Long form leptin receptor mRNA expression in the brain, pituitary, and other tissues in the pig

Much effort has focused recently on understanding the role of leptin, the obese gene product secreted by adipocytes, in regulating growth and reproduction in rodents, humans and domestic animals. We previously demonstrated that leptin inhibited feed intake and stimulated growth hormone (GH) and luteinizing hormone (LH) secretion in the pig. This study was conducted to determine the location of long form leptin receptor (Ob-Rl) mRNA in various tissues of the pig. The leptin receptor has several splice variants in the human and mouse, but Ob-Rl is the major form capable of signal transduction. The Ob-Rl is expressed primarily in the hypothalamus of the human and rodents, but has been located in other tissues as well. In the present study, a partial porcine Ob-Rl cDNA, cloned in our laboratory and specific to the intracellular domain, was used to evaluate the Ob-Rl mRNA expression by RT-PCR in the brain and other tissues in three 105 d-old prepuberal gilts and in a 50 d-old fetus. In 105 d-old gilts, Ob-Rl mRNA was expressed in the hypothalamus, cerebral cortex, amygdala, thalamus, cerebellum, area postrema and anterior pituitary. In addition, Ob-Rl mRNA was expressed in ovary, uterine body, liver, kidney, pancreas, adrenal gland, heart, spleen, lung, intestine, bone marrow, muscle and adipose tissue. However, expression was absent in the thyroid, thymus, superior vena cava, aorta, spinal cord, uterine horn and oviduct. In the 50 d-old fetus, Ob-Rl mRNA was expressed in brain, intestine, muscle, fat, heart, liver and umbilical cord. These results support the idea that leptin might play a role in regulating numerous physiological functions.     

A serological survey of cattle in the Thames-Coromandel district of New Zealand for antibodies to Ross River virus

AIM: To determine if cattle exposed to the southern saltmarsh mosquito (SSM), Aedes camptorhynchus, in the Thames-Coromandel district of New Zealand had been exposed to Ross River virus (RRV).

METHODS: A purposive sampling design was used to test cattle from seven farms located in close proximity to four sites infested with A. camptorhynchus in the Thames-Coromandel district. Sera from 207 cattle were tested for antibodies to RRV, using an ELISA and confi rmatory virus neutralisation test (VNT) as the gold standard.

RESULTS: All 207 cattle tested negative for antibodies to RRV using the ELISA and VNT.

CONCLUSIONS: This study found no evidence of exposure to RRV in cattle in locations in the Thames-Coromandel district of New Zealand where populations of SSM were present.     

Leptin mRNA expression and serum leptin concentrations as influenced by age, weight, and estradiol in pigs

Two experiments (EXP) were conducted to determine the roles of age, weight and estradiol (E) treatment on serum leptin concentrations and leptin gene expression. In EXP I, jugular blood samples were collected from gilts at 42 to 49 (n = 8), 105 to 112 (n = 8) and 140 to 154 (n = 8) d of age. Serum leptin concentrations increased (P < 0.05) with age and averaged 0.66, 2.7, and 3.0 ng/ml (pooled SE 0.21) for the 42- to 49-, 105- to 112-, and 140- to 154-d-old gilts, respectively. In EXP II, RNase protection assays were used to assess leptin mRNA in adipose tissue of ovariectomized gilts at 90 (n = 12), 150 (n = 11) or 210 (n = 12) d of age. Six pigs from each age group received estradiol (E) osmotic pump implants and the remaining animals received vehicle control implants (C; Day 0). On Day 7, back fat and blood samples were collected. Estradiol treatment resulted in greater (P < 0.05) serum E levels in E (9 +/- 1 pg/ml) than C (3 +/- 1 pg/ml) pigs. Serum leptin concentrations were not affected by age, nor E treatment. Leptin mRNA expression was not increased by age in C pigs nor by F in 90- and 150-d-old pigs. However, by 210 d of age, leptin mRNA expression was 2.5-fold greater (P < 0.01) in E-treated pigs compared to C animals. Serum insulin concentrations were similar between treatments for 210-d-old pigs. However, insulin concentrations were greater (P < 0.05) in E than C pigs at 90 d and greater in C than E animals at 150 d. Plasma glucose and serum insulin-like growth factor-I concentrations were not influenced by treatment. These results demonstrate that serum leptin concentrations increased with age and E-induced leptin mRNA expression is age- and weight-dependent.     

