Showing papers by "University of Guelph published in 1996"
TL;DR: UV-B exposure preferentially induces peroxidase-related enzymes, whereas O3 exposure invokes the enzymes of superoxide dismutase/ascorbate-glutathione cycle, and in contrast to O3, UV-B Exposure generated activated oxygen species by increasing NADPH-oxid enzyme activity.
Abstract: Earlier studies with Arabidopsis thaliana exposed to ultraviolet B (UV-B) and ozone (O3) have indicated the differential responses of superoxide dismutase and glutathione reductase. In this study, we have investigated whether A. thaliana genotype Landsberg erecta and its flavonoid-deficient mutant transparent testa (tt5) is capable of metabolizing UV-B- and O3-induced activated oxygen species by invoking similar antioxidant enzymes. UV-B exposure preferentially enhanced guaiacol-peroxidases, ascorbate peroxidase, and peroxidases specific to coniferyl alcohol and modified the substrate affinity of ascorbate peroxidase. O3 exposure enhanced superoxide dismutase, peroxidases, glutathione reductase, and ascorbate peroxidase to a similar degree and modified the substrate affinity of both glutathione reductase and ascorbate peroxidase. Both UV-B and O3 exposure enhanced similar Cu,Zn-superoxide dismutase isoforms. New isoforms of peroxidases and ascorbate peroxidase were synthesized in tt5 plants irradiated with UV-B. UV-B radiation, in contrast to O3, enhanced the activated oxygen species by increasing membrane-localized NADPH-oxidase activity and decreasing catalase activities. These results collectively suggest that (a) UV-B exposure preferentially induces peroxidase-related enzymes, whereas O3 exposure invokes the enzymes of superoxide dismutase/ascorbate-glutathione cycle, and (b) in contrast to O3, UV-B exposure generated activated oxygen species by increasing NADPH-oxidase activity.
1,246 citations
TL;DR: The concept of cooperative rearrangement was introduced in an attempt to unify these two views of the glass transition by demonstrating that such cooperativity, coupled with a thermodynamic glass transition, resulted naturally insystem dynamics such as those described by the WLFequation for temperatures near freezing.
Abstract: We report the first measurements of the glass transition temperature ${T}_{g}$ for thin freely standing polystyrene (PS) films. We have used Brillouin light scattering to measure ${T}_{g}$ for freely standing films of different thicknesses. We find that ${T}_{g}$ decreases linearly with film thickness $h$ for $h\ensuremath{\le}700\AA{}$, with a reduction of 70 K for a film with $h\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}290\AA{}$. These measurements characterize unambiguously the effects of the free surface on ${T}_{g}$ of thin polymer films. Results are compared to similar results for supported PS films [Keddie et al., Europhys. Lett. 27, 59 (1994)], and we find that their measured values are influenced strongly by the substrate.
1,052 citations
TL;DR: In this paper, an expert panel was convened to conduct a comprehensive aquatic ecological risk assessment based on several newly suggested procedures and included exposure and hazard subcomponents as well as the overall risk assessment.
