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Biomedical subjects

Samuel S Wu

Publications and source records attributed to Samuel S Wu.

16 recordsLinked to original sources

Multiple system utilization and mortality for veterans with stroke.

BACKGROUND AND PURPOSE: Many Veteran Health Administration (VHA) enrollees receive health services outside the VHA system. However, limited information is available about poststroke utilization and mortality by veterans who used multiple sources of health care. This study assessed the likelihood of 12-month poststroke rehospitalization and mortality of veterans who used VHA only versus those who used multiple sources of care. METHODS: Our retrospective observational study examined veterans living in Florida and diagnosed with acute stroke. We categorized users into 4 groups: VHA-only, VHA-Medicare, VHA-Medicaid, and VHA-Medicare-Medicaid based on their use of each health care program. Logistic regression models were fitted for 12-month poststroke general rehospitalization, recurrent stroke readmission, and mortality, adjusting for sociodemographic and clinical factors. RESULTS: The sample consisted of 29% VHA-only users, 61% VHA-Medicare users, 3% VHA-Medicaid users, and 7% VHA-Medicare-Medicaid triple users. Compared with the VHA-only users, multiple system users were significantly more likely to be rehospitalized for any cause and for recurrent stroke 12-months postindex. Mortality outcomes depended on when the outcome was measured; at the index admission date, we found no significant difference in mortality across the user groups; at the index discharge date, the VHA-only users was less likely to die within the first 12 months than the users of the 2 dual groups (VHA-Medicare and VHA-Medicaid). CONCLUSIONS: Multiple health care source use was common among VHA enrollees with acute stroke in Florida. Multiple system users were more likely to be rehospitalized and the mortality outcomes were dependent on when the outcome was measured.

Aged↗

Soleus H-reflex modulation in response to change in percentage of leg loading in standing after incomplete spinal cord injury.

Body weight support (BWS) is frequently used to retrain standing and walking in persons post spinal cord injury (SCI), but the effects of leg unloading using BWS on H-reflex excitability in this population are unknown. The purpose of the study was to assess the effect of two different loading conditions on soleus H-reflex while standing in persons with motor incomplete SCI (i-SCI) and non-injured persons. Eight persons with motor i-SCI (mean age 50.25 years) and five non-injured persons (mean age 48.6 years) participated in the study. Specific control of the loading conditions was achieved using a BWS system. To compare reflex modulation at 40% versus 0% BWS, soleus H-reflexes were evoked during standing and normalized to the maximum M wave amplitude. These studies revealed that (1) H-reflex excitability is significantly greater after SCI and is exhibited even during quiet standing; and (2) no significant modulation in reflex excitability was observed by change in loading conditions in either the non-injured or the i-SCI subjects. These findings suggest that non-injured persons and persons with i-SCI respond similarly to bilateral limb unloading during standing with no change in H-reflex amplitude. Our results suggest that BWS of up to 40% does not produce detectable changes in the excitability of the soleus H-reflex in persons with i-SCI.

Adult↗

Limited dose response to constraint-induced movement therapy in patients with chronic stroke.

OBJECTIVE: To compare outcomes in motor skill, perceived amount of use and ability of the paretic arm in daily activities between traditional Constraint-Induced Movement Therapy, consisting of 6 hours of in-clinic, therapist-guided task practice, and a shortened Constraint-Induced Movement Therapy, consisting of 1 hour of in clinic, therapist-guided task practice coupled with 5 hours of unsupervised practice at home. DESIGN: A secondary analysis of two previous randomized, controlled, double-blind, parallel group studies. SETTING: A research clinic. PARTICIPANTS: Thirty-nine individuals with hemiparesis from a chronic unilateral stroke who were able to extend the wrist 10 degrees and the fingers and thumb 10 degrees from a flexed position and were participants in one of the two studies examining the efficacy of adding neuroplasticity adjuvants to Constraint-Induced Movement Therapy. MAIN OUTCOME MEASURES: The Wolf Motor Function Test was used to assess motor skill and the Motor Activity Log amount of use and quality of movement scales were used to assess perceived amount of use and ability respectively. INTERVENTIONS: Constraint-Induced Movement Therapy plus donepezil in the CIMT-6 study (the traditional 6 hours of in-clinic task practice) and Constraint-Induced Movement Therapy plus repetitive transcranial magnetic stimulation in the CIMT-1 study (1 hour of in-clinic task practice). RESULTS: Motor skill gains after two weeks of therapy were equivalent for both groups (n=39; mean difference=2.81, P>0.22), but gains were not maintained six months later with either intervention protocol. Despite this, participants in the CIMT-6 group reported greater use (mean difference=1.52, P<0.001) and movement quality (mean difference=0.95, P<0.004) than those with less therapist-guided practice. Both groups had regressed somewhat in use and ability at the six-month follow-up. CONCLUSION: These results suggest that 6 hours of therapist-guided practice may not be necessary to facilitate motor skill gains, but may influence patterns of use.

