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Papers by Jodie Rummer

Journal of Experimental Biology, 2009

Journal of Experimental Biology, 2010

Journal of Experimental Biology, 2009

Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2008

We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-pr... more We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-protection against the stress associated with transfer from freshwater (FW) to seawater (SW) in juvenile rainbow trout (Oncorhynchus mykiss). In experimental Series I, juvenile trout reared in FW were transferred from 13.5 °C to 25.5 °C in FW, held for 2 h, returned to 13.5 °C for 12 h, and then transferred to 32 ppt SW at 13.5 °C. Branchial Hsp70 increased approximately 10-fold in the heat-shocked fish relative to the control by the end of recovery and remained high 2, 8, and 24 h post-salinity transfer. However, no clear differences could be detected in blood parameters (blood hemoglobin, hematocrit, MCHC, plasma Na+ and plasma osmolarity) or muscle water content between heat-shocked and sham-shocked fish in SW at any sampling interval (0, 2, 8, 24, 48, 120, 240 and 360 h post-SW transfer). In experimental Series II, trout acclimated to 8 °C were heat-shocked at 22 °C for 2 h, allowed to recover 18 h, and exposed to a more severe salinity transfer (either 36 or 45 ppt) than in Series I. Branchial Hsp70 levels increased approximately 6-fold in heat-shocked fish, but had declined to baseline after 120 h in SW. Plasma osmolarity and chloride increased in both groups upon transfer to 36 ppt; however, the increase was significantly less in heat-shocked fish when compared to the increase observed in sham-shocked fish at 24 h. No significant differences could be detected in branchial Na+/K+-ATPase activity or Na+/K+-ATPase α1a and α1b mRNA expression between the two groups. Our data indicate that a mild temperature shock has only modest effects on the ability of rainbow trout to resist osmotic stress during FW to SW transfer.

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2006

Many teleostean fish, including rainbow trout, regulate red blood cell (RBC) pH (pHi) in the pres... more Many teleostean fish, including rainbow trout, regulate red blood cell (RBC) pH (pHi) in the presence of a stress-induced acidosis such as hypoxia, hypercapnia, or exhaustive exercise. This is accomplished through activation of RBC Na+/H+ exchange (β-NHE), ultimately minimizing impairment to oxygen transport. Presence and characterization of the RBC β-NHE in fish is best tested in blood from cannulated, resting animals; however, several studies have used blood from stressed animals drawn from the caudal vein and stored prior to use. The effects of sampling procedures and storage on the β-NHE response is not known and is the focus of this study. Whole blood drawn from cannulated, resting rainbow trout was compared with RBCs obtained from the caudal vein rinsed and stored at 4 °C for 0, 6, 24, 48, 96 or 144 h. Isoproterenol (10− 5 M), a β-adrenergic agonist, was added to hypoxia/hypercapnia incubated RBCs in vitro. In all treatments, isoproterenol induced a large β-NHE response, and storage duration (≤ 96 h) had a minimal affect, indicating that rinsing and storing is an easy and viable means by which to obtain RBCs and investigate function. Storage for 144 h still resulted in a significant RBC β-NHE response; however, viability of RBCs may be compromised.

Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2008

We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-pr... more We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-protection against the stress associated with transfer from freshwater (FW) to seawater (SW) in juvenile rainbow trout (Oncorhynchus mykiss). In experimental Series I, juvenile trout reared in FW were transferred from 13.5°C to 25.5°C in FW, held for 2 h, returned to 13.5°C for 12 h, and then transferred to 32 ppt SW at 13.5°C. Branchial Hsp70 increased approximately 10-fold in the heat-shocked fish relative to the control by the end of recovery and remained high 2, 8, and 24 h post-salinity transfer. However, no clear differences could be detected in blood parameters (blood hemoglobin, hematocrit, MCHC, plasma Na + and plasma osmolarity) or muscle water content between heat-shocked and sham-shocked fish in SW at any sampling interval (0, 2, 8, 24, 48, 120, 240 and 360 h post-SW transfer). In experimental Series II, trout acclimated to 8°C were heat-shocked at 22°C for 2 h, allowed to recover 18 h, and exposed to a more severe salinity transfer (either 36 or 45 ppt) than in Series I. Branchial Hsp70 levels increased approximately 6-fold in heat-shocked fish, but had declined to baseline after 120 h in SW. Plasma osmolarity and chloride increased in both groups upon transfer to 36 ppt; however, the increase was significantly less in heat-shocked fish when compared to the increase observed in shamshocked fish at 24 h. No significant differences could be detected in branchial Na + /K + -ATPase activity or Na + /K + -ATPase α1a and α1b mRNA expression between the two groups. Our data indicate that a mild temperature shock has only modest effects on the ability of rainbow trout to resist osmotic stress during FW to SW transfer.

