Formation of tight junctions between neighboring podocytes is an early ultrastructural feature in experimental crescentic glomerulonephritis

PURPOSE: In crescentic glomerulonephritis (CGN), the development of cellular bridges between podocytes and parietal epithelial cells (PECs) triggers glomerular crescent formation. However, the sequential changes in glomerular ultrastructure in CGN are not well defined. This study investigated the time course of glomerular ultrastructure in experimental CGN. METHODS: Transmission electron microscopy (TEM) was performed using kidney samples from rats with nephrotoxic serum nephritis (NSN) from day 1 to day 14. Morphometric analysis was conducted on randomly selected glomeruli captured on TEM digital images. RESULTS: On day 1 of NSN, there was widespread formation of focal contacts between the cell bodies of neighboring podocytes, and tight junctions were evident at the site of cell-to-cell contact. This was confirmed by the increased expression of the tight junction molecule, zonula occludens-1 (ZO-1), which localized to the points of podocyte cell–cell body contact. On day 2, the interpodocyte distance decreased and the glomerular basement membrane thickness increased. Foot process effacement (FPE) was segmental on day 3 and diffuse by day 5, accompanied by the formation of podocyte cellular bridges with Bowman’s capsule, as confirmed by a decrease in podocyte-to-PEC distance. Fibrinoid necrosis and cellular crescents were evident in all glomeruli by days 7 and 14. In vitro, the exposure of podocytes to macrophage-conditioned media altered cellular morphology and caused an intracellular redistribution of ZO-1. CONCLUSION: The formation of tight junctions between podocytes is an early ultrastructural abnormality in CGN, preceding FPE and podocyte bridge formation and occurring in response to inflammatory injury. Podocyte-to-podocyte tight junction formation may be a compensatory mechanism to maintain the integrity of the glomerular filtration barrier following severe endocapillary injury

Dietary protein alters tubular iron accumulation after partial nephrectomy

Dietary protein alters tubular iron accumulation after partial nephrectomy. Reactive oxygen species (ROS) have been implicated in progression of disease in the rat remnant kidney (RK) model of chronic renal failure. Substantial amounts of iron accumulate in proximal tubular lysosomes of RK and could damage tubules by ROS generation. The effect of dietary protein intake on ROS, tubular damage and iron accumulation assessed by energy dispersive analysis was determined in RK (5/6 nephrectomy, N = 12) and sham-operated kidneys (SO, N = 10). In RK, mean lysosomal iron concentration, urinary iron and protein excretion and morphological damage were increased and GFR decreased. Dietary protein loading (40% vs. 12%) increased the number of iron-containing lysosomes (P < 0.05) and the mean lysosomal iron (P < 0.02) in proximal tubular cells after four weeks. In RK, high protein diet increased renal weight (P < 0.01), numerical density of iron-containing lysosomes and tubular damage (both P < 0.05). ROS generation, assessed by tissue and plasma malondialdehyde (MDA), was also increased (both P < 0.05). Plasma MDA correlated with tubular iron accumulation (r = 0.75). In RK fed a high protein diet (N = 18) treatment with the iron-chelator desferrioxamine reduced serum iron, urinary volume, and tubular iron accumulation and damage compared to controls (P < 0.01). In summary, in RK dietary protein manipulation altered urinary iron and protein excretion, proximal tubular iron accumulation, renal cortical ROS generation and ultra-structural damage. Desferrioxamine treatment reduced tubular lysosomal iron and ultrastructural damage. These results suggest a role for tubular iron as a determinant of tubular injury associated with dietary protein loading in rats with partial nephrectomy

The Potential of Autonomous Ship-Borne Hyperspectral Radiometers for the Validation of Ocean Color Radiometry Data

Calibration and validation of satellite observations are essential and on-going tasks to ensure compliance with mission accuracy requirements. An automated above water hyperspectral radiometer significantly augmented Australia’s ability to contribute to global and regional ocean color validation and algorithm design activities. The hyperspectral data can be re-sampled for comparison with current and future sensor wavebands. The continuous spectral acquisition along the ship track enables spatial resampling to match satellite footprint. This study reports spectral comparisons of the radiometer data with Visible Infrared Imaging Radiometer Suite (VIIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua for contrasting water types in tropical waters off northern Australia based on the standard NIR atmospheric correction implemented in SeaDAS. Consistent match-ups are shown for transects of up to 50 km over a range of reflectance values. The MODIS and VIIRS satellite reflectance data consistently underestimated the in situ spectra in the blue with a bias relative to the “dynamic above water radiance and irradiance collector” (DALEC) at 443 nm ranging from 9.8 × 10−4 to 3.1 × 10−3 sr−1. Automated acquisition has produced good quality data under standard operating and maintenance procedures. A sensitivity analysis explored the effects of some assumptions in the data reduction methods, indicating the need for a comprehensive investigation and quantification of each source of uncertainty in the estimate of the DALEC reflectances. Deployment on a Research Vessel provides the potential for the radiometric data to be combined with other sampling and observational activities to contribute to algorithm development in the wider bio-optical research community

Anterograde Transport of Herpes Simplex Virus Proteins in Axons of Peripheral Human Fetal Neurons: an Immunoelectron Microscopy Study

