Biomedical subjects

L Su

Publications and source records attributed to L Su.

At least 73 records · Page 4Linked to original sources

PubMed1997

Isolation of sooty mangabey simian T-cell leukemia virus type I [STLV-I(sm)] and characterization of a mangabey T-cell line coinfected with STLV-I(sm) and simian immunodeficiency virus SIVsmmPBj14.

It has been postulated that dual infections of humans with human immunodeficiency virus (HIV) and human T-cell leukemia/lymphotropic virus (HTLV) may potentiate disease progression. Counterparts of both of these pathogenic human retroviruses have been identified in various simian species indigenous to Asia and Africa, including sooty mangabey monkeys (Cercocebus atys). Using peripheral blood mononuclear cells (PBMC) from a mangabey naturally infected with both SIV and STLV-I, T-cell lines were established and maintained continuously for more than 3 years; these cell lines harbored only a newly identified mangabey STLV-I(sm) or both STLV-I(sm) and the acutely lethal variant SIVsmmPBj14. The dually infected cell line (FEd-P14) was established by de novo infection of mangabey PBMC with SIVsmmPBj14. This cell line was characterized by multiple assays which showed that structural proteins encoded by both viruses were produced in large quantities, but that the predominant viral glycoprotein on the cell surface was the STLV-I(sm) Env. Unusual interactions of the two retroviral glycoproteins were suggested by the formation of syncytia between Raji and the FEd-P14 cells, but not between Raji and simian cells infected with only one retrovirus or human cells infected with HTLV-I. The STLV-I(sm) strain obtained from the sooty mangabey was transmitted to normal macaque and mangabey PBMC and was shown to be unique by sequencing of the entire env gene. STLV-I(sm) from this African species was more closely related to "cosmopolitan" HTLV-I strains than to the prototypic STLV-I from an Asian pig-tailed macaque. In vitro and in vivo studies of STLV-I(sm) and SIVsmm, both isolated from a naturally infected mangabey monkey, may provide insight into disease induction and manifestations associated with coinfection by their human counterparts.

Animals↗

PubMed1997

Detection of simian T cell leukemia virus type I infection in seronegative macaques.

Simian species of Asian and African origin are naturally infected with the simian T cell leukemia virus type I (STLV-I). Like the closely related human T cell leukemia virus type I (HTLV-I), STLV-I is primarily cell associated, and typical infections exhibit low viral burdens. Four macaques experimentally inoculated with a new STLV-I strain isolated from a sooty mangabey monkey were examined over extended periods of time for signs of infection by (1) commercial enzyme immunoassay and immunoblot assay for cross-reactive serum antibodies to HTLV-I, (2) commercial HTLV-I p24gag antigen-capture assay on supernatants from cocultures of macaque peripheral blood mononuclear cells (PBMCs) with human PBMCs, and (3) nested PCR amplification of proviral sequences in macaque PBMC DNA. The nested PCR assay was 100% specific and detected a single STLV-I copy in 150,000 PBMCs. In addition, our data show that experimental infection of macaques with STLV-I can be serologically silent for more than 43 months.

Animals↗

PubMed1997

An RNA enhancer in a phage transcriptional antitermination complex functions as a structural switch.

Antitermination protein N regulates the transcriptional program of phage lambda through recognition of RNA enhancer elements. Binding of an arginine-rich peptide to one face of an RNA hairpin organizes the other, which in turn binds to the host antitermination complex. The induced RNA structure mimics a GNRA hairpin, an organizational element of rRNA and ribozymes. The two faces of the RNA, bridged by a sheared GA base pair, exhibit a specific pattern of base stacking and base flipping. This pattern is extended by stacking of an aromatic amino acid side chain with an unpaired adenine at the N-binding surface. Such extended stacking is coupled to induction of a specific internal RNA architecture and is blocked by RNA mutations associated in vivo with loss of transcriptional antitermination activity. Mimicry of a motif of RNA assembly by an RNA-protein complex permits its engagement within the antitermination machinery.

Amino Acid Sequence↗

PubMed1997

Hematopoietic stem cell-based gene therapy for acquired immunodeficiency syndrome: efficient transduction and expression of RevM10 in myeloid cells in vivo and in vitro.

