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Biomedical subjects

A J Barrett

Publications and source records attributed to A J Barrett.

At least 145 records · Page 8Linked to original sources
PubMed1993

Evolutionary families of peptidases.

The available amino acid sequences of peptidases have been examined, and the enzymes have been allocated to evolutionary families. Some of the families can be grouped together in 'clans' that show signs of distant relationship, but nevertheless, it appears that there may be as many as 60 evolutionary lines of peptidases with separate origins. Some of these contain members with quite diverse peptidase activities, and yet there are some striking examples of convergence. We suggest that the classification by families could be used as an extension of the current classification by catalytic type.

Amino Acid Sequence↗
PubMed1993

Frequency of anti-recipient alloreactive helper T-cell precursors in donor blood and graft-versus-host disease after HLA-identical sibling bone-marrow transplantation.

A substantial proportion of patients undergoing allogeneic bone-marrow transplantation (BMT) develop moderate-to-severe acute graft-versus-host disease (GVHD). Anti-recipient helper (interleukin-2-producing) T-lymphocyte precursors (HTLp) have an important role in the control and amplification of the alloreactive immune response that initiates GVHD. We used a limiting dilution assay to measure the frequency of HTLp in the blood of marrow donors for 25 patients undergoing genotypically HLA-identical BMT for chronic myeloid leukaemia (n = 20), acute myeloid leukaemia (4), or thalassaemia (1). HTLp frequencies in donor blood ranged from 1 in 18 x 10(3) to less than 1 in 500 x 10(3); they were significantly higher (p = 0.02) in patients with grade II-IV acute GVHD than in those with grade 0-1 GVHD. The HTLp assay seems sufficiently sensitive to detect clinically significant minor histocompatibility antigen differences between the donor and recipient. The assay should prove valuable in selecting the best donor/recipient combination and could indicate the need to intensify GVHD prophylaxis when the only available donor has a high HTLp frequency.

Adolescent↗
PubMed1993

Inhibition of cartilage proteoglycan release by a specific inactivator of cathepsin B and an inhibitor of matrix metalloproteinases. Evidence for two converging pathways of chondrocyte-mediated proteoglycan degradation.

OBJECTIVE: To investigate mechanisms of cartilage matrix destruction by a study of the effects of a specific inactivator of cathepsin B and an inhibitor of several matrix metalloproteinases (MMP) on cartilage proteoglycan release. METHODS: Cartilage explants were treated with either recombinant human interleukin-1 alpha (rHuIL-1 alpha) or retinoic acid in the presence or absence of the inhibitors, and proteoglycan release was quantitated. Tests for nonspecific effects of the inhibitors included reversibility, rates of protein synthesis and glycolysis, and effects on other rHuIL-1 alpha-mediated events. RESULTS: The cathepsin B inactivator inhibited rHuIL-1 alpha-stimulated proteoglycan release at nanomolar concentrations, but failed to significantly inhibit retinoic acid-stimulated proteoglycan release. An inhibitor of MMP was inhibitory to both rHuIL-1 alpha-stimulated release and retinoic acid-stimulated release. CONCLUSION: Cathepsin B is implicated in rHuIL-1 alpha-stimulated loss of cartilage proteoglycan. Its lack of involvement in retinoic acid-stimulated proteoglycan release suggests the existence of at least 2 pathways of cartilage proteoglycan breakdown, which may converge at the activation of a matrix prometalloproteinase.

Aggrecans↗
PubMed1993

The two cysteine endopeptidases of legume seeds: purification and characterization by use of specific fluorometric assays.

Two endopeptidases are present in the seeds of Vigna aconitifolia (moth bean), and their activities increase during germination. One enzyme, which we term "vignain," can be assayed with benzyloxycarbonyl-phenylalanyl-arginyl-7-(4-methyl)coumarylamide as substrate. The second is legumain (EC 3.4.22.34), which can be assayed with benzyloxycarbonyl-alanyl-alanyl-asparaginyl-7-(4-methyl)-coumarylamide. The enzymes were purified, and their specificities for substrates and inhibitors were examined. Vignain has properties expected of a cysteine endopeptidase of the papain family, with the exception of a remarkably low reactivity with iodoacetate. Legumain is a very atypical cysteine endopeptidase, being insensitive to inhibition by chicken cystatin and E-64 (L-3-carboxy-2,3-trans-epoxypropionyl-leucyl-amido(4-guanidino )butane), and reacting more rapidly with iodoacetamide than with iodoacetate. We discuss our findings in relation to the literature on the proteolytic enzymes of legume seeds.

Amino Acid Sequence↗
PubMed1993

The inhibition of interleukin 1-stimulated cartilage proteoglycan degradation by cysteine endopeptidase inactivators.

