The impact of sleep, physical activity and sedentary behaviour on symptoms of depression and anxiety before and during the COVID-19 pandemic in a sample of South African participants.

During lockdowns associated with the COVID-19 pandemic, individuals have experienced poor sleep quality and sleep regularity, changes in lifestyle behaviours, and heightened depression and anxiety. However, the inter-relationship and relative strength of those behaviours on mental health outcomes is still unknown. We collected data between 12 May and 15 June 2020 from 1048 South African adults (age: 32.76 ± 14.43 years; n = 767 female; n = 473 students) using an online questionnaire. Using structural equation modelling, we investigated how insomnia symptoms, sleep regularity, exercise intensity/frequency and sitting/screen-use (sedentary screen-use) interacted to predict depressive and anxiety-related symptoms before and during lockdown. We also controlled for the effects of sex and student status. Irrespective of lockdown, (a) more severe symptoms of insomnia and greater sedentary screen-use predicted greater symptoms of depression and anxiety and (b) the effects of sedentary screen-use on mental health outcomes were mediated by insomnia. The effects of physical activity on mental health outcomes, however, were only significant during lockdown. Low physical activity predicted greater insomnia symptom severity, which in turn predicted increased depressive and anxiety-related symptoms. Overall, relationships between the study variables and mental health outcomes were amplified during lockdown. The findings highlight the importance of maintaining physical activity and reducing sedentary screen-use to promote better sleep and mental health.

Induction of bone formation by transforming growth factor-beta2 in the non-human primate Papio ursinus and its modulation by skeletal muscle responding stem cells.

OBJECTIVES: Four adult non-human primates Papio ursinus were used to study induction of bone formation by recombinant human transforming growth factor-beta(2) (hTGF-beta(2)) together with muscle-derived stem cells. MATERIALS AND METHODS: The hTGF-beta(2) was implanted in rectus abdominis muscles and in calvarial defects with and without addition of morcellized fragments of striated muscle, harvested from the rectus abdominis or temporalis muscles. Expression of osteogenic markers including osteogenic protein-1, bone morphogenetic protein-3 and type IV collagen mRNAs from generated specimens was examined by Northern blot analysis. RESULTS: Heterotopic intramuscular implantation of 5 and 25 microg hTGF-beta(2) combined with 100 mg of insoluble collagenous bone matrix yielded large corticalized mineralized ossicles by day 30 with remodelling and induction of haematopoietic marrow by day 90. Addition of morcellized rectus abdominis muscle to calvarial implants enhanced induction of bone formation significantly by day 90. CONCLUSIONS: In Papio ursinus, in marked contrast to rodents and lagomorphs, hTGF-beta(2) induced large corticalized and vascularized ossicles by day 30 after implantation into the rectus abdominis muscle. This striated muscle contains responding stem cells that enhance the bone induction cascade of hTGF-beta(2). Induction of bone formation by hTGF-beta(2) in the non-human primate Papio ursinus may occur as a result of expression of bone morphogenetic proteins on heterotopic implantation of hTGF-beta(2); the bone induction cascade initiated by mammalian TGF-beta proteins in Papio ursinus needs to be re-evaluated for novel molecular therapeutics for induction of bone formation in clinical contexts.

The molecular genetics of circadian rhythms in Arabidopsis.

While a number of physiological and biochemical processes in plants have been found to be regulated in a circadian manner, the mechanism underlying the circadian oscillator remains to be elucidated. Advances in the identification and characterization of components of the plant circadian system have been made largely through the use of genetics in Arabidopsis thaliana. Results so far indicate that the generation of rhythmicity by the Arabidopsis clock relies on molecular mechanisms that are similar to those described for other organisms, but that a totally different set of molecular components has been recruited to perform these functions.

Picking out parallels: plant circadian clocks in context.

Molecular models have been described for the circadian clocks of representatives of several different taxa. Much of the work on the plant circadian system has been carried out using the thale cress, Arabidopsis thaliana, as a model. We discuss the roles of genes implicated in the plant circadian system, with special emphasis on Arabidopsis. Plants have an endogenous clock that regulates many aspects of circadian and photoperiodic behaviour. Despite the discovery of components that resemble those involved in the clocks of animals or fungi, no coherent model of the plant clock has yet been proposed. In this review, we aim to provide an overview of studies of the Arabidopsis circadian system. We shall compare these with results from different taxa and discuss them in the context of what is known about clocks in other organisms.