Abstract: The triazine herbicide atrazine (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine) is one of the most used pesticides in North America. Atrazine is principally used for control of certain annual broadleaf and grass weeds, primarily in corn but also in sorghum, sugarcane, and, to a lesser extent, other crops and landscaping. Atrazine is found in many surface and ground waters in North America, and aquatic ecological effects are a possible concern for the regulatory and regulated communities. To address these concerns an expert panel (the Panel) was convened to conduct a comprehensive aquatic ecological risk assessment. This assessment was based on several newly suggested procedures and included exposure and hazard subcomponents as well as the overall risk assessment. The Panel determined that use of probabilistic risk assessment techniques was appropriate. Here, the results of this assessment are presented as a case study for these techniques. The environmental exposure assessment concentrated on monitoring data from Midwestern watersheds, the area of greatest atrazine use in North America. This analysis revealed that atrazine concentrations rarely exceed 20 μg/L in rivers and streams that were the main focus of the aquatic ecological risk assessment. Following storm runoff, biota in lower-order streams may be exposed to pulses of atrazine greater than 20 μg/L, but these exposures are short-lived. The assessment also considered exposures in lakes and reservoirs. The principal data set was developed by the U.S. Geological Survey, which monitored residues in 76 Midwestern reservoirs in 11 states in 1992-1993. Residue concentrations in some reservoirs were similar to those in streams but persisted longer. Atrazine residues were widespread in reservoirs (92% occurrence), and the 90th percentile of this exposure distribution for early June to July was about 5 μg/L. Mathematical simulation models of chemical fate were used to generalize the exposure analysis to other sites and to assess the potential effects of reduction in the application rates. Models were evaluated, modified, and calibrated against available monitoring data to validate that these models could predict atrazine runoff. PRZM-2 overpredicted atrazine concentrations by about an order of magnitude, whereas GLEAMS underpredicted by a factor of 2 to 5. Thus, exposure models were not used to extrapolate to other regions of atrazine use in this assessment. The effects assessment considered both freshwater and saltwater toxicity test results. Phytoplankton were the most sensitive organisms, followed, in decreasing order of sensitivity, by macrophytes, benthic invertebrates, zooplankton, and fish. Atrazine inhibits photophosphorylation but typically does not result in lethality or permanent cell damage in the short term. This characteristic of atrazine required a different model than typically used for understanding the potential impact in aquatic systems, where lethality or nonreversible effects are usually assumed. In addition, recovery of phytoplankton from exposure to 5 to 20 μg/L atrazine was demonstrated. In some mesocosm field experiments, phytoplankton and macrophytes were reduced after atrazine exposures greater than 20 μg/L. However, populations were quickly reestablished, even while atrazine residues persisted in the water. Effects in field studies were judged to be ecologically important only at exposures of 50 μg/L or greater. Mesocosm experiments did not reveal disruption of either ecosystem structure or function at atrazine concentrations typically encountered in the environment (generally 5 μg/L or less). Based on an integration of laboratory bioassay data, field effects studies, and environmental monitoring data from watersheds in high-use areas in the Midwestern United States, the Panel concluded that atrazine does not pose a significant risk to the aquatic environment. Although some inhibitory effects on algae, phytoplankton, or macrophyte production may occur in small streams vulnerable to agricultural runoff, these effects are likely to be transient, and quick recovery of the ecological system is expected. A subset of surface waters, principally small reservoirs in areas with intensive use of atrazine, may be at greater risk of exposure to atrazine. Therefore, it is recommended that site-specific risk assessments be conducted at these sites to assess possible ecological effects in the context of the uses to which these ecosystems are put and the effectiveness and cost-benefit aspect of any risk mitigation measures that may be applied.
951 citations
TL;DR: To "outrace" chilling injury, oocytes contained in < 1 microliter of EG solution were placed onto electron microscope grids and plunged directly into N2 slush or LN2, and 30% of them cleaved after IVF, and half of these developed into blastocysts-- survival rates equivalent to those for oocytes that had been exposed to EG without any cooling.
Abstract: The objective of the research described was to devise an efficient procedure to cryopreserve in vitro-matured bovine oocytes, using in vitro fertilization (IVF) and development of resultant zygotes into blastocysts as criteria of oocyte survival. Oocytes at metaphase II were found to be extremely sensitive to chilling. Cooling them to O degrees C for as little as 5 sec significantly decreased their capability to cleave and develop further after IVF; after 80 sec at 0 degrees C, only approximately 10% of chilled oocytes developed into blastocysts. Oocytes were also adversely affected by brief exposures to 4 M and 5.5 M ethylene glycol (EG) solutions supplemented with sucrose; after being suspended in either of these EG solutions in plastic straws and plunged directly into liquid nitrogen (LN2), few of the oocytes were fertilized and developed. To "outrace" chilling injury, oocytes contained in < 1 microliter of EG solution were placed onto electron microscope grids and plunged directly into N2 slush or LN2. After such ultra-rapidly cooled oocytes were warmed, 30% of them cleaved after IVF, and half of these developed into blastocysts-- survival rates equivalent to those for oocytes that had been exposed to EG without any cooling. This method offers promise as a novel way to cryopreserve bovine oocytes.
