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PubMed1997

Effect of muscle glycogen availability on maximal exercise performance.

This investigation determined the influence of pre-exercise muscle glycogen availability on performance during high intensity exercise. Nine trained male cyclists were studied during 75 s of all-out exercise on an air-braked cycle ergometer following muscle glycogen-lowering exercise and consumption of diets (energy content approximately 14 MJ) that were either high (HCHO(80% CHO) or low (LCHO-25% CHO) in carbohydrate content. The exercise-diet regimen was successful in producing differences in pre-exercise muscle glycogen contents [HCHO: 578(SEM 55) mmol x kg(-1) dry mass; LCHO: 364 (SEM 58) P < 0.05 mmol x kg(-1) dry mass]. Despite this difference in muscle glycogen availability, there were no between trial differences for peak power [HCHO 1185 (SEM 50)W, LCHO 1179 (SEM 48)W], mean power [HCHO 547 (SEM 5)W, LCHO 554 (SEM 8)W] and maximal accumulated oxygen deficit [HCHO 54.4 (SEM 2.3) ml x kg(-1), LCHO 54.6 (SEM 2.0) ml x kg(-1)]. Postexercise muscle lactate contents (HCHO 95.9 (SEM 4.6) mmol x kg(-1) dry mass, LCHO 82.7 (SEM 12.3) mmol x kg(-1) dry mass, n = 8] were no different between the two trials, nor were venous blood lactate concentrations immediately after and during recovery from exercise. These results would indicate that increased muscle glycogen availability has no direct effect on performance during all-out high intensity exercise.

Adult↗

PubMed2000

Functional integrity of endothelium determines Ca2+ channel availability in smooth muscle: involvement of nitric oxide.

Endothelium regulates smooth muscle contractility in part via nitric oxide (NO). We tested the hypothesis that endothelial dysfunction, either produced by injury or simulated pharmacologically by reducing the bioavailability of NO, results in elevated Ca2+ channel availability (ngmax=maximum conductance/cell capacitance) in smooth muscle cells isolated from the vessel. Using basilar arteries of normotensive Wistar rats, we measured ngmax in smooth muscle cells from control vessels, from vessels in which endothelium was injured using Na fluoroscene plus light, and from vessels in which the bioavailability of NO was reduced by pretreatment with the NO scavenger 1H-imidazol-1 -yloxy,2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-3-oxide , potassium salt (C-PTIO), or the endothelial nitric oxide synthase (eNOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). Values of ngmax in these four groups of cells were 0.28+/-0.02 nS/pF (n=22), 0.51+/-0.05 nS/pF (n=15), 0.430+/-.03 nS/pF (n=12), and 0.47+/-0.04 nS/pF (n=14) (P<0.05, ANOVA), respectively. To determine whether larger currents associated with endothelial dysfunction exhibit altered sensitivity to exogenous NO, we quantified the response to various concentrations of NO donor, Na nitroprusside (SNP), in 37 cells from control vessels and 33 cells from vessels pretreated with L-NAME. SNP exhibited identical potency (half-maximum values, 18.7 and 21.1 nM) but greater apparent efficacy (maximum fractional block, 0.82 versus 0.63) in down-regulating Ca2+ channel currents in cells isolated from vessels with dysfunctional endothelium. Our results are consistent with a direct influence of endogenous NO on Ca2+ channel availability in smooth muscle cells, and indicate that Ca2+ channel availability in isolated smooth muscle cells may be a sensitive measure of the functional integrity of the endothelium in the parent vessel.

Animals↗

PubMed2002

Transmission disequilibrium test with discordant sib pairs when parents are available.

