title: Seasonal Variation in Bivalve Antioxidant Enzymes: Can they be used as indicators of heavy metal contamination?

authors: Gibson, Aimee Clare

subjects: Biomarkers

abstract: Seasonal variations in the activity of several enzymes (glutathione reductase (GR), glutathione S-transferase (GST), and glutathione peroxidase (GPx)) involved in the glutathione cellular defence system were measured in whole tissues of the common New Zealand cockle (Austrovenus stutchburyi) as biomarkers of oxidative stress.  Three sites (Glendowie, Panmure, and Tiraumea) were sampled in Tamaki Estuary, Auckland, New Zealand, that represented a heavy metal contamination gradient.  These sites were selected as metal contaminants can affect the activity of antioxidant enzymes by increasing the formation of reactive oxygen species, therefore these enzymes have been proposed as biomarkers of diminished health.  Cockles from the three sites were expected to show differences in enzyme activities due to the gradient in metal levels.  Sites were sampled monthly over a thirteen month period, from April 2007 - April 2008.  Environmental co-variables (sediment silt-clay fraction, organic matter content, chlorophyll a, median grain size, cockle condition index, water temperature and salinity) were also measured in order to relate biomarker activities to them.  From these measures it was established that a gradient existed in sediment properties, water parameters, and condition index, among the three study sites.  Condition index significantly correlated with both GPx (r = 0.761) and GST (r = 0.721) activity, therefore condition index provides a good measure of overall health.  The silt-clay fraction of the sediment also showed a significant negative correlation with both GPx (r = -0.558) and GST (r = -0.498).  GPx was the only enzyme to have significant correlations with metal concentrations including, Pb sediment concentration (r = -0.561), Cu sediment concentration (r = -0.539) and Cu tissue concentration (r = -0.530).  Therefore this enzyme showed the most promise as a biomarker of contamination.  The highest GPx and GST activities were measured in cockles from Glendowie, this site was characterised by lower concentrations of metals.  There was seasonality observed in the activity of GPx and GST.  The activity of these enzymes greatly increased from January onwards, and remained elevated for the remainder of the sampling period (until April 2008) this increase however, was more pronounced at Glendowie.  The increase in enzyme activity in January could have been the result of a number of reasons including 1) changes in the cockles metabolic status due to gonadal development and spawning 2) a combination of environmental co-variables not measured in this study, or 3) a recovery from a stress event that occurred prior to sampling.  Both GST and GPx showed promise as biomarkers of contamination; however GR did not as there were little differences in enzyme activities among sites.  Further annual sampling at these sites should be carried out to determine if the increased GST and GPx activities in summer were the result of an abnormal event or a typical seasonal variation that occurs annually.

text: Seasonal Variation in Bivalve Antioxidant Enzymes: Can they be used as indicators of heavy metal contamination? Seasonal variations in the activity of several enzymes (glutathione reductase (GR), glutathione S-transferase (GST), and glutathione peroxidase (GPx)) involved in the glutathione cellular defence system were measured in whole tissues of the common New Zealand cockle (Austrovenus stutchburyi) as biomarkers of oxidative stress.  Three sites (Glendowie, Panmure, and Tiraumea) were sampled in Tamaki Estuary, Auckland, New Zealand, that represented a heavy metal contamination gradient.  These sites were selected as metal contaminants can affect the activity of antioxidant enzymes by increasing the formation of reactive oxygen species, therefore these enzymes have been proposed as biomarkers of diminished health.  Cockles from the three sites were expected to show differences in enzyme activities due to the gradient in metal levels.  Sites were sampled monthly over a thirteen month period, from April 2007 - April 2008.  Environmental co-variables (sediment silt-clay fraction, organic matter content, chlorophyll a, median grain size, cockle condition index, water temperature and salinity) were also measured in order to relate biomarker activities to them.  From these measures it was established that a gradient existed in sediment properties, water parameters, and condition index, among the three study sites.  Condition index significantly correlated with both GPx (r = 0.761) and GST (r = 0.721) activity, therefore condition index provides a good measure of overall health.  The silt-clay fraction of the sediment also showed a significant negative correlation with both GPx (r = -0.558) and GST (r = -0.498).  GPx was the only enzyme to have significant correlations with metal concentrations including, Pb sediment concentration (r = -0.561), Cu sediment concentration (r = -0.539) and Cu tissue concentration (r = -0.530).  Therefore this enzyme showed the most promise as a biomarker of contamination.  The highest GPx and GST activities were measured in cockles from Glendowie, this site was characterised by lower concentrations of metals.  There was seasonality observed in the activity of GPx and GST.  The activity of these enzymes greatly increased from January onwards, and remained elevated for the remainder of the sampling period (until April 2008) this increase however, was more pronounced at Glendowie.  The increase in enzyme activity in January could have been the result of a number of reasons including 1) changes in the cockles metabolic status due to gonadal development and spawning 2) a combination of environmental co-variables not measured in this study, or 3) a recovery from a stress event that occurred prior to sampling.  Both GST and GPx showed promise as biomarkers of contamination; however GR did not as there were little differences in enzyme activities among sites.  Further annual sampling at these sites should be carried out to determine if the increased GST and GPx activities in summer were the result of an abnormal event or a typical seasonal variation that occurs annually.

year: 2009

title: Book Review: Faith Lacking Understanding: Theology ‘Through a Glass, Darkly’– By Randal Rauser

authors: Pratt, Douglas

subjects: book review

abstract: This article reviews the book: “Faith Lacking Understanding: Theology ‘Through a Glass, Darkly’”, by Randal Rauser.

text: Book Review: Faith Lacking Understanding: Theology ‘Through a Glass, Darkly’– By Randal Rauser This article reviews the book: “Faith Lacking Understanding: Theology ‘Through a Glass, Darkly’”, by Randal Rauser.

year: 2010

title: Memento Mori : Memento Maori – moko and memory

authors: Te Awekotuku, Ngahuia

subjects: tangi

abstract: Moko patterns, mau moko, “wearing ink” is often explained as an act of remembrance, a symbol of honour or success, of grieving or loss. Memento mori, remembering the dead and remembrance of death, pervades the Maori world, and is profoundly expressed in customary practice – haehae, upoko tuhi, and ta moko. These embodied and visceral experiences are described in waiata tangi, in whai korero, in moteatea, in the traditional context, and graphically recorded on the living flesh in our contemporary world. Mau moko celebrates identity, so modern memorial ornamentation mourns and reflects on this in ‘memento mori’; and also reinforces and engages reality in the correspondent notion of ‘memento Maori’; an assertion that claims dominion and understanding across generations, across time, across space.

text: Memento Mori : Memento Maori – moko and memory Moko patterns, mau moko, “wearing ink” is often explained as an act of remembrance, a symbol of honour or success, of grieving or loss. Memento mori, remembering the dead and remembrance of death, pervades the Maori world, and is profoundly expressed in customary practice – haehae, upoko tuhi, and ta moko. These embodied and visceral experiences are described in waiata tangi, in whai korero, in moteatea, in the traditional context, and graphically recorded on the living flesh in our contemporary world. Mau moko celebrates identity, so modern memorial ornamentation mourns and reflects on this in ‘memento mori’; and also reinforces and engages reality in the correspondent notion of ‘memento Maori’; an assertion that claims dominion and understanding across generations, across time, across space.

year: 2009-11