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Biomedical subjects

R A Wilson

Publications and source records attributed to R A Wilson.

At least 55 records · Page 3Linked to original sources
PubMed1999

Laparoscopic repair of bilateral and recurrent hernias.

The optimal inguinal hernia repair has been controversial for decades. Since the advent of minimally invasive surgery, laparoscopic techniques have added to the controversy. Laparoscopic hernia repair has been advocated by many experts for the repair of bilateral and recurrent inguinal hernias. This study reviews the experience of a single community-based teaching hospital using the total extraperitoneal (TEP)-approach laparoscopic hernia repair for treating patients with bilateral and/or recurrent inguinal hernias. Since the TEP approach was adopted in June 1993, a total of 457 patients were treated for bilateral (322 patients) and/or recurrent (175) inguinal hernias (40 patients had recurrent and bilateral hernias). A total of 779 hernias were repaired with this technique. The average age of this patient group was 47 years, and there were 413 males and 44 females. Operative time averaged 68.3 minutes per patient, and there were 26 (5.7%) minor complications. There were 2 (0.4%) major complications, an enterotomy and a cystotomy, both early in the series and both in patients with previous lower abdominal surgery. There have been no deaths. With an average follow-up of 30 months (range, 1-60 months), there have been three (0.2%) recurrences. These recurrences were due to technical problems (inadequate mesh coverage), and each was repaired with a laparoscopic transabdominal approach or an anterior open approach. The use of the TEP-approach laparoscopic hernia repair is safe and effective in patients with recurrent and/or bilateral inguinal hernias.

Abdominal Muscles↗
PubMed1998

Minimum CAG repeat in the human calmodulin-1 gene 5' untranslated region is required for full expression.

The human calmodulin-1 gene (hCALM1) contains a (CAG)7 repeat in its 5'-untranslated region (5'-UTR). We found this repeat to be stable and nonpolymorphic in the human population. To determine whether the repeat region affects hCALM1 expression and whether repeat expansions to numbers known to be associated with disease in other genes may alter expression, we tested luciferase reporter genes driven by the hCALM1 promoter and 5'-UTR containing 0, 7 (wild-type), 20, and 45 CAG repeats in human NT2/D1 teratoma cells. Interestingly, the repeat deletion, (CAG)0, decreased expression by 45%, while repeat expansions to (CAG)20 and (CAG)45, or the insertion of a scrambled (C,A,G)7 sequence did not alter gene expression. These data indicate (1) that the endogenous repeat element is required for full expression of hCALM1, and (2) that some triplet repeat expansions in the 5'-UTR of protein-coding genes may be well tolerated and even optimize gene expression.

Animals↗
PubMed1998

In the absence of IL-12, the induction of Th1-mediated protective immunity by the attenuated schistosome vaccine is impaired, revealing an alternative pathway with Th2-type characteristics.

Vaccination of mice with irradiated Schistosoma mansoni larvae confers high levels of immunity which is mediated by Th1-type lymphocytes. To investigate a possible role for IL-12 in the induction of protection, we have compared the immune response of IL-12 p40-deficient (KO) mice and their C57BL/6 (WT) counterparts following vaccination. Cultured lymph node cells from KO mice had markedly altered cytokine profiles with significantly decreased production of IFN-gamma increased IL-4. Correspondingly, KO mice had enhanced levels of IgE. After challenge, cells recovered from the lungs of KO mice secreted abundant IL-4 and IL-5 but little IFN-gamma, while flow cytometric and histological analysis of lung cell populations recorded a very high proportion of eosinophils. The levels of protection in KO mice were substantially lower than in their WT counterparts, demonstrating the importance of IL-12 and Th1-mediated immune responses. This conclusion is reinforced by the administration of rIL-12 to KO mice immediately after vaccination which led to increased IFN-gamma and the restoration of protective immunity. Nevertheless, the data also indicated that the limited levels of protection induced in KO mice occur via an IL-12-independent pathway, possibly mediated by Th2 cells.

