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PubMed2003

Role of feedback regulation of pantothenate kinase (CoaA) in control of coenzyme A levels in Escherichia coli.

Pantothenate kinase (CoaA) is a key regulator of coenzyme A (CoA) biosynthesis in Escherichia coli, and its activity is controlled by feedback inhibition by CoA and its thioesters. The importance of feedback inhibition in the control of the intracellular CoA levels was tested by constructing three site-directed mutants of CoaA that were predicted to be feedback resistant based on the crystal structure of the CoaA-CoA binary complex. CoaA[R106A], CoaA[H177Q], and CoaA[F247V] were purified and shown to retain significant catalytic activity and be refractory to inhibition by CoA. CoaA[R106A] retained 50% of the catalytic activity of CoaA, whereas the CoaA[H177Q] and CoaA[F247V] mutants were less active. The importance of feedback control of CoaA to the intracellular CoA levels was assessed by expressing either CoaA or CoaA[R106A] in strain ANS3 [coaA15(Ts) panD2]. Cells expressing CoaA[R106A] had significantly higher levels of phosphorylated pantothenate-derived metabolites and CoA in vivo and excreted significantly more 4'-phosphopantetheine into the medium compared to cells expressing the wild-type protein. These data illustrate the key role of feedback regulation of pantothenate kinase in the control of intracellular CoA levels.

Binding Sites↗
PubMed1982

Negative and positive feedback of central nervous system temperature in thermoregulation of pigeons.

Experimental alterations of spinal cord and hypothalamic temperature affecting behavioral and autonomic cold defense were investigated in pigeons under external cold load with access to instrumental heat reinforcement. Warming and cooling spinal cord resulted in negative-feedback effects on both instrumental and autonomic cold defense. Hypothalamic warming produced similar negative-feedback effects, whereas hypothalamic cooling produced either no effect or positive-feedback effects on both kinds of cold defense. As determined in previous studies, hypothalamic temperature displacements under heat-load conditions produced only negative-feedback effects on instrumental heat defense. However, only positive-feedback effects were observed on autonomic heat defense by panting. The diverse response patterns of autonomic and behavioral thermoregulatory effectors to changing hypothalamic temperature under heat- and cold-load conditions could be quantitatively described by a mathematical model that takes into account 1) a greater Q10 for intrahypothalamic transmission of the cold signal input than of the warm signal input, and 2) different weights of extra- and intrahypothalamic temperature signal inputs for the control of different effectors.

Animals↗
PubMed1985

Tubuloglomerular feedback after nephron or ureteral obstruction.

The effects of 1 day of single nephron, unilateral ureteral (UUO), and bilateral ureteral (BUO) obstruction on tubuloglomerular feedback were studied in anesthetized rats. Stop-flow pressure (SFP) was measured as an index of glomerular capillary pressure before, during, and after loop of Henle microperfusion. Tubuloglomerular feedback (delta SFP) showed an increased sensitivity to low loop perfusion rates and an increased maximal response after 1 day of single nephron obstruction or relief of UUO. Tubuloglomerular feedback was not significantly different from normal after release of BUO. Whole kidney glomerular filtration rate (GFR) was about 10% of normal after release of ureteral obstruction, and single nephron glomerular filtration rate (SNGFR) averaged one-third of normal. Paired measurements of SNGFR from proximal and distal tubules revealed no significant differences in control or in BUO kidneys, but a significant proximal-distal SNGFR difference was observed after UUO. The results suggest that tubuloglomerular feedback does not significantly contribute to the low GFR after release of BUO; after release of UUO, approximately one-fourth of the fall in GFR may be due to activation of the feedback mechanism.

Animals↗
PubMed2007

Simple models of assortment through environmental feedback.

Social evolution depends critically on assortment, or segregation versus even mixing, between cooperators and noncooperators. Altruistic traits, which reduce the absolute fitness of their bearers, cannot evolve without positive assortment (excess segregation). The question of how positive assortment can arise has been controversial, but most evolutionary biologists believe that common descent is the only effective general mechanism. Here I investigate another recently proposed mechanism for generating nonrandom assortment, termed environmental feedback. This requires only that two forms of a trait affect the quality of the local environment differently in such a way that all individuals are more likely to leave low-quality locales. Experiments with simple computational models confirm that environmental feedback generates significant levels of genetic similarity among non-kin within locales. The mechanism is fairly general, and can under some conditions produce levels of genetic similarity comparable to those resulting from close genealogical relationship. Environmental feedback can also generate the negative assortment necessary for the evolution of spiteful traits. Environmental feedback is expected to create positive frequency-dependent selection, which thus favor any social trait that becomes common in the population. Results from this stylized model suggest that environmental feedback could be important in the evolution of both cooperation and spite, within as well as between species.

