Publications by authors named "Heap L"

There is a spotlight on mental health, with government initiatives in Australia highlighting the importance of, and need for, greater focus on psychological wellbeing and on addressing psychosocial hazards at work. The growing body of evidence in Australia and internationally suggests that the mental health and wellbeing of lawyers is adversely affected by their work. This cross-disciplinary evidence highlights the need for mental health concerns to be addressed systemically to prevent psychosocial injury and for tailored, proactive psychological support services in the legal environment.

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Looming visual stimuli result in escape responses that are conserved from insects to humans. Despite their importance for survival, the circuits mediating visual startle have only recently been explored in vertebrates. Here we show that the zebrafish thalamus is a luminance detector critical to visual escape.

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The optic tectum of larval zebrafish is an important model for understanding visual processing in vertebrates. The tectum has been traditionally viewed as dominantly visual, with a majority of studies focusing on the processes by which tectal circuits receive and process retinally-derived visual information. Recently, a handful of studies have shown a much more complex role for the optic tectum in larval zebrafish, and anatomical and functional data from these studies suggest that this role extends beyond the visual system, and beyond the processing of exclusively retinal inputs.

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Many features of auditory processing are conserved among vertebrates, but the degree to which these pathways are established at early stages is not well explored. In this study, we have observed single cell activity throughout the brains of larval zebrafish with the goal of identifying the cellular responses, brain regions, and brain-wide pathways through which these larvae perceive and process auditory stimuli. Using GCaMP and selective plane illumination microscopy, we find strong responses to auditory tones ranging from 100 Hz to 400 Hz.

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The tectum has long been known as a hub of visual processing, and recent studies have elucidated many of the circuit-level mechanisms by which tectal neurons filter visual information. Here, we use population-scale imaging of tectal neurons expressing a genetically encoded calcium indicator to characterize tectal responses to non-visual stimuli in zebrafish. We identify ensembles of neurons responsive to stimuli for each of three sensory modalities: vision, audition, and water flow sensation.

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Article Synopsis
  • Neurofibromatosis 2 (NF2) is a genetic condition leading to brain tumors and reduced life expectancy, with limited understanding of how specific mutations affect mortality.
  • A study of 1,192 NF2 patients found that early diagnosis and intracranial meningiomas increased mortality, while mosaic mutations and certain types of genetic mutations correlated with lower mortality rates.
  • Patients diagnosed more recently showed improved survival rates, highlighting the potential benefits of advancements in diagnosis and treatment for NF2.
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Article Synopsis
  • Optogenetics is a technique that uses light, typically from a laser, to control and study neuronal activity but faces challenges due to scattering in brain tissue.
  • This study focuses on analyzing how laser beams degrade at various depths in zebrafish larvae brains, utilizing a specific laser and advanced focusing technology.
  • By combining experimental measurements and computational modeling, researchers reveal that it is possible to effectively target and illuminate individual neurons in dense tissue areas, even deeper than 100 μm.
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The cerebellum is a brain region responsible for motor coordination and for refining motor programs. While a great deal is known about the structure and connectivity of the mammalian cerebellum, fundamental questions regarding its function in behavior remain unanswered. Recently, the zebrafish has emerged as a useful model organism for cerebellar studies, owing in part to the similarity in cerebellar circuits between zebrafish and mammals.

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To investigate mechanisms predisposing to alcoholic brain damage, thiamine (vitamin B1 ), riboflavin (vitamin B2 ) and pyridoxine (vitamin B6 ) status was compared in persistent alcohol misusers (PAM) admitted for detoxification without evidence of significant brain damage, in alcoholics known to have severe chronic brain damage (BDAM), and in age, gender and ethnicity matched controls. Thus, activities of thiamine-dependent transketolase (ETK), riboflavin-dependent glutathione reductase, and pyridoxine-dependent aspartate amino transferase were assayed, together with the enzyme activities following addition of the appropriate co-factor. Twenty per cent of the PAM group had an abnormally low ETK activity and an abnormally high activation ratio, while 45% were abnormal in either one or both parameters.

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Some patients with chronic fatigue syndrome say they benefit from taking vitamin supplements. We assessed functional status for the B vitamins pyridoxine, riboflavin and thiamine in 12 vitamin-untreated CFS patients and in 18 healthy controls matched for age and sex. Vitamin-dependent activities--aspartate aminotransferase (AST) for pyridoxine, glutathione reductase (GTR) for riboflavin, transketolase (TK) for thiamine--were measured in erythrocyte haemolysates before and after in-vitro addition of the relevant vitamin.

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The contribution of impaired degradative processes to the cellular changes occurring in the brain as a consequence of chronic ethanol exposure was assessed. Male Wistar rats were fed nutritionally adequate liquid diets containing ethanol as 35% of total dietary calories. Controls were pair-fed identical amounts of the same diet in which ethanol was replaced by isocaloric glucose.

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The toxic effect of acetaldehyde on brain oxidative capacity and dopamine metabolism has been investigated in rat brains after a single intraperitoneal injection of acetaldehyde (5 mmol/kg) and the results compared with those from chronically ethanol fed rats. Acetaldehyde was present in rat brain 120 hr after a single dose of acetaldehyde, confirming that it is able to cross the blood-brain barrier. Brain catalase increased significantly after acetaldehyde or chronic ethanol administration although there were no other significant changes in the total brain activity of superoxide dismutase, glutathione peroxidase or glutathione reductase.

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Etoposide demonstrates incomplete and variable bioavailability after oral dosing, which may be due to its concentration and pH-dependent stability in artificial gastric and intestinal fluids. The use of agents that may influence etoposide stability and, thereby, bioavailability, was investigated in a number of clinical studies. Drugs that influence the rate of gastric emptying, while modulating the time of drug absorption, did not significantly alter the etoposide area under the concentration-time curve (AUC) or bioavailability.

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