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PubMed2000

Effects of competitive reward distribution on auditing and competitive responding.

This study allowed subjects to audit each other's responding during a series of competitive contests. Six pairs of female college students competed in 3-min contests in which the competitive response was a knob pull. A sum of money was divided using a proportional distribution or a 100%/0% reward distribution. In the proportional distribution, a subject's proportion of the sum was her proportion of the total number of responses. Also, in every contest either subject could make a response that would end the contest prematurely and give both subjects the same amount: a sum equal to 33% of the competitive total. Each subject could press either or both of two audit buttons that displayed her own and the other's response total for 10 s. Results replicated earlier findings in showing the superiority of the proportional distribution in total number of competitive responses made. No subject audited continuously, and only 1 audited most of the time. Most audits were interpersonal, including both own and other's scores. Auditing typically was more frequent in 100%/0% contests in which subjects were more likely to stop the contest when they were far behind. Winners were more likely to audit than were losers. Competitive response rates increased when the differences revealed by audits were small and decreased when they were large. Overall audit patterns were consistent with the view that feedback as "news" is more often sought when it can lead to improved outcomes.

Adult↗
PubMed1991

The competition diallel and the exploitation and interference components of larval competition in Drosophila melanogaster.

A logistic model of the competition diallel is presented based on two linear parameters for the exploitation component of competition, namely the acquisition rate (f) and utilization efficiency (u), and one linear parameter for the interference component of competition (i). This interference component encompasses all phenomena that are uniquely related to duocultures, such as resource partitioning, mutual stimulation, inhibition and complementation. The model uses yield-density regression coefficients (c-values), but could be adapted to suit other variates that account for both competitor density and relative frequency. In Drosophila larval competition most interference is negative and depresses the performance of duocultures with respect to monocultures, over and above that expected from shared exploitation of a common resource. Even in the closely controlled competitive conditions of these experiments this interference accounts for a considerable proportion of the total variation. The isolation of a general, and therefore predictable, interference component may prove useful in agriculture when assessing the relative importance of mixture effects to the yield potential of different crops.

Animals↗
PubMed1989

Competition among Strains of Rhizobium leguminosarum biovar trifolii and Use of a Diallel Analysis in Assessing Competition.

Competition between indigenous Rhizobium leguminosarum biovar trifolii strains and inoculant strains or between mixtures of inoculant strains was assessed in field and growth-room studies. Strain effectiveness under competition was compared with strain performance in the absence of competition. Field inoculation trials were conducted at Elora, Ontario, Canada, with soil containing indigenous R. leguminosarum biovar trifolii. The indirect fluorescent-antibody technique was used for the identification of nodule occupants. Treatments consisted of 10 pure strains, a commercial peat inoculant containing a mixture of strains, and an uninoculated control. Inoculant strains occupied 17.5 to 85% of nodules and resulted in increased dry weight and nitrogen content, as compared with the uninoculated control. None of the strains was capable of completely overcoming resident rhizobia, which occupied, on average, 50% of the total nodules tested. In growth-room studies single commercial strains were mixed in all possible two-way combinations and assessed in a diallel mating design. Significant differences in plant dry weight of red clover were observed among strain combinations. Specific combining ability effects were significant at the 10% level, suggesting that the effectiveness of strain mixtures depended on the specific strain combinations. Strains possessing superior effectiveness and competitive abilities were identified by field and growth-room studies. No relationship was detected between strain effectiveness and competitive ability or between strain recovery and host cultivar. The concentration of indigenous populations was not considered to be a limiting factor in the recovery of introduced strains at this site.

Journal Article↗
PubMed1994

Influence of changing temperature on growth rate and competition between two psychrotolerant Antarctic bacteria: competition and survival in non-steady-state temperature environments.

