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Biomedical subjects

S K Wu

Publications and source records attributed to S K Wu.

At least 19 recordsLinked to original sources
PubMed2001

Factors influencing sport participation among athletes with spinal cord injury.

OBJECTIVE: This exploratory study examined the relationships between pre- and post-injury sport participation among active individuals with spinal cord injury (SCI) in the United Kingdom. In particular, factors that influence individuals with SCI into sport were identified. METHODS: A total of 143 British individuals with SCI currently participating in wheelchair basketball, wheelchair rugby, wheelchair tennis, and wheelchair athletics were recruited. A total of 112 subjects were active prelesion, and 31 subjects were inactive preinjury. A Disability Sport Participation questionnaire developed by the authors was used for data collection. The questionnaire was distributed through the British Wheelchair Sport Associations. Personal, impairment, health and fitness, socialization, and participation data of athletes with SCI were collected. Groups of active preinjury and inactive preinjury were compared. RESULTS: For athletes who had been active pre-SCI, the in-hospital rehabilitation program and specialized sport club for people with disabilities were more important contexts for introducing the sport after injury to individuals. Friends and peers with disabilities were much more influential as initial and continuing socialization agents than rehabilitation therapists. The main reasons for athletes with SCI who participated in sports after injury were for fitness, fun, health, and competition, although many athletes noted that social aspects and rehabilitation also influenced their sport participation. CONCLUSION: This study identified social contexts, social agents, difficulties, sources of information, and reasons for sport participation of athletes with SCI. The results may offer some directions for the improvement of rehabilitation programs for people with SCI and also help the development of appropriate strategies to encourage people with SCI to participate in sports and leisure activities.

Adult↗
PubMed2001

Comparison of ball-and-racquet impact force between two tennis backhand stroke techniqes.

STUDY DESIGN: A mixed design for kinetic comparison of 2 types of one-handed backhand strokes and 2 skill levels in tennis. OBJECTIVES: To develop and evaluate a model to estimate the impact force on the racquet during tennis stroke, and to compare the peak impact force between one-handed backhand stroke with a long backswing and one-handed backhand stroke with a short backswing and between the beginning and advanced players. BACKGROUND: A one-handed backhand stroke is commonly used in tennis and may be associated with many upper extremity over-use injuries. An understanding of kinetics of the backhand stroke is essential for understanding injury mechanisms and prevention. METHODS AND MEASURES: Five male advanced tennis players and 4 male and 1 female beginning tennis players participated. Mean age was 32.2 +/- 7.0 years. Each subject was instructed to use the 2 types of one-handed backhand strokes to hit balls from a tennis ball machine. Three-dimensional coordinates of critical body and racquet landmarks were obtained. A mathematical model was developed to estimate the contact duration and the peak impact force during a stroke. RESULTS: The estimated peak impact forces were reproducible and comparable to those reported in the literature from direct measurements. A one-handed backhand stroke with a short backswing had a significantly shorter contact duration (0.008 +/- 0.003 seconds) and a greater peak resultant impact force (330.0 +/- 140.7) than that with a long backswing (0.016 +/- 0.004 seconds and 180.8 +/- 49.1 N). Skill level did not significantly affect the peak resultant impact force. CONCLUSION: A long backswing in a one-handed backhand stroke may reduce the load on the upper extremity and may assist in reducing the risks of tennis-related upper extremity over-use injuries.

Adult↗
PubMed2001

Classifiers and social control in wheelchair rugby.

The purpose of this study was to examine the features of wheelchair rugby classifiers in order to maintain social control in wheelchair rugby. The examination centered on the theme-resources used by classifiers to maintain the authority of International Wheelchair Rugby Federation (IWRF). Data were collected using participant observation methodology at national and international wheelchair rugby championships and a survey of the 14 IWRF authorized classifiers. The results of this study identified five essential features of IWRF classifiers. In particular, they need to have a background in medicine or physical therapy. In addition, IWRF classifiers use their medical and sporting knowledge and experience to control the wheelchair rugby classification process and to maintain fairness of competition. The results of this study may help to train Taiwanese professionals with medical or sporting backgrounds to become international classifiers and also to develop appropriate training programs for national classifiers.

Classification↗
PubMed2001

The prevalence and distribution of bone defects in patients with moderate to advanced periodontitis.