The transmission disequilibrium test (TDT) has been employed to map disease susceptibility loci (DSL), while being immune to the problem of population admixture. The customary TDT test (TDT(D)) was developed for affected child(ren) and their parents and was most often applied to case-parent trios. Recently, the TDT has been extended to the situations when (1) parents are not available but affected and nonaffected sibs from each family are available, (2) unrelated control-parent trios are available for combined analyses with case-parent trios (TDT(DC)), and (3) large pedigrees. For many diseases, affected children in the case-parent trios enlisted into the TDT(D) have unaffected sibs who can be recruited. We present an extension of the TDT by effectively incorporating one unaffected sib of each of the affected children in the case-parent trios into a single analysis (TDT(DS), where DS denotes discordant sib pairs). We have developed a general analytical method for computing the statistical power of the TDT(DS) under any genetic model, the accuracy of which is validated by computer simulations. We compare the power of the TDT(D), TDT(DC), and TDT(DS) under a range of parameter space and genetic models. We find that the TDT(DS) is generally more powerful than the TDT(DC) and TDT(D), particularly when the disease is prevalent (>30%) in the population. The relative power of the TDT(D) and the TDT(DS) largely depends upon the allele frequencies and genetic effects at the DSL, whereas the recombination rate, the degree of linkage disequilibrium, and the marker allele frequencies have little effect. Importantly, the TDT(DS) not only may be more powerful, it also has the advantage of being able to test for segregation distortion that may yield false linkage/association in the TDT(D).

Alleles↗

PubMed2003

Hot rocks or no hot rocks: overnight retreat availability and selection by a diurnal lizard.

I used radio telemetry to determine the effects of substrate size and composition on overnight retreat site selection by western fence lizards (Sceloporus occidentalis). In watersheds of northern California (USA), these lizards occupy two habitat types differing in substrate characteristics: rocky cobble bars found in the dry, active channels of rivers and grassy upland meadows. Rocky substrates, found almost exclusively on cobble bars, provided warmer potential retreat sites than all available retreat sites on meadows during the first 5 h of inactivity. Only cobble and sand substrates provided retreats with temperatures within the preferred daily active range (32-36 degrees C) during the inactive period for these lizards (1900-0900 hours). Females on a cobble bar used rocks as retreats on >90% of nights during the breeding season whereas females on a meadow used wood (>70% of nights) and burrows (>25% of nights). In contrast to females, cobble bar males used rocks significantly less frequently (<70%) and slept in the open air significantly more frequently (25% vs. <1%). Cobble bar females further, showed a significant preference for cobbles 15 cm thick, whereas the rocks used by males did not differ significantly in thickness from those measured in randomly placed transects. Rocks 15 cm thick were the warmest retreats commonly available on this habitat type. Thus, thermal microenvironments available to and chosen by gravid female lizards differ considerably between river and non-river habitats.

Adaptation, Physiological↗

PubMed2004

Competitive impacts and responses of an invasive weed: dependencies on nitrogen and phosphorus availability.

Changes in competitive interactions under conditions of enhanced resource availability could explain the invasion success of some problematic plant species. For one invader of North American grasslands, Centaurea diffusa (diffuse knapweed), we test three hypotheses: (1) under ambient (high resource) conditions, C. diffusa is better able to tolerate competition from the resident community (competitive response), (2) under ambient conditions, C. diffusa strong impacts the competitive environment (competitive effect), and (3) reductions in nitrogen and/or phosphorus availability diminish these advantages. In support of our first hypothesis, C. diffusa was the most tolerant to neighbor competition of the four focal species under current resource conditions. In opposition to our second hypothesis, however, neighborhoods that contained C. diffusa and those where C. diffusa had been selectively removed did not differ in their impact on the performance of target transplant individuals or on resource conditions. Reduction in resource availability influenced competitive tolerance but not competitive impact, in partial support of our last hypothesis. Reduction in soil nitrogen (via sucrose carbon addition) enhanced the degree of neighbor competition experienced by all species but did not change their relative rankings; C. diffusa remained the best competitor under low nitrogen conditions. Reduction of soil phosphorus (via gypsum addition) weakened the ability of C. diffusa to tolerate neighbor competition proportionately more than the other focal species. Consequently, under low phosphorus conditions, C. diffusa lost its competitive advantage and tolerated neighbor competition similarly to the other focal species. We conclude that C. diffusa invasion may be double-edged: C. diffusa is less limited by nitrogen than the other focal species and is better able to utilize phosphorus to its competitive advantage.

