The sulfonadyns: a class of aryl sulfonamides inhibiting dynamin I GTPase and clathrin mediated endocytosis are anti-seizure in animal models

We show that dansylcadaverine (1) a known in-cell inhibitor of clathrin mediated endocytosis (CME), moderately inhibits dynamin I (dynI) GTPase activity (IC50 45 μM) and transferrin (Tfn) endocytosis in U2OS cells (IC50 205 μM). Synthesis gave a new class of GTP-competitive dynamin inhibitors, the Sulfonadyns™. The introduction of a terminal cinnamyl moiety greatly enhanced dynI inhibition. Rigid diamine or amide links between the dansyl and cinnamyl moieties were detrimental to dynI inhibition. Compounds with in vitro inhibition of dynI activity <10 μM were tested in-cell for inhibition of CME. These data unveiled a number of compounds, e.g. analogues 33 ((E)-N-(6-{[(3-(4-bromophenyl)-2-propen-1-yl]amino}hexyl)-5-isoquinolinesulfonamide)) and 47 ((E)-N-(3-{[3-(4-bromophenyl)-2-propen-1-yl]amino}propyl)-1-naphthalenesulfonamide)isomers that showed dyn IC50 <4 μM, IC50(CME) <30 μM and IC50(SVE) from 12-265 μM. Both analogues (33 and 47) are at least 10 times more potent that the initial lead, dansylcadaverine (1). Enzyme kinetics revealed these sulfonamide analogues as being GTP competitive inhibitors of dynI. Sulfonadyn-47, the most potent SVE inhibitor observed (IC50(SVE) = 12.3 μM), significantly increased seizure threshold in a 6 Hz mouse psychomotor seizure test at 30 (p = 0.003) and 100 mg kg-1 ip (p < 0.0001), with similar anti-seizure efficacy to the established anti-seizure medication, sodium valproate (400 mg kg-1). The Sulfonadyn™ class of drugs target dynamin and show promise as novel leads for future anti-seizure medications.

An intellectual-disability-associated mutation of the transcriptional regulator NACC1 impairs glutamatergic neurotransmission

Advances in genome sequencing technologies have favored the identification of rare de novo mutations linked to neurological disorders in humans. Recently, a de novo autosomal dominant mutation in NACC1 was identified (NM_052876.3: c.892C > T, NP_443108.1; p.Arg298Trp), associated with severe neurological symptoms including intellectual disability, microcephaly, and epilepsy. As NACC1 had never before been associated with neurological diseases, we investigated how this mutation might lead to altered brain function. We examined neurotransmission in autaptic glutamatergic mouse neurons expressing the murine homolog of the human mutant NACC1, i.e., Nacc1-R284W. We observed that expression of Nacc1-R284W impaired glutamatergic neurotransmission in a cell-autonomous manner, likely through a dominant negative mechanism. Furthermore, by screening for Nacc1 interaction targets in the brain, we identified SynGAP1, GluK2A, and several SUMO E3 ligases as novel Nacc1 interaction partners. At a biochemical level, Nacc1-R284W exhibited reduced binding to SynGAP1 and GluK2A, and also showed greatly increased SUMOylation. Ablating the SUMOylation of Nacc1-R284W partially restored its interaction with SynGAP1 but did not restore binding to GluK2A. Overall, these data indicate a role for Nacc1 in regulating glutamatergic neurotransmission, which is substantially impaired by the expression of a disease-associated Nacc1 mutant. This study provides the first functional insights into potential deficits in neuronal function in patients expressing the de novo mutant NACC1 protein.

Acute-phase protein α-1-acid glycoprotein is negatively associated with feed intake in postpartum dairy cows

α-1-Acid glycoprotein (AGP) is an acute-phase protein that may suppress dry matter intake (DMI), potentially by acting on the leptin receptor in the hypothalamus. Our objectives were to characterize plasma AGP concentration and associations with DMI during the transition period, and to determine the utility of AGP to identify or predict cows with low DMI. Plasma samples (n = 2,086) from 434 Holstein cows in 6 studies were analyzed on d -21, -13 ± 2, -3, 1, 3, 7 ± 1, 14 ± 1, and 21 ± 1 relative to parturition. A commercially available ELISA kit specific for bovine AGP was validated, and 2 internal controls were analyzed on each plate with interplate variation of 15.0 and 17.3%, respectively. Bivariate analysis was used to assess the relationship between AGP and DMI. For significant associations, treatment(study) was added to the model, and quadratic associations were included in the model if significant. Plasma AGP concentration (±SEM) increased from 213 ± 37.3 μg/mL on d -3 to 445 ± 60.0 μg/mL on d 14. On d 3, AGP was associated negatively with DMI in a quadratic manner for wk 1 and wk 2 and linearly for wk 3. Day 7 AGP was associated negatively with DMI in a quadratic manner for wk 2 and linearly for wk 3. Similarly, d 14 AGP was negatively associated with DMI for wk 3 and wk 4. As d 3 AGP concentration increased over the interquartile range, a calculated 1.4 (8.5%), 0.5 (2.7%), and 0.4 (1.9%) kg/d reduction in predicted DMI was detected during wk 1, 2, and 3, respectively. Using bivariate analysis, d 3 AGP explained 10% of the variation in DMI during wk 1. We explored the clinical utility of d 3 AGP to diagnose low DMI, defined as wk 1 DMI >1 standard deviation below the mean. Receiver operating characteristic analysis identified a threshold of 480.9 μg/mL, providing 76% specificity and 48% sensitivity (area under the curve = 0.60). Limited associations occurred between AGP and blood biomarkers; however, AGP was associated with plasma haptoglobin concentration postpartum and incidence of displaced abomasum, retained placenta, and metritis. These results demonstrate a negative association between plasma AGP concentration and DMI in early-postpartum dairy cows, although its diagnostic performance was marginal. Further investigation into whether AGP directly suppresses DMI in dairy cattle is warranted.

Acute and subacute effects of a synthetic kisspeptin analog, C6, on serum concentrations of luteinizing hormone, follicle stimulating hormone, and testosterone in prepubertal bull calves

Kisspeptin (KP) is a neuropeptide integral in regulating puberty and gonadotropin releasing hormone. Compound 6 (C6), a KP analog, is more potent in vitro, has a longer half-life, and may have greater therapeutic applications than KP. To determine the acute and subacute effects of KP and C6 on serum concentrations of luteinizing hormone (LH), follicle stimulating hormones (FSH), and testosterone (T), prepubertal bull calves [12.1 ± 1.1 (SD) weeks of age; 91.2 ± 10.8 kg BW] were assigned to one of three treatment groups [Saline (n = 4), KP (n = 4; 20 nmoles), or C6 (n = 4; 20 nmoles). Treatments were administered intramuscularly once daily for four consecutive days. Blood samples were collected every 15 min for 6 h immediately following treatment administration on Day 1 (acute) and Day 4 (subacute). Serum concentrations of LH, FSH, and T were determined by radioimmunoassay. For each day, effects of treatment, time, and interactions on LH and FSH concentrations and pulse parameters were analyzed using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was a treatment × time interaction during Day 1 (P < 0.0001) and Day 4 (P = 0.02) such that LH concentrations were greatest following administration of C6 (albeit diminished during Day 4). Number of LH pulses were least (P = 0.02) and LH nadirs were highest (P = 0.04) following administration of C6 (P = 0.02). There was no effect of treatment (P = 0.95) or treatment × time interaction (P = 0.10) on serum FSH concentrations during Day 1. During Day 4 FSH concentrations (P = 0.02) and number of FSH pulses (P = 0.02) were least following administration of C6. There was no effect of treatment (P = 0.33), time (P = 0.19) or treatment × time interaction (P = 0.44) on T concentrations. In conclusion, acute and subacute C6 increased LH concentrations and subacute C6 decreased FSH concentrations and pulse parameters. Despite suppression of FSH with subacute daily administration of C6, altered frequency and timing of treatment with KP analogs may have application to affect the onset of puberty in livestock.