Animals↗
PubMed1998

Why don't we have a schistosomiasis vaccine?

Over the past 30 years there has been a concerted effort to understand host immune responses to schistosomes, with the ultimate aim of producing a vaccine for human use. In this issue, Bergquist and Colley, in summarizing recent meetings in Cairo, provide a detailed appraisal of progress towards that goal. It seems an appropriate time to ask why, with reference to Schistosoma mansoni, the development of a vaccine has proved so difficult. This question is explored here by Alan Wilson and Pat Coulson.

Journal Article↗
PubMed1998

Schistosome-induced portacaval haemodynamic changes in Rattus rattus are associated with translocation of adult worms to the lungs.

The presence of naturally portacaval shunts has been investigated in the vasculature of normal and Schistosoma mansoni-infected Rattus rattus. Using the technique of injecting Polystyrene microspheres in the superior mesenteric vein, we demonstrated that the presence of adult schistosomes in the lungs of R. rattus was not due to an innate anomaly of the rat vasculature but resulted from the formation of portacaval shunts during infection. In rats harbouring a bisexual infection, microspheres were only detected in the lungs from week 7. The development and increasing size of the shunts were maximal between weeks 7 and 10 and coincident with the translocation of adult worms from the portal tract to the lungs. At weeks 20-25, only 1-2% of the microspheres were recovered from the lungs, suggesting that the portacaval anastomoses have regressed due to reduction in portal hypertension after worm translocation. R. rattus with a male-only schistosome infection harboured adult worms in the lungs, indicating that the development of shunts does not solely depend upon egg deposition in the liver to generate hypertension. The relationships between the presence of the schistosomes in the lungs, the portacaval shunting and the resistance to reinfection is discussed.

Animals↗
PubMed1998

Induction of immunity to Schistosoma mansoni: interaction of schistosomula with accessory leucocytes in murine skin and draining lymph nodes.

A single exposure to radiation-attenuated cercariae of Schistosoma mansoni induces a high level of protective immunity in C57BL/6 mice, which is mediated by Th1 responses. Events in the skin and/or draining lymph nodes early after exposure are crucial for the induction of protection, and we have investigated the interactions of vaccinating parasites with host leucocytes in these 2 locations. We observed extensive lateral spreading of cercarial secretions along layers of the stratum corneum but not between keratinocytes. There was little direct contact with host leucocytes during the first 1-2 days when the parasites lay at the base of the epidermis, but cells accumulated in the underlying dermis. In contrast to normal parasites, attenuated larvae persisted in the dermis for > 10 days, often surrounded by aggregates of macrophages/dendritic cells. Whilst cells bearing MHC II, CD11b or CD11c markers were present in the lymph nodes, particularly in the periphery and paracortical areas, no obvious redistribution was seen as a result of parasite residence there for 5-15 days. However, ultrastructural observations revealed numerous cells with macrophage/dendritic morphology in the vicinity of parasites, in some instances closely adherent to the tegument. The observations strongly suggest that the tegument is a potent source of the antigens which prime the immune system in the lymph nodes of vaccinated mice for a protective response.

Animals↗
PubMed1998

Th1 cytokine mRNA expression dominates in the skin-draining lymph nodes of C57BL/6 mice following vaccination with irradiated Schistosoma mansoni cercariae, but is down-regulated upon challenge infection.

Vaccination of C57BL/6 mice with irradiated cercariae of Schistosoma mansoni results in the induction of high levels of immunity to subsequent infection. The events occurring in the lymph nodes draining the exposure site have been analysed ex vivo by reverse transcription-polymerase chain reaction (RT-PCR) and the timing of cytokine gene expression following exposure has been established. After vaccination, spatial separation of the T-helper type 1 (Th1) and Th2 responses was evident, with interferon-gamma (IFN-gamma), interleukin-2 (IL-2) and IL-12 mRNA peaking earlier than mRNA for IL-4, IL-5 and IL-10. In contrast to the profiles observed post-vaccination, following challenge the IL-4 mRNA was predominant in the draining lymph nodes, with IFN-gamma message levels barely detectable above the naive level. These observations are confirmed by the analysis of IL-4 and IFN-gamma mRNA using competitive PCR. From these studies it is clear that irradiated cercariae are more able to promote a protective Th1 response, with normal parasites eliciting higher IL-4 and IL-5 expression upon both primary and secondary stimulation.

