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Biomedical subjects

D P O'Brien

Publications and source records attributed to D P O'Brien.

At least 37 records · Page 2Linked to original sources
PubMed1999

Iatrogenic Mycobacterium infection after an epidural injection.

STUDY DESIGN: Case report. OBJECTIVES: Successful excision of the mass and identification of the causative agent by histologic and microbiologic studies. SUMMARY OF BACKGROUND DATA: Spinal pain, caused by an infective mass, developed in a 39-year-old man 3 months after an epidural injection for low back pain. METHODS: Exploratory surgery was performed to remove the mass, and histologic and microbiologic studies were conducted. RESULTS: The inflammatory mass was excised successfully, and several specimens were examined for bacteriologic presence. Histologic examination of the excised specimen showed chronic granulomatous inflammation, and subsequent microbiologic studies cultured an acid- and alcohol-fast bacillus that was later identified as Mycobacterium fortuitum. CONCLUSION: A review of the literature shows that this is a particularly uncommon micro-organism.

Adult↗
PubMed1999

Malonic aciduria in Maltese dogs: normal methylmalonic acid concentrations and malonyl-CoA decarboxylase activity in fibroblasts.

A family of Maltese dogs with malonic aciduria is reported. The propositus presented at 3 years of age with episodes of seizures and stupor with hypoglycaemia, acidosis, and ketonuria. Urinary organic acid assays showed elevated malonic acid without elevation of methylmalonic acid. Cultured fibroblasts had normal malonyl-CoA decarboxylase activity. Treatment with frequent feedings of a low-fat diet high in medium-chain triglycerides resulted in normalization of clinical signs and a resolution of the malonic aciduria. Two full siblings of the propositus had died at a young age of undiagnosed metabolic and neurological disease. Urine organic acid assays were performed on other family members. A half-sister showed mild malonic aciduria and other organic acid changes similar to the propositus, while the mother and half-brother showed mildly elevated ketone bodies. This family suggests further genetic and clinical heterogeneity in the malonic acidurias.

Animals↗
PubMed1999

Tumor necrosis factor alpha receptor I is important for survival from Streptococcus pneumoniae infections.

Tumor necrosis factor alpha (TNF-alpha) is important in resistance to various microorganisms and provides signals to the target cells through two different receptors, TNF-alpha receptor I (TNFRI) (p55 receptor) and TNFRII (p75 receptor). To delineate the significance of the two different signaling pathways in resisting infections with extracellular bacteria, we examined the resistance of mice to Streptococcus pneumoniae (serotype 6B). TNF-alpha needs to be present early in infections, since one injection of wild-type mice with anti-TNF-alpha leads to an increased susceptibility of these mice to S. pneumoniae. TNF-alpha signaling through the p55 receptor (but not the p75 receptor) is crucial in resisting S. pneumoniae infections, because intraperitoneal injection of 100 CFU/mouse killed p55-deficient mice by day 2 of infection, whereas 1,000,000 CFU/mouse was needed to kill half of the control mice. p55-deficient mice do not show evidence of a deficient acute-phase response. All three types of mice (p55 deficient, p75 deficient, and normal) showed comparable rises in the levels of two acute-phase proteins (serum amyloid P and C3) at 24, 48, and 72 h after the experimental infections, and all of the mice showed comparable influxes of neutrophils to the site of infection. Finally, it was demonstrated that p55-deficient mice can be protected from the lethal effects of S. pneumoniae infection by injection of antibodies specific for S. pneumoniae polysaccharide capsule.

Acute-Phase Reaction↗
PubMed1999

HERF1, a novel hematopoiesis-specific RING finger protein, is required for terminal differentiation of erythroid cells.

The AML1/core binding factor beta (CBFbeta) transcription factor is essential for definitive hematopoiesis; however, the downstream pathways through which it functions remain incompletely defined. Using a differential cloning approach to define components of this pathway, we have identified a novel gene designated HERF1 (for hematopoietic RING finger 1), whose expression during development is dependent on the presence of functional AML1/CBFbeta. HERF1 contains a tripartite RING finger-B box-alpha-helical coiled-coil domain and a C-terminal region homologous to the ret proto-oncogene-encoded finger protein. Expression of HERF1 during embryogenesis coincides with the appearance of definitive erythropoiesis and in adult mice is restricted to erythroid cells, increasing 30-fold during terminal differentiation. Importantly, inhibition of HERF1 expression blocked terminal erythroid differentiation of the murine erythroleukemia cell line MEL, whereas its overexpression induced erythroid maturation. These results suggest an important role for this protein in erythropoiesis.

