Helen Rutlidge

Shifting paradigms: development of high-efficiency biochar fertilizers based on nano-structures and soluble components

Many biochars have a complex carbon lattice structure with aromatic and aliphatic domains, acidic and basic groups, vacancies, metallic and non-metallic elements, and free radicals. Biochars also have separate mineral oxide, silicate and salt phases, and small and large organic molecules. In the rhizosphere, such constituents can be involved in chemical and biological processes along a soil–microbe–plant continuum, including nutrient cycling, metal chelation and stabilization, redox reactions, and free radical scavenging. It is hypothesized that the greater the amount of these nanoparticles and dissolved components, the greater will be plant and microbial responses. We provide suggestions for developing low-dose, high-efficiency biochar–nanoparticle composites, as well as initial field trial results and detailed characterization of such a biochar–fertilizer composite, to highlight the potential of such biochars.

Differential injurious effects of ambient and traffic-derived particulate matter on airway epithelial cells

Exposure to airborne particulate matter (PM) may promote development of childhood asthma and trigger acute exacerbations of existing asthma via injury to airway epithelial cells (AEC).

Metal and complementary molecular bioimaging in Alzheimer's disease

Alzheimers disease (AD) is the leading cause of dementia in the elderly, affecting over 27 million people worldwide. AD represents a complex neurological disorder which is best understood as the consequence of a number of interconnected genetic and lifestyle variables, which culminate in multiple changes to brain structure and function. These can be observed on a gross anatomical level in brain atrophy, microscopically in extracellular amyloid plaque and neurofibrillary tangle formation, and at a functional level as alterations of metabolic activity. At a molecular level, metal dyshomeostasis is frequently observed in AD due to anomalous binding of metals such as Iron (Fe), Copper (Cu), and Zinc (Zn), or impaired regulation of redox-active metals which can induce the formation of cytotoxic reactive oxygen species and neuronal damage. Metal chelators have been administered therapeutically in transgenic mice models for AD and in clinical human AD studies, with positive outcomes. As a result, neuroimaging of metals in a variety of intact brain cells and tissues is emerging as an important tool for increasing our understanding of the role of metal dysregulation in AD. Several imaging techniques have been used to study the cerebral metallo-architecture in biological specimens to obtain spatially resolved data on chemical elements present in a sample. Hyperspectral techniques, such as particle-induced X-ray emission (PIXE), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence microscopy (XFM), synchrotron X-ray fluorescence (SXRF), secondary ion mass spectrometry (SIMS), and laser ablation inductively coupled mass spectrometry (LA-ICPMS) can reveal relative intensities and even semi-quantitative concentrations of a large set of elements with differing spatial resolution and detection sensitivities. Other mass spectrometric and spectroscopy imaging techniques such as laser ablation electrospray ionization mass spectrometry (LA ESI-MS), MALDI imaging mass spectrometry (MALDI-IMS), and Fourier transform infrared spectroscopy (FTIR) can be used to correlate changes in elemental distribution with the underlying pathology in AD brain specimens. Taken together, these techniques provide new techniques to probe the pathobiology of AD and pave the way for identifying new therapeutic targets. The current review aims to discuss the advantages and challenges of using these emerging elemental and molecular imaging techniques, and highlight clinical achievements in AD research using bioimaging techniques.

Evaporative cooling of speleothem drip water

This study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as δ18O, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change.

Classification of Heterogeneous Solids Using Infrared Hyperspectral Imaging

Methods were explored for the classification of heterogeneous powder mixtures using Fourier transform infrared (FT-IR) hyperspectral image data. The images collected were non-congruent, meaning that samples of the same mixture do not have the same spatial arrangements of their components in their images. In order to classify such images on a one-image-per-object basis, dimension reduction was carried out so as to produce a score or feature vector for each image that preserved information about the heterogeneity of the sample. These feature vectors were then classified using discriminant analysis (DA) or soft independent modeling of class analogy (SIMCA). The most successful approach was the use of a median-interquartile range “super-spectrum” as the feature vector representing each image; using principal component analysis (PCA) DA classification, 87.5% of training samples were correctly classified using leave-one-out cross-validation, and 100% of a test set were correctly classified. This compares with 52.5% and 72%, respectively, when single-point spectra were used to classify the samples.

