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Biomedical subjects

G Murphy

Publications and source records attributed to G Murphy.

At least 217 records · Page 12Linked to original sources
PubMed1995

Tissue inhibitor of metalloproteinase-I and interstitial collagenase expression in autoimmune chronic active hepatitis and activated human hepatic lipocytes.

1. Activated hepatic lipocytes are central to the pathogenesis of liver fibrosis as the principal source of both interstitial collagens and matrix-degrading metalloproteinases. In progressive fibrosis there is a failure to degrade interstitial collagens with a reported decrease in collagenase activity. In these studies we investigate expression of the potent collagenase inhibitor, tissue inhibitor of metalloproteinase-1, and interstitial collagenase in end-stage autoimmune chronic active hepatitis and activated human hepatic lipocytes in culture. 2. Messenger RNA transcripts for interstitial collagenase and tissue inhibitor of metalloproteinase-1 in explanted human liver were quantified by ribonuclease protection assay and densitometric analysis. This indicated that tissue inhibitor of metalloproteinase-1 and interstitial collagenase expression in autoimmune chronic active hepatitis were also coordinately up-regulated. 3. Using Northern analysis of RNA from human lipocytes in primary culture on plastic, mRNA for interstitial collagenase could not be detected in unstimulated cells but was present after stimulation with tumour necrosis factor alpha. Tissue inhibitor of metalloproteinase-1 mRNA was present in unstimulated lipocytes and up-regulated fivefold in response to tumour necrosis factor alpha. Using activity assay of serum-free conditioned media, interstitial collagenase could not be detected in unstimulated primary cultures, primary cultures stimulated with tumour necrosis factor alpha or transforming growth factor beta-1 (n = 3 and n = 4 respectively) or in passaged lipocytes (n = 6). In contrast, free tissue inhibitor of metalloproteinase-1 activity was present in unstimulated and passaged cultures and this was increased in response to tumour necrosis factor alpha and transforming growth factor beta-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoimmune Diseases↗
PubMed1995

Folic acid prescription in pregnancy.

We resolved to prescribe folic acid supplements for all women who attended this practice during the first twelve weeks of pregnancy. Six months after this decision a prescription was recorded in only 13% of cases: this compared with 18% during the two months immediately following the decision. It was resolved to improve this performance and observations six months later revealed a prescription recorded in 63% of cases. Subsequently a new form for recording an antenatal consultation was devised and six months after its implementation, 100% recording of folate prescription for appropriate cases was observed. It was concluded that these simple audit exercises prompted changes in practice which helped to improve standards of patient care.

Adolescent↗
PubMed1994

Substitution of serine for glycine 883 in the triple helix of the pro alpha 1 (I) chain of type I procollagen produces osteogenesis imperfecta type IV and introduces a structural change in the triple helix that does not alter cleavage of the molecule by procollagen N-proteinase.

Type I procollagen secreted by dermal fibroblasts from an individual with osteogenesis imperfecta type IV was a mixture of normal molecules and molecules that were post-translationally overmodified. The individual was heterozygous for a G to A transition in the COL1A1 gene that resulted in the substitution of serine for glycine 883 in one or both of the pro alpha 1 (I) chains. The thermal stability of molecules containing overmodified chains was lower by 2 degrees C than that of normal molecules. However, following cleavage of the molecules with vertebrate collagenase, the temperature of denaturation of the overmodified A fragments (residues 1-775 of the helix did not contain the substitution) was 2 degrees C greater than that of A fragments from normal molecules. The rates of cleavage by procollogen N-proteinase (EC 3.4.214.14) (N-proteinase) of procollagen molecules in normal and osteogenesis imperfecta samples were not significantly different. The procollagen molecules in the osteogenesis imperfecta sample were also indistinguishable from those in control samples by rotary shadowing electron microscopy. The results suggest that this substitution of serine for glycine in the alpha 1 (I) chain of procollagen, like the substitution of aspartate for the same glycine previously described (Lightfoot, S. J., Holmes, D. F., Brass, A., Grant, M. E., Byers, P. H., and Kadler, K. E. (1992) J. Biol. Chem. 267, 25521-25528), can alter the structure of the triple helix N-terminal to the site of the substitution. However, in contrast to the aspartate for glycine substitution, the structural change is insufficient to delay the cleavage of the procollagen by N-proteinase and results in a mild rather than lethal phenotype.

Amino Acid Sequence↗
PubMed1994

Neutrophil collagenase (MMP-8) cleaves at the aggrecanase site E373-A374 in the interglobular domain of cartilage aggrecan.

Native and recombinant neutrophil collagenase (MMP-8) was shown to cleave at the E373-A374 'aggrecanase' site in the interglobular domain of aggrecan. The time course of digestion in vitro showed that MMP-8 cleaved initially at N341-F342, the predominant metalloproteinase site, before cleaving at the E373-A374 site. A synthetic peptide, IPENFFG, inhibited cleavage at E373-A374 but not N341-F342 in vitro, indicating that the E373-A374 sequence was a less preferred site for MMP-8 cleavage than N341-F342. IPENFFG also inhibited release of A374 RGSVI fragments from cartilage in explant culture, suggesting that a metalloproteinase cleaved at the aggrecanase site in situ. The possibility remains that 'aggrecanase' may be a metalloproteinase in cartilage.

Aggrecans↗
PubMed1994

Cell surface-mediated activation of progelatinase A: demonstration of the involvement of the C-terminal domain of progelatinase A in cell surface binding and activation of progelatinase A by primary fibroblasts.

