- Volume 38, Issue 4, 1993
Volume 38, Issue 4, 1993
- Article
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Affinity of the Gastric Pathogen Helicobacter Pylori for the N-Sulphated Glycosaminoglycan Heparan Sulphate
More LessSummaryBinding of 125I-heparan sulphate was a common property of Helicobacter pylori strains isolated from patients with gastroduodenal ulcer diseases. Binding was (i) saturable; (ii) reversible by the addition of unlabelled heparan sulphate and heparin; (iii) inhibited by unlabelled heparan sulphate, heparin, and heparin oligosaccharides but not by other glycosaminoglycans of comparable size (chondroitin sulphate and dermatan sulphate) or by highly glycosylated glycoproteins (hog gastric mucin and fetuin); (iv) reduced by heat treatment (80°C, 10 min) and exposure of the bacteria to pronase E, proteinase K, trypsin and chymotrypsin, but unaffected by treatment with pepsin and neuraminidase; and (v) time-, pH-, and ionic strength-dependent. Scatchard plot analysis of the binding data indicated the presence of one class of high-affinity receptor (Kd = 9 x 10-9 m) for heparan sulphate.
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Characterisation of a Helicobacter Pylori Phage (HP1)
More LessSummaryThe infection of two Helicobacter pylori strains with a phage-containing supernate of the lysogenic H. pylori strain IMMi 290/89 resulted in a lytic cycle and propagation of phage HP1. In negatively-stained preparations, the empty phage heads measured 55-60 nm in diameter and mature heads measured 50 nm. The flexible, striated phage tail was c. 170 nm in length and 9·5 nm in diameter. The phage showed a mean density of 1·40 g/cm3 in sucrose-density gradients and contained double-stranded DNA c. 22000 bp in length.
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The Role of Thymine Starvation in the Expression of Type IV Plasmid-Encoded Trimethoprim-Resistant Dihydrofolate Reductase
More LessSummaryHyperproduction of the type IV plasmid-encoded dihydrofolate reductase was studied in Escherichia coli J62-2 (pUK1123). Hyperproduction of the enzyme was shown to occur not simply as a response to a given concentration of trimethoprim but also to the presence of thymidine in the medium. Before hyperproduction occurred the bacteria began to elongate and die, thus showing the symptoms of thymine starvation. Hyperproduction also required the presence of L-methionine, adenine and glycine, suggesting that the elevated production of the enzyme was a response to the ability of trimethoprim to starve the cell of thymine metabolites.
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The Induction of Trimethoprim Resistance Encoded by the Type IV Dihydrofolate Reductase Gene
More LessSummaryThe effect of plasmid pUK1123, which confers low level resistance to trimethoprim when tested on solid minimal medium, but almost no resistance when tested on IsoSensitest agar, was investigated in liquid media. The growth of Escherichia coli J62-2, harbouring pUK1123, was unaffected in liquid minimal medium containing trimethoprim 10 mg/L. However, in IsoSensitest broth, exposure to this drug concentration resulted in bacteriostasis. After an initial delay, resistance to trimethoprim was induced in IsoSensitest broth containing trimethoprim 10mg/L, by the imposition of thymine starvation. This response was immediately reversible when trimethoprim was removed, confirming that resistance resulted from induction rather than selection of resistant mutants.
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Antiviral Properties of the Seed Extract of an Indian Medicinal Plant, Pongamia Pinnata, Linn., Against Herpes Simplex Viruses: In-Vitro Studies on Vero Cells
More LessSummaryPongamia pinnata, Linn., an Indian medicinal plant used in the Ayurvedha and Siddha traditional medicine systems, for treatment of clinical lesions of skin and genitalia, was evaluated for antiviral properties against herpes simplex virus type-1 (HSV-1) and type 2 (HSV-2) by in-vitro studies in Vero cells. A crude aqueous seed extract of P. pinnata completely inhibited the growth of HSV-1 and HSV-2 at concentrations of 1 and 20 mg/ml (w/v), respectively, as shown by complete absence of cytopathic effect.