Altruism↗
PubMedDate not supplied

Does feedback improve the quality of computerized medical records in primary care?

OBJECTIVE: The MediPlus database collects anonymized information from generalpractice computer systems in the United Kingdom, for research purposes. Data quality markers are collated and fed back to the participating general practitioners. The authors examined whether this feedback had a significant effect on data quality. METHODS: The data quality markers used since 1992 were examined. The authors determined whether the feedback of "useful" data quality markers led to a statistically significant improvement in these markers. Environmental influences on data quality from outside the scheme were controlled for by examination of the data quality scores of new entrants. RESULTS: Three quality markers improved significantly over the period of the study. These were the use of highly specific "lower-level" Read Codes (p=0.004) and the linkage of repeat prescriptions (p=0.03) and acute prescriptions (p=0.04) to diagnosis. Clinicians who fall below the target level for linkage of repeat prescriptions to diagnosis receive more detailed feedback; the effect of this was also statistically significant (p<0.01.) CONCLUSIONS: The feedback of four of the ten markers had a significant effect on data quality. The effect of more detailed feedback appears to have had a greater effect. The lessons learned from this approach may help improve the quality of electronic medical records in the United Kingdom and elsewhere.

Humans↗
PubMed1980

Inventory responding models people's acceptance of feedback 'derived' from tests and from interviews.

Sixty-four undergraduates were individually and randomly given one of four assessment procedures: The Rorschach, Minnesota Multiphasic Personality Inventory (MMPI), Structured Interview, or Unstructured Interview. Students then completed a series of 7-point Likert-type rating scales indicating their perception of the assessment. One week later students individually received identical personality descriptors, presented either as personality "feedback" or as a personality "test". Finally, students completed a second Likert-type rating task, again indicating their faith in the assessment and perception of the examiner's skill. Layne and Michels' model that inventory responding parallels people's acceptance of Barnum feedback was supported. Descriptor favorability significantly enhanced acceptance of both "feedback" and inventory items, while type of prior assessment had no significant effect on either behavior. Student perceptions of assessment accurately paralleled characteristics of each type of assessment. Finally, student faith in the assessment and perception of the examiner's skill failed to significantly increase from before to after receiving "feedback" It was concluded that inventory responding accurately models the Barnum Effect and that people accept feedback rationally, not gullibly.

Journal Article↗
PubMed1984

Students' perception of actual, trivial, and inaccurate personality feedback.

Examined the ability of college students at two levels of defensiveness to discriminate among three types of personality feedback: actual personality feedback based on the student's test scores, trivial feedback which is generally true of all students, and inaccurate feedback which was the exact opposite of the student's actual test scores. The students could reliably discriminate the three types of feedback on the dimensions of uniqueness, usefulness, accuracy, and as a source of new information about themselves. The results are discussed in the context of the Barnum literature to the effect that students can offer valid perceptions of personality descriptions of themselves.

Journal Article↗
PubMed1988

Short loop feedback control of the estrogen-induced luteinizing hormone surge in pigs.

