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Biomedical subjects

J Cheung

Publications and source records attributed to J Cheung.

At least 19 recordsLinked to original sources
PubMed2002

A new orthotic device in the non-operative treatment of idiopathic scoliosis.

A transverse force system, consisting of an anterior progression force counteracted by a posterior force and torque, acts on the vertebrae of a scoliotic spine. The aim of the newly introduced TriaC brace is to reverse this transverse force pattern by externally applied and constantly present orthotic forces. In the frontal plane the force system in the TriaC brace is in accordance with the force system of the conventional braces. However, in the sagittal plane the force system acts only in the thoracic region. As a result, there is no pelvic tilt, and it provides flexibility without affecting the correction forces during body motion. In the current preliminary study it is demonstrated that the brace prevents further progression of the Cobb angle and axial rotation in idiopathic scoliosis. The new brace has the added advantage of comfort for the wearer, and it offers a better cosmetic appearance, as well as, potentially, a better compliance.

Braces↗
PubMed2002

Isolation of various forms of sterol beta-D-glucoside from the seed of Cycas circinalis: neurotoxicity and implications for ALS-parkinsonism dementia complex.

The factors responsible for ALS-parkinsonism dementia complex (ALS-PDC), the unique neurological disorder of Guam, remain unresolved, but identification of causal factors could lead to clues for related neurodegenerative disorders elsewhere. Earlier studies focused on the consumption and toxicity of the seed of Cycas circinalis, a traditional staple of the indigenous diet, but found no convincing evidence for toxin-linked neurodegeneration. We have reassessed the issue in a series of in vitro bioassays designed to isolate non-water soluble compounds from washed cycad flour and have identified three sterol beta-d-glucosides as potential neurotoxins. These compounds give depolarizing field potentials in cortical slices, induce alterations in the activity of specific protein kinases, and cause release of glutamate. They are also highly toxic, leading to release of lactate dehydrogenase (LDH). Theaglycone form, however, is non-toxic. NMDA receptor antagonists block the actions of the sterol glucosides, but do not compete for binding to the NMDA receptor. The most probable mechanism leading to cell death may involve glutamate neuro/excitotoxicity. Mice fed cycad seed flour containing the isolated sterol glucosides show behavioral and neuropathological outcomes, including increased TdT-mediated biotin-dUTP nick-end labelling (TUNEL) positivity in various CNS regions. Astrocytes in culture showed increased caspase-3 labeling after exposure to sterol glucosides. The present results support the hypothesis that cycad consumption may be an important factor in the etiology of ALS-PDC and further suggest that some sterol glucosides may be involved in other neurodegenerative disorders.

Amyotrophic Lateral Sclerosis↗
PubMed2001

Overexpression of muscle specific kinase increases the transcription and aggregation of acetylcholine receptors in Xenopus embryos.

Muscle specific kinase (MuSK) mediates agrin-induced acetylcholine receptor (AChR) aggregation on muscle membrane at the neuromuscular junction (NMJ). To examine whether MuSK enhances NMJ formation during embryonic development in vivo, the level of expression of MuSK was manipulated in Xenopus embryos and the functional consequence at the NMJ was assessed. We found that overexpression of MuSK enhanced the formation of NMJ by increasing the aggregation of AChRs at innervated regions in developing embryos. The area of AChR aggregation increased by approximately 2-fold in MuSK injected embryos during the critical stages of NMJ formation. Interestingly, overexpression of MuSK in Xenopus embryos was found to induce the level of AChR transcript. Deletion of the Kringle domain in the MuSK construct did not attenuate the observed induction of AChR transcription and aggregation. Taken together, our findings provide the first demonstration that increased level of MuSK expression in vivo significantly elevate the aggregation and transcription of AChR at the NMJ in developing Xenopus embryos.

Animals↗
PubMed2001

Discovery of the human genome sequence in the public and private databases.

Genomes: Much heat has been generated in discussions about the key human genome sequence databases, generated by the Human Genome Project and Celera, and what specific features each offers genome researchers. Stephen W. Scherer and Joseph Cheung, who are intense users of both, offer a personal assessment of the developing contents.

Animals↗
PubMed2001

The expression profiles of neurotrophins and their receptors in rat and chicken tissues during development.

