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Pigs begin behavioural preparations for birth about 1-2 days before parturition. Prepartum sows wander to select a suitable site and then construct a maternal nest. The signal that initiates this behavioural cascade probably results from fetal maturation but is unknown. However, endogenous PGF2 alpha appears to be involved early on in an endocrine pathway that projects to the brain and can generate most of the prepartum behavioural components. This period of intense activity is followed by a quiescent phase of lying in the nest for some hours before fetal ejection occurs. Feedback from a completed nest or abdominal discomfort may both contribute to the end of nest building. In the postpartum phase, sows have to deal with the apparently conflicting drives of remaining passive to reduce accidental or deliberate damage to piglets, while at the same time responding actively to their needs. In commercial environments, animals frequently fail in this task. Although environmental influences on piglet survival have received much experimental attention, the genetic, social and endocrine drives that control sow behaviour after parturition remain poorly understood and their clarification is a major challenge for the future.

In this study, we examined the presence and concentrations of six polynuclear aromatic hydrocarbons (PAHs) in groundwater sources of Okrika mainland impacted by effluent discharges from a petroleum refinery into her surrounding Creeks. Sterile amber coloured bottles were used to collect 10 replicate borehole water samples from the mainland and fixed with concentrated H2SO4. Samples were transferred to the laboratory in iced coolers and analyzed using Gas chromatography coupled with Flame Ionization Detector (GC-FID). The interactions of the PAH components detected was determined using the Pearson product moment correlation coefficient (r) while spatial variance equality in means of concentrations was explored with the One-way ANOVA. Structure detection of observed inequalities was made with means plots. Concentrations of the PAHs were high and exceeded the WHO maximum permissible limit of 0.002mg/l in drinking water. Benzo(b)fluoranthene, with the highest mean concentration varied between 0.000370.51266 (0.08117±0.03330159)mg/l, fluoranthene varied between 0.00060-0.32890 (0.0473946±0.01769877)mg/l, while benzo(k)fluoranthene with the least mean concentration varied between 0.00017-0.08478 (0.0237385±0.00610045)mg/l. However, pyrene concentration ranged between 0.00015 and 0.24757 (0.0508440±0.01859716)mg/l, benzo(a)anthracene between 0.00020-0.21972 (0.0512660±0.01688275)mg/l, and chrysene between 0.00013 and 0.16571 (0.0488975±0.01090264)mg/l. Strong associations were observed between all the PAH components measured at P Fcrit(3.921478)] was recorded across the sampling locations at P

The Port Harcourt Refinery Company situated at Okrika Mainland discharges its effluent into the Creeks surrounding this coastal land. The current study examined the presence of polynuclear aromatic hydrocarbons in groundwater sources of the coastal settlement. Ten replicate samples were collected from 10 boreholes in the settlement using sterilized amber glass bottles and fixed with concentrated H2SO4. They were later analyzed using Gas chromatography (GC). The Pearson product moment correlation coefficient (r) was used to determine the interactions of the PAHs detected while the One-way ANOVA was used to determine spatial variance equality in means of the PAHs components at P Fcrit(3.85563)]. A further structure detection revealed that the inequalities were contributed by all the PAH components, especially between BH 3 and BH 1, BH 4 and BH 2 and 5, as well as between BH 6 and BH 10. Very strong associations were observed between the PAH components at P < 0.01. BH 8 recorded the highest contamination level of the various PAHs due basically to its proximity to the refinery’s effluent discharge point (Ekerekana Creek) and channel. Hence the source of these pollutants could best be fingerprinted to the nearby Port Harcourt Refinery Company’s effluent discharges. These PAHs are not only ingested by drinking contaminated waters, but are further consumed when this water is used to prepare foods. This creates a great cause for public health concerns especially as several PAHs are known carcinogens. It is therefore, recommended that technologically advanced techniques of water treatment be developed in order to take care of the presence of PAHs in drinking water sources of the coastal dwellers.

