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Biomedical subjects

H K Yuen

Publications and source records attributed to H K Yuen.

18 recordsLinked to original sources
PubMed1997

Positive talk training in an adult with traumatic brain injury.

Social skills often create a barrier to placement in less restrictive environments for persons with TBI. This case study illustrated the use of a positive talk program in the treatment of a person with long-standing social skill deficits. Occupational therapy intervention with speech-language consultation began with an evaluation of the cognitive barriers that influenced the client's social behavior. Work with the client's concrete concept formation, decreased memory, and poor generalization skills led to the development of the positive talk training program described. Through an understanding of the underlying cognitive deficits that influenced the client's behavior, the clinical team was able to develop an individual treatment plan. The intervention resulted in modification of behavior that would have required placing the client in a restricted environment. In the final analysis, the client's social skills improved to a level where he could be discharged to a less restrictive environment.

Adult↗
PubMed1996

An EPSP synthase inhibitor joining shikimate 3-phosphate with glyphosate: synthesis and ligand binding studies.

A novel EPSP synthase inhibitor 4 has been designed and synthesized to probe the configurational details of glyphosate recognition in its herbicidal ternary complex with enzyme and shikimate 3-phosphate (S3P). A kinetic evaluation of the new 3-dephospho analog 12, as well as calorimetric and (31)P NMR spectroscopic studies of enzyme-bound 4, now provides a more precise quantitative definition for the molecular interactions of 4 with this enzyme. The very poor binding, relative to 4, displayed by the 3-dephospho analog 12 is indicative that 4 has a specific interaction with the S3P site. A comparison of Ki(calc) for 12 versus the Ki(app) for 4 indicates that the 3-phosphate group in 4 contributes about 4.8 kcal/mol to binding. This compares well with the 5.2 kcal/mol which the 3-phosphate group in S3P contributes to binding. Isothermal titration calorimetry demonstrates that 4 binds to free enzyme with an observed Kd of 0.53 +/- 0.04 microM. As such, 4 binds only 3-fold weaker than glyphosate and about 150-fold better than N-methylglyphosate. Consequently, 4 represents the most potent N-alkylglyphosate derivative identified to date. However, the resulting thermodynamic binding parameters clearly demonstrate that the formation of EPSPS x 4 is entropy driven like S3P. The binding characteristics of 4 are fully consistent with a primary interaction localized at the S3P subsite. Furthermore, (31)P NMR studies of enzyme-bound 4 confirm the expected interaction at the shikimate 3-phosphate site. However, the chemical shift observed for the phosphonate signal of EPSPS x 4 is in the opposite direction than that observed previously when glyphosate binds with enzyme and S3P. Therefore, when 4 occupies the S3P binding site, there is incomplete overlap at the glyphosate phosphonate subsite. As a glyphosate analog inhibitor, the potency of 4 most likely arises from predominant interactions which occur outside the normal glyphosate binding site. Consequently, 4 is best described as an S3P-based substrate-analog inhibitor. These combined results corroborate the previous kinetic model [Gruys, K. J., Marzabadi, M. R., Pansegrau, P. D., & Sikorski, J. A. (1993) Arch. Biochem. Biophys. 304, 345-351], which suggested that 4 interacts well with the S3P subsite but has little, if any, interaction at the expected glyphosate phosphonate or phosphoenolpyruvate-Pi subsites.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1996

Treatment methodology. Guiding of behaviour through redirection in brain injury rehabilitation.

Confusion, agitation, and non-compliance are some of the most common behaviours exhibited by individuals with brain injury. The presence of these behaviours affects their daily functioning and social interactions with others. Management of these behaviours ranges from prevention and total ignoring to restraint, with the strategy of redirection cited most often in the literature. However, few guidelines exist on how to use redirection to manage clients who exhibit confusion and agitation beyond the acute phase of rehabilitation. This paper describes some of the intervention strategies that use guidance and redirection for individuals with brain injury in post-acute rehabilitation. Case examples are used to illustrate the various interventions.

Behavior Therapy↗
PubMed1994

Prosthesis training as a context for studying occupational forms and motoric adaptation.

