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The present study was carried out to investigate the artifertility potential of 2-[piperdinoethoxyphenyl]-3-[4-methoxyphenyl]-2H benzopyran (K-7) in rats. A single oral administration of 250 μg K-7 kg⁻¹ body mass after coitus prevented pregnancy in rats. The minimum effective dose in rats given K-7 orally for 1–4 days after coitus was 100 μg kg⁻¹ body mass. K-7 had weak oestrogenicity in ovariectomized immature rats but had no androgenic or anti-gonadotrophic activity. Studies in vivo showed that K-7 was a potent anti-oestrogenic compound and that at 100 μg kg⁻¹ it could mitigate the effect of 1.0 μg oestradiol. On the basis of the above results, K-7 appeared to exert its antifertility action(s) by its weak oestrogenic and its strong anti-oestrogenic activity. The anti-oestrogenic activity of K-7 was substantiated further by performing studies on the competition of K-7 for binding of [³H]oestradiol to rat uterine oestrogen receptors. A high affinity for binding to oestrogen receptors was displayed by K-7, with a relative binding affinity of 71%. These findings show that K-7 is an effective anti-oestrogenic compound and is a potent antifertility agent.

Summary. Milk samples were collected on Days 20, 24, 28 and 40 after insemination. The percentage of fat and the progesterone concentration in the milk were correlated (P < 0·01). Progesterone concentration in the milk of pregnant buffaloes (24·83 ± 3·85 ng/ml) was significantly higher than that in non-pregnant animals (2·89 ± 1·25 ng/ml) on Day 20 and the difference between the two increased with time after insemination. The detection of non-pregnant animals was 100% successful at all times but the diagnosis was correct for 66, 68, 81 and 83% of animals tested on Days 20, 24, 28 and 40 respectively and predicted as pregnant.

Summary. Administration of vasodilator, sodium nitrite (20 mg/kg body weight), 30 min before α-chlorohydrin treatment (90 mg/kg body weight) prevented the chlorohydrin-induced lesion in rat testis–epididymis complex. However, administration of vasodilator 90 min after α-chlorohydrin treatment did not prevent the chlorohydrin-induced lesion in the testis–epididymis complex. These observations suggest that the testicular vasculature is involved in drug action.

Summary.

The active male gerbils were administered with a single sub-lethal dose of 0·56 mg of cadmium chloride per 100 g of body weight in order to study the histological and enzyme histochemical changes after 12 and 24 hr. The testis autopsied after 12 hr showed a red colour due to hyperaemia. The spermatocytes, spermatids and the spermatozoa were displaced from their normal positions. Twenty-four hours after administration, the testis showed an intense red colour due to haemorrhage. The regular succession of the cells in the seminiferous epithelium was upset and the nuclei became pycnotic or showed fragmentation. The interstitium was oedematous and haemorrhagic and the Leydig cells showed necrosis. The histochemical results revealed inhibition of adenosine triphosphatase and 5-nucleotidase activities. In the majority of the tubules, succinic dehydrogenase activity was inhibited in the spermatogonia but the damaged cells showed an increased activity. An increase was also observed in the distended interstitium for sudanophilic lipids.

Department of Animal Sciences, University of Kentucky, Lexington, Kentucky 40506, U.S.A.

(Received 23rd April 1974)

In oviparous and ovoviviparous animals, the oestrous period is accompanied by striking changes in composition of blood (Urist, Schjeide & McLean, 1958). Limited information is available, however, on changes in the composition of the blood of mammals during the reproductive cycle. The research reported in this paper concerns changes in blood plasma biochemistry during the oestrous and dioestrous phases of the cycle in the ewe.

Six mature ewes which had shown two consecutive oestrous cycles of normalduration were bled from the jugular vein on the day of oestrus. The same six animals were bled 6 days later during dioestrus. For both phases, ewes were bled at 09.00 hours before daily feeding. The blood samples were spun at 1600 g for 10 min and the serum was frozen at -2°C until it was analysed. Blood serum

Summary.

