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Biomedical subjects

P Lavery

Publications and source records attributed to P Lavery.

11 recordsLinked to original sources
PubMed2001

The failure of Daudi cells to express the cellular prion protein is caused by a lack of glycosyl-phosphatidylinositol anchor formation.

The cellular prion protein (PrPc) is a glycosyl-phosphatidylinositol (GPI)-linked cell surface protein, which is expressed at high density on nervous tissues and at lower levels on most other solid-organ tissues. It is also expressed on peripheral blood mononuclear cells (PBMC) of all lineages. In lymphocytes, its level of expression is dependent upon the state of cell activation, and polyclonal anti-PrP antisera partially block lectin-induced T-cell activation, suggesting a functional role of the protein in this process. Using the monoclonal antibody (mAb) 3F4 we examined PrPc surface immunoreactivity on leukaemic cell lines of T- and B-cell origin, and unexpectedly observed a complete lack of PrPc cell-surface expression in Daudi cells, while all other cell lines displayed discernible reactivity. We demonstrated the intracellular presence of PrP-specific mRNA and PrP protein. The lack of surface PrPc is unrelated to the well-known defect of beta2-microglobulin (beta2m) expression in Daudi cells as other beta2m-deficient cells, such as the melanoma cell line F0-1 and spleen cells from beta2m gene-deleted mice, were not deficient in cell-surface PrPc. Daudi cells failed to bind antibodies directed against all GPI-linked cell surface proteins. In somatic hybridization experiments using murine spleen cells as partners, we observed de novo expression of human PrPc, CD55 and CD59, thus demonstrating in Daudi cells the availability of these gene products for GPI linkage and cell-surface expression.

Antibodies, Monoclonal↗
PubMed2001

Simple absorbance-based assays for ultra-high throughput screening.

In order to accommodate the predicted increase in screening required of successful pharmaceutical companies, miniaturized, high-speed HTS formats are necessary. Much emphasis has been placed on sensitive fluorescence techniques, but some systems, particularly enzymes interconverting small substrates, are likely to be refractory to such approaches. We show here that simple absorbance-based assays can be miniaturized to 10-microl volumes in 1536-well microplates compatible with the requirements for ultra-high throughput screening. We demonstrate that, with low-cost hardware, assay performance is wholly predictable from the 2-fold decrease in pathlength for fully filled 1536-well plates compared to 96- and 384-well microplates. A number of enzyme systems are shown to work in this high-density format, and the inhibition parameters determined are comparable with those in standard assay formats. We also demonstrate the utility of kinetics measurements in miniaturized format with improvements in assay quality and the ability to extract detailed mechanistic information about inhibitors.

Adenosine Triphosphatases↗
PubMed1999

The inhibition of human cytomegalovirus (hCMV) protease by hydroxylamine derivatives.

Aryl hydroxylamine derivatives have been synthesised that are some of the most potent inhibitors of hCMV protease prepared to date (IC50 14-60 nM). Mass spectrometry studies indicate that oxazinone derived hydroxylamines inhibit the enzyme by acylation of Ser132 whereas non-oxazinone derived hydroxylamines appear to inhibit via formation of a sulfinanilide at Cys138.

Amino Acid Sequence↗
PubMed1999

Disposable microbore high-pressure liquid chromatography columns for protein and peptide separations.

A range of high-performance liquid chromatography (HPLC) columns with internal diameters of 0.25 to 1.8 mm have been constructed by securing glass or plastic tubing into standard HPLC fittings. These were packed with chromatographic materials chosen for operation at moderate pressures with high flow rates. These columns were shown to be effective in a conventional HPLC instrument for peptide and protein separations in reverse-phase mode and for proteins in ion-exchange and size-exclusion modes. The simple construction and low cost of these microbore columns allow them to be considered as disposable. Using only small amounts of any type of packing material, they have the flexibility to be adapted to a wide range of analytical and micropreparative separations.

Chromatography, Gel↗
PubMed1998

Benzothiopyran-4-one based reversible inhibitors of the human cytomegalovirus (HCMV) protease.

A novel class of CMV protease inhibitors based on a benzothiopyran-S,S-dioxide nucleus has been discovered. Enzyme kinetic data supports a reversible mode of inhibition for a representative member of this class, 2-(3-pyridyl-N-oxide)benzothiopyran-4-one-S,S-dioxide, 1. Experiments in the presence and absence of the disulfide reducing agent DTT suggest that the inhibition by 1 is not due to oxidative inactivation of the enzyme. Also presented are results of some SAR studies of the benzothiopyranone ring system.

