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Study region: The Great Barrier Reef catchment is located adjacent to the world's largest coral reef system, the Great Barrier Reef, in eastern Queensland, Australia. Study focus: This study characterized the geologic and hydrogeologic settings and evaluated the influence of regional faults on groundwater flow. 3D geological models of six regions within the catchment were constructed using drill-log data from >49,000 wells, digital elevation models and surface geological maps. The 3D models were then integrated with potentiometric surface maps and faults data to conceptualize the hydraulic relationships of aquifer units and estimate groundwater development potentials. Potentiometric surfaces and fault orientations were used to conceptualize groundwater flow directions. New hydrological insights for the region: The 3D geological and hydrogeological characterizations revealed previously unknown faults and aquifer units in the study area. The study found that the central regions consisted of fractured and porous-unconfined aquifers, while confined aquifers, which extend to the coast and likely beyond, were also found in the northern and southern most regions. The orientations of the faults trended in NW-SE directions and could form conduits for south-easterly groundwater flow as opposed to the predominate easterly flow in the porous-unconfined and confined aquifers. The 3D models, aquifer connectivities and geometries provided crucial information to determine groundwater development potentials and offer a first step in developing local and regional groundwater flow and contaminant transport models.

Study region: This study investigates dissolved methane distribution in groundwater from the Richmond River Catchment (New South Wales, Australia) before proposed coal seam gas (CSG, or coal bed methane) development. Study focus: Unconventional gas exploration has rapidly expanded in recent years. However, the impact of these operations on groundwater systems is poorly understood. A total of 91 groundwater samples were analyzed from 6 geological units. Our observations act as regional baseline research prior to CSG extraction and may assist with long term impact assessment. New hydrological insights for the region: Methane was found in all geological units ranging between 0.26 and 4427 μg L−1 (median 10.68 μg L−1). Median methane concentrations were highest in chloride-type groundwater (13.26 μg L−1, n = 58) while bicarbonate-type groundwater had lower concentrations (3.71 μg L−1). Groundwater from alluvial sediments had significantly higher median methane concentrations (91.46 μg L−1) than groundwater from both the basalt aquifers (0.7 μg L−1) and bedrock aquifers (4.63 μg L−1); indicating geology was a major driver of methane distribution. Methane carbon stable isotope ratios ranged from –90.9‰ to –29.5‰, suggesting a biogenic origin with some methane oxidation. No significant correlations were observed between methane concentrations and redox indicators (nitrate, manganese, iron and sulphate) except between iron and methane in the Lismore Basalt (r2 = 0.66, p

