PCR-ELISA detection of Escherichia coli in milk

AIMS

The purpose of this study was to develop a reliable molecular procedure for the detection of Escherichia coli in milk.

METHODS AND RESULTS

Robust and expeditious DNA extraction and PCR techniques were evaluated using Enzyme-Linked Immunosorbent Assay (ELISA) detection of biotin-labelled amplicons to facilitate optimal detection of E. coli DNA.

CONCLUSIONS

It was found that 5 E. coli colony-forming units (cfu) could be detected per PCR reaction using the PCR-ELISA system, equating to a sensitivity of detection of 100 E. coli cfu ml(-1) pasteurized milk.

SIGNIFICANCE AND IMPACT OF THE STUDY

This approach should facilitate evaluation of milk contamination and enable rapid detection of E. coli mastitis, leading to correct deployment of relevant antibiotic therapy and improved animal welfare.

Near real time in vivo fibre optic confocal microscopy: sub-cellular structure resolved

We have built a fibre optic confocal reflectance microscope capable of imaging biological tissue in near real time. The measured lateral resolution is 3 micro m and axial resolution is 6 micro m. Images of epithelial cells, excised tissue biopsies, and the human lip in vivo have been obtained at 15 frames s-1. Both cell morphology and tissue architecture can be appreciated from images obtained with this microscope. This device has the potential to enable reflected light confocal imaging of internal organs for in situ detection of pathology.

Laser scanning confocal microscopy of cervical tissue before and after application of acetic acid

OBJECTIVES

The use of high-resolution in vivo confocal imaging may offer a clinically useful adjunct to standard methods for the diagnosis and screening of epithelial precancers. This study assesses the feasibility of real-time confocal reflectance imaging of cervical tissue and the use of acetic acid as a contrast agent to increase visualization of cell nuclei.

STUDY DESIGN

A confocal microscope was used to image cervical cells and colposcopically normal and abnormal cervical biopsy specimens. Images were obtained before and after the application of 6% acetic acid.

RESULTS

The confocal imaging system resolved subcellular detail throughout the entire epithelial thickness. Normal and abnormal tissues were clearly able to be differentiated. Addition of acetic acid enhanced nuclear signal in all acquired images.

CONCLUSION

High-contrast reflected light images of cervical tissue are attainable in near real time. Acetic acid significantly increases light scattering from cell nuclei, which may partially explain why acetowhitening occurs.

Near real time confocal microscopy of amelanotic tissue: dynamics of aceto-whitening enable nuclear segmentation

High resolution, in vivo confocal imaging of amelanotic epithelial tissue may offer a clinically useful adjunct to standard histopathologic techniques. Application of acetic acid has been shown to enhance contrast in confocal images of these tissues. In this study, we record the time course of aceto-whitening at the cellular level and determine whether the contrast provided enables quantitative feature analysis. Confocal images and videos of cervical specimens were obtained throughout the epithelium before, during and post-acetic acid after the application of 6% acetic acid. Aceto-whitening occurs within seconds after the application. The confocal imaging system resolved sub-cellular detail throughout the entire epithelial thickness and provided sufficient contrast to enable quantitative feature analysis.

Monocyte, macrophage and foreign body giant cell interactions with molecularly engineered surfaces

To elucidate the mechanisms involved in monocyte/macrophage adhesion and fusion to form foreign body giant cells on molecularly engineered surfaces, we have utilized our in vitro culture system to examine surface chemistry effects, cytoskeletal reorganization and adhesive structure development, and cell receptor-ligand interactions in in vitro foreign body giant cell formation. Utilizing silane-modified surfaces, monocyte/macrophage adhesion was essentially unaffected by surface chemistry, however the density of foreign body giant cells (FBGCs) was correlated with surface carbon content. An exception to the surface-independent macrophage adhesion were the alkyl-silane modified surfaces which exhibited reduced adhesion and FBGC formation. Utilizing confocal immunofluorescent techniques, cytoskeletal reorganization and adhesive structure development in in vitro FBGC formation was studied. Podosomes were identified as the adhesive structures in macrophages and FBGCs based on the presence of characteristic cytoplasmic proteins and F-actin at the ventral cell surface. Focal adhesion kinase (FAK) and focal adhesions were not identified as the adhesive structures in macrophages and FBGCs. In studying the effect of preadsorbed proteins on FBGC formation, fibronectin or vitronectin do not play major roles in initial monocyte/macrophage adhesion, whereas polystyrene surfaces modified with RGD exhibited significant FBGC formation. These studies identify the potential importance of surface chemistry-dependent conformational alterations which may occur in proteins adsorbed to surfaces and their potential involvement in receptor-ligand interactions. Significantly, preadsorption of alpha2-macroglobulin facilitated macrophage fusion and FBGC formation readily on the RGD surface in the absence of any additional serum proteins. As alpha2-macroglobulin receptors are not found on blood monocytes but are expressed only with macrophage development, these results point to a potential interaction between adsorbed 2-macroglobulin and its receptors on macrophages during macrophage development and fusion. These studies identify important surface independent and dependent effects in foreign body reaction development that may be important in the identification of biological design criteria for molecularly engineered surfaces and tissue engineered devices.

