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Summary.
The experiments reported here demonstrate for the first time that the isolated testicular capsule of the rat is capable of undergoing marked contraction following exposure to acetylcholine, carbachol, pilocarpine, norepinephrine, epinephrine, histamine and tetramethylammonium. Isoproterenol produces a relaxation of the isolated capsule but barium ions have essentially no effect at physiological doses.
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Summary.
The experiments reported here demonstrate that the isolated testicular capsules of both the adult rat and rabbit contain smooth muscle and are capable of undergoing marked contraction following exposure to a number of autonomic agents. In addition, the isolated testicular capsule of the rabbit displayed rhythmic spontaneous contractions. In contrast, no spontaneous activity and only negligible contractions to a few autonomic agents were observed from the isolated mass of testicular parenchymal tissue. It would therefore appear that the testicular capsule plays the major rôle in providing a propelling force for transporting large numbers of non-motile spermatozoa out of the testis and into the epididymis for acquisition of motility.
Department of Obstetrics, Division of Biological Sciences, Department of Statistics, Gynecology and Women's Health, NW509 Health Sciences Center
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Department of Obstetrics, Division of Biological Sciences, Department of Statistics, Gynecology and Women's Health, NW509 Health Sciences Center
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Search for other papers by J Wade Davis in
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Department of Obstetrics, Division of Biological Sciences, Department of Statistics, Gynecology and Women's Health, NW509 Health Sciences Center
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In a previous study, 50% calorie restriction in mice from d1.5 to 11.5 of pregnancy resulted in reduced placental weights and areas, relativel sparing of labyrinth zone area compared to junctional zone area, and dramatic changes in global gene expression profiles. However, little lasting effect was seen on adult offspring of these pregnancies, with a slight reduction in adiposity in males and some changes in liver gene expression in both sexes. The goals of the present study were to determine whether the placental changes induced by caloric restriction in early pregnancy had permanent, irreversible effects on the placenta, and whether the changes in liver gene expression in adult offspring were present before birth. There were no differences in placental weights or areas, or the areas of individual placental zones near term in mice that had previously been food restricted. Global gene expression profiles at d18.5 were indistinguishable in placentas from control and previously food-restricted mothers. In fetuses from restricted dams at d18.5, liver expression of Gck, a key regulator of glycogen synthesis, was reduced, whereas its expression was increased in livers from adult offspring of restricted dams. Ppara expression was also reduced in fetal livers from restricted dams at d18.5, but not in adult offspring livers. We conclude that alterations in the placenta caused by nutrient restriction in early pregnancy are reversible, and that alterations in gene expression in livers of adult offspring are not a result of changes initiated during pregnancy and maintained through adulthood.
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Summary. The 330 Merino ewes used in the study were placed with rams at a synchronized oestrus and, on Days 2–14 after mating, the ewes were placed in a feed lot and fed daily a low, medium or high ration (25%, 100% or 200% of maintenance respectively). Progesterone supplement was given to some ewes on Days 8–14 after mating by using a device containing 340 mg progesterone. Blood samples were taken from all ewes on Day 12 for measurement of plasma progesterone concentrations. On Day 14 after mating all ewes were returned to pasture. Pregnancy rate was determined by returns to oestrus and was later confirmed using ultrasound.
There was a decline in the peripheral progesterone concentrations with increasing ration. The pregnancy rate in ewes fed a high ration was significantly reduced when compared with those of ewes fed a medium or low ration (48% vs 68 and 67% respectively; P < 0·05). In ewes fed the high ration exogenous progesterone increased the pregnancy rate from 48 to 76% (P < 0·01). Progesterone treatment did not influence pregnancy rates in ewes fed medium or low rations. The number of fetuses per ewe pregnant was not influenced by level of nutrition or progesterone treatment.
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Summary. Eighteen sows (6 primiparous and 12 multiparous) were allotted randomly within parity to two lactational treatments: litter separation (LS; 6 h/day) plus boar exposure (BE; 1 h/day; N = 14) beginning 8 days before weaning (4 weeks) and no LS + no BE (controls; N = 4). Blood was collected from all sows via indwelling venous catheters at 20-min intervals for 5 h on Days −1, 0, 1, 2 and 3 from start of treatment. Control sows and those exposed to LS + BE not exhibiting oestrus during lactation were resampled on Days −1, 0, 1 and 2 from weaning. All 10 multiparous sows receiving LS + BE exhibited oestrus during lactation, whereas none of the 4 primiparous sows exposed to LS + BE or the 2 control multiparous and 2 control primiparous sows exhibited lactational oestrus. Overall concentrations of LH in serum were higher (P < 0·05) in sows receiving LS + BE than in control sows during lactation, whereas overall FSH was higher (P < 0·05) in primiparous than multiparous sows. Number and amplitude of pulses of LH were greater (P < 0·05) for treated primiparous than multiparous sows during lactation. Oestradiol-17β increased (P < 0·05) in sows during LS + BE and was higher (P < 0·01) in multiparous sows of this group than control multiparous or treated primiparous sows. Preweaning concentrations of cortisol and progesterone in serum were higher (P < 0·05) in treated than control sows for multiparous and primiparous animals.
