The effects of dietary level of tryptophan (TRP) and CP content and composition on voluntary feed intake, growth performance, and carcass characteristics in finishing pigs were studied in two experiments, with an equal number of females and castrated males. In Exp. 1, involving 120 Large White pigs from 44 to 99 kg BW with ad libitum access to feed, six treatments were compared according to a 2 x 3 factorial arrangement: 1) two levels of TRP (.09 and .13%), suboptimal and optimal for growth, respectively, 2) three types of CP supply (a 12.5% CP diet based on corn-soybean meal, and adequately balanced for essential amino acids [EAA] other than TRP; 15.7% CP diet with additional protein from corn gluten meal; 16.2% CP diet with additional nonessential amino acids [NEAA, in the form of L-glutamic acid.HCl and glycine], and the same levels of EAA as in the 12.5% CP diet. In Exp. 2, including four of the six previous factorial combinations (.09 and .13% TRP, 12.3 and 15.8% CP with additional protein), 32 pigs of 50-kg initial BW were used during 21 d, and further observations on meat quality characteristics, plasma free amino acid levels, and serotonin concentrations in the posterior hypothalamus were made. The major observed effects were interactions of different magnitude according to sex between TRP level and the amount and the composition of additional CP. At the suboptimal level of .09% TRP, the increase in protein content severely decreased daily feed intake and growth compared with the .13% level, especially in females. Conversely, the addition of NEAA at both TRP levels had little effect on daily feed intake and growth. Deficiency of TRP exerted a significant increase of pH in adductor femoris and semimembranosus muscles measured 45 min and 24 h postmortem, but only in females. Voluntary feed intake, as affected by dietary TRP and CP levels, was linearly related with concomitant changes in TRP to large neutral amino acids (TRP:LNAA) ratio both in feed and in plasma, which in turn was directly associated to hypothalamic serotonin concentration. It was concluded that an overly low concentration of serotonin in the hypothalamus, especially in females, as a result of TRP:LNAA imbalance, could be involved in the reduction of voluntary feed intake.

The expression of two human estrogen receptor-alpha (hERalpha) isoforms has been characterized within estrogen receptor-alpha-positive breast cancer cell lines such as MCF7: the full-length hERalpha66 and the N terminally deleted hERalpha46, which is devoid of activation function (AF)-1. Although hERalpha66 is known to mediate the mitogenic effects that estrogens have on MCF7 cells, the exact function of hERalpha46 in these cells remains undefined. Here we show that, during MCF7 cell growth, hERalpha46 is mainly expressed in the nucleus at relatively low levels, whereas hERalpha66 accumulates in the nucleus. When cells reach confluence, the situation reverses, with hERalpha46 accumulating within the nucleus. Although hERalpha46 expression remains rather stable during an estrogen-induced cell cycle, its overexpression in proliferating MCF7 cells provokes a cell-cycle arrest in G(0)/G(1) phases. To gain further details on the influence of hERalpha46 on cell growth, we used PC12 estrogen receptor-alpha-negative cell line, in which stable transfection of hERalpha66 but not hERalpha46 allows estrogens to behave as mitogens. We next demonstrate that, in MCF7 cells, overexpression of hERalpha46 inhibits the hERalpha66-mediated estrogenic induction of all AF-1-sensitive reporters: c-fos and cyclin D1 as well as estrogen-responsive element-driven reporters. Our data indicate that this inhibition occurs likely through functional competitions between both isoforms. In summary, hERalpha46 antagonizes the proliferative action of hERalpha66 in MCF7 cells in part by inhibiting hERalpha66 AF-1 activity.

The activity of the transactivation functions (activation function (AF)-1 and AF-2) of the estrogen receptor ␣ (ER␣) is cell-specific. This study aimed to decipher the yet unclear mechanisms involved in this differential cell sensitivity, with particular attention to the specific influence that cell differentiation may have on these processes. Hence, we comparatively evaluated the permissiveness of cells to either ER␣ AFs in two different cases: (i) a series of cell lines originating from a common tissue, but with distinct differentiation phenotypes; and (ii) cell lines that undergo differentiation processes in culture. These experiments demonstrate that the respective contribution that AF-1 and AF-2 make toward ER␣ activity varies in a cell differentiation stage-dependent manner. Specifically, whereas AF-1 is the dominant AF involved in ER␣ transcriptional activity in differentiated cells, the more a cell is de-differentiated the more this cell mediates ER␣ signaling through AF-2. For instance, AF-2 is the only active AF in cells that have achieved their epithelial-mesenchymal transition. Moreover, the stable expression of a functional ER␣ in strictly AF-2 permissive cells restores an AF-1-sensitive cell context. These results, together with data obtained in different ER␣-positive cell lines tested strongly suggest that the transcriptional activity of ER␣ relies on its AF-1 in most estrogen target cell types.

A double immunocytochemical procedure, with two different chromogens, was used to compare the respective distribution of estrogen receptor-immunoreactive cells and tyrosine hydroxylase-immunoreactive neurons on the same sections of the preoptic region of adult female rainbow trout (Oncorhynchus mykiss). Estrogen receptor-immunoreactive cells were observed in the anterior preoptic region surrounding the preoptic recess and its large lateral extensions. Tyrosine hydroxylase-immunoreactive cells were consistently detected in the ventral and ventrolateral walls of the preoptic recess, in an area that was named nucleus preopticus pars anteroventralis. Dopamine immunohistochemistry and Dil retrograde transport studies indicated that part of these catecholaminergic neurons are dopaminergic and could project to the pituitary. Double staining studies showed consistently that most estrogen receptor-positive cells located ventral to the large extensions of the preoptic recess are also tyrosine hydroxylase-positive, indicating that this region is a major target for estradiol feedback. The results are discussed in relation to the role of the nucleus preopticus pars anteroventralis in mediating the negative feedback actions of estradiol on the secretion of gonadotrophin (GTH2) secretion. A hypothesis is drawn in order to explain the synchronizing role of estradiol at the time of ovulation in rainbow trout.