Biomedical subjects

J C Ousey

Publications and source records attributed to J C Ousey.

43 records · Page 3Linked to original sources

PubMed1984

Preliminary studies of mammary secretions in the mare to assess foetal readiness for birth.

The status of the mare and foetus in relation to readiness for birth was assessed by measurement of the electrolytes sodium, potassium and calcium in mammary secretions pre-partum. Sixteen Thoroughbred mares were allowed to foal spontaneously and the ionic status of their mammary secretions was measured over three to five weeks pre-partum. From these measurements, a scoring system was developed where an ionic score of 35 points or more suggested that the mare was within 24 h of foaling. On the basis of this ionic score, 10 pony mares were induced with either oxytocin or fluprostenol and assessment of foal maturity was made by physical, behavioural and physiological criteria. Eight pony mares, induced when the ionic score was 35 points or more, delivered full term foals; two mares were induced when their scores were 30 and 20 points and delivered a full term and slightly immature foal respectively. These results suggest that foetal maturity may be related to electrolyte concentrations in mammary secretions and that an ionic score of 35 points or more may indicate that induction would be successful in terms of maturity of the newborn foal.

Animals↗

PubMed1984

Effects of fluprostenol administration in mares during late pregnancy.

The effectiveness of the prostaglandin F analogue fluprostenol in inducing labour in the mare was examined by giving sequential injections over the last 50 days of gestation. The behavioural and endocrine changes elicited by the drug in pregnant and non-pregnant animals and in foals were also studied. Fluprostenol (250 or 500 micrograms intramuscularly) failed to induce labour before 320 days gestation; thereafter its effect was capricious. Twelve mares foaled 1 to 36 h after the last test; eight delivered normal, viable, apparently 'term' foals and four produced stillborn/premature animals. Eight of the deliveries (five term and three pre-term foals) could be ascribed to the action of fluprostenol because they occurred 1 to 6 h after its administration, at a time when spontaneous foaling would have been unlikely. The other four mares foaled between 12 and 36 h after the fluprostenol injection and it is therefore doubtful whether there was a causal relationship between the two events. In the mares which delivered viable foals the pre-partum milk samples were characteristic of full term samples with respect to calcium, sodium and potassium. Those which delivered premature/stillborn foals had low calcium and a high sodium/potassium ratio in the pre-partum milk. Behavioural changes (sweating, increased respiration, defaecation etc), which varied in intensity between tests and individuals, were seen in all three groups of animals following the administration of fluprostenol. These changes were accompanied by rises in plasma cortisol and adrenocorticotrophic hormone concentration during the 2 h sampling period, suggesting a centrally mediated response to the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1984

Studies on equine prematurity 1: Methodology.

This paper describes the general management of mares and foals during the perinatal period and the methodology used in a collaborative research project on equine prematurity. Sixteen mares with dated pregnancies delivered 45 foals over three breeding seasons (1981 to 1983). In the majority, parturition was induced with oxytocin and/or fluprostenol; the remainder were allowed to foal spontaneously. Pre-colostral milk analysis provided a means of assessing the pre-foaling status of the mare. All were observed and monitored before, during and after parturition and the sampling protocol for both mare and newborn foal is discussed in detail. The foals were assessed for their degree of maturity at birth using behavioural, haematological, acid-base status and other criteria; they were then assigned to groups for further study and tests.

Animals↗

PubMed1984

Studies on equine prematurity 2: Post natal adrenocortical activity in relation to plasma adrenocorticotrophic hormone and catecholamine levels in term and premature foals.

Adrenocortical and medullary function was investigated during the immediate post natal period in premature and full term foals. High plasma cortisol concentrations were characteristic of the term foals in the first 2 h after birth and these were accompanied by significant arteriovenous differences in plasma cortisol across the umbilical circulation at birth, indicating enhanced adrenal activity before delivery. No such arteriovenous differences were detected in the premature group and post natal changes in plasma cortisol were minimal. The apparent inability of the premature foal adrenal to secrete cortisol was not due to the lack of endogenous adrenocorticotrophic hormone (ACTH) because high levels of this hormone were found immediately after birth in both groups of foals. Tests on the sensitivity of the foal adrenal to exogenous ACTH1-24 (0.125 mg intramuscularly [im]) showed that a maximum response to this hormone could be elicited in term foals on the day of birth. Subsequently basal cortisol levels and the response of the adrenal to ACTH1-24 declined. By contrast, only a slight response was observed following the same dose of ACTH1-24 in the premature group. Exposure to Depot ACTH1-24 over 24 h enhanced the basal secretion of cortisol in both premature and term foals but no consistent response to the same ACTH test dose could be elicited in the former. A wide range of total plasma catecholamine concentrations was observed in both groups of newborn foals. The highest values were seen in acidotic animals and there was a significant inverse relationship between blood pH and total plasma catecholamine level at delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1984

Studies on equine prematurity 4: Effect of salt and water loss on the renin-angiotensin-aldosterone system in the newborn foal.

