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Biomedical subjects

T Vinh

Publications and source records attributed to T Vinh.

17 recordsLinked to original sources
PubMed1999

Molecular approaches to the differentiation of Actinomyces species.

The definition of the genus Actinomyces relies heavily on traditional methods of taxonomy. This study sought to develop molecular tools for the identification of strains of Actinomyces israelii and Actinomyces gerencseriae. Oligonucleotide probes were designed and one of these successfully differentiated. A. gerencseriae from ten strains of A. israelii and three other Actinomyces species by DNA:DNA hybridization. However, probes based on known 16S rRNA sequences failed to hybridize to all the strains previously identified as A. israelii. Using the PCR technique, a region encoding a portion of the 16S rRNA was amplified from genomic DNA. The results showed that A. israelii can be divided into three different groups based on comparison of the amplified DNA sequences. This information should allow the development of probes that are specific for these newly identified groups of strains within the species A. israelii.

Actinomyces↗
PubMed1997

Identification and characterization of the dTDP-rhamnose biosynthesis and transfer genes of the lipopolysaccharide-related rfb locus in Leptospira interrogans serovar Copenhageni.

Immunity to leptospirosis is principally humorally mediated and involves opsonization of leptospires for phagocytosis by macrophages and neutrophils. The only protective antigen identified to date is the leptospiral lipopolysaccharide (LPS), which biochemically resembles typical gram-negative LPS but has greatly reduced endotoxic activity. Little is known about the structure of leptospiral LPS. A 2.1-kb EcoRI fragment from the chromosome of serovar Copenhageni was cloned in pUC18 in Escherichia coli, after which flanking regions were cloned from a genomic library constructed in bacteriophage lambda GEM12. Sequence analysis identified four open reading frames which showed similarity to the rfbC, rfbD, rfbB, and rfbA genes, transcribed in that order, which encode the four enzymes involved in the biosynthesis of dTDP-rhamnose for the assembly of LPS in Salmonella enterica, E. coli, and Shigella flexneri. An additional open reading frame downstream of the rfbCDBA locus showed similarity with the rhamnosyltransferase genes of Shigella and Yersinia enterocolitica but not Salmonella. Comparison of deduced amino acid sequences showed up to 85% similarity of the leptospiral proteins with those of other gram-negative bacteria. Polyacrylamide gel electrophoresis of recombinant clones identified the putative RfbCDBA proteins, while reverse transcriptase-mediated PCR analysis indicated that the rfbCDBA gene cluster was expressed in Leptospira. Moreover, it could restore normal LPS phenotype to a defined rfbB::Tn5 mutant of S. flexneri which was deficient in all four genes, thereby confirming the functional identification of a part of the leptospiral rfb locus.

ATP-Binding Cassette Transporters↗
PubMed1996

An analysis of a retrieved Prodigy femoral prosthesis.

Radiographic and histologic data of an autopsy-retrieved femur containing a Prodigy stem (DePuy, Warsaw, IN) in situ for 26 months were analyzed. The Prodigy is a porous-coated Anatomic Medullary Locking stem modified with a smooth groove, the Redux Groove, on its medial central portion. This Redux Groove, designed to increase stem flexibility and decrease periprosthetic bone resorption, decreases the porous surface area available for bone ingrowth. In this case, however, the decreased porous area did not affect diaphyseal bone ingrowth. Additionally, although there is a concern that the groove will provide a pathway for debris migration, no evidence of debris was found in the tissue at the groove site. Although the Redux Groove's value in decreasing periprosthetic bone loss is still uncertain, this case demonstrated less proximal bone loss than was reported in similar dual-energy x-ray absorptiometry studies of autopsy cases containing Anatomic Medullary Locking stems without a groove. Analysis of more cases with longer in situ intervals is necessary to determine if the groove decreases resorptive bone remodeling and if the groove becomes a conduit for particulate debris migration. It is emphasized that results of this one case may not be representative of all Prodigy cases.

Absorptiometry, Photon↗
PubMed1995

Morselized allograft in acetabular reconstruction. A postmortem retrieval analysis.

