Real-time PCR is widely used to study the relative abundance of mRNA due to its specificity, sensitivity, and repeatability quantification. However, relative quantification requires a reference gene, which should be stable in its expression, showing lower variation by experimental conditions or tissues. The aim of this study was to evaluate the stability of the expression of five commonly used reference genes (actb, ywhaz, b2m, sdha, and 18s rRNA) at different physiological stages (alert and emergency) in three different cattle breeds. In this study, five genes (actb, ywhaz, b2m, sdha, and 18s rRNA) were selected as candidate reference genes for expression studies in the whole blood from three cattle breeds (Romosinuano, Gyr, and Brahman) under heat stress conditions. The transcription stability of the candidate reference genes was evaluated using geNorm and NormFinder. The results showed that actb, 18SrRNA, and b2m expression were the most stable reference genes for whole blood of Gyr and Brahman breeds under two states of livestock weather safety (alert and emergency). Meanwhile, actb, b2m, and ywhaz were the most stable reference genes for the Romosinuano breed.

Global warming has been affecting animal husbandry and farming production worldwide via changes in organisms and their habitats. In the tropics, these conditions are adverse for agriculture and animal production in some areas, due to high temperatures and relative humidity, affecting competitiveness related to economic activities. These environments have deteriorated livestock production, due to periods of drought, reduction in forage quality and heat stress, eliciting negative effects on reproduction, weight gain, and reduced meat and milk production. However, the use of animals adapted to tropics such as breeds derived from subspecies Bos primigenius indicus and native breeds from tropical countries or their crossings, is an alternative to improve production under high-temperature conditions. Therefore, physiological adaptation including gene expression induced by heat stress have been studied to understand the response of animals and to improve cross-breeding between cattle breeds to maintain high productivity in adverse weather conditions. Heat stress has been associated with lower reproductive performance in cows, due to the impact on blastocyst production, decreased implantation and increased embryonic death. Thus, for decades, in vitro fertilization and embryo transfer techniques have focused on studying the optimal conditions for production of high-quality embryos to transfer. The aim of this review is to discuss the effects of heat stress in bovine embryos, and their physiological and genetic modulation, focusing on the genes that are related with major adaptability to heat stress conditions and their relationship with different embryonic stages.

La disposición inapropiada de sustancias que contienen mercurio puede causar toxicidad y acumulación en tejidos de peces. En el presente estudio se registra la concentración letal cincuenta (CL50) a 96 horas del mercurio para la cachama blanca [Piaractus brachypomus (Cuvier, 1818)]. Se calculó a través de una prueba semiestática de toxicidad aguda utilizando cloruro de mercurio (HgCl2) como fuente del metal. El experimento fue realizado en el Laboratorio de Toxicología de la Universidad del Tolima (Colombia), en condiciones controladas (28,09 ± 1,86 °C) y un fotoperiodo 12:12 (luz:oscuridad). Los alevinos (6,55 ± 1,3 g) fueron mantenidos en acuarios de vidrio con aireación constante, sin filtro y la alimentación fue suprimida 24 horas antes del inicio del experimento. Se emplearon 4 concentraciones de mercurio (Hg), con su respectiva replica, incluyendo un grupo control. Las concentraciones fueron: 0,45, 0,55, 0,65 y 0,75 mg Hg/l. Se realizó un análisis histopatológico con dos peces de cada tratamiento tomando muestras de branquias, cerebro y hígado. Los especímenes expuestos a las concentraciones más bajas (0,45 y 0,55 mg Hg/l) mostraron hiperactividad, a diferencia de los de las concentraciones más altas (0,65 y 0,75 mg Hg/l) los cuales evidenciaron disminución de su actividad. El análisis histopatológico mostró anomalías en branquias e hígado, como hiperplasia interlamelar y vaculizaciones lipídicas respectivamente, en respuesta a procesos de detoxificación. El valor de la CL50-96 h fue estimado utilizando el programa TSK (Trimmed-Spearman-Karber) y presentó un valor de 0,56 mg Hg/l. Este valor es cercano a lo registrado en otras especies de peces y representa el primer registro de toxicidad aguda para el mercurio en cachama blanca.

Aquaporins (AQPs) are proteins with various functions related to proper cell function and early development in mammals. The aim of this study was to evaluate the presence of AQPs and determine their mRNA levels in the cumulus oocyte complex (COC) of four bovine breeds and in blastocysts of five bovine crosses. Grade I, II and III COCs were collected by ovum pick up from non-lactating heifers of the Brahaman, Holstein, Gir and Romosinuano breeds. Embryos were produced in vitro up to the blastocyst stage of the bovine ♀Gir × ♂Holstein, ♀Holstein × ♂Gir, ♀Brahman × ♂Holstein, ♀Holstein × ♂Brahman, and ♀Romosinuano × ♂Holstein crosses. mRNA expression of AQP1-AQP12b was estimated in COC and embryos by real-time-PCR. The presence of the twelve AQPs in the COCs and bovine embryos was established. Additionally, significant differences were determined in the expression of AQP6 and AQP12b in COCs, as well as in transcripts levels of AQP4, AQP8 and AQP9 from bovine embryos. Gene expression of AQPs in COCs and bovine embryos is consistent with the previously described biological functions. This is the first report of AQPs in COC of Gir, Brahman, Holstein and Romosinuano and embryos of five crossbreeds between Bos indicus and B. taurus.

Background and Aim: Heat shock proteins are highly conserved proteins that work as molecular chaperones expressed in response to thermal stress. This study aimed to determine the expression profile of genes related to the heat stress response in whole blood obtained from the Romosinuano creole breed. Materials and Methods: Real-time polymerase chain reaction was performed to analyze the transcript of hsp90, hsp70, hsp60, and hsf1 in the whole blood of Romosinuano under different temperature-humidity indices (THIs). Results: The expression levels of the hsp70 and hsf1 genes at the high-THI level were higher (p = 0.0011 and p = 0.0003, respectively) than those at the low-THI level. In addition, no differences in the expression levels of the hsp60 and hsP90 genes were detected between the two THIs. Conclusion: The overexpression of hsf1 and hsp70 genes play an important role in protecting cells from damage induced by heat stress. Keywords: climate change, external environment, heat shock proteins, heat stress, mRNA, temperature-humidity index.