Amino Acid Sequence↗
PubMed1997

Klinefelter syndrome and non-Hodgkin lymphoma.

Patients with a 47,XXY karyotype (Klinefelter syndrome) appear to have an increased risk of developing cancer, especially male breast cancer and germ cell tumors, but rarely malignant hematologic disorders. We report a patient with a low grade B-cell non-Hodgkin lymphoma with a 47,XXY karyotype in both the tumor and constitutional cells. This is only the 13th reported case of malignant lymphoma in a patient with Klinefelter syndrome. Although some authors postulate that the 47,XXY karyotype may be a predisposing factor in the development of hematological malignancies, the lack of reported cases suggests that such associations may be no more than chance findings.

Aged↗
PubMed1996

Restricted TCR V beta repertoire in the human mixed lymphocyte reaction is determined by the TCR on the responder cell and not by the stimulating antigen on the stimulator cell.

The use of a restricted TCR repertoire has been reported in antigen-stimulated T cells. We have examined by flow cytometry and polymerase chain reaction the changes in the TCR variable beta (V beta) repertoire as they occur in the mixed leukocyte reaction. The HLA class I-negative lymphoblastoid B cell line, Daudi, an HLA class I-positive variant of the Daudi cell line, and the homozygous typing cell line HTC 9062 were used to stimulate HLA-mismatched responder cells from 8 individuals. The magnitude of HLA incompatibility in various combinations ranged from single DR10 and DR13 differences to full 6-antigen differences at the HLA-A, -B, and -DR loci. Using a panel of 19 V beta-specific oligonucleotide primers, changes in the level of TCR V beta mRNA were assessed. The observed V beta repertoire was not specific for the stimulator cell antigens used. We did not find a correlation between the number of mismatched HLA antigens and the number of V beta elements involved. It rather appeared that individual responder cells displayed a uniform V beta pattern following exposure to single and multiple HLA antigens. We conclude that the V beta repertoire was largely determined by factors associated with the TCR on the responder cells, and not as obviously influenced by the HLA antigen(s) on the stimulator cells.

Antigen Presentation↗
PubMed1994

Expression of early and late activation markers on peripheral blood T lymphocytes does not reliably reflect immune events in transplanted hearts.

Monoclonal antibodies directed against early (receptors for interleukin-2 and transferrin [IL-2R, TfR]) and late (PTA1, alpha 1 integrin VLA-1) activation antigens were used as probes to monitor cardiac transplant patients for episodes of acute graft rejection. Age- and sex-matched patient control groups consisting of 11 patients awaiting cardiac transplantation and 13 kidney transplant recipients with long-term grafts, respectively, were used to define an upper limit for normal activation antigen expression (mean + 3 SD) in patients. Expression of all cell markers was significantly higher in both patient control groups than in healthy control individuals. Therefore, the level of activation marker expression in heart patients awaiting transplantation was used as comparison for the patient population under study. Sequential monitoring of 24 heart transplant recipients failed to demonstrate a significant correlation of increased activation marker expression with clinical events of immune activation. Subsequently 62 consecutive endomyocardial biopsy scores in 36 patients were compared with the expression of IL-2R, TfR and VLA-1 on peripheral blood T cells. Neither increased cellular infiltration of the endocardium, nor of the myocardium, was associated with increasing proportions of IL-2R, TfR, or VLA-1 positive T cells. Elevated T-cell expression of the three markers combined indicated acute graft rejection with a sensitivity, specificity, and overall accuracy of 38%, 52%, and 43%, respectively. Acute graft rejection in biopsies with associated myofiber damage (biopsy rejection scores 2 and 3A,B) was not associated with a change in the proportion of activated T cells in circulation within the first 6 months after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Syllabification of bisyllabic nonwords: evidence from short-term memory errors.

Do errors in short-term memory for spoken stimuli sometimes combine one syllable from one to-be-remembered item with one syllable from another to-be-remembered item? If so, can the errors shed light on how the stimuli are syllabified? We report three experiments in which college students tried to recall five-item lists containing two CVCVC (consonant-vowel-consonant-vowel-consonant) nonwords and three filler digits. When the second vowel of the nonword was stressed, recombination errors tended to blend the initial CV of one nonword with the final CVC of another, especially if the middle consonant was an obstruent. When the first vowel was stressed, the error pattern depended on the type of vowel. CV/CVC recombinations were more common for tense vowels than for lax vowels. In general, CV/CVC recombinations tended to be more frequent relative to CVC/VC recombinations when the middle consonant was an obstruent than when it was a sonorant. The findings are discussed in relation to linguistic theories of syllabification and the results of previous experiments using metalinguistic tasks.

Auditory Perception↗