Analysis of SUMO1-conjugation at synapses

SUMO1-conjugation of proteins at neuronal synapses is considered to be a major post-translational regulatory process in nerve cell and synapse function, but the published evidence for SUMO1-conjugation at synapses is contradictory. We employed multiple genetic mouse models for stringently controlled biochemical and immunostaining analyses of synaptic SUMO1-conjugation. By using a knock-in reporter mouse line expressing tagged SUMO1, we could not detect SUMO1-conjugation of seven previously proposed synaptic SUMO1-targets in the brain. Further, immunostaining of cultured neurons from wild-type and SUMO1 knock-out mice showed that anti-SUMO1 immunolabelling at synapses is non-specific. Our findings indicate that SUMO1-conjugation of synaptic proteins does not occur or is extremely rare and hence not detectable using current methodology. Based on our data, we discuss a set of experimental strategies and minimal consensus criteria for the validation of SUMOylation that can be applied to any SUMOylation substrate and SUMO isoform.

DOI:http://dx.doi.org/10.7554/eLife.26338.001

Impact of visual, olfactory, and auditory cues on circulating concentrations of ghrelin in wethers

Ghrelin is a hormone that stimulates feed intake and regulates energy homeostasis. A link has been observed in sheep, in which simulated feedings at scheduled meal times resulted in an increase in ghrelin concentrations. The present study sought to characterize the effect of feeding cues outside of scheduled meal times on circulating ghrelin concentrations in sheep. Katahdin wethers (age 201 ± 4.9 d; weight 35 ± 1.2 kg) were not offered feed (CONT; = 5), offered 275 g of feed (FED; = 5), or fitted with a muzzle and offered 275 g of feed (SHAM; = 5) during the sampling period, which began 2.5 h after normally scheduled daily feeding time. Blood samples were collected via jugular catheter every 15 min for 2.5 h. Feed was offered for 15 min 0.5 h after the start of blood sampling. The CONT samples were collected on d 1, and FED and SHAM samples were collected on d 2. The active ghrelin present in the plasma was then analyzed by RIA. After the Shapiro-Wilk W goodness of fit test demonstrated that 1 SHAM wether was an outlier and it was removed, data were tested for effect of treatment (FED, SHAM, or CONT), time, and treatment × time interaction using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was no treatment or time effect ( > 0.05); however, there was a treatment × time interaction on plasma ghrelin concentrations ( = 0.0028) such that ghrelin concentrations in SHAM wethers were greater than in CONT wethers 15, 60, and 90 min after feeding, whereas ghrelin concentrations in SHAM wethers were greater than those in FED wethers 30, 60, 90, and 120 min after feeding ( < 0.05). Within the SHAM treatment, ghrelin concentrations were greater at 15 min than at -30 min. Moreover, ghrelin concentrations within the FED treatment were greater at -30 min than at 30, 45, 60, 90, 105, and 120 min and at -15 min than at 15 through 120 min. The area under the curve representing circulating concentrations of ghrelin in CONT, FED, and SHAM treatments, determined using the trapezoidal method, yielded a treatment effect with a tendency toward significance ( = 0.0866). These results indicate plasma ghrelin concentrations in scheduled meal-fed wethers are elevated following visual, olfactory, and auditory feeding cues outside of scheduled feeding times.

Phenothiazine-derived antipsychotic drugs inhibit dynamin and clathrin-mediated endocytosis

Chlorpromazine is a phenothiazine-derived antipsychotic drug (APD) that inhibits clathrin-mediated endocytosis (CME) in cells by an unknown mechanism. We examined whether its action and that of other APDs might be mediated by the GTPase activity of dynamin. Eight of eight phenothiazine-derived APDs inhibited dynamin I (dynI) in the 2-12 µm range, the most potent being trifluoperazine (IC50 2.6 ± 0.7 µm). They also inhibited dynamin II (dynII) at similar concentrations. Typical and atypical APDs not based on the phenothiazine scaffold were 8- to 10-fold less potent (haloperidol and clozapine) or were inactive (droperidol, olanzapine and risperidone). Kinetic analysis showed that phenothiazine-derived APDs were lipid competitive, while haloperidol was uncompetitive with lipid. Accordingly, phenothiazine-derived APDs inhibited dynI GTPase activity stimulated by lipids but not by various SH3 domains. All dynamin-active APDs also inhibited transferrin (Tfn) CME in cells at related potencies. Structure-activity relationships (SAR) revealed dynamin inhibition to be conferred by a substituent group containing a terminal tertiary amino group at the N2 position. Chlorpromazine was previously proposed to target AP-2 recruitment in the formation of clathrin-coated vesicles (CCV). However, neither chlorpromazine nor thioridazine affected AP-2 interaction with amphiphysin or clathrin. Super-resolution microscopy revealed that chlorpromazine blocks neither clathrin recruitment by AP-2, nor AP-2 recruitment, showing that CME inhibition occurs downstream of CCV formation. Overall, potent dynamin inhibition is a shared characteristic of phenothiazine-derived APDs, but not other typical or atypical APDs, and the data indicate that dynamin is their likely in-cell target in endocytosis.

Building a better dynasore: the dyngo compounds potently inhibit dynamin and endocytosis

Dynamin GTPase activity increases when it oligomerizes either into helices in the presence of lipid templates or into rings in the presence of SH3 domain proteins. Dynasore is a dynamin inhibitor of moderate potency (IC₅₀ ~ 15 μM in vitro). We show that dynasore binds stoichiometrically to detergents used for in vitro drug screening, drastically reducing its potency (IC₅₀ = 479 μM) and research tool utility. We synthesized a focused set of dihydroxyl and trihydroxyl dynasore analogs called the Dyngo™ compounds, five of which had improved potency, reduced detergent binding and reduced cytotoxicity, conferred by changes in the position and/or number of hydroxyl substituents. The Dyngo compound 4a was the most potent compound, exhibiting a 37-fold improvement in potency over dynasore for liposome-stimulated helical dynamin activity. In contrast, while dynasore about equally inhibited dynamin assembled in its helical or ring states, 4a and 6a exhibited >36-fold reduced activity against rings, suggesting that they can discriminate between helical or ring oligomerization states. 4a and 6a inhibited dynamin-dependent endocytosis of transferrin in multiple cell types (IC₅₀ of 5.7 and 5.8 μM, respectively), at least sixfold more potently than dynasore, but had no effect on dynamin-independent endocytosis of cholera toxin. 4a also reduced synaptic vesicle endocytosis and activity-dependent bulk endocytosis in cultured neurons and synaptosomes. Overall, 4a and 6a are improved and versatile helical dynamin and endocytosis inhibitors in terms of potency, non-specific binding and cytotoxicity. The data further suggest that the ring oligomerization state of dynamin is not required for clathrin-mediated endocytosis.

Pyrimidyn compounds: dual-action small molecule pyrimidine-based dynamin inhibitors

Dynamin is required for clathrin-mediated endocytosis (CME). Its GTPase activity is stimulated by phospholipid binding to its PH domain, which induces helical oligomerization. We have designed a series of novel pyrimidine-based "Pyrimidyn" compounds that inhibit the lipid-stimulated GTPase activity of full length dynamin I and II with similar potency. The most potent analogue, Pyrimidyn 7, has an IC50 of 1.1 μM for dynamin I and 1.8 μM for dynamin II, making it among the most potent dynamin inhibitors identified to date. We investigated the mechanism of action of the Pyrimidyn compounds in detail by examining the kinetics of Pyrimidyn 7 inhibition of dynamin. The compound competitively inhibits both GTP and phospholipid interactions with dynamin I. While both mechanisms of action have been previously observed separately, this is the first inhibitor series to incorporate both and thereby to target two distinct domains of dynamin. Pyrimidyn 6 and 7 reversibly inhibit CME of both transferrin and EGF in a number of non-neuronal cell lines as well as inhibiting synaptic vesicle endocytosis (SVE) in nerve terminals. Therefore, Pyrimidyn compounds block endocytosis by directly competing with GTP and lipid binding to dynamin, limiting both the recruitment of dynamin to membranes and its activation. This dual mode of action provides an important new tool for molecular dissection of dynamin's role in endocytosis.

