Considerations in the grouping of plant and fungal taxa for an epidemiologic study

Although exposure to airborne pollen grains and fungal spores has been implicated as a causative factor for acute exacerbation of asthma, the few epidemiologic studies that have attempted to evaluate the relationship between these bioaerosols and asthma have used only total counts (ignoring the relative importance of different taxa) or a few predominant pollen or spore types (ignoring less abundant but potentially relevant groups). This paper reports the development of hypothesis‐driven exposure metrics (based on known aeroallergen associations with allergic asthma and other hypersensitivity diseases, pollen allergen cross‐reactivity, and the presence of local sources in the city of Fresno, California, USA) for a 3.5 year epidemiologic study of childhood asthma. Outdoor regional and neighborhood concentrations of pollen and spores were measured using Hirst‐type, 7‐day samplers. Indoor and outdoor residential concentrations were measured at 84 selected homes with similar 24‐hour slit impactors. All pollen and spore concentrations were recorded in 2‐hour intervals to assist in understanding diurnal fluctuations in aeroallergen concentrations, identify exposures during the time periods that children are outdoors, and study interaction between aeroallergens and other air contaminants, which were the primary focus of the study. The 124 pollen taxa that were observed were reduced to 15 categories and the 66 fungal and algal taxa were reduced to five categories that will be used in microenvironmental models to generate individual daily exposure estimates for each of the 315 children. These new exposure metrics will allow examination of health effects for taxa traditionally associated with allergy and those with locally elevated concentrations in combination with exposures to other indoor and outdoor air contaminants.     

Predicting the occurrence of persistent hotspots in ecosystem variables

Ecological resources and services (e.g. organisms, nutrient cycling) are distributed heterogeneously across landscapes. While spatial variation has been studied extensively, the pattern of hotspots and coolspots persisting over time – called persistent spatial variation (PSV) – has not. Yet this pattern imparts key information to managers about whether resources will be found consistently in certain locations or vary unpredictably. Anticipating whether an ecosystem variable will display PSV is thus a valuable prospect. We tested the ability of attributes of variables (e.g. niche breadth, abundance, temporal scale) to predict the occurrence of PSV. Using a new measure of PSV based on the F‐value of analysis of variance, we were able to 1) decompose the pattern of persistent hotspots into spatial and temporal components – ‘spatial variation’ of site mean values and ‘stability’ of time series at each site – and 2) identify predictors of these patterns in temperate lakes and tropical coastal rock pools. We found PSV to be highly predictable (R2 = up to 0.80) from an estimate of stability taken at a single site, as well as from other factors related to stability. These factors included whether the variable was environmental (stable, slow) or was an aggregate of other variables (stabilized by statistical averaging). Species properties like niche position and abundance were modest predictors because they correlated with PSV components of site occupancy, spatial variation and stability. We conclude that PSV and the distribution of resources in space and time might be predicted from simple temporal indicators (e.g. stability at a single location) when data are scarce.     

2-Aminoethylphosphonate utilization in Pseudomonas putida BIRD-1 is controlled by multiple master regulators

Bacteria possess various regulatory mechanisms to detect and coordinate a response to elemental nutrient limitation. In pseudomonads, the two-component system regulators CbrAB, NtrBC and PhoBR, are responsible for regulating cellular response to carbon (C), nitrogen (N) and phosphorus (P) respectively. Phosphonates are reduced organophosphorus compounds produced by a broad range of biota and typified by a direct C-P bond. Numerous pseudomonads can use the environmentally abundant phosphonate species 2-aminoethylphosphonate (2AEP) as a source of C, N, or P, but only PhoBR has been shown to play a role in 2AEP utilization. On the other hand, utilization of 2AEP as a C and N source is considered substrate inducible. Here, using the plant-growth-promoting rhizobacterium Pseudomonas putida BIRD-1 we present evidence that 2AEP utilization is under dual regulation and only occurs upon depletion of C, N, or P, controlled by CbrAB, NtrBC, or PhoBR respectively. However, the presence of 2AEP was necessary for full gene expression, i.e. expression was substrate inducible. Mutation of a LysR-type regulator, termed AepR, upstream of the 2AEP transaminase-phosphonatase system (PhnWX), confirmed this dual regulatory mechanism. To our knowledge, this is the first study identifying coordination between global stress response and substrate-specific regulators in phosphonate metabolism.     

Efficient slow-growth conservation and assessment of clonal fidelity of Ullucus tuberosus Caldas microshoots

Plant Cell, Tissue and Organ Culture (PCTOC) - Slow-growth is a biotechnological tool for medium-term conservation of plant germplasm under in vitro conditions. In the present study, we assessed...     