Competition between two psychrotolerant bacteria was examined in glycerol-limited chemostat experiments subjected to non-steady-state conditions of temperature. One bacterium, a Brevibacterium sp. strain designated CR3/1/15, responded rapidly to temperature change, while a second, Hydrogenophaga pseudoflava, designated CR3/2/10, exhibited a lag in growth after a shift-down during a square-wave temperature cycle but not after a shift-up. The effects on competition and survival by these bacteria of both sine-wave and square-wave temperature changes between 2 and 16 degrees C over a 24-h cycle time were examined, as well as square-wave cycles over 12 and 96 h. The changing proportion of each bacterium in the chemostat was determined by plate counting at regular intervals. Under a sine-wave temperature cycle H. psedoflava outcompeted the Brevibacterium sp., but under square-wave temperature cycles the two bacteria coexisted because the lag by H. pseudoflava after the temperature shift-down favored the faster-responding Brevibacterium sp. The two bacteria thus exhibited different survival strategies, with H. pseudoflava adapted to effective competition under steady-state conditions and the Brevibacterium sp. adapted to rapid adaptation and survival in a changing environment. The degree of perturbation of the bacteria, expressed as a temperature challenge index (delta temp/delta time), was greater under a square-wave temperature cycle than under a sine-wave cycle of equivalent amplitude and frequency, and higher-temperature challenge favored the Brevibacterium sp. A computer model was developed to examine competition between the bacteria in transient environments. The frequency of the temperature cycle influenced competition, as with a longer cycle (96 h) the significance of the lag by H. pseudoflava decreased compared with that of a 24-h cycle, and H. pseudoflava predominated in a mixed culture with a 96-h cycle. The shift-down lag by H. pseudoflava, during which it adapted to low temperature, disadvantaged it in a changing temperature environment, but at a short cycle time (12 h) this disadvantage was countered by the incomplete loss of low-temperature adaptation between cycles and thus the carryover of some low-temperature adaptation. Also, it was demonstrated that, as well as consideration of the effect of temperature changes on inducing lags in growth, the loss of adaptation to low temperature between cycles had to be taken into account in the computer model if it was to reproduce the trends in the experimental data.

Antarctic Regions↗
PubMed1997

Orienteering competition injuries: injuries incurred in the Finnish Jukola and Venla relay competitions.

OBJECTIVES: The aim of this study was to find out the amount, type, and localisation of acute orienteering injuries in the 1995 Finnish Jukola (men's) and Venla (women's) relay competitions with 9724 participants. METHODS: Patient data were collected on a preplanned form at the first aid station. RESULTS: There were 244 acute competition injuries. The overall injury incidence was 2.5% (95% confidence interval (CI) 2.2 to 2.8), 2.3% in the men's relay and 3.2% in the women's relay, and the difference between incidences among men and women was statistically significant (odds ratio (OR) 1.4; 95% CI 1.1 to 1.9). The injury rates were also calculated per 1000 competition hours and per 1000 km and were 15.4 and 2.6 respectively. Most of the injuries could be treated at the first aid station. Female orienteers had more blisters (OR 4.4; 95% CI 2.5 to 7.9) and fewer wounds (OR 0.5; 95% CI 0.2 to 1.0) than male orienteers. Injuries occurred mostly in the lower extremities (70%), and ankle sprains accounted for 25% of all injuries. Injuries were more common during the first leg of both relays. CONCLUSIONS: This study shows the heavy workload in a first aid station of a big orienteering relay competition. It indicates a difference in injuries between the sexes and in the different stages of the relay, which should be further investigated in order to prevent orienteering competition injuries.

Ankle Injuries↗
PubMed2006

Retrospective injury epidemiology of one hundred one competitive Oceania power lifters: the effects of age, body mass, competitive standard, and gender.

The injury epidemiology of competitive power lifters was investigated to provide a basis for injury prevention initiatives in power lifting. Self-reported retrospective injury data for 1 year and selected biographical and training information were obtained via a 4-page injury survey from 82 men and 19 women of varying ages (Open and Masters), body masses (lightweight and heavyweight), and competitive standards (national and international). Injury was defined as any physical damage to the body that caused the lifter to miss or modify one or more training sessions or miss a competition. A total of 118 injuries, which equated to 1.2 +/- 1.1 injuries per lifter per year and 4.4 +/- 4.8 injuries per 1,000 hours of training, were reported. The most commonly injured body regions were the shoulder (36%), lower back (24%), elbow (11%), and knee (9%). More injuries appeared to be of a sudden (acute) (59%) rather than gradual (chronic) nature (41%). National competitors had a significantly greater rate of injury (5.8 +/- 4.9 per 1,000 hours) than international competitors (3.6 +/- 3.6 per 1,000 hours). The relative proportion of injuries at some body regions varied significantly as a function of competitive standard and gender. No significant differences in injury profile were seen between Open and Masters or between lightweight and heavyweight lifters. Power lifting appears to have a moderately low risk of injury, regardless of the lifter's age, body mass, competitive standard, or gender, compared with other sports. Future research should utilize a prospective cohort or case-controlled design to examine the effect of a range of other intrinsic and extrinsic factors on injury epidemiology and to assess the effects of various intervention strategies.