Plasma renin substrate concentration was measured in 18, four-day-old pony foals after the administration of the natriuretic agent frusemide. Thirteen foals had been delivered spontaneously; labour had been induced in the remaining five mares. Plasma aldosterone concentration was measured in 12 of the spontaneously delivered foals. Renin substrate concentration had risen sharply within 15 mins (P less than 0.005) and peaked at 1 h. The response was consistently greater in the induced foals. Serum sodium concentration fell rapidly in the induced foals (P less than 0.002 by 60 mins) but was better maintained in the spontaneous group. Individual serum potassium concentrations varied widely and were higher in both the induced group and smaller (30 kg or less) spontaneous foals. Plasma renin substrate concentration was positively correlated with plasma potassium in both groups (P less than 0.05, P less than 0.001 respectively). Plasma aldosterone rose significantly within 30 mins (P less than 0.025) and did not stabilise during the experiment. Plasma aldosterone was significantly correlated with renin substrate concentration in both lighter (P less than 0.005) and heavier (P less than 0.05) spontaneously delivered foals. It is suggested that maturation of renal sodium and potassium handling occurs late in gestation in the foal and is in part related to body mass. 'Premature' delivery following induced labour is associated with a more rapid loss of sodium when challenged with frusemide, even though the response of the renin-angiotensin system may be exaggerated.

Aldosterone↗

PubMed1984

Studies on equine prematurity 6: Guidelines for assessment of foal maturity.

This paper describes criteria used to assess maturity of the newborn foal and their clinical application to field cases of prematurity and dysmaturity. Premature and mature foals may be clearly distinguished by their behavioural and physical characteristics. Measurement of haematological parameters (mean cell volume, total white cell and differential counts), pancreatic beta cell activity (plasma glucose and insulin levels), adrenocortical-medullary function (plasma cortisol, adrenocorticotrophic hormone and catecholamines) and the renin-angiotensin system (plasma renin substrate concentrations) were found useful in evaluating the status of the newborn foal. Confirmation of the initial diagnosis can be made by response to various challenge tests eg, glucose tolerance test, short acting synthetic adrenocorticotrophic hormone (ACTH1-24) and frusemide. In the present investigation a small number of individuals appeared to be intermediate in maturity to the other two groups, indicating that a third state of maturity may be identified. The clinical implications of this work suggest that cortisol replacement therapy and administration of long acting synthetic ACTH1-24 may be of benefit.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Effects of norepinephrine and a combined norepinephrine and dobutamine infusion on systemic hemodynamics and indices of renal function in normotensive neonatal thoroughbred foals.

BACKGROUND: Norepinephrine is a potent vasopressor that increases arterial blood pressure but may have adverse effects on renal blood flow. The combination of norepinephrine and dobutamine may lead to improved renal perfusion compared to an infusion of norepinephrine alone. The effects of these drugs in the normotensive neonatal foal have not been reported. HYPOTHESIS: Norepinephrine increases arterial blood pressure. Adding dobutamine to a norepinephrine infusion will change the renal profile during the infusions without changing the arterial blood pressure. ANIMALS: Eight conscious Thoroughbred foals were used in this study. METHODS: Each foal received norepinephrine (0.1 microg/kg/min), combined norepinephrine (0.1 microg/kg/min) and dobutamine (5 microg/kg/min), and a control dose of saline in a masked, placebo-controlled study. Heart rate, arterial blood pressure (direct), and cardiac output (lithium dilution) were measured, and systemic vascular resistance, stroke volume, cardiac index, and stroke volume index were calculated. Urine output, creatinine clearance, and fractional excretion of sodium, potassium, and chloride were measured. RESULTS: Norepinephrine and a combined norepinephrine and dobutamine infusion increased arterial blood pressure and systemic vascular resistance and decreased heart rate and cardiac index as compared to saline. The combination resulted in higher arterial pressure than norepinephrine alone. There was no significant difference in urine output, creatinine clearance, or fractional excretion of electrolytes with either infusion as compared to saline. CONCLUSIONS AND CLINICAL IMPORTANCE: These data suggest that norepinephrine and a combined norepinephrine and dobutamine infusion cause unique hemodynamic effects without affecting indices of renal function, and this effect warrants further investigation.

Animals↗