PubMed Health⌕ Search

Biomedical subjects

J C Ousey

Publications and source records attributed to J C Ousey.

At least 37 records · Page 2Linked to original sources
PubMed1995

Immunohistochemical localisation of steroidogenic enzymes and phenylethanolamine-N-methyl-transferase (PNMT) in the adrenal gland of the fetal and newborn foal.

An increase in fetal adrenal cortisol output signals the onset of parturition in many animal species but, in the fetal horse, plasma concentrations of cortisol remain low for much of late pregnancy, with a rise occurring only very close to the time of birth (term 320-360 days). Immunohistochemistry was used to determine the localisation and changes in distribution of key steroidogenic enzymes for cortisol production; P450scc, P450C17 and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in adrenal tissue from fetal and newborn horses and these findings were correlated with the appearance of immunoreactive (IR)-phenylethanolamine-N-methyl-transferase (PNMT), a cortisol-dependent enzyme. Five micron sections of adrenal tissue from fetuses at Day 100-156 (n = 5), Day 244-295 (n = 8), greater than Day 300 (n = 4) and from newborn foals (n = 6), were stained using specific antibodies and the avidin-biotin-peroxidase technique. All 3 steroidogenic enzymes were present by Day 150, but in less than 20% of the cortical cells. By late gestation the steroidogenic enzymes were present in approximately 30% of the cells, but the distribution varied. P450SCC and P450C17 predominated in cortical cells proximal to the medulla; 3 beta HSD was present throughout the cortex, but more in the zona fasciculata. In foals after birth, IR-3 beta HSD and IR-P450SCC had increased substantially throughout the adrenal cortex, and IR-P450C17 was present in most cells of the presumptive zonae fasciculata and reticularis. IR-PMNT was localised to nuclei of scattered medullary cells at the medullary-cortical interface by Day 150.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Increase in plasma progestagen concentrations in the mare after foetal injection with CRH, ACTH or betamethasone in late gestation.

Maternal plasma progestagen concentrations increase about 20 days before parturition. The major contributors to the increase are reduced metabolites (ie 5 alpha-pregnanes). Precocious increases (ie less than 310 days of gestation) in these metabolites may occur in abnormal pregnancies. The effects of CRH, ACTH or betamethasone administered to the foetus at gestational ages ranging from about 250 to 320 days were examined. Sixteen healthy pony mares were used for foetal injection employing aseptic techniques. Water or normal saline were used as controls. Maternal plasma progestagen concentrations were measured using a commercial radioimmunoassay (RIA) progesterone kit and results were confirmed using gas chromatography-mass spectrometry (GC-MS). Results demonstrated clearly that an increase in maternal plasma progestagen concentrations occurred after injection of ACTH, CRH or betamethasone to the foetus, irrespective of gestational age. A comparable increase was not observed in the control animals. Of the 16 mares in which the foetus was injected, 13 produced viable foals at gestational ages ranging from 307 to 339 days whereas 3 mares delivered non-viable foals at 284 to 306 days gestation. The results support the hypothesis that the pre-parturient rise in progestagens occurring in the mare is the result of foetal adrenocortical activity.

Adrenocorticotropic Hormone↗
PubMed1992

The development of gluconeogenic enzymes in the liver and kidney of fetal and newborn foals.

The activities of glucose-6-phosphatase (G6P), fructose diphosphatase, phosphoenolpyruvate carboxykinase (PEPCK), aspartate and alanine transferases were measured in liver and kidney of fetal foals between 100-318 days of gestation (term approximately 335 days) and during the immediate postnatal period (0-48 h after birth). All 5 enzymes could be detected in the fetal liver and kidney at the youngest gestational age studied. Mean fetal activities were lower than those observed in their mothers and showed no change with gestational age for the majority of enzymes studied. However, renal PEPCK and renal and hepatic G6P did increase towards term. At birth, hepatic and renal activities of these two enzymes were higher than those found in late gestation or in the adult animals. There was no apparent change in the activities of any of the other enzymes at birth. In late gestation (80-90% gestation), the activities of G6P and PEPCK in the foal were low compared to those in other species at the same stage of gestation. Similarly, the perinatal increase in enzyme activity occurred closer to term in the foal than in most other species. These observations indicate that maturation of glucogenic capacity occurs relatively late in the fetal foal and suggests that this process may be dependent on the prepartum rise in fetal cortisol as occurs in other species.