This study examines whether hCG will block the estradiol-induced LH surge in ovariectomized gilts. Twenty post-puberal cross-bred gilts were ovariectomized at 6-7 months of age. Approximately 2 months later, the experiment was conducted, and all gilts were given estradiol benzoate (EB; 10 micrograms/kg, im) at 0 h. Controls (n = 6) received im saline 24 and 48 h after EB. Two groups of gilts received 2000 IU hCG im, at 24 h (hCG24; n = 5) or 48 h (hCG48; n = 5) after EB. The fourth group (n = 4) received hCG at 48 h and was then given iv a LHRH agonist (des-Gly10, [D-Ala6]LHRH ethylamide) in 100-ng boluses hourly from 54-96 h after EB. Blood samples for determination of LH and FSH were collected every 6 h from 0-96 h. In controls, EB alone suppressed LH from 3.9 +/- 1.9 ng/ml at 0 h to 1.0 +/- 0.2 during 6-48 h (negative feedback), but LH then increased to 4.5 +/- 0.5 between 54 and 96 h (positive feedback), with the peak of the surge (6.7 +/- 1.6) occurring at 72 h. Treatment with hCG did not alter LH during the negative feedback phase (1.1 +/- 0.1 and 1.0 +/- 0.1 for hCG24 and hCG48, respectively). However, there was no LH surge in gilts given hCG at 24 or 48 h (2.4 +/- 0.2 and 2.2 +/- 0.1 form 54-96 h; P less than 0.05). Hourly injections of the LHRH agonist evoked a surge in LH (8.3 +/- 1.3) and maintained elevated LH (4.5 +/- 0.6) between 54 and 96 h, similar (P greater than 0.05) to values for controls. Generally, FSH in gilts given hCG followed the same pattern as LH secretion during the negative feedback stage; however, due to randomization, means for the period from 0-48 h for gilts treated with hCG 24 or 48 h after EB were lower (P less than 0.05) than for controls or gilts given LHRH agonist (62.2 +/- 2.8 and 63.0 +/- 2.7 vs. 79.3 +/- 3.2 and 93.3 +/- 4.2 ng/ml, respectively). During the positive feedback phase (54-96 h), FSH was lower in gilts given hCG (hCG24, 63.4 +/- 2.3; hCG48, 67.3 +/- 2.0) than in controls (86.0 +/- 4.0), but in gilts given LHRH agonist, FSH was higher (1001.1 +/- 7.7) than in controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Feedback inhibition of leptin receptor/Jak2 signaling via Tyr1138 of the leptin receptor and suppressor of cytokine signaling 3.

Leptin is an adipocyte-derived hormone that communicates the status of body energy stores to the brain to regulate feeding and energy balance. The inability of elevated leptin levels to adequately suppress feeding in obesity suggests attenuation of leptin action under these conditions; the activation of feedback circuits due to high leptin levels could contribute to this leptin resistance. Using cultured cells exogenously expressing the long form of the leptin receptor (LRb) or an erythropoietin receptor/LRb chimera, we show that chronic stimulation results in the attenuation of LRb signaling and the establishment of a state in which the receptor is refractory to reactivation. Mutation of LRb Tyr1138 (the site that recruits signal transducer and activator of transcription 3) alleviated this feedback inhibition, suggesting that signal transducer and activator of transcription 3 mediates the induction of a feedback inhibitor, such as suppressor of cytokine signaling 3 (SOCS3), during chronic LRb stimulation. Indeed, manipulation of the expression or activity of the LRb-binding tyrosine phosphatase, SH2-domain containing phosphatase-2, by overexpression of wild-type and dominant negative isoforms or RNA interference-mediated knockdown did not alter the attenuation of LRb signals. In contrast, SOCS3 overexpression repressed LRb signaling, whereas RNA interference-mediated knockdown of SOCS3 resulted in increased LRb signaling that was not attenuated during chronic ligand stimulation. These data suggest that Tyr1138 of LRb and SOCS3 represent major effector pathways for the feedback inhibition of LRb signaling. Furthermore, we show that mice expressing an LRb isoform mutant for Tyr1138 display increased activity of the leptin-dependent growth and immune axes, suggesting that Tyr1138-mediated feedback inhibition may regulate leptin sensitivity in vivo.

Animals↗
PubMed1969

An instrument for producing deep muscle relaxation by means of analog information feedback.

An instrument that assists subjects in attaining deep muscle relaxation by means of analog information feedback is described. Subjects hear a tone with a pitch proportional to the electromyographic activity in a given muscle group. Results showed that subjects receiving this type of analog feedback reached deeper levels of muscle relaxation than those receiving either no feedback or irrelevant feedback. The basic method employed-electronic detection, immediate information feedback, and systematic shaping of responses-would seem potentially applicable to a variety of physiological events, and might be useful both in behavior therapy and in certain psychosomatic disorders.

Journal Article↗
PubMed1979

Effects of self-monitoring and feedback on residential electricity consumption.

