Showing papers by "University of Saskatchewan published in 1998"

Conceptualizing Willingness to Communicate in a L2: A Situational Model of L2 Confidence and Affiliation

Abstract: Why do some students seek, while others avoid, second language (L2) communication? Many language teachers have encountered students high in linguistic competence who are unwilling to use their L2 for communication whereas other students, with only minimal linguistic knowledge, seem to communicate in the L2 whenever possible. Despite excellent communicative competence, spontaneous and sustained use of the L2 is not ensured. A colleague, who teaches a L2 and whose L2 competence is excellent, is well known to avoid “like the plague” L2 communication in social settings. A related observation is that many learners have noticed that their willingness to communicate (WTC) varies considerably over time and across situations. Our aim in this article is twofold. First we wish to provide an account of the linguistic, communicative, and social psychological variables that might affect one's “willingness to communicate.” As demonstrated in the text below, and examination of WTC offers the opportunity to integrate psychological, linguistic, and communicative approaches to L2 research that typically have been independent of each other. We view the WTC model as having the potential to provide a useful interface between these disparate lines of inquiry. Our second goal is to suggest potential relations among these variables by outlining a comprehensive conceptual model that may be useful in describing, explaining, and predicting L2 communication. In an effort to move beyond linguistic or communicative competence as the primary goal of language instruction, this article represents an overt attempt to combine these disparate approaches in a common theme, that is, proposing WTC as the primary goal of language instruction.

The Saskatchewan Health and Back Pain Survey. The prevalence of neck pain and related disability in Saskatchewan adults.

Abstract: Study Design. Population-based, cross-sectional mailed survey. Objective. To determine the lifetime, period, and point prevalence of neck pain and its related disability among Saskatchewan adults and investigate the presence and strength of nonresponse bias. of Background Data. In Europe, the lifetime and point prevalence of neck pain is almost as high as the prevalence of low back pain. Similarly, chronic neck pain is highly prevalent and a common source of disability in the working-age population. However, no studies specifically have documented the prevalence of neck pain and its related disability in North America. Methods. The Saskatchewan Health and Back Pain Survey was mailed to 2184 randomly selected Saskatchewan adults aged 20-69 years. Fifty-five percent of the study population participated. The presence of nonresponse bias was investigated through logistic regression and wave analysis. The Chronic Pain Questionnaire was used to classify the severity of chronic neck pain. Results. The age-standardized lifetime prevalence of neck pain is 66.7% (95% confidence interval, 63.8-69.5), and the point prevalence is 22.2% (95% confidence interval, 19.7-24.7). The age-standaroized 6-month prevalence of low-intensity and low-disability neck pain is 39.7% (95% confidence interval, 36.7-42.7), whereas it Is 10.1% (95% confidence interval, 8.2-11.9) for high-intensitv and low-disability neck pain and 4.6% (95% confidence intervai, 3.3-5.8) for significantly disabling neck pain. The prevalence of low-intensity and low-disability neck pain decreases with age. More women experience high-disability neck pain than men. Wave analysis suggests that the point prevalence and 6-month prevalence of high-intensitv and low-disability neck pain are overestimated in this survey. Conclusion. This cross-sectional study shows that neck pain is highly prevalent in Saskatchewan and that it significantly disables 4.6% (95% confidence interval, 3.3-5.8) of the adult population.

Chemical alarm signalling in aquatic predator-prey systems: A review and prospectus

Abstract: The importance of chemical cues in predator-prey interactions has recently received increasing attention from ecologists. The sources of chemicals to which prey species respond often originate as cues released by the predator (reviewed by Kats and Dill, this issue). Alternatively, cues may be released by other prey animals when they detect or are attacked by a predator. Such cues, known as chemical alarm signals, are particularly common in aquatic systems. These signals provide the basis of our current review. Short-term behavioural responses of prey animals to alarm signals have received the most attention. Behavioural responses of prey resemble those exhibited to known predators, and are therefore likely to make receivers less vulnerable to predation. More recently, studies have shown that benefits to alarm signal receivers extend beyond the immediate behavioural response of nearby conspecifics over a few minutes. For example, alarm signals are important in mediating the learning of unknown pred...

