- Melbourne, Victoria, Australia
- Senior Lecturer in Animal Biology at Deakin University conducting independent and collaborative research in environme... moreSenior Lecturer in Animal Biology at Deakin University conducting independent and collaborative research in environmental and human toxicology, and aquatic animal physiology using cell biology, molecular biology, in vitro and in vivo approaches.edit
The study describes a novel and environment friendly route of biosynthesis of nanohydroxyapatite (nHAP). Bacillus licheniformis mediated synthesis of nHAP has been carried out with different phosphate concentrations (2%, 5%, 10% and 20%... more
The study describes a novel and environment friendly route of biosynthesis of nanohydroxyapatite (nHAP). Bacillus licheniformis mediated synthesis of nHAP has been carried out with different phosphate concentrations (2%, 5%, 10% and 20% w/v) of potassium dihydrogen orthophosphate monobasic (K 2 HPO 4). The synthesis is supported by a two-step mechanism–(i) solubilization of P by organic acids extracellularly secreted by the bacterial strain and (ii) gelation of P and Ca. The nHAP particles were characterized using electron microscopy and XRD analysis. Powdered crystalline particles with a size range of 30±5 nm were obtained with shape and size dependent on phosphate concentrations. The particles showed no adverse effect on plant growth-promoting bacteria. Evaluation of nHAP prepared by this route with 2% P source provides scope for a wide range of applications, especially as a nano-fertilizer.
Research Interests:
Aquatic nanotoxicologists and ecotoxicologists have begun to identify the unique properties of the nanomaterials (NMs) that potentially affect the health of wildlife. In this review the scientific aims are to discuss the main challenges... more
Aquatic nanotoxicologists and ecotoxicologists have begun to identify the unique properties of the nanomaterials (NMs) that potentially affect the health of wildlife. In this review the scientific aims are to discuss the main challenges nanotoxicologists currently face in aquatic toxicity testing, including the transformations of NMs in aquatic test media (dissolution, aggregation and small molecule interactions), and modes of NM interference (optical interference, adsorption to assay components and generation of reactive oxygen species) on common toxicity assays. Three of the major OECD (Organisation for Economic Co-operation and Development) priority materials, titanium dioxide (TiO2), zinc oxide (ZnO) and silver (Ag) NMs, studied recently by the Natural Sciences and Engineering Research
Council of Canada (NSERC), National Research Council of Canada (NRC) and the Business Development Bank of Canada (BDC) Nanotechnology Initiative (NNBNI), a Canadian consortium, have been identified to cause both bulk effect, dissolution-based (i.e. free metal), or NM-specific toxicity in aquatic organisms. TiO2 NMs are most toxic to algae, with toxicity being NM size-dependent and principally associated with binding of the materials to the organism. Conversely, dissolution of Zn and Ag NMs and the subsequent release of their ionic metal counterparts appear to represent the primary mode of toxicity to aquatic organisms for these NMs. In recent years, our understanding of the toxicological
properties of these specific OECD relevant materials has increased significantly. Specifically, researchers have begun to alter their experimental design to identify the different behaviour of these materials as colloids and, by introducing appropriate controls and NM characterisation, aquatic nanotoxicologists are now beginning to possess a clearer understanding of the chemical and physical properties of these materials in solution, and how these materials may interact with organisms. Arming nanotoxicologists with this understanding, combined with knowledge of the physics,
chemistry and biology of these materials is essential for maintaining the accuracy of all future toxicological assessments.
Council of Canada (NSERC), National Research Council of Canada (NRC) and the Business Development Bank of Canada (BDC) Nanotechnology Initiative (NNBNI), a Canadian consortium, have been identified to cause both bulk effect, dissolution-based (i.e. free metal), or NM-specific toxicity in aquatic organisms. TiO2 NMs are most toxic to algae, with toxicity being NM size-dependent and principally associated with binding of the materials to the organism. Conversely, dissolution of Zn and Ag NMs and the subsequent release of their ionic metal counterparts appear to represent the primary mode of toxicity to aquatic organisms for these NMs. In recent years, our understanding of the toxicological
properties of these specific OECD relevant materials has increased significantly. Specifically, researchers have begun to alter their experimental design to identify the different behaviour of these materials as colloids and, by introducing appropriate controls and NM characterisation, aquatic nanotoxicologists are now beginning to possess a clearer understanding of the chemical and physical properties of these materials in solution, and how these materials may interact with organisms. Arming nanotoxicologists with this understanding, combined with knowledge of the physics,
chemistry and biology of these materials is essential for maintaining the accuracy of all future toxicological assessments.
