Biomedical subjects

H K Wong

Publications and source records attributed to H K Wong.

At least 19 recordsLinked to original sources

PubMed2002

A case report of neurologically unstable fracture of the lumbosacral spine in a patient with ankylosing spondylitis.

INTRODUCTION: Fracture/dislocation is uncommonly reported in ankylosing spondylitis involving the lumbosacral spine. CLINICAL PICTURE: We report an 18-month follow-up of a case of neurologically unstable traumatic fracture of the lumbosacral spine in ankylosing spondylitis. TREATMENT/OUTCOME: Posterior decompression, alar-transverse fusion and instrumentation were performed. Anterior diskectomy and fusion were done 6 weeks later. There was solid bony fusion on follow-up and the patient had improvement of 2 Frankel grades and was able to ambulate. CONCLUSION: Combined approaches and longer fixations to stabilise the spine may be required. In the lumbosacral spine, this poses a problem vis-à-vis limited levels of fixation in the sacrum.

Accidental Falls↗

PubMed2001

Generation and biochemical analysis of human effector CD4 T cells: alterations in tyrosine phosphorylation and loss of CD3zeta expression.

Human effector T cells have been difficult to isolate and characterize due to their phenotypic and functional similarity to the memory subset. In this study, a biochemical approach was used to analyze human effector CD4 T cells generated in vitro by activation with anti-CD3 and autologous monocytes for 3 to 5 days. The resultant effector cells expressed the appropriate activation/differentiation markers and secreted high levels of interferon gamma (IFN-gamma) when restimulated. Biochemically, effector CD4 T cells exhibited increases in total intracellular tyrosine phosphorylation and effector-associated phosphorylated species. Paradoxically, these alterations in tyrosine phosphorylation were concomitant with greatly reduced expression of CD3zeta and CD3epsilon signaling subunits coincident with a reduction in surface T-cell receptor (TCR) expression. Because loss of CD3zeta has also been detected in T cells isolated ex vivo from individuals with cancer, chronic viral infection, and autoimmune diseases, the requirements and kinetics of CD3zeta down-regulation were examined. The loss of CD3zeta expression persisted throughout the course of effector T-cell differentiation, was reversible on removal from the activating stimulus, and was modulated by activation conditions. These biochemical changes occurred in effector T cells generated from naive or memory CD4 T-cell precursors and distinguished effector from memory T cells. The results suggest that human effector T-cell differentiation is accompanied by alterations in the TCR signal transduction and that loss of CD3zeta expression may be a feature of chronic T-cell activation and effector generation in vivo. (Blood. 2001;97:3851-3859)

CD3 Complex↗

PubMed2001

Paired cylindrical interbody cage fit and facetectomy in posterior lumbar interbody fusion in an Asian population.

STUDY DESIGN: The intervertebral disc heights and interfacetal distances of normal lower lumbar segments were measured from MRI scans of 150 male subjects. OBJECTIVES: To investigate the probabilities of paired cylindrical interbody cage placement across the facet joints of the lower lumbar spine in an Asian population with respect to the spinal segmental level, facetectomy, and the restoration of normal intervertebral height. SUMMARY OF BACKGROUND DATA: Cylindrical interbody cage devices often require extensive facetectomy for insertion through a posterior approach in a posterior lumbar interbody fusion (PLIF) procedure. This is because the transverse dimension of a pair of cages could far exceed the interfacetal interval of the lumbar segment. METHODS: One hundred and fifty MRI scans of the lumbosacral spine of male patients between the ages of 18 and 55 years undergoing investigation for low back pain were collected for this study. The interfacetal distances and intervertebral disc heights were measured from transverse and sagittal images, respectively, at L3/L4, L4/L5 and L5/S1. Degenerated discs were not measured. The inner, mid, and outer interfacetal distances were compared with the dimensions of paired cages of 13, 15, and 17 mm in diameter to obtain the proportion of lumbar segments at a particular spinal level that would accommodate paired cages of different diameters and under conditions of varying degrees of facetectomy. RESULTS: Without facetectomy, there was no lumbar segment that could accommodate paired cages as well as restore intervertebral height. With hemi-facetectomy, very few segments at L3/L4 and L4/L5 could fit paired cages. At L5/S1, fewer than 9% of segments could fit paired cages and restore intervertebral heights. The proportion of segments that could accommodate paired cages increased with near-total facetectomy: 25% of L5/S1 segments could accommodate 15-mm cages with restoration of intervertebral heights. CONCLUSIONS: Paired cylindrical cage installation in the majority of patients is likely to require near-total or total facetectomy, with implications for potential segmental instability. Among the three lumbar segments studied, L5/S1 had the highest proportion of segments that could accommodate paired cages and at the same time restore intervertebral height.