BACKGROUND: Alveolar bone defect is one of the common features of periodontitis and may vary in its form, extent, and distribution among teeth and individuals. The purpose of this study was to analyze the prevalence and distribution of different forms of bone defects in Taiwanese patients with moderate to advanced periodontitis. METHODS: One hundred and thirty-seven Taiwanese patients with moderate to advanced periodontitis comprising a total sample of 3542 teeth were studied. During periodontal surgery, osseous defects were explored and classified as interproximal crater, 1-wall, 2-wall, 3-wall, hemiseptal and circumferential defects. Among them, some were also recorded as complicated defects. RESULTS: Among 3542 existing teeth, 1376 were examined surgically and 483 teeth had bone defects. There was an increase in bone defects from anterior to posterior. The frequencies of defects in anterior and posterior segments were significantly different. More defects were found on the right side than on the left side. Yet there was no difference between the maxillary and mandibular arch. Interproximal surfaces of the first and second molars had the highest prevalence of bone defects. Crater was the most common defect type (26.50%), followed by circumferential (23.40%) and 3-wall defect (20.08%). More than 40% also presented with complicated defects. CONCLUSIONS: There was an increase in bone defects from anterior to posterior. Interproximal aspects were more frequently involved than buccal or lingual aspects. Crater, circumferential and 3-wall defects were more common than other defect types. The treatment of complicated defects, which comprise over 40% of all defects, presents a challenging task for periodontists.

Adult↗
PubMed1999

Biopharmaceutics of transmucosal peptide and protein drug administration: role of transport mechanisms with a focus on the involvement of PepT1.

Non-invasive delivery of peptide and protein drugs will soon become a reality. This is due partly to a better understanding of the endogenous transport mechanisms, including paracellular transport, endocytosis, and carrier-mediated transport of mucosal routes of peptide and protein drug administration. This paper focuses on work related to the elucidation of structure-function, intracellular trafficking, and regulation of the intestinal dipeptide transporter, PepT1.

Biological Transport↗
PubMed1998

Molecular role for the Rab binding platform of guanine nucleotide dissociation inhibitor in endoplasmic reticulum to Golgi transport.

Guanine nucleotide dissociation inhibitor (GDI) regulates the recycling of Rab GTPases involved in vesicle targeting and fusion. We have analyzed the requirement for conserved amino acid residues in the binding of Rab1A and the function of GDI in transport of cargo between the endoplasmic reticulum (ER) and the Golgi apparatus. Using a new approach to monitor GDI-Rab interactions based on the change in fluorescence associated with the release of methylanthraniloyl guanosine di(tri)phosphate-GDP (mGDP) from Rab, we show that residues previously implicated in the binding of the synapse-specific Rab3A, including Gln-236, Arg-240, and Thr-248, are essential for the binding of Rab1A. Mutation of each of these residues has potent effects on the ability of GDI to remove Rab1A from membranes and inhibit ER to Golgi transport in vitro. Given the sequence divergence between Rab1A and 3A (35% identity), these residues are proposed to play a general role in GDI function in the cell. In contrast, several other residues found within or flanking the Rab-binding region were found to have differential effects in the recognition and recycling of Rab1A and 3A, and therefore direct selective interaction of GDI with individual Rab proteins. Intriguingly, mutation of one residue, Arg-70, led to a reduction of Rab1A binding, failed to extract Rab1A from membranes in vitro, yet bound membranes tightly and potently inhibited ER to Golgi transport. These results provide evidence that novel membrane-associated factor(s) mediate Rab-independent GDI interaction with membranes.

Biological Transport↗
PubMed1998

Molecular identification of a role for tyrosine 167 in the function of the human intestinal proton- coupled dipeptide transporter (hPepT1).

hPepT1 is a proton-coupled peptide transporter that mediates the absorption of di- and tripeptides. Here we show that tyrosine 167 (Y167) in transmembrane domain 5 (TMD5) of this 12-transmembrane spanning protein contributes to its transport function. We identified this particular amino acid by a computer model of the arrangement of the TMDs of hPepT1 and investigated its role by site-directed mutagenesis and dipeptide uptake studies. [3H]Gly-sar uptake in cells transiently transfected with Y167A-hPepT1 was abolished completely, even though the level of Y167A-hPepT1 expression by Western blot analysis and cell surface expression by immunofluorescence microscopy was similar to those of the wild type. Therefore, mutation affected transport function, but apparently not the steady-state protein level or trafficking of the transporter to the plasma membrane. Moreover, mutation of Y167 into phenylalanine, serine, or histidine all abolished gly-sar uptake in transfected HEK 293 cells. Taken together, these findings suggest that Y167 plays an essential role in hPepT1 function, perhaps due to the unique chemistry of its phenolic side chain.