613 citations
TL;DR: Eradication of Helicobacter pylori provides potential cure in the majority of patients with peptic ulcer disease, and eradication rates of more than 90% have been reported, using omeprazole in combination with two antimicrobials.
Abstract: The discovery of Helicobacter pylori (H. pylori) opened the doors to new insight and therapy for peptic ulcer disease. Earlier eradication treatment modalities based on bismuth compounds, with or without additional antimicrobials, were not well accepted mainly because of the, at least hypothetical, risks for neurological and/or renal side effects. The first proton pump inhibitor, omeprazole, had been proven as a very effective short-term anti-ulcer therapy, but after withdrawal of the drug, the recurrence rate was high. theoretically, acid suppression was believed to increase the H. pylori infestation as the environment became more neutral. On the other hand, acid suppression could increase the effect of acid labile antimicrobials. This was not investigated before the studies presented in this thesis were performed.A small pilot study (Paper I) in 24 patients showed that 7 out of 8 patients treated for fourteen days with omeprazole 40 mg o.m. + amoxicillin 750 mg b.i.d. were cleared of H. pylori, while it remained in 7/8 patients on omeprazole as monotherapy and in 2/7 patients on amoxicillin as monotherapy. However, the eradication rates 4 weeks after treatment were 5/8, 0/8 and 1/7 in the three groups, respectively. These results were confirmed in a large study (Paper II) comprising 248 consecutive patients with active duodenal ulcer disease. All had an initial treatment period for two weeks with omeprazole 40 mg o.m., followed by continued omeprazole in combination with amoxicillin 750 mg b.i.d. or amoxicillin placebo for a further two weeks. In the dual therapy group, 54% of patients were H. pylori eradicated compared to 4% in the omeprazole mono therapy group. Furthermore, the duodenal ulcer relapse rate was significantly lower in the combination group compared to the monotherapy group (p<0,001). Paper III represents a study that was preformed to assess whether improved results could be obtained by adding two antimicrobials to omeprazole. In total 787 patients were randomized to six treatment arms, where omeprazole was combined with two of the three antimicrobials amoxicillin, metronidazole and c!arithromycin in various doses and combinations. The results showed that one week's treatment was sufficient for a very high eradication rate. A combination of omeprazole 20 mg b.i.d. + amoxicillin 1000 mg b.i.d. + clarithromycin 500 mg b.i.d. was superior to a combination with a lower clarithromycin dose of 250 mg b.i.d. or amoxicillin in combination with metronidazole, but not significantly better than the other two arms containing metronidazole+ clarithromycin in a dose of 250 mg b.i.d. 500 mg b.i.d. Paper IV was designed to establish whether or not acid suppression is necessary during antimicrobial treatment. In total 539 patients were randomized. Eradication rates with omeprazole added to antimicrobials were much higher than in treatment groups not receiving omeprazole. In metronidazole resistant strains, only 76% were eradicated in comparison to 95% in susceptible strains. Amoxicillin resistance did not occur and clarithromycin resistance was found in only 3% of patients. Thus, papers I-IV proved the efficacy ofthe new treatment modality, which, however, represented high costs in the short-term perspective.The cost-effectiveness of various treatment strategies in regular use at that time was evaluated in paper V. The economic model showed that in comparison to continuous therapy with gastric acid suppressive drugs, the extra initial cost for eradication therapy was paid within one year and, in comparison to intermittent therapy, within three years.Conclusion: These studied have shown convincingly that eradication of H. pylori with a combination of gastric acid suppression and two antimicrobials (amoxicillin and clarithromycin) is the most effective treatment in PUD, giving a high eradication rate and consequently lower peptic ulcer recurrence. Thus, this treatment strategy is also very cost-effective for society.
