Nitric oxide effects on shortening velocity and power production in the rat diaphragm

The present experiments tested nitric oxide (NO) effects on shortening velocity and power production in maximally activated rat diaphragm. Diaphragm fiber bundles (n = 10/group) were incubated at 37 degrees C in Krebs-Ringer solution containing no added drug (control), the NO synthase inhibitor N omega-nitro-L-arginine (L-NNA; 10 mM), the NO donor sodium nitroprusside (SNP; 1 mM), or a combination (L-NNA + SNP) Loaded shortening velocity was measured via the load-clamp technique over a range of afterloads. Force-velocity data were fitted to the Hill equation to determine maximum velocity of shortening (Vmax). Unloaded shortening velocity was measured in control and L-NNA-treated bundles (n = 12/group) by using the slack test. Maximal isometric force and unloaded shortening velocity were not altered by L-NNA. In contrast, L-NNA decreased maximum velocity of shortening (P < 0.05), loaded shortening velocity (P < 0.0001), and power production (P < 0.0001). All L-NNA effects were prevented by coincubating fiber bundles with L-NNA + SNP. SNP alone had no effect on any variable. These data indicate that endogenous NO is essential for optimal myofilament function during active shortening.

Detection and imaging of nitrogen dioxide with the degenerate four-wave-mixing and laser-induced-fluorescence techniques

The spectroscopic techniques of degenerate four-wave mixing (DFWM) and laser-induced fluorescence (LIP) have been applied to the detection of minor species for combustion diagnostics. We compare the results obtained when these techniques are used to detect NO(2). Previous results show that DFWM signals increase for NO(2) when buffer gas is added and that LIP signals are greatly reduced under the same circumstances. We make direct quantitative comparisons of these two techniques and discuss their suitability for making measurements of NO(2) in combustion environments.

Organochlorine contaminants in the estuarine and coastal marine environments of the Fiji Islands

No information has been published on the presence of organochlorine pesticides and polychlorinated biphenyls in the Fiji Islands. This paper reports the first data on the concentration of a range of organochlorine compounds in sediments and shellfish in the estuarine and coastal marine environment around Fiji. Twenty-three sediment and two shellfish samples were analysed for 22 pesticides and related residues, and PCBs. While a significant number of organochlorines (20 pesticide related species and PCBs) was detected, the concentrations were generally very low (< 10 ng g), indicative of a relatively 'less contaminated' marine environment. Relatively high concentrations were observed only near the two major ports (Suva and Lautoka), with Suva harbour samples having the largest number of detectable species and the largest total concentrations of organochlorines (up to 91 ng g). No PCBs were detected in areas away from major industrial centres. The variations in the concentrations found, and the possible sources and movement of the organochlorine contaminants are discussed.