title: Dietary supplementation and intragastric infusions of L-tryptophan reduce food intake

authors: Aidney, Fraser Charles

subjects: L-tryptophan

abstract: Select free amino acids have been suggested to promote early satiation. Initial studies indicate that L-tryptophan may play an important role in reducing appetite. The current set of experiments examined whether dietary and intragastrically administered L-tryptophan decreases food consumption and whether this effect is specific to eating stimulated by energy (calorie) needs or by pleasant taste (reward). A link between a satiating action of L-tryptophan and activity of the anorexigenic oxytocin circuit has also been investigated. Supplementation of milk formula-based diets with tryptophan reduced energy deprivation-induced consumption of these formulas in mice. Tryptophan enrichment had no effect on water intake, which precludes the involvement of taste- or thirst-related mechanisms in tryptophan-driven hypophagia. Intragastrically administered L-tryptophan decreased deprivation-induced chow intake. It also reduced hedonics-driven consumption of palatable saccharin and milk, but not of sucrose solutions in non-deprived mice, suggesting a link with feeding reward mechanisms unrelated to sucrose. Finally, oxytocin receptor blockade with very low doses of an antagonist just prior to intragastric L-tryptophan administration, completely abolished early termination of deprivation-induced food intake by this amino acid. Overall, the data indicate that dietary supplementation and intragastric delivery of free L-tryptophan reduce eating behaviour stimulated by energy needs and palatability, and that the effect of L-tryptophan is mediated by the anorexigenic oxytocin system.

text: Dietary supplementation and intragastric infusions of L-tryptophan reduce food intake Select free amino acids have been suggested to promote early satiation. Initial studies indicate that L-tryptophan may play an important role in reducing appetite. The current set of experiments examined whether dietary and intragastrically administered L-tryptophan decreases food consumption and whether this effect is specific to eating stimulated by energy (calorie) needs or by pleasant taste (reward). A link between a satiating action of L-tryptophan and activity of the anorexigenic oxytocin circuit has also been investigated. Supplementation of milk formula-based diets with tryptophan reduced energy deprivation-induced consumption of these formulas in mice. Tryptophan enrichment had no effect on water intake, which precludes the involvement of taste- or thirst-related mechanisms in tryptophan-driven hypophagia. Intragastrically administered L-tryptophan decreased deprivation-induced chow intake. It also reduced hedonics-driven consumption of palatable saccharin and milk, but not of sucrose solutions in non-deprived mice, suggesting a link with feeding reward mechanisms unrelated to sucrose. Finally, oxytocin receptor blockade with very low doses of an antagonist just prior to intragastric L-tryptophan administration, completely abolished early termination of deprivation-induced food intake by this amino acid. Overall, the data indicate that dietary supplementation and intragastric delivery of free L-tryptophan reduce eating behaviour stimulated by energy needs and palatability, and that the effect of L-tryptophan is mediated by the anorexigenic oxytocin system.

year: 2016

title: The controlled in vitro susceptibility of gastrointestinal pathogens to the antibacterial effect of manuka honey

authors: Lin, Shih-Min (Sam)

subjects: biology

abstract: The susceptibility of common gastrointestinal bacteria against manuka honey with median level non-peroxide antibacterial activity (equivalent to that of 16.5% phenol) was investigated by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using a standardized manuka honey with the broth microdilution method. The measured sensitivity of bacteria showed that manuka honey is significantly more effective than artificial honey (a mixture of sugars as in honey), indicating that osmolarity is not the only factor that is responsible for the antibacterial activity of the honey. Most tested gastrointestinal pathogens have MIC and MBC values in the range of 5–10% of honey, other than Enterobacter spp. which was in the range of 10–17%. The difference in efficacy between the honey with and without hydrogen peroxide removed was also studied, and it was found that both hydrogen peroxide and the non-peroxide components contribute to the bacteriostatic and bactericidal activity of the honey. It was also found that treatment against multi-antibiotic resistant microorganisms such as Salmonella typhimurium DT104 and ESBL-producing organisms with manuka honey may be promising.