590 citations
TL;DR: The essay covers the socialization process, nature of the self, processes of growth and development, person-in-context, and a statement on the linkage between macro- and micro-environmental influences on identity.
540 citations
TL;DR: This work proposes a scheme applicable to all species that distinguishes different classes of genes, provides a single name for all genes of a given function and greatly facilitates comparative studies.
513 citations
TL;DR: A review examines many of the scientific and technical aspects involved in using immobilized microbial cells in environmental applications, with a particular focus on cells encapsulated in biopolymer gels.
Abstract: Immobilized microbial cells have been used extensively in various industrial and scientific endeavours. However, immobilized cells have not been used widely for environmental applications. This review examines many of the scientific and technical aspects involved in using immobilized microbial cells in environmental applications, with a particular focus on cells encapsulated in biopolymer gels. Some advantages and limitations of using immobilized cells in bioreactor studies are also discussed.
503 citations
TL;DR: The authors argued that most of the facts characterising small-scale businesses, including high failure rates, reliance on bank credit rather than equity finance, relatively low interest rate margins, and credit rationing, can be explained by a tendency for those who are excessively optimistic to dominate new entrants.
Abstract: This paper argues that most of the facts characterising small-scale businesses, including high failure rates, reliance on bank credit rather than equity finance, relatively low interest rate margins, and credit rationing, can be explained by a tendency for those who are excessively optimistic to dominate new entrants. Drawing on findings in psychology, we model entrants as relatively naive optimisers. Banks on the other hand are viewed as well informed and efficient processors of information. 'The over-weening conceit which the greater part of men have of their own abilities, is an ancient evil remarked by the philosophers and moralists of all ages. Their absurd presumption in their own good fortune, has been less taken notice of. It is, however, if possible still more universal. There is no man living who, when in tolerable health and spirits, has not some share of it. The chance of gain is by every man more or less overvalued, and the chance of loss is by most men under-valued, and scarce by any man, who is in tolerable health and spirits, valued more than it is worth.'
469 citations
TL;DR: Water vapour and CO2 fluxes were measured using the eddy correlation method above and below the overstorey of a 21m tall aspen stand in the boreal forest of central Saskatchewan as part of the Boreal Ecosystem-Atmosphere Study (BOREAS) as discussed by the authors.
Abstract: Water vapour and CO2 fluxes were measured using the eddy correlation method above and below the overstorey of a 21-m tall aspen stand in the boreal forest of central Saskatchewan as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). Measurements were made at the 39.5-m and 4-m heights using 3-dimensional sonic anemometers (Kaijo-Denki and Solent, respectively) and closed-path gas analysers (LI-COR 6262) with 6-m and 4.7-m long heated sampling tubing, respectively. Continuous measurements were made from early October to mid-November 1993 and from early February to late-September 1994. Soil CO2 flux (respiration) was measured using a LI-COR 6000-09 soil chamber and soil evaporation was measured using Iysimetry.
The leaf area index of the aspen and hazelnut understorey reached 1.8 and 3.3, respectively. The maximum daily evapotranspiration (E) rate was 5–6 mm d−1. Following leaf-out the hazelnut and soil accounted for 22% of the forest E. The estimated total E was 403 mm for 1994. About 88% of the precipitation in 1994 was lost as evapotranspiration.
