Mechanisms underlying Retinoic acid-induced chemoattraction in molluscan neurons

Retinoic acid, a derivative of vitamin A, is known to play diverse roles in development and regeneration. Previous research in the mollusc Lymnaea stagnalis has shown that a gradient of all-trans retinoic acid attracts the growth cones of cultured neurons. The present study investigates the sub-cellular mechanisms within the growth cones of Lymnaea pedal A neurons which mediate the attractive response to a gradient of alltrans retinoic acid. In this study, the mechanism of growth cone turning is shown to be local, as neurites mechanically isolated from their cell body retain the capacity to turn towards an exogenous gradient of all-trans retinoic acid. The turning response is dependent on the initiation of protein synthesis and calcium influx, but does not appear to involve signaling through protein kinase C (PKC). The retinoid X receptor (RXR), which classically functions as a transcription factor, was also shown to be involved in the turning response, functioning locally through a non-genomic pathway. These data show, for the first time in any species, that all-trans retinoic acid's chemotropic action involves a local mechanism involving non-genomic signaling through the RXR. As retinoic acid is known to playa role in regeneration, understanding the mechanisms underlying retinoic acid signaling may lead to further advances in regenerative neuroscience.

Rittermere Farm Craft Studio Fonds, 1951-2006

During the 1950’s, the Rittenhouse family of Vineland in the Niagara Peninsula opened a craft store and studio. Within a short period of time, they realized that resources for the craft of rug hooking were in demand and they began to build their business around this niche. Edna Rittenhouse, the mother, was the wool dyer; Margaret Rowan, the daughter, was the pattern designer; Ted Rowan, the son-in-law, changed careers and became the manager of the family business. The 1960’s were a prosperous time, not only in the Niagara Peninsula, but also for the Rittenhouse business. Edna Rittenhouse had been hooking rugs for decades but she and her family worked at developing and sharing newer techniques with newer materials. Shading manuals were authored and published; students became teachers; creativity abounded in the demand for and the creation of new designs. Instead of using woolen yarn, they were using pure woolen fabric; instead of using a standard cutter, they began using a uniquely designed cutter; instead of using frames, they employed a table top method. The new material and technique resulted in a rug with a smooth, uniform texture and a soft nap. Since many crafters belonged to crafters guilds, Margaret and Ted Rowan began promoting the idea of a guild for rug hookers and in time the Ontario Hooking Craft Guild was also a reality. A joint project between Chatelaine magazine and the Rittermere studio for Canada’s centennial year of 1967 was extremely well received within the circle of hooking crafters and the Rittermere Farm Craft Studio became a North American landmark for crafters. From this point onward the studio had a large customer base not only in North America but also overseas. The studio remained popular until 1984 when Margaret and Ted Rowan decided to retire. The Rittermere name has been preserved in the name of Rittermere-Hurst-Field which is a similar business located in Aurora which is just north of Toronto.

Identification and characterization of retinoic acid-induced morphological and electrophysiological changes in an invertebrate nervous system

The vitamin A metabolite, retinoic acid (RA) is known to play an important role in the development, patterning and regeneration of nervous tissue, both in the embryo and in the adult. Classically, RA is known to mediate the transcription of target genes through the binding and activation ofits nuclear receptors: the retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Recently, mounting evidence from many animal models has implicated a number of RA-mediated effects operating independently of gene transcription, and thus highlights nove~ nongenornic actions of RA. For example, recent work utilizing cultured neurons from the pond snaa Lymnaea stagnalis, has shown that RA can elicit a regenerative response, growth cone turning, independently of "classical" transcriptional activation While this work illustrates a novel regeneration-inducing effect in culture, it is currently -unknown whether RA also induces regeneration in situ. This study has sought to determine RA's regenerative effucts at the morphological and molecular levels by utilizing an in situ approach focusing on a single identified dopaminergic neuron which possesses a known "mapped" morphology within the CNS. These studies show, for the first time in an invertebrate, that RA can increase neurite outgrowth of dopaminergic cells that have undergone a nerve-crush injury. Utilizing Western blot analysis, it was shown that this effect appears to be independent of any changes in whole CNS expression levels of either the RAR or RXR. Additionally, utilizing immunohistochemistry, to examine protein localization, there does not appear to be any obvious changes in the RXR expression level at the crush site. Changes in cell morphology such as neurity extension are known to be modulated by changes in neuronal firing activity. It has been previously shown that exposure to RA over many days can lead to changes in the electrophysiological properties of cultured Lymnaea neurons; however, no studies have investigated whether short-term exposure to RA can elicit electrophysiological changes and/or changes in firing pattern of neurons in Lymnaea or any other species. The studies performed here show, for the first time in any species, that short-tenn treatment with RA can elicit significant changes in the firing properties of both identified dopaminergic neurons and peptidergic neurons. This effect appears to be independent of protein synthesis, activation of protein kinase A or phospholipase C, and calcium influx but is both dose-dependent and isomer-dependent. These studies provide evidence that the RXR, but not RAR, may be involved, and that intracellular calcium concentrations decrease upon RAexposure with a time course, dose-dependency and isomer-dependency that coincide with the RA-induced electrophysiological changes. Taken together, these studies provide important evidence highlighting RA as a multifunctional molecule, inducing morphological, molecular and electrophysiological changes within the CNS, and highlight the many pathways through which RA may operate to elicit its effects.

