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Biomedical subjects

D Lee

Publications and source records attributed to D Lee.

At least 235 records · Page 13Linked to original sources
PubMed1999

Reconstruction of soft-tissue defects using serratus anterior adipofascial free flap.

The serratus anterior muscle has been suggested as a versatile and reliable flap for reconstruction of head and neck and extremity injuries. The adipofascial layer overlying the serratus anterior muscle is the anatomic layer, which is supplied by the same branch of thoracodorsal artery. Even though great progress has occurred in the prevention of postoperative adhesion of extremity injuries, the problem has not been completely solved and is still of special importance in complex injuries. Between March of 1995 and February of 1996, seven patients underwent reconstructive operation as a result of soft-tissue defects of the upper or lower extremities or the scalp. We transferred free adipofascial tissue overlying the serratus anterior muscle in three patients and both serratus anterior muscle and adipofascial tissue in four patients. A free adipofascial flap overlying serratus anterior muscle was transferred when a gliding surface was required, owing to the exposure of tendons and neurovascular structures. The average duration from operation to follow-up examination was 8 months (from 4 to 16 months). The results of the operations were satisfactory in functional and cosmetic aspects. This kind of flap was very effective in reconstruction of soft-tissue defects and gliding surfaces for these reasons: easy dissection, the capability of obtaining a long vascular pedicle, large-sized flap, composite flap including muscle or rib, and the fact that there was no serious functional or cosmetic deficit at the donor site.

Adult↗
PubMed1999

Effect of various ions, pH, and osmotic pressure on oxidation of elemental sulfur by Thiobacillus thiooxidans.

The oxidation of elemental sulfur by Thiobacillus thiooxidans was studied at pH 2.3, 4.5, and 7.0 in the presence of different concentrations of various anions (sulfate, phosphate, chloride, nitrate, and fluoride) and cations (potassium, sodium, lithium, rubidium, and cesium). The results agree with the expected response of this acidophilic bacterium to charge neutralization of colloids by ions, pH-dependent membrane permeability of ions, and osmotic pressure.

Acidithiobacillus thiooxidans↗
PubMed1999

The amino-terminal C/H1 domain of CREB binding protein mediates zta transcriptional activation of latent Epstein-Barr virus.

Latent Epstein-Barr virus (EBV) is maintained as a nucleosome-covered episome that can be transcriptionally activated by overexpression of the viral immediate-early protein, Zta. We show here that reactivation of latent EBV by Zta can be significantly enhanced by coexpression of the cellular coactivators CREB binding protein (CBP) and p300. A stable complex containing both Zta and CBP could be isolated from lytically stimulated, but not latently infected RAJI nuclear extracts. Zta-mediated viral reactivation and transcriptional activation were both significantly inhibited by coexpression of the E1A 12S protein but not by an N-terminal deletion mutation of E1A (E1ADelta2-36), which fails to bind CBP. Zta bound directly to two related cysteine- and histidine-rich domains of CBP, referred to as C/H1 and C/H3. These domains both interacted specifically with the transcriptional activation domain of Zta in an electrophoretic mobility shift assay. Interestingly, we found that the C/H3 domain was a potent dominant negative inhibitor of Zta transcriptional activation function. In contrast, an amino-terminal fragment containing the C/H1 domain was sufficient for coactivation of Zta transcription and viral reactivation function. Thus, CBP can stimulate the transcription of latent EBV in a histone acetyltransferase-independent manner mediated by the CBP amino-terminal C/H1-containing domain. We propose that CBP may regulate aspects of EBV latency and reactivation by integrating cellular signals mediated by competitive interactions between C/H1, C/H3, and the Zta activation domain.

Acetyltransferases↗
PubMed1999

Using the CLARION cochlear implant in cochlear ossification.

