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Biomedical subjects

L Wong

Publications and source records attributed to L Wong.

At least 73 records · Page 4Linked to original sources
PubMed1999

Analysis of cholinesterase inactivation and reactivation by systematic structural modification and enantiomeric selectivity.

We show here with a congeneric series of Rp- and Sp-alkoxymethyl phosphonothiolates of known absolute stereochemistry that chiral selectivity in their reaction with acetylcholinesterase can be described in terms of discrete orientational and steric requirements. Stereoselectivity depends on acyl pocket dimensions, which govern leaving group orientation and a productive association of the phosphonyl oxygen in the oxyanion hole. Overall geometry is consistent with a pentavalent intermediate where the attacking serine and leaving group are at apical positions. Oxime reactivation of the phosphonylated enzyme occurs through a similar associative intermediate presumably forming an oxime phosphonate. The oximes of differing structure show distinct angles of attacking the phosphate where the attack angles and access to the phosphorus are constrained in the sterically impacted gorge. Hence, efficacy of oxime reactivation is dependent on both oxime and conjugated phosphonate structures.

Animals↗
PubMed1999

A differential requirement for the COOH-terminal region of the epidermal growth factor (EGF) receptor in amphiregulin and EGF mitogenic signaling.

The epidermal growth factor receptor (EGFR) mediates the actions of a family of bioactive peptides that include epidermal growth factor (EGF) and amphiregulin (AR). Here we have studied AR and EGF mitogenic signaling in EGFR-devoid NR6 fibroblasts that ectopically express either wild type EGFR (WT) or a truncated EGFR that lacks the three major sites of autophosphorylation (c'1000). COOH-terminal truncation of the EGFR significantly impairs the ability of AR to (i) stimulate DNA synthesis, (ii) elicit Elk-1 transactivation, and (iii) generate sustained enzymatic activation of mitogen-activated protein kinase. EGFR truncation had no significant effect on AR binding to receptor but did result in defective GRB2 adaptor function. In contrast, EGFR truncation did not impair EGF mitogenic signaling, and in c'1000 cells EGF was able to stimulate the association of ErbB2 with GRB2 and SHC. Elk-1 transactivation was monitored when either ErbB2 or a truncated dominant-negative ErbB2 mutant (ErbB2-(1-813)) was overexpressed in cells. Overexpression of full-length ErbB2 resulted in a strong constitutive transactivation of Elk-1 in c'1000 but only slightly stimulated Elk-1 in WT or parental NR6 cells. Conversely, overexpression of ErbB2-(1-813) inhibited EGF-stimulated Elk-1 transactivation in c'1000 but not in WT cells. Thus, the cytoplasmic tail of the EGFR plays a critical role in AR mitogenic signaling but is dispensable for EGF, since EGF-activated truncated EGFRs can signal through ErbB2.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Divalent cations and the electrostatic potential around DNA: Monte Carlo and Poisson-Boltzmann calculations.

The predictions of counterion condensation theory for divalent ions were tested by comparison with the results of Monte Carlo calculations on an all-atom model of DNA. Monovalent-divalent competition at the polyelectrolyte surface was investigated by varying the partial molar volume of divalent ions. To assess the viability of using Poisson-Boltzmann (PB) calculations for determining divalent ion concentrations at DNA surfaces, Monte Carlo (MC) calculations were compared with PB calculations using different models of the dielectric continuum. It was determined that, while standard PB calculations of divalent ion surface densities are about 25-30% below those predicted by MC techniques, and somewhat larger than errors previously determined for monovalent ions, errors due to the use of the mean-field approximation of PB theory are smaller than those arising from common assumptions regarding the dielectric continuum.

Animals↗
PubMed1999

Human endogenous retrovirus with a high genomic sequence homology with IDDMK(1,2)22 is not specific for Type I (insulin-dependent) diabetic patients but ubiquitous.

