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Biomedical subjects

David Goodman

Publications and source records attributed to David Goodman.

13 recordsLinked to original sources
PubMed2007

Schimke immunoosseous dysplasia: suggestions of genetic diversity.

Schimke immunoosseous dysplasia (SIOD), which is characterized by prominent spondyloepiphyseal dysplasia, T-cell deficiency, and focal segmental glomerulosclerosis, is a panethnic autosomal recessive multisystem disorder with variable expressivity. Biallelic mutations in switch/sucrose nonfermenting (swi/snf) related, matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1 (SMARCAL1) are the only identified cause of SIOD. However, among 72 patients from different families, we identified only 38 patients with biallelic mutations in the coding exons and splice junctions of the SMARCAL1 gene. This observation, the variable expressivity, and poor genotype-phenotype correlation led us to test several hypotheses including modifying haplotypes, oligogenic inheritance, or locus heterogeneity in SIOD. Haplotypes associated with the two more common mutations, R820H and E848X, did not correlate with phenotype. Also, contrary to monoallelic SMARCAL1 coding mutations indicating oligogenic inheritance, we found that all these patients did not express RNA and/or protein from the other allele and thus have biallelic SMARCAL1 mutations. We hypothesize therefore that the variable expressivity among patients with biallelic SMARCAL1 mutations arises from environmental, genetic, or epigenetic modifiers. Among patients without detectable SMARCAL1 coding mutations, our analyses of cell lines from four of these patients showed that they expressed normal levels of SMARCAL1 mRNA and protein. This is the first evidence for nonallelic heterogeneity in SIOD. From analysis of the postmortem histopathology from two patients and the clinical data from most patients, we propose the existence of endophenotypes of SIOD.

Algorithms↗
PubMed2006

Pre-landing muscle timing and post-landing effects of falling with continuous vision and in blindfold conditions.

The present study examined the effect of continuous vision and its occlusion in timing of pre-landing actions during free falls. When vision is occluded, muscle activation is hypothesized to start relative to onset of the fall. However, when continuous vision is available onset of action is hypothesized to be relative to the moment of touchdown. Six subjects performed 6 randomized sets of 6 trials after becoming familiar with the task. The 36 trials were divided in 2 visual conditions (vision and blindfold) and 3 heights of fall (15, 45 and 75 cm). EMG activity was recorded from the gastrocnemius and rectus femoris muscles during the falls. The latency of onset (L(o)) and the lapse from EMG onset to touchdown (T(c)) were obtained from these muscles. Vertical forces were recorded to assess the effects of pre-landing activity on the impacts at collision with and without continuous vision. Peak amplitude (F(max)), time to peak (T(max)) and peak impulse normalized to momentum (I(norm)) were used as outcome measures. Within flight time ranges of approximately 50-400 ms, the results showed that L(o) and T(c) follow a similar linear trend whether continuous vision was available or occluded. However, the variability of T(c) for each of the muscles was larger in the vision occluded condition. Analyses of variance showed that the rectus femoris muscle started consistently earlier in no vision trials. Finally, impact forces were not different in vision or blindfold conditions, and thus, they were not affected by minor differences in the timing of muscles prior to landing. Thus, it appears that knowing the surroundings before falling may help to reduce the need for a continuous visual input. The relevance of such input cannot be ruled out for falls from high landing heights, but cognitive factors (e.g., attention to specific cues and anticipation of a fall) may play a dominant role in timing actions during short duration falls encountered daily.

Adult↗
PubMed2005

Video gaming promotes concussion knowledge acquisition in youth hockey players.

While the positive uses for video games in an educational setting have also been established, the educational aim is usually made explicit. The goal of this research was to develop a video game wherein the educational aspect was implicitly embedded in the video game, such that the gaming activity remained interesting and relevant. Following a pilot study to confirm the usability of an in-house developed game, two studies were conducted with 11-17 year old hockey players (N(1)=130, N(2)=39). Results demonstrated that participants playing the experimental version of the video game scored significantly higher on a concussion symptoms questionnaire, in a significantly faster time, than participants playing the control version of the game. Most participants indicated that they enjoyed the game and would play it again. These results suggest that educational material can be conveyed successfully and in an appealing manner via video game play.

