Introduction: A perspective from the humanities-science boundary

The articles in this special issue range across such influences on climate as solar emissions, orbital precession, atmosphere, oceans, and precipitation, and generally approach, each in some context, human implications of these phenomena. The common underlying theme of all of the papers is the effect the phenomena have on radiation balance as measured by global average temperature. This introductory paper undertakes a formulation of radiation balance theory that makes it serviceable to students of regional science. The objective is to go beyond inference of cause and effect by correlation to causal accounts of cause and effect through regional climatic and cultural processes. This is accomplished primarily by revisualization of the energy system with regions as dependent spatiotemporal entities, and temporally through a protocol for regional episode definition.This special issue ofHuman Ecology consists of the American Anthropological Association Invited Symposium on Global Climate Change.     

Wide‐field color imaging of scatter‐based tissue contrast using both high spatial frequency illumination and cross‐polarization gating

This study characterizes the scatter‐specific tissue contrast that can be obtained by high spatial frequency (HSF) domain imaging and cross‐polarization (CP) imaging, using a standard color imaging system, and how combining them may be beneficial. Both HSF and CP approaches are known to modulate the sensitivity of epi‐illumination reflectance images between diffuse multiply scattered and superficially backscattered photons, providing enhanced contrast from microstructure and composition than what is achieved by standard wide‐field imaging. Measurements in tissue‐simulating optical phantoms show that CP imaging returns localized assessments of both scattering and absorption effects, while HSF has uniquely specific sensitivity to scatter‐only contrast, with a strong suppression of visible contrast from blood. The combination of CP and HSF imaging provided an expanded sensitivity to scatter compared with CP imaging, while rejecting specular reflections detected by HSF imaging. ex vivo imaging of an atlas of dissected rodent organs/tissues demonstrated the scatter‐based contrast achieved with HSF, CP and HSF‐CP imaging, with the white light spectral signal returned by each approach translated to a color image for intuitive encoding of scatter‐based contrast within images of tissue. The results suggest that visible CP‐HSF imaging could have the potential to aid diagnostic imaging of lesions in skin or mucosal tissues and organs, where just CP is currently the standard practice imaging modality.      

Myoepithelial Cells of Submucosal Glands Can Function as Reserve Stem Cells to Regenerate Airways after Injury

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Characteristics of Chloride Transport in Human Red Blood Cells

The efflux of chloride-36 from human erythrocytes under steady-state conditions is a saturable process that is competitively inhibited by bicarbonate and noncompetitively inhibited by acetate. This chloride self-exchange flux is reversibly dependent on the pH of the medium between 5.7 and 9.6 with a maximum flux at pH 7.8. The increase in chloride flux between pH 5.7 and 7.8 is inexplicable by the fixed charge hypothesis. The interpretations are made that chloride transport in human erythrocytes is carrier mediated, that bicarbonate utilizes the same transport mechanism, and that the mechanism can be titrated with hydrogen ions into less functional forms for chloride transport.     

Age-dependent prospecting and recruitment to a breeding colony of Short-tailed Shearwaters Puffinus tenuirostris

In a small colony of Short-tailed Shearwaters Puffinus tenuirostris , monitored annually since 1947, many of the young ringed as nestlings returned to their natal colony for one or more years before breeding for the first time. These 'prospectors' were first recorded at 4.1 ± 0.1 (range 2–7) years old; they started breeding at 7.0 ± 0.2 (4–14) years old. Overall, 31% of all prospectors bred on their natal island with no significant annual variation in this proportion. However, 8% of all natal recruits started breeding without having been recorded prospecting and bred first when significantly younger (5.6 ± 0.4 years old) than those first recorded prospecting. Shearwaters which subsequently bred at their natal colony started prospecting when significantly older (4.3 ± 0.1) than those that did not breed at their natal colony (4.0 ± 0.1 years). Non-natal recruits spent significantly less time prospecting (1.0 ± 0.1 years) than prospectors born on the island (1.9 ± 0.1 years). The shearwaters appeared to become progressively more faithful to the colony during their prospecting period.     

Effects of a 4 °C increase in temperature on partitioning of leaf area and dry mass, root respiration and carbohydrates

1. Plants of Bellis perennis, Dactylis glomerata and Poa annua were grown from seed in controlled-environment cabinets at either 16 or 20 °C; at the higher temperature all three species had increased total dry mass and leaf area when assessed on the basis of chronological time. On the basis of thermal time (summation of degree-days above 0 °C; days °C) temperature decreased the dry mass in P. annua.
2. Partitioning was assessed as a change in the allometric coefficients relating shoot and root dry mass, leaf and plant mass, leaf area and plant mass, and leaf area and leaf mass. Of the 12 relationships examined only three were affected by temperature: there was increased partitioning towards the shoot relative to the root in D. glomerata and increased partitioning towards leaf area rather than leaf mass in D. glomerata and B.perennis .
3. Root respiration was unaffected by temperature of growth in D. glomerata and P.annua but was lower in B. perennis grown at elevated temperature.
4. Root respiration acclimated to temperature in P. annua and B. perennis (i.e. when measured at the same temperature, respiration was higher in plants grown at 16 °C).
5. Root soluble carbohydrate concentration was unaffected by temperature of growth in any of the species. Feeding sucrose to the roots for a short period had no effect on the rate of respiration of B. perennis or D. glomerata but increased root respiration of P. annua .     

