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Biomedical subjects

T T Le

Publications and source records attributed to T T Le.

At least 19 recordsLinked to original sources
PubMed2001

Asymptomatic primary Epstein-Barr virus infection occurs in the absence of blood T-cell repertoire perturbations despite high levels of systemic viral load.

Primary infection with the human herpesvirus, Epstein-Barr virus (EBV), may result in subclinical seroconversion or may appear as infectious mononucleosis (IM), a lymphoproliferative disease of variable severity. Why primary infection manifests differently between patients is unknown, and, given the difficulties in identifying donors undergoing silent seroconversion, little information has been reported. However, a longstanding assumption has been held that IM represents an exaggerated form of the virologic and immunologic events of asymptomatic infection. T-cell receptor (TCR) repertoires of a unique cohort of subclinically infected patients undergoing silent infection were studied, and the results highlight a fundamental difference between the 2 forms of infection. In contrast to the massive T-cell expansions mobilized during the acute symptomatic phase of IM, asymptomatic donors largely maintain homeostatic T-cell control and peripheral blood repertoire diversity. This disparity cannot simply be linked to severity or spread of the infection because high levels of EBV DNA were found in the blood from both types of acute infection. The results suggest that large expansions of T cells within the blood during IM may not always be associated with the control of primary EBV infection and that they may represent an overreaction that exacerbates disease.

Antibodies, Viral↗
PubMed2001

Cytotoxic T cell polyepitope vaccines delivered by ISCOMs.

CD8 alphabeta cytotoxic T lymphocyte (CTL) polyepitope or polytope vaccines have traditionally been delivered using recombinant vector or DNA based delivery modalities. Here we show the delivery of polytope vaccines in the form of either synthetic polypeptides or recombinant polytope proteins by ImmunoStimulatory COMplexes (ISCOMs(R)). Induction of multiple protective CTL responses by these polytope-ISCOM formulations were comparable to viral vector or DNA based delivery modalities as assessed by IFNgamma ELISpot, chromium release and viral challenge assays. Measurement of CTL responses specific for the different epitopes revealed immunodominance patterns, which were largely independent of the vaccine vector or the order of the epitopes in the polytope. ISCOMs thus emerge as a viable human delivery modality for protein-based polytope vaccines.

Amino Acid Sequence↗
PubMed2001

Nuclear gems and Cajal (coiled) bodies in fetal tissues: nucleolar distribution of the spinal muscular atrophy protein, SMN.

SMN, the affected protein in spinal muscular atrophy (SMA), is a cytoplasmic protein that also occurs in nuclear structures called "gems" and is involved in snRNP maturation. Coilin-p80 is a marker protein for nuclear Cajal bodies (coiled bodies; CBs) which are also involved in snRNP maturation, storage or transport. We now show that gems and CBs are present in all fetal tissues, even those that lack gems/CBs in the adult. Most gems and CBs occur as separate nuclear structures in fetal tissues, but their colocalization increases with fetal age and is almost complete in the adult. In adult tissues, up to half of all gems/CBs are inside the nucleolus, whereas in cultured cells they are almost exclusively nucleoplasmic. The nucleolar SMN is often more diffusely distributed, compared with nucleoplasmic gems. Up to 30% of cells in fetal tissues have SMN distributed throughout the nucleolus, instead of forming gems in the nucleoplasm. The results suggest a function for gems distinct from Cajal bodies in fetal nuclei and a nucleolar function for SMN. Spinal cord, the affected tissue in SMA, behaves differently in several respects. In both fetal and adult motor neurons, many gems/CBs occur as larger bodies closely associated with the nucleolar perimeter. Uniquely in motor neurons, gems/CBs are more numerous in adult than in fetal stages and colocalization of gems and CBs occurs earlier in development. These unusual features of motor neurons may relate to their special sensitivity to reduced SMN levels in SMA patients.

Adult↗
PubMed2001

Risk behaviours of young Indo-Chinese injecting drug users in Sydney and Melbourne.