Reproductive disorders in sheep (Ovis aries) have been linked to ingestion of subterranean clovers (Trifolium brachycalycinum Katzn. & Morley, T. subterraneum L., and T. yanninicum Katzn. & Morley) containing high levels of the phytoestrogenic isoflavones formononetin (7-hydroxy-4-methoxyisoflavone; FM), genistein (5,7,4-trihydroxyisoflavone; GE), and biochanin A (5,7-dihydroxy-4-methoxyisoflavone; BA)

Two experiments were designed to investigate release patterns of oxytocin into plasma during oestrus and the early luteal phase. In Exp. 1, blood samples were collected from 5 ewes every 30 min for 10 h during 6 days around oestrus and the early luteal phase. During oestrus concentrations of oxytocin were generally low (1.27 +/- 0.54 pg/ml; mean +/- s.d.) but with occasional pulses up to 6 pg/ml. By Day 5 mean basal concentrations had risen to 4.5 +/- 2.1 pg/ml with a fluctuating release pattern. In Exp. 2, a method was developed for continuous blood sampling from conscious, unrestrained ewes. On the predicted day of oestrus following an untreated oestrous cycle, 8-ml blood samples were collected every minute for two 35-min periods (8 ewes: 16 sampling periods). For 6 ewes a ram was introduced to the pen for part of this time, and resulting behaviour was recorded. Additional blood samples were assayed for LH and progesterone to determine the stage of the cycle. Overall mean oxytocin concentrations ranged from 1.5 +/- 0.53 to 6.8 +/- 5.25 pg/ml in different animals. Ewes which were both in oestrus and exposed to the ram showed a pulsatile oxytocin release pattern consisting of low baseline concentrations with short-duration pulses superimposed (duration 1-4 min; amplitude 2.5-31.7 pg/ml; frequency 3.18/h). Coitus was not temporally associated with pulsatile release. However, the importance of the presence of the ram was indicated by total separation of 2 oestrous ewes from the ram until after experimentation. In these animals only 1 pulse of oxytocin was detected in 2.7 h of sampling. It is concluded that, although mean oxytocin concentrations at oestrus were low, short duration pulses were released into the plasma at this time. This effect may be dependent on the presence of a ram.

Anoestrous Romney Marsh ewes with or without progesterone pretreatment were injected with multiple low-doses of gonadotrophin-releasing hormone followed by a single, larger bolus. Blood samples were taken at twelve-hourly intervals for progesterone radioimmunoassay. Ewes were slaughtered on day 3 or 5 after the bolus injection, and the ovaries were collected for histology and immunocytochemical examination for oxytocin-immunocreactivity. The corpora lutea of all ewes killed on day 3 had similar weights and morphology. The ovaries of those ewes which were not pretreated with progesterone also contained some luteinized cysts. Ewes slaughtered on day 5 were separated into 2 groups according to plasma progesterone profiles, which were either rising (‘normal’), or falling after a transitory rise (‘abnormal’). Those ewes pretreated with progesterone all had a ‘normal’ progesterone profile whereas, of 14 ewes not pretreated with progesterone, 6 were ‘normal’ and 8 ‘abnormal’. Corpora lutea were significantly lighter in the ‘abnormal’ group and the ovaries of most of these ewes also contained luteinized cysts. All corpora lutea and luteinised cysts showed staining for oxytocin-immunoreactivity although the staining intensity was variable. In corpora lutea from ‘normal’ ewes oxytocin was restricted to large luteal cells. In addition tissues from ‘abnormal’ ewes also contained many cells with an atypical elongated shape which stained for oxytocin-immunoreactivity. These results show that progesterone pretreatment is needed for both normal morphological and endocrine development of corpora lutea in anoestrous ewes stimulated with gonadotrophin-releasing hormone.

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.

Pigs begin behavioural preparations for birth about 1-2 days before parturition. Prepartum sows wander to select a suitable site and then construct a maternal nest. The signal that initiates this behavioural cascade probably results from fetal maturation but is unknown. However, endogenous PGF2 alpha appears to be involved early on in an endocrine pathway that projects to the brain and can generate most of the prepartum behavioural components. This period of intense activity is followed by a quiescent phase of lying in the nest for some hours before fetal ejection occurs. Feedback from a completed nest or abdominal discomfort may both contribute to the end of nest building. In the postpartum phase, sows have to deal with the apparently conflicting drives of remaining passive to reduce accidental or deliberate damage to piglets, while at the same time responding actively to their needs. In commercial environments, animals frequently fail in this task. Although environmental influences on piglet survival have received much experimental attention, the genetic, social and endocrine drives that control sow behaviour after parturition remain poorly understood and their clarification is a major challenge for the future.