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2008

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2008

Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2010

Tunas (family Scombridae) are exceptional among most teleost fishes in that they possess vascular... more Tunas (family Scombridae) are exceptional among most teleost fishes in that they possess vascular heat exchangers which allow heat retention in specific regions of the body (termed ‘regional heterothermy’). Seemingly exclusive to heterothermic fishes is a markedly reduced temperature dependence of blood–oxygen (blood–O2) binding, or even a reversed temperature dependence where increasing temperature increases blood–O2 affinity. These unusual binding properties have been documented in whole blood and in haemoglobin (Hb) solutions, and they are hypothesised to prevent oxygen loss from arteries to veins within the vascular heat exchangers and/or to prevent excessive oxygen unloading to the warm tissues and ensure an adequate supply of oxygen to tissues positioned efferent to the heat exchangers. The temperature sensitivity of blood–O2 binding has not been characterised in an ectothermic scombrid (mackerels and bonitos), but the existence of the unusual binding properties in these fishes would have clear implications for their proposed association with regional heterothermy. Accordingly, the present study examined oxygenation of whole blood of the chub mackerel (Scomber japonicus) at 10, 20 and 30°C and at 0.5, 1 and 2% CO2. Oxygen affinity was generally highest at 20°C for all levels of CO2. Temperature-independent binding was observed at low (0.5%) CO2, where the PO2 at 50% blood–O2 saturation (P 50) was not statistically different at 10 and 30°C (2.58 vs. 2.78 kPa, respectively) with an apparent heat of oxygenation (∆H°) close to zero (−6 kJ mol−1). The most significant temperature-mediated difference occurred at high (2%) CO2, where the P 50 at 10°C was twofold higher than that at 20°C with a corresponding ∆H° of +43 kJ mol−1. These results provide clear evidence of independent and reversed open-system temperature effects on blood oxygenation in S. japonicus, and it is therefore speculated that these unusual blood–O2 binding characteristics may have preceded the evolution of vascular heat exchangers and regional heterothermy in fishes.

Journal of Experimental Biology, 2010

Like most teleosts, sablefish (Anoplopoma fimbria Pallas 1814) blood exhibits a moderate Root eff... more Like most teleosts, sablefish (Anoplopoma fimbria Pallas 1814) blood exhibits a moderate Root effect (~35% maximal desaturation), where a reduction in blood pH dramatically reduces O(2) carrying capacity, a mechanism important for oxygenating the eye and filling the swim bladder (SB) in teleosts. Although sablefish lack a SB, we observed a well-defined choroid rete at the eye. The adrenergically mediated cell swelling typically associated with a functional red blood cell (RBC) beta-adrenergic Na(+)/H(+) exchanger (betaNHE), which would normally protect RBC pH, and thus O(2) transport, during a generalized acidosis, was not observed in sablefish blood. Neither isoproterenol (a beta-agonist) nor 8-bromo cAMP could elicit this response. Furthermore, RBC osmotic shrinkage, known to stimulate NHEs in general and betaNHE in other teleosts such as trout and flounder, resulted in no significant regulatory volume increase (RVI), further supporting the absence of a functional RBC betaNHE. The onset of the Root effect occurs at a much lower RBC pH (6.83-6.92) than in other teleosts, and thus RBC betaNHE may not be required to protect O(2) transport during a generalized acidosis in vivo. Phylogenetically, sablefish may represent a fifth group of teleosts exhibiting a secondary reduction or loss of betaNHE activity. However, sablefish have not lost the choroid rete at the eye (unlike in the other four groups), which may still function with the Root effect to oxygenate the retina, but the low pH onset of the Root effect may ensure haemoglobin (Hb)-O(2) binding is not compromised at the respiratory surface during a general acidosis in the absence of RBC betaNHE. The sablefish may represent an anomaly within the framework of Root effect evolution, in that they possess a moderate Root effect and a choroid rete at the eye, but lack the RBC betaNHE and the SB system.

