[Show abstract][Hide abstract] ABSTRACT: Bisphenol A (BPA) is a ubiquitous industrial chemical used in the production of a wide variety of items. Previous studies suggest BPA exposure may result in neuro-disruptive effects; however, data are inconsistent across animal and human studies. As part of the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA), we sought to determine whether female and male rats developmentally exposed to BPA demonstrated later spatial navigational learning and memory deficits. Pregnant NCTR Sprague-Dawley rats were orally dosed from gestational day 6 to parturition, and offspring were directly orally dosed until weaning (postnatal day 21). Treatment groups included a vehicle control, three BPA doses (2.5μg/kg/day-[2.5], 25μg/kg/day-, and 2500μg/kg/day-) and a 0.5μg/kg/day ethinyl estradiol (EE)-reference estrogen dose. At adulthood, 1/sex/litter was tested for seven days in the Barnes maze. The 2500 BPA group sniffed more incorrect holes on day 7 than those in the control, 2.5 BPA, and EE groups. The 2500 BPA females were less likely than control females to locate the escape box in the allotted time (p value=0.04). Although 2.5 BPA females exhibited a prolonged latency, the effect did not reach significance (p value=0.06), whereas 2.5 BPA males showed improved latency compared to control males (p value=0.04), although the significance of this result is uncertain. No differences in serum testosterone concentration were detected in any male or female treatment groups. Current findings suggest developmental exposure of rats to BPA may disrupt aspects of spatial navigational learning and memory.
Full-text · Article · Oct 2015 · Hormones and Behavior
[Show abstract][Hide abstract] ABSTRACT: This study was designed to characterize potential sexually dimorphic immunological responses following a lipopolysaccharide (LPS) challenge in beef cattle. Six female (heifers) and five male (bulls) Brahman calves (average age=253±19.9 and 288±47.9 days; average body weight=194±11kg and 247±19kg for heifers and bulls, respectively) were challenged with LPS (0.25μg LPS/kg body weight). Following administration of LPS, all cattle displayed increased sickness behavior beginning at 0.5h, with heifers on average displaying less sickness behavior than bulls. A febrile response was observed in all animals following LPS administration, with a maximum response observed from 4 to 5.5h. The average rectal temperature response was greater in heifers than bulls. In all cattle there were elevated serum concentrations of cortisol from 0.5 to 8h, TNF-α from 1 to 2.5h, IL-6 from 2 to 8h, and IFN-γ from 2.5 to 7h after LPS challenge. Additionally, serum concentrations of TNF-α were greater in heifers than bulls from 1.5 to 2h after the LPS challenge. Concentrations of IFN-γ were also greater on average in bulls than heifers. Leukopenia occurred from 1 to 8h, with a decreased neutrophil to lymphocyte ratio for the first 5h among all calves. These data demonstrate the existence of a sexually dimorphic acute-phase response in pre-pubertal Brahman calves. Specifically, heifers may have a more robust acute response to LPS challenge, even though bulls display more signs of sickness.
Published by Elsevier B.V.
