Prolonged Elevated Concentrations of Estradiol Do Not Affect Conception Rates in Beef Cattle

Following treatments causing either prolonged elevated concentrations of estradiol associated with development of persistent follicles or inhibited elevated concentrations of estradiol and development of persistent follicles, conception rates were compared. Beef females received either four norgestomet implants for 9 days (day 0 = treatment initiation; n=59) or one norgestomet implant for 7 days and three additional norgestomet implants for 2 days (n=60). All implants were removed on day 9 followed by estrous detection and AI for 7 days. Treatment and day interacted to affect estradiol concentrations from day 0 to day 9 with elevated estradiol in females treated with one norgestomet implant for 7 days. Conception rates to AI were similar across treatments. Prolonged elevated concentrations of estradiol associated with development of persistent ovarian follicles do not affect fertility when persistent ovarian follicles are not allowed to ovulate

Suppression of p75 Neurotrophin Receptor Surface Expression with Intrabodies Influences Bcl-xL mRNA Expression and Neurite Outgrowth in PC12 Cells

Background: Although p75 neurotrophin receptor (p75NTR) is the first neurotrophin receptor isolated, its diverse physiological functions and signaling have remained elusive for many years. Loss-of-function phenotypic analyses for p75NTR were mainly focused at the genetic level; however these approaches were impacted by off-target effect, insufficient stability, unspecific stress response or alternative active splicing products. In this study, p75NTR surface expression was suppressed for the first time at the protein level by endoplasmic reticulum (ER) retained intrabodies. Results: Three monoclonal recombinant antibody fragments (scFv) with affinities in the low nanomolar range to murine p75NTR were isolated by antibody phage display. To suppress p75NTR cell surface expression, the encoding genes of these scFvs extended by the ER retention peptide KDEL were transiently transfected into the neuron-like rat pheochromocytoma cell line PC12 and the mouse neuroblastoma x mouse spinal cord hybrid cell line NSC19. The ER retained intrabody construct, SH325-G7-KDEL, mediated a downregulation of p75NTR cell surface expression as shown by flow cytometry. This effect was maintained over a period of at least eight days without activating an unfolded protein response (UPR). Moreover, the ER retention of p75NTR resulted in downregulation of mRNA levels of the anti-apoptotic protein Bcl-xL as well as in strong inhibition of NGF-induced neurite outgrowth in PC12 cells. Conclusion: The ER retained intrabody SH325-G7-KDEL not only induces phenotypic knockdown of this p75NTR but als

The Incidence of Precocious Puberty in Developing Beef Heifers

In the current cow-calf production system in the United States when restricted breeding seasons are used a heifer must calve by two years of age to obtain maximum lifetime productivity. Heifers that reach puberty at a younger age and have ≥3 estrous cycles have a greater chance of conceiving early in their first breeding season than contemporaries. Due to the longer postpartum period of an estrus of first-calf cows calving at two years age, heifers that conceive early in the breeding season have a greater opportunity to initiate estrous cycles before the next breeding season and become pregnant. In contrast, heifers that do not reach puberty until after the breeding season starts, conceive later in the breeding season and subsequently calve later the following year. Calving late in the calving season increases the chances of heifers not becoming pregnant during the following breeding season and being lost from the herd. Therefore, age at puberty is an important reproductive trait in developing replacement heifers. Improved management practices and selection of reproductive traits have enhanced the physiological processes associated with attainment of puberty to maximize the number of heifers that reach puberty before the breeding season. Development of replacement heifers in the presence of a mature sterile bull is a management practice that decreases the age at which puberty is attained compared to heifers developed in the absence of a bull. However. increased selection pressure applied to age of puberty in heifers and the subsequent decrease in age at puberty has some disadvantages. Heifers reaching puberty and initiating estrous cycles at a young age while still suckling their dams are often exposed to fertile bulls during the darns breeding season or to intact male calves before weaning. Exposure to fertile bulls during this time period could result in heifers that become pregnant at a very young age and calve as yearlings. These heifers usually conceive late in the breeding season and calve late or after the normal calving season as yearlings. These heifers are of small body size which increases the chances of dystocia that sometimes results in loss of the calf and/or heifer, increased labor and time required for postpartum recovery. The combination of small body size and increased dystocia result in the majority of these animals failing to conceive during the following breeding season. Money invested in developing the heifer would be lost. In addition, precocious puberty in heifers that are destined to be sold as market animals results in heifers becoming pregnant prior to entering the feedlot. Pregnant feedlot heifers have decreased feed efficiency and growth rate compared to nonpregnant heifers which is a factor for lower prices paid by feedlots for heifers compared to steers. The research objectives were to determine the percentage of heifers developed at the University of Nebraska research station that exhibit precocious puberty and if exposure to bulls would affect the incidence of precocious puberty

