Organophosphate insecticide exposure and effects in a non-target bird species

Coturnix quail (Coturnix coturnix) were exposed to four different organophosphorus (OP) pesticides (dicrotphos (DCP), ethoprop (ETP), methamidophos (MMP), and naled (NLD)) either by oral gavage or by being enclosed upon a OP-sprayed simulated field of barley for 6 hours in controlled, replicated experiments. The selected OPs varied in solubility. Responses were measured as inhibition of cholinesterase (ChE) activity in plasma and brain. Oral doses were at one-third the estimated median lethal dose while the spray application rates used were expected to produce 60% inhibition of plasma ChE activity 24 hours following removal from the field. Oral doses caused significant inhibition of ChE activity in plasma (33-93%, p<0.001) and brain (17-61%, p<0.001), confirming that each OP was a ChE inhibitor and bioavailable via the oral route. Recovery from inhibition of ChE activity following oral doses was relatively uniform in plasma (17.6 hours ≤ half-life (t1/2) ≤ 24.5 hours) but slower and more variable in brain (64.8 hours ≤ t1/2 ≤ 128 hours). Responses to field exposures could not be explained by observations of consumption of contaminated feed. Responses to field exposures were inconsistent with those to oral doses with 3 of 4 OPs. The response to field exposures with MMP, the most hydrophilic OP, was generally consistent with the response to oral doses. ChE activity in both tissues was lower following field exposures than following oral doses, significantly so in brain (p<0.001), indicating the field dose was larger than the oral dose. Recovery from inhibition of ChE activity in plasma (t1/2=17.7 hours) and brain (t1/2=125 hours) following simulated field exposures were within the ranges observed following oral doses. The response to field exposures with DCP and NLD, the OPs of intermediate solubility, varied from the response to oral doses. ChE activity in plasma was significantly lower following field exposures than following oral doses (p ≤ 0.002), while the opposite significant relationship was observed in brain (p ≤ 0.009). Recovery from inhibition of ChE activity was prolonged in plasma (DCP, t1/2=41.3 hours; NLD, t1/2=34.7 hours) and brain (DCP, t1/2=34.7 hours) relative to recovery following oral doses. The response to field exposure to ETP, the most lipophilic OP, obviously differed from the response to oral doses. Field exposures produced only moderate inhibition of ChE activity in plasma and no significant inhibition of ChE activity in brain. The conclusion drawn was that the exposure of quail to the OPs on the simulated field was primarily via the dermal route and that quail skin served as a reservoir for storage and delayed release of the OPs, a reservoir effect that increased with increasing lipophilicity of the OP. Polynomial regression was used to investigate the extent to which inhibition of ChE activity in the brains of quail exposed for 6 hours on the simulated field could be predicted by log of the octanol:water partition coefficients (Kow) of the OPs. Quadratic polynomial curves were significantly fit to brain ChE activity inhibition data at both 24 (r2=0.888, p<0.001) and 72 hours (r2=0.871, p<0.001) post-exposure. These curves indicate that OPs having log Kow in the range of 0 to 1.5 will be those most rapidly absorbed and distributed under field conditions. A similar effort to predict the further inhibition of brain ChE activity in quail associated with the additional exposure to the pesticide spray itself yielded a significant quadratic polynomial curve at 24 hours post-exposure (r2=0.621, p=0.013). Comments are provided as to the utility and relevance of the findings in ecological risk assessment for pesticide registration. Quail were exposed to DCP and dehydration in controlled, crossed experiments to determine if dehydration could confound the diagnosis of OP exposure using inhibition of ChE activity in quail tissues. Measures of plasma osmolality (Posm) and hematocrit (Hct) quantified dehydration. DCP exposure caused significant inhibition of ChE activity in brain (38%, p<0.001) and plasma (26%, p<0.001). Dehydration caused a significant increase in plasma ChE activity (min. 55%, p<0.001). Variation in the change in plasma ChE activity in response to dehydration was significantly and positively correlated with dehydration-induced variation in both the change in Posm (r2=0.284, p<0.001) and the change in Hct (r2=0.081, p=0.018). The observed correlations suggest plasma ChE activity in quail is not limited to plasma but instead occupies some larger pool of body water. The effects of dehydration on plasma ChE activity masked the inhibitory effects of DCP. Combined dehydration and DCP exposure produced plasma ChE activity that was not significantly different from control values. A method to adjust plasma ChE activities for the confounding effects of dehydration and enable the diagnosis of OP exposure in dehydrated, DCP-exposed quail was developed. Quail received radio telemetry implants measuring body temperature and heart rate and were given sublethal oral doses of DCP, ETP, MMP, NLD, and vehicle alone. Observations were made before and after exposure and under thermoneutral and cold-stressed conditions. Significant hypothermia and tachycardia were observed under thermoneutral conditions following doses of DCP (1.20ºC, p<0.001; 98.4 beats per minute (bpm), p<0.001) and ETP (1.21ºC, p=0.004; 133 bpm, p<0.001). A set of quail exposed to ETP and NLD, but excluded from statistical analyses, failed to thermoregulate under cold-stressed conditions, suggesting that effects on thermoregulation which are sublethal under thermoneutral conditions can become lethal under cold-stressed conditions

Does the World Need U.S. Farmers Even if Americans Don’t?