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

We studied the effects of spinal intrathecal fentanyl on oxytocin secretion in 20 healthy women prior to an elective caesarean delivery at term under spinal anaesthesia. The women were randomly allocated into two groups with respect to spinal anaesthesia. Group I (n=10) received intrathecal bupivacaine (15 mg) plus fentanyl (25 microgram), and Group II (n=10) received intrathecal bupivacaine (15 mg) alone, prior to caesarean section. The two groups were comparable demographically. Altogether, ten samples of 4.5 ml of blood (taken every 60 s) were obtained before and ten samples were obtained after the intrathecal administration of the drug and establishment of the T6 block, and plasma oxytocin concentrations were assayed for each subject. Oxytocin was measured by RIA. We found no significant differences in plasma oxytocin concentrations of individual subjects before and after intrathecal injection. In addition, there were no significant differences in plasma oxytocin concentrations between the two groups when pooled samples from the subjects were compared for the pre- and post-intrathecal injection phases. We conclude that the spinal intrathecal administration of fentanyl does not suppress oxytocin secretion in pregnant women who are not in labour at term.

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.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.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.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.

Subterranean clovers (Trifolium brachycalycinum Katzn. and Morley, T. subterraneum L., and T. yanninicum Katzn. & Morley) contain phytoestrogenic isoflavones. High levels of these componds are responsible for sheep (Ovis aries) reproductive disorders

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.

The aim of this study was to show that the pig uterus synthesizes oxytocin. Uteri were obtained from 2-7 pigs at regular intervals during the oestrous cycle, throughout pregnancy, at parturition and in lactational anoestrus. Localization of mRNA encoding oxytocin was by in situ hybridization and oxytocin concentrations were measured by radioimmunoassay. As reproductive status changed, mRNA encoding oxytocin varied significantly (P < 0.05). Uterine tissue type was a significant factor in determining synthesis of mRNA encoding oxytocin (P < 0.001). In luminal epithelia, concentrations of mRNA encoding oxytocin were greater at oestrus than during day 14 of the luteal phase (P < 0.01) or at any stage of pregnancy (P < 0.05), with concentrations minimal at parturition. This trend was also exhibited in uterine circular muscle. In longitudinal muscle, concentrations of mRNA encoding oxytocin were lower during late pregnancy than at oestrus (P < 0.05) or during the luteal phase (P < 0.05). Concentrations were minimal at parturition. The oxytocin content in endometrial and myometrial tissue was positively correlated across reproductive status (P < 0.02, r = 0.402, n = 35). These data are the first indication that the uterine endometrium and musculature of the pig express mRNA encoding oxytocin. The luminal epithelium of animals at oestrus was particularly rich in mRNA encoding oxytocin, whilst late pregnant and parturient animals did not show a rise in mRNA encoding oxytocin. Local uterine synthesis of oxytocin may therefore be more important in control of the oestrous cycle than in pregnancy or at parturition in pigs.

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.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 (p0.001).The 30-day mortality rate was 2.7% (1/37) and 11.9% (15/126) for groups A and B, respectively (p0.005). 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).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.