Aging↗
PubMed1991

Tissue glycogen and glucose 6-phosphatase levels in fetal and newborn foals.

Glycogen and glucose 6-phosphatase levels were measured in a variety of tissues from fetal, newborn and adult pregnant mares. Hepatic and renal glucose 6-phosphatase activities increased with increasing gestational age and rose further in the 24 h after birth to values similar to those observed in maternal tissues. The glycogen content of fetal liver and skeletal muscle also increased in late gestation, whereas that of fetal lung and cardiac muscle decreased toward term. No significant change in renal glycogen content with fetal age was observed. The values of hepatic glycogen and glucose 6-phosphatase found in the fetal foal near term were less than those observed previously in fetal sheep and pigs at a similar stage of gestation. These observations suggest that, in late gestation, the fetal foal has a limited glucogenic capacity compared with other domestic species and may have difficulty maintaining an adequate glucose supply during adverse conditions.

Animals↗
PubMed1991

Effects of placental pathology on maternal plasma progestagen and mammary secretion calcium concentrations and on neonatal adrenocortical function in the horse.

Between 1985 and 1990, 25 Thoroughbred mares were classified as having an abnormal pregnancy on the basis of precocious signs of impending parturition. Throughout the remainder of their pregnancies, plasma progestagen and mammary secretion calcium concentrations were monitored. After parturition, evidence of placental pathology was recorded and their foals were assessed with regard to adrenocortical function and behaviour. Seven pony mares were used to establish a model of placental pathology and, following induced placental separation, were subjected to the same protocol. Control animals consisted of 35 Thoroughbred mares and 39 pony mares, all considered to have normal pregnancies. Of the 25 abnormal mares, 16 had precociously increased plasma progestagen concentrations, 17 had precociously increased mammary calcium concentrations and 24 had an abnormal placenta. Eighteen live foals resulted, of which 11 appeared abnormal on the basis of behaviour. Adrenocortical function was assessed in 13; 4 had normo- and 3 hypofunction and 6 were intermediate. These results were independent of gestational age at delivery. Of 13 foals examined for plasma progestagens, 7 had normal and 6 abnormal concentrations. Following placental separation in the pony mares, maternal plasma progestagen concentrations increased in 4 of the 7 mares within 4-11 days and in 1 after 42 days; there was placental pathology in 3 of these mares, 1 of which aborted at 287 days gestation. There was no increment in progestagens in the remaining 2 mares, which aborted at 240 days and 271 days. It was concluded that placental dysfunction may be diagnosed from early plasma progestagen increments prior to 308 days gestation; and that foals that survive birth in these circumstances may be physiologically immature but often have normal or intermediate adrenocortical function, irrespective of gestational age. This is in contrast to foals born prematurely without maternal plasma progestagen or mammary secretion calcium increments.

Adrenocorticotropic Hormone↗
PubMed1991

Studies of bone marrow and leucocyte counts in peripheral blood in fetal and newborn foals.

Clinical and pathological records of 124 foals were studied. The foals were assigned to six groups; normal, premature, dysmature, bacterially infected, neonatal maladjustment syndrome and Equid herpesvirus type 1 (EHV-1) infected. Also, 6 pony fetuses were sampled via catheters in the umbilical vein and artery between 280 and 310 days gestation. Bone marrow aspiration was performed on a further 14 foals. Premature foals had significantly lower neutrophil counts than normal foals up to 5 h. Foals with bacterial infections had significantly lower neutrophil counts up to age 12 h. EHV-1 infected foals had significantly lower neutrophil counts up to age 24 h and significantly lower lymphocyte counts than all other groups up to age 12 h. Premature foals showed a higher neutrophil count and neutrophil/lymphocyte (N:L) ratio in survivors compared with non-survivors when all ages were considered, although the differences were not significant before 35 h. Discriminant analysis showed a 99% chance that the EHV-1 group could be identified from all other groups except dysmature foals, where discrimination between the two groups was about 90%. In catheterized fetuses, age-related increases in neutrophil counts and the N:L ratio occur from 280 to 310 days of gestation. In one preparation available for study leading up to parturition, the N:L ratio widened during the 3 days pre-partum. The bone marrow aspirates showed no significant changes in the myeloid:erythroid (M:E) ratio during the first 4 days post partum. The left shift (LS) index was significantly higher in foals suffering bacterial infection compared with normal or dysmature foals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Production of 5 alpha-dihydroprogesterone during late pregnancy in the mare.

