Showing papers by "University of Oklahoma published in 1982"

Baroreceptor reflex control of heart rate: a predictor of sudden cardiac death.

Abstract: SUMMARY To explore the possibility that the analysis of autonomic reflexes could identify subgroups at high risk of ventricular fibrillation, we studied chronically instrumented mongrel dogs randomly divided into two groups. Twelve dogs served as controls and 17 were studied 3-4 weeks after anterior wall myocardial infarction (MI). After recovery, the dogs were given bolus i.v. injections of phenylephrine, 10 tg/kg, and nitroprusside, 100 ptg/kg, to raise or lower systolic arterial pressure 30-50 mm Hg. The RR intervals were plotted against the systolic pressure during the preceding beats, and the slope (baroreflex slope) was determined by least-squares-fit linear regression. On a subsequent day, the left circumflex coronary artery was occluded for 2 minutes, beginning with the last minute of an exercise stress test and continuing for 1 minute after the cessation of exercise (MI group only). The dogs could be divided into two groups based on their response to this test; 11 dogs (65%) had ventricular fibrillation (susceptible), whereas six dogs (35%) did not (resistant). The baroreflex slope (control 20.49 ± 8.59; resistant 10.95 ± 4.68; susceptible 4.60 ± 1.77 msec/mm Hg) and the heart rate response to a 30-mm Hg increase in arterial pressure (control - 56.5 ± 14.8; resistant -40.0 ± 12.2; susceptible - 12.9 ± 5.0 beats/min) for the susceptible dogs were significantly different from those of the control and resistant dogs. This may indicate that the resistant dogs have a greater capability to activate strong vagal reflexes, which reduce vulnerability to ventricular fibrillation. We conclude that anterior wall MI significantly attenuates the baroreceptor reflex control of heart rate and that analysis of the heart rate response to arterial pressure increases allows identification of subgroups of dogs at higher risk for ventricular fibrillation. A prospective study in patients with MI is warranted.

A Modified Model of Power in the Marketing Channel

Abstract: A modified model for examining power and its sources in marketing channels is developed and tested. The results of testing this model indicate that its predictive ability is no better than that of ...

The nature of natural laws

Abstract: That laws of nature play a vital role in explanation, prediction, and inductive inference is far clearer than the nature of the laws themselves. My hope here is to shed some light on the nature of natural laws by developing and defending the view that they involve genuine relations between properties. Such a position is suggested by Plato, and more recent versions have been sketched by several writers.~ But I am not happy with any of these accounts, not so much because they lack detail or engender minor difficulties, though they do, but because they share a quite fundamental defect. My goal here is to make this defect clear and, more importantly, to present a rather different version of this general conception of laws that avoids it. I begin by considering several features of natural laws and argue that these are best explained by the view that laws involve properties, that this involvement takes the form of a genuine rela.tion between properties, and, finally, that the relation is a metaphysically necessary one. In the second section I start at the other end, and by reflecting on the nature of properties arrive at a similar account of natural laws. In the final section I develop this account in more detail, with emphasis on the nature of the relation between properties it invokes. Along the way several natural objections to the account are answered. I. Nowadays there is widespread agreement that natural laws are true statements of the form ' ¥ x (G x D Fx)', where 'G' and 'F' are predicates that make no reference to any particular spatio-temporal locations. This general view is often known as the regularity theory, for although variants are possible, all share the Humean conviction that there is no necessity in nature and, hence, that laws record only actual or de facto regularities. Laws require something more than mere regularities, however, for not every true universal generalisation with purely qualitative predicates expresses law. For Hume this something more was psychological, a certain sort of expectation fostered by habit. Recent regularity theorists have favoured logical, pragmatic, or epistemological additions, however, urging that a generalisation qualifies as a law only if it is integrated into a comprehensive deductive system, if we have acquired the habit of projecting predicates coextensive with those it contains, if For Plato's remarks see Phaedo, pp. 103if; more recent versions of this position are …

Team Learning: a Potential Solution To the Problems of Large Classes:

