title: Characterisation of an acute anorexigenic action of l-tryptophan: a link with neural mechanisms regulating appetite

authors: Gartner, Sarah Nicole

subjects: Tryptophan

abstract: Recent evidence suggests that individual amino acids may promote hypophagia, however, our understanding of processes underlying their anorexigenic action is extremely limited. The few human and laboratory animal studies performed to date suggest that a free essential amino acid, l-tryptophan (TRP) reduces food intake. It is unclear, however, whether TRP acutely affects consumption driven by energy needs or by palatability, and whether central mechanisms underlie TRP-induced hypophagia. This thesis provides a detailed characterisation of ingestive behavioural effects induced by TRP administered intragastrically or (in order to bypass the gut) via an intraperitoneal (IP) injection in laboratory rodents prior to a meal as well as relevant neural processes triggered by TRP.
The first set of experiments explored whether an intragastric preload of TRP affects energy- and palatability-induced feeding in mice. A conditioned taste aversion (CTA) test was used to assess whether hypophagia is unrelated to sickness. Finally, c-Fos immunohistochemistry was employed to detect changes in activation of feeding-related brain sites induced by an anorexigenic dose of intragastric TRP. TRP generated a short-lasting reduction in the intake of energy-dense standard chow in deprived animals and energy-dense palatable chow in sated mice. Anorexigenic doses of TRP did not cause a CTA. TRP failed to affect intake of palatable yet calorie-dilute or noncaloric solutions (10% sucrose, 4.1% Intralipid or 0.1% saccharin) even for higher TRP doses that decreased water intake in thirsty mice. c-Fos analysis revealed an increase in activation of key feeding-related brain areas, especially in the brainstem and hypothalamus. Overall, intragastric TRP was found to diminish energy-driven food consumption as well as (at high doses) thirst-induced water intake and affect activation of relevant central circuits.
In the second set of experiments, I investigated whether anorexigenic and brain activation effects persist when TRP bypasses the gut, i.e., TRP is injected directly in the IP cavity in rats. The effect of IP TRP was examined in both energy- and palatability-induced feeding. 30 and 100 mg/kg IP TRP suppressed chow intake in energy deprived rats. Only a higher 100 mg/kg IP TRP dose reduced consumption of palatable chow and palatable sucrose, saccharin and Intralipid solutions in sated animals. Thirst-driven water intake was reduced after 30 and 100 mg/kg IP TRP. Neither 30 nor 100 mg/kg IP TRP caused a CTA. c-Fos analysis showed the most pronounced effect of IP TRP on hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei and the nucleus of the solitary tract in the brainstem. It can be concluded that IP TRP suppresses energy deprivation-induced intake of chow and thirst-induced water intake within the same dose range, whereas higher doses are necessary to reduce consumption of palatable solutions in sated animals. IP TRP hypophagia is accompanied by activation of central circuitry that encompasses brainstem and hypothalamic sites, though changes are not as prominent as with intragastric TRP.
Intragastric and IP TRP administered at hypophagic doses increases c-Fos immunoreactivity in the hypothalamic PVN and SON. As these sites host neurons that synthesise a key satiety mediator, oxytocin (OT), the third and final set of studies explored a hypothesis that TRP’s anorexigenic action relies on enhanced activity of the OT system. By employing double-immunohistochemistry, I determined that the lowest effective dose of intragastric and IP TRP increased the activation of both PVN and SON OT neurons, although the effect was more pronounced after intragastric administration. Intragastric TRP upregulated OT mRNA in the hypothalamus. A blood-brain barrier-penetrant OT receptor antagonist, L-368,899, reversed hypophagia induced by TRP administered via both routes. Unlike the lowest effective dose of intragastric TRP which decreases only feeding, IP TRP at the lowest effective dose diminishes both food and water intake. Hence it was confirmed that L-368,899 pre-treatment does not affect TRP-driven reduction in drinking. The findings suggest therefore a functional relationship between TRP and OT in the regulation of energy-driven food intake.
Overall, the findings presented herein shed more light on the nature of anorexigenic properties of TRP. It appears that TRP acutely suppresses ingestive behaviour driven by energy, but it is a very weak inhibitor of palatability-motivated consumption. While both intragastric and IP TRP also decreased water intake, the fact that a low dose of the intragastric amino acid was sufficient to decrease feeding but not drinking, strongly suggests that a direct interaction of TRP with the gastric mucosa is a crucial contributor to reduced energy intake. TRP engages broad brain circuits relevant to feeding, especially the hypothalamus and brainstem. OT appears to be a candidate molecule potentially mediating TRP’s effect on food intake.

