On the Trail of Atmospheric Mutagens and Carcinogens: A Combined Chemical/Microbiological Approach

Major ecological problems of our polluted troposphere includeairborne toxic chemicals, acid rain and photochemical smog,all three of which are now recognized as being closely relatedchemical phenomena. We also recognize that inorder to developcost-effective strategies for their control, which protect publichealth and the environment, there must be close scientific interactionsbetween chemists and biological scientists. For example, ofrapidly emerging importance is the development of risk assessmentevaluations for specific aspects of each of these problem areas.In preparing such assessments, chemists must define the "exposure,"and biological scientists the "effects." In this paper, I discuss an example of how such close interactionsproved indispensible in our search for atmospheric mutagensand carcinogens. Thus, an integrated chemical/ microbiologicalprocedure for the isolation and identificationof particulatechemical mutagens in respirable diesel soot and ambient particlesis described. Emphasis is placed on our use of the short-term,Ames Salmonella typhimurium bacterial mutagenicity test as arapid, and relatively inexpensive, means of following the biologicalactivities of these environmental mutagens through the chemicalsteps of their separation, isolation and identification fromhighly complex environmental samples. Possible mechanisms offormation of these particulate mutagens are discussed. Theyinclude the reactions of polycyclic aromatic hydrocarbons presenton the surfaces of combustion-generated particles with gaseousco-pollutants such as nitrogen dioxide plus nitric acid, andozone. In discussing this research on a societally "relevant" problem,we illustrate the importance of "Science as a Way of Knowing."We further suggest that this integrated approach to scientificproblem solving by chemical and biological scientists mightserve as an example of a discussion topic on human ecology forundergraduate courses in the natural sciences.     

Ribulose 1, 5-bisphosphate Carboxylase/ Oxygenase Activities in Leaves of Greenhouse Roses

An enzyme assay was developed to measure the initial and Mg²⁺–CO₂activated forms of Ribulose 1,5-bisphosphate Carboxylase/Oxygenase(Rubisco) in rose leaves. The assay was verified by co-extractionof the leaflets with partially purified spinach Rubisco andthrough correlation with net photosynthetic rates of individualleaflets (r²=0.7324). Changes in activities were measured asa function of depth of leaves in the canopy for two cultivarsof greenhouse hybrid tea roses. Initial Rubisco activity declinedwith increasing canopy depth for both cultivars. The activatedform of the enzyme, however, remained constant with canopy depthfor cv. Red Success; but increased with canopy depth, then declinedafter mid-canopy in the cv. Royalty. Rubisco activities werealso measured in the cv. Red Success grown in CO₂ enriched environments(100 mm³ dm^–3) at three humidity levels. The activitieswere not significantly affected by humidity treatment. However,there was a trend for plants grown at lower humidity to havehigher activated activities. Key words: Humidity, Rubisco, Rosa ? hybrida, Royalty, Red Success     

Survival of Wood Duck Ducklings and Broods in Mississippi and Alabama

ABSTRACT Although North American wood ducks (Aix sponsa) are well-studied throughout their range, researchers know little about demographic and environmental factors influencing survival of ducklings and broods, which is necessary information for population management. We studied radiomarked female and duckling wood ducks that used nest boxes and palustrine wetlands at Noxubee National Wildlife Refuge (NNWR) in Mississippi, USA, in 1996–1999, and riverine wetlands of the Tennessee-Tombigbee Rivers and Waterway (TTRW) system in Alabama in 1998–1999. We estimated survival of ducklings and broods and evaluated potentially important predictors of duckling survival, including age and body mass of brood-rearing females, hatch date of ducklings, duckling mass, brood size at nest departure, inter-day travel distance by ducklings, site and habitat use, and daily minimum air temperature and precipitation. At NNWR, survival of 300 radiomarked ducklings ranged from 0.15 (95% CI = 0.04-0.27) to 0.24 (95% CI = 0.13-0.38) and was 0.21 (95% CI = 0.15-0.28) for 1996–1999. Our overall estimate of brood survival was 0.64 (n = 91; 95% CI = 0.54-0.73). At TTRW, survival of 129 radiomarked ducklings was 0.29 in 1998 (95% CI = 0.20-0.41) and 1999 (95% CI = 0.13-0.45) and was 0.29 (95% CI = 0.20-0.40) for 1998–1999. Our overall estimate of brood survival was 0.71 (n = 38; 95% CI = 0.56-0.85). At NNWR, models that included all predictor variables best explained variation in duckling survival. Akaike weight (w_i) for the best model was 0.81, suggesting it was superior to other models (<0.01 < w_i < 0.18). We detected 4 competing models for duckling survival at TTRW. Inter-day distance traveled by ducklings was important as this variable appeared in all 4 models; duckling survival was positively related to this variable. Patterns of habitat-related survival were similar at both study areas. Ducklings in broods that used scrub-shrub habitats disjunct from wetlands containing aggregations of nest boxes had greater survival probabilities than birds remaining in wetlands with such nest structures. Managers may increase local wood duck recruitment by promoting availability of suitable brood habitats (e.g., scrub-shrub wetlands) without aggregations of nest boxes that may attract predators and by dispersing nest boxes amid or adjacent to these habitats. We did not determine an optimal density of nest boxes relative to local or regional population goals, which remains important research and conservation needs.     

