3 resultados para Color changes

em Deakin Research Online - Australia


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A new family of [3]polynorbornane frameworks exhibiting conformationally preorganized aromatic thiourea (cleft-like) receptors have been designed and synthesized for anion recognition. These show excellent affinity for the biologically relevant dihydrogenphosphate (H2PO4-) and dihydrogenpyrophosphate (H2P2O72-) anions (among others), which are bound in 1:1 and 2:1 (host:anion) ratio, respectively. Moreover, visually striking color changes accompany guest binding, enabling this family to act as colorimetric anion sensors.

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Damaged skeletal muscle fibres are replaced with new contractile units via muscle regeneration. Regenerating muscle fibres synthesize functionally distinct isoforms of contractile and regulatory proteins but little is known of their functional properties during the regeneration process. An advantage of utilizing single muscle fibre preparations is that assessment of their function is based on the overall characteristics of the contractile apparatus and regulatory system and as such, these preparations are sensitive in revealing not only coarse, but also subtle functional differences between muscle fibres. We examined the Ca2+- and Sr2+-activated contractile characteristics of permeabilized fibres from rat fast-twitch (extensor digitorum longus) and slow-twitch (soleus) muscles at 7, 14 and 21 days following myotoxic injury, to test the hypothesis that fibres from regenerating fast and slow muscles have different functional characteristics to fibres from uninjured muscles. Regenerating muscle fibres had ∼10% of the maximal force producing capacity (Po) of control (uninjured) fibres, and an altered sensitivity to Ca2+ and Sr2+ at 7 days post-injury. Increased force production and a shift in Ca2+ sensitivity consistent with fibre maturation were observed during regeneration such that Po was restored to 36–45% of that in control fibres by 21 days, and sensitivity to Ca2+ and Sr2+ was similar to that of control (uninjured) fibres. The findings support the hypothesis that regenerating muscle fibres have different contractile activation characteristics compared with mature fibres, and that they adopt properties of mature fast- or slow-twitch muscle fibres in a progressive manner as the regeneration process is completed.

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Purpose

The aim of this study was to investigate the relationship between clinical macular changes and retinal function in age-related macular degeneration (AMD).

Methods
We recruited 357 participants with visual acuity of better than 20/60 in the study eye, including 64 individuals with normal fundi and 293 AMD participants classified into 12 subgroups based upon the International Classification and Grading System. Visual function in the study eye was assessed using two steady-state tests (achromatic 14 Hz flicker [F14Hz] and isoluminant blue color [BCT]) and two adaptation measurements (cone photo-stress recovery rate [CRR] and rod dark adaptation recovery rate [RRR]). The groups were compared on their average psychophysical measurements and ranked according to functional deficiency.

Results  
Both adaptation parameters were significantly abnormal when only hard and/or intermediate drusen were evident (compared to controls, P < 0.023) and yielded considerably worse outcomes in cases with more advanced fundus changes (P < 0.001), but provided limited ability to discriminate between these cases (linear trend, CRR t = 0.68, P = 0.50 and RRR t = 1.76, P = 0.08). Steady-state measurements, however, declined gradually along the entire hierarchy of fundus changes (linear trend, F14Hz t = 10.16, P < 0.001 and BCT t = 11.19, P < 0.001) with F14Hz being able to detect significant functional change as early as in the intermediate drusen group, when compared to controls (P = 0.003).

Conclusions
Steady state thresholds (F14Hz and BCT) and clinical signs showed significant concordance across the spectrum of early AMD fundus changes. This suggests that these tests may be an effective tool for monitoring progression of AMD to supplement clinical grading.