A cadmium-binding protein (Cd-BP) has been isolated and characterized using ¹⁰⁹Cd to elucidate the nature of the binding of cadmium to rat testis. The protein labelled with ¹⁰⁹Cd was isolated using Sephadex gel filtration with G-75 and G-25. The cadmium bound selectively in vivo to a low molecular weight protein and ¹⁰⁹Cd remained bound to the Cd-BP at pH 7·0, but dissociated from it at pH 2·0. The ultraviolet absorption spectra were characteristically different at the two pH values. The molecular weight of the protein was 15,000 as determined by Sephadex G-75 gel filtration. Disc-gel electrophoresis showed one major and two minor bands. All these observations suggest that rat testis Cd-BP, though similar in some respects, differs from Cd-BP of liver and kidney in absorption spectra, molecular weight and disc-gel electrophoresis.

Summary.

Rabbit antiserum to sheep lh inhibited uterine growth in adult rats following uterine trauma on Day 4 of pseudopregnancy. The weights of the horns subjected to trauma were similar to those obtained in rats ovariectomized at the time of trauma and given only progesterone, and in rats with the adenohypophysis transplanted beneath the kidney capsule on the day of ovulation. Antiserum to lh given to rats with an autotransplanted pituitary did not alter decidual growth. Oestrone restored maximal uterine growth in rats receiving lh antiserum and in rats with an autotransplanted pituitary. Simultaneous injections of fsh and lh resulted in maximal decidual cell response in pituitary autotransplanted rats, while either, given alone, had only slight stimulatory effects. It is suggested that lh antiserum inhibits the oestrogen production necessary for maximal uterine growth. Luteinizing hormone does not appear to be necessary, unless in minute quantity, for production of progesterone in amounts large enough to support maximal uterine growth after trauma.

The effects of time postpartum and suckling status on the oestradiol-induced LH surge in ewes and some of the possible mechanisms involved were investigated. Lambs were removed from nonsuckled ewes at parturition (day 0) and the ewes hand-milked 12 and 48 h later to prevent discomfort. Nonsuckled ewes on day 1, 7, 14 or 28, and suckled ewes on day 7 or 28 postpartum were injected i.m. with 50 μg oestradiol benzoate (hour 0). A further eight suckled ewes were given oestradiol on day 1 (as above), and four were also given naloxone (1 mg kg⁻¹ h⁻¹) from 10 until 14 h after administration of oestradiol benzoate. There was no LH surge in response to oestradiol on day 1. In nonsuckled ewes the onset of the LH surge was significantly (P < 0.05) delayed when oestradiol was administered on day 7 (17.4 ± 1.5 h), compared with when it was injected on days 14 and 28 postpartum (14.4 ± 1.7 and 14.0 ± 1.4 h). The LH surge was also delayed (P < 0.05) when oestradiol was administered on day 7 (18.0 ± 2.8 h) in suckled ewes. There was no difference in the duration or amplitude of the LH surge with time postpartum in nonsuckled ewes. Suckling significantly (P<0.05) reduced the amplitude of the LH surge on both day 7 (21.0 ± 2.4 versus 26.4 ± 2.3 ng ml⁻¹) and day 28 (23.6 ± 3.2 versus 28.8 ± 2.9 ng ml⁻¹), but had no effect on the onset or duration of the surge. There was no difference in the timing or the amplitude of the oestradiol peak following the oestradiol benzoate challenge with time postpartum. Naloxone had no effect on the mean LH concentration (control, 2.3 ± 1.6; naloxone-treated, 2.2 ± 1.5 ng ml⁻¹) or on the pattern of LH secretion on day 1. In conclusion, time postpartum influenced the timing of the onset, while suckling reduced the amplitude, of the oestradiol-induced LH surge. The lack of an oestradiol-induced LH surge on day 1 postpartum in the ewe is due to a nonopioidergic mechanism.

