The effect of decreasing digital image resolution on teledermatology diagnosis

OBJECTIVE

To determine the effect of degraded digital image resolution (as viewed on a monitor) on the accuracy and confidence of dermatologic interpretation.

MATERIALS AND METHODS

Eight dermatologists interpreted 180 clinical cases divided into three Logical Competitor Sets (LCS) (pigmented lesions, non-pigmented lesions, and inflammatory dermatoses). Each case was digitized at three different resolutions. The images were randomized and divided into (9) 60-image sessions. The physicians were completely blinded concerning the image resolution. After 60 seconds per image, the viewer recorded a diagnosis and level of confidence. The resultant ROC curves compared the effect of LCS, level of clinical difficulty, and resolution of the digital image. One-way analysis of variance (ANOVA) compared the curves.

RESULTS

The areas beneath the ROC curves did not demonstrate any consistently significant difference between the digital image resolutions for all LCS and levels of difficulty. The only significant effect observed was amongst pigmented lesions (LCS-A) where the ROC curve area was significantly smaller in the easy images at high resolution compared to low and medium resolutions. For all other ROC curve comparisons within LCS-A, at all other levels of difficulty, as well as within the other LCS at all levels of difficulty, none of the differences was significant.

CONCLUSION

A 720 x 500 pixel image can be considered equivalent to a 1490 x 1000 pixel image for most store-and-forward teledermatology consultations.

Effect of lithium on ionic balance and polyphosphoinositide metabolism during larval vegetalization of the sea urchin Paracentrotus lividus

Treatment of Paracentrotus lividus embryos with lithium, which is known to block the polyphosphoinositide (PPI) cycle, induces their development into vegetalized larvae. We have investigated how ionic balance and PPI metabolism were affected in such vegetalized embryos. Exposure to 80 mM lithium for 3 1/2 hr at the morula stage induced an accumulation of lithium into the embryos, concomitant with a decrease in intracellular sodium and potassium contents. Intracellular lithium was totally expelled 6 hr after removal of this ion from the external medium. We found that intracellular levels of all PPI-cycle intermediates were altered after vegetalization: PIP2 and PIP increased, while PI decreased. Finally, vegetalized embryos showed a significant depression of IP3 mass. The degree of change in inositol phosphates increased as the intracellular accumulation of lithium increased. The change in morphology (vegetalization) also correlated well with the increase in lithium accumulation. This is consistent with the hypothesis that lithium alters the PPI cycle.

The calcium loading of secretory granules. A possible key event in stimulus-secretion coupling

The review focuses on calcium accumulation by secretory organelles. The observation that secretory granules contain variable and often important quantities of calcium (1-200 mM of total calcium) can be interpreted as a maturation index. A progressive loading with calcium would be permitted by a Ca2(+)-transport mechanism on the granular membrane and calcium-binding molecules in the granular core. The saturation of this store by the stimulus-induced calcium transient would permit in mature (calcium-loaded) granules the ionic crisis leading to exocytosis. The inside of secretory organelles being acidic, calcium influx into the granule can be driven by calcium-proton exchange. The calcium-proton exchanger could be a Ca2(+)-ATPase.

The abundance of Aplysia gliagrana depends on Ca2+ and/or Na+ concentrations in sea water

The glial cells surrounding the identified giant nerve cell bodies R2 or LP1 of Aplysia punctata were studied by quantitative electron microscopy. They contain specific, electron-dense but non-osmiophilic membrane-bound granules, approximately 0.3 microns in diameter, called gliagrana. Similar glial granules are more often found in marine than in freshwater molluscs, possibly because they represent a calcium store used to compensate excess Na+ in the extracellular milieu of marine species and to regulate perineuronal calcium concentration. In agreement with this hypothesis, the abundance of gliagrana (= number of glial granules per microns 2) is found to be higher in animals adapted to low Ca2+ artificial sea water than in animals kept in high Ca2+ (or low Na+) conditions. This finding is not observed after 1 week but after 2 weeks of adaptation.

Ca(2+)-ATPase and Mg(2+)-ATPase in Aplysia glial and interstitial cells: an EM cytochemical study

The localization of Ca(2+)- and Mg(2+)-ATPases was determined in Aplysia central and peripheral nervous system, using an electron microscopic cytochemical method. The enzyme activity appeared localized to the membrane of glial granules (gliagrana), particularly in the peripheral nervous system of the esophagus, and on the plasma membrane of central glial cells adjacent to neuronal cell bodies. No calcium- and/or magnesium-ATPase activity was detectable on the plasma membrane of glial cells surrounding nerve axons in the pleuro-visceral connectives. These findings are discussed along two main lines: (a) the calcium-ATPase of the gliagrana coincides with a high intragranular calcium and/or proton concentration; and (b) the presence of a calcium-ATPase activity at the glio-neuronal interface around the neuronal cell bodies coincides with the use of calcium ions as charge carriers of the action potential, and its absence at the level of the axon with the concurrent functional use of sodium ions.

The Desheathed Periphery of Aplysia Giant Neuron. Fine Structure and Measurement of [Ca2+]o Fluctuations with Calcium-selective Microelectrodes

The visceral ganglion of Aplysia was mechanically desheathed after protease softening of the connective tissue to permit the positioning of ion-selective electrodes in the vicinity of the neuronal membrane. The effects of this treatment on satellite glia and neuronal cytology were observed by electron microscopy. The intracellular alterations were not suggestive of serious membrane damage but the cohesion between glial and neuronal membranes was affected-the glial processes appeared to retract from the trophospongium and in some cases the neuronal membrane was completely naked. The external calcium activity [Ca2+]o at the surface of identified giant neuron, R2, was measured using double-barrelled calcium-selective microelectrodes. A decrease of approximately 1 mM in [Ca2+]o could be recorded only during trains of action potentials induced by intracellular depolarizing current injection, and when the electrode was pushed firmly against the neuron surface. A recovery from this decrease in [Ca2+]o could sometimes, but not always, be observed during the phase of induced neuronal activity.

The lacunar glial zone at the periphery of Aplysia giant neuron: volume of extracellular space and total calcium content of gliagrana

The relative volume of perineuronal extracellular space, the number of gliagrana and their total calcium content have been measured in Aplysia punctata and A. californica, at the periphery of giant neurons R2 and LP1. After chemical fixation, the extracellular space amounts to 26% of the periganglionic glial zone, but this increases to 36% after quick freezing and freeze-substitution. The glial cytoplasm contains gliagrana, membrane-bound granules approximately 0.3 micron in diameter. The number of gliagrana per micron 2 of section, defined as "abundance", was counted in electron micrographs of chemically fixed tissues. The abundance of gliagrana appears to be directly proportional to the volume of the extracellular space when the values are averaged per individual Aplysia. The total calcium concentration of the gliagrana is measured by X-ray microanalysis on sections of ganglia processed by rapid freezing and freeze-substitution in the presence of oxalic acid: it was found to be very high. An individual granule may contain 100 mM Ca in A. californica and 50 mM in A. punctata but in both species the calcium concentration varies along a wide range as if there were different functional states of the granules with respect to this concentration. The total calcium stored in the specific granules of the glial zone was estimated. It was calculated that should the glial calcium store be entirely diluted in the extracellular space of the glial zone, it would raise the calcium concentration of this space by approximately 1 mM (0.1-2.7 mM). These findings are discussed with regard to the hypothesis of glial cells regulating the perineuronal calcium concentration.