Validity of surrogates for determination of 30–1000 Hz magnetic field exposure for video display terminal users in office settings

In studies investigating adverse reproductive outcomes associated with video display terminal (VDT) usage, amounts of time spent in front of a VDT or magnetic field (MF) levels in front of the VDT are used as surrogate measures of subject's MF exposure. However, the relevance of such surrogates to actual exposures has not been demonstrated, and the validity of the use of such measures as a surrogate for the actual MF exposure is only speculative. This study examines 1) measurements of MFs at frequencies of approximately 30–1000 Hz at a fixed distance from the VDTs, 2) reported hours of VDT use, and 3) reported distance between the VDT and the subject's waist as surrogate measures for the average MF exposure level of a VDT user during one 8 h workday. The results showed a weak correlation between the average exposure level of a VDT user and the MF 46 cm from a VDT (R = 0.52, n = 67, P < 0.001). This study showed no association between self-reported hours of VDT usage, or self-reported distance between waist and VDT, and the average MF exposures. Moreover, individuals' average MF exposures did not seem to be affected by other variables, such as position of a VDT on the desk, hours of desk use, and the VDT type (color vs. monochrome). These findings indicate that VDT exposures within office settings are complex and cannot be easily predicted by surrogates. © 1996 Wiley-Liss, Inc.     

Alkaline phosphatase and phosphoamino acid phosphatases in normal and cancerous tissues of the human larynx

The activities of alkaline phosphatase and phosphoamino acid phosphatases were measured in normal and cancerous regions of the human larynx. For each larynx, alkaline phosphatase and phosphotyrosine phosphatase activities were higher in the tumor than in the corresponding normal tissue. Phosphothreonine and phosphoserine phosphatase activities were relatively low and there were no consistent trends. The increased alkaline phosphatase activity in the tumors supports histological observations that ossification of cartilage seems to occur at the site of invasion; the phosphatase acting on phosphotyrosine could serve as a regulator of cell differentiation during tumorigenesis.     

The role of novelty and fat and sugar concentration in food selection by captive tufted capuchins (Sapajus apella)

Capuchins, like other primates, use feedback from sensory cues and digestion to make decisions about which foods to consume and which to avoid. However, little is known about how capuchins make consumption decisions when simultaneously presented with novel and familiar foods, or how food familiarity and macronutrient concentration together influence food choice, topics with potential implications for developmental and health research. In this study, we evaluated the role of familiarity, as well as fat and sugar concentration, in the food selections of captive tufted capuchins (Sapajus apella). In the first experiment, over 10 sessions, subjects were assigned to either a group that chose between one familiar and one novel food item both high in fat or sugar (high condition), or to a group that chose between one familiar and one novel food item both low in fat or sugar (low condition). In the second experiment, subjects were divided into three groups, familiarized with food over five feeding sessions, and then offered the familiarized food and a novel food that varied in fat or sugar for 10 sessions. When offered foods high in fat, capuchins showed no clear signs of neophobia, forming an initial preference for the novel food, rejecting foods less frequently, and selecting foods faster than when offered foods low in fat. These trends were generally not observed in response to foods with sugar. When presented with options that varied in macronutrient concentration, subjects showed an initial interest in the novel food irrespective of whether it was high in fat or sugar, yet formed a final preference for the higher-concentration item. Findings suggest that the concentration of fat or sugar in novel foods may be an important mediator of exploratory behavior and that capuchins rely on immediate feedback from taste and other sensory cues to make consumption decisions.     

Isolation and characterization of magbane, a magnesium-lethal mutant of paramecium.

Discerning the mechanisms responsible for membrane excitation and ionic control in Paramecium has been facilitated by the availability of genetic mutants that are defective in these pathways. Such mutants typically are selected on the basis of behavioral anomalies or resistance to ions. There have been few attempts to isolate ion-sensitive strains, despite the insights that might be gained from studies of their phenotypes. Here, we report isolation of "magbane," an ion-sensitive strain that is susceptible to Mg2+. Whereas the wild type tolerated the addition of > or =20 mm MgCl2 to the culture medium before growth was slowed and ultimately suppressed (at >40 mm), mgx mutation slowed growth at 10 mm. Genetic analysis indicated that the phenotype resulted from a recessive single-gene mutation that had not been described previously. We additionally noted that a mutant that was well described previously (restless) is also highly sensitive to Mg2+. This mutant is characterized by an inability to control membrane potential when extracellular K+ concentrations are lowered, due to inappropriate regulation of a Ca2+-dependent K+ current. However, comparing the mgx and rst mutant phenotypes suggested that two independent mechanisms might be responsible for their Mg2+ lethality. The possibility that mgx mutation may adversely affect a transporter that is required for maintaining low intracellular Mg2+ is considered.