Research Interests:
The silver ion (Ag+) is well documented to be a potent inhibitor of sodium (Na+) transport in fish. However, it has not been determined whether silver nanoparticles (Ag NPs) elicit this same effect and, if so, if the NP itself and/or the... more
The silver ion (Ag+) is well documented to be a potent inhibitor of sodium (Na+) transport in fish. However, it has not been determined whether silver nanoparticles (Ag NPs) elicit this same effect and, if so, if the NP itself and/or the dissociation of ionic Ag+ causes this effect. Citrate-capped Ag NPs were dialyzed in water to determine the dissolution rate of ionic Ag+ from the NPs and the maximum concentration of free Ag+ released from the NPs was used as a paired Ag+ control to distinguish NP effects from ionic
metal effects. The maximum concentration of ionic Ag+ released
from these NPs over 48 h was 0.02 μg l−1. Juvenile rainbow trout
were exposed to 1.0 mg l−1 citrate-capped Ag NPs and dialyzed
citrate-capped Ag NPs or 10 μg l−1 and 0.02 μg l−1 ionic Ag+ (as
AgNO3) as controls. Both nondialyzed and dialyzed Ag NPs and 10
μg l−1 ionic Ag+ significantly inhibited unidirectional Na+ influx by
over 50% but had no effect on unidirectional Na+ efflux. Na+,K+-ATPase was significantly inhibited by the Ag NPs with no discernible effect on carbonic anhydrase activity. This study is the first to show that sodium regulation is disrupted by the presence of citrate-capped Ag NPs, and the results suggest that there are nanospecific effects.
metal effects. The maximum concentration of ionic Ag+ released
from these NPs over 48 h was 0.02 μg l−1. Juvenile rainbow trout
were exposed to 1.0 mg l−1 citrate-capped Ag NPs and dialyzed
citrate-capped Ag NPs or 10 μg l−1 and 0.02 μg l−1 ionic Ag+ (as
AgNO3) as controls. Both nondialyzed and dialyzed Ag NPs and 10
μg l−1 ionic Ag+ significantly inhibited unidirectional Na+ influx by
over 50% but had no effect on unidirectional Na+ efflux. Na+,K+-ATPase was significantly inhibited by the Ag NPs with no discernible effect on carbonic anhydrase activity. This study is the first to show that sodium regulation is disrupted by the presence of citrate-capped Ag NPs, and the results suggest that there are nanospecific effects.
Research Interests:
A role for acid-sensing ion channels (ASICs) to serve as epithelial channels for Na uptake by the gill of freshwater rainbow trout was investigated. We found that the ASIC inhibitors 4,6-diamidino-2- phenylindole and diminazene decreased... more
A role for acid-sensing ion channels (ASICs) to serve as epithelial
channels for Na uptake by the gill of freshwater rainbow trout was
investigated. We found that the ASIC inhibitors 4,6-diamidino-2-
phenylindole and diminazene decreased Na uptake in adult rainbow trout in a dose-dependent manner, with IC50 values of 0.12 and 0.96 M, respectively. Furthermore, we cloned the trout ASIC1 and ASIC4 homologs and demonstrated that they are expressed differentially in the tissues of the rainbow trout, including gills and isolated mitochondrion-rich cells. Immunohistochemical analysis using custom-made anti-zASIC4.2 antibody and the Na-K-ATPase (alpha5-subunit) antibody demonstrated that the trout ASIC localizes to Na/K-ATPase-rich cells in the gill. Moreover, three-dimensional rendering of confocal micrographs demonstrated that ASIC is found in the apical region of mitochondrion-rich cells. We present a revised model whereby ASIC4 is proposed as one mechanism for Na uptake from dilute freshwater in the gill of rainbow trout.