This paper is a retrospective review of 5 patients with various degrees of cochlear ossification who were implanted with the CLARION Multi-Strategy Cochlear Implant. Preoperative computed tomography scans, intraoperative findings, surgical technique, and hearing outcomes are discussed in a case report format. Full implantation was achieved in all cases by a systematic approach that included drill-through of proximal obstruction (2 cases), scala vestibuli insertion (2 cases), and complete drill-out (1 case). The only complication was delayed wound healing in a patient with sickle cell disease, chronic active hepatitis, and steroid dependency on antimetabolite therapy. Early results show that the 4 patients with at least 3 months of experience have a mean open-set sentence recognition score of 55% and a mean open-set word recognition score of 24%. The conclusion is that implantation of the Clarion device in ossified cochleas can be successful in all degrees of ossification and can provide significant hearing benefit.

Adolescent↗
PubMed1999

Occupational performance needs of a shelter population.

Practice in shelters for people who are homeless is an exciting and challenging opportunity for occupational therapists. However, there is a paucity of knowledge about the occupational performance needs of this population. In the present study, 25 persons at a shelter were interviewed using the Canadian Occupational Performance Measure (COPM). Data were analyzed using both qualitative and quantitative methods. Several major themes emerged including spirituality, "we want what everyone wants", choosing satisfaction, diverse health concerns, power of relationships, the importance of environment to well-being, and poverty. Altruism in the midst of adversity and individuality were minor themes. Instrumental activities of daily living, such as access to employment, financial management, housing, and recreation, were reported as more important than basic activities of daily living. Participants and interviewers also responded to general questions regarding the use of the COPM in the assessment process. The COPM was found to be useful for assessing the occupational performance needs of this population, but should be augmented by inquiry about environmental concerns, relationships, housing, and spirituality.

Adolescent↗
PubMed1999

Reduced visual evoked responses in multiple sclerosis patients with optic neuritis: comparison of functional magnetic resonance imaging and visual evoked potentials.

The limited application of functional magnetic resonance imaging (fMRI) for investigations of multiple sclerosis (MS) patients has already shown that deficits of the motor, cognitive and visual systems may be identified by differences in the patterns of activation in response to a suitable stimulus. In MS patients with unilateral optic neuritis, the area of activation in the primary visual cortex, measured by fMRI techniques, is dramatically reduced in response to stimulation of the affected eye. The latency of the major positive component of the visual evoked potential (VEP) recorded upon stimulation of the affected eye is significantly increased in these patients, as compared to the unaffected eye and normal volunteers. We have found a correlation between the neural response measured using fMRI and the latency of the VEP. fMRI signal responses have the potential to provide more detailed topographic information relating to functional deficits in MS.

Evoked Potentials, Visual↗
PubMed1999

D5 dopamine receptors mediate estrogen-induced stimulation of hypothalamic atrial natriuretic factor neurons.

Whereas progesterone and dopamine share a common central pathway to modulate sexual behavior in female rats, the way in which estrogen is involved remains unclear. In a long-term rat hypothalamic cell culture system, atrial natriuretic factor-producing neurons were identified as candidate sites for integration of sex steroid action. Estrogen induces the expression of progesterone receptors in atrial natriuretic factor neurons and also augments neuronal functions by increasing expression of constitutively active D5 receptors that generate cAMP in a ligand-independent manner. Such a cross-talk mechanism allows estrogen to exert its effects via the adenylyl cyclase-cAMP system by augmenting dopamine receptor activity, an action that may play an important integrative role in facilitating female sexual behavior.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1999

Free fatty acid-induced insulin resistance is associated with activation of protein kinase C theta and alterations in the insulin signaling cascade.