Neurotrophic factors are target-derived proteins that promote the survival and differentiation of the innervating neurons. Increasing evidence indicate the involvement of these factors and receptors during the formation and maturation of the neuromuscular junction. To gain further insight on the expression pattern of these factors and receptors in developing spinal cord and skeletal muscle during the critical stages of synapse formation, a systematic study was performed with chicken and rat tissues using Northern blot analysis. The expression of all the neurotrophins was detected in skeletal muscle early in development, coincidental with the appearance of their corresponding receptors in the spinal cord. Taken together, the similar regulatory patterns observed in both rat and chicken tissues suggest that the potential roles of neurotrophins at the neuromuscular synapse are conserved throughout evolution.

Animals↗
PubMed2001

Disruption of a novel gene (IMMP2L) by a breakpoint in 7q31 associated with Tourette syndrome.

Gilles de la Tourette syndrome (GTS) is a complex neuropsychiatric disorder characterized by multiple motor and phonic tics. We identified a male patient with GTS and other anomalies. It was determined that he carried a de novo duplication of the long arm of chromosome 7 [46,XY,dup(7)(q22.1-q31.1)]. Further molecular analysis revealed that the duplication was inverted. The distal chromosomal breakpoint occurred between the two genetic markers D7S515 and D7S522, which define a region previously shown to be disrupted in a familiar case of GTS. Yeast and bacterial artificial chromosome clones spanning the breakpoints were identified by means of FISH analysis. To further characterize the distal breakpoint for a role in GTS, we performed Southern blot hybridization analysis and identified a 6.5-kb SacI junction fragment in the patient's genomic DNA. The DNA sequence of this fragment revealed two different breaks in 7q31 within a region of approximately 500 kb. IMMP2L, a novel gene coding for the apparent human homologue of the yeast mitochondrial inner membrane peptidase subunit 2, was found to be disrupted by both the breakpoint in the duplicated fragment and the insertion site in 7q31. The cDNA of the human IMMP2L gene was cloned, and analysis of the complete 1,522-bp transcript revealed that it encompassed six exons spanning 860 kb. The possible role of IMMP2L and several other candidate genes within the region of chromosomal rearrangement, including NRCAM, Leu-Rch Rep, and Reelin, is discussed. The 7q31 breakpoint interval has also been implicated in other neuropsychiatric diseases that demonstrate some clinical overlap with GTS, including autism and speech-language disorder.

Adolescent↗
PubMed2001

Identification of the human cortactin-binding protein-2 gene from the autism candidate region at 7q31.

Human chromosome 7q31 contains putative susceptibility loci for autism (AUTS1) and speech and language disorder (SPCH1). We report here the identification and characterization of a novel gene encoding cortactin-binding protein-2 (CORTBP2), which is located 45 kb telomeric to the cystic fibrosis transmembrane conductance regulator gene (CFTR) at 7q31.3. The full-length (5975-bp) gene was isolated and found to be composed of 23 exons encompassing 170 kb of DNA. In addition to being a positional candidate for AUTS1, CORTBP2 was expressed at highest levels in the brain, as shown by northern blot analysis. Subsequent mutation analysis of CORTBP2 in 90 autistic patients identified two polymorphisms, including a leucine to valine change caused by a T to G substitution in exon 15. However, comparison of allele frequencies between autistic and control populations (n=96) showed no significant difference, suggesting that this variant is not a susceptibility factor for autism.

Amino Acid Sequence↗
PubMed2001

Expression of Eph receptors in skeletal muscle and their localization at the neuromuscular junction.

The participation of ephrins and Eph receptors in guiding motor axons during muscle innervation has been well documented, but little is known about their expression and functional significance in muscle at later developmental stages. Our present study investigates the expression and localization of Eph receptors and ephrins in skeletal muscle. Prominent expression of EphA4, EphA7, and ephrin-A ligands was detected in muscle during embryonic development. More importantly, both EphA4 and EphA7, as well as ephrin-A2, were localized at the neuromuscular junction (NMJ) of adult muscle. Despite their relative abundance, they were not localized at the synapses during embryonic stages. The concentration of EphA4, EphA7, and ephrin-A2 at the NMJ was observed at postnatal stages and the synaptic localization became prominent at later developmental stages. In addition, expression of Eph receptors was increased by neuregulin and after nerve injury. Furthermore, we demonstrated that overexpression of EphA4 led to tyrosine phosphorylation of the actin-binding protein cortactin and that EphA4 was coimmunoprecipitated with cortactin in muscle. Taken together, our findings indicate that EphA4 is associated with the actin cytoskeleton. Since actin cytoskeleton is critical to the formation and stability of NMJ, the present findings raise the intriguing possibility that Eph receptors may have a novel role in NMJ formation and/or maintenance.