Adolescent↗

PubMed2001

2'-deoxyguanosine oxidation is associated with decrease in the DNA-binding activity of the transcription factor Sp1 in liver and kidney from diabetic and insulin-resistant rats.

Over the years, several lines of evidence have emerged supporting the role of oxidative stress in the development of diabetic complications. This could involve the increase in the production of reactive oxygen species and the decrease in antioxidative defense systems. Modulation of the level of intracellular reactive oxygen species is likely to affect the intracellular redox homeostasis, which is crucial for numerous biological events such as the transcriptional activation of genes. In this work we studied the binding of the redox transcription factors Sp1 and NF-kappaB extracted from kidney and liver of streptozotocin diabetic (STZ) and fructose-fed rats using electrophoretic mobility shift (EMSA) assay. In addition, the level in 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) was assessed within DNA by high performance liquid chromatography with electrochemical detection (HPLC-EC). A decrease in the affinity of Sp1 to DNA was observed in the kidney of STZ rats and fructose-fed rats (15% +/- 8.3 and 54% +/- 6.9, respectively, versus control group set to 100%). This was also found to occur to a lower extent, in the liver. Interestingly, higher levels of 8-oxodGuo, a biomarker of DNA oxidation, were measured in the kidney of diabetic rats. Therefore, the modification in the binding efficiency of Sp1 or NF-kappaB could be related to reactive oxygen species-mediated DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

T cell signaling abnormalities in systemic lupus erythematosus are associated with increased mutations/polymorphisms and splice variants of T cell receptor zeta chain messenger RNA.

OBJECTIVE: T cells from patients with systemic lupus erythematosus (SLE) display antigen receptor-mediated signaling aberrations associated with defective T cell receptor (TCR) zeta chain protein and messenger RNA (mRNA) expression. This study was undertaken to explore the possibility that coding-region mutations/polymorphisms of the TCR zeta chain could account for its decreased expression and altered signaling in SLE T cells. METHODS: TCR zeta chain mRNA from 48 SLE patients, 18 disease controls, and 21 healthy volunteers was reverse transcribed, amplified by polymerase chain reaction, and cloned, and complementary DNA (cDNA) was sequenced. DNA sequences from multiple clones were analyzed for silent single-nucleotide polymorphisms, mutations, and splice variations, to promote the identification of heterozygosity. RESULTS: DNA sequence analysis revealed several widely distributed missense mutations and silent polymorphisms in the coding region of the TCR zeta chain, which were more frequent in SLE patients than in patients with other rheumatic diseases or healthy controls (P < 0.0001). Several of the missense mutations were located in the 3 immunoreceptor tyrosine activation motifs or the GTP binding domain, and this could lead to functional alterations in the TCR zeta chain. A splice variant of the TCR zeta chain with a codon CAG (glutamine) insertion between exons IV and V was found in half of the SLE and control samples. Two larger spliced isoforms of the TCR zeta chain, with an insertion of 145 bases and 93 bases between exons I and II, were found only in SLE T cells. We also identified various alternatively spliced forms of the TCR zeta chain resulting from the deletion of individual exons II, VI, or VII, or a combined deletion of exons V and VI; VI and VII; II, III, and IV; or V, VI, and VII in SLE T cells. The frequency of the deletion splice variants was significantly higher in SLE than in control samples (P = 0.004). These variations were observed in cDNA and may not reflect the status of the genomic DNA. CONCLUSION: These findings demonstrate that heterogeneous mutations/polymorphisms and alternative splicing of TCR zeta chain cDNA are more frequent in SLE T cells than in T cells from non-SLE subjects and may underlie the molecular basis of known T cell signaling abnormalities in this disease.