To examine the mechanism by which free fatty acids (FFAs) induce insulin resistance in vivo, awake chronically catheterized rats underwent a hyperinsulinemic-euglycemic clamp with or without a 5-h preinfusion of lipid/heparin to raise plasma FFA concentrations. Increased plasma FFAs resulted in insulin resistance as reflected by a approximately 35% reduction in the glucose infusion rate (P < 0.05 vs. control). The insulin resistance was associated with a 40-50% reduction in 13C nuclear magnetic resonance (NMR)-determined rates of muscle glycogen synthesis (P < 0.01 vs. control) and muscle glucose oxidation (P < 0.01 vs. control), which in turn could be attributed to a approximately 25% reduction in glucose transport activity as assessed by 2-[1,2-3H]deoxyglucose uptake in vivo (P < 0.05 vs. control). This lipid-induced decrease in insulin-stimulated muscle glucose metabolism was associated with 1) a approximately 50% reduction in insulin-stimulated insulin receptor substrate (IRS)-1-associated phosphatidylinositol (PI) 3-kinase activity (P < 0.05 vs. control), 2) a blunting in insulin-stimulated IRS-1 tyrosine phosphorylation (P < 0.05, lipid-infused versus glycerol-infused), and 3) a four-fold increase in membrane-bound, or active, protein kinase C (PKC) theta (P < 0.05 vs. control). We conclude that acute elevations of plasma FFA levels for 5 h induce skeletal muscle insulin resistance in vivo via a reduction in insulin-stimulated muscle glycogen synthesis and glucose oxidation that can be attributed to reduced glucose transport activity. These changes are associated with abnormalities in the insulin signaling cascade and may be mediated by FFA activation of PKC theta.

Animals↗
PubMed1999

Altered properties of neuronal sodium channels associated with genetic resistance to pyrethroids.

Genetic resistance to pyrethroid insecticides involves nervous system insensitivity linked to regulatory and structural genes of voltage-sensitive sodium channels. We examined the properties and relative density of sodium channels in central neurons of susceptible and pyrethroid-resistant (Pyr-R) insects that were homozygous for the amino acid substitution V421M in the I-S6 transmembrane segment. Pyr-R sodium channels show approximately 21-fold lower sensitivity to the synthetic pyrethroid permethrin and a approximately 2-fold increased sensitivity to the alpha-scorpion toxin LqhalphaIT. Pyr-R channels also exhibit altered gating properties, including a approximately 13 mV positive shift in voltage-dependent activation and approximately 7 mV positive shift in steady-state inactivation. Consistent with these changes in gating behavior, Pyr-R central neurons are less excitable, as evidenced by an approximately 11 mV elevation of action potential threshold. No differences in sodium channel density are evident. The altered properties of Pyr-R sodium channels provide a plausible molecular basis for nervous system insensitivity associated with pyrethroid resistance.

Animals↗
PubMed1999

Effects of Na-K-2Cl cotransport regulators on outflow facility in calf and human eyes in vitro.

PURPOSE: Cultured human trabecular meshwork (TM) cells possess substantial Na-K-Cl activity, which is involved in the regulation of TM cell volume. The hypothesis in the present study was that drugs that affect the cotransporter might alter aqueous humor outflow facility (C) in the intact eye. The effects of agents and conditions known to modulate Na-K-CI cotransport activity and/or TM cell volume on C in perfused anterior segments were investigated. METHODS: Human and calf eyes were dissected and perfused, and C was determined according to standard published methods. Perfusates with modified osmolarity were used to cause alterations in TM cell volume. Cl-free perfusate and/or bumetanide (10(-5) M) was used to inhibit Na-K-Cl cotransport activity, and vasopressin (10(-7) M, 10(-8) M) was used to stimulate cotransport activity. RESULTS: In human eyes, hypo-osmotic perfusate decreased C 12%, whereas hyper-osmotic perfusate increased C 44%. These changes lasted approximately 30 minutes, after which C began to normalize. Inhibition of Na-K-Cl cotransport using Cl-free medium or bumetanide resulted in facility increases of 27% and 22%, respectively. There was an additive increase in C with bumetanide plus Cl-free media. Stimulating Na-K-Cl cotransport with 10(-8)M and 10(-7)M vasopressin resulted in 28% and 35% decreases in C, respectively. The results were similar in calf eyes: Cl-free medium or bumetanide resulted in 41% and 52% increases in C, whereas 10(-8) M and 10(-7) M vasopressin resulted in 14% and 19% decreases in C, respectively. CONCLUSIONS: Modulation of Na-K-Cl cotransport results in changes in C that may be mediated in part by cell volume changes.

