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At least 19 recordsLinked to original sources
PubMed1972

Competition, competitive repulsion, and coexistence.

This manuscript is concerned with concepts rather than abstruse details or mathematics. Discussed are: competition; extended competition, proposed for competition in the strict sense, extended and modified by all related interactions including predation, parasitism, disease, and even cooperation, all of which can be "weapons of competition"; competitive repulsion, proposed for the sum of forces that determine spacings, including ecologic spacings, of individuals and populations; Darwin (biotic) equilibriums; competitive extinction, Gause's principle, limited and limiting resources, and single-resource competition; de facto coexistence of competing species, exemplified by green plants competing for sunlight; niche competition; the two concepts of competitive exclusion; devision of resources and of their utilizers; cause and effect in real situations; and niches, niche overlap, and coexistence. Stressed is the complexity of the real world, and the confusion that can and does arise from modeling it too simply.

Biological Evolution↗
PubMed1977

Antigenic competition between heterologous erythrocytes in mice. Immunological and histological studies exploring mechanisms of the antigenic competition.

To explore the mechanisms of antigenic competition, immunological and histological studies were made on mice using non-crossreacting heterologous erythrocyte antigens, i.e. sheep (SRBC), horse (HRBC) and chicken (CRBC) erythrocytes. Deficiency in the competition-inducing capacity of CRBC which we demonstrated in a previous paper was corroborated by the results that under any experimental conditions examined CRBC were unable to induce the competition. Of interest in the studies was that when anti-HRBC antibody responses of mice pre-injected with SRBC, i.e. competing antigen, were examined on day 2 and day 4 of HRBC-immunization, the day-2 response was revealed to be significantly enhanced, whereas the day-4-response was markedly suppressed as a result of the antigenic competition. By contrast, pre-injection with CRBC, i.e. non-competing antigen, did not affect at all either day-2 or day-4 anti-HRBC response of mice. Histological features of the spleens of mice either being prepared for antigenic competition or undergoing competitively suppressed antibody response were characterized by prominent regeneration of hyperplastic germinal centres, involving appearance of numerous tingible bodies and distinct collars of small lymphocytes which suggested massive proliferation and degeneration of lymphocytes. The spleens of mice in the immunological state indifferent to antigenic competition were characterized by huge lymphatic follicles which contained very few tingible bodies and were circumscribed by a markedly attenuated zone of small lymphocytes. From all these results, we suggest that massive proliferation and differentiation of T lymphocytes, probably toward regulatory (suppressor) T cells, could account for a mechanism of antigenic competition, and that deficient competition-inducing capacity of CRBC should be ascribed to weakness of their capacity in activation of the regulatory T lymphocytes.

Animals↗
PubMed1992

Intensity and direction as dimensions of competitive state anxiety and relationships with competitiveness.

This study examined differences in intensity and direction of symptoms of competitive state anxiety in high and low competitive subjects from the sports of rugby union, basketball, soccer, and field hockey. The 69 men were dichotomized via a median-split into high and low competitive groups based on their scores on the Sport Orientation Questionnaire. All subjects completed a modified version of the Competitive State Anxiety Inventory-2 30 minutes prior to competition. This inventory included the original intensity scale plus a direction scale on which subjects rated the extent the experienced intensity of each symptom was either facilitative or debilitative to subsequent performance. There were no significant group differences on intensity of cognitive anxiety or of somatic anxiety or on direction of somatic anxiety; however, the highly competitive group of 34 subjects reported their anxiety as more facilitative and less debilitative than the low competitive group (n = 35). This supports the proposal that sports performers' directional perceptions of their anxiety symptoms may provide further understanding of the competitive state-anxiety response.

Adult↗
PubMed1989

The behavioural effects of MK-801: a comparison with antagonists acting non-competitively and competitively at the NMDA receptor.