Centaurea↗

PubMed2004

Bottom-up effects of nutrient availability on flower production, pollinator visitation, and seed output in a high-Andean shrub.

Soil nutrient availability directly enhances vegetative growth, flowering, and fruiting in alpine ecosystems. However, the impacts of nutrient addition on pollinator visitation, which could affect seed output indirectly, are unknown. In a nutrient addition experiment, we tested the hypothesis that seed output in the insect-pollinated, self-incompatible shrub, Chuquiraga oppositifolia (Asteraceae) of the Andes of central Chile, is enhanced by soil nitrogen (N) availability. We aimed to monitor total shrub floral display, size of flower heads (capitula), pollinator visitation patterns, and seed output during three growing seasons on control and N addition shrubs. N addition did not augment floral display, size of capitula, pollinator visitation, or seed output during the first growing season. Seed mass and viability were 25-40% lower in fertilised shrubs. During the second growing season only 33% of the N addition shrubs flowered compared to 71% of controls, and a significant (50%) enhancement in vegetative growth occurred in fertilised shrubs. During the third growing season, floral display in N addition shrubs was more than double that of controls, received more than twice the number of insect pollinator visits, and seed output was three- to four-fold higher compared to controls. A significant (50%) enhancement in vegetative growth again occurred in N addition shrubs. Results of this study strongly suggest that soil N availability produces strong positive bottom-up effects on the reproductive output of the alpine shrub C. oppositifolia. Despite taking considerably longer to be manifest in comparison to the previously reported top-down indirect negative effects of lizard predators in the same study system, our results suggest that both bottom-up and top-down forces are important in controlling the reproductive output of an alpine shrub.

Animals↗

PubMed2005

Effects of carotenoid availability during laying on reproduction in the blue tit.

Carotenoids are antioxidant pigments involved in several physiological processes and signalling in animals that cannot synthesise them and therefore must acquire them from food. We experimentally investigated the effects of carotenoid availability in the diet during egg laying on antioxidant deposition in egg yolk and the related effects on nestling condition, female body condition and parental investment in the blue tit (Parus caeruleus). Carotenoid supplementation of egg-laying females resulted in a significant increase in carotenoid concentration in egg yolk, but not in vitamin E or A concentration. There was no relationship between yellow plumage colour of adult females and carotenoid deposition in eggs, and no differential effect of feeding treatment depending on female colour. Nestlings from eggs laid by carotenoid supplemented females had longer tarsi, had faster development of the immune system as reflected by leukocyte concentration in blood, and grew brighter yellow feathers than nestlings from control females. However, nestlings from the two groups did not differ significantly in body mass, plasma antioxidants or plumage colour hue. At the time of chick rearing, carotenoid-fed females had increased plasma vitamin E levels compared to controls. However, females from the two treatment groups did not differ significantly in body condition or feeding rate. These results suggest that carotenoid availability is limiting during egg laying, and that females may have to balance the benefits of investing in egg quality against the potential costs of impairing their own future antioxidant protection. In addition, there may be considerable variation in carotenoid availability not only across seasons, but also among different stages of the breeding season.

Animals↗

PubMed2005

Balancing food availability and hydrodynamic constraint: phenotypic plasticity and growth in Simulium noelleri blackfly larvae.

Organisms through phenotypic plasticity can cope with multiple changed environmental conditions. Theory predicts that animals in streams and rivers should be able to balance demands of the needs to obtain food efficiently and to adjust response to hydrodynamic variability. This study examined effects of variations in food availability and current velocity on the feeding structure and growth rate of Simulium noelleri blackfly larvae. The larvae developed larger labral fans and more rays under slow current and low food regimes than in fast current and high food conditions. In both fast and slow current regimes, growth rates were higher and development periods to the final-instar stage were shorter in high food treatments. The estimated flux rates of food particles through labral fans under high food treatments for both fast and slow current regimes were higher than those under low food treatments. Although both food and current velocity appeared to have selected for flexibility of feeding structure and growth rate, food availability was a more important factor for phenotypic and developmental plasticity than current velocity. The results indicate a strong link between environmental changes in food availability and current velocity, phenotypic plasticity, and growth rate of S. noelleri. This study suggests that plasticity of ecomorphs with macroevolutionary significance may play a role in the early evolutionary stages of blackfly larvae.

