Occasional intraguild predation structuring small mammal assemblages: the marsupial Didelphis aurita in the Atlantic Forest of Brazil

The didelphid marsupial, Didelphis aurita, is suggested as an intraguild predator and as key‐species in small mammal assemblages of the Atlantic Forest of Brazil. The field experiments required to test this hypothesis are complex to implement, but the recent revival of regression methods offers a viable alternative. Here we use the dynamic and static regression methods to determine the importance of D. aurita as a competitor and intraguild predator. Capture–recapture data from two localities in the Rio de Janeiro State were used, Garrafão (municipality of Guapimirim), a coastal forest of the Serra do Mar, and Barra de Maricá, a costal sand dune vegetation. Population and microhabitat variables were monitored from April 1997 to April 2003 in Garrafão, and from January 1986 to July 1990 in Barra de Maricá. Microhabitat variables were related to Canopy, Plant, Litter and Rock covers, Obstruction from 0 to 1.5 m, and Number of logs. Exploitation competition was tested by the dynamic method, which models the effects of D. aurita on the per capita growth rate of a species. Interference by predation or competition was tested by the static method, where the abundance of D. aurita at trap stations was regressed against the abundance of other small mammals, after removal of any variation associated with microhabitat factors. Exploitation competition was not detected, but the interference of D. aurita was pervasive, affecting all small mammals studied in the two localities. The clear avoidance of D. aurita by all small mammals tested in two localities of different physiognomies indicates that it functions as an intraguild predator, even if actual predation by D. aurita is an occasional event.     

toxin-mediated insect resistance in plants

We are currently in an interesting phase of plant biotechnology releases, both for the scientists responsible for these innovations who are beginning to see their ideas realized, and for the biotechnology companies that are starting to see a return on their investment. One of the most notable examples, is the introduction of transgenic crops that are engineered to express a Bacillus thuringiensis toxin that confers resistance to insect predation. However, the picture is not altogether positive - there is concern that the introduction of this technology was premature or should not have happened at all, and that the valuable insecticidal properties of Bacillus thuringiensis will be lost.     

Unusual pattern of bacterial ice nucleation gene evolution

Bacterial ice nucleation activity (INA+ phenotype) can be traced to the product of a single gene, ina. A remarkably sparse distribution of this phenotype within three bacterial genera indicates that the ina gene may have followed an unusual evolutionary path. Southern blot analyses, coupled with assays for ice-nucleating ability, revealed that within four bacterial species an ina gene is present in some strains but absent from others. Results of hybridization experiments using DNA fragments that flank the ina gene suggested that the genotypic dimorphism of ina may be anomalous. A phylogenetic analysis of 16S ribosomal RNA gene sequences from a total of 14 ina+ and ina- bacterial strains indicated that the ina+ bacteria are not monophyletic but instead phylogenetically interspersed among ina- bacteria. The relationships of ina+ bacteria inferred from ina sequence did not coincide with those inferred from the 16S data. These results suggest the possibility of horizontal transfer in the evolution of bacterial ina genes.      

Notes on Scleroderma,Puff balls and Geastrum of Azad Jammu and Kashmir,Pakistan

Six species of mushrooms allied to the Family Sclerodermataceae, Lycoperdaceae and Geastraceae have been described for the first time from Azad Jammu and Kashmir. These are Scleroderma aurantium, Calvatia verrucosia sp. nov., Lycoperdon pedicellaton sp. nov. L. sphaericon sp. nov., L. echinulaton sp. nov., and Geastrum heptaplex sp. nov.     

Transgene-mediated and elicitor-induced perturbation of metabolic channeling at the entry point into the phenylpropanoid pathway

3H-l-Phenylalanine is incorporated into a range of phenylpropanoid compounds when fed to tobacco cell cultures. A significant proportion of (3)H-trans-cinnamic acid formed from (3)H-l-phenylalanine did not equilibrate with exogenous trans-cinnamic acid and therefore may be rapidly channeled through the cinnamate 4-hydroxylase (C4H) reaction to 4-coumaric acid. Such compartmentalization of trans-cinnamic acid was not observed after elicitation or in cell cultures constitutively expressing a bean phenylalanine ammonia-lyase (PAL) transgene. Channeling between PAL and C4H was confirmed in vitro in isolated microsomes from tobacco stems or cell suspension cultures. This channeling was strongly reduced in microsomes from stems or cell cultures of transgenic PAL-overexpressing plants or after elicitation of wild-type cell cultures. Protein gel blot analysis showed that tobacco PAL1 and bean PAL were localized in both soluble and microsomal fractions, whereas tobacco PAL2 was found only in the soluble fraction. We propose that metabolic channeling of trans-cinnamic acid requires the close association of specific forms of PAL with C4H on microsomal membranes.     