Adult↗
PubMed1991

Competitive (AP7) and non-competitive (MK-801) NMDA receptor antagonists differentially alter glucose utilization in rat cortex.

The effects of D,L-2-amino-7-phosphonoheptanoic acid (AP7), a competitive N-methyl-D-aspartate (NMDA) receptor antagonist, and MK-801, a non-competitive NMDA receptor antagonist, on regional brain metabolism were studied in unanesthetized, freely moving rats by using the quantitative [14C]2-deoxyglucose autoradiographic procedure. AP7 (338 or 901 mg/kg) produced a dose-dependent decrease of metabolic activity throughout most of the regions studied including sensory, motor, and limbic cortices. In contrast, MK-801 (0.1 or 1.0 mg/kg) resulted in a dose-dependent decrease of metabolic activity in sensory cortices, and an increase in limbic regions such as the hippocampal stratum lacunosum moleculare and entorhinal cortex. MK-801 also produced a biphasic response in agranular motor cortex, whereby the low dose increased while the high dose decreased labeling. In addition, MK-801 produced heterogeneous effects on regional cerebral metabolism in sensory cortices. Metabolic activity decreased in layer IV relative to layer Va following MK-801 treatment in primary somatosensory (SI) and visual (VI) cortices, suggesting a shift in activity from afferent fibers innervating layer IV to those innervating layer Va. MK-801 administration also decreased metabolic activity in granular SI relative to dysgranular SI, and in VI relative to secondary visual cortex (VII), thus providing a relative sparing of activity in dysgranular SI and VII. Thus, the non-competitive NMDA receptor antagonist suppressed activity from extrinsic neocortical sources, enhancing relative intracortical activity and stimulating limbic regions, while the competitive NMDA antagonist depressed metabolic activity in all cortical regions.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1993

The problem of partial competition in the quantitative characterization of interactions by competitive binding assays.

Binding expressions are derived and analytical procedures developed for the quantitative characterization of inhibitor binding that is only partially competitive with the interaction between an acceptor and the ligand that is being monitored. Two such situations are considered: (i) that in which the partial competition reflects binding of inhibitor to fewer acceptor sites than available to ligand; and (ii) that in which the partial competition reflects binding of inhibitor to acceptor sites in addition to those occupiable by ligand. The potential efficacy of the suggested analyses is then explored by their application to simulated data that span the likely range of experimental behavior. Quantitative analysis of the displacement of [3H]nitrobenzylthioinosine from cultured leukemic cells by an adduct of 5'-S-(2-amino-ethyl)-N6-(4-nitrobenzyl)-5'-thioadenosine with fluorescein-5-isothiocyanate is used to establish that the cells possess 6% fewer sites (150,000 cf. 159,000 sites/cell) for the fluorescent adduct than for the tritiated ligand, and that the binding is 10-fold weaker (binding constant of 0.28 cf. 2.8 nM-1). Corresponding analysis of results obtained with bovine aorta endothelial cells indicates that a 3-fold weaker interaction (binding constant of 1.1 cf. 3.3 nM-1) occurs between the fluorescent adduct and 79% of the cell sites accessible to the tritiated ligand. The present analytical procedures extend the utility of competitive binding assays for the quantitative screening of potential inhibitors by removing the inherent limitation of existing analyses that all acceptor sites be accessible to both the competing solute and the indicator ligand.

Adenosine↗
PubMed1993

Are the disparate pharmacological profiles of competitive and un-competitive NMDA antagonists due to different baseline activities of distinct glutamatergic pathways? (Hypothesis).