Full-text · Article · Jun 2015 · Veterinary Immunology and Immunopathology
[Show abstract][Hide abstract] ABSTRACT: This study characterized physiological responses to repeated transportation (TRANS) of gestating cows of differing temperaments. Cows were classified as Calm (C; = 10), Intermediate (I; = 28), or Temperamental (T; = 10). Based on artificial insemination date and pregnancy confirmation, cows were TRANS for 2 h on d 60 (TRANS1), 80 (TRANS2), 100 (TRANS3), 120 (TRANS4), and 140 (TRANS5) ± 5 d of gestation. Indwelling vaginal temperature (VT) monitoring devices were inserted 24 h before each TRANS with VT recorded from 2 h before TRANS and averaged into 5-min intervals through 30 min after TRANS. Serum samples were collected before loading and on unloading from the trailer to determine concentrations of cortisol, glucose, and nonesterified fatty acids (NEFA). Data were analyzed by repeated measures analysis in SAS. Serum cortisol concentrations were affected by temperament ( < 0.001), with T cows having the greater concentrations of cortisol before each TRANS event. All cows (100%) regardless of temperament exhibited elevations in cortisol following each TRANS event. Peak VT was greater ( < 0.001) at TRANS1 relative to all other TRANS events regardless of cow temperament. During TRANS, the T cows tended ( < 0.09) to have greater peak VT (39.86 ± 0.15°C) compared to C (39.41 ± 0.16°C) and I cows (39.55 ± 0.08°C). Area under the VT curve decreased ( = 0.002) from TRANS1 through TRANS5. Pre-TRANS serum glucose concentration at TRANS1 was greater ( < 0.03) for T (68.13 ± 4.31mg/dL) compared to I (53.42 ± 2.78 mg/dL) and C cows (52.76 ± 4.60 mg/dL). The C and I cows had greater changes in NEFA concentration between pre- and post-transport, and T cows showed the least change ( < 0.001). Cow VT and serum glucose concentration decreased in all temperaments ( < 0.01) with repeated TRANS; however, serum NEFA concentration post-TRANS did not vary ( > 0.10) with repeated TRANS events. Serum glucose concentrations were affected ( < 0.02) by a TRANS event by temperament interaction with T cows taking more TRANS events to decrease their change in glucose concentration compared to C and I cows. These results demonstrate that temperament influences physiological responses to stress in gestating Brahman cows. Although repeated transport in our study is confounded with day of gestation, seasonal changes, and learning from repeated handling and transport, repeated transport is a useful model of repeated stress in studying the effects of temperament.
No preview · Article · Feb 2015 · Journal of Animal Science
[Show abstract][Hide abstract] ABSTRACT: This study addressed equine sperm quality following exposure to seminal plasma stored under different conditions. Objectives were to compare fresh versus snap-frozen homologous seminal plasma; to compare homologous versus allologous frozen seminal plasma; and to determine the optimal processing/freezing method for long-term preservation of seminal plasma. For the latter objective, seminal plasma was subjected to the following storage conditions: immediate storage of seminal plasma at-20,-80, or-196 o C (Groups 20, 80 and 196, respectively); storage of seminal plasma at 4 o C for 24 h prior to freezing at-20,-80, or-196 o C (Groups 4-20, 4-80, and 4-196, respectively); or storage of raw semen at 4 o C for 24 h prior to isolating seminal plasma and freezing at-20,-80, or-196 o C (Groups RW-20, RW-80, and RW-196, respectively). Seven ejaculates were collected from each of three fertile stallions that served as sperm donors and seminal-plasma donors. Seminal plasma was also obtained from seven other stallions by centrifugation and filtration of raw semen. Following exposure of sperm to seminal plasma treatments and cooled storage of extended semen for 24 h, sperm motion characteristics (total motility [TMOT, %], progressive motility [PMOT, %], curvilinear velocity [VCL, µm/s]), plasma membrane intactness (PMI, %), acrosomal membrane intactness (AI, %), and sperm DNA quality (COMP, %) were evaluated. Comparison of fresh versus frozen homologous seminal plasma revealed no effect of treatment on any experimental endpoint (P > 0.05). Progressive motility was higher in semen exposed to frozen allologous seminal plasma, as compared to frozen homologous seminal plasma, for one of three stallions (P < 0.05). Storage method for seminal plasma did not impact PMI or COMP; however, Group RW-20 yielded lower TMOT than Group 4-80 (P < 0.05). Group RW-20 yielded lower VCL than all other treatments. Highest VCL was detected in Groups 80, 196, 4-80, and 4-196. A treatment x stallion interaction was detected for PMOT. No difference was observed for two stallions (P > 0.05); however, Group 20 yielded higher PMOT than Groups 80 or 196 for the remaining stallion (P < 0.05). Our findings suggest that: 1) seminal plasma can be frozen for later use, obviating the need to process fresh semen to supply seminal plasma, 2) allologous seminal plasma may be beneficial for selected stallions, and 3) semen should not be stored in the raw form for an extended period prior to processing seminal plasma for frozen storage. Introduction The effects of seminal plasma on sperm function are an active area of investigation in the horse, in areas as broad as the effects of seminal plasma on post-breeding endometritis;
