title: Diurnal fluctuations in seawater pH influence the response of a calcifying macroalga to ocean acidification

authors: Cornwall, Christopher E.

subjects: ocean acidification

abstract: Coastal ecosystems that are characterized by kelp forests encounter daily pH fluctuations, driven by photosynthesis and respiration, which are larger than pH changes owing to ocean acidification (OA) projected for surface ocean waters by 2100. We investigated whether mimicry of biologically mediated diurnal shifts in pH—based for the first time on pH time-series measurements within a kelp forest—would offset or amplify the negative effects of OA on calcifiers. In a 40-day laboratory experiment, the calcifying coralline macroalga, Arthrocardia corymbosa, was exposed to two mean pH treatments (8.05 or 7.65). For each mean, two experimental pH manipulations were applied. In one treatment, pH was held constant. In the second treatment, pH was manipulated around the mean (as a step-function), 0.4 pH units higher during daylight and 0.4 units lower during darkness to approximate diurnal fluctuations in a kelp forest. In all cases, growth rates were lower at a reduced mean pH, and fluctuations in pH acted additively to further reduce growth. Photosynthesis, recruitment and elemental composition did not change with pH, but δ¹³C increased at lower mean pH. Including environmental heterogeneity in experimental design will assist with a more accurate assessment of the responses of calcifiers to OA.

text: Diurnal fluctuations in seawater pH influence the response of a calcifying macroalga to ocean acidification Coastal ecosystems that are characterized by kelp forests encounter daily pH fluctuations, driven by photosynthesis and respiration, which are larger than pH changes owing to ocean acidification (OA) projected for surface ocean waters by 2100. We investigated whether mimicry of biologically mediated diurnal shifts in pH—based for the first time on pH time-series measurements within a kelp forest—would offset or amplify the negative effects of OA on calcifiers. In a 40-day laboratory experiment, the calcifying coralline macroalga, Arthrocardia corymbosa, was exposed to two mean pH treatments (8.05 or 7.65). For each mean, two experimental pH manipulations were applied. In one treatment, pH was held constant. In the second treatment, pH was manipulated around the mean (as a step-function), 0.4 pH units higher during daylight and 0.4 units lower during darkness to approximate diurnal fluctuations in a kelp forest. In all cases, growth rates were lower at a reduced mean pH, and fluctuations in pH acted additively to further reduce growth. Photosynthesis, recruitment and elemental composition did not change with pH, but δ¹³C increased at lower mean pH. Including environmental heterogeneity in experimental design will assist with a more accurate assessment of the responses of calcifiers to OA.

year: 2013

title: Characterizing the Catalytic Action of μ-Calpain on Myofibrillar Protein Structure

authors: Fraser-Smith, Emma Louise

subjects: Calpain

abstract: Solving the problem of inconsistent meat tenderness is a top priority of the meat industry. This requires a greater understanding of the processes that affect meat tenderness and the adoption of such information by the meat industry. It is essential that we understand the mechanism of meat tenderisation of which, the calpain protease system is believed to play a central role.
This thesis focuses on three aspects; characterisation of calpain activity, the effect of porcine μ-calpain on myofibril degradation and the effect of μ-calpain on specific proteins desmin and troponin-T.
To study the effect of calpain activity, fluorogenic assays were used to determine: μ-calpain concentration for optimal peptide cleavage; calcium requirements and the effect of chelating substances on the activity of μ-calpain. In addition, the affinity of μ-calpain for substrates CalS-I and CalS-III were assessed.
The effect of μ-calpain on myofibril degradation was evaluated through the use of myofibrillar fragmentation index and density marker beads. Myofibrils were digested at three different temperatures for varying time periods. Conflicting results were displayed and it was concluded that these methods are not accurate, thus further research should be conducted to ensure inconsistencies are eliminated.
Specific proteins desmin and troponin-T have previously been shown to exhibit degradation in the presence of calcium and μ-calpain. SDS-polyacrylamide electrophoresis, western blotting and densitometry measurements were utilized to investigate this effect. It was concluded that μ-calpain plays a significant role in the post mortem proteolysis of myofibrillar protein.
This thesis provides information and strives to give a better understanding of the proteolytic changes that occur within muscle. Understanding how these mechanisms affect meat on a cellular level, can help to control the influence they inflict on meat quality.

text: Characterizing the Catalytic Action of μ-Calpain on Myofibrillar Protein Structure Solving the problem of inconsistent meat tenderness is a top priority of the meat industry. This requires a greater understanding of the processes that affect meat tenderness and the adoption of such information by the meat industry. It is essential that we understand the mechanism of meat tenderisation of which, the calpain protease system is believed to play a central role.
This thesis focuses on three aspects; characterisation of calpain activity, the effect of porcine μ-calpain on myofibril degradation and the effect of μ-calpain on specific proteins desmin and troponin-T.
To study the effect of calpain activity, fluorogenic assays were used to determine: μ-calpain concentration for optimal peptide cleavage; calcium requirements and the effect of chelating substances on the activity of μ-calpain. In addition, the affinity of μ-calpain for substrates CalS-I and CalS-III were assessed.
The effect of μ-calpain on myofibril degradation was evaluated through the use of myofibrillar fragmentation index and density marker beads. Myofibrils were digested at three different temperatures for varying time periods. Conflicting results were displayed and it was concluded that these methods are not accurate, thus further research should be conducted to ensure inconsistencies are eliminated.
Specific proteins desmin and troponin-T have previously been shown to exhibit degradation in the presence of calcium and μ-calpain. SDS-polyacrylamide electrophoresis, western blotting and densitometry measurements were utilized to investigate this effect. It was concluded that μ-calpain plays a significant role in the post mortem proteolysis of myofibrillar protein.
This thesis provides information and strives to give a better understanding of the proteolytic changes that occur within muscle. Understanding how these mechanisms affect meat on a cellular level, can help to control the influence they inflict on meat quality.

year: 2006

title: Ka Mahuta, Ngāti Hauā and the importance of translation theory

authors: Roa, Raukura

subjects: Waiata Māori

abstract: In this paper, I provide an English translation of one Māori waiata - Ka Mahuta – a waiata of Ngāti Hauā, along with a discussion of the relevance of translation theory and of culturally appropriate translation processes that fully involve those whose guidance, support, knowledge and understanding are of critical importance.

text: Ka Mahuta, Ngāti Hauā and the importance of translation theory In this paper, I provide an English translation of one Māori waiata - Ka Mahuta – a waiata of Ngāti Hauā, along with a discussion of the relevance of translation theory and of culturally appropriate translation processes that fully involve those whose guidance, support, knowledge and understanding are of critical importance.

year: 2003-09