Regulation of laminin gene expression in the expansion of mouse blastocysts

This study aims to elucidate gene expression of laminin and its role in expansion of the blastocyst during mouse early embryo-genesis. The gene expression of laminin, in particular the B1 subunit and the synthesis of laminin polypeptides, was examined during the expansion of blastocyst by a RNA-blot hybridization with 32P-labeled laminin B1 cDNA and immunoprecipitation followed by a SDS-PAGE, respectively. Laminin B1 transcript was actively expressed in the blastocyst stage of embryos. The gene expression of laminin B1 and the synthesis of laminin protein were also increased when blastocyst was expanded. Treatments of cAMP analogue, isobutylmethylxanthine, forskolin, and cholera toxin, which are known to stimulate the blastocyst expansion, increased laminin B1 transcript levels and synthesis of laminin polypeptides. Treatment with retinoic acid, a known regulator of laminin gene expression, not only increased the gene expression of laminin but stimulated the blastocoel expansion without a significant increase in intracellular cAMP levels. These results indicate that laminin gene expression may play an important role in the process of blastocyst expansion in the mouse preimplantation embryos.

Activation of intracellular pathways with forskolin and phorbol ester increases LHRH mRNA level in the rat hypothalamus superfused in vitro

Two intracellular signal transduction mechanisms such as cAMP-protein kinase a and phosphatidylinositol (PI) turnover-protein kinase c are known to be dually involved in the regulation of luteinizing hormone-releasing hormone (LHRH) release. However, it is not yet evident that the activation of two intracellular pathways affects the LHRH gene expression. The present study aims, therefore, to determine whether the activation of two intracellular pathways affects changes in LHRH mRNA. To this end, we took advantage of an in vitro superfusion system, where rat hypothalamic tissues were superfused with media containing forskolin (FKN) and/or phorbol-12-myristate-13-acetate (PMA). Superfusates were collected at 10-min intervals and LHRH release was determined by radioimmunoassay. After a 2-h superfusion period, the post-superfusion hypothalami were recovered and poly (A) RNA fractions were isolated. Alterations in LHRH mRNA in response to FKN and/or PMA were determined by an RNA-blot hybridization assay using a 32P-end-labeled LHRH oligonucleotide (29-mer) probe. In vitro perfusion of hypothalamic fragments with PMA and/or FKN stimulated LHRH release as well as LHRH mRNA. The combined infusion of FKN and PMA did not produce an additive effect on the LHRH mRNA levels, but it was effective in synergistically increasing LHRH secretion in vitro. These data clearly demonstrate that the biosynthetic machinery of LHRH is influenced by activation of two intracellular pathways, both cAMP-protein kinase a and phosphatidyl-inositol turnover-protein kinase c, indicating the transsynaptic regulation of hypothalamic LHRH gene expression.

Progesterone increases messenger ribonucleic acid (mRNA) encoding luteinizing hormone releasing hormone (LHRH) level in the hypothalamus of ovariectomized estradiol-primed prepubertal rats

In order to investigate the mechanism underlying ovarian steroid action on gene expression of hypothalamic luteinizing hormone releasing hormone (LHRH), changes in LHRH mRNA level were determined by RNA-blot hybridization assay. Twenty-eight-day-old female rats were ovariectomized (OVX) and implanted with Silastic capsule containing either 17 beta-estradiol (E) or vehicle (V). Two days later (day 30), OVX + E-primed rats were given s.c. progesterone (P, 1 mg) 6 h prior to decapitation. Four experimental groups were studied: (1) intact, (2) OVX + V, (3) OVX + E, and (4) OVX + E + P-treated rats. Poly(A) RNA fractions from hypothalami (40-50/group) were isolated, blotted onto nitrocellulose paper and hybridized with 32P-end-labeled LHRH oligonucleotides (29 mer) which are complementary to rat LHRH mRNA. The hypothalamic LHRH mRNA signal markedly attenuated 2 days following ovariectomy. E replacement to OVX rats slightly increased LHRH mRNA level, which is lower than that of the intact group. However, a single injection of P to OVX + E-treated rats notably augmented the LHRH mRNA level over that observed in the intact group. In addition, LHRH content and release in vitro were examined to correlate with changes in LHRH gene expression. Ovariectomy and the replacement of E and/or P resulted in a similar fashion of changes in LHRH release and content as compared to alteration of LHRH mRNA level. This study clearly demonstrates that P increases LHRH mRNA level in the hypothalamus of OVX + E-primed immature rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple forms of alkaline phosphatase in mouse preimplantation embryos