Animals↗
PubMed1999

Optimization of an automated DNA purification protocol for neonatal screening.

CONTEXT: Collection of blood from newborns is a standard clinical procedure used for genetic screening. Typically, blood from a heel prick is absorbed onto standard collection paper and dried before analysis of metabolites, proteins, hormones, and more recently DNA. OBJECTIVE: To evaluate strategies to purify DNA for use with automated workstations. DESIGN: Two factors were used to evaluate several DNA purification protocols: residual heme contamination and amplification yield. The protocol that produced DNA with the lowest heme content and the highest amplification yield was selected. In combination with those two performance factors, the protocol with the fewest number of steps was chosen to reduce reagent use and processing time. SETTING: Industrial research and development laboratory. RESULTS: Robust amplification of DNA isolated from dried blood spots was demonstrated using both fluorescence and agarose gel-based detection methods. In addition, the samples had consistent DNA volumes and had no detectable cross-contamination. Suggested instrument settings, equipment, and supplies were included for automated processing of DNA from dried blood spots. CONCLUSION: A 4-step DNA processing protocol was developed for dried blood spots. The protocol could be performed in either a manual or automated format, making it possible to process hundreds of samples in 1 day.

Blood Chemical Analysis↗
PubMed1998

Molecular analysis of skewed Tcra-V gene use in T-cell receptor beta-chain transgenic mice.

The influence of beta-chain diversity on the expressed T-cell receptor (TCR) alpha-chain repertoire was investigated using transgenic mice which exclusively express a single rearranged TCR beta-chain gene. Analysis of these mice using alpha-chain-specific recombinant cDNA libraries showed that expression of the transgene-encoded beta chain results in significant skewing in Tcra-V gene segment usage vs nontransgenic mice. Skewing was most pronounced towards alpha chains using TCRA-V segments. Sequence analysis of Tcra-V8-containing genes from transgenic T cells revealed predominant use of a single Tcra-J segment (Tcra-J24), which was not detected in Tcra-V8 containing genes isolated from nontransgenic T cells. Further analysis revealed that co-expression of Tcra-V8 with Tcra-J24 in beta-transgenic mice is exhibited almost exclusively by CD4+ T cells, and is associated with a limited number of closely related N-regions. Analysis of transgenic CD8+ T cells demonstrated predominant co-expression of Tcra-V8 with another Tcra-J (Tcra-J30), together with a different, limited N-region sequence. We conclude that the composition of expressed beta chains can profoundly influence the selection of companion alpha chains expressed in the periphery, and that alpha-chain N and J regions play a crucial role in discriminating between class I vs class II major histocompatibility complex (MHC)-restricted recognition. Further, these results are in agreement with recent data concerning the crystal structure of the TCR, and most consistent with a model for TCR structure in which the complementarity determining region (CDR)3alpha domain participates in direct contact with the MHC.

Amino Acid Sequence↗
PubMed1998

19F NMR in the measurement of binding affinities of chloroeremomycin to model bacterial cell-wall surfaces that mimic VanA and VanB resistance.

BACKGROUND: The emergence of bacteria that are resistant to vancomycin, the drug of choice against methicillin-resistant Staphylococcus aureus, has made the study of the binding characteristics of glycopeptides to biologically relevant depsipeptides important. These depsipeptides, terminating in D-alanyl-D-lactate, mimic the cell-wall precursors of resistant bacteria. RESULTS: The use of 19F-labelled ligands in the study of the therapeutically important vancomycin series of antibiotics is demonstrated. The substantial simplification of spectra that occurs when such labelled ligands are employed is used in the measurement of binding affinities of depsipeptides to chloroeremomycin (CE). Large enhancements of binding affinities are found at a model bacterial cell-wall surface (constituted from depsipeptides that are anchored into vesicles) relative to those measured in free solution. CONCLUSIONS: Surface-enhanced binding, previously shown for strongly dimerizing glycopeptide antibiotics to normal -D-alanyl-D-alanine-terminating cell-wall precursors, is now demonstrated for CE to the surface of models of VanA- and VanB-resistant bacteria. The effect of depsipeptide chain length is shown to be critically important in producing and maximizing this enhancement.