OBJECTIVE: To investigate patterns of drug use and injection-related risk behaviours among young Indo-Chinese injecting drug users (IDUs). METHOD: Cross-sectional survey. A structured questionnaire was administered to 184 Indo-Chinese IDUs aged 15 to 24 in Sydney and Melbourne. Participants were recruited using snowball sampling techniques; measures included patterns of heroin and other drug use, injection-related risk behaviours, perceived susceptibility to HIV and HCV infection and access to services. RESULTS: Despite perceived high availability of sterile injecting equipment, 36% had ever shared a needle and syringe and 22% had done so in the preceding month. Lifetime sharing was significantly associated with duration of injecting, history of incarceration and residence in Sydney. Sharing of injecting paraphernalia other than needles and syringes was also common, with young women and Sydney residents significantly more likely to report sharing equipment in the preceding month. CONCLUSIONS: Young Indo-Chinese IDUs are at high risk of infection with hepatitis C and other blood-borne viruses. Results indicate an urgent need for culturally appropriate and sustainable risk reduction programs which specifically target this population. IMPLICATIONS: Health services must respond swiftly to implement effective blood-borne virus prevention programs for young Indo-Chinese IDUs. Failure to do so may sustain the current epidemic of hepatitis C among IDUs.

Adolescent↗
PubMed2000

The exon 2b region of the spinal muscular atrophy protein, SMN, is involved in self-association and SIP1 binding.

Spinal muscular atrophy (SMA) is caused by mutations in the SMN (survival of motor neurons) gene and there is a correlation between disease severity and levels of functional SMN protein. Studies of structure-function relationships in SMN protein may lead to a better understanding of SMA pathogenesis. Self-association of the spinal muscular atrophy protein, SMN, is important for its function in RNA splicing. Biomolecular interaction analysis core analysis now shows that SMN self-association occurs via SMN regions encoded by exons 2b and 6, that exon 2b encodes a binding site for SMN-interacting protein-1 and that interaction occurs between exon 2- and 4-encoded regions within the SMN monomer. The presence of two separate self-association sites suggests a novel mechanism by which linear oligomers or closed rings might be formed from SMN monomers.

Antibodies, Monoclonal↗
PubMed2000

The relationship between SMN, the spinal muscular atrophy protein, and nuclear coiled bodies in differentiated tissues and cultured cells.

The spinal muscular atrophy protein, SMN, is a cytoplasmic protein that is also found in distinct nuclear structures called "gems." Gems are closely associated with nuclear coiled bodies and both may have a direct role in snRNP maturation and pre-RNA splicing. There has been some controversy over whether gems and coiled bodies colocalize or form adjacent/independent structures in HeLa and other cultured cells. Using a new panel of antibodies against SMN and antibodies against coilin-p80, a systematic and quantitative study of adult differentiated tissues has shown that gems always colocalize with coiled bodies. In some tissues, a small proportion of coiled bodies (<10%) had no SMN, but independent or adjacent gems were not found. The most striking observation, however, was that many cell types appear to have neither gems nor coiled bodies (e.g., cardiac and smooth muscle, blood vessels, stomach, and spleen) and this expression pattern is conserved across human, rabbit, and pig species. This shows that assembly of distinct nuclear bodies is not essential for RNA splicing and supports the view that they may be storage sites for reserves of essential proteins and snRNPs. Overexpression of SMN in COS-7 cells produced supernumerary nuclear bodies, most of which also contained coilin-p80, confirming the close relationship between gems and coiled bodies. However, when SMN is reduced to very low levels in type I SMA fibroblasts, coiled bodies are still formed. Overall, the data suggest that gem/coiled body formation is not determined by high cytoplasmic SMN concentrations or high metabolic activity alone and that a differentiation-specific factor may control their formation.

Animals↗
PubMed2000

Delineation of a minimal interval and identification of 9 candidates for a tumor suppressor gene in malignant myeloid disorders on 5q31.

Interstitial deletion or loss of chromosome 5 is frequent in malignant myeloid disorders, including myelodysplasia (MDS) and acute myeloid leukemia (AML), suggesting the presence of a tumor suppressor gene. Loss of heterozygosity (LOH) analysis was used to define a minimal deletion interval for this gene. Polymorphic markers on 5q31 were identified using a high-resolution physical and radiation hybrid breakpoint map and applied to a patient with AML with a subcytogenetic deletion of 5q. By comparing the DNA from leukemic cells to buccal mucosa cells, LOH was detected with markers D5S476 and D5S1372 with retention of flanking markers D5S500 to D5S594. The D5S500-D5S594 interval, which covers approximately 700 kb, thus represents a minimal localization for the tumor suppressor gene. Further refinement of the physical map enabled the specification of 9 transcription units within the encompassing radiation hybrid bins and 7 in flanking bins. The 9 candidates include genes CDC25, HSPA9, EGR1, CTNNA1, and 5 unknown ESTs. Reverse-transcription polymerase chain reaction confirms that all of them are expressed in normal human bone marrow CD34(+) cells and in AML cell lines and thus represent likely candidates for the MDS-AML tumor suppressor gene at 5q31.

