title: Propagating action potentials and the regeneration of acetabularia mediterranea: a pilot study

authors: Lertsithichai, Somak

abstract: A study of the relationship between the cell membrane electrical activity and the observed polar regeneration in anucleate isolated stalk segments of Acetabularia may help answer the question of how a single cell can ‘break symmetry’ and establish a definite polarity. Such studies have been carried out extensively by Novak and Bentrup and their colleagues since 1972, but their results contain unresolved inconsistencies and although their experimental technique overcomes the problems arising from conventional microelectrode techniques, it gives a restricted and electrically perturbative environment for the cell.
In an attempt to overcome these limitations the work in this thesis describes the development of a new technique for measuring the electrical activity of the cell membrane with minimum perturbation from the measuring system. In addition it gives more precise and detailed information about the region of action potential initiation and subsequent propagation. 
The results of measurements using this technique on a variety of intact cells and various cell segments, including anucleate stalk segments are presented and discussed. The results provide strong evidence for the hypothesis that the region of action potential initiation is strongly correlated with the region of current growth. They do not however appear to provide any support for the suggestion of Novak and Bentrup that propagating action potentials are an essential component of the mechanism for ‘symmetry breaking’ in initially unpolarised anucleate stalk segments.

text: Propagating action potentials and the regeneration of acetabularia mediterranea: a pilot study A study of the relationship between the cell membrane electrical activity and the observed polar regeneration in anucleate isolated stalk segments of Acetabularia may help answer the question of how a single cell can ‘break symmetry’ and establish a definite polarity. Such studies have been carried out extensively by Novak and Bentrup and their colleagues since 1972, but their results contain unresolved inconsistencies and although their experimental technique overcomes the problems arising from conventional microelectrode techniques, it gives a restricted and electrically perturbative environment for the cell.
In an attempt to overcome these limitations the work in this thesis describes the development of a new technique for measuring the electrical activity of the cell membrane with minimum perturbation from the measuring system. In addition it gives more precise and detailed information about the region of action potential initiation and subsequent propagation. 
The results of measurements using this technique on a variety of intact cells and various cell segments, including anucleate stalk segments are presented and discussed. The results provide strong evidence for the hypothesis that the region of action potential initiation is strongly correlated with the region of current growth. They do not however appear to provide any support for the suggestion of Novak and Bentrup that propagating action potentials are an essential component of the mechanism for ‘symmetry breaking’ in initially unpolarised anucleate stalk segments.

year: 1980

title: Spectroscopic and synthetic studies of lichen metabolites

authors: Ronaldson, Kathlyn Joy

abstract: Lichen metabolites from various Nephroma and Pseudocyphellaria species have been subjected to a number of spectroscopic and synthetic investigations. Hypoiodite reaction of 15α-acetoxyhopan-17(21)-en-24-ol yielded a complex mixture of products, while similar reaction of 7-oxohopan-22-ol resulted in cleavage of the side-chain. Preparation of an α-sulphenylated 15-ketone was achieved as the first step in a carbonyl transposition sequence. Complete assignment of the ¹³C nmr spectra of four pentacyclic and two ring A-cleaved stictane derivatives provided evidence of the boat-ring B. The low frequency infrared spectra of a number of stictane and hopane triterpenoids yielded structurally significant correlations. Two depsidonal constituents of N. australe were demonstrated to be hypostictic acid and hyposalazinic acid. The reactions of mercuric acetate with unsaturated compounds are reviewed and anomalous products of Jones reagent oxidation investigated.

text: Spectroscopic and synthetic studies of lichen metabolites Lichen metabolites from various Nephroma and Pseudocyphellaria species have been subjected to a number of spectroscopic and synthetic investigations. Hypoiodite reaction of 15α-acetoxyhopan-17(21)-en-24-ol yielded a complex mixture of products, while similar reaction of 7-oxohopan-22-ol resulted in cleavage of the side-chain. Preparation of an α-sulphenylated 15-ketone was achieved as the first step in a carbonyl transposition sequence. Complete assignment of the ¹³C nmr spectra of four pentacyclic and two ring A-cleaved stictane derivatives provided evidence of the boat-ring B. The low frequency infrared spectra of a number of stictane and hopane triterpenoids yielded structurally significant correlations. Two depsidonal constituents of N. australe were demonstrated to be hypostictic acid and hyposalazinic acid. The reactions of mercuric acetate with unsaturated compounds are reviewed and anomalous products of Jones reagent oxidation investigated.

