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Biomedical subjects

G Hennen

Publications and source records attributed to G Hennen.

At least 109 records · Page 6Linked to original sources
PubMed1985

Receptor-binding and down-regulatory properties of 22000-Mr human growth hormone and its natural 20000-Mr variant on IM-9 human lymphocytes.

Our earlier binding studies of the 22000- and 20000-Mr variants of human growth hormone (somatotropin) to pregnant-rabbit liver and mammary receptors [Closset, Smal, Gomez & Hennen (1983) Biochem. J. 214, 885-892] suggested that the 20000-Mr variant was a lower-affinity analogue of the 22000-Mr molecule. Since the receptor population in these tissues is not fully characterized, we have now investigated the binding of both variants to the well-characterized and highly specific human-growth-hormone receptor of the human lymphocyte IM-9 cell line. The maximum bindability of radioiodinated 22000- and 22000-Mr to IM-9 cells was 60 and 45% respectively. Both hormone variants have essentially the same binding characteristics: slow association (equilibrium reached in 8-10h at 30 degrees C), poor reversibility ('tight binding'), linear Scatchard plot, same specificity as shown by lack of competition by bovine, porcine or equine growth hormones or human growth hormone-(32-46)-(missing in the 20000-Mr variant),-(1-134)- and -(141-191)-peptides. Both unlabelled hormones inhibit binding of both tracers completely, with the 20000-Mr variant being only half as potent as the 22000-Mr one. The apparent affinity is 2.8 X 10(9)M-1 for the 22000-Mr variant and 1.6 X 10(9)M-1 for the 20000-Mr variant. This decreased affinity of the 20000-Mr variant appears to be due to a lower association rate constant. Concentrations (5 ng/ml) of the two variants that occupy about 15% of the total sites induce a marked down-regulation of the receptors after 18h incubation, but the 20000-Mr variant (50% decrease) has a smaller effect than the 22000-Mr variant (75% decrease). Thus the only consequence of the residues-32-46 deletion in the 20000-Mr variant is a lower association rate and affinity for the IM-9 lymphocyte human-growth-hormone receptor. The close binding characteristics of the two forms suggest that the known differences in their insulin-like effects cannot be explained by differences in the nature of their interaction with the human-growth-hormone receptor.

Binding Sites↗
PubMed1985

The ontogeny of hypothalamic pituitary function in the pig. I. Pituitary LH and FSH in the fetus and neonate.

Pituitaries were collected from fetal and postnatal pigs from day 55 p.c. until 6 weeks after birth at closely spaced intervals. LH and FSH in individual pituitaries were quantified by both homologous RIA and homologous RRA. No significant difference was found between results obtained by RIA and RRA. Both LH and FSH are first detected by RIA and RRA in the porcine fetal pituitary at 75 days p.c. Thereafter both LH and FSH pituitary content rises until term. LH pituitary concentration in both male and female fetuses and FSH pituitary concentration in males exhibit a peak just before birth. FSH pituitary concentration in females rises until birth and thereafter remains elevated. A statistically significant sex difference was found postnatally with regard to FSH content and concentration but not for LH.

Animals↗
PubMed1985

Follicle-stimulating hormone-secreting pituitary adenomas.

This retrospective study concerns 40 patients with an apparently nonsecretory pituitary adenoma who were operated on during an 11-yr period from 1971 to 1981. Among them, 6 men had elevated serum FSH levels. LH levels were normal in 5 and slightly elevated in 1. Testosterone levels were low in 2 patients and within normal limits in 2 others. Sexual impotency had developed from 6 months to 1 yr before surgery in all patients. Primary hypogonadism could be eliminated on clinical grounds (recent onset of hypogonadism, previous fertility of 5 of the 6, and postoperative improvement). After transsphenoidal adenomectomy, FSH levels returned to normal values in all, and clinical recovery occurred in most patients. Tumor tissue obtained at operation stained positively for the gonadotropins, but was negative for other pituitary hormones in all patients. The most probable explanation for these findings was that the tumors were responsible for the elevated FSH secretion. This explanation is supported by the immunocytochemical identification of gonadotropin-containing cells in the tumors. We conclude that these 6 men from a series of 40 patients who presented with pituitary tumor but no GH, PRL, or ACTH hypersecretion had primary gonadotropinomas.

Adenoma↗
PubMed1985

[Ultrastructural localization of pituitary hormones by immunocytochemical reactions in ultrathin sections of adenomas].

Human pituitary adenomas were fixed in glutaraldehyde and embedded in epon. Ultrathin sections were incubated either with anti-hGH, anti-hPRL or anti-hLH. They were incubated with second step goat anti-rabbit immunoglobulins linked to gold particles. Two PRL secreting adenomas, one GH and PRL secreting adenoma, one ACTH secreting adenoma and two non secreting adenomas were studied. The specificity and the limits of the method were discussed in relation with the results obtained in light microscopy with the PAP method.

Adenoma↗
PubMed1984

A highly sensitive radioimmunoassay for human growth hormone using a monoclonal antibody.

