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ABSTRACT
Freshly dispersed or cultured (18 h) ovine anterior pituitary cells were fractionated on 55% sigmoidal Percoll gradients. This resulted in the separation of two sub-populations of cells at densities of 1·075 g/ml (peak I) and 1·055 g/ml (peak II). Radioimmunoassay of fractions from a gradient on which cells were separated before culture showed the profiles of GH and prolactin to be virtually superimposable. After culture, however, the lactotroph population exhibited an apparent shift in its density profile, the lighter population increasing at the expense of the denser one. Immunocytochemistry of the cells remaining in the denser peak (peak I) showed that it consisted of about 65% somatotrophs which was approximately a three-fold enrichment over the proportion of somatotrophs present in the original cell preparation (24%). Refractionation studies indicated that the change in the density profile of the lactotrophs was due to an actual reduction in their density rather than a loss of viability of the denser sub-population. Secretion data showed the purified somatotrophs to be more responsive than the crude cell preparation to the regulatory factors, GH-releasing hormone and somatostatin. This enriched cell population should prove useful in the detailed study of GH secretion.
J. Endocr. (1987) 115, 395–403
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ABSTRACT
Prolactin and GH are distinct hormones that have been conventionally thought to be produced and secreted by separate cells in the anterior pituitary gland. Recently it has been suggested that some cells (somatomammotrophs) may secrete both hormones. We have examined the occurrence of somatomammotrophs in sheep anterior pituitary tissue using immunogold labelling. Of a number of procedures used, double labelling using first antibodies raised in different species proved the least susceptible to apparent co-localization of hormones due to artifacts. Using this approach it was shown that a large proportion of the cells in the sheep anterior pituitary glands examined were mammotrophs or somatotrophs, showing no significant co-localization of GH and prolactin. Of 1800 cells examined, only two were somatomammotrophs. One of these, from a female animal, contained GH and prolactin in different granules within the same cell. The other, from a male animal, showed co-localization of these two hormones within the same granules.
Journal of Endocrinology (1990) 124,67–73
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ABSTRACT
Peripheral blood mononuclear cells were collected from a sheep immunized against progesterone-11α-hemisuccinate-ovalbumin. Following fusion with NS1 mouse myeloma or heteromyeloma cells, a large number of hybrid colonies was established. These were screened for the production of sheep antibodies to progesterone. Twenty-four cell lines were cloned and one was stabilized. This cell line, O/MP.1A9.D7B2, produced a high-affinity ovine immunoglobulin G1 (dissociation constant 4·8 pmol/l) with a high degree of specificity for progesterone. The antibody was substituted into a competitive enzyme-linked immunosorbant assay for the measurement of progesterone in bovine milk, originally established using an ovine polyclonal antibody, and the results were compared. The monoclonal antibody produced an assay with a lower limit of detection and a greater degree of discrimination than the polyclonal antiserum.
Journal of Endocrinology (1990) 126, 217–222
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ABSTRACT
Human somatomedin C has been purified from Cohn fraction IV paste by a simplified procedure using chromatofocusing, hydroxylapatite chromatography and reverse-phase high performance chromatography. The purified material has a specific activity by somatomedin C radioimmunoassay of 9160 units/mg (1 unit is defined as the amount of somatomedin present in 1 ml normal adult male human serum), representing a 650 000-fold purification, and possesses sulphation, mitogenic and insulin-like activities (specific activities of 3388 units/mg, 832 units insulin equivalents/mg and 1122 units/mg respectively). Somatomedin C is shown to be a potent stimulator of DNA synthesis (50% maximum stimulation at 150 fmol/ml) in isolated chondrocytes derived from costal cartilage, a major physiological target tissue.
J. Endocr. (1986) 110, 151–158
