The effect of opioid antagonism and environmental restriction on plasma oxytocin and vasopressin concentrations in parturient gilts.

Oxytocin plays an important role at parturition due to its involvement in uterine contractions, foetal expulsion and the onset of maternal behaviour. The role of the related neurohypophysial hormone, vasopressin, is less clear; however, there is some evidence that it is also involved in maternal behaviour and its role in osmotic regulation is well established. The aim of this study was to investigate the inhibitory effects of endogenous opioids on these hormones during the expulsive phase of parturition in the pig, and to examine how opioid restraint interacts with environmental restriction. The subjects of this study were 31 Large Whitex Landrace primiparous sows (gilts). An indwelling jugular catheter was implanted under general anaesthesia at 12 days before the expected parturition day (EPD). From 5 days before the EPD 15 of the gilts were individually housed in a restrictive parturition crate without straw and 16 were individually housed in a straw-bedded pen. Blood samples were taken with increasing frequency towards and during parturition through a catheter extension to reduce disturbance. At 7.5 min after the birth of the first piglet half of the gilts in each environment received a dose of the opioid receptor antagonist naloxone (1 mg/kg, i.v.) with the remaining gilts receiving saline as a control. Overall, there was no effect of environment on either circulating oxytocin or vasopressin. However, both oxytocin and vasopressin were inhibited by endogenous opioids during the expulsive phase. The inhibitory effects of opioids on these hormones did not appear to have any adverse effects on the progress of parturition as judged by cumulative piglet birth intervals. The regulation of the opioid inhibition of oxytocin and vasopressin during parturition is discussed in relation to other neurotransmitters and whether opioid inhibition of these neurohypophysial hormones is part of the 'normal' physiological response to parturition or whether it is stress-induced.

Indomethacin blocks pre-partum nest building behaviour in the pig (Sus scrofa): effects on plasma prostaglandin F metabolite, oxytocin, cortisol and progesterone.

In the pig, nest building occurs in the day preceding parturition (gestation=114--116 days). Nest building behaviour can be induced in pregnant, pseudopregnant and cyclic female pigs following injection of prostaglandin F2alpha. Here we investigated behaviour and endocrine changes after the administration of indomethacin, which inhibits cyclo-oxygenase enzymes and thus prostaglandin synthesis. In experiment 1, pregnant primiparous pigs (gilts) were blood sampled through jugular vein catheters every 20 min from 1000 h on day 113 of pregnancy and behaviour was recorded until birth. Two hours after pre-partum nest building began, animals received 4 mg/kg indomethacin (n=7) or control vehicle (n=8) intramuscularly. Indomethacin-treated animals showed less nest building than controls between 1 and 5 h after injection (P<0.05), during which time they were mostly inactive and lay down for longer than controls. From 5 h before birth until birth there was no significant treatment difference in nest building behaviour. There was a tendency for the start of birth to be delayed in indomethacin-treated animals. Plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha (a major metabolite of prostaglandin F2 alpha) rose during pre-injection nest building and then fell following indomethacin treatment, but was not significantly different between groups when behaviour differed. Plasma oxytocin, cortisol and progesterone were not significantly affected by treatment. In experiment 2, indomethacin-treated non-pregnant gilts (n=7) did not show any changes in activity or posture compared with vehicle-treated controls (n=6) between 90 and 150 min after treatment. These results suggested that indomethacin treatment reversibly and specifically inhibits porcine pre-partum nest building by a mechanism that may involve endogenous prostaglandin F2 alpha synthesis inhibition but is independent of circulating oxytocin, cortisol and progesterone concentrations.

c-fos mRNA expression associated with PGF(2alpha)-induced nest-building behaviour in female pigs.

