The use of ultra-violet setting glue for microelectrode fabrication
Abstract The characteristics of glues which set in ultra-violet light are described with respect to their advantages for microelectrode assembly.
Presynaptic Actions and Dopamine in the Neostriatum
There are now very detailed anatomical descriptions of the structure of the neostriatum at the electronmicroscopic level (see e.g. Pasik et al., 1978) and it seems that axo-axonic synapses are rare. It should be said at the outset then, that the term presynaptic as used here does not necessarily imply any such anatomical substrate. The examples which we will discuss in detail employ very different methodologies and therefore need to be described separately in the sections below. There are three illustrations of interactions of neostriatal neurotransmitters which each warrant the use of the term “presynaptic”. In the case of the action of dopamine on cortico-striatal synapses (section 1) the action is thought to be presynaptic on physiological evidence. In the other two cases, the actions are identified in slices of striatal tissue which do not contain dopamine (DA) cell bodies. Since changes in DA release are observed they must be thought of as the results of actions on DA terminals in the slices, although perhaps not due to morphologically defined synapses on them.
New method for analysis of enzymatic reactions: Thermolysin-catalyzed synthesis of aspartame precursor
Aspartame is an artificial sweetener which is 200 times sweeter than sucrose. A precursor of aspartame, N-(benzyloxycarbonyl)-l-aspartyl-l-phenylalanine methyl ester (Z-APM) was synthesized and hydrolyzed with thermolysin in an aqueous monophasic system. Graphical plotting methods and/or nonlinear regression have been used to analyze enzymatic reactions because of the nonlinearity of enzymatic rate equations. There are, however, problems: the former require accurate measurement of the initial reaction rate and the latter gives no analytical information. The authors proposed a method to solve the nonlinear enzymatic rate equations with respect to the concentration of a product with the Taylor expansion, especially for the reversible Theorell-Chance mechanism (Murakami, Y., Hirata, M., and Hirata, A., J. Ferment. Bioeng., 82, 246–252, 1996). This solution, however, is complex for practical use. In this paper, a simpler solution to explain the thermolysin-catalyzed synthesis of Z-APM is obtained. New methods to determine the kinetic parameters, especially for the reversible Theorell-Chance mechanism, based on the approximated solution are proposed. The results calculated using the obtained kinetic parameters can satisfactorily explain the experimental results, which demonstrates the effectiveness of the proposed analysis. We must know the relation between the concentrations of substrates and a product, and accurately evaluate of the result obtained using Taylor expansion when we determine the kinetic parameters using our newly developed methods. The methods to determine the kinetic parameters of the reversible Theorell-Chance mechanism described in this paper is, however, expected to be applied to general enzymatic reactions.