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Biomedical subjects

L S Honig

Publications and source records attributed to L S Honig.

59 records · Page 4Linked to original sources
PubMed1981

Effects of biochemical inhibitors on positional signalling in the chick limb bud.

In 3- to 4-day embryonic chick limb buds, a region at the posterior margin of the limb, the zone of polarizing activity, appears to be responsible for signalling positional information along the anteroposterior axis. Our experiments were designed to test which biosynthetic processes are required for polarizing activity. We have treated polarizing regions with biochemical inhibitors, and then assayed their abilities to induce limb reduplications when grafted into anterior sites on host limb buds and also measured their capacities for protein, RNA, and DNA synthesis. DNA synthesis, and possibly oxidative phosphorylation, do not seem to be required for polarizing activity. But, glycolysis and protein and RNA synthesis are necessary, although not sufficient, for polarizing region activity. Activity seems particularly sensitive to inhibitors (actinomycin D and alpha-amanitin) of RNA synthesis.

Animals↗
PubMed1979

Microtubule protein preparations from C6 glial cells and their spontaneous polymer formation.

C6 cell tubulin is indistinguishable from hog brain tubulin with respect to its molecular weight, amino acid composition, and colchicine-binding activity. Moreover, microtubule assembly systems from both sources form the same structures: rings, ribbons, tubules, and drug-induced polymers. There is, nevertheless, a difference between the cultured cell and brain systems which lies in the nature of their microtubule-associated accessory proteins. C6 microtubule preparations exhibit few rings at 0 degrees C, have low polymerization yield, and have a low content of accessory proteins. The addition of brain accessory proteins enhances the numbers of rings, and the yield of microtubules, to levels comparable with those of brain preparations. The polymerizing ability of C6 microtubule protein decays much faster than that of brain, but it can be restored by the addition of brain accessory protein. The results suggest that C6 accessory proteins are more labile than their brain counterparts.

Animals↗
PubMedDate not supplied

Developmental changes revealed by immunohistochemical markers in human cerebral cortex.

The developing human cerebral cortex is distinguished by a particularly wide subplate, a transient zone in which crucial cell-cell interactions occur. To further understand the role of the subplate in human brain development, we have studied the immunohistochemical expression of certain neuronal (GAP-43, MAP-2, parvalbumin) and astroglial (vimentin, GFAP) markers in the developing visual cortex from gestational ages of 14 weeks to 9 months post-term. At 14-22 weeks, immunoreactivity to GAP-43, a protein involved in axonal outgrowth, was most prominent in the subplate and marginal zone neuropil and in the fibers of the radiations running near the ventricular zone; at 22-42 weeks, GAP-43 immunoreactive fibers were observed in the maturing cortical plate. Immunoreactivity for the microtubule-associated protein MAP-2 was present in the differentiating cortical plate at 14 weeks, but at 22-42 weeks was most prominent in the somata and dendrites of differentiated neurons, particularly the Cajal-Retzius neurons of the marginal zone, in neurons of the subplate and in those forming cortical layer 5. Parvalbumin immunoreactivity did not appear until 26 weeks, when stained neurons were in a sparse band of cells in layer 6 and upper subplate. Vimentin and GFAP did not stain differentiated neuronal cells. Vimentin immunoreactivity appeared early in neuroepithelial and radial glial cells, decreasing after 35 weeks, with a concomitant increase in GFAP immunoreactivity in radial glial and maturing astrocytic cells. Our results show that despite the greater complexity of the developing human neocortex, molecular markers are expressed in spatial and temporal patterns similar to those observed in non-human primates, carnivores and rodents. These protein markers should prove useful in developmental staging, and in providing a framework in which to examine congenital disorders of cerebral development.

Biomarkers↗