Changes in the progesterone metabolite 5 alpha-dihydroprogesterone (5 alpha-DHP) in maternal plasma in late gestation, and possible sites of production of this steroid were studied in pony and Thoroughbred mares by an enzyme-linked immunosorbant assay for 5 alpha-DHP. In Thoroughbred mares, plasma 5 alpha-DHP increased from 63.7 +/- 10.5 ng/ml (27 days pre-partum) to 161.7 +/- 30.8 ng/ml (1 day pre-partum) falling to 90.2 +/- 16.1 ng/ml on the day of parturition. In pony mares, values rose from 30.8 +/- 8.1 ng/ml (27 days pre-partum) to 79.1 +/- 30.8 ng/ml (3 days pre-partum) and then decreased to 28.2 +/- 7.1 ng/ml on the day of parturition. Concentrations of 5 alpha-DHP were greater in the umbilical and uterine veins than in the corresponding umbilical and uterine artery samples. Tissues incubated with isotopically-labelled substrates showed that the fetal placenta converted pregnenolone to progesterone (47.5 +/- 9.0%). Endometrium metabolised [3H]pregnenolone to progesterone and 5 alpha-DHP (11.0 +/- 3.0% and 7.8 +/- 2.4%, respectively), and [14C]progesterone to 5 alpha-DHP (9.3 +/- 2.5%). Deuterium-labelled substrates were used to confirm the identity of these products by gas chromatography-mass spectrometry. Negligible amounts of 5 alpha-DHP were formed by other fetal tissues (adrenal, liver, kidney and testis). The results show that 5 alpha-DHP production in late pregnancy is derived primarily from endometrial metabolism of pregnenolone and/or progesterone.

5-alpha-Dihydroprogesterone↗
PubMed1991

Metabolic changes in thoroughbred and pony foals during the first 24 h post partum.

Metabolic rates, rectal temperatures and respiratory quotients (RQ) were determined during the first 24 h post partum in Thoroughbred and pony foals and in relation to environmental temperature. Both breeds had high metabolic rates (greater than 200 W/m2) during the first hour post partum when they were wet and shivering; by 4 to 24 h values were fairly steady at about 153 and 105 W/m2 for Thoroughbred and pony foals, respectively. At birth, rectal temperature was lower in Thoroughbred foals than in pony foals; values increased during the first hour, and then decreased. At 24 h of age, both breeds had a rectal temperature of 38.4 degrees C. RQ values were high (greater than 0.9) at birth in both breeds, declining to about 0.82 by 4 to 24 h of age. At similar environmental temperatures, the metabolic rates per unit area of Thoroughbred foals were higher than those of pony foals at all ages. The results indicate that breed differences may exist between the thermal responses of newborn Thoroughbred and pony foals.

Animals↗
PubMed1991

The placenta as a determinant of fetal well-being in normal and abnormal equine pregnancies.

One hundred twenty-four horse placentas were evaluated according to gross appearance, weight and surface area. Grossly abnormal placentas were photographed, and histological sections were taken from abnormal appearing areas, and from representative areas (pregnant horn, non-pregnant horn, body and cervical pole) in both normal and abnormal placentas. Information about the resulting foals was obtained and correlations examined. Histological sections were reviewed and related to the resulting foals. Four normal fresh placentas were infused with dyes to ascertain the blood supply to various areas. Foal weight was statistically related to both allantochorionic surface area and allantochorionic weight. When normal placental surface area was divided by foal weight and related to gestational age, a statistical (P less than 0.0001 and r = 0.829) relationship emerged. Long cords were seen frequently with fetal demise. Histological abnormalities in the placenta were highly associated with fetal demise or fetal abnormalities, with only 2 normal Thoroughbred foals resulted from the 23 placentas exhibiting abnormal histology. Among the ponies, the same relationship held, with 3 normal ponies delivered from 9 abnormal placentas. Normal placentas were associated with normal offspring in most cases. Perfusion studies indicated that, in the four placentas studied, one umbilical artery supplied the cervical area and the non-pregnant horn, whereas the other supplied the pregnant horn. The body had a mixed supply from both arteries. This study evaluated the feto-placental unit in terms of normal and abnormal measurements and histology related to foal outcome. The presence of abnormal histological appearance of the placenta appeared to be more closely associated with foal abnormality than the percentage of placental area involved in the abnormal process. More information is needed before placental blood supply can be related to abnormal processes.