During the growing season, the magnitude of half-hourly eddy fluxes of CO2 from the atmosphere into the forest reached 1.2 mg CO2 m−2 s−1 (33 μmol C m−2 s−1) during the daytime. Downward eddy fluxes at the 4-m height were observed when the hazelnut was growing rapidly in June and July. Under well-ventilated night-time conditions, the eddy fluxes of CO2 above the aspen and hazelnut, corrected for canopy storage, increased exponentially with soil temperature at the 2-cm depth. Estimates of daytime respiration rates using these relationships agreed well with soil chamber measurements. During the 1994 growing season, the cumulative net ecosystem exchange (NEE) was -3.5 t C ha−1 y−1 (a net gain by the system). For 1994, cumulative NEE, ecosystem respiration (R) and gross ecosystem photosynthesis (GEP = R - NEE) were estimated to be -1.3, 8.9 and 10.2 t C ha−1 y−1 respectively. Gross photosynthesis of the hazelnut was 32% of GEP.
435 citations
TL;DR: In this paper, X-ray diffraction and electron microscopic analyses indicated that the Fe-rich material collected was predominantly ferrihydrite and poorly crystallized lepidocrocite, while the Mn-rich mixture was a mixture of poorly crystallised Mn oxyhydroxides.
TL;DR: Based on the kernel integrated square difference and applying a central limit theorem for degenerate V-statistic proposed by Hall (1984), the authors proposed a consistent nonparametric test of closeness between two unknown density functions under quite mild conditions.
Abstract: Based on the kernel integrated square difference and applying a central limit theorem for degenerate V-statistic proposed by Hall (1984), this paper proposes a consistent nonparametric test of closeness between two unknown density functions under quite mild conditions. We only require the unknown density functions to be bounded and continuous. Monte Carlo simulations show that the proposed tests perform well for moderate sample sizes.
TL;DR: In this article, a review examines methods to sterilize soil or inhibit microbial activity in soil, often necessary for experiments involving microbial survival, enzyme measurements, soil respiration, biodegradation or as controls in direct soil DNA extraction-PCR analysis.
TL;DR: It is shown that centroradialis is expressed in the inflorescence apex a few days after floral induction, and interacts with the floral-meristem-identity gene floricaula to regulate flower position and morphology.
Abstract: Flowering plants exhibit two types of inflorescence architecture: determinate and indeterminate. The centroradialis mutation causes the normally indeterminate inflorescence of Antirrhinum to terminate in a flower. We show that centroradialis is expressed in the inflorescence apex a few days after floral induction, and interacts with the floral-meristem-identity gene floricaula to regulate flower position and morphology. The protein CEN is similar to animal proteins that associate with lipids and GTP-binding proteins. We propose a model for how different inflorescence structures may arise through the action and evolution of centroradialis.
TL;DR: A 3-year field trial indicated that yield and survival of transgenic plants were significantly improved, supporting the hypothesis that tolerance of oxidative stress is important in adaptation to field environments.
Abstract: Transgenic alfalfa (Medicago sativa) expressing Mn-superoxide dismutase cDNA tended to have reduced injury from water-deficit stress as determined by chlorophyll fluorescence, electrolyte leakage, and regrowth from crowns. A 3-year field trial indicated that yield and survival of transgenic plants were significantly improved, supporting the hypothesis that tolerance of oxidative stress is important in adaptation to field environments.
TL;DR: The influence of electromechanical stress or transmembrane potential on membrane discharge and rupture seems to be a function of various factors such as membrane properties, external medium, and the protocols of electroporators.
Abstract: The study of the electroporation on biomembranes has become one of the most exciting topics in the biophysical and biotechnological areas. Researchers all over the world have been focused on four major areas: measurements of transmembrane potential (TMP); dynamics of electroporation such as time sequence, properties of electropores such as size, structure, and population; membrane permeabilization and breakdown theory; and the effects of secondary factors such as ions type and cell growth stage on electroporation. This article reviews some of the recent discoveries and theories on this subject. Studies on TMP and pore dynamics remain a difficult task. Since the area of electroporation on a biomembrane is small (less than 0.1% of total surface area) and the time sequence of electropores is in the submicrosecond range measuring devices with subtle detection and time resolution are required. While more and more studies have shown the formation sequence of electropore(s) at specific locations on vario...