Analysis of synaptic vesicle endocytosis in synaptosomes by high-content screening

Small molecules modulating synaptic vesicle endocytosis (SVE) may ultimately be useful for diseases where pathological neurotransmission is implicated. Only a small number of specific SVE modulators have been identified to date. Slow progress is due to the laborious nature of traditional approaches to study SVE, in which nerve terminals are identified and studied in cultured neurons, typically yielding data from 10-20 synapses per experiment. We provide a protocol for a quantitative, high-throughput method for studying SVE in thousands of nerve terminals. Rat forebrain synaptosomes are attached to 96-well microplates and depolarized; SVE is then quantified by uptake of the dye FM4-64, which is imaged by high-content screening. Synaptosomes that have been frozen and stored can be used in place of fresh synaptosomes, reducing the experimental time and animal numbers required. With a supply of frozen synaptosomes, the assay can be performed within a day, including data analysis.

Triennial Growth Symposium: neural regulation of feed intake: modification by hormones, fasting, and disease

Appetite is a complex process that results from the integration of multiple signals at the hypothalamus. The hypothalamus receives neural signals; hormonal signals such as leptin, cholecystokinin, and ghrelin; and nutrient signals such as glucose, FFA, AA, and VFA. This effect is processed by a specific sequence of neurotransmitters beginning with the arcuate nucleus and orexigenic cells containing neuropeptide Y or agouti-related protein and anorexigenic cells containing proopiomelanocortin (yielding the neurotransmitter α-melanocyte-stimulating hormone) or cells expressing cocaine amphetamine-related transcript. These so-called first-order neurons act on second-order orexigenic neurons (containing either melanin-concentrating hormone or orexin) or act on anorexigenic neurons (e.g., expressing corticotropin-releasing hormone) to alter feed intake. In addition, satiety signals from the liver and gastrointestinal tract signal through the vagus nerve to the nucleus tractus solitarius to cause meal termination, and in combination with the hypothalamus, integrate the various signals to determine the feeding response. The activities of these neuronal pathways are also influenced by numerous factors such as nutrients, fasting, and disease to modify appetite and hence affect growth and reproduction. This review will begin with the central nervous system pathways and then discuss the ways in which hormones and metabolites may alter the process to affect feed intake with emphasis on farm animals.

The pthaladyns: GTP competitive inhibitors of dynamin I and II GTPase derived from virtual screening

We report the development of a homology model for the GTP binding domain of human dynamin I based on the corresponding crystal structure of Dictyostelium discoidum dynamin A. Virtual screening identified 2-[(2-biphenyl-2-yl-1,3-dioxo-2,3-dihydro-1H-isoindole-5-carbonyl)amino]-4-chlorobenzoic acid (1) as a approximately 170 microM potent inhibitor. Homology modeling- and focused library-led synthesis resulted in development of a series of active compounds (the "pthaladyns") with 4-chloro-2-(2-(4-(hydroxymethyl)phenyl)-1,3-dioxoisoindoline-5-carboxamido)benzoic acid (29), a 4.58 +/- 0.06 microM dynamin I GTPase inhibitor. Pthaladyn-29 displays borderline selectivity for dynamin I relative to dynamin II ( approximately 5-10 fold). Only pthaladyn-23 (dynamin I IC(50) 17.4 +/- 5.8 microM) was an effective inhibitor of dynamin I mediated synaptic vesicle endocytosis in brain synaptosomes with an IC(50) of 12.9 +/- 5.9 microM. This compound was also competitive with respect to Mg(2+).GTP. Thus the pthaladyns are the first GTP competitive inhibitors of dynamin I and II GTPase and may be effective new tools for the study of neuronal endocytosis.

Enhancement technology improves palatability of normal and callipyge lambs

The objective of this research was to determine if BPI Processing Technology (BPT) improved palatability of normal (NN) and callipyge (CN) lamb meat and to determine the mechanism by which palatability was improved. Ten ewe and 10 wether lambs of each phenotype were slaughtered, and carcass traits were assessed by a trained evaluator. The LM was removed at 2 d postmortem. Alternating sides served as controls (CON) or were treated with BPT. Muscles designated BPT were injected to a target 120% by weight with a patented solution containing water, ammonium hydroxide, carbon monoxide, and salt. Muscle pH, cooking loss, Warner-Bratzler shear force (WBS), sarcomere length, cooked moisture retention, and desmin degradation were measured. A trained sensory panel and a take-home consumer panel evaluated LM chops. Callipyge had a heavier BW and HCW, less adjusted fat thickness, reduced yield grades, and greater conformation scores than NN (P < 0.05). For LM, NN had shorter sarcomeres, smaller WBS values, greater juiciness ratings, more off-flavors, reduced consumer ratings for raw characteristics (like of portion size, like of color, like of leanness, overall like of appearance) and greater consumer ratings for eating characteristics (like of juiciness, like of flavor) than CN (P < 0.05). For LM, BPT had greater cooked moisture retention, smaller WBS values, greater juiciness ratings, less off-flavors, and greater consumer ratings for raw characteristics (like of portion size, like of color, overall like of appearance) and eating characteristics (like of juiciness, like of flavor) than CON (P < 0.05). Significant phenotype × treatment interactions occurred for LM muscle pH, desmin degradation, tenderness, consumer like of texture/tenderness, and consumer overall like of eating quality (P < 0.05). For LM, BPT increased muscle pH more for NN than CN (P < 0.01) and increased desmin degradation for NN but decreased desmin degradation for CN (P < 0.01). The BPT enhancement improved LM tenderness ratings for CN more than NN (P < 0.05). For consumer like of texture/tenderness, BPT improved ratings for CN more than NN (P < 0.01). For consumer overall like of eating quality, BPT improved ratings for CN more than NN (P < 0.05). In summary, BPT had little to no effect on sarcomere length and desmin degradation, but improved palatability of NN and CN lamb by increasing cooked moisture retention, improving consumer acceptability of CN to near-normal levels.

Interaction of kisspeptin and the somatotropic axis

Kisspeptin, a regulator of gonadotropin-releasing hormone, has been hypothesized as an integrator of nutrition and hormones critical to metabolism and the regulation of reproduction. Growth hormone (GH) is necessary for optimal reproduction and recent evidence suggests that its secretion may be influenced by kisspeptin. The objectives of this study were to determine whether the effect of kisspeptin to stimulate GH release is due to an interaction with growth hormone-releasing hormone (GHRH) or somatostatin (SS), or an effect at the hypothalamus. Intravenous injection and infusion of kisspeptin [500 pmol/kg BW (650 ng/kg)/h × 5 h] to cows (n = 5) increased serum concentrations of luteinizing hormone (LH) but not GH. Pretreatment with kisspeptin injection and infusion in cows (n = 5) reduced the stimulatory effect of GHRH (0.05 μg/kg BW) on GH secretion. However, the magnitude of the GH response to GHRH (assessed by incremental AUC) was not affected by kisspeptin. In these same cows, administration of kisspeptin prevented the increase in GH induced by SS infusion (0.5 μg/kg BW/ h × 1.5 h) withdrawal. Peripheral administration of kisspeptin [200 and 1,000 pmol/kg BW (260 and 1,300 ng/kg)] increased serum concentrations of LH but not GH in ewes (n = 8). However, concentrations of GH were stimulated by central kisspeptin treatment [100 and 200 pmol/kg BW (130 and 260 ng/kg)] in ewes. In addition to activating the gonadotropic axis, kisspeptin can activate the somatotropic axis in ruminants. Present data support the concept of a central site of action for this effect.

Comparative aspects of the endotoxin- and cytokine-induced endocrine cascade influencing neuroendocrine control of growth and reproduction in farm animals

Disease in animals is a well-known inhibitor of growth and reproduction. Earlier studies were initiated to determine the effects of endotoxin on pituitary hormone secretion. These studies found that in sheep, growth hormone (GH) concentration was elevated, whereas insulin-like growth factor-I (IGF-I) was inhibited, as was luteinizing hormone (LH). Examination of the site of action of endotoxin in sheep determined that somatotropes expressed the endotoxin receptor (CD14) and that both endotoxin and interleukin-I beta activated GH secretion directly from the pituitary. In the face of elevated GH, there is a reduction of IGF-I in all species examined. As GH cannot activate IGF-I release during disease, there appears to be a downregulation of GH signalling at the liver, perhaps related to altered nitration of Janus kinase (JAK). In contrast to GH downregulation, LH release is inhibited at the level of the hypothalamus. New insights have been gained in determining the mechanisms by which disease perturbs growth and reproduction, particularly with regard to nitration of critical control pathways, with this perhaps serving as a novel mechanism central to lipopolysaccharide suppression of all signalling pathways. This pathway-based analysis is critical to the developing novel strategies to reverse the detrimental effect of disease on animal production.