We consider the implications of trends in the number of U.S. farmers and food imports on the question of what role U.S. farmers have in an increasingly global agrifood system. Our discussion stems from the argument some scholars have made that American consumers can import their food more cheaply from other countries than it can produce it. We consider the distinction between U.S. farmers and agriculture and the effect of the U.S. food footprint on developing nations to argue there might be an important role for U.S. farmers, even if it appears Americans don’t need them. For instance, we may need to protect U.S. farmland and, by implication, U.S. farmers, for future food security needs both domestic and international. We also explore the role of U.S. farmers by considering the question of whether food is a privilege or a right. Although Americans seem to accept that food is a privilege, many scholars and commentators argue that, at least on a global scale, food is a right, particularly for the world’s poor and hungry. If this is the case, then U.S. farmers might have a role in meeting the associated obligation to ensure that the poor of the world have enough food to eat. We look at the consequences of determining that food is a right versus a privilege and the implications of that decision for agricultural subsidies as well as U.S. agriculture and nutrition policies.Food Security and Poverty,

Function and Regulation of Virulence-Associated Siderophores in Uropathogenic Enterobacterales

Siderophores are small molecules created by fungi and bacterial cells to help obtain iron. This may extend to cells in iron-limiting environments within host organisms. Certain siderophores are associated with increased virulence in urinary tract infections (UTIs). Siderophore system activity is typically regulated by feedback inhibition via ferric uptake regulator (Fur) which, in the presence of cytosolic iron, binds to a ~19 base pair inverted DNA repeat (9-1-9) called a Fur box. Once bound to this motif, the iron-Fur complex suppresses siderophore expression when adequate bacterial iron status is achieved. Many organisms produce more than one siderophore, and in the case of certain E. coli strains, up to four. This has been frequently interpreted as an example of biological redundancy, where multiple biological systems are deployed to fulfill a common function, in this case iron acquisition. While this may provide a backup option in the event that one system fails, it would also introduce new metabolic costs to bacteria. In this thesis we have tested the redundancy hypothesis for siderophore systems commonly possessed by Escherichia coli isolates recovered from patients with urinary tract infections. The virulence-associated siderophore yersiniabactin (Ybt) is commonly secreted by infection-associated E. coli isolates and has also been shown to bind a broad range of metal ions in addition to iron (III). Nevertheless, Ybt has been understood to function in the manner of a canonical siderophore. E. coli that secrete Ybt are also capable of secreting the prototypical siderophore enterobactin (Ent). To test the hypothesis that Ent and Ybt are redundant for iron acquisition, we developed an assay that measures siderophore-dependent growth in iron-limited cultures. Contrary to this hypothesis, we found that the ability of E.coli to secrete Ybt does not compensate for the loss of Ent in the test system, and that Ent is uniquely necessary for siderophore-dependent growth. Growth of an Ent-deficient strain was rescued by addition of purified Ybt to the medium, leading us to determine whether Ybt secretion was inadequate to compensate for the absence of Ent. This led to the discovery that, relative to Ent, peak Ybt production is achieved late in the bacterial growth cycle at higher cell density. This is not attributable to Fur regulation alone. We considered that Ybt production is attributable to the density-dependent regulation characteristic of quorum sensing (QS) mechanisms. Consistent with this, we found that Ybt acts as the autoinducer in a QS autoregulatory circuit. In the initial low cell density conditions of our siderophore-dependent growth assay when extracellular Ybt concentrations are low, the Ybt system is less activated than the Ent system and unable to compensate for the absence of Ent. These data are consistent with a regulatory model in which the Ybt system is an autoinducer and YbtA, an AraC-like transcription factor, is the cellular Ybt sensor that activates further Ybt biosynthesis. To our knowledge, this is the first QS mechanism found to control siderophore production in E. coli and the first in which the siderophore plays a dual role as autoinducer. The results suggest a virulence-associated role for Ybt production at high bacterial population densities. We compared another virulent-associated siderophore called aerobactin (Aer) to Ent. When looking at production of siderophores over a bacterial growth curve we observed a delay in Aer production, similar to what is found in Ybt. This potentially suggest that a similar alternative regulation system could apply to Aer. We also tested possible theories about what a potential non redundant function of Aer. We were unable to prove any one function but have found a possible connection between Aer and antibiotic resistance

How Old Are Marshes on the East Coast, USA? Complex Patterns in Wetland Age Within and Among Regions

