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Biomedical subjects

G Hennen

Publications and source records attributed to G Hennen.

At least 127 records · Page 7Linked to original sources
PubMed1978

Estrogens delay the postpartum recovery of the LH-RH-induced gonadotropin release.

In 27 healthy postpartum women, who were neither lactating nor receiving any therapy, LH-RH stimulation tests (50 micrograms i.v.) were performed on days 7, 14, 21 and 28 of the puerperium. In a second group of 9 postpartum women an i.m. injection of 10 mg estradiol valerianate was administered within the 3rd postpartum day, and an LH-RH stimulation test was performed on days 14 and 21 of the puerperium. Blood was withdrawn at standard intervals and LH and FSH measured by radioimmunoassay. No significant FSH and LH response was found on day 7. On day 14 there was a significant release of FSH but no LH was released. On days 21 and 28 there was a significant release of FSH and LH but the magnitude of the FSH response was greater than that of the LH release. The administration of estrogens did inhibit the recovery of the pituitary from its refractoriness: on day 14 no release of LH and FSH was observed; on day 21, only a significant release of FSH could be detected in the second group of postpartum women. This emphasizes the major role played by steroids in the regulation of the hypothalamo-pituitary-gonadal function.

Estradiol↗
PubMed1978

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

The properties of porcine follitropin and its subunits which have not yet been characterized are presented. The porcine follitropin obtained has a biological potency of 81 times the National Institutes of Health Porcine Follitropin P-1 preparation. Its contamination by lutropin and thyrotropin amounted to 1 and 0.5 percent by weight respectively, as measured by radioimmunoassay. The alpha and beta subunits of porcine follitropin were obtained by incubation in an acidic urea solution followed by anion exchange chromatography. The amino acid composition of porcine follitropin alpha subunit was found to be identical to that of alpha chain of porcine lutropin and thyrotropin. These porcine alpha chains differ, nevertheless, markedly in their carbohydrate composition particularly with respect to their mannose and galactose contents. The amino-terminal residue of the follitropin alpha subunit is threonyl. The carboxy-terminal end of the alpha chain is of variable length. Cysteyl residue was detected at the aminoterminal end of the follitropin beta chain with glutamic acid at its carboxy-terminal end. Cross-contamination of the alpha and beta subunit preparations was measured by specific radioimmunoassay and amounted to 0.5 and 0.1 percent by weight respectively.

Amino Acids↗
PubMed1978

Porcine follitropin. The amino-acid sequence of the beta subunit.

The amino acid sequence of the porcine beta subunit has been established by studies of peptides isolated after tryptic, thermolytic and staphylococcal protease treatments of the reduced and carboxymethylated chain. The primary structure of the amino-terminal region of the molecule has been solved by automatic sequencing of the reduced and tritium-labeled carboxymethylated subunit. The amino acid sequence of porcine follitropin beta subunit differs from that of its human counterpart by several amino acid replacements, deletion or addition of one or several residues. The porcine chain appears shorter at both its amino and carboxy-terminal ends. The chemical evolution of follitropin is briefly considered and compared to these of thyrotropin and lutropin.

Amino Acid Sequence↗
PubMed1978

Study of follitropin receptors in testis using a homologous system. Binding of porcine follitropin to plasma membranes from immature porcine testis and correlation with adenylate cyclase stimulation.

The properties of follitropin receptors in immature porcine testis were determined using highly purified porcine follitropin. 1. The characteristics of follitropin binding to a subcellular fraction rich in plasma membranes were studied using a 125I-labelled follitropin with high specific activity (75-100 Ci/g) and high binding activity. The binding is dependent on time, temperature and pH. It is specific to follitropin as demonstrated by the very low binding activity of the follitropin alpha and beta subunits and of the other glycoprotein hormones. Scatchard analysis of binding data indicated an equilibrium association constant of 2 x 10(10) M-1 and a concentration of high affinity binding sites of 500 fmol/mg membrane proteins. 2. A sensitive radio-ligand receptor assay was developed. Fifty percent inhibition of binding was obtained with as little as 2 ng of porcine follitropin. Ovine and bovine follitropins and pregnant mare serum gonadotropin gave binding inhibition curves parallel to that given by porcine follitropin. With equine and human follitropin, significantly different slopes were recorded. 3. Kinetics of dissociation of labelled follitropin from its testis receptors showed the presence of at least two compartments with fast and slow dissociation rate constants. The ratio between the sizes of the slow and fast compartments appeared dependent upon preincubation time. 4. A temporal correlation was observed between binding of follitropin to testis receptors and activation of membrane bound adenylate cyclase.

Adenylyl Cyclases↗
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

Thyroliberin and gonadoliberin tests during pregnancy and the puerperium.

Highly specific and sensitive radioimmunoassays for HTSH, HFSH and HLH have been used in order to investigate pituitary thyrotrophic and gonadotrophic functions of pregnant and puerperal women. The radioimmunoassay system for HFSH, using reagents prepared in our laboratory, is described. Thirty-three women were studied during pregnancy and post-partum. Forty-one TRH tests were performed. Basal levels of TSH, and increase in serum TSH after intravenous injection of TRH were similar in pregnant and puerperal women and in a control group. Thirty-three LH-RH tests were also performed. Basal levels of LH and FSH remained undetectable throughout pregnancy and in early puerperium. Furthermore, after intravenous injection of LH-RH neither LH nor FSH activity could be detected. It has thus been demonstrated that pituitary responsiveness to TRH during pregnancy and the puerperium is similar to that of non-pregnant young women. In contrast, a complete cessation of pituitary gonadotrophic functions is observed during the same period.

Adolescent↗
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↗
PubMed1976

Chemical study of the topography of porcine lutropin (LH) using dinitrofluorobenzene and dansyl chloride.

Treatment of porcine lutropin beta-subunit by increasing amounts of dansyl chloride shows that only one fluorescent group can be bound to the free subunit, namely on tyrosine beta-37. This modification prevents reassociation with native chi-subunit. In contrast to dansyl chloride, dinitrofluorobenzene reacts preferentially with tyrosine beta-59. This substitution does not interfere with the reassociation with the native chi-subunit. By using equimolar ratio of dansyl chloride and porcine lutropin chi-subunit it is possible to modify this subunit on a single site, which is found to be a tyrosine residue. The monodansylated X-subunit is still able to recombine with native B-subunit but its fluorescence is found to be markedly quenched upon binding. In addition, the O-dansyl-tyrosyl fluorescence quenching by potassium iodide is more effective on the recombined dimer than on the free chi-subunit. Both reconstituted dimers (native xhi chi dinitrophenylated beta and dansylated chi chi native beta) are without biological activity. It is not clear whether the substituted phenolic groups are essential or whether the added groups prevent the chi beta dimer from taking the active conformation. This alternative is discussed in the light of recent data from this laboratory and others.

Amino Acids↗
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↗