01 May 1996-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: The results suggest that green contrast can be utilized for target detection if target recognition has been established by means of the colour vision system.
Abstract: Honeybees Apis mellifera were trained to distinguish between the presence and the absence of a rewarded coloured spot, presented on a vertical, achromatic plane in a Y-maze. They were subsequently tested with different subtended visual angles of that spot, generated by different disk diameters and different distances from the decision point in the device. Bees were trained easily to detect bee-chromatic colours, but not an achromatic one. Chromatic contrast was not the only parameter allowing learning and, therefore, detection: α
min, the subtended visual angle at which the bees detect a given stimulus with a probability P
0 = 0.6, was 5° for stimuli presenting both chromatic contrast and contrast for the green photoreceptors [i.e. excitation difference in the green photoreceptors, between target and background (green contrast)], and 15° for stimuli presenting chromatic but no green contrast. Our results suggest that green contrast can be utilized for target detection if target recognition has been established by means of the colour vision system. The green-contrast signal would be used as a far-distance signal for flower detection. This signal would always be detected before chromatic contrast during an approach flight and would be learned in compound with chromatic contrast, in a facilitation-like process.
TL;DR: Bacteria are very small (∼ 1.5 μm3) but have the largest surface area to volume ratio of any life form as mentioned in this paper, which is mainly due to the overall anionic charge of bacterial surfaces imparted by the macromolecules which make up their fabric.
TL;DR: The large sequence divergence among its 34 North American members indicates that the genus Daphnia originated during the Mesozoic, even though many lineages exhibit extreme morphological stasis.
Abstract: Despite extensive studies on the ecology and evolution of the freshwater microcrustacean Daphnia, there is little understanding of the evolutionary history of the genus. Past attempts at reconstructing phylogenetic relationships among Daphnia species have been highly controversial, mainly because of the poor taxonomy of the genus. However, following a revised taxonomy of the daphniid fauna of North America, we conducted a comprehensive appraisal of systematic relationships within the genus through the analysis of sequence diversity in 503 b.p. of the 12S rRNA gene of the mtDNA. The large sequence divergence among its 34 North American members indicates that the genus Daphnia originated during the Mesozoic, even though many lineages exhibit extreme morphological stasis. Results from both cladistic and phenetic analyses indicate the presence of three subgenera comprised of 15 species complexes. Only four of these lineages have shown active speciation over the past 3 Ma, suggesting that cladogenesis in the genus has been constrained. Our study also reveals that interspecific hybridization occurs between taxa which show very large sequence divergence (up to 14%), suggesting that reproductive isolation within the genus evolves slowly.
TL;DR: n-MVs were capable of killing cultures of P. aeruginosa with permeability resistance against gentamicin, indicating that the fusion of n-MV to the outer membrane liberated autolysins into the periplasm, where they degraded the peptidoglycan and lysed the cells.
Abstract: Pseudomonas aeruginosa releases membrane vesicles (MVs) filled with periplasmic components during normal growth, and the quantity of these vesicles can be increased by brief exposure to gentamicin. Natural and gentamicin-induced membrane vesicles (n-MVs and g-MVs, respectively) are subtly different from one another, but both contain several important virulence factors, including hydrolytic enzyme factors (J. L. Kadurugamuwa and T. J. Beveridge, J. Bacteriol. 177:3998-4008, 1995). Peptidoglycan hydrolases (autolysins) were detected in both MV types, especially a periplasmic 26-kDa autolysin whose expression has been related to growth phase (Z. Li, A. J. Clarke, and T. J. Beveridge, J. Bacteriol. 178:2479-2488, 1996). g-MVs possessed slightly higher autolysin activity and, at the same time, small quantities of gentamicin. Both MV types hydrolyzed isolated gram-positive and gram-negative murein sacculi and were also capable of hydrolyzing several glycyl peptides. Because the MVs were bilayered, they readily fused with the outer membrane of gram-negative bacteria. They also adhered to the cell wall of gram-positive bacteria. g-MVs were more effective in lysing other bacteria because, in addition to the autolysins, they also contained small amounts of gentamicin. The bactericidal activity was 2.5 times the MIC of gentamicin, which demonstrates the synergistic effect of the antibiotic with the autolysins. n-MVs were capable of killing cultures of P. aeruginosa with permeability resistance against gentamicin, indicating that the fusion of n-MV to the outer membrane liberated autolysins into the periplasm, where they degraded the peptidoglycan and lysed the cells. g-MVs had even greater killing power since they liberated both gentamicin and autolysins into these resistant cells. These findings may help develop a conceptually new group of antibiotics designed to be effective against hard-to-kill bacteria.
