Biomedical subjects

G H Zeilmaker

Publications and source records attributed to G H Zeilmaker.

At least 91 records · Page 5Linked to original sources

PubMed1976

Prolactin and delayed pseudopregnancy in the rat.

In (RXU)F1 hybrid rats delayed pseudopregnancy was induced in three different ways: 1) by removal of all recent corporl lutea on day 2 of pseudopregnancy, 2) by removal of the in situ ovaries from ovarian graft-bearing animals on day 0 of pseudopregnancy, 3) by administration of 1 mg of ergocornine hydrogenmaleinate (ECO) on day 1 of pseudopregnancy. These procedures ended pseudopregnancy and in 50-60% of the animals a delayed pseudopregnancy with a duration of 6-15 days was observed after the experimental cycle. After sterile copulation two daily prolactin peaks were observed. Removal of the ovaries in situ (from ovarian graft-bearing animals) or of recently formed corpora lutea (from non-grafted animals) caused the disappearance of the prolactin peak at 19.00 h, without affecting the occurrence of the 03.00 h peak. The administration of ECO caused the disappearance of both prolactin peaks. Until the day of estrus prior to delayed pseudopregnancy there were no differences in prolactin concentrations at 03.00 or 19.00 h between animals which became delayed pseudopregnant and those which remained cyclic. In the latter animals the 03.00 h surges decreased slowly in the luteectomized and the ovariectomized animals and were no longer present 7-9 days after copulation. In animals becoming delayed pseudopregnant both prolactin peaks were present from day 0 of delayed pseudopregnancy onwards. Progesterone cencentrations during delayed pseudopregnancy were relatively low when delayed pseudopregnancy had a duration of 6-9 days. When delayed pseudopregnancy lasted 10 days or more normal progesterone values were found.

Animals↗

PubMed1976

Effect of hysterectomy on serum luteinizing hormone concentrations and on corpus luteum function in the rat.

Serum progesterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations were estimated in intact and hysterectomized pseudopregnant rats. Progesterone concentrations increased significantly from day 2 of pseudopregnancy (PSP) onwards, and a plateau was reached on days 4 and 5. No significant differences in progesterone concentrations between intact and long-term hysterectomized animals were observed until day 10 of PSP. In the intact rats, progesterone concentrations decreased after day 8, but in the hysterectomized rats they remained elevated until days 18-20 of PSP. No differences between FSH concentrations in intact and hysterectomized rats were found. In hysterectomized rats, however, LH concentrations were significantly lower than those in the intact rats on days 2-7 of PSP. When hysterectomy was performed on day 2 of PSP (acute hysterectomy) lower LH concentrations were also found in the hysterectomized animals compared with sham-operated animals. No differences in progesterone concentrations were found between sham-operated controls and acutely hysterectomized animals on days 3-8 of PSP. It was found that LH concentrations in ovariectomized long-term hysterectomized rats were lower than those in ovariectomized, but otherwise intact, animals. In contrast to its effect on tonic LH secretion, long-term hysterectomy had no influence on the surge of LH during the afternoon of proestrus. In both intact and long-term hysterectomized rats the duration of PSP was not significantly altered after transplantation of an ovary under the kidney capsule and the removal of the ovaries in situ. It is concluded that hysterectomy leads to a decreased LH secretion by the pituitary gland, but has no influence on the maximal progesterone concentrations during PSP. The significance of these findings, particularly with regard to the prolongation of PSP after hysterectomy, is discussed.

Animals↗

PubMed1976

Serum follicle-stimulating hormone, luteinizing hormone and progesterone concentrations in pseudopregnant rats treated with medroxyprogesterone acetate.

Pseudopregnant rats were treated early in pseudopregnancy with 1 or 10 mg medroxyprogesterone acetate (MPA). Serum FSH, LH and progesterone concentrations were determined on days 2-20 of pseudopregnancy in treated and control rats. The mean duration of pseudopregnancy was 13-5 days in the control animals, but when animals were treated with 1 mg MPA a dioestrous period of 21-4 days was observed. A period with leucocytic vaginal smears of at least 2 months was observed after treatment with 10 mg MPA. Injection with MPA on day 3 of pseudopregnancy did not affect the serum FSH concentrations during the subsequent days. The progesterone pattern was alike in the three groups of animals, i.e. the duration of the activity of the corpora lutea was similar in all groups. However, 10 mg MPA slightly lowered progesterone concentrations on days 4-8 of pseudopregnancy. In the saline-treated rats, LH concentrations decreased from days 2-5, and remained low until they increased after day 11 of pseudopregnancy. This increase was delayed until day 20 in the animals treated with 1 mg MPA, and was not observed in the animals treated with 10 mg MPA. It is argued that the increase of LH concentration at the end of pseudopregnency is not instrumental in the decrease of peripheral progesterone concentration but rather that the decrease in the progesterone concentration leads to the increase in the LH concentration.

Animals↗

PubMed1976

Comparative analysis of cell distribution in the pigment epithelium and the visual cell layer of chimaeric mice.

In chimaeras of both rdrdCC in equilibrium ++ cc and rdrdcc in equilibrium ++CC combinations two types of distribution were observed. In a majority of the chimaeras both retinal layers were chimaeric; whereas in a few cases the pigment epithelium was chimaeric but the visual cell layer was made of ++ cells only. No spatial relation was observed in the distribution of the cells in the two layers. The two eyes of the individuals were nearly always identical with regard to occurrence of chimaerism in the two layers. The findings are discussed in the light of the possible site and mode of expression of the rd gene.

Animals↗

PubMed1975

Serum luteinizing hormone, follicle-stimulating hormone, prolactin and progesterone concentrations and follicular development in the pseudopregnant rat after unilateral ovariectomy.

Serum LH, FSH, prolactin and progesterone concentrations and follicular size were measured in rats during pseudopregnancy after unilateral ovariectomy (ULO) on day 1. This operation did not affect the duration of pseudopregnancy. Following pseudopregnancy compensatory ovulation occurred. After ULO progesterone concentrations remained low as compared with control values but the progesterone secretion per ovary was increased slightly. After ULO, LH concentrations were significantly increased on days 3 and 4 of pseudopregnancy. FSH concentrations were increased 5 h after the operation and again on day 4-7 of pseudopregnancy when compared with sham-operated control animals. During pseudopregnancy prolactin secretion increased each night. Increased prolactin levels were observed 18 and 36 h after ULO. The number of medium-sized follicles had increased 24 h after ULO. From the present study it is concluded that progesterone secretion by the corpora lutea can be increased to a limited degree by the increased release of gonadotrophins. Furthermore, it is concluded that a rapid increase in FSH concentrations after ULO is responsible for the initiation of the compensatory follicular growth.

Animals↗

PubMed1974