Corticostriatal glutamatergic neurons impinging on the so-called "direct" striato-thalamic pathways appear to act as a driving force with respect to psychomotor functions, whereas corticostriatal glutamatergic neurons projecting to the "indirect" striato-thalamic route appear to mediate inhibition of the thalamus and thus act as a "brake" with respect to psychomotor functions. The GABAergic striatal projection neurons pertaining to the "direct" pathway mediating behavioural stimulation appear to be phasically activated, whereas GABAergic striatal projection neurons pertaining to the "indirect" pathway mediating suppression of behaviour must be assumed to display a high tonic activity. Such an organization could explain some of the behavioural differences between competitive and un-competitive NMDA antagonists, since the binding of competitive NMDA antagonists is inhibited by glutamate, whereas the binding of un-competitive NMDA antagonists is enhanced by the presence of NMDA receptor agonists, a phenomenon called use/agonist dependence.

Animals↗
PubMed1996

Comparison of the patterns of altered cerebral glucose utilisation produced by competitive and non-competitive NMDA receptor antagonists.

Recent studies indicate that competitive and non-competitive NMDA receptor antagonists can be readily distinguished by their effects on local cerebral glucose utilisation (1CGU). In the present study we compare the effects of the novel NMDA antagonist, (+)-1-methyl-1phenyl-1,2,3,4-tetrahydroisoquinoline (FR115427) on 1CGU, comparing its metabolic profile with that of the non-competitive NMDA receptor antagonist, dizocilpine (MK801) and of the competitive NMDA receptor antagonist CGS19755, using the 2-deoxyglucose metabolic mapping approach. Local cerebral glucose utilisation was measured in 80 anatomically discrete regions of the conscious rat brain using [14C]2-deoxyglucose quantitative autoradiography. Studies were initiated 10 min after the administration of FR115427 (0.1-3 mg/kg i.v.; n = 20), dizocilpine (0.03-0.3 mg/kg; n = 15), CGS19755 (1-30 mg/kg; n = 15) or saline (2 ml/kg; n = 5). Dizocilpine produced characteristic alterations in 1CGU with widespread increases in 1CGU in primary olfactory and limbic areas while reducing 1CGU in somatosensory and motor cortex. FR115427 produced a pattern of altered 1CGU which was broadly similar to that elicited by dizocilpine with increases in 1CGU in the pontine nuclei, presubiculum and hippocampus and reductions in somatosensory and motor cortex and within components of the auditory system. However, FR115427 was approximately 30-fold less potent than dizocilpine in this regard. In limbic structures, the effects of FR115427 were less pronounced than those produced by dizocilpine. Increases in 1CGU of 62-98% were found in retrosplenial, piriform and entorhinal cortex of dizocilpine-treated rats whereas these areas appeared relatively unaffected following FR115427 administration. A comparison of the pattern of metabolic response produced by each of these agents was performed by constructing a hierarchy of regional responsiveness using the f statistic: while focal differences in the metabolic profiles of dizocilpine and FR115427 were evident, a plot of the regional f values for dizocilpine and FR115427 revealed a strong overall relationship between the metabolic responses with a Pearson's product moment correlation of 0.78. In contrast, the correlation between the patterns produced by CGS19755 and that for dizocilpine or FR115427 was poor (r = 0.28 and 0.5 respectively).

Animals↗
PubMed1994

The utility of excitatory amino acid (EAA) antagonists as analgesic agents. II. Assessment of the antinociceptive activity of combinations of competitive and non-competitive NMDA antagonists with agents acting at allosteric-glycine and polyamine receptor sites.

The present study examined the utility of using low-dose combinations of agents acting within the NMDA receptor complex to produce analgesic effects without producing motor dysfunction. In particular, we assessed the antinociceptive activity in the formalin test of combinations of competitive (APV) and non-competitive (MK-801) NMDA receptor antagonists with agonist and antagonists acting at allosteric-glycine and polyamine receptors. Both the competitive NMDA receptor antagonist APV and the non-competitive NMDA antagonist MK-801 produced dose-dependent analgesic effects in the late, but not the early, phase of the formalin test. The antinociceptive activity of APV was significantly enhanced by combination with a non-analgesic dose of the allosteric-glycine agonist glycine, and was reduced by combination with the allosteric-glycine antagonist 7-CKA which also reversed the glycine-induced enhancement of the antinociceptive effects of APV. The antinociceptive activity of MK-801 was significantly enhanced by combination with a non-analgesic dose of the polyamine agonist spermine, and reduced by combination with the polyamine receptor antagonist IFEN which also reversed the spermine-induced enhancement of the antinociceptive effects of MK-801. The enhancement of the antinociceptive activity of APV and MK-801 by glycine and spermine, respectively, was not accompanied by increases in motor dysfunction. Thus, by using specific combination of agents acting within the NMDA receptor complex, it was possible to produce effective antinociception in the formalin test at doses of NMDA receptor antagonists which did not produce motor dysfunction.