AIMS/HYPOTHESIS: It has been reported recently that a novel human endogenous retroviral gene, insulin-dependent diabetes mellitus (IDDM)K(1,2)22, was expressed in the plasma of Type I diabetic patients but not in that of nondiabetic control subjects. This investigation was initiated to determine the specificity of the selective expression of IDDMK(1,2)22 in diabetic patients. METHODS: We isolated the total RNA from the plasma and lymphocytes of 13 new onset Type I diabetic patients and 10 normal control subjects and amplified it by reverse transcriptase polymerase chain reaction. We then determined the presence of IDDMK(1,2)22 with a specific primer set, U3/R-poly(A), used in a recent report and the 5 'SAg/3 'SAg primer set recognizing the putative superantigen encoding the region of the IDDMK(1,2)22 envelope (env) gene. In addition, we carried out nested PCR of the U3/R-poly(A) polymerase chain reaction product using U3N/R primers. RESULTS: We found no difference in the presence of the polymerase chain reaction products between diabetic patients and all nondiabetic subjects tested. Sequencing of the U3/R-poly(A) polymerase chain reaction products showed that the exact sequence of IDDMK(1,2)22 was not present in any of the samples tested, neither in the plasma of diabetic patients nor in that of nondiabetic control subjects. Endogenous retroviral sequences with 90-93% sequence homology to IDDMK(1,2)22 were, however, equally present in both the diabetic and nondiabetic subjects. CONCLUSION/INTERPRETATION: We conclude that a human endogenous retroviral gene with high sequence homology with IDDMK(1,2)22 is not specific for diabetic patients but, rather, is ubiquitous.

Base Sequence↗
PubMed1999

Kleisli: a new tool for data integration in biology.

One of the central problems in bioinformatics is data retrieval and integration. The existing biological databases are geographically distributed across the Internet, complex and heterogeneous in data types and data structures, and constantly changing. With the current rapid growth of biomedical data, the challenge is how large volumes of data retrieved from multiple databases can be transformed and integrated automatically and flexibly. This article describes a powerful new tool, the Kleisli system, for complex queries across multiple databases and data integration.

Computational Biology↗
PubMed1999

Children who are cruel to animals: a revisit.

OBJECTIVE: There is a paucity of research regarding children who are cruel to animals (CTA). Previous studies have suggested that being CTA is linked with recurrent aggression in adulthood. In this report, children with persistent conduct problems who are CTA are examined. METHOD: A clinic-referred sample of 141 children and a community sample of 36 children between the ages of 5-12 were assessed using a test battery of questionnaires for parents, teachers and the child on mental health symptoms, self-perception, demographics and psychosocial factors. Forty of the clinic-referred children and one of the community group were rated by their parents as sometimes or definitely cruel to animals. The CTA, non-CTA and community samples were compared. RESULTS: The CTA group had more conduct symptoms compared with the non-CTA group. However, the older CTA group unexpectedly reported a higher self-esteem compared with the non-CTA group. There was no significant difference between the two clinic-referred groups in gender, attention deficit hyperactivity disorder and internalising symptoms, and psychosocial factors. CONCLUSION: Being CTA is possibly a marker of a subgroup of conduct disorder which has a poor prognosis.

Aggression↗
PubMed1999

A novel treatment of patients with chronic hepatitis C.

OBJECTIVES: Interferon alpha-2b therapy for Chronic Hepatitis C patients has been unsatisfactory. Recombinant Granulocyte Macrophage Colony-Stimulating Factor has been shown to have anti-viral effects in vivo and in vitro via cytokines release. Recently its effects on chronic hepatitis B and possibly chronic hepatitis C were reported. We, decided to conduct a pilot study to evaluate the anti-viral effects of recombinant human GM-CSF mono-therapy in patients with chronic hepatitis C and to assess its side effects. METHODS: A total of 10 patients (male/female: 5/5) (age: 34-60, mean: 45) seen in our center between 2/95 to 2/96 were randomly selected to receive recombinant human Granulocyte Macrophage Colony-Stimulating-Factor at 125 ug/m2 subcutaneously daily for two weeks followed by three times weekly for another 8 weeks. Biochemical (ALT) and viral (HCV-RNA) responses were measured prior to treatment and at weeks four and eight. Side effects were recorded. RESULTS: Six out of the ten patients treated had significant viral reduction but none became negative. Eight out the ten patients treated showed biochemical improvement and three out of the eight had normalized liver enzymes. Age, sex, stage of the disease did not influence the response but there seems to be a tendency for patients with higher pre-treatment viral level to respond virally. Side effects are minimal and well-tolerated. CONCLUSION: Recombinant human Granulocyte Macrophage Colony-Stimulating-Factor in the dose used has anti-viral effects in the majority of the chronic hepatitis C patients studied. Side effects are minimal and well tolerated. Further study with higher doses and longer duration is needed to prove its clinical efficacy in treating patients with chronic hepatitis C.

Adult↗
PubMed1999

[Effects of 17 beta-estradiol on intracellular free calcium, inositol-1,4,5-trisphophate and calmodulin in human osteoblast-like osteosarcoma cell line TE85].

