Showing papers by "University of Guelph published in 1993"

Ascites in poultry

Abstract: Research on ascites occurring in meat-type chickens reared at moderate and low altitude has shown that the pathogenesis is similar to that of the high altitude disease. Pulmonary hypertension (PH) caused by increased blood flow or increased resistance to flow in the lung results in right ventricular hypertrophy (RVH), valvular insufficiency, increased venous pressure and ascites. The structure of the avian heart, with its thin-walled right ventricle and muscular right atrioventricular valve, allows PH to induce heart failure quickly. The sudden increase in pulmonary hypertension syndrome (PHS) in meat-type chickens in the 1980s was associated with a rapid increase in growth rate and feed conversion. This was a result of a combination of genetic selection for fast-growing, heavy broilers with low feed conversion and a more dense, high caloric, pelleted food that supplied all the nutrients required for rapid growth and encouraged a high nutrient intake. PHS in meat-type chickens is usually primary pulmonary hypertension, that is, PH that occurs without evidence of prior heart or lung disease that could account for the increase in blood flow or resistance to flow that results in the increased pressure in the pulmonary arteries. The lungs of birds are firm and fixed in the thoracic cavity and they do not expand to draw air into the lung. The blood and air capillaries form a rigid network that allows only minimal expansion of the blood capillaries when more blood flow is required. Air is moved through the lung by abdominal movement which draws air in and out of the air sacs. The anatomy and physiology of the avian respiratory system are important in the susceptibility of meat-type chickens to PHS. The small stature of the modern meat-type chicken, the large, heavy breast mass, the pressure from abdominal contents on air sacs, and the small lung volume compared to body weight, may all be involved in the increased incidence of PHS. There is limited space for blood flow in the avian lung. Factors that increase blood flow or increase resistance to flow are additive. Increased blood viscosity caused by the polycythaemia of hypoxia, or increased erythrocyte rigidity of high Na (+), are more likely to produce PH in fast-growing than in slow-growing birds. Increased flow due to cold exposure is also additive. Ascites caused by PH is a production-related disease at low altitude. It can be prevented easily by restricting growth rate. It is possible that some meat-type chickens of the phenotype we have created have reached the limit of blood flow through their lungs and that future improvements in growth rate will only be possible if the lung and abdominal cavity capacities are enlarged.

Lag as a determinant of human performance in interactive systems

Abstract: The sources of lag (the delay between input action and output response) and its effects on human performance are discussed. We measured the effects in a study of target acquisition using the classic Fitts' law paradigm with the addition of four lag conditions. At the highest lag tested (225 ms), movement times and error rates increased by 64% and 214% respectively, compared to the zero lag condition. We propose a model according to which lag should have a multiplicative effect on Fitts' index of difficulty. The model accounts for 94% of the variance and is better than alternative models which propose only an additive effect for lag. The implications for the design of virtual reality systems are discussed.

Reproducibility of random amplified polymorphic DNA (RAPD) analysis among laboratories

Abstract: Random amplified polymorphic DNA (RAPD) analysis appears to offer a cost- and time-effective alternative to restriction fragment-length polymorphism (RFLP) analysis. However, concerns about the ability to compare RAPD results from one laboratory to another have not been addressed effectively. DNA fragments that were amplified by five primers and shown to be reproducibly polymorphic between two oat cultivars (within the Ottawa laboratory) were tested in six other laboratories in North America. Four of the six participants amplified very few or no fragments using the Ottawa protocol. These same participants were able to generate a considerable number of amplified fragments by using their own protocols. The reproducibility of results among laboratories was affected by two factors. First, different laboratories amplified different size ranges of DNA fragments, and, consequently, small and large polymorphic fragments were not always reproduced. Second, although reproducible results were obtained with four of the primers, reproducible results were not obtained with the fifth primer, using the same reaction conditions. It is suggested that if the overall temperature profiles (especially the annealing temperature) inside the tubes are identical among the laboratories, then RAPD fragments are likely to be reproducible.

Superoxide dismutase enhances tolerance of freezing stress in transgenic alfalfa (Medicago sativa L.).