The selective non-competitive NMDA receptor antagonist, MK-801, potently blocked convulsions induced in the mouse by N-methyl-DL-aspartic acid (NMDLA) with an i.v. ED50 dose of 0.2 mg/kg. Similar doses of MK-801 were also effective in blocking seizures induced by pentylenetetrazol (PTZ), electroshock and by sound in audiogenic seizure-prone animals. Other less selective non-competitive NMDA receptor antagonists including phencyclidine (PCP), thienylcyclohexylpiperidine (TCP), (+)-N-allylnormetazocine [+)-NANM, (+)-SKF 10,047) and ketamine also blocked NMDLA-induced seizures with a rank order of potency of MK-801 greater than PCP greater than TCP = (+)-NANM greater than ketamine. The competitive NMDA receptor antagonist, 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) blocked NMDLA-induced seizures with an ED50 of 4.5 mg/kg, 22- and 560-fold more potently than the competitive antagonists, 2-DL-amino-7-phosphonoheptanoic acid (2-APH) and 2-DL-amino-5-phosphonovaleric acid (2-APV), respectively. MK-801 was the most potent of the non-competitive antagonists to induce a motor syndrome including head weaving, body rolling, increased locomotion and ataxia, characteristic of the behavioural response to PCP in the mouse. The syndrome was also present following injection of the competitive NMDA receptor antagonists, although they were generally less potent (probably a reflection of poor brain penetration) and less efficacious than the non-competitive antagonists. For all compounds except CPP, the anticonvulsant ED50 dose was close to the minimum effective dose to induce motor stimulation: CPP was 5- to 10-fold more potent as an anticonvulsant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Analysis of the effect of competitive trait anxiety on performance in Taekwondo competition.

This study examined the effect of competitive trait anxiety on performance in open- (sparring) and closed- (forms) skills in Taekwondo. 58 subjects responded to the Sports Competition Anxiety Test immediately prior to competition. Subjects were categorized into groups showing high, medium, and low competitive anxiety to assess whether differences on the variables of sparring and forms were significantly related with scores on competition anxiety, age, or gender after adjusting for the covariate of years of competition. Multivariate analysis of covariance showed no significant differences between subjects and the normative samples on competitive anxiety scores except for boys, whose scores were significantly higher than those of a normative sample of male youth athletes.

Adolescent↗
PubMed1986

The origin and use of the terms competitive and non-competitive in interactions among chemical substances in biological systems.

The terms competition and competitive were in use for appropriate types of interaction in human and animal behaviour from the seventeenth century. In the nineteenth and early twentieth centuries they reached more technical uses in biology, especially in darwinian studies; and in chemistry in describing competing reactions, surface phenomena and the influence of substituent groupings in reactant molecules. Use of competitive and non-competitive to describe enzyme inhibitors had a specific beginning when J. B. S. Haldane (following premonitory work of others) applied the terms in 1927 and 1930 to types of inhibition already differentiated by Michaelis and co-workers. The theoretical background in kinetics and stereochemistry so acquired gave a firmness to the application of the terms in biochemistry. The first examples concerned glycosidases, especially beta-D-fructofuranosidase or invertase, and interactions of carbon monoxide and oxygen at iron-porphyrin systems. They were thus of interest in toxicology and in enzyme and carrier studies. The sphere of application of the biochemically-defined terms expanded greatly when, following investigation of sulphonamide action, it was realized that concepts of enzyme inhibition by structurally related compounds offered a route to understanding the action of existing medicaments and to the production of new ones. Ideas and terminology based on competitive and non-competitive enzyme inhibition and receptor occupancy have subsequently been applied in many ways. Examples include application to the analysis of feedback inhibition and other processes of metabolic control; to receptor relationships among neurotransmitters and medicaments; and to understanding interactions at sensory receptors.

Animals↗
PubMed1991

Genetic differences in the effects of competitive and non-competitive NMDA receptor antagonists on locomotor activity in mice.

The effects of non-competitive (MK-801, phencyclidine, and ketamine) and competitive (CGP 39551, CGS 19755, and NPC 12626) N-methyl-D-aspartate (NMDA) receptor antagonists on locomotor activity in inbred CBA and C57, and in outbred NMRI mice were examined. Administration of the non-competitive NMDA antagonists produced a dose-dependent increase in well-coordinated locomotor activity at lower doses, followed by a bizarre behavioral syndrome (head weaving, body rolling, rotations, ataxia) after higher doses. The pharmacological profile of the competitive antagonists CGP 39551, CGS 19755, and NPC 12626 was more complex. CGP 39551 dose-dependently inhibited locomotor activity, whereas CGS 19755 and NPC 12626 displayed a biphasic action, that is low doses inhibited locomotor activity, whereas higher doses produced mild behavioral stimulation. The behavioral effects of NMDA antagonists appear to be genetically determined, since CBA animals were most sensitive to both non-competitive and competitive antagonists, followed by NMRI and C57 animals. The differential effects of NMDA antagonists in various strains of mice suggest that the observed behavioral differences may be due to genetic differences in the NMDA/glutamate receptor channel complex.

Amino Acids↗
PubMed1989

A comparison of the anticonvulsant effects of competitive and non-competitive antagonists of the N-methyl-D-aspartate receptor.