Adaptation, Physiological↗

PubMed2006

Correlated variation of floral and leaf traits along a moisture availability gradient.

Variation in flower size is an important aspect of a plant's life history, yet few studies have shown how flower size varies with environmental conditions and to what extent foliar responses to the environment are correlated with flower size. The objectives of this study were to (1) develop a theoretical framework for linking flower size and leaf size to their costs and benefits, as assessed using foliar stable carbon isotope ratio (delta(13)C) under varying degrees of water limitation, and then (2) examine how variation in flower size within and among species growing along a naturally occurring moisture availability gradient correlates with variation in delta(13)C and leaf size. Five plant species were examined at three sites in Oregon. Intra- and inter-specific patterns of flower size in relation to moisture availability were the same: the ratios of the area of flower display to total leaf area and of individual flower area to leaf area were greater at sites with more soil moisture compared to those sites with less soil moisture. The increase in flower area per unit increase in leaf area was greater at sites with more soil moisture than at sites where water deficit can occur. Values of delta(13)C, an index of water-use efficiency, were greater for plants with larger floral size. The patterns we observed generalize across species, irrespective of overall plant morphology or pollination system. These correlations between flower size, moisture availability, and delta(13)C suggest that water loss from flowers can influence leaf responses to the environment, which in turn may indirectly mediate an effect on flower size.

Carbon Isotopes↗

PubMed2002

Effects of light and soil water availability on leaf photosynthesis and growth of Arisaema heterophyllum, a riparian forest understorey plant.

The effects of soil-water availability on leaf light acclimation and whole-plant carbon gain were examined in Arisaema heterophyllum Blume, a riparian deciduous forest understorey plant. Photosynthesis, above-ground morphology and ramet biomass accumulation (relative growth rate: RGR of a corm for a full leaf life-span) were measured on plants raised under three light treatments combined with two soil water conditions. The two higher light treatments during growth (high: max. 550 micro mol photons m(-2) s(-1); medium: 150 micro mol photons m(-2) s(-1)) resulted in a twofold increase in RGRs, 30% higher photosynthetic capacities and 20% less photosynthetic low-light use efficiency than those under a low light condition (50 micro mol photons m(-2) s(-1)). Leaf area was the smallest and leaf mass area ratio was the largest under the high light treatment. Water stress decreased both photosynthetic rate and leaf area and, hence, RGR in all the light regimes. However, water stress did not alter the general patterns of physiological and morphological responses to different light regimes. We estimated that higher photosynthetic low-light use efficiency and larger leaf area in the low light leaf would lead to a threefold carbon gain as compared with the high light leaf under simulated low light conditions. Both experimental and simulation results suggest that the physiological and morphological acclimations tend to be beneficial to carbon gain when light availability is low, whereas they favor increased water use efficiency when light availability is sufficiently high.

Journal Article↗

PubMed2006

Three-dimensional numerical modeling and computational fluid dynamics simulations to analyze and improve oxygen availability in the AMC bioartificial liver.

A numerical model to investigate fluid flow and oxygen (O(2)) transport and consumption in the AMC-Bioartificial Liver (AMC-BAL) was developed and applied to two representative micro models of the AMC-BAL with two different gas capillary patterns, each combined with two proposed hepatocyte distributions. Parameter studies were performed on each configuration to gain insight in fluid flow, shear stress distribution and oxygen availability in the AMC-BAL. We assessed the function of the internal oxygenator, the effect of changes in hepatocyte oxygen consumption parameters in time and the effect of the change from an experimental to a clinical setting. In addition, different methodologies were studied to improve cellular oxygen availability, i.e. external oxygenation of culture medium, culture medium flow rate, culture gas oxygen content (pO(2)) and the number of oxygenation capillaries. Standard operating conditions did not adequately provide all hepatocytes in the AMC-BAL with sufficient oxygen to maintain O(2) consumption at minimally 90% of maximal uptake rate. Cellular oxygen availability was optimized by increasing the number of gas capillaries and pO(2) of the oxygenation gas by a factor two. Pressure drop over the AMC-BAL and maximal shear stresses were low and not considered to be harmful. This information can be used to increase cellular efficiency and may ultimately lead to a more productive AMC-BAL.

