Mucus membrane-bound

Mucoadhesive polymers exhibiting strong complexing properties are capable of inhibiting intestinal brush border membrane-bound proteases through a far distance inhibitory effect [65]. In vivo, the mucoadhesive polymer is separated from the brush border membrane by a mucus layer [30]. Although there is no direct contact between polymer- and membrane-bound enzymes, it could be shown that inhibition takes place. The exploitation of this far distance effect seems to be a very promising alternative to small molecular mass inhibitors, which are currently used as inhibitors of brush border membrane-bound proteases. 

Early work on the effects of JP-8 inhalation in rats showed an inverse relationship between increases in airway epithelial permeability ("TcDTPA clearance) and decreased concentrations of the tachykinin substance P in bronchoalveolar lavage fluid (BALF) (Hays et al. 1995). Substance P has a strong affinity for the neurokinin receptor NK, one of a family of plasma-membrane-bound neurokinin receptors that mediate protective reflex responses—such as bronchoconstriction, increased vascular permeability, vasodilatation, mucus secretion, and enhanced mucociliary activity—to airway exposure to mechanical or chemical irritants. 

The initial step in olfaction is the binding of an odorant to an odor binding protein (OBP). This step is essential since most odorants are hydrophobic in nature, and they could not otherwise pass through a polar mucus membrane to reach the olfactory receptors (OR). Thus, odor molecules are bound to the OBP and either simply solubilized by the OBP or perhaps actively transported to the OR by the OBP. Once at the OR, the odorant may be released to interact with the OR or the odorant-OBP complex is sensed by the OR — this has not been determined (Figure 1.5) [52]. The... 

The 10 20 million olfactory sensory neurons in the human nose are confined to a relatively small patch of tissue located high in the nasal cavity. When odorants, e.g., carvone in Fig. 2, are deposited within the mucus covering the distal ends of the olfactory receptor cells, they interact with some of the membrane-bound, G-protein-coupled receptors [9]. This interaction initiates a transduction process that converts physicochemical information in the odorant, e.g., its structure or other attributes, into electrical energy that is conveyed in the form of pulses (action potentials) along olfactory axons to the brain. 

Histamine is a low-molecular-weight amine compound formed by decarboxylation of histidine and is stored in basophil and mast cell granules. The release of histamine from these cells is triggered by antigen cross-linking IgE bound to specific receptors on the surface membranes of mast cells and basophils. The tissue effects of histamine are evident within 1 to 2 minutes, but it is rapidly metabolized within 10 to 15 minutes. The major effects of histamine on target tissues include increased capillary permeability, contraction of bronchial and vascular smooth muscle, and hypersecretion of mucus glands. 

---