Apart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fu...

The identity, localization and physiological significance of enzymes involved in sugar uptake and accumulation were determined for endocarp tissue of pods of Kentucky Wonder pole beans (Phaseolus vulgaris). An intracellular, alkaline invertase (pH optimum, 8) was assayed in extracted protein, as well as enzymes involved in sucrose synthesis, namely, uridinediphosphate (UDP-glucose pyrophosphory...

Insulin crosses the blood-brain barrier (BBB) via receptor-mediated transcytosis and has been suggested to augment uptake of peripheral substances across the BBB. The delta-opioid receptor-selective peptide D-penicillamine(2,5) (DPDPE), a Met-enkephalin analog, produces analgesia via a central nervous system-derived effect. In vitro (K(cell), microl. min(-1). mg(-1)) and in situ (K(in), microl....

In order to explore new treatment modalities for cancer, it is important to identify qualitative or quantitative differences in metabolic processes between normal and malignant cells. Previous in vitro and in vivo studies have shown that acute myelogenous leukemia cells have elevated receptor-mediated uptake of low density lipoproteins (LDL), compared to normal WBC. High receptor-mediated uptak...

The effects of chilling temperatures, in light or dark, on the isolated thylakoids and leaf discs of cucumber (Cucumis sativa L. "Marketer") and spinach (Spinacia oleracea L. "Bloomsdale") were studied. The pretreatment of isolated thylakoids and leaf discs at 4 C in the dark did not affect the phenazine methosulfate-dependent phosphorylation, proton uptake, osmotic response to sucrose, Ca(2+)-...

Erwinia rhapontici is able to convert sucrose into isomaltulose (palatinose, 6-O-alpha-D-glucopyranosyl-D-fructose) and trehalulose (1-O-alpha-D-glucopyranosyl-D-fructose) by the activity of a sucrose isomerase. These sucrose isomers cannot be metabolized by plant cells and most other organisms and therefore are possibly advantageous for the pathogen. This view is supported by the observation t...

High doses of intravenous protamine cause generalized vascular permeability changes in brain and other organs, and concomitant hypoproteinemia. The present investigations test the hypothesis that protamine has a dual action of both binding serum proteins and of undergoing absorptive-mediated transcytosis through microvascular endothelial barriers. Binding of albumin to protamine was demonstrate...

Trehalose, an alpha,alpha-diglucoside, induced a rapid blackening and death of shoot tips of Cuscuta reflexa (dodder) cultured in vitro. The onset of toxic symptom was delayed if any of the several sugars which support the in vitro growth of Cuscuta was supplied with trehalose. The rate of trehalose uptake or its accumulation in the tissue was not affected by sugar cofeeding. The levels of tota...

A new subfamily of sucrose transporters from Arabidopsis (AtSUT4), tomato (LeSUT4), and potato (StSUT4) was isolated, demonstrating only 47% similarity to the previously characterized SUT1. SUT4 from two plant species conferred sucrose uptake activity when expressed in yeast. The K(m) for sucrose uptake by AtSUT4 of 11.6 +/- 0.6 mM was approximately 10-fold greater than for all other plant sucr...