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Immunohistological Characterisation of Acute Herpes Simplex Virus Infection of Lumbar Dorsal Root Ganglia in the Rat
More LessSummaryAfter inoculation of herpes simplex virus (HSV) into the dorsal skin of the hind paw of rats, HSV antigen was detected in dorsal root ganglion neurones by immunohistochemistry. Antigen was first detected 2 days after inoculation. Between 2 and 4 days after inoculation, numerous small-type unmyelinated neurones gave positive staining reactions for HSV antigens. Necrosis of neuronal cells was evident by 4 days. Antigen was not detected 6 or 9 days after inoculation. Immunohistological studies of co-cultivated ganglia removed from the infected monolayers, immediately after cytopathic effect first appeared or 24 h later, uniformly revealed virus antigen staining of small-type unmyelinated neuronal cells.
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Analysis of an Outbreak of Variably Methicillin-Resistant Staphylococcus Aureus with Chromosomal RFLPs and Mec Region Probes
More LessSummaryAn outbreak of infections with multi-resistant Staphylococcus aureus with unusual methicillin resistance at a Melbourne hospital was investigated by examining restriction fragment length polymorphisms (RFLPs) of total DNA digested with the rare-cutting endonuclease SmaI. The polymorphisms were identified by pulsed-field gel electrophoresis (PFGE) and were analysed numerically to give quantitative estimates of genetic distances between isolates. The majority of the isolates were found to belong to one group, with only minor genetic differences between the isolates that showed varying resistance to methicillin, thereby suggesting development of resistant variants from one clonal type during the outbreak. These results were confirmed by DNA hybridisation analysis with specific resistance gene probes for parts of a multi-resistance gene cluster (including methicillin) in the chromosome. Analysis of the RFLP patterns of S. aureus isolates is potentially a useful procedure in clinical epidemiology.
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Intracellular Persistence of Chlamydial Major Outer-Membrane Protein, Lipopolysaccharide and Ribosomal RNA After Non-Productive Infection of Human Monocytes with Chlamydia Trachomatis Serovar K
More LessSummaryThe replication of Chlamydia trachomatis serovar K was studied in human peripheral blood monocytes (PBMo). The intracellular fate of the bacteria was examined by determining the presence of chlamydial major outer-membrane protein (MOMP), lipopolysaccharide (LPS) and ribosomal RNA (rRNA). In-vitro infection of PBMo with C. trachomatis serovar K was not productive. However, chlamydial MOMP antigen, demonstrated by immunofluorescence, was present in PBMo for up to 14 days. Infected monocytes also contained chlamydial rRNA, measured by in-vitro hybridisation, and LPS, measured by enzyme immunoassay, for up to 14 days. These data are compatible with the hypothesis that the infection of PBMo with C. trachomatis may play a role in the systemic distribution of chlamydial antigens, leading to systemic manifestations of urogenital chlamydial infection.
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Immunoglobulin-A Detection and the Investigation of Clinical Toxoplasmosis
More LessSummaryCurrent serological methods for the investigation of Toxoplasma gondii infection are unreliable for the diagnosis of congenital disease, reactivated infection associated with the acquired immune deficiency syndrome (AIDS), or the determination of the date of onset of infection. An enzyme-linked immunosorbent assay (ELISA) and an immunosorbent agglutination assay (ISAGA) were developed for the detection of toxoplasma-specific immunoglobulin-A (IgA) and used to investigate patients in these three categories. The IgA ISAGA and IgA ELISA were found to be reproducible and specific tests. The IgA ISAGA demonstrated enhanced sensitivity. Measurement of IgA in patients with toxoplasma-associated lymphadenopathy of known duration and AIDS patients with toxoplasma infection was of limited value. Detection of specific IgA by ISAGA was more sensitive than conventional methods for the diagnosis of congential toxoplasmosis. We recommend the investigation of infant sera with IgA ISAGA. IgA estimation is not indicated in other clinical situations.
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Characteristics of an Avirulent Campylobacter Jejuni Strain and its Virulence-Enhanced Variants
More LessSummaryThe virulence of Campylobacter jejuni for 11-day-old chick embryos is associated with the ability to invade the chorio-allantoic membrane, to resist phagocytosis and to survive and proliferate in vivo. The pathogenicity of a well characterised avirulent C. jejuni strain was enhanced by passaging it intravenously and chorio-allantoically through chick embryos. The resulting isogenic variants had greatly increased ability to survive in vivo. In this study, the morphological and cell-surface characteristics of the avirulent parental strain were compared with those of the more virulent variants to determine whether pathogenicity was associated with one or more cell-surface constituents. Changes associated with the increased virulence of the two variants included alterations in cultural and cellular morphology, loss of flagella, expression of a new outer-membrane protein, alterations in cell-surface carbohydrates and decreases in cell-surface hydrophobicity.
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