Aged↗

Racial and gender differences in the viability of extremely low birth weight infants: a population-based study.

OBJECTIVE: The purpose of this study is to provide a race- and gender-specific model for predicting 1-year survival rates for extremely low birth weight (ELBW) infants by using population-based data. METHODS: Birth and death certificates were analyzed for all children (N = 5076) with birth weights between 300 g and 1000 g who were born in Florida between 1996 and 2000. Semiparametric, multivariate, logistic regression analysis was used to model 1-year survival probabilities as a function of birth weight, gestational age, mother's race, and infant's gender. Estimated survival rates among different race/gender groups were compared by using odds ratios (ORs). RESULTS: One-year survival rates for 5076 ELBW infants born between 1996 and 2000 did not change during the 5-year period (60-62%). The survival rate at < or = 500 g was < or = 14% (n = 716). Survival rates at 501 to 600 g and 601 to 700 g were 36% and 62%, respectively. The survival rate reached > 85% for infants of > 800 g. Modeling indicated a survival advantage for female infants, compared with male infants (OR: 1.7; 95% confidence interval: 1.5-1.9), and for black infants, compared with white infants (OR: 1.3; 95% confidence interval: 1.1-1.5). Black female infants had 2.1 greater odds of survival than did white male infants. CONCLUSIONS: This population-based study highlights the significant race and gender differences in 1-year survival rates for ELBW infants, as well as the interactions of these 2 factors. These findings can assist obstetricians and neonatologists not only in the care of ELBW infants but also in frank discussions with families.

Black or African American↗

CIMT as a behavioral engine in research on physiological adjuvants to neurorehabilitation: the challenge of merging animal and human research.

A physiological adjuvant to neuroplasticity cannot put new knowledge into the brain - it can only augment behavioral rehabilitation, which does replace knowledge in the brain lost due to injury. Clinical trials of adjuvant agents should therefore incorporate behavioral engines: behavioral therapies that have a potent effect and minimize error variance due to variability in subject attributes and the administration of the therapy. We consider in some detail the attributes of behavioral engines with a particular focus on constraint induced movement therapy. Human trials of physiological adjuvants to neuroplasticity are predicated on discoveries from animal research. Because human trials are expensive and carry risk of injury, it behooves us to lay a comprehensive foundation for these trials with animal studies (also incorporating behavioral engines) and to carefully mesh animal and clinical work. We review in detail our own and others' work involving human subjects with brain lesions and animal models of brain injury using donepezil, a central acetyl cholinesterase inhibitor, d-cycloserine, a partial agonist at the NMDA receptor glycine site, d-amphetamine, and methylphenidate in an effort to elucidate the strengths and weakness of animal and human neurorehabilitation science with respect to this mesh between animal and human subject research. We consider modifications in current approaches that might more efficiently advance neurorehabilitation science.

Animals↗

Risk factors for infant maltreatment: a population-based study.

CONTEXT: Of the approximately 900,000 children who were determined to be victims of abuse or neglect by US child protective services in 2002, the birth-to-3 age group had the highest rate of victimization (1.6%) and children younger than 1 accounted for the largest percentage of victims (9.6%). OBJECTIVE: To identify perinatal and sociodemographic risk factors associated with maltreatment of infants up to 1 year of age. DESIGN AND SETTING: Observational cohort study. PARTICIPANTS: 189,055 children born in 1996 in Florida. MAIN OUTCOME MEASURE: Infant maltreatment, defined as a verified report of abuse, neglect, or threatened harm that occurred between day 3 of life and 1 year. RESULTS: 1,602 children (.85%) of the 1996 birth cohort had verified instances of maltreatment by age 1. Of 15 perinatal and sociodemographic variables studied, 11 were found to be significantly related to infant maltreatment. Five factors had adjusted relative risks (RR) of two or greater: Mother smoked during pregnancy (RR 2.8); more than two siblings (RR 2.7); Medicaid beneficiary (RR 2.1); unmarried marital status (RR 2.0); low birth weight infant (RR 2.0). Infants who had four of these five risk factors had a maltreatment rate seven times higher than the population average. CONCLUSIONS: Data on nearly all risk factors found to be significantly associated with infant maltreatment are available on the birth certificate. Such information can be incorporated into a population-based risk-assessment tool that could identify subpopulations at highest risk for infant maltreatment. Because resources are limited, these groups should be given priority for enrollment in child abuse prevention programs.