Gene delivery via the hematopoietic stem cell (HSC) offers an attractive means to introduce antiviral genes into both T cells and macrophages for acquired immunodeficiency syndrome (AIDS) gene therapy. An amphotropic retroviral vector encoding a bicistronic gene coexpressing RevM10 and the murine CD8alpha' chain (lyt2) was developed to transduce HSC/progenitor cells. After transduction of CD34+ cells isolated from human umbilical cord blood, the lyt2 molecule detected by flow cytometry was used to monitor the level of gene transduction and expression and to enrich RevM10-expressing cells by cell sorting without drug selection. Using this quantitative method, high levels of gene transduction and expression (around 20%) were achieved by high-speed centrifugation of CD34+ cells with the retroviral supernatant (spinoculation). After reconstitution of human bone marrow implanted in SCID mice (SCID-hu bone) with the transduced HSC/progenitor cells, a significant number of donor-derived CD14+ bone marrow cells were found to express the RevM10/lyt2 gene. Finally, replication of a macrophage-tropic human immunodeficiency virus-type 1 (HIV-1) isolate was greatly inhibited in the lyt2+/CD14+ cells differentiated from transduced CD34+ cells after the enrichment of lyt2+ population. Thus, the RevM10 gene did not appear to inhibit the differentiation of HSC/progneitor cells into monocytes/macrophages. The level of retrovirus-mediated RevM10 expression in monocytes/macrophages derived from transduced HSCs is sufficient to suppress HIV-1 replication.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Heteromultimeric complexes of CD40 ligand are present on the cell surface of human T lymphocytes.

CD40 ligand (CD40L), a 33-kDa type II membrane glycoprotein expressed primarily on activated CD4+ T lymphocytes, is responsible for the helper function of T cells on resting B cells in a non-antigen-dependent, non-major histocompatability complex-restricted fashion. Interaction of CD40L with its receptor CD40 induces proliferation of and isotype switching in B lymphocytes. Recently we solved the x-ray structure of recombinant soluble CD40L and showed that, similar to other members of the tumor necrosis factor family, CD40L indeed exists as a trimer. We now report that, under normal physiological conditions, CD40L molecules exist as heteromultimeric complexes. These CD40L complexes, made of the full length and smaller fragments of CD40L, are present on the cell surface of T lymphocytes and are capable of interacting with CD40 molecule. A prominent fragment with a mass of 31 kDa accounts for as much as half of the CD40L on the surface of Jurkat cells. N-terminal sequence data revealed that this fragment lacks the cytoplasmic tail. A minor 18-kDa fragment of CD40L was also characterized which lacks the cytoplasmic tail, transmembrane region, and stalk region of the extracellular domain. The presence of CD40L heteromultimeric variants implies an additional regulation of the functional activity of this ligand complex.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1997

Identification of HIV-1 determinants for replication in vivo.

Pathogenic organisms are frequently attenuated after long-term culture in vitro. The mechanisms of the attenuation process are not clear, but probably involve mutations of functions required for replication and pathogenicity in vivo. To identify these functions, a direct comparison must be made between attenuated genomes and those that remain pathogenic in vivo. In this study, we used the heterochimeric SCID-hu Thy/Liv mouse as an in vivo model to define human immunodeficiency virus type 1 (HIV-1) determinants which are uniquely required for replication in vivo. The Lai/IIIB isolate and its associated infectious molecular clones (e.g., HXB2) were found to infect T cell lines but failed to replicate in the SCID-hu Thy/Liv model. When a lab worker was accidentally infected by Lai/IIIB, however, HIV-1 was isolated only from infection of primary PBMC, and not from infection of T cell lines. We hypothesized that the lab worker was exposed to a heterogeneous viral stock which had been attenuated by passage in immortalized T cell lines. Either a rare family member from this stock was selected for in vivo replication or, alternatively, an attenuated genotype dominant in vitro may have reverted to become more infectious in vivo. To address this hypothesis, we have used the SCID-hu Thy/Liv model to study the replication of HXB2 and of HXB2 recombinant viruses with HIV-1 fragments isolated from the infected lab worker. HXB2 showed no or very low levels of replication in the Thy/Liv organ. Replacement of its subgenomic fragment encoding the envelope gene with a corresponding fragment from the lab worker isolate generated a recombinant virus (HXB2/LW) which replicated actively in SCID-hu mice. The NEF mutation in the HXB2 genome is still present in HXB2/LW. Thus, the LW sequences encode HIV-1 determinants which enhance HIV replication in vivo in a NEF-independent mechanism. The specific determinants have been mapped to the V1-V3 regions of the HIV-1 genome. Six unique mutations in the V3 loop region of HXB2/LW have been identified which contribute to the increased replication in vivo.