Abstract: Activated oxygen or oxygen free radicals have been implicated in a number of physiological disorders in plants including freezing injury. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide into O2 and H2O2 and thereby reduces the titer of activated oxygen molecules in the cell. To further examine the relationship between oxidative and freezing stresses, the expression of SOD was modified in transgenic alfalfa (Medicago sativa L.). The Mn-SOD cDNA from Nicotiana plumbaginifolia under the control of the cauliflower mosaic virus 35S promoter was introduced into alfalfa using Agrobacterium tumefaciens-mediated transformation. Two plasmid vectors, pMitSOD and pChlSOD, contained a chimeric Mn-SOD construct with a transit peptide for targeting to the mitochondria or one for targeting to the chloroplast, respectively. The putatively transgenic plants were selected for resistance to kanamycin and screened for neomycin phosphotransferase activity and the presence of an additional Mn-SOD isozyme. Detailed analysis of a set of four selected transformants indicated that some had enhanced SOD activity, increased tolerance to the diphenyl ether herbicide, acifluorfen, and increased regrowth after freezing stress. The F1 progeny of one line, RA3-ChlSOD-30, were analyzed by SOD isozyme activity, by polymerase chain reaction for the Mn-SOD gene, and by polymerase chain reaction for the neo gene. RA3-ChlSOD-30 had three sites of insertion of pChlSOD, but only one gave a functional Mn-SOD isozyme; the other two were apparently partial insertions. The progeny with a functional Mn-SOD transgene had more rapid regrowth following freezing stress than those progeny lacking the functional Mn-SOD transgene, suggesting that Mn-SOD serves a protective role by minimizing oxygen free radical production after freezing stress.

Genetic and statistical properties of residual feed intake

Abstract: Residual feed intake is defined as the difference between actual feed intake and that predicted on the basis of requirements for production and maintenance of body weight. Formulas were developed to obtain genetic parameters of residual feed intake from knowledge of the genetic and phenotypic parameters of the component traits. Genetic parameters of residual feed intake were determined for a range of heritabilities (h2 = .1, .3, or .5) for component traits of feed intake and production, and genetic (rg = .1, .5, or .9) and environmental (re = .1, .5, or .9) correlations between them. Resulting heritability of residual feed intake ranged from .03 to .84 and the genetic correlation between residual feed intake and production ranged from -.90 to .87. Heritability of residual feed intake depends considerably on the environmental correlation between feed intake and production. Residual feed intake based on phenotypic regression of feed intake on production usually contains a genetic component due to production. Residual feed intake based on genotypic regression of feed intake on production is genetically independent of production and its use is equivalent to use of a selection index restricted to hold production constant. Multiple-trait selection on residual feed intake, based on either phenotypic or genetic regressions, and production is equivalent to multiple-trait selection on feed intake and production. Residual energy intake in dairy cattle was examined as an example. Heritability of residual energy intake based on genotypic regression was close to zero and indicated that measurement of feed intake provides little additional genetic information over and above that provided by milk production and body weight. The principles outlined in this study have broader application than just to residual feed intake and apply to any trait that is defined as a linear function of other traits.

Gendering organizational analysis

Abstract: Introduction PART ONE: ORGANIZATIONAL ANALYSIS: A CRITIQUE Differential Recruitment and Control - Joan Acker and Donald R Van Houten The Sex Structuring of Organizations Room For Women - Peta Tancred-Sheriff and E Jane Campbell A Case Study in the Sociology of Organizations Gender and Organizations - Jeff Hearn and P Wendy Parkin A Selective Review and a Critique of a Neglected Area PART TWO: TOWARDS FEMINISM AS RADICAL ORGANIZATIONAL ANALYSIS Sex and Organizational Analysis - Gibson Burrell Organization, Gender and Culture - Albert J Mills A Feminist Perspective on State Bureaucracy - Judith Grant and Peta Tancred-Sheriff PART THREE: FROM THEORY TO APPLICATION: EXPLORATIONS IN FEMINIST ORGANIZATIONAL ANALYSIS Sex Ratios, Sex Role Spillover and Sex at Work - Barbara A Gutek and Aaron Groff Cohen A Comparison of Men's and Women's Experiences Women Managers' Perceptions of Gender and Organizational Life - Deborah Sheppard 'The Clerking Sisterhood' - Susan Porter Benson Rationalization and the Work Culture of Saleswomen in American Department Stores 1890-1960 Merit and Gender - Clare Burton Organizations and the Mobilization of Masculine Bias PART FOUR: CONTEMPORARY VOICES An/Other Silent Voice? - Marta B Calas Representing 'Hispanic Women' in Organizational Texts Using the 'F' Word - Marta B Calas and Linda Smircich Feminist Theories and the Social Consequences of Organizational Research Re-Visioning Women Managers' Lives - Ella Louise Bell and Stella Nkomo Gendering Organizational Theory - Joan Acker