Blotting, Western↗
PubMed1998

Dihydroorotate dehydrogenase inhibitors: quantitative structure-activity relationship analysis.

PURPOSE: The main purpose of this study is to analyze the quantitative structure-activity relationship of two series of dihydroorotate dehydrogenase inhibitors (leflunomide and quinoline carboxylic acid analogues), and to determine the structural requirements for optimum activity of these analogues. METHODS: A new CQSAR program was used in deriving regression equations and calculating the octanol/water partition coefficient and the molar refractivity values. The molecular modeling was performed using the HyperChem program. RESULTS: Statistically significant correlations were obtained using a combination of 3-4 parameters. The structural requirements for optimum activity and critical regions for the inhibitory activity of dihydroorotate dehydrogenase were identified. CONCLUSIONS: The quantitative structure-activity relationship analysis demonstrated that two series of dihydroorotate dehydrogenase inhibitors may bind to different binding sites on the enzyme. These results provide a better understanding of dihydroorotate dehydrogenase inhibitor-enzyme interactions, and may be useful for further modification and improvement of inhibitors of this important enzyme.

Animals↗
PubMed1998

Mutations in GDI1 are responsible for X-linked non-specific mental retardation.

Rab GDP-dissociation inhibitors (GDI) are evolutionarily conserved proteins that play an essential role in the recycling of Rab GTPases required for vesicular transport through the secretory pathway. We have found mutations in the GDI1 gene (which encodes uGDI) in two families affected with X-linked non-specific mental retardation. One of the mutations caused a non-conservative substitution (L92P) which reduced binding and recycling of RAB3A, the second was a null mutation. Our results show that both functional and developmental alterations in the neuron may account for the severe impairment of learning abilities as a consequence of mutations in GDI1, emphasizing its critical role in development of human intellectual and learning abilities.

Brain↗
PubMed1997

Cutaneous sinus tract caused by vertical root fracture.

This report presents a rare case of odontogenic cutaneous sinus tract caused by a vertical root fracture. The root-fractured molar was probably caused by an accidental blow by a cow 3 years ago. Despite all treatments by physicians and surgeons for nearly 1 year, the sinus tract recurred repeatedly. After diagnosis and extraction of the fractured molar by the dentist, the sinus tract healed uneventfully in a month.

Adult↗
PubMed1997

Mss4 does not function as an exchange factor for Rab in endoplasmic reticulum to Golgi transport.

Mss4 and its yeast homologue, Dss4, have been proposed to function as guanine nucleotide exchange factors (GEFs) for a subset of Rab proteins in the secretory pathway. We have previously shown that Rab1A mutants defective in GTP-binding potently inhibit endoplasmic reticulum to Golgi transport, presumably by sequestering an unknown GEF regulating its function. We now demonstrate that these mutants stably associate with Mss4 both in vivo and in vitro and that Mss4 effectively neutralizes the inhibitory activity of the Rab1A mutants. An equivalent Rab3A mutant (Rab3A[N135I]), a Rab protein specifically involved in regulated secretion at the cell surface, associates with Mss4 as efficiently as the Rab1A[N124I] mutant. Although Rab3A[N135I] prevents the ability of Mss4 to neutralize the inhibitory effects of Rab1A mutants on transport, it has no effect on Rab1 function or endoplasmic reticulum to Golgi transport. Furthermore, quantitative immunodepletion of Mss4 fails to inhibit transport in vitro. We conclude that Mss4 and its yeast homologue, Dss4, are not GEFs mediating activation of Rab, but rather, they interact with the transient guanine nucleotide-free state, defining a new class of Ras-superfamily GTPase effectors that function as guanine nucleotide-free chaperones (GFCs).

Biological Transport↗
PubMed1996

Structure and mutational analysis of Rab GDP-dissociation inhibitor.

The crystal structure of the bovine alpha-isoform of Rab GDP-dissociation inhibitor (GDI), which functions in vesicle-membrane transport to recycle and regulate Rab GTPases, has been determined to a resolution of 1.81 A. GDI is constructed of two main structural units, a large complex multisheet domain I and a smaller alpha-helical domain II. The structural organization of domain I is surprisingly closely related to FAD-containing monooxygenases and oxidases. Sequence-conserved regions common to GDI and the choroideraemia gene product, which delivers Rab to catalytic subunits of Rab geranylgeranyltransferase II, are clustered on one face of the molecule. The two most sequence-conserved regions, which form a compact structure at the apex of GDI, are shown by site-directed mutagenesis to play a critical role in the binding of Rab proteins.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Structural insights into the function of the Rab GDI superfamily.