Biozzi-strain mice were immunized with a highly purified preparation of 20K variant of hGH. Spleen-cells were fused with SP2/0Ag14 myeloma cells. Clone productions were screened for specificity toward 20K and 22K hGH and for the affinity constant of antibody-antigen reaction. For the selected monoclonal antibody, Ka was 1.02.10(11) L/M using 22K hGH as both tracer and reference preparation. No cross reactivity was found with PRL and other pituitary hormones; hPL reactivity was 0.002 percent that of hGH. According to these antibody characteristics, a highly sensitive RIA system was developed and used for specific GH measurement in human serum. Using logit-log co-ordinates, the slope of the standard curve was -1.099 and the minimum detected dose was 0.5 uIU/ml. Excellent correlation (r = 0.9575) was found between assay data in this system and those of a conventional RIA method using specific polyclonal rabbit antiserum. The International Reference preparation (66/217) could adequately be used to calibrate the monoclonal antibody system since the in house internal 22K GH standard and international one were equally well recognized by the monoclonal antibody.

Animals↗
PubMed1983

Purification of the 22000- and 20000-mol.wt. forms of human somatotropin and characterization of their binding to liver and mammary binding sites.

Quantitative data concerning the binding of 22000-mol.wt. human somatotropin and its 20000-mol.wt. variant are described using pregnant-rabbit liver and mammary-gland receptors. The purification and the complete chemical characterization of both human somatotropin and its 20000-mol.wt. variant is also presented. Contamination of the 20000-mol.wt.-variant preparation by 22000-mol.wt. hormone was found to be 0.5% by weight as measured in radioimmunoassay using monoclonal antibody. Labelling of human somatotropin and its 20000-mol.wt. variant using the Iodogen method is described as well as the characterization of the binding to pregnant-rabbit liver and mammary-gland receptor preparations. The maximum binding capacity of the 125I-labelled human somatotropin was between 50 and 60% to liver particulate receptor, whereas that of the 20000-mol.wt. variant was 30%. The specificity of binding of both forms to rabbit hepatic and mammary-gland receptor was found to be similar for both proteins in the same system. The affinity constants and capacity were respectively 0.7 X 10(10)M-1 and 815 fmol/mg of protein for human somatotropin and 0.6 X 10(10)M-1 and 1.250 fmol/mg of protein for the 20000-mol.wt. variant. These data suggest that both proteins behave as partial agonists to the receptors studied.

Animals↗
PubMed1981

Demonstration of plasma human chorionic gonadotropin beta-subunit during pregnancy using LH-hCG receptors from immature porcine testis.

In an attempt to provide better assessment of human chorionic gonadotropin beta-subunit (hCG-beta) secretion in pregnant women, a method was developed for complete removal of hCG by porcine-purified receptors before measurement of the free hCG-beta subunit by radioimmunoassay. Blood samples of 111 pregnant women were collected and the following results were obtained: (1) Extensive removal (over 96%) of hCG allows quantitative determination of the free hCG-beta subunit by a specific radioimmunoassay. Our data demonstrate the presence of circulating hCG-beta subunit during pregnancy, a fact that was still under controversy until now. (2) In contrast with the hCG profile drug during pregnancy the free hCG-beta subunit exhibits a plasma concentration peak (400 +/- 132 ng/ml; mean +/- 1 SD) at the 12th-13th week, indicating that the changes in plasma levels of intact hCG and free hCG-beta subunit are unrelated.

Animals↗
PubMed1981

Transient neonatal hyperthyrotropinemia: a factitious syndrome due to the presence of heterophilic antibodies in the plasma of infants and their mothers.

In a national screening program for neonatal hypothyroidism, our criterion for diagnosis is a plasma TSH value exceeding 40 microunits/ml on the fifth day of life. Excluding cases with obvious thyroid abnormalities, we identified a group of 14 neonates with unexplained plasma TSH elevation out of 10,261 screened. The mothers of these infants also exhibited high plasma TSH immunoreactivity; both mother and child in these instances were clinically euthyroid. The material responsible for this TSH immunoreactivity had the following characteristics. After parturition, it disappears from circulation within 2 months in the infants and within 4-6 months in the mother, its apparent molecular weight approximated 150,000 daltons, and its affinity for protein A-Sepharose and its binding properties suggested that the material was an immunoglobulin. Binding is observed typically for heterologous immunoglobulin and human TSH. The heterophilic character of these immunoglobulins explains their interference in many RIA systems, including the TSH RIA commonly used in neonatal screening programs for hypothyroidism.

Antibodies, Heterophile↗
PubMed1979

Development and application of homologous radioimmunoassays for porcine gonadotrophins.

Antisera were raised against highly purified preparations of porcine luteinizing hormone (pLH) and follicle-stimulating hormone (pFSH). Highly specific and sensitive radioimmunoassay systems were developed. The antisera to LH and FSH were used at working dilutions of 1:500,000 and 1:200,000 respectively and the sensitivities of the assays were 0.1 ng LH/ml serum (3 x 10(-12) mol/l) and 0.5 ng FSH/ml serum (1.5 x 10(-11) mol/l). The LH and FSH preparations used as standards were 1.2 and 81 times as potent as NIH-LH-S15 and NIH-FSH-P1 respectively. Both assays were validated and adapted for the measurement of the gonadotrophin content of porcine serum. The concentrations of LH and FSH in blood were measured simultaneously in prepubertal sows throughout a 24 h period, in adult sows during the oestrous cycle and in both prepubertal and adult animals after treatment with LH releasing hormone.

Animals↗