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C Martin

Publications and source records attributed to C Martin.

At least 865 records · Page 48Linked to original sources
PubMed1988

Prolonged time course of glutamate-operated single channel currents in neuromuscular preparations of small crayfish and a membrane current triggered by glutamate channel gating.

Single channel currents activated by glutamate were recorded by means of the patch-clamp technique in the abdominal superficial extensor muscle and the claw opener muscle of small (1-3 months old) and large (greater than 16 months old) crayfish. It was found that in small crayfish the time course of glutamate-operated single channel currents was prolonged by a factor of about 4 in these two preparations. In the abdominal superficial extensor muscle, single channel currents activated by 5 mmol/l glutamate had a mean burst length of tau = 2-3 ms in large crayfish and a mean burst length of tau = 8-9 ms in small crayfish. In the claw opener, for large crayfish tau congruent to 0.5 ms and for small crayfish tau = 1.5-2.5 ms resulted (500 mumol/l glutamate). Moreover, single channel currents with long time courses often slowly increased their amplitudes during the open time of the channel and current amplitudes did not decline completely to the baseline after channel closing. In addition, single channel currents with relatively constant amplitude were often followed by a small increasing and decreasing membrane current. The latter results suggest that glutamate channel gating might trigger a membrane current.

Animals↗
PubMed1988

Quisqualate-activated single channel currents in neuromuscular preparations of small and large crayfish.

Single channel currents elicited by 1-5 mumol/l quisqualate in neuromuscular preparations in large (greater than 16 month old) and small (1-3 month old) crayfish were recorded by means of the patch-clamp technique. In preparations from large crayfish single channel currents of variable amplitude (-1 to -12 pA) were induced by quisqualate. The mean burst lengths of these currents were tau approximately equal to 1-2 ms. In the opener muscle of the first walking leg and the contractor epimeralis muscle of small crayfish the mean burst lengths of single channel currents evoked by quisqualate were prolonged by a factor of about 4 (tau approximately equal to 5 ms). Moreover, in the opener muscle of the first walking leg of small crayfish single channel currents of small amplitude (-0.5 to -2.5 pA) were preferentially evoked by quisqualate. By contrast, in the contractor epimeralis muscle of small crayfish mainly single channel currents of large amplitude (-10 to -12 pA) were elicited by quisqualate. The results suggest that at the stage of neuromuscular development characterizing the small crayfish, gating properties of excitatory postsynaptic channels are different from those in adult crayfish. Furthermore, the results obtained in the opener muscle of the first walking leg of small crayfish are consistent with those obtained previously by means of the noise analysis technique.

Animals↗
PubMed1988

Molecular properties of p-(dimethylamino)benzaldehyde bound to liver alcohol dehydrogenase: a Raman spectroscopic study.

We have studied the binding nature of an aromatic aldehyde to the catalytic site of liver alcohol dehydrogenase from horse (LADH) using preresonance Raman spectroscopy. The compound p-(dimethylamino)benzaldehyde (DABA) is converted to the corresponding alcohol in the presence of nicotinamide adenine dinucleotide (NADH) and a catalytic amount of enzyme at neutral pH. A stable ternary complex of LADH/NADH/DABA can be formed if enzyme and coenzyme are in excess at high pH [Jagodzinski, P. W., Funk, G. F., & Peticolas, W. L. (1982) Biochemistry 21, 2193-2202]. We have obtained the preresonance Raman spectrum of bound DABA by subtracting the contribution of the binary complex of LADH/NADH from the spectrum of this stable ternary complex. In order to understand the normal mode patterns of DABA, four isotopically labeled DABA derivatives were synthesized and their Raman spectra, in solution and in the ternary complex, were measured. Three of these compounds contain substitutions in the functionally important aldehyde moiety: (i) In one such substitution, the aldehydic hydrogen atom was replaced by a deuterium; (ii) in another, this hydrogen atom was replaced by deuterium, and the aldehydic carbon atom was replaced by 13C; and (iii) in the third derivative, only the carbon atom was replaced by 13C. The fourth derivative has had the two hydrogen atoms at the 3- and 5-positions of the DABA ring replaced by deuterium atoms. We find that many of the spectral modes are fairly extended, involving both stretching and bending motions of the entire molecule, although a few modes are quite localized. We find that the normal mode structure of DABA changes considerably when it binds to LADH/NADH. As a model for the bound DABA, we have examined the zinc complexes of DABA (and all four isotopically labeled samples) in anhydrous diethyl ether and methylene chloride. A striking correspondence between the Raman spectra of the enzyme-bound DABA and DABA-Zn complexes in solution is found, which extends to all the isotopically labeled derivatives. This suggests that one of the major roles of LADH in the binding of DABA is to provide a divalent zinc ion to form a first-sphere Lewis acid complex. The data also suggest other interactions between enzyme-bound DABA with its protein surroundings and with the coenzyme NADH are quite minor. An estimate of the carbonyl bond character of bound DABA had been made on the basis of the response of Raman bands to isotopic labeling and on trends observed in spectra of DABA in solvents of various polarities.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohol Dehydrogenase↗
PubMed1988

[Multiple pregnancy].

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Embryonic and Fetal Development↗