[Show abstract][Hide abstract] ABSTRACT: Previously, it was reported that intraluteal implants containing prostaglandin E1 or E2 (PGE1 and PGE2) in Angus or Brahman cows prevented luteolysis by preventing loss of mRNA expression for luteal LH receptors and luteal unoccupied and occupied LH receptors. In addition, intraluteal implants containing PGE1 or PGE2 upregulated mRNA expression for FP prostanoid receptors and downregulated mRNA expression for EP2 and EP4 prostanoid receptors. Luteal weight during the estrous cycle of Brahman cows was reported to be lesser than that of Angus cows but not during pregnancy. The objective of this experiment was to determine whether intraluteal implants containing PGE1 or PGE2 alter vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2), angiopoietin-1 (ANG-1), and angiopoietin-2 (ANG-2) protein in Brahman or Angus cows. On Day 13 of the estrous cycle, Angus cows received no intraluteal implant and corpora lutea were retrieved, or Angus and Brahman cows received intraluteal silastic implants containing vehicle, PGE1, or PGE2 on Day 13 and corpora lutea were retrieved on Day 19. Corpora lutea slices were analyzed for VEGF, FGF-2, ANG-1, and ANG-2 angiogenic proteins via Western blot. Day-13 Angus cow luteal tissue served as preluteolytic controls. Data for VEGF were not affected (P > 0.05) by day, breed, or treatment. PGE1 or PGE2 increased (P < 0.05) FGF-2 in luteal tissue of Angus cows compared with Day-13 and Day-19 Angus controls but decreased (P < 0.05) FGF-2 in luteal tissue of Brahman cows when compared w Day-13 or Day-19 Angus controls. There was no effect (P > 0.05) of PGE1 or PGE2 on ANG-1 in Angus luteal tissue when compared with Day-13 or Day-19 controls, but ANG-1 was decreased (P < 0.05) by PGE1 or PGE2 in Brahman cows when compared with Day-19 Brahman controls. ANG-2 was increased (P < 0.05) on Day 19 in Angus Vehicle controls when compared with Day-13 Angus controls, which was prevented (P < 0.05) by PGE1 but not by PGE2 in Angus cows. There was no effect (P > 0.05) of PGE1 or PGE2 on ANG-2 in Brahman cows. PGE1 or PGE2 may alter cow luteal FGF-2, ANG-1, or ANG-2 but not VEGF to prevent luteolysis; however, species or breed differences may exist.
[Show abstract][Hide abstract] ABSTRACT: Abstract Text:
The objectives of this study were to determine if prenatal stress (PNS) or postnatal temperament affect age and BW at first sperm, puberty and sexual maturity. Based on temperament pregnant Brahman cows were assigned to a control (n=44; C) or transport group (n=45; transportation stress for 2 h on 60, 80, 100, 120 and 140±5d of gestation; PNS). At weaning bulls (n=25 C and n=18 PNS) were selected for this study. Temperament was assessed at weaning using temperament score [TS; (PS+EV)/2], pen score (PS; 1=Calm and 5=Excitable), and exit velocity (EV=m/s). These TS were then converted into temperament classes of calm (TS= < 1.78, n= 26), intermediate (TS=1.7 to 2.90, n= 9) and temperamental (TS= > 2.90, n= 8). Bulls were measured every 2 wk from 10 mo of age for BW, scrotal circumference (SC), and right and left testis length. Electroejaculation was used to collect semen when SC reached 24 cm. Semen was analyzed for sperm motility and concentration using a hemacytometer. Sexual maturation was characterized by first sperm (the first visible sperm in the ejaculate), puberty (50 X 106 sperm in the ejaculate) and sexual maturity (500 X 106 sperm in the ejaculate). Paired testes volume (PTV) was calculated as PTV=[0.0396125 X (average testes length) X (SC) 2]. Dependent variables were analyzed using repeated measures, mixed linear models. Fixed effects included temperament class, treatment, and interaction effects. Random animal effects were across repeated days. Age at first sperm, puberty and sexual maturity were similar between C and PNS bulls (P=0.47, 0.73, 0.99, respectively). Times between first sperm and puberty (P=0.32) and puberty to sexual maturity (P=0.92) were not affected by PNS. Temperamental bulls had a greater (P=0.009) time (69.25±11.45 d) from puberty to sexual maturity than calm (28.47±7.53 d) or intermediate bulls (38.19±9.95 d). BW at first sperm was greater for PNS (382.16±11.29 kg) than C bulls (353.19±10.55 kg). Scrotal circumference at first sperm was greater (P=0.03) in temperamental (26.8±0.7 cm) than calm (25.5±0.5 cm) or intermediate (25.1±0.6 cm) bulls. There was a tendency for temperamental bulls to have a greater PTV at first sperm (P=0.06) and sexual maturity (P=0.07) than calm or intermediate bulls. While PNS influenced BW, SC and PTV at first sperm, ages at puberty or sexual maturity were not affected by PNS. Temperamental bulls had retarded sexual development between puberty and sexual maturity.
