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Biomedical subjects

U Potter

Publications and source records attributed to U Potter.

6 recordsLinked to original sources
PubMed2004

Hyperphagocytic haemocytes in Manduca sexta.

We have discovered a new type of haemocyte in the larval stage of the tobacco hornworm moth Manduca sexta that has extreme phagocytic ability; each cell can engulf up to 500 bacteria. This level of phagocytosis may be unprecedented among animal cells. Although these hyperphagocytic cells (HP) only represent about 1% of the circulating haemocytes, they are responsible for sequestering the majority of the bacteria by circulating haemocytes when non-pathogenic, heat-killed Escherichia coli are injected into the haemolymph. Extreme phagocytosis by HP is not limited to Gram-negative bacteria since heat-killed Staphylococcus aureus as well as positively and negatively charged microspheres are also highly phagocytosed. Evidence is presented to show that phagocytosis by HP is involved in the early stages of nodule formation in infected insects. In addition, HP are also present in non-infected insects, characterised by their distinctive spreading morphology, which becomes impaired following hyperphagocytosis of bacteria. This is the first time that a dedicated "professional" phagocytic class of haemocyte has been reported for an invertebrate. The importance of these specialised cell types in the M. sexta immune response and their role in nodule formation is discussed.

Animals↗
PubMed2001

Oral toxicity of Photorhabdus luminescens W14 toxin complexes in Escherichia coli.

Previous attempts to express the toxin complex genes of Photorhabdus luminescens W14 in Escherichia coli have failed to reconstitute their oral toxicity to the model insect Manduca sexta. Here we show that the combination of three genes, tcdA, tcdB, and tccC, is essential for oral toxicity to M. sexta when expression in E. coli is used. Further, when transcription from native toxin complex gene promoters is used, maximal toxicity in E. coli cultures is associated with the addition of mitomycin C to the growth medium. In contrast, the expression of tcdAB (or the homologous tcaABC operon) with no recombinant tccC homolog in a different P. luminescens strain, K122, is sufficient to confer oral toxicity on this strain, which is otherwise not orally toxic. We therefore infer that P. luminescens K122 carries a functional tccC-like homolog within its own genome, a hypothesis supported by Southern analysis. Recombinant toxins from both P. luminescens K122 and E. coli were purified as high-molecular-weight particulate preparations. Transmission electron micrograph (TEM) images of these particulate preparations showed that the expression of tcdAB (either with or without tccC) in E. coli produces visible approximately 25-nm-long complexes with a head and tail-like substructure. These data are consistent with a model whereby TcdAB constitutes the majority of the complex visible under TEM and TccC either is a toxin itself or is an activator of the complex. The implications for the potential mode of action of the toxin complex genes are discussed.

Administration, Oral↗
PubMed1999

The incorporation of a stent-graft into the porcine aorta and the inflammatory response to the endoprosthesis.

The fate of a non-sutured anastomosis and the inflammatory response to an endoprosthesis in a porcine aorta was determined. Self-expanding aorto-aortic endovascular prostheses were deployed into the infrarenal aorta of Large White pigs by the transfemoral route, in accordance with Home Office regulations. Animals were followed up at intervals to 1 year. The aortas were explanted and specimens were subjected to light microscopy. Thirteen animals, mean weight 103 kg, underwent placement of a prosthesis. There was early evidence of a neointima at 4 weeks and a well-developed neointima by 12 weeks, with complete incorporation of the endoprosthesis. The early acute inflammatory reaction seen at 4 weeks had become chronic by 12 and was largely absent by 26 weeks. There was no evidence of atypia. Complete incorporation of the non-sutured anastomosis is seen in this model. The acute inflammatory reaction to the prosthesis seen at 4 weeks had largely subsided by 26 weeks.

Acute Disease↗
PubMed1978

An evaluation of Coomassie Brilliant Blue as a stain for quantitative microdensitometry of protein in section.

The specificity and stoichiometry of the binding of Coomassie Brilliant Blue (CBB) to protein in section has been examined using both frozen protein matrices and plant material. The maximum adsorbance of the stain, bound and in solution, was found to be 620 nm although variation in the results at this wavelength necessitated measurements to be made at 600 nm. After enzyme treatments of sectioned plant material embedded in resin, all CBB-binding biological material was shown to be sensitive to non-specific protease. The relationship between optical density at 600 nm and section thickness was tested statistically against the Lambert-Beer law, using microdensitometry of cryostat-sectioned, frozen genatine solution. The analyses showed conclusively that, under these conditions, CBB adheres strongly to the Lambert-Beer relationship. CBB may thus be considered as a very specific protein stain, eminently suited both to cytological observation and quantitative microdensitometry.

Densitometry↗