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Biomedical subjects

L Wong

Publications and source records attributed to L Wong.

At least 91 records · Page 5Linked to original sources
PubMed1998

Butyl-2-cyanoacrylate fixation of mandibular osteotomies.

Butyl-2-cyanoacrylate is an easily applied, bioresorbable, noninfective glue that may provide an alternative to conventional craniofacial fixation techniques. Recent studies have demonstrated that the healing and strength of glue fixation of bone fragments in the craniofacial skeleton is equivalent to that of plate and screw fixation. We sought to determine if this glue could also provide strength and healing in a more stressed environment, that of the mandible. Fourteen New Zealand White rabbits underwent mandibular osteotomies at the angle. The osteotomy was fixed with either a microplate (n = 4) or glue (n = 10). Mandibles were assessed 10 weeks postoperatively and classified according to bone healing, condylar morphology, and dental morphology. Callus and nonunion were more prevalent in the glued group, whereas condylar resorption was similar in both experimental groups. Despite the poor bony healing in the glued group, the teeth did not decay but modified their standard form to meet the demands of the anatomic deformity. Butyl-2-cyanoacrylate does not offer the biomechanical stability afforded by plates and screws in bone subject to large forces.

Animals↗
PubMed1998

Integration of bioInformatics tools at the National University of Singapore (NUS).

In the past decade "Big Science" such as the Genome Project has generated an enormous amount of data in the life sciences. Concurrently, the synergy of this project with existing research has quickened the pace of biological discovery. But the major drawback that is beginning to be felt worldwide is the primitive level of organisation in the data accumulated. Without a proper framework or knowledge scaffold to hang and interconnect the various bits of data and information, the national knowledge-to-data ratio is declining rapidly. We are trying to serve a solution to this enigma by providing a World Wide Web (WWW) interface to Biosoftware and at the same time have come up with a database integration tool that can query heterogeneous, geographically scattered and disparate databases simultaneously. In this report we will talk about BioInformatics in general with specific reference to BioInformatics Centre (BIC) at the National University of Singapore.

Computational Biology↗
PubMed1998

Using Kleisli to Bring Out Features in BLASTP Results.

BLASTP gives a good overall indication of what function a protein might have. However, analysis of BLASTP reports to discover various domain features in the protein is still tedious. We address this problem by using the modern data integration system, Kleisli, to bring out annotated features of BLASTP results. We further strengthen our solution by incorporating additional information from SEG, ClustalW, hmmPfam, etc. It is also noteworthy that the codes of our implementation is sufficiently short to be presented in its entirety.

Journal Article↗
PubMed1998

Hunting TPR Domains Using Kleisli.

We have two objectives. First, we want to build a system for detecting tetratricopeptide repeats in protein sequences. Second, we want to demonstrate how the general bioinformatics database integration system called Kleisli can help build such a system easily. We achieve these two objectives by showing that short and clear programs can be written in Kleisli, using its high-level query language CPL, to build a TPR domain hunter by integrating WU-BLAST2.0, HMMER, Entrez, and PFAM.

Journal Article↗
PubMed1998

Reforming the household registration system: a preliminary glimpse of the blue chop household registration system in Shanghai and Shenzhen.

"For decades, the household registration system has functioned as a powerful device in halting rural influxes into Chinese cities. The exigencies of the reform call for reform of the hukou system [China's household registration]. One of the many attempts is the blue chop household registration system. Both Shanghai and Shenzhen have introduced this practice. In addition to promotion of real estate and investment, it creams off those more desirable migrants into the permanent population of the two cities. In view of the present situation of linking welfare provision with household registration status, this selective migration policy seems to be a sensible step forward."

Asia↗
PubMed1998

Plaque mineralisation in vitro.