year: 1980

title: Honouring our ancestors: Reclaiming the power of Māori maternities

authors: Simmonds, Naomi Beth

abstract: Māori¹ maternal knowledges are intimately tied to ancestors, to ancestral knowledges, and to whenua (land).² Iwi (tribes), hapū (smaller tribal groupings), and whānau (families)³ have their own maternal knowledges, which are woven into their cosmologies, histories, songs, carvings, place names, chants, and incantations. These knowledges, though spatially and temporally specific, speak to the sanctity of the maternal body, the power and prestige of women’s reproductive capabilities, and the empowering collective approach to raising children. Māori knowledges pertaining to pregnancy, childbirth, and parenting were imparted generation to generation as they were lived, embodied and emplaced by our ancestors, sustaining the sacred and empowering approach to maternities within our communities.
This chapter considers the challenges and possibilities of reclaiming Māori maternal knowledges and their associated practices and ceremonies for Māori women and whānau in contemporary Aotearoa-New Zealand. Three key themes frame this chapter. First, I consider the ways in which colonialism has served to silence Māori maternal knowledges to such an extent that whānau are left trying to find meaning in the voices, knowledges, and advices of others. Indigenous women are largely birthing within Western ideologies and institutions that do not adequately provide for Indigenous ways of being and birthing. The chapter then considers the ways in which women and whānau are reclaiming ancient knowledges and practices in new and contemporary ways. I seek to illustrate the ways in which traditional practices and ritual customs have the potential to transform and empower individual and collective experiences of birth and afterbirth. The chapter ends with arguing that Indigenous maternities, Māori maternities, are an important site of decolonization. Reclaiming the messages and embodied practices left to us by our ancestors can provide an empowering collective approach to pregnancy, birth, and afterbirth, and can facilitate a “decolonized pathway” (Simpson 28) into and through the world for our children and for generations to come.

text: Honouring our ancestors: Reclaiming the power of Māori maternities Māori¹ maternal knowledges are intimately tied to ancestors, to ancestral knowledges, and to whenua (land).² Iwi (tribes), hapū (smaller tribal groupings), and whānau (families)³ have their own maternal knowledges, which are woven into their cosmologies, histories, songs, carvings, place names, chants, and incantations. These knowledges, though spatially and temporally specific, speak to the sanctity of the maternal body, the power and prestige of women’s reproductive capabilities, and the empowering collective approach to raising children. Māori knowledges pertaining to pregnancy, childbirth, and parenting were imparted generation to generation as they were lived, embodied and emplaced by our ancestors, sustaining the sacred and empowering approach to maternities within our communities.
This chapter considers the challenges and possibilities of reclaiming Māori maternal knowledges and their associated practices and ceremonies for Māori women and whānau in contemporary Aotearoa-New Zealand. Three key themes frame this chapter. First, I consider the ways in which colonialism has served to silence Māori maternal knowledges to such an extent that whānau are left trying to find meaning in the voices, knowledges, and advices of others. Indigenous women are largely birthing within Western ideologies and institutions that do not adequately provide for Indigenous ways of being and birthing. The chapter then considers the ways in which women and whānau are reclaiming ancient knowledges and practices in new and contemporary ways. I seek to illustrate the ways in which traditional practices and ritual customs have the potential to transform and empower individual and collective experiences of birth and afterbirth. The chapter ends with arguing that Indigenous maternities, Māori maternities, are an important site of decolonization. Reclaiming the messages and embodied practices left to us by our ancestors can provide an empowering collective approach to pregnancy, birth, and afterbirth, and can facilitate a “decolonized pathway” (Simpson 28) into and through the world for our children and for generations to come.

year: 2017