PubMed Health⌕ Search

Biomedical subjects

C Delouis

Publications and source records attributed to C Delouis.

At least 55 records · Page 3Linked to original sources
PubMed1982

[Kinetics of lymphocyte sub-populations and plasma cells in the mammary gland of primiparous sows in relation to gestation and lactation].

Qualitative and quantitative changes in pig lymphocyte sub-populations (T, B, L and nulls) were studied in the mammary gland of primiparous sows, as well as the appearance and development of plasma cells in relation to the 3 phases of mammary development: gestational, colostral and lacteal phases. Results showed: 1) An early colonisation of mammary epithelium from the beginning of the gestation phase by the three T, B and L lymphocyte subpopulations; 2) The presence of activated T lymphocytes, especially during the colostral phase; 3) The appearance of plasma cells during the colostral phase and their increase during the lacteal phase; 4) Not only the T, B and L lymphocyte subpopulations increased during the lactation but there was also a special increase in null lymphocyte subpopulation. These results give new data which are particularly important in allowing us to envisage immunization schemes for the pregnant sows, with the aim of enhancing local mammary or lactogenic immunity by transfer of antibodies and lymphocytes to the newborns.

Animals↗
PubMed1980

Effects of various hormone treatments on induction of lactation in the ewe.

In Exp. I and II, 52 of 68 ewes were induced into lactation with twice-daily injections of estradiol-17 beta (E2-beta) and progesterone (P4; .5 and 1.25 mg/kg body weight/day) for 7 days. Additional treatments were twice-daily injections (days 18 to 20) of hydrocortisone, growth hormone, thyroxine and thyrotropin releasing hormone alone or in various combinations. In Exp. III, 12 ewes were induced into lactation. In this experiment, all ewes were injected with E2-beta and hydrocortisone, as previously, but four ewes (III-2) had P4 injections extended to day 20, and four ewes (III-3) were not injected with P4. Across experiments, lowest milk yields during lactation and the lowest percentage of ewes induced into lactation (58%) occurred when only E2-beta and P4 were injected. Inclusion of hydrocortisone injections (50 mg/day) induced the highest percentage of ewes into lactation (86%, 38 of 44), the highest peak daily yields of milk and the highest total yields during lactation. Including injections of growth hormone, thyroxine or thyrotropin releasing hormone alone or in combinations did not produce better results than injections of E2-beta and P4 alone. Injections of E2-beta and hydrocortisone without concurrent injections of P4 were less effective. Intramuscular injections of P4 (10 mg/day) from days 8 to 20 did not inhibit lactogenesis or subsequent lactation. Across all experiments, 76% of multiparous (52/68) and 50% of nulliparous (6/12) ewes produced greater than 100 ml milk/day during their lactation (34 to 95 days). However, yields of milk for ewes that lactated were only 25 to 50% of those from postpartum ewes. The importance of including injections of hydrocortisone in the induction procedure was established, but determination of optimum time to inject and potential importance of other hormones requires additional research.

Animals↗
PubMed1980

[Short-term effect of prolactin on its receptor].

It is known that prolactin (PRL) when injected chronically is able to increase the level of its own receptors. We have shown here that, after a single IV injection of PRL to lactating rabbits, total prolactin-receptor levels (measured after in vitro desaturation of injected prolactin by a MgCl2 treatment of the membranes) decreased from 41.6 to 18.4 p. 100 (specific binding) in 6 hrs. The same results were obtained in organ-culture of the rabbit mammary gland in the presence of prolactin; in addition, the down-regulation of prolactin receptors could be counteracted by lysosomotropic agents (chloroquine NH4Cl) in vitro. These results showed that prolactin could, at short term, induce a down regulation of its receptors, and that this effect might be related to an endocytosis of hormone-receptor complex and lysosome degradation.

Ammonium Chloride↗
PubMed1980

Lactogenesis induced by prostaglandin F2 alpha in pregnant rabbits.

PGF2 alpha may have a primarily luteolytic action and hence diminish Pg secretion. This triggers the release of PRL and other hormones of the lactogenic complex with the consequent production of milk substances in the mammary gland. Later, when the uterine tissue is depleted of Pg, pregnancy is terminated.

Animals↗
PubMed1979

Stimulation of milk synthesis in the rabbit by fish pituitary extract.

The lactogenic properties of extracts of the pituitary glands of salmon and trout were evaluated by using the organ culture technique with rabbit mammary explants. Crude extracts and fractions obtained after chromatography on Ultrogel and selected for their capacity to compete with ovine prolactin in a rabbit mammary gland radioreceptor assay were added to the culture medium. The criteria of lactogenesis were lactose synthetase activity, casein synthesis, measurements of the concentration of casein messenger RNA and the histology of mammary glands. All these tests led to the conclusion that salmon and trout pituitary glands contain a prolactin-like principle capable of initiating milk synthesis in the rabbit mammary cell.