Adolescent↗
PubMed2005

Effect of mouthguards on the transmission of force across the human jaw.

OBJECTIVE: To determine if impact responses (stiffness and damping values) of the jaw and neck are significantly different between mouthguards of varying material and manufacturing properties, in controlled conditions involving specified upper limb orientation and applied loading. DESIGN: Quasi-experimental design. SETTING: Simon Fraser University biomechanical laboratory. PARTICIPANTS: Twelve male subjects between the ages of 19 to 28 participated in this study. All subjects were healthy, had no missing teeth, and had no mechanical (orthodontic) appliances. MAIN OUTCOME MEASUREMENTS: For each condition, the system stiffness and damping values were estimated using the free vibration technique. Stiffness and damping values are relevant because they are the major determinants of impact force and, potentially, injury risk. It is the first study to show experimentally the quantitative effects of mouthguard in situ. RESULTS: All the mouthguards lowered the system stiffness as compared with the no mouthguard condition (P < 0.001). There was no observed effect on stiffness between the 2 limb orientation positions. Excitation weight had an unexpected effect on system stiffness (P = 0.041), with increasing weight leading to increased stiffness. CONCLUSIONS: The findings suggest that wearing any mouthguard is better than wearing none at all due to their ability to reduce system stiffness and damping values after a blow to the chin.

Adult↗
PubMed2005

Energy-minimization bias: compensating for intrinsic influence of energy-minimization mechanisms.

Anecdotal and scientific evidence suggest humans tend to undershoot targets in rapid movements. We investigated whether this undershoot bias derives from energy minimization mechanisms. Participants performed 200 trials of two tasks: (1) a simple slider push to a target, and (2) a modified version of (1), designed so overshooting was less energy consuming than undershooting. Results support that the undershoot bias found in (1), as well as the overshoot bias found in (2), results from an energy minimization mechanism. Energy minimization might be inherent to biological systems. Movement biases were un desirable for maximal performance. Nonetheless, participants presented biases despite financial incentives to perform maximally. Participants did, however, appear sensitive to systematic errors produced by the attraction to less energy costly responses. We suggest that the motor system is constrained such that maximal performance trades off with energetic optimality although humans are able to learn and compensate for the energy minimization biases.

Adult↗
PubMed2004

Recombinant antigen-based antibody assays for the diagnosis and surveillance of lymphatic filariasis - a multicenter trial.

The development of antifilarial antibody responses is a characteristic feature of infection with filarial parasites. It should be possible to exploit this fact to develop tools to monitor the progress of the global program to eliminate lymphatic filariasis (LF); however, assays based on parasite extracts suffer from a number of limitations, including the paucity of parasite material, the difficulty of assay standardization and problems with assay specificity. In principle, assays based on recombinant filarial antigens should address these limitations and provide useful tools for diagnosis and surveillance of LF. The present multicenter study was designed to compare the performance of antibody assays for filariasis based on recombinant antigens Bm14, WbSXP, and BmR1. Coded serum specimens were distributed to five participating laboratories where assays for each antigen were conducted in parallel. Assays based on Bm14, WbSXP, or BmR1 demonstrated good sensitivity (>90%) for field use and none of the assays demonstrated reactivity with specimens from persons with non-filarial helminth infections. Limitations of the assays are discussed. Well-designed field studies are now needed to assess sampling methodology and the application of antibody testing to the monitoring and surveillance of LF elimination programs.

Journal Article↗
PubMed2004

School professionals' perceptions about the impact of chronic illness in the classroom.