Membrane Potential and Catecholamine Secretion by Bovine Adrenal Chromaffin Cells: Use of Tetraphenylphosphonium Distribution and Carbocyanine Dye Fluorescence

Changes in plasma membrane potential of isolated bovine adrenal chromaffin cells were measured independently by two chemical probe methods and related to corresponding effects on catecholamine secretion. The lipophilic cation tetraphenylphosphonium (TPP+) and the carbocyanine dye 3,3'-dipropylthiadicarbocyanine [DiS-C3-(5)] were used. The necessity of evaluating the subcellular distribution of TPP+ among cytoplasmic, mitochondrial, secretory granule, and bound compartments was demonstrated and the resting plasma membrane potential determined to be -55 mV. The relationship between membrane potential and catecholamine secretion was determined in response to variations in extracellular K+ and to the presence of several secretagogues including cholinergic receptor ligands, veratridine, and ionophores for Na+ and K+. The dependence of potential on K+ concentration fit the Goldman constant field equation with a Na/K permeability ratio of 0.1. The dependence of both K+- and veratridine-evoked catecholamine secretion on membrane potential exhibited a potential threshold of about -40 mV before a significant rise in secretion occurred. This is likely related to the threshold for opening of voltage-sensitive Ca2+ channels. Acetylcholine and nicotine evoked a large secretory response without a sufficiently sustained depolarization to be detectable by the relatively slow potential sensitive chemical probes. Decamethonium induced a detectable depolarization of the chromaffin cells. Veratridine and gramicidin evoked both membrane depolarization and catecholamine release. By contrast the K ionophore valinomycin evoked significant levels of secretion without any depolarization. This is consistent with its utilization of an intracellular source of Ca2+ and the independence of its measured secretory response on extracellular Ca2+.     

Air quality improvement and cognitive decline in community-dwelling older women in the United States: A longitudinal cohort study

BackgroundLate-life exposure to ambient air pollution is a modifiable risk factor for dementia, but epidemiological studies have shown inconsistent evidence for cognitive decline. Air quality (AQ) improvement has been associated with improved cardiopulmonary health and decreased mortality, but to the best of our knowledge, no studies have examined the association with cognitive function. We examined whether AQ improvement was associated with slower rate of cognitive decline in older women aged 74 to 92 years.Methods and findingsWe studied a cohort of 2,232 women residing in the 48 contiguous US states that were recruited from more than 40 study sites located in 24 states and Washington, DC from the Women’s Health Initiative (WHI) Memory Study (WHIMS)-Epidemiology of Cognitive Health Outcomes (WHIMS-ECHO) study. They were predominantly non-Hispanic White women and were dementia free at baseline in 2008 to 2012. Measures of annual (2008 to 2018) cognitive function included the modified Telephone Interview for Cognitive Status (TICSm) and the telephone-based California Verbal Learning Test (CVLT). We used regionalized universal kriging models to estimate annual concentrations (1996 to 2012) of fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) at residential locations. Estimates were aggregated to the 3-year average immediately preceding (recent exposure) and 10 years prior to (remote exposure) WHIMS-ECHO enrollment. Individual-level improved AQ was calculated as the reduction from remote to recent exposures. Linear mixed effect models were used to examine the associations between improved AQ and the rates of cognitive declines in TICSm and CVLT trajectories, adjusting for sociodemographic (age; geographic region; race/ethnicity; education; income; and employment), lifestyle (physical activity; smoking; and alcohol), and clinical characteristics (prior hormone use; hormone therapy assignment; depression; cardiovascular disease (CVD); hypercholesterolemia; hypertension; diabetes; and body mass index [BMI]). For both PM_2.5 and NO₂, AQ improved significantly over the 10 years before WHIMS-ECHO enrollment. During a median of 6.2 (interquartile range [IQR] = 5.0) years of follow-up, declines in both general cognitive status (β = −0.42/year, 95% CI: −0.44, −0.40) and episodic memory (β = −0.59/year, 95% CI: −0.64, −0.54) were observed. Greater AQ improvement was associated with slower decline in TICSm (β_{PM2.5improvement} = 0.026 per year for improved PM_2.5 by each IQR = 1.79 μg/m³ reduction, 95% CI: 0.001, 0.05; β_{NO2improvement} = 0.034 per year for improved NO₂ by each IQR = 3.92 parts per billion [ppb] reduction, 95% CI: 0.01, 0.06) and CVLT (β_{PM2.5 improvement} = 0.070 per year for improved PM_2.5 by each IQR = 1.79 μg/m³ reduction, 95% CI: 0.02, 0.12; β_{NO2improvement} = 0.060 per year for improved NO₂ by each IQR = 3.97 ppb reduction, 95% CI: 0.005, 0.12) after adjusting for covariates. The respective associations with TICSm and CVLT were equivalent to the slower decline rate found with 0.9 to 1.2 and1.4 to 1.6 years of younger age and did not significantly differ by age, region, education, Apolipoprotein E (ApoE) e4 genotypes, or cardiovascular risk factors. The main limitations of this study include measurement error in exposure estimates, potential unmeasured confounding, and limited generalizability.ConclusionsIn this study, we found that greater improvement in long-term AQ in late life was associated with slower cognitive declines in older women. This novel observation strengthens the epidemiologic evidence of an association between air pollution and cognitive aging.

Diana Younan and colleagues investigate whether air quality improvement is associated with rate of cognitive decline in community-dwelling older women in the United States.