Dynamic dialysis utilizing a hollow fibre unit as a rapid method for studying protein binding.

A useful approach for determining the binding ability which occurres in a protein-small molecule system was studied by a method of dynamic dialysis utilizing a hollow fibre unit. A dependency on experimental variables in the absence of protein was examined in order to characterize the nature of the dialytic process. It was shown that the rate of small molecule escaped across the dialytic membrane was dependent on stirring or flowing rate, temperature and pH, but independent on buffer strength or viscosity. The protein binding ability was examined by means of comparing amounts of small molecules in the absence and presence of protein. Kinetic parameters for the binding behaviour analysed from the Scatchard plot in the present experiment were in agreement with values previously reported.     

Embryonic stem cell-derived neuron models of Parkinson's disease exhibit delayed neuronal death

Establishment of a Parkinson's disease (PD) neuron model was attempted with mouse embryonic stem (ES) cells. ES cell lines over-expressing mouse nuclear receptor-related 1 (Nurr1), together with human wild-type and alanine 30 --> proline (A30P) and alanine 53 --> threonine (A53T) mutant alpha-synuclein were established and subjected to differentiation into dopaminergic neurons. The ES cell-derived dopaminergic neurons expressing wild-type or mutant alpha-synuclein exhibited the fundamental characteristics consistent with dopaminergic neurons in the substantia nigra. The ES cell-derived PD model neurons exhibited increased susceptibility to oxidative stress, proteasome inhibition, and mitochondrial inhibition. Cell viability of PD model neurons and the control neurons was similar until 28 days after differentiation. Nonetheless, after that time, PD model neurons gradually began to undergo neuronal death over the course of 1 month, showing cytoplasmic aggregate formation and an increase of insoluble alpha-synuclein protein. Such delayed neuronal death was observed in a mutant alpha-synuclein protein level-dependent manner, which was slightly inhibited by a c-jun N-terminal kinase inhibitor and a caspase inhibitor. Such cell death was not observed when the same ES cell lines were differentiated into oligodendrocytes. The ES cell-derived PD model neurons are considered as prospective candidates for a new prototype modelling PD that would allow better investigation of the underlying neurodegenerative pathophysiology.     

Enhancement of local anaesthesia action by organic acid salts. (I): Possible change of excitability in nerve fibre membrane

Measurements of action potentials recorded from giant nerve fibres of the crayfish abdomen showed that by addition of an organic acid salt to a local anaesthetic solution, the onset of anaesthetic action became more rapid and the duration of action was prolonged. Similar results were also obtained in rat vagal nerves. The chemical structure of compounds having these enhancing effects was found to have, in common, a carboxyl group connected with either a benzene ring or an aliphatic hydrocarbon. Topical application of anaesthetic solutions to the skin of flexor side of the forearm in humans revealed that the duration of anaesthesia evaluated by the apparent decrease of the number of pain points was significantly prolonged by the addition of salicylate. The use of local anaesthetics combined with organic acid salts would be promising in clinical practice to enhance their action greatly.     

Inhibitory effect of gymnemic acid on intestinal absorption of oleic acid in rats

Gymnemic acid, a mixture of triterpene glycosides extracted from the leaves of Gymnema sylvestre, is known to inhibit the intestinal absorption of glucose in human and rats. This work examined the effect of gymnemic acid on oleic acid absorption by the method of intestinal perfusion in rats. The results showed the following. (i) Gymnemic acid potently inhibited the absorption of oleic acid in intestine. (ii) This inhibition was dose dependent and reversible. (iii) The extent of inhibition and the recovery progress were extremely similar to that of glucose absorption. (iv) Taurocholate did not affect the inhibitory effect of gymnemic acid on oleic acid absorption, but lowering its concentration facilitated the recovery from the inhibition. (v) The absorption of oleic acid was not affected by other glycosides such as phloridzin, stevioside, and glycyrrhizin. These new findings are important for understanding the roles of gymnemic acid in therapy of diabetes mellitus and obesity.