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Biomedical subjects

G Saunders

Publications and source records attributed to G Saunders.

At least 19 recordsLinked to original sources
PubMed2007

RNA interference in parasitic helminths: current situation, potential pitfalls and future prospects.

RNA interference (RNAi) has become an invaluable tool for the functional analysis of genes in a wide variety of organisms including the free-living nematode Caenorhabditis elegans. Recently, attempts have been made to apply this technology to parasitic helminths of animals and plants with variable success. Gene knockdown has been reported for Schistosoma mansoni by soaking or electroporating different life-stages in dsRNA. Similar approaches have been tested on parasitic nematodes which clearly showed that, under certain conditions, it was possible to interfere with gene expression. However, despite these successes, the current utility of this technology in parasite research is questionable. First, problems have arisen with the specificity of RNAi. Treatment of the parasites with dsRNA resulted, in many cases, in non-specific effects. Second, the current RNAi methods have a limited efficiency and effects are sometimes difficult to reproduce. This was especially the case in strongylid parasites where only a small number of genes were susceptible to RNAi-mediated gene knockdown. The future application of RNAi in parasite functional genomics will greatly depend on how we can overcome these difficulties. Optimization of the dsRNA delivery methods and in vitro culture conditions will be the major challenges.

Animals↗
PubMed2005

Accelerated re-epithelialization in beta3-integrin-deficient- mice is associated with enhanced TGF-beta1 signaling.

The upregulation of TGF-beta1 and integrin expression during wound healing has implicated these molecules in this process, but their precise regulation and roles remain unclear. Here we report that, notably, mice lacking beta(3)-integrins show enhanced wound healing with re-epithelialization complete several days earlier than in wild-type mice. We show that this effect is the result of an increase in TGF-beta1 and enhanced dermal fibroblast infiltration into wounds of beta(3)-null mice. Specifically, beta(3)-integrin deficiency is associated with elevated TGF-beta receptor I and receptor II expression, reduced Smad3 levels, sustained Smad2 and Smad4 nuclear localization and enhanced TGF-beta1-mediated dermal fibroblast migration. These data indicate that alpha(v)beta(3)-integrin can suppress TGF-beta1-mediated signaling, thereby controlling the rate of wound healing, and highlight a new mechanism for TGF-beta1 regulation by beta(3)-integrins.

Animals↗
PubMed2003

New algorithms for multi-class cancer diagnosis using tumor gene expression signatures.

MOTIVATION: The increasing use of DNA microarray-based tumor gene expression profiles for cancer diagnosis requires mathematical methods with high accuracy for solving clustering, feature selection and classification problems of gene expression data. RESULTS: New algorithms are developed for solving clustering, feature selection and classification problems of gene expression data. The clustering algorithm is based on optimization techniques and allows the calculation of clusters step-by-step. This approach allows us to find as many clusters as a data set contains with respect to some tolerance. Feature selection is crucial for a gene expression database. Our feature selection algorithm is based on calculating overlaps of different genes. The database used, contains over 16 000 genes and this number is considerably reduced by feature selection. We propose a classification algorithm where each tissue sample is considered as the center of a cluster which is a ball. The results of numerical experiments confirm that the classification algorithm in combination with the feature selection algorithm perform slightly better than the published results for multi-class classifiers based on support vector machines for this data set. AVAILABILITY: Available on request from the authors.

Algorithms↗
PubMed2003

Emergency ambulances on the public highway linked with inconvenience and potential danger to road users.