Sea‐level dynamics, sediment availability, and marine energy are critical drivers of coastal wetland formation and persistence, but their roles as continental‐scale drivers remain unknown. We evaluated the timing and spatial variability of wetland formation from new and existing cores collected along the Atlantic and Gulf coasts of the United States. Most basal peat ages occurred after sea‐level rise slowed (after ~4,000 years before present), but predominance of sea‐level rise studies may skew age estimates toward older sites. Near‐coastal sites tended to be younger, indicating creation of wetlands through basin infilling and overwash events. Age distributions differed among regions, with younger wetlands in the northeast and southeast corresponding to European colonization and deforestation. Across all cores, wetland age correlated strongly with basal peat depth. Marsh age elucidates the complex interactions between sea‐level rise, sediment supply, and geomorphic setting in determining timing and location of marsh formation and future wetland persistence

Exceeding octave tunable Terahertz waves with zepto-second level timing noise

Spectral purity of any millimeter wave (mmW) source is of the utmost interest in low-noise applications. Optical synthesis via photomixing is an attractive source for such mmWs, which usually involves expensive spectrally pure lasers with narrow linewidths approaching monochromaticity due to their inherent fabrication costs or specifications. Here, we report an alternative option for enhancing the spectral purity of inexpensive semiconductor diode lasers via a self-injection locking technique through corresponding Stokes waves from a fiber Brillouin cavity exhibiting greatly improved phase noise levels and large wavelength tunability of ~1.8 nm. We implement a system with two self-injected diode lasers on a common Brillouin cavity aimed at difference frequency generation in the mmW and THz region. We generate tunable sub-mmW (0.3 and 0.5 THz) waves by beating the self-injected two wavelength Stokes light on a uni-travelling carrier photodiode and characterize the noise performance. The sub-mmW features miniscule timing noise levels in the zepto-second (zs.Hz^-0.5) scale outperforming the state of the art dissipative Kerr soliton based micro-resonator setups while offering broader frequency tunability. These results suggest a viable inexpensive alternative for mmW sources aimed at low-noise applications featuring lab-scale footprints and rack-mounted portability while paving the way for chip-scale photonic integration.Comment: 31 page

Does the World Need U.S. Farmers Even if Americans Don't?

We consider the implications of trends in the number of U.S. farmers and food imports on the question of what role U.S. farmers have in an increasingly global agrifood system. Our discussion stems from the argument some scholars have made that American consumers can import their food more cheaply from other countries than it can produce it. We consider the distinction between U.S. farmers and agriculture and the effect of the U.S. food footprint on developing nations to argue there might be an important role for U.S. farmers, even if it appears Americans don't need them. For instance, we may need to protect U.S. farmland and, by implication, U.S. farmers, for future food security needs both domestic and international. We also explore the role of U.S. farmers by considering the question of whether food is a privilege or a right. Although Americans seem to accept that food is a privilege, many scholars and commentators argue that, at least on a global scale, food is a right, particularly for the world's poor and hungry. If this is the case, then U.S. farmers might have a role in meeting the associated obligation to ensure that the poor of the world have enough food to eat. We look at the consequences of determining that food is a right versus a privilege and the implications of that decision for agricultural subsidies as well as U.S. agriculture and nutrition policies

Brillouin laser-driven terahertz oscillator up to 3 THz with femtosecond-level timing jitter

The terahertz (THz) frequency range, spanning 0.1 to 10 THz, is a field ripe for innovation with vast, developing potential in areas like wireless communication and molecular spectroscopy. Our work introduces a dual-wavelength laser design that utilizes stimulated Brillouin scattering in an optical fiber cavity to effectively generate two highly coherent optical Stokes waves with differential phase noise inherently mitigated. To guarantee robust operation, the Stokes waves are optically injected into their respective pump lasers, which also serves to greatly improve the resulting coherence. The frequency difference between the two wavelengths is converted into THz waves through a uni-traveling-carrier photodiode. This innovative design facilitates the generation of THz waves with phase noise levels of less than -100 dBc/Hz, translating to timing noise below 10~$\mathrm{as} / \sqrt{\mathrm{Hz}}$ at 10 kHz Fourier frequency, over a carrier frequency range from 300 GHz to 3 THz. This development in phase noise reduction establishes a new benchmark in the spectral purity of tunable THz sources. Such advances are pivotal for applications to move beyond oscillator constraints

Local links and learning: Resilience in regional, rural and remote schools. Fostering community ties and harnessing learning opportunities to boost resilience

In recent years, schools in regional, rural and remote NSW have been affected by floods, drought, bushfires, animal plagues and other major disruptions, including COVID-19. It is vital that a school community's local capabilities are leveraged and boosted, so that they are ready to deal with future disruptions. This report focusses on two ways to boost the resilience of regional, rural and remote school communities: improving links between schools and their local communities, and opportunities for contextualised student learning and professional learning of school staff