Elucidation of the Retinoid Signalling Pathway Involved in Axon Guidance in Lymnaea stagnalis and Xenopus laevis

The vitamin A metabolite, retinoic acid (RA), is known to play a crucial role in several developmental processes including axial patterning and differentiation. More recently, RA has been implicated in the regenerative process acting through its classical signaling pathway, the nuclear receptors, retinoic acid receptor (RAR) and retinoid X receptor (RXR), to mediate gene transcription. Moreover, RA has been shown to act as a guidance molecule for growth cones of regenerating motorneurons of the pond snail, Lymnaea stagnalis. Our lab has recently shown that RA can induce this morphological response independent of nuclear transcription, however, the role of the retinoid receptors in RA-induced chemoattraction is still unknown. Here, I show that the retinoid receptors, RXR and RAR, may mediate the growth cones response to the metabolically active retinoic acid isomers, all-trans and 9-cis RA, in Lymnaea stagnalis. Data presented here show that both an RXR and RAR antagonist can block growth cone turning in response to application of both isomers. Because no prior investigations have shown growth cone turning of individual vertebrate neurons, I aimed to show that both retinoic acid isomers were capable of inducing growth cone turning of embryonic spinal cord neurons in the frog, Xenopus laevis. For the first time in Xenopus, I showed that both all-trans and 9-cis RA were able to induce significantly more neurite outgrowth from cultured embryonic spinal cord neurons and induce positive growth cone turning of individual growth cones. In addition, I showed that the presence of the RXR antagonist, HX531, blocked 9-cis RA-induced growth cone turning and the RARβ antagonist, LE135, blocked all-trans RA-induced growth cone turning in this species. Evidence provided here shows for the first time, conservation of retinoic acid-induced growth cone turning in a vertebrate model system. In addition, these data show that the receptors involved in this morphological response may be the same in vertebrates and invertebrates.

Understanding the Intersection of Reformed Faith and Dutch Immigrant Culture in Ontario Independent Christian Schools: Principals’ Experiences and Perspectives

In the aftermath of World War II, a wave of Dutch Reformed immigrants arrived in Ontario, many of whom joined the Christian Reformed Church. Following familiar cultural patterns, history, and their Reformed Christian faith, these immigrants settled in Ontario with remarkable institutional completeness (Breton, 1964). They quickly established independent, parent-operated Christian schools across Ontario. The primary purpose of the schools was to educate children through a comprehensive biblically based school program, yet this religious purpose often intersected with a Dutch immigrant ethnic culture. Van Dijk (2001) states that “the schools were the most important organization in maintaining the religious and ethnic identity of Calvinists” (p. 66). In this qualitative study I explore the intersection of Reformed faith and Dutch Canadian immigrant ethnic culture in Christian schools through the experiential and professional lens of eight retired principals. Employing a theoretical framework informed by Berger’s (1967) Sacred Canopy, I suggest that the intersection of faith and culture was experienced in the schools and was embodied by the schools themselves. Findings point to this intersection being located in the participants’ experience of (a) Dutchness, (b) the struggle for Christian education, (c) the ties that bound the school community together, and (d) the cloud of witnesses that founded and continues to support and encourage the Christian school community. The study offers insight into a Dutch Reformed immigrant group’s experience carving out a niche for themselves on the educational landscape in Ontario. This study also offers suggestions on how Christian schools can broaden their canopy and become more ethnically and denominationally diverse in the future.