Child Abuse↗

Donepezil as an adjuvant to constraint-induced therapy for upper-limb dysfunction after stroke: an exploratory randomized clinical trial.

Donepezil, a primarily central acetylcholinesterase inhibitor, could potentiate learning in subjects with stroke by amplifying cholinergic input to the cerebral cortex from the nucleus basalis of Meynert. We tested this possible adjuvant effect of donepezil in a prospective randomized, double-blind, placebo-controlled, parallel-group study of 20 subjects 1 or more years following stroke undergoing constraint-induced therapy (CIT) for upper-limb dysfunction. CIT had substantial and significant effects on both primary outcome measures, the Wolf Motor Function Test (WMFT) and the Motor Activity Log (amount), and all secondary measures, including the Box and Block Test, the Actual Amount of Use Test, the Fugl-Meyer Motor Scale-Upper Extremity, and the Caregiver Strain Index. Subjects receiving donepezil achieved differential gains on the WMFT approaching statistical significance (p = 0.067, corrected for multiple comparisons), but not on other measures. This study is inconclusive, but a larger randomized controlled trial with adequate statistical power should be pursued because of the potential benefits of the treatment to stroke survivors.

Arm↗

Increased severity of acute cerebral ischemic injury correlates with enhanced stem cell induction as well as with predictive behavioral profiling.

An 8-vessel-occlusion (8VO) method was developed to compare with the conventional 4-vessel-occlusion (4VO) in hippocampal ischemic damage and progenitor cell induction 10 days following ischemia in female rats. Eight posture-relevant tests were performed following ischemia to correlate grades of postural abnormality with the histological outcome. The total hippocampal living cell ratio including 7 hippocampal subregions in 8VO group (n=11) was much lower than that in 4VO group (n=10, 51+/-5% vs. 78+/-4, p<0.01). In 4VO group, BrdU positive cells were mainly located in the subgranular zone (SGZ) with a count of 54+/-20/mm2 (7micro-thick slice), comparable to the maximal level following global ischemia in male gerbils and rats reported so far referring to slice-thickness differences (50-60 micro-thick slices). Similarly, nestin-bearing cells were 29+/-11/ mm2. In 8VO group, BrdU and nestin positive cells increased by 10 times. Triple staining of BrdU, nestin and DAPI demonstrated that BrdU-immunoreactivity was extensively distributed in the hippocampal hilus while the nestin was mainly located along the SGZ. Most of nestin labeling was not co-localized with the BrdU, indicating that establishment of these cells might precede BrdU injections (8 and 9d post ischemia). Behavioral scores were much greater for 8VO group than for 4VO group and composite postural scores well correlated with the hippocampal cell loss. In conclusion, severe ischemia correlates with vigorous induction of the hippocampal progenitor cells in rats while behavioral profiling of posture changes permits prediction of severity of damage.

Animals↗

Combination antiretroviral therapy results in a rapid increase in T cell receptor variable region beta repertoire diversity within CD45RA CD8 T cells in human immunodeficiency virus-infected children.

Human immunodeficiency virus (HIV) type 1 disrupts the T cell receptor (TCR) variable region (V) beta repertoire in CD8 T cells by impairing thymic capacity and skewing postthymic cellular maturation. The TCR repertoire was examined using spectratyping of CDR3 length diversity within CD45RA and CD45RO CD8 T cells in HIV-infected and healthy children. In healthy children, CDR3 lengths displayed Gaussian distribution in both CD45RA and CD45RO subsets. Vbeta families in HIV-infected children displayed a large proportion of perturbations in both subsets. High virus load and advanced immunosuppression correlated with increased perturbations within CD45RA but not CD45RO CD8 T cells. After therapy and virus suppression, there was rapid reestablishment of Gaussian distributions in CD45RA cells. HIV-1-induced disruption of TCR diversity within CD45RA CD8 T cells correlates with disease progression. Suppression of viral replication by treatment results in the rapid correction of TCR diversity in this CD8 subset because of emergence of new T cells from the thymus.

Adolescent↗

Quantitative trait loci for growth trajectories in Populus.

