Showing papers by "Memorial University of Newfoundland published in 2001"

Albuminuria and risk of cardiovascular events, death, and heart failure in diabetic and nondiabetic individuals

Abstract: ContextMicroalbuminuria is a risk factor for cardiovascular (CV) events. The relationship between the degree of albuminuria and CV risk is unclear.ObjectivesTo estimate the risk of CV events in high-risk individuals with diabetes mellitus (DM) and without DM who have microalbuminuria and to determine whether levels of albuminuria below the microalbuminuria threshold increase CV risk.DesignThe Heart Outcomes Prevention Evaluation study, a cohort study conducted between 1994 and 1999 with a median 4.5 years of follow-up.SettingCommunity and academic practices in North and South America and Europe.ParticipantsIndividuals aged 55 years or more with a history of CV disease (n = 5545) or DM and at least 1 CV risk factor (n = 3498) and a baseline urine albumin/creatinine ratio (ACR) measurement.Main Outcome MeasuresCardiovascular events (myocardial infarction, stroke, or CV death); all-cause death; and hospitalization for congestive heart failure.ResultsMicroalbuminuria was detected in 1140 (32.6%) of those with DM and 823 (14.8%) of those without DM at baseline. Microalbuminuria increased the adjusted relative risk (RR) of major CV events (RR, 1.83; 95% confidence interval [CI], 1.64-2.05), all-cause death (RR, 2.09; 95% CI, 1.84-2.38), and hospitalization for congestive heart failure (RR, 3.23; 95% CI, 2.54-4.10). Similar RRs were seen for participants with or without DM, even after adjusting for other CV risk factors (eg, the adjusted RR of the primary aggregate end point was 1.97 [95% CI, 1.68-2.31] in those with DM and 1.61 [95% CI, 1.36-1.90] in those without DM).Compared with the lowest quartile of ACR (<0.22 mg/mmol), the RRs of the primary aggregate end point in the second quartile (ie, ACR range, 0.22-0.57 mg/mmol) was 1.11 (95% CI, 0.95-1.30); third quartile, 1.38 (95% CI, 1.19-1.60; ACR range, 0.58-1.62 mg/mmol); and fourth quartile, 1.97 (95% CI, 1.73-2.25; ACR range, >1.62 mg/mmol) (P for trend <.001, even after excluding those with microalbuminuria). For every 0.4-mg/mmol increase in ACR level, the adjusted hazard of major CV events increased by 5.9% (95% CI, 4.9%-7.0%).ConclusionsOur results indicate that any degree of albuminuria is a risk factor for CV events in individuals with or without DM; the risk increases with the ACR, starting well below the microalbuminuria cutoff. Screening for albuminuria identifies people at high risk for CV events.

Enriched rehabilitative training promotes improved forelimb motor function and enhanced dendritic growth after focal ischemic injury

Abstract: Chronic impairment of forelimb and digit movement is a common problem after stroke that is resistant to therapy. Previous studies have demonstrated that enrichment improves behavioral outcome after focal ischemia; however, postischemic enrichment alone is not capable of enhancing fine digit and forelimb function. Therefore, we combined environmental enrichment with daily skilled-reach training to assess the effect of intensive task-specific rehabilitation on long-term functional outcome. Rats were subjected to either endothelin-1-induced focal ischemia or sham surgery and subsequently designated to enriched-rehabilitation or standard-housing treatment groups starting 15 d after ischemia. Functional assessment of the affected forelimb at 4 and 9 weeks after treatment revealed that ischemic plus enrichment (IE) animals had improved approximately 30% on the staircase-reaching task and were indistinguishable from sham animals for both latency and foot faults in a beam-traversing task. In contrast, ischemic plus standard (IS) animals remained significantly impaired on both tasks. Interestingly, both ischemic groups (IE and IS) relied on the nonaffected forelimb during upright weight-bearing movements, a pattern that persisted for the duration of the experiment. Dendritic arborization of layer V pyramidal cells within the undamaged motor cortex was examined using a Golgi-Cox procedure. IE animals showed enhanced dendritic complexity and length compared with both IS and sham groups. These results suggest that enrichment combined with task-specific rehabilitative therapy is capable of augmenting intrinsic neuronal plasticity within noninjured, functionally connected brain regions, as well as promoting enhanced functional outcome.

