The in situ architecture of Escherichia coli ribosomal RNA derived by electron spectroscopic imaging and three-dimensional reconstruction.

The structures of the large and small ribosomal subunits of Escherichia coli were reconstructed using spectroscopic electron microscopy and quaternion-assisted angular reconstitution to resolutions of better than 4 nm. In addition, the distributions of phosphorus within these complexes were reconstructed. The three-dimensional reconstruction of the distribution of this atomic element is an extension of microanalysis (in two dimensions) for phosphorus identification and mapping, as a signature of the arrangement of the phosphate backbones of the constituent ribosomal RNAs. The results on both the phosphorus reconstructions and the total reconstructions (protein and ribosomal RNA) reveal several passageways through both subunits. The structures correspond favourably with other independent reconstructions of the whole E. coli ribosome from cryoelectron micrographs and their accompanying models of translation (Frank et al., Nature, 376, 441-444, 1995; Stark et al., Structure, 3, 815-821, 1995). The overall reconstructions in conjunction with the phosphorus (rRNA) distributions are the first to be achieved synchronously for this nucleoprotein complex.

The effect of early referral and intervention on the developmentally disabled infant: evaluation at 18 months of age.

This study examines the age of referral and the effect of early intervention for the physically handicapped child. Fifty children were referred before 9 months of age, and they were compared with 55 children referred after 9 months of age. At 18 months of age, the children in the earlier referred group showed greater developmental progress in acquisition of skills in all of the six areas tested: perceptual-fine motor (P less than 0.0003), cognition (P less than 0.0001), language (P less than 0.0004), social-emotional (P less than 0.0001), self-care (P less than 0.0001), and gross motor (P less than 0.0002). The results show that, at least in the short term, there is a critical age for onset of intervention to achieve the most benefit for the developmentally disabled child. Family physicians should be alert to early warning signs of neurological deficits in order to obtain early treatment for these children.