The 1.81 A crystal structure of Rab GDP-dissociation inhibitor (GDI), a protein that plays a critical role in the recycling of Rab GTPases involved in membrane vesicular transport, has been recently determined. Biochemical studies implicate a highly conserved region involved in Rab binding, which is common to both GDI and the evolutionarily-related choroideremia gene product (CHM/REP) required for Rab prenylation. Here, we summarize the mechanisms by which members of the GDI superfamily might function to coordinate events leading to membrane fusion, and we discuss the unexpected, yet striking structural homology of GDI to FAD-binding proteins.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Induction of superoxide dismutase isozymes by tumor necrosis factor-alpha and lipopolysaccharide in cultured normal and hyperplastic gingival fibroblasts.

To determine whether lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF-alpha) are involved in the induction of superoxide dismutase (SOD) in gingival tissue, we examined their effect on induction of SOD isozymes in cultured normal (NGF) and phenytoin-induced hyperplastic (PHF) gingival fibroblasts. Treatment of both NGFs and PHFs with 10 to 50 ng/mL TNF-alpha for 24 hours increased the level of manganese SOD (MnSOD) to as much as four times the level of untreated cultures. PHFs, but not NGFs, were shown to be responsive to TNF-alpha in eliciting a significant increase in copper-zinc SOD (Cu/ZnSOD), albeit in a lesser amount than MnSOD. Additionally, treatment of both types of cells with 5 to 50 mg/mL of LPS for 24 hours also elicited an increase in the levels of MnSOD. Again, an LPS-induced increase in Cu/ZnSOD levels could only be demonstrated in PHFs, but not in NGFs. These observations were further confirmed by comparing the achromatic bands associated with SOD isozymes exhibited in the electrophoretogram using a nondenaturing polyacrylamide electrophoresis technique. These results indicate that TNF-alpha and LPS were capable of inducing both MnSOD and Cu/ZnSOD simultaneously in PHF fibroblasts. PHFs may be inherently more capable than NGFs in combating oxidative stress.

Anticonvulsants↗
PubMed1995

A structure-function study of bovine pancreatic phospholipase A2 using polymerized mixed liposomes.

A new combinatorial approach that includes the genetic variation of protein structure and the chemical modification of phospholipid structure in polymerized mixed liposomes was used to delineate the structure-function relationships in the interfacial catalysis of bovine pancreatic phospholipase A2 (PLA2). Based on previous structural and mutational studies, several bovine PLA2 mutants were generated in which a positive charge of putatively important lysyl side chains was reversed (K10E, K53E, K56E, and K116E) or neutralized (K56Q and K116Q). Kinetic parameters of bovine wild type and mutant PLA2s determined using polymerized mixed liposomes consisting of 1-hexadecanoyl-2-(1-pyrenedecanoyl)-sn-glycero-3-phosphoethanolamine (or -phosphoglycerol) and 1,2-bis[12-(lipoyloxy)dodecanoyl]-sn-glycero-3-phosphoglycerol showed that Lys-53 is involved specifically in the interaction with a substrate bound in the active site. Also, these results showed that Lys-10 and Lys-116 are involved in the interaction of bovine PLA2 with anionic interfaces but not in the interaction with the active site-bound substrate. In particular, Lys-116 makes more significant contribution than Lys-10 by approximately 1.0 kcal/mol to the binding to anionic interfaces. Most importantly, Lys-56 was shown to participate in the interaction with both the active site-bound substrate and anionic interfaces. These findings establish Lys-56 and Lys-116 as essential residues for the binding of bovine pancreatic PLA2 to anionic interfaces. Lastly, our structure-function analysis based on the use of polymerized mixed liposomes was further supported by equilibrium binding measurements of these proteins using 1,2-bis[12-(lipoyloxy)dodecanoyl]-sn-glycero-3-phosphoglycerol polymerized liposomes and by kinetic analyses using monomeric substrates, 1,2-dihexanoyl-sn-glycero-3-phosphoethanolamine and -phosphoglycerol.

Animals↗
PubMed1994

Effects of specific fatty acid acylation of phospholipase A2 on its interfacial binding and catalysis.

