Chronotype at the beginning of secondary school and school timing are both associated with chronotype development during adolescence

The misalignment between late chronotypes and early school start times affect health, performance and psychological well-being of adolescents. Here we test whether, and how, the baseline chronotype (i.e. chronotype at the beginning of secondary school) and the school timing affect the magnitude and the direction of the developmental change in chronotype during adolescence. We evaluated a sample of Argentinian students (n = 259) who were randomly assigned to attend school in the morning (07:45 a.m.–12:05 p.m.), afternoon (12:40 p.m.–05:00 p.m.) or evening (05:20 p.m.–09:40 p.m.) school timings. Importantly, chronotype and sleep habits were assessed longitudinally in the same group of students along secondary school (at 13–14 y.o. and 17–18 y.o.). Our results show that: (1) although chronotypes partially align with class time, this effect is insufficient to fully account for the differences observed in sleep-related variables between school timings; (2) both school timing and baseline chronotype are independently associated with the direction and the magnitude of change in chronotype, with greater delays related to earlier baseline chronotypes and later school timings. The practical implications of these results are challenging and should be considered in the design of future educational timing policies to improve adolescents’ well-being.Scientific Report

Circadian Modulation of Gene Expression, but not Glutamate Uptake, in Mouse and Rat Cortical Astrocytes

Circadian clocks control daily rhythms including sleep-wake, hormone secretion, and metabolism. These clocks are based on intracellular transcription-translation feedback loops that sustain daily oscillations of gene expression in many cell types. Mammalian astrocytes display circadian rhythms in the expression of the clock genes Period1 (Per1) and Period2 (Per2). However, a functional role for circadian oscillations in astrocytes is unknown. Because uptake of extrasynaptic glutamate depends on the presence of Per2 in astrocytes, we asked whether glutamate uptake by glia is circadian.We measured glutamate uptake, transcript and protein levels of the astrocyte-specific glutamate transporter, Glast, and the expression of Per1 and Per2 from cultured cortical astrocytes and from explants of somatosensory cortex. We found that glutamate uptake and Glast mRNA and protein expression were significantly reduced in Clock/Clock, Per2- or NPAS2-deficient glia. Uptake was augmented when the medium was supplemented with dibutyryl-cAMP or B27. Critically, glutamate uptake was not circadian in cortical astrocytes cultured from rats or mice or in cortical slices from mice.We conclude that glutamate uptake levels are modulated by CLOCK, PER2, NPAS2, and the composition of the culture medium, and that uptake does not show circadian variations

Bienvenida sonrisa : Parte II

La Facultad de Odontología de la Universidad Nacional de La Plata, desde el año 1997, desarrolla un Programa de Salud Bucal en la ciudad de La Plata y sus alrededores, a través de la Asignatura Odontología Preventiva y Social. Esto ha permitido obtener datos estadísticos y de relevamiento de zonas, que impulsa la formulación de nuevas iniciativas en poblaciones vulnerables donde el índice de incidencia de enfermedades bucodentales, es elevado. Entendemos a la salud bucal como un valor que no debe ser considerado como un privilegio, sino como un derecho de todas las personas, reforzando el trabajo multidisciplinario de manera de que la salud recuperada, se mantenga a lo largo del tiempo, con el objetivo de disminuir las desigualdades en salud y con el propósito de brindar atención a poblaciones de difícil acceso, por este motivo, creemos que es fundamental la gestión del Trabajo Social , trabajando de forma efectiva con la comunidad, colaborando en la promoción de la salud y prevención de la enfermedad. Teniendo conocimiento de que la escuela es un espacio privilegiado y del encuentro con el otro, enfocamos nuestros esfuerzos en colaborar para modificar la realidad que se presenta.Este Proyecto surge debido a la necesidad de la Comunidad Educativa perteneciente a la Escuela Nº 45 “Manuel Rocha” del barrio El Mondongo de la Ciudad de La Plata, quienes manifiestan la carencia de información y atención de la comunidad educativa en cuanto a acciones preventivas. Este proyecto se lleva a cabo desde fines del 2019, atravesando el contexto de Pandemia por el virus causante de la enfermedad Covid-19, reacondicionando nuestras actividades.Facultad de Odontologí

A time to kill, and a time to heal: pathophysiological interactions between the circadian and the immune systems