Domestic pigs, Sus scrofa, build a maternal nest on the day before parturition. A model for nest building has been established in pigs, in which exogenously administered prostaglandin (PG) F(2alpha) may be used to elicit nesting behaviour in cyclic, pseudopregnant and pregnant pigs. The central mechanisms mediating this response are unknown. The present study determined regional brain activity using semi-quantitative analysis of c-fos mRNA, after induction of nest-building behaviour by PGF(2alpha) in Large White pseudopregnant pigs. Oestradiol valerate injections (5 mg/day) were given on days 11-15 of the oestrous cycle to induce pseudopregnancy. The pigs were housed individually in pens (2.8 x 1.7 m) containing straw. On the test day (day 46 or 47 of pseudopregnancy) animals were injected with 3 ml saline (n=5) or 15 mg of PGF(2alpha) (Lutalyse, Upjohn; n=6) intramuscularly. Pigs treated with PGF(2alpha), but not saline, displayed bouts of rooting, pawing and gathering straw, which we interpret as nest building behaviour. The pigs were killed 65 min after treatment, which was 30 min after peak nest building activity, and the brain, uterus and ovaries removed for processing using in situ hybridisation. Saline-treated pigs had elevated levels of c-fos mRNA, compared to background, in the pituitary, corpus luteum and uterus, and a lower, but elevated, level of expression in cerebellum, cortex, hippocampus and olfactory bulb. PGF(2alpha)-treated pigs had significantly higher levels of c-fos mRNA expression than saline-treated pigs in the parvocellular and magnocellular regions of the hypothalamic paraventricular nucleus, the supraoptic nucleus (including the pars dorso-medialis), the neural lobe of the pituitary gland and the cerebellum. PGF(2alpha)-treated pigs also had significantly higher c-fos induction in corpus luteum. These data show that the pattern of c-fos mRNA expression in specific brain areas is different between pigs that show PGF(2alpha)-induced nest building and saline-injected controls.

Prostaglandin F2alpha-induced nest-building behaviour is associated with increased hypothalamic c-fos and c-jun mRNA expression.

Intramuscular injection of the naturally occurring prostaglandin F2alpha (PGF2alpha) to sexually mature female pigs induces luteolysis and rapidly elicits a behavioural response consistent with pre-partum nest-building. Intramuscular injection of the synthetic prostaglandin F2alpha (cloprostenol) also induces luteolysis but no nest-building behaviour is observed. The effects of PGF2alpha, but not cloprostenol, on nest-building behaviour may be mediated via peripheral PGF2alpha receptors (FP) or via direct action on central FP receptors. We have previously shown FP receptor mRNA to be localized in porcine paraventricular nucleus (PVN), supraoptic nucleus (SON) and pars dorso-medialis of the suproptic nucleus (SOD), suprachiasmatic nucleus, choroid plexus and anterior and intermediate pituitary lobes. In this experiment, we examined hypothalamic expression of the immediate early genes c-fos and c-jun mRNA after treatment with PGF2alpha or cloprostenol. Twenty-one 8-month-old nulliparous female pigs (gilts) were injected intramuscularly with a luteolytic dose of PGF2alpha (15 mg), cloprostenol (175 microg) or saline control, their behaviour was recorded and they were killed 60 min later. Coronal hypothalamic sections and control ovarian tissues were incubated with 45-mer oligonucleotide probes complementary to porcine c-fos and c-jun genes using standard in situ hybridization histochemistry techniques. Significantly higher c-fos and c-jun mRNA expression was found in PGF2alpha-treated compared to saline or cloprostenol-treated pigs in the PVN, SON and SOD. Significantly higher c-fos and c-jun mRNA expression was found in corpus lutea of PGF2alphaand cloprostenol-treated pigs compared to saline controls. Treatment with PGF2alpha induced nest-building behaviour whereas treatment with cloprostenol and saline did not. This suggests that PGF2alpha, or one of its metabolites, and not cloprostenol, crosses the blood-brain barrier and acts directly on hypothalamic receptors to mediate its effect on nest-building behaviour.

Does prolactin mediate induced nest-building behaviour in pseudopregnant gilts treated with PGF2alpha?