Source of an egg kairomone for Trissolcus basalis, a parasitoid of Nezara viridula

Abstract. The eggs of the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), are successfully attacked by Trissolcus basalis (Woll.) (Hymenoptera: Scelionidae) and are recognized as hosts by a secretion applied to the egg chorion. This secretion is produced by the follicular cells in the proximal region of the ovariole of the female pentatomid and functions as an adhesive for attaching the eggs to the oviposition substrate. The adhesive and kairomone activity could be partially removed with water. This water extract elicited host recognition behaviour in T. basalis when applied to glass beads which stuck together as the extract dried. The adhesive and kairomonal activity was removed completely with acetone since acetone-washed host eggs were not recognized by T. basalis. Application of the acetone extract to glass beads stimulated ovipositional probes by T. basalis. The adhesive appeared to be composed of a mucopolysaccharide–protein complex.     

Gibberellic Acid Sensitivity Determines the Length of the Extension Zone in Wheat Leaves

To test the hypothesis that gibberellic acid (GA) sensitivityaffects the length of the extension zone (LEZ) of leaf No. 1of wheat seedlings, we performed a gene dosage experiment usingRht dwarfing genes that condition GA insensitivity. We utilizednearly isogenic lines, at Rht-dosage levels of 0, 2 and 4 alleles.Anatomical markers (distances between successive stomates) wereused to infer the distribution of growth along the axis of theleaf. Interstomatal distance (ISD) and LEZ were inverse linearfunctions of Rht-dosage. The number of stomates matured perhour was independent of Rht-dosage. The relationship betweenISD and distance along the axis within the extension zone (EZ)was indistinguishable from linear. Rht-dosage did not affectthe slope of the regression of ISD against distance along theEZ. A-REST (AR; ancymidol, a potent GA synthesis inhibitor)reduced LEZ. Wild type was more sensitive to AR than doubledwarf. AR affected growth of leaf No. 1 more than length ofthe coleoptile, regardless of Rht-dosage. AR-dosage affectedcell division, whereas Rht-dosage did not. Extension zone, elongation, gibberellic acid, Rht, wheat, Triticum aesiivum L.     

Cyclic Variations in Nitrogen Uptake Rate in Soybean Plants: Uptake During Reproductive Growth

Net uptake of by non-nodulated soybean plants [Glycme max(L ) Merr cv Ransom] growing in flowing hydroponicculture was measured daily during a 63 d period of reproductivedevelopment between the first florally inductive photopenodand late seed growth Removal of from a replenished solution containing 10 mol m^– was determined by ion chromatography Uptake of continued throughout reproductive development The net uptakerate of cycled between maxima and minima with a periodicity of oscillation of 3 to 7 d during the floralstage and about 6 d during the fruiting stage. Coupled withincreasing concentrations of carbon and C:N ratios in tissues,the oscillations in net uptake rates of are evidence that the demand for carbohydrate by reproductiveorgans is contingent on the availability of nitrogen in theshoot pool rather than that the demand for nitrogen followsthe flux of carbohydrate into reproductive tissues. Key words: Nitrate uptake rate, carbon-nitrogen partitioning, Glycme max (L ) Merrill     

QUESTIONNAIRE PRACTICE: WHAT HAPPENS WHEN THE JAR SCALE IS PLACED BETWEEN TWO “OVERALL” ACCEPTANCE SCALES?

ABSTRACT

Using the observational analysis of two different foods as test products, this note examined some interesting findings that emerge when the just‐about‐right (JAR) scale was placed after the overall liking rating, and before the preference ranking. The JAR data appeared to be statistically uncorrelated with the overall rating scales. First, this fortuitous observation from several studies suggests that the JAR scale can play a diagnostic role to determine how the consumer feels about changing the product. Second, the statistical analysis of the JAR ratings (e.g., bipolar nature of the JAR scale, its skewness and kurtosis) all suggest that the appropriate measure is %JAR, an incidence metric, rather than scale average, ought to be used both to report the results, and to create models relating to the JAR versus sensory magnitude or versus liking, respectively.

PRACTICAL APPLICATIONS

The results of the present analysis suggest that overall acceptance/liking can be the last question in the questionnaire design. That location is very important for the sensory analysis of foods eaten over time and then rated, as well as personal care and cosmetic studies where the products are used over time periods, and where the true evaluation of performance ought to be made at the end of the trial. In these long‐term uses, overall liking is generally the last question given at the end of the time period of product evaluation. The facts that the just‐about‐right (JAR) scales are independent of this final overall liking rating suggest that the integrity of the overall evaluation and usefulness of JAR as diagnostics will not be compromised.