Keywords: prenatal stress, temperament, bull sexual maturity
[Show abstract][Hide abstract] ABSTRACT: Abstract Text: The effect of prenatal transportation stress (PNS) on secretion of LH before and after GnRH stimulation in sexually mature Brahman bulls was studied in 12 control and 11 PNS bulls. Control bulls were derived from non-transported pregnant cows, and PNS bulls were derived from cows transported for a 2-h period at 60, 80, 100, 120, and 140 ± 5 d of gestation. Temperament of each bull was assessed at weaning by pen score (PS; 1 = calm and 5 = excitable), exit velocity (EV; m/sec) and temperament score [TS = (PS + EV)/2]. Bulls were electroejaculated every 2 wk beginning at a scrotal circumference of 24 cm through sexual maturity (i.e., 500,000,000 sperm/ejaculate). Within 7-21 d after reaching sexual maturity, bulls were fitted with jugular vein cannulas, and blood samples were collected at 15-min intervals for 6 h to determine the pattern of LH release. GnRH was then administered intravenously (10 ng/kg BW) and blood collection continued at 15-min intervals for an additional 8 h. Concentrations of LH in serum were determined by RIA. Amplitude of a detectable LH pulse, baseline concentration of LH, and area under the LH curve (AUC) were calculated for the 4-h period immediately preceding GnRH administration. Luteinizing hormone pulse incidence was evaluated using Pulse XP algorithm. The amplitude and height of the GnRH-induced LH release, AUC post-GnRH administration, and the duration of the GnRH-induced LH release were determined. Data were analyzed using a fixed effect model, with treatment and temperament classification included in the model. The occurrence of LH pulses during the pre-GnRH period was compared between treatment groups by chi-square analysis. More PNS bulls exhibited an LH pulse before GnRH injection (10 of 11; P < 0.01) than control bulls (3 of 12). No other characteristic associated with the release of LH during the pre-GnRH treatment evaluated in this study differed between groups (P > 0.1). All bulls responded similarly to exogenous GnRH, with the exception of the duration of the LH response which was greater (P = 0.02) in PNS bulls (268 ± 18 min) relative to control bulls (207 ± 16 min). Pattern of LH secretion before GnRH and duration of GnRH-induced LH release differed between PNS and control bulls. Stress during prenatal development may affect secretion of LH in sexually mature Brahman bulls.
Keywords: Bulls, Prenatal Stress, LH
[Show abstract][Hide abstract] ABSTRACT: Abstract Text:
Environmental, physiological, psychological, and managerial stressors have been implicated as causes of reproductive disorders and decreased fertility in animals and humans. Herd reproductive efficiency and the stud industry depend upon the sperm producing capabilities and libido of bulls and stallions. With respect to male reproductive physiology, the steroidogenic and spermatogenic functions of the testis can be negatively impacted by stress-induced secretion of endogenous glucocorticosteroids (GC) as well as by treatment with exogenous GC agonists. The testes’ gametogenic function, a primary component of male fertility, is dependent upon appropriate transmission, receipt, and processing of specific endocrine signals. The deleterious effects of stress upon reproductive performance are presumably signaled by GC activation of the glucocorticoid receptor (NR3C1). Questions related to molecular mechanisms whereby stress affects specific components of the hypothalamic-pituitary-testicular (HPT) axis of male rodents, primates, cattle, sheep, pigs, horses and other species have been pursued by the use of in vitro and in vivo methods. This paper will provide a targeted overview of potential impacts of stressors upon the endocrine aspects of the HPT axis, with particular focus on direct testicular effects. Specific data to be presented are derived from studies of the influences of endogenous and exogenous GC on androgen biosynthesis and gene expression in testes of bulls and stallions. Chronic administration of a synthetic GC has been reported to increase the incidence of abnormal spermatozoa by direct action or perhaps by disruption of the endocrine or genetic mechanisms that support sperm production in bulls and stallions. Acute elevation of the systemic concentration of GC by pharmacologic methods or by mimicry of physiologic stress have inhibited testicular steroidogenesis and transiently decreased the systemic concentration of testosterone. The inhibitory action of endogenous GC concentrations on testicular steroidogenesis under stressed and non-stressed conditions indicates that activity of the hypothalamic-pituitary-adrenal axis may be of critical importance in establishment or maintenance of a functional HPT axis during prenatal, prepubertal, and postpubertal life. Homeostatic regulation of reproductive processes involves a physiological integration of the adrenal and testicular axes. The biologic and economic importance of deleterious influences of stress upon male reproductive processes dictate a thorough evaluation of adrenal–testicular interrelationships in domestic livestock species.