Cysteine endopeptidase inactivators were tested as inhibitors of interleukin 1-stimulated proteoglycan release from bovine nasal septum cartilage explants. Hydrophilic inactivators showed no inhibition at concentrations up to 100 microM. In contrast, lipophilic inactivators gave significant inhibition, which was both reversible and specific. No effects on interleukin 1 signal transduction were detected, but rates of proteoglycan synthesis were apparently increased. Our results suggest that one or more of the lysosomal cathepsins B, L and S mediate cytokine-stimulated proteoglycan degradation, and the turnover of newly synthesized proteoglycan, but that effective inhibitors must pass through membranes.

Animals↗
PubMed1993

A new test for infection by Entamoeba histolytica.

Entamoeba histolytica is a common parasite of the human intestine, and in a significant percentage of cases it invades the tissues. Virulent strains of the organism produce the proteinose histolysain, which almost certainly facilitates the invasive behaviour. Histolysoin has been isolated, a selective assay developed, and specific antisera raised against the enzyme. As described here by Alfredo Luaces, Lyda Osorio and Alan Barren, the ENZYMEBA test for infection by E. histolytica combines the specificities of both antibodies and enzyme assay to achieve a high degree of sensitivity and selectivity. Circulating antibodies to histolysain were detected in a solid-phase enzyme immunoassay, the results suggesting that a humoral immune response is induced by histolysain during the formation of liver abscess.

Journal Article↗
PubMed1993

The in vitro effects of interferon-gamma, interferon-alpha, and tumour-necrosis factor-alpha on erythroid burst-forming unit growth in patients with non-leukaemic myeloproliferative disorders.

We have studied the effects of interferons gamma (IFN-gamma) and alpha (IFN-alpha), and tumour-necrosis factor-alpha (TNF) on circulating 14-day erythroid progenitor cell (BFU-E) growth in vitro from patients with non-leukaemic myeloproliferative disorders (MPD) compared with normal controls. IFN-gamma (1000 U/ml) inhibited BFU-E growth in all controls studied (mean growth +/- SE = 61% +/- 6%, n = 10). In 7 of 11 MPD studied there was no inhibition, and in some cases clear enhancement of BFU-E growth by IFN-gamma. When cultured in the presence of recombinant erythropoietin (rEpo) 1 U/ml, both IFN-alpha and TNF (at 100 and 1000 U/ml) produced a similar degree of inhibition of BFU-E growth in MPD and controls. The inhibition by 100 U/ml IFN-alpha was abrogated, partially in controls but completely in MPD, by increasing the dose of rEpo to 5 U/ml. Similarly, the increase in rEpo dose enhanced BFU-E growth in cultures with 100 U/ml TNF, but had little effect on cultures containing 1000 U/ml of either IFN-alpha or TNF. The aberrant in vitro response to IFN-gamma demonstrated in some of these patients may be of relevance to the pathophysiology of MPD. These results fail to demonstrate a differential in vitro effect for IFN-alpha on MPD BFU-E growth compared with controls and suggest that the in vitro suppression of haemopoiesis by IFN-alpha when used in MPD treatment is non-specific.

Cells, Cultured↗
PubMed1993

T cell and NK cell mediated graft-versus-leukaemia reactivity following donor buffy coat transfusion to treat relapse after marrow transplantation for chronic myeloid leukaemia.

Two patients with chronic myeloid leukaemia in cytogenetic relapse following T lymphocyte-depleted BMT were treated with transfusions of donor buffy coat leucocytes. In both patients the marrow reverted to a completely normal karyotype and was negative for the BCR-ABL fusion gene transcript by polymerase chain reaction analysis. Before buffy coat transfusion the cytotoxic T lymphocyte precursor frequency against pre-BMT patient leukaemia cells (Lk-CTLP) was lower than that against pre-BMT patient PHA-transformed lymphocytes (Ly-CTLP) in both cases. At 2 weeks (case 1) and 8 weeks (case 2) after transfusion this ratio inverted so that Lk-CTLP predominated. Natural killer (NK) function fell initially and then recovered to exceed pre-transfusion values prior to normalization of the bone marrow karyotype. These changes in cytotoxic T lymphocytes and NK cells following donor buffy coat transfusions for patients with relapsed chronic myeloid leukaemia after marrow transplantation support the concept of a graft-versus-leukaemia effect mediated by both MHC restricted and non-restricted pathways.

Adult↗
PubMed1992

Simultaneous genotypic and immunophenotypic analysis of interphase cells using dual-color fluorescence: a demonstration of lineage involvement in polycythemia vera.

Fluorescent in situ hybridization has become a useful technique by which chromosomal abnormalities may be shown in interphase cells. We present a dual-fluorescence method whereby a chromosomal and immunophenotypic marker can be visualized simultaneously in the same interphase cell. Two patients with the myeloproliferative disorder polycythemia vera and trisomy for chromosome 8 have been studied using this technique and selective involvement of the myeloid and erythrocyte lineages has been shown by the detection of the trisomy in immunophenotyped cells. Simultaneous analysis of genotype and immunophenotype in individual cells from patients with myeloproliferative disorders or leukemia may help identify the developmental and lineage status of cells in which molecular alterations have resulted in clonal advantage.

Aged↗
PubMed1992

Changing trends in allogeneic bone marrow transplantation for leukemia in the 1980s.