Contained acetabular defects often are repaired at revision surgery using morselized bone allograft. The extent to which this graft becomes incorporated is unknown, and the value of radiographs for predicting allograft incorporation is unclear. To better understand the effectiveness of morselized allograft in revision hip arthroplasty, the authors studied postmortem specimens from 3 patients treated with this type of graft. Histologic analysis of acetabular components in situ for 18 months showed allograft fragments invested with loose myxofibrous tissue. Vascularized tissue had penetrated the allograft fragments to a depth of 4 mm. In peripheral areas, the vascularized ingrowth was accompanied by partial osteoclastic resorption of graft trabeculae and application of living bone to allograft fragments. After 53 months in situ, graft fragments had remodeled and showed progressive vascular ingrowth. By 83 months, the graft almost completely had incorporated. Morselized allograft bone is useful for restoring bone deficiency within contained acetabular defects. The graft does incorporate, but the extent of graft incorporation cannot be predicted accurately by postoperative radiographs.

Acetabulum↗
PubMed1994

Immunochemical studies of opsonic epitopes of the lipopolysaccharide of Leptospira interrogans serovar hardjo.

Leptospiral lipopolysaccharides (LPS) are the main antigens responsible for immunity in leptospirosis. In this investigation we studied the nature of the antigenic determinants of LPS extracted from Leptospira interrogans serovar hardjo (reference strain Hardjoprajitno). The reactions of anti-LPS monoclonal antibodies (mAbs) MUM/F1-4/hardjo (IgM) and MUM/F1-6/hardjo (IgG) with whole cell lysates in Western immunoblotting analysis were unaffected by proteinase K treatment. Periodate treatment of the LPS destroyed the binding of MUM/F1-6/hardjo but preserved that of MUM/F1-4/hardjo. Alkaline phosphatase decreased significantly the binding of MUM/F1-4/hardjo to the LPS but only slightly that of MUM/F1-6/hardjo. On the other hand, phosphodiesterase totally destroyed the binding capacity of both monoclonal antibodies in enzyme immunoassays (EIA). A number of mono- and oligosaccharides was used in EIA inhibition studies. Mannose-6-phosphate and galactose-6-phosphate inhibited the binding of MUM/F1-4/hardjo (50% inhibition at a concentration of 5 mM) to the antigen, but glucose-6-phosphate did not. Galactosamine and mannosamine inhibited the binding of MUM/F1-6/hardjo (50% inhibition at a concentration of 3-4 mM), whereas only a weak inhibition was observed with glucosamine. In contrast, N-acetylated amino sugars did not show any inhibition. An O-acetyl group also appears to be involved in the antigen-antibody binding process.

Antibodies, Bacterial↗
PubMed1994

Characterization of an antigenic oligosaccharide from Leptospira interrogans serovar pomona and its role in immunity.

An antigenic oligosaccharide fraction derived from the lipopolysaccharide of Leptospira interrogans serovar pomona was isolated by endo-glycosidase H digestion and column chromatography. The oligosaccharide contained rhamnose, ribose, glucose, and glucosamine and inhibited the binding of opsonic, protective monoclonal antibodies directed against the lipopolysaccharide. When conjugated to diphtheria toxoid, the oligosaccharide elicited the production of agglutinating, opsonic antibodies.

Agglutination↗
PubMed1991

DNA image cytometry. A prognostic tool in squamous cell carcinoma of the esophagus?

In 45 patients who underwent an esophagus resection due to a squamous cell carcinoma, in addition to the TNM classification and usual morphologic criteria, the paraffin-embedded material underwent deparaffinization, was rehydrated, and was mechanically and enzymatically processed into a single-cell solution. For evaluating the DNA histogram this was analyzed with the help of automatic single-cell cytophotometric study. The method, contrary to that of flow cytometric study, allows for the selective analysis of tumor cells due to the electronically, previously given selection criteria, whereas artifacts, stroma, and infection cells remain excluded from analysis. The multivariate analysis shows that the prognosis is only correlated with DNA content of the tumor cells. Patients with diploid tumors had a median survival time of 32 months as compared with the 22 months of patients with hypotriploid tumors, and 6.5 months with hypertriploid tumors. DNA cytometric analysis should be included when diagnosing patients with esophagus carcinoma.

