Optimizing the immunohistochemical signal from the transferrin receptor in liver tissue

Summary Cellular expression of the transferrin receptor is determined by the proliferative state and iron requirements of the cell. Previous immunohistochemical studies using a number of anti-(transferrin receptor) monoclonal antibodies confirmed the biochemical evidence that hepatocytes express the receptor, although the distribution shown was patchy with only a small number of cells showing positive staining. In the present study, a number of techniques have been compared to optimize detection of the immunohistochemical signal from the transferrin receptor in human liver tissue. Using an alkaline phosphatase detection system, widespread expression of this receptor with both cytoplasmic and membrane staining was found in all parenchymal and non-parenchymal cells.     

Distamycin and penta-N-methylpyrrolecarboxamide binding sites on native DNA. A comparison of methidiumpropyl-EDTA-Fe(II) footprinting and DNA affinity cleaving

Using two direct methods we have studied the binding locations and site sizes of distamycin and penta-N-methylpyrrolecarboxamide on three DNA restriction fragments from pBR322 plasmid. We find that methidiumpropyl-EDTA.Fe(II) footprinting and DNA affinity cleaving methods report common binding locations and site sizes for the tri- and pentapeptides bound to heterogeneous DNA. The tripeptide distamycin binds 5-base-pair sites with a preference for poly(dA).poly(dT) regions. The pentapeptide binds 6-7-base-pair sites with a preference for poly(dA).poly(dT) regions. These results are consistent with distamycin binding as an isogeometric helix to the minor groove of DNA with the four carboxamide N-H's hydrogen bonding five A + T base pairs. The data supports a model where each of the carboxamide N-H's can hydrogen bond to two bases, either O(2) of thymine or N(3) of adenine, located on adjacent base pairs on opposite strands of the helix. In most (but not all) cases the tri- and pentapeptide can adopt two orientations at each A + T rich binding site.     

Biosynthesis of Callose and Cellulose by Detergent Extracts of Tobacco Cell Membranes and Quantification of the Polymers Synthesized in vitro

The conditions that favor the in vitro synthesis of cellulose from tobacco BY-2 cell extracts were determined. The procedure leading to the highest yield of cellulose consisted of incubating digitonin extracts of membranes from 11-day-old tobacco BY-2 cells in the presence of 1 mM UDP-glucose, 8 mM Ca2+ and 8 mM Mg2+. Under these conditions, up to nearly 40% of the polysaccharides synthesized in vitro corresponded to cellulose, the other polymer synthesized being callose. Transmission electron microscopy an...