The effect of natural toxicants and other chemicals on the kidney.

Repeated administration of ochratoxin A (OTA) caused renal morphological dose-related changes, that were associated with proximal tubular and glomerular damage the latter showing oedema and prominent PAS staining suggestive of glomerular basement membrane thickening. On the other hand, the combined administration of repeated doses of OTA and aflatoxin B[1] (2. 5 mg and 100 ug per kg, respectively), appeared to have a synergistic effect, characterized by severe disruption of proximal tubules and general morphological derrangement of the glomerulus, involving intense and faint staining nuclei (suggestive of cell necrosis) and cytoplasmic vacuolation, which was not seen with either toxin alone. When clinical biochemical parameters were measured after repeated administration of a low dose of OTA, enzymuria, glucosuria, polyuria and proteinuria were observed, with glucose and alkaline phosphatase as the most sensitive parameters. Metabolic studies performed in vitro showed that isolated pig and rat glomeruli incorporate different amino acids linearly for several hours at different rates and perform oxidative metabolism of glucose and fatty acids to CO[2] also linearly. For pig glomeruli the order of amino acid incorporation was LEU >> PRO = HIS > LYS > GLY and for rat glomeruli it was TRP >> PHE > TYR = LEU > PRO > HIS. The same amino acids were incorporated in a similar way in rat tubules, but the incorporation rate is 10-fold lower. When de novo synthesis of protein by pig glomeruli exposed to different chemicals was assessed, using proline (PRO) as the precursor, adriamycin (ADR) and ethacrynic acid (ETA) inhibited protein synthesis more than 2-bromoethanamine (BEA) and streptomycin (STR), and much more than puromycin aminonucleoside (PAN). When isolated rat glomeruli were exposed to low concentrations of OTA, there was a generalized inhibition on de novo synthesis of protein from the six amino acids tested and the aromatic amino acids (TRP, TYR and PHE) were more sensitive to OTA effect than PRO. Low concentrations of OTA (10 - 100 uM) enhanced glomerular and tubular glucose metabolism to CO[2] and only high concentrations of the mycotoxin (1000 uM) caused significant inhibition of glomerular and proximal tubular linolenic acid metabolism

Effects on LDEF exposed copper film and bulk

Two forms of copper were exposed to the Long Duration Exposure Facility (LDEF) Mission 1 environment: a copper film, initially 74.2 plus or minus 1.1 nm thick sputter coated on a fused silica flat and a bulk piece of oxygen-free, high conductivity (OFHC) copper. The optical density of the copper film changed from 1.33 to 0.70 where exposed, and the film thickness increased to 106.7 plus or minus 0.5 nm where exposed. The exposed area appears purple by reflection and green by transmission for the thin film and maroon color for the bulk copper piece. The exposed areas increased in thickness, but only increase in the thickness of the thin film sample could be readily measured. The increase in film thickness is consistent with the density changes occurring during conversion of copper to an oxide. However, we have not been able to confirm appreciable conversion to an oxide by x-ray diffraction studies. We have not yet subjected the sample to e-beams or more abusive investigations out of concern that the film might be modified

The interaction of atomic oxygen with copper: An XPS, AES, XRD, optical transmission, and stylus profilometry study

The University of Alabama in Huntsville (UAH) experiment A-0114 was designed to study the reaction of material surfaces with low earth orbits (LEO) atmospheric oxygen. The experiment contained 128 one-inch circular samples; metals, polymers, carbons, and semiconductors. Half of these samples were exposed on the front of the Long Duration Exposure Facility (LDEF) and remaining on the rear. Among metal samples, copper has shown some interesting new results. There were two forms of copper samples: a thin film sputter-coated on fused silica and a solid piece of OFHC copper. They were characterized by x-ray and Auger electron spectroscopies, x-ray diffraction, and high resolution profilometry. Cu 2p core level spectra were used to demonstrate the presence of Cu2O and CuO and to determine the oxidation states

A brief critical review on the behavior of historical timber structures affected by biological agents and other external factors

The durability of the historical timber structures is significantly influenced by the quality of the timber used for its construction, by its physical and mechanical properties, but also by the negative action of various biological agents (xylophage insects and fungal rot) as well as that of external factors (climatic or technologically-resulted humidity, air temperature, chemical compounds, radiations, etc.). The paper highlights the effects of the most noteworthy biological agents present in the temperate climate onto historical timber, as well as the effects of moisture (with an emphasis on the provisions of Eurocode 5 and EN 335-1 in regard to the matter), those of high temperature, of aggressive chemical compounds and of various radiations (ultraviolet, infrared, gamma, etc.). As a final point, the paper briefly describes the main courses of action required to counter the effects of the action of biological agents and of other external factors on the historical timber structures

Compatibility issues regarding mortars for repairs and additions in interventions on historic masonry

The functions of the materials used for interventions on historic fabric are multiple, and go beyond the plain repairing or completion of damaged parts or in need of strengthening. This is a significant reason (among others) due to which the recourse to original materials, traditional, or with otherwise akin properties, is not always enough. In regard to the composition of mortars, reproducing the original recipes is often difficult. However, the existence of contemporary mortars based on hydraulic lime or trass, the composition and physico-mechanical properties of which are sufficiently known, reliable, and compliant with contemporary standards, allow for compatible interventions with good results in regard to rainwater protection. An effective mortar recipe depends on a clear understanding of its role in masonry, in respect of each of its functions. The technical requirements that a mortar must meet in order to be compatible with the historic fabric are mechanical strength, water absorption (absorption of water while in the state of immersion, capillary absorption and vapour permeability - each with different implications in regard to the physical behaviour of the masonry), adhesion the substrate, contraction, vibration resistance and freeze-thaw cycles. The paper presents some guidelines regarding these compatibility issues and the decision factors that contribute to the design of contemporary compatible recipes of mortars for repairs and additions in interventions on historic masonry