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Biomedical subjects

K A Freeman

Publications and source records attributed to K A Freeman.

15 recordsLinked to original sources
PubMed2000

A comparison of video modeling with in vivo modeling for teaching children with autism.

The present study was designed to compare the effectiveness of video modeling with in vivo modeling for teaching developmental skills to children with autism. A multiple baseline design across five children and within child across the two modeling conditions (video and in vivo) and across tasks was used. Each child was presented two similar tasks from his or her curriculum; one task was used for the video condition, while the other was used for the in vivo condition. Video modeling consisted of each child watching a videotape of models performing the target behavior, whereas in vivo modeling consisted of the children observing live models perform the target behavior. After the observations, children were tested for acquisition and generalization of target behaviors. Results suggest that video modeling led to faster acquisition of tasks than in vivo modeling and was effective in promoting generalization. Results are discussed in terms of video modeling's motivating and attention maintaining qualities.

Autistic Disorder↗
PubMed1999

The bedtime pass: an approach to bedtime crying and leaving the room.

OBJECTIVE: To evaluate a novel intervention for bedtime problems. DESIGN: We used an ABAB withdrawal-type experimental design. SETTING: The intervention was prescribed in an outpatient primary health care context and evaluated in the home setting. PARTICIPANTS: Two normally developing boys aged 3 and 10 years were the primary participants. Twenty parents and 23 practicing pediatricians rated the acceptability of the intervention. INTERVENTION: A bedtime pass, exchangeable for 1 excused departure from the bedroom after bedtime. MAIN OUTCOME MEASURES: For both primary participants, instances of crying and/or coming out from the bedroom after bedtime; for the 20 parents and 23 pediatricians, comparative ratings of acceptability for the pass and 2 other commonly used approaches to bedtime problems (ignoring crying and letting children sleep with their parents). RESULTS: Crying and coming out from the bedroom reduced to zero rates in both children. Pediatricians rated using the pass as significantly more acceptable than letting children sleep with parents and equivalent to ignoring. Parents rated the pass as more acceptable than either alternative. CONCLUSION: The bedtime pass provides pediatricians with a readily usable, potentially effective, and highly acceptable novel intervention for bedtime problems, one of the most common complaints in outpatient pediatrics.

Adult↗
PubMed1999

Investigative interviewing with children: evaluation of the effectiveness of a training program for child protective service workers.

OBJECTIVE: Previous research suggests that training workshops on investigative interviewing conducted with front-line workers, such as police officers or child protective service (CPS) workers, may result in improved knowledge about appropriate strategies to use. Limited research has addressed whether such training programs result in improvements in actual interviewing skills. The present investigation assessed the impact of a training workshop on CPS workers' knowledge about conducting and behavior during investigative interviews. METHOD: Twelve CPS workers participated. To evaluate the impact of the training, a quasi-experimental design was used. Participants completed outcome measures prior to, immediately following, and 3 months following the training. Outcome measures included (a) a questionnaire to assess knowledge about interviewing practices, (b) simulated interviews with a confederate to assess participant behavior during an investigative interview, and (c) questionnaires to gather information related to the simulated interviews (e.g., materials requested for use during interview, abuse status of confederate). All participants completed 6 hours of training during 3 weekly 2-hour sessions. RESULTS: Participants' knowledge on the topic, as well as several interviewing skills during simulated interviews, improved following the training. However, the training failed to impact several key interviewing skills such as the types of questions asked or the length of the interview. CONCLUSIONS: Knowledge-based workshop training programs may not adequately prepare CPS workers to conduct appropriate investigative interviews with children who were allegedly abused. Further, knowledge about how to conduct such interviews may not be the best indicator of whether someone is prepared for this aspect of the job.

Adult↗
PubMed1998

Why functional assessment is enough: a response to Reiss and Havercamp.

Reiss and Havercamp (1997) recently suggested that sensitivity theory offers a basis from which to assess and treat challenging behavior exhibited by people with developmental disabilities. They contended that this approach would lead to more effective and durable interventions than would reliance on functional assessment. We respond to their claim that functional assessment is "not enough." After briefly reviewing and critiquing sensitivity theory, we outline the basic tenets of behavior analysis and describe literature on the development and use of functional assessment methodologies with individuals with developmental disabilities exhibiting challenging behavior, responding to several of Reiss and Havercamp's comments about the utility of this approach. Finally, we discuss several limitations of behavior analysis and functional assessment, providing examples of how these limitations are being addressed.

