Visualisation of bacterial sequestration and bactericidal activity within hydrating Hydrofiber wound dressings.

The fluid handling and microbiological properties of a non-antimicrobial Hydrofiber(NAH) wound dressing have been compared with those of a silver salt-containing Hydrofiber (SCH). Fluorescent dyes (BacLight, Live/Dead Kit) were added to fresh cultures of two wound pathogens (Pseudomonas aeruginosa and Staphylococcus aureus), and used to visualise their viability. Live bacteria stained green and dead/dying bacteria turned red. When inoculated into samples of the NAH and SCH dressings, the viability of the bacteria could be effectively monitored over time using a rapid form of confocal laser scanning microscopy (RCLSM--Leica UK). When the NAH dressing was hydrated with stained bacterial culture, its fibres swelled quickly, reducing interstitial spaces between the fibres, resulting in the formation of a cohesive gel. Bacteria became immobilised in the gel, forming characteristic clumps, but remained largely green (viable) for more than 20 h with no apparent increase in numbers. The SCH initially behaved in a similar manner, however, using 3-D data from RCLSM time-lapse sequences P. aeruginosa was observed to turn progressively red (i.e. died) within 1.5-3 h and S. aureus similarly turned red within 5-7 h of contact with the SCH dressing. The ability of both Hydrofiber dressings to sequester and immobilise potentially pathogenic wound micro-organisms has been demonstrated. Additionally the SCH dressing was shown to kill immobilised bacteria, as a consequence of the ionic silver bactericide. These properties of the Hydrofiber dressings may contribute to providing an environment that is supportive to wound healing.

Immunolocalization of caveolin-1 in rat and human mesothelium.

Flask-shaped vesicles have been described as caveolae in mesothelial cells in a number of animal species based on morphological criteria only. Using an antibody against caveolin-1, said to be a biochemical marker of caveolae, immunoelectron microscopy suggests that many but not all such vesicles in mesothelial cells are caveolae. Mesothelial cells from different anatomical sites showed obvious variations in both the population density and distribution of these flask-shaped vesicles and in their density of immunostaining. Lung and pericardial sac had the highest staining density. In some sites (e.g., lung, bladder, colon) caveolae were equally distributed between apical and basolateral surfaces, whereas in others (e.g., spleen, liver), they were predominantly apical. Additional immunopositive sites in the peritoneal membrane were identified, including the epineurium of peripheral nerves and the endothelium of lymphatic vessels. We further suggest that variations in the number of mesothelial cell caveolae and the density of their immunolabeling may have implications for our understanding of certain diseases such as malignant mesothelioma, especially in view of the recent hypothesis that it may be caused by SV40, a virus that appears to enter cells via caveolae.

Can artifact mimic the pathology of the peritoneal mesothelium?

OBJECTIVE: A peritoneal biopsy registry was established to examine morphological and functional changes to the peritoneum during peritoneal dialysis (PD). During the early stages of this study, it became clear that surgical trauma to the peritoneum at the time of biopsy could cause a variety of changes to the surface. We examined the effects of surgical trauma in a rat biopsy model. DESIGN: Rat peritoneum was subjected to a variety of traumas that might occur at biopsy and compared with peritoneal biopsies that had been collected, using the suture method described here, from PD patients. Changes in the quality of non-PD biopsies taken before and after the development of the suture technique were evaluated. RESULTS: In the rat model, external massaging of the peritoneum induced moderate loss of microvilli. Brief light touching caused distortion of the mesothelial surface. Pressing resulted in mesothelial denudation and thin strands of presumed cellular remains. Rubbing caused complete loss of mesothelial cells and their basement membrane. Air drying caused progressive loss of microvilli and eventual cellular distortion. Comparison with peritoneal biopsies from PD patients revealed similarities with certain types of trauma, namely, air drying and pressing. Collection of peritoneal biopsies using the suture method significantly improved specimen quality compared with specimens taken before its introduction (p < 0.025%). CONCLUSION: These results illustrate the sensitivity of the mesothelium to mechanical trauma, the possibility of confusing trauma with genuine pathology, and, hence, the necessity of employing a trauma-free method of biopsy collection, such as the technique described here.

Morphologic changes in the peritoneal membrane of patients with renal disease.

This study examined the morphologic features of the parietal peritoneal membranes of 130 patients undergoing peritoneal dialysis (PD) and compared them with the features of the peritoneal membranes of normal individuals, uremic predialysis patients, and patients undergoing hemodialysis. The median thickness of the submesothelial compact collagenous zone was 50 microm for normal subjects, 140 microm for uremic patients, 150 microm for patients undergoing hemodialysis, and 270 microm for patients undergoing PD (P < 0.001 for all versus normal subjects). Compact zone thickness increased significantly with the duration of PD therapy [0 to 24 mo, 180 microm (n = 58); 25 to 48 mo, 240 microm (n = 24); 49 to 72 mo, 300 microm (n = 13); 73 to 96 mo, 750 microm (n = 16); >97 mo, 700 microm (n = 19)]. Vascular changes included progressive subendothelial hyalinization, with luminal narrowing or obliteration. These changes were absent in samples from normal subjects but were present in 28% of samples from uremic patients and 56% of biopsies from patients undergoing PD. In the PD group, the prevalence of vasculopathy increased significantly with therapy duration (P = 0.0001). The density of blood vessels per unit length of peritoneum was significantly higher for patients with membrane failure and was correlated with the degree of fibrosis (P = 0.01). For the first time, a comprehensive cross-sectional analysis of the morphologic changes in the peritoneal membranes of patients undergoing PD is provided. The infrequency of fibrosis in the absence of vasculopathy suggests that vasculopathy may predispose patients to the development of fibrosis. This study provides a sufficiently large cohort of samples to allow structure-function relationships to be established, as well as providing a repository of tissue for further studies.