Aged↗
PubMed1999

Speech recognition after implantation of the ossified cochlea.

OBJECTIVE: Insertion of complex, multichannel cochlear implant (CI) electrode arrays into ossified cochleas is now performed routinely. This study describes the hearing results obtained in a consecutive series of 21 patients with obstructed cochleas and compares these results to those in patients with open cochleas. The purpose of this study was to determine whether patients with ossification have speech perception results that are inferior to those of patients with no evidence of cochlear bone formation. STUDY DESIGN: Retrospective analysis of consecutive clinical series. METHODS: CI database review of 191 CI procedures at the University of Miami Ear Institute between 1990 and 1997 showed that 24 (13%) procedures were performed on patients with ossified cochleas. Open-set speech recognition scores obtained on the 11 pediatric and 7 adult English-speaking patients are compared to scores of 51 adult and 61 pediatric English-speaking CI patients with open scala. RESULTS: Results of open-set speech recognition measures in adults and children with ossified cochleas were not significantly different from those of the reference groups. CONCLUSION: Speech recognition results of patients with ossified cochleas are essentially equal to those of patients with open cochleas. Degree of obstruction appears to have less effect on outcome than other factors such as duration of profound deafness or communication methodology in children among this group.

Adolescent↗
PubMed1999

Lysophosphatidylcholine induces arachidonic acid release and calcium overload in cardiac myoblastic H9c2 cells.

Lysophosphatidylcholine (lyso-PC) and arachidonate are products of phosphatidylcholine hydrolysis by phospholipase A(2). In this study, the modulation of arachidonate release by exogenous lyso-PC in rat heart myoblastic H9c2 cells was examined. Incubation of H9c2 cells with lyso-PC resulted in an enhanced release of arachidonate in both a time- and dose-dependent fashion. Lyso-PC species containing palmitoyl (C(16:0)) or stearoyl (C(18:0)) groups evoked the highest amount of arachidonate release, while other lysophospholipid species were relatively ineffective. Cells treated with phospholipase A(2) inhibitors resulted in the attenuation of the enhanced arachidonate release in the presence of lyso-PC. Lyso-PC caused the translocation of phospholipase A(2) from the cytosol to the membrane fraction and induced an increase in Ca2+ flux from the medium into the cells. Nimodipine, a specific Ca(2+)-channel blocker, partially attenuated the lyso-PC-induced rise in intracellular Ca2+. Concurrent with Ca2+ influx, lyso-PC caused an enhancement of protein kinase C activity. The lyso-PC-induced arachidonate release was attenuated when cells were pre-incubated with specific protein kinase C and mitogen activated protein kinase kinase inhibitors. Taken together, these results strongly indicate that the lyso-PC-induced increases in levels of intracellular calcium and stimulation of protein kinase C lead to the activation of cytosolic phospholipase A(2) which results in the enhancement of arachidonate release in H9c2 cells.

Animals↗
PubMed1999

Hearing results with deep insertion of cochlear implant electrodes.

OBJECTIVE: This study aimed to investigate the relationship of electrode insertion length and speech recognition in patients using Nucleus-22 cochlear implants. STUDY DESIGN: The study design was a retrospective review of a consecutive clinical series. SETTING: The study was conducted at an academic medical center. PATIENTS: Thirty-one postlingually deafened adults with at least 6 months' experience with a Nucleus-22 cochlear implant using Spectra-22 processor and SPEAK strategy participated. MAIN OUTCOME MEASURES: Open-set speech recognition scores for words and sentences were measured. RESULTS: Insertion length ranged from 22 rings (estimated 17 mm) to 32 rings (estimated 25 mm). Mean word recognition score was 35%. Mean sentence score was 69.6%. Statistical analysis showed no correlation between insertion depth and word or sentence scores. CONCLUSION: Insertion of the Nucleus-22 array beyond 22 rings does not improve performance in speech recognition. This finding cannot be generalized to other electrodes or processing strategies.

Adult↗