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Biomedical subjects

J Theron

Publications and source records attributed to J Theron.

At least 19 recordsLinked to original sources
PubMed2006

A second RGD motif in the 1D capsid protein of a SAT1 type foot-and-mouth disease virus field isolate is not essential for attachment to target cells.

The amino acid sequence motif Arg-Gly-Asp (RGD), located in the surface-exposed betaG-betaH loop of the 1D protein of different serotypes and subtypes of foot-and-mouth disease virus (FMDV), is highly conserved and participates in binding of FMDV to susceptible cells. Previous sequence analyses of the 1D-encoding region of a FMDV serotype SAT1 field isolate from Namibia (NAM/307/98) indicated the presence of a second RGD motif upstream of the conserved betaG-betaH loop RGD. The role of these RGD sequences in virus infection was investigated by mutating the betaG-betaH loop RGD to a KGE tripeptide, using a genome-length infectious chimeric cDNA clone. Although the infectivity of the derived mutant viruses for baby hamster kidney cells (BHK-21) was lost, subsequent replacement of the KGE sequence with RGD in the mutant cDNA clone led to recovery of infectious viruses. Furthermore, viral RNA replication could be demonstrated with the genetically engineered mutant and non-mutant viruses. The presence of virus particles in the transfected cells could be also demonstrated by electron microscopy. These results demonstrate that, in contrast to the betaG-betaH loop RGD motif, the second RGD sequence in the capsid protein 1D of NAM/307/98 does not function as a ligand for receptor binding in BHK-21 cells.

Amino Acid Motifs↗
PubMed2006

Ultrasound-assisted transthoracic biopsy: fine-needle aspiration or cutting-needle biopsy?

The present study compared the diagnostic yield of ultrasound-assisted cutting-needle biopsy (CNB) and fine-needle aspiration biopsy (FNAB) in chest lesions. A physician performed ultrasound and FNAB with a 22-G spinal needle in all patients, directly followed by a 14-G CNB in patients without contraindication. A total of 155 consecutive lesions arising from the lung (74%), pleura (12%), mediastinum (11%) or chest wall (3%) in patients with a final diagnosis of lung carcinoma (74%), other malignant tumours (12%), non-neoplastic disease (9%) or unknown (5%) were prospectively included. The overall diagnostic yield was 87%. Combined specimens were obtained in 123 lesions (79%). In these, yields of FNAB, CNB and both methods combined were 82, 76 and 89%, respectively. FNAB was significantly better than CNB in lung carcinoma (95 versus 81%) but CNB was superior in noncarcinomatous tumours and in benign lesions. On-site cytology was 90% sensitive and 100% specific for predicting a positive FNAB. One patient required drainage for pneumothorax (0.6%). Ultrasound-assisted fine-needle aspiration biopsy performed by chest physicians is an accurate and safe initial diagnostic procedure in patients with a high clinical probability of lung carcinoma. All other patients should undergo concurrent fine-needle aspiration biopsy and cutting-needle biopsy.

Adult↗
PubMed2006

Transbronchial needle aspirates: how many passes per target site?

Transbronchial needle aspiration is a bronchoscopic sampling method for a variety of bronchial and pulmonary lesions. The present study investigated whether and how serial needle passes contribute to the yield of transbronchial needle aspiration at specific target sites. A total of 1,562 needle passes, performed at 374 target sites in 245 patients with neoplastic disease (82%), non-neoplastic disease (15%) or undiagnosed lesions (3%), were prospectively recorded and rated for anatomical location, size, bronchoscopic appearance and underlying disease. Positive aspirates were obtained in 75% of patients and at 68% of target sites. A diagnosis was established with the first, second, third and fourth needle pass at 64, 87, 95 and 98% of targets, respectively. The absolute yield varied strongly with target site features, but the stepwise increment to the maximum yield provided by serial passes was similar across target sites. In conclusion, three transbronchial needle passes per site are appropriate when only a tissue diagnosis is sought and when alternative sites or sampling modalities are available. At least four or five passes should be carried out at lymph node stations critical for the staging of lung cancer.

Adolescent↗
PubMed2004

Segment specific inverted repeat sequences in bluetongue virus mRNA are required for interaction with the virus non structural protein NS2.