Multisymplectic Geometry, Variational Integrators, and Nonlinear PDEs

Abstract: This paper presents a geometric-variational approach to continuous and discrete mechanics and field theories Using multisymplectic geometry, we show that the existence of the fundamental geometric structures as well as their preservation along solutions can be obtained directly from the variational principle In particular, we prove that a unique multisymplectic structure is obtained by taking the derivative of an action function, and use this structure to prove covariant generalizations of conservation of symplecticity and Noether' s theorem Natural discretization schemes for PDEs, which have these important preservation properties, then follow by choosing a discrete action functional In the case of mechanics, we recover the variational symplectic integrators of Veselov type, while for PDEs we obtain covariant spacetime integrators which conserve the corresponding discrete multisymplectic form as well as the discrete momentum mappings corresponding to symmetries We show that the usual notion of symplecticity along an infinite-dimensional space of fields can be naturally obtained by making a spacetime split All of the aspects of our method are demonstrated with a nonlinear sine-Gordon equation, including computational results and a comparison with other discretization schemes

Agricultural use of antibiotics and the evolution and transfer of antibiotic-resistant bacteria

Abstract: Microbial Resistance to antibiotics is on the rise, in part because of inappropriate use of antibiotics in human medicine but also because of practices in the agricultural industry. Intensive animal production involves giving livestock animals large quantities of antibiotics to promote growth and prevent infection. These uses promote the selection of antibiotic resistance in bacterial populations. The resistant bacteria from agricultural environments may be transmitted to humans, in whom they cause disease that cannot be treated by conventional antibiotics. The author reviews trends in antibiotic use in animal husbandry and agriculture in general. The development of resistance is described, along with the genetic mechanisms that create resistance and facilitate its spread among bacterial species. Particular aspects of resistance in bacterial species common to both the human population and the agrifood industry are emphasized. Control measures that might reverse the current trends are highlighted.

Length of huntingtin and its polyglutamine tract influences localization and frequency of intracellular aggregates.

Abstract: It is unclear how polyglutamine expansion is associated with the pathogenesis of Huntington disease (HD). Here, we provide evidence that polyglutamine expansion leads to the formation of large intracellular aggregates in vitro and in vivo. In vitro these huntingtin-containing aggregates disrupt normal cellular architecture and increase in frequency with polyglutamine length. Huntingtin truncated at nucleotide 1955, close to the caspase-3 cleavage site, forms perinuclear aggregates more readily than full-length huntingtin and increases the susceptibility of cells to death following apoptotic stimuli. Further truncation of huntingtin to nucleotide 436 results in both intranuclear and perinuclear aggregates. For a given protein size, increasing polyglutamine length is associated with increased cellular toxicity. Asymptomatic transgenic mice expressing full-length huntingtin with 138 polyglutamines form exclusively perinuclear aggregates in neurons. These data support the hypothesis that proteolytic cleavage of mutant huntingtin leads to the development of aggregates which compromise cell viability, and that their localization is influenced by protein length.

Measurements and modelling of snow interception in the boreal forest

Abstract: Snow accumulation and ablation processes are particularly important to the hydrology of cold climate forests. In order to calculate the distribution of snow cover and the loss of snow to sublimation, the amount of snowfall intercepted by forest canopies must be determined. This paper introduces a physically-based snowfall interception model that scales snowfall interception processes from branch to canopy. Previous models of snow interception have neglected the persistent presence and subsequent unloading of intercepted snow in cold climates and hence have only been applicable to regions where snow is quickly lost from the canopy. To investigate how snow is intercepted at the forest stand scale, measurements of wind speed, air temperature, above- and below-canopy snowfall, accumulation of snow on the ground and the load of snow intercepted by a suspended, weighed, full-size conifer were collected from spruce and pine stands in the southern boreal forest. These data show that interception increases at a declining rate with increasing snowfall, to a point where the intercepted load overcomes the strength of branches to support it. Leaf area, tree species and initial canopy snow load determine the snow storage capacity of the canopy. These factors, canopy coverage and snowfall are used to calculate snow interception, presuming an exponential decay in incremental interception as cumulative snowfall increases. The subsequent unloading of intercepted snow is additionally modelled as an exponential function of time. The sensitivity of the combined model to temperature, wind speed, snowfall, snow load and canopy structure is examined for weekly time-steps. The examination shows that interception efficiency is particularly sensitive to snowfall amount, canopy density and time since snowfall. A comparison of the model with weekly measurements of snow interception suggests that the method can be used to calculate snow interception successfully in a physically-based manner.