Amino Acid Sequence↗

PubMed1997

HIV-1 pathogenesis and therapeutic intervention in the SCID-hu Thy/Liv mouse: a model for primary HIV-1 infection in the human thymus.

The SCID-hu Thy/Liv mouse is a model for the analysis of human thymopoiesis. It has been constructed by engrafting fragments of human fetal liver and thymus into the immunodeficient C.B-17 scid/scid (SCID) mouse. The resulting 'Thy/Liv' organ promotes long-term differentiation of human T cells. Given the apparently normal physiology of the SCID-hu Thy/Liv organ, it has been used to explore the pathophysiologic mechanisms of HIV-1 infection in vivo, and to test therapeutic modalities such as anti-HIV-1 drugs and haematopoietic stem cell (HSC)-based gene therapy. In this review, I will summarise what we have learned from the SCID-hu Thy/Liv model, with a focus on recent findings in HIV-1 replication and therapy. Unique HIV-1 determinants have been identified which are required for replication in the Thy/Liv organ but not for replication in PBMC or in T cell lines in vitro. The mechanism of HIV-1 induced thymus depletion is not clear. It is correlated with high levels of HIV-1 replication. Both direct and indirect mechanisms may be involved. In addition to preclinical evaluation of anti- HIV-1 drugs, the SCID-hu Thy/Liv mouse has also been successfully used to test the feasibility of HSC-based gene therapy. A number of improved SCID-hu models have been constructed to meet different requirements. Using these SCID-hu Thy/Liv models, current/future efforts will provide insightful information for understanding pathogenesis and designing therapeutic interventions against HIV-1 infection in humans, especially in paediatric patients. Copyright 1997 John Wiley & Sons, Ltd.

Journal Article↗

PubMed1997

The T cell activation factor NF-ATc positively regulates HIV-1 replication and gene expression in T cells.

Clinical deterioration in human immunodeficiency virus type 1 (HIV-1) infection is associated with increased levels of viral replication and burden in the peripheral blood and lymphoid organs. T cell activation and ensuing cellular gene activation can be critical for HIV-1 replication. The hypothesis that the nuclear factor of activated T cells (NF-AT) may influence HIV-1 replication is therefore compelling given the tight correlation of HIV-1 transcriptional induction to T cell activation. We report that certain NF-AT(Rel) family members productively bind the kappaB regulatory elements, synergize with NF-kappaB and Tat in transcriptional activation of HIV-1, and enhance HIV-1 replication in T cells. These results link regulatory factors critical to T cell commitment directly to HIV-1 replication.

Cells, Cultured↗

PubMed1997

Distinguishing features of focal cemento-osseous dysplasia and cemento-ossifying fibromas. II. A clinical and radiologic spectrum of 316 cases.