Identification of Cerebral Metal Ion Imbalance in the Brain of Aging Octodon degus

The accumulation of redox-active transition metals in the brain and metal dyshomeostasis are thought to be associated with the etiology and pathogenesis of several neurodegenerative diseases, and Alzheimer’s disease (AD) in particular. As well, distinct biometal imaging and role of metal uptake transporters are central to understanding AD pathogenesis and aging but remain elusive, due inappropriate detection methods. We therefore hypothesized that Octodon degus develop neuropathological abnormalities in the distribution of redox active biometals, and this effect may be due to alterations in the expression of lysosomal protein, major Fe/Cu transporters, and selected Zn transporters (ZnTs and ZIPs). Herein, we report the distribution profile of biometals in the aged brain of the endemic Chilean rodent O. degus—a natural model to investigate the role of metals on the onset and progression of AD. Using laser ablation inductively coupled plasma mass spectrometry, our quantitative images of biometals (Fe, Ca, Zn, Cu, and Al) appear significantly elevated in the aged O. degus and show an age-dependent rise. The metals Fe, Ca, Zn, and Cu were specifically enriched in the cortex and hippocampus, which are the regions where amyloid plaques, tau phosphorylation and glial alterations are most commonly reported, whilst Al was enriched in the hippocampus alone. Using whole brain extracts, age-related deregulation of metal trafficking pathways was also observed in O. degus. More specifically, we observed impaired lysosomal function, demonstrated by increased cathepsin D protein expression. An age-related reduction in the expression of subunit B2 of V-ATPase, and significant increases in amyloid beta peptide 42 (Aβ42), and the metal transporter ATP13a2 were also observed. Although the protein expression levels of the zinc transporters, ZnT (1,3,4,6, and 7), and ZIP7,8 and ZIP14 increased in the brain of aged O. degus, ZnT10, decreased. Although no significant age-related change was observed for the major iron/copper regulator IRP2, we did find a significant increase in the expression of DMT1, a major transporter of divalent metal species, 5′-aminolevulinate synthase 2 (ALAS2), and the proto-oncogene, FOS. Collectively, our data indicate that transition metals may be enriched with age in the brains of O. degus, and metal dyshomeostasis in specific brain regions is age-related.

High rates of organic carbon processing in the hyporheic zone of intermittent streams

Organic carbon cycling is a fundamental process that underpins energy transfer through the biosphere. However, little is known about the rates of particulate organic carbon processing in the hyporheic zone of intermittent streams, which is often the only wetted environment remaining when surface flows cease. We used leaf litter and cotton decomposition assays, as well as rates of microbial respiration, to quantify rates of organic carbon processing in surface and hyporheic environments of intermittent and perennial streams under a range of substrate saturation conditions. Leaf litter processing was 48% greater, and cotton processing 124% greater, in the hyporheic zone compared to surface environments when calculated over multiple substrate saturation conditions. Processing was also greater in more saturated surface environments (i.e. pools). Further, rates of microbial respiration on incubated substrates in the hyporheic zone were similar to, or greater than, rates in surface environments. Our results highlight that intermittent streams are important locations for particulate organic carbon processing and that the hyporheic zone sustains this fundamental process even without surface flow. Not accounting for carbon processing in the hyporheic zone of intermittent streams may lead to an underestimation of its local ecological significance and collective contribution to landscape carbon processes.

Groundwater supports intermittent-stream food webs

Stream food webs are changing in response to anthropogenic stressors, such as nutrient enrichment and water extraction. One way to monitor these changes is to examine shifts in the relative importance of autotrophic and detrital energetic pathways in food webs. This understanding is particularly pertinent in intermittent streams whose prevalence is projected to increase because of a changing climate and groundwater extraction. We used the stable-isotope values (δ13C and δ15N) of autotrophic and detrital basal resources and the tissue of consumers to examine the relative importance of these 2 energetic pathways during wet and dry phases in 5 groundwater-influenced intermittent streams. In addition, we used surface-water biogeochemical data to estimate the use of groundwater-derived dissolved inorganic C (DIC) in food webs. Autotrophic basal resources were the dominant C source for primary consumers during wet (>95%, on average) and dry (>77%, on average) hydrological phases. 13C-depleted autotrophs and consumers and negative correlations between the δ13C values of autotrophs and consumers with aqueous CO2 concentrations, indicated that primary producers probably are assimilating microbial respired CO2 from groundwater. Overall, we suggest that groundwater discharge is probably central to foodweb productivity in these streams by extending the duration of wetted habitat for autotrophic growth during dry phases and by delivering dissolved resources that potentially contribute to the energetic base of producers and consumers. Consequently, extended periods of reduced flow (and cease-to-flow events) caused by groundwater extraction or changed climatic conditions may reduce the overall productivity of groundwater-influenced intermittent streams.

Corrigendum: Identification of Cerebral Metal Ion Imbalance in the Brain of Ageing Octodon degus

[This corrects the article on p. 66 in vol. 9, PMID: 28405187.].