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Biomedical subjects

C McLean

Publications and source records attributed to C McLean.

At least 73 records · Page 4Linked to original sources
PubMed1985

A sensitive and specific immunoradiometric assay (IRMA) for human thyroid stimulating hormone.

A liquid phase "two-site" immunoradiometric assay (IRMA) specific for human thyroid stimulating hormone (hTSH) is described. The assay is based on the simultaneous addition of affinity purified sheep anti hTSH IgG-I 125 and rabbit anti hTSH antiserum to standards and unknowns followed by 4h incubation at room temperature. The separation of free labelled sheep IgG-I125 from that bound to hTSH is achieved by the addition of sheep anti-rabbit IgG Fc fragment antiserum. The radiolabelled sheep anti-hTSH IgG-I 125 was pretreated with solid phase urinary postmenopausal gonadotropins to remove cross reaction with FSH and LH. The assay is specific for hTSH and no cross reaction with the other anterior pituitary glycoproteins or protein hormones has been found. In addition it is characterized by a wide operating range, rapid equilibration of reactants and high sensitivity (0.02 microU/ml). The precision of dose estimates was less than 10% between 0.25-2.5 microU/ml and less than 2.5% over the range 2.5-60 microU/ml.

Antibody Specificity↗
PubMed1984

The effect of capsular polysaccharide and lipopolysaccharide of Bacteroides fragilis on polymorph function and serum killing.

The determinant responsible for the ability of Bacteroides spp. to inhibit polymorph phagocytic killing of aerobic organisms has not yet been identified. Therefore, the roles of lipopolysaccharide and capsular polysaccharide of B. fragilis were investigated. Serum-resistant and serum-sensitive strains of Proteus mirabilis were used to indicate inhibition of phagocytic killing and serum killing of aerobes. Whole organisms of B. fragilis, purified lipopolysaccharide and capsular polysaccharide were added to an in-vitro phagocytosis system. Results showed that greater than 10(7) bacteroides/ml inhibited both serum and phagocytic killing. Concentrations below 10(7)/ml had little effect on either process. Purified capsular polysaccharide (10 or 100 micrograms/ml), either alone in the system or in combination with sub-inhibitory concentrations of B. fragilis also markedly inhibited serum and phagocytic killing. Lipopolysaccharide (9 micrograms/ml) appeared relatively inert. B. ovatus, reputedly non-capsulated, produced identical results to those obtained with B. fragilis, but an encapsulated strain of Streptococcus pneumoniae did not inhibit serum or phagocytic killing.

Bacteroides fragilis↗
PubMed1981

Purification and characterization of amino-terminal pro-opiocortin peptides from human pituitary glands.

Two cystine-containing peptides isolated from human pituitaries were partially sequenced. The peptides are fragments derived from the amino-terminal of pro-opiocortin (NPOC) and have been chemically characterized as NPOC 1-28 (which lacks gamma-MSH) and NPOC 2-59. Their availability enables us to investigate new putative biological roles for the amino-terminal conserved sequence of pro-opiocortin.

Amino Acid Sequence↗
PubMed1980

Purification and characterization of a gamma-melanotropin precursor from frozen human pituitary glands.

A new melanocyte-stimulating peptide has been isolated from acid extracts of frozen human pituitary glands by salt/ethanol fractionation, Sephadex G-75 gel filtration and DEAE- and cM-cellulose ion-exchange chromatography. The peptide is glycosylated, has an N-terminal tryptophan residue and an apparent mol.wt. of 16000 as estimated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Its amino acid analysis closely resembles residues Trp-105 to Gln-29 predicted for the common precursor protein of bovine corticotropin and beta-lipotropin by Nakanishi, Inoue, Kita, Nakamura, Chang, Cohen & Numa [(1979) Nature (London) 278, 423-427]. This fragment is expected to have melanotropin activity due to the tetrapeptide -His-Phe-Arg-Trp- (residues -51 to -48) of the predicted sequence of the common precursor. It was found to have a molar potency of 1 X 10(-5) relative to alpha-melanotropin in the frog skin bioassay. These characteristics are consistent with the isolated melanotropin peptide being a non-corticotropin, non-lipotropin peptide of the human common precursor protein of corticotropin and lipotropin. The peptide neither potentiates the adrenal weight-maintenance activity of corticotropin-(1-24)-tetracosapeptide when administered to hypophysectomized rats, nor stimulates release of non-esterified fatty acids from isolated rat epididymal cells. A second N-terminal-tryptophan glycopeptide was also isolated, which had an amino-acid composition similar to that predicted for the bovine common precursor protein, residues Trp-105 to Gly-35.