Computational secondary structure prediction of all 10 Bluetongue virus (BTV-10) RNA transcripts and mutant inverted repeat transcripts were performed. Transcripts with intact 5' and 3' inverted repeat sequences, all indicated base-pairing between the 5' and 3' ends when optimal folding parameters were applied. Secondary structure analysis of the mutant transcripts lacking the inverted repeat sequences indicated alterations in the secondary structures resulting from altered base-pairing. The importance of the inverted repeat sequences in RNA--protein binding was subsequently investigated. Deletion mutant clones lacking the 5' and/or 3' inverted repeat sequences have been constructed. A baculovirus recombinant expressing the BTV NS2 protein and radioactively synthesized RNA transcripts were subjected to nitrocellulose RNA--protein binding assays. The cumulative results suggested that the inverted repeat deletion mutants display weaker binding compared to BTV-10 segment 8 with intact 5' and 3' inverted repeat sequences. Inverted repeats may influence RNA--protein binding by altering the secondary structure of the RNA and consequently the specific NS2 protein-binding sites may no longer be available.

Base Sequence↗
PubMed2004

The occurrence of campylobacters in water sources in South Africa.

Campylobacter spp., mainly C. jejuni and C. coli, are recognized as significant human bacterial pathogens, being responsible for increasing numbers of gastroenteritis cases worldwide. Several reports have indicated that environmental waters are potential reservoirs and transmitting vehicles for these bacteria. The purpose of this study was thus to examine the occurrence of campylobacters in drinking and environmental water sources of South Africa, a country with a warmer climate and higher microbial pollution levels than those previously addressed in the Northern Hemisphere where similar investigations have been undertaken. Various types of water samples (five drinking water, four ground water, 11 surface water and four raw sewage) were collected from different parts of South Africa. Detection was by enrichment in Bolton broth prior to plating on both selective mCCDA or through a 0.6microm membrane filter on non-selective blood agar isolation media. Out of 100 initially selected Campylobacter-like isolates, only 22 did not grow aerobically and were subsequently identified as Campylobacter spp. by biochemical tests. However, the results obtained by 16S rRNA sequence analysis indicated that only three of these strains (13.6%) were Campylobacter jejuni and the remaining 19 strains were identified as Arcobacter butzleri. The spread of Arcobacter via water warrants further investigation, especially in view of the higher levels of detection and pathogenic nature of these bacteria.

Campylobacter↗
PubMed2003

[Endovascular treatment of a cervical vertebral artery pseudoaneurysm using covered stents. One case report].

Covered stents have been successfully used in the treatment of fusiform aneurysms and post dissection aneurysms in peripheral arteries as well as in post-traumatic arteriovenous fistulas. We report a case where a pseudoaneurysm of the cervical vertebral artery was excluded by placement of two covered stents, preserving patency of the parent artery, in a 15-year-old patient.

Adolescent↗
PubMed2002

Early surgical treatment of Cyrano-nose haemangiomas with Rethi incision.

Nasal haemangiomas may cause great social distress. Complete involution of these haemangiomas does not usually result in a return to normality. The subcutaneous tumour infiltrates the alar cartilages, resulting in a globular aspect of the nasal tip. In this location, haemangiomas are slow to regress, and contour deformities result from the fibrofatty tissue that remains after total involution and also from definitive deformation of the nasal cartilages. Surgery to remove the affected tissue and preserve the anatomy seems to be the best treatment for these tumours. We report six cases of nasal haemangiomas removed using the Rethi incision and a double rim incision. This procedure allows complete dissection of the tumour, and leaves only a small scar. The alar cartilages are returned to their anatomical position to allow normal growth. Surgery is performed at around 2 years of age; skin excision is not necessary because spontaneous skin retraction occurs. Our patients were evaluated by their parents, the surgeon and members of the dermatology staff not involved in their treatment. Pain, scar and final aspect were evaluated using statistical analysis. The parents and surgeon rated the postoperative results as very satisfactory or satisfactory. The dermatology staff also reported improvement after surgery. The scar is nearly invisible and the procedure allows excision of large nasal haemangiomas.

Child, Preschool↗
PubMed2002

Emerging waterborne infections: contributing factors, agents, and detection tools.