Genetic‐Quantitative Study of the First‐Service Pregnancy Probability of Murrah Heifers

Because of the importance of reproduction in stock breeding systems, it is necessary to find selection criteria that increase reproductive efficiency. The aim of this study was to estimate genetic parameters for the probability of conception on first service (PROB) in Murrah heifers, and its association with other traits of economic interest [age at first calving (AFC), service period, calving interval and milk yield at 270 days], with the purpose of evaluating their use as selection criteria. Reproductive information and first lactation records of 1200 Murrah heifers were used to perform two‐trait analyses between PROB and the other characteristics. Bayesian inference was used to estimate the variance components, considering PROB as threshold and the other as linear factors. The results demonstrate that this trait has heritability of 0.15, indicating the possibility of a genetic gain by using it for selection. With respect to the genetic correlation estimates, the only high‐magnitude association was with AFC (?0.899), which is the current criterion indicating sexual precocity of females. In the light of the parameters estimated, the first‐service pregnancy rate is an alternative for indication of sexual precocity, although presenting a smaller genetic gain than the current standard AFC. Nevertheless, additional research should be conducted regarding this trait to assess the economic importance of its use in dairy buffalo production systems.     

Tracking the evolution of a hydrothermal event plume with a RAFOS neutrally buoyant drifter

The migration and evolution of a deep ocean hydrothermal event plume were tracked with a neutrally buoyant RAFOS float. The float remained entrained in the plume for 60 days, and the plume vorticity was calculated directly from the anticyclonic motion of the float. Concentrations of suspended particles, particulate iron, and dissolved manganese in the plume did not decay significantly during the 60 days, which indicates that event plumes would be easily detectable a year after formation.     

Occurrence and characteristics of sclerotic lesions in uterine arteries of sterile and multiparous pigs

Sows and gilts of the Great White Polish (GWP) breed were classified into groups of 10 each: gilts 8 mo of age (A), sows over 1 yr old with an average litter size of five (BI) and eleven (BII), 2- to 3-yr-old sows with an average litter size of five (CI) and nine (CII), 4- to 6-yr-old sows with an average litter size of six (DI) and nine (DII). Gilts of group A were necropsied on d 10 of the estrous cycle while sows were necropsied 120 to 360 d postpartum. A blood sample obtained by vena cava puncture immediately before exsanguination was quantitated for total cholesterol, free cholesterol, cholesterol ester, total lipid, triglyceride, high and low density lipoprotein and chylomicrons. Postmortem angiograms of the uterine vasculature were evaluated for occurrence of arteriosclerotic lesions of the arteries and their branches. Sections of blood vessels from areas of restriction were examined histologically and quantitated for lipids and proteolytic and lipolytic enzyme activities. With the exception of high density lipoproteins and chylomicrons, serum concentrations of various lipids increased (P less than .01) with age. Restrictions of the lumen were found in uterine arteries and their branches of most gilts in group A and in sows in groups B, C and D, irrespective of litter size. Histology of uterine artery revealed preatherosclerotic lesions in groups B through D. No relationship between the incidence and degree of sclerotic lesions and litter size was evident. However, the incidence and degree of sclerotic lesions increased with age and parity. Results from histopathology were supported by results from measurement of lipids and enzyme activities of the uterine artery wall. Conception rates of sows in groups C and D were lower than those of group B. Many of these sows (70%) failed to conceive during 1 yr even though they displayed normal estrous cycles.     

Serum Levels of Cardiac Markers NT‐proANP and NT‐proBNP in Brachycephalic bitches at Different Gestational Stages

The aim of this study was to determine serum levels of natriuretic peptide precursors (NT‐proANP and NT‐proBNP) during pregnancy in brachycephalic bitches. Fifteen healthy multiparous bitches were selected for this prospective study. Serum levels of NT‐proANP and NT‐proBNP were measured during anoestrous and at 14, 35, 42, 49 and 56 days (2nd, 5th, 6th, 7th and 8th weeks) of pregnancy. Fourteen animals had normal gestations, and one bitch developed single foetus syndrome. The natriuretic peptide levels of this animal were not included in this study; however, it is important to report that its NT‐proANP levels were four times greater than those of normal patients. There was no significant difference (p = 0.072) in NT‐proBNP levels between anoestrous (0.20 ± 0.10 ng/ml) and the different pregnancy weeks (0.27 ± 0.12 ng/ml). There was a positive correlation (p < 0.0001) between NT‐proANP and gestational age, and the levels of this marker increased significantly (p < 0.0001) during the 6th (0.26 ± 0.06 ng/ml), 7th (0.28 ± 0.04 ng/ml) and 8th weeks (0.29 ± 0.05 ng/ml) when compared to anoestrous (0.18 ± 0.02 ng/ml). NT‐proANP serum levels are correlated with gestational development and may be indicative of cardiovascular adaptation in canine brachycephalic pregnancy.     