Animals↗
PubMed1991

Plasma progestagen concentrations in the normal and dysmature newborn foal.

Radioimmunoassay (RIA) and gas chromatography-mass spectrometry (GC-MS) were used to determine plasma progestagen concentrations in the normal and premature foal. Radioimmunoassay provides a profile of plasma progestagens with respect to time but, due to the non-specific nature of the technique and without prior chromatographic purification, quantitative data based on RIA analysis must be interpreted with caution. In contrast, the greater specificity of GC-MS allows identification of specific plasma progestagens and measuring of multiple analytes in a single analysis. Both techniques demonstrated a marked difference in plasma progestagen concentrations between the normal and abnormal foal. GC-MS studies demonstrated that the plasma steroid profile was dominated by pregnenolone and 5-pregnene-3 beta, 20 beta-diol. Measuring the amounts of these 2 steroids in a single analysis demonstrated persistent high concentrations in premature foals, whereas concentrations decreased rapidly in the first few hours following birth in the normal foal. Preliminary analyses of urinary concentrations in the 2 steroids demonstrated again differences between normal and abnormal foals.

Animals↗
PubMed1990

Hypoxanthine phosphoribosyltransferase activity in tissues and hypoxanthine concentrations in plasma and CSF of the horse in comparison with other species.

1. Plasma hypoxanthine and xanthine concentrations are very low in the horse and low in rat, mouse and greyhound compared to concentrations in beagles, man, sheep and rabbit. 2. Activities in erythrocytes of the main enzyme metabolizing hypoxanthine, hypoxanthine phosphori-bosyltransferase, show a similar pattern (Tax et al., 1976, Comp. Biochem. Physiol. 54B, 209-212); thus low activities have been found where plasma concentrations were low. 3. Hypoxanthine phosphoribosyltransferase activities in horse tissue other than erythrocytes are similar to those in man and rabbit with high activities in brain; this enzyme may therefore be functionally important in equine brain.

Adenosine Triphosphate↗
PubMed1989

Evaluation of three strip tests for measuring electrolytes in mares' pre-partum mammary secretions and for predicting parturition.

Three strip test kits which measure calcium and/or magnesium in mares' mammary secretions were compared and assessed for their accuracy in:- 1) measuring these electrolytes compared to standard laboratory measurements, and 2) predicting the time of parturition. Daily samples of mammary secretions were obtained pre-partum from 35 Thoroughbred mares and allocated a score. Measurement of mammary secretion calcium and/or magnesium by the strip tests and laboratory methods correlated significantly (P less than 0.001). The results obtained for prediction of parturition were analysed by two methods. Method i) indicated that the majority of mares had a maximum score on the day of birth. However, the second method of analysis included all prepartum scores and this demonstrated that maximum scores occurred on more occasions prior to the day of birth than on the day of birth itself. The number of nights spent attending mares, and the percentage of occasions when foaling was missed, were also calculated for given strip test scores. The results indicate that the test kits are not particularly accurate in predicting time of parturition although they are a reliable means of measuring mammary secretion calcium and/or magnesium. It is suggested that the test kits may be more helpful by indicating when it is not necessary to attend mares at night.

Animals↗
PubMed1987

Plasma concentrations of progestagens, oestrone sulphate and prolactin in pregnant mares subjected to natural challenge with equid herpesvirus-1.