Adult↗

PubMed2001

Ischemia-induced apoptosis in primary cultures of astrocytes.

Astrocytes participate in a wide variety of important physiological processes and pathological insults, including ischemia. Information on the mechanism of astroglial injury and death during ischemic insult, however, is scarce. In this study, we investigated the mode of astrocytic cell death using an in vitro ischemic model. Cultured astrocytes exhibited several distinct morphological and biochemical features of apoptosis under ischemia. At 4 h of ischemia, Annexin V staining demonstrated an early commitment of some astrocytes to apoptosis. Condensed nuclei became visible from 4 h and the number increased with ischemic incubation time. Electron microscopy showed compacted and segregated chromatin along the edges of nuclear membranes. The number of TUNEL-positive nuclei and the degree of DNA laddering increased with ischemic incubation. Caspase-3, but not caspase-1, activity was increased in ischemia-injured astrocytes. Swollen mitochondria and vacuoles found in some cells with chromatin condensation indicated that these apoptotic-like cells might die of necrosis. The results imply that astrocytes are capable of undergoing apoptosis without the presence of other cell types, such as neurons. Ischemia can induce apoptosis in astrocytes contributing to the pathogenesis of ischemic injury in the CNS.

Animals↗

PubMed2001

Identification of differentially expressed genes in human memory (CD45RO+) CD4+ T lymphocytes.

The precise nature and development of the memory (CD45RO+) CD4+ T lymphocytes remain unknown. In this study, we analyzed differential gene expression of human memory CD4+ T lymphocytes in relation to their naive counterparts. A suppression subtractive hybridization technique was used to isolate and clone differentially expressed genes in the memory subset with respect to the naive subset. We screened approximately 300 clones by dot blot analysis and sequenced 23 differentially expressed clones. GenBank sequence homology search showed that these clones included genes for transcription factors, enzymes and immunomodulatory molecules. Differential expression of a subset of these genes was further confirmed by RT-PCR and densitometric analysis revealed that they were expressed five to eightfold more in memory than naive CD4+ T lymphocytes. Collectively, these results suggest that multiple genes with different functions contribute to the development of immunological memory in human T lymphocytes.

CD4-Positive T-Lymphocytes↗

PubMed2001

Linear correlation between axial and lateral bone mineral density of lumbar vertebrae.

The placement of most spinal interbody devices is above the cancellous region of the vertebral bodies. Dual X-ray absorptiometry (DXA) scans of patients are usually taken from the anterior-posterior or the lateral projection. DXA scans taken in vitro from the axial direction would most closely indicate the bone mineral density (BMD) of the bone at this region. So far, in vitro studies have not been conducted to determine the correlation between axial and lateral scans. Because lateral DXA BMD scans are noninvasive and have low radiation dosage, they could be used as a predictive tool to determine the quality of cancellous bone at the centrum of the vertebral bodies, where spinal interbody devices are commonly placed.

Absorptiometry, Photon↗

PubMed2000

Loss of heterozygosity at the short arm of chromosome 3 in microdissected cervical intraepithelial neoplasia.