Keywords: Stress; Steroidogenesis; Spermatogenesis
[Show abstract][Hide abstract] ABSTRACT: Abstract Text:
Eighteen Quarter Horses were utilized in a randomized complete design to evaluate age-related effects on inflammation and cartilage turnover after induction of a single inflammatory insult using lipopolysaccharide (LPS). Treatments consisted of age with yearlings (n = 3 males, n = 3 females), 2/3 yr olds (n = 2 males, n = 4 females), or mature 5 to 8 yr olds (n = 2 males, n = 4 females) for a 14 d experiment. For 14 d prior to the start of the experiment all horses were housed in individual stalls and fed diets that met or exceeded NRC (2007) requirements. On d 0, horses were challenged with an intra-articular injection of LPS. Radial carpal joints were randomly assigned to receive LPS using 0.5 ng LPS solution obtained from Escherichia coli O55:B5, or sterile lactated Ringer’s solution as a contralateral control. Synovial fluid was collected prior to LPS injection (0 h) and 6, 12, 24, 168, and 336 h post-injection. Samples were later analyzed using commercial ELISA kits for prostaglandin E2 (PGE2), collagenase cleavage neoepitope (C2C), and carboxypeptide of type II collagen (CPII). Rectal temperature (RT), heart rate (HR), and respiratory rate (RR) were monitored prior to sample collection over the first 24 h, and carpal circumference and joint surface temperature were recorded. Data were analyzed using PROC MIXED procedure of SAS. All values for RT, HR, and RR were within normal range and unaffected by treatment (P ≤ 0.21). Joint circumference was not influenced by treatment (P = 0.84), but circumference and surface temperature increased (P ≤ 0.01) across all treatments in response to intra-articular LPS. Synovial PGE2 levels were influenced by age with yearlings tending to have lesser (P = 0.09) values than 2/3 yr olds and mature horses. This was particularly evident at 12 h when PGE2 values peaked for all horses and yearlings had lesser values (P ≤ 0.01) than mature horses. Synovial C2C was influenced by treatment with yearlings and 2/3 yr olds having lesser (P ≤ 0.01) concentrations than mature horses. Synovial CPII was influenced by treatment at 24, 168 and 336 h with yearlings having lesser concentrations (P ≤ 0.01, P ≤ 0.06, and P ≤ 0.03, respectively) compared to 2/3 yr olds and mature horses. These results indicate that inflammation and corresponding cartilage turnover in response to LPS administration vary with age.