Genetic and physical mapping of the RPP13 locus, in Arabidopsis, responsible for specific recognition of several Peronospora parasitica (downy mildew) isolates.

Fifteen isolates of the biotrophic oomycete Peronospora parasitica (downy mildew) were obtained from a population of Arabidopsis thaliana plants that established naturally in a garden the previous year. They exhibited phenotypic variation in a set of 12 Arabidopsis accessions that suggested that the parasite population consisted of at least six pathotypes. One isolate, Maks9, elicited an interaction phenotype of flecking necrosis and no sporulation (FN) in the Arabidopsis accession Nd-1, and more extensive pitting necrosis with no sporulation (PN) in the accession Ws-2. RPP13 was designated as the locus for a single dominant resistance gene associated with the resistance in Nd-1 and mapped to an interval of approximately 60 kb on a bacterial artificial chromosome (BAC) contig on the lower arm of chromosome 3. This locus is approximately 6 cM telomeric to RPP1, which was previously described as the locus for the PN interaction with five Peronospora isolates, including resistance to Maks9 in Ws-2. New Peronospora isolates were obtained from four other geographically distinct populations of P. parasitica. Four isolates were characterized that elicited an FN phenotype in Nd-1 and mapped resistance to the RPP13 locus. This suggests that the RPP13 locus contains either a single gene capable of multiple isolate recognition or a group of tightly linked genes. Further analysis suggests that the RPP11 gene in the accession Rld-0 may be allelic to RPP13 but results in a different recognition capability.     

NEIL3-Dependent Regulation of Cardiac Fibroblast Proliferation Prevents Myocardial Rupture

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Molecular Epidemiology of Antimicrobial-Resistant Commensal Escherichia coli Strains in a Cohort of Newborn Calves

Pulsed-field gel electrophoresis (PFGE) was used to investigate the dissemination and diversity of ampicillin-resistant (Amp^r) and nalidixic acid-resistant (Nal^r) commensal Escherichia coli strains in a cohort of 48 newborn calves. Calves were sampled weekly from birth for up to 21 weeks and a single resistant isolate selected from positive samples for genotyping and further phenotypic characterization. The Amp^r population showed the greatest diversity, with a total of 56 different genotype patterns identified, of which 5 predominated, while the Nal^r population appeared to be largely clonal, with over 97% of isolates belonging to just two different PFGE patterns. Distinct temporal trends were identified in the distribution of several Amp^r genotypes across the cohort, with certain patterns predominating at different points in the study. Cumulative recognition of new Amp^r genotypes within the cohort was biphasic, with a turning point coinciding with the housing of the cohort midway through the study, suggesting that colonizing strains were from an environmental source on the farm. Multiply resistant isolates dominated the collection, with >95% of isolates showing resistance to at least two additional antimicrobials. Carriage of resistance to streptomycin, sulfamethoxazole, and tetracycline was the most common combination, found across several different genotypes, suggesting the possible spread of a common resistance element across multiple strains. The proportion of Amp^r isolates carrying sulfamethoxazole resistance increased significantly over the study period (P < 0.05), coinciding with a decline in the most common genotype pattern. These data indicate that calves were colonized by a succession of multiply resistant strains, with a probable environmental source, that disseminated through the cohort over time.     

Direct and Indirect (Foodweb Mediated) Effects of Metal Exposure on the Growth of Yellow Perch (Perca flavescens): Implications for Ecological Risk Assessment

Yellow perch (YP) are metal tolerant fish that form large populations in many metal-impacted regions across Canada. While they are able to survive and reproduce successfully in environments with water and sediment metal concentrations that are toxic to many invertebrates, perch experience a suite of direct and indirect impacts. YP were studied in a series of Canadian Precambrian Shield lakes near Sudbury, Ontario, along a gradient of metal exposure downwind from metal smelters. In lakes at the high end of our exposure gradient, concentrations of metals (Cu, Ni, and Cd) in YP liver and kidney were well above levels seen in fish from reference lakes. Direct effects linked to metal-exposure were observed, ranging from effects at the cellular level, to effects in organs and tissues, individuals, and populations. In addition to direct or physiological effects, we also documented indirect, foodweb-mediated effects of metals on YP in the most contaminated lakes resulting from the elimination of metal-sensitive large benthic invertebrates and their replacement by small metal-tolerant taxa. The most common indication of such indirect effects on YP is severely stunted growth coupled with a high degree of zooplankton dependence throughout their life. Such indirect effects have important implications for ecological risk assessment (ERA) because they indicate that higher trophic levels may be functionally altered even though the functional groups that they depend on are present and abundant. Although the functional groups important to yellow perch can be abundant in metal-impacted lakes, their benthic communities are impoverished and this is strongly reflected in their size structure upon which energy transfer to higher trophic levels depends. Thus indirect (foodweb-mediated) effects can be important in situations where invertebrate size structure is impacted in such a way as to reduce the efficiency of energy transfer to higher trophic levels, and therefore measures should be taken to protect and/or restore large sensitive benthic species.