Growth trajectories are a biological process important to plant and animal breeding, and to evolutionary genetic studies. In this article, we report the detection of quantitative trait loci (QTLs) responsible for growth trajectories in poplars that are used as a model system for the study of forest biology. These QTLs were localized on a genetic linkage map of polymorphic markers using a statistical mapping method incorporating growth-curve models. The effects of the QTLs on growth are described as a function of age, so that age-specific changes in QTL effects can be readily projected throughout the entire growth process. The QTLs identified display increased effects on growth when trees age, yet the timing of QTL activation is earlier for stem height than diameter, which is consistent with the ecological viewpoint of canopy competition. The implications of the results for breeding and silviculture are discussed.

Genetic Linkage↗

Managed care organizational characteristics and health care use among children with special health care needs.

OBJECTIVE: To examine the relationship between features of managed care organizations (MCOs) and health care use patterns by children. DATA SOURCES: Telephone survey data from 2,223 parents of children with special health care needs, MCO-administrator interview data, and health care claims data. STUDY DESIGN: Cross-sectional survey data from families about the number of consequences of their children's conditions and from MCO administrators about their plans' organizational features were used. Indices reflecting the MCO characteristics were developed using data reduction techniques. Hierarchical models were developed to examine the relationship between child sociodemographic and health characteristics and the MCO indices labeled: Pediatrician Focused (PF) Index, Specialist Focused (SF) Index, and Fee for Service (FFS) Index, and outpatient use rates and charges, inpatient admissions, emergency room (ER) visits, and specialty consultations. DATA COLLECTION/EXTRACTION METHODS: The telephone and MCO-administrator survey data were linked to the enrollment and claims files. PRINCIPAL FINDINGS: The child's age, gender, and condition consequences were consistent predictor variables related to health care use and charges. The PF Index was associated with decreased outpatient use rates and charges and decreased inpatient admissions. The SF Index was associated with increased ER visits and decreased specialty consultations, while the FFS Index was associated with increased outpatient use rates and charges. CONCLUSION: After controlling for sociodemographic and health characteristics, the PF, SF, and FFS indices were significantly associated with children's health care use patterns.

Adolescent↗

The use of estrogens and related compounds in the treatment of damage from cerebral ischemia.

There are 750,000 new cases of stroke each year in the United States, and brain damage from stroke leads to high health care costs and disabilities. Needed, but currently not available, are therapies that can be administered prior to, during, or after cerebral ischemia that reduce or eliminate neuronal damage from stroke. To address this issue, we began to assess the neuroprotective effects of estrogens and related compounds in stroke neuroprotection to determine whether these compounds had potential for clinical application. First, we demonstrated that 17 beta-estradiol (E2) pretreatment exerted potent neuroprotection of the cerebral cortex over a wide dose range and pretreatment interval. Thereafter, we assessed the ability of a variety of non-feminizing estrogens to protect brain tissue from stroke. We observed that pretreatment with 17 alpha-estradiol, the complete enantiomer of E2 (ENT-E2), 2-adamantylestrone, and the enantiomer of 17-desoxyestradiol, were as effective as E2 in pretreatment protection from stroke damage. These data suggest that non-estrogen receptor mechanisms are involved in brain neuroprotection under our treatment conditions. We then determined whether the observed E2 protection could be extended to times after the onset of the cerebral ischemic event. Using a formulation of E2 that rapidly delivers the steroid, a necessary condition for acute therapy of an ongoing stroke, we demonstrated that 100 mg E2/kg could protect brain tissue for up to 3 h after the onset of the stroke. To determine whether this therapeutic window could be extended with higher doses of the steroid, we conducted a dose-response assessment of E2 when administered at 6 h after the onset of the ischemic event. While the effectiveness of the 100 micro g E2/kg was reduced at this time interval, higher doses of E2 were effective. E2, at doses of 500 and 1000 micro g/kg, reduced infarct volume by more than 50%, even with this 6-h delay in treatment. Collectively, these data indicate that estrogens could prove to be useful therapies in preventing brain damage from strokes.

Animals↗

A hierarchical statistical model for estimating population properties of quantitative genes.

BACKGROUND: Earlier methods for detecting major genes responsible for a quantitative trait rely critically upon a well-structured pedigree in which the segregation pattern of genes exactly follow Mendelian inheritance laws. However, for many outcrossing species, such pedigrees are not available and genes also display population properties. RESULTS: In this paper, a hierarchical statistical model is proposed to monitor the existence of a major gene based on its segregation and transmission across two successive generations. The model is implemented with an EM algorithm to provide maximum likelihood estimates for genetic parameters of the major locus. This new method is successfully applied to identify an additive gene having a large effect on stem height growth of aspen trees. The estimates of population genetic parameters for this major gene can be generalized to the original breeding population from which the parents were sampled. A simulation study is presented to evaluate finite sample properties of the model. CONCLUSIONS: A hierarchical model was derived for detecting major genes affecting a quantitative trait based on progeny tests of outcrossing species. The new model takes into account the population genetic properties of genes and is expected to enhance the accuracy, precision and power of gene detection.