OBJECTIVES: Occupational therapy authors frequently emphasize the importance of the use of objects in the development of motor skill. This study investigated the use of object-produced visual input in learning control of flexion and extension of an above-elbow training prosthesis. METHOD: Fifty-two male college students were randomly assigned to two training procedures: (a) two 1.5-min periods in which they used a flashlight attached to the hook of the prosthesis to connect dots on paper with light, or (b) the same time periods in which they had the opportunity to practice moving an equally weighted prosthesis, but without the light or dots. To assess motoric adaptation after training under one of the two conditions, each subject traced a continuous line through a maze with a pen attached to the hook. Deviations from the line were measured reliably. RESULTS: Data analysis with a Mann-Whitney test revealed that subjects in the group that trained with added materials traced with significantly more skill than subjects in the other group (one-tailed U = 225.5, p = .02). CONCLUSION: As predicted by occupational therapy theory, the object-produced visual input enhanced the learning of a motor skill relevant to rehabilitation. Although there is a need for more study across different occupations and populations, clinicians are urged to consider the possible benefits of the use of objects in the development of motor skills, as opposed to objectless exercise. Prosthetic training provides a useful context for future research addressing theoretical issues in motor learning.

Adolescent↗
PubMed1993

Differential scanning calorimetric study of 5-enolpyruvoyl shikimate-3-phosphate synthase and its complexes with shikimate-3-phosphate and glyphosate: irreversible thermal transitions.

The thermal denaturation of native Escherichia coli 5-enolpyruvoyl shikimate-3-phosphate (EPSP) synthase, its binary complex with shikimate-3-phosphate (S3P) and its ternary complex with S3P and glyphosate have been studied using highly-sensitive differential scanning calorimetry (DSC). All observed transitions are strongly scanning-rate-dependent and irreversible. Consistent with these observations, the data were better fit by a simple irreversible model than by the controversial reversible model more commonly employed. The results obtained provide additional support for the application of irreversible models to the thermal denaturation of proteins. The calculated parameters, activation energy (Ea), enthalpy of denaturation (delta H) and transition temperature (Tm), obtained from fitting to an irreversible model agree well with values obtained from approximation techniques. Further, the results show that the formation of the ternary complex greatly enhances the thermal stability of the enzyme (delta Tm = 10.6 degrees C), while the binding of S3P alone increases the transition temperature only slightly (delta Tm = 3 degrees C). The heat of binding calculated at the transition temperature also demonstrates the greater stability of the ternary complex (delta H = -70 kcal/mol) versus the binary complex (delta H = -10 kcal/mol).

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1993

Improved productivity through purposeful use of additional template for a woman with cortical blindness.

A single-subject study with an ABAB design investigated an adaptation of a work activity through the purposeful use of an additional template to improve productivity for a woman with cortical blindness resulting from anoxic brain damage. The activity required the subject to outline brackets (as parts of a handi-rack woodwork project) by tracing a template on a piece of pine board. During the baseline phase of the study, the subject used one template to outline the brackets. During the intervention phase, the subject used an additional template after receiving a brief training in its use. Productivity was measured by the number of potentially usable outlined brackets. Data analysis revealed that in the intervention phases, productivity improved significantly and accuracy increased. The application of tapping the subjects' intact sensory system was valuable for determining her vocational potential. The rationale of using an additional template to improve productivity was explained by the theory of affordance.

Adult↗
PubMed1993

Self-feeding system for an adult with head injury and severe ataxia.

This report describes a customized self-feeding system designed to increase the independence of a person with a head injury who is unable to use his arm for self-feeding. The client has spastic hemiparesis in the right upper extremity and profound ataxia in the left upper extremity. Due to the severity of these disabilities, the client required total assistance at every meal since his injury 6.5 years ago. The self-feeding system described consists of an adapted spoon, a spoon holder, a scoop dish, and a dish stand. The client scoops food from the scoop dish with the adapted spoon held in his mouth and then transfers the spoon to a magnetic holder for positioning. This adaptation allows the client to position the spoon with his chin without demanding fine motor coordination. The self-feeding system is evaluated with a BAB single case research withdrawal design. Results indicate that this self-feeding system provides a viable alternative to assisting independence in self-feeding as measured by the cost-benefit ratio and nutrition intake. The client used the self-feeding system for 12 months at the rehabilitation center and has continued using the equipment at his nursing home.

Adult↗
PubMed1992

EPSP synthase: binding studies using isothermal titration microcalorimetry and equilibrium dialysis and their implications for ligand recognition and kinetic mechanism.