The mechanisms of desiccation tolerance in developing seeds

Abstract: Desiccation tolerance is one of the most fundamental properties of seeds. It is acquired late in seed development and is considered necessary for the completion of the plant's life cycle, as an adaptive strategy to enable seed survival during storage or environmental stress, and to ensure better dissemination of the species. The role of water status in desiccated tissues and problems related to testing tolerance in seeds are reviewed. The molecular mechanisms of desiccation tolerance has received extensive consideration only during this past decade. There is a general consensus that desiccation tolerance involves the protection of cellular membranes from the deleterious effect of water removal and the resultant necessity to maintain the bilayer structure in the absence of an aqueous environment. Therefore, some aspects of desiccation-induced membrane injury are described. Several strategies for coping with cellular desiccation have been identified the presence of high amounts of non-reducing sugars, the efficiency of free radical-scavenging systems and the expression of desiccation- and/or ABA-regulated genes. These molecular mechanisms allowing cellular protection are reviewed together with their respective role in dessication tolerance. It is concluded that desiccation tolerance is not likely to be ascribed to a single mechanism but rather to a multifactorial property in which each component is equally critical.

Biosynthesis and expression of cell-surface polysaccharides in gram-negative bacteria

Abstract: Publisher Summary This chapter provides an overview of the molecular mechanisms involved in synthesis and expression of cell-surface polysaccharides in Gram-negative bacteria. Biosynthesis of many cell-surface components, including polysaccharides, involves enzymes and enzyme complexes found in the cytoplasmic membrane. The peptidoglycan layer is located immediately external to the cytoplasmic membrane and this layer is required for cell shape and rigidity. Gram-negative bacteria possess a periplasm that contains a variety of proteins and enzymes, including some involved in import and export of macromolecules. Biosynthesis of bacterial cell-surface polysaccharides involves a series of sequential processes: (1) biosynthesis of activated precursors in the cytoplasm, (2) formation of repeating units, (3) polymerization of repeating units, and (d) export of polysaccharides to the cell surface. The assembly of polysaccharide repeating units and subsequent polymerization reactions occur at the cytoplasmic membrane, using precursors synthesized in the cytoplasm. Genes for biosynthesis of cell-surface polysaccharides are chromosomal and are arranged in clusters of one or more transcriptional units. The synthesis of lipopolysaccharide (LPS) may be subject to complex regulation, but on-off switching is not possible due to the essential structural requirement for the lipid A-core LPS molecule. Most bacteria use extracellular polysaccharides (EPSs) for protection, and many regulatory strategies are directed to modulating EPS synthesis in response to appropriate environmental cues. Application of genetic and biochemical approaches has facilitated detailed analysis of complex, multicomponent systems, such as those involved in synthesis of cell-surface polysaccharides.

Reshaping Fatherhood: Finding the Models

Abstract: One of the reasons that the “conduct” of fatherhood has been slow to change is lack of exposure to appropriate paternal role models. This research was designed to examine how fathers of young children (one child < 6 years of age) shaped fatherhood roles according to various models in their lives. Following the qualitative research principles of grounded theory and comparative analysis, three key themes emerged. First, there was a void with respect to identifiable and meaningful role models. Their own fathers were not seen as good role models. Second, these fathers tended not to model their behavior after a particular individual, but, rather, their models were fragmented as they selected particular behaviors to incorporate into their roles. A third theme to emerge was the emphasis that was placed by these men on providing a role model to their children, in the absence of role models in their own lives.