text: Characterisation of an acute anorexigenic action of l-tryptophan: a link with neural mechanisms regulating appetite Recent evidence suggests that individual amino acids may promote hypophagia, however, our understanding of processes underlying their anorexigenic action is extremely limited. The few human and laboratory animal studies performed to date suggest that a free essential amino acid, l-tryptophan (TRP) reduces food intake. It is unclear, however, whether TRP acutely affects consumption driven by energy needs or by palatability, and whether central mechanisms underlie TRP-induced hypophagia. This thesis provides a detailed characterisation of ingestive behavioural effects induced by TRP administered intragastrically or (in order to bypass the gut) via an intraperitoneal (IP) injection in laboratory rodents prior to a meal as well as relevant neural processes triggered by TRP.
The first set of experiments explored whether an intragastric preload of TRP affects energy- and palatability-induced feeding in mice. A conditioned taste aversion (CTA) test was used to assess whether hypophagia is unrelated to sickness. Finally, c-Fos immunohistochemistry was employed to detect changes in activation of feeding-related brain sites induced by an anorexigenic dose of intragastric TRP. TRP generated a short-lasting reduction in the intake of energy-dense standard chow in deprived animals and energy-dense palatable chow in sated mice. Anorexigenic doses of TRP did not cause a CTA. TRP failed to affect intake of palatable yet calorie-dilute or noncaloric solutions (10% sucrose, 4.1% Intralipid or 0.1% saccharin) even for higher TRP doses that decreased water intake in thirsty mice. c-Fos analysis revealed an increase in activation of key feeding-related brain areas, especially in the brainstem and hypothalamus. Overall, intragastric TRP was found to diminish energy-driven food consumption as well as (at high doses) thirst-induced water intake and affect activation of relevant central circuits.
In the second set of experiments, I investigated whether anorexigenic and brain activation effects persist when TRP bypasses the gut, i.e., TRP is injected directly in the IP cavity in rats. The effect of IP TRP was examined in both energy- and palatability-induced feeding. 30 and 100 mg/kg IP TRP suppressed chow intake in energy deprived rats. Only a higher 100 mg/kg IP TRP dose reduced consumption of palatable chow and palatable sucrose, saccharin and Intralipid solutions in sated animals. Thirst-driven water intake was reduced after 30 and 100 mg/kg IP TRP. Neither 30 nor 100 mg/kg IP TRP caused a CTA. c-Fos analysis showed the most pronounced effect of IP TRP on hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei and the nucleus of the solitary tract in the brainstem. It can be concluded that IP TRP suppresses energy deprivation-induced intake of chow and thirst-induced water intake within the same dose range, whereas higher doses are necessary to reduce consumption of palatable solutions in sated animals. IP TRP hypophagia is accompanied by activation of central circuitry that encompasses brainstem and hypothalamic sites, though changes are not as prominent as with intragastric TRP.
Intragastric and IP TRP administered at hypophagic doses increases c-Fos immunoreactivity in the hypothalamic PVN and SON. As these sites host neurons that synthesise a key satiety mediator, oxytocin (OT), the third and final set of studies explored a hypothesis that TRP’s anorexigenic action relies on enhanced activity of the OT system. By employing double-immunohistochemistry, I determined that the lowest effective dose of intragastric and IP TRP increased the activation of both PVN and SON OT neurons, although the effect was more pronounced after intragastric administration. Intragastric TRP upregulated OT mRNA in the hypothalamus. A blood-brain barrier-penetrant OT receptor antagonist, L-368,899, reversed hypophagia induced by TRP administered via both routes. Unlike the lowest effective dose of intragastric TRP which decreases only feeding, IP TRP at the lowest effective dose diminishes both food and water intake. Hence it was confirmed that L-368,899 pre-treatment does not affect TRP-driven reduction in drinking. The findings suggest therefore a functional relationship between TRP and OT in the regulation of energy-driven food intake.
Overall, the findings presented herein shed more light on the nature of anorexigenic properties of TRP. It appears that TRP acutely suppresses ingestive behaviour driven by energy, but it is a very weak inhibitor of palatability-motivated consumption. While both intragastric and IP TRP also decreased water intake, the fact that a low dose of the intragastric amino acid was sufficient to decrease feeding but not drinking, strongly suggests that a direct interaction of TRP with the gastric mucosa is a crucial contributor to reduced energy intake. TRP engages broad brain circuits relevant to feeding, especially the hypothalamus and brainstem. OT appears to be a candidate molecule potentially mediating TRP’s effect on food intake.

year: 2018

title: Testing use of mitochondrial COI sequences for the identification and phylogenetic analysis of New Zealand caddisflies (Trichoptera)

authors: Hogg, Ian D.