Aging↗
PubMed2001

Relation between sodium-lithium countertransport and hypertriglyceridemia in type V hyperlipidemia.

Sodium-lithium countertransport (SLC) kinetics were measured in 30 patients with type V hyperlipidemia, 30 patients with type IIB hyperlipidemia on similar treatment, and 30 age- and sex-matched healthy controls. Clinical and laboratory data including basic anthropometry and blood pressure were obtained and blood was taken for detailed lipid biochemistry, glucose, insulin, and leptin measurements. Patients with type V hyperlipidemia were normotensive but more obese than controls, had elevated triglycerides, very low-density lipoprotein, glucose, and insulin; and reduced HDL cholesterol compared with type IIb controls. The median SLC activity (0.23 v 0.21 mmol Li+/L RBC/h) and median maximal velocity (0.33 v 0.31 mmol Li+/L RBC/h) were increased, but not significantly, compared to controls. In patients with type V hyperlipidemia SLC maximal velocity correlated with log triglycerides (r2 = 0.853; P < .001) and log very low-density lipoprotein (VLDL) triglycerides (r2 = 0.947; P < .001). Sodium-lithium countertransport maximal velocity correlated weakly with the homeostasis model assessment index of insulin resistance (r2 = 0.224; P = .06). The sodium affinity of the transporter did not differ between the groups and was independent of any of clinical or biochemical parameter studied. We conclude that VLDL triglyceride is strongly correlated with SLC maximal velocity and activity in patients with type V hyperlipidemia.

Adult↗
PubMed2001

IL-25 induces IL-4, IL-5, and IL-13 and Th2-associated pathologies in vivo.

We have characterized a cytokine produced by Th2 cells, designated as IL-25. Infusion of mice with IL-25 induced IL-4, IL-5, and IL-13 gene expression. The induction of these cytokines resulted in Th2-like responses marked by increased serum IgE, IgG(1), and IgA levels, blood eosinophilia, and pathological changes in the lungs and digestive tract that included eosinophilic infiltrates, increased mucus production, and epithelial cell hyperplasia/hypertrophy. In addition, our studies show that IL-25 induces Th2-type cytokine production by accessory cells that are MHC class II(high), CD11c(dull), and lineage(-). These results suggest that IL-25, derived from Th2 T cells, is capable of amplifying allergic type inflammatory responses by its actions on other cell types.

Amino Acid Sequence↗
PubMed2001

Medical informatics--the state of the art in the Hospital Authority.

Since its inception in 1990, the Hospital Authority (HA) has strongly supported the development and implementation of information systems both to improve the delivery of care and to make better information available to managers. This paper summarizes the progress to date and discusses current and future developments. Following the first two phases of the HA information technology strategy the basic infrastructural elements were laid in place. These included the foundation administrative and financial systems and databases; establishment of a wide area network linking all hospitals and clinics together; laboratory, radiology and pharmacy systems with access to results in the ward. A major push into clinical systems began in 1994 with the clinical management system (CMS), which established a clinical workstation for use in both ward and ambulatory settings. The CMS is now running at all major hospitals, and provides single logon access to almost all the electronically collected clinical data in the HA. The next phase of development is focussed on further support for clinical activities in the CMS. Key elements include the longitudinal electronic patient record (ePR), clinical order entry, generic support for clinical reports, broadening the scope to include allied health and the rehabilitative phase, clinical decision support, an improved clinical documentation framework, sharing of clinical information with other health care providers and a comprehensive data repository for analysis and reporting purposes.

China↗
PubMed2001

Cdk5 is involved in neuregulin-induced AChR expression at the neuromuscular junction.

