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Biomedical subjects

S A Fowler

Publications and source records attributed to S A Fowler.

At least 19 recordsLinked to original sources
PubMed1994

Prolongation of the intravascular retention of hemoglobin modified with a long-chain fatty acid derivative.

To develop hemoglobin (Hb) derivatives with an increased circulatory half-life, Hb was chemically modified with long chain fatty acid analogs. One compound, sodium 1-hexadecyl 6-(2-iodoacetamido)hexyl phosphate, specifically modified the Cys-93 beta residues of human hemoglobin (HbA) as determined by sulfhydryl titration analysis. The resulting modified Hb derivative, FAHbA, was isolated and was shown to have a two-fold longer circulatory half-life than native HbA in a rat low-dose acute transfusion model.

Animals↗
PubMed1993

Allosteric kinetics and equilibria of triligated, cross-linked hemoglobin.

Using modulated excitation, we have measured the forward and reverse rates of the allosteric transition between relaxed (R) and tense (T) quaternary structures for triply ligated hemoglobin (Hb), cross-linked between the alpha chains at Lys 99. Oxygen, carbon monoxide, and water were used as ligands and were studied in phosphate and low Cl- bis-Tris buffers at neutral pH. Since the cross-link prohibits disproportionation, triply ligated aquomet Hb species with ferrous beta chains were specifically isolated by isoelectric focusing. Modulated excitation provides rate pairs and therefore gives equilibrium constants between quaternary structures. To coordinate with that information, oxygen binding curves of fully ferrous and tri-aquomet Hb were also measured. L3, the equilibrium constant between three liganded R and T structures, is determined by modulated excitation to be of order unity for O2 or CO (1.1 to 1.5 for 3O2 and 0.7 for 3CO bound), while with three aquomet subunits it is much greater (> or = 23). R-->T conversion rates are similar to those found for HbA, with weak sensitivity to changes in L3. The L3 values from HbXL O2 were used to obtain a unique allosteric decomposition of the ferrous O2 binding curve in terms of KT, KR, and L3. From these values and the O2 binding curve of tri-aquomet HbXL, L3 was calculated to be 2.7 for the tri-aquomet derivative. Consistency in L3 values between equilibrium and modulated excitation data for tri-aquomet-HbXL can be achieved if the equilibrium constant for O2 binding to the alpha chains is six times lower than that for binding to the beta chains in the R state, while the cooperative properties remain homogeneous. The results are in quantitative agreement with other studies, and suggest that the principal effect of the cross-link is to decrease the R state and T state affinity of the alpha subunits with almost no change in the affinity of the beta subunits, leaving the allosteric parameters L and c unchanged.

Allosteric Regulation↗
PubMed1992

Isolation and characterization of the triply oxidized derivative of a cross-linked hemoglobin.

Hemoglobin A, cross-linked between Lys 99 alpha 1 and Lys 99 alpha 2, was used to obtain a partially oxidized tetramer in which only one of the four hemes remains reduced. Because of the absence of dimerization, asymmetric, partially oxidized derivatives are stable. This is evidenced by the fact that eight of the ten possible oxidation states could be resolved by analytical isoelectric focusing. A triply oxidized hemoglobin population HbXL+3 was isolated whose predominant component was (alpha + alpha +, beta + beta 0). This triferric preparation was examined as a possible model for the triliganded state of ferrous HbA. The aquomet and cyanomet derivatives were characterized by their CD spectra and their kinetic reactions with carbon monoxide. CD spectra in the region of 287 nm showed no apparent change in quaternary structure upon binding ligand to the fourth, ferrous heme. The spectra of the oxy and deoxy forms of the cyanomet and aquomet derivatives of HbXL+3 differed insignificantly and were characteristic of the normal liganded state. Upon addition of inositol hexaphosphate (IHP), both the oxy and deoxy derivatives of the high-spin triaquomet species converted to the native deoxy conformation. In contrast, IHP had no such effect on the conformation of the low-spin cyanomet derivatives of HbXL+3. The kinetics of CO combination as measured by stopped-flow and flash photolysis techniques present a more complex picture. In the presence of IHP the triaquomet derivative does bind CO with rate constants indicative of the T state whether these are measured by the stopped-flow technique or by flash photolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspirin↗
PubMed1992

An analysis of the effects of multiple setting events on the social behavior of preschool children with special needs.

We examined the effects of four combinations of setting events on the social interactions of 7 preschool children with social delays. In Study 1, the status of the teacher, activity materials, and peer varied across conditions. In Study 2, the status of the teacher and materials varied across conditions. Within the combinations of setting events, we also examined teacher behavior. Teacher presence and absence was varied in both studies. The type and rate of teacher prompting were varied in Study 2. The four combinations of setting events produced different rates of social behavior by the children with social delays. The optimal combination of setting events for promoting peer interaction and reducing teacher-child interaction included teacher absence from the activity, a limited number and form of materials, and children paired with a socially skilled partner.

Aggression↗
PubMed1992

Generalization and maintenance of preschool children's social skills: a critical review and analysis.

