Brian McMahon | University of Calgary (original) (raw)
Papers by Brian McMahon
This study was conducted to determine long-term toxic effects, on selected species of fish and in... more This study was conducted to determine long-term toxic effects, on selected species of fish and invertebrates, of mine depressurization at concentrations non-lethal in acute toxicity tests. The study also includes chronic toxicity experiments, studies of sublethal effects of groundwater, and a 1 iterature review. The results of groundwater monitoring indicate that during 6 mo of storage, there was a decl ine in concentration of almost all chemical parameters tested. However, in contrast to previous studies, some heavy metals (iron, lead, nickel, and zinc) showed an increase in concentration with storage time. Mine depressurization groundwater was acutely toxic to the three species of invertebrates tested. The 96 h LC so for the two mayfly species, Caenis simuZans and ParaZeptophZebia cornuta, was N a All concentrations are expressed in mg/L unless otherwise stated. b NA-not availab1e.
Cambridge University Press eBooks, Apr 29, 1988
Journal of Neurophysiology, 2002
The cellular mechanisms that determine specificity of synaptic connections between mutually conne... more The cellular mechanisms that determine specificity of synaptic connections between mutually connected neurons in the nervous system have not yet been fully examined in vertebrate and invertebrate species. Here we report on a novel form of synaptic interaction during early stages of synapse formation between reciprocally connected Lymnaea neurons. Specifically, using soma-soma synapses between an identified dopaminergic neuron (also known as the giant dopamine cell), right pedal dorsal 1 (RPeD1), and a FMRFamidergic neuron, visceral dorsal 4 (VD4), we demonstrate that although reciprocal inhibitory synapses re-form between the somata after 24–36 h of pairing, VD4 is, however, the first cell to establish synaptic contacts with RPeD1 (within 12–18 h). We show that VD4 “captures” RPeD1 first as a postsynaptic cell by suppressing its transmitter secretory machinery during early stages of cell-cell pairing. The VD4-induced suppression of transmitter release from RPeD1 was transient, and i...
Canadian Journal of Zoology, 1983
Renal function was investigated in the stenohaline Catostomus commersoni held at water pH 7.3 for... more Renal function was investigated in the stenohaline Catostomus commersoni held at water pH 7.3 for 5 days. Urine displayed remarkably low levels of Na+, Cl−, K+, Ca2+, and Mg2+ and was very acidic (mean pH 6.5). Renal electrolyte conservation was characterized by almost complete reabsorption of NaCl and to a lesser degree, K+, Ca2+, and Mg2+. Net H+ excretion was + 11.2 μequiv∙kg−1∙h−1, resulting primarily from a high titratable acid content. The physiological consequences of exposure to ambient pH 4.3 for 4 days included disturbances in plasma acid–base status with relatively minor changes in both plasma ion levels and renal output (E). A mixed metabolic and respiratory acidosis developed, which was not compensated for by increased renal H+ excretion. Both plasma NaCl levels and ENa+ decreased but ECl− remained unchanged. EK+ was correlated with plasma hyperkalemia. No changes in plasma levels or excretion of Ca2+ or Mg2+ occurred. These findings provide some physiological evidence ...
Journal of Experimental Biology, 1969
Recent palaeontological evidence (Jarvik, 1967; White, 1966) indicates that the Dipnoi should be ... more Recent palaeontological evidence (Jarvik, 1967; White, 1966) indicates that the Dipnoi should be regarded as a specialized group of fishes, which have been structurally different from the Rhipidistia (now thought to have included the prototetrapods) for as long as the fossil record can yet show. However, the homology of the dipnoan lung with that of the tetrapod, and the similarities of organization and development between living Dipnoi and Amphibia, might indicate a closer relationship between the two groups than can be revealed by palaeontological studies. The level of organization seen in the living Dipnoi is not thought to be basically different from that of the Devonian forms and a study of the physiology of these animals must expand our knowledge of the development of vertebrate physiological mechanisms. Since the Dipnoi are adapted to a habitat very similar to that in which the first terrestrial verte-brates are thought to have evolved, and since they possess functional aeria...