TL;DR: It is too early to conclude positively that a truly universal mechanism for both senescence and postharvest stress-induced membrane damage exists, but the picture emerging from numerous studies devoted to this topic is of membrane lipids undergoing extensive chemical degradation.
TL;DR: Researchers are encouraged to consider a broader range of methods for assessing coping, including semistructured interviews, customized checklists tailored to their specific hypotheses and objectives, daily diaries, and traditional trait measures.
Abstract: Hundreds of studies have now used standardized checklists to assess respondents' self reports of coping with naturally occurring stress. This article presents a critical review of the conceptual and methodological issues involved in the use of these checklists. As they are currently employed, conventional checklists render an incomplete and distorted portrait of coping. Specifically, these checklists are grounded in too narrow a conception of coping; the application and interpretation of checklists in the typical study are not faithful to a transactional model of stress and coping; statistical controls cannot eliminate the effects of key person and situation variables on coping; and no consistent interpretation can be assigned to coping scale scores. Researchers are encouraged to consider a broader range of methods for assessing coping, including semistructured interviews, customized checklists tailored to their specific hypotheses and objectives, daily diaries, and traditional trait measures.
TL;DR: It is concluded that the broiler still possesses a good ability to control its feed intake based on desire to normalize energy intake, as energy intake is decreased, or there is increased protein intake, the bird deposits less carcass fat.
TL;DR: In this article, the Barker and Summerson method is modified to provide a simple and fast method of measuring lactic acid and other compounds such as muramic acid and glyceraldehyde that will release acetaldehyde on incubation in hot sulfuric acid.
Abstract: The Barker and Summerson method of assaying lactic acid colorimetrically is modified to provide a simple and fast method of measuring lactic acid and other compounds such as muramic acid and glyceraldehyde that will release acetaldehyde on incubation in hot sulfuric acid. The assay can be done with open tubes and no more complicated equipment than a spectrophotometer. A further modification allows a relatively specific determination of formaldehyde.
TL;DR: In this paper, an empirical analysis of farmers' decisions in light of variations in climate and other forces is based on a survey of 120 farm operators in southwestern Ontario, and some farmers were affected by variable climatic conditions over a six-year-period.
Abstract: Assumptions underlying impact assessments of climatic change for agriculture are explored conceptually and empirically. Variability in climatic conditions, the relevance of human decision-making, and the role of non-climatic forces are reviewed and captured in a model of agricultural adaptation to climate. An empirical analysis of farmers' decisions in light of variations in climate and other forces is based on a survey of 120 farm operators in southwestern Ontario. Many farmers were affected by variable climatic conditions over a six-year-period, and some undertook strategic adaptations in their farm operations. Frequency of dry years was the key climatic stimulus to farming adaptations. However, only 20 percent of farmers were sufficiently influenced by climatic conditions to respond with conscious changes in their farm operations.
TL;DR: This article summarizes the accepted mechanism of chlorophyll degradation in fruit and vegetables, and extends it to include the degradation of pheophorbides into colourless compounds.