In sows resampled at weaning, the number of pulses of LH was greater (P < 0·05) in treated primiparous than in control sows. Postweaning concentrations of FSH in serum were unaffected by preweaning treatments. It was concluded that (1) litter separation and boar exposure increased basal and pulsatile secretion of LH in multiparous and primiparous sows; (2) lack of ovarian follicular development and oestradiol secretion may preclude expression of oestrus in primiparous sows during lactation, despite elevated concentrations of FSH and LH in serum; and (3) if elevated concentrations of cortisol and progesterone inhibit the onset of oestrous cycles, in response to litter separation and boar exposure during lactation, the effect is limited to primiparous sows.
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Prostaglandin F2α (PGF2α)-induced release of ovarian oxytocin was investigated to determine whether the effect in vivo was local. [3H]PGF2α infused downstream into a single ovarian lymphatic was transferred into the adjacent ovarian vasculature (estimated transfer 1.1 and 1.7%, two experiments). When unlabelled PGF2α was infused in a similar manner (76 pmol min−1), there was a prompt eightfold increase in ovarian oxytocin release from the adjacent ovary containing a corpus luteum, but no effect on the opposite corpus luteum, showing that the effect was local. Instillation of 2% lignocaine into the ovarian vascular pedicle did not affect PGF2α-induced oxytocin release, supporting the idea that neural mechanisms are not involved. Repeated doses of PGF2α given close-arterially produced a successive reduction in oxytocin release. This effect was prevented by a prior infusion of insulin-like growth factor-I (IGF-I), which itself gave a small, but significant, increase in oxytocin release. The results show that PGF2α in ovarian lymphatics acts locally and directly to stimulate ovarian oxytocin secretion, that repeated exposure of the corpus luteum to pulses of PGF2α can result in tachyphylaxis, and that this latter effect can be ameliorated by IGF-I infused in vivo.
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The effect of space flight in a National Aeronautics and Space Administration (NASA) shuttle was studied in pregnant rats. Rats were launched on day 9 of gestation and recovered on day 20 of gestation. On day 20 of gestation, rats were unilaterally hysterectomized and subsequently allowed to go to term and deliver vaginally. There was no effect of space flight on pituitary and ovary mass postpartum. In addition, space flight did not alter healthy and atretic ovarian antral follicle populations, fetal wastage in utero, plasma concentrations of progesterone and luteinizing hormone (LH) or pituitary content of follicle stimulating hormone (FSH). Space flight significantly increased plasma concentrations of FSH and decreased pituitary content of LH at the postpartum sampling time. Collectively, these data show that space flight, initiated during the postimplantation period of pregnancy, and concluded before parturition, is compatible with maintenance of pregnancy and has minimal effects on postpartum hypophyseal parameters; however, none of the ovarian parameters examined was altered by space flight.
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Summary. The effect of the presence of a preimplantation embryo on protein concentration, rate of protein synthesis, β-glucuronidase and acid phosphatase activities, steroid metabolism and prostaglandin F production in caruncular and intercaruncular tissue have been studied for sheep at Day 15 of pregnancy. The rate of protein synthesis in both tissues was greater in pregnant than in non-pregnant animals, although the difference was only significant in caruncular endometrium. The effect in caruncular tissue was mimicked in ovariectomized animals treated with oestradiol. Localized changes in the caruncular tissue were observed in respect of PGF with an increased tissue concentration, an enhanced basal release when the tissue was incubated in the presence of indomethacin, and a decreased net production. Maximum production of PGF in the 2 tissues was unaffected by the presence of an embryo but it was enhanced by oestradiol or progesterone treatment in intercaruncular tissue of ovariectomized ewes. β-Glucuronidase and acid phosphatase activities and steroid metabolism were unaffected by pregnancy. However, in ovariectomized animals oestradiol treatment stimulated β-glucuronidase activity in endometrium and myometrium. Progesterone treatment stimulated acid phosphatase activity in the intercaruncular endometrium.
The results show that amongst several endometrial constituents investigated relatively few changes were detected by Day 15 post coitum, one day before definitive attachment. Those changes that did occur were associated with the dynamics of PGF production and the rate of protein synthesis, and were consistent with the production of a PGF binding component in caruncular endometrium which may be concerned with the protection of luteal function by redirection of uterine PGF production.
Canonical variate analysis revealed that changes on Day 15 of pregnancy were mimicked most closely in caruncular tissue by treatment of ovariectomized ewes with oestradiol and progesterone, and in intercaruncular tissue by oestradiol treatment only.