Nest-building behaviour occurs 6-24 h before parturition in pigs (gestation=116 days). Pseudopregnancy in pigs (induced with oestradiol valerate injections) lasts 50-80 days. We have shown that prostaglandin F2alpha (PG) administration on day 47 of pseudopregnancy induces nest-building and changes to plasma prolactin, oxytocin, cortisol and progesterone similar to those seen before normal parturition. Peripheral prolactin has been proposed as a modulator of nest-building. This study assessed nest-building behaviour in prolactin-deprived gilts. Jugular vein catheters were inserted on day 39 of pseudopregnancy and blood samples collected daily from days 40-48. Animals were injected im with either 40 mg bromocriptine in 2 ml 70% ethanol (n=8) or vehicle (n=7) at 17.00 h on day 46 and 09.00 h on day 47 of pseudopregnancy. PG (15 mg Lutalyse: Upjohn) was injected im at 11.00 h on day 47. Blood and behavioural samples were taken from 90 min before PG to 6 h post-PG. Plasma prolactin increased in control but not bromocriptine treated animals following PG (P<0.05). Elevations in oxytocin, cortisol and progesterone (P<0.05) above pre-PG concentrations were also seen, but of these only progesterone showed between group differences [greater (P<0.05) in control gilts on both days 47 and 48]. PG significantly (P<0.05) increased both the rate and proportion of total time spent performing straw/floor-directed behaviours not including foraging (an index of nesting behaviour) in both treatment groups with no significant differences between groups. There were also no significant differences between groups in time spent performing pen fixture directed activities before or after PG. Bromocriptine suppressed the rise in prolactin concentrations after PG without suppressing nest-building behaviour. We conclude that peripheral prolactin is not an essential component of the nest-building complex in pigs.

Efficacy and cost-effectiveness of preoperative IABP in patients with ejection fraction of 0.25 or less.

BACKGROUND: The purposes of this study are to determine whether patients with severe left ventricular dysfunction benefit from prophylactic insertion of an intraaortic balloon pump and to evaluate its cost-effectiveness. METHODS: Between January 1991 and December 1995, 163 consecutive patients with a left ventricular ejection fraction of 0.25 or less underwent isolated coronary artery bypass grafting. An intraaortic balloon pump was inserted before operation in 37 patients (group A). The remaining 126 patients underwent operation without preoperative insertion of the device (group B). Preoperatively, 91.9% (34/37) of group A patients and 54.8% (69/126) of group B patients were in New York Heart Association functional class III or IV (p < 0.001). RESULTS: The 30-day mortality rate was 2.7% (1/37) and 11.9% (15/126) for groups A and B, respectively (p < 0.005). All deaths occurred in patients in functional class III or IV. In group B, 28 patients (22.2%) required an intraaortic balloon pump after cardiotomy for low cardiac output, 42.9% (12/28) of whom died. Median postoperative hospital stay was 9.9 days and 12.0 days, and mean hospital charges were $50,627 and $54,818 for survivors in groups A and B; respectively (p = not significant). CONCLUSIONS: Our experience suggests that patients with severe left ventricular dysfunction undergoing coronary artery bypass grafting may benefit from preoperative intraaortic balloon pump insertion, especially patients in functional class III or IV. This approach improved survival significantly, reduced hospital stay, and was more cost-effective.

Effects of ovariohysterectomy on prostaglandin F2alpha-induced nesting behaviour in pigs.

Exogenously administered prostaglandin (PG) F2alpha induces behaviour similar to prepartum nest building in pregnant, pseudopregnant and nonpregnant female postpubescent pigs (Sus scrofa). These effects may be regulated by PGF2alpha-induced endocrine changes within the reproductive tract, such as those that initiate luteolysis. This study investigated the short-term effects of ovariohysterectomy on PGF2alpha-induced nesting behaviour in nonpregnant females. Cyclic 9-month-old virgin female pigs (gilts) received an oral dose (20 mg/day) of a synthetic progestogen (altrenogest; Regumate porcine, Hoechst, Milton Keynes, UK) for 18-21 days to synchronize oestrus. The gilts were then ovariohysterectomized (n=8) or sham-operated (n=7) on Days 3-8 after oestrus. They were housed individually and initially subjected to a series of control behavioural tests to establish the effect of ovariohysterectomy on their responses to the experimenters, novel objects, straw bedding and space restriction. Ovariohysterectomized gilts had a shorter latency to approach the experimenters than sham-operated animals, but there were no differences in their responses to a novel object, straw bedding or space restriction. Twelve to 16 days after oestrus, corresponding to the midluteal phase in sham-operated gilts, they were treated intramuscularly with 15 mg PGF2alpha (0.12 mg/kg, dinoprost; Lutalyse, Upjohn, Crawley, UK). PGF2alpha treatment induced a significant increase in straw gathering in ovariohysterectomized but not in sham-operated gilts. Other nesting behaviours, including rooting and pawing at straw, were induced in all animals. These results show that the uterus and ovaries are not required for the expression of PGF2alpha-induced nesting behaviour and the removal of the reproductive tract appears to have facilitated increased levels of gathering. This suggests that PGF2alpha induces luteolysis and nest building separately, and that PGF2alpha or a metabolite, may act centrally to mediate directly its effects on prepartum nest building in the pig.