OBJECTIVE: To study the effects of 17 beta-estradiol (E2) on intracellular free calcium ([Ca2+]i), inositol-1,4,5-trisphophate (IP3) and calmodulin (CaM) in human osteoblast-like cell line TE85. METHODS: Using Fluo-3/AM as fluorescent indicator, the [Ca2+]i was measured by laser confocal microscopy system. The IP3 content was determined by anion-exchange chromatography. CaM content was detected by a high sensitive assay based on stimulation of Ca(2+)-dependent phosphodiesterase activity. RESULTS: E2 at dose of 0.1 and 1.0 nmol/L increased fluorescent level by 4.7 and 6.1 times. Pretreatment with thapsigargin (100 nmol/L), the E2 caused only 1.5 times elevation in fluorescence. E2 induced a concommitant bi-peak increase in IP3 content. At the presence of E2(1.0 nmol/L), the CaM content increased by 85.2%. Tamoxifen did not affect the effect of E2 on [Ca2+]i, IP3 and CaM content. But, the inhibitor of phospholipase C (neomycin) and pertusis toxin depressed them partly or completely. CONCLUSIONS: E2 regulate bone cells function by way of Ca2+/CaM activation.

Adolescent↗
PubMed1998

Zf9, a Kruppel-like transcription factor up-regulated in vivo during early hepatic fibrosis.

Wound repair in the liver induces altered gene expression in stellate cells (resident mesenchymal cells) in a process known as "activation." A zinc finger transcription factor cDNA, zf9, was cloned from rat stellate cells activated in vivo. Zf9 expression and biosynthesis are increased markedly in activated cells in vivo compared with cells from normal rats ("quiescent" cells). The factor is localized to the nucleus and the perinuclear zone in activated but not quiescent cells. Zf9 mRNA also is expressed widely in nonhepatic adult rat tissues and the fetal liver. The zf9 nucleotide sequence predicts a member of the Kruppel-like family with a unique N-terminal domain rich in serine-proline clusters and leucines. The human zf9 gene maps to chromosome 10P near the telomere. Zf9 binds specifically to a DNA oligonucleotide containing a GC box motif. The N-terminal domain of Zf9 (amino acids 1-201) is transactivating in the chimeric GAL4 hybrid system. In Drosophila schneider cells, full length Zf9 transactivates a reporter construct driven by the SV40 promoter/enhancer, which contains several GC boxes. A physiologic role for Zf9 is suggested by its transactivation of a collagen alpha1(I) promoter reporter. Transactivation of collagen alpha1(I) by Zf9 is context-dependent, occurring strongly in stellate cells, modestly in Hep G2 cells, and not at all in D. schneider cells. Our results suggest that Zf9 may be an important signal in hepatic stellate cell activation after liver injury.

Amino Acid Sequence↗
PubMed1998

Coordinated induction of VEGF receptors in mesenchymal cell types during rat hepatic wound healing.

Homology PCR has been used to identify receptor tyrosine kinases (RTKs) expressed during activation of rat hepatic stellate cells, the key fibrogenic mesenchymal element in the liver. Partial cDNAs encoding several RTKs were cloned from stellate cells activated in vivo, including those of Flt-1, Flk-1, c-met, PDGFR, and Tyro10/DDR2. RNAse protection from cells activated in vivo demonstrated biphasic induction of flt-1 and flk-1 mRNAs, receptors for vascular endothelial growth factor (VEGF). Culture-activation of stellate cells was associated with increased [125I]VEGF binding and Flt-1 and Flk-1 receptor protein. Induction of VEGF binding sites correlated with an 2.5-fold increase in DNA synthesis in response to VEGF, but only if cells were activated by growth on collagen 1, whereas cells maintained in a quiescent state on a basement membrane-like substratum (EHS matrix) were nonproliferative. In both stellate and endothelial cells VEGF-induced mitogenesis was augmented by co-incubation with basic fibroblast growth factor (bFGF), a cytokine with known synergy with VEGF. These findings suggest that the cellular targets of VEGF in liver may not be confined to sinusoidal endothelial cells, and that VEGF responses reflect combined effects on both hepatic stellate cells and sinusoidal endothelium.

Animals↗
PubMed1998

A common requirement for the catalytic activity and both SH2 domains of SHP-2 in mitogen-activated protein (MAP) kinase activation by the ErbB family of receptors. A specific role for SHP-2 in map, but not c-Jun amino-terminal kinase activation.

