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Biomedical subjects

J Paquin

Publications and source records attributed to J Paquin.

12 recordsLinked to original sources
PubMed1990

Inflammation and cartilage metabolism in rheumatoid arthritis. Studies of the blood markers hyaluronic acid, orosomucoid, and keratan sulfate.

Single analyses of peripheral blood of rheumatoid arthritis (RA) patients showed a significant reduction in the mean value for keratan sulfate (KS) compared with that in control subjects, but the mean value for orosomucoid (OM) was elevated compared with that in control subjects. Some RA patients displayed highly elevated levels of hyaluronic acid (HA), while others exhibited normal levels. There was a significant inverse correlation between OM and KS content in RA patients, as well as a direct correlation between HA and OM. In longitudinal studies of RA patients, parallel changes in OM and HA and inverse changes between KS and OM or HA were commonly observed. Clinical analyses revealed that there was an inverse correlation between KS and morning stiffness, and direct correlations between the number of tender joints and HA, and between HA or the erythrocyte sedimentation rate and the number of joints with effusions. The reason(s) for the inverse correlation between KS and OM as an index of systemic inflammation remains to be established. Circulating HA represents an index of joint inflammation, for which a marker has not been previously available.

Adult↗
PubMed1989

Rat plasma kallikrein: purification, NH2-terminal sequencing and development of a specific radioimmunoassay.

Rat plasma kallikrein (rPK) was purified to homogeneity form plasma using affinity and high-performance liquid chromatography techniques, and subjected to NH2-terminal sequencing. The data showed that the sequenced segments of the regulatory (heavy) and catalytic (light) chains of the proteinase, respectively, display 73 and 91% sequence similarity with their counterpart in human plasma kallikrein. This sequence homology in conjunction with the determined molecular structure and inhibitor sensitivity support the identity of the isolated enzyme as plasma kallikrein. A polyclonal antiserum against rPK was obtained after immunization of rabbits with the purified enzyme, and a specific radioimmunoassay was developed. Since Tyr-iodinated rPK was not recognized by the antiserum, two alternative approaches were found to be successful. These included the use of a tracer consisting of rPK modified with either the affinity reagent 125I-labeled DTyr-Glu-Phe-Lys-Arg chloromethyl ketone or with the Bolton Hunter reagent. The usable range of the assay is between 15-150 fmol per tube. The antibody was shown to bind both monomeric and dimeric forms of rPK. Denaturation of the enzyme in sodium dodecyl sulfate does not abolish immune recognition only as long as the regulatory subunit is attached to the catalytic chain. Oxidation or reduction of rPK results in complete loss of immunoreactivity. This observation suggests that perhaps the disulfide linkage of the catalytic and regulatory polypeptides somehow helps to protect the antigenic epitope from denaturation. Alternatively, the epitope(s) recognized by the antibody spans a domain which includes both Tyr and Cys residues necessary for immune recognition.

Amino Acid Sequence↗
PubMed1988

Selective cleavage of proenkephalin-derived peptides (less than 23,300 daltons) by plasma kallikrein.

The ability of human plasma kallikrein to hydrolyze several proenkephalin-derived peptides has been studied, including the synthetic peptides BAM 12P and peptides E, F, and B as well as synenkephalin-containing peptides (8.6, 18.2, and 23.3 kDa) purified from bovine adrenal medulla chromaffin granules. All the identified cleavages occurred either COOH-terminal to or between pairs of basic amino acids, with plasma kallikrein recognizing Lys-Lys, Lys-Arg, and Arg-Arg as processing signals. Moreover, plasma kallikrein was found to cleave at the COOH terminus of the basic pairs of amino acids preceding enkephalin sequences thereby releasing the biologically active form of the peptide with the free NH2-terminal Tyr needed for receptor recognition.

Adrenal Medulla↗
PubMed1988

Structural and immunological homology of human and porcine pituitary and plasma IRCM-serine protease 1 to plasma kallikrein: marked selectivity for pairs of basic residues suggests a widespread role in pro-hormone and pro-enzyme processing.

IRCM-serine protease 1 (SP1), originally isolated from porcine pituitaries and exhibiting preference for cleavage at pairs of basic residues has now been isolated in sufficient quantities to be structurally characterized from both porcine and human pituitaries and plasmas. Whereas the porcine protease shows a high degree of amino acid sequence homology to human plasma pre-kallikrein, the human homologue exhibits an identity of sequence in the first 25 residues of each chain (regulatory and catalytic chains). In addition, human plasma and pituitary IRCM-SP1 and human plasma pre-kallikrein show virtually identical immunological and molecular properties. These data strongly suggest that IRCM-SP1 and plasma pre-kallikrein originate from the same gene product. Purified extracts from perfused rat pituitaries show that 32% of the IRCM-SP1 activity found in normal rat pituitaries, still remain. These data together with the demonstrated association of IRCM-SP1 with particulate fractions of the pituitary suggest that IRCM-SP1 represents a tissue form of plasma pre-kallikrein. The characterization of the digestion products obtained upon reaction of IRCM-SP1 with pro-insulin, ACTH1-39, pro-dynorphin and pro-enkephalin-derived peptides, somatostatin-28, and a pro-renin-like peptide confirmed the high degree of cleavage selectivity of this enzyme for pairs of basic residues.