Naloxone prevents interruption of parturition and increases plasma oxytocin following environmental disturbance in parturient sows.

Experiments in rodents have suggested that environmental disturbance can disrupt parturition through an opioid-mediated inhibition of oxytocin secretion. To test this hypothesis in a large animal model, 14 primiparous female pigs were allowed to commence parturition in a strawed pen. Five of these gilts were allowed to continue parturition undisturbed in this pen, while the remainder were moved to a farrowing crate immediately after the birth of the first piglet. At this time, pigs were injected subcutaneously with either the opioid antagonist naloxone (n = 4; dose 1 mg/kg body weight) or saline (n = 5). Whereas the undisturbed pigs all gave birth to a second piglet within 53 min, in three of the five disturbed and saline-treated pigs no further births occurred for 2 h, at which time oxytocin was administered subcutaneously to restart parturition. By contrast, all of the naloxone-treated pigs gave birth spontaneously within 2 h, although mean interbirth intervals were still prolonged compared to undisturbed pigs. In a second experiment, nine primiparous female pigs with chronic catheters preplaced in the external jugular vein were similarly moved after the birth of their first piglet and either injected with naloxone (n = 5) or saline (n = 4). Again, parturition was interrupted in three out of four saline-treated animals for at least 2.5 h, but resumed promptly when exogenous oxytocin was administered. Plasma concentrations of oxytocin in these pigs were significantly lower than in naloxone-treated pigs, five out of six of which gave birth spontaneously to one or more piglets within 2.5 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin F2alpha-induced nest-building in pseudopregnant pigs. I. Effects of environment on behaviour and cortisol secretion.

Pigs may be susceptible to stress when they are strongly motivated to nest-build in a space-restricted environment. This study aimed to explore whether nest-building behaviour could be induced by prostaglandin F2alpha (PG) administration to pseudopregnant gilts and to determine whether induced behaviour and cortisol output differed between animals chronically placed in either farrowing crates or pens. Jugular vein catheters were placed on Day 39 of pseudopregnancy and blood samples collected daily from Day 40 to Day 48. On Day 42, gilts were either restricted to farrowing crates 1.6 x 0.6 m with no straw (C: n = 11) or left in pens 2.8 x 1.74 m with straw (P: n = 11). On Day 47, blood and behaviour sampling was from 90 min pre-PG (Dinoprost; Lutalyse, Upjohn, Kalamazoo, MI) to 6 h post-PG. PG injection successfully induced nest-building behaviour in P gilts within 15 min of injection. Penned gilts engaged in more straw/floor-directed behaviour than C gilts (p < 0.01), whereas attempts in C gilts seemed partial or incomplete. Conversely, C gilts showed increased (p < 0.05) amounts of fixture-directed behaviour, whereas P gilts did not post-PG. For both groups, cortisol increased significantly (p < 0.05) post-PG compared to pre-PG values. Cortisol concentrations in C gilts were significantly greater than in P gilts prior to and after PG (p < 0.05) on Day 47, whereas there were no significant differences in concentrations of cortisol between C and P on other days. These results demonstrate that PG can induce nest-building behaviour in the absence of foetal signals. Whereas the pseudopregnant gilt seemed to chronically adapt to the imposition of a farrowing crate, gilts subsequently attempting to nest-build showed increases in cortisol output when compared to their penned counterparts, suggesting that a stress was imposed by the space-restricted environment.

Prostaglandin F2alpha-induced nest-building in pseudopregnant pigs. II. Space restriction stress does not influence secretion of oxytocin, prolactin, oestradiol or progesterone.