Activities of Daily Living↗
PubMed1996

Transient loss of dopamine autoreceptor control in the presence of highly potent dopamine agonists.

The concentrations of endogenous ligands generally remain in a bounded range around a basal level, a manifestation of control. The dopaminergic system is an excellent example of a control system in which a negative feedback signal is associated with receptor occupancy of a D2-like dopamine autoreceptor. A consequence of the control theory is that autoreceptor occupancy by an agonist results in dopamine levels below the basal, whereas similar stimulation by a dopamine competitive antagonist results in an increase of dopamine to levels above the basal. These consequences of control theory were tested and verified in the rat striatum by infusing graded doses of either the agonist, quinpirole, or the antagonist, sulpiride, into the rat striatum via a microdialysis probe and sampling dopamine and metabolite levels at various times after the start of infusion. Control was maintained even at the very highest doses of these compounds, i.e., striatal dopamine concentration rose in response to the antagonist and fell in response to the agonist. In contrast, administration of each of two high affinity dopamine agonists, 7-OH-DPAT and PPHT showed dose-dependent control only up to certain doses. Above these doses the dopamine concentration actually increased to levels well above basal, an indication of loss of control. These findings suggest that the control of this endogenous ligand does not extend to the very highest levels of autoreceptor occupancy.

Animals↗
PubMed1995

The relationship between vessel wall tension and the magnitude and frequency of oscillation in rat aorta.

Aortic rings from adult normotensive rats display spontaneous rhythmic activity that is enhanced by vasoconstricting agents. Graded doses of norepinephrine as well as combinations of norepinephrine and vasodilators produced levels of tension that were inversely related to the magnitude of oscillation and directly related to the frequency. A similar result occurred with KCl stimulation. Oscillations were only slightly affected by removal of the endothelium. These results, when combined with other reported studies, suggest that the oscillations in rat aorta are a manifestation of feedback control that may involve the cyclic release of one or more agents affecting calcium channels.

Animals↗
PubMed1994

A quantitative study of dopamine control in the rat striatum.

The control of dopamine release by negative feedback via dopaminergic autoreceptors has been well established. Using previously derived mathematical equations, we have incorporated this feedback component into a mass-action binding model in which the rate of ligand release is a function of the quantity that is bound. A consequence of this model is that competitive antagonists augment release, whereas competing agonists reduce such release. In order to obtain values of the parameters needed in the feedback equations, in vivo microdialysis was used to deliver drugs locally to the rat striatum and to monitor the resulting changes in extracellular dopamine levels. The dopamine agonists apomorphine and quinpirole and the antagonists haloperidol and sulpiride were individually infused into the rat striatum via the microdialysis probe, and the effect of each on extracellular dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic levels was recorded. The data obtained from the microdialysis experiments were used to construct dopamine's control curve, a new quantitative concept that describes the feedback control of the dopaminergic system. Once known, the ligand's control curve has predictive value that may be useful in the design of efficient drug tests. Alterations of dopamine's control curve, which may occur with aging, drug addiction and pathological states, can now be studied and may provide new insights for potential therapeutic strategies.

Animals↗
PubMed1992

Effects of neonatal transection of the infraorbital nerve upon the structural and functional organization of the ventral posteromedial nucleus in the rat.

The present study examined the way in which an indirect partial deafferentation of the medial portion of the ventrobasal complex (VPM/VPL) induced by neonatal transection of the infraorbital nerve (ION) altered the structural and functional properties of its constituent neurons. This manipulation significantly reduced the volume of the contralateral VPM/VPL. In addition, cell counts in Nissl-stained material revealed a significant reduction of the number of VPM/VPL neurons contralateral to neonatal ION transection. We also analyzed the effect of neonatal ION transection on the soma-dendritic morphology of individual neurons in the ventral posteromedial nucleus of the thalamus (VPM) by intracellular injection of horseradish peroxidase (HRP) in vivo and Lucifer yellow in fixed slices. Neonatal transection of the ION resulted in increased dendritic length, area, and volume of VPM neurons in both preparations; however only the changes observed in fixed slices reached statistical significance. Alterations in the functional characteristics of VPM neurons were also observed following neonatal nerve damage. There was a significant decrease in the percentage of vibrissae-sensitive neurons and a corresponding increase in the percentages of neurons responsive to guard hair deflection or that were unresponsive to peripheral stimulation. Neonatal nerve damage also resulted in significantly longer latencies of VPM cells after stimulation of either trigeminal nucleus principalis or subnucleus interpolaris. The present results indicate that the development of normal response properties and soma-dendritic morphology of VPM neurons is dependent upon intact afferent input during development. Indirect partial deafferentation of VPM/VPL by neonatal transection of the ION results in reduced neuron number, which may result in decreased competition among the dendrites of these neurons. This proposal is consistent with observations of increased dendritic dimensions of VPM neurons contralateral to neonatal ION damage.