Keywords: LPS, horse, synovial fluid, PGE2, CPII, C2C
[Show abstract][Hide abstract] ABSTRACT: Abstract Text:
The objective of this study was to determine if feeding of yeast cell wall (YCW) to pregnant cows influences cow performance as well as postnatal calf growth and immunity. Multiparous cows were assigned by predicted calving date into either the control (C; n=24) or supplemented (Y; n=24) groups. The Y cows were fed 4 g of YCW in 230 g of ground corn top-dressed on 1.81 kg of corn gluten and soybean meal (4:1) from approximately 90 d prepartum through 28 d postpartum. Weight and body condition score (BCS) were taken at 28-d intervals prepartum and postpartum. Within 24 hr of parturition, the BW and BCS of cows and BW of calves were recorded, and blood samples from calves were obtained to determine white blood cell numbers. These procedures were repeated on d 14 and 28 postpartum, and continued at 28-d intervals through weaning. Weaning weights were adjusted to 180 d of age. Cows were observed for estrus twice daily starting d 28 postpartum through first estrus. Data were analyzed using the MIXED procedure in SAS. Yeast supplementation did not affect cow prepartum BW (P=0.39) or BCS (P=0.14), postpartum BW (P=0.97) or BCS (P=0.89), or the postpartum interval (P=0.98; C=56.2±3.3, Y=56.3±3.2 d). Calf weight was not different at birth; however, on d 14 and at weaning, C males tended to be heavier than Y group males as well as females from the C and Y groups (P=0.08, 0.07, respectively). At d 28 C males were heavier than Y males or females (P=0.02). There was a tendency for 180-d adjusted weaning weight to be heavier for C males than either Y males or C and Y females (P=0.0563). There was also a treatment by day interaction in which C calves were heavier than Y calves (P=0.01) and a calf sex by day interaction with males being heavier than females preweaning (P=0.01). Treatment did not affect the white blood cell profile of calves on d 0 or 28 as C and Y calves had similar percentages (P > 0.2) of lymphocytes, monocytes, segmented neutrophils, banded neutrophils and eosinophils. The C males demonstrated a greater growth rate than prenatally supplemented calves in the neonatal and preweaning periods. These data suggest that prenatal YCW supplementation to healthy mature cows in a low stress environment does not benefit cow or calf performance.
Keywords: yeast cell wall, calf performance, cow performance
[Show abstract][Hide abstract] ABSTRACT: Abstract Text:
Seventeen yearling Quarter horses were used in a randomized complete block design to evaluate potential of dietary CLA to mitigate intra-articular inflammation and cartilage metabolism following a single inflammatory insult. Horses were blocked by age, BW and sex and randomly assigned to treatment for a 56-day trial. Treatments consisted of a commercial concentrate offered at 1% BW (as fed) supplemented with either 1% soybean oil (CON; n=6), 0.5% soybean oil and 0.5% CLA (LOW; n=5; Lutalin®, BASF Corp.), or 1% CLA (HIGH; n=6; 55% purity) top-dressed daily. Horses were fed individually at 12 h intervals and offered 1% BW daily (as-fed) coastal bermudagrass (Cynodon dactylon) hay. On day 42, an LPS challenge was conducted. Carpal joints were randomly assigned to receive intra-articular injections of 0.5 ng LPS derived from Escherichia coli 055:B5 or sterile lactated Ringer’s solution as a contralateral control. Synovial fluid samples were taken via arthrocentesis at pre-injection h 0 and 6, 12, 24, 168 and 336 h post-injection, and were analyzed for prostaglandin E2 (PGE2), carboxypeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C) using commercial ELISA kits. Vitals, including heart rate, rectal temperature and respiration rate were monitored at 0, 6, 12 and 24 h; and carpal circumference and surface temperatures were also recorded. Data were analyzed using PROC MIXED procedure of SAS. Vitals were not significantly different across treatments (P ≥ 0.13) and remained within normal ranges throughout the LPS challenge. Synovial PGE2 concentrations were not influenced by dietary treatment (P = 0.15). Synovial C2C concentrations were influenced by treatment (P = 0.05) with LOW and HIGH horses having lesser C2C than CON. Across all treatments C2C concentrations varied over time (P < 0.01) with values decreasing from 0 h to 6 h, peaking at 12 h and decreasing to 336 h. Levels of synovial CPII tended to be influenced by treatment (P =0.10) with LOW and HIGH horses having greater concentrations compared to CON. Regardless of diet, CPII concentrations increased over time (P < 0.01) with levels peaking at 24 h and decreasing to 336 h. In conclusion, CLA supplementation did not influence PGE2 concentrations following the LPS challenge; however, horses receiving CLA had lesser C2C and greater CPII concentrations, indicating less degradation and greater synthesis of cartilage in response to acute inflammation.
