Seasonal adaptations in physiology exhibited by many animals involve an interface between biological timing and specific neuroendocrine systems, but the molecular basis of this interface is unknown. In this study of Siberian hamsters, we show that the availability of thyroid hormone within the hypothalamus is a key determinant of seasonal transitions. The expression of the gene encoding type III deiodinase (Dio3) and Dio3 activity in vivo (catabolism of T(4) and T(3)) is dynamically and temporally regulated by photoperiod, consistent with the loss of hypothalamic T(3) concentrations under short photoperiods. Chronic replacement of T(3) in the hypothalamus of male hamsters exposed to short photoperiods, thus bypassing synthetic or catabolic deiodinase enzymes located in cells of the ependyma of the third ventricle, prevented the onset of short-day physiology: hamsters maintained a long-day body weight phenotype and failed to undergo testicular and epididymal regression. However, pelage moult to a winter coat was not affected. Type II deiodinase gene expression was not regulated by photoperiod in these hamsters. Collectively, these data point to a pivotal role for hypothalamic DIO3 and T(3) catabolism in seasonal cycles of body weight and reproduction in mammals.

Our data suggest that severe HPA-1a NAIT is underdiagnosed in the absence of routine antenatal screening. Serious bleeding complications and ICH, however, occur less frequently in first cases of NAIT than suspected from the literature, and the costs of screening and possible intervention must be balanced against the procedural risks.

Outcomes of Zika virus (ZIKV) infection in pregnant women vary from the birth of asymptomatic offspring to abnormal development and severe brain lesions in fetuses and infants. There are concerns that offspring affected in utero and born without apparent symptoms may develop mental illnesses. Therefore, animal models are important to test interventions against in utero infection and health sequelae in symptomatic and likely more widespread asymptomatic offspring. To partially reproduce in utero infection in humans, we directly inoculated selected porcine conceptuses with ZIKV. Inoculation resulted in rapid trans-fetal infections, persistent infection in conceptuses, molecular pathology in fetal brains, fetal antibody and type I interferon responses. Offspring infected in utero showed ZIKV in their fetal membranes collected after birth. Some in utero affected piglets were small, depressed, had undersized brains, and showed seizures. Some piglets showed potentially increased activity. Our data suggest that porcine model of persistent in utero ZIKV infection has a strong potential for translational research and can be used to test therapeutic interventions in vivo.