Evaluation of immune system function in neonatal pigs born vaginally or by Cesarean section

Full term crossbred sows were selected to study the interaction of the immune system, hypothalamus-pituitary-adrenal axis, and growth in pigs born by Cesarean section (c-section; n=4 sows) or vaginal birth (n=4 sows). Gestation length and birth weight did not differ between vaginal birth and c-section pigs (P=0.34 and 0.62, respectively). Blood and tissue samples were collected from 44 pigs at birth. Forty-five pigs were weaned at 13 d. On d 14, pigs received an i.p. injection of lipopolysaccaride (LPS; 150 microg/kg) or saline at min 0, and blood samples were collected at -20, -10, 0, 5, 10, 20, 40, 60, 90, and 120 min. Vaginal birth pigs had 21% greater average daily gain than c-section pigs on d 14 (P<0.01). Basal serum concentrations of adrenocorticotrophin (ACTH) and cortisol were greater in c-section than vaginal birth pigs at birth (P<0.01) but were not different at 14 d (P=0.99 and 0.80, respectively). LPS increased serum concentrations of ACTH, cortisol, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha; P<0.01) but the response was not different between c-section and vaginal birth (P>0.22). Basal serum concentrations of TNF-alpha tended to be greater in c-section vs vaginal birth pigs at 14 d (P=0.0967); however, basal serum concentrations of IFN-gamma tended to be lower in c-section pigs vs vaginal birth pigs at 14 d (P=0.0787). Expression of interleukin (IL)-6, IL-6 receptor, IL-1beta, and TNF-alpha mRNA did not differ between vaginal birth and c-section pigs but changed in an age and tissue dependent manner. Thus, reduced growth rate of c-section pigs is associated with altered immune system function.

Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle1,2

The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.

Interleukin-1beta and tumor necrosis factor-alpha mediation of endotoxin action on growth hormone

In humans and sheep, endotoxin (LPS) administration results in increased growth hormone (GH) concentrations. To determine the role of cytokines in the effect of LPS on GH, sheep were challenged with IL-1beta or TNF-alpha. GH data were compared with results with LH, where the major effects of LPS are known to act via the hypothalamus. Intracerebroventricular (icv) administration of IL-1beta or TNF-alpha did not alter plasma concentrations of GH. Endotoxin was then administered intravenously (iv) in combination with icv injection of IL-1 receptor antagonist (IL-1RA), TNF antagonist (sTNF-R1), or saline. Administration of LPS increased GH (P < 0.0001), although coadministration of IL-1ra or sTNF-R1 icv did not alter GH response to LPS. In contrast, plasma concentrations of LH were profoundly inhibited by icv administration of either cytokine (P < 0.03), but the LH response to LPS was not altered by cytokine antagonists. Intravenous administration of either IL-1beta or TNF-alpha increased plasma concentrations of GH (P < 0.0001). Administration of IL-1RA and sTNF-R1 iv prevented LPS-induced increases in GH. Although LH was suppressed by high iv doses of IL-1beta (P = 0.0063), the antagonists did not alter the LH response to LPS. To determine whether LPS might directly activate GH release, confocal microscopy revealed colocalization of CD14, the LPS receptor, with GH and, to a lesser extent, LH and some prolactin (PRL)-containing cells, but not ACTH or TSH. These data are consistent with the effects of LPS on GH secretion originating through peripheral cytokine presentation to the pituitary, as well as a potential to act directly on selective populations of pituitary cells via CD14.

Melanocortin-4 receptor in sheep: a potential site for therapeutic intervention in disease models

Reduced appetite combined with increased metabolic rate and decreased lean body mass is a major consequence of disease and other stressors. Studies in rodent species suggest that an understanding of appetite regulation may provide methodologies for intervention to prevent the deterioration of body mass such as observed with cancer or infectious diseases. For example, melanocortin-4 receptor (MC4-R) antagonists have shown a remarkable ability to reverse or prevent cachexia in rodents with sarcoma or treated with endotoxin. Studies in sheep have indicated that a number of peptide neurotransmitters may have a role in regulating appetite in this species. For example, agouti related protein mRNA and protein levels are dramatically altered with fasting in sheep. Moreover, agouti related protein, neuropeptide Y, melanin concentrating hormone and orexin are potent stimuli to increase feed intake in sheep. Recent studies have indicated that one of these neurotransmitters, NPY, can work in principal to improve appetite in endotoxin-treated sheep. Current studies are examining the role that MC4-R antagonists may have in the prevention or correction of body mass wasting diseases as well as practical applications in animal production.

Intracerebroventricular melanin-concentrating hormone stimulates food intake in sheep

Melanin-concentrating hormone (MCH) stimulates feeding when injected intracerebroventricularly (ICV) in rats. At present it is not clear whether the function of MCH is similar in ruminants, which are species with a continuous delivery of nutrients. Therefore the current investigation sought to determine the role of MCH in sheep. In the first experiment, six, castrate male sheep were satiated and received one of four treatments [saline, 0.1, or 1.0 nmol/kg MCH, and NPY (0.1 nmol/kg)] injected ICV over 30s, then infused ICV for 6 h ( approximately 500 microl/h). Food intake was measured for 2 h before and at 2, 4, 6, 8, 12 and 24 h. In this experiment, feed intake was increased (P<or=0.05) in NPY treated sheep only. In the second experiment, the same sheep were fed to satiety and then randomized to receive one of six treatments [saline and either 0.1, 1.0 or 5.0 nmol/kg MCH, 0.1 nmol/kg NPY, or MCH+NPY (0.1 nmol/kg)] injected ICV over 30 s. Food intake was measured for 2 h before and at 2, 4, 6, 8, 12, and 24 h after ICV injection. All doses of MCH as well as NPY resulted in greater (P<or=0.05) food intake than saline. In order to determine whether MCH expression was regulated by fasting, brains from fed and 3-day fasted sheep were fixed in situ, sectioned in the coronal plane, and subjected to dual-label immunohistochemistry using Fos as a marker for neuronal activity. Nutritional state (fed or fasted) did not alter Fos expression in MCH neurons. Finally, using real time PCR, MCH mRNA was unchanged by fasting. In this study we found bolus ICV MCH to be a potent stimulus to food intake in sheep, but MCH was not regulated by fasting.

Leptin, tumor necrosis factor-α (TNF), and CD14 in ovine adipose tissue and changes in circulating TNF in lean and fat sheep2

Four studies were designed to determine whether 1) tumor necrosis factor-alpha (TNF) and the Lipopolysaccharide (LPS) binding ligand, CD14, are produced by sheep adipose tissue; 2) nutritional reserves and/or short-term fasting affect circulating concentrations of TNF; 3) there is a relationship between TNF and metabolic factors in sheep; and 4) inflammation alters circulating concentrations of leptin. In Exp. 1 and 2, ewes were assigned, based on ultrasonic assessments of last-rib subcutaneous fat measurements to fat (fat thickness > 1 cm; mean = 1.52 +/- 0.03 cm) or thin (fat thickness < 1 cm; mean = 0.25 +/- 0.03 cm) groups. Fat and thin ewes were assigned to fed or fasted groups for a total of four groups (fed-fat; fasted-fat; fed-thin; fasted-thin). Fed-ewes had ad libitum access to feed, and fasted-ewes were prohibited feed 48 h before initiation of sample collection. In Exp. 1, subcutaneous fat samples were collected from just above the last rib for detection of TNF and CD14 mRNA, and immunoreactivity. Tumor necrosis factor-alpha-like immunoreactivity in adipocytes was sparse, more pronounced in cells in fed-ewes than fasted-ewes, and localized to membranes between adjacent cells in nucleated regions. Immunoreactivity for CD14 was minimally observed but present in adipocytes and widely expressed in infiltrating monocytes and epithelial vascular cells. Leptin was detected in adipocytes. In Exp. 2, plasma samples collected every 6 h for 24 h were analyzed for plasma concentrations of TNF. Fat ewes had greater plasma concentrations of TNF than thin ewes (P = 0.039). In Exp. 3, wethers were injected i.v. with interleukin-1beta or TNF. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not affected by treatment (P > 0.39). In Exp. 4, wethers were injected with LPS. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not altered by LPS (P > 0.20). These results provide evidence: 1) of TNF-like immunoreactivity within fat tissue; 2) that elements within fatty tissues have CD14 that may allow adipocyte function to be directly affected by LPS; 3) that plasma concentrations of leptin are not altered by LPS treatment; and 4) that circulating concentrations of TNF are elevated with obesity in sheep.