subjects: aquatic insects

abstract: We tested the hypothesis that cytochrome c oxidase subunit 1 (COI) sequences would successfully discriminate recognised species of New Zealand caddisflies. We further examined whether phylogenetic analyses, based on the COI locus, could recover currently recognised superfamilies and suborders. COI sequences were obtained from 105 individuals representing 61 species and all 16 families of Trichoptera known from New Zealand. No sequence sharing was observed between members of different species, and congeneric species showed from 2.3 to 19.5% divergence. Sequence divergence among members of a species was typically low (mean = 0.7%; range 0.0–8.5%), but two species showed intraspecific divergences in excess of 2%. Phylogenetic reconstructions based on COI were largely congruent with previous conclusions based on morphology, although the sequence data did not support placement of the purse-cased caddisflies (Hydroptilidae) within the uncased caddisflies, and, in particular, the Rhyacophiloidea. We conclude that sequence variation in the COI gene locus is an effective tool for the identification of New Zealand caddisfly species, and can provide preliminary phylogenetic inferences. Further research is needed to ascertain the significance of the few instances of high intra-specific divergence and to determine if any instances of sequence sharing will be detected with larger sample sizes.

text: Testing use of mitochondrial COI sequences for the identification and phylogenetic analysis of New Zealand caddisflies (Trichoptera) We tested the hypothesis that cytochrome c oxidase subunit 1 (COI) sequences would successfully discriminate recognised species of New Zealand caddisflies. We further examined whether phylogenetic analyses, based on the COI locus, could recover currently recognised superfamilies and suborders. COI sequences were obtained from 105 individuals representing 61 species and all 16 families of Trichoptera known from New Zealand. No sequence sharing was observed between members of different species, and congeneric species showed from 2.3 to 19.5% divergence. Sequence divergence among members of a species was typically low (mean = 0.7%; range 0.0–8.5%), but two species showed intraspecific divergences in excess of 2%. Phylogenetic reconstructions based on COI were largely congruent with previous conclusions based on morphology, although the sequence data did not support placement of the purse-cased caddisflies (Hydroptilidae) within the uncased caddisflies, and, in particular, the Rhyacophiloidea. We conclude that sequence variation in the COI gene locus is an effective tool for the identification of New Zealand caddisfly species, and can provide preliminary phylogenetic inferences. Further research is needed to ascertain the significance of the few instances of high intra-specific divergence and to determine if any instances of sequence sharing will be detected with larger sample sizes.

year: 2009

title: Ko Te Kawa Tūpanapana i ngā Hau Tūpua a Tāwhiri-mātea : The validation, revitalisation and enhancement of Māori environment knowledge of weather and climate

authors: Skipper, Apanui Sonny

subjects: Maori Environmental knowledge

abstract: KO TE KAWA TŪPANAPANA I NGĀ HAU TŪPUA A TĀWHIRI-MĀTEA – THE RITUALISTIC FORMS GOVERNING THE SUPERNATURAL WINDS OF TĀWHIRI-MĀTEA
Mankind has always gazed skyward observing the im immense power generated by forked lightning when it strikes the land. The resounding thunder booming across the landscape never failed to capture the awe and imagination of a people. Māori were no different. The legacy of their Polynesian ancestors, who populated most of the Islands of Te Moana-nui-a-Kiwa, the largest ocean on the planet, based on belief, courage, and navigational expertise, honed over many millenia, reached Aotearoa approximately in the 12 century. These highly skilled ancestors from the tropics applied a formalised process of settling a new land. It also required their own weatherlore to be recalibrated to the local conditions, in order to survive in a much harsher, colder climate.

Over the centuries the descendants of these early Polynesian settlers, developed an extensive localised knowledge of weather, climate, and seasonal indicators to accurately predict daily weather, monthly or annual climate conditions. The ongoing lessons learned especially after experiencing a fatality were incorporated into cultural practices of important everyday activities such as ahuwhenua, te mahi hī ika, kohi rongoā, whakaako tamariki, gathering pounamu, whakatū rāhui, and kaitiakitanga, in order to minimise further loss of life.

Formal recognition of these contributions was made at the inaugural Māori Climate Forum in Wellington in 2003, where a number of Māori elders highlighted the importance of giving a greater account of Māori knowledge of environmental change. Among the many priorities identified for research at this forum, an opportunity based on a challenge from a Māori elder led to the development of a pilot project to explore traditional Māori understandings of weather–climate variability and change. 

One of the key outcomes from this work was the identification of Māori environmental indicators to anticipate local weather and climate conditions and thereby manage the risk associated with weather-climate extremes. However, in spite of the work achieved, there remain unanswered questions about the use and ongoing efficacy of environmental indicators to forecast and monitor weather and climate risks, including how new opportunities might be created to promote learning about subtle signals in nature that can reveal much about changes in weather and climate conditions. 

