An investigation of ethylene inhibition of growth in etiolated Avena sativa coleoptiles /

Growth rates of etiolated Avena sativa coleoptiles in pH 7.0 buffered medium are stimulated in a synergistic manner by IAA and 320 ~l/l carbon dioxide. The suggestion that carbon dioxide stimulated growth involves dark fixation is supported by the ability of 1 mM malate to replace carbon dioxide, with neither factor able to stimulate growth in the presence of the other (Bown, Dymock and Aung, 1974). The regulation of Avena coleoptile growth by ethylene has been investigated in the light of this data and the well documented antagonism between carbon dioxide and ethylene in the regulation of developmental processes. The influence of various permutations of ethylene, IAA, carbon dioxide and malate on the rates of growth, l4c-bicarbonate incorporation, l4C-bicarbonate fixation, and malate decarboxylation have been investigated. In the presence of 320 ~l/l carbon dioxide, 10.8 ~l/l ethylene inhibited growth both in the absence and presence of 20 ~M IAA with inhibition times, of 8-10 and 12-13 minutes respectively. In contrast ethylene inhibition of growth was not significant in the absence of growth stimulation by CO2 or 1 mM malate, and the normal growth increases in response to CO2 and malate were blocked by the simultaneous application of ethylene. The rates of incorporation and dark fixation of l4C-bicerbonate were not measurably. influenced by ethylene, IAA or malate, either prior to or during the changes in growth ,ates induced by these agents. The data does not support the hypothesis that ethylene inhibition of growth results from an inhibition of dark fixation, but suggests that ethylene may inhibit a process which is subsequent to fixation.

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.

Is GABA involved in regulating plant growth and development? /

Rapid and large accumulation of GABA (y-aminobutyric acid) in response to a number of plant stresses has been well documented. But the role(s) of GABA in plants is not well defined. In recent years, the possibility of GABA involvement in regulating plant growth and development has been raised. In the present study, this possibility was examined. First, to rapidly and accurately determine GABA levels in plant tissues, a spectrometric method for GABA determination was developed based on a commercially available enzyme Gabase. Seventy mM LaCb almost completely removed water-soluble pigments from plant tissues which greatly interfere with the absorbance reading at 340nm. Inactivation of GAD (glutamate decarboxylase) by immediately adding methanol to a frozen plant tissue powder was suggested to prevent GABA production during extraction. The recovery of GABA with this method was approximately 100%. Second, the relationship between GABA levels and hypocotyl elongation in soybean seedlings was analyzed using different approaches to regulate in vivo GABA levels and the elongation of hypocotyls. The following major observations were made. (1) Mechanical stimulation by stroking elevated GABA levels and concurrently induced a rapid and significant reduction in hypocotyl elongation. (2) External GABA was demonstrated to penetrate into the hypocotyls using '*C-GABA. Application of external GABA elevated in vivo GABA levels, but failed to inhibit hypocotyl elongation. (3) LaCla and blue light irradiation caused an inhibition in the elongation of dark-grown hypocotyls, whereas GABA levels were not significantly affected. (4) Ca^was suggested to be involved in the signal transduction pathway leading from mechanical stimulation to GABA production, as indicated by the ability of La'* to inhibit GABA production in stimulated hypocotyls. (5) Bicuculline, saclofen and baclofen (agonists and antagonists of GABA receptors in animals) had no effect on hypocotyl elongation. It might indicate that GABA-binding components which are structurally similar to animal GABA receptors and functionally capable of regulating plant growth may not exist in plants. Therefore, the conclusion was drawn that GABA alone is not sufficient to inhibit hypocotyl elongation. Third, chloride influx in isolated Asparagus cells was enhanced by lOmM GABA during a 3 hour incubation, but the effect was not specific for GABA. Chloride efflux was not influenced by GABA. Both influx and efflux of chloride were significantly inhibited by NPPB, a chloride channel blocker. These results suggest that GABA does not influence the activity of plant chloride channels.

An investigation into differences between indoleacetic acid and fusicoccin in their influence on RNA synthesis, protein synthesis and growth in Avena coleoptile tissue