This paper summarizes the results of a retrospective review of generalization in the context of social skills research with preschool children. A review of studies from 22 journals (1976 to 1990) that assessed generalization as part of social interaction research provided information concerning the prevalence of studies that have assessed generalization, common practices concerning the production and assessment of generalization, and the overall success of obtaining generalization and maintenance of social behaviors. A comparison of the most and least successful studies, with respect to generalization, revealed some differences concerning the practices employed by studies within each group. Differences differentially related to the production of generalization are discussed and recommendations are provided to guide and support future research efforts.

Behavior Therapy↗
PubMed1991

Reactivity in self-recording: obtrusiveness of recording procedure and peer comments.

Reactivity refers to behavior change that occurs during self-recording without specific programming of consequences. We analyzed the effects of obtrusiveness of recording procedure and peer comments on reactivity to self-recording. Three first-grade students in Experiment 1 completed math questions during a 5-min work period. When we gave the children recording devices and told them to try to complete more questions than the highest number they had previously completed, math performance increased, as did the number of verbalizations about it. Two children showed more reactivity when they used the more obtrusive recording device. Because the increase in math performance corresponded closely to increases in peer comments, we manipulated peer comments directly in Experiment 2. Four second-grade students completed a math task and an alphabet task. Three of the students showed increased math performance during periods when peer comments occurred compared to periods when peer comments did not occur. Although the data from the math task suggested that peer comments can enhance reactivity, we did not observe this relationship with the alphabet task. These results suggest that the conditions necessary to produce desirable results through self-recording are complex and contextually specific.

Auditory Perception↗
PubMed1988

A comparison of two intervention roles: peer monitor and point earner.

Two fifth-grade students' high levels of off-task and disruptive behavior decreased rapidly during an intervention in which they were appointed peer monitors or point earners. The children worked in dyads in which one child served as a peer monitor and the other child earned points from his or her monitor for good behavior. Points were accumulated as part of a group contingency. We introduced the two appointments in an independent math period and alternated the appointments across days. The peer monitor and point earner roles, when alternated on an every-other-day basis, were equally effective in reducing the students' inappropriate behavior. Furthermore, their behavior during intervention fell well within the range of inappropriate behavior levels exhibited by classmates. The speed with which both students completed their math problems increased during both appointments. The accuracy of their academic work, however, varied; one student improved slightly and the other student decreased slightly in accuracy.

Achievement↗
PubMed1987

Language training for generalization.

This paper presents a classroom-based language intervention program for preschool children with language delays or deficits. A major goal of the program is to ensure that children acquire missing skills through daily speech therapy and that they actively generalize these skills from therapy times to other classroom activities. This paper presents data collected with two children during daily speech therapy sessions and daily play activities. Instances in which the children generalized new language acquired in therapy to play activities will be discussed as well as instances in which the children failed to generalize new language. In addition, the influence of peer and teacher language usage on children's language production will be discussed. Finally, recommendations to enhance generalization of language skills within and across school settings will be presented.

Child↗
PubMed1986

Binding of iron by factor IX. Possible role for beta-hydroxyaspartic acid.

In concentrations exceeding 1 mg/ml, bovine factor IX exhibits a pink color that arises from a broad absorption band with a lambda max = 500 nm. Analysis by x-ray fluorescence reveals the presence of iron but no other transition metals in the factor IX preparation. Quantitative analysis by atomic absorption spectroscopy indicates that 1 g atom of iron is bound tightly to 1 mol of factor IX. The iron is removed slowly (t1/2 = 3 h) by EDTA. In contrast, prothrombin binds no detectable iron, and factor X binds less than 0.2 g atom/mol. alpha-Hydroxybutyrate chelates Fe3+ with sufficient stability to preclude formation of [Fe(OH)3]n. It is proposed that factor IX binds iron with physiologically significant affinity and that the beta-hydroxyaspartate residue in factor IX is a chelator for the bound metal.

Animals↗
PubMed1986

Role reversals: an analysis of therapeutic effects achieved with disruptive boys during their appointments as peer monitors.

Three 7-year-old boys with histories of negative interactions were appointed to monitor individual classmates during daily noon recess. As monitors, the boys awarded points to their classmates for playing appropriately and, on rare occasions, withdrew a point for negative interactions. The three boys immediately decreased their own rates of negative interactions during the sessions in which they were appointed as monitors. Two of the boys concomitantly increased their rates of positive interactions. Their reductions in negative interactions were not maintained during reversals and did not clearly generalize to the morning or afternoon recess periods. Subsequent appointment of the boys as peer monitors during the morning recess produced similar improvements in their behavior. Results suggest that appointment to the role of peer monitor may itself function as an intervention.

Child↗
PubMed1985

Identification of proteins in contact lens surface deposits by immunofluorescence microscopy.

Worn soft contact lenses from five asymptomatic subjects were examined by immunofluorescence microscopy for type of protein on the lens surface. Lysozyme was the predominant protein component identified by this technique. IgA was also identified in deposits on all five lenses, but the staining was less intense than that for lysozyme. Lactoferrin was identified on the surface of four lenses, one of which stained intensely for this protein and three less intensely. IgG was identified on two contact lenses; the staining was less intense than that for lysozyme. New, never-worn soft contact lenses did not stain for any of the proteins examined in this study. We conclude that several normal tear proteins are capable of contributing to surface deposits on soft contact lenses, and all worn soft contact lenses have protein adherent to their surface as a result of normal wear.