Abstract: of credit hours that can be taught by graduate faculty. In attempting to cope with these problems, many institutions have been forced to substantially increase class sizes to capitalize on the economies of scale. Unfortunately, this move to larger classes has often led to changes in both the instructional strategies that are employed and the content of the courses that are being taught. For example, the great majority of large classes are taught by the lecture method and student performance is evaluated through the use of true/false and multiple choice exams. This curtails both the

Activation of Protein C In Vivo

Abstract: An endothelial cell-associated cofactor that greatly enhances the rate of protein C activation by thrombin has recently been described. The observation that the cofactor binds thrombin with unusually high affinity (K(d) = 0.5 nM) suggested that low level thrombin infusion into dogs might lead to the selective activation of protein C. Infusion of thrombin (1 U/min per kg body wt) into the jugular vein of dogs leads to the formation of a systemic anticoagulant activity within 5 min of starting the infusion. The plasma has a prolonged partial thromboplastin time and Factor X(a) clotting time, but there is no change in the thrombin clotting time. The systemic anticoagulant activity is identified as activated protein C for the following reasons: (a) anti-canine activated protein C IgG antibodies inhibit the anticoagulant activity; (b) the anticoagulant activity can be partially purified from the plasma of dogs infused with thrombin by barium citrate adsorption; (c) the anticoagulant has chromatographic properties on QAE Sephadex indistinguishable from those of activated protein C, and (d) the rate at which this anticoagulant is inhibited in citrated canine plasma is identical to that of canine activated protein C. The in vivo activation of protein C appears to be receptor mediated since it occurs at low thrombin concentration and since it can be progressively inhibited by simultaneous infusion of diisopropylphospho-thrombin with thrombin. The activation of protein C at low levels of thrombin is selective, since neither the platelet count nor the Factor V levels are altered. Thrombin infusion leads to an elevation in circulating plasminogen activator levels. This appears to be mediated through the activation of protein C since coinfusion of diisopropylphospho-thrombin with thrombin inhibits the increase in plasminogen activator levels. Pretreatment of dogs with dicumarol blocks both the formation of anticoagulant activity and the rise in plasminogen activator. When the dicumarol-treated dogs are supplemented with isolated protein C and thrombin is infused, the anticoagulant activity again appears and the circulating levels of plasminogen activator are again elevated. These studies illustrate that low levels of thrombin in vivo can activate protein C, which in turn can inhibit blood coagulation and initiate fibrinolysis by elevating circulating plasminogen activator levels.

Vision and electroreception: Integration of sensory information in the optic tectum of the weakly electric fishApteronotus albifrons

Abstract: The responses of single neurons to visual and electrosensory stimulation were studied in the optic tectum of the weakly electric fishApteronotusalbifrons. Most of the cells recorded in the region of the tectum studied, the anterior medial quadrant, were poorly responsive or completely insensitive to flashes of light or to bursts of AC electrical stimuli applied to the entire fish. However, these cells gave vigorous responses to moving visual or electrosensory stimuli. Most cells showed differences in their response contingent upon the direction of the stimulus movement and most received input from both the visual and electrosensory systems. Electrosensory responses to moving stimuli were depressed by jamming stimuli, 4 Hz amplitude modulation of the animal's electric organ discharge, presented simultaneously with the moving stimulus. However, the jamming signal presented alone typically evoked no response. Moving visual stimuli, presented simultaneously with the electrosensory, were usually able to restore the magnitude of a response toward its value in the unjammed situation. For most of the cells studied the receptive fields for vision and electroreception were in register. In some cases the visual and electrosensory components could be separated by presenting the two types of stimuli separately, or by presenting both simultaneously but with some amount of spatial separation, which causes the two to be misaligned relative to the fish. In other cases the individual responses could not be separated by spatial manipulations of the two stimuli and in these cases differences in the alignment of the two types of stimuli could cause changes in the intensity of the cells' responses.