Tissue glutathione, nutrition, and oxidative stress.

Abstract: Glutathione, a cysteine-containing tripeptide, is the most abundant nonprotein thiol in mammalian cells. Glutathione plays an important role in the detoxification of xenobiotic compounds and in the...

Effect of level of supplemental chromium on performance, serum constituents, and immune status of stressed feeder calves

Abstract: The effects of level of supplemental Cr from high-Cr yeast on performance, blood chemistry profile, morbidity, and immune status were investigated using 84 Charolais-crossed steer calves in a completely randomized design. Calves of 236-kg average weight, after transportation from Saskatchewan to Ontario, were randomly assigned to four treatments; 0, .2, .5, and 1 ppm of supplemental Cr, incorporated into a corn-silage diet. Blood was collected via jugular venipuncture at d 0, 7, 14, 21, and 28 and analyzed for metabolites, minerals, immunoglobulins, hematocrit (Hct), and leucocyte counts. Hemagglutinating antibody titers to human red blood cells (HRBC) were quantified after immunizations on d 0 and 14. Contact sensitivity after sensitization and challenge with dinitrochlorobenzene was also measured. A 27% increase (P < .05) in ADG was observed at d 30 for calves that were fed .2 and 1 ppm of supplemental Cr. Dry matter intake also increased (P < .05) for the .2- and 1-ppm Cr treatments. A linear decrease (P < .05) in serum cortisol with increasing Cr level was observed at d 28. Chromium supplementation decreased (P < .05) morbidity, as well as rectal temperatures at d 2 and 5. Peak primary antibody titers to HRBC (P < .05) and immunoglobulin G1 concentrations (P = .06) at d 14 were higher for steers that received the Cr supplementation. However, Cr treatment had no effect on expression of contact sensitivity. Chromium supplementation increased (P < .05) Hct on d 14 and 21 and serum Ca and Mg on d 7.(ABSTRACT TRUNCATED AT 250 WORDS)

The Enzymatic Coagulation of Milk

Abstract: After milk has been treated with chymosin or other milk coagulating enzymes, there is little apparent reaction for some time, and then the milk coagulates rapidly. This phenomenon, which is the first step of cheesemaking, results from two processes, the first being the attack on κ-casein, which stabilizes the casein micelles, by the proteolytic enzymes (chymosin, pepsin or microbial proteinases) contained in the rennet, and the second being the subsequent clotting of the micelles which have been destabilized by this enzymatic attack. These processes have been described as the primary and secondary stages of the renneting reaction. This sequential description of the reaction is, however, somewhat oversimplified, since it is not necessary for the enzymatic reaction to be complete before aggregation of partly renneted micelles can occur. Indeed, the milk may begin to clot well before the enzymatic cleavage of the κ-casein is complete.1,2,3

GENCALC: Software to Facilitate the Use of Crop Models for Analyzing Field Experiments

Abstract: A number of crop simulation models use as model inputs certain coefficients that account for differences among cultivars. These coefficients, often referred to as genotype coefficients, allow the models to simulate performance of diverse genotypes under different soil, weather, and management conditions. The models therefore can potentially be used to resolve the genotype X environment interaction into underlying coefficients. GENCALC (Genotype Coefficient Calculator) is a software package that facilitates the calculation of these coefficients for use in existing crop models. In GENCALC, the coefficients for a genotype are estimated iteratively by running the appropriate crop model with model input data and approximate coefficients, comparing the model output with actual data, and then altering the coefficients until the simulated and measured values match. The coefficients are determined in a specified sequence, starting with those that relate to developmental aspects. GENCALC also allows for calculation of averages (+/- SD) for the coefficients determined from specific experiments. This facilitates the selection of coefficients with the lowest variability, which can then be stored in crop-specific database files. GENCALC comprises several programs and requires additional models and model input files, so a hard disk with approximately 2 Mb free space is required. GENCALC will run on any IBM or IBM-compatible computer with DOS version 3.0 or later.