Adult↗
PubMed1985

The use of peer monitors to reduce negative interaction during recess.

The negative interactions of a midly retarded child, Dennis, were reduced in three daily recess periods, with the use of a point system. Adult monitors initiated the intervention in the morning recess; reductions achieved during adult monitoring were maintained in that recess during two subsequent conditions: peer monitoring and self-monitoring. Dennis' negative interactions were reduced next in the afternoon recess by peer monitors. Again, reductions were maintained during a subsequent self-monitoring condition. Finally, during the noon recess, Dennis was trained to serve as a peer monitor for Ed, a moderately retarded classmate. Dennis' rate of negative interactions quickly decreased following his appointment as a peer monitor. The results show that a point system, originally designed for adult monitoring, can be adapted without loss of program effectiveness for peer monitoring or self-monitoring. The results also suggest that classmates who serve as peer monitors may benefit significantly from their role. The conditions under which these therapeutic effects occur and the role that treatment order effects may play in this process require further investigation.

Aggression↗
PubMed1985

Training prosocial behaviors to young children: an analysis of reciprocity with untrained peers.

We examined the effects of a social skills training package on the play behaviors of three young girls. Two children were taught to invite their peers to play and to use social amenities during their conversations with other children. A combined reversal and multiple baseline across responses design demonstrated that both children directed more social behaviors to their classroom peers after training and that these two children's play invitations were maintained in the later absence of experimental contingencies. In addition, both target children received a greater number of play invitations from their peers during the free play periods. In contrast, a third child's play invitations were not reciprocated by peers; her invitations subsequently decreased in rate after training was discontinued. An interdependent group contingency produced a reciprocal exchange of invitations between this child and her classroom peers. A reversal design demonstrated partial maintenance of subject-peer exchanges after the group intervention was discontinued. The results obtained with the three target children suggest that peer reciprocity may facilitate the maintenance of children's play invitations over time.

Behavior Therapy↗
PubMed1984

Surface deposits on worn hard contact lenses.

Giant papillary conjunctivitis (GPC) is associated with deposits on contact lenses. We used scanning electron microscopy to study the anterior surface of 30 hard contact lenses, both cleaned and not cleaned, worn by patients with GPC and with keratoconus and by asymptomatic subjects. Uncleaned lenses worn by asymptomatic subjects for one day had deposits on about 5% of the surface. In most cases, the deposits were removed completely by one cleaning. Uncleaned lenses worn by patients with GPC or keratoconus had deposits on about 90% of the surface. Most of these deposits were removed by one cleaning. However, residual deposits after cleaning were greater on lenses from patients with keratoconus than on those from patients with GPC. Lenses from asymptomatic subjects rarely had residual deposits after cleaning. We found that the types of deposits on worn soft and hard contact lenses are similar, that there are fewer deposits on hard lenses than on soft lenses, and that deposits on hard lenses, unlike those on soft lenses, generally can be removed by one cleaning.

Conjunctivitis↗
PubMed1984

Positive peer pressure: the effects of peer monitoring on children's disruptive behavior.

Classroom peers can serve as powerful sources of reinforcement in increasing or maintaining both the positive and negative behaviors of their classmates. In two experiments, we examined the effectiveness of a peer-monitored token system on reducing disruption and nonparticipation during a transition period of a kindergarten class for behaviorally impaired children. Additionally, the effect of providing and subsequently withholding corrective feedback to peer mediators on the accuracy of their point awards was evaluated. Results in Experiment 1 suggest that both teacher- and peer-monitored interventions were successful in decreasing disruption and increasing participation of monitored peers. Experiment 2 further demonstrated that peer monitors could successfully initiate the token system without prior adult implementation. Analysis of the point awards in both experiments indicates that peer monitors consistently awarded points that were earned. However, when corrective feedback was withdrawn the peer monitors frequently awarded points that were not earned, i.e., they rarely withheld points for undesirable behavior. Even so, the monitored peers' disruptive behavior was maintained at low rates.

Child↗
PubMed1982

Cell surface variations of the human upper tarsal conjunctiva.

Fifteen specimens of the upper tarsal conjunctiva were obtained from subjects with biomicroscopically normal conjunctivae. Ten specimens were examined by scanning electron microscopy and five by transmission electron microscopy. This examination was performed to examine cells with variant surface morphologic appearance that may be signs of the initial changes typical of those seen in the diseased conjunctiva. Although most specimens had cells with a characteristic uniform distribution of microvilli, seven specimens had cells with nonuniform microvillar patterns. In these seven specimens, less than 5% of the cells showed these changes. Cell surface variations marked by reduced cell diameters and alterations in the microvillar distribution were categorized into two groups: cells with microvilli that were grouped together to form tufts of varying height and number, and cells with a single, centralized group of microvilli. These variations were seen with increased frequency in disease, and it is postulated that the microvillar changes described in this study represent a continuum of adaptive responses of cells to insult and disease.

Conjunctiva↗