Loss of heterozygosity (LOH) is a common genetic finding in many human neoplasms, including cervical cancer. The detection of LOH at specific loci in the precursor of cervical cancer, cervical intraepithelial neoplasia (CIN) may help in elucidating the evolution of this cancer, which has a clearly defined histological premalignant phase. However, molecular genetic investigation of CIN is difficult because many of the lesions are very small and sometimes ill defined topographically. In this study we analyzed eighteen polymorphic microsatellite repeats on chromosome 3p in CINs using a method of primer extension pre-amplification (PEP) for whole genome amplification combined with microdissection. These markers encompass chromosome region 3pter-3p12. LOH at one or more loci was detected in five (33%) out of the 15 informative cases with low grade CIN (CIN 1), while 22 (92%) out of 24 cases with high grade CIN (CIN 2 and 3) (P<0.01). The highest incidence (41%) of LOH was detected at locus D3S1038 (3p26.1-3p25.2). Frequent LOH (more than 20%) was also found at other loci including D3S1110 (3p25.3-3p25.1) (31%), D3S656 (3p25.1) (24%), D3S1076 (3p21.2-3p21.1) (29%), D3S1300 (3p21.1-3p14.2) (24%), D3S1600 (3p14.2-3p14.1) (24%), and D3S1079 (3p13) (25%). The results from this study taken together with others indicate that the genetic alterations on chromosome 3p are common in high grade of CIN and are probably early events in cervical carcinogenesis. Tumor suppressor gene(s) that play a role in cervical neoplasm may be located on the short arm of chromosome 3, likely at or near 3p26.1-25.1, 3p21.2-21.1, and 3p14.2-13.

Alleles↗

PubMed2000

The quantification of technetium in generator-derived pertechnetate using ICP-MS.

Previous analytical methods employed to measure 99Tc:99mTc ratios in chromatographic 99mTc generators, derived from fission-based 99Mo, were limited in monitoring the ratios in low activity generators, over the extent of their elution regimes. For regulatory purposes, ICP-MS was employed to measure total technetium in generator eluates down to a level of 200 pg ml(-1) (200 ppt). Measured 99Tc:99mTc ratios compared very well with the theoretically computed values, ranging from 47:1 for a first elution of a generator with a long ingrowth time to 1.4:1 for the 17th elution of a generator with a short ingrowth time.

Calibration↗

PubMed2000

Human skin Langerhans cells are targets of dengue virus infection.

Dengue virus (DV), an arthropod-borne flavivirus, causes a febrile illness for which there is no antiviral treatment and no vaccine. Macrophages are important in dengue pathogenesis; however, the initial target cell for DV infection remains unknown. As DV is introduced into human skin by mosquitoes of the genus Aedes, we undertook experiments to determine whether human dendritic cells (DCs) were permissive for the growth of DV. Initial experiments demonstrated that blood-derived DCs were 10-fold more permissive for DV infection than were monocytes or macrophages. We confirmed this with human skin DCs (Langerhans cells and dermal/interstitial DCs). Using cadaveric human skin explants, we exposed skin DCs to DV ex vivo. Of the human leukocyte antigen DR-positive DCs that migrated from the skin, emigrants from both dermis and epidermis, 60-80% expressed DV antigens. These observations were supported by histologic findings from the skin rash of a human subject who received an attenuated tetravalent dengue vaccine. Immunohistochemistry of the skin showed CD1a-positive DCs double-labeled with an antibody against DV envelope glycoprotein. These data demonstrate that human skin DCs are permissive for DV infection, and provide a potential mechanism for the transmission of DV into human skin.

Blood Cells↗

PubMed2000

Immune cell signaling in lupus.

The fate of the lymphocyte is determined by integration of signals delivered after the binding of antigen to the surface antigen receptor, signals delivered by cytokines that bind to their surface receptors, and signals initiated after the engagement of other surface receptors, known as costimulatory molecules. The summation of this input determines whether the immune cell will become stimulated, ignore the signal (anergy), or die (apoptosis). Antigen-receptor signaling events are abnormal in lupus lymphocytes, manifested by increased calcium responses and hyperphosphorylation of several cytosolic protein substrates. Further down, at the gene transcription level, the activity of the nuclear factor kappaB is decreased. These events are underwritten by defective T cell receptor zeta chain expression, overexpression of the gamma chain of the Fc(epsilon)RI that functions as an alternate of zeta chain, and decreased p65 -Rel A protein that is responsible for the inducible NFkappaB activity. Accumulated research data have enabled us to begin deciphering the molecular basis of the abnormal lupus lymphocyte and may lead to the development of new medicinal treatments for lupus.