Bone Marrow Cells↗
PubMed2000

The human centromeric survival motor neuron gene (SMN2) rescues embryonic lethality in Smn(-/-) mice and results in a mouse with spinal muscular atrophy.

Proximal spinal muscular atrophy (SMA) is a common motor neuron disease in humans and in its most severe form causes death by the age of 2 years. It is caused by defects in the telomeric survival motor neuron gene ( SMN1 ), but patients retain at least one copy of a highly homologous gene, centromeric SMN ( SMN2 ). Mice possess only one survival motor neuron gene ( Smn ) whose loss is embryonic lethal. Therefore, to obtain a mouse model of SMA we created transgenic mice that express human SMN2 and mated these onto the null Smn (-/-)background. We show that Smn (-/-); SMN2 mice carrying one or two copies of the transgene have normal numbers of motor neurons at birth, but vastly reduced numbers by postnatal day 5, and subsequently die. This closely resembles a severe type I SMA phenotype in humans and is the first report of an animal model of the disease. Eight copies of the transgene rescues this phenotype in the mice indicating that phenotypic severity can be modulated by SMN2 copy number. These results show that SMA is caused by insufficient SMN production by the SMN2 gene and that increased expression of the SMN2 gene may provide a strategy for treating SMA patients.

Animals↗
PubMed2000

The survival motor neuron (SMN) protein: effect of exon loss and mutation on protein localization.

Spinal muscular atrophy (SMA) is caused by mutations in the telomeric copy of the survival motor neuron gene (SMN1) but not mutations in the centromeric copy (SMN2). The critical difference between the two genes is a nucleotide difference in exon 7 that affects splicing and causes this exon to be spliced out of most SMN2 transcripts. A majority of the SMN1 gene transcripts contain exon 7. To investigate the effect of exon loss or mutations in SMN on protein localization, 15 SMN constructs were prepared and transfected into COS-7 cells and fibroblasts derived from a type I SMA patient. Loss of exon 5 (Iso5-SMN), a putative nuclear localization signal in exon 2, and the G279V point mutation had little effect on SMN localization. Loss of both exons 5 and 7 (Iso57-SMN) resulted in low gem numbers and the localization of the majority of the SMN protein to the cytoplasm. Cells expressing constructs lacking only exon 7 (Iso7-SMN) did not produce large numbers of gems in general, although there were a few cells that had a staining pattern similar to cells transfected with a full-length (Full-SMN) construct. HeLa cells stably transfected with full-length SMN or Iso7-SMN did not overexpress SMN, and both constructs produced a similar localization of the protein, although Iso7-SMN formed gems less efficiently. Removal of the amino-terminus, deletion of the conserved domain in exon 2A, and the mutation Y272C all caused accumulation of SMN in the nucleus, sometimes in large aggregates. These findings suggest that the amino-terminal domain of SMN is essential for the correct cellular distribution of SMN, whereas Iso7-SMN is capable of forming gems, albeit at a reduced efficiency.

Animals↗
PubMed2000

In vivo targeted repair of a point mutation in the canine dystrophin gene by a chimeric RNA/DNA oligonucleotide.

In the canine model of Duchenne muscular dystrophy in golden retrievers (GRMD), a point mutation within the splice acceptor site of intron 6 leads to deletion of exon 7 from the dystrophin mRNA, and the consequent frameshift causes early termination of translation. We have designed a DNA and RNA chimeric oligonucleotide to induce host cell mismatch repair mechanisms and correct the chromosomal mutation to wild type. Direct skeletal muscle injection of the chimeric oligonucleotide into the cranial tibialis compartment of a six-week-old affected male dog, and subsequent analysis of biopsy and necropsy samples, demonstrated in vivo repair of the GRMD mutation that was sustained for 48 weeks. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of exons 5-10 demonstrated increasing levels of exon 7 inclusion with time. An isolated exon 7-specific dystrophin antibody confirmed synthesis of normal-sized dystrophin product and positive localization to the sarcolemma. Chromosomal repair in muscle tissue was confirmed by restriction fragment length polymorphism (RFLP)-PCR and sequencing the PCR product. This work provides evidence for the long-term repair of a specific dystrophin point mutation in muscle of a live animal using a chimeric oligonucleotide.

