Kinetic and stoichiometric assessment of the antioxidant activity of flavonoids by electron spin resonance spectroscopy

There is current interest in the use of naturally occurring flavonoids as antioxidants for the preservation of foods and the prevention of diseases such as atherosclerosis and cancers. To establish the molecular characteristics required for maximum antioxidant activity, electron spin resonance (ESR) spectroscopy has been used to determine the stoichiometry and kinetics of the hydrogen-donating ability of 15 flavonoids and d-alpha-tocopherol to galvinoxyl, a resonance-stabilized, sterically protected aryloxyl radical. The second-order reaction rates, which will be governed by O-H bond dissociation energies, were myricetin > morin > quercetin > fisetin approximately catechin > kaempferol approximately luteolin > rutin > d-alpha-tocopherol > taxifolin > tamarixetin > myricetin 3',4',5'-trimethyl ether > datiscetin > galangin > hesperitin approximately apigenin. Reactivity is highly dependant on the configuration of OH groups on the flavonoid B and C rings, there being little contribution from the A ring to antioxidant effectiveness. Highest reaction rates and stoichiometries were observed with flavonols capable of being oxidized to orthoquinones or extended paraquinones. However, rates and stoichiometries did not always correlate and the data suggest that kinetic factors may be of greater importance within a biological context.     

Preparation of tetrahydroagathic acid: a serum metabolite of isocupressic acid, a cattle abortifacient in ponderosa pine

Isocupressic acid (1) was used to synthetically prepare a mixture of (8S,13R,S)-labda-15,19-dioic acid (tetrahydroagathic acid) (5) via a two-step oxidation procedure followed by hydrogenation of the double bonds at C13 and C8. Reduction of the C8,17 double bond was stereospecific producing only the 8S isomer and confirmed by the nOe interaction between the resulting C17 and C20 methyl groups. The 13R and 13S isomers of 5 were separated and analyzed by HPLC/MS, and (13S)-tetrahydroagathic acid was isolated and identified by comparison to a standard prepared by hydrogenation of naturally occurring (13S)-dihydroagathic acid (4). (13R,S)-dihydroagathic acid was prepared by selective sodium metal-catalyzed hydrogenation of the C13,14 allylic double bond of agathic acid (3). The prepared compounds were then used as standards to confirm the presence of 4 and 5 and their respective 13R and 13S isomers in bovine serum samples. Tetrahydroagathic acid was shown to be the only metabolite detected in serum samples taken from a suspected cattle abortion case submitted for diagnosis; and, thus, 5 could be a valuable diagnostic marker for pine needle-induced abortions.     

Toxigenic type D Pasteurella multocida in New South Wales pig herds—prevalence and factors associated with infection

Between March and July 1987, a study was undertaken to determine the prevalence of and factors associated with toxigenic type D Pasteurella multocida infection in New South Wales pig herds. Toxigenic type D P. multocida was isolated from the nasal cavities of pigs in one (2%) of 50 randomly selected herds. Toxigenic isolates were also recovered from 2 (8%) of a separate group of 25 herds that had purchased pigs from a known infected piggery in South Australia (herd SA). Snout abnormalities were present in 9.4%, 3.2% and 1.8% of grower pigs in the 3 affected herds. Isolation of toxigenic P. multocida was significantly associated (p less than 0.0001) with the occurrence of clinically affected pigs in the herd. Purchase of at least 5 pigs from herd SA was associated with an elevated risk (p less than 0.05) of isolation of toxigenic P. multocida.     