Background: The current standard of practice for cremating patients with cardiac implantable electronic devices (CIEDs) is surgical explantation before cremation to mitigate the risk of device explosion. This surgery may conflict with patient or family beliefs, whereas cremation of CIEDs may create occupational hazards., Objective: This study sought to establish an ex vivo model for screening CIED behavior during cremation., Methods: Seven CIEDs underwent testing including projectile/sound testing, impact testing, and gas analysis. In the projectile test, devices were heated until thermal failure (explosion) and filmed with a high-speed camera and microphone. For impact testing, brick structures were built to assess damage after explosion. Gas chromatography-mass spectrometry identified released gases. Findings were compared with occupational health standards, where available., Results: The implantable loop recorder and leadless pacemaker produced minimal kinetic energy and impact risk with thermal failure. The remaining devices demonstrated explosive disintegration at thermal temperatures <500°C. The pacemakers and implantable cardiac defibrillators produced sound levels >120 dB and resulted in damage to brick structures. Small quantities of benzene and hydrogen fluoride were produced but at quantities within acceptable occupational exposure limits in a cremation chamber., Conclusion: All tested CIEDs experienced explosion at temperatures below crematorium standards. The smallest devices produced minimal risk of damage or injury, suggesting that they may safely remain in situ during cremation, whereas the larger devices produced more kinetic energy, testing chamber damage, and louder explosions, suggesting potential risk with cremation. Cadaveric testing in full-sized cremation chambers is required to determine real-world risk., Competing Interests: Disclosures T.R.M. has received speaker/consulting honoraria from Abbott, Inc and Biosense Webster, Inc and research support from Circa Scientific, Inc and LuxMed Systems. A.D. has received speaker/consulting honoraria from Abbott, Inc, Biosense Webster, Inc, and Biotronik; and research support from Medtronic, Inc, Abbott, Inc, Circa Scientific, Inc, and Biosense Webster, Inc. N.K., P.Z., J.W., and D.K. have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Antibiotics, among the most used medications in children, affect gut microbiome communities and metabolic functions. These changes in microbiota structure can impact host immunity. We hypothesized that early-life microbiome alterations would lead to increased susceptibility to allergy and asthma. To test this, mouse pups between postnatal days 5-9 were orally exposed to water (control) or to therapeutic doses of azithromycin or amoxicillin. Later in life, these mice were sensitized and challenged with a model allergen, house dust mite (HDM), or saline. Mice with early-life azithromycin exposure that were challenged with HDM had increased IgE and IL-13 production by CD4 + T cells compared to unexposed mice; early-life amoxicillin exposure led to fewer abnormalities. To test that the microbiota contained the immunological cues to alter IgE and cytokine production after HDM challenge, germ-free mice were gavaged with fecal samples of the antibiotic-perturbed microbiota. Gavage of adult germ-free mice did not result in altered HDM responses, however, their offspring, which acquired the antibiotic-perturbed microbiota at birth showed elevated IgE levels and CD4 + cytokines in response to HDM, and altered airway reactivity. These studies indicate that early-life microbiota composition can heighten allergen-driven Th2/Th17 immune pathways and airway responses in an age-dependent manner., (© 2022. The Author(s), under exclusive licence to Society for Mucosal Immunology.)

Background: The left internal thoracic artery is the ideal conduit for coronary artery revascularization due to superior patency compared with venous grafts. The hemodynamic effects of an arterio-venous fistula on the native in situ internal thoracic artery and the potential for coronary flow steal after revascularization with the internal thoracic artery, are not well-characterized., Methods: Fifteen chronic hemodialysis patients with functioning left upper extremity arterio-venous fistulas were evaluated with the use of transthoracic color Doppler analysis. Flow characteristics of the left and right internal thoracic arteries at baseline, with arterio-venous fistula occluded, and during hemodialysis were recorded. Peak systolic and diastolic velocities for the right and left internal thoracic arteries were calculated for each fistula state (occluded, open, and on-dialysis). One-way analysis of variance was used to compare the different means., Results: Mean flow velocity calculations failed to identify any statistically significant differences between the ipsilateral and contralateral internal thoracic artery in any fistula state. In addition, mean internal thoracic flow velocities were similar between the different fistula states., Conclusions: Changes in arteriovenous fistula flow state did not significantly alter Doppler flow hemodynamics of either the ipsilateral or contralateral in-situ internal thoracic artery. Further studies of the possible effects on internal thoracic arteries used as pedicled coronary grafts may be required.

We hypothesized that cardiovascular responses to static muscle contraction are mediated via changes in extracellular concentrations of monoamines (norepinephrine, dopamine and serotonin) following the administration of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, an AMPA-receptor antagonist) into the rostral (RVLM) or caudal (CVLM) ventrolateral medulla. For the RVLM experiments (n= 8), a 2-min static muscle contraction increased the mean arterial pressure (MAP) and heart rate (HR) by 23 +/- 2 mmHg and 28 +/- 8 bpm, respectively. During this contraction, the concentrations of norepinephrine, dopamine, and serotonin within the RVLM increased by 278 +/- 52%, 213 +/- 23%, and 232 +/- 24%, respectively. Microdialysis of CNQX (1.0 microM) for 30 min into the RVLM attenuated the increases in MAP and HR ( 11 +/- 2 mmHg and 14 +/- 5 bpm) without a change in developed muscle tension. The levels of norepinephrine, dopamine, and serotonin within the RVLM were also attenuated. In contrast, microdialysis of CNQX into the CVLM (n= 8) potentiated the contraction-evoked responses in MAP ( 21 +/- 2 vs 33 +/- 5 mmHg) and HR ( 25 +/- 5 vs 46 +/- 8 bpm) without any effect on the monoamine levels within the CVLM region. These results suggest that AMPA-receptor blockade within the RVLM and CVLM has opposing effects on cardiovascular responses during static muscle contraction. In addition, such receptor blockade modulates extracellular concentrations of monoamines within the RVLM but not in the CVLM. These results provide evidence that AMPA receptors within the ventrolateral medulla play a role in exercise pressor reflex., (Copyright 2001 Academic Press.)