2-Amino-5-phosphonovalerate↗
PubMed1996

Co-operative, competitive and non-competitive interactions between modulators of P-glycoprotein.

We measured the effects of individual modulators and of pairs of modulators of the multidrug resistance pump, P-glycoprotein, on the accumulation of labelled daunomycin into multidrug-resistant P388 leukemia cells at 37 degrees C and developed a kinetic analysis which enables such data to be modelled in terms of co-operative, competitive or non-competitive interaction between pairs of modulators. The modulators verapamil, cyclosporin and trifluoperazine interacted with P-glycoprotein as single molecules, while vinblastine, mefloquine, dipyridamole, tamoxifen and quinidine displayed Hill numbers close to 2, suggesting that pairs of modulator molecules need to act together in order to bring about effective reversal of P-glycoprotein. When the modulators were presented to P-glycoprotein in pairs, we found examples of both competitive and non-competitive behaviour. We interpret these results on a model in which two modulatory sites exit on the MDR pump. To one of these, mefloquine, vinblastine and tamoxifen bind preferentially; to the other, verapamil, dipyridamole, trifluoperazine and quinidine bind (but mefloquine and tamoxifen only weakly if at all). Cyclosporin A can interact with both sites.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Does quasi-local competition lead to pattern formation in metapopulations? An explicit resource competition model.

In metapopulations, competitive interactions may extend beyond the confines of the local population such that members of neighbouring habitat patches affect each other adversely (quasi-local competition). We derive a model for quasi-local competition from first principles, assuming that individuals compete for shared resources and members of a population spend a certain fraction of their foraging time in the adjacent populations. Contrary to the results of Doebeli and Killingback [2003. Theor. Popul. Biol. 64, 397-416], our model does not produce spatial patterns of population densities in homogeneous environments. Quasi-local competition nevertheless contributes to pattern formation by amplifying the effect of heterogeneities in the external environment, and this amplification can be extremely strong when dispersal is absent. We discuss why apparently similar models lead to contrasting results.

Competitive Behavior↗
PubMed1999

The iso-competition point for counterion competition binding to DNA: calculated multivalent versus monovalent cation binding equivalence.

In this paper we introduce an important parameter called the iso-competition point (ICP), to characterize the competition binding to DNA in a two-cation-species system. By imposing the condition of charge neutralization fraction equivalence theta1 = ZthetaZ upon the two simultaneous equations in Manning's counterion condensation theory, the ICPs can be calculated. Each ICP, which refers to a particular multivalent concentration where the charge fraction on DNA neutralized from monovalent cations equals that from the multivalent cations, corresponds to a specific ionic strength condition. At fixed ionic strength, the total DNA charge neutralization fractions thetaICP are equal, no matter whether the higher valence cation is divalent, trivalent, or tetravalent. The ionic strength effect on ICP can be expressed by a semiquantitative equation as ICPZa/ICPZb = (Ia/Ib)Z, where Ia, Ib refers to the instance of ionic strengths and Z indicates the valence. The ICP can be used to interpret and characterize the ionic strength, valence, and DNA length effects on the counterion competition binding in a two-species system. Data from our previous investigations involving binding of Mg2+, Ca2+, and Co(NH3)63+ to lambda-DNA-HindIII fragments ranging from 2.0 to 23.1 kbp was used to investigate the applicability of ICP to describe counterion binding. It will be shown that the ICP parameter presents a prospective picture of the counterion competition binding to polyelectrolyte DNA under a specific ion environment condition.

Binding, Competitive↗
PubMedDate not supplied

Kinetic analysis of LY320236: competitive inhibitor of type I and non-competitive inhibitor of type II human steroid 5alpha-reductase.