We have previously shown that prostaglandin F2alpha (PG) is capable of inducing nest-building behaviour in pseudopregnant gilts and established a protocol. This experiment examined which reproductive endocrine systems might mediate these behavioural responses, in the presence or absence of a space restriction stress. Pseudopregnancy was induced with 5 mg/day i.m. (intramuscular) injections of oestradiol valerate (OV) on Days 11-15 of the oestrous cycle, jugular vein catheters were placed on Day 39 of pseudopregnancy, and blood samples were collected daily from Day 40 to Day 48. On Day 42, gilts were either space restricted to farrowing crates 1.6 x 0.6 m (C: n = 11) or left in pens 2.8 x 1.74 m (P: n = 11). On Day 47, blood samples were collected from all animals every 15 min from 90 min prior to a single i.m. injection of 15 mg of prostaglandin F2alpha (PG: Lutalyse, Upjohn, Crowley, West Sussex) to 120 min post-PG and then hourly for 4 h and assayed for oxytocin, prolactin, progesterone, and oestradiol. Results showed that mean daily concentrations of prolactin and progesterone were significantly lower (p < 0.05 respectively) in C than P gilts from Day 42 to Day 46 of pseudopregnancy. There were no significant differences in mean daily concentrations of oxytocin and oestradiol between C and P gilts during this time. For both groups, oxytocin, prolactin, and progesterone concentrations increased significantly (p < 0.05) post-PG when compared to their respective pre-PG values. However, for both groups, oestradiol concentrations were unaffected by PG injection. The prostaglandin-induced increases in oxytocin, prolactin, and progesterone concentrations did not differ between groups. We conclude that coincident changes in oestradiol secretion does not influence nesting behaviour and that space restriction stress associated with nest-building does not influence secretion of oxytocin, prolactin, oestradiol, or progesterone.

Annuloplasty and aortoplasty as modifications of the Ross procedure for the correction of geometric mismatch.

BACKGROUND AND AIM OF THE STUDY: Pulmonary autograft replacement of the aortic valve (the Ross procedure) is reliable and durable; however, geometric mismatch of the autograft and systemic outflow tract may lead to poor results. Manipulation of the aortic annulus and sinotubular diameters to match the autograft can prevent geometric mismatch, and improve results. METHODS: Annuloplasty and/or aortoplasty were combined with the Ross procedure in 26 of 44 patients (median age 42.5 years; range: 3 days to 62 years) undergoing surgery between April 1994 and July 1998. Plication of the aortic annulus at either two or three of the commissures was done in five cases, aortic annulus fixation with an external pericardial pledget incorporated in the proximal suture line in 12 cases, and tailoring aortoplasty in nine patients. RESULTS: There was one operative death. Two patients required reoperation; one for progressive autograft dysfunction and one for homograft dysfunction. Annular fixation was performed on the patient requiring reoperation for autograft dysfunction. Doppler echocardiography during the follow up (median 9 months; range: 1-50 months) revealed 10 patients with trace 1+ and one patient with 2+ aortic insufficiency. Trace 1+ and 2+ aortic stenosis were present in one patient each. None of the patients undergoing commissural plication had significant regurgitation or stenosis. Both patients with stenosis underwent annular fixation. Aortoplasty was associated with 1+ insufficiency in two patients. CONCLUSION: Prevention of geometric mismatch between the autograft and systemic outflow tract at the annulus and sinotubular junction by plication techniques allows better performance of the autograft, and extends the Ross procedure to patients who otherwise may be unable to undergo such surgery. Fixation may provide similar benefit, but appears to be more susceptible to insufficiency and stenosis.

Behavioral responses to intramuscular injections of prostaglandin F(2 alpha) in female pigs.

This study investigated the effect of different doses (0-1.25 mg/kg IM) of prostaglandin (PG) F(2 alpha) on the behavior of female pigs (Sus scrofa). Six-month-old cyclic nulliparous sows (gilts) were housed and tested individually in strawed pens (2.8 x 1.7 m). All doses of PGF(2)alpha induced rooting, pawing at the ground, and gathering straw. In the hour following treatment the frequency of pawing increased with increasing dose to reach a maximum level with the highest dose given. The frequency to gather straw was highest in pigs treated with the lowest dose (0.008 mg/kg). The frequency of oronasal contact with the floor and pen walls was unaffected by dose. Scratching, locomotion, and changes in body posture were highest following treatment with the three highest doses of PGF(2 alpha). Many of the behaviors observed following PGF(2 alpha) treatment are characteristic of prepartum nesting behavior in pregnant sows. We conclude that two key components of maternal nest-building behavior, pawing, and gathering straw, are affected differentially by different doses of PGF(2 alpha). The implications of these results on the mechanisms underlying maternal nest building in pigs are discussed.

Effect of oxytocin on the pattern of electromyographic activity in the oviduct and uterus of the ewe around oestrus.

