A Mixture of Paraphenylenediamine and Imidazole: Its Effect on the Extraction of Lipid Droplets during Electron Microscopy Staining

To prevent extraction of lipids during a double staining procedure for electron microscopy, the tissue slices, double fixed with glutaraldehyde and osmium tetroxide to preserve microvesicular lipid droplets in the cytoplasm, were immersed for 2 hr in veronal buffer (pH 9.0) containing 0.5% p-phenylenediamine and 0.5% imidazole immediately after postfixation. The stained sections of the immersed tissue slice showed blackened, well circumscribed lipid droplets similar to those in corresponding unstained sections. Moreover, highly contrasting features of the cellular architecture could be visualized with the double stained, as well as routinely prepared sections.     

PHYTOREMEDIATION OF HEPTACHLOR AND HEPTACHLOR EPOXIDE IN SOIL BY CUCURBITACEAE

Plants in the family of Cucurbitaceae family are known to up take organochlorines. This study was designed to screen seven cultivars of the Lagenaria siceraria species of the Cucurbitaceae family to determine their capacity to remediate heptachlor- and heptachlor epoxide-contaminated soil. The seven Lagenaria cultivars were grown in contaminated and uncontaminated Molokai soil for 13 weeks. The results showed that all the plants tolerated heptachlor and heptachlor epoxide at levels of 0.169 and 0.376 μg/g, respectively, in the soil and were able to bear a limited number of immature fruits during the short study period. All seven Lagenaria cultivars showed some ability to up take heptachlor epoxide into their vines with bioaccumulation factors varying from 1.0 to 5.2. The two contaminants were not detected in the fruits and heptachlor itself was not detected in the vines. The mean concentrations of heptachlor in the soil of all the pots including the no-plant control were not significantly different from that in the initial soil, which might be due to the gradual release of the soil soil-bound heptachlor residues. In the soil, all pots showed a significant decrease for heptachlor epoxide as compared to the initial level, but there was no significant difference between the no-plant control pots and the planted pots of six of the seven cultivars. The local Hyotan cultivar showed the largest decrease, from 0.376 down to 0.050 μg/g dry soil, and was the only cultivar showing a significant difference in the soil heptachlor epoxide concentration with the no-plant control.     

Spectral densities of nitrogen nuclei in Escherichia coli ribonuclease HI obtained by 15N NMR relaxation and molecular dynamics

Summary Spectral densities of the ¹⁵N amide in Escherichia coli ribonuclease HI, obtained from NMR relaxation experiments, were compared with those calculated using a molecular dynamics (MD) simulation. All calculations and comparisons assumed that the auto-correlation function describing the internal motions of the molecule was independent of the auto-correlation function associated with overall rotational diffusion. Comparisons were limited to those residues for which the auto-correlation function of internal motions rapidly relaxed and reached a steady state within 205 ps. The results show the importance of frequency components as well as amplitudes of internal motions in order to obtain a meaningful comparison of MD simulations with NMR data.     

Effects of rat fetuin on stimulation of bone resorption in the presence of parathyroid hormone.

Rat fetuin, which is the rat counterpart of human alpha 2-HS glycoprotein and bovine fetuin, is only detectable in calcified tissues such as bone matrices and dentin, and bone cells such as osteoblasts and osteocytes immunohistochemically. The effect of this protein on bone resorption was examined to study its physiological role in bone metabolism. Rat fetuin increased bone resorption in the presence of low concentrations of parathyroid hormone (PTH), but it had no activity on bone resorption without PTH. The increase in bone resorption by PTH and PTH plus rat fetuin was inhibited by the addition of chymostatin, an inhibitor for cathepsin L. Moreover, we found that when type I collagen from rat was preincubated with rat fetuin, the digestion of rat type I collagen by cathepsin L was increased. These findings suggest that rat fetuin present in bone matrix is important in bone resorption.