channels for Na uptake by the gill of freshwater rainbow trout was
investigated. We found that the ASIC inhibitors 4,6-diamidino-2-
phenylindole and diminazene decreased Na uptake in adult rainbow trout in a dose-dependent manner, with IC50 values of 0.12 and 0.96 M, respectively. Furthermore, we cloned the trout ASIC1 and ASIC4 homologs and demonstrated that they are expressed differentially in the tissues of the rainbow trout, including gills and isolated mitochondrion-rich cells. Immunohistochemical analysis using custom-made anti-zASIC4.2 antibody and the Na-K-ATPase (alpha5-subunit) antibody demonstrated that the trout ASIC localizes to Na/K-ATPase-rich cells in the gill. Moreover, three-dimensional rendering of confocal micrographs demonstrated that ASIC is found in the apical region of mitochondrion-rich cells. We present a revised model whereby ASIC4 is proposed as one mechanism for Na uptake from dilute freshwater in the gill of rainbow trout.
Research Interests:
Acid-sensing ion channels (ASICs) are epithelial Na+ channels gated by external H+. Recently, it has been demonstrated that ASICs play a role in Na+ uptake in freshwater rainbow trout. Here, we investigate the potential involvement of... more
Acid-sensing ion channels (ASICs) are epithelial Na+ channels gated by external H+. Recently, it has been demonstrated that ASICs play a role in Na+ uptake in freshwater rainbow trout. Here, we investigate the potential involvement of ASICs in Na+ transport in another freshwater fish species, the zebrafish (Danio rerio). Using molecular and histological techniques we found that asic genes and the ASIC4.2 protein are expressed in the gill of adult zebrafish. Immunohistochemistry revealed that mitochondrion-rich cells positive for ASIC4.2 do not co-localize with Na+/K+-ATPase-rich cells, but co-localize with cells expressing vacuolar-type H+-ATPase. Furthermore, pharmacological inhibitors of ASIC and Na+/H+-exchanger significantly reduced uptake of Na+ in adult zebrafish exposed to low-Na+ media, but did not cause the same response in individuals exposed to ultra-low-Na+ water. Our results suggest that in adult zebrafish ASICs play a role in branchial Na+ uptake in media with low Na+ concentrations and that mechanisms used for Na+ uptake by zebrafish may depend on the Na+ concentration in the acclimation medium.
Research Interests:
Inorganic phosphate (Pi) is an essential nutrient for all organisms, but in seawater, Pi is a limiting nutrient. This study investigated the primary mechanisms of Pi uptake in Pacific hagfish (Eptatretus stoutii) using ex vivo... more
Inorganic phosphate (Pi) is an essential nutrient for all organisms, but in seawater, Pi is a limiting nutrient. This study investigated the primary mechanisms of Pi uptake in Pacific hagfish (Eptatretus
stoutii) using ex vivo physiological and molecular techniques. Hagfish were observed to have the capacity to absorb Pi from the environment into at least three epithelial surfaces: the intestine, skin, and gill. Pi uptake in all tissues was concentration dependent, and saturable Pi transport was observed in the skin and gill at 2.0 mmol/l Pi. Gill and intestinal Pi uptake was sodium dependent, but Pi uptake into the skin increased under low sodium conditions. Gill Pi transport exhibited an apparent affinity constant 0.23– 0.6 mmol/l Pi. A complete sequence of a type II sodium phosphate cotransporter (Slc34a) was obtained from the hagfish gill. Phylogenetic analysis of the hagfish Slc34a transporter indicates that it is earlier diverging than, and/or ancestral to, the other identified vertebrate Slc34a transporters (Slc34a1, Slc34a2, and Slc34a3). With the use of RT-PCR, the hagfish Slc34a transcript was detected in the intestine, skin, gill, and kidney, suggesting that this may be the transporter involved in Pi uptake into multiple epithelia in the hagfish. This is the first measurement of Pi
uptake across the gill or skin of any vertebrate animal and first sodium phosphate cotransporter identified in hagfish.
stoutii) using ex vivo physiological and molecular techniques. Hagfish were observed to have the capacity to absorb Pi from the environment into at least three epithelial surfaces: the intestine, skin, and gill. Pi uptake in all tissues was concentration dependent, and saturable Pi transport was observed in the skin and gill at 2.0 mmol/l Pi. Gill and intestinal Pi uptake was sodium dependent, but Pi uptake into the skin increased under low sodium conditions. Gill Pi transport exhibited an apparent affinity constant 0.23– 0.6 mmol/l Pi. A complete sequence of a type II sodium phosphate cotransporter (Slc34a) was obtained from the hagfish gill. Phylogenetic analysis of the hagfish Slc34a transporter indicates that it is earlier diverging than, and/or ancestral to, the other identified vertebrate Slc34a transporters (Slc34a1, Slc34a2, and Slc34a3). With the use of RT-PCR, the hagfish Slc34a transcript was detected in the intestine, skin, gill, and kidney, suggesting that this may be the transporter involved in Pi uptake into multiple epithelia in the hagfish. This is the first measurement of Pi
uptake across the gill or skin of any vertebrate animal and first sodium phosphate cotransporter identified in hagfish.
