Cellular leakage

Cyclotides, circular mini-proteins bearing a cystine knot motif, are produced by plants as part of their defense mechanism. These cyclic proteins are thermostable and were recently shown to disrupt the membrane of human lymphoma cell line HeLa, causing cellular leakage. The combined approach growth- and non-growth-associated pattern provided the accumulation of 370-mg cyclotide kalata Bl/gdw within Oldenlandia affinis cells in culture. " ... 

Erianthridin 17 (200 xM) was highly phytotoxic to duckweed provoking cellular leakage, complete growth inhibition and significant chlorophyll... 

Cellular leakage as determined by changes in conductivity of treatments minus control conductivity changes of cucumber cotyledons as affected by exposure to different DHZ concentrations. Error bars are + 1 SE of the mean of six plates 50 pM acifluorfen used as positive control. Tissues were incubated in solutions in darkness for 18 h and then exposed to light. (From Galindo, J. C. G. etal. 1999, Phytochemistry 52, 805-813. With permission.)... 

Duke, S. O. and Kenyon, W. H. 1993. Peroxidizing activity determined by cellular leakage. In Boger, P. and Sandmann, G. (Eds.), Target Assays for Modern Herbicides and Related Phytotoxic Compounds, Lewis Publishers, Boca Raton, FL, 61-66... 

Figure 3. Effects of gabaculine and dioxoheptanoic acid (DA) on efficacy of acifluorfen (AF) on cellular leakage as measured by electrolyte increase in the bathing media of cucumber cotyledon discs incubated in the various treatment solutions for 20 h in darkness before exposure to light (time 0).

Duckweed (Lemna pausicostata L.) has proved to be a sensitive bioassay for AAL-toxin, FBj and related compounds (75). Duckweed is a small aquatic plant that can be easily grown in the laboratory (75). Phytotoxic effects can be easily quantified by measuring chlorophyll loss and cellular leakage (74). AAL-toxin was about 10-fold more active than FBj in the duckweed bioassay, causing maximal effect at a 0.1 pM concentration. FBi, FB2 and FB3 caused effects identical to those of AAL-toxin in duckweed at 1 pM. The hydrolysis products, APi and AP2 were much less active, and FAi and FA2 were completely inactive in the duckweed bioassay (75). 

One of the primary ways in which cold causes injury to cells is by the loss of the capability to regulate cellular volume. This occurs because of the decrease in the available energy (ATP) caused by hypothermia and ischemia which is needed by the membrane-bound ion pumps, the increased rate of leakage of ions through the plasma membrane, and the decreased activity of the membrane-bound ion pumps, especially the Na-pump. 

Liposomes that remain impermeable to their contents cannot release these compounds without interaction with cells. This cellular interaction occurs by three different mechanisms (Fig. 11) [57], Of these, fusion and adsorption usually involve drug leakage, whereas effective drug delivery results from en-docytosis. 

Pharmacology Ketoconazole, an imidazole broad-spectrum antifungal agent, impairs the synthesis of ergosterol, the main sterol of fungal cell membranes, allowing increased permeability and leakage of cellular components. Pharmacokinetics ... 

A novel bioassay for nystatin based on the use of a microbial sensor was recently reported. Nystatin is believed to bind to the steron present in the membranes of sensitive cells, leading to the formation of pores. The subsequent death of the microorganism is preceded by leakage of cellular materials. Microbial death can be detected by means of an oxygen electrode. 

Assays are frequently needed to detect marked and acute cytotoxicity that may confound the interpretation of cell-based efficacy assays. Neutral red uptake is one of the most commonly used cytotoxicity assays and is used in the regulatory phototoxicity assay on NT3 fibroblasts [13]. It has been show to be more sensitive than assays for mitochondrial reductive capacity such as the tetrazolium reductase assays, ATP depletion assays, or for cell permeabilization or mpture such as dye uptake or lactate dehydrogenase leakage. Lysosomes take up, protonate and trap neutral red when cellular ATP production is sufficient to maintain pH gradients. 

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