Clearing the cobwebs: An analysis of the timing of youth concussion legislation in U.S. states.

After decades of ignoring head injury in youth sports, U.S. states passed youth concussion legislation with stipulations about when athletes can return to play. Why were some states slower to pass laws than others? We consider this question through the lens of institutional medicalization, where medically informed policies are enacted. Our study recognizes the uneven nature of policy enactment across time and space with event history methods. We explore the influence of high school sport participation and other variables on the timing of legislation in all fifty states, 2007-2014. States with more high school football participation, as well as states with a strong college football presence, passed concussion laws later. Conversely, states with stronger orientations toward gender egalitarianism adopted laws sooner. These factors reflect sources of receptivity and resistance that underlie the process of institutional medicalization. Our approach offers one of the few quantitative studies of institutional medicalization and provides a template for future quantitative research in this area.

New mouse lines for the analysis of neuronal morphology using CreER(T)/loxP-directed sparse labeling.

BACKGROUND: Pharmacologic control of Cre-mediated recombination using tamoxifen-dependent activation of a Cre-estrogen receptor ligand binding domain fusion protein [CreER(T)] is widely used to modify and/or visualize cells in the mouse. METHODS AND FINDINGS: We describe here two new mouse lines, constructed by gene targeting to the Rosa26 locus to facilitate Cre-mediated cell modification. These lines should prove particularly useful in the context of sparse labeling experiments. The R26rtTACreER line provides ubiquitous expression of CreER under transcriptional control by the tetracycline reverse transactivator (rtTA); dual control by doxycycline and tamoxifen provides an extended dynamic range of Cre-mediated recombination activity. The R26IAP line provides high efficiency Cre-mediated activation of human placental alkaline phosphatase (hPLAP), complementing the widely used, but low efficiency, Z/AP line. By crossing with mouse lines that direct cell-type specific CreER expression, the R26IAP line has been used to produce atlases of labeled cholinergic and catecholaminergic neurons in the mouse brain. The R26IAP line has also been used to visualize the full morphologies of retinal dopaminergic amacrine cells, among the largest neurons in the mammalian retina. CONCLUSIONS: The two new mouse lines described here expand the repertoire of genetically engineered mice available for controlled in vivo recombination and cell labeling using the Cre-lox system.

Genetically-directed, cell type-specific sparse labeling for the analysis of neuronal morphology.

BACKGROUND: In mammals, genetically-directed cell labeling technologies have not yet been applied to the morphologic analysis of neurons with very large and complex arbors, an application that requires extremely sparse labeling and that is only rendered practical by limiting the labeled population to one or a few predetermined neuronal subtypes. METHODS AND FINDINGS: In the present study we have addressed this application by using CreER technology to non-invasively label very small numbers of neurons so that their morphologies can be fully visualized. Four lines of IRES-CreER knock-in mice were constructed to permit labeling selectively in cholinergic or catecholaminergic neurons [choline acetyltransferase (ChAT)-IRES-CreER or tyrosine hydroxylase (TH)-IRES-CreER], predominantly in projection neurons [neurofilament light chain (NFL)-IRES-CreER], or broadly in neurons and some glia [vesicle-associated membrane protein2 (VAMP2)-IRES-CreER]. When crossed to the Z/AP reporter and exposed to 4-hydroxytamoxifen in the early postnatal period, the number of neurons expressing the human placental alkaline phosphatase reporter can be reproducibly lowered to fewer than 50 per brain. Sparse Cre-mediated recombination in ChAT-IRES-CreER;Z/AP mice shows the full axonal and dendritic arbors of individual forebrain cholinergic neurons, the first time that the complete morphologies of these very large neurons have been revealed in any species. CONCLUSIONS: Sparse genetically-directed, cell type-specific neuronal labeling with IRES-creER lines should prove useful for studying a wide variety of questions in neuronal development and disease.

Minority adolescents and substance use risk/protective factors: a focus on inhalant use.