The Function of Marine Critical Transition Zones and the Importance of Sediment Biodiversity

Abstract: Estuaries and coastal wetlands are critical transition zones (CTZs) that link land, freshwater habitats, and the sea. CTZs provide essential ecological functions, including decomposition, nutrient cycling, and nutrient production, as well as regulation of fluxes of nutrients, water, particles, and organisms to and from land, rivers, and the ocean. Sediment-associated biota are integral to these functions. Functional groups considered essential to CTZ processes include heterotrophic bacteria and fungi, as well as many benthic invertebrates. Key invertebrate functions include shredding, which breaks down and recycles organic matter; suspension feeding, which collects and transports sediments across the sediment–water interface; and bioturbating, which moves sediment into or out of the seabed. In addition, macrophytes regulate many aspects of nutrient, particle, and organism dynamics above- and belowground. Animals moving within or through CTZs are vectors that transport nutrients and organic matter across terrestrial, freshwater, and marine interfaces. Significant threats to biodiversity within CTZs are posed by anthropogenic influences; eutrophication, nonnutrient pollutants, species invasions, overfishing, habitat alteration, and climate change affect species richness or composition in many coastal environments. Because biotic diversity in marine CTZ sediments is inherently low whereas their functional significance is great, shifts in diversity are likely to be particularly important. Species introductions (from invasion) or loss (from overfishing or habitat alteration) provide evidence that single-species changes can have overt, sweeping effects on CTZ structure and function. Certain species may be critically important to the maintenance of ecosystem functions in CTZs even though at present there is limited empirical evidence that the number of species in CTZ sediments is critical. We hypothesized that diversity is indeed important to ecosystem function in marine CTZs because high diversity maintains positive interactions among species (facilitation and mutualism), promoting stability and resistance to invasion or other forms of disturbance. The complexity of interactions among species and feedbacks with ecosystem functions suggests that comparative (mensurative) and manipulative approaches will be required to elucidate the role of diversity in sustaining CTZ functions.

Traveling Wave Fronts of Reaction-Diffusion Systems with Delay

Abstract: This paper deals with the existence of traveling wave front solutions of reaction-diffusion systems with delay. A monotone iteration scheme is established for the corresponding wave system. If the reaction term satisfies the so-called quasimonotonicity condition, it is shown that the iteration converges to a solution of the wave system, provided that the initial function for the iteration is chosen to be an upper solution and is from the profile set. For systems with certain nonquasimonotone reaction terms, a convergence result is also obtained by further restricting the initial functions of the iteration and using a non-standard ordering of the profile set. Applications are made to the delayed Fishery–KPP equation with a nonmonotone delayed reaction term and to the delayed system of the Belousov–Zhabotinskii reaction model.

Antifreeze proteins of teleost fishes.

Abstract: ▪ Abstract Marine teleosts at high latitudes can encounter ice-laden seawater that is approximately 1°C colder than the colligative freezing point of their body fluids. They avoid freezing by produ...

Isolation and characterization of antioxidative peptides from gelatin hydrolysate of Alaska pollack skin.

Abstract: Gelatin extracted from Alaska pollack skin was hydrolyzed with serial digestions in the order of Alcalase, Pronase E, and collagenase using a three-step recycling membrane reactor. The fraction from the second step, which was hydrolyzed with Pronase E, was composed of peptides ranging from 1.5 to 4.5 kDa and showed high antioxidative activity. Two different peptides showing strong antioxidative activity were isolated from the hydrolysate using consecutive chromatographic methods including gel filtration on a Sephadex G-25 column, ion-exchange chromatography on a SP-Sephadex C-25 column, and high-performance liquid chromatography on an ODS column. The isolated peptides, P1 and P2, were composed of 13 and 16 amino acid residues, respectively; and both peptides contained a Gly residue at the C-terminus and the repeating motif Gly-Pro-Hyp. The antioxidative activities of the purified peptides were measured using the thiobarbituric acid method, and the cell viability was measured with MTT assay. The results showed that P2 had potent antioxidative activity on peroxidation of linoleic acid. Moreover, the cell viability of cultured liver cells was significantly enhanced by addition of the peptide. These results indicate that the purified peptide, P2, from gelatin hydrolysate of Alaska pollack skin is a natural antioxidant which has potent antioxidative activity.