OBJECTIVES: The main aim was to survey interactions between the public highway users and emergency ambulances using lights and sirens. The objectives were to identify negative and positive experiences, and to assess the frequency and consequences of these events. METHODS: Because of a poor response from a random postal pilot, a quota sample of 200 was adopted with a response of 65%. This provided data on demographics, details of previous interactions, and possible third party effects. Participant perception of psychological stress in negative interactions was also recorded. Possible links between the recorded interactions were assessed using the chi(2) tests of association. RESULTS: The passage of an emergency ambulance using lights and sirens caused the public to move from their chosen position in most cases (61%). Horns or sirens were used frequently (86%), but they were not always applied in unison with the warning lights. A significant association was found between the satisfactory handling of events by the ambulance crews and the use of audible warning devices (p<0.001). Twenty per cent of avoidance manoeuvres necessitated reversing, which was associated with a third party affect (p<0.005). Roughly one third of the participants found interactions stressful and felt that the events could have been avoided. Most public road users (91%) believed that they acted in a controlled manner. CONCLUSIONS: The findings suggest that most participants had interacted with the emergency ambulances in a positive manner, while a smaller but significant fraction of the public road users found the interactions difficult to handle. A third party effect was identified in avoidance manoeuvres. Further longitudal research with random sampling is recommended.

Adult↗
PubMed1999

The effectiveness of benzimidazole derivatives for the treatment and prevention of histomonosis (blackhead) in turkeys.

The benzimidazole derivatives, albendazole and fenbendazole were evaluated for their effectiveness in the treatment and prevention of histomonosis (blackhead) in turkeys. Histomonosis was produced in 5 week-old birds by placing them on broiler breeder litter known to be contaminated with Heterakis gallinae ova and the protozoan Histomonas meleagridis. In the first trial, at the onset of confirmed clinical disease, birds were treated orally with metronidazole, a compound known to be effective against Histomonas. Those receiving metronidazole had significantly greater mean body weight gains during the treatment period and the 2 weeks following treatment than untreated controls. Treated birds also had significantly lower caecal and liver lesion scores. These findings served to validate the method of disease reproduction and establish its suitability for testing the benzimidazoles. Similar trials were conducted to determine the therapeutic value of albendazole at 100.0 mg/kg of body weight and fenbendazole at 10.0 mg/kg body weight, administered orally twice a day for 5 consecutive days. Under these conditions, both drugs were found to be ineffective as treatments. A final trial was conducted to assess the prophylactic value of albendazole and fenbendazole administration. At the time of placement on contaminated litter, birds were medicated as previously described with the exception that treatment was continued for 14 consecutive days, the approximate incubation period for histomonosis. The trial was terminated on the 16th day. In the case of both albendazole and fenbendazole, treatment was associated with a significant increase in mean body weight gain and lower caecal and liver lesion scores. It is believed that the observed prophylactic effect may be attributed to the destruction of the transport vector e.g., Heterakis larvae, or to direct killing of the flagellated form of Histomonas which is normally found in the caecal lumen and is considered to be more sensitive to chemotherapeutic agents than the amoeboid form found in tissues.

Albendazole↗
PubMed1997

Extracellular pH affects regulation of the pcbAB gene in Penicillium chrysogenum.

The effect of extracellular pH and dissolved oxygen on regulation of the pcbAB gene in P. chrysogenum was examined, using Northern analysis and a reporter gene fusion. It was found that ambient pH markedly affected levels of pcbAB mRNA whereas maintenance of dissolved oxygen concentration above 10% had no detectable effect. The presence of a DNA-binding protein, which binds upstream of the pcbAB translational start codon, was also related to ambient pH. In all fermentations, pcbAB mRNA was most abundant at around the late exponential/early stationary phase of a culture.

Fermentation↗
PubMed1997

Can foxes be controlled by reducing their fertility?

A model based on data from research in New South Wales conducted by the Cooperative Research Centre for the Biological Control of Vertebrate Pest Populations suggests that the effectiveness of fertility control in reducing the abundance of foxes (Vulpes vulpes) can be strongly influenced by environmental variability. The model includes age-specific recruitment and survival as functions of resources indexed by rainfall. It is assumed that fertility control will affect only female foxes and that the use of a baiting regime to deliver a contraceptive agent will result in fixed proportional changes in pregnancy rates. By comparing the variability in the rate of increase of treated and untreated fox populations, the model predicts that: (i) frequent baiting, every one or two years, will be more effective than applications of baits at longer time intervals; (ii) the abundance of foxes will decline more rapidly, with higher levels of fertility control; (iii) infertility which lasts for only one breeding season is less effective than permanent sterility which allows for accumulation of sterile animals in the population; and (iv) highly variable results are likely to be the outcome of low-frequency baiting with an agent that produces only temporary infertility.