Animals↗
PubMed1978

Role of prolactin and glucocorticoids in the expression of casein genes in rabbit mammary gland organ culture. Quantification of casein mRNA.

Milk synthesis is initiated solely by prolactin in the pseudopregnant rabbit and glucocorticoids potentiate this action of prolactin. In organ culture, prolactin, in the presence or in the absence of insulin, enhances casein synthesis and cortisol (inactive alone) amplifies this action. Measurements of casein mRNA concentration in total cellular RNA, by hybridization with DNA complementary to casein mRNA, revealed that the stimulation of casein synthesis by the glucocorticoid is accompanied by an increase in the amount of casein mRNA. A systematic comparison of variations of these two parameters indicated that the major effect of glucocorticoids on lactogenesis in the rabbit at this stage of mammary gland development is mediated through an increase in the quantity of casein mRNA available for translation. No simultaneous control of casein mRNA translation by cortisol was observed.

Animals↗
PubMed1978

Role of spermidine in casein gene expression in the rabbit.

Spermidine concentration in rabbit mammary gland was estimated during pregnancy, lactation and after the induction of milk synthesis by prolactin and glucocorticoids in vivo and in vitro. It was observed that mammogenesis and lactogenesis during preganancy and the initiation of milk secretion at parturition are accompanied by an enhancement of spermidine concentration in the mammary gland. By contrast, the initiation of these phenomena by hormone injections does not require such variations of spermidine concentration. In organ culture, a slight increase in spermidine concentration was obtained under the influence of an hormonal combination including insulin, prolactin and cortisol. Spermidine added to the culture medium was unable to mimic cortisol action. An amplification of casein synthesis and a parallel increase of casein mRNA concentration was provoked by cortisol even when spermidine synthesis was blocked. Thus, one of the major actions of glucocorticoids during lactogenesis in the rabbit is not mediated through an increase in spermidine concentration in the mammary gland.

Animals↗
PubMed1978

Stabilization of casein mRNA by prolactin and glucocorticoids.

Prolactin injected into pseudopregnant rabbits led to a parallel enhancement of casein synthesis and casein mRNA concentration. When this stimulation was followed by a withdrawal of prolactin obtained by injections of bromocriptine, the rate of casein synthesis progressively diminished. In the presence of endogenous prolactin after the initial stimulation, the decline of casein synthesis was delayed. Hydrocortisone acetate injected with bromocriptine after the initial stimulation by prolactin was able to maintain a high rate of casein synthesis. Measurements of casein mRNA concentration by hybridization with casein cDNA indicated that in all cases the amount of casein mRNA was correlated with the magnitude of casein synthesis. This suggests that the lactogenic hormones, prolactin and glucocorticoids, which were previously demonstrated to be responsible for the enhancement of casein mRNA concentration are involved in their stabilization.

Animals↗
PubMed1978

Physiology of colostrum production.

The mammary gland growth--appearance of a lobulo-alveolar structure--, the secretion of colostrum and lactogenesis occur when precise endocrine equilibrium take place during gestation and lactation in the cow and the sow. The formation of alveoli requires hormonal sequences including first, ovarian and foetoplacental hormones--estrogens and progesterone--and, then, antepituitary--prolactin--and adrenal--corticoids--hormones. These sequences appear during pregnancy and lead to a near complete development of the mammary gland at parturition in the cow and the sow. Administrations of ovarian steroids which produce the same variations of levels of these hormones in plasma as during the pregnancy allow the lobulo-alveolar structure to develop in the non pregnant dried cow. The synthesis of specific products of milk--casseins and lactose--remains low throughout pregnancy and then increase sharply after calving or farrowing. Around parturition, the secretion of colostrum takes place when plasma levels of progesterone drop very fast and those of estrogens increase and are at the highest level observed during gestation. A few hours later, the plasma levels of prolactin and corticoids increase significantly. The colostrum secretion, the appearance of high affinity IgG1 receptors and the specific uptake of IgG1 in maternal serum coincide with a complicated hormonal environment in which a lower progesteronemia and a higher prolactinemia seem to play a major role. Estrogens--especially 17 beta-estradiol--are required for the apperance of new epithelial mammary cells which acquire specific binding sites for IgG1 later. After injections of 17 beta-estradiol and progesterone to non pregnant, dried cows, the IgG1 secretion takes place when the plasma levels of these steroids decrease. On the other hand, the secretion of colostrum is the same as in a normal parturition when calving is induced by dexamethasone or dexamethasone + estradiol benzoate injections. After parturition, there is a lower uptake of proteins from the serum when prolactin and corticoids induce the onset of copious mileticulum, of the Golgi apparatus, of mitochondria and of the appearance of a polarized structure which depress the possibilities of migration of proteins from the serum through the cell.

Animals↗