Small for gestational age and age at menarche in a contemporary population-based U.S. sample.

Children born small for gestational age (SGA) may be at risk for earlier puberty and adverse long-term health sequelae. This study investigates associations between SGA and age at menarche using secondary data on 1,027 female children in a population-based U.S. birth cohort that over-sampled non-marital births, which in the U.S. is a policy-relevant population. SGA was defined as <10th percentile of weight for gestational age compared to the national U.S. distribution. We estimated unadjusted and adjusted Ordinary Least Squares (OLS) models of associations between SGA and age at menarche in years, as well as unadjusted and adjusted logistic regression models of associations between SGA and early menarche (before age 11). SGA was not significantly associated with earlier age at menarche, even when adjusting for maternal sociodemographic characteristics, prenatal smoking, and maternal pre-pregnancy overweight and obesity. Similarly, SGA was not significantly associated with the odds of menarche occurring before age 11. However, maternal non-Hispanic Black race-ethnicity, Hispanic ethnicity, and pre-pregnancy obesity all had independent associations with average earlier age at menarche and menarche before age 11. Thus, maternal risk factors appear to play more influential roles in determining pubertal development.

Microglia provide structural resolution to injured dendrites after severe seizures.

Although an imbalance between neuronal excitation and inhibition underlies seizures, clinical approaches that target these mechanisms are insufficient in containing seizures in patients with epilepsy, raising the need for alternative approaches. Brain-resident microglia contribute to the development and stability of neuronal structure and functional networks that are perturbed during seizures. However, the extent of microglial contributions in response to seizures in vivo remain to be elucidated. Using two-photon in vivo imaging to visualize microglial dynamics, we show that severe seizures induce formation of microglial process pouches that target but rarely engulf beaded neuronal dendrites. Microglial process pouches are stable for hours, although they often shrink in size. We further find that microglial process pouches are associated with a better structural resolution of beaded dendrites. These findings provide evidence for the structural resolution of injured dendrites by microglia as a form of neuroprotection.

The GluN2A Subunit Regulates Neuronal NMDA receptor-Induced Microglia-Neuron Physical Interactions.

Microglia are known to engage in physical interactions with neurons. However, our understanding of the detailed mechanistic regulation of microglia-neuron interactions is incomplete. Here, using high resolution two photon imaging, we investigated the regulation of NMDA receptor-induced microglia-neuron physical interactions. We found that the GluN2A inhibitor NVPAAM007, but not the GluN2B inhibitor ifenprodil, blocked the occurrence of these interactions. Consistent with the well-known developmental regulation of the GluN2A subunit, these interactions are absent in neonatal tissues. Furthermore, consistent with a preferential synaptic localization of GluN2A subunits, there is a differential sensitivity of their occurrence between denser (stratum radiatum) and less dense (stratum pyramidale) synaptic sub-regions of the CA1. Finally, consistent with differentially expressed GluN2A subunits in the CA1 and DG areas of the hippocampus, these interactions could not be elicited in the DG despite robust microglial chemotactic capabilities. Together, these results enhance our understanding of the mechanistic regulation of NMDA receptor-dependent microglia-neuronal physical interactions phenomena by the GluN2A subunit that may be relevant in the mammalian brain during heightened glutamatergic neurotransmission such as epilepsy and ischemic stroke.