Anti-Bacterial Agents↗
PubMed1998

Ecarin Clotting Time: a predictive coagulation assay for the antithrombotic activity of argatroban in the rat.

We studied the use of the Ecarin Clotting Time (ECT) as a predictive assay of the antithrombotic effects of argatroban in a new tissue factor-dependent model of venous thrombosis and a model of arterial thrombosis in the rat. Heparin was used as a reference anticoagulant. Infusions of argatroban dose-dependently increased the ECT across the range of doses required for antithrombotic activity in models of venous and arterial thrombosis (1.25-40 microg/kg/min). The TT was only useful as a marker in the case of venous thrombosis, since, in the arterial thrombosis model, the clotting times were >200 s in the majority of animals receiving antithrombotic doses. The aPTT is not sufficiently sensitive to be predictive of an antithrombotic effect in the venous model, and shows only modest increases in the arterial thrombosis model. Heparin did not significantly increase the ECT at antithrombotic doses in the venous thrombosis model, and only increased the ECT by 53% at 40 microg/kg/min in the arterial model, despite a marked antithrombotic effect. Both the TT and aPTT were dose-dependently increased by heparin at doses active in the venous model, whereas both parameters were >200 s at doses active in the arterial thrombosis model. Thus, the ECT provides a predictive marker for the antithrombotic activity of argatroban in both venous and arterial thrombosis, at least in the rat.

Animals↗
PubMed1997

Microchimerism and rejection in clinical transplantation.

BACKGROUND: Haemopoietic microchimerism has been identified in recipients of solid-organ transplants and is thought by some to be critical for the development and maintenance of immunological tolerance. The aim of this study was to correlate prospectively the persistence of donor cells with clinical outcome in recipients of kidney, kidney and pancreas, and liver transplants. METHODS: Persistence of donor cells in recipient peripheral blood was assessed at 3 days, and at 1, 3, 6, and 12 months after transplantation by a two-stage nested PCR technique to detect donor MHC HLA DR gene specifically. A pretransplant blood sample was collected from each patient to serve as an individual negative control. Seven liver, six kidney and pancreas, and 17 kidney patients were enrolled. 12 of the 17 kidney patients and all of the kidney and pancreas, and liver recipients were suitable for analysis. Exact matches for donors and recipients at the HLA DR loci (n = 1) or inability to obain primer pair specificity among similar HLA DR types (n = 4), meant that we were unable to analyse five patients. FINDINGS: Donor DNA was detected in 20 (80%) of 25, ten (40%) of 25, seven (30%) of 23, five (22%) of 23, and six (32%) of 19 recipients at 3 days, and 1, 3, 6 and 12 months post-transplant, respectively. Within individuals, the detection of donor DNA varied over time; only two patients had detectable donor DNA at all times. Analysis of the whole group of transplant patients showed a similar frequency and severity of rejection episodes in patients with and without microchimerism as defined by detectable donor DR genes. INTERPRETATION: These data suggest that a significant percentage of the recipients had persistent donor class II DNA in the peripheral circulation for at least 1 year after transplantation. We showed that a pretransplant blood sample is critical to avoid a false-positive result, and suggest that detectable chimerism may vary over time in individual patients. Therefore, analysis of microchimerism with a single, post-transplant analysis may not help in making clinical decisions for individual patients.

Graft Rejection↗
PubMed1997

Nimodipine for treatment of idiopathic epilepsy in dogs.

OBJECTIVE: To evaluate efficacy and safety of the calcium channel antagonist nimodipine in dogs with idiopathic epilepsy. DESIGN: Prospective clinical trial. ANIMALS: 10 dogs with idiopathic epilepsy. Dogs were included if seizures were inadequately controlled despite treatment with barbiturates and serum phenobarbital concentrations were > 25 micrograms/ml, if dogs had intolerable adverse effects when treated with barbiturates, or if dogs had mild, inadequately treated seizures. PROCEDURES: Dogs were treated with nimodipine (2.5 mg/kg [1.1 mg/lb] of body weight, PO, q 12 h), and other medications were slowly withdrawn. Dogs were monitored for seizure frequency and severity as well as any adverse effects to the medication. RESULTS: Few adverse effects were reported. Seizure control, however, was generally inadequate. All but 2 dogs were withdrawn from the study because of poor seizure control. Plasma nimodipine concentrations were low, with a mean peak concentration of 105.3 ng/ml. CLINICAL IMPLICATIONS: Nimodipine was not successful in controlling seizures in dogs used in this study.