Visual orienting deficits in high-functioning people with autism

Abstract: There has been renewed interest in the idea that attentional dysfunction may underlie autistic symptomatology (e.g., Bryson, Wainwright-Sharp, & Smith, 1990; Dawson & Lewy, 1989a, 1989b). Existing research indicates problems with overfocused attention (Lovaas et al., 1971; Rincover & Ducharme, 1987), and with shifting attention between sensory modalities (Courchesne et al., 1990). These phenomena were examined further by using Posner's (1978) visual orienting task with a group of high-functioning autistic adolescents and adults, and matched normal controls. Our results indicate that autistic people have difficulty processing briefly presented cue information. Evidence of problems disengaging and shifting attention within the visual modality was also provided. The findings can be seen as consistent with previous behavioral, autonomic, and electrophysiological research which has revealed impairments in the registration, processing, and response to external stimuli.

Selected factors limiting the microbial degradation of recalcitrant compounds

Abstract: The focus of this review is to examine some of the reasons biodegradation may not take place in the environment even though its occurrence in the laboratory has been demonstrated. Some approaches for dealing with chemical persistence will be discussed. In addition, the potential of bioremediation as an in situ clean-up technology will be considered.

Germline chimeric chickens from dispersed donor blastodermal cells and compromised recipient embryos

Abstract: Stage-X blastoderms, within intact eggs from White Leghorn hens, were exposed to 500–700 rads of gamma radiation from a 60Co source prior to injection, into the subgerminal cavity, of approximately 100 or 200–400 dispersed cells from stage-X blastoderms isolated from eggs laid by Barred Plymouth Rock hens. Embryos developing past day 14 of incubation and hatched chicks were assessed for donor and recipient cell contribution to the melanocyte population through examination of black and yellow down pigmentation, respectively (Barred Plymouth Rocks have a recessive allele at the I locus while the White Leghorns have a dominant allele at the I locus). Of the 809 embryos injected with approximately 100 cells, 192 developed past day 14 and black pigmentation, indicating somatic chimerism, was observed on 118 of the 192 (58%) embryos and chicks. Of the 296 embryos injected with 200–400 donor cells, 86 developed past day 14 of incubation. Somatic chimerism was observed on 55 of the 86 (64%) embryos and chicks. To test for germline chimerism, birds surviving to maturity were mated to Barred Plymouth Rocks. Five somatically chimeric females were produced when approximately 100 cells were injected, and one was a germline chimera. Six somatic female chimeras were produced following the injection of 200–400 cells, three of which proved to be germline chimeras by the presence of Barred Rock chicks among their offspring. Two of the nine males produced by injecting approximately 100 cells were germline chimeras.(ABSTRACT TRUNCATED AT 250 WORDS)

Long‐Term Effect of Five Tillage Systems on Corn Response and Soil Structure

Abstract: Tillage systems need to be compared over an extended period of time to determine their transitional and long-term impacts on crop growth and soil properties. A 15-yr experiment established in 1976 compared reduced tillage systems with conventional fall moldboard plowing for production of continuous corn (Zea mays L.) on a Maryhill silt loam soil (Typic Hapludalf. Corn plant growth and yield and soil properties were compared for five tillage systems: fall plow (fall mold-board plow + spring secondary tillage), fall chisel plow (fall chisel plow + spring secondary), spring plow, spring plow/secondary (spring plow + secondary), and no-till. No-till consistently resulted in slower plant growth than most or all of the other tillage systems [...]

Mechanism of silicate binding to the bacterial cell wall in Bacillus subtilis.

Abstract: To investigate the chemical mechanism of silicate binding to the surface of Bacillus subtilis, we chemically modified cell wall carboxylates to reverse their charge by the addition of an ethylenediamine ligand. For up to 9 weeks, mixtures of Si, Al-Fe-Si, and Al-Fe-Si plus toxic heavy metals were reacted with these cells for comparison with control cells and abiotic solutions. In general, more Si and less metal were bound to the chemically modified surfaces, thereby showing the importance of an electropositive charge in cell walls for fine-grain silicate mineral development. The predominant reaction for this development was the initial silicate-to-amine complexation in the peptidoglycan of ethylenediamine-modified and control cell walls, although metal ion bridging between electronegative sites and silicate had an additive effect. The binding of silicate to these bacterial surfaces can thus be described as outer sphere complex formation because it occurs through electrostatic interaction.