Prior research has indicated that frequent feedback could reduce residential electricity consumption by 10% to 15%. However, because feedback was primarily given in written form, this procedure might not be practical. The present study evaluated a potentially more practical feedback procedure during peak-use periods with high electricity consuming households. The study was conducted during the winter in an upper-middle class neighborhood of almost identical, all-electric townhouses (N = 71) that averaged about 170 KWH per day per household for a monthly bill of over $200. Twelve households received daily written feedback. Sixteen households (self-monitoring) were taught to read their outdoor electricity meter and to record KWH used every day. A comparison group was composed of 14 households that had volunteered to participate and 29 others that had only given permission to have their meters read. During a 1-month period that the procedures were in effect, the feedback group reduced consumption by 13% and the self-monitoring group by about 7%. These reductions, relative to the comparison group, were maintained during an early spring 1-month follow-up period and, to a lesser extent, during a 6-week warm spring period. Self-monitoring participants were highly reliable and persistent meter readers. Reductions in electricity use were reported by households to be largely attributable to lowering of the heat thermostat, and large monetary and KWH savings were found. Techniques to make self-monitoring cost-effective important components of the self-monitoring procedure, methods to apply self-monitoring more broadly, and plans to combine behavioral procedures with physical technology are discussed.

Journal Article↗
PubMed1979

The effects of feedback on blood pressure discrimination.

Discrimination of blood pressure in the natural environment as a function of feedback was assessed. Seventeen normotensives screened for blood pressure lability were randomly assigned to two groups. These subjects were then asked to estimate their systolic and diastolic blood pressure values two times per day over a 4-week period. Feedback for accuracy of blood pressure discriminations was implemented across the two groups in a multiple baseline fashion, using a feedback withdrawal condition in Group I to assess maintenance effects over time. Results showed improvement in discrimination accuracy for subjects in both groups when feedback was used, and no decrement in performance over a 2-week period after feedback was removed for subjects in Group I. Discrimination of systolic pressures improved at a slightly faster rate than discrimination of diastolic pressures.

Adolescent↗
PubMed1982

The effects of videotape modeling and daily feedback on residential electricity conservation, home temperature and humidity, perceived comfort, and clothing worn: Winter and summer.

Two studies were conducted in all-electric townhouses and apartments in the winter (N = 83) and summer (N = 54) to ascertain how energy conservation strategies focusing on thermostat change and set-backs and other low-cost/no-cost approaches would affect overall electricity use and electricity used for heating and cooling, the home thermal environment, the perceived comfort of participants, and clothing that was worn. The studies assessed the effectiveness of videotape modeling programs that demonstrated these conservation strategies when used alone or combined with daily feedback on electricity use. In the winter, the results indicated that videotape modeling and/or feedback were effective relative to baseline and to a control group in reducing overall electricity use by about 15% and electricity used for heating by about 25%. Hygrothermographs, which accurately and continuously recorded temperature and humidity in the homes, indicated that participants were able to live with no reported loss in comfort and no change in attire at a mean temperature of about 62 degrees F when home and about 59 degrees F when asleep. The results were highly discrepant with prior laboratory studies indicating comfort at 75 degrees F with the insulation value of the clothing worn by participants in this study. In the summer, a combination of strategies designed to keep a home cool with minimal or no air conditioning, in conjunction with videotape modeling and/or daily feedback, resulted in overall electricity reductions of about 15% with reductions on electricity for cooling of about 34%, but with feedback, and feedback and modeling more effective than modeling alone. Despite these electricity savings, hygrothermograph recordings indicated minimal temperature change in the homes, with no change in perceived comfort or clothing worn. The results are discussed in terms of discrepancies with laboratory studies, optimal combinations of video-media and personal contact to promote behavior change, and energy policies that may be mislabeled as sacrificial and underestimate the effectiveness of conservation strategies such as those investigated in these studies.

Journal Article↗
PubMed1988

Task clarification, performance feedback, and social praise: Procedures for improving the customer service of bank tellers.

Customer service for bank tellers was defined in terms of 11 verbal behavior categories. An audio-recording system was used to track the occurrence of behaviors in these categories for six retail banking tellers. Three behavior management interventions (task clarification, performance feedback, and social praise), applied in sequence, were designed to improve overall teller performance with regard to the behavioral categories targeted. Clarification was accomplished by providing clear delineation of the various target categories, with specific examples of the behaviors in each. Feedback entailed presentation of ongoing verbal and visual information regarding teller performance. Praise consisted of verbal recognition of teller performance by branch managers. Results showed that clarification effects emerged quickly, producing an overall increase in desired behaviors of 12% over baseline. Feedback and praise effects occurred more gradually, resulting in overall increases of 6% and 7%, respectively. A suspension of all procedures led to a decline in overall performance, whereas reinstatement of feedback and praise was again accompanied by performance improvement. These findings extend the generality of behavior management applications and help to distinguish between possible antecedent and consequent effects of performance feedback.