The distinguishing histopathologic features of focal cemento-osseous dysplasia (FCOD) (including lesions occurring in both anterior and posterior jaws) and cemento-ossifying fibroma (COF) (ossifying fibroma and cementifying fibroma) were demonstrated in our earlier work. The aim of the current study was to further refine their clinical and radiographic features. We have assessed 18 clinical and radiographic parameters by univariate comparisons (chi-squared and Student t tests), and a multivariate assessment (logistic regression) in 241 cases of FCOD and 75 of COF. These cases were diagnosed from a combination of clinical, radiographic, and histopathologic information. FCOD was seen predominantly in black women, with a peak incidence in the fourth and fifth decades, whereas COF showed no female predilection except in the fourth decade (p < 0.005). COF occurred in patients an average of 10 years younger than patients with FCOD (p < 0.0001). Most patients with FCOD were asymptomatic (62%); the average lesion size was 1.8 cm. More than half of patients with COF displayed jaw expansion and a considerably larger size lesion (mean 3.8 cm, p < 0.001). The mandible was the most frequent site for both FCOD (86%) and COF (70%). Radiographically, a well-defined border was observed in 53% of cases of FCOD and 85% of cases of COF (p < 0.01). Cases of FCOD mostly demonstrated an irregularly mixed radio-opacity (69%), whereas 53% of COFs presented as a radiolucency (p < 0.005). In FCOD, there was a close association with tooth apices (70.6%, p < 0.0001) or with previous extraction sites (21%, p < 0.05); however, the majority of COF cases (86%) showed no relationship with either. Combining the radiographic feature of a periapical location with the pathology of multiple curetted fragments and "ginger root" bony trabeculae, allowed 90% sensitivity and 89% specificity in a logistic regression model to predict the lesion to be an FCOD. These findings provide guidelines not only to distinguish these two entities clinically, but also aid in reaching an accurate diagnosis histopathologically.

Adolescent↗

PubMed1997

Distinguishing features of focal cemento-osseous dysplasias and cemento-ossifying fibromas: I. A pathologic spectrum of 316 cases.

Focally expressed cemento-osseous dysplasia (periapical cemento-osseous dysplasia and focal cemento-osseous dysplasia) and cemento-ossifying fibroma (ossifying fibroma and cementifying fibroma) are two clinically recognized entities that are not easily differentiated histopathologically because of the lack of recognition of specific microscopic features. We have assessed 20 pathologic parameters for their ability to distinguish reliably between the two. Included in this study were 241 cases of focally expressed cemento-osseous dysplasia and 75 cases of cemento-osseous fibroma diagnosed from a combination of clinical, radiographic, and histopathologic information. Results revealed that 92.5% of focally expressed cemento-osseous dysplasia were composed of multiple small fragments of tissue whereas 88.0% of cemento-osseous fibromas showed a large intact specimen. Thick curvilinear trabeculae ("ginger root" pattern) or irregularly shaped cementum-like masses were typically seen in focally expressed cemento-osseous dysplasia, whereas thin isolated trabeculae with prominent osteoblastic rimming were more commonly observed in cemento-osseous fibroma. The stroma of focally expressed cemento-osseous dysplasia often displayed characteristic cavernous-like vascularity that was almost always associated with bony trabeculae. Free hemorrhage was frequently interspersed in the artifactual spaces throughout focally expressed cemento-osseous dysplasia. In contrast, the cases of cemento-osseous fibroma showed more cellularity in the stroma in which a storiform pattern was present in more than half the lesions studied. Giant cells, when present in cemento-osseous fibroma, were clustered in the center of the cellular stroma. The features described here allowed distinction histopathologically in 94% of cases studied. Three progressive stages of focally expressed cemento-osseous dysplasia and subtypes of cemento-osseous fibroma may be recognizable microscopically.

Blood Vessels↗

PubMed1997

RevM10-expressing T cells derived in vivo from transduced human hematopoietic stem-progenitor cells inhibit human immunodeficiency virus replication.

A key feature of the pathogenesis of human immunodeficiency virus type 1 (HIV-1) infection is the gradual loss of CD4-positive T cells. A number of gene therapy strategies have been designed with the intent of inhibiting HIV replication in mature T cells. As T cells are products of hematolymphoid differentiation, insertion of antiviral genes into hematopoietic stem cells could serve as a vehicle to confer long-term protection in progeny T cells derived from transduced stem cells. One such "cellular immunization" strategy utilizes the gene coding for the HIV-1 rev trans-dominant mutant protein RevM10 which has been demonstrated to inhibit HIV-1 replication in T-cell lines and in primary T cells. In this study, we used a Moloney murine leukemia virus-based retrovirus encoding a bicistronic message coexpressing RevM10 and the murine CD8-alpha' chain (Lyt2). This vector allows rapid selection of transgene-expressing cells as well as quantitation of transgene expression. We demonstrate that RevM10-transduced CD34-enriched hematopoietic progenitor-stem cells (HPSC) isolated from human umbilical cord blood or from granulocyte colony-stimulating factor-mobilized peripheral blood can give rise to mature thymocytes in the SCID-hu thymus/liver mouse model. The phenotypic distribution of HPSC-derived thymocytes is normal, and expression of the transgene can be detected by flow cytometric analysis. Moreover, we demonstrate that RevM10 can inhibit HIV replication in T cells derived from transduced HPSC after expansion in vitro. This is the first demonstration of anti-HIV efficacy in T cells derived from transduced human HPSC.