Growth stimulation of Avena coleoptile tissue by indoleacetic acid (IAA) and fusicoccin (FC) was compared by measuring both their influence on RNA and protein synthesis during IAA or FC stimulated growth. FC stimulated growth more than IAA during the initial four hour exposure, after which the growth rate gradually declined to the control rate. FC, but not IAA, increased the uptake of 3H-Ieucine into tissue and the specific radioactivity of extracted protein. Cycloheximide inhibited the incorporation of 3H-Ieucine into protein by approximately 60% to 70% in all cases. In the presence of cycloheximide 3H-radioactivity accumulated in FC-treated tissue, whereas IAA did not seem to influence 3H-accumulation. These results suggest that FC stimulated leucine uptake into the tissue and that increased specific activity of coleoptile protein is due to increased leucine uptake, not an increased rate of protein synthesis. There was no measurable influence of IAA and/or FC on RNA and protein synthesis during the initial hours of a growth stimulation. Inhibitors of RNA and protein synthesis, actinomycin D and cycloheximide, respectively, severely inhibited IAA enhanced growth but only partially inhibited FC stimulated growth. The data are consistent with suggestions that a rapidly turning over protein participates in IAA stimulated growth, and that a continual synthesis of RNA and proteins is an absolute requirement for a long term growth response to IAA. On the contrary, FC-stimulated growth exhibited less dependency on the transcription and translation processes. The data are consistent with proposals suggesting different sites of action for FC and IAA stimulated growth. l?hen compared to CO2-free air, CO2 at 300 ppm had no significant influence on coleoptile growth and protein synthesis in the presence or absence of lAA or FC. Also, I mM malate, pH 6.0 did not influence growth of coleoptiles in the presence or absence of lAA. This result was obtained despite reports indicating that 300 ppm CO2 or I mM malate stimulates growth and protein synthesis. This lack of difference between CO2-treated and untreated tissue could indicate either that the interstitial space CO2 concentration is not actually different in the two treatments due to significant endogenous respiratory CO2 or else the data would suggest a very loose coupling between dark CO2 fixation and growth. IAA stimulated the in vivo fixation of 14c-bicarbonate (NaHI4c03) by about 25% and the addition of cycloheximide caused an inhibition of bicarbonate fixation within 30 min. Cycloheximide has also been reported to inhibit IAA-stimulated H+ excretion. These data are consistent with the acid growth theory and suggest that lAA stimulated growth involves dark CO2 fixation. The roles of dark CO2 fixation in lAA-stimulated growth are discussed.

Test of Hockman and Oldham's job characteristics model in a post-secondary educational setting

One hundred and seventy-two subj ects participated in this quantitative, correlational survey which tested Hackman and Oldham's Job Characteristics Model in an educational setting. Subjects were Teaching Masters, Chairmen and Deans from an Ontario community college. The data were collected via mailed questionnaire, on all variables of the model. Several reliable, valid instruments were used to test the variables. Data analysis through Pearson correlation and stepwise multiple regression analyses revealed that core job characteristics predicted certain critical psychological states and that these critical psychological states, in turn were able to predict various personal and work outcomes but not absenteeism. The context variable, Satisfaction with Co-workers, was the only consistent moderating variable between core characteristics and critical psychological states; however, individual employee differences did moderate the relationship between critical psychological states and all of the personal and work outcomes except Internal Work Motivation. Two other moderator variables, Satisfaction with Context and Growth Need Strength, demonstrated an ability to predict the outcome General Job Satisfaction. The research suggests that this model may be used for job design and redesign purposes within the community college setting.

Individual differences in risk-taking and associated characteristics : a test of specificity in executive functions /

Multiple measures have been devised by clinicians and theorists from many different backgrounds for the purpose of assessing the influence of the frontal lobes on behaviour. Some utilize self-report measures to investigate behavioural characteristics such as risktaking, sensation seeking, impulsivity, and sensitivity to reward and punishment in an attempt to understand complex human decision making. Others rely more on neuroimaging and electrophysiological investigation involving experimental tasks thought to demonstrate executive functions in action, while other researchers prefer to study clinical populations with selective damage. Neuropsychological models of frontal lobe functioning have led to a greater appreciation of the dissociations among various aspects of prefrontal cortex function. This thesis involves (1) an examination of various psychometric and experimental indices of executive functions for coherence as one would predict on the basis of highly developed neurophysiological models of prefrontal function, particularly those aspects of executive function that involve predominantly cognitive abilities versus processes characterized by affect regulation; and (2) investigation of the relations between risk-taking, attentional abilties and their associated characteristics using a neurophysiological model of prefrontal functions addressed in (1). Late adolescence is a stage in which the prefrontal cortices undergo intensive structural and functional maturational changes; this period also involves increases in levels of risky and sensation driven behaviours, as well as a hypersensitivity to reward and a reduction in inhibition. Consequently, late adolescence spears to represent an ideal developmental period in which to examine these decision-making behaviours due to the maximum variability of behavioural characteristics of interest. Participants were 45 male undergraduate 18- to 19-year olds, who completed a battery of measures that included self-report, experimental and behavioural measures designed to assess particular aspects of prefrontal and executive functioning. As predicted, factor analysis supported the grouping of executive process by type (either primarily cognitive or affective), conforming to the orbitofrontal versus dorsolateral typology; risk-taking and associated characteristics were associated more with the orbitofrontal than the dorsolateral factor, whereas attentional and planning abilities tended to correlate more strongly with the dorsolateral factor. Results are discussed in light of future assessment, investigation and understanding of complex human decision-making and executive functions. Implications, applications and suggestions for future research are also proposed.

The analysis of Metarhizium robertsii potential as endophytic plant root coloniser, plant growth enhancer and antagonist to bean root pathogen Fusarium solani f. sp. phaseolis.