Cell Culture Techniques↗

PubMed2005

Evaluation of heavy metal availability prior to an in situ soil phytoremediation program.

Metal mobility and the fractionation of elements and thus the biological uptake of Zn, Pb and Cd by plants were investigated using a simplified analytical procedure for soluble and bioavailable metals using a four-step sequential extraction procedure. Results showed that there was a low proportion of immediately soluble metals, as well as a high proportion of metals that could be released and would so be available for plant uptake. In the sequential extraction procedure, considering the total partition, there was a large proportion of Pb, Cd and Zn extracted in a readily mobile form. In acidic soils the content of metals in ready mobile form (exchangeable-bound to carbonates as well as to Fe and Mn oxides) and bound to organic matter constitutes an important source of potentially available elements. The same pattern was observed in alkaline soils, where almost 80% of the metals could be remobilized and be potentially available to plants. Knowing the metal partitioning and mobility of heavy metals it is very important for evaluating the phytoremediation efficiency.

Biodegradation, Environmental↗

PubMed2006

In vitro availability of some essential minerals in commonly eaten processed and unprocessed Caribbean tuber crops.

The levels of three essential minerals Ca, Fe and Mg and the extent of their availability were assessed in four commonly eaten Caribbean tuber crops [dasheen (Xanthosoma spp.), Irish potato (Solanum tuberosum), sweet potato (Ipomoea batatas) and yellow yam (Dioscorea cayenensis)] in their processed and unprocessed states. Calcium was highest in cooked dasheen (5150+/-50 mg/kg) while Magnesium was highest in uncooked Irish potato (3600+/-200 mg/kg). There was no significant loss of calcium from the food samples upon cooking. All the uncooked food samples displayed higher levels minerals assessed compared to the cooked samples except for cooked Irish potato that recorded the level of iron (182.25+/-8.75 mg/kg). Availability of these minerals in the cooked and uncooked tubers crops upon digestion also showed a similar pattern. In conclusion, the consumption of these tuber crops in the Caribbean may not be responsible for the reported cases of iron deficiency in the region. However, the availability of minerals from these tuber crops when consumed with other foods (the usual practice in the Caribbean) needs further investigation.

Calcium↗

PubMed2006

Availability of integrated care for co-occurring substance abuse and psychiatric conditions.

The co-occurrence of psychiatric conditions and substance abuse presents significant challenges for behavioral healthcare providers. The need for integrated care has received substantial recent attention from clinical, research, and funding entities. However, the availability of integrated care has been low, carrying potential adverse implications for quality of care and treatment outcomes. This article describes the prevalence and key correlates of the availability of integrated care for co-occurring conditions within public and private-sector addiction treatment programs. Several organizational attributes, caseload characteristics, and service provision patterns were associated with the availability of integrated care.

Adult↗

PubMed2006

Clinical information system availability and use in urban and rural hospitals.

Clinical information systems (CIS) capture clinical data to support more efficient and effective decision making and clinical care delivery. Only a few estimates of CIS availability and use in hospitals are available nationally. The purpose of the current research is to examine differences in CIS availability and use between urban and rural hospitals. A survey addressing this purpose was completed by 74 (63.7%) of Iowa hospitals. Rural hospitals lag behind urban hospitals in terms of many CIS applications. More than 80% of the urban hospitals, but only between 30 and 40% of the rural hospitals, reported using computers to collect basic clinical information for potential use in an electronic medical record (EMR) and computerized provider order entry (CPOE) system. Comparison of CIS within one state's urban and rural hospitals sheds light on variation in clinical support applications, decision support, and electronic medical record "readiness" in these settings.

Decision Making, Computer-Assisted↗

PubMed2006

Evaluation of a commercially available human serum amyloid A (SAA) turbidimetric immunoassay for determination of feline SAA concentration.

