The role of proestrus on fertility and postovulatory uterine function in the cow

Modern protocols to synchronize ovulations for timed artificial insemination and timed embryo transfer that include manipulations in the proestrus period (i.e., between luteolysis and estrus) affect fertility in cattle. Specifically, stimulating pre-ovulatory follicle growth and exposure to estrogens after CL regression increase the proportion of cows pregnant and decrease late embryo mortality. Such effects may be due to both preovulatory actions of estrogens and post-ovulatory actions of progesterone, as concentrations of the later hormone may be changed in response to manipulations conducted during proestrus. In the first portion of this paper we describe strategies used recently to manipulate the proestrus period in protocols for synchronization of ovulation, and to present evidence of their effects on fertility. Manipulations of timing and prominence of sex steroids during the proestrus and early diestrus that affect fertility may act on targets such as the endometrium. This tissue expresses receptors for both estrogens and progesterone and these hormones change endometrial function to support conceptus growth and pregnancy maintenance. However, specific cellular and molecular mechanisms through which fertility is affected via manipulations of the proestrus are poorly understood. In the second portion of this paper we describe a well-defined animal model to study changes in endometrial function induced by manipulations conducted during the proestrus. Such manipulations induced endometrial changes on sex steroid receptors expression, cell proliferation, oxidative metabolism and eicosanoid synthesis in the uterus, but not on glucose transport to uterine lumen. In summary, evidence is accumulating to support a positive role of increasing duration and estrogen availability during the proestrus on fertility to synchronization protocols. Such positive effects may be through changes in endometrial function to stimulate conceptus growth and survival.

Estudo da motilidade gástrica em ratas prenhes diabéticas e não diabéticas

Several hormonal and physiological changes that occur during pregnancy directly affect gastrointestinal motility (GI), however, very little is known about the relationship between the electrical and mechanical activities of the stomach and its implications. The aim of this study was to compare the female sex hormones, with profiles of gastrointestinal motility using AC biosusceptometry (BAC) in pregnant rats. Seven female Wistar rats (weighing 250-350 g) were used and all procedures were approved by the local Ethics Committee of animal. Laparotomy was performed on anesthetized rats and a magnetic marker (3.5 mm in diameter and 3.0 mm height) was implanted in the distal stomach. After 10 days of recuperation, the mice were put to mate until confirmation of pregnancy. Fed animals were anesthetized (mg pentobarbital 30 / kg) and kept supine for recording the signal with a sensor 30 min BAC placed on the abdominal surface on days 0, 7, 14 and 20 of gestation. Statistical analysis was performed by Student's t test statistical Newman-Keuls and a P value of .05 was considered statistically significant. The frequency of contraction of the stomach was 74 mHz ± 3, 67 ± 7 mHz, 59 mHz ± 6 (p <0.05 vs day -1) and 71 ± 5 mHz on days -0, -7, -14, and -20, respectively. The values of 44 ± 15 pg / mL and 31 ± 9 pg / ml 25 ± 6 pg / ml, 22 ± 9 pg / ml on days -0, -7, -14 and -20, respectively, obtained by 17ß- estradiol were not statistically significant. The values of progesterone were 13 ± 6 pg / ml at 54 ± 15 pg / ml, 127 ± 42 pg / ml (p <0.05 vs day-1), 22 ± 13 pg / mL on day -0, - 7, -14 and -20, respectively. A linear correlation (Pearson's test) between the lower frequency gastric and increased levels of progesterone was 80% (p <0.0000001). Until then, the relationship between changes in motility and hormone were not described in detail, but with the work that we were able to demonstrate the high correlation between progesterone concentration ...

Utilização de gonadotropina coriônica equina em protocolos de inseminação artificial em tempo fixo em bovinos de corte

Current cattlemen must seek methods to maximum reproductive efficiency of their beef herds, making the business competitive and enhancing greater profitability. For the cow-calf producers, efficiency translates into more cows producing one calf every year. Fixed-time artificial insemination (TAI) is one of several technologies that producers utilize to reach this goal. Postpartum anestrus is one of the biggest obstacles to overcome in order to obtain suitable results at the end of the breeding season. The TAI protocols are efficient in re-establishing cyclicity in noncycling cows during the postpartum period, streamlining the use of labor on farms, allowing the use of artificial insemination (AI) on a large scale, and introducing superior genetics to the herd. The protocols that are most commonly used in Brazil are based on progesterone (P4) releasing devices that prevent premature estrus and ovulation; and estradiol (E2) to synchronize the initiation of a new follicular wave. In such protocols, administration of equine chorionic gonadotropin (eCG) helps the development of the follicle, increases ovulation rate, improves the endocrine and uterine environment during proestrus and diestrus, and improves fertility. The use of eCG in TAI protocols for suckled cows, non-lactating cows and heifers increases the pregnancy rate allowing more calves at the end of the breeding season and higher profitability to the cattlemen

Estresse término na reprodução de vacas leiteiras

Climate change in tropical countries, like Brazil, causes major problems in dairy production due to an increase of heat stress effects. In recent years, milk production in Brazil increased 36.07%. The Southeast region remains a leader in production with herds of high producing Holstein cattle (mostly), which is more susceptible to heat stress. Thermal stress decreases fertility in direct and indirect ways. Conception rates are reduced of 40-60% during cooler months of the year and 10-20% in the warmer months. Negative effects of heat stress involve changes in reproductive hormones, follicular development, oocytes, and embryos, and decreased dry matter intake. Several studies discuss change in reproductive hormones, such as reduction in plasma concentration of GnRH, LH, and oestradiol, which lead to decreased detection of estrus and ovulation. Various methods are being studied to bypass these negative effects and increase the fertility of dairy cows under heat stress. Cooling systems are the most advantageous and can be associated with technologies such as ET and TAI

Avaliação in vivo do potencial estrogênico de amostra de água para consumo humano produzida por estação de tratamento do estado de São Paulo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudo de variações bioquímicas e genotoxicidade induzidas por mistura de contaminantes em tilápia (Oreochromis niloticus), como biomarcadores de contaminação ambiental

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análises histopatológicas, bioquímicas e moleculares sobre os efeitos da interação entre o uso de altas doses de decanoato de nadrolona e o exercício resistido durante a fase pós-púbere sobre a próstata de ratos em processo de envelhecimento

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação ecotoxicológica de metais/metalóides e interferentes endócrinos em frações de substâncias húmicas de diferentes tamanhos moleculares

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito do tratamento com Raloxifeno sobre o processo de reparo de reimplante dentário tardio. Estudo histológico em ratas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ocorrência de alteradores endócrinos e fármacos nas águas de abastecimento público e ETE, em duas cidades da área de abrangência da UGRHI-21 e 22

Pós-graduação em Química - IQ

Estudo de interação entre um hormônio estrógeno e modelos simples de membrana biológica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Identificação das proteínas que compõem a glândula prostática do Gerbilo da Mongólia por espectrometria de massas pelo método Shotgun

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos da flutamida na morfologia dos órgãos reprodutivos e fígado de Rhinella schneideri (Anura: Bufonidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A influência da testosterona nas glândulas reprodutivas acessórias de Artibeus planirostris (Chiroptera: Phyllostomidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sistema NPPC-NPR2 na espécie bovina: identificação em folículos antrais e modulação na concentração de nucleotídeos cíclicos e na expressão gênica de PDE3 em complexos cumulus-oócito

Pós-graduação em Biociências - FCLAS