scholarly journals Variations in the Response of Pituitary Lactotrophs to Oxytocin during the Rat Estrous Cycle

Endocrinology ◽  
2010 ◽  
Vol 151 (4) ◽  
pp. 1806-1813 ◽  
Author(s):  
Joël Tabak ◽  
Arturo E. Gonzalez-Iglesias ◽  
Natalia Toporikova ◽  
Richard Bertram ◽  
Marc E. Freeman
Keyword(s):  
Estrous Cycle ◽  
Large Body ◽  
Female Rats ◽  
Stimulatory Action ◽  
Peripheral Tissues ◽  
Releasing Hormone ◽  
Wide Range ◽  
Portal Plasma ◽  
Releasing Effect ◽  
Dose Dependent

Although removal of dopamine inhibition is established as a major factor in prolactin (PRL) release, a large body of evidence suggests that hypothalamic oxytocin (OT) may serve as a PRL-releasing hormone in the rat. PRL release is modulated by estradiol (E2), which rises between diestrus and proestrus of the estrous cycle, causing a PRL surge in the afternoon of proestrus. Given that E2 strongly modulates OT actions in both central and peripheral tissues, OT action on lactotrophs might also be modulated by the stage of the estrous cycle. To test this hypothesis, we have monitored PRL release and intracellular calcium levels ([Ca2+]i) induced by OT in pituitary lactotrophs obtained from female rats in either diestrus 1 or proestrus. We found that both secretory and [Ca2+]i responses to OT are significantly increased in lactotrophs obtained on proestrus. Moreover, we show that these differences are due to an increase in both the number of OT-responding lactotrophs and the magnitude of their individual [Ca2+]i responses. Both secretory and [Ca2+]i responses were abolished by a specific OT antagonist. Finally, dose-dependent studies show that the increased PRL-releasing effect of OT on proestrus is significant over a wide range of concentrations, particularly those observed in hypophyseal portal plasma. These results suggest that the rising E2 titers that culminate on proestrus facilitate the stimulatory action of OT on lactotrophs and support the notion that OT is a PRL-releasing hormone with an important role in the production of the proestrous surge of PRL.

scholarly journals Using Vaginal Impedance Measurement to Identify Proestrus in Rats Given Luteinizing Hormone Releasing Hormone (LHRH) Agonist

2020 ◽  
Vol 59 (3) ◽  
pp. 282-287
Author(s):  
Kari L Chesney ◽  
Caroline Chang ◽  
Elizabeth C Bryda
Keyword(s):  
Luteinizing Hormone ◽  
Estrous Cycle ◽  
False Positive ◽  
False Negative ◽  
Impedance Measurement ◽  
Female Rats ◽  
Impedance Measurements ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Vaginal Cytology

Vaginal cytology is the most common method of monitoring the estrous cycle in rats; however, this test requires specific technical training and can be subject to interpretation. Vaginal impedance offers a quicker and less technically challenging alternative and has been used successfully to identify estrus in normally cycling breeder rats. We hypothesize that vaginal impedance can also be used to stage the estrous cycle in rats that have been given luteinizing hormone releasing hormone (LHRH) for timed mating. Vaginal impedance measurements and vaginal cytology were performed in LHRH-primed female rats (n = 36) at the expected peak of proestrus and paired with proven stud males. Breeding success was determined by gross necropsy to detect embryo implantation sites in the female rats. We found that the predictive rates of vaginal cytology and impedance measurement for proestrus were similar; however, both methods resulted in high proportions of false positive and false negative determinations (28% and 31%, respectively). We further hypothesized that females respond to LHRH at variable rates, resulting in variable times of peak proestrus. To test this, vaginal impedance measurements were performed multiple times throughout the expected day of proestrus in LHRH-primed female rats (n = 36). Females were either paired with a male 24 h after reaching the proestrus threshold (n = 18) or paired according to our standard protocol at 1300 h on the day after the expected proestrus (n = 18). Sequential measurements reduced false positive and negative rates (14% and 8%, respectively). Pregnancy rates did not differ based on the time of pairing during expected estrus. Overall, we determined vaginal impedance can be more successful than vaginal cytology at identifying proestrus in the rat, but only if multiple measurements are taken.

DISAPPEARANCE RATE OF BOVINE PROLACTIN FROM PLASMA OF FEMALE RATS STUDIED AT INTERVALS OF UP TO 160 MINUTES BY RADIOIMMUNOASSAY

1970 ◽  
Vol 64 (4) ◽  
pp. 718-725 ◽  
Author(s):  
A. A. van der Gugten ◽  
H. G. Kwa
Keyword(s):  
Intravenous Administration ◽  
Female Rats ◽  
Disappearance Rate ◽  
Blood Samples ◽  
Dose Dependent

ABSTRACT Plasma values resulting from the intravenous administration of 300, 100, 30 and 10 μ of bovine prolactin to rats on day 1 of pregnancy were followed by taking blood samples after 10, 20, 40, 80 and 160 minutes respectively. The rate of disappearance was found to be dose-dependent and to vary in time in the same rat. It is suggested that at least two processes of elimination take place: 1. a (possibly excretory) process, which can bring »unphysiologically high« prolactin levels down to approximately its treshold level of 1.7 μg/ml and 2. a process, which breaks down the hormone into »immunoreactive« polypeptides. This process can degrade 10 μg of bovine prolactin quantitatively within 10 minutes, but appears to become rapidly »saturated« by larger amounts of the hormone.