Effect of hyperlipidemic diets on follicular steroidogenesis and development in Brahman crossbred females

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.Not availabl

Development of a persistent ovarian follicle during estrous synchronization affects fertility and follicular recruitment in cattle

Three experiments were conducted to evaluate the effects of development of a persistent ovarian follicle and associated elevation in 17$\beta$-estradiol on: (1) fertility at the subsequent estrus if artificial insemination or embryo transfer was performed; and (2) recruitment of additional follicles during superstimulation of follicular development with FSH. The objective of first experiment was to determine if development of a persistent ovarian follicle and associated increase in 17$\beta$-estradiol during estrous synchronization decreases conception rates after artificial insemination. Development of a persistent ovarian follicle resulted in elevated circulation concentrations of 17$\beta$-estradiol for 6-10 days compared to 1-2 days preceding behavioral estrus which is typically observed. Interval from simulated luteal regression until observation of estrus was decreased by development of a persistent ovarian follicle. Pregnancy rate was decreased when a persistent follicle is ovulated and cows were inseminated. In addition, pregnancy rate was negatively correlated (r = $-$0.39) to circulating concentrations of 17$\beta$-estradiol preceding estrus. The objective of the second experiment was to determine if elevated 17$\beta$-estradiol preceding ovulation associated with a persistent ovarian follicle alters pregnancy rates after transfer of an embryo on day 7 of the estrous cycle. Development of a persistent follicle during estrous synchronization resulted in elevated 17$\beta$-estradiol preceding ovulation similar to experiment 1. However, elevated 17$\beta$-estradiol did not alter pregnancy rate when an embryo was transferred on day 7 of the estrous cycle. The objective of the third experiment was to determine if development of a persistent ovarian follicle suppresses recruitment of additional follicles during FSH treatment. Development of a persistent ovarian follicle for 5 days but not 2 or 8 days preceding initiation of FSH stimulation was able to suppress recruitment of subordinate follicles and reduce the number of corpora lutea, total ova and transferable embryos observed on day 7 after estrus. Results from these studies indicate that pregnancy rates could be improved if estrous synchronization programs more precisely controlled timing of behavioral estrus and follicular development

Race, concentrated disadvantage, and recidivism: A test of interaction effects

This study sought to explore if the structural characteristics of a community (specifically what sociologists term concentrated disadvantage) interact with race in predicting recidivism. The literature on recidivism stresses the effects of individual factors. This study considered whether effects of the community in which an ex-prisoner lives should be further explored. Of particular interest was the possibility of interaction between concentrated disadvantage and race. Results showed that race strongly predicts recidivism (Blacks being much more likely to recidivate than Whites). This remained the case in spite of multiple controls accounting for racial differences. Neither concentrated disadvantage nor the interaction between it and race had significant effects on recidivism. The study considered what might account for the lingering racial effect, and why the community does not affect the likelihood of recidivism.

Progesterone Metabolism by the Liver and Brain During the Estrous Cycle of Heifers

Heifers were used to evaluate progesterone metabolism in the liver and brain during the estrous cycle. Blood samples were collected from the carotid artery and jugular, portal and hepatic veins. Progesterone concentrations in the hepatic vein were less than in portal and jugular veins and the carotid artery, but there were no differences between the carotid artery and jugular and portal veins. Progesterone concentrations in the hepatic, portal and jugular veins represented 25, 89 and 86 percent of concentrations in the carotid artery, respectively. During the estrous cycle much of the progesterone in blood is metabolized by the liver

Regulation of LH Secretion by Progesterone in Heifers

Heifers experienced either a: 1) large magnitude of change in progesterone; 2) medium magnitude of change in progesterone; or 3) small magnitude of change in progesterone. During the 24 hours following the progesterone shift, heifers with the large magnitude progesterone shift had a greater LH pulse frequency than heifers with a medium or small magnitude of shift in progesterone. Despite the large or medium magnitude progesterone shift, LH pulse frequency did not differ from heifers in which a small change in progesterone occurred. We conclude that amount of progesterone in circulation is more important in regulation of LH secretion than magnitude of shift in amount of progesterone