Hyperkalemia has been implicated in the pathogenesis of metabolic acidosis in chronic renal insufficiency because acidosis is ameliorated after administration of medications that correct hyperkalemia: mineralocorticoids, diuretics, intestinal K+-binding agents. However, the acidosis-ameliorating effect of these medications may be a consequence not of their ability to correct hyperkalemia, but of their ability to directly stimulate renal or intestinal excretion of acid. To investigate the specific effect of correcting hyperkalemia, balance studies were performed wherein hyperkalemia was corrected solely by restriction of dietary K+ in three patients with moderate chronic renal insufficiency (Ccreat 36, 44, and 58 ml/min/1.73 m2, respectively). Reduction of K+ intake was effected by substitution of Na+ for K+ in the electrolyte supplement to a whole-food diet of low K+ content. This maneuver resulted in correction of hyperkalemia and sustained amelioration of metabolic acidosis in each patient. Net acid excretion increased only transiently, and not enough to fully account for the magnitude of the increment in plasma [HCO3-], suggesting that an extrarenal mechanism of HCO3- input to the systemic circulation was the major factor that ameliorated the systemic acidosis. Evidence of an extrarenal mechanism was obtained only during the phase of decreasing plasma [K+]. Subsequently, during sustained normokalemia, the increased plasma [HCO3-] was maintained as a consequence of a sustained increase in total renal H+ secretion, evidenced by complete reabsorption of the increased filtered load of HCO3- and no reduction in net acid excretion from control values. These results indicate that in some patients with moderate chronic renal insufficiency, metabolic acidosis is ameliorated when hyperkalemia is corrected by restriction of dietary K+ (Na+ substitution) without otherwise changing diet composition and without administration of medication. Amelioration of the acidosis is predominantly effected by extrarenal mechanisms, and is sustained by an increase in the set point at which plasma [HCO3-] is regulated by the kidney.

Steady-state plasma and urine acid-base composition was assessed in 19 studies of 16 normal subjects who ingested constant amounts of one of three diets that resulted in different rates of endogenous noncarbonic acid production (EAP) within the normal range. Renal net acid excretion (NAE) was used to quantify EAP since the two variables are positively correlated in normal subjects. A significant positive correlation was observed between plasma [H+] and plasma PCO2, and between plasma [HCO3-] and plasma PCO2, among the subjects. Multiple correlation analysis revealed a significant interrelationship among plasma [H+], plasma PCO2, and NAE (r = 0.71, P less than 0.001), and among plasma [HCO3-], plasma PCO2, and NAE (r = 0.77, P less than 0.001). The partial correlation coefficients indicated a significant positive correlation between plasma [H+] and NAE, and a significant negative correlation between plasma [HCO3-] and NAE, when plasma PCO2 was held constant. These findings indicate that two factors influence the level at which plasma [H+] is maintained in normal subjects: (1) the steady-state rate of endogenous noncarbonic acid production, and (2) the setpoint at which plasma PCO2 is regulated by the respiratory system. Plasma [HCO3-] is also co-determined by these two factors. In disease states, therefore, both factors must be known before a disturbance in acid-base homeostasis can be excluded.