Prepubertal (immature) and mature female rabbits were actively immunized against testosterone-3-oxime-bovine serum albumin over a period of 11 weeks. The antibody titre was significant in all animals by 5 weeks. The concentration of FSH in prepubertal animals decreased significantly (P< 0·001) between weeks 1 and 5, but no significant changes were observed in the concentration of LH at any time. After immunization for 8 weeks, there was a significant (P< 0·05) increase in the serum concentration of androgen and the percentage of bound testosterone also increased (P< 0·05). The serum concentration of oestradiol increased after immunization for 11 weeks, compared with values at 8 weeks (P<0·05) and oestradiol binding also rose by week 5 (P<0·01). Libido was not affected and significantly (P< 0·005) increased numbers of ovulations were noted in immunized animals. These results suggest that immunization of the female rabbit against testosterone may disrupt the normal regulation of follicular maturation.
You are looking at 51 - 60 of 345 items for
- Abstract: Chemicals* x
- Abstract: Pollutants x
- Abstract: Plastics x
- Abstract: Pesticides x
- Abstract: BPA x
- Abstract: Phthalates x
- Abstract: POPs x
- Abstract: Additives x
- Abstract: Xenoestrogens x
- Abstract: Parabens x
- Abstract: disrupting x
R. W. ARMSTRONG, J. GAULDIE and E. V. YOUNGLAI
R. E. J. DYBALL and R. J. WRIGHT
A. R. C. Institute of Animal Physiology, Babraham, Cambridge, CB2 4AT
(Received 12 April 1977)
Both electrical stimulation with steel microelectrodes and injection of iron salts into the preoptic area lead to an increased concentration of luteinizing hormone (LH) in the plasma and ovulation (Everett & Radford, 1961; Dyer & Burnet, 1976).
Initially, iron salts were thought to excite nerve cells but Fe2+ and Fe3+ ions, like most cations, when applied to nerve cells by micro-iontophoresis, inhibit firing (Dyer & Burnet, 1976). Dyer & Burnet (1976) proposed a number of alternative explanations for the electrochemical stimulation of ovulation. They suggested that ferrous or ferric ions might kill or damage some neurones and the resulting cell disruption might lead in turn to the liberation of a sufficient quantity of luteinizing hormone releasing hormone (LH-RH) into the hypophysial portal vessels to cause a surge of LH. Alternatively, ovulation might be stimulated by
SHEILA B. CARTER
It is well established that the time of ovulation in the rat is related to the environmental light/dark cycle (Everett, 1948). Rats also show a diurnal rhythm of spontaneous running, and it seemed a theoretical possibility that the effect of light on the luteinizing hormone (LH)-release mechanism might be mediated via general bodily activity. As a first step in testing this hypothesis, the relationship of ovulation time to the activity cycle was investigated under conditions of constant darkness, both activity patterns and oestrous cycles having first been disrupted by prolonged exposure to constant light.
Twelve regularly cyclic control rats were exposed to 14 h light and 10 h darkness daily, and were kept for at least 8 days in individual cages, each having an activity wheel attached. The number of revolutions/h was recorded by means of a Miniscript recorder. Daily vaginal smears were taken, and on a day of oestrus
S. E. Inkster, R. N. Clayton and S. A. Whitehead
The effects of neonatal monosodium l-glutamate (MSG) treatment on pituitary responsiveness to LH-releasing hormone (LHRH) and on pituitary LHRH receptors have been investigated in the intact adult female rat. Three- to four-month-old rats treated with MSG (4 mg/g body wt) on days 2, 4, 6, 8 and 10 after birth had significantly reduced ovarian and pituitary weights, showed an absence or disruption of ovarian cyclicity after puberty, and had significantly higher concentrations of serum prolactin despite normal levels of LH. In-vitro pituitary LH responses to LHRH were in the normal range for one group of treated animals whilst in a second group the LH responses were markedly enhanced. In contrast, the total number of pituitary LHRH receptors were significantly reduced in all MSG-treated animals showing that the increased pituitary responsiveness of MSG-treated animals is not attributable to an increase in pituitary LHRH receptors.
J. Endocr. (1985) 107, 9–13
P. SÖDERSTEN, S. HANSEN and B. SREBRO
Male rats were treated daily with oil or 100 μg of the antioestrogen, ethamoxytriphetol (MER-25), for the first 10 days of life and, when adult, lesions were made in the suprachiasmatic nuclei (SCN) of the hypothalamus or control lesions were made above the SCN and the rats were tested for sexual behaviour. Treatment with MER-25 enhanced the daily rhythmicity in both mounting and lordosis behaviour and SCN lesions disrupted these behavioural rhythms and the rhythm in the mounting behaviour of oil-treated rats. Rats treated with MER-25 and with SCN lesions showed high levels of mounting and lordosis behaviour throughout the light: darkness cycle. These results support the hypothesis that sexual differentiation by perinatal androgen stimulation uncouples the central rhythm generator from the neural substrates of sexual behaviour in rats.