Animals↗
PubMed1999

Analysis of mutations in the tudor domain of the survival motor neuron protein SMN.

Autosomal recessive childhood onset spinal muscular atrophy (SMA) is a leading cause of infant mortality caused by mutations in the survival motor neuron (SMN) gene. The SMN protein is involved in RNA processing and is localised in structures called GEMs in the nucleus. Nothing is yet understood about why mutations in SMN gene result in the selective motor neuron loss observed in patients. The SMN protein domains conserved across several species may indicate functionally significant regions. Exon 3 of SMN contains homology to a tudor domain, where a Type I SMA patient has been reported to harbour a missense mutation. We have generated missense mutants in this region of SMN and have tested their ability to form GEMs when transfected into HeLa cells. Our results show such mutant SMN proteins still localise to GEMs. Furthermore, exon 7 deleted SMN protein appears to exert a dominant negative effect on localisation of endogenous SMN protein. However, exon 3 mutant protein and exon 5 deleted protein exert no such effect.

Amino Acid Sequence↗
PubMed1998

Prevalence of hepatitis B, hepatitis C, and GB virus C/hepatitis G virus infections in liver disease patients and inhabitants in Ho Chi Minh, Vietnam.

The prevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), and GB virus C or hepatitis G virus (GBV-C/HGV) infections was determined in 289 patients with liver disease in Ho Chi Minh City and 890 healthy inhabitants of its rural area, Dalat City, Vietnam, respectively. Serum HCV RNA and GBV-C/HGV RNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). HBsAg, HCV antibodies, and GBV-C/HGV RNA were detected in 139 (47%), 69 (23%), and ten (3%) subjects, respectively, often accompanied by elevated serum levels of alanine aminotransferase. HBsAg and HCV antibodies or HCV antibodies and GBV-C/HGV RNA were detectable simultaneously in 8% and 2% of the patients, respectively. In the inhabitants, HBsAg, HCV antibodies, and GBV-C/HGV RNA were found in 51 (5.7%), nine (1.0%), and 11 (1.2%) subjects, respectively. Thus, the prevalence of HBsAg, HCV antibodies, and GBV-C/HGV RNA was significantly higher in liver disease patients than those in the general population. In the samples from 69 patients and nine inhabitants who were seropositive for HCV antibodies, HCV RNA was detectable in 42 (61%) and 4 (44%), respectively. In patients with liver disease, ten belonged to HCV genotype 1a, ten to HCV 1b, three to HCV 2a, four to HCV 2b, and two to HCV 3a by PCR with genotype-specific primers. Nine patients had mixed genotypes, and the remaining four were not classified. Of the GBV-C/HGV RNA-positive individuals, two patients and two inhabitants were positive for HBsAg, while none of the residents had HCV antibodies, although six HCV antibodies (60%) and four HCV RNA (40%) were found in patients. When a phylogenetic tree of GBV-C/HGV was constructed based on the nucleotide sequences, the 21 isolates were classified into at least two genotypes; four isolates belonged to G2, and 17 to G3. The results indicate that in Ho Chi Minh HCV infection prevails with broad distribution of genotypes together with HBV infection among patients with liver disease. This study suggests that GBV-C/HGV infection occurs independently in the two different districts in association with HCV infection.

Adolescent↗
PubMed1998

Spit tobacco intervention in dental practice: recommendations for clinicians.

To address ST use effectively, awareness needs to be raised regarding its harmful affects and addictive nature. Clinicians can and should take a leadership role in the control of ST by addressing ST use with patients. The recommendations provide clinicians with practical tools and strategies for intervention with ST users and potential users. Although many of these strategies require training and time, it should be emphasized that even minimal intervention can be effective in combating ST use.

Adolescent↗
PubMed1997

Randomised feasibility trial of pre-exposure rabies vaccination with DTP-IPV in infants.