This study tested the hypothesis that the administration of oxytocin in doses equivalent to endogenous concentrations at and around oestrus could affect uterine and oviductal muscular activity at the time of gamete transport. Four ewes were fitted with recording electrodes in the left ampulla, ampullary-isthmic junction, utero-tubal junction and uterine horn. After surgical recovery, recordings from conscious free-standing animals were made for up to 10 h per day from Day -3 to Day +3 relative to oestrus in each ewe. Daily blood samples were taken for progesterone radioimmunoassay, and a vasectomized ram used to assess oestrus. A range of physiological doses of oxytocin (10-100 mU), or control saline injections were given intravenously. Electromyographic (EMG) activity was measured before and after injections. Spontaneous activity throughout the reproductive tract was low on Day -3 but increased to peak at oestrus (P < 0.05), when the pattern of activity consisted of short (2-10 s) co-ordinated high amplitude bursts (2-5 min-1). After oestrus, as overall activity declined, longer episodes of activity appeared but these occurred with a much slower frequency (1-4 h-1). Responsiveness to oxytocin was greatest on the day of oestrus at all electrode sites. Elevated responsiveness (relative to Day -3, the late luteal phase) was seen from Day -1 to Day +2 at the ampullary-isthmic junction and uterus, but on the day of oestrus only at the ampulla and utero-tubal junction. Duration of increased EMG activity after oxytocin injection ranged from 5 to 20 min. These results show for the first time that the uterine and oviductal musculatures of the ewe in vivo reached a peak in sensitivity to physiological concentrations of oxytocin at oestrus. When combined with information on oxytocin receptor populations and endogenous circulating concentrations, this suggest that endogenous oxytocin could influence oviduct and myometrial activity at this time.

Actions of oxytocin and vasopressin on oestrogen-induced electromyographic activity recorded from the uterus and oviduct of anoestrous ewes.

Oxytocin and the related peptide [Arg8]vasopressin (AVP) have previously been shown to bind with equally high affinity to oxytocin binding-sites (presumed oxytocin receptors) present within the uterus and oviduct of oestrous ewes. There is a possibility, therefore, that AVP mediates oxytocic actions through these binding sites. For the present study, ewes in seasonal anoestrus were treated with oestradiol-17 beta (50 micrograms subcutaneously, daily for 2-4 days). It was shown initially that this treatment stimulated the development of high-affinity oxytocin binding-sites (Kd 4.4 +/- 0.8 nmol L-1) which had similar affinity for AVP (Kd 4.2 +/- 0.9 nmol L-1) in the myometrium. The efficacy of oxytocin and AVP in vivo were compared by recording electromyographic (EMG) activity from the ampullary-isthmic junction of the left oviduct and the left uterine horn of four conscious ewes. Before oestradiol treatment there was no EMG response to oxytocin even at supraphysiological (1000 mU) doses. During oestradiol treatment, EMG activity was consistently increased in response to injections of 25 mU and 100 mU oxytocin via the jugular vein, but not to saline or 100 mU AVP. Higher doses of AVP were not investigated because of the possibility of cardiovascular side effects. A subsequent blood sampling experiment showed that maximal concentrations of oxytocin and AVP (achieved in peripheral plasma during the first 2 min following injection into the jugular vein) were of a similar order of magnitude after injection of equivalent doses of the two peptides. It is concluded that AVP probably does not mediate biological activity through the oxytocin receptor in non-pregnant ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic detection of pulmonary valve papillary fibroelastoma.

Papillary fibroelastomas of the heart are rare lesions usually discovered at autopsy or incidentally at surgery. Although these lesions are benign and generally asymptomatic, they can cause valvular dysfunction or embolize to vital structures. In this case report, we describe a pulmonary valve papillary fibroelastoma detected by echocardiography in an adult. Most of the 12 cases of pulmonary valve papillary fibroelastoma reported in the literature were discovered incidentally at autopsy or during surgery. To our knowledge, this is the first reported case of pulmonary valve papillary fibroelastoma detected by echocardiography. Rest imaging before exercise echocardiography for evaluation of atypical chest pain in a 42-year-old white female demonstrated a mass on the pulmonary valve. The mass was further characterized by transesophageal echocardiography and excised during open heart surgery. Pulmonary valve papillary fibroelastoma was diagnosed histopathologically. This case illustrates the additional diagnostic value of comprehensive 2D imaging in the rest phase before doing exercise echocardiography.