Serum amyloid A (SAA) is an acute-phase protein in cats likely to be useful for diagnosing and monitoring inflammatory diseases, especially if rapid, reliable and automated assays can be made available. A commercially available automated human SAA turbidimetric immunoassay (SAA-TIA) was evaluated for determination of SAA in cats. Intra-assay and inter-assay imprecisions were in the ranges 2.1-9.9% and 7.0-12.5%, respectively, and without significant inaccuracy. Eighty-eight cats were divided into groups according to (A) the presence or absence of an acute-phase response (APR) (n = 23 and 65, respectively) and (B) clinical diagnosis (clinically healthy cats, cats diagnosed with inflammatory/infectious diseases, endocrine/metabolic diseases, neoplastic diseases, and miscellaneous disorders (n=43, 13, 8, 4 and 20, respectively)). The observed SAA concentrations were, as expected, different for (A) cats with and without an APR and (B) cats with inflammatory/infectious diseases compared to other diagnostic groups, except neoplastic diseases. In conclusion, the SAA concentration in cats could be measured reliably using the commercially available TIA designed for measuring human SAA, which should facilitate implementation of the parameter for routine diagnostic purposes.

Acute-Phase Reaction↗

PubMed2006

Validation of a commercially available human immunoturbidimetric assay for haptoglobin determination in canine serum samples.

Haptoglobin is a positive acute-phase protein with a valuable role as a marker of inflammation in both human and veterinary medicine. The aim of this study was to validate a commercially available immunoturbidimetric method designed for human haptoglobin determination (Izasa SA, Barcelona, Spain) for its use in canine samples. Cross-reactivity between anti-human haptoglobin antiserum and canine haptoglobin was found when agarose gel immunodiffusion and ELISA tests were performed. The use of canine pooled serum with haptoglobin concentration of 6.3 g/L as standard provided higher analytical range than commercially available standards. Intra-assay and inter-assay coefficients of variation were 2.49% and 4.60%, respectively. A linear regression model between immunoturbidimetric results and a previously validated spectrophotometric method (Tridelta Development Limited, Ireland) yielded a slope at 95% confidence interval of 0.94 (0.86, 1.02) and y-intercept at 95% confidence interval of 0.11 (-0.59, 0.82). No significant differences were produced by anticoagulants, lipaemia and bilirubinaemia, although haemolysis significantly decreased haptoglobin. A significant increase of haptoglobin concentration was detected in inflammatory conditions such as pyometra and leishmaniasis, in neoplastic conditions, and after glucocorticoid administration. Canine serum haptoglobin concentration can be reliably measured using the commercially available Izasa immunoturbidimetric method developed for human haptoglobin determination. This method is precise and accurate, provides a wider analytical range than previous reported methods, and can be easily automated and used for routine haptoglobin determination in canine samples.

Animals↗

PubMed1978

Relation of cytolytic activity of an ether-deoxy lysophosphatidylcholine analog to available membrane surface. Comparison of normal and tumor cells from mice.

1-Hexadecylpropanediol-3-phosphorylcholine, an ether-deoxy analog of lysophosphatidylcholine, has been employed to study the sensitivity of various types of mouse cells with respect to changes in membrane permeability induced by lysophosphatidylcholine. Cells used included erythrocytes, thymocytes, spleen cells and macrophage, as well as 4 different tumors (2 lymphomas, 1 Ehrlich acites and 1 methylcholanthren-induced fibrosarcoma). The sensitivity to the lysophosphatide (on a per-cell basis) of the above cell types varied by a factor of 65. When lytic concentrations were related to available membrane surface, this variation was reduced to a factor of 2.5. No principal difference was observed between the sensitivity of normal versus tumor cell membranes with respect to lysophosphatidylcholine lysis. Membrane surface, available for lysophosphatidylcholine, has been estimated from binding equilibria of 14C-labelled deoxy-lysophosphatidylcholine to the cells under standardized conditions. This method is based on the finding that binding equilibria of lysophospholipids to cells are predominantly determined by the available membrane surface.

Animals↗