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Biomedical subjects

H L Frisch

Publications and source records attributed to H L Frisch.

6 recordsLinked to original sources
PubMed1991

The effects of lithium, rubidium, cesium and magnesium ions on the close packing of persistence-length DNA fragments.

By application of scaled particle theory to persistence-length DNA fragments in sedimentation-equilibrium at speeds high enough to maintain close packing, the range of interhelical electrostatic repulsion was evaluated with LiCl, RbCl, CsCl, and MgCl2 as supporting electrolytes. Analysis of the data in terms of the Zimm cluster function confirmed that the net interaction between helices is purely repulsive in all cases. At constant ionic strength the electrostatic radius of the rod-like DNA decreases as the counterion changes from Li+ to Rb+ to Cs+. In contrast to univalent counterions, electrostatic radius increases with Mg2+ concentration, except at very low (mM) MgCl2 concentrations. All solutions undergo a reversible transition to a turbid, optically anisotropic phase at a slightly salt-dependent, critical DNA concentration, as observed previously for NaDNA.

Animals↗
PubMed1979

Dynamics of skeletal pattern formation in developing chick limb.

During development of the embryonic chick limb the skeletal pattern is laid out as cartilaginous primordia, which emerge in a proximodistal sequence over a period of 4 days. The differentiation of cartilage is preceded by changes in cellular contacts at specific locations in the precartilage mesenchyme. Under realistic assumptions, the biosynthesis and diffusion through the extracellular matrix of a cell surface protein, such as fibronectin, will lead to spatial patterns of this molecule that could be the basis of the emergent primordia. As cellular differentiation proceeds, the size of the mesenchymal diffusion chamber is reduced in descrete steps, leading to sequential reorganizations of the morphogen pattern. The successive patterns correspond to observed rows of skeletal elements, whose emergence, in theory and in practice, depends on the maintenance of a unique boundary condition at the limb bud apex.

Animals↗
PubMed1977

Sex stereotypes in adult-infant play.

24 14-month-old infants played with adult strangers in a laboratory playroom. To examine the effects of sex-role labeling on adult behavior, each infant was introduced as a boy and as a girl in 2 different sessions. After controlling for the adult's scores on the Spence-Helmreich Attitudes toward Women Scale, the adults were found to engage in more Encouragement for Activity and more Male Role Toy Choice when playing with children designated as boys. They showed more Interpersonal Stimulation and more Nurturance Play when playing with children designated as girls. No significant differences were observed between the behavior of the real girls and boys. Men and women showed some differences in their style of play.

Attitude↗