Due to the fact that many of the elders that provided the basis of this thesis have passed away, a great sense of responsibility has remained with me to complete this research. To identify the gaps in the previous research, to ground-truth it, to consolidate and carefully document the level of localised environmental knowledge of weather and climate specifically with iwi from Tainui-Hauraki, Te Whānau-a-Apanui, and Ngāi Tahu. A total of 56 interviews and 17 group wānanga were conducted during 2009-2016. Examples of Māori Environmental Knowledge were also sourced from numerous personal conversations with knowledge holders from 1989-2003, adding to the body of knowledge that was analysed to provide further context. A conceptual framework coined `Ngā Whenu Tapu e Waru’ was created from identifying the key themes of the interviews to inform how Māori Environmental Knowledge was described in the three regions. This study has yielded understandings of wind, rain, thunder, lightning, and cloud classifications; weather and climate indicators; spiritual signs of misfortune and death; memory techniques; longitudinal weather predictions, and lunar calendars in each region.

This thesis is underpinned by a Kaupapa Māori theory and research methodology that links to a body of transformative research and literature conducted by Māori scholars based on the knowledge and experience of tūpuna  Māori. 

Heoti anō rā kei ngā kākahi whakairoiro, kei ngā matataiko, nau piki mai, nau kake mai ki tēnei wānanga nui whakaharahara.

text: Ko Te Kawa Tūpanapana i ngā Hau Tūpua a Tāwhiri-mātea : The validation, revitalisation and enhancement of Māori environment knowledge of weather and climate KO TE KAWA TŪPANAPANA I NGĀ HAU TŪPUA A TĀWHIRI-MĀTEA – THE RITUALISTIC FORMS GOVERNING THE SUPERNATURAL WINDS OF TĀWHIRI-MĀTEA
Mankind has always gazed skyward observing the im immense power generated by forked lightning when it strikes the land. The resounding thunder booming across the landscape never failed to capture the awe and imagination of a people. Māori were no different. The legacy of their Polynesian ancestors, who populated most of the Islands of Te Moana-nui-a-Kiwa, the largest ocean on the planet, based on belief, courage, and navigational expertise, honed over many millenia, reached Aotearoa approximately in the 12 century. These highly skilled ancestors from the tropics applied a formalised process of settling a new land. It also required their own weatherlore to be recalibrated to the local conditions, in order to survive in a much harsher, colder climate.

Over the centuries the descendants of these early Polynesian settlers, developed an extensive localised knowledge of weather, climate, and seasonal indicators to accurately predict daily weather, monthly or annual climate conditions. The ongoing lessons learned especially after experiencing a fatality were incorporated into cultural practices of important everyday activities such as ahuwhenua, te mahi hī ika, kohi rongoā, whakaako tamariki, gathering pounamu, whakatū rāhui, and kaitiakitanga, in order to minimise further loss of life.

Formal recognition of these contributions was made at the inaugural Māori Climate Forum in Wellington in 2003, where a number of Māori elders highlighted the importance of giving a greater account of Māori knowledge of environmental change. Among the many priorities identified for research at this forum, an opportunity based on a challenge from a Māori elder led to the development of a pilot project to explore traditional Māori understandings of weather–climate variability and change. 

One of the key outcomes from this work was the identification of Māori environmental indicators to anticipate local weather and climate conditions and thereby manage the risk associated with weather-climate extremes. However, in spite of the work achieved, there remain unanswered questions about the use and ongoing efficacy of environmental indicators to forecast and monitor weather and climate risks, including how new opportunities might be created to promote learning about subtle signals in nature that can reveal much about changes in weather and climate conditions. 

Due to the fact that many of the elders that provided the basis of this thesis have passed away, a great sense of responsibility has remained with me to complete this research. To identify the gaps in the previous research, to ground-truth it, to consolidate and carefully document the level of localised environmental knowledge of weather and climate specifically with iwi from Tainui-Hauraki, Te Whānau-a-Apanui, and Ngāi Tahu. A total of 56 interviews and 17 group wānanga were conducted during 2009-2016. Examples of Māori Environmental Knowledge were also sourced from numerous personal conversations with knowledge holders from 1989-2003, adding to the body of knowledge that was analysed to provide further context. A conceptual framework coined `Ngā Whenu Tapu e Waru’ was created from identifying the key themes of the interviews to inform how Māori Environmental Knowledge was described in the three regions. This study has yielded understandings of wind, rain, thunder, lightning, and cloud classifications; weather and climate indicators; spiritual signs of misfortune and death; memory techniques; longitudinal weather predictions, and lunar calendars in each region.

This thesis is underpinned by a Kaupapa Māori theory and research methodology that links to a body of transformative research and literature conducted by Māori scholars based on the knowledge and experience of tūpuna  Māori. 

Heoti anō rā kei ngā kākahi whakairoiro, kei ngā matataiko, nau piki mai, nau kake mai ki tēnei wānanga nui whakaharahara.

year: 2020