B Krings | PubMed Health

PubMed1989

Superoxide Dismutase Activity in Needles of Norwegian Spruce Trees (Picea abies L.).

The activity of superoxide dismutase was investigated in needles of spruce trees. To obtain maximum activity, needles were homogenized in the presence of Triton X-100 and polyvinylpyrrolidone. Superoxide dismutase activity was measured in dialyzed extracts with a modified epinephrine assay (HP Misra, I Fridovich [1972] J Biol Chem 247: 3170-3175) at pH 10.2. The extracts contained 70 to 120 units of superoxide dismutase per milligram protein. One unit of superoxide dismutase was completely inhibited in the presence of 20 micromolar NaCN. On native polyacrylamide gels three electromorphs were visualized after staining for activity. All three species were sensitive to CN(-) and H(2)O(2) and were therefore assumed to be Cu/Zn-superoxide dismutases. Superoxide dismutase activity was dependent on the age of the needles and declined by approximately 25% within 3 to 4 years.

Journal Article↗

PubMed1979

Further studies on hypothalamic-pituitary-testicular function in old rats.

The dysfunction of the hypothalamic-pituitary-gonadal axis in old age was studied in 24-month old male Wistar rats which were compared with 3-month old animals. The hypothalamic LH-RH content and the pituitary LH were significantly lower in the old than in the young adult animals. The plasma concentrations of LH and testosterone were significantly higher in the young rats. The primary cause of these age-dependent changes probably is a hypothalamic dysfunction. When isolated Leydig cells of young and old rats were incubated in vitro, the testosterone secretion per cell was significantly smaller in old than in young cells with as well as without HCG stimulation. In vivo stimulation of rats by iv injection of biologically active iodinated hCG revealed that the intratesticular uptake of the gonadotrophin was not different in young and old rats. The testosterone response, however, was significantly reduced in old age. An in vitro "desensitisation" experiment in which the LH receptor capacity was artificially reduced demonstrated that the 40% reduction of receptor capacity in old testes as described earlier will not impair the testicular uptake of gonadotrophin from blood. Repeated injection of hCG results in equally elevated testosterone concentrations in young and old rats.

Age Factors↗