Salt appetite consequent on sodium depletion in the suckling rat pup

The ontogeny of the behavioral ability to compensate for sodium deficit was studied in the rat. The experiments showed that: (1) Before weaning age, sodium-depleted pups will increase their avidity for 3% NaCl solution; (2) the ability to select and drink a salt solution in response to a sodium deficit continues to evolve between 17–24 days of age, and that pups at these ages will modify their intake of salt and water as do adult rats when rectifiying plasma osmolality; (3) The increased appetite for sodium is evident even when depleted preweanlings are dehydrated and provided with solid NaCl tablets to lick, showing that sodium appetite and hydrational status are already dissociated at this age; and finally, (4) sodium depletion first induces an increase in intake of orally infused 3% NaCl solution in 12-day-old pups. The picture of the development of salt appetite in the suckling rat that these findings present is of a precocious competence to meet a challenge to sodium homeostasis. In this respect salt appetite emerges in parallel to the other ingestive behaviors © 1993 John Wiley & Sons, Inc.     

Exercise but not Prostanoids Enhance Levels of Vascular Endothelial Growth Factor and other Proliferative Agents in Human Skeletal Muscle Interstitium

In the present study we examined whether exercise and prostanoids have an effect on the muscle interstitial concentration of vascular endothelial growth factor (VEGF) and on the proliferative effect of muscle interstitial fluid. Dialysate from resting and exercising human skeletal muscle, obtained either during control conditions or during cyclooxygenase inhibition, was examined for its content of VEGF and for its effect on endothelial cell proliferation. Microdialysis probes with high (960 kDa) and low (5 kDa) molecular-mass cut-off membranes were placed in the vastus lateralis muscle of healthy young males. The subjects performed one-legged knee extensions (20 W). The concentration of VEGF in the 960 kDa dialysate was greater (   P < 0.05  ) during exercise compared to at rest (67 ± 28 vs. 230 ± 22 pg ml⁻¹). The rate of endothelial cell proliferation was 2.7-fold higher (   P < 0.05  ) with the 960 kDa dialysate from resting muscle than with perfusate and was 5.8-fold higher (   P < 0.05  ) than the perfusate value with dialysate from exercising muscle. VEGF was not enhanced with exercise in the 5 kDa dialysate, yet the exercise dialysate induced a 1.9-fold higher (   P < 0.05  ) proliferation than the resting dialysate. Cyclooxygenase inhibition did not affect the VEGF concentration or the proliferating effect of the dialysates (   P > 0.05  ). This study demonstrates for the first time that VEGF is present in the interstitium of human skeletal muscle and that exercise enhances the interstitial concentration of VEGF and of other, as yet unidentified, angiogenic compounds. Products of cyclooxygenase do not appear to have an effect on the release of VEGF or other proliferative agents in human skeletal muscle.     

Clinical implications of daytime sleepiness for the academic performance of middle school‐aged adolescents with attention deficit hyperactivity disorder

This study investigated the relative impact of total time slept per night and daytime sleepiness on the academic functioning of 100 middle school‐aged youth (mean age = 11.9) with attention deficit hyperactivity disorder (ADHD). The primary goal of the study was to determine if total time slept per night and/or daytime sleepiness, as measured by youth self‐report on the Pediatric Daytime Sleepiness Scale (PDSS), predicted academic functioning above and beyond symptoms of ADHD and relevant covariates, such as intelligence, achievement scores and parent education level. Self‐reported daytime sleepiness but not self‐reported total time slept per night was associated significantly with all academic outcomes. When examined in a hierarchical regression model, self‐reported daytime sleepiness significantly predicted parent‐rated homework problems and academic impairment and teacher‐rated academic competence above and beyond symptoms of ADHD and relevant covariates, but did not predict grade point average or teacher‐rated academic impairment. The implications of these findings for understanding more clearly the association between ADHD and sleep and the functional implications of this relationship are discussed.     

Prospective examination of adolescent sleep patterns and behaviors before and during COVID-19

Study ObjectivesTo prospectively examine changes in adolescent sleep before and during the COVID-19 pandemic in adolescents with and without ADHD.MethodsParticipants were 122 adolescents (ages 15–17; 61% male; 48% with ADHD). Parents reported on adolescents’ sleep duration and difficulties initiating and maintaining sleep (DIMS); adolescents reported on sleep patterns, sleep duration, delayed sleep/wake behaviors, and daytime sleepiness before (September 2019 to February 2020) and during (May–June 2020) COVID-19. Adolescents also reported on their health behaviors, COVID-19-related negative affect, and difficulties concentrating due to COVID-19.ResultsParents reported adolescents had more DIMS during COVID-19 than before COVID-19, with clinically elevated rates increasing from 24% to 36%. Both bedtimes and waketimes shifted later during COVID-19, and adolescents reported more delayed sleep/wake behaviors. Adolescents also reported less daytime sleepiness and longer school night sleep duration during COVID-19. In considering differences between adolescents with and without ADHD, adolescents with ADHD did not experience an increase in school night sleep duration and were less likely to obtain recommended sleep duration during COVID-19. In the full sample, controlling for ADHD status, COVID-19-related sadness/loneliness was associated with increases in DIMS, and spending less time outside and more COVID-19-related worries/fears were associated with increases in delayed sleep/wake behaviors during COVID-19.ConclusionsCOVID-19 had negative and positive impacts on adolescent sleep. Adolescents with ADHD did not experience the benefit of increased school night sleep duration during COVID-19 like adolescents without ADHD. Negative affect and health behaviors may be useful intervention targets for reducing negative impacts of COVID-19 for adolescent sleep.     

The effect of acute exercise on collagen turnover in human tendons: influence of prior immobilization period

Mechanical loading of human tendon stimulates collagen synthesis, but the relationship between acute loading responses and training status of the tendon is not clear. We tested the effect of prolonged load deprivation on the acute loading-induced collagen turnover in human tendons, by applying the same absolute load to a relative untrained Achilles tendon (2-week immobilization period prior to acute loading) and a habitually loaded contra-lateral Achilles tendon, respectively, within the same individuals. Eight untrained, healthy males had one lower limb totally immobilized for 2 weeks, whereas the contra-lateral leg was used habitually. Following the procedure both Achilles tendons and calf muscles were loaded with the same absolute load during a 1-h treadmill run. Tissue collagen turnover was measured by microdialysis performed post-immobilization but pre-exercise around both Achilles tendons and compared to values obtained by 72-h post-exercise. Power Doppler was used to monitor alterations in intratendinous blood flow velocity of the Achilles tendon and MRI used to quantitate changes in tendon cross-section area. Acute loading resulted in an increased collagen synthesis 72 h after the run in both Achilles tendons (p < 0.05) with no significant difference. No signs of acute tendon overloading were demonstrated by Power Doppler, and tendon cross-section area did not change as a result of immobilization and reloading. The present study indicates that 2 weeks of tendon load deprivation is not sufficient to affect the normal adaptive response to loading determined as increased collagen synthesis of peritendinous Achilles tendon tissue in humans.