Factors affecting force loss with prolonged stretching

Abstract: The purpose of this study was to investigate the factors underlying the force loss occurring after prolonged, static, passive stretching. Subjects were tested before and 5-10 min following 20 min of static, passive stretching of the quadriceps (N=12) or a similar period of no stretch (control, N=6). Measurements included isometric maximal voluntary contraction (MVC) force, surface integrated electromyographic (iEMG) activity of the quadriceps and hamstrings, evoked contractile properties (twitch and tetanic force), and quadriceps inactivation as measured by the interpolated twitch technique (ITT). Following stretching, there was a significant 12% decrement in MVC with no significant changes in the control group. Muscle inactivation as measured by the ITT and iEMG increased by 2.8% and 20.2%, respectively. While twitch forces significantly decreased 11.7%, there was no change in tetanic force post-stretch. Although possible increases in muscle compliance affected twitch force, a lack of tetanic force change would suggest that post-stretch force decrements are more affected by muscle inactivation than changes in muscle elasticity.

Comparison of volatiles, phenolics, sugars, antioxidant vitamins, and sensory quality of different colored carrot varieties.

Abstract: Four different colored carrots, orange, purple with orange core, yellow, and white, were examined for their content of phenolics, antioxidant vitamins, and sugars as well as their volatiles and sensory responses. A total of 35 volatiles were identified in all carrots, 27 positively. White carrot contained the highest content of volatiles, followed by orange, purple, and yellow. In total, 11, 16, 10, and 9 phenolic compounds were determined for the first time in orange, purple, yellow, and white carrots, respectively. Of these, chlorogenic acid was the most predominant phenolic compound in all carrot varieties. Differences (p < 0.05) in relative sweetness, the contents of vitamin C and alpha- and beta-carotenes, and certain flavor characteristics were observed among the colored carrot varieties examined. Purple carrots contained 2.2 and 2.3 times more alpha- and beta-carotenes (trace in yellow; not detected in white) than orange carrots, respectively. Purple carrot may be used in place of other carrot varieties to take advantage of its nutraceutical components.

Biogenic carbon cycling in the upper ocean: effects of microbial respiration.

Abstract: Food-web processes are important controls of oceanic biogenic carbon flux and ocean-atmosphere carbon dioxide exchange Two key controlling parameters are the growth efficiencies of the principal trophic components and the rate of carbon remineralization We report that bacterial growth efficiency is an inverse function of temperature This relationship permits bacterial respiration in the euphotic zone to be computed from temperature and bacterial production Using the temperature-growth efficiency relationship, we show that bacterial respiration generally accounts for most community respiration This implies that a larger fraction of assimilated carbon is respired at low than at high latitudes, so a greater proportion of production can be exported in polar than in tropical regions Because bacterial production is also a function of temperature, it should be possible to compute euphotic zone heterotrophic respiration at large scales using remotely sensed information

Multisite, multifrequency tensor decomposition of magnetotelluric data

Abstract: Accurate interpretation of magnetotelluric data requires an understanding of the directionality and dimensionality inherent in the data, and valid implementation of an appropriate method for removing the effects of shallow, small-scale galvanic scatterers on the data to yield responses representative of regionalscale structures. The galvanic distortion analysis approach advocated by Groom and Bailey has become the most adopted method, rightly so given that the approach decomposes the magnetotelluric impedance tensor into determinable and indeterminable parts, and tests statistically the validity of the galvanic distortion assumption. As proposed by Groom and Bailey, one must determine the appropriate frequency-independent telluric distortion parameters and geoelectric strike by fitting the seven-parameter model on a frequencyby-frequency and site-by-site basis independently. Although this approach has the attraction that one gains a more intimate understanding of the data set, it is rather time-consuming and requires repetitive application. We propose an extension to Groom-Bailey decomposition in which a global minimum is sought to determine the most appropriate strike direction and telluric distortion parameters for a range of frequencies and a set of sites. Also, we show how an analytically-derived approximate Hessian of the objective function can reduce the required computing time. We illustrate application of the analysis to two synthetic data sets and to real data. Finally, we show how the analysis can be extended to cover the case of frequency-dependent distortion caused by the magnetic effects of the galvanic charges.

Phytoplankton population dynamics at the Bermuda Atlantic Time-series station in the Sargasso Sea