Journal of Experimental Biology, 2009

Journal of Experimental Biology, 2010

Journal of Experimental Biology, 2009

Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2008

We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-pr... more We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-protection against the stress associated with transfer from freshwater (FW) to seawater (SW) in juvenile rainbow trout (Oncorhynchus mykiss). In experimental Series I, juvenile trout reared in FW were transferred from 13.5 °C to 25.5 °C in FW, held for 2 h, returned to 13.5 °C for 12 h, and then transferred to 32 ppt SW at 13.5 °C. Branchial Hsp70 increased approximately 10-fold in the heat-shocked fish relative to the control by the end of recovery and remained high 2, 8, and 24 h post-salinity transfer. However, no clear differences could be detected in blood parameters (blood hemoglobin, hematocrit, MCHC, plasma Na+ and plasma osmolarity) or muscle water content between heat-shocked and sham-shocked fish in SW at any sampling interval (0, 2, 8, 24, 48, 120, 240 and 360 h post-SW transfer). In experimental Series II, trout acclimated to 8 °C were heat-shocked at 22 °C for 2 h, allowed to recover 18 h, and exposed to a more severe salinity transfer (either 36 or 45 ppt) than in Series I. Branchial Hsp70 levels increased approximately 6-fold in heat-shocked fish, but had declined to baseline after 120 h in SW. Plasma osmolarity and chloride increased in both groups upon transfer to 36 ppt; however, the increase was significantly less in heat-shocked fish when compared to the increase observed in sham-shocked fish at 24 h. No significant differences could be detected in branchial Na+/K+-ATPase activity or Na+/K+-ATPase α1a and α1b mRNA expression between the two groups. Our data indicate that a mild temperature shock has only modest effects on the ability of rainbow trout to resist osmotic stress during FW to SW transfer.

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2006

Many teleostean fish, including rainbow trout, regulate red blood cell (RBC) pH (pHi) in the pres... more Many teleostean fish, including rainbow trout, regulate red blood cell (RBC) pH (pHi) in the presence of a stress-induced acidosis such as hypoxia, hypercapnia, or exhaustive exercise. This is accomplished through activation of RBC Na+/H+ exchange (β-NHE), ultimately minimizing impairment to oxygen transport. Presence and characterization of the RBC β-NHE in fish is best tested in blood from cannulated, resting animals; however, several studies have used blood from stressed animals drawn from the caudal vein and stored prior to use. The effects of sampling procedures and storage on the β-NHE response is not known and is the focus of this study. Whole blood drawn from cannulated, resting rainbow trout was compared with RBCs obtained from the caudal vein rinsed and stored at 4 °C for 0, 6, 24, 48, 96 or 144 h. Isoproterenol (10− 5 M), a β-adrenergic agonist, was added to hypoxia/hypercapnia incubated RBCs in vitro. In all treatments, isoproterenol induced a large β-NHE response, and storage duration (≤ 96 h) had a minimal affect, indicating that rinsing and storing is an easy and viable means by which to obtain RBCs and investigate function. Storage for 144 h still resulted in a significant RBC β-NHE response; however, viability of RBCs may be compromised.

Comparative Biochemistry and Physiology C-toxicology & Pharmacology, 2008

We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-pr... more We have investigated whether mild heat shock, and resulting Hsp70 expression, can confer cross-protection against the stress associated with transfer from freshwater (FW) to seawater (SW) in juvenile rainbow trout (Oncorhynchus mykiss). In experimental Series I, juvenile trout reared in FW were transferred from 13.5°C to 25.5°C in FW, held for 2 h, returned to 13.5°C for 12 h, and then transferred to 32 ppt SW at 13.5°C. Branchial Hsp70 increased approximately 10-fold in the heat-shocked fish relative to the control by the end of recovery and remained high 2, 8, and 24 h post-salinity transfer. However, no clear differences could be detected in blood parameters (blood hemoglobin, hematocrit, MCHC, plasma Na + and plasma osmolarity) or muscle water content between heat-shocked and sham-shocked fish in SW at any sampling interval (0, 2, 8, 24, 48, 120, 240 and 360 h post-SW transfer). In experimental Series II, trout acclimated to 8°C were heat-shocked at 22°C for 2 h, allowed to recover 18 h, and exposed to a more severe salinity transfer (either 36 or 45 ppt) than in Series I. Branchial Hsp70 levels increased approximately 6-fold in heat-shocked fish, but had declined to baseline after 120 h in SW. Plasma osmolarity and chloride increased in both groups upon transfer to 36 ppt; however, the increase was significantly less in heat-shocked fish when compared to the increase observed in shamshocked fish at 24 h. No significant differences could be detected in branchial Na + /K + -ATPase activity or Na + /K + -ATPase α1a and α1b mRNA expression between the two groups. Our data indicate that a mild temperature shock has only modest effects on the ability of rainbow trout to resist osmotic stress during FW to SW transfer.

