Effects of phthalic acid esters on the liver and thyroid

The effects, over periods from 3 days to 9 months of administration, of diets containing di-2-ethylhexyl phthalate are very similar to those observed in rats administered diets containing hypolipidemic drugs such as clofibrate. Changes occur in a characteristic order commencing with alterations in the distribution of lipid within the liver, quickly followed by proliferation of hepatic peroxisomes and induction of the specialized P-450 isoenzyme(s) catalyzing omega oxidation of fatty acids. There follows a phase of mild liver damage indicated by induction of glucose-6-phosphatase activity and a loss of glycogen, eventually leading to the formation of enlarged lysosomes through autophagy and the accumulation of lipofuscin. Associated changes are found in the kidney and thyroid. The renal changes are limited to the proximal convoluted tubules and are generally similar to changes found in the liver. The effects on the thyroid are more marked. Although the levels of thyroxine in plasma fail to about half normal values, serum triiodothyronine remains close to normal values while the appearance of the thyroid varies, very marked hyperactivity being noted 7 days after commencement of treatment, this is less marked at 14 days, but even after 9 months treatment there is clear cut evidence for hyperactivity with colloid changes which indicate this has persisted for some time. Straight chain analogs of di-2-ethylhexyl phthalate, di-n-hexyl phthalate and di-n-oxtyl phthalate differ entirely in their short-term effects on the liver and kidney but have similar effects on the thyroid. The short-term in vivo hepatic effects of the three phthalate esters can be reproduced in hepatocytes in tissue culture. All three phthalate esters, as well as clofibrate, have early marked effects on the metabolism of fatty acids in isolated hepatocytes. The nature of these changes is such as to increase storage of lipid in the liver. A hypothesis is presented to explain the progress from these initial metabolic effects to the final formation of liver tumors

Recent Applications in Combined Transmission Electron Microscopy and Microanalysis

An AEI CORA has recently been used to examine a wide number of applications mainly in the biological field. This instrument with its unique double field condenser/objective lens combines the normal accepted high resolution performance of a transmission electron microscope with X-ray analysis of areas down to a 250°A in diameter.Environmental pollution is one field in which this technique excels. Although the dangers of handling asbestos are well known and stringent controls operate in industrial use, an individual can be at risk in domestic use, especially when handling some of the home repair kits. Certain spackling compounds were examined by dispersing a small quantity in distilled water and drying down onto a carbon coated grid. As can be seen from the micrograph Fig la many fibres exist, similar in appearance to asbestos.</jats:p

Strioscopic Dark Field Imaging with the AEI EM801S

Insufficient contrast is generally the main limitation in resolving fine detail in biological specimens. Various preparation techniques such as staining and shadowing have been devised to improve image contrast, but these usually result in loss of resolution. It is therefore advantageous to be able to increase the contrast in the microscope image without recourse to special preparation techniques. The two techniques commonly used to gain such an improvement are Dark Field Imaging and Objective Defocus, the latter suffering the disadvantage of image interpretation due to the filtering of specific frequencies depending upon the amount of defocus and the spherical aberration of the lens. Dark field images can be formed by various techniques, displaced objective aperture, tilted illumination, contrast stop objective aperture and annular condenser aperture, the latter two collectively termed strioscopy. Since biological specimens are predominately amorphous thus giving only diffuse scattering with a few ring maxima and no discrete reflections, a strioscopic technique is preferred.</jats:p

Intracellular binding of lanthanum in root tips of barley (Hordeum vulgare)

By means of electron microscopy and X-ray energy spectroscopy (CORA in the transmission mode) it was shown that lanthanum may enter the cytoplasmic phase of undifferentiated cells in barley root tips. The nucleolus in particular proved to be a site with a high affinity for lanthanum. This finding is discussed in relation to the inhibition of root growth which has been reported to occur when root tips are exposed to polyvalent cations