Dose-independent threshold illumination for non-invasive time-lapse fluorescence imaging of live cells

Fluorescent microscopy employs monochromatic light for excitation, which can adversely affect the cells being observed. We reported earlier that fibroblasts relax their contractile force in response to green light of typical intensity. Here we show that such effects are independent of extracellular matrix and cell lines. In addition, we establish a threshold intensity that elicits minimal or no adverse effect on cell contractility even for long-time exposure. This threshold intensity is wavelength dependent. We cultured fibroblasts on soft 2D elastic hydrogels embedded with fluorescent beads to trace substrate deformation and cell forces. The beads move towards cell center when cells contract, but they move away when cells relax. We use relaxation/contraction ratio (λ(r)), in addition to traction force, as measures of cell response to red (wavelength, λ=635–650 nm), green (λ=545–580 nm) and blue (λ=455–490 nm) lights with varying intensities. Our results suggest that intensities below 57, 31 and 3.5 W/m(2) for red, green and blue lights, respectively, do not perturb force homeostasis. To our knowledge, these intensities are the lowest reported safe thresholds, implying that cell traction is a highly sensitive readout of the effect of light on cells. Most importantly, we find these threshold intensities to be dose-independent; i.e., safe regardless of the energy dosage or time of exposure. Conversely, higher intensities result in widespread force-relaxation in cells with λ(r) > 1. Furthermore, we present a photo-reaction based model that simulates photo-toxicity and predicts threshold intensity for different wavelengths within the visible spectra. In conclusion, we recommend employing illumination intensities below aforementioned wavelength-specific thresholds for time-lapse imaging of cells and tissues in order to avoid light-induced artifacts in experimental observations

Evidence-based and heuristic approaches for customization of care in cardiometabolic syndrome after spinal cord injury

Component and coalesced health risks of the cardiometabolic syndrome (CMS) are commonly reported in persons with spinal cord injuries (SCIs). These CMS hazards are also co-morbid with physical deconditioning and elevated pro-atherogenic inflammatory cytokines, both of which are common after SCI and worsen the prognosis for all-cause cardiovascular disease. This article describes a systematic procedure for individualized CMS risk assessment after SCI, and emphasizes evidence-based and intuition-centered countermeasures to disease. A unified approach will propose therapeutic lifestyle intervention as a routine plan for aggressive primary prevention in this risk-susceptible population. Customization of dietary and exercise plans then follow, identifying shortfalls in diet and activity patterns, and ways in which these healthy lifestyles can be more substantially embraced by both stakeholders with SCI and their health care providers. In cases where lifestyle intervention utilizing diet and exercise is unsuccessful in countering risks, available pharmacotherapies and a preferred therapeutic agent are proposed according to authoritative standards. The over-arching purpose of the monograph is to create an operational framework in which existing evidence-based approaches or heuristic modeling becomes best practice. In this way persons with SCI can lead more active and healthy lives

Natural Law in Islam

This chapter will introduce the basic, theoretical architecture of com- peting Islamic natural law theories from the pre-modern period (ninth to fourteenth centuries). Specifically, it will outline juristic debates in the usul al-fiqh genre on reason as a source of law, where revelation is silent. Thereafter it will reflect on a range of doctrinal debates in which many of those same pre-modern jurists came to a legal determination without reference to scriptural (or any other) texts. Drawing on a curious heur- istic they labelled huquq Allah and huquq al-ʿibad (the claims of God and the claims of individuals), I will show that despite not invoking (expressly or otherwise) any natural law account of Islamic law, jurists nonetheless developed law based on a mode of rationality that could be called anything from ‘rational’ to ‘common-sense’ to ‘pragmatic’. Whether or not the huquq Allah/huquq al-ʿibad heuristic is proof posi- tive of natural law in Islam is less important than recognising the scope of questions that have yet to be examined. But as I will suggest in the third and concluding part, there are political reasons (some of which enjoy disciplinary cover) that help explain why some questions are not asked, and why some answers are deemed naïve, if not impolitic