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The core oscillatory mechanism consisting of gene transcription and translation is a unique feature and the astonishing discovery in circadian biology is that the rhythm of gene transcription reflects the behavioral rhythm almost perfectly. This means that the clock gene oscillation generated by the core loop in each suprachiasmatic nucleus neuron is coupled and amplified, and harmonized strongly so that oscillating activities are spread into the whole brain and to all those peripheral organs which contain peripheral clocks. Additionally, circadian changes are induced in behavior and hormone secretion. Investigations of biological clocks open the fascinating perspective to analyze the integrational mechanism of 'time', providing a bridge between single genes and the living organism as a whole.
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ABSTRACT
Plasminogen activator (PA) activity in the rat uterus was measured at fixed intervals post partum in order to determine whether this serine protease increases during the acute remodelling of tissue which occurs in the involuting uterus. Plasminogen activator activity was measured by an indirect method based on the hydrolysis of the chromogenic substrate S-2251 by PA-generated plasmin. At the time of parturition the control level of PA activity was 0·033 ± 0·018 (s.d.) μmol/4 mg uterine wet weight per 30 min. This activity increased fourfold to a peak of 0·131 ±0·036 at 3 days post partum, and then it declined steadily towards the control level during the next 7 days. Concomitantly, uterine weight decreased to 25% of the control weight by 3 days post partum, and it continued to decrease until day 15. In the 30 days post partum during which PA activity was monitored there was no significant change in plasmin inhibitors in the uterine extracts. The results suggest a correlation between PA activity and the process of tissue remodelling which occurs during involution of the rat uterus. This increase in PA might serve to activate a latent collagenase since the measured peak in PA activity happens to coincide with a reported increase in collagenolytic activity in the involuting rat uterus.
J. Endocr. (1985) 104, 295–298
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ABSTRACT
A rat oestrogen receptor-β-galactosidase fusion protein was expressed using a pEX2/rat oestrogen receptor cDNA construct. Scatchard analysis of [3H]oestradiol-17β binding to the cell lysate revealed that the fusion protein had functional binding sites specific for oestradiol with a dissociation constant of 1·49 nmol/l. The relative molecular weight (M r) of the fusion protein was determined as 180 000 by immunoblot analysis of the cell lysate employing a monoclonal antibody to the human oestrogen receptor.
The protein was isolated by means of SDS-PAGE and subsequent electroblotting. By immunization with the purified materials on nitrocellulose membrane, a polyclonal antibody to the rat oestrogen receptor was raised in a rabbit. Binding of [3H]oestradiol to the oestrogen receptor from the rat uterus was inhibited by the antibody in a dose-dependent manner. The antibody was also able to recognize the oestrogen receptor occupied by [3H]oestradiol. Thus, the antibody could react with both forms of the receptor molecule, either occupied or unoccupied by the hormone. In immunoblot analysis of the cytosol fraction of the rat uterus, a single band of M r 67 000, the size of the oestrogen receptor, was detected by the antibody. Moreover, when the antibody was applied to immunohistochemical examination of paraffin-embedded pituitary and brain sections of the rat, immunostaining was observed in cells of the anterior pituitary and in neurones in specific regions of the brain. The immunoreactivity was restricted exclusively to cell nuclei in both tissues.
These results demonstrate that the polyclonal antibody obtained in the present study was specific to the oestrogen receptor, and that it would be a powerful tool to detect and analyse the receptors in various target tissues for oestrogen.
Journal of Endocrinology (1992) 135, 333–341
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Abstract
Increases in blood volume are observed during normal gestation and these are reversed shortly after delivery. Although both atrial (A-type) natriuretic peptide (ANP) and brain (B-type) natriuretic peptide (BNP) have been described, the role of these peptides in pregnancy and the postpartum period are unclear. This study was designed to examine the effects of pregnancy, labour and delivery on plasma levels of ANP and BNP. Plasma levels of ANP and BNP were determined during normal pregnancy, 30 min after separation of the placenta (immediately postpartum) and between 5 and 72 h postpartum (late postpartum; puerperium). Since the assay sensitivity was 20 pg/ml plasma (for both ANP and BNP), values less than this were assigned a value of 20 pg/ml to calculate means. Plasma levels of ANP and BNP were significantly higher at term pregnancy than during the first trimester (ANP increased from 20 ± 0·2 to 57 ± 10 pg/ml (s.e.m.), P<0·001; BNP increased from 25 ± 2 to 49 ± 9 pg/ml, P<0·01). The plasma level of ANP then rose to 157 ± 38 pg/ml 30 min after separation of the placenta, being significantly (P<0·01) higher than that seen at term pregnancy. It declined significantly (P<0·001) to 32 ± 3 pg/ml in the late postpartum period. In contrast, the plasma level of BNP 30 min after separation of the placenta was 80 ± 25 pg/ml, and increased to 116 ± 17 pg/ml in the late postpartum period, significantly (P<0·01) higher than the level at term pregnancy. We conclude that ANP and BNP may play a role in controlling blood volume during normal human pregnancy at term and during transition to the postpartum period. Changes in ANP immediately postpartum and BNP in the later postpartum period appear to be differentially regulated.
Journal of Endocrinology (1994) 140, 393–397