Abstract: Phytoplankton populations were analyzed using flow cytometry in monthly samples at the Bermuda Atlantic Time-series Study (BATS) station in the Sargasso Sea from 1989–1994 for picoplankton ( Synechococcus and Prochlorococcus ) and from 1992–1994 for eukaryotic phytoplankton in order to better understand the mechanisms that dictate seasonal and inter-annual patterns in the phytoplankton community. The eukaryotic phytoplankton were dominated by populations of small nanoplankton (mostly 2–4 μm diameter), though populations of coccolithophores and sometimes pennate diatoms also could be distinguished. Flow cytometric measurements of population abundances, individual cell light scattering (which can be related to cell size), and chlorophyll fluorescence were made. Synechococcus and the eukaryotic phytoplankton reached their greatest concentrations during the spring bloom each year when the water column was deeply mixed and nutrients were detectable in surface waters. The maximum cell concentration for Prochlorococcus was in the summer and fall of each year, with a deeper sub-surface maximum than Synechococcus . Picoplankton chlorophyll fluorescence and estimated cell size were greater at depth than near the surface, and were lowest in midsummer for both Synechococcus and Prochlorococcus . In the summer and fall, Prochlorococcus cells were often smallest at mid-depth, even when fluorescence per cell and cell concentration were lower at the surface. For the eukaryotes (including coccolithophores), cell concentrations were high during the spring in both 1992 and 1993, and in fall 1992. At these times, mean cell size and fluorescence were low. Improved size and carbon estimates were made and it was found that the estimated contribution of phytoplankton carbon to total particulate organic carbon, integrated over the upper 200 m, averaged 33% (range 21–43%) with no pronounced seasonal pattern.

Purification and characterization of antioxidative peptides from protein hydrolysate of lecithin-free egg yolk

Abstract: The protein extracted from lecithin-free egg yolk, normally discarded by lecithin processing plants, was hydrolyzed with the aid of Alcalase, a commercial enzyme. The hydrolysate was separated through a series of ultrafiltration membranes with molecular weight cutoffs of 10, 5, and 1 kDa; and three types of permeates including 10 K (permeate from 10 kDa), 5 K (permeate from 5 kDa), and 1 K (permeate from 1 kDa) were obtained. The antioxidative efficacy of hydrolysates so obtained was investigated and compared with α-tocopherol. Furthermore, two different peptides showing strong antioxidative activity were isolated from the hydrolysates by using consecutive chromatographic methods including ion exchange chromatography on a SP-Sephadex C-25 column, gel filtration on a Sephadex G-25 column, and high-performance liquid chromatography on an octadecylsilane column. The purity of the peptides was identified using capillary electrophoresis. The isolated peptides were composed of 10 and 15 amino acid residues, and both contained a leucine residue at their N-terminal positions.

Emotion and Ethical Decision-Making in Organizations

Abstract: While the influence of emotion on individuals' ethical decisions has been identified by numerous researchers, little is known about how emotions influence individuals' ethical decision process. Thus, it is not clear whether different emotions promote and/or discourage ethical decision-making in the workplace. To address this gap, this paper develops a model that illustrates how emotion affects the components of individuals' ethical decision-making process. The model is developed by integrating research findings that consider the two dimensions of emotion, arousal and feeling state, into an applied cognitive-developmental perspective on the process of ethical decision-making. The model demonstrates that certain emotional states influence the individual's propensity to identify ethical dilemmas, facilitate the formation of the individual's prescriptive judgments at sophisticated levels of moral development, lead to ethical decision choices that are consistent with the individual's prescriptive judgements, and promote the individual's compliance with his or her ethical decision choices. In particular, the model suggests that individuals experiencing arousal and positive affect resolve ethical dilemmas in a manner consistent with more sophisticated cognitive moral structures. Implications for theory and practice are discussed.

A reaction–diffusion model for a single species with age structure. I Travelling wavefronts on unbounded domains

Abstract: In this paper, we derive the equation for a single species population with two age classes and a fixed maturation period living in a spatially unbounded environment. We show that if the mature deat...

A model of the impact of mission statements on firm performance

Abstract: A relationship between mission and organizational performance was modeled by drawing on previous research. The model was tested with data from 83 large Canadian and US organizations. We found that mission statements can affect financial performance, however, not as one might have anticipated initially. Several mediating elements were observed to exist. For instance, “commitment to the mission” and the “degree to which an organization aligns its internal structure, policies and procedures with its mission” were both found to be positively associated with “employee behavior”. It was this latter variable which was observed, in turn, to have the most direct relationship with financial performance.

Calcium and bone metabolism in pregnancy and lactation

Abstract: Pregnancy and lactation both place significant demands on the mother to provide sufficient calcium (among other minerals and nutrients) to the fetus and neonate. Despite facing similar demands for calcium during pregnancy and lactation, the maternal adaptations differ significantly between these two reproductive periods. Women lose 300 to 400 mg of calcium daily through breast milk, and this calcium demand is met by a 5–10% loss of skeletal mineral content during 6 months of exclusive lactation. Most importantly, the lost mineral is fully restored within a few months of weaning, such that women who have breastfed do not have a long-term deficit in skeletal mineral content. This article will review our present understanding of the adaptations in mineral metabolism that occur during pregnancy and lactation, and will focus on recent evidence that the breast itself plays a central role in regulating the adaptations during lactation.