An Experimental Analysis of Social Spacing in Tamias Striatus

Abstract: We report on a series of experiments performed on a population of free-living eastern chipmunks, Tamias striatus, inhabiting a forest in northwestern Pennsylvania. The experiments were designed to examine, via perturbations of food supply and/or population density, the relationship between home range size, food availability, and population density. When food levels were increased within an area, a simultaneous effect was noted: mean home range size decreased and population density increased through recruitment from neighboring habitats. Whether the cause of the decreased patterns of movement was the increased food supply or the elevated population density was deter- mined in subsequent experiments. When population density was held constant and food supplies were experimentally increased, there was a significant reduction in mean home range sizes when compared to the normal (control) situation. When food supplies were undisturbed, but population density was greatly reduced, there was no change in the mean home range size over that determined at higher densities. Our results suggest that, in eastern chipmunks, food supply is a primary determinant of mean home range size, whereas population density, at least at the levels we examined experimentally, has no effect on movement patterns. These results are in accord with those theories relating movement patterns to resource abundance, but are not in accord with hypotheses suggesting that home range sizes and population density are inversely associated.

Biliary bacteria: significance and alterations after antibiotic therapy.

Abstract: • Patients undergoing urgent and complex biliary operations were studied to determine (1) whether bactibilia is associated with postoperative complications and (2) whether antibiotic therapy influences biliary bacteriology. Aerobic and anaerobic cultures were performed on hepatic bile obtained at surgery in 134 patients. Cultures were repeated four to seven days postoperatively in 111 patients who had indwelling biliary tubes. Positive operative bile cultures were associated with an increased incidence of wound infection and postoperative renal dysfunction. Postoperative bile cultures showed a significant increase in the number of patients having bactibilia, and a significant alteration in the types of organisms isolated. Anaerobes were cultured from 15% of operative and 23% of postoperative cultures. Antibiotic therapy did not sterilize bile, but merely altered biliary bacteriology. Furthermore, prolonged aminoglycoside therapy was associated with a high incidence of renal dysfunction, especially in elderly patients. ( Arch Surg 1982;117:445-449.

Listening as information processing

Abstract: This paper argues that much of the conceptual confusion in understanding the process of listening can be alleviated by adopting an information processing approach to listening. A model is presented and listening strategies are discussed.

Foraging in a simulated natural environment: there's a rat loose in the lab

Abstract: Rats were required to earn their food in a large room having nine boxes placed in it, each of which contained food buried in sand. In different phases of the experiment the amount of time allowed for foraging, the amount of food available in each food patch, and the location of the different available amounts were varied. The rats exhaustively sampled all patches each session but seemed to have fairly strong preferences for certain locations over others. If position preferences were for patches containing small amounts of food, the sensitivity to amount available was increased so that when location was compensated for, a pattern of optimal foraging was evident. The importance of environmental constraints in producing optimal behavior and the relation of the observed behavior to laboratory findings are discussed.

On Becoming a Physical Educator: Occupational Choice and the Anticipatory Socialization Process

Abstract: This paper reviews selected recruitment resources to physical education based on Lortie's (1975) paradigm of occupational choice and the anticipatory socialization process. Based on data from physical education entry studies (Mulling, 1981; Pooley, 1970; Woodford, 1977; Templin, Note 1), examples of how selected resources both attract and facilitate entrance into the field are presented. Such resources as the interpersonal and service dimensions of teaching, a desire for continued association with sport, time compatibility, job security, eased entrance, and various socializing agents are shown to have some degree of influence on one's decision to enter physical education. Finally, various implications of the data are discussed in relation to the professional preparation process.

Changes in language behavior as a function of veracity

Abstract: In this experiment 20 subjects were placed in a situation designed to elicit a number of truthful and untruthful statements. Differences in these statements were examined by the SLCA III and LEXIC programs to find variables that discriminate between truth-tellers and liars. The results indicate that when lying, individuals use fewer words, and, as a consequence, fewer unique words with larger type-token ratios and smaller perceptual-cognitive activity measures, use fewer past tense verb forms, and that males tend to use a greater number of indicative mood sentences and fewer subjunctive mood sentences. When used in a discriminant function equation, 14 of the SLCA III and LEXIC variables were able to provide an adequate level of classification for the veracity of the subjects' statements.