The ErbB family of receptors, which include the epidermal growth factor receptor (EGFR), ErbB2, ErbB3, and ErbB4 mediate the actions of a family of bioactive polypeptides. EGF signals through EGFR, whereas heregulin (HRG) signaling is initiated through binding to either ErbB3 or ErbB4. In this report we studied the role of protein-tyrosine phosphatase SHP-2 in ErbB-mediated activation of mitogen-activated protein kinase (MAPK) by overexpressing SHP-2 mutants in COS-7 cells. We demonstrate that enzymatic activity and both NH2- and COOH-terminal SH2 domains of SHP-2 are required for EGF-induced MAPK activation, but not for c-Jun amino-terminal kinase stimulation or MAPK activation which occurred in response to myristoylated son of sevenless, activated Ras, or phorbol ester. Dominant-negative forms of SHP-2 had no effect on EGF-stimulated interaction of GRB2 with EGFR or SHC, nor did they influence phosphorylation of SHC and SHC/EGFR association. The same mutant SHP-2 structures that inhibited EGF-mediated stimulation of MAPK also blocked HRG alpha/beta-induced MAPK activation. EGF or HRG beta caused SHP-2 SH2 domains to engage multiple phosphotyrosine proteins, and mutation of either domain disrupted these associations. These results demonstrate that SHP-2 performs a common and essential function(s) in ligand-stimulated MAPK activation by the ErbB family of receptors.

Animals↗
PubMed1998

Magnetic resonance imaging analysis of lumbar disc changes below scoliosis fusions. A prospective study.

STUDY DESIGN: The authors of this prospective study examined the preoperative and 3-year postoperative magnetic resonance images of 14 patients undergoing anterior and posterior fusion and/or posterior fusion only for scoliosis. All magnetic resonance images were ready by two independent neuroradiologists, who were blinded to the purposes of the study, for the presence of disc narrowing, signal decrease on T2, or herniated nucleus pulposus before and after surgery. Particular attention was paid to the disc changes at the level directly below the end vertebral level of the fusion and two levels below the fusion in the lumbosacral spine existing before surgical intervention. OBJECTIVES: To evaluate the potential for disc degeneration distal to long scoliosis fusions with end fusion levels in the mid to lower lumbar spine. SUMMARY OF BACKGROUND DATA: The determination of end levels of fusion for contructs presently used to manage adult scoliotic deformity has been evaluated in terms of correction of curvature and late decompensation in coronal and sagittal plane balance after fusion. However, the natural history of the caudal, free-motion segments in terms of degeneration and/or correlation with pain has not yet been addressed. METHODS: Fourteen patients undergoing scoliosis fusion underwent magnetic resonance imaging before surgery and approximately 3 years after surgery. The scans were reviewed by two independent neuroradiologists who looked at three degenerative indices at the disc below the area of scoliosis fusion. The authors analyzed rates of change of the three degenerative indices in the pre- and postoperative magnetic resonance images and created associations between the observed changes on the magnetic resonance images and the clinical outcomes of pain, the presence or absence of solid fusion, and the need for repeat surgery. RESULTS: Estimates of the rates of change of the three degenerative indices one or two levels below the fusion were as follow: the chance of disc narrowing, .2-34%; the chance of a decreasing signal on T2, 5-54%, with a 23% incidence among this group; and the chance of herniated nucleus pulposus, 0-34%. There was a significant correlation between the presence of back and/or leg pain and the signal decrease one level below the fusion (P = .04). CONCLUSIONS: If these results are corroborated in a larger sample size, surgeons who manage deformity may have to consider altering fusion levels at the time of fusion based on magnetic resonance imaging predictors. The present data may help to inform patients about the risk of developing junctional degenerative changes and potential symptoms from these changes below scoliosis fusions.

Adolescent↗
PubMed1998

Factors affecting the resting pH of in vitro human microcosm dental plaque and Streptococcus mutans biofilms.

The aim was to examine factors that potentially control the resting pH, defined as the pH unaffected by meals, of microcosm dental plaques and Streptococcus mutans biofilms under standard conditions, and to examine the effect of supplying urea at concentrations found intraorally. Microcosm plaques were cultured from plaque bacteria-enriched saliva in an 'artificial mouth' with a continuous supply of a medium including 0.25% mucin [Basal Medium Mucin, (BMM), 3.6 ml/hr per plaque] and a periodic supply of sucrose. The steady-state resting pH was 6.4 (range +/- 0.1) in BMM containing no urea and supplied at the standard flowrate. This is a robust property of the ecosystem. In one experiment with a replicated (n = 9) set of measurements, the resting pH was approx. pH 6.3, 6.4, 6.7 and 7.3 with 0, 1, 5 and 20 mmol/l urea in the BMM. The magnitude of sucrose- and urea-induced pH responses was unaffected by elevating the resting pH to produce parallel pH curves. The sucrose-induced pH curves were analogous to those classically reported by Stephan that showed an association between caries activity and increasingly acidic plaque pH responses to glucose. Stopping the BMM flow caused a pH rise, indicating continuing net alkali generation from BMM components in the absence of a fluid flow. Step. mutans monoculture biofilms had an acidic resting pH of 5.0 to 5.3, which increased to 6.8 following an adventitious superinfection by Bacillus cereus. It was concluded that the resting pH in plaque results from a delicate balance between alkali and acid generation, which is in turn dependent both on the bacterial composition of the plaque and on the supply of substrates and buffers from, and metabolite clearance into, flowing oral fluid. In vivo the resting pH will vary with site-specific changing saliva flows. Urea continuously supplied at concentrations normal for saliva and gingival crevicular fluid can raise the resting pH of microcosm plaque by an amount tat in vivo would probably be significant in reducing dental caries.