Mouse embryos were extracted with 0.5% Triton X-100 and subjected to cellulose acetate electrophoresis. In fertilized eggs, two forms of alkaline phosphatase (ALP), a slow-moving form and a fast-moving form, were observed. As cleavage proceeded, the fast-moving form disappeared, and the slow-moving form, the mobility of which was similar to that of the slow-moving form of the kidney, became gradually dominant up to the blastocyst stage (named 'embryonic' form). With blastulation, another fast-moving form showing a similar mobility to the lung ALP began to appear in blastocysts and showed a transient dominance in hatched blastocysts. After implantation, both the embryonic form and the fast-moving form gradually faded, and were eventually replaced by the new form, which may be named 'fetal form' in Day 7 embryos. These results clearly demonstrated that ALP activity does exist in embryos at all stages of preimplantation development. Moreover, the changes in multiple forms of ALP correlated with embryonic development may suggest that these multiple forms may have differential roles in the process of early development.

Testosterone stimulates LH-RH-like mRNA level in the rat hypothalamus

To elucidate whether testosterone (T) replacement to castrated male rats may promote luteinizing hormone-releasing hormone (LH-RH) biosynthesis in the hypothalamus, an RNA-blot hybridization assay was employed. Poly(A) mRNA fractions from hypothalami (40-50) of intact, castrated plus vehicle, and castrated plus T group were isolated, blotted on nitrocellulose paper and hybridized with 32P-end labelled LH-RH oligonucleotides (29 mer) which is complementary to the rat LH-RH mRNA. LH-RH-like mRNA level markedly attenuated 2 weeks following castration and T replacement significantly increased LH-RH-like mRNA level, comparable to about 80% of that observed in intact male rats. In addition, LH-RH contents and release from hypothalami were studied, to examine the correlation with LH-RH gene expression and secretory activity of LH-RH. Castration significantly reduced LH-RH contents and LH-RH release in vitro. T replacement restored LH-RH contents and release comparable to those shown in the intact group. This study demonstrates for the first time that T replacement increases LH-RH-like mRNA level in the hypothalami of castrated rats suggesting that T may act at the pretranslational level. This change in LH-RH gene expression is parallel with alteration of LH-RH content and release.

Effect of chronic administration of progesterone on the naloxone-induced LHRH release from hypothalami of ovariectomized, estradiol-primed prepubertal rats

To test the hypothesis that progesterone (P) administered in a high dose and for a long duration would influence in vitro LHRH release by naloxone, silastic capsules containing P (50 mg/ml) or vehicle were implanted sc in ovariectomized, estradiol-primed (OVX+E) prepubertal rats. Following a 48 hr exposure to P, rats were sacrificed and mediobasal hypothalamic (MBH) fragments were obtained. In addition, in other OVX+E primed rats, a single injection of P (1 mg) was given sc 6 hr prior to decapitation. Naloxone or control medium were infused into superfusion chambers containing MBH fragments derived from these animals for 2 hr following a 1 hr control period. Infusion of naloxone (1 x 10(-4) M) markedly stimulated in vitro LHRH release from MBH from rats pre-exposed to P for 48 hr, whereas it was unable to do so in other groups examined. These data clearly indicate that the ability of naloxone (1 x 10(-4) M) to stimulate LHRH release is dependent on the duration of P administration.

A study of the renin-angiotensin system and the blood volume in the nephrotic syndrome

The plasma renin activity (PRA), plasma aldosterone level, and blood volume were studied in 12 patients with idiopathic nephrotic syndrome. As a whole, the patients with the nephrotic syndrome showed significant elevations of the PRA and plasma aldosterone but not in blood volume compared to the normal controls. Six patients who had a larger blood volume than the control group had decreased PRA, while the other 6 patients who had a smaller blood volume than the control group had an increased PRA. Also noted was that there was no histopathological difference of kidney diseases between the patients with increased blood volume and decreased blood volume. Though there was no correlation between serum albumin, PRA, and plasma aldosterone levels, there was a tendency of increased blood volume as serum albumin decreased.

The effects of prostaglandin E-1 and F-2 alpha on maturation of mouse oocytes in vitro

The direct effects of prostaglandin E-1 (PGE-1) and F-2 alpha (PGF-2alpha) on isolated mouse oocytes were examined in a microtube culture method. In oocytes exposed to PGE-1, meiotic resumption was suppressed at the anaphase I stage, presenting an irregular arrangement of the chromosomes along with the spindle fibres which were characterized by nondisjunction of the tetrads. PGF-2alpha was less potent in suppressing oocyte maturation than PGE-1. The critical time of the action of PGE-1 was between 7-5 and 12 hr of incubation.