http://www.damtp.cam.ac.uk/user/gold/pdfs/teaching/turing1952.pdf

The Chemical Basis of Morphogenesis

1. Plant Nutrients. 2. The Soil as a Plant Nutrient Medium. 3. Nutrient Uptake and Assimilation. 4. Plant Water Relationships. 5. Plant Growth and Crop Production. 6. Fertilizer Application. 7. Nitrogen. 8. Sulphur. 9. Phosphorus. 10. Potassium. 11. Calcium. 12. Magnesium. 13. Iron. 14. Manganese. 15. Zinc. 16. Copper. 17. Molybdenum. 18. Boron. 19. Further Elements of Importance. 20. Elements with More Toxic Effects. General Readings. References. Index.

/pdf/principles-of-plant-nutrition-2k4wl46ou6.pdf

Principles of plant nutrition

The epithelia of a number of glands and cavitary organs of the rat and guinea pig have been surveyed, and in all cases investigated, a characteristic tripartite junctional complex has been found between adjacent cells. Although the complex differs in precise arrangement from one organ to another, it has been regularly encountered in the mucosal epithelia of the stomach, intestine, gall bladder, uterus, and oviduct; in the glandular epithelia of the liver, pancreas, parotid, stomach, and thyroid; in the epithelia of pancreatic, hepatic, and salivary ducts; and finally, between the epithelial cells of the nephron (proximal and distal convolution, collecting ducts). The elements of the complex, identified as zonula occludens (tight junction), zonula adhaerens (intermediary junction), and macula adhaerens (desmosome), occupy a juxtaluminal position and succeed each other in the order given in an apical-basal direction. The zonula occludens (tight junction) is characterized by fusion of the adjacent cell membranes resulting in obliteration of the intercellular space over variable distances. Within the obliterated zone, the dense outer leaflets of the adjoining cell membranes converge to form a single intermediate line. A diffuse band of dense cytoplasmic material is often associated with this junction, but its development varies from one epithelium to another. The zonula adhaerens (intermediate junction) is characterized by the presence of an intercellular space ( approximately 200 A) occupied by homogeneous, apparently amorphous material of low density; by strict parallelism of the adjoining cell membranes over distances of 0.2 to 0.5 micro; and by conspicuous bands of dense material located in the subjacent cytoplasmic matrix. The desmosome or macula adhaerens is also characterized by the presence of an intercellular space ( approximately 240 A) which, in this case, contains a central disc of dense material; by discrete cytoplasmic plaques disposed parallel to the inner leaflet of each cell membrane; and by the presence of bundles of cytoplasmic fibrils converging on the plaques. The zonula occludens appears to form a continuous belt-like attachment, whereas the desmosome is a discontinuous, button-like structure. The zomula adhaerens is continuous in most epithelia but discontinuous in some. Observations made during experimental hemoglobinuria in rats showed that the hemoglobin, which undergoes enough concentration in the nephron lumina to act as an electron-opaque mass tracer, does not penetrate the intercellular spaces beyond the zonula occludens. Similar observations were made in pancreatic acini and ducts where discharged zymogen served as a mass tracer. Hence the tight junction is impervious to concentrated protein solutions and appears to function as a diffusion barrier or "seal." The desmosome and probably also the zonula adhaerens may represent intercellular attachment devices.

/pdf/junctional-complexes-in-various-epithelia-9u1kkdzfat.pdf

Junctional complexes in various epithelia

Thermodynamic analysis of the permeability of biological membranes to non-electrolytes

http://science.sciencemag.org/content/sci/168/3934/939.full.pdf

Cryobiology: The Freezing of Biological Systems

A contribution to the theory of permeability of thin films

The permeability of natural membranes

The concept of a barrier between blood, on the one hand, and the brain on the other derives from the classical studies of Ehrlich and of Goldmann on vital staining; it was noted that a large variety of acid dyes, of which trypan blue was one, would pass out of the blood into the tissues of the body making them voloured; the brain and spinal cord stood out in contrast to the rest of the tissues in that, with the exception of highly localized regions, such as the area postrema, they remained unstained. In the thirties and forties of this century some doubt was cast on this concept of a barrier between blood and brain; thus King in 1938 (1) argued that the essential phenomenon was one of failure to stain, and this could have been due to the absence of suitable connective tissue to take up the stain.

Hugh Davson

Papers

A contribution to the theory of permeability of thin films

The permeability of natural membranes

The Blood Brain Barrier

The mechanism of drainage of the cerebrospinal fluid.

The hydration of the cornea.