BACKGROUND: Pre-exposure vaccination against rabies generally simplifies treatment and could be especially beneficial to children in countries where the disease is enzootic. We studied the feasibility of administering to infants pre-exposure rabies vaccination with combined diphtheria, tetanus, whole-cell pertussis, and inactivated poliomyelitis vaccine (DTP-IPV). METHODS: 84 Vietnamese infants were randomly assigned to groups that received three doses of DTP-IPV vaccine at 2, 3, and 4 months of age alone (n = 43) or with two doses of purified Vero cell rabies vaccine (PVRV) at 2 and 4 months (n = 41). The safety and immunogenicity data of the groups were compared. FINDINGS: All infants in both groups developed protective antibody concentrations against diphtheria, tetanus, pertussis, and polio. All infants who received the PVRV vaccine developed protective antibody concentrations against rabies. No serious adverse effects were reported, nor did systemic reactions differ between groups. INTERPRETATION: Administration of PVRV with DTP-IPV proved safe, and elicited what are presumed to be protective antibody concentrations to all antigens in all 41 infants. Confirmation of these results could lead to integration of pre-exposure rabies vaccination into Expanded Programme on Immunisation (EPI) sessions in selected countries where rabies is enzootic.

Antibodies, Bacterial↗
PubMed1997

The survival motor neuron protein in spinal muscular atrophy.

The 38 kDa survival motor neuron (SMN) protein is encoded by two ubiquitously expressed genes: telomeric SMN (SMN(T)) and centromeric SMN (SMN(C)). Mutations in SMN(T), but not SMN(C), cause proximal spinal muscular atrophy (SMA), an autosomal recessive disorder that results in loss of motor neurons. SMN is found in the cytoplasm and nucleus. The nuclear form is located in structures termed gems. Using a panel of anti-SMN antibodies, we demonstrate that the SMN protein is expressed from both the SMN(T) and SMN(C) genes. Western blot analysis of fibroblasts from SMA patients with various clinical severities of SMA showed a moderate reduction in the amount of SMN protein, particularly in type I (most severe) patients. Immunocytochemical analysis of SMA patient fibroblasts indicates a significant reduction in the number of gems in type I SMA patients and a correlation of the number of gems with clinical severity. This correlation to phenotype using primary fibroblasts may serve as a useful diagnostic tool in an easily accessible tissue. SMN is expressed at high levels in brain, kidney and liver, moderate levels in skeletal and cardiac muscle, and low levels in fibroblasts and lymphocytes. In SMA patients, the SMN level was moderately reduced in muscle and lymphoblasts. In contrast, SMN was expressed at high levels in spinal cord from normals and non-SMA disease controls, but was reduced 100-fold in spinal cord from type I patients. The marked reduction of SMN in type I SMA spinal cords is consistent with the features of this motor neuron disease. We suggest that disruption of SMN(T) in type I patients results in loss of SMN from motor neurons, resulting in the degeneration of these neurons.

Animals↗
PubMed1996

An aqueous extract of the leaves of Chromolaena odorata (formerly Eupatorium odoratum) (Eupolin) inhibits hydrated collagen lattice contraction by normal human dermal fibroblasts.

Chromolaena odorata (formerly Eupatorium odoratum) is used as a traditional medicine in Vietnam (Nghiem, 1992), where its Vietnamese common name is "co hoi." While it has been widely considered a weed by agriculturalists (Holm et al., 1991), the aqueous extract and the decoction from the leaves of this plant have been used throughout Vietnam for the treatment of soft tissue wounds, burn wounds, and skin infections. A number of clinical studies done by Vietnamese as well as foreign medical workers has demonstrated the efficacy of this extract on the wound-healing process. In this article, the effect of the Eupolin extract on hydrated collagen lattice contraction by human dermal fibroblasts, an in vitro model of wound contraction, is described. The significant inhibition of collagen gel contraction by Eupolin extract at 50 to 200 micrograms/ml is demonstrated in various concentrations of collagen. When the extract at 50 to 150 micrograms/ml was washed out of the lattices and replaced by fresh medium without Eupolin, the contraction of collagen by cells was resumed. The visualization of cells in the lattices by incubation in a tetrazolium salt for 2 h showed live cells at 50 to 150 micrograms/ml of extract. In contrast, all cells were killed in the higher extract doses of 300 or 400 micrograms/ml. These preliminary results showing the inhibitory effect of Eupolin extract on collagen contraction suggest that a clinical evaluation of its effect on wound contraction and scar quality should be made. This work illustrates that traditional remedies that are used by folk practitioners to improve healing can be examined in a scientific manner using in vitro wound-healing models. It could be that the synergistic properties of components of the natural extract contribute to the positive effects demonstrated on various wound-healing mechanisms.

Cells, Cultured↗