N alpha-p-tosyl-L-lysine chloromethylketone (TLCK), a serine esterase inhibitor, as well as cytochalasin B and monensin, antagonists of secretory pathways, inhibited CD4+ CTLs, whereas the absence of extracellular Ca+2 or the presence of Ca+2 channel blockers partially inhibited cytotoxicity. CD4+ CTLs induced apoptosis of target cell nuclei and membrane damage simultaneously. The CD4+ clones synthesized perforin and granzyme B and expressed the granule-associated protein TIA-1. Our studies indicate that two distinct mechanisms may contribute to cytolysis by CD4+ clones: (1) a Ca+2-dependent mechanism associated with the cytotoxic granules and (2) a Ca+2-insensitive mechanism.

Base Sequence↗