Algorithms↗

Neuroprotective effects of a novel non-receptor-binding estrogen analogue: in vitro and in vivo analysis.

BACKGROUND AND PURPOSE: Although estrogens are neuroprotective, hormonal effects limit their clinical application. Estrogen analogues with neuroprotective function but lacking hormonal properties would be more attractive. The present study was undertaken to determine the neuroprotective effects of a novel 2-adamantyl estrogen analogue, ZYC3. METHODS: Cytotoxicity was induced in HT-22 cells by 10 mmol/L glutamate. 17beta-Estradiol (E2) or ZYC3 was added immediately before the exposure to glutamate. Cell viability was determined by calcein assay. The binding of E2 and ZYC3 to human alpha (ERalpha) and beta (ERbeta) estrogen receptors was determined by ligand competition binding assay. Ischemia/reperfusion injury was induced by temporary middle cerebral artery occlusion (MCAO). E2 or ZYC3 (100 microg/kg) was administered 2 hours or immediately before MCAO, respectively. Infarct volume was determined by 2,3,5-triphenyltetrazolium chloride staining. Cerebral blood flow was recorded during and within 30 minutes after MCAO by a hydrogen clearance method. RESULTS: ZYC3 significantly decreased toxicity of glutamate with a potency 10-fold that of E2. ZYC3 did not bind to either ERalpha or ERbeta. Infarct volume was significantly reduced to 122.4+/-17.6 and 83.1+/-19.3 mm(3) in E2 and ZYC3 groups, respectively, compared with 252.6+/-15.6 mm(3) in the ovariectomized group. During MCAO, both E2 and ZYC3 significantly increased cerebral blood flow in the nonischemic side, while no significant differences were found in the ischemic side. However, E2 and ZYC3 significantly increased cerebral blood flow in both sides within 30 minutes after reperfusion. CONCLUSIONS: Our study shows that ZYC3, a non-receptor-binding estrogen analogue, possesses both neuroprotective and vasoactive effects, which offers the possibility of clinical application for stroke without the side effects of estrogens. It also suggests that both the neuroprotective and vasoactive effects of estrogen are receptor independent.

Adamantane↗

Race/ethnicity: who is counting what?

Misclassification of race and ethnicity in administrative data may produce misleading results if it is overlooked or ignored. In this study, we examined the racial/ethnic classifications of 1,084 veterans with stroke in Florida who received inpatient and outpatient services within the Department of Veterans Affairs (VA) healthcare system and who were also eligible for Medicare between 2000 and 2001. We compared the reliability of racial/ethnic classifications between VA inpatient data, VA outpatient data, and Medicare data. Our results showed that (1) the rate of unknown racial/ethnic classification in VA outpatient and inpatient data was high, (2) minimizing the unknowns by substituting known values from other data when available would greatly enhance the overall and individual classification reliability, (3) black and white classifications in the VA data had stronger agreement with Medicare data, and (4) Medicare data may under-represent Hispanic patients.

Databases, Factual↗

Problems with dressing in the frail elderly.

OBJECTIVE: Dressing is an important activity of daily living, yet many older adults have difficulty due to impairments. The purpose of this study was to explore the use of assistive devices for dressing by older persons with impairments, and to look at differences among frail elders with no dressing difficulty, upper-extremity-only dressing difficulty, lower-extremity-only dressing difficulty, and both upper- and lower-extremity dressing difficulty. METHOD: We conducted in-home interviews and functional assessments with 1,101 elderly persons with activities of daily living and/or instrumental activities of daily living limitations in Western New York and Northern Florida. Participants were assigned to one of four groups based on Functional Independence Measure item scores for upper-extremity dressing and lower-extremity dressing. Descriptive statistics were used to report results. RESULTS: Compared to women, there were relatively more men with lower-extremity dressing difficulty than with upper-extremity dressing difficulty. The group with both upper- and lower-extremity dressing difficulty reported the highest level of pain and scored lowest on all measures of functional status and mental status. The most commonly used dressing devices were associated with lower-extremity dressing. CONCLUSION: There are differences in gender, health status, functional status, and mental status among elderly persons grouped by upper- or lower-extremity dressing difficulty. Results suggest that therapists should consider such differences as gender and type of difficulty (upper- or lower-extremity dressing) in both therapeutic approaches and recommendations for assistive devices. Pain is another important consideration, but it can often be reduced during dressing by using assistive devices.

Activities of Daily Living↗