Isothermal titration calorimetry measurements are reported which give important new binding constant (Kd) information for various substrate and inhibitor complexes of Escherichia coli EPSP synthase (EPSPS). The validity of this technique was first verified by determining Kd's for the known binary complex with the substrate, shikimate 3-phosphate (S3P), as well as the herbicidal ternary complex with S3P and glyphosate (EPSPS.S3P.glyphosate). The observed Kd's agreed very well with those from previous independently determined kinetic and fluorescence binding measurements. Further applications unequivocally demonstrate for the first time a fairly tight interaction between phosphoenolpyruvate (PEP) and free enzyme (Kd = 390 microM) as well as a correspondingly weak affinity for glyphosate (Kd = 12 mM) alone with enzyme. The formation of the EPSPS.PEP binary complex was independently corroborated using equilibrium dialysis. These results strongly suggest that S3P synergizes glyphosate binding much more effectively than it does PEP binding. These observations add important new evidence to support the hypothesis that glyphosate acts as a transition-state analogue of PEP. However, the formation of a catalytically productive PEP binary complex is inconsistent with the previously reported compulsory binding order process required for catalysis and has led to new studies which completely revise the overall EPSPS kinetic mechanism. A previously postulated ternary complex between S3P and inorganic phosphate (EPSPS.S3P.Pi, Kd = 4 mM) was also detected for the first time. Quantitative binding enthalpies and entropies were also determined for each ligand complex from the microcalorimetry data. These values demonstrate a clear difference in thermodynamic parameters for recognition at the S3P site versus those observed for the PEP, Pi, and glyphosate sites.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1991

Differential scanning calorimetry of plant cell walls.

High-sensitivity differential scanning calorimetry has been used to study the phase transition of cell wall preparations of the elongating and mature regions of soybean hypocotyls and of celery epidermis and collenchyma strands. A step-like transition believed to be glass transition was observed in walls isolated from the elongating region of soybean hypocotyls at 52.9 degrees C. Addition of 1 mM CaCl2 to the cell wall preparation increased the transition temperature to 60.8 degrees C and greatly reduced the transition magnitude. In walls from the mature region, the transition was small and occurred at a higher temperature (60.1 degrees C). Addition of calcium to the mature region cell wall had little effect on the transition. Based on the known interactions between calcium and pectin, we propose that calcium affects the glass transition by binding to the polygalacturonate backbone of wall pectin, resulting in a more rigid wall with a smaller transition at a higher temperature. The mature region either has more calcium in the wall or has more methyl-esterified pectin, making it less responsive to added calcium.

Journal Article↗
PubMed1990

Fieldwork students under stress.

Many times there are no ideal answers to any of the interpersonal conflicts addressed. Often the solutions to these situations may depend on an individual's characteristics or personality. By analyzing the situation and the supervisor's attitude and then changing his or her way of responding to that situation, however, the student may improve his or her problem-solving skills. The student can modify the strategies taught in these seminars to suit his or her individual needs and particular situations. A seminar like this can provide students, and thus future therapists and student supervisors, with a solid background in dealing more tactfully with a variety of conflict-ridden situations in the workplace.

Burnout, Professional↗
PubMedDate not supplied

The effect of sports on level of community integration as reported by persons with spinal cord injury.

OBJECTIVE: The purpose of this study was to determine whether participation in sports by persons with spinal cord injuries (SCIs) affected level of community integration as defined by the World Health Organization and as measured by the Craig Handicap Assessment and Reporting Technique (CHART). METHOD: Forty-eight participants were recruited from a camp for persons with physical disabilities as well as from SCI support groups. Participants were divided into groups of athletes (n = 30) and nonathletes (n = 18) on the basis of their self-reported level of sports participation. RESULTS: Athletes scored significantly higher on four of five subsections of the CHART (physical independence, mobility, occupation, social integration), indicating greater levels of community integration than nonathletes. CONCLUSION: These findings extend the literature outlining the physical and psychological benefits of sports. Occupational therapists have a unique opportunity to use the occupation of sports to integrate the roots of the profession with the cultural demands of society.

Adolescent↗
PubMedDate not supplied

Comparison of three wheelchair cushions for effectiveness of pressure relief.

OBJECTIVE: Previous studies have suggested that no single wheelchair pressure-relieving cushion material was optimal for all persons with spinal cord injury (SCI). The purpose of this study was to compare the effectiveness of the short-term pressure-relieving ability of the three most commonly prescribed wheelchair cushions (Roho, Jay, Pindot) for a person with SCI. METHOD: The number of pressure sensors registering at the buttock-cushion interface during wheelchair sitting was measured by the Xsensor Pressure Mapping System after 5 min of sitting. An alternating treatments research design, with an initial baseline and a final treatment phase ending with the most effective cushion for relieving pressure, was used for the clinical evaluation. Measurements were compared using visual inspection and a Wilcoxon signed ranks test. RESULTS: Data analyses indicated that the number of pressure sensors that registered potential harmful levels of pressure at the buttock-cushion interface for the Roho cushion was significantly less than those of the Jay and Pindot cushions. CONCLUSION: The Roho cushion was more effective in relieving pressure at the seating surface than the Jay and Pindot cushions.

Adult↗