Applying two-photon excitation fluorescence lifetime imaging microscopy to study photosynthesis in plant leaves

This study investigates to which extent two-photon excitation (TPE) fluorescence lifetime imaging microscopy can be applied to study picosecond fluorescence kinetics of individual chloroplasts in leaves. Using femtosecond 860 nm excitation pulses, fluorescence lifetimes can be measured in leaves of Arabidopsis thaliana and Alocasia wentii under excitation-annihilation free conditions, both for the F0- and the Fm-state. The corresponding average lifetimes are ~250 ps and ~1.5 ns, respectively, similar to those of isolated chloroplasts. These values appear to be the same for chloroplasts in the top, middle, and bottom layer of the leaves. With the spatial resolution of ~500 nm in the focal (xy) plane and 2 μm in the z direction, it appears to be impossible to fully resolve the grana stacks and stroma lamellae, but variations in the fluorescence lifetimes, and thus of the composition on a pixel-to-pixel base can be observed

Do the results of the new trials change the standard treatment of metastatic renal cell cancer?

Item does not contain fulltextWith the emergence of novel angiogenesis inhibitors, we are moving to a new era for patients with metastasized renal cell carcinoma. Since the results achieved reflect more a modification of the natural course of the disease than a cure, past achievements should not be neglected. Low-risk patients with clear cell histology, especially those with pulmonary metastasis only, should still be offered cytokine therapy. For intermediate-risk patients sunitinib is the treatment of choice. For high-risk patients, temsirolimus has to date provided the most convincing data, its availability is however limited. Data with sorafenib and sunitinib in the high-risk group are still anecdotal. The toxicity profiles of these 2 drugs are different and might particularly relate to patients with known cardiovascular co-morbidity. No sufficient data are available regarding sequential use. After cytokine failure, sorafinib is the treatment of choice. Patients should preferably be treated within clinical trials to answer unaddressed questions. It is well known that the strict entry criteria used within the clinical studies were applied very flexibly when drugs have been approved. These aspects require a careful follow-up to ascertain optimal use and to prevent misuse. Finally, the costs of prolonged treatment will be enormous, and only meaningful survival advantages will convince the health authorities to make these new treatments available for all patients