Because microorganisms are easily dispersed, display physiological diversity, and tolerate extreme conditions, they are ubiquitous and may contaminate and grow in water. The presence of waterborne enteric pathogens (bacteria, viruses, and protozoa) in domestic water supplies represents a potentially significant human health risk. Even though major outbreaks of waterborne disease are comparatively rare, there is substantial evidence that human enteric pathogens that are frequently present in domestic water supplies are responsible for low-level incidence of waterborne microbial disease. Although these diseases are rarely debilitating to healthy adults for more than a few hours to a few days, enteric pathogens can cause severe illness, even death, for young children, the elderly, or those with compromised immune systems. As the epidemiology of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors. New microbial pathogens have emerged, and some have spread worldwide. Alternative testing strategies for waterborne diseases should significantly improve the ability to detect and control the causative pathogenic agents. In this article, we provide an overview of the current state of knowledge of waterborne microbial pathogens, their detection, and the future of new methods in controlling these infectious agents.

Adaptation, Physiological↗
PubMed2002

Evaluation of a novel heminested PCR assay based on the phosphoglucosamine mutase gene for detection of Helicobacter pylori in saliva and dental plaque.

A novel heminested PCR protocol was developed for the specific detection of Helicobacter pylori at low copy numbers. A set of primers specific for the phosphoglucosamine mutase gene (glmM) of H. pylori produced a 765-bp fragment that was used as template for the heminested primer pair delineating a 496-bp fragment. By using agarose gel electrophoresis for detection of the heminested PCR-amplified products, amplification of H. pylori genomic DNA was achieved at concentrations as low as 0.1 pg, equivalent to 5 x 10(2) bacteria. A study was subsequently undertaken to evaluate the heminested PCR for detection of H. pylori in dental plaque and saliva. Specimens collected from 58 individuals were cultured, and PCR was subsequently performed on the oral cultures. Identification of H. pylori in the same series of saliva and dental plaque specimens was carried out with PCR using a primer pair specific for the H. pylori urease B gene and by the heminested PCR assay. The identity of the amplified products was confirmed by DNA sequencing. Our results demonstrate that the heminested PCR assay was specific for detection of H. pylori, yielding no false-positive results, and that H. pylori had a low prevalence (approximately 3%) in specimens obtained from the oral cavity.

DNA Primers↗
PubMed2001

The use of glass wool as an attachment surface for studying phenotypic changes in Pseudomonas aeruginosa biofilms by two-dimensional gel electrophoresis.

Two-dimensional polyacrylamide gel electrophoresis was used to demonstrate phenotypic differences between Pseudomonas aeruginosa biofilm cells and the planktonic counterpart cells under defined culture conditions. Glass wool was used as a substratum for cell attachment as it affords a large surface-to-volume ratio (1 g with a mean diameter of 15 microns = 1300 cm2), supports the growth of biofilms, allows for free movement of cells between the inter-strand spaces, and it facilitates the exchange of nutrients and oxygen. It also allows for the separation of the biofilm biomass from the surrounding surface influenced planktonic (SIP) cells for further characterization. Comparative analysis of the respective proteomes indicated striking differences in the protein patterns of planktonic, biofilm and SIP cells. We selected 41 proteins, the levels of which varied in a significant and reproducible way in the respective protein profiles. In the biofilm cells, a general up-regulation of the spots was seen, but in SIP cells expression of these spots were generally down-regulated. Altogether six unique proteins were seen in the planktonic cells, while the biofilm and SIP cells contained five and two unique proteins, respectively. Glass wool, therefore, appears to be an ideal attachment surface for the study of biofilm development.

Bacterial Adhesion↗
PubMed2001

A sensitive seminested PCR method for the detection of Shigella in spiked environmental water samples.

A rapid seminested polymerase chain reaction (PCR) method for the specific, sensitive detection of virulent Shigella spp. in spiked environmental water samples was developed. A set of primers specific for the invasion plasmid antigen gene (ipaH) of virulent Shigella spp. and enteroinvasive Escherichia coli produced a 620-bp fragment that was used as template for the seminested primer pair delineating a 401-bp fragment. By using agarose gel electrophoresis for detection of the seminested PCR-amplified products, a detection limit of 1.6 x 10(3) cfu S. flexneri was obtained with amplification reactions from crude bacterial lysates. The PCR procedure coupled with an enrichment culture incubated for 6 h detected as few as 1.6 S. flexneri organisms in pure culture. Treated sewage, ground, surface and drinking water samples collected from various sources were seeded with S. flexneri and incubated in GN broth for 6 h before detection by seminested PCR. A detection limit lower than 14 cfu/ml was achieved in some water samples. The results indicate that the described seminested PCR has the advantage of a rapid turnaround time and it fulfills the requirements of sensitivity and specificity for use in an environmental laboratory.