Journal of Experimental Biology, 1979
Enforced activity causes a marked depression of haemolymph pH in Cancer magister. Both lactate co... more Enforced activity causes a marked depression of haemolymph pH in Cancer magister. Both lactate concentration and PCO2 of the haemolymph are elevated immediately following exercise but resting PCO2 is restored within 30 min whereas resting lactate levels are not restored for at least 8 h. The haemolymph acid-base disturbance is caused largely by elevated haemolymph lactate levels but a Davenport analysis based on measurements of pH and total CO2 reveals a marked discrepancy between the amount of metabolic acid buffered by the haemolymph and the lactate anion concentration. This appears due to a more rapid release of lactate from the tissues than H+ ions produced with lactate.
Journal of Experimental Biology, 1982
Acid-toxicity tests were performed using two crayfish species, Procambarus clarki Girard and Orco... more Acid-toxicity tests were performed using two crayfish species, Procambarus clarki Girard and Orconectes rusticus Girard to determine the median lethal pH (LC5O) after 4 days exposure to acid. Four-day LC50 values of pH 2*5-2-8 were observed, indicating that these animals are more acid-tolerant than most fish species. Haemolymph acid-base variables and major ion concentrations were measured during 4 days exposure of P. clarki to sublethal acid H2SO4, pH 3-8) levels. A major haemolymph acidosis was observed. While minimal changes were seen in haemolymph [Cl−], [K+], and [Mg2+], haemolymph [Na+] decreased. Haemolymph [Ca2+] increased significantly during acid exposure, suggesting that dissolution of exoskeletal carbonate buffers was being employed as a compensatory mechanism for the acidosis; this process would be expected to contribute to exoskeletal rigidity problems in the long term.
Journal of Experimental Biology, 1982
Severe experimental anaemia caused a rise in Pcoco2 and an associated fall in pH (respiratory aci... more Severe experimental anaemia caused a rise in Pcoco2 and an associated fall in pH (respiratory acidosis) in arterial and venous blood of both flounder and trout in vivo. In some trout, but not in flounder, there was also a rise in blood lactate, indicating metabolic acidosis. In vitro, blood buffer capacities declined with haematocrit, a factor which contributed to the extent of the acidoses in vivo. However, haematocrit did not influence the pK1 of the plasma HCO3−/H2CO3 system or the actual measurement of blood pH. The Donnan ratio for HCO3− varied linearly with pH over the range 7.0–7.6, indicating a passive distribution of HCO3− across the trout erythrocyte. The present data, together with other recent results, indicate that the teleost red blood cell does play a role in plasma HCO3− dehydration and CO2 excretion, and therefore opposes the theory of Haswell & Randall (1978) that the erythrocyte is functionally impermeable to HCO3−.
Journal of Crustacean Biology, 1999
The effects of GABA and two inhibitory neuropeptides were tested on the cardiovascular system of ... more The effects of GABA and two inhibitory neuropeptides were tested on the cardiovascular system of intact Cancer magister. A pulsed-Doppler flow meter was used to record heart rate and hemolymph flow rates through each arterial system in C. magister. Summation of arterial flow rates gave a value for cardiac output, and division of this by rate yielded stroke volume of the heart. The insect neuropeptides SchistoFLRFamide and leucomyosuppressin and the neurotransmitter Y-aminobutyric acid (GABA) were infused into the pericardial sinus of the crab so as to achieve final circulating concentrations between 10 12 mol�l1 and 105 mol�l-1. Both SchistoFLRFamide and leucomyosuppressin had similar effects. Neither hormone had an effect on heart rate, but stroke volume was significantly depressed, leading to a decrease in total cardiac output. Hemolymph flow through the sternal artery and anterolateral artery decreased. Effects on flow through the posterior and anterior aortae were slight and variable, while flow through the hepatic arteries remained stable. Threshold for these responses occurred at circulating concentrations of 10 8 mol�l 1 and above, and the effects of SchistoFLRFamide were of longer duration compared with those induced by leucomyosuppressin. These peptides may play a role in digestion during quiescent periods, by diverting hemolymph away from locomotory structures and toward the digestive glands. GABA induced a large bradycardia with related decrease in flows, but induced no differential effects on flow through any arterial system. Effects of GABA were of short duration, with both heart rate and flows recovering quickly after infusion. Effects were seen at circulating concentrations of 10-6 mol�l-1 and above. All these substances are reported to have inhibitory effects on isolated or semi-isolated heart preparations. Inhibition of stroke volume (by the peptides) was seen in the in vivo preparations used here, but heart rate was unaffected. Thus, opposing effects of "cardioactive" hormones, previously reported between in vitro and in vivo preparations is not consistent, and is dependent on the actual hormone and the pathway it acts upon in modulating cardiac activity.
