Effects of neonatal dexamethasone or methylprednisolone on rat growth and neurodevelopment

Glucocorticoids in a Neonatal Hyperoxic Lung Injury Model: Pulmonary and Neurotoxic effects

BACKGROUND

We aimed to compare the effect of dexamethasone (Dex), hydrocortisone (Hc), and methylprednisolone (Mpz) at equivalent doses on somatic growth, lung healing, and neurotoxicity in a hyperoxic rat model. We hypothesized that Mpz and Hc would be superior to Dex with less neurotoxicity by exerting similar therapeutic efficacy on the injured lung.

METHODS

Neonatal rats were randomized to control, bronchopulmonary dysplasia (BPD), Dex, Hc, and Mpz groups. All drugs were administered daily following day 15 over 7 days. Histopathological and immunohistochemical analyses of the lung and brain were performed on day 22.

RESULTS

All types had much the same impact on lung repair. Oxidative markers in the lung were similar in the steroid groups. While nuclear factor erythroid 2-related factor and heat-shock protein 70 dropped following steroid treatment, no difference was noted in other biochemical markers in the brain between the study groups. Apoptotic activity and neuron loss in the parietal cortex and hippocampus were noted utmost in Dex, but alike in other BPD groups.

CONCLUSIONS

Mpz does not appear to be superior to Dex or Hc in terms of pulmonary outcomes and oxidative damage in the brain, but safer than Dex regarding apoptotic neuron loss.

IMPACT

This is the first study that compared the pulmonary efficacy and neurotoxic effects of Dex, Hc, and Mpz simultaneously in an established BPD model. This study adds to the literature on the importance of possible antioxidant and protective effects of glucocorticoid therapy in an oxidative stress-exposed brain. Mpz ended up with no more additional neuron loss or apoptosis risk by having interchangeable effects with others for the treatment of established BPD. Mpz and Hc seem safe as a rescue therapy in terms of adverse outcomes for established BPD in which lung and brain tissue is already impaired.

Morpho-functional characteristics of rat fetal thyroid gland are affected by prenatal dexamethasone exposure

Thyroid hormones (TH) and glucocorticoids strongly contribute to the maturation of fetal tissues in the preparation for extrauterine life. Influence of maternal dexamethasone (Dx) administration on thyroid glands morpho-functional characteristics of near term rat fetuses was investigated applying unbiased stereology. On the 16th day of pregnancy dams received 1.0mg/Dx/kg/b.w., followed by 0.5mg/Dx/kg/b.w. on the 17th and 18th days of gestation. The control females received the same volume of saline. The volume of fetal thyroid was estimated using Cavalieri's principle; the physical/fractionator design was applied for the determination of absolute number of follicular cells in mitosis and immunohistochemically labeled C cells; C cell volume was measured using the planar rotator. The functional activity of thyroid tissue was provided from thyroglobulin (Tg) and thyroperoxidase (TPO) immunohistochemical staining. Applying these design-based modern stereological methods it was shown that Dx treatment of gravid females led to a significant decrease of fetal thyroid gland volume in 19- and 21-day-old fetuses, due to decreased proliferation of follicular cells. The Tg and TPO immunohistochemistry demonstrated that intensive TH production starts and continues during the examined period in control and Dx-exposed fetuses. Under the influence of Dx the absolute number of C cells was lower in both groups of near term fetuses, although unchanged relation between the two populations of endocrine cells, follicular and C cells suggesting that structural relationships within the gland are preserved. In conclusion maternal glucocorticoid administration at the thyroid gland level exerts growth-inhibitory and maturational promoting effects in near term rat fetuses.

Staging perspectives in neurodevelopmental aspects of neuropsychiatry: agents, phases and ages at expression

Neurodevelopmental risk factors have assumed a critical role in prevailing notions concerning the etiopathogenesis of neuropsychiatric disorders. Staging, diagnostic elements at which phase of disease is determined, provides a means of conceptualizing the degree and extent of factors affecting brain development trajectories, but is concurrently specified through the particular interactions of genes and environment unique to each individual case. For present purposes, staging perspectives in neurodevelopmental aspects of the disease processes are considered from conditions giving rise to neurodevelopmental staging in affective states, adolescence, dopamine disease states, and autism spectrum disorders. Three major aspects influencing the eventual course of individual developmental trajectories appear to possess an essential determinant influence upon outcome: (i) the type of agent that interferes with brain development, whether chemical, immune system activating or absent (anoxia/hypoxia), (ii) the phase of brain development at which the agent exerts disruption, whether prenatal, postnatal, or adolescent, and (iii) the age of expression of structural and functional abnormalities. Clinical staging may be assumed at any or each developmental phase. The present perspective offers both a challenge to bring further order to diagnosis, intervention, and prognosis and a statement regarding the extreme complexities and interwoven intricacies of epigenetic factors, biomarkers, and neurobehavioral entities that aggravate currents notions of the neuropsychiatric disorders.

Slight differences in incubation temperature affect early growth and stress endocrinology of wood duck (Aix sponsa) ducklings

Early developmental experiences, such as incubation conditions, can have important consequences for post-hatching fitness in birds. Although the effects of incubation temperature on phenotype of avian hatchlings are poorly understood, recent research suggests that subtle changes in incubation conditions can influence hatchling characteristics, including body size and condition. We designed an experiment to explore the effects of incubation temperature on hatching success, survival to 9 days post hatch, growth and the hypothalamo–pituitary–adrenal (HPA) axis in wood ducks (Aix sponsa). Wood duck eggs were collected from nest boxes and experimentally incubated at three temperatures (35.0, 35.9 and 37.0°C), each falling within the range of temperatures of naturally incubated wood duck nests. Survival and growth were monitored in ducklings fed ad libitum for 9 days post hatch. In addition, baseline and stress-induced plasma corticosterone concentrations were measured in 2 and 9 day old ducklings. Hatching success and survival to 9 days was greatest in ducks incubated at the intermediate temperature. Ducklings incubated at 35.9°C and 37.0°C had 43% higher growth rates than ducklings incubated at 35.0°C. In addition, ducklings incubated at 35.0°C had higher baseline (17–50%) and stress-induced (32–84%) corticosterone concentrations than ducklings incubated at 35.9°C and 37.0°C at 2 and 9 days post hatch. We also found a significant negative correlation between body size and plasma corticosterone concentrations (baseline and stress-induced) in 9 day old ducklings. To our knowledge, this is the first study to demonstrate that thermal conditions experienced during embryonic development can influence the HPA axis of young birds. Our results illustrate that subtle changes (<1.0°C) in the incubation environment can have important consequences for physiological traits important to fitness.