Research Interests:
After a meal, dogfish exhibit a metabolic alkalosis in the bloodstream and a marked excretion of basic equivalents across the gills to the external seawater. We used the H+, K+-ATPase pump inhibitor omeprazole to determine whether these... more
After a meal, dogfish exhibit a metabolic alkalosis in the bloodstream and a marked excretion of basic equivalents across the gills to the external seawater. We used the H+, K+-ATPase pump inhibitor omeprazole to determine whether these post-prandial alkaline tide events were linked to secretion of H+ (accompanied by Cl–) in the stomach. Sharks were fitted with indwelling stomach tubes for pretreatment with omeprazole (five doses of 5mg omeprazole perkilogram over 48 h) or comparable volumes of vehicle (saline containing 2% DMSO) and for sampling of gastric chyme. Fish were then fed an involuntary meal by means of the stomach tube consisting of minced flatfish muscle (2% of body mass) suspended in saline (4% of body mass total volume). Omeprazole pretreatment delayed the post-prandial acidification of the gastric chyme, slowed the rise in Cl– concentration of the chyme and altered the patterns of other ions, indicating inhibition of H+ and accompanying Cl– secretion. Omeprazole also greatly attenuated the rise in arterial pH and bicarbonate concentrations and reduced the net excretion of basic equivalents to the water by 56% over 48h. Arterial blood CO2 pressure (PaCO2) and plasma ions were not substantially altered. These results indicate that elevated gastric H+ secretion (as HCl) in the digestive process is the major cause of the systemic metabolic alkalosis and the accompanying rise in base excretion across the gills that constitute the alkaline tide in the dogfish.
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We have previously identified an unknown cell type in the gills of Murray cod affected with chronic ulcerative dermatopathy (CUD), a condition that causes severe erosion of epidermis surrounding cephalic and lateral line sensory canals.... more
We have previously identified an unknown cell type in the gills of Murray cod affected with chronic ulcerative dermatopathy (CUD), a condition that causes severe erosion of epidermis surrounding
cephalic and lateral line sensory canals. The condition arises in aquaculture facilities that utilize groundwater, with the cause of the condition suggested to be an unknown contaminant
(s). Light and transmission electron microscopy were used to characterize and quantify the unknown cells in CUD-affected Murray cod. The cells were identified as rodlet cells and were
characterized by their oval or round shape, basally located nucleus, thick fibrillar capsule surrounding the cell, and multiple rodlet sacs containing a central electron-dense core within the
cell. Rodlet cells were present in the gills, kidney and intestine of non-CUD-affected and CUD-affected Murray cod; however, differences in the numbers were observed between the groups of
fish. A significantly greater number of rodlet cells were observed in the gills and collecting ducts of CUD-affected fish. This is the first report of rodlet cells in Murray cod, and we suggest that the
increased rodlet cell numbers in CUD-affected Murray cod may be in response to unknown water contaminant(s) present in the groundwater that give rise to CUD.
cephalic and lateral line sensory canals. The condition arises in aquaculture facilities that utilize groundwater, with the cause of the condition suggested to be an unknown contaminant
(s). Light and transmission electron microscopy were used to characterize and quantify the unknown cells in CUD-affected Murray cod. The cells were identified as rodlet cells and were
characterized by their oval or round shape, basally located nucleus, thick fibrillar capsule surrounding the cell, and multiple rodlet sacs containing a central electron-dense core within the
cell. Rodlet cells were present in the gills, kidney and intestine of non-CUD-affected and CUD-affected Murray cod; however, differences in the numbers were observed between the groups of
fish. A significantly greater number of rodlet cells were observed in the gills and collecting ducts of CUD-affected fish. This is the first report of rodlet cells in Murray cod, and we suggest that the
increased rodlet cell numbers in CUD-affected Murray cod may be in response to unknown water contaminant(s) present in the groundwater that give rise to CUD.