Animals↗
PubMed1998

Nitric oxide produced in the lungs of mice immunized with the radiation-attenuated schistosome vaccine is not the major agent causing challenge parasite elimination.

Mice vaccinated with radiation-attenuated cercariae of Schistosoma mansoni exhibit high levels of protection against a challenge with normal larvae. The immune effector mechanism, which operates against schistosomula in the lungs, requires CD4+ T cells capable of producing interferon-gamma (IFN-gamma). This cytokine can stimulate production of nitric oxide (NO), via its ability to up-regulate inducible nitric oxide synthase (iNOS). We have therefore evaluated the potential role of NO in the effector mechanism operating in vaccinated mice. Evidence for the production of NO in the lungs of such animals was obtained from assays on antigen-stimulated airway cell cultures. Enhanced levels of NO, compared with those in cultures from control mice, were detected both after vaccination and after challenge; elevated levels of iNOS mRNA were also present in whole lung after challenge. However, administration of an iNOS inhibitor to vaccinated mice after percutaneous challenge did not significantly increase the worm burden. Furthermore, when mice with a disrupted iNOS gene were vaccinated they showed a highly significant level of protection. Although NO from activated macrophages can mediate cytotoxic killing of newly transformed schistosomula in vitro, we have demonstrated that the addition of erythrocytes to these larvicidal assays abolishes its effects. We interpret this to mean that once migrating schistosomula enter the bloodstream they will be protected against the cytotoxic actions of NO. Our data thus provide little evidence to implicate NO as a major component of the pulmonary effector response to S. mansoni in vaccinated mice.

Animals↗
PubMed1998

African trypanosome infections in mice that lack the interferon-gamma receptor gene: nitric oxide-dependent and -independent suppression of T-cell proliferative responses and the development of anaemia.

Infection of mice with African trypanosomes leads to a severe immunosuppression, mediated by suppressor macrophages. Using ex vivo macrophage culture and in vivo cell transfer, it has been shown that nitric oxide (NO) is a potent effector product of these cells and causes both lymphocyte unresponsiveness and dyserythropoiesis. We explored the role of NO in vivo during trypanosome infection using mice with a disrupted interferon-gamma-receptor gene, which were unable to respond with macrophage activation and NO synthesis. These mice were less effective at controlling parasitaemia than the wild types, but showed an improved splenic T-cell responsiveness and reduced anaemia during the early stages of infection. The data indicate that, in the mouse, NO is a significant mediator of immunosuppression only in early infection. Beyond day 10 of infection, NO-independent mechanisms are of primary significance and the control of parasitaemia and T-cell responsiveness are not directly related.

Anemia↗
PubMed1998

Noninvasive diagnosis of gastroesophageal inflammation using dipyridamole thallium-201 tomography.