Endotoxin inhibition of luteinizing hormone in sheep

Administration of endotoxin suppresses circulating concentration of luteinizing hormone (LH) in a number of species, including rats, sheep, cattle, and non-human primates. Specifically, endotoxin administration decreases circulating concentration of LH and LH pulses frequency in castrated male sheep. Endotoxin could alter circulating concentrations of LH via actions at the hypothalamus through altered GnRH production and/or release, or endotoxin could alter circulating concentrations of LH at the level of the pituitary via inhibition of LH production and release or inhibition of LH in response to GnRH. The site of endotoxin suppression of circulating concentrations of LH as well as possible mediators of endotoxin suppression of circulating concentrations of LH, including cortiocotropin-releasing hormone, arginine vasopressin, glucocorticoids, inflammatory cytokines, prostaglandins, and opioids, are discussed.

Estradiol plus progesterone treatment modulates select elements of the proinflammatory cytokine cascade in steers: attenuated nitric oxide and thromboxane B2 production in endotoxemia

Estradiol plus progesterone (EP) implants have been shown to favorably alter the time course or decrease the severity of many of the clinical manifestations associated with coccidiosis and endotoxemia in calves. This study evaluated the effect of EP treatment on plasma tumor necrosis factor-alpha (TNF), thromboxane (TXB), prostacyclin (PRC), nitrite and nitrate (NO[x]), and cortisol. Holstein steer calves were divided into four groups: control, EP, endotoxin (LPS), and EP + LPS (n = five/group). Estradiol/progesterone pellets (Synovex-S) were implanted subcutaneously when calves reached 20 wk of age. One week after implantation, calves were injected i.v. with endotoxin (i.e., lipopolysaccharide; LPS, 0.6 microgram/kg of BW) or nonpyrogenic saline placebo. Body temperature was measured and blood was collected before injection and at 1, 2, 3, 4, 6, and 8 h thereafter. Plasma concentrations of TNF, cortisol, TXB, PRC, NO[x], were measured. Body temperature increased in both LPS and LPS-EP calves, but had returned to normal by 6 h in the LPS-EP group (P < 0.05). Plasma TNF and cortisol increased after LPS (P < 0.01), but were not differentially affected by EP treatment. Likewise, EP did not affect the magnitude of increase in LPS-induced PRC, but EP decreased the magnitude of increase in TXB (P < 0.05). Plasma NO[x]) levels were increased (P < 0.01) in calves after LPS; treatment with EP attenuated the LPS-associated increase in plasma NO[x] levels. These results suggest that EP exerts specific effects on different components of the proinflammatory cytokine cascade. Although the initiation of responses mediated by TNF, cortisol, and PRC do not seem to be differentially affected by EP, components of the nitric oxide- and TXB-axis responses to LPS are decreased in calves pretreated with EP.

Luteinizing hormone and growth hormone secretion in ewes infused intracerebroventricularly with neuropeptide Y

Neuropeptide Y (NPY) provides an important hypothalamic link between nutritional status and neuroendocrine mechanisms regulating growth and reproduction. The objective of the following series of experiments was to determine the effects of single or continuous administration of NPY on secretion of luteinizing hormone (LH) and (or) growth hormone (GH). In experiment 1, four ovariectomized (OVX) ewes and four OVX + estrogen-treated ewes each received, in a 4 x 4 Latin Square arrangement of treatments, a single injection of 0, 0.5, 5, or 50 microg NPY via an intracerebroventricular (i.c.v.) cannulae to determine the effects on secretion of GH. NPY significantly elevated serum GH at the 50 microg dose regardless of estrogen exposure (P = 0.003). In experiment 2, eight OVX ewes were infused i.c.v. with NPY or saline (n = 4/trmt) continuously for 20 h in a linearly increasing dose, ending at 50 microg/h NPY. Blood samples were collected via jugular cannulae every 10 min during hour -4-0 (interval 1, pre-treatment), hour 6-10 (interval 2) and hour 16-20 (interval 3) relative to the initiation of infusion (0 h). Mean LH and LH pulse frequency were lower in NPY- versus saline-infused ewes during intervals 2 and 3 (P < 0.01), but NPY had no discernable effect on serum GH (P > 0.10). In experiment 3, four OVX ewes were continuously infused with NPY as in experiment 2, except that the maximum 50 microg/h dose was achieved after only 10 h of infusion. Blood samples were collected every 10 min, beginning 4 h before and continuing until 4h after the NPY infusion. Mean serum LH changed significantly over time (P = 0.0001), decreasing below pre-treatment levels by hour 3 of NPY infusion (P < 0.01), and returning to pre-treatment concentrations following the end of infusion (P > 0.15). Serum GH also changed significantly over time (P < 0.001). Mean GH levels tended to be greater than pre-treatment levels by hour 2 of infusion (P < 0.08), but thereafter returned to basal levels. Serum GH also increased following the end of NPY infusion (P < 0.03). From these data we conclude that NPY exerts a persistent inhibitory effect on secretion of LH, and may stimulate the secretion of GH during the initiation and cessation of infusion of NPY. These observations support a role for NPY in mediating the effects of undernutrition on both LH and GH, and also provide evidence for potential mechanisms by which leptin, acting through NPY, may stimulate the secretion of GH.

Leptin in horses: tissue localization and relationship between peripheral concentrations of leptin and body condition

Obesity has been a major concern in the horse industry for many years, and the recent discovery of leptin and leptin receptors in numerous nonequine species has provided a basis for new approaches to study this problem in equine. The objectives were to: 1) clone a partial sequence ofthe equine leptin and leptin receptor genes so as to enable the design of primers for RT-PCR determination of leptin and leptin receptor gene presence and distribution in tissues, 2) develop a radioimmunoassay to quantify peripheral concentrations of leptin in equine, 3) determine if peripheral concentrations of leptin correlate with body condition scores in equine, and 4) determine if changing body condition scores would influence peripheral concentrations of leptin in equine. In Experiment 1, equine leptin (GenBank accession number AF179275) and the long-form of the equine leptin receptor (GenBank accession number AF139663) genes were partially sequenced. Equine leptin receptor mRNA was detected in liver, lung, testis, ovary, choroid plexus, hypothalamus, and subcutaneous adipose tissues using RT-PCR. In Experiment 2, 71 horses were categorized by gender, age, and body condition score and blood samples were collected. Sera were assayed for leptin using a heterologous leptin radioimmunoassay developed for equine sera. Serum concentrations of leptin increased in horses with body condition score (1 = thin to 9 = fat; r = 0.64; P = 0.0001). Furthermore, serum concentrations of leptin were greater in geldings and stallions than in mares (P = 0.0002), and tended to increase with age of the animal (P = 0.08). In Experiment 3, blood samples, body weights, and body condition scores were collected every 14 d from 18 pony mares assigned to gain or lose weight over a 14-wk interval based on initial body condition score. Although statistical changes (P = 0.001) in body condition scores were achieved, congruent statistical changes in peripheral concentrations of leptin were not observed, likely due to the small range of change that occurred. Nonetheless, serum concentrations of leptin tended to be greater in fat-restricted mares than in thin-supplemented mares (P = 0.09). We conclude that leptin and leptin receptors are present in equine tissues and that peripheral concentrations of leptin reflect a significant influence of fat mass in equine.