Monomeric phospholipase A2 (PLA2) from the venom of Agkistrodon piscivorus piscivorus (App-D49) was treated with 3-acyloxy-4-nitrobenzoic acids to acylate the epsilon-amino groups of two lysines (Lys-7 and Lys-10) in the amino terminal region. Resulting 7,10-diacylated-App-D49s, with acyl groups ranging from lauroyl to palmitoyl, spontaneously aggregated in solution. By contrast, 7,10-dioctanoyl-App-D49 existed as a monomer under the same condition. Kinetic and interfacial binding properties of diacylated enzymes indicated that they catalyzed the hydrolysis at the interface as a monomer. When compared to nonacylated App-D49, diacylated enzymes showed slightly increased activity or decreased activity toward monodispersed 1,2-dibutyryl-sn-glycero-3-phosphocholine, Triton X-100/1,2-dilauroyl-sn-glycero-3-phosphocholine mixed micelles, and small unilamellar vesicles (SUV) of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Toward densely-packed liquid-crystalline phospholipid bilayers, such as large unilamellar vesicles (LUV) of POPC, however, diacylated enzymes exhibited a large increase in activity, which reacted up to 250-fold for 7,10-dilauroyl-App-D49 ((kcat/Km)app = (1.0 +/- 0.02) x 10(6) M-1 s-1). Measurements of the penetration of individual diacylated enzymes into 2-oleoyl-3-palmitoyl-sn-glycero-1-phosphocholine (i.e., D-POPC) monolayers indicated that the acyl groups enhanced the interfacial binding of protein by interacting with hydrocarbon moieties of phospholipids and that these hydrophobic interactions remained effective even when the phospholipid packing density was high. Furthermore, fluorometric measurements of the binding of diacylated enzymes to polymerized vesicles of 1,2-bis[12-(lipoyloxy)dodecanoyl]-sn-glycero-3-phosphocholine showed that the hydrophobic interactions increased the enzymatic activity toward LUV by accelerating the migration of enzyme molecules to vesicle surfaces. The analysis of the kinetic course of POPC LUV hydrolysis showed that diacylated enzymes as a catalyst were superior to nonacylated App-D49 in that they were not only more catalytically efficient but also able to catalyze more turnovers without being trapped in product-containing vesicles. In summary, the acylation of App-D49 by 3-acyloxy-4-nitrobenzoic acids provides a simple and convenient way of converting the enzyme into a highly active form toward densely-packed liquid-crystalline phospholipid bilayers, which might have potential industrial and biomedical applications.

Acylation↗
PubMed1994

A continuous fluorometric assay for phospholipases using polymerized mixed liposomes.

A versatile continuous fluorometric assay for phospholipases A2, C, and D has been developed utilizing polymerized mixed liposomes made of pyrene-containing phospholipids (5 mol%) uniformly inserted in the polymerized liposomes of 1,2-bis[12-(lipoyloxy)dodecanoyl]-sn-glycero-3-phosphoglycerol (BLPG) and its derivatives. 1-Hexadecanoyl-2-(1-pyrenedecanoyl)-sn-glycero-3-phosphocholine was used for phospholipase A2 and N-(1-pyrenesulfonyl)-egg phosphatidyl ethanolamine for phospholipases C and D. Fluorescence emission of pyrene moieties in polymerized mixed liposomes was strongly quenched by BLPG molecules and, thus, the hydrolysis of pyrene-containing phospholipids and the subsequent displacement of pyrene moieties from the liposomes resulted in a large increase in fluorescence intensity. All the phospholipases tested selectively and rapidly hydrolyzed the inserted pyrene-containing phospholipids, which were readily monitored by measuring an increase in fluorescence emission at 380 nm. Assay conditions for individual phospholipases were optimized by altering interfacial properties of polymerized liposomes, such as surface charge, and subsequently by changing the chemical structure of hydrolyzable phospholipids. Phospholipase activities were linearly proportional to enzyme concentrations in the range from 0.1 to 50 ng. Specific activity determined for phospholipases from a wide variety of sources ranged from 0.5 to 100 mumol/min/mg. Polymerized mixed liposomes are exceptionally stable against chemical and physical degradation and the assay requires only a small amount of pyrene-containing phospholipids. In addition, the polymerized matrix of BLPG (and its derivatives), due to its inertness to the phospholipase hydrolysis, allows the direct measurement of the equilibrium dissociation constant for a protein-liposome complex.

Fluorometry↗