OBJECTIVE: Esophagitis, a complication of GERD, and gastric erosions are common findings in dyspeptic patients. Unfortunately, these findings cannot be predicted based on symptoms alone and require endoscopy for an accurate diagnosis. Noninvasive diagnosis of other gastrointestinal pathology by radiopharmaceuticals (GA 67, Tc 99m pertechnetate) has previously been studied. We hypothesized that endoscopically documented esophagitis and/or gastric erosions could also be detected by using dipyridamole thallium-201 imaging and, if they were of sufficient accuracy, could serve as a useful, noninvasive screening test for esophagitis and/or gastric erosions. METHODS: A pilot study was undertaken in 12 patients undergoing endoscopy for symptoms of GERD or dyspepsia. Esophagitis was defined as the presence of either erosions or ulceration and gastric erosions were defined as discrete mucosal breaks measuring > or = 1 mm. Dipyridamole thallium-201 imaging was performed the following day on all 12 patients. A standard dose of dipyridamole (0.56 mg/kg) was infused over 4 min, followed by a 3-mCi dose of thallium-201. Initial stress tomographic images and reinjection (1 mCi) resting tomographic images 3-4 h later were obtained using a gamma camera. Tomographic images were read blinded to the endoscopy results. Thallium-201 uptake was graded on a 0-3+ scale using the liver uptake as the internal comparative standard (2+ = uptake equal to the liver). Abnormal thallium uptake was defined as > or = 2+ in the area of the esophagus or stomach. RESULTS: Seven women and five men (mean age 41 yr, range 25-60 yr) were studied. Eight patients were taking histamine-2 receptor antagonists and none were on proton pump inhibitors, or promotility agents. All five patients with endoscopic esophagitis had a positive thallium-201 tomographic image. Seven patients had no evidence of esophagitis, and three had positive thallium-201 tomograms. Dipyridamole thallium-201 imaging sensitivity, specificity, and positive and negative predictive values for esophagitis were 100%, 57%, 63%, and 100%, respectively. All three patients with gastric erosions had positive thallium-201 tomograms. Six of nine patients without gastric erosions had positive tomograms. The sensitivity, specificity, and positive and negative predictive values of DT 201 gastric erosions were 100%, 33%, 33%, and 100%, respectively. CONCLUSIONS: Dipyridamole thallium-201 tomographic imaging has good sensitivity (100%) in detecting esophagogastric mucosal erosions, but its poor specificity (33-57%) results in an unacceptable accuracy as a screening test. Additionally, the cost of radiopharmaceuticals requires that sensitivity and specificity be at least equal to that of endoscopy for this test to be clinically valuable as a screening test. However, a noninvasive test for these diseases is inherently appealing, and further research in this area seems to be warranted.

Adult↗
PubMed1998

Mutational analysis of AREA, a transcriptional activator mediating nitrogen metabolite repression in Aspergillus nidulans and a member of the "streetwise" GATA family of transcription factors.

The transcriptional activator AREA is a member of the GATA family of transcription factors and mediates nitrogen metabolite repression in the fungus Aspergillus nidulans. The nutritional versatility of A. nidulans and its amenability to classical and reverse genetic manipulations make the AREA DNA binding domain (DBD) a useful model for analyzing GATA family DBDs, particularly as structures of two AREA-DNA complexes have been determined. The 109 extant mutant forms of the AREA DBD surveyed here constitute one of the highest totals of eukaryotic transcription factor DBD mutants, are discussed in light of the roles of individual residues, and are compared to corresponding mutant sequence changes in other fungal GATA factor DBDs. Other topics include delineation of the DBD using both homology and mutational truncation, use of frameshift reversion to detect regions of tolerance to mutational change, the finding that duplication of the DBD can apparently enhance AREA function, and use of the AREA system to analyze a vertebrate GATA factor DBD. Some major points to emerge from work on the AREA DBD are (i) tolerance to sequence change (with retention of function) is surprisingly great, (ii) mutational changes in a transcription factor can have widely differing, even opposing, effects on expression of different structural genes so that monitoring expression of one or even several structural genes can be insufficient and possibly misleading, and (iii) a mutational change altering local hydrophobic packing and DNA binding target specificity can markedly influence the behavior of mutational changes elsewhere in the DBD.

Amino Acid Sequence↗
PubMed1998

Interferon gamma is a key cytokine in lung phase immunity to schistosomes but what is its precise role?

