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Biomedical subjects

P D Rossdale

Publications and source records attributed to P D Rossdale.

At least 19 recordsLinked to original sources
PubMed2004

Effects of manipulating intrauterine growth on post natal adrenocortical development and other parameters of maturity in neonatal foals.

REASONS FOR PERFORMING STUDY: Intrauterine growth retardation (IUGR) impairs post natal adaptive responses and is associated with increased adrenocortical activity in many species. OBJECTIVES: To determine whether a restricted or enhanced intrauterine environment affects neonatal adaptation and adrenocortical function in horses. METHODS: Embryos from large (577 kg) Thoroughbred (TB) mares were transferred to smaller (343 kg) pony (P) mares and vice versa, to create a restricted (TB-in-P, n = 11) or enhanced (P-in-TB, n = 8) intrauterine environment. Control groups (TB-in-TB, n = 8; P-in-P, n = 7) were also included. RESULTS: Thirty foals were born live at full term (range 314-348 days) and 4 (3 TB-in-P, 1 P-in-TB) were stillborn between 275 and 335 days. TB-in-P foals were significantly (P<0.05) lighter than TB-in-TB, but heavier than P-in-P foals. TB-in-P foals took longer to first stand and suck and some had fetlock hyperextension and low (<4 g/l) plasma immunoglobulin G concentrations. Other foal groups showed normal behavioural responses. Haematological parameters were normal in all 4 groups of foals. Plasma ACTH levels were high at birth and plasma cortisol concentrations increased after delivery and returned to baseline within 6 h post partum in all but the TB-in-P foals, which had elevated levels until 48 h post partum. Plasma cortisol concentrations increased in all groups following exogenous ACTH administered on Days 1 and 5 postpartum. CONCLUSIONS: The TB-in-P foals showed IUGR and impaired post natal adaptive responses with basal hypercortisolaemia. POTENTIAL RELEVANCE: Foals born following IUGR may require clinical assistance in the early post natal period, but appear mature with respect to adrenocortical function.

Adrenal Cortex↗
PubMed2003

Ontogeny of uteroplacental progestagen production in pregnant mares during the second half of gestation.

In pregnant mares during late gestation, little, if any, progesterone (P4) is found in the maternal circulation. Hence, quiescence of the equine uterus is believed to be maintained by metabolites of pregnenolone and P4 known as progestagens, which are produced by the uteroplacental tissues. However, little is known about the ontogeny, distribution, or actual rates of uteroplacental progestagen production in pregnant mares and their fetuses during the second half of pregnancy. Therefore, the present study measured the rates of uteroplacental uptake and output of eight specific progestagens in chronically catheterized, pregnant pony mares from 180 days to term. No significant uteroplacental uptake of any of the eight individual progestagens was observed from the uterine circulation. In contrast, significant uteroplacental uptake was observed for five of the eight individual progestagens from the umbilical circulation, and the uptakes increased toward term. The major uteroplacental progestagen outputs were 5 alpha-pregnane-3,20-dione (5 alphaDHP) and 20 alpha-hydroxy-5 alpha-pregnan-3-one (20 alpha 5P). These were released into both the umbilical and uterine circulations at rates that increased toward term. The majority of the total uteroplacental 20 alpha 5P output was distributed into the uterine circulation at all gestational ages studied. In contrast, distribution of the total uteroplacental 5 alphaDHP output switched from preferential delivery into the uterine circulation before 220 days of gestation to release predominantly into the umbilical circulation after 260 days. These findings demonstrate that uteroplacental progestagen production changes during the second half of gestation, which may have important implications for the maintenance of pregnancy and the onset of labor in the mare.

Animals↗
PubMed2002

Influence of maternal size on placental, fetal and postnatal growth in the horse. I. Development in utero.