Dental calculus is plaque mineralised by deposition of calcium and phosphate resulting from interactions between the oral microbial plaque flora and components of oral fluids. An artificial-mouth microcosm dental plaque culture system has been developed to study aspects of plaque mineralisation, including pH control. Five plaques were grown from saliva under simulated oral conditions in a mucin-containing medium, and sucrose was applied to mimic meals. The plaques were mineralised with a urea-based, calcium-phosphate-monofluorophosphate-urea (CPMU) mineralising solution. Alkaline pH oscillations were generated by the plaques in response to CPMU applications, and an acidic oscillation followed sucrose applications. Plaque mineralisation by the CPMU procedure was almost totally dependent on the urea present in the mineralising solution, but total mineralisation also increased as the resting pH increased as a result of urea in the medium. Following four CPMU applications with a sucrose application every 12 hours improved plaque viability and mineralisation. The plaque mineral formed resembled a carbonated hydroxyapatite; other potential calcium phosphate minerals were undetectable except for calcium carbonate. A wide range of mineral deposition patterns in plaque were seen by electron microscopy.

Acids↗
PubMed1998

Development of software tools at BioInformatics Centre (BIC) at the National University of Singapore (NUS).

There is burgeoning volume of information and data arising from the rapid research and unprecedented progress in molecular biology. This has been particularly affected by the Human Genome Project which is trying to completely sequence three billion nucleotides of the human genome (1),(1a). Other genome sequencing projects are also contributing substantially to this exponential growth in the number of DNA nucleotides and proteins sequenced. The number of journals, reports and research papers and tools required for the analysis of these sequences has also increased. For this the life sciences today needs tools in information technology and computation to prevent degeneration of this data into an inchoate accretion of unconnected facts and figures. The recently formed BioInformatics Centre (BIC) at the National University of Singapore (NUS) provides access to various commonly used computational tools available over the World Wide Web (WWW)--using a uniform interface and easy access. We have also come up with a new database tool. BioKleisli, which allows you to interact with various geographically scattered, heterogeneous, structurally complex and constantly evolving data sources. This paper summarises the importance of network access and database integration to biomedical research and gives a glimpse of current research conducted at BIC.

Animals↗
PubMed1998

From sequence to structure to literature: the protocol approach to bioinformation.

Until the recent advent of high-throughput experimental data-acquisition in biology, the computational analysis of the biological data was predominantly on an ad hoc basis--i.e., the application of a given piece of software on the biological data depended on the need of the moment. This "functional approach" often resulted in piecemeal computational analysis with large amount of intervening "dead-time". The present high-throughput availability of experimental biological data requires a more streamlined and integrated "protocol approach". In this work, we illustrate such a user-friendly protocol using a common question frequently faced by a wet-lab bench-biologist--"Now that I have a DNA or protein sequence, what can I do with it using a computer?" As phrased, this question is steeped in the functional approach. In contrast, the protocol approach would re-phrase the same question as "Now that I have a DNA or protein sequence, what can a computer do for me?" Our integrating tool can start with a sequence and build a substantial custom data-warehouse of computationally derived sequence information, structure information and relevant published literature, that is continually updated.

Amino Acid Sequence↗
PubMed1998

Characterization of phospholipids in pre-alpha HDL: selective phospholipid efflux with apolipoprotein A-I.

Previously, we have shown that lipid-free apoA-I, when incubated with fibroblasts, will produce lipoproteins of pre-alpha mobility (Asztalos, B. F., et al. 1997. Arterioscler. Thromb. Vasc. Biol. 17: 1630-1636). In order to understand the nature of these pre-alpha particles, we further characterized their lipid content. The pre-alpha particles are high density lipoproteins, having a median density of 1.08 g/ml. They have a surface charge of -18.45 mV. The phospholipid composition of these particles showed that they have 4% each of phosphatidyl ethanolamine and inositol; 69% phosphatidyl choline and 18% sphingomyelin. This phospholipid composition is different from those of plasma HDL (81% phosphatidyl choline, 13% sphingomyelin), plasma membrane on the fibroblasts, and whole fibroblast phospholipid. To demonstrate that the pre-alpha mobility resides in the lipids, lipids from pre-alpha lipoproteins were reconstituted with lipid-free apoA-I. The resultant particles retained their pre-alpha mobility. We conclude that apoA-I may react with specific regions of plasma membrane to acquire this unusual lipid composition and that pre-alpha mobility is caused in part by the unusual phospholipid composition.

Apolipoprotein A-I↗
PubMed1997

Early genes induced in hepatic stellate cells during wound healing.