Vaccination of mice with radiation-attenuated cercariae of Schistosoma mansoni induces a high level of protection against challenge with normal larvae. The immune effector mechanism, which operates in the lungs, is a cell-mediated delayed-type hypersensitivity response and involves the formation of a tight focus of mononuclear cells around embolised larvae. CD4+ T cells with Th1 characteristics are a major component of the infiltrate. They secrete abundant interferon gamma (IFN gamma) upon antigen stimulation in vitro, whilst in vivo neutralisation of the cytokine results in 90% abrogation of immunity. IFN gamma can induce a large number of genes and an attempt has been made to identify the ones which are essential components of the effector mechanism. Inducible nitric oxide synthase (iNOS) is such a candidate and nitric oxide (NO) is produced by cultures of airway leucocytes from the lungs of vaccinated mice post-challenge. However, the continued resistance of mice with a disrupted iNOS gene indicates that NO has only a minor role in the protective response. Mice with a disrupted IFN gamma receptor gene have been used to dissect the role of the cytokine. After vaccination and challenge, CD4+ T cells from the pulmonary interstitium have reduced levels of ICAM-1 and LFA-1 expression, compared to wild-type animals, which coincides with a reduced cohesiveness of foci. However, immunity is not significantly impaired in mice with a disrupted ICAM-1 gene, and focus formation is normal. Similarly, a role has not been found for CD2/CD48 interactions in cell aggregation. Possible IFN gamma-inducible molecules yet to be fully investigated include other ligand-receptor pairs, chemokines, and tumour necrosis factor alpha.

Animals↗
PubMed1998

Cytokines as determinants of resistance and pathology in human Schistosoma mansoni infection.

The role of different cytokines in the peripheral blood mononuclear cell (PBMC) proliferative response and in in vitro granuloma formation was evaluated in a cross-sectional study with patients with the different clinical forms and phases of Schistosoma mansoni infection, as well as a group of individuals "naturally" resistant to infection named normal endemic (NE). The blockage of IL-4 and IL-5 using anti-IL-4 and anti-IL-5 antibodies significantly reduced the PBMC proliferative response to soluble egg (SEA) and adult worm (SWAP) antigens in acute (ACT), chronic intestinal (INT) and hepatosplenic (HS) patients. Similar results were obtained in the in vitro granuloma formation. Blockage of IL-10 had no significant effect on either assay using PBMC from ACT or HS. In contrast, the addition of anti-IL-10 antibodies to PBMC cultures from INT patients significantly increased the proliferative response to SEA and SWAP as well as the in vitro granuloma formation. Interestingly, association of anti-IL-4 and anti-IL-10 antibodies did not increase the PBMC proliferative response of these patients, suggesting that IL-10 may act by modulating IL-4 and IL-5 secretion. Addition of recombinant IL-10 decreased the proliferative response to undetectable levels when PBMC from patients with the different clinical forms were used. Analysis of IFN-gamma in the supernatants showed that PBMC from INT patients secreted low levels of IFN-gamma upon antigenic stimulation. In contrast, PBMC from NE secreted high levels of IFN-gamma. These data suggest that IL-10 is an important cytokine in regulating the immune response and possibly controlling morbidity in human schistosomiasis mansoni, and that the production of IFN-gamma may be associated with resistance to infection.

Animals↗
PubMed1998

Comparison of the Difco EZ Coil rapid detection system and Petrifilm test kit-HEC for detection of Escherichia coli O157:H7 in fresh and frozen ground beef.

The Difco EZ Coli Rapid Detection System was compared to the 3M Petrifilm method for detection of Escherichia coli O157:H7 in raw ground beef. Raw meatballs (25 g) were inoculated with 10 to 15 cells of Escherichia coli O157:H7, stored for various times and at different temperatures, and then stomached for 2 min in 225 ml of EZ Coli enrichment broth, which was then incubated at 42 degrees C for 18 to 24 h. A 1-ml sample of the enrichment broth was loaded into the top of the detector tips and the remaining EZ Coli broth held at 35 degrees C before streaking onto MacConkey sorbitol agar and tryptic soy agar with yeast extract. A duplicate set of meatballs were tested using the 3M Petrifilm Test Kit-HEC for hemorrhagic Escherichia coli O157:H7. In this method raw meatballs (25 g) were enriched for 6 h in modified EC broth containing novobiocin at 37 degrees C prior to inoculation of the Petrifilm E. coli Count Plates, which were incubated at 42 degrees C for 18 h. The immunoblot ELISA was performed following this incubation. Presumptive positive isolates from both methods were confirmed using Oxoid E. coli Latex Agglutination and Difco Pasco ID Tripanels. Both methods permitted detection of 10 to 15 cells of E. coli O157:H7 per ml (i) immediately following inoculation, (ii) after 3 days of refrigerated storage at 8 degrees C, and (iii) after 30 days in frozen storage at -20 degrees C. The Difco EZ Coli Detection System proved to be a simpler and faster screening method with identification of negative and presumptive positive samples within 15 to 18 h.