In recent years there has been a burgeoning interest in the occurrence of the neurohypophysial hormones-oxytocin and vasopressin-outside the central nervous system. Much of this has focussed on the presence of the peptides in the gonads, and stems from the demonstration of significant amounts of oxytocin in the corpus luteum of the sheep ovary by Wathes and Swann (1982). This demonstration was followed rapidly by similar observations in other laboratories. Thus it was shown: that there was a higher concentration of oxytocin in the ovarian vein than in the corresponding artery of sheep in the luteal phase of the oestrous cycle (Flint and Sheldrick 1982); that the peptide was present in the bovine corpus luteum (Wathes et al. 1983); and that this probably represented the uterotonic substance 'contractin' that Fields et al. (1980) had extracted from bovine corpus luteum (Fields et al. 1983). Moreover, all of these studies brought to light observations which had been recorded at the beginning of the century. In their first description of the milk let-down effect of pituitary extracts, Ott and Scott (1910) showed that an aqueous extract of corpus luteum increased milk flow in the lactating goat, and this observation was confirmed using ovine corpus luteum in the lactating cat (Mackenzie 1911; Schafer and Mackenzie 1911). The discovery of oxytocin in the ruminant ovary, and the claims for its possible presence in the ovaries of other species, including man, raised the question of the possibility of its presence in the male gonad. So it was that an oxytocin-like peptide was sought and found in the testes of man and other species (Nicholson et al. 1984). The discovery of a biologically active molecule in a tissue raises a number of questions. In what cells of the tissue is the substance located and is it synthesized by them or accumulated by them? What is the chemical nature of the molecule; in the present case, is gonadal oxytocin identical with hypothalamic oxytocin? What is the physiological role of the molecule in that location? In the present paper we shall attempt to review the answers that have been provided to these questions so far, for both ovarian and testicular oxytocin. We have chosen to bias this article towards a review of the contributions from our laboratory in Bristol and thus say very little about the vasopressin-like peptides that also occur in the gonads. We attempt to direct the reader to work on such peptides by reference at the appropriate places, and further consideration can be found in the reviews by Clements and Funder (1986) and Wathes (1989), although the 'vasopressin' has not been studied as extensively as the oxytocin.

We studied the effects of spinal intrathecal fentanyl on oxytocin secretion in 20healthy women prior to an elective caesarean delivery at term under spinal anaesthesia. The women were randomly allocated into two groups with respect to spinal anaesthesia. Group I (n = 10) received intrathecal bupivacaine (15mg) plus fentanyl (25μg), and Group II (n = 10) received intrathecal bupivacaine (15mg) alone, prior to caesarean section. The two groups were comparable demographically. Altogether, ten samples of 4.5ml of blood (taken every 60 s) were obtained before and ten samples were obtained after the intrathecal administration of the drug and establishment of the T6 block, and plasma oxytocin concentrations were assayed for each subject. Oxytocin was measured by RIA. We found no significant differences in plasma oxytocin concentrations of individual subjects before and after intrathecal injection. In addition, there were no significant differences in plasma oxytocin concentrations between the two groups when pooled samples from the subjects were compared for the pre- and post-intrathecal injection phases. We conclude that the spinal intrathecal administration of fentanyl does not suppress oxytocin secretion in pregnant women who are not in labour at term.

An acutely stressful stimulus such as relocation from a familiar strawed pen to an unfamiliar farrowing crate during birth has been shown to interrupt the birth process and inhibit oxytocin secretion (Lawrence et al, 1992). Both of these departures from normal parturition could be prevented by administration of the μ opioid antagonist naloxone. A likely site of action for this effect is presynaptic μ receptors on noradrenergic nerve terminals in the hypothalamus (Onaka et al, 1995). Such a neuro-endocrine control system, if active in the day prior to birth, might influence the timing of the onset of parturition and its subsequent efficiency even in the absence of a stressful stimulus. This experiment tested this hypothesis.

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)

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.