Animal Behaviour, 1989
Page 1. Biology of the Land Crabs Warren W. Burggre, and Brian R. McMaho, Page 2. Biology of the ... more Page 1. Biology of the Land Crabs Warren W. Burggre, and Brian R. McMaho, Page 2. Biology of the Land Crabs Interest in land crabs l1as burgeoned in reecm vcars. .1s biologists have incrcasinglv Iod1sed on 11 1t-cvolulion of Ic I rcst1 ialitv. ...
Journal of Experimental Biology
The effects of exposure to 0.94% (300 mosmol1−1) sodium chloride on plasma electrolyte and acid-b... more The effects of exposure to 0.94% (300 mosmol1−1) sodium chloride on plasma electrolyte and acid-base status were examined in the freshwater stenohaline teleost Catostomus commersoni (Lacépède), the white sucker. Four days' exposure to this maximum sublethal salinity resulted in an increase in plasma concentrations of both sodium and chloride but a decrease in the Na+/Cl− ratio. Since the plasma concentrations of free amino acids and other strong ions - Ca2+, Mg2+ and K+ - remained unchanged, plasma strong ion difference (SID) decreased. Additionally, plasma pH and bicarbonate concentration decreased at constant Pcoco2 The changes in electrolyte and acid-base status that occurred after the 96 h were not appreciably altered after a further 2–3 weeks of saline exposure. The ambient calcium concentration had no influence on these results. Haemolymph non-bicarbonate buffer capacity (β) calculated as Δ[HCO3−]/ ΔpH, increased in saline-exposed fish. Consequently ΔH+, the apparent proto...
Comparative Biochemistry and Physiology Part A: Physiology
... Telephone: (604) 728-3301; Fax: (604) 728-3452; School of Biological Sciences, University ofS... more ... Telephone: (604) 728-3301; Fax: (604) 728-3452; School of Biological Sciences, University ofSydney, Sydney, New South Wales, Australia ... have not previously been determined, but other inorganic ions (eg calcium, magnesium, chloride and hydrogen; Mangum, 1980, 1983 ...
Zoological Science, Dec 25, 2004
Molecules to Organisms, 1998
Biology of the Lobster, 1995
Biology of the Land Crabs, 1988
This study was conducted to determine long-term toxic effects, on selected species of fish and in... more This study was conducted to determine long-term toxic effects, on selected species of fish and invertebrates, of mine depressurization at concentrations non-lethal in acute toxicity tests. The study also includes chronic toxicity experiments, studies of sublethal effects of groundwater, and a 1 iterature review. The results of groundwater monitoring indicate that during 6 mo of storage, there was a decl ine in concentration of almost all chemical parameters tested. However, in contrast to previous studies, some heavy metals (iron, lead, nickel, and zinc) showed an increase in concentration with storage time. Mine depressurization groundwater was acutely toxic to the three species of invertebrates tested. The 96 h LC so for the two mayfly species, Caenis simuZans and ParaZeptophZebia cornuta, was N a All concentrations are expressed in mg/L unless otherwise stated. b NA-not availab1e.
Cambridge University Press eBooks, Apr 29, 1988
Journal of Neurophysiology, 2002
The cellular mechanisms that determine specificity of synaptic connections between mutually conne... more The cellular mechanisms that determine specificity of synaptic connections between mutually connected neurons in the nervous system have not yet been fully examined in vertebrate and invertebrate species. Here we report on a novel form of synaptic interaction during early stages of synapse formation between reciprocally connected Lymnaea neurons. Specifically, using soma-soma synapses between an identified dopaminergic neuron (also known as the giant dopamine cell), right pedal dorsal 1 (RPeD1), and a FMRFamidergic neuron, visceral dorsal 4 (VD4), we demonstrate that although reciprocal inhibitory synapses re-form between the somata after 24–36 h of pairing, VD4 is, however, the first cell to establish synaptic contacts with RPeD1 (within 12–18 h). We show that VD4 “captures” RPeD1 first as a postsynaptic cell by suppressing its transmitter secretory machinery during early stages of cell-cell pairing. The VD4-induced suppression of transmitter release from RPeD1 was transient, and i...