Animals↗

PubMed1997

[Senility-preventing effect of erlingcankang decoction].

Experiments with Erlingcankang Decoction showed that when given to silk worms it could noticeably prolong the growth period of larvae and raise an average of 10-day survival of the male moths; when given to mice it could prolong their life; and when given to on old rats it could markedly raise the contents of SOD in the liver and red cells, lower the content of MAO-B in the brain, LF in the brain and adrenal gland and also LPO in the liver.

Aging↗

PubMed1997

Spindle epithelial tumor with thymus-like differentiation: a case report with cytologic, histologic, immunohistologic, and ultrastructural findings.

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a rare and distinctive low-grade neoplasm of thymic or related branchial pouch differentiation. The tumor usually presents in the thyroid or lateral neck of children and adolescents and could mimic spindle-cell carcinoma, synovial sarcoma, or malignant teratoma. We report the clinical, cytologic, histologic, immunohistochemical, and ultrastructural features of a SETTLE present for 10 years in a 15-year-old boy. The fine-needle aspirate, initially interpreted as synovial sarcoma, contained numerous clusters of bland spindle cells, with a few detached sheets of columnar mucous cells in a homogeneous background of dissociated spindle cells. Mitoses, necrosis, and atypia were not present. The excised tumor was a well-circumscribed, white-tan mass, with occasional microcysts. Microscopically, the mass consisted of a lobulated, highly cellular, spindle-cell neoplasm arranged in intersecting, whorled, and storiform fascicles separated by fibrous bands. Entrapped within the fibrous bands were squamous-lined cysts and benign-appearing glands lined by columnar epithelium with goblet cells or ciliated pseudostratified epithelium. Immunohistochemically, the spindle cells showed diffuse reactivity for cytokeratins, smooth muscle actin, muscle-specific actin, and MIC-2, and they were negative for epithelial membrane antigen, calcitonin, and thyroglobulin. Ultrastructurally, numerous perinuclear tonofilaments, some aligned with mature desmosomes, were identified in the spindle cells. Occasional cells showed thin filaments with fusiform dense bodies occupying the peripheral cytoplasm. These findings distinguish SETTLE from ectopic thymoma, synovial sarcoma, medullary carcinoma, and teratoma, and they support a thymic epithelial origin for SETTLE, possibly with myoepithelial differentiation.

Adolescent↗

PubMed1997

Sun awareness at Mayo High School.

Using a survey that I created, I examined the attitudes, knowledge, and activities among fellow high school students concerning the sun. One part of the questionnaire evaluated the students' knowledge of the sun and the second part studied their attitudes toward protection while in the sun. Based on the results of this survey, I found that the majority of students attending Mayo High School are involved in outdoor activities and that physical appearance (a tanned look) among these students has priority over the risks that accompany sun exposure.

Adolescent↗

PubMed1997

Characterization of gpt deletion mutations in transgenic Chinese hamster cell lines.

The transgenic cell lines G12 and G10, each with a bacterial gpt gene stably integrated at a single but different position in the Chinese hamster genome, were evaluated for deletion of the gpt transgene following exposures to several clastogens. More than 150 independently cloned G12 and G10 6-thioguanine-resistant mutants have been characterized by polymerase chain reaction (PCR) amplification and Southern blots in this study. Despite differences in the integration sites for the gpt gene in the G12 and G10 cells, PCR amplification of the gpt gene from both cell lines can be performed using the same single set of primers. By PCR deletion screening, about 20% of recovered spontaneous 6-thioguanine resistant (6TG) gpt G12 mutants had deleted the transgene, whereas the deletion mutant frequency was increased to about 50% of the X-ray- and bleomycin-induced G12 mutants. In contrast, both spontaneous and induced deletion frequencies are considerably higher for the G10 cell line. Among spontaneous G10 mutants, up to 50% have deleted the gpt transgene, whereas almost all of the X-ray- and bleomycin-induced G10 mutants have lost the integrated gene sequence. These results are discussed in the context of the transgene integration sites and the influences of the surrounding genome that may render certain genetic regions prone to deletion.

