Segmentation in the vertebrate nervous system

Although there is good evidence that growing axons can be guided by specific cues during the development of the vertebrate peripheral nervous system, little is known about the cellular mechanisms involved. We describe here an example where axons make a clear choice between two neighbouring groups of cells. Zinc iodide-osmium tetroxide staining of chick embryos reveals that motor and sensory axons grow from the neural tube region through the anterior (rostral) half of each successive somite. 180 degrees antero-posterior rotation of a portion of the neural tube relative to the somites does not alter this relationship, showing that neural segmentation is not intrinsic to the neural tube. Furthermore, if the somitic mesoderm is rotated 180 degrees about an antero-posterior axis, before somite segmentation, axons grow through the posterior (original anterior) half of each somite. Some difference therefore exists between anterior and posterior cells of the somite, undisturbed by rotation, which determines the position of axon outgrowth. It is widespread among the various vertebrate classes.     

Comparison of human adult and fetal hemoglobin: Aminophenol-induced methemoglobin formation

Summary Human fetal hemoglobin was more susceptible to methemoglobin formation in the presence of aminophenols than was adult hemoglobin. This was due to the intrinsic properties of the proteins rather than the presence of methemoglobin reductases.This work was supported by a grant from the National Institute of General Medical Sciences GM-17184.     

Effect of fatty acids on fetal rat bone in culture

Zusammenfassung Nachweis, dass Fettsäuren (Palmitin-, Stearin- und Ölsäuren) in sehr niedrigen Konzentrationen die Kalziumabgabe und die Knochenresorption in fötalen Ratten in vitro fördern.

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The studies were supported by USPHS grant No. AM 11262. The albumin monomer was kindly supplied by Drs.J. Brand andL. Raisz.     

Demonstrating stratification in a European American population

Population stratification occurs in case-control association studies when allele frequencies differ between cases and controls because of ancestry. Stratification may lead to false positive associations, although this issue remains controversial. Empirical studies have found little evidence of stratification in European-derived populations, but potentially significant levels of stratification could not be ruled out. We studied a European American panel discordant for height, a heritable trait that varies widely across Europe. Genotyping 178 SNPs and applying standard analytical methods yielded no evidence of stratification. But a SNP in the gene LCT that varies widely in frequency across Europe was strongly associated with height (P < 10(-6)). This apparent association was largely or completely due to stratification; rematching individuals on the basis of European ancestry greatly reduced the apparent association, and no association was observed in Polish or Scandinavian individuals. The failure of standard methods to detect this stratification indicates that new methods may be required.