G. T. Campbell

Adrenergic neurons: Are they present on microvessels in cheek pouches of hamsters?

Catecholaminergic innervation was investigated in the cheek pouch, mesentery, and cremaster muscle of the hamster. These tissues were removed from normal hamsters after anesthetization with sodium pentobarbital. They were prepared immediately for visualization of catecholamines by using a glyoxylic acid fluorescent technique. Visualization was accomplished via a Zeiss fluorescent microscope with a 470-nm barrier and a 420-nm excitation filter. No fluorescence was observed in or around the microvessels of the cheek pouch; however, intense fluorescence was demonstrated around and along microvessels in the mesentery and cremaster muscle. Thus, within the limitations of this technique, this study demonstrates that local catecholamines, either as a component of adrenergic neurons or a part of the local tissue milieu, are nondetectable in the microvessels within the cheek pouch as compared to mesenteric and muscle tissue of the hamster.

Development and retention of phenotypically specialized cells in pituitary allografts in the hamster (Mesocricetus auratus).

SummaryWe used immunohistochemistry to identify cells present in pituitary allografts in the hamster. Hypophyses removed from neonatal hamsters or adenohypophyses removed from adult females were placed beneath renal capsules of hypophysectomized adult females. Serum PRL, LH, and GH concentrations were measured at two, five, and eight weeks after placement of allografts. Allografts were removed after eight weeks and stained for cells containing PRL, LH, FSH, GH, or ACTH. Allografts did not release LH or GH. Those of adult adenohypophyseal tissue released significantly more PRL. The morphology of allografts of neonatal hypophyseal tissue resembled that of the adult adenohypophysis in situ. Lactotrophs, corticotrophs, somatotrophs and LH-cells were observed; very few FSH-cells were present. Allografts of adult adenohypophyseal tissue contained pituitary cells, numerous cavities, often enclosing lymphoid cells, and fibrous tissue. Atypical lactotrophs were the numerically dominant cells in these allografts; all other cells were present. The LH-cells outnumbered FSH-cells. These observations suggest that: (a) development of normal adenohypophyseal morphology can occur in an ectopic position; (b) intracellular hormones are present in cells in an ectopic site; (c) development and retention of intracellular FSH is more dependent on occupation of the normal position of the adenohypophysis than is retention of intracellular LH; and (d) release of PRL occurs from atypical cells in allografts of adult adenohypophyseal tissue.

Variations in the response of enzyme-dissociated rat pituitary cells to thyrotropin releasing hormone.

Abstract While exploring the interaction between thyrotropin releasing hormone (TRH) and normal rat anterior pituitary cells in monolayer culture we observed that cells dissociated with the use of trypsin did not respond to TRH with an increase in either TSH or prolactin (PRL) release. The dissociated cells were cultured for 3 days, then washed to remove serum proteins and exposed to 10−6M TRH for 3 hours. TSH and PRL secretion from stimulated and unstimulated cultures was determined by radio-immunoassay and normalized using cell protein. When such trypsin-dissociated cells were exposed to 0.5 mM dibutyryl cyclic AMP the release of both TSH and PRL doubled indicating that the intracellular secretory machinery was functional and that the block to TRH was proximal to the formation of cyclic AMP and presumably at the level of a TRH surface receptor. Previous studies have shown that such trypsin-dissociated cells respond to LHRH and a crude hypothalamic extract with a dose dependent increase in LH, FSH and ACTH release. This rules out a non-specific effect of trypsin. When pituitary cells were dissociated with a non-trypsin technique, the unstimulated release of both TSH and PRL was comparable to that found with the trypsin-dissociated cultures. However, these cultures did respond to TRH with an increase in TSH release although again no effect was seen with PRL. The susceptibility of the cells to trypsin suggests the possibility that a protein moiety may be closely associated with the function of the receptor.

An immunohistochemical study of adenohypophyseal cells containing follicle-stimulating hormone and luteinizing hormone during the phase of selective follicle-stimulating hormone release in postnatal female rats

SummarySerum concentration of follicle-stimulating hormone (FSH) in the juvenile female rat increases independently from that of luteinizing hormone (LH). The objective of this study was to determine whether this increase in serum FSH is accompanied by a proliferation of FSH-cells greater than the proliferation of LH-cells. Thus, we measured circulating FSH and LH in female rats on days 3, 10, 13, 17, and 20, calculated the percentages of adenohypophyseal cells that contained FSH or LH on days 3, 10, and 20, and determined whether cells containing only FSH existed on day 10. Serum FSH concentrations on days 10 and 13 were significantly greater than those on days 3, 17, or 20. No differences existed in serum LH concentrations. Cells containing FSH or LH were distributed throughout the entire adenohypophyses of 3, 10, and 20-day-old females. Clusters of these cells were observed in the ventral regions of adenohypophyses of 3-day-old females. The percentages of adenohypophyseal cells containing FSH increased significantly from ∼9% in 3-day-old rats to ∼17% in 10-day-old rats and then decreased to ∼14% in 20-day-old animals. At all ages the percentages of adenohypophyseal cells containing FSH were similar to the percentages of cells containing LH. At 10 days of age, all cells containing FSH also contained LH and all cells containing LH also contained FSH. These data suggest that the increase in serum FSH in the juvenile female rat is associated with an increase in the percentage of adenohypophyseal cells containing FSH and that at this time all cells containing FSH also contain LH.

Dissociation between increased growth hormone and prolactin secretion during the morning hours of early pregnancy in the rat

We investigated whether serum growth hormone (GH) concentration changes in association with the rise in serum prolactin (PRL) concentration known to occur during the early morning hours in the pregnant rat. Animals were kept in a room with the lights on from 0500 to 1900 hours (hr) daily and decapitated for the collection of trunk blood at 2200 or 2400 hr on Day 6 of pregnancy or at 0200, 0400, 0800 or 1000 hr on Day 7 of pregnancy. Serum GH concentration rose more than 4-fold from low levels at 2200 and 2400 hr to higher levels at 0400 and 0800 hr and then declined by 1000 hr. Serum prolactin (PRL) concentration followed a similar pattern except that it returned to low levels earlier, by 0800 hr. Serum luteinizing hormone, follicle-stimulating hormone and thyroid-stimulating hormone concentrations showed no significant changes. Serum GH levels at 0800 hr in pregnant rats were higher than those observed in cyclic rats (13 time periods sampled). The results demonstrate that serum GH concentration is elevated during a circumscribed period in the 6- to 7-day pregnant rat. The time of onset of the rise is similar to that for serum PRL but the elevation in GH levels persists longer than that for PRL.