Abstract: Green colour losses in processed and minimally processed fruit and vegetable products are associated with decreases in the quality of such products. Chlorophyll, the pigment responsible for the characteristic green colour of several fruit and vegetables, can degrade to undesirable grey-brown compounds such as pheophorbide and pheophytin. This degradation is mediated by acid and the enzyme chlorophyllase. Pheophorbide can be further metabolized to colourless compounds in metabolically active tissue. This article summarizes the accepted mechanism of chlorophyll degradation in fruit and vegetables, and extends it to include the degradation of pheophorbides into colourless compounds. Strategies for the control of chlorophyll degradation in food products are also discussed.
TL;DR: In this paper, the conductivity and phase structure of composite polyether-alkali metal salt solid electrolytes are analyzed and discussed and it is suggested that the competition between the Lewis base ether oxygens in the polyether chains and filler Lewis base centres in the complexation of alkali metal cations leads to the formation of different types of complexes and therefore to the modification of the polymer electrolyte ultrastructure.
TL;DR: The data demonstrated that caffeine ingestion can be an effective ergogenic aid for exercise that is as brief as 4-6 min, however, the mechanism is not associated with muscle glycogen sparing.
Abstract: Jackman, M., P. Wendling, D. Friars, and T. E. Graham.Metabolic, catecholamine, and endurance responses to caffeine during intense exercise. J. Appl. Physiol. 81(4): 1658–1663, 1996.—This study exa...
TL;DR: Growth regulation by stimulatory and inhibitory mitotic signals is presented as a candidate for an energy-independent determinant of the upper limit to functional maximum uptake capacity of the small intestine.
Abstract: In digesting and absorbing dietary nutrients, the gastrointestinal tract consumes approximately 20% of all incoming energy. A substantial proportion of this consumption is due to the rapid turnover of cellular protein, which permits abrupt changes in gut size to occur, matching capacity with delivery. If it is size of the alimentary tract that constrains nutrient uptake, greater than 20% allocation of ME intake above maintenance to the gut would improve the growth rate of a young animal but the efficiency of ME utilization for growth would deteriorate. Less than 15% allocation in birds seems injurious to both growth rate and efficiency of growth. Nutrient transport capacity of the intestine may be modulated independent of size; in the case of glucose, an up- or down-regulation of the number of brush-border glucose transporters matches absorptive capacity with delivery. The maximum uptake capacity of a small intestine for glucose at any moment in time is a function of its length, the flow rate of digesta, and the distributed-in-space kinetic parameters of transport (e.g., Vmax and Km). An example maximum uptake capacity for glucose in sheep is calculated at 2,112 g/d, assuming continuous digesta flow. Intermittency of flow reduces the uptake capacity to a functional level of 295 g/d, demonstrating a constraining influence of the periodicity of the migrating myoelectric complex. Growth regulation by stimulatory and inhibitory mitotic signals is presented as a candidate for an energy-independent determinant of the upper limit to functional maximum uptake capacity of the small intestine. Both size and functional capacity of the intestine must be considered in assessing the impact this tissue may have on the rest of the animal.
TL;DR: Some general information on properties of PCP is provided and the influence of nutrient amendment, temperature and pH on PCP degradation by various aerobic and anaerobic microorganisms is reviewed.
Abstract: Pentachlorophenol (PCP) was the most prevalent wood preservative for many years worldwide. Its widespread use had led to contamination of various environments. Traditional methods of PCP clean-up include storage in land-fill sites, incineration and abiotic degradation processes such as photodecomposition. Some aerobic and anaerobic microorganisms can degrade PCP under a variety of conditions. Axenic bacterial cultures, Flavobacterium sp., Rhodococcus sp., Arthrobacter sp., Pseudomonas sp., Sphingomonas sp., and Mycobacterium sp., and fungal cultures, Phanerochaete sp. and Trametes sp. exhibit varying rates and extent of PCP degradation. This paper provides some general information on properties of PCP and reviews the influence of nutrient amendment, temperature and pH on PCP degradation by various aerobic and anaerobic microorganisms. Where information is available, proposed degradation pathways, intermediates and enzymes are reviewed.