Heifers were studied to determine whether computer-assisted quantitative echotexture analysis of ultrasound images reflect functional and endocrine characteristics of dominant and subordinate follicles at specific stages of development. Heifers were examined using transrectal ultrasonography each day until ovariectomy on day 3 (n = 8) and day 6 (n = 9) of wave 1, day 1 of wave 2 (n = 7), or after onset of pro-oestrus ≥ 17 days after ovulation (n = 8) to obtain growing, early-static, late-static and regressing dominant follicles of wave 1, subordinate follicles, preselection follicles and preovulatory dominant follicles. Ultrasound images of the follicles were obtained in vitro and analysed using custom-developed computer algorithms. Mean pixel (picture element) values (grey-scale: black = 0, white = 255) for the follicle wall and stroma increased (P < 0.05) progressively from the growing to the regressing phases of the dominant follicle of wave 1. The antrum and wall of subordinate follicles had higher (P < 0.05) mean pixel values than that of the corresponding dominant follicles. Pixel heterogeneity (a measure of variation of grey-scale values of pixels) of images of the follicle antrum and wall increased (P < 0.05) progressively during the early-static to regressing phases. A progressive increase (P < 0.05) in the slope of the regression line of pixel values for the follicle wall was detected from the growing to the regressing phases of the dominant follicle of wave 1. The regression line of the wall of the preovulatory dominant follicle had the lowest (P < 0.05) slope. Oestradiol concentration in the follicular fluid decreased (P < 0.05) from the growing to the late-static phase, while a marked decrease (P < 0.05) in the androstenedione concentration was recorded between the growing and the early-static phases of the dominant follicle. Progesterone content did not increase until follicles were in the final stages of regression. Pixel heterogeneity of the antrum and wall, and the slope of the follicle wall regression line were negatively correlated (P < 0.001) with oestradiol and the oestradiol:progesterone ratio in follicular fluid. The results of this study support the hypothesis that echotexture characteristics of ultrasound images of the follicle antrum and wall are correlated with the functional and endocrine status of a follicle.

Nulliparous heifers (n = 58) were studied to determine whether computer-assisted quantitative echotexture analysis of ultrasound images reflects the functional and histomorphological characteristics of the corpus luteum. The ovaries of heifers were examined daily by transrectal ultrasonography from day −2 (day 0 = ovulation) until the day of ovariectomy during metoestrus (day 3; n = 8), early dioestrus (day 6; n = 9), mid-dioestrus (mean, day 10; n = 7), or pro-oestrus (mean, day 18; n = 8; Expt 1). High resolution ultrasound images of corpora lutea were obtained in vitro, and were digitized and analysed using custom-developed computer algorithms optimized for ultrasonography. Cryostat sections of corpora lutea were examined for lipid distribution, and corpora lutea were homogenized to determine the content of progesterone, total protein, cholesterol and triglyceride. In Expt 2, heifers (n = 26) were ovariectomized as in Expt 1, and ovaries were prepared for histomorphometric evaluation. Pixel values (brightness of picture elements) of ultrasound images of corpora lutea were characterized as high during metoestrus, low during early and mid-dioestrus, and increasing again during pro-oestrus (P < 0.05). Changes (P < 0.001) in volume density of luteal cells were characterized as increasing from metoestrus (40.7 ± 0.4%) to mid-dioestrus (55.8 ± 2.8%) and decreasing again at pro-oestrus (41.5 ± 0.9%). The proportion of blood vascular components decreased (P < 0.001) progressively from 31.0 ± 1.0% in metoestrus to 15.6 ± 1.1% in pro-oestrus. Pixel values of ultrasound images of corpora lutea were correlated with luteal (r = −0.72, P < 0.05) and plasma (r = −0.71, P < 0.03) progesterone concentration, and to the volume densities of luteal cells (r = −0.75, P < 0.02) and connective tissue (r = 0.69, P < 0.03). Estimates of triglyceride, protein and cholesterol content of corpora lutea were not correlated with pixel values of ultrasound images. Protein and cholesterol content did not change while triglyceride concentration increased during pro-oestrus (P < 0.05). Results support the hypothesis that ultrasound images reflect luteal and plasma progesterone content, and histomorphological characteristics of the corpus luteum.