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2008

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2008

Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2010

Tunas (family Scombridae) are exceptional among most teleost fishes in that they possess vascular... more Tunas (family Scombridae) are exceptional among most teleost fishes in that they possess vascular heat exchangers which allow heat retention in specific regions of the body (termed ‘regional heterothermy’). Seemingly exclusive to heterothermic fishes is a markedly reduced temperature dependence of blood–oxygen (blood–O2) binding, or even a reversed temperature dependence where increasing temperature increases blood–O2 affinity. These unusual binding properties have been documented in whole blood and in haemoglobin (Hb) solutions, and they are hypothesised to prevent oxygen loss from arteries to veins within the vascular heat exchangers and/or to prevent excessive oxygen unloading to the warm tissues and ensure an adequate supply of oxygen to tissues positioned efferent to the heat exchangers. The temperature sensitivity of blood–O2 binding has not been characterised in an ectothermic scombrid (mackerels and bonitos), but the existence of the unusual binding properties in these fishes would have clear implications for their proposed association with regional heterothermy. Accordingly, the present study examined oxygenation of whole blood of the chub mackerel (Scomber japonicus) at 10, 20 and 30°C and at 0.5, 1 and 2% CO2. Oxygen affinity was generally highest at 20°C for all levels of CO2. Temperature-independent binding was observed at low (0.5%) CO2, where the PO2 at 50% blood–O2 saturation (P 50) was not statistically different at 10 and 30°C (2.58 vs. 2.78 kPa, respectively) with an apparent heat of oxygenation (∆H°) close to zero (−6 kJ mol−1). The most significant temperature-mediated difference occurred at high (2%) CO2, where the P 50 at 10°C was twofold higher than that at 20°C with a corresponding ∆H° of +43 kJ mol−1. These results provide clear evidence of independent and reversed open-system temperature effects on blood oxygenation in S. japonicus, and it is therefore speculated that these unusual blood–O2 binding characteristics may have preceded the evolution of vascular heat exchangers and regional heterothermy in fishes.

Journal of Experimental Biology, 2010

Like most teleosts, sablefish (Anoplopoma fimbria Pallas 1814) blood exhibits a moderate Root eff... more Like most teleosts, sablefish (Anoplopoma fimbria Pallas 1814) blood exhibits a moderate Root effect (~35% maximal desaturation), where a reduction in blood pH dramatically reduces O(2) carrying capacity, a mechanism important for oxygenating the eye and filling the swim bladder (SB) in teleosts. Although sablefish lack a SB, we observed a well-defined choroid rete at the eye. The adrenergically mediated cell swelling typically associated with a functional red blood cell (RBC) beta-adrenergic Na(+)/H(+) exchanger (betaNHE), which would normally protect RBC pH, and thus O(2) transport, during a generalized acidosis, was not observed in sablefish blood. Neither isoproterenol (a beta-agonist) nor 8-bromo cAMP could elicit this response. Furthermore, RBC osmotic shrinkage, known to stimulate NHEs in general and betaNHE in other teleosts such as trout and flounder, resulted in no significant regulatory volume increase (RVI), further supporting the absence of a functional RBC betaNHE. The onset of the Root effect occurs at a much lower RBC pH (6.83-6.92) than in other teleosts, and thus RBC betaNHE may not be required to protect O(2) transport during a generalized acidosis in vivo. Phylogenetically, sablefish may represent a fifth group of teleosts exhibiting a secondary reduction or loss of betaNHE activity. However, sablefish have not lost the choroid rete at the eye (unlike in the other four groups), which may still function with the Root effect to oxygenate the retina, but the low pH onset of the Root effect may ensure haemoglobin (Hb)-O(2) binding is not compromised at the respiratory surface during a general acidosis in the absence of RBC betaNHE. The sablefish may represent an anomaly within the framework of Root effect evolution, in that they possess a moderate Root effect and a choroid rete at the eye, but lack the RBC betaNHE and the SB system.