Animals↗

PubMed2000

Influence of PLIF cage size on lumbar spine stability.

STUDY DESIGN: In vitro biomechanical testing on functional spine units with posterior lumbar interbody fusion cage implants of progressively larger sizes. OBJECTIVES: To determine the influence of increasing cage size on the restoration of spine stability after total facetectomy. SUMMARY OF BACKGROUND DATA: Bilateral insertion of cages in posterior lumbar interbody fusion commonly involves facetectomy. To restore stability with no additional instrumentation, the cages must provide sufficient distraction of the vertebrae and adequate tension in the anulus. The size of cages is therefore an important consideration in posterior lumbar interbody fusion. METHODS: Eight human lumbar functional spine units were obtained and divided into two equal groups; one group underwent bending tests and the other twisting. The functional spinal units were tested intact, after total bilateral facetectomy and with three sets of cages that were progressively larger in size. RESULTS: After facetectomy, the functional spine unit's stiffness reduced significantly from that of the intact spine in extension (48% of intact), lateral bending (25%), and torsion (39%). With the posterior insertion of small cages into the facetectomized functional spine units, only extension stiffness was restored to the intact level, whereas flexion stiffness reduced significantly (41% of intact). The medium cages restored the lateral bending stiffness of the facetectomized functional spine units; only the large cages managed to restore the torsional stiffness. Flexion stiffness of the facetectomized functional spine units with cages remained significantly less than that of the intact spine, regardless of cage size. CONCLUSION: In the facetectomized lumbar spine unit, cage size influences lateral bending and torsional stability.

Biomechanical Phenomena↗

PubMed1999

Abnormal NF-kappa B activity in T lymphocytes from patients with systemic lupus erythematosus is associated with decreased p65-RelA protein expression.

Numerous cellular and biochemical abnormalities in immune regulation have been described in patients with systemic lupus erythematosus (SLE), including surface Ag receptor-initiated signaling events and lymphokine production. Because NF-kappa B contributes to the transcription of numerous inflammatory genes and has been shown to be a molecular target of antiinflammatory drugs, we sought to characterize the functional role of the NF-kappa B protein complex in lupus T cells. Freshly isolated T cells from lupus patients, rheumatoid arthritis (RA) patients, and normal individuals were activated physiologically via the TCR with anti-CD3 and anti-CD28 Abs to assess proximal membrane signaling, and with PMA and a calcium ionophore (A23187) to bypass membrane-mediated signaling events. We measured the NF-kappa B binding activity in nuclear extracts by gel shift analysis. When compared with normal cells, the activation of NF-kappa B activity in SLE patients was significantly decreased in SLE, but not in RA, patients. NF-kappa B binding activity was absent in several SLE patients who were not receiving any medication, including corticosteroids. Also, NF-kappa B activity remained absent in follow-up studies. In supershift experiments using specific Abs, we showed that, in the group of SLE patients who displayed undetectable NF-kappa B activity, p65 complexes were not formed. Finally, immunoblot analysis of nuclear extracts showed decreased or absent p65 protein levels. As p65 complexes are transcriptionally active in comparison to the p50 homodimer, this novel finding may provide insight on the origin of abnormal cytokine or other gene transcription in SLE patients.

Autoradiography↗

PubMed1998

Saturation of ecosystems with toxic metals in Sudbury basin, Ontario, Canada.

Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, Ontario. The combination of logging, smelting, fires and erosion resulted in an unusual anthropogenic ecosystem of denuded barren land with lifeless lakes, or a micro-desert. Since the 1970s, however, the concerted efforts made to reduce the emissions and rehabilitate parts of the degraded ecosystem have resulted in improvements in water quality, and recoveries in phytoplankton, zooplankton, zoobenthos and fish communities but have had little impact on toxic metal concentrations in many lakes. We show that most of the catchments in the Sudbury basin have become saturated with Cu and Ni, and some with Zn and Pb. It is estimated that mobilization of metals stored in soils and glacial overburden by surface runoff, groundwater drainage and wind re-working of tailings can sustain the high concentrations of Cu and Ni in many lakes for well over 1000 years. Strategies to immobilize the pollutant metals in the watershed rather than further emission controls may be required for dealing with high levels of toxic metals in surface waters of the saturated ecosystems.

Copper↗

PubMed1997

Direct spinal curvature digitization in scoliosis screening--a comparative study with Moiré contourgraphy.

The forward bending test, widely used in scoliosis screening, is associated with high false-positive rates. We postulate that direct surface measurement of the spinal curvature by digitization of the spinous processes used in combination with the forward bending test could increase the predictive value of detecting scoliosis without sacrificing sensitivity. Sixty consecutive patients referred from a school screening program were included in this study. All had moiré contourgraphy, spinous process digitization, and erect frontal radiographs of the spine. The number of false positives from the forward bending test was 35. Moiré contourgraphy did not reduce the number of false positives significantly. A posterior spinal deformity of 10 degrees or more predicted scoliosis in all patients, with 15 false-positive readings. Direct measurement of the spinal curvature by spinous process digitization can be an effective second-stage screening tool for scoliosis in centers where all the screened positives are referred to a single center.

Adolescent↗

PubMed1996

The human papillomavirus type 16 E7 protein complements adenovirus type 5 E1A amino-terminus-dependent transactivation of adenovirus type 5 early genes and increases ATF and Oct-1 DNA binding activity.

We have previously shown that conserved region 1 (CR1) of the adenovirus type 5 (Ad5) E1A protein synergizes with CR3 in the transactivation of Ad5 early genes (H.K. Wong and E. B. Ziff, J. Virol. 68:4910-4920, 1994). CR1 lies within the E1A amino terminus and binds host regulatory proteins such as the RB protein, p107, p130, and p300. Since simian virus 40 (SV40) large T antigen and human papillomavirus type 16 (HPV16) E7 protein also bind host regulatory factors, we investigated whether these viral proteins can complement E1A mutants which are defective in early gene activation. We show that the HPV16 E7 protein but not SV40 T antigen can complement mutations in the Ad5 E1A CR1 in the transactivation of viral early promoters. The inability of SV40 T antigen to complement suggests that RB binding on its own is not sufficient for early promoter transactivation by the E1A amino terminus. Nuclear runoff assays show that complementation by HPV16 E7 restores the ability of the E1A mutants to stimulate early gene expression at the level of transcription. Furthermore, nuclear extracts from the E7-transformed cells show increased binding activity of ATF and Oct-1, factors that can recognize the elements of Ad5 early genes, consistent with gene activation by E1A and E7 at the transcriptional level.

3T3 Cells↗

PubMed1994

Complementary functions of E1a conserved region 1 cooperate with conserved region 3 to activate adenovirus serotype 5 early promoters.

The amino-terminal region of the adenovirus type 5 E1a protein including conserved regions (CRs) 1 and 2 binds the 105-kDa retinoblastoma protein and a second, 300-kDa, cellular protein. We show that mutant viruses with deletions of CR1 which release the binding of either p105 or p300 still activate early promoters and infect cells productively. However, mutations which disrupt binding of both proteins disrupt early promoter activity and block the viral life cycle. Ela CR3, which has an established role in early promoter activation, can act in trans to the amino-terminal functions. This suggests that the amino terminus provides distinct, redundant functions related to p300 and Rb binding that synergize with CR3 to transactivate early genes.

3T3 Cells↗