Rapid [Gamma]-amino acid synthesis and the inhibition of the growth and development of oblique banded leaf-roller larvae

The hypothesis that rapid y-aminobutyric acid (GABA) accumulation is a plant defense against phytophagous insects was investigated. Simulation of mechanical damage resulting from phytophagous insect activity increased soybean (Glycine max L.) leaf GABA 10- to 25-fold within 1 to 4 min. Pulverizing leaf tissue resulted in a value of 2. 15 (±O. 11 SE) ~mol GABA per gram fresh weight. Increasing the GABA levels in a synthetic diet from 1.6 to 2.6 Jlffiol GABA per gram fresh weight reduced the growth rates, developmental rates, total biomass (50% reduction), and survival rates (30% reduction) of cultured Oblique banded leaf-roller (OBLR) (Choristonellra rosacealla Harris) larvae. In field experiments OBLR larvae were found predominantly on young terminal leaves which have a reduced capacity to produce GABA in response to mechanical damage. Glutamate decarboxylase (GAD) is a cytosolic enzyme which catalyses the decarboxylation of L-Glu to GABA. GAD is a calmodulin binding enzyme whose activity is stimulated dramatically by increased cytosolic H+ or Ca2 + ion concentrations. Phytophagous insect activity will disrupt the cellular compartmentation of H+ and Ca2 +, activate GAD and subsequent GABA accumulation. In animals GABA is a major inhibitory neurotransmitter. The possible mechanisms resulting in GABA inhibited growth and development of insects are discussed.

(Re)writing the other/self : autoethnography in the transcultural arena of representation

Abstract: In Imperial Eyes Mary Louise Pratt (1992: 7, emphasis original) defines autoethnography as "instances in which colonized subjects undertake to represent themselves in ways that engage with the colonizer's own terms ... in response to or in dialogue with . . . metropolitan representations." Although Pratt's conceptualization of autoethnography has much to offer post-colonial studies, it has received little attention in the field. In this thesis, I interrogate Pratt's notion of autoethnography as a theoretical tool for understanding the self-representations of subordinate peoples within transcultural terrains of signification. I argue that autoethnography is a concept that allows us to move beyond some theoretical dualisms, and to recognize the (necessary) coexistence of subordinate peoples' simultaneous accommodation of and resistance to dominant representations of themselves. I suggest that even when autoethnographic expressions seem to rely on or to reproduce dominant knowledges, their very existence as speech acts implicitly resists dominant discourses which objectify members of oppressed populations and re-create them as Native Informants. I use Pratt's concept to analyze two books by Islamic feminist sociologist Fatima Memissi. Memissi's Dreams ofTrespass and Scheherazade Goes West illustrate the simultaneity of accommodation and disruption evident in autoethnographic communication. Across the two books, Memissi shows herself renegotiating the discourses which discipline her (and her speech). She switches back and forth between the positions of reader and author, demonstrates the reciprocity of the disciplinary gaze (she looks back at her dominants, reading their own reading of her representation of her social group), and provides a model of autoethnographic dialogue.

Does Gamma-aminobutyric acid function as a plant resistance mechanism against phytophagous insect activity? /

Gamma-aminobutyric acid (GAB A) is a ubiquitous non-protein amino acid synthesized via the decarboxylation of L-glutamate in a reaction catalyzed by the cytosolic enzyme L-glutamate decarboxylase (GAD). In animals it functions as an inhibitory neurotransmitter. In plants it accumulates rapidly in response to various stresses, but its function remains unclear. The hypothesis that GABA accumulation in leaf tissue may function as a plant resistance mechanism against phytophagous insect activity was investigated. GABA accumulation in response to mechanical stimulation, mechanical damage and insect activity was demonstrated. In wt tobacco (Nicotiana tabacum cv Samsun), mechanical stimulation or damage caused GABA to accumulate within 2 min from mean levels of 14 to 37 and 1~9 nmol g-l fresh weight (FW), respectively. In the transgenic tobacco strain CaMVGAD27c overexpressing Petunia GAD, the same treatments caused GABA to accumulate from 12 to 59 and 279 nmol g-l FW, respectively. In the transgenic tobacco strain CaMVGADilC 11 overexpressing Petunia GAD lacking an autoinhibitory domain, mechanical stimulation or damage caused GABA to accumulate from 180 to 309 and 630 nmol g-l FW, respectively. Ambulatory activity by tobacco budworm (TBW) larvae (Heliothis virescens) on leaves of CaMVGAD27c tobacco caused GABA to accumulate from 28 to 80 nmol g-l FW within 5 min. Ambulatory and leaf-rolling activity by oblique banded leaf roller (OBLR) larvae (Choristoneura rosaceana cv Harris) on wt soybean leaves (Glycine max cv Harovinton) caused GABA to accumulate from 60 to 1123 nmol g-l FW within 20 min. Increased GABA levels in leaf tissue were shown to affect phytophagous preference in TBW larvae presented with wt and transgenic tobacco leaves. When presented with leaves of Samsun wt and CaMVGAD27c plants, TBW larvae consumed more wt leaf tissue (640 ± 501 S.D. mm2 ) than transgenic leaf tissue (278 ± 338 S.D. mm2 ) nine times out of ten. When presented with leaves of Samsun wt and CaMVGAD~C11 plants, TBW larvae consumed more transgenic leaf tissue (1219 ± 1009 S.D. mm2 ) than wt leaf tissue (28 ± 31 S.D. mm2 ) ten times out of ten. These results indicate that: (1) ambulatory activity of insect larvae on leaves results in increased GABA levels, (2) transgenic tobacco leaves with increased capacity for GABA synthesis deter feeding, and (3) transgenic tobacco leaves with constitutively higher GABA levels stimulate feeding.