The interacting influences of maternal size and fetal genotype on placental and fetal development in the mare were assessed by comparing conventional within-breed Thoroughbred (Tb-in-Tb, n = 7) and Pony (P-in-P, n = 7) control pregnancies established by artificial insemination (AI) with between-breed (Tb-in-P, n = 8; deprived in utero condition and P-in-Tb, n = 7; luxurious in utero condition) experimental pregnancies established by embryo transfer. All foals were born spontaneously and the mean (+/- SEM) duration of gestation in the two groups of control mares was significantly different (P < 0.001) at 325 +/- 3.0 days for the P-in-P pregnancies and 339 +/- 3.0 days for the Tb-in-Tb pregnancies, whereas the durations of gestation for the two experimental groups were very similar and midway between those of the control pregnancies at 332 +/- 2.8 days for the Tb-in-P and 331 +/- 2.7 days for the P-in-Tb. Mean (+/- SEM) foal birth weight and the mean (+/- SEM) values for the mass, gross area and volume of the allantochorion were all highest in the seven Tb-in-Tb pregnancies (53.1 +/- 2.6 kg, 3.8 +/- 0.3 kg, 12.9 +/- 0.3 x 10(3) cm(2), 3.5 +/- 0.2 l, respectively) and lowest in the seven P-in-P control pregnancies (24.0 +/- 1.3 kg, 1.7 +/- 0.1 kg, 8.3 +/- 0.3 x 10(3) cm(2), 1.8 +/- 0.1 l, respectively). These parameters were higher in the seven P-in-Tb pregnancies (37.9 +/- 2.1 kg, 2.7 +/- 0.1 kg, 10.1 +/- 0.5 x 10(3) cm(2), 2.5 +/- 0.1 l, respectively) than in the eight Tb-in-P (33.0 +/- 2.4 kg, 2.3 +/- 0.2 kg, 9.0 +/- 0.5 x 10(3) cm(2), 2.1 +/- 0.1 l) experimental pregnancies. Foal birth weight was positively correlated with the mass (r = 0.84, P < 0.001), gross area (r = 0.87, P < 0.001) and volume (r = 0.91, P < 0.001) of the allantochorion, and maternal weight was also positively correlated with both the mass and gross area of the allantochorion (r = 0.64 and 0.69, respectively; both P < 0.001). Application of stereology to multiple random biopsies recovered from each placenta produced mean values for the surface density of microcotyledons on the allantochorion (S(v)). Values were higher in Thoroughbred than in Pony mares regardless of the breed of fetus being carried. Multiplication of S(v) by the volume of the allantochorion to give the total microscopic area of fetomaternal contact at the placental interface was also positively correlated with foal birth weight (r = 0.84, P < 0.001). Foal birth weight was determined by the microscopic area of fetomaternal contact of the placenta and there were no differences in foal weight per m(2) of placenta regardless of fetal or maternal genomes. Thus, the results indicate that in equids, maternal size interacts with both the maternal and fetal genotypes to control the rate and extent of fetal growth by influencing the gross area of the diffuse allantochorion, and the density, complexity and depth of the microcotyledons on its surface.

Analysis of Variance↗
PubMed2001

Organogenesis of lung and kidney in Thoroughbreds and ponies.

Equine lung and kidney organogenesis has not previously been examined with the use of unbiased stereological techniques. The present study examined healthy (control) pony and Thoroughbred lungs and kidneys to establish baseline data of organ development from before birth until maturity at age 3-18 years. Whole left lungs and kidneys were collected from 45 equine postmortem examinations (34 Thoroughbred, 11 pony). Stereological techniques were used to estimate whole kidney, cortex and medulla volume, total glomerular number and volume-weighted mean glomerular volume, lung volume, total terminal bronchiolar duct ending number and total gas exchange surface area. Lungs were demonstrated to be more developed at birth in ponies compared with Thoroughbreds. Thoroughbreds showed continued lung development after birth, a unique micromorphogenic postnatal development. Kidneys were developed equally in ponies and Thoroughbreds. This study has provided data on the baseline development of the equiune lung and kidney which can be used in further studies to examine whether the development of these organs is affected by specific illnesses.

Animals↗
PubMed2001

Measurement of serum amyloid A in the neonatal foal using a latex agglutination immunoturbidimetric assay: determination of the normal range, variation with age and response to disease.

This paper describes the use of a latex agglutination assay to measure serum amyloid A (SAA) in the neonatal foal. The normal range and response to clinical disease was determined. This retrospective study evaluated SAA concentrations over the first 3 days postpartum of 226 Thoroughbred foals judged to be clinically healthy. The normal range for each day was determined; levels were found to be significantly highest on Day 2 (Day 1 vs. Day 2 P<0.0001). The 95th percentile for Days 1-3 was 27.1 mg/l. Clinical records of 133 foals, presented as first or second opinion cases, were evaluated. Foals were divided into 4 groups; septicaemia (S), focal infection (FI), failure of passive transfer (FPT) and noninfectious disease (NI). There was a statistically significant difference (P<0.0001) between SAA concentrations of control foals compared to Groups S and FI. There was no statistically significant difference between controls and Groups FPT and NI. When Group NI was compared to Groups S and FI, there was a statistically significant difference (P<0.0001). The authors suggest that SAA determined by this latex agglutination assay might be a helpful aid in the diagnosis of septicaemia and focal infection in neonatal foals; levels >100 mg/l are highly suggestive of infection in young foals.

Age Factors↗
PubMed2000

Establishment and characterization of equine autonomic ganglion cell lines to enable direct testing of candidate toxins involved in equine dysautonomia (grass sickness).

To enable direct testing of a range of potential toxins or pathogens that might be involved in grass sickness, equine thoracic sympathetic chain ganglion cell lines were established from primary cell cultures by retroviral-mediated transduction of the temperature-sensitive mutant of the establishment oncogene encoding SV40 large T antigen. Morphological and behavioral features, temperature dependence, and immunocytochemical characteristics of the cell lines were investigated. The majority of cells were noradrenergic neurons in which dopamine-beta-hydroxylase, the enzyme that catalyzes norepinephrine synthesis, and neuropeptide Y coexisted. Cells treated with plasma from grass sickness cases that had previously been shown to induce autonomic nervous system damage when injected into normal horses showed significantly decreased mitochondrial function after 1 day. After 3 days exposure most cells showed severe degeneration in contrast to those treated with normal plasma. Liver and lung cell lines were also susceptible to plasma, suggesting that the toxin is not specifically neurotoxic.