ICK1, a cyclin-dependent protein kinase inhibitor from Arabidopsis thaliana interacts with both Cdc2a and CycD3, and its expression is induced by abscisic acid

Abstract: Cyclin-dependent kinase (CDK) inhibitor genes encode low molecular weight proteins which have important functions in cell cycle regulation, development and perhaps also in tumorigenesis. The first plant CDK inhibitor gene ICK1 was recently identified from Arabidopsis thaliana. Although the C-terminal domain of ICK1 contained an important consensus sequence with the mammalian CDK inhibitor p27Kip1, the remainder of the deduced ICK1 sequence showed little similarity to any known CDK inhibitors. In vitro assays showed that recombinant ICK1 exhibited unique kinase inhibitory properties. In the present study we characterized ICK1 in terms of its gene structure, its interaction with both A. thaliana Cdc2a and CycD3, and its induction by the plant growth regulator, abscisic acid (ABA). ICK1 was expressed at a relatively low level in the tissues surveyed. However, ICK1 was induced by ABA, and along with ICK1 induction there was a decrease in Cdc2-like histone H1 kinase activity. These results suggest a molecular mechanism by which plant cell division might be inhibited by ABA. ICK1 clones were also identified from independent yeast two-hybrid screens using the CycD3 construct. The implication that ICK1 protein could interact with both Cdc2a and CycD3 was confirmed by in vitro binding assays. Furthermore, deletion analysis indicated that different regions of ICK1 are required for the interactions with Cdc2a and CycD3. These results provide a mechanistic basis for understanding the role of CDK inhibitors in cell cycle regulation in plant cells.

Accumulation of an Acidic Dehydrin in the Vicinity of the Plasma Membrane during Cold Acclimation of Wheat

Abstract: Expression of the acidic dehydrin gene wcor410 was found to be associated with the development of freezing tolerance in several Gramineae species. This gene is part of a family of three homologous members, wcor410 , wcor410b , and wcor410c , that have been mapped to the long arms of the homologous group 6 chromosomes of hexaploid wheat. To gain insight into the function of this gene family, antibodies were raised against the WCOR410 protein and affinity purified to eliminate cross-reactivity with the WCS120 dehydrin-like protein of wheat. Protein gel blot analyses showed that the accumulation of WCOR410 proteins correlates well with the capacity of each cultivar to cold acclimate and develop freezing tolerance. Immunoelectron microscope analyses revealed that these proteins accumulate in the vicinity of the plasma membrane of cells in the sensitive vascular transition area where freeze-induced dehydration is likely to be more severe. Biochemical fractionation experiments indicated that WCOR410 is a peripheral protein and not an integral membrane protein. These results provide direct evidence that a subtype of the dehydrin family accumulates near the plasma membrane. The properties, abundance, and localization of these proteins suggest that they are involved in the cryoprotection of the plasma membrane against freezing or dehydration stress. We propose that WCOR410 plays a role in preventing the destabilization of the plasma membrane that occurs during dehydrative conditions.

Design for individuals, design for groups: tradeoffs between power and workspace awareness

Abstract: Users of synchronous groupware systems act both as individuals and as members of a group, and designers must try to support both roles. However, the requirements of individuals and groups often conflict, forcing designers to support one at the expense of the other. The tradeoff is particularly evident in the design of interaction techniques for shared workspaces. Individuals demand powerful and flexible means for interacting with the workspace and its artifacts, while groups require information about each other to maintain awareness. Although these conflicting requirements present real problems to designers, the tension can be reduced in some cases. We consider the tradeoff in three areas of groupware design: workspace navigation, artifact manipulation, and view representation. We show techniques such as multiple viewports, process feedthrough, action indicators, and view translations that support the needs of both individuals and groups.