A discursive analysis of children's recreational adult-organized sport : when do children get to play?

Adult-organized children's sport attracts millions of participants in Canada and the United States each year. Though there is a great deal of research that considers children's sport, little of it focuses on recreational or house league sport and less of it offers a deep examination of children's experience of their participation. Using observations, interviews, and focus groups involving ten participants in mixed-gender recreational basketball, this qualitative research project examined their experiences. With Foucault's concepts of correct training and the panoptic gaze in mind, I used discourse and deconstruction analyses to consider the children's descriptions along with my observations of their basketball experience. I was particularly looking for prevalent discourses on sport, childhood, and gender and how they affected their experiences. Despite the league's discursive emphasis on fun, participation, fairness, and respect, that was not necessarily what the children experienced. While most stated they enjoyed their season many also expressed serious disappointments. Size and particularly skill very much determined who was most involved in the action and thus actually played baskethaW. Gender also played a significant role in their sport experiences. My findings invite questions about what genuine sport participation actually is and how it might be alternatively imagined.

Structural studies and gabbro mylonitization within the Barton Bay Deformation Zone, Geraldton, Ontario /

Structures related to ductile siMple shear parallel to the Bankf ield-Tonbill Fault, define a 5km wide zone, the Barton Bay Deformation Zone. Structures present within this zone Include; simple shear fabrics S, C and C , asymmetric Z shaped folds with rotated axes, boudinage and pinch and swell structures and a subhorlzontal extension llneation. The most highly deformed rock is a gabbro mylonite which occurs in the fault zone. The deformation of this gabbro has been traced in stages from a protomylonite to an ultramylonite In which feldspar and chlorite grainslze has been reduced from over 100 microns to as little as 5 microns. Evidence from the mylonite and the surrounding structure indicates that deformation within the Barton Bay Deformation Zone is related to a regional simple shear zone, the Bankf ield-Tombill Fault. Movement along this shear zone was in a south over north oblique strike slip fashion with a dextral sense of displacement.

Novices' learning from the Internet : an exploration of navigation behaviours, learner-related factors, and mental effort

The current study was an exploration of why some novices are more successful than their peers when learning from the Internet by examining the relations among time spent with relevant information and changes in invested mental effort during Internet navigations as well as achievement. Navigation behaviours and learner characteristics were investigated as predictors of time spent with relevant information and changes in mental effort. Undergraduates (N = 85, Mage = 20 years, 5 months) searched the Internet for information corresponding to a low knowledge topic for 20 min while their eye gaze and pupil size were recorded. Pupil diameter was used as an objective, continuous measure of mental effort. Participants also completed questionnaires or computer tasks pertaining to s e l f-regulated learning characteristics (general intrinsic goal orientation and effort regulation) and cognitive factors (working memory control, distractibility and cognitive style). All analyses controlled for general mental ability, reading comprehension, topic and Internet knowledge, and overall motivation. A greater proportion of time spent with relevant information predicted higher scores on an achievement test. Interestingly, time spent with relevant information partially mediated the positive relation between the frequency of increases in invested mental effort and achievement. Surprisingly, intrinsic goal orientation was negatively related to time spent with relevant information and effort regulation was negatively related to the frequency of increases in invested mental effort. These findings have implications for supports when novices guide their own learning, especially when using the Internet.