Effects of oestrogen supplementation and space restriction on PGF2alpha-induced nest-building in pseudopregnant gilts.

This study examined the role of oestrogen supplementation on PGF2alpha-induced nest-building in pseudopregnant gilts. Oestradiol valerate (5 mg/day) injections were given on Days 11-15 of the oestrous cycle to induce pseudopregnancy. A further series of injections of either oestradiol valerate (5 mg/day) or vehicle were given on days 44-46 of pseudopregnancy to reflect more closely the hormone profile seen in pregnancy. Nest-building was induced by a single intramuscular injection of 15 mg of PGF2alpha (Lutalyse) on Day 47 of pseudopregnancy. The gilts were housed in pens (2.8 x 1.7 m) containing straw in experiment 1 or chronically confined in crates (0.6 x 1.7 m) that did not contain straw on days 44-48 of pseudopregnancy for experiment 2. Oestrogen supplemented gilts had significantly higher concentrations of circulating 17beta-oestradiol on day 47 of pseudopregnancy but there were no significant differences between treatments for circulating levels of prolactin, progesterone, cortisol or oxytocin, or for any behavioural measure in either experiment. These results indicate that there is no direct effect of supplementing already pseudopregnant gilts with oestradiol valerate on PGF2alpha-induced nest-building. The results also show that the pre-partum environment has a pronounced effect on nest-building behaviours and that non-pregnant pigs might be a useful model for pre-partum nest-building in this species.

Restricting maternal space during parturition in the pig. Effects on oxytocin, vasopressin and cortisol secretion following vagino-cervical stimulation and administration of naloxone.

This experiment studied the effects on endocrine and birth parameters of parturient pigs produced by restricting maternal freedom of movement without otherwise altering environment. Six primiparous pigs (gilts) were each given a jugular catheter under anaesthesia 7 days before parturition and commenced birth in a strawed pen, 2.0 m x 1.5 m in size. Continuous automated blood sampling (3 ml min-1) from unrestrained gilts began following the birth of the first piglet (stage 1) and continued for 2 h. After at least 30 min of blood collection, maternal space was reduced to 2.0 m x 0.55 m by placing rails across the pen (stage 2). The scope for movement in stage 2 was similar to that offered by a farrowing crate. After at least 25 min each gilt was given the opioid antagonist naloxone (1 mg kg-1 i.v.: stage 3). At each stage, vagino-cervical stimulation (VCS) was applied to mimic foetal ejection. Non-cervically stimulated oxytocin (OT) secretion between stages 1 and 2 was unchanged (P > 0.05) but increased significantly relative to both stages 1 and 2 following naloxone treatment for 15-20 min (P < 0.05, paired t-tests on log10 data). Following VCS in all stages plasma OT rose (P < 0.05) for 1-2 min in a similar way to that seen previously following foetal ejection, the increases being proportionally similar irrespective of stage or baseline secretion. Cortisol secretion did not increase as a consequence of space restriction (mean +/- SEM concentrations were 28.6 +/- 8.51 pmol l-1 and 32.3 +/- 11.8 pmol l-1 in stages 1 and 2, respectively). In addition, VCS did not significantly affect cortisol output. Lysine vasopressin concentrations were not affected as a consequence of either stage or VCS. Parturition was not interrupted following space restriction of gilts. These data suggest that reducing maternal space allowance during parturition is not stressful when the process does not involve the movement of animals to novel surroundings.

Release of oxytocin and prostaglandin f(2alpha) around teasing, natural service and associated events in the mare.

Mating has been shown in many species to provoke the release of oxytocin (OT). In our study, various stimuli were applied to mares to study release of OT and prostaglandin F(2alpha) (PGF(2alpha)) associated with mating. Blood samples were collected from mares around the time of teasing both in oestrus and dioestrus and at mating. For comparison, blood samples were also collected at the time of manual manipulation of the genital tract and after intrauterine infusion of 500 ml phosphate buffered saline (PBS). Additional samples were collected 16 to 18 h after mating. Mating caused a significant increase in OT in all mares and teasing caused a significant OT response in 6 of 10 oestrous and 3 of 5 dioestrous mares. However, mating and teasing had no significant effect on concentrations of 15-keto-13,14-dihydro-PGF(2alpha) (PGFM). Manual manipulation of the clitoris, vagina and cervix caused significant OT release in all mares and intrauterine infusion of 500 ml PBS caused significant OT release in three of the five mares. However, only one mare had a significant PGF(2alpha) response during manual manipulation and only one responded positively to intrauterine infusion of 500 ml PBS. We concluded that events around mating, including stimulation of the genital tract and uterine distension, often caused an increase in circulating concentrations of OT but only rarely in PGFM.