Here we describe an important involvement of Cdk5/p35 in regulating the gene expression of acetylcholine receptor (AChR) at the neuromuscular synapse. Cdk5 and p35 were prominently expressed in embryonic muscle, and concentrated at the neuromuscular junction in adulthood. Neuregulin increased the p35-associated Cdk5 kinase activity in the membrane fraction of cultured C2C12 myotubes. Co-immunoprecipitation studies revealed the association between Cdk5, p35 and ErbB receptors in muscle and cultured myotubes. Inhibition of Cdk5 activity not only blocked the NRG-induced AChR transcription, but also attenuated ErbB activation in cultured myotubes. In light of our finding that overexpression of p35 alone led to an increase in AChR promoter activity in muscle, Cdk5 activation is sufficient to mediate the up-regulation of AChR gene expression. Taken together, these results reveal the unexpected involvement of Cdk5/p35 in neuregulin signaling at the neuromuscular synapse.

Animals↗
PubMed2001

Hospital utilisation expectancies in New Zealand, 1980-98.

The need to synthesise mortality and morbidity information to achieve a more global and relevant measure of population health status is well recognised, with health expectancy indices being the most common approach used to date. Using New Zealand hospital discharge and mortality data over the 1980-98 period, we introduce readers to a newly developed health index, the Hospital Utilisation Expectancy (HUE). We describe how HUE changes with age and over time. New Zealand national and regional trends are described. The methodological strengths of the measure and its applications in the health sector are discussed.

Adolescent↗
PubMed2000

Cloning and characterization of muscle-specific kinase in chicken.

Muscle-specific kinase (MuSK) is part of the receptor complex that is involved in the agrin-induced formation of the neuromuscular junction. In the rodent, prominent mRNA expression of MuSK is restricted to skeletal muscle while the expression of agrin can also be detected in brain and certain nonneuronal tissues. The recent identification of Xenopus MuSK reveals that MuSK can be detected in tissues other than skeletal muscle, such as the neural tube, eye vesicles, and spleen. In this study, we describe the cloning and characterization of the chicken ortholog of MuSK and demonstrate that the regulation of MuSK expression in muscle is conserved from avian to rodent. Abundant mRNA expression of MuSK can be detected in early embryonic chick muscle and is up-regulated after nerve injury. More importantly, we also demonstrate that, in the chicken, MuSK mRNA is expressed during development in brain and liver, suggesting possible novel functions for MuSK. Furthermore, the regulatory profile of MuSK expression in chick muscle closely parallels that observed for acetylcholine receptor, in terms of both mRNA expression and protein localization. Finally, studies with paralyzed chicken muscle as well as with cultured chick myotubes demonstrate the dependence of MuSK on both electrical activity and trophic factors.

Animals↗
PubMed2000

Effects of lipids in patients with familial hypercholesterolaemia on the kinetics of the sodium-lithium countertransporter.

Sodium-lithium countertransport kinetics were measured in 87 patients (50 male; 37 female) with heterozygous familial hypercholesterolaemia (FH) and a group of 38 age range and sex-distribution matched controls. Basic clinical data including basic anthropometry, blood pressure were obtained and blood was taken for detailed lipid biochemistry, glucose and insulin measurement. Patients with FH had elevated total cholesterol, low-density lipoprotein (LDL)-cholesterol and apolipoprotein B concentrations compared to controls. The activity and log transformed maximal velocity (Vmax) of the sodium-lithium countertransporter unlike the affinity (Km) were reduced in patients with FH compared to controls (geometric means 0.172 vs 0.217 mmol Li+/L.RBC.hr; P = 0.02; 0.237 vs. 0.317 mmol Li+/L.RBC.hr; P = 0.009 respectively). In multiple regression analysis, log normalised SLC activity correlated weakly with log triglyceride (beta = 0.225; P = 0.06) and cholesterol (beta = -0.112 P = 0.06). Log Vmax correlated with log triglyceride (beta = 0.307; P = 0.02), and high-density lipoprotein (HDL) (beta = 0.74; P = 0.03) whilst Km correlated with HDL (beta = 1.73; P<0.001) and apoAI (beta = -1.76; P = 0.0048), LDL (beta = -0.14; P = 0.05), and creatine kinase (beta = 0.003; P = 0.01). Cholesterol and triglyceride concentrations rather than insulin resistance seem to be the key features affecting the environmental alteration of sodium lithium countertransporter Vmax in patients with familial hypercholesterolaemia.

Adult↗