The effects of lead upon collagen synthesis and proline hydroxylation in the Swiss mouse 3T6 fibroblast.

The effects of lead upon collagen synthesis and proline hydroxylation were examined in the Swiss mouse 3T6 fibroblast. The results indicate that lead reduces proline hydroxylation in stationary phase cultures of 3T6 cells, resulting in increased cellular retention of unhydroxylated procollagen. Inhibition of proline hydroxylation by lead was prevented by increasing the extracellular $\text{Fe}{}^{\mathrm{2+}}\text{Pb}{}^{\mathrm{2+}}$ molar ratio. Interference by lead in the hydroxylation of proline in logarithmic phase cultures of 3T6 cells resulted in increases in the 0.5 n HClO₄ soluble/insoluble hydroxyproline ratio. This was attributed to an increase in the rate of breakdown of lead-induced unhydroxylated procollagen. Kinetic analysis of the lead-iron interaction with proline hydroxylase suggests that the mechanism is competitive.     

Unbalancedness and Efficiency in Estimating Components of Variance: MINQUE and ANOVA Procedure

We consider the one-way classification random model. Using a measure of unbalancedness some MINQ-Estimation procedures and ANOVA-procedure have been investigated with respect to their sensibility to unbalancedness. Further if we define the efficiency of a design N as the ratio of the MSE (.)'s of the balanced and the unbalanced case we obtain for three MINQE-procedures upper and lower bounds of the minimum efficiency.     

THE INTRINSIC MECHANISM OF CHROMATIN DECONDENSATION AND ITS ACTIVATION IN HUMAN SPERMATOZOA*

In vitro decondensation of human sperm chromatin induced by the activation of an intrinsic mechanism was studied by light microscopy, scanning and transmission electron microscopy. Morphological evidence was provided to support the concept that this mechanism is essential for the chromatin decondensation occurring in vivo. Prostatic zinc is hypothesized to preserve this potential decondensation ability from oxidative destruction, by reversibly binding to free thiol-groups. The unique occurrence of disulphide-stabilized structures in eutherian spermatozoa may serve to protect the spermatozoon from structural degradation by its own proteolytic activity during the relatively slow passage through the eutherian egg investments.     

SEDIMENTARY STRUCTURES IN CAMBRIAN LIMESTONES STUDIED BY RADIOGRAPHY

The paper deals with radiographic studies of Middle Cambrian 'fragment limestone', and Upper Cambrian anthraconite concretions from Bornholm (Denmark). A very simple method provides good insight into the sedimentary structures of the rocks and hence a good foundation for interpretation of the lithogenesis.