Androgen binding to cytosol prepared from epididymides of sexually mature castrated rabbits: evidence for a cytoplasmic receptor.

The presence of androgen-binding activity in cytosol prepared from the major anatomical segments (caput, corpus, and cauda) of the epididymis of castrated sexually mature rabbits has been demonstrated. A portion of this binding activity is likely to be the epididymal androgen receptor. When epididymal cytosol from adult castrated rabbits is analyzed on low-ionic strength (0.01 MKCl) sucrose gradients, two peaks of macromolecular binding could be detected, one congruent to 4.6S and one congruent to 8S. On gradients containing 1.0 M KCl, only one sedimenting form congruent to 4.6S could be demonstrated, suggesting that the 8S component is composed of aggregates. If cytosol was preincubated with labeled androgen, followed by an incubation with unlabeled androgen, and subsequently analyzed for binding on low-ionic strength gradients, only the congruent to 8S peak could be detected, indicating that most of the binding in the congruent to 4.6S region was rapidly dissociable. This suggests that binding in this region was to moieties other than receptor. Since androgen binding proteins (ABP) of testicular origin would have been cleared from the epididymis at the timepoints that we concentrated on for most of these studies, the 4.6S binding probably represents the association of androgen with plasma testosterone binding globulin (TeBG). The binding of androgen to the receptor can be inhibited by cyproterone, while this antiandrogen does not inhibit binding to either ABP or TeBG at the concentration used.     

Adrenocortical regulation of protein metabolism during prolonged physical stress]

Experiments on Wistar male rats revealed depression of labeled amino acid incorporation into the tissue proteins as a result of swimming. When prolonged swimming was accompanied by an enhanced adrenocortical activity the block of the protein synthesis in the liver proved to disappear. Adrenalectomy excluded the activation of alanine-aminotranspherase and a drop of the free amino acids in the liver during physical exercise: corticosterone administration to adrenalectomized animals restored these shifts.     

Atomic absorption determination of zinc, copper, cadmium, and lead in tissues solubilized by aqueous tetramethylammonium hydroxide

Rat liver and kidney homogenates and homogeneous rat hair samples were prepared for atomic absorption spectrophotometric analysis by digestion with an appropriate concentration of aqueous tetramethylammonium hydroxide (TMAH). The endogenous tissue levels of Zn, Cu, Cd and Pb, the reproducibility of the analyses, and the recovery of added metal standards compare favorably with the results obtained by standard wet ashing procedures using concentrated nitric acid or nitric-perchloric acids. The use of 5% HNO₃ standard curve in calculations for the TMAH-treated samples leads to slightly lower results compared to the method of additions due to viscosity and surface tension effects on the aspiration rate of these samples. Moreover, the TMAH digestion method allows faster and safer processing and handling of samples in comparison to acid digestion procedures.     

Changes of telomere lengths in human intracranial tumours

The termini of human chromosomes comprise stretches of G-rich repeats that are about 5–20 kilobase (kb) in length. The size of the telomeres can be determined by hybridization with probes specific for these (ttaggg)_n sequences after digestion of chromosomal DNA with appropriate restriction enzymes and electrophoretic separation of the fragments. Here, probing with the ³²P-labelled synthetic (TTAGGG)₃ oligonucleotide revealed length changes of the telomeres occurring in intracranial tumours. Among 60 samples analysed, 41.7% showed telomere elongation, and 21.7% telomere reduction, whereas 36.7% of the tumours exhibited equal lengths compared with the patients' peripheral blood leukocytes. Most of the elongated glioma telomeres exceeded in length those of untransformed astrocytes derived from human fetal tissue.