Carcinoma, Squamous Cell↗
PubMed1991

[Image analysis of DNA cytometry for assessing prognosis after resection of esophageal cancer].

Esophagus cancer is a heterogeneous disease with considerable differences in malignant behaviour. Some relevant factors for prognosis are known. In this study we analyzed DNA-ploidy as a potential prognostic parameter in esophagus carcinoma. Paraffin embedded histological material from 50 patients with an esophagus cancer, obtained by resection, were selected for analysis. Tumor areas within the paraffin material were identified by HE-stained reference sections. One 50 microns section was dewaxed, rehydrated and mechanically and enzymatically treated to a suspension of 10,000 cells/ml. 1 ml of the suspension, containing bare nuclei with small rests of cytoplasma was centrifuged on glass slides. The fixed nuclei were air-dried and stained by Feulgen-SITS technique, which allows quantitative measurement of DNA. The DNA analysis was carried out with a computer-controlled single cell cytophotometry (Leytas 2, Leitz, Wetzlar). In contrast to the flow cytometry with image cytometry only tumors cells were measured. Overlapping nuclei, dirt and other artefacts as well as inflammatory cells were efficiently eliminated. With the DNA image cytometry we could differentiate between diploid and hypotriploid, hypertriploid aneuploid tumors. Best prognosis had diploid and hypotriploid tumors, the worst hypertriploid carcinomas. In the multivariate analysis the DNA-content of the tumor cells in esophagus cancer was the only prognostic parameter. DNA-content of tumor cells may become considerably clinical relevant in esophagus cancer for the decision to perform a resection or palliative treatment. In patients with hypertriploid tumors an adjuvant oncological therapy may increase the prognosis.

Adenocarcinoma↗
PubMed1986

Ultrastructure and chemical composition of lipopolysaccharide extracted from Leptospira interrogans serovar copenhageni.

Lipopolysaccharide (LPS) from Leptospira interrogans serovar copenhageni was prepared from the aqueous phase of a phenol/water extract. Electron microscopic examination of negatively stained LPS showed a mixture of ribbon-like, round and ring structures. Carbohydrate analysis of the preparations revealed pentoses, hexoses, heptoses, hexosamines, and a 2-keto-3-deoxyonic acid which was chromatographically different from authentic 2-keto-3-deoxyoctonic acid (KDO). The major fatty acids of the LPS were hydroxylauric, palmitic and oleic acids. Although the leptospiral LPS preparations did not contain KDO or hydroxymyristic acid, they were otherwise morphologically and chemically similar to the LPS of other Gram-negative bacteria.

Chemical Phenomena↗
PubMed1986

Glycolipoprotein cytotoxin from Leptospira interrogans serovar copenhageni.

Lipopolysaccharide (LPS), glycolipoprotein (GLP) and lipid extract were prepared from Leptospira interrogans serovar copenhageni. GLP, lipid extract or purified fatty acids from lipid extract produced cytotoxic effects seen as cell enzyme leakage followed by cytotoxic death when tested in mouse fibroblast L929 cells in tissue culture. All extracts also agglutinated mouse erythrocytes but purified LPS was not cytotoxic. Neither GLP nor LPS were pyrogenic but both gelled Limulus amoebocyte lysate. Specific anti-GLP IgG neutralized the cytotoxic and haemagglutinating effect of GLP; however, at higher concentrations it enhanced the cytotoxicity of GLP and mediated lysis of the erythrocytes. A high dose of leptospires (i.e. 10(10) organisms) killed weanling mice causing pathological changes similar to those seen in acute leptospirosis. Similar results were obtained with live, dead, pathogenic and saprophytic leptospires. The results suggest that toxicity is involved in leptospiral infection and that lipid components either of whole leptospires or of a leptospiral GLP may contribute to the pathogenesis of acute leptospirosis.

Animals↗
PubMed1986

Interactions of virulent and avirulent leptospires with primary cultures of renal epithelial cells.

