Common pathway for the induction of hexose transport by insulin and stress

The effect of stress (heat shock, arsenite, or Semliki Forest virus [SFV] infection) on the induction of increased hexose transport has been compared with that of insulin. All four treatments increase the Vmax for transport by BHK cells three- to five-fold, with little effect (less than 40% decrease) on Km. Hydrogen peroxide and phenylarsine oxide (PAO) prevent the increase in hexose transport induced by stress treatments as effectively as they do that induced by insulin. Pinocytosis is not affected by any of the four treatments. On the other hand, the induction by insulin is sensitive to amiloride, whereas that by arsenite is not. Rat embryo fibroblasts, which respond poorly to insulin, respond well to arsenite, heat shock, or SFV infection. It is concluded that the stress response is mediated by certain compounds that may be common to those required for the action of insulin, but that those compounds act at a stage subsequent to the function of the insulin receptor.     

Ascaris lumbricoides: zonal localization of immunoreactive collagen in the cuticle

Monoclonal antibodies that were raised against cuticular components from the free-living nematode Panagrellus silusiae were found to react with a cuticular collagenous domain from Ascaris lumbricoides. One of these monoclonal antibodies was used to localize the collagenous epitope within sectioned Ascaris cuticles. By indirect immunofluorescence, accessible binding sites were observed in the basal zone of the cuticle. Immunological staining occurred in the innermost lamella of the basal zone, i.e., basal lamella, in which the fibrillar palisade gave a strong response. The three layers of the spiral fiber system of the basal zone exhibited a distinctive immunofluorescence pattern. In each of these layers, irregular shaped blocks, often quadrangular, were immunostained; whereas, adjacent blocks were immunonegative. Immunostaining was, for the most part, absent from the cortical and medial zones of the cuticle as well as from other tissues within the worm.     

Diffusion through Narrow Pores: Movement of Ions,Water and Nonelectrolytes through Track-etched PETP Membranes

The rates at which ions (⁸⁶Rb⁺, [³H]-choline, ³⁶Cl), ³H₂O and nonelectrolytes ([¹⁴C]-urea, [¹⁴C]-glycerol, and [¹⁴C]-sugars) equilibrate across track-etched polyethyleneterephthalate (PETP) membranes (isotopic diffusion) have been measured by a `static' and a `dynamic' technique under conditions where no net flow takes place; the two techniques give essentially the same results. All tracers diffuse faster the longer the membranes are etched, consistent with an increase in pore size. Water and neutral solutes diffuse at rates that are relatively independent of ionic strength, pH or the presence of divalent cations. Diffusion of cations is decreased by high ionic strength, by reducing pH or by addition of divalent catons; diffusion of chloride is increased by these procedures. Treatment of the membrane with diazomethane to reduce the negative fixed charge decreases diffusion of cations and increases that of anions; diffusion of water and neutral solutes is unaffected by methylation except in the membranes with the narrowest pores (i.e., those etched for the shortest time), in which case diffusion is reduced. We conclude (1) that the special features of flow near a charged surface apply to ions but not to water or nonelectrolytes and (2) that calculation of absolute rates of diffusion leads to values for the radii of pores through track-etched PETP membranes that are in remarkably good agreement with measured values. Received: 14 August 1995/27 November 1995     

Macromolecular naloxone: a novel long-acting polymer-bound drug.

A widely applicable, prolonged-action drug delivery system has been developed using naloxone, a pure narcotic antagonist, as a model. The drug is attached to an inert, water soluble polymer by reversible covalent bonds, whose slow cleavage releases active drug. Naloxone, attached to a hydrazine-substituted polysaccharide by a hydrazone bond, antagonizes morphine analgesia more than 25 times longer than free naloxone.     

Purification ofPseudomonas fluorescens subsp.cellulosa endoglucanases produced inEscherichia coli

Both plasmid pPFC4, which contains 10.6 kb, and a derivative of pPFC4—viz., pPFC4-4.6—which contains 4.6 kb ofPseudomonas fluorescens subsp.cellulosa DNA, direct the synthesis of six distinct endoglucanases inEscherichia coli. Two of these enzymes were purified to homogeneity in a single step by means of anion exchange HPLC. One enzyme has a molecular weight of 30.0 ± 1.0 kDa, an isoelectric point of 7.5, and a specific activity of 3470 U of activity/mg of protein, whereas the other has a molecular weight of 38.5 ± 1.0 kDa, an isoelectric point of 6.7, and a specific activity of 18,050 U of activity/mg of protein. On the basis of the amino acid composition, the 38.5 kDa enzyme appears to be a modified version of the 30.0 kDa enzyme. Thus, the multiplicity of endoglucanases produced inE. coli/pPFC4-4.6 cells may be owing to the posttranslational modification of a smaller number of primary translation products.     

Virally mediated membrane changes: inverse effects on transport and diffusion (Short Communication)

SENDAI VIRUS MODIFIES THE CELL SURFACE IN TWO WAYS: (a) by inhibiting facilitated transport and (b) by enhancing passive diffusion.