Intercellular contacts

The viscosity of mucus is affected by binding between calcium and the mucus, which probably arises from an ionic interaction with the sialic acid in the mucin. These variations are indicated by a change in the pH, viscoelastic properties, water, and protein content of cervical mucus. Calcium is needed to establish an intercellular contact and the assembly of tight junction in the cervical epithelium. Changes in extracellular calcium affect the permeability of tight junctions and play a role in regulating the production of cervical mucus.Prostaglandin concentrations... 

Fetal pig epidermis contains hyaluronic acid and chondroitin 4-sulfate containing mucopolysaccharide (S15) as does human epidermis (M13), and some of the enzymes of uronic acid metabolism are present in human epidermis (F24). Also Barker et al. (B6) have shown uptake of radioactive sulfate into epidermis, and Braun-Falco et al. (B33) have shown that psoriatic epidermis is more active than normal epidermis in accumulating radioactive sulfate in vitro. There is also a suggestion that methionine sulfur may be preferentially accumulated in psoriatic lesions (B26, L6). There seems to be little doubt, therefore, that mucopolysaccharides are formed, and there is some suggestion that they may be formed in greater amounts in psoriatic skin lesions. The next section will consider the possibility that they are of importance in the cell membrane and intercellular contact. 

Similar experiments carried out with the wild type (Gerisch et al, 1975) showed that periodic signals of cAMP, in contrast to constant stimuli, accelerate cell differentiation by inducing the precocious synthesis of proteins involved in the aggregation process. Initial experiments demonstrated the induction of proteins necessary for the establishment of intercellular contacts similar experiments (Klein Darmon, 1977 Juliani Klein, 1978 Chisholm, Hopkinson Lodish, 1987 Kimmel, 1987 Mann Firtel, 1987 Mann, Pinko Firtel, 1988) established that the periodic signals of cAMP induce a differentiation programme in which other proteins such as adenylate cyclase, the cAMP receptor, and phosphodiesterase are synthesized. These developmental responses depend on the periodic nature of the stimulation and do not occur when the cAMP stimulus remains constant. 

In addition to regulating organized tissue functions, E-, N-, and VE-cadherin-mediated intercellular contacts have been shown to suppress cell proliferation [24—26]. This phenomenon is thought to be a consequence of cadherin-induced alterations in the cytoskeleton structure [27], and to contribute to the abrogation of cell proliferation of confluent tissue cultures. 

Durand RE, Sutherland RM. Effects of intercellular contact on repair of radiation damage. Exp Cell Res 1972 71 75-80. 

Roth, S. and White, D., 1972, Intercellular contact and cell-surface galactosyl transferase activity, Proc. Natl. Acad. Sci. U.S. 69 485. 

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