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Biomedical subjects

J Closset

Publications and source records attributed to J Closset.

At least 91 records · Page 5Linked to original sources
PubMed1977

Bovine follitropin. Isolation and characterization of the native hormone and its alpha and beta subunits.

1) A reproducible procedure was developed for the purification of bovine follitropin. 2) The method involved ammonium sulfate precipitation, ion exchange and adsorption chromatography, concanacaline-A-Sepharose chromatography and gel filtration. 3) A specific radioligand receptor assay was used to monitor each chromatographical step. 4) The potency of highly purified bovine follitropin as measured by Steelman and Pohley bioassay was 62 times the NIH-FSH-B1 standard preparation. 5) Contaminations of bovine follitropin by other glycoprotein hormones such as thyrotropin and lutropin amounted to 3 and 0.45 per cent by weight respectively as measured by specific radioimmunoassays and radioligand receptor assays. 6) The subunits alpha and beta of bovine follitropin were obtained by incubation in acidic urea, the chains being then separated by anion exchange chromatography. The subunits were subjitted to complete characterization. The amino-terminal residue of the alpha subunit is phenylalanine while a half cystine residue was found at the aminoterminal end of the beta chain. 8) Cross-contamination of the alpha and beta subunit preparations was measured by specific radioimmunoassays and amounted to 0.02 and 0.1 per cent by weight respectively.

Amino Acids↗
PubMed1977

Human thyrotropin and its alpha and beta subunits.

A new procedure is described for the isolation of human thyrotropin using ion exchange chromatography and gel filtration only. Thyroid stimulating activity of the final preparation of our human thyrotropin amounted to 0.5 IU/mg by bioassay. The alpha and beta subunit of the hormone were also obtained by a new procedure. In this method the native hormone was incubated in an acidified 8 M urea solution and the chains were then separated by ion exchange chromatography and gel filtration. The amino-terminal residues of the alpha and beta chains were valine and phenylalanine respectively. The beta chain appears shorter at its carboxy-terminal end by one methionine residue than its bovine counterpart. Cross-contamination of the subunit preparations were measured by radioimmunoassay. The beta chain exhibited a contamination of about 3 percent of the alpha subunit by weight. The alpha subunit is contaminated by about one percent of the beta chain by weight.

Amino Acids↗
PubMed1976

Porcine thyrotropin. The amino-acid sequence of the alpha and beta subunits.

The amino acid sequences of both the alpha and beta subunits of porcine thyrotropin have been studied. Bovine thyrotropin primary structure was taken as a model for ordering the tryptic peptides of porcine thyrotropin. The amino acid sequence of the alpha subunit is identical to that of porcine luteinizing hormone, while oligosaccharide side-chains differ in composition. The primary structure of the beta subunit differs from that of bovine thyrotropin by six amino acid replacements, in positions 22, 24, 26, 36, 62 and 69, and by the absence of a methionyl residue at the carboxy terminus. Chemical evolutions of thyrotropin and luteinizing hormone are compared.

Amino Acid Sequence↗
PubMed1975

Conformational studies on parvalbumins by circular dichroism.

Structural variations of two parvalbumins, Whiting III and Pike III, in various denaturing conditions, have been studied by circular dichroism. CD signals are depressed from 4 urea. For Pike III, acidic pH, sodium dodecyl sulfate or complete removal of Ca2+ show little effect in the far ultraviolet region but rather strong effects in the near ultraviolet. For Whiting III similar results are obtained at acidic pH. Carboxymethylated Whiting III (0.15 Ca2+/mol) shows, on the contrary, decreased CD signals in the far and in the near ultraviolet spectra. Addition of Ca2+ fully restores the native CD spectra in both proteins. Ca2+ binding produces structural modifications which are found to vary according to parvalbumin and which seem in any case different from those described for troponin C.

Animals↗
PubMed1975

Human luteinizing hormone. Isolation and characterization of the native hormone and its alpha and beta subunits.

A new procedure is described for the isolation of the alpha and beta chains of the hormone. In this method, thenative hormone is incubated in acidic urea and the chains are then separated by ion-exchange chromatography. The amino-terminal residue of the alpha subunit is valine. The carboxy-terminal end of the alpha subunit is of variable length. No amino-terminal residue was detected for the beta chain; glycine was found at its carboxy-terminal end by the selective titration method. The amino acid and carbohydrate compositions of the hormone and both subunits are presented. The beta chain contains sialic acid and is devoid of galactosamine in contrast to the beta subunits of other species. Contamination of our human lutenizing hormone preparation by other pituitary glycoprotein hormones such as thyroid-stimulating hormone and follicle-stimulating hormone amounted to 0.5 and 0.25 percent by weight respectively. Cross-contamination of the initial alpha and beta subunit preparations was measured by specific radioimmunoassays and amounted to 4.1 and 2 percent by weight respecitively. Further extensive purification of these subunit preparations was then performed by means of affinity chromatography using immunosorbants. The final preparations exhibited a residual cross-contamination amounting to 0.2 and 0.02 percent by weight for the alpha and beta subunits respectively.

Amino Acid Sequence↗
PubMed1975

Selective radioimmunoassays for human luteinizing hormone (hLH) and human chorionic gonadotropin (hCG).

Highly specific radioimmunoassay systems were developed for measurement of hLH and hCG using antisera purified by affinity chromarography or simple adsorption to select the antibodies reacting specifically with either gonadotropin. Such systems permit specific measurement of lLH and hCG in samples containing both. These assays are suitable for various clinical and physiological studies, particularly, study of pituitary functions in the presence of chorionic or trophoblastic secretion.

Chorionic Gonadotropin↗