Evaluation of intrinsic and extrinsic factors affecting pregnancy rate in dual-purpose cows under tropical conditions.

Embryo transfer (ET) in bovines was created with the purpose of increasing the pregnancy rate (PR) of animals with high genetic value; however, multiple factors have been found to affect the success of this reproductive biotechnology. These factors are frequently grouped in intrinsic and extrinsic factors. Thus, the objective of the present experiments was to assess the effect of intrinsic and extrinsic factors on the pregnancy rate under tropical conditions. To do this a total of 648 embryo transfer (ET) procedures were performed between January and December 2021. The intrinsic factors were size and location of the corpus luteum, body condition, genetic group, age and parity; while extrinsic factors were location of the farm, environmental comfort, season in which the ET was carried out, prevailing weather conditions, and the preservation, quality, and the development stage of embryos at the time of ET. A χi2 was used for analysis of main effects, and logistic regression analysis to calculate the probability of pregnancy and the association between intrinsic or extrinsic factors; additionally, a multivariate analysis of data clusters was used to find a linkage between the effects. While recipient female age had a negative effect (Odds ratio = 0.345-0.871) on PR (p < 0.05), being higher in younger cows, the rest of the intrinsic factors did not affect the PR. The significant (p < 0.05) extrinsic factors were THI category, season of year and type of embryo preservation, showing that the highest PR (p < 0.05) was obtained in the comfort THI category, during the winter season and using fresh embryos for transfer. The clustering analysis did not show any linkage between PR and intrinsic factors, while a linkage (p < 0.05) was found with season of the year and embryo preservation as extrinsic factors. It is concluded that age of the recipient cow and environmental conditions at the time of the embryo transfer are key factors to be considered for a successful pregnancy rate from in-vitro ET programs using dual-purpose cows under tropical conditions.

Kinematic and Morphometric Assessment of Fresh Semen, before, during and after Mating Period in Brahman Bulls.

The objective of the present study was to determine the effects that the reproductive season has on the motility, kinematics, morphology, and sperm morphometry of Brahman bulls evaluated with a commercial CASA system. The experiment was carried out at the Costa Rica Institute of Technology from March to August 2021. A total of eight Brahman bulls were used. A total of 28 ejaculates were collected in the pre-mating period (PMP), during it (DMP), and after it (AMP) using an electroejaculator. The sperm concentration was measured with the Accuread photometer. The motility was measured using a Spermtrack® counting chamber. The analyses were performed with the CASA-Mot ISAS®v1 system. The morphology was analyzed using a microscope with a negative phase contrast objective. Morphometry was evaluated with the CASA-Morph. The sperm concentration did not present differences between the PMP and AMP; however, it was significantly higher than DMP (p > 0.05). Regarding the progressiveness variables, linearity on forward progression (LIN), straightness (STR), and wobble (WOB) were higher (p < 0.05) DMP. A kinematic principal component analysis grouped all the variables into three factors and an effect on the reproductive period was found (p < 0.05) in the parameters of the head and middle part of the sperm, such as width and perimeter, which were greater in the PMP. The length of the sperm head in the PMP and DMP did not show differences; however, both were larger (p < 0.05) than AMP. The insertion distance of the middle piece of the sperm was significantly greater than DMP. Finally, the PMP contained cells with a larger insertion angle (p < 0.05) than AMP. These findings are important to understand the implications of reproductive status on sperm quality and to consider them in andrological evaluations.

Prevalence and risk factors of coccidiosis in calves from Veracruz, México.

The objectives of the present study were: (1) to determine the prevalence of Eimeria spp. sporulated oocysts in calves from 26 Municipalities in the Central Zone of the State of Veracruz, Mexico, (2) to identify the Eimeria spp. infecting calves, and (3) to identify the risk factors associated with the presence of Eimeria spp. in tropical cattle. A total of 930 individual fecal samples were analyzed by using the McMaster technique; then, oocysts were maintained in 2.5% potassium dichromate to allow sporulation. The general prevalence of calves with Eimeria spp. oocysts was 39.7% (370/930). Of a total of 10 identified species, Eimeria canadensis was the most observed, followed by Eimeria bovis and Eimeria zuernii. The statistical analysis showed an association between the age of the calves (5 to 9 months), the presence of other animals, the physiographic regions and the restricted type of husbandry with the presence of Eimeria spp. in calves (P<0.05). Protective risk factors, such as: routine coprological analysis was also associated with a decrease in infection. These data demonstrate the presence of coccidia in cattle from the State of Veracruz, additionally to the necessary measures that must be taken to control this parasitosis.