CLA, Synovial, LPS, Cartilage
[Show abstract][Hide abstract] ABSTRACT: In rodents, livestock and primate species, a single dose of the synthetic glucocorticoid dexamethasone acutely lowers testosterone biosynthesis. To determine the mechanism of decreased testosterone biosynthesis, stallions were treated with 0.1mg/kg dexamethasone 12h prior to castration. Dexamethasone decreased serum concentrations of testosterone by 60% compared to saline-treated control stallions. Transcriptome analyses (microarrays, northern blots and quantitative PCR) of testes discovered that dexamethasone treatment decreased concentrations of glucocorticoid receptor alpha (NR3C1), alpha actinin 4 (ACTN4), luteinizing hormone receptor (LHCGR), squalene epoxidase (SQLE), 24-dehydrocholesterol reductase (DHCR24), glutathione S-transferase A3 (GSTA3) and aromatase (CYP19A1) mRNAs. Dexamethasone increased concentrations of NFkB inhibitor A (NFKBIA) mRNA in testes. SQLE, DHCR24 and GSTA3 mRNAs were predominantly expressed by Leydig cells. In man and livestock, the GSTA3 protein provides a major 3-ketosteroid isomerase activity: conversion of Δ(5)-androstenedione to Δ(4)-androstenedione, the immediate precursor of testosterone. Consistent with the decrease in GSTA3 mRNA, dexamethasone decreased the 3-ketosteroid isomerase activity in testicular extracts. In conclusion, dexamethasone acutely decreased the expression of genes involved in hormone signaling (NR3C1, ACTN4 and LHCGR), cholesterol synthesis (SQLE and DHCR24) and steroidogenesis (GSTA3 and CYP19A1) along with testosterone production. This is the first report of dexamethasone down-regulating expression of the GSTA3 gene and a very late step in testosterone biosynthesis. Elucidation of the molecular mechanisms involved may lead to new approaches to modulate androgen regulation of the physiology of humans and livestock in health and disease.
No preview · Article · Jul 2014 · The Journal of Steroid Biochemistry and Molecular Biology
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was to estimate the heritability of 3 measures of temperament in Brahman and Brahman-influenced calves (n = 1,209). Individual animal pen scores (PS) were determined by a trained observer who evaluated groups of 5 or 4 calves at a time for willingness to be approached by a human. Exit velocity (EV) was the rate (m/s) at which each calf exited a squeeze chute. Temperament score (TS) was calculated individually as (PS + EV)/2. Temperament was evaluated at 5 different times of record (28 d pre-weaning, weaning, 28 d post-weaning, 56 d post-weaning, and yearling). Contemporary groups (n = 34) were comprised of calves of the same sex born in the same season of the same yr. There were an average of 36 calves per contemporary group and group size ranged from 3 to 78 calves. Average weaning age (186 d) ranged from 105 to 304 d. Calves were born from 2002 through 2012. Random effects included additive genetic and the permanent environmental variance. The fixed effects analyzed were age of dam, sex of calf, contemporary group, fraction of Brahman (2 levels: 1 and 0.5), age of calf at record, and weaning age. At weaning, the mean PS was 2.68 ± 0.1, the mean EV was 2.41 ± 0.1, and the mean TS was 2.48 ± 0.1. The PS was affected by fraction of Brahman (P = 0.034) and tended to be affected by age of dam (P = 0.06). The EV was affected by contemporary group (P < 0.001) and tended to be affected by weaning age (P = 0.074). Contemporary group affected TS (P < 0.001). All 3 methods of temperament evaluation were affected by time of record (P < 0.001). The regression coefficients for PS, EV, and TS were 0.0023 ± 0.0014, 0.0022 ± 0.0012, and 0.0015 ± 0.0012 m⋅s(-1)⋅d(-1) of age, respectively. Estimates of maternal genetic effects were always 0 and omitted from final models. Estimates of heritability were 0.27 ± 0.1, 0.49 ± 0.1, and 0.43 ± 0.1 for EV, PS, and TS, respectively. Estimates of permanent environmental variances as proportions of phenotypic variance were 0.33 ± 0.1, 0.23 ± 0.1, and 0.33 ± 0.1 for EV, PS, and TS, respectively. There appears to be sufficient additive genetic variance for selective improvement of temperament characteristics in Brahman cattle.