Base Sequence↗
PubMed2001

Mucous membrane pemphigoid: HLA-DQB1*0301 is associated with all clinical sites of involvement and may be linked to antibasement membrane IgG production.

BACKGROUND: Class I human leucocyte antigens (HLA) -A, -B, -Cw and class II HLA-DRB1, -DQB1 alleles were determined in 131 British Caucasian patients with mucous membrane pemphigoid (MMP) using serological and DNA-based methods. OBJECTIVES: To analyse the class I and II alleles expressed in well-defined clinical and immunopathological subgroups of MMP, in order to establish whether specific alleles or haplotypes might in part explain disease susceptibility, clinical sites of involvement or disease severity. METHODS: Subgroups of patients were analysed according to the following clinical criteria: age of onset, sex, sites of clinical involvement (oral, ocular, skin, nasal, genital, pharyngeal, oesophageal, laryngeal, perianal), disease severity and history of autoimmune disease. Subgroups were also analysed according to the following immunopathological criteria: autoantibody profile, the presence of circulating antibasement membrane IgG or IgA antibodies and the detection of target basement membrane zone (BMZ) antigens (BP230 and BP180) by IgG autoantibodies. RESULTS: Class I HLA typing showed no significant disease or subgroup associations. Class II DRB1 typing showed a significantly increased allelic frequency in MMP vs. controls for DRB1*11 (RR = 2.08, Pc < 0.0000056). For DQB1, MMP vs. controls, there was a significantly increased allelic frequency for DQB1*0301 (Pc < 0.00000028) in both males and females; all clinical sites of involvement, with the exception of laryngeal, oesophageal and perianal sites and in patients with detectable circulating anti-BMZ IgG compared with those negative for IgG (P < 0.0096, Pc < 0.019). A positive trend was noted in patients with ocular involvement compared with no ocular involvement and in patients with a clinical score > or = 10 compared with < 10. We found no difference in DQB1*0301 allele frequency between subgroups with or without BP180 or BP230 target antigens. Haplotype frequencies showed an increase in DRB1*04, DQB1*0301 (Pc < 0.000066) and DRB1*11, DQB1*0301 (Pc < 0.000002) among patients compared with controls. CONCLUSIONS: The DQB1*0301 allele confers a predisposition to all subgroups of MMP and may have a role in T-cell recognition of basement membrane antigens, resulting in the production of anti-BMZ IgG autoantibodies. The positive trend between increased allelic expression of DQB1*0301 in patients with ocular disease and in those with a higher clinical score, further suggests a role for this allele in disease severity.

Adult↗
PubMed2001

Current status of carotid bifurcation angioplasty and stenting based on a consensus of opinion leaders.

OBJECTIVE: Carotid bifurcation angioplasty and stenting (CBAS) has generated controversy and widely divergent opinions about its current therapeutic role. To resolve differences and establish a unified view of CBAS' present role, a consensus conference of 17 experts, world opinion leaders from five countries, was held on November 21, 1999. METHODS: These 17 participants had previously answered 18 key questions on current CBAS issues. At the conference these 18 questions and participants' answers were discussed and in some cases modified to determine points of agreement (consensus), near consensus, (prevailing opinion), or divided opinion (disagreement). RESULTS: Conference discussion added two modified questions, placing a total of 20 key questions before the participants, representing four specialties (interventional radiology, seven; vascular surgery, six; interventional cardiology, three; neurosurgery, one). It is interesting that consensus was reached on the answers to 11 (55%) of 20 of the questions, and near consensus was reached on answers to 6 (30%) of 20 of the questions. Only with the answers to three (15%) of the questions was there persisting controversy. Moreover, both these differences and areas of agreement crossed specialty lines. Consensus Conclusions: CBAS should not currently undergo widespread practice, which should await results of randomized trials. CBAS is currently appropriate treatment for patients at high risk in experienced centers. CBAS is not generally appropriate for patients at low risk. Neurorescue skills should be available if CBAS is performed. When cerebral protection devices are available, they should be used for CBAS. Adequate stents and technology for performing CBAS currently exist. There were divergent opinions regarding the proportions of patients presently acceptable for CBAS treatment (<5% to 100%, mean 44%) and best treated by CBAS (<3% to 100%, mean 34%). These and other consensus conclusions will help physicians in all specialties deal with CBAS in a rational way rather than by being guided by unsubstantiated claims.