Amino Acid Sequence↗
PubMed1987

Chromogranin A can act as a reversible processing enzyme inhibitor. Evidence from the inhibition of the IRCM-serine protease 1 cleavage of pro-enkephalin and ACTH at pairs of basic amino acids.

Bovine parathyroid chromogranin A inhibits the cleavage of Z-Ala-Lys-Arg-AMC by either trypsin or IRCM-serine protease 1 (IRCM-SP1), a putative novel processing enzyme originally isolated from porcine pituitary anterior and neurointermediate lobes. On larger substrates, chromogranin A is a reversible competitive inhibitor of the cleavage at pairs of basic amino acids by IRCM-SP1. The substrates tested included pituitary ACTH and adrenal medulla pro-enkephalin-derived peptides such as the 8.6 kDa synenkephalin-containing precursor and peptide B. Chromogranin A is itself selectively processed by IRCM-SP1, and ACTH was shown to compete for such cleavage. These data suggest that chromogranins as a class of acidic proteins could participate in the tissue-specific processing of pro-hormones.

Adrenocorticotropic Hormone↗
PubMed1986

Influence of resident Salmonella on contamination of broiler flocks.

An epidemiological survey was made of 5329 samples from 10 poultry operations to determine the relationship between total poultry farm environment and incidences of Salmonella contamination of broiler flocks. Samples were analyzed from walls, drinkers, feeders, litter, insects, water, chicks, broilers, and feed to determine the effect of common sanitary practices on Salmonella contamination of flocks. Results indicated that although similar hygienic practices had been taken on the 10 poultry farms examined, great variation exists in Salmonella contamination among the farms. Among the sources studied, the most important source of contamination was determined to be the resident Salmonella of the flock i.e., the strain isolated on chicks' first day in the poultry house. This source was more important than Salmonella isolated during the rearing period. However, the precise conditions of Salmonella contamination in poultry flocks remain to be elucidated.

Animals↗
PubMed1985

Channeling between the active sites of formiminotransferase-cyclodeaminase. Binding and kinetic studies.

Formiminotransferase-cyclodeaminase, a circular tetramer of dimers, binds four tetrahydropteroylpolyglutamates/octamer, which indicates that these polyglutamate sites are formed by one type of subunit interface. The transferase and deaminase are separate catalytic sites as determined by inhibition studies with (6R)-tetrahydropteroylglutamate and by the observation that the activities can operate simultaneously. Under conditions where the transferase is saturated with tetrahydropteroyl(glutamate)n substrate, exogenously added formimino intermediate is utilized by the deaminase only if at least one of the substrate/intermediate pair is a monoglutamate. These properties indicate the existence of only one polyglutamate site/pair of catalytic sites. Kinetic specificity for each activity as measured by Vm/Km increases for longer polyglutamates, but does not differentiate among 4, 5, 6, and 7 glutamates. The enzyme shows distinct preference for hexaglutamate based on Kd as well as on Km values. With all substrates, Vm of the deaminase is greater than that of the transferase, allowing for potential channeling of the intermediate between active sites. Efficiency of channeling, optimal with pentaglutamate, does not correspond with affinity for binding. This demonstrates that a steric requirement predominates over simple sequestering of intermediates on the enzyme surface as the fundamental mechanism for channeling.

Ammonia-Lyases↗
PubMed1985

Preparation of tritium-labeled tetrahydropteroylpolyglutamates of high specific radioactivity.

Tritium-labeled [6S]-tetrahydropteroylpolyglutamates of high radiospecific activity were prepared from the corresponding pteroylpolyglutamates. Malic enzyme and D,L-[2-3H]malate were used as a generating system to produce [4A-3H]NADPH which was coupled to the dihydrofolate reductase-catalyzed reduction of chemically prepared dihydropteroylpolyglutamate derivatives. Passage of the reaction mixtures through a column of immobilized boronate effectively removed NADPH, and the tetrahydropteroylpolyglutamates were subsequently purified by chromatography on DEAE-cellulose. Overall yields of the [6S]-tetrahydro derivatives were 18-48% and the radiospecific activities were 3-4.5 mCi X mumol-1.

Chromatography↗
PubMed1979

Neuroendocrine effects of apomorphine: characterization of response patterns and application to schizophrenia research.

Apomorphine, a direct-acting dopamine agonist, stimulates release of growth hormone (hGH) and suppresses release of prolactin (PRL) from the anterior pituitary. Previous studies comparing the magnitude of these responses in schizophrenics and controls suggest that many acute (and some chronic) schizophrenics have exaggerated hGH responses; many chronic schizophrenics (and patients with tardive dyskinesia) have blunted hGH responses to apomorphine, and possibly blunted PRL responses. The present studies extend and confirm these findings in chronic schizophrenics; in addition, several studies were undertaken to further characterize these apomorphine-induced endocrine responses. Studies in which apomorphine was given on 2 or 3 separate occasions to each of five subjects indicate that the hGH response is a highly reproducible individual index, but PRL suppression is a less satisfactory measure. hGH responses to apomorphine were consistently antagonized by pretreatment with haloperidol, supporting the concept that the hGH-releasing effect of apomorphine is mediated by its action on dopamine receptors. Cyproheptadine pretreatment was associated with erratic increases or decreases in the hGH response to apomorphine, but did not alter PRL levels or apomorphine-induced PRL suppression. The relationship of these findings to biological hypotheses of schizophrenia and to neuroleptic-induced receptor changes is discussed.

Adult↗