Research Interests:
Chronic ulcerative dermatopathy (CUD) is a disfiguring condition affecting Murray cod cultured in untreated groundwater. This study sought to further investigate the possible etiology of the syndrome and determine whether groundwater... more
Chronic ulcerative dermatopathy (CUD) is a disfiguring condition affecting Murray cod cultured in untreated groundwater. This study sought to further investigate the possible etiology of the syndrome and determine whether groundwater pre-treatment could suppress the development of CUD in juvenile Murray cod.
Electrolyte enrichment or pre-treatment with UV irradiation delayed the onset of CUD. In contrast, preconditioning of groundwater either in a vegetated earthen pond or in the presence of artificial macrophytes drastically reduced both the incidence and severity of CUD, with more than 90% of fish exhibiting no visual signs. Haematology and blood parameters were assessed for future diagnostic potential, but no changes in
blood parameters were observed, even in advanced CUD-affected fish. This paper identified that the treatment of groundwater via an earthen pond and in the presence of an artificial macrophyte are two highly effective methods of preventing CUD arising in juvenile Murray cod.
Electrolyte enrichment or pre-treatment with UV irradiation delayed the onset of CUD. In contrast, preconditioning of groundwater either in a vegetated earthen pond or in the presence of artificial macrophytes drastically reduced both the incidence and severity of CUD, with more than 90% of fish exhibiting no visual signs. Haematology and blood parameters were assessed for future diagnostic potential, but no changes in
blood parameters were observed, even in advanced CUD-affected fish. This paper identified that the treatment of groundwater via an earthen pond and in the presence of an artificial macrophyte are two highly effective methods of preventing CUD arising in juvenile Murray cod.
Research Interests:
This study examined the osmoregulatory capability of Murray cod, Maccullochella peelii peelii, affected by chronic ulcerative dermatopathy (CUD) in intensive aquaculture. This condition appears to arise only in facilities utilizing... more
This study examined the osmoregulatory capability of Murray cod, Maccullochella peelii peelii, affected by chronic ulcerative dermatopathy (CUD) in intensive aquaculture. This condition appears to arise only in facilities utilizing groundwater, with the causative agent suggested to be a water-borne factor. Healthy
Murray cod (~700 g) were transferred to a CUD-affected farm to monitor the progression of the syndrome and began to show signs of CUD after approximately five months. In order to evaluate possible effects of CUD on osmoregulation; plasma electrolyte concentrations, osmolality, and Na+,K+-ATPase activities were
measured, and gill histology and immunohistochemistry were analyzed. Plasma electrolyte concentrations and osmolality of CUD-affected Murray cod were consistent with reference values determined for non CUDaffected fish. A greater number of gill mucous cells were observed in Murray cod cultured at the CUD-affected farm compared to non CUD-affected fish. We also found an un-identified cell type that was present solely in the gills of CUD-affected Murray cod. Gill Na+,K+-ATPase activity was significantly higher in severely CUDaffected Murray cod compared to individuals transferred to the CUD-affected farm. While there appeared to be some minor changes in the gills of CUD-affected fish, this study demonstrated that Murray cod were able to effectively osmoregulate, although, perhaps at an energetic cost.
Murray cod (~700 g) were transferred to a CUD-affected farm to monitor the progression of the syndrome and began to show signs of CUD after approximately five months. In order to evaluate possible effects of CUD on osmoregulation; plasma electrolyte concentrations, osmolality, and Na+,K+-ATPase activities were
measured, and gill histology and immunohistochemistry were analyzed. Plasma electrolyte concentrations and osmolality of CUD-affected Murray cod were consistent with reference values determined for non CUDaffected fish. A greater number of gill mucous cells were observed in Murray cod cultured at the CUD-affected farm compared to non CUD-affected fish. We also found an un-identified cell type that was present solely in the gills of CUD-affected Murray cod. Gill Na+,K+-ATPase activity was significantly higher in severely CUDaffected Murray cod compared to individuals transferred to the CUD-affected farm. While there appeared to be some minor changes in the gills of CUD-affected fish, this study demonstrated that Murray cod were able to effectively osmoregulate, although, perhaps at an energetic cost.