text: The controlled in vitro susceptibility of gastrointestinal pathogens to the antibacterial effect of manuka honey The susceptibility of common gastrointestinal bacteria against manuka honey with median level non-peroxide antibacterial activity (equivalent to that of 16.5% phenol) was investigated by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using a standardized manuka honey with the broth microdilution method. The measured sensitivity of bacteria showed that manuka honey is significantly more effective than artificial honey (a mixture of sugars as in honey), indicating that osmolarity is not the only factor that is responsible for the antibacterial activity of the honey. Most tested gastrointestinal pathogens have MIC and MBC values in the range of 5–10% of honey, other than Enterobacter spp. which was in the range of 10–17%. The difference in efficacy between the honey with and without hydrogen peroxide removed was also studied, and it was found that both hydrogen peroxide and the non-peroxide components contribute to the bacteriostatic and bactericidal activity of the honey. It was also found that treatment against multi-antibiotic resistant microorganisms such as Salmonella typhimurium DT104 and ESBL-producing organisms with manuka honey may be promising.

year: 2011

title: A New Technique for Measuring Runup Variation Using Sub-Aerial Video Imagery

authors: Salmon, Summer Anne

subjects: Wave Runup

abstract: Video monitoring of beaches is becoming the preferred method for observing changes to nearshore morphology. Consequently this work investigates a new technique for predicting the probability of inundation that is based on measuring runup variation using video. Runup is defined as the water-level elevation maxima on the foreshore relative to the still water level and the waterline is defined as the position where the MWL intersects the beach face. Tairua, and Pauanui Beaches, on the north east coast of the North Island of New Zealand, were used as the field site in this study and represent two very different beaches with the same incoming wave and meteorological conditions. Tairua is most frequently in an intermediate beach state, whereas Pauanui is usually flatter in nature.

In order to rectify runup observations, an estimate of the runup elevation was needed (Z). This was estimated by measuring the variation of the waterline over a tidal cycle from time-averaged video images during a storm event and provided beach morphology statistics (i.e. beach slope (α) and beach intercept (b)) used in the rectification process where Z=aX+b. The maximum swash excursions were digitized from time-stacks, and rectified to provide run-up timeseries with duration 20 minutes. Field calibrations revealed a videoed waterline that was seaward of the surveyed waterline. Quantification of this error gave a vertical offset of 0.33m at Tairua and 0.25m at Pauanui. 

At Tairua, incident wave energy was dominant in the swash zone, and the runup distributions followed a Rayleigh distribution. At Pauanui, the flatter beach, the runup distributions were approximately bimodal due to the dominance of infragravity energy in the swash signal. The slope of the beach was a major control on the runup elevation; runup at Pauanui was directly affected by the deepwater wave height and the tide, while at Tairua there was no correlation. Overall, the results of the study indicate realistic runup measurements, over a wide range of time scales and, importantly, during storm events. However, comparisons of videoed runup and empirical runup formulae revealed larger deviations as the beach steepness increased. Furthur tests need to be carried out to see if this is a limitation of this technique, used to measure runup. The runup statistics are consistently higher at Tairua and suggests that swash runs up higher on steeper beaches. However, because of the characteristics of flatter beaches (such as high water tables and low drainage efficiencies) the impact of extreme runup elevations on such beaches are more critical in regards to erosion and/ or inundation.

