Invasion mechanisms attachment

The solution providing the slowest response time but the least invasive configuration would have been attaching the sensor to the outer surface of the outer pipe. For this option, the sensor would be embedded in a material that is mechanically fixed or welded to the pipe, shown in Figure 9-50. If the attachment block was strapped or otherwise mechanically attached to the pipe, it would be made out... 

Virus restriction and modification by the host We have already seen that one form of host resistance to virus arises when there is no receptor site on the cell surface to which the virus can attach. Another and more specific kind of host resistance involves destruction of the viral nucleic acid after it has been injected. This destruction is brought about by host enzymes that cleave the viral DNA at one or several places, thus preventing its replication. This phenomenon is called restriction, and is part of a general host mechanism to prevent the invasion of foreign nucleic acid. 

EPEC causes a degeneration of the microvillus brush border, with cupping and pedestal formation of the plasma membrane at the sites of bacterial attachment and reorganization of cytoskeletal proteins [43, 44], Invasion has been observed in some clinical specimens, but the mechanism of how this bacteria produces diarrhea is not fully understood. Some possibilities include an increase in permeability and loss in microvilli leading to malabsorption. 

The adherence mechanisms involved in Salmonella infection have been studied in great deal. Disease associated with S. enterica serovars is initiated by attachment to and invasion of hosf cells, followed by subse-quenf inflammation of the lamina propria and lymph nodes (Darwin and Miller, 1999). Several genetically defined fimbrial or piliar adhesins con-tribufe fo fhe initial attachment and the overall infection process of Salmonella. Some of fhese include t)q)e 1 fimbriae (Fim), plasmid-encoded (PE) fimbriae, long polar (LP) fimbriae, and thin aggregative fimbriae (curli). However, many ofher putative fimbrial operons have been identified within various S. enterica serovar genomes, but the expression of fhese proteins is currently undefined. 

The invasive probe, with thin ring electrodes mounted on a 4 mm diameter plastic rod, is attached to a computer-controlled placement rig so as to allow it to be positioned anywhere in the region of interest (see figure 1), As movement of the probe is a mechanical process, each measurement takes about one minute to complete, requiring over an hour to probe the entire region. Interested readers should consult Lucas et al.[12] for a more detailed discussion of this technique. 

Tethering of hyaluronan to different cell types can occur by at least two independent mechanisms. One of these is by binding to the hyaluronan receptor, CD44, as described above for chondrocytes. A second likely mechanism is transmembrane interaction of nascent hyaluronan with hyaluronan synthase. Thus, in several cell types, hyaluronan in the process of extrusion across the plasma membrane appears to be tethered by sustained attachment to hyaluronan synthase or associated proteins on the cytoplasmic face of the plasma membrane ([29] also Chapter 21 in this volume). Some pathogenic bacteria have hyaluronan capsules that may also be tethered in this way. These capsules would represent a primitive form of pericellular matrix which acts to facilitate bacterial invasion by inhibiting phagocytosis [36] and/or by promoting adhesion to host tissues [37]. 

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