Activation of mesenchymal cells is a central event in the wound healing response of most tissues. In liver, the mesenchymal element responsible for organ fibrosis is the hepatic stellate cell (HSC) (formerly known as lipocyte or Ito cell). The phenotypic cascade of stellate cell activation in liver fibrosis has been well documented and involves both marked morphologic changes and upregulation of several functional components including extracellular matrix, cytokine receptors, contractile filaments and metalloproteinases. However, the genetic regulation of stellate cell activation is poorly understood. In an attempt to clone genes that are involved in the regulation of HSC activation we have combined cDNA library amplification by PCR with subtraction hybridization/differential screening, and have successfully identified genes induced in vivo during early stellate cell activation in a rat model of liver fibrosis. The subtracted cDNA library comprised less than 100 unique sequences. Of these, 13 clones with sizes ranging from 322 to 745 were sequenced and characterized. Gene induction in HSCs was monitored by RNAse protection assay during early liver injury induced by the hepatotoxin CCl4. The sequenced cDNAs corresponding to the known genes included type II transforming growth factor beta receptor, glutathione peroxidase I, transferrin and several clones encoding cellular retrotransposons, whose expression was not previously identified in non-parenchymal liver cells. In addition, one partial cDNA predicted a zinc-finger motif, suggesting a possible role of a novel transcriptional regulator. Our approach represents a valuable strategy for clarifying in vivo regulatory mechanisms of mesenchymal cell activation in wound healing.

Animals↗
PubMed1997

Proton equilibria in the minor groove of DNA.

Poisson-Boltzmann calculations by Pack and co-workers suggest the presence of regions of increased hydrogen ion density in the grooves of DNA. As an experimental test of this prediction, we have attached proton-sensitive probes, with variable linker lengths, to random-sequence DNA at G sites in the minor groove. The amino groups of beta-alanine, gamma-aminobutyric acid (GABA), and epsilon-aminocaproic acid have been coupled at pH 5, via a formaldehyde link, to the exocyclic amino group of guanine, utilizing a reaction that has been extensively investigated by Hanlon and co-workers. The resulting adducts at pH 5 retained duplex B form but exhibited typical circular dichroism (CD) changes previously shown to be correlated with the presence of a net positive charge in the minor groove. Increases in the solvent pH reversed the CD spectral changes in a manner suggesting deprotonation of the carboxylic acid group of the adduct. These data were used to calculate an apparent pK(a) for the COOH. The pK(a) was increased by 2.4 units for beta-alanine, by 1.7 units for GABA, and by 1.5 units for epsilon-amino caproic acid, relative to their values in the free amino acid. This agrees well with Poisson-Boltzmann calculations and the energy minimization of the structures of the adducts that place the carboxyl groups in acidic domains whose hydrogen ion density is approximately 2 orders of magnitude greater than that of bulk solvent.

Alanine↗
PubMed1997

The enhancement of wound healing with human skin allograft.

Although clean incisional wounds can be closed easily, contaminated wounds, wounds with tissue loss that cannot be closed primarily, and chronic wounds are generally not closed and suffer the effects of being open. It follows that wound healing would be enhanced if these wounds could be closed. This article describes how skin allograft biologic dressings are used to close such wounds temporarily to bestow the benefits of wound closure. It also describes the benefits of human skin allografts and the history and basic science related to their use. Reference is made to newer wound covers that have the potential to provide similar benefits to open wounds.

Adult↗
PubMed1997

Brachial neuritis presenting as anterior interosseous nerve compression--implications for diagnosis and treatment: a case report.

Brachial plexus neuropathy may present as an isolated peripheral nerve lesion, suggesting local compression, when in fact the pathophysiology is a diffuse proximal inflammation. The type of management depends on an accurate diagnosis of the diffuse lesion with electromyography. A descriptive case of isolated anterior interosseus nerve palsy is presented and the literature is reviewed. Analysis of the reported cases reveals that anterior interosseus nerve palsies resulting from different etiologies are included in the same series and that treatment recommendations are highly specialty-oriented. Cases of brachial plexus neuritis-induced anterior interosseus nerve palsy should be managed conservatively, while surgical decompression may be performed for specific instances of direct trauma.

Adult↗
PubMed1997

Endocrine abnormalities in ovulatory women with polycystic ovaries on ultrasound.