Full-text · Article · May 2014 · Journal of Animal Science
[Show abstract][Hide abstract] ABSTRACT: The influence of temperament on the alteration of metabolic parameters in response to a lipopolysaccharide(LPS) challenge was investigated. Brahman bulls were selected based on temperament score. Bulls (10 months; 211±5kg BW; n = 6, 8 and 7 for Calm, Intermediate and Temperamental groups, respectively) were fitted with indwelling jugular catheters to evaluate peripheral blood concentrations of glucose, blood urea nitrogen (BUN),non-esterified fatty acids (NEFA), insulin, epinephrine and cortisol before and after LPS administration (0.5 μg/kg BW LPS). Feed intake was also recorded. Intermediate bulls consumed more feed than the Temperamental bulls during the challenge (p = 0.046). Pre-LPS glucose (p = 0.401) and BUN (p = 0.222) did not differ among the temperament groups. However, pre-LPS insulin (p = 0.023) was lower, whereas pre-LPS NEFA (p < 0.001),cortisol (p < 0.001) and epinephrine (p < 0.001) were greater in Temperamental than in Calm and Intermediate bulls. Post-LPS glucose was increased in Calm and Intermediate bulls but not in Temperamental bulls(p < 0.001). Insulin concentrations post-LPS were greater in Calm than in Intermediate and Temperamental bulls (p < 0.001). Concentrations of NEFA post-LPS were greater in Temperamental than in Calm and Intermediate bulls (p < 0.001). Serum BUN concentration increased post-LPS, with values being greater in Calm and Intermediate than in Temperamental bulls (p = 0.012). Collectively, these data demonstrate that animal temperament is related to the metabolic responses of Brahman bulls following a provocative endotoxin challenge.Specifically, Temperamental bulls may preferentially utilize an alternate energy source (i.e. NEFA) to a greater degree than do bulls of Calm and Intermediate temperaments. The use of circulating NEFA from lipolysis may reduce the negative metabolic consequences of an immune response by allowing for a prompt answer to increasing energy demands required during immunological challenge, compared with the time required for glycogenolysis and gluconeogenesis.
No preview · Article · Feb 2014 · J Anim Physiol a Anim Nutr
[Show abstract][Hide abstract] ABSTRACT: RF-amide related peptide 3 (RFRP3), the mammalian homologue of avian gonadotropin-inhibitory hormone (GnIH), has been shown to negatively regulate the secretion of LH and may contribute to reproductive seasonality in some species. Herein, we examined the presence and potential role of the RFRP3-signaling system in regulating LH secretion in the mare during the breeding and non-breeding seasons. Hypothalamic NPVF mRNA (the precursor mRNA for RFRP3) was detected at the level of the dorsomedial nucleus (DMH) and paraventricular nucleus (PVN), but expression did not change with season. A greater number of RFRP3-expressing cells was observed throughout the rostral-caudal extension of the DMH. Further, adenohypophyseal expression of the RFRP3 receptor (NPFFR1) during the winter anovulatory season did not differ from that during either the follicular or luteal phases of the estrous cycle. When tested in primary adenohyphyseal cell culture, or in vivo during both the breeding and non-breeding seasons, neither equine nor ovine peptide sequences for RFRP3 suppressed basal or GnRH-mediated release of LH. However, infusion of RF9, an RFRP3 receptor-signaling antagonist, into seasonally-anovulatory mares induced a robust increase in secretion of LH both before and following continuous treatment with GnRH. Results indicate that the cellular machinery associated with RFRP3 function is present in the equine hypothalamus and adenohypophysis. However, evidence for functionality of the RFRP3 signaling network was only obvious when an antagonist (RF9) was employed. As GnRH-induced release of LH was not affected by RF9, its actions may occur upstream from the gonadotrope to stimulate or disinhibit secretion of GnRH.
Full-text · Article · Jan 2014 · Biology of Reproduction
[Show abstract][Hide abstract] ABSTRACT: This introductory chapter offers a basic overview of male reproduction, specifically the anatomy and physiology of the male reproductive system. Comprehension of normal anatomy and physiology is necessary to (1) fully understand the severity of toxicant-induced damage to structures and/or functions of the male reproductive system, (2) design more powerful experiments that analyze potential male reproductive toxicants, and (3) identify numerous potential targets of toxicants in the male reproductive system. This chapter begins with an overview of the hypothalamic-pituitary-testicular axis and its interaction with additional components of the male reproductive system. This is then followed by detailed presentation of the composition of the testis and the interrelationships of the testicular cells, spermatogenesis, the excurrent ducts that carry spermatozoa out of the testis, the accessory sex glands that supply the seminal plasma of semen, the cellular communication within the testis, the reproductive tract's development, and normal male sexual behavior. The chapter's conclusion emphasizes the foundational importance of the male reproductive system to desgining, conducting, and interpreting reproductive toxicology research.