Regulation of the growth hormone and luteinizing hormone response to endotoxin in sheep

Infectious disease processes cause physiological adaptations in animals to reorder nutrient partitioning and other functions to support host survival. Endocrine, immune and nervous systems largely mediate this process. Using endotoxin injection as a model for catabolic disease processes (such as bacterial septicemia), we have focused our attention on regulation of growth hormone (GH) and luteinizing hormone (LH) secretion in sheep. Endotoxin produces an increase in plasma GH and a decrease in plasma LH concentrations. This pattern can be reproduced, in part, by administration of various cytokines. Antagonists to both interleukin-1 (IL-1) and tumor necrosis factor (TNF) given intravenously (IV) prevented the endotoxin-stimulated increase in GH. Since endotoxin will directly stimulate GH and LH release from cultured pituitary cells, the data suggest a pituitary site of action of the endotoxin to regulate GH. Studies with portal vein cannulated sheep indicated that gonadotropin releasing hormone was inhibited by endotoxin, suggesting a central site of action of endotoxin to regulate LH. However, other studies suggest that endotoxin may also regulate LH secretion at the pituitary. Thus, IL-1 and TNF regulate GH release from the pituitary gland while endotoxin induces a central inhibition of LH release.

Effect of body fat mass and nutritional status on 24-hour leptin profiles in ewes

This study was designed to determine the effect of feeding or fasting of fat or thin ewes on 24-h leptin profiles. Ewes were assigned, based on ultrasonic assessments of last-rib subcutaneous fat measurements, into fat (fat thickness > 1 cm; mean = 1.52 +/- 0.03 cm; range 1.14 to 2.18 cm) or thin (fat thickness < 1 cm; mean = 0.25 +/- 0.03 cm; range 0.03 to 0.84 cm) groups. Fat and thin ewes were then assigned to either fed or fasted (deprived of feed) groups consisting of five ewes per group. Thus, four groups existed and were designated as fat-fed, fat-fasted, thin-fed, and thin-fasted. Fed ewes had ad libitum access to feed throughout the study. Fasted ewes were prohibited access to feed beginning 48 h preceding the experiment. Plasma samples were collected for leptin analysis from ewes every 15 min for 24 h beginning 48 h after the initiation of feed restriction or the congruent interval in fed ewes. Data were subjected to CLUSTER pulse analysis procedures. Profiles of plasma concentrations of leptin were episodic in nature and did not differ in a diurnal manner. Fed ewes had greater mean concentrations of leptin, area under the curve, number of peaks, peak height, peak nadir, and a shorter interval between peaks than fasted ewes (P < or = 0.05). Fat ewes had greater mean concentrations of leptin, area under the curve, number of peaks, peak height, peak nadir, and a shorter interval between peaks than thin ewes (P < 0.02). There also was a tendency for a body condition x treatment interaction for number of peaks (P = 0.073) and interval between peaks (P = 0.056). These results provide evidence that plasma concentrations of leptin are episodic in nature and are influenced by nutritive state and fat thickness over the ribs, but display no circadian variation.

Breeding ewes out-of-season using melengestrol acetate, one injection of progesterone, or a controlled internal drug releasing device

A series of studies was designed to identify methods of improving out-of-season breeding success in ewes. In Experiment 1, 190 mature ewes were assigned to receive in April, either: (A) a control ration of 0.3 kg corn twice daily for 8 d before ram introduction (control ewes n=49), (B) the control ration containing 0.125 mg of melengestrol acetate (MGA) in 0.3 kg corn (MGA8a ewes n=46), (C) the control ration or 7.5 d followed by 1 feeding of 0.5 mg MGA in 0.3 kg corn (MGA1 ewes n=48), or (D) the control ration plus a 20 mg i.m. injection of progesterone on D 8 (P ewes n=47). Ewes were exposed to rams for 21 d. A greater percentage of MGA8a and P ewes lambed than did control ewes (P < 0.04). The lambing rate was greatest among MGA8a (P < 0.02 vs. control), intermediate among P ewes (P < 0.19 vs. control) and least among MGA1 and control ewes (P > 0.79). In Experiment 2, 70 mature ewes were assigned to receive in June, either: (A) a control ration of 0.3 kg of corn twice daily for 8 d before to ram introduction (control ewes n=25), (B) the control ration containing 0.125 mg of MGA per 0.3 kg corn (MGA8b ewes n=21), or (C) the control ration and simultaneous treatment of ewes with a progesterone-containing controlled internal-drug releasing device (CIDR ewes n=24). Ewes were exposed to rams for 21 d. Both CIDR and MGA8b ewes exhibited estrus earlier than did control ewes (P < 0.01). The CIDR ewes exhibited estrus earlier than did the MGA8b ewes (P < 0.05). A greater percentage of ewes treated with CIDR or MGA8b lambed than did control ewes (P < 0.01), with more CIDR ewes lambing than MGA8b ewes (P < 0.01). The lambing rate was greater in CIDR ewes than in control ewes (P < 0.04). These data provide evidence that several options exist to improve pregnancy success in ewes bred out of season and that success varies with method of treatment.

Central infusion of leptin into well-fed and undernourished ewe lambs: effects on feed intake and serum concentrations of growth hormone and luteinizing hormone

Leptin has been implicated in the regulation of feed intake, growth, and reproduction. The objective of this study was to determine if centrally administered leptin would affect feed intake and the secretion of growth hormone (GH) and luteinizing hormone (LH) in ewe lambs. Eighteen ewe lambs were ovariectomized and fitted with intracerebroventricular (i.c.v.) cannulae. Lambs were randomly assigned to receive either a maintenance diet (fed), or a diet that provided 38% of maintenance requirements (diet-restricted) for 14 weeks. Subsequently, recombinant ovine leptin or vehicle was continuously infused, via i.c.v. cannulae, in a linearly increasing dose for 8 days, reaching a maximum of 1.25 microg/kg per h. Feed intake was recorded on days -1 to 7. Blood was collected via jugular cannulae every 10 min for 4 h on days 0, 2, 4, 6 and 8 for the determination of serum leptin, insulin, LH and GH. Leptin suppressed feed intake in fed lambs on days 4 to 7 (P<0.001), but had no effect on feed intake in diet-restricted lambs (P>0.25). Fed lambs had greater serum concentrations of leptin than diet-restricted lambs (P=0.007). Also, although not different on day 0 (pretreatment), on day 8 serum leptin concentrations were greater in leptin-treated lambs than in saline-treated lambs (P=0.003). Insulin was lower in diet-restricted than in fed lambs (P=0.003), but was not affected by leptin treatment (P=0.82). LH pulse frequencies were lower in diet-restricted lambs than in fed lambs (P=0.038), but were not affected by leptin treatment (P=0.85). Mean serum GH was greater in diet-restricted than in fed lambs (P<0.01). In diet-restricted lambs treated with leptin or saline, mean GH did not differ on day 0, but increased in response to leptin treatment (P<0.006). Treatment of fed lambs with leptin did not affect serum GH (P>0.32). From this work, we propose that leptin represents an important functional link between adipose stores and hypothalamic function in ruminants. We demonstrate that leptin concentrations change in response to reduced nutritional status, and that leptin has the ability to regulate multiple physiological processes in lambs, including both feed intake and secretion of GH.