The coastal environment is of great importance to Māori. Damage to the coast and coastal waahi tapu (places of spiritual importance) caused by erosion and inundation, adversely affects the spiritual and cultural well-being of Māori. For this reason, a chapter was dedicated to investigating the practices used by Māori to protect and preserve the coasts in accordance with tikanga Māori (Māori protocols). Mimicking nature was and still is a practice used by Māori to restore the beaches after erosive events, and includes replanting native dune plants and using natural materials on the beaches to stabilize the dunes. Tapu and rahui (the power and influence of the gods) were imposed on communities to prohibit and prevent people from free access to either food resources or to a particular place, in order to protect people and/ or resources. Interpretations of Māori oral histories provide insights into past local hazards and inform about the safety and viability of certain activities within an area. Environmental indicators were used to identify and forecast extreme weather conditions locally.  Māori knowledge of past hazards, and the coastal environment as a whole, is a valuable resource and provides a unique source of expertise that can contribute to current coastal hazards management plans in New Zealand and provide insights about the areas that may again be impacted by natural hazards.

text: A New Technique for Measuring Runup Variation Using Sub-Aerial Video Imagery Video monitoring of beaches is becoming the preferred method for observing changes to nearshore morphology. Consequently this work investigates a new technique for predicting the probability of inundation that is based on measuring runup variation using video. Runup is defined as the water-level elevation maxima on the foreshore relative to the still water level and the waterline is defined as the position where the MWL intersects the beach face. Tairua, and Pauanui Beaches, on the north east coast of the North Island of New Zealand, were used as the field site in this study and represent two very different beaches with the same incoming wave and meteorological conditions. Tairua is most frequently in an intermediate beach state, whereas Pauanui is usually flatter in nature.

In order to rectify runup observations, an estimate of the runup elevation was needed (Z). This was estimated by measuring the variation of the waterline over a tidal cycle from time-averaged video images during a storm event and provided beach morphology statistics (i.e. beach slope (α) and beach intercept (b)) used in the rectification process where Z=aX+b. The maximum swash excursions were digitized from time-stacks, and rectified to provide run-up timeseries with duration 20 minutes. Field calibrations revealed a videoed waterline that was seaward of the surveyed waterline. Quantification of this error gave a vertical offset of 0.33m at Tairua and 0.25m at Pauanui. 

At Tairua, incident wave energy was dominant in the swash zone, and the runup distributions followed a Rayleigh distribution. At Pauanui, the flatter beach, the runup distributions were approximately bimodal due to the dominance of infragravity energy in the swash signal. The slope of the beach was a major control on the runup elevation; runup at Pauanui was directly affected by the deepwater wave height and the tide, while at Tairua there was no correlation. Overall, the results of the study indicate realistic runup measurements, over a wide range of time scales and, importantly, during storm events. However, comparisons of videoed runup and empirical runup formulae revealed larger deviations as the beach steepness increased. Furthur tests need to be carried out to see if this is a limitation of this technique, used to measure runup. The runup statistics are consistently higher at Tairua and suggests that swash runs up higher on steeper beaches. However, because of the characteristics of flatter beaches (such as high water tables and low drainage efficiencies) the impact of extreme runup elevations on such beaches are more critical in regards to erosion and/ or inundation.

The coastal environment is of great importance to Māori. Damage to the coast and coastal waahi tapu (places of spiritual importance) caused by erosion and inundation, adversely affects the spiritual and cultural well-being of Māori. For this reason, a chapter was dedicated to investigating the practices used by Māori to protect and preserve the coasts in accordance with tikanga Māori (Māori protocols). Mimicking nature was and still is a practice used by Māori to restore the beaches after erosive events, and includes replanting native dune plants and using natural materials on the beaches to stabilize the dunes. Tapu and rahui (the power and influence of the gods) were imposed on communities to prohibit and prevent people from free access to either food resources or to a particular place, in order to protect people and/ or resources. Interpretations of Māori oral histories provide insights into past local hazards and inform about the safety and viability of certain activities within an area. Environmental indicators were used to identify and forecast extreme weather conditions locally.  Māori knowledge of past hazards, and the coastal environment as a whole, is a valuable resource and provides a unique source of expertise that can contribute to current coastal hazards management plans in New Zealand and provide insights about the areas that may again be impacted by natural hazards.

year: 2008