Study on NGF and VEGF during the Equine Perinatal Period-Part 2: Foals Affected by Neonatal Encephalopathy

Neonatal Encephalopathy (NE) may be caused by hypoxic ischemic insults or inflammatory insults and modified by innate protective or excitatory mechanisms. Understanding the underlying pathophysiology is important in formulating a rational approach to diagnosis. The preliminary aim was to clinically characterize a population of foals spontaneously affected by NE. The study aimed to: (i) evaluate nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) levels in plasma samples obtained in the affected population at parturition from the mare’s jugular vein, umbilical cord vein and foal’s jugular vein, as well as in amniotic fluid; (ii) evaluate the NGF and VEGF content in the plasma of foals affected by NE during the first 72 h of life/hospitalization; (iii) evaluate NGF and VEGF levels at birth/admission in relation to selected mare’s and foal’s clinical parameters; (iv) evaluate the relationship between the two trophic factors and thyroid hormone levels (TT3 and TT4) in the first 72 h of life/hospitalization; and (v) assess the mRNA expression of NGF, VEGF and brain-derived neurotrophic factor (BDNF), and their cell surface receptors, in the placenta of mares that delivered foals affected by NE. Thirteen affected foals born from mares hospitalized for peripartum monitoring (group NE) and twenty affected foals hospitalized after birth (group exNE) were included in the study. Dosage of NGF and VEGF levels was performed using commercial ELISA kits, whereas NGF, VEGF, and BDNF placental gene expression was performed using a semi-quantitative real-time PCR. In group NE, NGF levels decreased significantly from T0 to T24 (p = 0.0447) and VEGF levels decreased significantly from T0 to T72 (p = 0.0234), whereas in group exNE, only NGF levels decreased significantly from T0 to T24 (p = 0.0304). Compared to healthy foals, a significant reduction of TT3 levels was observed in both NE (T24, p = 0.0066; T72 p = 0.0003) and exNE (T0, p = 0.0082; T24, p < 0.0001; T72, p < 0.0001) groups, whereas a significant reduction of TT4 levels was observed only in exNE group (T0, p = 0.0003; T24, p = 0.0010; T72, p = 0.0110). In group NE, NGF levels were positively correlated with both TT3 (p = 0.0475; r = 0.3424) and TT4 levels (p = 0.0063; r = 0.4589). In the placenta, a reduced expression of NGF in the allantois (p = 0.0033) and a reduced expression of BDNF in the amnion (p = 0.0498) were observed. The less pronounced decrease of the two trophic factors compared to healthy foals, their relationship with thyroid hormones over time, and the reduced expression of NGF and BDNF in placental tissues of mares that delivered affected foals, could be key regulators in the mechanisms of equine NE.

Characterizing zoo-housed Bactrian camel (Camelus bactrianus) reproduction using gonadal steroid metabolite analysis in feces

Millions of people globally depend on camelids, which demands an increased knowledge of their reproduction. We used zoo-housed Bactrian camels (Camelus bactrianus) to better understand camelid reproductive physiology. Our specific objectives were to: 1) validate the use of fecal hormone metabolite analysis to characterize camel reproductive physiology during sexual maturity and pregnancy; and 2) determine the influence of season on male and female reproduction. We collected fecal samples from 1 male and 3 females housed at Lincoln Park Zoo (Chicago, IL, USA) 1 to 2 times per week for 3.5 years. Extracted hormones were analyzed using enzyme immunoassays for progestogen (FPM), estrogen (FEM), and androgen (FAM) metabolite concentrations. One female sexually matured during our study as evidenced by increased FEM baseline. Results demonstrated seasonal effects on male androgen production with FAMs higher (P < 0.05) January to June (mean ± SEM: 664.6 ± 22.6 ng/g wet feces), compared to July to December (401.6 ± 17.5 ng/g wet feces). One female experienced a persistent corpus luteum, a reproductive abnormality, which was identified by prolonged elevated FPM. FPMs increased during pregnancy for two females (452.9 ± 24.9 and 294.4 ± 19.8 ng/g wet feces) with a gestation of 404 d and 442 d, respectively. The third female never conceived. The FEMs varied (P < 0.05) during the year with no clear seasonal patterns (monthly mean range: 213.1-371.0 ng/g wet feces). Fecal hormone metabolite analysis is a validated method for assessing male seasonality and female pregnancy in the Bactrian camel and can for their management and conservation in zoos and the wild.