Response of the Rieger begonia to ozone and sulphur dioxide

Ozone (O₃) and sulphur dioxide (SO₂) are at present the two most pervasive air pollutants in the urban and suburban areas in which most Rieger begonias are grown. These air pollutants have been shown to impair crop productivity and quality in many other species. Controlled environment experiments were therefore conducted to elucidate the responses of ‘Schwabenland Red’ to separate or bombined O₃ and SO₂ at different growth stages.Plants at the early vegetative or prefloral stages had much more leaf damage after combined O₃ + SO₂ than after separate gases at 15 p.p.h.m. O₃ or 60 p.p.h.m. SO₂ for 5 days in a synergistic type of response. Exposure for an additional day at twice these concentrations greatly increased leaf damage. Growth reductions were not found after 2 weeks but delaying measurements until 8 weeks after treatment revealed some growth reductions.Experiments were conducted with flowering plants using O₃ of 0, 10, 20 or 30 p.p.h.m. in all combinations with SO₂ at 0, 60, 120 or 180 p.p.h.m. Fully developed leaves were damaged, and undamaged leaves were smaller and lighter on plants exposed to 20 p.p.h.m. or more O₃, 120 p.p.h.m. or more SO₂, or any combination of O₃ and SO₂ at or above 10 and 60 p.p.h.m., respectively.     

The effect of the molluscicide Frescon on smooth and cross-striated muscles of Lymnaea stagnalis and Helix aspersa

The molluscicide Frescon (N-(triphenylmethyl)morpholine) induces prolonged, irreversible contractions (contractures) in the isolated heart ventricle, penis retractor, and foot muscles of the aquatic snail Lymnaea stagnalis. It also causes contracture of the penis retractor muscle, but not the heart ventricle, of the terrestrial snail Helix aspersa. Since Frescon-induced contracture is not accompanied by a depolarization of the sarcolemma of Lymnaea heart ventricle muscle cells, it is suggested that the action of this molluscicide is associated with a membrane potential-independent activation of the contractile machinery. The rapid response of Lymnaea musculature to Frescon suggests that the direct contracture-inducing action of this molluscicide could explain its toxicity to the whole animal.     

Enzootic pneumonia: comparison of cough and lung lesions as predictors of weight gain in swine.

A prospective cohort study was undertaken in a commercial swine herd to determine the relationship between weight gain and the occurrence of enzootic pneumonia (EP). Estimates of the association between EP and weight gain were obtained from multiple linear regression models, using coughing episodes or slaughter checks as indicators of EP status. Models were estimated for pigs in 2 different age groups: roasters (n = 1084, sold at 32 to 50 kg) and market hogs (n = 1162, sold at 100 to 110 kg). The relationship between presence of lung lesions at slaughter and previous coughing episodes was also investigated. Throughout the study period, clinical evaluations were performed weekly, and coughing episodes recorded for each pig. Lungs were inspected at slaughter, and scores were expressed as the percentage of the lung with gross pneumonic lesions. Coughing and lung scores were significantly correlated, after adjusting for other covariates (R = 0.32 and 0.59, respectively, for market hogs and roasters). However, the agreement beyond chance between coughing history and lung lesions at slaughter was poor among both roasters and market hogs (kappa = 0.17 and 0.07, respectively). Although very specific, weekly assessment of coughing was not a sensitive indicator of lung lesions at slaughter. In multiple regression, lung score was a highly significant predictor of lower final weight in pigs of both age groups (P < 0.001 in the selected regression models).(ABSTRACT TRUNCATED AT 250 WORDS)     

Neutral models for the analysis of broad-scale landscape pattern

The relationship between a landscape process and observed patterns can be rigorously tested only if the expected pattern in the absence of the process is known. We used methods derived from percolation theory to construct neutral landscape models,i.e., models lacking effects due to topography, contagion, disturbance history, and related ecological processes. This paper analyzes the patterns generated by these models, and compares the results with observed landscape patterns. The analysis shows that number, size, and shape of patches changes as a function of p, the fraction of the landscape occupied by the habitat type of interest, and m, the linear dimension of the map. The adaptation of percolation theory to finite scales provides a baseline for statistical comparison with landscape data. When USGS land use data (LUDA) maps are compared to random maps produced by percolation models, significant differences in the number, size distribution, and the area/perimeter (fractal dimension) indices of patches were found. These results make it possible to define the appropriate scales at which disturbance and landscape processes interact to affect landscape patterns.