scholarly journals Bioinsecticides based on plant essential oils: a short overview

2020 ◽  
Vol 75 (7-8) ◽  
pp. 179-182
Author(s):  
Murray B. Isman
Keyword(s):  
Essential Oils ◽  
Crop Protection ◽  
Large Body ◽  
Regulatory Agencies ◽  
The European Union ◽  
Plant Essential Oils ◽  
The Past ◽  
Wide Range ◽  
The Usa ◽  
Regulatory Challenges

AbstractInterest in the discovery and development of plant essential oils for use as bioinsecticides has grown enormously in the past 20 years. However, successful commercialization and utilization of crop protection products based on essential oils has thus far lagged far behind their promise based on this large body of research, most notably because with the exceptions of the USA and Australia, such products receive no special status from regulatory agencies that approve new pesticides for use. Essential oil-based insecticides have now been used in the USA for well over a decade, and more recently have seen use in the European Union (EU), Korea, and about a dozen other countries, with demonstrated efficacy against a wide range of pests and in numerous crop systems. For the most part these products are based on commodity essential oils developed as flavor and fragrance agents for the food and cosmetic industries, as there are formidable logistic, economic, and regulatory challenges to the use of many other essential oils that otherwise possess potentially useful bioactivity against pests. In spite of these limitations, the overall prospects for biopesticides, including those based on essential oils, are encouraging as the demand for sustainably-produced and/or organic food continues to increase worldwide.

Shifts in preferred learning strategy across the estrous cycle in female rats

2004 ◽  
Vol 45 (5) ◽  
pp. 330-338 ◽  
Author(s):  
Donna L Korol ◽  
Emily L Malin ◽  
Kristine A Borden ◽  
Rachel A Busby ◽  
Julia Couper-Leo
Keyword(s):  
Estrous Cycle ◽  
Learning Strategy ◽  
Female Rats

Evelyn Pickering De Morgan's Allegories of Imprisonment

1997 ◽  
Vol 25 (2) ◽  
pp. 293-317
Author(s):  
Elise Lawton Smith
Keyword(s):  
Large Body ◽  
Great Majority ◽  
Feminist Perspective ◽  
Social Constraints ◽  
Still Life ◽  
Spiritual Transcendence ◽  
Wide Range

Evelyn pickering De Morgan (1855–1919) produced a large body of work, primarily paintings but also some sculptural projects, during a career spanning half a century. The great majority of her images include women as protagonists, often as allegorical personifications but with an unusually wide range of characteristics. She created women as members of a constructed and often constraining civilization, who exhibit at times a sort of drooping resignation, but she also represented women as powerful natural elements, actively in control of their destinies. Her art stands out as an attempt to blend metaphysical concerns about material embodiment and spiritual transcendence, grounded in the Platonic ideal, with concerns about social constraints and creative freedom that can be interpreted from a feminist perspective. By translating these fundamental issues about what it means to be human and, more specifically, female into an allegorical language that was unusual for a woman artist of the period (in fact, called “imprudently ambitious” by one critic1), she moved beyond the socially accepted “female iconography” of still life, landscape, and domestic narrative. Overlapping and sometimes contradictory attitudes toward the roles of women can be traced in her oeuvre, particularly in a body of images related to the theme of imprisonment.

The anorectic effect of fenfluramine is influenced by sex and stage of the estrous cycle in rats

2005 ◽  
Vol 288 (6) ◽  
pp. R1486-R1491 ◽  
Author(s):  
Lisa A. Eckel ◽  
Heidi M. Rivera ◽  
Deann P. D. Atchley
Keyword(s):  
Food Intake ◽  
Estrous Cycle ◽  
Female Rats ◽  
Male Rats ◽  
Gonadal Hormone ◽  
Estrous Female ◽  
Male And Female Rats ◽  
Daily Food ◽  
Hormone Status ◽  
Anorectic Effect

The controls of food intake differ in male and female rats. Daily food intake is typically greater in male rats, relative to female rats, and a decrease in food intake, coincident with the estrous stage of the ovarian reproductive cycle, is well documented in female rats. This estrous-related decrease in food intake has been attributed to a transient increase in the female rat's sensitivity to satiety signals generated during feeding bouts. Here, we investigated whether sex or stage of the estrous cycle modulate the satiety signal generated by fenfluramine, a potent serotonin (5-HT) releasing agent. To examine this hypothesis, food intake was monitored in male, diestrous female, and estrous female rats after intraperitoneal injections of 0, 0.25, and 1.0 mg/kg d-fenfluramine. The lower dose of fenfluramine decreased food intake only in diestrous and estrous females, suggesting that the minimally effective anorectic dose of fenfluramine is lower in female rats, relative to male rats. Although the larger dose of fenfluramine decreased food intake in both sexes, the duration of anorexia was greater in diestrous and estrous female rats, relative to male rats. Moreover, the magnitude of the anorectic effect of the larger dose of fenfluramine was greatest in estrous rats, intermediate in diestrous rats, and least in male rats. Thus our findings indicate that the anorectic effect of fenfluramine is modulated by gonadal hormone status.

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