Animals↗
PubMed1998

Colicinogeny among Escherichia coli serotypes, including O157:H7, representing four closely related diarrheagenic clones.

Twenty-seven diarrheagenic Escherichia coli (DEC) strains from five closely related, genetically distinct clones (DEC 3, 4, 8, 9, and 10), representing serotypes commonly associated with Shiga-like toxin production, i.e., O15:H-, O26:(H11, H-), O111:(H8, H11, H-), and O157:H7, were evaluated for colicinogeny on Luria agar or Luria agar containing 0.25 microgram/ml mitomycin C to induce colicin production. Ten (37%) of the DEC strains tested were colicinogenic. One of 11 serotype O157:H7 strains, DEC strain 4E, produced a colicin identified as Col D. DEC strains 8B, 9D, and 10B produced Col E1, whereas DEC strain 10A produced Col E2. DEC strains 8A, 8E, 10C, 10E, and 10F produced "untypable" colicins that killed almost all Pugsley Colicin Reference Set strains and the other DEC strains tested. To aid with further characterization of the colicins, plasmids extracted from each colicin-producing (Col+) DEC strain were used to transform E. coli strain DH5 alpha. All Col+ DH5 alpha transformants contained one plasmid ranging in size from 1.3 to 10 kb. Some transformants were stable colicin producers whereas others were unstable. The inhibitory activity and colicin sensitivity and insensitivity profiles of the Col+ transformants were similar to those of the corresponding Col+ donor DEC strains. It appears that the untypable colicins are novel and, thus, warrant further study. Colicin production by some of the DEC strains evaluated partly explains why they were insensitive to standard colicins in a previous study.

Animals↗
PubMed1998

Destruction of Escherichia coli O157:H7 and Salmonella typhimurium in Lebanon bologna by interaction of fermentation pH, heating temperature, and time.

Fermented meats have caused food-borne illness due to enterohemorrhagic Escherichia coli. Consumption of Lebanon bologna was epidemiologically associated wit a recent outbreak of salmonellosis. The present study was conducted to determine the effect of pH (after the fermentation step), final heating temperature, and time on destruction of E. coli O157:H7 and Salmonella typhimurium in Lebanon bologna. Raw Lebanon bologna mix was inoculate with either of the pathogens (ca.10(8) CFR/g and fermented for 12 h at 80 degrees F (26.7 degrees C) and then at 100 degrees F (37.8 degrees C) unit the pH reached wither 5.2 or 4.7. The mix was then heated to 110, 115, or 120 degrees F (43.3, 46.1, or 48.9 degrees C). The bologna was sampled at various times, decimally diluted, and plated on either McConkey sorbitol agar or XLD agar to enumerate E. coli O157:H7 and S. typhimurium, respectively. Fermentation alone reduced populations of both pathogens by < 2 log units and heating alone reduced populations of E. coli O157:H7 by < 3 log units. A combination of fermenting to either pH 5.2 or 4.7, followed by heating at 110 degrees F (43.3 degrees C) for 20h, 115 degrees F (46.1 degrees C) for 10 h, or 120 degrees F (48.9 degrees C) for 3 h reduced populations of both pathogens by > 7 log units. Overall S. typhimurium cells were either equally or significantly less resistant (P < 0.01) than cells of E. coli O157:H7. Significantly interactions (P < 0.01) among the three factors for the destruction of E. coli O157:H7 were observed. A process-specific regression equation was developed to predict the destruction of E. coli O157:H7 in Lebanon bologna.

Colony Count, Microbial↗