Postnatal function of the somatotrophic axis in pigs born naturally or by Caesarian section

This study was designed to determine what effects the birth process would have on development of the somatotrophic axis in neonatal pigs. Eight crossbred sows were selected (n = 4 natural birth and n = 4 Caesarian section) for the present study. Blood and tissue samples from 38 pigs were collected at birth. Twenty pigs were maintained with natural birth sows until sacrificed for blood and tissue collection at 2 wk of age. Gestational age at birth did not differ (P > 0.16) between natural birth and C-section pigs. Average daily gain (ADG) from birth until 2 wk of age was reduced (P < 0.0001) by 39.3% in the C-section pigs as compared to the natural birth pigs. Serum growth hormone (GH) did not differ (P > 0.86) at birth, but was greater (P < 0.024) at 2 wk in C-section pigs. Serum insulin-like growth factor 1 (IGF-1) was greater at birth (P < 0. 0025) and at 2 wk of age (P < 0.035) in the natural birth pigs. Serum concentration of IGF-2 did not differ at birth (P > 0.8) but was greater (P < 0.043) in natural birth pigs at 2 wk of age. Pituitary content of GH mRNA and GH-releasing hormone receptor mRNA did not differ (P > 0.90) between groups regardless of age; however, expression of both mRNAs declined (P < 0.0003) from birth until 2 wk of age. There tended to be a birth type X age interaction (P < 0. 082) for liver IGF-1 mRNA such that C-section pigs had a greater expression at 2 wk of age. Liver IGF-1 mRNA expression increased (P < 0.0001) in both groups from birth to 2 wk of age. Liver expression of GH receptor mRNA was greater in C-section pigs at birth (P < 0. 04) and 2 wk of age (P < 0.03). These data provide evidence that the natural birth process affects postnatal development and/or function of the somatotrophic axis in the neonatal pig.

Effect of cerebroventricular infusion of insulin and (or) glucose on hypothalamic expression of leptin receptor and pituitary secretion of LH in diet-restricted ewes

The objective was to determine the effect of central infusion of insulin and (or) glucose on hypothalamic expression of leptin receptor and pituitary secretion of LH in the ewe. Twenty-two ovariectomized ewes (32 wk of age) were fitted with two lateral cerebroventricular (LCV) cannulae and fed 33% of NRC requirements for 8 wk. Ewes (n> or =5/group) were then infused, via LCV cannulae, with artificial cerebrospinal fluid (aCSF) or aCSF containing physiological concentrations of insulin (INS), glucose (GLU), or INS + GLU; the mass of each increasing linearly from Day 0 (mass = 0 units/h) to Day 8 (mass of INS = 80 mIU/hr and GLU = 10 mg/hr). Jugular serum was collected every 12 min for 4 hr on Days 0, 2, and 4. Ewes treated with INS or INS + GLU had greater (P<0.06) mean concentrations of LH than aCSF treated ewes on Day 2 (13.8+/-1.8 and 12.5+/-1.3 > 8.0+/-3.3 ng/ml). Furthermore, on Day 4, concentrations of LH in INS treated ewes exceeded that (P<0.07) of aCSF treated ewes (14.8+/-2.0 > 7.4+/-3.0 ng/ml). Expression of NPY mRNA did not differ between treatments (P = 0.87). Leptin receptor mRNA expression was dramatically reduced (P<0.0002) in INS+GLU versus aCSF treated ewes. These data provide evidence to suggest that insulin may be an important component of hypothalamic mechanisms regulating secretion of LH and expression of leptin receptors in undernourished ruminants.

Non-surgical catheterization of the jugular vein in young pigs

Current methods utilized for serial blood collection in the young pig are limited due to the stress and/or discomfort to which the pig is exposed. Thus, we have developed a non-surgical, minimally invasive cannulation technique which allows jugular vein catheter placement in the young pig without causing extended discomfort or stress. The procedure described is rapid (approximately 8 min/pig) and relatively simple, requiring only minimal anaesthesia for immobilization of the pig during the procedure. Routinely, 2-week-old piglets are standing in their pens within 15-20 min from initiation of the procedure. Piglets recover rapidly from the procedure and display no clinical indications of pain or discomfort. Serum concentrations of cortisol, a standard indicator of stress and/or discomfort, are asymptomatic within 2 h of completing the procedure (k = 26.14+/-3.03 ng/ml). Stress is limited to the initial immobilization of the piglets. With this technique of cannulation, we routinely maintain catheter patency for 2 days, and often for as long as 5 days.

Birth by caesarian section alters postnatal function of the hypothalamic-pituitary-adrenal axis in young pigs

Eight crossbred sows were selected for the present study (n = 4 vaginal delivery and n = 4 Caesarian section [C-section]). Gestation length did not differ between vaginal delivery and C-section pigs (113.6 +/- .1 and 113.2 +/- .3 d, respectively; P > .16). Blood and tissue samples from 38 pigs were collected at birth. All remaining pigs were sustained with vaginal-delivery sows until 2 wk of age (n = 39). At 2 wk of age, remaining pigs were catheterized for blood sample collection to assess pituitary-adrenal responsiveness to an injection of corticotropin-releasing hormone (CRH; 10 microg/kg). Blood samples were collected at -30, -15, 0, 5, 10, 20, 40, 60, and 90 min; pigs received CRH or saline at time 0. Pigs were killed and tissue samples were collected immediately following the last blood sample. Serum concentrations of ACTH and cortisol (CS) were measured. Total RNA was isolated from the pituitary and adrenal glands to evaluate gene expression for mRNA specific for pro-opiomelanocortin (POMC) and for the ACTH receptor. Centrifuged clot:blood ratio was reduced in the C-section pigs at birth (P < .001) and at 2 wk of age (P < .043), compared with the vaginally delivered pigs. Basal serum concentration of ACTH was greater in C-section than in vaginally delivered pigs at birth (P = .01) but did not differ at 2 wk of age (P = .42). Basal serum concentration of CS was not different at birth (P = .86) but was greater in C-section pigs than in vaginally delivered pigs at 2 wk of age (P < .04). Serum concentration of ACTH was not different (P > .99) between the two groups of pigs following the CRH challenge. However, serum concentration of CS was greater (P < .05) in C-section pigs following the CRH challenge. Expression of ACTH receptor mRNA tended to be greater in C-section pigs at birth (P < .063) and at 2 wk of age (P < .016). There was no difference in POMC mRNA between treatments (P > .73); however, there was a developmental increase (P < .001) from birth to 2 wk of age. These data indicate that the birth process plays an important role in postnatal function of the hypothalamic-pituitary-adrenal axis in young pigs.

The role of leptin in nutritional status and reproductive function

Infertility associated with suboptimal nutrition is a major concern among livestock producers. Undernourished prepubertal animals will not enter puberty until they are well fed; similarly, adult, normally cyclic females will stop cycling when faced with extreme undernutrition. Work in our laboratory has focused on how body fat (or adiposity) of an animal can communicate to the brain and regulate reproductive competence. In 1994, the discovery in rodents of the obese (ob) gene product leptin, secreted as a hormone from adipocytes, provided a unique opportunity to understand and hence regulate whole body compositional changes. There is now evidence that similar mechanisms are functioning in livestock species in which food intake, body composition, and reproductive performance are of considerable economic importance. Leptin has been reported to be a potent regulator of food intake and reproduction in rodents. There is evidence indicating that at least some of the effects of leptin occur through receptor-mediated regulation of the hypothalamic protein neuropeptide Y (NPY). NPY is a potent stimulator of food intake, is present at high concentrations in feed-restricted cattle and ewes, and is an inhibitor of LH secretion in these livestock species. In our investigations in sheep, we have cloned a partial cDNA corresponding to the ovine long-form leptin receptor, presumably the only fully active form, and have localized the long-form leptin receptor in the ventromedial and arcuate nuclei of the hypothalamus. Leptin receptor mRNA expression was colocalized with NPY mRNA-containing cell bodies in those regions. We have also determined that hypothalamic leptin receptor expression is greater in feed-restricted ewes than in well-fed ewes. These observations provide a foundation for future investigations into the nutritional modulators of reproduction in livestock.

Methscopolamine bromide blocks hypothalamic-stimulated release of growth hormone in ewes

Twenty-five nonlactating ewes were used to test the hypothesis that methscopolamine bromide (MB) blocks secretion of growth hormone (GH) by affecting hypothalamic rather than pituitary mechanisms. Ewes were randomly assigned to receive a s.c. injection of 96 mg of MB or 2 mL of saline at min = 0. Saline-treated ewes were assigned to receive a subsequent (at +60 min) i.v. injection of 10 microg of growth hormone-releasing hormone (GHRH) to test pituitary responsiveness or .3 mg of clonidine to test hypothalamic responsiveness. Methscopolamine bromide-treated ewes were assigned to receive a subsequent (at +60 min) i.v. injection of 10 microg of GHRH, .3 mg of clonidine, or 2 mL of saline. Jugular blood samples were collected at 10-min intervals from -120 min to +240 min, and serum concentrations of GH were quantified with a RIA. No difference was detected in serum concentrations of GH with respect to MB vs saline treatment (P = .20). Concentrations of GH increased in saline-pretreated ewes following injections of clonidine or GHRH (P < .01). Treatment of ewes with MB, however, limited the ability of clonidine-induced mechanisms to increase concentrations of GH, but did not affect pituitary responsiveness to GHRH (P < .01). These data support the hypothesis that MB inhibits hypothalamic and not pituitary mediated mechanisms that regulate the secretion of GH.