Animals↗
PubMed1996

Factors affecting DNA-binding proteins and pcbC transcript levels in Penicillium chrysogenum.

Proteins extracted from Penicillium chrysogenum grown in either complex or defined medium were used in electromobility shift assays. With a probe DNA covering the region -10 to -132 relative to the pcbC translation start codon, four protein/DNA complexes (designated A-D) were reproducibly observed. Two of the four DNA/protein complexes routinely detected in extracts from liquid cultures (A and B) were also detectable with protein extracts from P. chrysogenum spores. Generally, with proteins from liquid cultures, there was a correlation between increased levels of the complexes and increased levels of the pcbC transcript. In addition, the detectable levels of the complexes and the pcbC transcript showed some relationship to the extracellular pH of the medium. In defined medium, with glucose as the carbon source, the pcbC transcript was not detectable in extracts from the wild-type strain at any time, whereas with the high penicillin-producing strain P-2, a pcbC transcript was detected. In complex medium, the pcbC transcript was detectable during the exponential phase of cultures of the wild-type or P-2, even when glucose levels were as high as 2.5% (w/v).

Blotting, Northern↗
PubMed1995

Detection of a protein which binds specifically to the upstream region of the pcbAB gene in Penicillium chrysogenum.

The upstream region of the pcbAB gene from Penicillium chrysogenum was screened for protein-binding sites using an electromobility shift assay. A specific protein/DNA interaction was detected within a fragment covering the region -387 to -242 relative to the pcbAB translational start codon. The appearance of this protein and pcbAB mRNA in culture extracts occurred at the same time point in fermentations, suggesting that the protein might be a transcription activator. The putative upstream activating sequence was located more precisely using cross-competition assays. These indicated the involvement of the 7-bp motif TGCCAAG in the binding of the protein.

Base Sequence↗
PubMed1995

Thymic nurse cell rescue of early CD4+CD8+ thymocytes from apoptosis.

We have now developed temperature sensitive lines of thymic nurse cells (TNCs), using the SV40 viral mutant tsA58, that maintain the ability to selectively internalize a subpopulation of alpha beta TCR+CD4+CD8+ thymocytes in vitro. One line, tsTNC-1, was shown to be able to rescue a subset of CD4+CD8+ thymocytes from programmed cell death at 32 degrees C, the temperature at which binding and internalization were detected. Rescue was significantly diminished at 38 degrees C, the temperature at which thymocyte binding was not observed. The rescued population of thymocytes showed a reduced level of apoptosis as measured by the DNA fragmentation assay. TNC rescue resulted in a shift of CD4+CD8+ thymocytes from immature TCRlow PNArhigh cells to the more mature TCRint PNArlow phenotype but no changes in cell surface levels of HSA nor CD69 were detected. The rescue activity of tsTNC-1 cells at 32 degrees C was significantly reduced with the addition of antibodies to either class I or class II MHC antigens. These results suggest that we have established TNC lines, using the SV40 viral mutant tsA58, that have the ability to rescue a subset of the TNC interactive thymocyte population from programmed cell death. The thymocyte population rescued by TNCs matures to a phenotype within the double positive stage of development that is indicative of positive selection.

Animals↗
PubMed1994

Use of INT to determine the respiratory activity of immobilised and free Penicillium chrysogenum.