We report that the isolated C-terminal domain of progelatinase A is inhibitory to the activation of this proenzyme by primary skin fibroblast plasma membranes but is unable to inhibit organomercurial-induced self-cleavage and activation. Ligand binding studies demonstrate that fibroblasts stimulated with concanavalin A to activate progelatinase A have a significantly enhanced level of cell surface-associated progelatinase A. Tissue inhibitor of metalloproteinases-2 (TIMP-2), an effective inhibitor of membrane-mediated progelatinase A activation, is able to abolish the enhanced level of cell surface-associated progelatinase A that occurs following stimulation. TIMP-1, a poor inhibitor of membrane activation, is unable to inhibit the cell surface binding of progelatinase A. The enhancement in the binding of 125I-progelatinase A to fibroblasts following concanavalin A stimulation can be blocked by the inclusion of excess C-terminal gelatinase A but not by a truncated form of gelatinase A lacking the C-terminal domain. Scatchard analysis of the binding of 125I-progelatinase A to concanavalin A-stimulated fibroblasts has identified 950,000 gelatinase binding sites per cell with a Kd of 1.3 x 10(-8) M. Analysis of non-stimulated fibroblasts has identified 500,000 sites per cell with a Kd of 2.6 x 10(-8) M. We propose that membrane-mediated activation of progelatinase A involves binding of the proenzyme through its C-terminal domain to the cell surface and that TIMP-2 can inhibit activation by interaction with progelatinase A through the C-terminal domain, thus preventing binding of the proenzyme.

Amino Acid Sequence↗
PubMed1994

Matrilysin is much more efficient than other matrix metalloproteinases in the proteolytic inactivation of alpha 1-antitrypsin.

alpha 1-antitrypsin, the primary physiologic inhibitor of human leukocyte elastase, is proteolytically inactivated by several matrix metalloproteinases including interstitial collagenase, stromelysin and 92 kDa gelatinase. In this report, we describe the catalytic effects of matrilysin, a recently identified metalloproteinase, upon alpha 1-antitrypsin. Matrilysin was found to be approximately 30-fold more effective than 92kDa gelatinase, 70-fold more effective than collagenase, and 180-fold more effective than stromelysin. Cleavage of alpha 1-antitrypsin by matrilysin produced two fragments of approximately 50 kDa and 4 kDa. The single cleavage occurred at the Phe352-Leu353 peptide bond, a locus within alpha 1-antitrypsin's active-site loop. These results suggest that apart from its activity against extracellular matrix, matrilysin provides a mechanism for the regulation of leukocyte elastase activity through its capacity to degrade alpha 1-AT.

Amino Acid Sequence↗
PubMed1994

Solution structure of the active domain of tissue inhibitor of metalloproteinases-2. A new member of the OB fold protein family.

Homonuclear two-dimensional and three-dimensional 1H nuclear magnetic resonance spectroscopy has been used to obtain essentially complete sequence-specific assignments for 123 of the 127 amino acid residues present in the truncated form of tissue inhibitor of metalloproteinases-2 (delta TIMP-2), the active N-terminal domain of the protein. Analysis of the through-space nuclear Overhauser effect data obtained for delta TIMP-2 allowed determination of both the secondary structure of the domain and also a low-resolution tertiary structure defining the protein backbone topology. The protein contains a five-stranded antiparallel beta-sheet that is rolled over on itself to form a closed beta-barrel, and two short helices which pack close to one another on the same barrel face. A comparison of the delta TIMP-2 structure with other known protein folds reveals that the beta-barrel topology is homologous to that seen in proteins of the oligosaccharide/oligonucleotide binding (OB) fold family. The common structural features include the number of beta-strands and their arrangement, the beta-barrel shear number, an interstrand hydrogen bond network, the packing of the hydrophobic core, and a conserved beta-bulge. Superpositions of the beta-barrels from delta TIMP-2 and two previously known members of the OB protein fold family (staphylococcal nuclease and Escherichia coli heat-labile enterotoxin) confirmed the similarity in beta-barrel topology. The three-dimensional structure of delta TIMP-2 has allowed a more detailed interpretation than was previously possible of the functional significance of available protein sequence and site-directed mutagenesis data for the TIMP family. Furthermore, the structure has revealed conserved surface regions of potential functional importance.

Amino Acid Sequence↗
PubMed1994

The National Cancer Data Base report on prostate cancer.

BACKGROUND: Previous Commission on Cancer studies on prostate cancer have examined time trends in disease stage, treatment patterns, and survival. The most current National Cancer Data Base data for prostate cancer are reviewed in this report. METHODS: Two Calls for Data have yielded a total of 85,813 prostate cancer reports from hospital registries across the country. RESULTS: The proportion of early stage, curable prostate cancers diagnosed in the United States has increased. In 1990, African-American patients were more likely to be diagnosed with metastatic prostate cancer than were non-Hispanic whites. The proportion of patients treated by prostatectomy increased between 1974 and 1990. Consistent with the pattern of more advanced disease at diagnosis, African-American patients were less likely to have received prostatectomy or radiation treatment and more likely to have received only hormonal treatment. Prostate cancer survival was associated strongly with disease stage. African-American men had a lower 5-year survival than did non-Hispanic white men. CONCLUSIONS: This information provides national points of reference against which individual hospital performance can be compared and should be particularly helpful to cancer committees, tumor boards, and cancer registrars for the monitoring and evaluation of prostate cancer management in hospital cancer programs. Not all segments of the population-at-risk are benefiting from earlier detection of prostate cancer. Improvements in early detection have important consequences for treatment patterns, allowing the increased use of curative surgical or radiotherapeutic treatment.

Black or African American↗