Type I and type II steroid 5alpha-reductases (5alpha-R) catalyze the conversion of testosterone (T) to dihydrotestosterone (DHT). LY320236 is a benzoquinolinone (BQ) that inhibits 5alpha-R activity in human scalp skin (Ki(typeI)=28.7+/-1.87 nM) and prostatic homogenates (Ki(typeII)=10.6+/-4.5 nM). Lineweaver-Burk, Dixon, and non-linear analysis methods were used to evaluate the kinetics of 5alpha-R inhibition by LY320236. Non-linear modeling of experimental data evaluated V(max) in the presence or absence of LY320236. Experimental data modeled to the following equation 1v=+ fixing the In0c value equal to 1.0 or 0 are consistent with non-competitive or competitive inhibition, respectively. LY320236 is a competitive inhibitor of type I 5alpha-R (In0c=0, Ki=3.39+/-0.38, RMSE = 1.300) and a non-competitive inhibitor of type II 5alpha-R (In0c=1, Ki=29. 7+/-3.4, RMSE = 0.0592). These data are in agreement with linear transformation of the data using Lineweaver-Burk and Dixon analyses. These enzyme kinetic data support the contention that the BQ LY320236 is a potent dual inhibitor with differing modes of activity against the two known human 5alpha-reductase isozymes. LY320236 represents a class of non-steroidal 5alpha-R inhibitors with potential therapeutic utility in treating a variety of androgen dependent disorders.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1992

Antagonism of kinin effects on epithelial by Hoe 140: apparently competitive and non-competitive interactions.

1. Hoe-140, a potent kinin receptor antagonist, was investigated for its ability to inhibit the effects of lysylbradykinin (kallidin) on a cultured colonic epithelium, HCA-7 Colony 29, derived from a human adenocarcinoma. 2. Measurements of electrogenic chloride secretion (as short circuit current), and of intracellular Ca2+ (from Fura-2 fluorescence) were used to assess the action of lysylbradykinin in the absence and presence of Hoe 140. 3. From short circuit current data, Hoe 140 appeared to be a competitive antagonist with a Ki value of 5 nM. However, with measurements of intracellular Ca2+ Hoe 140 was apparently a non-competitive antagonist with a Ki of between 4-6 nM. 4. Because of the unexpected finding of non-competitive antagonism, measurements were made with a second antagonist pair, histamine and mepyramine. Mepyramine behaved as a competitive antagonist against responses to histamine with a Ki value of approximately 5 nM when short circuit current measurements were evaluated. However, when intracellular Ca2+ concentration was used as a measure mepyramine, 30 nM, produced a near parallel shift in the response curve, but at 100 nM the maximal response was depressed. 5. The reasons why the apparent type of antagonism depends upon the method of measurement is discussed, bearing in mind that the increase in intracellular Ca2+ is a signal which precedes the increase in short circuit current.

Adenocarcinoma↗
PubMed1994

Managed competition: an analysis of consumer concerns. The Working Group on Managed Competition.

Advocates for health care reform (representing a broad range of constituencies) raise serious concerns about the ability of managed competition to meet the health care needs of the American people. Similarities in managed competition proposals include establishment of a collective purchasing authority, creation of health plans, standardization of rules and requirements, and limitation on tax subsidies. Managed competition proposals vary as to whether they call for true universality, meaningful cost containment, and fair financing. The article raises questions about managed competition, including the technical feasibility; the link to employment; the role for insurance companies; severing the link between insurance and income, age, or health status; comprehensive benefits; cost containment; the role for managed care; universality of coverage; and the role for insurance companies to make treatment decisions.

Competitive Medical Plans↗
PubMed1992

The behavior of multihospital chains in increasingly competitive California hospital markets: pro- or anti-competitive?

In previous literature, no evidence of competitive advantage has been found from hospital affiliation with chains. In this paper, the role of chains in hospital adaptation to a more competitive environment is examined further. Two dimensions of hospital behavior are examined: the propensity to engage in contractual arrangements with insurers, and the effect of a changed competitive environment on preferred acquisition targets by chains. We find evidence that chains behave pro-competitively in the short run, and discuss policy implications of the observed market restructuring in the longer run.

California↗