Acids↗
PubMed1998

Domiciliary oxygen and smoking: an explosive combination.

Home oxygen therapy has been used to provide symptomatic relief of breathlessness for more than 20 yr. Continuous low-flow oxygen can improve exercise tolerance and decrease pulmonary hypertension in patients suffering from chronic obstructive airway disease. The majority of these patients have been long-time smokers. Despite routine warnings about potential dangers, a considerable number of patients will continue to smoke whilst on oxygen. The incidence of burn injuries related to this practice is not known. Reports of such incidents are, however, very rare. Twenty-one patients who sustained head and neck burn injuries secondary to cigarette related ignition of their oxygen delivery system were admitted to our burn unit over a 7-yr period (1990-1997). All patients (mean age 60.4 yr) had been informed about the associated risks but did not shut off their supplemental oxygen system during smoking. The mean size of their burn injuries was 2% of the total body surface, mainly affecting the face, ears, and neck. The average duration of the hospital stay was 3.6 days. Two patients required split-thickness skin grafting. Whether chronically ill patients on domiciliary oxygen who continue to smoke covertly are amenable to medical advice to abandon this habit is questionable. A more aggressive education about the explosive nature of their activity should help to prevent them from using tobacco and oxygen at the same time.

Adult↗
PubMed1998

A real-time algorithm to improve the response time of a clinical multigas analyser.

OBJECTIVE: An algorithm to improve the response time of a clinical respiratory multigas analyser is presented. METHODS: The algorithm involves the application of a second order differential equation to the analyser gas output signals in real-time. The adjusted analyser output signals are compared with those of a quadrupole respiratory mass spectrometer sampling and analysing simultaneously. RESULTS: Our results show a close correlation between the adjusted clinical gas analyser and the mass spectrometer signals. Lung volumes derived from a non-invasive sinusoidal inert gas forcing technique, in a model test lung, using the adjusted clinical gas analyser and the mass spectrometer signals demonstrated comparable results. CONCLUSIONS: The algorithm provides an improvement on the relatively slow response times of the clinical gas analyser for breath-by-breath time-dependent applications. The same algorithm can also be applied to other instruments which have slow response times.

Algorithms↗
PubMed1998

Fixation of the craniofacial skeleton with butyl-2-cyanoacrylate and its effects on histotoxicity and healing.

Butyl-2-cyanoacrylate is an easily applied, biocompatible, bioresorbable polymer glue that provides an alternative to conventional rigid fixation techniques. Our aim was to determine if cyanoacrylate fixation of the bone flap in a rabbit craniotomy model provides the healing and strength afforded by plate and screw fixation. We also investigated the inflammatory responses of adjacent tissues including the scalp, cranium, and brain. A unilateral parietal bone flap was elevated in 33 adult New Zealand rabbits. The bone was fixed in position with cyanoacrylate (n = 13), fixed with a microplate and screws (n = 14), or was replaced without fixation (sham-control, n = 6). Normal scar formation and no residual polymer were found in scalp specimens. Neuropathologic analysis identified the presence of residual polymer on the surface of 2 of the 13 rabbit brains. Histopathologic analysis of the bone flap-to-skull interface revealed no difference in the degree but rather in the quality of inflammation and healing between the plate and screw and polymer fixation groups. Microdensitometric analysis of the bone gap revealed nearly equivalent bone density in the cyanoacrylate and plated groups, tending to less density in the sham group (p = 0.11 and 0.09, respectively). An additional study focusing on neurotoxicity was performed in 20 adult rabbits with 3-week and 11-week recovery periods and similarly found the absence of a marked inflammatory response to the polymer. In conclusion, bone healing and soft-tissue inflammation were comparable between cyanoacrylate and plate and screw fixation groups. Although butyl-2-cyanoacrylate glue fixation may provide a reasonable alternative to hardware fixation, further investigations are necessary to identify its ideal utilization.

Animals↗