An evaluation of snow accumulation and ablation processes for land surface modelling

Abstract: This paper discusses the development and testing of snow algorithms with specific reference to their use and application in land surface models. New algorithms, developed by the authors, for estimating snow interception in forest canopies, blowing snow transport and sublimation, snow cover depletion and open environment snowmelt are compared with field measurements. Existing algorithms are discussed and compared with field observations. Recommendations are made with respect to: (a) density of new and aged snow in open and forest environments; (b) interception of snow by evergreen canopies; (c) redistribution and sublimation of snow water equivalent by blowing snow; (d) depletion in snow-covered area during snowmelt; (e) albedo decay during snowmelt; (f) turbulent transfer during snowmelt; and (g) soil heat flux during meltwater infiltration into frozen soils. Preliminary evidence is presented, suggesting that one relatively advanced land surface model, CLASS, significantly underestimates the timing of snowmelt and snowmelt rates in open environments despite overestimating radiation and turbulent contributions to melt. The cause(s) may be due to overestimation of ground heat loss and other factors. It is recommended that further studies of snow energetics and soil heat transfer in frozen soils be undertaken to provide improvements for land surface models such as CLASS, with particular attention paid to establishing the reliability of the models in invoking closure of the energy equation. #1998 John Wiley & Sons, Ltd.

HSP90 interacts with and regulates the activity of heat shock factor 1 in Xenopus oocytes.

Abstract: Transcriptional activation of heat shock genes is a reversible and multistep process involving conversion of inactive heat shock factor 1 (HSF1) monomers into heat shock element (HSE)-binding homotrimers, hyperphosphorylation, and further modifications that induce full transcriptional competence. HSF1 is controlled by multiple regulatory mechanisms, including suppression by additional cellular factors, physical interactions with HSP70, and integration into different cellular signaling cascades. However, the signaling mechanisms by which cells respond to stress and control the HSF1 activation-deactivation pathway are not known. Here we demonstrate that HSP90, a cellular chaperone known to regulate several signal transduction molecules and transcription factors, functions in the regulation of HSF1. The existence of HSF1-HSP90 heterocomplexes was shown by coimmunoprecipitation of HSP90 with HSF1 from unshocked and heat-shocked nuclear extracts, recognition of HSF1-HSE complexes in vitro by using HSP90 antibodies (Abs), and recognition of HSF1 in vivo by HSP90 Abs microinjected directly into oocyte nuclei. The functional impact of HSP90-HSF1 interactions was analyzed by using two strategies: direct nuclear injection of HSP90 Abs and treatment of cells with geldanamycin (GA), an agent that specifically blocks the chaperoning activity of HSP90. Both HSP90 Abs and GA delayed the disassembly of HSF1 trimers during recovery from heat shock and specifically inhibited heat-induced transcription from a chloramphenicol acetyltransferase reporter construct under control of the hsp70 promoter. HSP90 Abs activated HSE binding in the absence of heat shock, an effect that could be reversed by subsequent injection of purified HSP90. GA did not activate HSE binding under nonshock conditions but increased the quantity of HSE binding induced by heat shock. On the basis of these findings and the known properties of HSP90, we propose a new regulatory model in which HSP90 participates in modulating HSF1 at different points along the activation-deactivation pathway, influencing the interconversion between monomeric and trimeric conformations as well as transcriptional activation. We also put forth the hypothesis that HSP90 links HSF1 to cellular signaling molecules coordinating the stress response.

Increased oxidative stress in rat liver and pancreas during progression of streptozotocin-induced diabetes.