The timing of parturition in the pig is altered by intravenous naloxone.

This experiment tested the hypothesis that opioid antagonists could influence the timing of the onset and progress of parturition in the pig. Primiparous pigs (gilts) received a jugular catheter on Days 104 to 106 of pregnancy. At 1400 h on Day 112 the gilts received 10 mg PGF2alpha, i.m. to induce parturition. At 1000 h on Day 113 (i.e., 20 h later) gilts received either saline (n=6), 1 mg/kg, i.v. naltrexone (n=4) or 1 mg/kg, i.v. naloxone (n=5). Blood samples were taken daily from Days 108 to 116. On Day 113, blood samples were taken hourly from 0500 to 0900 h and then every 30 min until 2400 h, or until the birth of the last piglet (BLP) (whichever was sooner) and assayed for progesterone, oxytocin (OT), cortisol and PRL. Additional blood samples for OT and cortisol assay were taken every minute from 0930 to 1100 h on Day 113 and for 30 min during parturition. Naloxone, but not naltrexone, delayed the onset of parturition relative to saline controls (by 14 h 21 min; P<0.05). Duration of parturition and rate of births were not significantly affected by treatment. Mean plasma OT increased in the 4 h following naloxone but not saline treatment, during which time OT plasma pulse amplitude was reduced in naloxone and naltrexone-treated animals relative to saline treated controls. The PRL secretion rose following treatment in saline treated animals, consistent with approaching parturition, but failed to rise in opioid antagonist treated animals. Progesterone concentrations remained elevated in naloxone-treated animals for longer than in the other groups. These data suggest that a rapid change in overall effect of parenteral administration of naloxone to parturient pigs occurs from delaying its onset when administered as in these experiments, to facilitating its progress when given during parturition (earlier experiments). The delay of onset of parturition may be mediated by interference with hypothalamic control of OT or PRL release.

Influence of environmental temperature on PGF(2alpha)-induced nest building in female pigs.

Domestic pigs build a maternal nest in the day preceding parturition. We have shown that prostaglandin F(2alpha) (PGF(2alpha)) induces nest building behaviour in non-pregnant pigs. The aim of this experiment was to examine the effects of different environmental temperatures on PGF(2alpha)-induced nest building. Data were collected from 9 Large White (LW) and 10 Large Black (LB) 8-9-month-old nulliparous sows (gilts). The pigs were housed in social groups between experiments and tested individually in pens (1.8mx1.8m) containing straw, within an environmentally controlled chamber. Pigs were habituated to the testing pens (maintained at 17 degrees C) and tested once at each of three temperatures (low, 5 degrees C; moderate, 17 degrees C; high, 30 degrees C). During testing the temperature of the chamber was adjusted at 09.00h and had reached set point by10.00h. The pigs were injected intramuscularly with 3ml saline at 10.30h and 0.1mg/kg PGF(2alpha) (Lutalyse, Upjohn) at 11.30h. Behaviour was scored for 1h after treatment with saline and 1h after treatment with PGF(2alpha) using one/zero sampling from video recordings. Nest building behaviour (rooting, pawing and gathering straw) was induced by PGF(2alpha) at all temperatures in both LW and LB breeds. There was a significant increase in rooting behaviours with decreasing temperature. No significant effects of temperature were found on the scores for gather or paw. The pigs spent more time lying down at the high compared to the low temperature after both saline and PGF(2alpha) treatment. Other behaviours unrelated to nest building but induced by PGF(2alpha), such as scratching, were unaffected by temperature. The results show that the nest building behaviour of non-pregnant pigs can be induced by exogenous PGF(2alpha) treatment, and that some, but not all, aspects of PGF(2alpha)-induced nest building (rooting but not pawing or gathering) are altered by environmental temperature.