Stage-specific gene regulation is important in determining cell function during development. Immature B cells expressing membrane-bound immunoglobulin M (mIgM) are sensitive to antigen-induced tolerance, whereas mature B cells are activated by antigen. Previous studies have established an association between Egr-1 gene induction and antigen receptor (mIgM)-mediated activation of mature B cells. Here it is shown that the immature B cell line WEHI-231 and tolerance-sensitive bone marrow-derived B cells do not express Egr-1. It is further shown that lack of inducible expression in these cells is due to specific methylation of the Egr-1 gene. Thus, covalent inactivation of an activation-associated gene may explain tolerance sensitivity at specific stages of B cell development.
Physico-chemical investigations of enamel from deciduous teeth of a small number of children with and without pre-natal fluoride supplementation (PNF) exhibited the following differences between the PNF and non-PNF enamel, with the former showing: (a) more homogeneous and less extensive patterns of acid-etching; (b) denser crystal populations in intra-prismatic regions; (c) larger prism dimensions; (d) greater total mineral density (wt%ash); (e) higher degree of crystallinity; (f) smaller a-axis dimensions; and (g) more fluoride and less carbonate contents. On the basis of these preliminary findings, further studies with larger numbers of samples would seem appropriate.
In 1916-17 a study was made of children in the schools of Chapel Hill, N. C, by applying the Stanford Revision of the Binet tests. 1 Of the children examined those were selected for comparative study who fell between the ages of 9 years 0 months and 12 years 11 months, a total of 77 cases. Most of these were in Grades IV, V, and VI. The results at once showed a distribution of scores differing from the "normal," and investigation of the social and economic classes from which the children came brought to light an interesting correlation. The children of this school came from three economic classes: Families of members of the faculty of the University of North Carolina; families resident in the town of Chapel Hill, the fathers being small tradesmen, artisans, teamsters, etc.; and families resident on farms in the country outside Chapel Hill. The median IQ of the "faculty" group of children was found to be highest in these tests, that of the "town" group distinctly lower, and that of the "country" group lower still. The authors, in their discussion of these results, seek explanation in terms of heredity as the main determining factor. Environmental differences between faculty and town children were plainly much less here than between groups used in other surveys made at Columbus and at Cambridge; and, in fact, one environmental difference, that between town and country life, was considered as being based further back upon selective factors working upon native differences.The writers of the present paper were interested in amplification of the original study by making re-examinations on the same and another basis four years later. The subjects of this later study were different individual persons from those of the earlier but were taken from the same social classes and to a certain extent, indeed, from the same families.Stanford Revision Examination.--The first aim of the present writers was to duplicate in detail the procedure of the earlier study, and thus to throw further light upon the validity of the results.
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