Comparative studies of murine anionic and cationic arylsulfatase B

Summary Murine brain possesses an anionic form of arylsulfatase B which accounts for approximately 12–16% of nonmicrosomal arylsulfatase activity. This isozyme is antigenically similar to cationic arylsulfatase B, displays a similar developmental profile, and can be converted to a form resembling the cationic species by prior treatment with neuraminidase.This research was supported in part by National Institutes of Health Grant: GM 27707.     

A phage repressor-operator complex at 7 A resolution

The crystal structure of a complex between the DNA-binding domain of phage 434 repressor and a synthetic 434 operator shows that the protein, very similar in conformation to gamma repressor, binds to B-form DNA with the second alpha-helix of a helix-turn-helix motif lying in the major groove.     

Cadmium in the atmosphere

Summary Cadmium is present naturally in the air mainly as a result of volcanic emissions and release by vegetation. Anthropogenic sources, which overall give rise to emissions one order of magnitude greater than natural sources, are largely primary non-ferrous metals production and waste incineration. Measured concentrations of airborne cadmium are typically < 1 ng m^–3 at remote sites, 0.1–10 ng m^–3 at rural sites and 1–100 ng m^–3 at urban and industrial sites, dependent upon the nature and proximity of local sources. Particle sizes are generally <2 m, and often considerably smaller, consistent with an anthropogenic source and a long atmospheric life-time. Cadmium deposition to the land occurs with fluxes varying from 0.05 ng cm^–2 month^–1 in Greenland to circa 1000 ng cm^–2 month^–1 in the vicinity of major industrial sources. The possible significance of a motor vehicular source of airborne cadmium is also reviewed.     

Independent recruitment of a conserved developmental mechanism during leaf evolution

Vascular plants evolved in the Middle to Late Silurian period, about 420 million years ago. The fossil record indicates that these primitive plants had branched stems with sporangia but no leaves. Leaf-like lateral outgrowths subsequently evolved on at least two independent occasions. In extant plants, these events are represented by microphyllous leaves in lycophytes (clubmosses, spikemosses and quillworts) and megaphyllous leaves in euphyllophytes (ferns, gymnosperms and angiosperms). Our current understanding of how leaves develop is restricted to processes that operate during megaphyll formation. Because microphylls and megaphylls evolved independently, different mechanisms might be required for leaf formation. Here we show that this is not so. Gene expression data from a microphyllous lycophyte, phylogenetic analyses, and a cross-species complementation experiment all show that a common developmental mechanism can underpin both microphyll and megaphyll formation. We propose that this mechanism might have operated originally in the context of primitive plant apices to facilitate bifurcation. Recruitment of this pathway to form leaves occurred independently and in parallel in different plant lineages.