J. STEWART and S. G. SPICKETT
Three parameters of the diuretic response to a water load are defined these are: diuretic lag, rate of diuresis and total output/input. A heterogeneous stock of mice was set up using the strains A/Cam, CBA/FaCam, SF/Cam and Peru. Directional selection was made from this stock for rate of diuresis, and total output/input. The initial generations of selection showed positive and significant parent-offspring regressions and hence demonstrated genetic variation in these parameters. Two positive disruptive selection experiments were set up to explore the relationship between diuretic lag at 4 and 8 weeks of age. These experiments show also that there is genetic variation in diuretic lag and that gene manifestation at 4 weeks and at 8 weeks is different.
The genetic variation affecting diuretic response to water load is discussed with respect to concepts of 'normal' physiology.
A. A. EL-BANNA and B. SACHER
A total of 1548 eggs was transferred to the oviducts of rabbits ovariectomized 45 days to 7 months earlier. The pattern of egg transport was disrupted, and the majority of eggs were in the vagina 60–72 h after transfer.
To determine the role of the ovarian hormones on egg transport, the effects of various combinations of oestrogen and progesterone were studied. None of the hormonal treatments produced the normal transport pattern and large proportions of transferred eggs were retained in the oviducts.
It is concluded that as long as progesterone is the dominant hormone, eggs move very slowly through the isthmus, and that a surge of oestrogen is required to modify the action of progesterone and to speed the movement of eggs to the uterus.
NANCY C. SMITH and M. G. BRUSH
The high levels of progesterone circulating in the foeto—placental unit during human pregnancy (Zander, 1965) suggest that the hormone may have some major function there other than as a precursor for steroid biosynthesis. Therefore the intracellular distribution of progesterone in tissues of the human foeto—placental unit was studied to determine if it is preferentially associated with a particular subcellular fraction.
Placental tissue (50 g) was cut from various sites on placentae obtained within 1 h of delivery. Homogenization and cell disruption in 0·25 m-sucrose was carried out with an emulsifier-mixer (Silverson) and a Potter—Elvehjem homogenizer with a loosely fitting Teflon pestle. Differential centrifugation was carried out at 800 g for 10 min, at 10000 g for 10 min and at 105000 g for 60 min. All particulate fractions were washed once. Using methylene blue staining, the crude nuclear fraction (800 g) was estimated to be 10–30% contaminated with unbroken
S. HANSEN, P. SÖDERSTEN, P. ENEROTH, B. SREBRO and K. HOLE
Ovariectomized rats exposed to constant plasma levels of oestradiol showed a daily rhythm in lordosis behaviour, with high levels of lordosis occurring during the dark portion of the daily light: darkness cycle and low levels during the light period. Similarly treated male rats failed to show a rhythm in lordosis behaviour. However, neonatal castration permitted the expression of the lordosis rhythm in male rats; conversely, an injection of 1·25 mg testosterone propionate on day 4 of life abolished the rhythm in female rats. Pinealectomy, adrenalectomy or depletion of brain 5-hydroxytryptamine levels did not affect the periodicity in lordosis behaviour but lesions in the suprachiasmatic nuclei of the hypothalamus disrupted the rhythm. It is suggested that the daily rhythm in lordosis behaviour participates in the control of the termination of heat in the female rat and that the perinatal hormone milieu may exert permanent effects on periodic functions.
E Jiménez, G P Vinson and M Montiel
Isoelectric focusing analysis showed a single angiotensin II (All)-receptor complex migrating to pI 6·8 in nuclear preparations, while in plasma membranes a charge heterogeneity of the All receptor subtype AT1 was observed. 125I-Labelled All binding sites were found in intact nuclei and were not detected in nuclear extracts. Neither disruption of cytoskeletal elements by colchicine nor prevention of endosome acidification by chloroquine had any effect on nuclear accumulation of AIL Nevertheless, the monovalent ionophore monensin inhibited nuclear accumulation of 125I-Labelled All. Our findings are consistent with the hypothesis that processing through the Golgi apparatus could be involved in the nuclear accumulation of AIL
Journal of Endocrinology (1994) 143, 449–453