A primary culture system for the cells of mouse renal-tubular epithelium was established and used to observe the adhesion of leptospires. Virulent strains of serovars copenhageni and ballum attached themselves to epithelial cells within 3 h of infection whereas an avirulent variant of serovar copenhageni did not adhere to epithelial cells at all within the experimental period of 24 h. The saprophytic Leptospira biflexa serovar patoc became attached non-specifically to inert glass surfaces as well as to the cells. The adhesion of leptospires to epithelial cells was not inhibited by homologous antibody.

Adhesiveness↗
PubMed1986

A monoclonal antibody reacting with a determinant on leptospiral lipopolysaccharide protects guinea pigs against leptospirosis.

An IgA monoclonal antibody (MUM/F1-1/copenhageni) was produced from a mouse immunised with Leptospira interrogans serovar copenhageni. The antibody showed partial serogroup specificity by agglutination and by reaction in enzyme immunoassay, and opsonised homologous leptospires for phagocytosis by cultured mouse macrophages. Immunodiffusion and Western-blotting experiments indicated that MUM/F1-1/copenhageni reacted with a carbohydrate determinant in the leptospiral lipopolysaccharide. Daily administration of purified MUM/F1-1/copenhageni IgA before and after challenge with 2 X 10(8) virulent homologous leptospires passively protected newborn guinea pigs against lethal leptospirosis.

Animals↗
PubMed1984

Adhesion of leptospires to mouse fibroblasts (L929) and its enhancement by specific antibody.

The adhesion of leptospires (Leptospira interrogans serovar. copenhageni L45) to mouse L-cells was studied by microscopic observations. Within 3 h of infection of monolayers many leptospires adhered to 95-100% of the cells, and intracellular leptospires were demonstrated by electron microscopy. No specific site of attachment on the cells or the leptospires was observed. Avirulent or dead leptospires adhered poorly but attachment of the saprophytic leptospire L. biflexa serovar. patoc occurred on cell and glass surfaces. After adhesion, microvilli on the cell surfaces disappeared within 6 h of infection and cell damage was observed after 12 h. The adhesion was greatly enhanced by the presence of specific antiserum at a subagglutinating concentration. No direct penetration by leptospires of the host cells was observed with transmission and scanning electron microscopy. It appears that (1) adhesion of leptospires to L-cells precedes cell damage, and (2) leptospires may enter cells either through damaged membranes, or by a phagocytosis-like mechanism.

Adhesiveness↗
PubMed1984

Phagocytosis of virulent and avirulent leptospires by guinea-pig and human polymorphonuclear leukocytes in vitro.

Chemiluminescence (CL) and electron microscopy were used to study the phagocytosis of both virulent and avirulent strains of Leptospira interrogans serovar copenhageni by guinea-pig and human polymorphonuclear leukocytes (PMN). A significant CL response was observed when guinea-pig PMN were incubated with virulent leptospires in the presence but not in the absence of specific immune serum. This response was markedly enhanced by the addition of guinea-pig complement. Phagocytosis was confirmed by the observation of intracellular leptospires in guinea-pig PMN by electron microscopy. The phagocytosis of avirulent leptospires by guinea-pig PMN and of both virulent and avirulent leptospires by human PMN required the presence of both specific immune serum and complement. Thus the ability of leptospires to resist phagocytosis by PMN in the absence of immune serum does not appear to be a major determinant of virulence.

Animals↗
PubMed1983

[Destructive cervical spondylitis. An unusual initial manifestation of ankylosing spondylitis].

Erosions of vertebral bodies and intervertebral discs are usually considered as late manifestations of ankylosing spondylitis. Yet they may occur early and indeed constitute the first sign of the disease. This is illustrated by the case reported here, where a 19-year-old woman with an 18-months diagnosis of ankylosing spondylitis was found to have severe destructive lesions of the 6th cervical vertebra without discal lesion nor cervical ankylosis. Surgical biopsy excluded a tumoral or infectious process. Spinal fusion (C4-C7) was performed, and cervical pain was completely relieved with non-steroidal anti-inflammatory drugs.

Adult↗