ABSTRACT Herpes simplex virus (HSV) reactivates from latency in the neurons of dorsal root ganglia (DRG) and is subsequently transported anterogradely along the axon to be shed at the skin or mucosa. Although we have previously shown that only unenveloped nucleocapsids are present in axons during anterograde transport, the mode of transport of tegument proteins and glycoproteins is not known. We used a two-chamber culture model with human fetal DRG cultivated in an inner chamber, allowing axons to grow out and penetrate an agarose barrier and interact with autologous epidermal cells in the outer chamber. After HSV infection of the DRG, anterograde transport of viral components could be examined in the axons in the outer chamber at different time points by electron and immunoelectron microscopy (IEM). In the axons, unenveloped nucleocapsids or focal collections of gold immunolabel for nucleocapsid (VP5) and/or tegument (VP16) were detected. VP5 and VP16 usually colocalized in both scanning and transmission IEM. In contrast, immunolabel for glycoproteins gB, gC, and gD was diffusely distributed in axons and was rarely associated with VP5 or VP16. In longitudinal sections of axons, immunolabel for glycoprotein was arrayed along the membranes of axonal vesicles. These findings provide evidence that in DRG axons, virus nucleocapsids coated with tegument proteins are transported separately from glycoproteins and suggest that final assembly of enveloped virus occurs at the axon terminus.</jats:p

Measurements of evaporation from a mine void lake and testing of modelling approaches

Pit lakes often form in the void that remains after open cut mining operations cease. As pit lakes fill, hydrological and geochemical processes interact and these need to be understood for appropriate management actions to be implemented. Evaporation is important in the evolution of pit lakes as it acts to concentrate various constituents, controls water level and changes the thermal characteristics of the water body. Despite its importance, evaporation from pit lakes is poorly understood. To address this, we used an automated floating evaporation pan and undertook measurements at a pit lake over a 12 month period. We also developed a new procedure for correcting floating pan evaporation estimates to lake evaporation estimates based on surface temperature differences. Total annual evaporation was 2690 mm and reflected the strong radiation inputs, high temperatures and low humidity experienced in this region. Measurements were used to test the performance of evaporation estimates derived using both pan coefficient and aerodynamic modelling techniques. Daily and monthly evaporation estimates were poorly reproduced using pan coefficient techniques and their use is not recommended for such environments. Aerodynamic modelling was undertaken using a range of input datasets that may be available to those who manage pit lake systems. Excellent model performance was achieved using over-water or local over-land meteorological observations, particularly when the sheltering effects of the pit were considered. Model performance was reduced when off-site data were utilised and differences between local and off-site vapor pressure and wind speed were found to be the major cause

The Potential of Autonomous Ship-Borne Hyperspectral Radiometers for the Validation of Ocean Color Radiometry Data

Calibration and validation of satellite observations are essential and on-going tasks to ensure compliance with mission accuracy requirements. An automated above water hyperspectral radiometer significantly augmented Australia’s ability to contribute to global and regional ocean color validation and algorithm design activities. The hyperspectral data can be re-sampled for comparison with current and future sensor wavebands. The continuous spectral acquisition along the ship track enables spatial resampling to match satellite footprint. This study reports spectral comparisons of the radiometer data with Visible Infrared Imaging Radiometer Suite (VIIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua for contrasting water types in tropical waters off northern Australia based on the standard NIR atmospheric correction implemented in SeaDAS. Consistent match-ups are shown for transects of up to 50 km over a range of reflectance values. The MODIS and VIIRS satellite reflectance data consistently underestimated the in situ spectra in the blue with a bias relative to the “dynamic above water radiance and irradiance collector” (DALEC) at 443 nm ranging from 9.8 × 10−4 to 3.1 × 10−3 sr−1. Automated acquisition has produced good quality data under standard operating and maintenance procedures. A sensitivity analysis explored the effects of some assumptions in the data reduction methods, indicating the need for a comprehensive investigation and quantification of each source of uncertainty in the estimate of the DALEC reflectances. Deployment on a Research Vessel provides the potential for the radiometric data to be combined with other sampling and observational activities to contribute to algorithm development in the wider bio-optical research community

Measurements of evaporation from a mine void lake and testing of modelling approaches

Pit lakes often form in the void that remains after open cut mining operations cease. As pit lakes fill, hydrological and geochemical processes interact and these need to be understood for appropriate management actions to be implemented. Evaporation is important in the evolution of pit lakes as it acts to concentrate various constituents, controls water level and changes the thermal characteristics of the water body. Despite its importance, evaporation from pit lakes is poorly understood. To address this, we used an automated floating evaporation pan and undertook measurements at a pit lake over a 12 month period. We also developed a new procedure for correcting floating pan evaporation estimates to lake evaporation estimates based on surface temperature differences. Total annual evaporation was 2690 mm and reflected the strong radiation inputs, high temperatures and low humidity experienced in this region. Measurements were used to test the performance of evaporation estimates derived using both pan coefficient and aerodynamic modelling techniques. Daily and monthly evaporation estimates were poorly reproduced using pan coefficient techniques and their use is not recommended for such environments. Aerodynamic modelling was undertaken using a range of input datasets that may be available to those who manage pit lake systems. Excellent model performance was achieved using over-water or local over-land meteorological observations, particularly when the sheltering effects of the pit were considered. Model performance was reduced when off-site data were utilised and differences between local and off-site vapor pressure and wind speed were found to be the major cause