Cholinergic activities affect olfactory bulb (OB) information processing and associated learning and memory. However, the presence of intrinsic cholinergic interneurons in the OB remains controversial. As a result, morphological and functional properties of these cells are largely undetermined. We characterized cholinergic interneurons using transgenic mice that selectively mark choline acetyltransferase (ChAT)-expressing cells and immunolabeling. We found a significant number of intrinsic cholinergic interneurons in the OB. These interneurons reside primarily in the glomerular layer (GL) and external plexiform layer (EPL) and exhibit diverse distribution patterns of nerve processes, indicating functional heterogeneity. Further, we found these neurons express ChAT and vesicular acetylcholine transporter (VAChT), but do not immunoreact to glutamatergic, GABAergic or dopaminergic markers and are distinct from calretinin-expressing interneurons. Interestingly, the cholinergic population partially overlaps with the calbindin D28K-expressing interneuron population, revealing the neurotransmitter identity of this sub-population. Additionally, we quantitatively determined the density of VAChT labeled cholinergic nerve fibers in various layers of the OB, as well as the intensity of VAChT immunoreactivity within the GL, suggesting primary sites of cholinergic actions. Taken together, our results provide clear evidence showing the presence of a significant number of cholinergic interneurons and that these morphologically and distributionally diverse interneurons make up complex local cholinergic networks in the OB. Thus, our results suggest that olfactory information processing is modulated by dual cholinergic systems of local interneuron networks and centrifugal projections.
The mammalian nose is a multi-functional organ with intricate internal structures. The nasal cavity is lined with various epithelia, such as olfactory, respiratory and squamous epithelia which differ markedly in anatomical locations, morphology and functions. In adult mice, the nose is covered with various skull bones, limiting experimental access to internal structures, especially those in the posterior, such as the main olfactory epithelium (MOE). Here we describe an effective method for obtaining almost entire and intact nasal tissues with preserved anatomical organization. Using surgical tools under a dissecting microscope, we sequentially remove the skull bones surrounding the nasal tissue. This procedure can be performed on both paraformaldehyde-fixed and fleshly dissected, skinned mouse heads. The entire deboning procedure takes about 20–30 min, which is significantly shorter than the experimental time required for conventional chemical-based decalcification. In addition, we present an easy method to remove air bubbles trapped between turbinates, which is critical for obtaining intact thin horizontal or coronal or sagittal sections from the nasal tissue preparation. Nasal tissue prepared using our method can be used for whole mount observation of the entire epithelia, as well as morphological, immunocytochemical, RNA in situ hybridization and physiological studies, especially in studies where region-specific examination and comparison are of interest.
Objective. To evaluate the success of a teaching certificate program by qualitatively evaluating the content and extent of participants' reflections. Methods. Two investigators independently identified themes within midpoint and final reflection essays across six program years. Each essay was evaluated to determine the extent of reflection in prompted teaching-related topic areas (strengths, weaknesses, assessment, feedback). Results. Twenty-eight themes were identified within 132 essays. Common themes encompassed content delivery, student assessment, personal successes, and challenges encountered. Deep reflection was exhibited, with 48% of essays achieving the highest level of critical reflection. Extent of reflection trended higher from midpoint to final essays, with significant increases in the strengths and feedback areas. Conclusion. The teaching certificate program fostered critical reflection and self-reported positive behavior change in teaching, thus providing a high-quality professional development opportunity. Such programs should strongly consider emphasizing critical reflection through required reflective exercises at multiple points within program curricula.
Researchers have begun to extensively examine pathological (or addictive-like) media use during adolescence and adulthood. However, few studies have examined precursors to these types of behavior (termed problematic media use) in early childhood, with even fewer examining predictors of this behavior over time. The present longitudinal study examined bidirectional associations between television (TV) content (educational, prosocial, and violence) and problematic media use over a 1-year period during early childhood. Participants included 443 children (M age at Wave 1 = 29.68 months) and their parents. Results revealed that early educational media was protective against developing problematic media use over time. However, early problematic media use was not predictive of future media content choices longitudinally. Additionally, problematic media use was moderately stable over time. Implications for parents and policymakers regarding the importance of early media content for later outcomes and consideration of media use trajectories are discussed.
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