Left Ventricular Hypertrophy in the Renal Patient

Abstract: Physiologically, left ventricular hypertrophy is primarily an adaptive remodeling process, compensating for an increase in workload placed on the heart with the aim of minimizing ventricular wall stress. Two contrasting models of adaptation may develop depending on the patterns of stress imposed.

Enzymes from fish and aquatic invertebrates and their application in the food industry

Abstract: Enzymatic methods have become an important and indispensable part of the processes used by the modern food and feed industry to produce a large and diversified range of products for human and animal consumption. Aquatic environment contains the largest pool of diversified genetic material and, hence represents an enormous potential for different sources of enzymes. In recent years, recovery and characterization of enzymes from fish and aquatic invertebrates has been achieved and some interesting and novel applications related to marine enzymes in food processing have emerged. This review summarizes information related to digestive and muscular enzymes in fish and aquatic invertebrates. In addition, important developments in food applications of marine enzymes are reported.

Angiotensin I converting enzyme inhibitory peptides purified from bovine skin gelatin hydrolysate.

Abstract: Bovine skin gelatin was hydrolyzed with sequenial protease treatments in the order of Alcalase, Pronase E, and collagenase using a three-step ultrafiltration membrane reactor. The molecular weight distributions of the first, second, and third hydrolysates were 4.8−6.6, 3.4−6.6, and 0.9−1.9 kDa, respectively. The angiotensin I converting enzyme (ACE) inhibitory activity of the third hydrolysate (IC50 = 0.689 mg/mL) was higher than that of the first and second hydrolysates. Two different peptides showing strong ACE inhibitory activity were isolated from the hydrolysate using consecutive chromatographic methods including gel filtration chromatography, ion-exchange chromatography, and reversed-phase high-performance liquid chromatography. The isolated peptides were composed of Gly-Pro-Leu and Gly-Pro-Val and showed IC50 values of 2.55 and 4.67 μM, respectively. Keywords: ACE inhibitory peptide; bovine skin; three-step ultrafiltration membrane reactor; gelatin hydrolysate

A systematic study of fuzzy PID controllers-function-based evaluation approach

Abstract: A function-based evaluation approach is proposed for a systematic study of fuzzy proportional-integral-derivative (PID)-like controllers. This approach is applied for deriving process-independent design guidelines from addressing two issues: simplicity and nonlinearity. To examine the simplicity of fuzzy PID controllers, we conclude that direct-action controllers exhibit simpler design properties than gain-scheduling controllers. Then, we evaluate the inference structures of direct-action controllers in five criteria: control-action composition, input coupling, gain dependency, gain-role change, and rule/parameter growth. Three types of fuzzy PID controllers, using one-, two- and three-input inference structures, are analyzed. The results, according to the criteria, demonstrate some shortcomings in Mamdani's two-input controllers. For keeping the simplicity feature like a linear PID controller, a one-input fuzzy PID controller with "one-to-three" mapping inference engine is recommended. We discuss three evaluation approaches in a nonlinear approximation study: function-estimation-based, generalization-capability-based and nonlinearity-variation-based approximations. The study focuses on the last approach. A nonlinearity evaluation is then performed for several one-input fuzzy PID controllers based on two measures: nonlinearity variation index and linearity approximation index. Using these quantitative indices, one can make a reasonable selection of fuzzy reasoning mechanisms and membership functions without requiring any process information. From the study we observed that the Zadeh-Mamdani's "max-min-gravity" scheme produces the highest score in terms of nonlinearity variations, which is superior to other schemes, such as Mizumoto's "product-sum-gravity" and "Takagi-Sugeno-Kang" schemes.

Classroom interactions: Gender of teacher, gender of student, and classroom subject

Abstract: An observational study investigated the effects of gender of teacher, gender of student, and classroom subject (mathematics vs. English literature/language) on teacher–student interactions. A total of 597 high school students (294 males and 303 females) and 36 teachers (28 males and 8 females) were observed in either 18 mathematics classes or 18 literature/language classes. Students and teachers were predominately Caucasian, with the majority of students from a lower- or middle-class background. Observations were coded using the interactions for sex equity in classroom teaching (INTERSECT) observational instrument. It was found that female mathematics teachers, male literature/language teachers, and female literature/language teachers tended to interact somewhat more with male students than with female students. This tendency was not the result of male students having initiated more direct verbal interactions with teachers.