Equine Neonatal Encephalopathy: Facts, Evidence, and Opinions

Neonatal encephalopathy (NE) and neonatal maladjustment syndrome (NMS) are terms used for newborn foals that develop noninfectious neurologic signs in the immediate postpartum period. Cerebral ischemia, hypoxia, and inflammation leading to neuronal and glial dysfunction and excitotoxicity are considered key mechanisms behind NE/NMS. Attention has been placed on endocrine and paracrine factors that alter brain cell function. Abnormal steroid concentrations (progestogens, neurosteroids) have been measured in critically ill and NE foals. In addition to supportive treatment, antimicrobials should be considered. Controversies regarding the pathophysiology, diagnosis, and treatment of NE and NMS will remain until controlled mechanistic and therapeutic studies are conducted.

Determination of reference intervals for umbilical cord arterial and venous blood gas analysis of healthy Thoroughbred foals

Although umbilical cord blood gas analysis is considered the best way to assess in utero oxygenation in human neonates, there is limited evaluation of this method in equine neonatology. Our objectives were to assess the practicality of obtaining umbilical cord blood gas samples in the field and to determine umbilical cord arterial and venous blood gas reference intervals (RI) for healthy, newborn foals. Thoroughbred foals >320 days gestation from healthy mares with uneventful pregnancies at one stud farm were evaluated. All parturitions were observed, with paired umbilical arterial and venous whole-blood samples obtained immediately following parturition for blood gas and lactate concentrations measured in duplicate. Apgar scores were assigned immediately and 10 min after birth, with all foals subsequently examined on days 1-28 to monitor for development of perinatal asphyxia syndrome. Foals were excluded from analysis based on abnormalities of stage 2 labour, Apgar scores and gross and histological placental assessment. Data was analysed using a Student's t-test, Pearson's correlation and the Robust method with P ≤ 0.05 significant. Umbilical cord samples were simple to obtain with minimal disruption to the foaling environment. Of the n = 34 foals assessed, n = 7 were excluded based on premature placental separation deliveries. The mean time for stage 2 labour and blood gas analysis after parturition was 17.3 ± 5.1 min and 5.0 ± 2.3 min, respectively. RI were identified for umbilical arterial and venous pH (7.19-7.42 vs. 7.34-7.44), PO₂ (15.5-48.39 mmHg vs. 16.6-52.7 mmHg), PCO₂ (49.5-82.29 mmHg vs. 45.4-63.1 mmHg), SO₂ (9.19-76.89% vs. 39.9-84.88%), bicarbonate (27.3-38.7 mmol/l vs. 27.7-37.8 mmol/l), base excess (0.36-12.9 mmol/l vs. 1.97-13.1 mmol/l), TCO₂ (28.99-40.3 mmHg vs. 29.0-39.5 mmHg) and lactate (1.4-7.3 mmol/l vs. 1.3-4.9 mmol/l). Umbilical arterial samples had lower pH (P < 0.0001), PO₂ (P = 0.002) and SO₂ (P < 0.0001) and higher PCO₂ (P < 0.0001) and lactate (P < 0.0001) than venous samples. The initial Apgar score was positively correlated to umbilical arterial SO₂ (r = 0.4, P = 0.05) and negatively with umbilical arterial TCO₂ (r = -0.6, P = 0.004). Overall, umbilical cord sampling was simple and minimally disruptive, with RI obtained for blood gas measurements. RI for umbilical blood gas measurements from a larger population of healthy and unhealthy foals is required to evaluate the accuracy of this method for assessing in utero oxygenation.