The specific oxygen uptake rates (OUR) of kappa-carrageenan-immobilised and free cell cultures of Penicillium chrysogenum were determined using an oxygen electrode in a closed chamber. This was compared with the respiratory activity determined by the extent of staining with iodo-nitrophenyl tetrazolium chloride (INT). The degree of INT staining correlated with the OUR; an increase in INT deposition corresponding to an increase in the measured OUR. The INT staining technique could therefore be used to determine cell respiratory activity. In this way a profile of fungal cell activity throughout immobilised cell aggregates and free cell pellets was determined. In both types of cell culture, after the initial growth period only the peripheral biomass was observed to be active.

Fermentation↗
PubMed1994

Structural analysis of the human nov proto-oncogene and expression in Wilms tumor.

We have cloned and sequenced the nov gene (novH) which is the homolog of the chicken nov proto-oncogene overexpressed in avian nephroblastomas. The novH gene is highly conserved and encodes a putative IGF-binding protein similar to that of chicken. We report that relative to autologous normal kidney expression of novH is elevated in Wilms tumors containing predominantly stromal elements and is inversely correlated in these tumors to the expression of WT1. Our results suggest that the regulation of IGFII expression by WT1 and increase of novH in Wilms tumors might be interrelated and represent a key element in tumor development in human.

Amino Acid Sequence↗
PubMed1993

Physiological studies related to the immobilization of Penicillium chrysogenum and penicillin production.

Using the production of penicillin by Penicillium chrysogenum as a model system, certain physiological aspects of immobilized and free cell cultures were compared. Reducing the immobilized viable spore loading (from 4 x 10(4) to 2 x 10(3) spores ml-1 gel) and initial bead diameter (from 3.5-4.0 to 1.5-2.0 mm) gave rise to an increase in the penicillin titer from 0.2 to 1.2 g l-1. Using these conditions in immobilized cell culture the growth phase was prolonged and the duration of expression of the isopenicillin N synthase gene (pcbC) was significantly extended when compared with free cell culture (150 h as opposed to 100 h). During the period of maximum penicillin production, different penicillin biosynthetic intermediates accumulated in the broth of free and immobilized cell cultures, reflecting a fundamental difference in cell physiology. Although the maximum specific productivity of penicillin production was reduced by immobilization, the average specific productivity increased when compared to free cell fermentation.

Biotechnology↗
PubMed1993

Brachial plexus injury in two red-tailed hawks (Buteo jamaicensis).

Two red-tailed hawks (Buteo jamaicensis), found near Deltaville, Virginia (USA), were evaluated because of inability to use a wing. Results of needle electromyographic studies of the affected wing muscles in both hawks were compatible with denervation. On euthanasia, one hawk had extensive axon and myelin loss with multifocal perivascular lymphocytic inflammation of its brachial plexus and radial nerve. Demyelination and axon loss in the dorsal white matter of the spinal cord on the affected side also were found at the origin of the brachial plexus. The other hawk's wing had not returned to functional status > 2 yr after injury.

Animals↗
PubMed1992

Transcript analysis of penicillin genes from Penicillium chrysogenum.

The presence of a transcriptional control simultaneously affecting the expression of the three penicillin biosynthetic genes, pcbAB, pcbC, and penDE (pen genes), was demonstrated in Penicillium chrysogenum. Using probes specific to each gene, it was observed that the highest level of expression of the pen genes occurred during exponential growth, in both the original ancestral strain (NRRL1951) and a high-penicillin producing strain P2. Expression also occurred in the presence of high concentrations of glucose, indicating that carbon catabolite repression was not directly involved in the regulation. Transcription of the pen genes appeared to cease as the growth rate decreased. Growth was limited in a fermenter by the rate of oxygen transfer. The phosphoglycerate kinase gene (pgk), used as a control, was strongly induced by the reduced oxygen levels, suggesting a stress-related response. By maintaining optimum growth conditions in fermenters, no induction of the pgk gene was observed whereas expression of the pen genes could be maintained. It was also possible to re-establish expression of the pen genes, after normal cessation, by the addition of cycloheximide to the culture medium.

Cycloheximide↗