Leptin Chronic Effect on Differentiation, Ion Currents and Protein Expression in N1E-115 Neuroblastoma Cells.

<b>Background and Objective:</b> Arcuate nucleus (ARC), a component of appetite-regulatory factors, contains populations of both orexigenic and anorexigenic neurons and one of the fundamental components of its system is leptin. Studies have evidenced the critical neurotrophic role in the development of ARC. To determine such effects on neuron development, N1E-115 neuroblastoma cells were used as an ARC model. <b>Materials and Methods:</b> N1E-115 neuroblastoma cells were treated with leptin [10 nM] for 24, 48 and 72 hrs. Dimethyl sulfoxide (DMSO) 1.5% was used as a known drug that promotes neurite expression. Cells percentage (%) that developed neurites was evaluated by bright field microscopy. Patch-clamp electrophysiology was used to analyze membrane ion currents, RT-PCR for quantifying changes in mRNA expression of anorexic peptides, proopiomelanocortin (POMC) and cocaine and amphetamine-related transcript (CART), in addition to principal Na_v, Ca_v ion channel subunits. <b>Results:</b> N1E-115 cells treated with leptin show neurite expression after 24 hrs of treatment, similar effects were obtained with DMSO. Leptin (time-dependent) increases the inward current in comparison with the control value at 72 hrs. Outward currents were not affected by leptin. Leptin and DMSO increased Na⁺ and Ca²⁺ current without changes in the kinetic properties. Lastly, leptin promotes an increase in mRNA level expression of transcripts to POMC, CART, Na_v1.2 and Ca_v1.3. <b>Conclusion:</b> Leptin chronic treatment promotes neurite expression, Up-regulation of Na⁺ and Ca²⁺ ion channels determining neuronal excitability, besides increasing the mRNA level expression of anorexic peptides POMC and CART in neuroblastoma N1E-115.

Leptin regulation of inward membrane currents, electrical activity and LH release in isolated bovine gonadotropes.

Leptin, a peptide hormone produced by adipocytes, is recognized as one of the signals involved in the onset of reproductive activity. The leptin receptor has been found in hypothalamic neurons and pituitary gonadotropes, suggesting that the hormone may act at both sites to stimulate the secretion of GnRH and consequently, FSH and LH. In response to a stimulus such as a hypothalamic secretagogue, gonadotropes respond with changes in electrical activity, intracellular Ca2+ and hormone release. The main aim of this report was to investigate whether leptin promotes a change in the electrical and secretory activities of bovine gonadotropes. After 48 h of treatment with leptin (10 nM) significant changes in the action potential properties were observed in gonadotropes, which included an increase in amplitude, time-to-pike and post-hyperpolarization, as well as a decrease in firing threshold. Likewise, leptin induced a significant (∼1.3-fold) up-regulation of voltage-gated Na+ channel current density, and a selective increase (∼2.1-fold) in Ca2+ current density through high voltage-activated channels. Consistent with this, leptin enhanced GnRH-induced secretion of LH measured by ELISA. We suggest that leptin enhances membrane expression of voltage-gated Na+ and Ca2+ channels, which results in a modulation of the action potential properties and an increase in hormone release from gonadotropes.

Ghrelin increases growth hormone production and functional expression of NaV1.1 and Na V1.2 channels in pituitary somatotropes.

