Correlative microscopy approach for biology using X-ray holography, X-ray scanning diffraction and STED microscopy.

We present a correlative microscopy approach for biology based on holographic X-ray imaging, X-ray scanning diffraction, and stimulated emission depletion (STED) microscopy. All modalities are combined into the same synchrotron endstation. In this way, labeled and unlabeled structures in cells are visualized in a complementary manner. We map out the fluorescently labeled actin cytoskeleton in heart tissue cells and superimpose the data with phase maps from X-ray holography. Furthermore, an array of local far-field diffraction patterns is recorded in the regime of small-angle X-ray scattering (scanning SAXS), which can be interpreted in terms of biomolecular shape and spatial correlations of all contributing scattering constituents. We find that principal directions of anisotropic diffraction patterns coincide to a certain degree with the actin fiber directions and that actin stands out in the phase maps from holographic recordings. In situ STED recordings are proposed to formulate models for diffraction data based on co-localization constraints.

Combined in-situ imaging of structural organization and elemental composition of substantia nigra neurons in the elderly.

Human dopaminergic system in general, and substantia nigra (SN) neurons, in particular, are implicated in the pathologies underlying the human brain aging. The interplay between aberrations in the structural organization and elemental composition of SN neuron bodies has recently gained in importance as selected metals: Fe, Cu, Zn, Ca were found to trigger oxidative-stress-mediated aberration in their molecular assembly due to concomitant protein (alpha-synuclein, tau-protein) aggregation, gliosis and finally oxidative stress. In the present study, we demonstrate an integrated approach to the analysis of the structural organization, assembly, and metals' accumulation in two distinct areas of SN: in the neuromelanin neurons and neuropil. By using the highly brilliant source of PETRA III and the Kirkpatrick-Baez nano-focus, large area histological brain slices are scanned at the sub-neuronal resolution, taking advantage of continuous motor movement and reduced acquisition time. Elemental analysis with synchrotron radiation based X-ray Fluorescence (SRXRF) is combined with X-ray Phase Contrast Imaging (XPCI) to correct for inherent aberrations in the samples' density and thickness, often referred to as the mass thickness effect. Based on the raw SRXRF spectra, we observed the accumulation of P, S, Cl, K, Ca, Fe, Cu and Zn predominantly in the SN neurons. However, upon the mass thickness correction, the distributions of Cl became significantly more uniform. Simultaneously with the fluorescence signal, the Small Angle X-ray Scattering (SAXS) is recorded by a pixel detector positioned in the far-field, enabling fast online computation of the darkfield and differential phase contrast (DPC). The data has demonstrated the SN neurons and neuropil produces excellent contrast which is due to their different mass density and scattering strength, indicative of differences in local structure and assembly therein. In all, the results show that combined SRXRF-XPCI-SAXS experiments can robustly serve as a unique tool for understanding the interplay between the chemical composition and structural organization that may drive the biochemical age-related processes occurring in the human dopaminergic system.

Collective lipid bilayer dynamics excited by surface acoustic waves.

We use standing surface acoustic waves to induce coherent phonons in model lipid multilayers deposited on a piezoelectric surface. Probing the structure by phase-controlled stroboscopic x-ray pulses we find that the internal lipid bilayer electron density profile oscillates in response to the externally driven motion of the lipid film. The structural response to the well-controlled motion is a strong indication that bilayer structure and membrane fluctuations are intrinsically coupled, even though these structural changes are averaged out in equilibrium and time integrating measurements. Here the effects are revealed by a timing scheme with temporal resolution on the picosecond scale in combination with the sub-nm spatial resolution, enabled by high brilliance synchrotron x-ray reflectivity.

Effects of interleukin-2 immunotherapy on renal function.

Recombinant interleukin-2 (IL-2) infusions have recently been evaluated as a new form of immunotherapy for the treatment of malignancies. This form of therapy has been complicated by the development of fluid retention, azotemia, and hypophosphatemia. To evaluate the effects of IL-2 on renal function, we prospectively studied eight patients who received IL-2 (10(5) micron/kg every eight hours intravenously [IV]) for five days as the initial phase of a treatment protocol using IL-2 plus lymphokine activated killer (LAK) cells. Dopamine and fluids were used to maintain blood pressure and all patients received indomethacin (100 mg/d). IL-2 therapy produced a syndrome similar to endotoxemia with the development of respiratory alkalosis (pH = 7.44 +/- .2, pCO2 = 30 +/- 2) and hypotension (mean BP, 71.3 mm Hg). These changes were accompanied by marked sodium avidity, edema formation, and mild elevations of BUN and creatinine. Hypophosphatemia, hypocalcemia, and hypomagnesemia were commonly seen. No defects in renal calcium, magnesium, phosphorous, net acid excretion, or glycosuria were demonstrated. We conclude: (1) IL-2 induces an increase in vascular permeability causing the development of edema, sodium avidity, and prerenal azotemia as occurs during endotoxemia; (2) IL-2 therapy induces respiratory alkalosis with the subsequent intracellular shift of phosphorous accompanied by increased renal phosphorous reabsorption; and (3) there is no evidence of renal tubular dysfunction (renal tubular acidosis [RTA], renal leak of glucose, phosphorous, or magnesium).