Animals↗
PubMed1997

Elimination of T-cell-receptor beta-chain diversity in transgenic mice restricts antigen-specific but not alloreactive responses.

The contribution of T-cell-receptor beta-chain diversity to the T-cell antigen-specific repertoire was investigated using single-chain T-cell-receptor transgenic mice. Animals that express the rearranged beta-chain gene from a T hybridoma with specificity for a hen egg lysozyme peptide, designated HEL (85-96) were analysed for their ability to respond to a panel of diverse antigens. Transgenic mice exhibited a significantly elevated response to HEL (85-96) which was shown to be due to an increased frequency of HEL (85-96)-specific T-cell progenitors. This increased frequency of specific progenitors resulted in the ability of transgenic mice to respond to the peptide in the absence of antigen priming. Conversely, transgenic mice failed to respond to any other antigen tested. Furthermore, this apparent deficiency was associated with a significant decrease in the frequency of antigen-specific T-cell progenitors in transgenic mice. Surprisingly, the ability to launch an alloresponse was unaffected by the exclusive expression of the transgene-derived beta-chain. These results indicate that beta-chain diversity is crucial for the ability of the T-cell population to elicit a rapid and robust response to the profusion of different antigen/major histocompatibility complex (MHC) ligands potentially encountered by an individual. Furthermore, these results suggest a lesser role for beta-chain diversity in contributing to allorecognition, and support a model in which the direct recognition of peptide-mediated conformational MHC forms is the major contributor to the alloreactive response exhibited by the majority of T cells.

Animals↗
PubMed1997

Coordinate transcription and V(D)J recombination of the kappa immunoglobulin light-chain locus: NF-kappaB-dependent and -independent pathways of activation.

To further elucidate the potential role of mitogens and cytokines in regulation of the kappa immunoglobulin light-chain locus, we have characterized the activation of transcription factor binding, kappa germ line transcription, DNase I hypersensitivity, and Vkappa-to-Jkappa recombination upon induction of model pre-B-cell lines. We find that both lipopolysaccharide (LPS) and gamma interferon (IFN-gamma) are capable of activating germ line transcription, DNase I hypersensitivity, and recombination of the kappa locus. We also find that transforming growth factor beta is capable of completely inhibiting LPS activation of transcription and recombination but has no apparent effect on activation of transcription factor binding, including activation of NF-kappaB. To address the functional role of NF-kappaB in LPS and IFN-gamma induction of these events, we blocked the nuclear translocation of NF-kappaB by overexpression of a dominant negative mutant of IkappaB-alpha (IkappaB deltaN). Overexpression of the IkappaB deltaN protein results in an inhibition of LPS but not IFN-gamma activation of germ line transcription, DNase I hypersensitivity, and Vkappa-to-Jkappa recombination. Our results demonstrate that activation of NF-kappaB is necessary but not sufficient for LPS activation of transcription and recombination at kappa. These results also suggest that NF-kappaB is not required for IFN-gamma activation of transcription or recombination. These results are important in establishing that there are multiple independent pathways of activation of both transcription and recombination.

B-Lymphocytes↗
PubMed1997

Drainage of the exocrine pancreas in clinical transplantation: comparison of bladder versus enteric drainage in a consecutive series.

The purpose of this study was to define the incidence of urologic and metabolic complications after simultaneous kidney/pancreas transplantation (SKPT) with bladder drainage (BD). Review of 55 SKPT with BD performed between 1989 and 1995 demonstrated patient, kidney, and pancreas survival rates of 95%, 89%, and 78%, respectively, with a mean follow-up of 41 months (range 12-78 months). Over this follow-up period 78% of these patients experienced a urinary tract infection, 27% had hematuria, and 38% had at least one hospital admission for dehydration. Recent experience with primary enteric drainage of the exocrine secretions of the transplanted pancreas (n = 11) has demonstrated the total absence of these complications (follow-up range 2-12 months). These results suggest the value of continuous re-evaluation of surgical techniques as the care of transplant patients evolve.

Acidosis↗