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Neonicotinoid pesticides (NN) were recently reported to exhibit adverse effects in higher vertebrates. Moreover, NNs are routinely transferred from mother to offspring, raising concerns about their effects on future generations. The fetal and neonatal periods are the most critical to the formation of neural circuits in the brain through neurogenesis and differentiation, neuronal migration, axon guidance, and synaptogenesis. NN exposure throughout the fetal and neonatal periods was found to affect the neurobehavior of the offspring, but the stage-specific neurobehavioral effects are unclear. We exposed fetal and neonatal mice to a no-observed-adverse-effect level (NOAEL) of clothianidin (CLO) for 4 days during each of four developmental stages: neurite proliferation and differentiation (fetal days 9–12, CLO-1), neurite outgrowth (fetal days 15–18, CLO-2), synapse formation and astrocyte differentiation (days 1–4 after birth, CLO-3), and synapse remodeling (days 11–14 after birth, CLO-4). CLO’s neurobehavioral effects were evaluated in juveniles and adults, revealing that CLO-1 and CLO-2 caused behavioral abnormalities in adult mice. CLO-3 significantly increased locomotor activity and decreased juvenile neurons in the hippocampal dentate gyrus in adulthood. Comprehensive gene analysis of CLO-3 revealed high expression of genes related to neurite outgrowth and axonal branching in the hippocampus in juveniles and adults. These results revealed developmental stage-specific effects of a NOAEL of CLO in the fetal and neonatal periods, suggesting that the susceptibility of the fetus and neonate to CLO varies by developmental stage.

Diamide insecticides activate ryanodine receptors expressed in lepidopteran skeletal muscle and promote Ca²⁺ release in the sarcoplasmic reticulum, causing abnormal contractions and paralysis, leading to death of the pest. Although they had been thought not to act on nontarget organisms, including mammals, adverse effects on vertebrates were recently reported, raising concerns about their safety in humans. We investigated the neurotoxicity of the acute no-observed-adverse-effect level of chlorantraniliprole (CAP), a diamide insecticide, in mice using clothianidin (CLO), a neonicotinoid insecticide, as a positive control. The CLO-administered group showed decreased locomotor activities, increased anxiety-like behaviors, and abnormal human-audible vocalizations, while the CAP-administered group showed anxiety-like behaviors but no change in locomotor activities. The CAP-administered group had greater numbers of c-fos–immunoreactive cells in the hippocampal dentate gyrus, and similar to the results in a CLO-administered group in our previous study. Blood corticosterone levels increased in the CLO-administered group but did not change in the CAP-administered group. Additionally, CAP was found to decreased 3-Methoxytyramine and histamine in mice at the time to maximum concentration. These results suggest that CAP-administered mice are less vulnerable to stress than CLO-administered mice, and the first evidence that CAP exposure increases neuronal activity and induces anxiety-like behavior as well as neurotransmitter disturbances in mammals.

The expression of sex determining region of the Y chromosome (Sry) in the fetal gonads is important for male development. In a mouse model of disorders of sex development (C57BL/6 (B6)-XYᴾᴼˢ), the gonadal phenotype and the timing of Sry expression differ due to differences among B6 substrains as the genetic background. Since differences in Sry expression among B6 substrains have been speculated, the present study examined Sry expression in B6J, B6JJmsSlc, and B6NCrl mice. These substrains differed in the number of Sry-expressing cells in the gonads of embryonic mice at each developmental stage, with B6NCrl having more than the other strains. The substrains differed also in the number of Sry-expressing cells between the left and right gonads, with B6J and B6NCrl, but not B6JJmsSlc, showing left gonad-dominant Sry expression. Substrain differences existed also in the distribution of Sry-expressing cells in the medial and lateral directions of gonads. In addition, in the left gonad-dominant Sry-expressing substrains B6J and B6NCrl, the medial and central regions of the left gonad had more Sry-expressing cells than those of the right gonad. Substrains of B6 mice have not always been considered in sex differentiation studies. In the present study, however, we observed substrain differences in the number of Sry-expressing cells, left–right distribution, and medial/lateral distribution during the early stages of gonadal development in B6 mice. Therefore, future studies on sex differentiation in B6 mice should consider substrain differences.

C57BL/6J-XYPOS (B6J-XYPOS) mice, which have the Y chromosome derived from Mus musculus poschiavinus on a B6J genetic background, form ovotestes or ovaries. Previously, we replaced the genetic background of B6J-XYPOS mice with B6N and found that individuals with testes also appeared in addition to those with ovaries or ovotestes. To investigate the effect of the B6J genetic sequence on the testis differentiation, the genetic background of B6N-XYPOS mice was replaced with B6J again. The recovery of the B6J genetic background significantly decreased the incidence of testes; only ovaries developed. These results indicate that the testicular differentiation process tends to be perturbed especially in the B6J substrain. This shows the importance of substrain differences in mice usually treated as B6 collectively.

Paneth cells secrete bactericidal substances in response to bacterial proliferation on the mucosal surface without directly contacting bacteria. However, the induction mechanism of this transient secretion has not been clarified, although nervous system and/or immunocompetent cells in the lamina propria (LP) might be involved. In this study, we ultrastructurally and immunohistochemically investigated which LP cells are localized beneath Paneth cells and examined the relationship between the Paneth cell‐derived cellular processes which extended into the LP and the LP cells. The results showed that various cells—including blood capillary, subepithelial stromal cell, and nerve fiber—were present in the LP beneath Paneth cells. Endothelial cells of blood capillary were the cells most frequently found in this location; they were situated within 1 μm of the Paneth cells and possessed fenestration on the surfaces adjacent to Paneth cells. The Paneth cells rarely extended the cellular processes toward the LP across the basal lamina. Most of the cellular processes of Paneth cells contacted the subepithelial stromal cells. Immunohistochemistry revealed that the CD34+CD31−αSMA− stromal cells preferentially localized in the LP beneath the intestinal crypt base, while PDGFRαhiαSMA+ stromal cells mainly localized around the lateral portions of the intestinal crypt and PDGFRαhiαSMA− stromal cells localized in the intestinal villus. From these findings, the existence of blood capillaries beneath Paneth cells might reflect the active exocrine function of Paneth cells. Furthermore, subepithelial stromal cells, probably with a CD34+CD31−αSMA− PDGFRα−/lo phenotype, beneath the crypt base might affect Paneth cell activity by interacting with their cellular processes. Anat Rec, 301:1074–1085, 2018. © 2018 Wiley Periodicals, Inc.