OBJECTIVE: To identify changes in practice and outcome of bone marrow transplants for leukemia in the 1980s. DESIGN: Comparison of key explanatory and outcome variables in five 2-year cohorts, from 1980 through 1981 to 1988 through 1989, using a large database of detailed clinical information. PATIENTS: Recipients (7788) of bone marrow transplants for acute lymphoblastic, acute myelogenous, or chronic myelogenous leukemia reported to the International Bone Marrow Transplant Registry, Milwaukee, Wis, by 185 transplant teams worldwide. RESULTS: Linear increases occurred during the periods 1980 through 1981 to 1988 through 1989 as follows with 95% confidence intervals: (1) transplants for chronic myelogenous leukemia from 14% +/- 2% to 35% +/- 2%; (2) transplants from unrelated donors from 1% +/- 1% to 7% +/- 1%; (3) preparative regimens without radiation from 3% +/- 1% to 30% +/- 2%; and (4) use of methotrexate plus cyclosporine to prevent graft-vs-host disease from 2% +/- 1% to 55% +/- 2%. Among recipients of human lymphocyte antigen-identical sibling bone marrow, the 2-year probability of treatment-related mortality decreased by 6% to 22%. The probability of relapse decreased from 46% +/- 6% to 38% +/- 6% in intermediate leukemia but did not change appreciably in early or advanced leukemia. Probabilities of leukemia-free survival improved from 51% +/- 4% to 57% +/- 3% in early leukemia, from 28% +/- 4% to 36% +/- 5% in intermediate leukemia, and from 12% +/- 4% to 18% +/- 5% in advanced leukemia. A separate analysis of a homogenous population of patients indicated that improvements in outcome in the 1980s were due to improvements in transplant practice rather than improved patient selection. CONCLUSIONS: Modest increases in leukemia-free survival rates occurred after human lymphocyte antigen-identical sibling bone marrow transplants in the 1980s. Improvements were due primarily to reductions in treatment-related mortality with little or no change in relapse risk. More effective antileukemia strategies and continued reductions in treatment-related toxic effects are needed.

Adult↗
PubMed1992

Quantification of peptide aldehyde ligands immobilized for the affinity chromatography of endopeptidases.

A method is described for quantification of aldehyde and aldehyde semicarbazone groups attached to an insoluble matrix. Semicarbazones are converted to aldehydes, and the aldehydes are coupled with 4-phenylazoaniline. The excess reagent is washed off, and the remainder then displaced with salicylaldehyde. The quantity of the phenylazoaniline/salicylaldehyde adduct is determined spectrophotometrically, allowing the calculation of the amount of aldehyde or semicarbazone per unit volume of the matrix. Analyses by the new method show that four matrices offered commercially for this type of immobilization differ greatly in coupling capacity and stability of the conjugate under conditions of affinity chromatography.

Aldehydes↗
PubMed1992

Bone marrow transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia.

Philadelphia chromosome (Ph1)-positive acute lymphoblastic leukemia (ALL) has a poor prognosis when treated with conventional chemotherapy. We analyzed the outcome of 67 HLA-identical sibling bone marrow transplants (BMTs) for Ph1-positive ALL reported to the International Bone Marrow Transplant Registry (IBMTR). Twenty-one of 67 (31%) transplant recipients survived in continuous complete remission more than 2 years after transplant. Two-year actuarial probabilities (95% confidence interval) of leukemia-free survival were 38% (23% to 55%) for 33 patients transplanted in first remission, 41% (23% to 61%) for 22 patients transplanted after relapse, and 25% (9% to 53%) for 12 patients failing to achieve remission with conventional chemotherapy. These data indicate that transplants are effective treatment for Ph1-positive ALL.

Adolescent↗
PubMed1992

The effects of selective matrix degradation on the short-term compressive properties of adult human articular cartilage.

The effects of proteoglycan and collagen digestion on the transient response of human articular cartilage when tested in unconfined compression were determined. Small cylindrical specimens of cartilage, isolated from the femoral head of the hip joint and from the femoral condyles of the knee joint, were subjected to a suddenly applied compressive load using a test apparatus designed to yield a transient oscillatory response. From this response values of the elastic stiffness and the viscous damping coefficient were determined. Cathepsin D and cathepsin B1 were used to digest the proteoglycan in some specimens, while in other specimens leukocyte elastase was used to attack the non-helical terminal regions of the Type II tropocollagen molecules and possibly the Type IX collagen molecule and thereby disturb the integrity of the collagen mesh. The results showed that proteoglycan digestion alone reduced the viscous damping coefficient but it did not significantly alter the elastic stiffness as determined from the oscillatory response. In contrast, the action of elastase reduced both the damping coefficient and the elastic stiffness of the cartilage. The results demonstrated the role of proteoglycans in regulating fluid transport in cartilage and hence controlling the time-dependent viscous properties. The elastic stiffness was shown to be dependent on the integrity of the collagen fibre network and not on the proteoglycans.

Aged↗