Polycystic-appearing ovaries (PAO) on ultrasound have been described in a variety of endocrinopathies and also occur in ovulatory women. By some investigators this is merely referred to as 'PCO' (polycystic ovaries). Although there is controversy in this regard, we do not consider women with PAO/PCO who have no known endocrine disturbance to have polycystic ovary syndrome (PCOS) and therefore prefer not to use the term 'PCO' which is often equated with PCOS. We studied 15 ovulatory women with normal-appearing (NAO) ovaries on ultrasound and 15 matched ovulatory women with PAO/PCO. Compared to ovulatory women, 25 other women were studied who were considered to have PCOS. Of these, 15 were overweight and 10 were of normal weight. All the PCOS women had serum concentrations of luteinizing hormone (LH), testosterone, unbound testosterone, androstenedione and dihydroepiandrosterone sulphate (DHEAS) which were significantly higher (P < 0.01) than values in the normal women, regardless of ovarian morphology. These values were similar in the two groups of ovulatory women with NAO and PAO/PCO. Fasting insulin was elevated in women with PCOS with increased body weight (P < 0.01) and was higher than in ovulatory women with NAO and PAO/PCO and than in women of normal weight with PCOS. Serum insulin-like growth factor (IGF)-I and binding protein (BP)-3 were similar in all groups but serum IGFBP-1 was significantly (P < 0.01) lower in those women with PCOS with increased body weight, compared to all other groups. Compared to values in ovulatory women with NAO, serum IGFBP-1 was also significantly (P < 0.05) lower in women with PAO/PCO and those women with PCOS of normal weight. These lower values were similar in women with PAO/PCO and in normal weight women with PCOS. On an individual basis, an elevation of at least one serum androgen value was found in 33% of women with PAO/PCO. These data confirm that increased body weight accentuates the metabolic alterations in PCOS, but suggest that subtle endocrine disturbances, similar to those that are found in PCOS, may be uncovered in up to a third of ovulatory women with PAO/PCO. It appears that a disturbance of the IGF/IGFBP-1 axis is common and apparently closely associated with alterations in ovarian morphology.

Adult↗
PubMed1997

Normolipidemic subjects with low HDL cholesterol levels have altered HDL subpopulations.

Epidemiological studies have established that plasma concentration of HDL is inversely correlated with the risk of coronary heart disease, even in the absence of increased LDL cholesterol levels. We postulate that specific HDL subpopulations may be responsible for antiatherogenic properties of HDL. HDL subpopulations were quantitated by two-dimensional gel electrophoresis in 79 normolipidemic healthy male subjects. To eliminate the influence of diet, volunteers consumed an average American diet for 6 weeks. After the diet period, subjects were stratified according to their HDL cholesterol (HDL-C) levels to low HDL-C < 0.91 mmol/L (< 35 mg/dL), medium > 0.91 < 1.30 mmol/L (> 35 < 50 mg/dL), and high > or = 1.30 mmol/L (> or = 50 mg/dL) groups. Plasma triglycerides and insulin levels were in the normal range, but subjects with low HDL-C levels had higher concentrations of plasma triglycerides and insulin than subjects with medium or high HDL-C concentrations. The absolute concentration (mg/dL) of apoA-I in the largest alpha-migrating HDL subpopulation (alpha 1) was (P < .01) lower in the low HDL-C subjects compared with the medium and high HDL-C groups. The relative concentration (percent distribution) of apoA-I was decreased (P < .01) in alpha 1 and increased (P < .01) in alpha 3 subpopulations. A positive correlation between HDL-C and alpha 1 (P < .001) and a negative correlation between HDL-C and alpha 3 were observed. The inverse correlation of apoA-I distribution (relative concentration) between alpha 1 and alpha 3 suggests an interconversion of alpha 1 and alpha 3 subpopulations, possibly by cholesteryl ester transfer protein. Pre-beta subpopulations showed an inverse trend with HDL-C, while the pre-alpha subpopulation behaved similarly to the alpha-migrating subpopulation. Colocalization of apoA-I and apoA-II particles in the different HDL subpopulations demonstrated that alpha 1, pre-beta 1, and pre-beta 2 subpopulations are apoA-I-only particles rather than apoA-I:A-II particles.

Adult↗