Anoestrous Romney Marsh ewes with (+P) and without (-P) progesterone pretreatment were induced to ovulate by multiple low-dose injection of GnRH followed by a bolus injection of GnRH. Luteal function was assessed by twice daily measurement of plasma progesterone. Animals were slaughtered on Days 3 or 5 after the end of GnRH treatment and CL and endometrium were recovered. In all Day-5 ewes, blood samples were collected at 30-min intervals for 8 h on Days 3 and 5 for measurement of PGFM and oxytocin. At slaughter 92% of the Group +P ewes had ovulated compared with 54% of the Group -P ewes. The ovaries of some of the Group -P ewes only contained luteinized cysts either alone or in association with CL. In the ewes that ovulated, progesterone profiles were normal in all Group +P ewes, whereas Group -P ewes had 'normal' or 'abnormal' profiles in which plasma progesterone was declining prematurely. All of the CL from ewes with abnormal progesterone profiles were associated with follicular cysts, and were significantly smaller and with a lower progesterone content on Day 5. PGFM levels decreased (P less than 0.05) between Days 3 and 5 in ewes in Groups +P and -P with 'normal' CL but increased (P less than 0.01) in Group -P ewes with 'abnormal' CL. Oxytocin levels were lower in Group -P ewes with 'abnormal' CL on Day 5, than in 'normal' ewes in Groups -P (P less than 0.01) or +P (P less than 0.05). In 3/5 Day-5 ewes with 'abnormal' CL there was a clear association between a major peak of oxytocin and a rise in PGFM during the frequent sampling period on Day 3 or Day 5, and endometrial oxytocin binding sites were present at slaughter. This suggests that the premature regression of 'abnormal' CL occurs via the normal luteolytic mechanism. Although ewes in Groups +P and -P with 'normal' CL had similar progesterone profiles, plasma oxytocin was significantly higher (P less than 0.05) in the Group -P ewes and oxytocin binding sites were present only in this group, suggesting that progesterone pretreatment can influence the production of both oxytocin and its receptor.

Oestrus was synchronized in 8 cyclic heifers by progesterone treatment (PRID), after which the animals were monitored for one control cycle to measure the inter-oestrous interval. Osmotic minipumps containing saline (controls, N = 3) or oxytocin (N = 5) were implanted subcutaneously on Day 10 of the second cycle, and removed 12 days later. Jugular venous blood samples were collected daily for measurement of progesterone, and every 2 days for oxytocin. In addition, blood samples were taken every 10 min from 1 h before to 3 h after minipump insertion for measurement of plasma 15-keto-13,14-dihydroprostaglandin-F-2 alpha (PGFM) and every 30 min over the same period for measurement of progesterone and oxytocin. The lengths of the first untreated cycle in both groups of heifers were 20.2 +/- 0.56 (mean +/- s.e.m.) days compared with 25.4 +/- 0.81 days after oxytocin treatment (P less than 0.001). Oxytocin plasma concentrations in treated animals rose from less than 10 pg/ml to 70-500 pg/ml by 2 h after the start of oxytocin infusion and remained elevated until treatment was withdrawn. There was no increase in PGFM concentrations immediately after minipump insertion. Plasma progesterone concentrations were similar in treated and control animals but remained at mid-luteal levels for an average of 5 days longer in treated heifers. It is concluded that continuous administration of oxytocin can extend the luteal life-span in cattle.

INTERNATIONAL agencies and national governments frequently require per capita national income figures for a large number of purposes on a comprehensive and comparable basis. The obvious and simple method for obtaining these figures is to take each country's national accounts measure of, for example, per capita GDP, and convert it to a common currency using the relevant exchange rate. It is, however, well-known that this procedure is liable to be misleading. Firstly national accounts are not to be taken as precise statistics, and in any case they are not always compiled on an identical basis. Secondly, many countries operate a number of exchange rates, depending on the class of transaction. And finally, the claim that international trade will lead to the equalisation of the prices of non-traded as well as traded goods appears dubious in practice, and as a consequence even free market exchange rates will only provide the appropriate set of conversion factors for traded goods. As a consequence, there is considerable interest in looking at alternative and possibly more reliable methods of comparing income levels. The best known of these alternative methods is the Purchasing Power Parity (PPP) method, and its most recent and comprehensive realisation is in the United Nations International Comparison Project (ICP), reported in Kravis et al. (1975, 1978a). If a common set of international prices, denominated in terms of some numeraire currency (conventionally US dollars) is obtainable, then it is a conceptually simple (although in practice, timeconsuming and expensive) matter to put the national accounts of all countries on a common basis in terms of this numeraire currency. The question therefore is whether it is possible to obtain such a set of international prices. Essentially there are two problems here: (i) prices in different countries are expressed in terms of local currencies, and, even if available, market exchange rates will not in general provide a reliable method of conversion between currencies, and (ii) relative prices, which are unit free, will vary between countries (this is of course the text-book "index number problem"). If one is prepared to ignore (ii), then a solution to (i) is obtained by the Geary-Khamis procedure, which is discussed in Gilbert (1981a). The GearyKhamis procedure is the source of the set of international prices used in the ICP estimates.