Current clinical data show a strong correlation between time of day and illness manifestation or immune activity. For example, symptoms of rheumatoid arthritis occur during the morning (Katz et al. 2002) most asthma attacks during the night (Reinberg 2006), and the effects of immunization also change with daytime (Langlois et al. 1995). Taken together, these reports suggest a strong regulation exerted by the circadian clock on the immune system, which will be reviewed in this article. Moreover, clock-controlled rhythms in several variables exert a feedback regulation on the circadian oscillator itself, a mechanism that we shall also consider in this paper.Sociedad Argentina de Fisiologí

A better alignment between chronotype and school timing is associated with lower grade retention in adolescents

Abstract Schools start early in the morning all over the world, contrasting with adolescents’ late chronotype. Interestingly, lower academic performance (i.e. grades or qualifications) was associated with later chronotypes. However, it is unclear whether it is a direct effect of chronotype or because students attend school too early to perform at their best. Moreover, little is known about how this affects students’ academic success beyond their grades. To address this gap in knowledge, we studied how school timing and chronotype affect grade retention (i.e. repeat a year) in a unique sample of students randomly assigned to one of three different school timings (starting at 07:45, 12:40, or 17:20). Even when controlling for academic performance, we found that later chronotypes exhibit higher odds of grade retention only in the morning, but not in later school timings. Altogether, ensuring a better alignment between school timing and students’ biological rhythms might enhance future opportunities of adolescents

Glutamate uptake in rat cortical astrocytes depends on sodium and a high affinity transporter.

<p>A, Glutamate uptake in sodium-free buffer (LiCl) was significantly lower than in culture medium with sodium (n = 3, mean±SEM). Uptake was initiated with 500 µM glutamate. B, <i>Trans</i>-2,4-PDC, a high-affinity transporter inhibitor (100 µM), reduced glutamate uptake (mean±SEM, n = 3) by 55–65%. Uptake was initiated with 1 µM glutamate. C, Glutamate uptake was 18 times higher in cultures immunopositive for GLAST (GLAST+). All cells which expressed GLAST also expressed GFAP. Separate cultures of cells immunonegative for GLAST (GLAST-) were also immunonegative for GFAP and did not uptake glutamate (n = 3 cultures per cell type and concentration, mean±SEM).</p

B27 or dB-cAMP as culture supplements do not induce a circadian rhythm in glutamate uptake.

<p>A, Uptake was measured in rat cortical astrocytes with (black line) or without B27 supplements (gray line) (500 µM tritiated glutamate, n = 3 cultures per time point; mean±SEM). B, A 10-day treatment of rat astrocytes with dB-cAMP (250 µM, black line) significantly increased overall glutamate uptake (500 µM tritiated glutamate), but did not induce circadian rhythmicity (n = 3 cultures per time point; mean±SEM).</p

Glutamate uptake in mouse cortical slices is dose dependent, but not circadian.

<p>A–B, Two independent experiments showing that glutamate uptake is approximately 10 fold higher for a 10 µM glutamate concentration than for a 1 µM concentration. In addition, glutamate uptake did not show circadian variations at any concentration (mean±SEM). n = 3 for each time and concentration (A), n = 2 for each time and concentration (B).</p

Glutamate uptake depends on the <i>Clock</i> and <i>Per2</i> genes.

<p>Dose–response curves for glutamate uptake were generated comparing wild-type astrocyte cultures and either <i>Clock/Clock</i> or <i>Per2^m</i> mutant astrocytes. A, Glutamate uptake was significantly reduced in astrocytes derived from <i>Clock/Clock</i> mutants compared to wild-type (+/+) glia (n = 3 cultures per concentration, mean±SEM). B, Glutamate uptake was significantly reduced in astrocytes derived from <i>Per2^m</i> mutants compared to wild-type (+/+) glia (n = 3 per concentration, mean±SEM).</p

Glutamate uptake in slices of somatosensory cortex is not circadian.

<p>Explants were taken either 2 h before dusk (ZT 10, black squares) or 2 h before dawn (ZT 23, gray circles) and cultured for 36 h <i>in vitro</i> until 10-min uptake of 25 µM tritiated glutamate was measured. White and black bars on top of the X axis represent the projected subjective day and subjective night, respectively. (n = 3 slices per time point; mean±SEM).</p