Canadian Journal of Zoology, 1983
Renal function was investigated in the stenohaline Catostomus commersoni held at water pH 7.3 for... more Renal function was investigated in the stenohaline Catostomus commersoni held at water pH 7.3 for 5 days. Urine displayed remarkably low levels of Na+, Cl−, K+, Ca2+, and Mg2+ and was very acidic (mean pH 6.5). Renal electrolyte conservation was characterized by almost complete reabsorption of NaCl and to a lesser degree, K+, Ca2+, and Mg2+. Net H+ excretion was + 11.2 μequiv∙kg−1∙h−1, resulting primarily from a high titratable acid content. The physiological consequences of exposure to ambient pH 4.3 for 4 days included disturbances in plasma acid–base status with relatively minor changes in both plasma ion levels and renal output (E). A mixed metabolic and respiratory acidosis developed, which was not compensated for by increased renal H+ excretion. Both plasma NaCl levels and ENa+ decreased but ECl− remained unchanged. EK+ was correlated with plasma hyperkalemia. No changes in plasma levels or excretion of Ca2+ or Mg2+ occurred. These findings provide some physiological evidence ...
Journal of Experimental Biology, 1969
Recent palaeontological evidence (Jarvik, 1967; White, 1966) indicates that the Dipnoi should be ... more Recent palaeontological evidence (Jarvik, 1967; White, 1966) indicates that the Dipnoi should be regarded as a specialized group of fishes, which have been structurally different from the Rhipidistia (now thought to have included the prototetrapods) for as long as the fossil record can yet show. However, the homology of the dipnoan lung with that of the tetrapod, and the similarities of organization and development between living Dipnoi and Amphibia, might indicate a closer relationship between the two groups than can be revealed by palaeontological studies. The level of organization seen in the living Dipnoi is not thought to be basically different from that of the Devonian forms and a study of the physiology of these animals must expand our knowledge of the development of vertebrate physiological mechanisms. Since the Dipnoi are adapted to a habitat very similar to that in which the first terrestrial verte-brates are thought to have evolved, and since they possess functional aeria...
Journal of Experimental Biology, 1979
Enforced activity causes a marked depression of haemolymph pH in Cancer magister. Both lactate co... more Enforced activity causes a marked depression of haemolymph pH in Cancer magister. Both lactate concentration and PCO2 of the haemolymph are elevated immediately following exercise but resting PCO2 is restored within 30 min whereas resting lactate levels are not restored for at least 8 h. The haemolymph acid-base disturbance is caused largely by elevated haemolymph lactate levels but a Davenport analysis based on measurements of pH and total CO2 reveals a marked discrepancy between the amount of metabolic acid buffered by the haemolymph and the lactate anion concentration. This appears due to a more rapid release of lactate from the tissues than H+ ions produced with lactate.
Journal of Experimental Biology, 1982
Acid-toxicity tests were performed using two crayfish species, Procambarus clarki Girard and Orco... more Acid-toxicity tests were performed using two crayfish species, Procambarus clarki Girard and Orconectes rusticus Girard to determine the median lethal pH (LC5O) after 4 days exposure to acid. Four-day LC50 values of pH 2*5-2-8 were observed, indicating that these animals are more acid-tolerant than most fish species. Haemolymph acid-base variables and major ion concentrations were measured during 4 days exposure of P. clarki to sublethal acid H2SO4, pH 3-8) levels. A major haemolymph acidosis was observed. While minimal changes were seen in haemolymph [Cl−], [K+], and [Mg2+], haemolymph [Na+] decreased. Haemolymph [Ca2+] increased significantly during acid exposure, suggesting that dissolution of exoskeletal carbonate buffers was being employed as a compensatory mechanism for the acidosis; this process would be expected to contribute to exoskeletal rigidity problems in the long term.
Journal of Experimental Biology, 1982
Severe experimental anaemia caused a rise in Pcoco2 and an associated fall in pH (respiratory aci... more Severe experimental anaemia caused a rise in Pcoco2 and an associated fall in pH (respiratory acidosis) in arterial and venous blood of both flounder and trout in vivo. In some trout, but not in flounder, there was also a rise in blood lactate, indicating metabolic acidosis. In vitro, blood buffer capacities declined with haematocrit, a factor which contributed to the extent of the acidoses in vivo. However, haematocrit did not influence the pK1 of the plasma HCO3−/H2CO3 system or the actual measurement of blood pH. The Donnan ratio for HCO3− varied linearly with pH over the range 7.0–7.6, indicating a passive distribution of HCO3− across the trout erythrocyte. The present data, together with other recent results, indicate that the teleost red blood cell does play a role in plasma HCO3− dehydration and CO2 excretion, and therefore opposes the theory of Haswell & Randall (1978) that the erythrocyte is functionally impermeable to HCO3−.
