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Our results suggest that the higher Ca -sensitivity of arterial contraction in 1-week-old compared to 10- to 12-week-old rats is due to a greater Rho-kinase activity. Constitutively active Rho-kinase contributes to MX-induced contraction in 10- to 12-week-old rats. In 1-week-old rats, additional Rho-kinase activation is involved. This remodelling of the Rho-kinase pathway is associated with its increased contribution to adrenergic arterial pressure responses.

The fine structure of the melting curve for the linear ColB1 DNA ha been obtained. To In the present study we fixed the melted regions with glyoxal to determine the ColEB1 regions whose melting corresponded to peaks in the fine structure of the melting curve.This method h"a earlier been used for localizing the AT-rich regions in T7 DNA revealed by the fine structure of the melting curves /12/. Glyoxal reacts with the amino-and iminogroups of bases and prevents complementary pairing; the product of its reaction with guanine is highly stable /13/.Glyoxal was used to fix the denatured regions appearing in DNA molecules at pre-chosen temperatures within the melting range. The set of denaturation maps subsequently constructed from electron micrographs made it possible to determine the size and location of the DNA regions corresponding to peaks in the fine structure of the melting curve. A combination of spectrophotometry and electron-microscopic visualization of the partially denatured molecules reveals the complete picture of the heat denaturation process. Using these results we construct'ed a map of the distribution of averaged GC-pair content over the ColEl DNA molecule.

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