Animals↗
PubMed1991

Control and stability of ligand receptor interaction in the presence of a competitive compound.

The law of mass action is almost universally applied to both endogenous ligands and drugs that interact with specific cellular receptors. The concentration, and hence the receptor binding, of a foreign drug molecule will depend on its pharmacokinetic properties, whereas an endogenous ligand is subject to intrinsic control since the concentration (z) remains within limits around an equilibrium level. We have previously examined this control for ligand-receptor interactions proceeding according to mass action in which the ligand is produced (rate F), eliminated exponentially (rate constant E) and controlled by a feedback function of receptor occupancy, phi (y), where y is the bound concentration. The current study examines the control of an endogenous ligand in the presence of a second compound (agonist or antagonist) that interacts with the same receptor. From a computer solution of the set of differential equations, illustrated in both time-plots and phase plane (y-z) plots, it is shown that if the second agent is a pure competitive antagonist the bound concentration of the endogenous agonist ligand may not decrease appreciably, even for large doses of the antagonist. Instead the level of binding depends on certain parameters of the control function. Further, the computer simulation shows how these parameters affect the time course of released ligand resulting from administration of an antagonist and the suppression of such release when the second compound is an agonist.

Animals↗
PubMed1991

Determination of the functional dissociation constant of a partial agonist by comparison with a higher efficacy agonist.

A formula derived by Gero and Tallarida (1977) relates the equilibrium dissociation constant of a partial agonist (P) and that of a second agonist (A) of greater efficacy that acts on the same receptor. The second agonist may or may not be a strong agonist. Accordingly, if the dissociation constant (K) of one of the compounds is known, say from the method of partial irreversible receptor blockade, then the dissociation constant for the other may be determined from the complete concentration-effect curves of the compounds and the derived formula: kp = KA (Ap-Ai)Pi/(Ap + KA)Ai, where Pi and Ai are equieffective concentrations of P and A, Ap = the concentration of A that gives an effect = the maximum effect of P. The practical use of this formula is illustrated here for several agonists, and for each, the value of K obtained is compared to that obtained by partial irreversible receptor blockade. In all cases tested, the agreement is quite good, thus suggesting that this method may be a practical alternative.

Adrenergic alpha-Agonists↗
PubMed1977

Assuring reliable performance of antibiotic assay media.

The Microbiological Assay Branch of the National Center for Antibiotics Analysis assays over 100,000 samples of antibiotic products annually, using more than 1000 Ib dehydrated media. The media must be consistently dependable to produce accurate, reliable test results. To assure that the supply of media will meet the established requirements, each lot before purchase is subjected to a series of trials designed to examine growth support, sensitivity, and behavioral and physical factors. Actual antibiotic assays are conducted with the test medium, and performance is rated against a control medium. Controls on the system reduce the variables to allow appraisal of the medium itself.

Anti-Bacterial Agents↗
PubMedDate not supplied

Chaos and control in mass-action binding of endogenous compounds.

Endogenous compounds, such as hormones and neurotransmitters, interact with cellular receptors in controlled reactions governed by the mass-action law. Autoreceptors, a subset of the receptor pool, when activated by the endogenous ligand, result in a negative feedback that reduces the further release of ligand. This paper discusses and illustrates this control system when the concentrations (free and bound) are near or slightly beyond the limits of effective feedback control. Specifically, a forced periodic input function, simulating periodic release of the ligand, is used in the simulation of this controlled binding reaction in which a parameter representing the upper limit of control is varied. The solution of the system differential equations, representing free and bound ligand, is shown to pass from periodic to chaotic as the parameter is varied.

Computer Simulation↗