Amino Acids↗
PubMed1980

The development of a radioimmunoassay for Tamm--Horsfall glycoprotein in serum.

The Tamm-Horsfall glycoprotein prepared by salt precipitation from urine was found to comprise a heterogeneous collection of aggregates. These could be disaggregated with 8m-urea, following which chromatography on a column of Bio-Gel A.15m yielded a homogeneous glycoprotein of mol.wt. 73000 together with several unidentified impurities. Gel filtration of normal plasma showed the glycoprotein to exist predominantly in a form that is eluted identically with the purified preparation. In one case, material of higher molecular weight was also detected. The purified glycoprotein was used to develop a rapid specific radioimmunoassay for its measurement in human serum or plasma by the use of the Tamm-Horsfall glycoprotein, labelled with (125)I by the chloramine-t method as the tracer, an antiserum raised in rabbits, and separation of the bound and free fractions by a second antibody covalently linked to magnetizable particles. Parallelism was demonstrated between the standard preparation and samples. Recovery of added standard to serum varied between 99 and 109%. Total assay time was less than 4h with an intra-assay and inter-assay coefficient of variation of less than 10%. There were no significant differences in the ranges covered with regard to either age or sex, and no circadian rhythm was observed in normal subjects. A physiological range of 70-540ng/ml was established based on serum samples from 95 subjects with normal renal function, as defined by their serum creatinine and urea concentrations. No Tamm-Horsfall glycoprotein was detected in the serum of six anephric patients.

Amino Acids↗
PubMed1976

Evidence of ambiguous processing and selective degradation in the noncapsid proteins of rhinovirus 1A.

Pulse-chase kinetics and extensive pactamycin mapping studies show that the translation of rhinovirus 1A proceeds in the order: initiate-P1-S-P2-terminate, where P1 is the precursor to the capsid proteins, S is a stable primary gene product, and P2 is the precursor to a family of noncapsid products. Initial examination of the molar stoichiometry of the families of rhinoviral proteins in infected cells suggested that both the P1 and P2 regions were translated more frequently than the S region. However, we show that this apparent asymmetry in translation is an artifact arising from two phenomena: (i) ambiguous cleavage sites which result in two alternative products from the S region, having apparent molecular weights of 47,000 and 38,000, and (ii) several fates for the P2 precursors, including degradation of 35 to 45% of the P2 family to small unidentifiable products. Another artifact, a time-dependent shift in the pactamycin mapping position of polypeptide r-39, was traced to a selective inhibition of the rate of cleavage of its precursor (peak 76). The processing rate of the capsid precursor (peak 92) was not retarded by pactamycin.

Capsid↗
PubMed1976

Organic acids in urine from human newborns.

The pattern of organic acids in urine from 15 normal newborn infants was investigated by gas chromatography/mass spectrometry of trimethylsilylated derivatives. The urine contains large amounts of succinic, fumaric, 2-ketoglutaric, and 3-hydroxy-3-methylglutaric acids, which are all fairly small components of urine from adults. On the other hand, hippuric acid is a small component in the urine from newborn infants, but a large component later in life. An additional number of differences can be seen. Some previously unrecognized aliphatic dicarboxylic acids were also observed, which are present to some extent in urine from adults.

Chromatography, Gas↗