Abstract: 1. Oxygen free radicals have been suggested to be a contributory factor in complications of diabetes mellitus. There are many reports indicating the changes in parameters of oxidative stress in diabetes mellitus. In this study we aimed to identify whether oxidative stress occurs in the liver and pancreas in the initial stages of development of diabetes. 2. We therefore investigated the lipid peroxide level (thiobarbituric acid-reactive substances, TBARS) and activities of antioxidant enzymes [superoxide dismutase (SOD), catalase and glutathione peroxidase] in liver and pancreas of control and streptozotocin-induced diabetic rats at various stages of development of diabetes. 3. Male Sprague-Dawley rats were divided into two groups: group I, control (n = 42) and group II, diabetic (n = 42). Each group was further subdivided into seven groups consisting of six rats each. Rats in these subgroups were studied at weekly intervals (0 to 6 weeks). Plasma glucose levels, TBARS levels and activities of antioxidant enzymes were measured in liver and pancreas at various time intervals. 4. There was a significant (P < 0.05) and progressive increase in TBARS levels of liver and pancreas in the diabetic group. Total SOD and Cu-Zn-SOD activity increased (P < 0.05) with progression of diabetes while Mn-SOD activity showed no significant change in either tissue. Catalase and glutathione peroxidase activities increased significantly (P < 0.05) in liver and pancreas. 5. Immunohistochemical study of pancreatic islet revealed a decrease in the expression of insulin with progression of diabetes. However, glucagon and somatostatin showed an increase in immunoreactivity and a difference in their distribution pattern. 6. The findings of the present study suggest that oxidative stress starts at early onset of diabetes mellitus and increases progressively. In conclusion, the structural damage to these tissues or complications of diabetes mellitus may be due to oxidative stress.

Intervention within days for some orbital floor fractures : the white-eyed blowout

Abstract: Management of blowout fractures involving the orbital floor has been controversial over the past several decades. One school of thought recommends conservative treatment for 4 to 6 months while another recommends a 'wait and watch' period of 2 weeks before intervention. The authors have encountered a group of patients with such fractures, commonly children (less than 16 years of age), who have sustained a blow to the periocular area, yet have marked motility restrictions in up and down gaze, minimal soft tissue signs of trauma, lack of enophthalmos, and very minimal evidence of floor disruption on radiologic exam. A 2-week waiting period has been found to be of little benefit in these persons and possibly harmful to their motility. We advocate surgery within the first few days after injury as it may help to avoid permanent motility restriction. The authors have termed this entity 'the white-eyed blowout fracture.'

Review of oxidative stress in brain and spinal cord injury: suggestions for pharmacological and nutritional management strategies.

Abstract: Much of the damage that occurs in the central nervous system (CNS) following trauma is due to secondary effects of glutamate excitotoxicity, Ca2+ overload, and oxidative stress, three mechanisms that in a spiraling interactive cascade end in neuronal death. Oxidative stress activates mechanisms that result in a neutrophil-mediated inflammation that also causes secondary damage. Mechanisms of oxidative stress are reviewed, with particular attention paid to lipid peroxidation and the central role of reduced glutathione in scavenging peroxides. We suggest that decreasing oxidative stress will greatly reduce the amount of secondary damage due to trauma. Oxidative stress can be minimized by 1) maintaining reduced-glutathione levels through the administration of cysteine precursors such as N-acetylcysteine and 2) limiting neutrophil invasion by administering platelet-activating factor antagonists such as BN 52021. Aggressive nutritional support following CNS trauma can also contribute to maximizing antioxidant defenses. Furthermore, we suggest that flavonoids such as quercetin have the potential to be therapeutically effective because of their free radical quenching, iron chelating, and anti-inflammatory properties.

Coupled Modelling of Forest Snow Interception and Sublimation

Abstract: A series of process-based algorithms has been developed to describe the accumulation, unloading and sublimation of intercepted snow in forest canopies. These algorithms are unique in that they scale up the physics of interception and sublimation from small scales, where they are well understood, to forest stand-scale calculations of intercepted snow sublimation. Evaluation of results from the set of algorithms against measured interception and sublimation, in a southern boreal forest jack pine stand during late winter, found that the coupled model provides reasonable approximations of both interception and sublimation losses on half-hourly, daily and event bases. Cumulative errors in the estimate of intercepted snow load over 23 days of test were 0.06 mm SWE, with a standard deviation of 0.46 mm SWE. Sublimation losses during the evaluation were high, approximately two-thirds of snowfall within this period. Seasonal intercepted snow sublimation as a portion of annual snowfall at the model test site was lower than sublimation during the tests, ranging from 13% for a mixed spruce-aspen, 31% for the mature pine and 40% for a mature spruce stand. The results indicate that sublimation can be a significant abstraction of water from mature evergreen stands in northern forests and that the losses can be calculated by application of process-based algorithms.