Despite the fact that inhalant use is a growing problem among youth in the United States, relatively little attention has been paid to the demographic and social factors related to its use. This study used data from a household survey of adolescents in Washington state, and found that race/ethnicity was a strong predictor of lifetime prevalence of inhalant use, with Native-American youth being particularly likely to use inhalants. Comparing the age at initiation of inhalant use to other legal and illegal substances, we found that cigarettes and inhalants showed the lowest age at initiation. We conducted logistic regressions on lifetime prevalence of inhalant use, and compared these models to other substances. In general, we found that attachment to parents. parents' drug use, and school attachment were strong predictors of lifetime use of marijuana, alcohol, and inhalants. However, while peer drug use was a strong predictor of marijuana and alcohol use, it was not a significant predictor of adolescents' use of inhalants. Our final set of analyses included inhalant use in regression models predicting other problem behaviors: these analyses demonstrated that inhalant use was a strong predictor of involvement in problem behavior.

Two neuropharmacological types of rabbit ON-alpha ganglion cells express GABAC receptors.

The major inhibitory neurotransmitters GABA and glycine provide the bulk of input to large-field ganglion cells in the retina. Whole-cell patch-clamp recordings were used to characterize the glycine- and GABA-activated currents for morphologically identified ON-alpha ganglion cells in the rabbit retina. Cells identified as ON-alpha cells by light evoked currents were intracellularly stained and examined by light microscopy which revealed dendritic stratification in the vitreal half of the inner plexiform layer and confirmed their physiological identity. All Ca(2+)-mediated synaptic influences were abolished with Co(2+), revealing two types of ON-alpha cell characterized by their different inhibitory current profiles. One group exhibited larger glycine- than GABA-activated currents, while the other group had larger GABA- than glycine-activated currents. Both cell types demonstrated strychnine-sensitive glycine-activated currents and bicuculline-sensitive GABAA-activated currents. Surprisingly, both cell types expressed functional GABAC receptors demonstrated by their sensitivity to TPMPA. In addition, the cells with larger glycine-activated currents also possessed GABAB receptors, whereas those with larger GABA-activated currents did not. Immunocytochemical experiments confirmed the presence of glycine, GABAA, and GABAC receptor subunits on all physiologically identified ON-alpha ganglion cells in this study. In addition, the GABAB receptor immunolabeled puncta were present on the cells with larger glycine-activated currents, but not on the cells with the larger GABA-activated currents. In conclusion, the presence of different functional GABA and glycine receptors determined physiologically correlated well with the specific GABA and glycine receptor immunolabeling for two neuropharmacological types of rabbit ON-alpha ganglion cells.

Evidence for glycine, GABAA, and GABAB receptors on rabbit OFF-alpha ganglion cells.

Inhibitory synaptic transmission via GABA and glycine receptors plays a crucial role in shaping the excitatory response of neurons in the retina. Whole-cell recordings were obtained from ganglion cells in the intact rabbit eyecup preparation to correlate GABA- and glycine-activated currents with the presence of their specific receptors on morphologically identified a ganglion cells. Alpha ganglion cells were chosen based upon their large somata when viewing the retinal surface, and responses to light and dark spots were used to identify OFF-alpha ganglion cells. Light responses were abolished by superfusion of Ringer's containing cobalt to synaptically isolate the cell by blocking all Ca(2+)-mediated transmitter release. Pressure pulses of GABA and glycine were delivered to an area that encompassed the dendritic field while receptor antagonists were applied through superfusion to characterize the direct inhibition onto the ganglion cell. Physiological results indicated that OFF-alpha cells did not have any GABAc receptor-activated currents, but did express currents mediated by ionotropic GABAA receptors and metabotropic GABAB receptors that were blocked by their specific antagonists bicuculline and CGP55845, respectively. The amplitudes of strychnine-sensitive glycine-activated currents were always larger than the currents elicited by GABA. Confocal optical sections of physiologically identified, sulforhodamine B-stained cells displayed the localization of glycine and GABAA receptor subunit labeling dispersed over the stained dendrites. Although scant labeling of GABAB receptors was found on the more distal dendrites, the majority of these receptors were congregated at the soma and on the proximal dendrites close to the soma. No GABAc receptor immunoreactivity was found anywhere on these cells. Therefore, the immunocytochemical results corroborated the physiological evidence demonstrating that OFF-alpha ganglion cells in the rabbit retina express functional GABAA, GABAB, and glycine receptors, but no GABAc receptors.