The anticonvulsant activity of two competitive antagonists of the N-methyl-D-aspartate (NMDA) receptor, 2-amino-7-phosphonoheptanoic acid (APH) and 3-[2-carboxypiperazin-4-yl]-propyl-1-phosphonate (CPP), and two non-competitive NMDA antagonists, phencyclidine (PCP) and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801), were compared in 4 models of induced seizures in mice. All 4 drugs protected against tonic extensor seizures induced by pentylenetetrazol (PTZ), by submaximal (15 mA) electroconvulsive shock (ECS) and by maximal (50 mA) ECS. Similar orders of potency (i.e., MK-801 greater than PCP greater than or equal to CPP greater than APH) were seen in each of the 3 seizure models. All 4 drugs failed to block clonic seizures induced by picrotoxin in the dose ranges that protected from tonic seizures. These data are consistent with other data demonstrating that competitive and non-competitive NMDA antagonists have similar pharmacologic effects. These results also support the suggestion that the anticonvulsant effects of competitive and non-competitive NMDA antagonists are mediated by the NMDA receptor-ionophore complex.

2-Amino-5-phosphonovalerate↗
PubMed1992

Intracerebroventricular application of competitive and non-competitive NMDA antagonists induce similar effects upon rat hippocampal electroencephalogram and local cerebral glucose utilization.

In this study we have used electrophysiological and metabolic markers to investigate the effects of competitive and non-competitive NMDA antagonists in rats after central or peripheral administration. The non-competitive antagonist, MK-801, induced dose-dependent suppression of rat hippocampal EEG energy both after intraperitoneal (i.p.) and intracerebroventricular (i.c.v.) application. Similar effects were observed after i.p. and i.c.v. application of the competitive antagonist, DL-CPP-ene. Whereas the MK-801 was more potent after i.p. application, DL-CPP-ene was more potent after i.c.v. administration. Intracerebroventricular administration of MK-801 and DL-CPP-ene resulted in similar changes in the pattern of local cerebral glucose utilization in the olfactory tubercle and regions of the limbic system such as the anteroventral thalamus, hippocampus and entorhinal cortex. Intravenous (i.v.) administration of MK-801 induced increases in glucose metabolism similar to those observed after i.c.v. application. In contrast, i.v. administration of DL-CPP-ene induced only small decreases of glucose utilization in several regions of the central sensory system. Thus the blockade of glutamatergic (NMDA) transmission results in decreased hippocampal EEG activity which is paralleled by increased metabolic activity in this area. We conclude from EEG recordings and [14C]2-deoxyglucose uptake experiments that both non-competitive and competitive NMDA antagonists produce the same pattern of alterations after i.c.v. administration. Apparent differences in efficacy after peripheral administration may be largely due to differences in bioavailability.

Animals↗
PubMed1992

Differential behavioural and neurochemical effects of competitive and non-competitive NMDA receptor antagonists in rats.

The behavioural and biochemical effects of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists, dizocilpine and memantine, and the competitive NMDA receptor antagonist, CGP 39551, were investigated in rats. Systemic injections of dizocilpine (0.33 mg/kg) increased locomotion and rearing in an open field, whereas memantine (20 mg/kg) increased only locomotor activity. CGP 39551 (10 and 20 mg/kg) did not change open field activity. Dopamine (DA) metabolism--as measured by the ratio of dihydroxyphenylacetic acid/dopamine (DOPAC/DA)--increased in response to dizocilpine in the prefrontal cortex and the nucleus accumbens. Memantine enhanced DOPAC/DA in the prefrontal cortex, the nucleus accumbens and to a lesser degree in the posterior striatum. In contrast to non-competitive NMDA receptor antagonists, CGP 39551 did not increase DA metabolism of subcortical structures and even decreased DOPAC/DA in the prefrontal cortex. These results indicate that competitive and non-competitive NMDA receptor antagonists affect spontaneous locomotion differentially in rats. The biochemical data imply that the stimulant actions non-competitive NMDA receptor antagonists are at least partially due to activation of ascending dopaminergic systems. Potential mechanisms involved in the differential effects of both types of NMDA receptor antagonists are discussed.

2-Amino-5-phosphonovalerate↗
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↗
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↗
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↗
PubMed1978

Resolution by graphical methods of the equations for allosteric competitive inhibition and activation in Michaelian enzyme and transport systems. Application to the competitive inhibition of glucose transport in brain by phlorizin and phloretin.