Direct measurement of organic carbon content in soils by the Leco CR-12 carbon analyzer

Abstract: A straightforward procedure is described for soil organic carbon (C) measurement in soil samples that may contain carbonates by using the Leco CR‐12 Carbon Analyzer. At a temperature of 840°C, a measured oxygen flow of 3.6 L min‐1, lancing flow of 1.0 L min‐1, soil organic C content can be directly measured on 0.20 to 0.40 g of samples, which have previously been ground to pass 40‐mesh sieve, for most medium‐ and fine‐textured soils. The organic C is combusted and measured within 2 min. A larger sample size of up to 2.5 g is suggested for sandy soils of low organic C content.

MMS2, encoding a ubiquitin-conjugating-enzyme-like protein, is a member of the yeast error-free postreplication repair pathway

Abstract: Among the three Saccharomyces cerevisiae DNA repair epistasis groups, the RAD6 group is the most complicated and least characterized, primarily because it consists of two separate repair pathways: an error-free postreplication repair pathway, and a mutagenesis pathway. The rad6 and rad18 mutants are defective in both pathways, and the rev3 mutant affects only the mutagenesis pathway, but a yeast gene that is involved only in error-free postreplication repair has not been reported. We cloned the MMS2 gene from a yeast genomic library by functional complementation of the mms2-1 mutant [Prakash, L. & Prakash, S. (1977) Genetics 86, 33–55]. MMS2 encodes a 137-amino acid, 15.2-kDa protein with significant sequence homology to a conserved family of ubiquitin-conjugating (Ubc) proteins. However, Mms2 does not appear to possess Ubc activity. Genetic analyses indicate that the mms2 mutation is hypostatic to rad6 and rad18 but is synergistic with the rev3 mutation, and the mms2 mutant is proficient in UV-induced mutagenesis. These phenotypes are reminiscent of a pol30-46 mutant known to be impaired in postreplication repair. The mms2 mutant also displayed a REV3-dependent mutator phenotype, strongly suggesting that the MMS2 gene functions in the error-free postreplication repair pathway, parallel to the REV3 mutagenesis pathway. Furthermore, with respect to UV sensitivity, mms2 was found to be hypostatic to the rad6Δ1–9 mutation, which results in the absence of the first nine amino acids of Rad6. On the basis of these collective results, we propose that the mms2 null mutation and two other allele-specific mutations, rad6Δ1–9 and pol30-46, define the error-free mode of DNA postreplication repair, and that these mutations may enhance both spontaneous and DNA damage-induced mutagenesis.

Understanding Participant Perspectives: Q-Methodology in National Forest Management

Abstract: Many policy practitioners and theorists have argued that value-free, objective solutions to policy problems do not exist. While participant values and subjective viewpoints influence policy problems, empirically determining participant perspectives and preferences has been a daunting task. This paper demonstrates how Q-methodology, a technique for systematically revealing subjective perspectives, can contribute to better problem identification and definition, estimation and specification of policy options, and selection, implementation and evaluation of policies. Two case studies in National Forest management are reviewed and demonstrate how Q-methodology can (1) identify important internal and external constituencies; (2) define participant viewpoints and perceptions; (3) provide sharper insight into participant preferred management directions; (4) identify criteria that are important to participants, (5) explicitly outline areas of consensus and conflict; and (6) develop a common view toward the policy.

The treatment of flat areas and depressions in automated drainage analysis of raster digital elevation models

Abstract: Methods developed to process raster digital elevation models (DEM) automatically in order to delineate and measure the properties of drainage networks and drainage basins are being recognized as potentially valuable tools for the topographic parameterization of hydrological models. All of these methods ultimately rely on some form of overland flow simulation to define drainage courses and catchment areas and, therefore, have difficulty dealing with closed depressions and flat areas on digital land surface models. Some fundamental assumptions about the nature of these problem topographic features in DEM are implicit in the various techniques developed to deal with them in automated drainage analysis. The principal assumptions are: (1) that closed depressions and flat areas are spurious features that arise from data errors and limitations of DEM resolution; (2) that flow directions across flat areas are determined solely by adjacent cells of lower elevation; and (3) that closed depressions are caused exclusively by the underestimation of DEM elevations. It is argued that while the first of these assumptions is reasonable, given the quality of DEMs generally available for hydrological analysis, the others are not. Rather it seems more likely that depressions are caused by both under- and overestimation errors and that flow directions across flat areas are determined by the distribution of both higher and lower elevations surrounding flat areas. Two new algorithms are introduced that are based on more reasonable assumptions about the nature of flat areas and depressions, and produce more realistic results in application. These algorithms allow breaching of depression outlets and consider the distribution of both higher and lower elevations in assigning flow directions on flat areas. The results of applying these algorithms to some real and hypothetical landscapes are presented. © 1998 John Wiley & Sons, Ltd.