Opioid modulation of gonadotropin releasing hormone release from the hypothalamic preoptic area in the pig

Two experiments (Exp) were conducted to examine in vitro the release of gonadotropin releasing hormone (GnRH) from the hypothalamus after treatment with naloxone (NAL) or morphine (MOR). In Exp 1, hypothalamic-preoptic area (HYP-POA) collected from 3 market weight gilts at sacrifice and sagitally halved were perifused for 90 min prior to a 10 min pulse of morphine (MOR; 4.5 × 10⁻⁶ M) followed by NAL (3.1 × 10⁻⁵ M) during the last 5 min of MOR (MOR + NAL; N=3). The other half of the explants (n=3) were exposed to NAL for 5 min. Fragments were exposed to KCl (60 mM) at 175 min to assess residual GnRH releasability. In Exp 2, nine gilts were ovariectomized and received either oil vehicle im (V; n=3); 10 μg estradiol-17β/kg BW im 42 hr before sacrifice (E; n=3); .85 mg progesterone/kg BW im twice daily for 6 d prior to sacrifice (P₄; n=3). Blood was collected to assess pituitary sensitivity to GnRH (.2 μg/kg BW) on the day prior to sacrifice. On the day of sacrifice HYP-POA explants were collected and treated as described in Exp 1 except tissue received only NAL. In Exp 1, NAL increased (P<.05) GnRH release. This response to NAL was attenuated (P<.05) by coadministration of MOR. Cumulative GnRH release after NAL was greater (P<.05) than after MOR + NAL. All tissues responded similarly to KCl with an increase (P<.05) in GnRH release. In Exp 2, pretreatment luteinizing hormone (LH) concentrations were lower (P<.05) in E gilts compared to V and P₄ animals with P₄ being lower (P<.05) than V gilts. LH response to GnRH was lower (P<.05) in E pigs than in V and P₄ animals, while the responses was similar between V and P₄ gilts. NAL increased GnRH release in all explants, whereas, KCl increased GnRH release in 6 of 9 explants. These results indicate that endogenous opioid peptides may modulate in vitro GnRH release from the hypothalamus in the gilt.     

Use of Porcine Luteinizing Hormone at Oestrous Onset in a Protocol for Fixed‐Time Artificial Insemination in Gilts

The aim of this study was to evaluate the effect of porcine luteinizing hormone (pLH) given at oestrous onset in gilts, by different routes and doses, on the interval between onset of oestrus and ovulation (IOEO) and reproductive performance using a single fixed‐time artificial insemination (FTAI). A total of 153 gilts were submitted to oestrous detection at 8‐h intervals and assigned to three groups: control – without hormone application and inseminated at 0, 24 and 48 h after oestrous onset; VS2.5FTAI – 2.5 mg pLH by the vulvar submucosal route at oestrous onset and a single FTAI 16 h later; IM5FTAI – 5 mg pLH by the intramuscular route at oestrous onset and a single FTAI 16 h later. More VS2.5FTAI gilts (47.1%; p < 0.05) ovulated within 24 h after oestrous onset than control gilts (25.5%) whereas IM5FTAI gilts had an intermediate percentage (31.4%; p > 0.05). The IOEO tended to be shorter (p = 0.06) in VS2.5FTAI (30.2 ± 1.4 h) than in control (34.7 ± 1.4 h) gilts, but there was no difference (p > 0.05) between control and IM5FTAI (32.8 ± 1.4 h) gilts. Farrowing rate was not different (p > 0.05) among treatments. Total born piglets (TB) was lower (p < 0.05) in VS2.5FTAI (12.3 ± 0.4) than in control gilts (14.1 ± 0.4), whereas intermediate TB was observed in IM5FTAI gilts (13.3 ± 0.4). Due to the advancement of ovulation, reduction of the hormonal dose and the ease of application, the vulvar submucosal route would be the best option for FTAI protocols, but their negative impact on litter size remains to be elucidated. Taking into account the good fertility results obtained in IM5FTAI gilts whose ovulation was not advanced, the possibility of a single FTAI without any hormonal treatment should be further investigated, to establish reliable FTAI protocols for gilts.