Exclusion of atrial thrombus by transesophageal echocardiography

To determine whether transesophageal echocardiography (TEE) is useful in ruling out the presence of atrial thrombus, we performed TEE in 20 patients immediately before valve replacement or valve repair and within 3 days of an autopsy in one patient. Mitral stenosis was the predominant lesion in three patients, mitral regurgitation was seen in 11 patients, five patients had mitral prosthesis malfunction, one patient had a tricuspid prosthesis malfunction, and one patient had aortic stenosis. Eight patients were in atrial fibrillation. Four patients demonstrated spontaneous contrast in the associated atria. Nine patients were receiving oral anticoagulation. Mean left atrial diameter was 5.3 +/- 1.3 mm. TEE revealed no evidence for atrial thrombus in 18 of the 21 patients; this finding was confirmed by careful inspection of the atria including the appendages. TEE demonstrated a left atrial thrombus in two patients and a right atrial thrombus in another (confirmed at the time of surgery or at autopsy). In all cases transthoracic echocardiography was negative. Our data suggest that TEE is useful in ruling out atrial thrombus, and therefore may be a useful test preceding interventions associated with an increased risk of embolism from the atria such as cardioversion, mitral valvuloplasty, or valve replacement.

Value of transesophageal echocardiography as an adjunct to transthoracic echocardiography in evaluation of native and prosthetic valve endocarditis

To determine if transesophageal echocardiography provides better visualization of valvular vegetations than transthoracic echocardiography, we used both methods to evaluate 24 consecutive patients (mean age, 54 years; 15 female patients and nine male patients) referred for symptoms suggestive of infectious endocarditis. Ten of the 24 patients had one or more valvular prostheses. Echocardiograms were classified as positive or negative based on visualization of valvular vegetations or abscesses. Of ten patients with a final diagnosis of infectious endocarditis on extended follow-up, transthoracic echocardiography was positive in five patients. Transesophageal echocardiography not only yielded abnormal findings in all ten of these patients, but also revealed additional information in four of the five patients with abnormal transthoracic echocardiographic examinations. Among the 14 patients who, on subsequent follow-up, were found not to have infectious endocarditis, transthoracic echocardiography was normal in 13 and falsely abnormal in one. Transesophageal echocardiography revealed no evidence of infectious endocarditis in any of these patients. The ten patients who were determined to have infectious endocarditis all had positive blood cultures and no alternative cause for their clinical presentation; in seven patients in this group who underwent operative or postmortem evaluation, infectious endocarditis was confirmed. All patients without infectious endocarditis were demonstrated to have other causes for their clinical presentation. We conclude that transesophageal echocardiography is a highly valuable test in the work-up of patients with suspected infectious endocarditis, especially those patients with inconclusive or normal transthoracic echocardiograms. In addition, transesophageal echocardiography may be of benefit to patients with previously documented infectious endocarditis and a complicated clinical course in whom additional cardiac lesions are suspected but not demonstrated by transthoracic echocardiography.

Transesophageal color Doppler echocardiography of the normal St. Jude Medical mitral valve prosthesis

Transesophageal color flow Doppler findings are reported in 36 patients with a St. Jude Medical mechanical mitral valve prosthesis who had no auscultatory evidence for prosthetic valve dysfunction. Multiple jets consistent with mitral regurgitation originating from the central and lateral portion of the prosthesis were found in all patients. Maximum jet length ranged from 11 to 51 mm (mean 21 +/- 9 mm). Maximum jet area ranged from 0.2 to 4.1 cm3 (mean 1.2 +/- 0.9 cm2). The color M-mode Doppler interrogation showed two distinct components of the regurgitant jet: brief early systolic flow consistent with valve closure followed by holosystolic regurgitant flow consistent with transvalvular leakage. Four patients (11%) had a maximum regurgitant jet length exceeding 30 mm and absence of early systolic closure regurgitant flow by M-mode color imaging, suggesting clinically silent paravalvular leakage. Two pin-sized paravalvular suture line defects were confirmed in one patient at cardiac transplantation. We conclude that transesophageal echocardiography is a highly sensitive method for detection of mitral regurgitation in the St. Jude Medical mitral prosthesis. Clinically silent paravalvular leakage should be suspected if the maximum jet length exceeds 30 mm and color M-mode interrogation fails to demonstrate an early systolic closure regurgitant flow component.

Two-dimensional echocardiographic identification of left ventricular pseudoaneurysm

Nine patients with proved left ventricular pseudoaneurysm after transmural myocardial infarction were studied by two-dimensional echocardiography. In all patients two-dimensional echocardiography successfully displayed the pseudoaneurysm. The unique two-dimensional echocardiographic characteristics of pseudoaneurysm include: a sharp discontinuity of the endocardial image at the site of the pseudoaneurysm communication with the left ventricular cavity, and the presence of a relatively narrow orifice in comparison with the maximum diameter of the pseudoaneurysm fundus; visualization of the maximum diameter of the pseudoaneurysm fundus frequently required a slightly different tomographic view than that required for demonstration of the orifice. The distinctive echocardiographic features of pseudoaneurysm in these patients and technical implications for optimal visualization are described. Most of the pseudoaneurysms we encountered and many of those previously described were located posteriorly. We found the use of inferior angulated view modified from the standard apical four-chamber view extremely helpful in detecting the orifice in patients with posterior or posterolateral pseudoaneurysms. We conclude that two-dimensional echocardiography is an important technique for diagnosis of left ventricular pseudoaneurysm.

Two-dimensional echocardiographic detection of right-sided cardiac intracavitary thromboembolus with pulmonary embolism

Five patients with pulmonary embolism, in whom right-sided intracardiac thromboembolus was detected by echocardiography and confirmed by either angiography, surgery or postmortem examination, are described. One of these patients died from massive pulmonary embolism after right heart catheterization. In two patients treated medically, either partial or total lysis of the thromboembolus was demonstrated echocardiographically; in another two patients, the right atrial thromboembolus was successfully removed surgically. Typical locations and echocardiographic characteristics of right-sided thromboemboli are described. The potential usefulness of two-dimensional echocardiography in both the diagnosis and the management of patients with right-sided intracardiac thromboembolism is discussed.

Detection of left ventricular aneurysm on two dimensional echocardiography

The differentiation of left ventricular aneurysm from diffuse left ventricular dilation and hypokinesia may have important therapeutic consequences. Thus the diagnostic accuracy of wide angle two dimensional echocardiography for the detection of left ventricular aneurysm was evaluated in a prospective study of 26 consecutive patients with the clinical suspicion of left ventricular aneurysm referred over a 10 month period. Every patients was examined with two dimensional echocardiography and left ventricular cineangiography, and findings were interpreted by two independent observers. A dilated hypokinetic left ventricle without aneurysm formation on cineangiography in nine patients was identified in all with two dimensional echocardiography. A left ventricular aneurysm on cineangiography in 17 patients was correctly identified in 14 with the two dimensional study, as were the site and extent of the lesion (apical in 12, anterior in 1 and inferior in 1). One apical aneurysm was interpreted on the two dimensional study as apical dyskinesia; one anterior and one posterobasal aneurysm were missed with this technique. Mural thrombi were correctly identified with two dimensional echocardiography in seven of seven patients. It is concluded that two dimensional echocardiography is an accurate noninvasive method that allows differentiation of left ventricular aneurysm from diffuse left ventricular dilation in the majority of patients. It provides information regarding the resectability of the aneurysm and may obviate cineangiography in many cases.