Angioplasty↗
PubMed2000

Atrophy of the corpus callosum correlates with white matter lesions in patients with cerebral ischaemia.

Many studies of white matter high signal (WMHS) on T2-weighted MRI have disclosed that it is related to cerebral ischaemia and to brain atrophy. Atrophy of the corpus callosum (CC) has also been studied in relation to ischaemia. Our objective was to test the hypothesis that CC atrophy could be due to ischaemia. We therefore assessed CC, WMHS and brain atrophy in patients with risk factors without strokes (the risk factor group) and in those with infarcts (the infarct group), to investigate the relationships between these factors. We studied 30 patients in the infarct group, 14 in the risk factor group, and 29 normal subjects. Using axial T1-weighted MRI, cortical atrophy and ventricular enlargement (brain atrophy) were visually rated. Using axial T2-weighted MRI, WMHS was assessed in three categories: periventricular symmetrical, periventricular asymmetrical and subcortical. Using the mid-sagittal T1-weighted image, the CC was measured in its anterior, posterior, mid-anterior and mid-posterior portions. In the normal group, no correlations were noted between parameters. In the infarct group, there were significant correlations between CC and brain atrophy, and between CC atrophy and WMHS. After removing the effects of age, gender and brain atrophy, significant correlations were noted between some CC measures and subcortical WMHS. In the risk factor group, there were significant correlations between CC and brain atrophy and between CC atrophy and WMHS. After allowance for age, gender and brain atrophy, significant correlations between some CC measures and periventricular WMHS remained. The hypothesis that CC atrophy could be due to cerebral ischaemia was supported by other analyses. Namely, for correlations between the extent of infarcts and partial CC atrophy in patients with anterior middle cerebral artery (MCA) and with posterior MCA infarcts, there were significant correlations between the extent of infarct and mid-anterior CC atrophy in the former, and posterior CC atrophy in the latter. Our findings could indicate that CC atrophy is associated with cerebral ischaemia.

Adult↗
PubMed2000

Detection of toxigenic Vibrio cholerae from environmental water samples by an enrichment broth cultivation-pit-stop semi-nested PCR procedure.

A pit-stop semi-nested PCR assay for the detection of toxigenic Vibrio cholerae in environmental water samples was developed and its performance evaluated. The PCR technique amplifies sequences within the cholera toxin operon specific for toxigenic V. cholerae. The PCR procedure coupled with an enrichment culture detected as few as four V. cholerae organisms in pure culture. Treated sewage, surface, ground and drinking water samples were seeded with V. cholerae and following enrichment, a detection limit of as few as 1 V. cholerae cfu ml(-1) was obtained with amplification reactions from crude bacterial lysates. The proposed method, which includes a combination of enrichment, rapid sample preparation and a pit-stop semi-nested PCR, could be applicable in the rapid detection of toxigenic V. cholerae in environmental water samples.

Cholera Toxin↗
PubMed2000

Molecular techniques for determining microbial diversity and community structure in natural environments.

The ability to quantify the number and kinds of microorganisms within a community is fundamental to the understanding of the structure and function of an ecosystem. The simple morphology of most microbes provides few clues for their identification and physiological traits are often ambiguous. In addition, many organisms resist cultivation, which is essential to their characterization. Recombinant DNA techniques have provided a means whereby many of the obstacles associated with cultivation and description can be overcome and subsequently has allowed many new insights into the complexity of natural microbial communities. Molecular approaches based on 16S ribosomal RNA (rRNA) sequence analysis allow direct investigation of the community structure, diversity, and phylogeny of microorganisms in almost any environment, while quantification of the individual types of microorganisms or entire microbial communities may be addressed by nucleic acid hybridization techniques. Furthermore, the use of fluorescently labeled population-specific rRNA probes allows microscopic examination of individual cells in complex microbial assemblages as well as their interactions in situ. In this review, we discuss strategies for characterizing microbial communities without the need for cultivation.

DNA, Ribosomal↗