Amantadine-dyazide interaction.

To document an interaction between amantadine hydrochloride and Dyazide that had apparently produced amantadine toxicity, a patient was given amantadine alone for 1 week, followed by amantadine plus Dyazide for another week, under controlled conditions. A diuretic effect was observed after Dyazide was added to the regimen, but the urine amantadine excretion fell, and the drug''s plasma concentration increased. It was concluded that one or both of the components of Dyazide (hydrochlorothiazide and triamterene) reduce the clearance of amantadine and can produce higher plasma concentrations and toxic effects.     

Neurocalcin-actin interaction.

Neurocalcin is an N-myristoylated calcium-binding protein which belongs to a novel family of neuronal calcium sensors. Here we show, by cosedimentation, co-immunoprecipitation and cross-linking approaches, that myristoylated neurocalcin directly interacts with actin in a calcium-dependent manner. We used EDC cross-linking and obtained one novel 64 kDa entity composed of one actin molecule and one neurocalcin molecule, as demonstrated with IAEDANS-actin and neurocalcin-specific antibodies. This interaction could modulate the rod outer segment-guanylate cyclase 1-neurocalcin interface.     

Lysozyme-agarose interaction.

It has been observed that the elution volumes of hen egg-white lysozyme on agarose columns exceeded by far the total volumes of the corresponding columns. Similar results have been obtained also on polyacrylamide-agarose gel columns. This anomalous behaviour of lysozyme on agarose columns is interpreted in terms of an interaction between the enzyme and agarose which resembles in some way the physiological substrates of lysozyme.     

Platelet-tumor cell interaction.

Several reports have appeared with regard to the potential role of platelets in tumor cells metastasis. Our in vitro studies with colon tumor cells in normals and in patients give some evidence against platelet aggregation as the determinant factor in tumor cell invasion and metastasis. Dimethylhydrazine induced colon tumors in Wistar rats demonstrate characteristic features of tumor cell dissociation in the invasion line and changes in intercellular adhesion.     

The interaction of spectrin-actin and synthetic phospholipids. II. The interaction with phosphatidylserine.

Sonicated vesicles of phosphatidylserine and phosphatidylserine/phosphatidylcholine mixtures were recombined with spectrin-actin from human erythrocyte ghosts. Morphological properties and physicochemical characteristics of the recombinates were studied with freeze etch electron microscopy, 31P NMR and differential scanning calorimetry. Sonicated dimyristoyl phosphatidylserine vesicles show a decrease in enthalpy change of the lipid phase transition upon addition of spectrin-actin. These vesicles collapse and fuse, into multilamellar structures in the presence of spectrin-actin, as demonstrated by freeze fracturing and NMR. Spectrin-actin cannot prevent the salt formation between phosphatidylserine and Ca2+, all phosphatidylserine is withdrawn from the lipid phase transition. In contrast a protection against the action of Mg2+ could be observed. Mixed bilayers of dimyristoyl phosphatidylserine/dimyristoyl phosphatidylcholine show phase separations at molar ratios above 1/1 (van Dijck, P.W.M., de Kruijff, B., Verkleij, A.J., van Deenen, L.L.M. and de Gier, J. (1978) Biochim. Biophys. Acta 512, 84--96). These phase spearations can be prevented by spectrin-actin. Ca2+-induced lateral phase separations in cocrystallizing phosphatidylserine/phosphatidylcholine mixtures, can be reduced by spectrin-actin. Formation of the Ca2+-phosphatidylserine salt, occurring in addition to lateral phase separation when mixtures contain more than 30 mol % phosphatidylserine, cannot be prevented by spectrin-actin.     

Biochemistry of carbohydrate-protein interaction.

Recognition of glycoconjugates is an important event in biological systems, and is frequently in the form of carbohydrate-protein interactions. To thoroughly understand these interactions, well-defined carbohydrate ligands must be available. Naturally derived glycoconjugates can be highly purified, and their structures (including conformational structures) can be elucidated to provide such ligands. This requires highly effective methods of separation, such as various forms of high-performance liquid chromatography. Alternatively, structurally well-defined glycoconjugates can be synthesized for this purpose. These include conjugates of carbohydrate derivatives to proteins, lipids, and nonbiological carriers and polymers. The efficacy of these conjugates is amply demonstrated in the studies of carbohydrate-binding proteins from animals. Hepatic carbohydrate receptors, requiring calcium for binding, recognize only the terminal sugar residues. Although different sugar specificities are manifested by different species, there is some commonality in the requirement of the substituents of the sugar rings. Clustering of the target sugars in proper geometric arrangement greatly enhances the binding by these proteins. Some other animal carbohydrate-binding proteins, however, may require penultimate sugars for optimal binding.