Animals↗
PubMed2000

Stereological estimation of volume-weighted mean glomerular volume from arbitrary sections of the equine kidney.

Mean glomerular volume has previously been estimated, using stereological techniques, specifically the point-sampled intercept (PSI), either from isotropic or from vertical sections. As glomeruli are approximately spherical structures, the same stereological technique was carried out on vertical and arbitrary sections to determine whether section orientation had any effect on mean glomerular volume estimation. Equine kidneys from 10 individuals were analysed using the PSI method of estimating volume-weighted mean glomerular volume (MGV); for each kidney, arbitrary and vertical sections were analysed. MGVs were not significantly different between arbitrary and vertical sections (P = 0.691) when analysing the data with the paired t test; when plotting MGV estimates from arbitrary sections against those from vertical sections the intercept was found not to be significantly different from zero (P > 0.8) and the slope of the regression line not to be significantly different from 1.0 (P > 0.4). For the estimation of MGV in equine kidneys using PSI, arbitrary sections may be used if it is not possible to use isotropic or vertical sections, but some caution must be exercised in the interpretation of results so gained.

Animals↗
PubMed1998

The effects of intrafetal ACTH administration on the outcome of pregnancy in the mare.

Enhanced adrenocortical activity in the fetus is related to the onset of parturition in many species. The aim of this study was to determine the effect of injection of fetal ACTH on gestational length and fetal viability in the horse. Pony mares (n=23) were studied from 300 days gestation. Seven control mares (Group 1) received three consecutive intrafetal injections of sterile water, while fetuses of a further 16 mares received Depot ACTH1-24. These mares were either allowed to foal spontaneously (Group 2, n=4) or delivery was induced within 3 days of the last fetal injection (Group 3, n=7); 5 mares aborted within 48 h of intrafetal ACTH injection. Maternal plasma progestagen concentrations increased significantly (P<0.05) in Groups 2 and 3 mares following intrafetal ACTH injection, compared with Group 1 mares. All Group 1 mares delivered live foals at a median gestational age of 327 days (interquartile range, 323 334), except one that aborted 16 days after the last fetal injection. Gestational length was significantly (P<0.05) shortened in Group 2 mares (median 314 [312-314]) days compared with controls. Group 1 and Group 2 foals showed normal postnatal adaptive responses and endocrine (plasma cortisol/progestagens) patterns. Group 3 mares delivered live foals at 306 (306-308) days gestation except one that aborted. Their foals were less mature compared with Groups 1 and 2 foals. Eight ACTH-injected fetuses were meconium-stained at delivery, including four that were aborted. Eight mares had thickened placentae, including three that aborted. The data show that both precocious maturation of the equine fetus and a significant reduction in gestational length compared with controls may be achieved in pony mares by intrafetal ACTH injections. This is probably mediated via adrenal regulation of fetal maturation and production of maternal progestagens.

Adrenocorticotropic Hormone↗
PubMed1998

Glomerular filtration rate, effective renal plasma flow, blood pressure and pulse rate in the equine neonate during the first 10 days post partum.

The aim of this study was to determine glomerular filtration rate (GFR), effective renal plasma flow (RPF) and filtration fraction (FF) values in Pony foals during the first 10 days post partum in order to assess any age-related changes and the reliability of the single injection inulin/p-aminohippurate (PAH) method. Arterial blood pressure and pulse rate were determined in Pony and Thoroughbred (TB) foals during the first 10 days post partum to establish age-related changes, differences between breeds and possible interrelationships with GFR and RPF. Inulin and PAH were injected intravenously (i.v.) in healthy Pony foals (n = 6) on Days 1, 2, 4, 7 and 10 post partum. Blood samples were collected via the contralateral jugular catheter over a 4 h period. Plasma clearances of inulin and PAH showed that GFR and RPF, respectively, remained relatively constant throughout the post natal period, and were similar to values reported for mature horses. The GFR measurements obtained using the inulin method gave clearance values that were significantly higher (P < 0.01) than those of creatinine clearance performed in a separate group of Pony foals (n = 7). Blood pressure and pulse rates were measured using an electronic sphygmomanometer in TB (n = 6) and Pony foals (n = 7) on Days 1, 2, 3, 4, 7 and 10 postpartum. There were no significant differences in these measurements between the breeds, and both cardiovascular parameters increased during the first 3 days post partum. Values remained unchanged for the rest of the study period. Although measurements of GFR, RPF, blood pressure and pulse rates were not determined in the same animals, blood pressure and pulse rates did not appear to correlate with either GFR or RPF in the Pony foals during the post natal period.

Aging↗