Journal Article↗
PubMed1980

An experiment to test generalization of feedback from frontalis EMG.

60 subjects participated in a test of the effectiveness of frontalis EMG feedback as a generalized relaxation technique. The experiment was performed in two parts. In the first part, 30 subjects were randomly allocated to a group receiving frontalis EMG feedback (n = 10), a group receiving non-contingent feedback (n = 10) and a group instructed to relax themselves (n = 10). Each group received one baseline session and five training sessions. EMG measurements from the frontalis, trapezius and masseter muscles taken prior to and immediately after the final training session indicated that the frontalis feedback group was more effective in lowering frontalis and masseter EMG activity (though not trapezius activity) than the controls. The second part of the experiment was identical to the first with the exception that the subsidiary muscle sites were the forearm and leg extensors. The results showed that frontalis feedback was no more effective than controls in lowering the EMG levels of these muscles.

Biofeedback, Psychology↗
PubMed2005

Positive feedback loop of interleukin-1beta upregulating production of inflammatory mediators in human intervertebral disc cells in vitro.

OBJECT: Interleukin-1beta (IL-1beta) induces neurological symptoms in intervertebral disc herniation (IDH). Recently, the existence of a positive feedback loop of IL-1beta, which encourages an inflammatory reaction or degeneration in the cells of tendon, has been reported. The authors hypothesized that there is a positive feedback loop of IL-1beta in the cells of IDH. METHODS: Eight human intervertebral disc specimens were harvested during spinal surgery for lumbar disc herniation. The cells were stimulated in serum-free medium with or without exogenous IL-1beta. The messenger RNA (mRNA) was extracted for reverse-transcription polymerase chain reaction (PCR) and real-time PCR to quantify the mRNA of endogenous IL-1beta, IL-6, cyclooxygenase-2 (COX-2), and matrix metalloproteinases (MMPs). The cells were then stimulated in serum-free medium with or without exogenous IL-1beta, and then exogenous IL-1beta was removed. After 2, 4, and 6 days, the medium was collected, and enzyme-linked immunosorbent assay was used to measure the protein concentration of endogenous IL-1beta. The mRNA expressions of endogenous IL-1beta, IL-6, COX-2, and MMPs were increased significantly depending on the concentration of exogenous IL-1beta. The protein concentration of endogenous IL-1beta was increased over time. CONCLUSIONS: There was a positive feedback loop of IL-1beta in the cells of IDH. Furthermore, the productions of IL-6, COX-2, MMP-1, and MMP-3 were upregulated as a result of the increasing concentration of IL-1beta in a positive feedback loop of IL-1beta. The authors concluded that this positive feedback loop of IL-1beta upregulated the production of mediators and thus can cause cessation of symptoms in IDH.

Adolescent↗
PubMed2001

Retraining reaching in chronic stroke with real-time auditory feedback.

Stroke is the third leading cause of death in the United States. The aim of the present study was to enhance the motor recovery of patients in the chronic stroke period by means of upper extremity trajectory modification through real-time auditory feedback. A system of hardware, software, and feedback algorithms was developed. Two groups of patients in the chronic stroke period were trained on the system, one with practice and feedback and one with practice alone. Twenty reach parameters were defined and analyzed for differences between the first and last training sessions, between adaptation and learning trials, and among three targets. This study demonstrated that modification of the reach trajectory can be accomplished during the chronic stroke period either with practice alone or through practice accompanied by auditory feedback. However, improved path performance requires auditory feedback training, and cannot be achieved by practice alone.

Acoustic Stimulation↗
PubMed1984

Sensory feedback therapy and theoretical knowledge of motor control and learning.

Generally the application of artificial sensory feedback therapy (e.g. EMG biofeedback) in neuromuscular rehabilitation is conceived as a psychophysiological operant conditioning technique. Until now there are almost no attempts to link these methods to modern psychological theories of motor control. In the present article a critical review is given of four theoretical systems concerning motor control: closed-loop theory, open-loop theory, schema-theory, and finally a brief overview is presented of recently developed notions on heterarchical and distributed control. Artificial sensory feedback therapy (e.g. EMG feedback) is described against this theoretical background, with an emphasis on the role of feedback in motor learning and motor control. The implications of these theories for new directions in sensory feedback therapy are discussed.

Biofeedback, Psychology↗