Interactions of dimethyl sulfoxide with lipid and protein monolayers

Cryopreservation of articular cartilage

Cryopreservation has numerous practical applications in medicine, biotechnology, agriculture, forestry, aquaculture and biodiversity conservation, with huge potentials for biological cell and tissue banking. A specific tissue of interest for cryopreservation is the articular cartilage of the human knee joint for two major reasons: (1) clinically, there exists an untapped potential for cryopreserved cartilage to be used in surgical repair/reconstruction/replacement of injured joints because of the limited availability of fresh donor tissue and, (2) scientifically, successful cryopreservation of cartilage, an avascular tissue with only one cell type, is considered a stepping stone for transition from biobanking cell suspensions and small tissue slices to larger and more complicated tissues. For more than 50years, a great deal of effort has been directed toward understanding and overcoming the challenges of cartilage preservation. In this article, we focus mainly on studies that led to the finding that vitrification is an appropriate approach toward successful preservation of cartilage. This is followed by a review of the studies on the main challenges of vitrification, i.e. toxicity and diffusion, and the novel approaches to overcome these challenges such as liquidus tracking, diffusion modeling, and cryoprotective agent cocktails, which have resulted in the recent advancements in the field.

Percutaneous absorption-enhancing activity of urea derivatives

The effect of urea and urea derivatives on the percutaneous absorption of salicylic acid and sodium salicylate through the skin of rabbit from petrolatum ointment was investigated. It was found that addition of urea or urea derivatives to the ointment base significantly increased the percutaneous absorption of the drugs in proportion to the concentration of the additive. The percutaneous absorption-enhancing activities of these compounds were that urea derivatives with the more and longer alkyl substituents showed the stronger activities. These activities of urea and urea derivatives were ascribed to the binding of these compounds with the lipids and proteins of the stratum corneum of the skin and the swelling of the tissues, which leads to the reduction of the barrier property of the layer. The preliminary skin irritation test showed that urea and urea derivatives were quite non-irritating to the skin. These results suggest that urea derivatives have a strong possibility to be developed as a percutaneous absorption enhancer.

Dimethyl sulfoxide as a cholesterol-lowering agent in cultured fibroblasts exposed to low density lipoproteins

Confluent cultures of human skin fibroblasts were exposed to medium containing high levels of low density lipoproteins (LDL-cholesterol equivalent to 400 micrograms per ml) and 0 or 2% dimethyl sulfoxide (DMSO). The uptake and accumulation of cellular cholesterol from LDL were reduced significantly (30%) in the DMSO-treated cells as compared to the controls. The reduction in cellular sterol was due almost exclusively to a significant decrease (50%) in cholesterol ester accumulation. Incubation of cells with 125I-labelled LDL showed clearly that DMSO did not act by increasing the secretion of cholesterol from the cell, but rather by significantly decreasing the binding, internalization and degradation of exogenous LDL. De novo synthesis of cholesterol from [14C]acetate was measured and found to correlate inversely with cellular sterol levels in either control or DMSO-treated cells.

Phospholipid membrane stabilization by dimethylsulfoxide and other inducers of Friend leukemic cell differentiation

A large number of low molecular weight polar cryoprotective agents have recently been found to induce erythroid differentiation of Friend leukemic cells in vitro. The effect of these agents on membrane fluidity in phospholipid vesicles was studied by determining the solid-to-liquid crystalline phase transition using differential scanning calorimetry. Some of the inducing agents studies were found to raise the normal transition temperature (Tc) by a few degrees. All of these agents were found to produce a separate transition at a much higher temperature. Changes in the head group of the phospholipid, the pH, the presence of divalent cations, and the addition of other membrane-active compounds were found to significantly influence the inducing agent's effects on the Tc of phospholipid membranes. The ability of the different agents to produce a new transition at a high temperature was found to correlate well with their ability to induce Friend leukemic cell differentiation. The possible mechansims of action of the chemical inducers, and the significance of the observed membrane effects on differentiation and malignancy are discussed. It is concluded that inducing agents decrease the fluidity and stabilize phospholipid membranes, and that their effects in cell differentiation might be initiated by a similar change in the properties of cell membranes.

The effect of dimethyl sulfoxide on the neuronal excitability and cholinergic transmission in Aplysia ganglion cells

The effects of DMSO on single nerve cells of Aplysia were investigated by various electrophysiological methods. 1. Although the increase in permeability of the biological membranes produced by DMSO has been well documented, we found that DMSO at concentration of less than 20% actually decreases the permeability of the neuronal membranes, probably toward potassium and chloride ions. This change in ionic permeability reversibly depolarizes the resting membranes and makes the neurons more excitable. 2. The falling phase of the spike is prolonged by 8% DMSO, because it blocks the active increase in potassium permeability. This change suppresses the high frequency discharge, because the refractory period of each spike is increased. Neither the rising phase nor the absolute firing level is appreciably altered by DMSO when these are examined after the depolarization is cancelled. 3. Dilute DMSO (less than 1%) facilitates cholinergic trasmission because it blocks ACh-esterase activity. DMSO at concentrations of more than 10% ultimately blocks cholinergic transmission entirely, because it also depresses cholinoceptive receptor activity (probably by allosteric interaction). The action of 1-10% DMSO is complicated, because both facilitatory and inhibitory effects take place at the same time. 4. In cholinergic synapses, excitatory transmission is more susceptible to DMSO than inhibitory transmission. This is because the activity of the excitatory receptor is blocked more readily than that of the inhibitory receptor. The depressing effects of DMSO are not specific to the cholinergic system, however, since the activities of GABA and glutamate receptors are similarly depressed.