Near real time confocal microscopy of cultured amelanotic cells: sources of signal, contrast agents and limits of contrast

The use of high resolution, in vivo confocal imaging for noninvasive assessment of tissue pathology may offer a clinically important adjunct to standard histopathological techniques. To augment the present understanding of both the capabilities and limitations of in vivo confocal imaging, we investigated cellular sources of image contrast in amelanotic tissues, how contrast can be enhanced with external agents and how contrast is degraded by the scattering of overlying cells. A high-resolution reflected light confocal microscope was constructed and used to obtain images of various types of unstained amelanotic cells in suspension in real time before and after the addition of contrast agents. Reflectance images were compared to phase contrast images and electron micrographs to identify morphology visible with real time reflected light confocal microscopy. Mechanisms which decrease image contrast, including interference effects and scattering in overlying layers of cells, were considered. In amelanotic epithelial cells, fluctuations in the nuclear index of refraction provide signal which can be imaged even under several overlying cell layers. Acetic acid is an external contrast agent which can enhance this nuclear backscattering. Image contrast is degraded by the presence of multiple scattering in overlying cell layers. The degradation of image contrast by cell scattering depends on the scattering phase function; in vitro models which use polystyrene microspheres to approximate tissue underestimate the actual degradation caused by cell scattering. The loss in contrast can be explained using a finite difference time domain model of cellular scattering. We conclude that near real time reflected light confocal microscopy can be used to study cell morphology in vivo. Contrast degradation due to overlying tissue is a concern and cannot adequately be modeled using conventional tissue phantoms; however, acetic acid may be used to substantially increase intrinsic contrast, allowing imaging at significant depths despite distortion from overlying layers. © 1998 Society of Photo-Optical Instrumentation Engineers.

Biocompatibility of poly(etherurethane urea) containing dehydroepiandrosterone

Poly(etherurethane urea) (PEUU) elastomers, with their broad range of mechanical properties and high biocompatibility, are used clinically for medical applications. However, the possibility exists for the ether soft segment of PEUU to degrade in long-term uses. To retard degradation, antioxidants that scavenge reactive oxygen intermediates are added. In this study, we incorporated dehydroepiandrosterone (DHEA), which functions by the alternate mechanism of modulating or down-regulating adherent macrophage activity, to retard the biodegradation of PEUUs. Biocompatibility of PEUU samples containing 1% DHEA, 5% DHEA, and 5% vitamin E (alpha-tocopherol) by weight were studied in vivo and in vitro. The biocompatibility was initially evaluated by examination of the inflammatory cellular exudate. Compared to PEUU without additives and PEUU with 5% vitamin E, the addition of 5% DHEA to PEUU caused a decrease in the total leukocyte exudate concentration at 4 days. The addition of 5% DHEA also caused lower macrophage adhesion and FBGC formation compared to the other materials at 7 days. Despite these short-term effects, the biocompatibility at later time points (14, 21, and 70 days) was similar for all materials. Transmission infrared analysis of the materials revealed that more than 70% of the DHEA had leached out of the samples by 3 days implantation. Furthermore, through attenuated total reflectance Fourier transform analysis and scanning electron microscopy, it was determined that unlike vitamin E, DHEA did not enhance long-term PEUU biostability. The effect of DHEA on inflammatory cell activity appeared to be dose dependent, with improved biocompatibility in vivo for higher loading levels of DHEA, but the overall effect was limited owing to the rapid diffusion of the water-soluble DHEA from the PEUU.

Aphagia and adipsia after preferential destruction of nerve cell bodies in hypothalamus

Microinjections of the excitatory neurotoxin kainic acid into the lateral hypothalamus of rats produced a period aphagia and adipsia. Kainate-treated rats displayed transient motor effects during the first hours after the injection but did not show the persisting sensory-motor and arousal disturbances typically observed in animals with electrolytic lesions in this part of the hypothalamus. Histological examination revealed a significant reduction in the number of nerve cell bodies in the lateral hypothalamus. Silver-stained material indicated no evidence of damage to fiber systems passing through the affected region. Assays of dopamine in hypothalamus, striatum, and telencephalon did not indicate significant differences between experimental and control animals. These results are in agreement with recent reports of the anatomical and biochemical effects of intracerebral kainic acid injections and suggest that the observed effect on feeding behavior is related to the destruction of neurons in the lateral hypothalamus.