BACKGROUND: Children with chronic health conditions spend most of their day in the school system. The complexity of illness management and disease sequela can alter their school experience. However, little is known about what educators are concerned about if these children are in their classroom. OBJECTIVE: To assess educators' perceptions of the impact of having children with different chronic health conditions in the classroom. METHODS: Teachers and other school professionals in 23 elementary schools were surveyed about the impact of having a child with each of 6 chronic health conditions--AIDS, asthma, congenital heart disease, diabetes mellitus, epilepsy, and leukemia--in the classroom. They responded to 13 statements about the potential academic impact on the child, impact on peers, personal risk or liability, and additional time or attention demands for the teacher. Total scores were determined for the degree of perceived impact for each issue and chronic health condition and the proportion of teachers with negative perceptions for different issues. RESULTS: The mean total scores (2.4 of 5) showed overall a positive perception by school professionals about children with chronic conditions in the classroom. Acquired immunodeficiency syndrome and epilepsy were perceived to have the most impact and asthma the least impact. The 2 educator issues (time or extra attention and personal risk or liability) were of the most concern to educators. Fifty-three percent were concerned about an emergency occurring with the child in the classroom and 27% were concerned about legal liability. Educator concerns of the risk of classroom emergencies or death were disproportionate to the clinical risk of the conditions especially for epilepsy and congenital heart disease. CONCLUSIONS: Overall school professionals have positive attitudes about children with chronic health conditions in the classroom, but concerns about specific diseases and issues exist. If parents provide most of the disease information, some of the educators' concerns voiced in this study may not be addressed. Health care professionals can help by providing educators with appropriate information about the risk and functional impact of childhood chronic health conditions.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Heart rate variability of recently concussed athletes at rest and exercise.

PURPOSE: The objective of this study was to assess the neuroautonomic cardiovascular regulation in recently concussed athletes at rest and in response to low-moderate steady-state exercise, using heart rate variability (HRV). METHODS: A 5-min ECG sample was taken at rest from the 14 concussed athletes at 1.8 (+/- 0.2) days postinjury and again at 5 d later. Once asymptomatic at rest, the concussed athletes and their matched controls (N = 14) participated in an exercise protocol. The protocol consisted of a 2-min warm-up with a pedaling frequency between 50 and 60 rpm against a load of 40 W. After the warm-up, the athletes engaged in a low-moderate intensity steady state 10-min exercise bout where the pedaling frequency and load increased to 80-90 rpm and 1.5 W x kg(-1) body weight, respectively. The protocol was repeated 5 d later. A 5-min ECG sample from minutes 4 to 9 of the low-moderate intensity steady state exercise bout was used to assess HRV during exercise. Mixed model ANOVA were used to analyze the data. RESULTS: No difference at rest was detected between the concussed athletes and their matched controls in any of the HRV variables measured. However, across both exercise tests, the concussed group demonstrated a significant decrease in the mean RR interval, and low- and high-frequency power (P < 0.05) in relation to their matched controls. CONCLUSION: Low-moderate steady-state exercise elicits a neuroautonomic cardiovascular dysfunction in concussed athletes that is not present in a rested state. This dysfunction alludes to an exercise induced uncoupling between the autonomic and cardiovascular systems.

Adolescent↗
PubMed2004

Conscious and effortful or effortless and automatic: a practice/performance paradox in motor learning.

High cognitive effort has been frequently related to better indices of motor learning through the study of many different paradigms. However, automaticity presumably invokes minimal cognitive processing but has often been related to high-level motor performance, which suggests a paradox. The objective of this study was to approach this paradox by examining the viability of the use of different cognitive strategies during practice and performance which promote the benefits of high cognitive effort and automaticity. Members of the university community (14 men and 15 women) divided into 3 groups practiced a discrete precision task. All participants completed four sessions totaling 320 trials and were tested on retention and transfer seven days later. Findings suggest that it is indeed possible to benefit from both effortful and minimal cognitive processing strategies and that they should be used complementarily.

Adult↗
PubMed2003

Use of serum protein electrophoresis to monitor patients with post-transplant lymphoproliferative disorder.

Post-transplant lymphoproliferative disorder (PTLD) is a potentially life-threatening complication of solid organ transplantation. Reduction in immunosuppression is usually the first line of therapy and is often curative. While undergoing treatment, imaging studies including MRI and CT scans are commonly used to follow the disease course. Laboratory studies such as lactate dehydrogenase and Epstein-Barr virus PCR can also be used to monitoring disease status. We report here a case of PTLD developing 48 months post renal transplant. A monoclonal protein (M protein) was demonstrated at diagnosis with a corresponding antibody expressed on the malignant lymphocytes. The patient was followed with serial serum protein electrophoreses (SPEP) to monitor his response to therapy. The amount of M protein paralleled the disease course, decreasing as the clinical symptoms improved. This case illustrates the utility of using SPEP to monitor patients with PTLD.

Adult↗