Low-molecular-weight organic acids in rhizosphere soils of durum wheat and their effect on cadmium bioaccumulation

Abstract: Cadmium (Cd) accumulation has been found to vary between cultivars of durum wheat (Triticum turgidum var. durum), and it is hypothesized that low-molecular-weight organic acids (LMWOAs) produced at the soil-root interface (rhizosphere) may play an important role in the availability and uptake of Cd by these plants. The objective of this study, therefore, was to (1) investigate the nature and quantity of LMWOAs present in the rhizosphere of durum wheat cultivars Arcola (low Cd accumulator) and Kyle (high Cd accumulator) grown in three different soils: Yorkton, Sutherland and Waitville, and (2) determine the relationship between Cd accumulation in these plants and LMWOAs present in the rhizosphere. Plants were grown for two weeks in pot-cultures under growth chamber conditions. Oxalic, fumaric, succinic, L-malic, tartaric, citric, acetic, propionic and butyric acids were found and quantified in the water extracts of rhizosphere soil, with acetic and succinic acids being predominant. No water extractable LMWOAs were identified in the bulk soil. Total amount of LMWOAs in the rhizosphere soil of the high Cd accumulator (Kyle) was significantly higher than that for the low Cd accumulator (Arcola) in all three soils. Furthermore, large differences in amounts of LMWOAs were found in the rhizosphere soil for the same cultivars grown in different soils and followed the pattern: Sutherland > Waitville > Yorkton. Extractable soil Cd (M NH4Cl) and Cd accumulation in the plants also followed the same soil sequence as LMWOA production. Cadmium accumulation by the high and low Cd accumulating cultivars was proportional to the levels of LMWOAs found in the rhizosphere soil of each cultivar. These results suggest that the differing levels of LMWOAs present in the rhizosphere soil played an important role in the solubilization of particulate-bound Cd into soil solution and its subsequent phytoaccumulation by the high and low Cd accumulating cultivars.

Living with a person who has parkinson's disease: The Spouse's perspective by stage of disease

Abstract: The objective of this study was to examine the experience of spouses caregiving for their spouse with Parkinson's disease (PD) and to determine whether their experiences differed by stage of disease. By using a cross-sectional design and mail questionnaire data from 380 spouse caregivers across 23 sites of the Parkinson Study Group, key caregiver variables were examined by stage of PD. Three categories of variables--caregiver role strain (10 measures), caregiver situation (four measures), and caregiver characteristics (four measures)--were analyzed by using t tests with Bonferroni correction. Specific types and amounts of role strain accumulated as the disease progressed, and they differed significantly between stages (p < 0.05). In the caregiving situation, the mean number of caregiving tasks tripled by stage 4/5. Negative changes in lifestyle plus decreases in predictability in caregivers' lives increased significantly in late-stage disease (p < 0.05). Caregiver characteristics of physical health and preparedness did not significantly differ across stages of disease. Depression was significantly higher by stage 4/5. Mutuality, the positive quality of the relationship as perceived by the caregiving spouse, declined beginning at stage 2. Caregiver strain is experienced across all stages of PD and accumulates significantly as the disease progresses. This study defines types and amounts of strain by stage of disease, which will be helpful in designing formal intervention trials to provide more effective help for spouse caregivers.

Measuring the ability to meet family needs in an intensive care unit.

Abstract: Objective: To measure the ability to meet family needs in an intensive care unit (ICU).Design: Descriptive survey.Setting: University hospital ICU.Subjects: Ninety-nine next of kin respondents and 16 secondary family respondents were recruited.Interventions: A modified Society of Critical Ca