A brief exposition of the theory of competition in systems conforming to simple Michaelis-Menten kinetics is given. Emphasis is placed on an operational distinction between: 10 True competition between substrate and inhibitor for a single, common binding site: fully competitive inhibition, type IA. 20 False competition between S and I for two separate sites that are associated allosterically: pseudocompetitive inhibition, type Ib. 30 A simple graphical test is presented that differentiates between the two types of inhibitor and permits calculation of the four dissociation constants governing the partial reactions of a two-site allosteric model. This test is equally applicable to certain cases of activation: affinity-type activation, type Ib. 40 The usefulness of the proposed test is illustrated using data from the literature, dealing with the effect of phlorizin and phloretin on the D-glucose transport system in brain.

Allosteric Site↗
PubMed1988

Differential effects of competitive and non-competitive N-methyl-D-aspartate antagonists on glucose use in the limbic system.

The effects on cerebral glucose utilisation of 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP, a competitive N-methyl-D-aspartate (NMDA) receptor antagonist), and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801, a non-competitive NMDA receptor antagonist) have been examined in conscious rats. Cerebral glucose utilisation was assessed quantitatively with 14C-2-deoxyglucose autoradiography. MK-801 (0.05-5 mg/kg, i.v.) markedly increased glucose use in a number of limbic brain areas such as the mamillary body, anterior thalamic nucleus, posterior cingulate cortex and hippocampus. CPP (3-30 mg/kg, i.v.), in contrast, effected minimal alterations in glucose use in the limbic system. The functional consequences in vivo, as reflected in local cerebral glucose use, of competitive blockade of the NMDA receptor differ markedly from blockade with non-competitive antagonists.

Animals↗
PubMed1981

Complex competitive and non-competitive inhibition of rat lung angiotensin-converting enzyme by inhibitors containing thiol groups: captopril and SA 446.

1. The kinetics of the inhibitory action of four different angiotensin-converting enzyme inhibitors was evaluated in vitro with rat lung enzyme and the substrate hippuryl-histidyl-leucine. 2. Enzyme velocity against substrate concentration curves were fitted squares to hyperbolae by a weighted least squares iterative method to obtain apparent values of Km, Vmax. and K/V at each concentration of inhibitor. 3. The inhibitory constants Ki and Ki' were obtained by weighted linear regressions of K/V against i and 1/V against i respectively. 4. Teprotide was the least potent inhibitor with a Ki of near 20 nmol/l whereas captopril (SQ 14 225) and SA 446 were both approximately 10 times and MK 421 approximately 20 times more potent. 5. Two inhibitors which lacked thiol groups [teprotide or SQ 20 881 and N-(1-S-1-carboxy-3-phenylpropyl)-L-Ala-L-Pro or MK 421] produced a purely competitive pattern of inhibition with increased apparent Km but no change in apparent Vmax.. 6. Two inhibitors containing thiol groups [captopril or SQ 14 225 and 2-(2'-hydroxyphenyl)-3-(3-mercaptopropanoyl)-4-thiazolidine carboxylic acid or SA 446] both produced a mixed competitive and non-competitive pattern of inhibition with increased apparent Km and decreased Vmax.. 7. It is possible that thiol-containing inhibitors might produce non-competitive inhibition of converting enzyme by forming strong bonds with zinc near the active site of the enzyme.

3-Mercaptopropionic Acid↗
PubMed1975

Antigenic competition between heterologous erythrocytes in mice: interference with competition-inducing effect of sheep erythrocytes by inclusion of non-competing antigen.

Antigenic competition was studied on reciprocal combinations of non-cross-reacting erythrocyte (RBC) antigens, i.e., sheep erythrocytes (SRBC), horse erythrocytes (HRBC), and chicken erythrocytes (CRBC), as competing antigen or as test antigen. Unlike SRBC and HRBC, CRBC did not induce antigenic competition, and mice previously injected with CRBC showed normal direct and indirect hemolysin plaque-forming cell (PFC) responses to the other RBC subsequently injected. Formaldehyde-treated (F) SRBC that retained the capacity to prime mouse for secondary anti-SRBC antibody response but lost the capacity to elicit primary antibody response also could not induce antigenic competition. CRBC or F-SRBC, i.e., non-competing antigen, included with SRBC interfered with the competition-inducing effect of the latter RBC. When mice that had been injected with SRBC together with either one of the non-competing antigens were subsequently immunized with HRBC their anti-HRBC PFC responses were significantly restored, whereas mice pre-injected with SRBC alone showed markedly suppressed PFC responses to HRBC. Although the non-competing antigen was found not to affect both the direct and indirect PFC responses to the simultaneously injected SRBC, the response of the immune system to the non-competing antigen should alter the concurrent response to SRBC, and probably should prevent the generation of the suppressor thymus-derived (T) lymphocytes, allowing the generation of the helper T lymphocytes for IgM and IgG anti-SRBC antibody formation.

Animals↗