Surface hydrophobicity and water transport of the toad urinary bladder: effects of vasopressin

A catheter friction tester using balance sensor: Combined evaluation of the effects of mechanical properties of tubing materials and surface coatings

In this study, we introduce a new experimental approach to characterize the forces emerging from simulated catherization. This setup allows for a linear translation of urinary catheters in vertical direction as controlled by an actuator. By employing silicone-based elastomer with a duct of comparable diameter with catheters as urethra model, sliding contacts during the translation of catheters along the duct is generated. A most unique design and operation feature of this setup is that a digital balance was employed as the sensor to detect emerging forces from simulated catherization. Moreover, the possibility to give a variation in environment (ambient air vs. water), clearance, elasticity, and curvature of silicone-based urethra model allows for the detection of forces arising from diverse simulated catherization conditions. Two types of commercially available catheters varying in tubing materials and surface coatings were tested together with their respective uncoated catheter tubing. The first set of testing on the catheter samples showed that this setup can probe the combined effect from flexural strain of bulk tubing materials and slipperiness of surface coatings, both of which are expected to affect the comfort and smooth gliding in clinical catherization. We argue that this new experimental setup can provide unique and valuable information in preclinical friction testing of urinary catheters.

Multiple roles for surface-active phospholipid in hypertension

The elusiveness of the agent responsible for primary hypertension and the diversity of its impact upon the body, as reflected by the widely differing and almost independent avenues of research in this field, indicate that the answer could lie with a particularly common substance in the body acting at various levels of fundamental physiological function. This hypothesis pursues some basic physics of phospholipid whereby a change in quantity or quality can affect the capability to generate extreme surface activity manifest as the numerous properties which this agent can impart to blood and to adjacent surfaces by adsorption. Nine possible roles are traced by which surface-active phospholipid could impinge upon neurogenic control of blood pressure, the effects of circulating relaxing factors, blood rheology, atherosclerosis, and the major renal aspects of control by diuresis and association with the antihypertensive neutral renomedullary lipid. This multi-faceted approach offers mechanisms by which diet can affect blood pressure in addition to the traditional emphasis upon the deposition of atheroma.

A physical approach to coeliac disease

The morphological changes used to confirm a diagnosis of coeliac disease (CD) are precisely those predicted if the surface energy of the interface between duodenal epithelium and the luminal contents were raised to levels comparable to those demonstrated by the hydrophobic nature of the stomach wall. This hypothesis pursues the concept that, in coeliac patients, the gastric mucosal barrier (GMB) is effectively extended from the stomach to coat the duodenum, thus closing the window of absorption in the Gl tract. If studies are correct which indicate that the GMB is a physical reality provided by an adsorbed monolayer of surface-active phospholipid (surfactant) which renders surfaces hydrophobic, then it could also act as a barrier to the absorption of nutrients in the duodenum. Gluten, or its more active polypeptide fragment gliadin, exacerbates the situation in CD by acting as very effective carriers for the insoluble phospholipid which is deposited at the duodenal surface where they are digested by brush-border and pancreatic enzymes.