Covid-19 and the impact on young athletes.

The Covid-19 pandemic has disrupted organised sport in the community as authorities cancelled, greatly modified or postponed sporting participation as part of a strategy to reduce transmission of the virus. This had a significant impact on young athletes and their families in relation to their psycho-social, physical and career progression considerations. The disruption is likely to continue for some years, considering the constraints of lockdowns, the need to overcome dysfunctional national logistics for delivery of medical care, fund and implement an efficacious vaccine programme locally, nationally and worldwide, develop sufficient herd immunity and create an environment of confidence in the safety of returning to sports for participants, coaches, umpires, administrators and observers. This article will consider the interim challenges regarding the physical and psychosocial importance of maintaining an active sporting programme for young athletes, reflect on safety measures for modifying sporting equipment and environmental protections to allow safest participation in training and competition and provide advice on protocols for a gradual return to sport for the young athlete after infection with Covid-19.

High-speed volumetric two-photon fluorescence imaging of neurovascular dynamics.

Understanding the structure and function of vasculature in the brain requires us to monitor distributed hemodynamics at high spatial and temporal resolution in three-dimensional (3D) volumes in vivo. Currently, a volumetric vasculature imaging method with sub-capillary spatial resolution and blood flow-resolving speed is lacking. Here, using two-photon laser scanning microscopy (TPLSM) with an axially extended Bessel focus, we capture volumetric hemodynamics in the awake mouse brain at a spatiotemporal resolution sufficient for measuring capillary size and blood flow. With Bessel TPLSM, the fluorescence signal of a vessel becomes proportional to its size, which enables convenient intensity-based analysis of vessel dilation and constriction dynamics in large volumes. We observe entrainment of vasodilation and vasoconstriction with pupil diameter and measure 3D blood flow at 99 volumes/second. Demonstrating high-throughput monitoring of hemodynamics in the awake brain, we expect Bessel TPLSM to make broad impacts on neurovasculature research.

Generating switchable and reconfigurable optical vortices via photopatterning of liquid crystals.

Liquid-crystal fork gratings are demonstrated through photopatterning realized on a DMD-based microlithography system. This supplies a new strategy for generating fast switchable, reconfigurable, wavelength-tolerant and polarization-insensitive optical vortices. The technique has great potential in broad fields such as OAM-based quantum computations, optical communications, and micromanipulation.

Growth of pulmonary microvasculature in ventilated preterm infants.

RATIONALE: Density-based morphometric studies have demonstrated decreased capillary density in infants with bronchopulmonary dysplasia (BPD) and in BPD-like animal models, leading to the prevailing view that microvascular development is disrupted in BPD. OBJECTIVE: To perform a comprehensive analysis of the early and late effects of ventilation on pulmonary microvascular growth in preterm infants. METHODS: Postmortem lung samples were collected from ventilated preterm infants who died between 23 and 29 wk ("short-term ventilated") or between 36 and 39 wk ("long-term ventilated") corrected postmenstrual age. Results were compared with age-matched infants or stillborn infants ("early" and "late" control subjects). Microvascular growth was studied by anti-platelet endothelial cell adhesion molecule (PECAM)-1 immunohistochemistry, quantitative stereology, analysis of endothelial cell proliferation, and Western blot analysis of pulmonary PECAM-1 protein levels. MEASUREMENTS: Measurements were made of capillary density, volume of air-exchanging parenchyma, volume of microvascular endothelial cells, Ki67 labeling index of endothelial cells, and PECAM-1/actin protein levels. MAIN RESULTS: Lungs of long-term ventilated infants showed a significant (more than twofold) increase in volume of air-exchanging parenchyma and a 60% increase in total pulmonary microvascular endothelial volume compared with late control subjects, associated with 60% higher pulmonary PECAM-1 protein levels. The marked expansion of the pulmonary microvasculature in ventilated lungs was, at least partly, attributable to brisk endothelial cell proliferation. The microvasculature of ventilated lungs appeared immature, retaining a saccular architectural pattern. CONCLUSIONS: The pulmonary microvasculature of ventilated preterm infants displayed marked angiogenesis, nearly proportionate to the growth of the air-exchanging lung parenchyma. These results challenge the paradigm of microvascular growth arrest as a major pathogenic factor in BPD.