The soil-inhabiting insect-pathogenic fungus Metarhizium robertsii also colonizes plant roots endophytically, thus showing potential as a plant symbiont. M robertsii is not randomly distributed in soils but preferentially associates with the plant rhizosphere when applied in agricultural settings. Root surface and endophytic colonization of switchgrass (Panicum virgatum) and haricot beans (Phaseolus vulgaris) by M robertsii were examined after inoculation with fungal conidia. Light and confocal microscopies were used to ascertain this rhizosphere association. Root lengths, root hair density and emergence of lateral roots were also measured. Initially, M robertsii conidia adhered to, germinated on, and colonized, roots. Furthermore, plant roots treated with Metarhizium grew faster and the density of plant root hairs increased when compared with control plants. The onset of plant root hair proliferation was initiated before germination of M robertsii on the root (within 1-2 days). Plants inoculated with M robertsii AMAD2 (plant adhesin gene) took significantly longer to show root hair proliferation than the wild type. Cell free extracts of M robertsii did not stimulate root hair proliferation. Longer term (60 days) associations showed that M robertsii endophytically colonized individual cortical cells within bean roots. Metarhizium appeared as an amorphous mycelial aggregate within root cortical cells as well as between the intercellular spaces with no apparent damage to the plant. These results suggested that not only is M robertsii rhizosphere competent but displays a beneficial endophytic association with plant roots that results in the proliferation of root hairs. The biocontrol of bean (Phaseolis vulgaris) root rot fungus Fusarium solani f. sp. phaseolis by Metarhizium robertsii was investigated in vitro and in vivo. Dual cultures on Petri dishes showed antagonism of M robertsii against F. solani. A relative inhibition of ca. 60% of F. solani growth was observed in these assays. Cell free culture filtrates of M robertsii inhibited the germination of F. solani conidia by 83% and the inhibitory metabolite was heat stable. Beans plants colonized by M robertsii then exposed to F. solani showed healthier plant profiles and lower disease indices compared to plants not colonized by M robertsii. These results suggested that the insect pathogenic/endophytic fungus M robertsii could also be utilized as a biocontrol agent against certain plant pathogens occurring in the rhizosphere.

Inhibition of human lung cancer cell proliferation and survival by wine

Compounds of plant origin and food components have attracted scientific attention for use as agents for cancer prevention and treatment. Wine contains polyphenols that were shown to have anti-cancer and other health benefits. The survival pathways of Akt and extracellular signal-regulated kinase (Erk), and the tumor suppressor p53 are key modulators of cancer cell growth and survival. In this study, we examined the effects of wine on proliferation and survival of human Non-small cell lung cancer (NSCLC) cells and its effects on signaling events.

Metaphorical Interpretation: Measuring and Facilitating Growth.

Abstract A total of 378 grade 9 students participated in this study to address the problem that although metaphorical literacy and thought are expected and necessary for success in junior and senior high school and beyond, metaphorical concepts and thought are not required to be explicitly taught to these students. The students were from 20 different classes from 4 levels: English language learners (ELL), school to work (SSTW), applied, and academic. All were from 7 secondary schools within a board in southern Ontario. Nine classes made up the control group and 11 classes made up the treatment group. All classes were given 3 pretests and the posttest. The treatment group was given Socratic lessons and direct instruction on metaphorical thought and expressions during 1 semester and in conjunction with their other classroom material. The pretest scores (TOLD, Peabody, preproverbs concrete, and preproverbs abstract) did not reveal any effect of gender, but the academic students had higher scores than the applied students. The SSTW student results are more variable: (a) for the TOLD test, SSTW scores were between those of the academic and applied students; (b) for Peabody scores, SSTW students’ scores are the same as academic and are greater than applied; (c) for preproverbs concrete and preproverbs abstract, the SSTW scores are not different from the applied scores. The postproverbs concrete and postproverbs abstract scores for the treatment groups also showed no effect of gender but revealed that all students who received the treatment did better on their post scores. The positive changes of the treatment group illustrate a measured movement from literal understanding to abstract understanding using direct Socratic instruction and proverbs as a medium.

Posttraumatic Growth: A Mediated-Moderation Model

The primary goal was to test a mediated-moderation model in which dispositional optimism was the moderator and its role was mediated by problem-focused coping. A secondary goal was to demonstrate that posttraumatic growth could be differentiated from maturation and normal development. Two groups of participants were recruited and completed questionnaires twice with a 60-day interval: One group (Trauma), described a traumatic experience and the second group (Non-trauma), described a significant experience. Contrary to the hypothesis, only problem-focused coping and deliberate rumination predicted posttraumatic growth, and these findings were only observed in concurrent analyses. Furthermore, the results indicated that there was no significant difference between groups on growth scores at either Time 1 or Time 2. The findings suggest that the term “posttraumatic growth” may refer to the context in which growth occurs rather than to some developmental process that uniquely follows trauma.

Inhibition of human lung cancer cell proliferation and survival by wine

Compounds of plant origin and food components have attracted scientific attention for use as agents for cancer prevention and treatment. Wine contains polyphenols that were shown to have anti-cancer and other health benefits. The survival pathways of Akt and extracellular signal-regulated kinase (Erk), and the tumor suppressor p53 are key modulators of cancer cell growth and survival. In this study, we examined the effects of wine on proliferation and survival of human Non-small cell lung cancer (NSCLC) cells and its effects on signaling events.