Carbon monoxide and nitric oxide as coneurotransmitters in the enteric nervous system: Evidence from genomic deletion of biosynthetic enzymes

Nitric oxide (NO) and carbon monoxide (CO) seem to be neurotransmitters in the brain. The colocalization of their respective biosynthetic enzymes, neuronal NO synthase (nNOS) and heme oxygenase-2 (HO2), in enteric neurons and altered intestinal function in mice with genomic deletion of the enzymes (nNOSΔ/Δ and HO2Δ/Δ) suggest neurotransmitter roles for NO and CO in the enteric nervous system. We now establish that NO and CO are both neurotransmitters that interact as cotransmitters. Small intestinal smooth muscle cells from nNOSΔ/Δ and HO2Δ/Δ mice are depolarized, with apparent additive effects in the double knockouts (HO2Δ/Δ/nNOSΔ/Δ). Muscle relaxation and inhibitory neurotransmission are reduced in the mutant mice. In HO2Δ/Δ preparations, responses to electrical field stimulation are nearly abolished despite persistent nNOS expression, whereas exogenous CO restores normal responses, indicating that the NO system does not function in the absence of CO generation.

Protein fluctuations are sensed by stimulated infrared echoes of the vibrations of carbon monoxide and azide probes

The correlation functions of the fluctuations of vibrational frequencies of azide ions and carbon monoxide in proteins are determined directly from stimulated photon echoes generated with femtosecond infrared pulses. The asymmetric stretching vibration of azide bound to carbonic anhydrase II exhibits a pronounced evolution of its vibrational frequency distribution on the time scale of a few picoseconds, which is attributed to modifications of the ligand structure through interactions with the nearby Thr-199. When azide is bound in hemoglobin, a more complex evolution of the protein structure is required to interchange the different ligand configurations, as evidenced by the much slower relaxation of the frequency distribution in this case. The time evolution of the distribution of frequencies of carbon monoxide bound in hemoglobin occurs on the ≈10-ps time scale and is very nonexponential. The correlation functions of the frequency fluctuations determine the evolution of the protein structure local to the probe and the extent to which the probe can navigate those parts of the energy landscape where the structural configurations are able to modify the local potential energy function of the probe.

Basis of guanylate cyclase activation by carbon monoxide.

Kinetics of CO association with guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] and dissociation from carboxy guanylate cyclase have been studied at pH 7.5 by flash photolysis, yielding rate constants at 23 degrees C of 1.2 +/- 0.1 x 10(5) M-1.sec-1 and 28 +/- 2 sec-1, respectively. While the CO combination rate constant is the same as for the T state of hemoglobin, the CO dissociation rate constant is much higher than expected for a six-coordinate carboxyheme protein; yet the absorption spectrum is indicative of a six-coordinate heme. The two observations are reconciled by a reaction mechanism in which CO dissociation proceeds via a five-coordinate intermediate. This intermediate is structurally very similar to the five-coordinate nitrosyl heme derivative of guanylate cyclase and is presumably responsible for the observed 4-fold activation of guanylate cyclase by CO. Thus, we provide a model that explains enzyme activities of the nitrosyl and carboxy forms of the enzyme on the basis of a common mechanism.

Testing the validity of the lognormal probability model : computer analysis of carbon monoxide data from U.S. cities /

Mode of access: Internet.

Occupational exposure to carbon monoxide.

Mode of access: Internet.

The equilibrium between carbon oxysulfide, carbon monoxide and sulfur ...

Thesis t.-p. pasted over the cover of the issue reprinted from the Journal of the American chemical society, vol. XXXVII, no. 9, September, 1915, which has title: The equilibrium between carbon oxysulfide, carbon monoxide and sulfur, by Gilbert N. Lewis and William N. Lacey.

Control techniques for carbon monoxide emissions from stationary sources.

Includes bibliographies.

Air quality criteria for carbon monoxide.

Includes bibliographies.

Development of a methodology for designing carbon monoxide monitoring networks /

Mode of access: Internet.

National performance audit program : 1980 proficiency surveys for sulfur dioxide, nitrogen dioxide, carbon monoxide, sulfate, nitrate, lead and high volume flow /

Mode of access: Internet.

CO in vehicle inspection stations : feasibility of achieving the NIOSH recommended carbon monoxide standards in New Jersey motor vehicle inspection stations /

Mode of access: Internet.

School bus carbon monoxide intrusion. Technical report.

Mode of access: Internet.

The FTC cigarette test method for determining tar, nicotine, and carbon monoxide yields of U.S. cigarettes : report of the NCI expert committee.

"T667"--P. [4] of cover.

Evaluation of length-of-stain gas indicator tubes for measuring carbon monoxide in air. Technical note.

National Highway Traffic Safety Administration, Washington, D.C.