A variety of ion channels are expressed in the plasma membrane of somatotropes within the anterior pituitary gland. Modification of these channels is linked to intracellular Ca2+ levels and therefore to hormone secretion. Previous investigations have shown that the gut-derived orexigenic peptide hormone ghrelin and synthetic GH-releasing peptides (GHRPs) stimulate release of growth hormone (GH) and increase the number of functional voltage-gated Ca2+ and Na+ channels in the membrane of clonal GC somatotropes. Here, we reveal that chronic treatment with ghrelin and its synthetic analog GHRP-6 also increases GH release from bovine pituitary somatotropes in culture, and that this action is associated with a significant increase in Na+ macroscopic current. Consistent with this, Na+ current blockade with tetrodotoxin (TTX) abolished the ghrelin- and GHRP-6-induced increase in GH release. Furthermore, semi-quantitative and real-time RT-PCR analysis revealed an upregulation in the transcript levels of GH, as well as of NaV1.1 and NaV1.2, two isoforms of TTX-sensitive Na+ channels expressed in somatotropes, after treatment with ghrelin or GHRP-6. These findings improve our knowledge on (i) the cellular mechanisms involved in the control of GH secretion, (ii) the molecular diversity of Na+ channels in pituitary somatotropes, and (iii) the regulation of GH and Na+ channel gene expression by ghrelin and GHRPs.

Seroprevalence and correlates of Toxoplasma gondii infection in domestic pigs in Veracruz State, Mexico.

Toxoplasma gondii infection in pigs has epidemiological concern for its contributing role in human infections. We determined seroprevalence of T. gondii infection in 402 domestic pigs raised in backyards in Veracruz State, Mexico using the modified agglutination test (MAT; cut off 1:25); 182 (45.3%) of the 402 pigs were seropositive with MAT titers of 1:25 in 28, 1:50 in 22, 1:100 in 18, 1:200 in 30, 1:400 in 35, 1:800 in 23, 1:1,600 in 11, and 1:3,200 or higher in 15. Seropositive pigs were found in 137 (53.3%) of 257 homes in all 7 municipalities surveyed. Multivariate analysis showed that T. gondii seropositivity in pigs was associated with tropical-humid climate (OR = 4.32; 95% CI 1.47-12.62; P = 0.007) of the raising municipalities, feeding with leftovers (OR = 2.83; 95% CI 1.01-7.91; P = 0.04), storing pig food in the owner's home (OR = 2.39; 95% CI 1.09-5.22; P = 0.02), and free ranging (OR = 3.48; 95% CI 1.49-8.15; P = 0.003). Results indicate that backyard pigs in Veracruz have the highest seroprevalence of T. gondii infection obtained by MAT in pigs studied in Mexico so far. The correlates of T. gondii infection found in the present study may be useful for an optimal planning of preventive measures against T. gondii infection in pigs. Results also remark the risk of T. gondii infection in humans by ingestion of raw or undercook pork in Mexico.

Potassium Current Is Not Affected by Long-Term Exposure to Ghrelin or GHRP-6 in Somatotropes GC Cells.

Ghrelin is a growth hormone (GH) secretagogue (GHS) and GHRP-6 is a synthetic peptide analogue; both act through the GHS receptor. GH secretion depends directly on the intracellular concentration of Ca(2+); this is determined from the intracellular reserves and by the entrance of Ca(2+) through the voltage-dependent calcium channels, which are activated by the membrane depolarization. Membrane potential is mainly determined by K(+) channels. In the present work, we investigated the effect of ghrelin (10 nM) or GHRP-6 (100 nM) for 96 h on functional expression of voltage-dependent K(+) channels in rat somatotropes: GC cell line. Physiological patch-clamp whole-cell recording was used to register the K(+) currents. With Cd(2+) (1 mM) and tetrodotoxin (1 µ m) in the bath solution recording, three types of currents were characterized on the basis of their biophysical and pharmacological properties. GC cells showed a K(+) current with a transitory component (I A) sensitive to 4-aminopyridine, which represents ~40% of the total outgoing current; a sustained component named delayed rectifier (I K), sensitive to tetraethylammonium; and a third type of K(+) current was recorded at potentials more negative than -80 mV, permitting the entrance of K(+) named inward rectifier (KIR). Chronic treatment with ghrelin or GHRP-6 did not modify the functional expression of K(+) channels, without significant changes (P < 0.05) in the amplitudes of the three currents observed; in addition, there were no modifications in their biophysical properties and kinetic activation or inactivation.