Alanine Transaminase↗

PubMed1997

[Genetic subtyping of HIV-1 strains by heteroduplex mobility assay].

DNA fragments of HIV-1 env gene were amplified by nested PCR from uncultured peripheral blood mononuclear cells (PBMCs) obtained from 24 HIV-1 infected individuals. The PCR products were separated by melting and annealing with denatured PCR product prepared from reference plasimd of representative subtypes. Heteroduplex were then formed between the single-stranded DNA from the two sources and were analysed on polyacrylamide gels. The results from heteroduplex mobility assay (HMA) were compared with HIV-1 subtype results determined by DNA sequencing. With advantages of high speed, low cost and high specificity, HMA is a reliable screening method for HIV-1 subtyping.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Replication across O6-methylguanine by human DNA polymerase beta in vitro. Insights into the futile cytotoxic repair and mutagenesis of O6-methylguanine.

Replication in vivo across unrepaired O6-methylguanine (m6dG) lesions by mammalian DNA polymerase beta (pol beta) during short patch repair may contribute to the cytotoxicity and mutagenesis of m6dG. We have employed in vitro steady state kinetic analysis to investigate the replication of oligonucleotide templates containing site-specific m6dG by human pol beta. Our results show that m6dG is a strong but not absolute block to replication by pol beta. pol beta exhibits mixed kinetic discrimination during overall replication across dG and m6dG. pol beta preferentially inserts dTMP rather than dCMP opposite m6dG. However, pol beta extends from the dC-m6dG base pair more efficiently than from the dT-m6dG base pair. This is in strong contrast to other polymerases such as the exonuclease-deficient Klenow fragment of Escherichia coli DNA polymerase I (exo-KF) that preferentially extends dT-m6dG by a factor of 10 over dC-m6dG. When both insertion and extension are considered, pol beta has a 15-fold overall preference for incorporation of the mutagenic substrate dTTP rather than the nonmutagenic substrate dCTP during replication across m6dG. This suggests that pol beta, in concert with the T:G-specific thymine DNA glycosylase, may be intricately involved in the futile cytotoxic repair induced by m6dG. Our results also suggest that replication across m6dG by pol beta may contribute to m6dG-induced G --> A transition mutations.

Base Sequence↗

PubMed1996

Positive effect of overexpressed protein-tyrosine phosphatase PTP1C on mitogen-activated signaling in 293 cells.

PTP1C, an SH2 domain-containing protein-tyrosine phosphatase, is predominantly expressed in hematopoietic cells, in which it negatively regulates cellular signaling. However, this enzyme is also expressed in many non-hematopoietic cells. We demonstrate here that in non-hematopoietic 293 cells, overexpression of a catalytically inactive mutant of PTP1C strongly suppressed the stimulatory effects of the epidermal growth factor or serum on cell proliferation, early gene transcription, and DNA synthesis. Similarly, the phosphorylation of the mitogen-activated protein kinase and mitogen-activated protein kinase kinase activity was markedly inhibited by overexpression of mutant PTP1C. The inhibitory effect of mutant PTP1C was overcome by cotransfection with wild-type PTP1C, but not with the structurally related PTP2C. Furthermore, expression of the mutant phosphatase resulted in hyperphosphorylation on tyrosine of a 95-kDa protein that was co-immunoprecipitated with the mutant, but not with the wild-type protein. These results suggest that, unlike in hematopoietic cells, PTP1C in 293 cells plays a positive role in epidermal growth factor- or serum-activated mitogenesis. Thus, PTP1C participates in multiple signaling pathways, where the enzyme, depending on its target molecules, may function as either a positive or negative mediator.

Cell Division↗