Journal of Crustacean Biology, 1999
The effects of GABA and two inhibitory neuropeptides were tested on the cardiovascular system of ... more The effects of GABA and two inhibitory neuropeptides were tested on the cardiovascular system of intact Cancer magister. A pulsed-Doppler flow meter was used to record heart rate and hemolymph flow rates through each arterial system in C. magister. Summation of arterial flow rates gave a value for cardiac output, and division of this by rate yielded stroke volume of the heart. The insect neuropeptides SchistoFLRFamide and leucomyosuppressin and the neurotransmitter Y-aminobutyric acid (GABA) were infused into the pericardial sinus of the crab so as to achieve final circulating concentrations between 10 12 mol�l1 and 105 mol�l-1. Both SchistoFLRFamide and leucomyosuppressin had similar effects. Neither hormone had an effect on heart rate, but stroke volume was significantly depressed, leading to a decrease in total cardiac output. Hemolymph flow through the sternal artery and anterolateral artery decreased. Effects on flow through the posterior and anterior aortae were slight and variable, while flow through the hepatic arteries remained stable. Threshold for these responses occurred at circulating concentrations of 10 8 mol�l 1 and above, and the effects of SchistoFLRFamide were of longer duration compared with those induced by leucomyosuppressin. These peptides may play a role in digestion during quiescent periods, by diverting hemolymph away from locomotory structures and toward the digestive glands. GABA induced a large bradycardia with related decrease in flows, but induced no differential effects on flow through any arterial system. Effects of GABA were of short duration, with both heart rate and flows recovering quickly after infusion. Effects were seen at circulating concentrations of 10-6 mol�l-1 and above. All these substances are reported to have inhibitory effects on isolated or semi-isolated heart preparations. Inhibition of stroke volume (by the peptides) was seen in the in vivo preparations used here, but heart rate was unaffected. Thus, opposing effects of "cardioactive" hormones, previously reported between in vitro and in vivo preparations is not consistent, and is dependent on the actual hormone and the pathway it acts upon in modulating cardiac activity.
Animal Behaviour, 1989
Page 1. Biology of the Land Crabs Warren W. Burggre, and Brian R. McMaho, Page 2. Biology of the ... more Page 1. Biology of the Land Crabs Warren W. Burggre, and Brian R. McMaho, Page 2. Biology of the Land Crabs Interest in land crabs l1as burgeoned in reecm vcars. .1s biologists have incrcasinglv Iod1sed on 11 1t-cvolulion of Ic I rcst1 ialitv. ...
Journal of Experimental Biology
The effects of exposure to 0.94% (300 mosmol1−1) sodium chloride on plasma electrolyte and acid-b... more The effects of exposure to 0.94% (300 mosmol1−1) sodium chloride on plasma electrolyte and acid-base status were examined in the freshwater stenohaline teleost Catostomus commersoni (Lacépède), the white sucker. Four days' exposure to this maximum sublethal salinity resulted in an increase in plasma concentrations of both sodium and chloride but a decrease in the Na+/Cl− ratio. Since the plasma concentrations of free amino acids and other strong ions - Ca2+, Mg2+ and K+ - remained unchanged, plasma strong ion difference (SID) decreased. Additionally, plasma pH and bicarbonate concentration decreased at constant Pcoco2 The changes in electrolyte and acid-base status that occurred after the 96 h were not appreciably altered after a further 2–3 weeks of saline exposure. The ambient calcium concentration had no influence on these results. Haemolymph non-bicarbonate buffer capacity (β) calculated as Δ[HCO3−]/ ΔpH, increased in saline-exposed fish. Consequently ΔH+, the apparent proto...
Comparative Biochemistry and Physiology Part A: Physiology
... Telephone: (604) 728-3301; Fax: (604) 728-3452; School of Biological Sciences, University ofS... more ... Telephone: (604) 728-3301; Fax: (604) 728-3452; School of Biological Sciences, University ofSydney, Sydney, New South Wales, Australia ... have not previously been determined, but other inorganic ions (eg calcium, magnesium, chloride and hydrogen; Mangum, 1980, 1983 ...
Zoological Science, Dec 25, 2004
Molecules to Organisms, 1998
Biology of the Lobster, 1995
Biology of the Land Crabs, 1988