Multiparous pregnant mares, on two studfarms, were studied following natural challenge with equid herpesvirus-1 (EHV-1). They were divided into three groups according to serum complement fixation titres: Group A (N = 11) were not challenged and delivered normal foals; Group B (N = 13) were challenged but delivered normal foals; Group C (N = 23) were challenged and delivered infected foals which were stillborn or lived for less than 31 h. In Groups A and B mean (+/- s.d.) gestational age at delivery was 343 (+/- 8) and 339 (+/- 8) days respectively, whereas in Group C it was significantly (P less than 0.01) shorter (294 +/- 44 days). Group C mares had significantly lower pre-partum concentrations of progestagens except for 2 mares in which the values were comparable to those of mares in Groups A and B; one of these 2 mares delivered a live foal which survived for 31 h. Thin-layer chromatography showed that substances eluting in RF positions similar to 20 alpha-dihydroprogesterone and 5 alpha-pregnane-3,20-dione, were the main progestagen metabolites in plasma at 275-295 and 305-335 days gestation respectively. Incubation of liver, placenta, gonads, kidney and brain revealed no significant difference in the ability of virus-infected and non-infected fetal tissues to metabolize labelled progesterone in the presence of NADPH. Concentrations of plasma oestrone sulphate pre partum, from all groups of mares, were related to gestational age. Plasma prolactin concentrations were elevated at parturition in mares in Groups A and B but lower values were observed in Group C. We conclude that (1) endocrine patterns in maternal peripheral blood of mares with EHV-1 infected fetuses are similar to those of mares carrying normal fetuses and probably are related to gestational age at the time of delivery; and (2) substantial quantities of progestagen metabolites are found in the plasma of late-term pregnant mares.

Abortion, Veterinary↗
PubMed1987

Sympathoadrenal and other responses to hypoglycaemia in the young foal.

The effects of insulin-induced hypoglycaemia on plasma catecholamines, cortisol and metabolites have been examined in newborn and 7-14-day-old foals. The fall in plasma glucose elicited by the highest dose of insulin (1.0 i.u./kg) given to the neonates was slower in onset and less severe in effect than 0.5 i.u./kg in the older foals. There was a significant inverse correlation between the concentrations of glucose and adrenaline (but not noradrenaline) in plasma once the glucose level had fallen below 2 mmol/l; the adrenergic response to hypoglycaemia was greater in the 7-14-day-old foals than in the neonates. No significant changes in glucose or catecholamines were seen after fasting alone. The adrenocortical response to hypoglycaemia was poor after birth, but significant changes occurred in the older foals with a 3-fold increase in plasma cortisol at 60 min after 0.5 i.u. insulin/kg. There were significant increases in plasma FFA after hypoglycaemia in both groups of animals, but the rise was less pronounced in the neonates. A significant positive correlation was found between plasma adrenaline and FFA values. Hypoglycaemia also resulted in a significant rise in plasma lactate and a slow fall in alpha-amino nitrogen. These findings show that hypoglycaemia in the foal is followed by stimulation of the adrenal medullary component of the sympathetic system and by activation of the adrenal cortex with a number of consequent metabolic changes. The hypoglycaemic effects of insulin were more intense and the response more rapid in the older foals than in the neonates, which exhibited some degree of insulin resistance.

Animals↗
PubMed1986

Study of arterial blood pressure in newborn foals using an electronic sphygmomanometer.

An electronic sphygmomanometer which functions on oscillometric principles, was used to measure arterial blood pressure in foals. Its accuracy was assessed by comparison with results obtained by direct measurement in anaesthetised pony foals, aged 34 to 64 days. Correlations between data obtained by the two methods were highly significant but the sphygmomanometric readings were consistently lower than those obtained by direct measurement. An equation was derived from the pooled values for mean, systolic and diastolic pressure measurements. This was used as a correction factor when the oscillometric method was employed in the field on Thoroughbred foals, during the first three days post partum, and on pony foals during the first day only. There were no significant differences between systolic, diastolic and mean values in Thoroughbreds on Days 1, 2 or 3 after birth. Measurements recorded on the first day after foaling were significantly lower (P less than 0.025) in ponies than in Thoroughbreds. Blood pressure measurements in Thoroughbreds and ponies were substantially higher than those reported previously using the ultrasonic Doppler technique.

Animals↗