Artificial kidney structure

The symmetric, microporous polymer membranes made by phase inversion are widely used for separations on a laboratory and industrial scale.22 Typical applications range from the clarification of turbid solutions to the removal of bacteria or enzymes, the detection of pathological components, and the detoxification of blood in an artificial kidney. The separation mechanism is that of a typical depth filter which traps the particles somewhere within the structure. In addition to the simple "sieving" effect, microporous phase inversion membranes often show a high tendency of adsorption because of their extremely large internal surface. They are, therefore, particularly well suited when a complete re-... 

For the design of the C-DAK 4000 artificial kidney, and the many similar hemodialysis devices (Daugirdas and Ing, 1988), rates of permeation of the species through the candidate membranes are necessary. Estimates for the permeability of pure species in a microporous membrane can be made from the molecular diffusivity, and pore diameter, porosity, and tortuosity of the membrane (Seader and Henley, 1998), as shown in Example 19.1. For this reason, considerable laboratory experimentation is required when selecting membranes in the molecular structure design step. 

Figure 1 shows a electron micrograph of a cuprammonium rayon hollow fiber made by wet spinning. The sample was prepared by fixing the network structure just after coagulation to maintain it in a condition similar to the wet state. We can see a fine network in Figure 1. This fine network cannot be seen after drying the hollow fiber, presumably because of contraction. However, the fine network reappears when the dry hollow fiber is swollen by water as shown in Figure 2. The network of the membrane once dried and then swollen in water becones somewhat smaller than the original. The properties of membranes for artificial kidneys depend strongly on this fine network structure.

The brief discussion presented suggests that tanplate-synthesized porous carbons with carefully controlled pore structure may soon find applications in the immobilization of biomolecules (proteins, enzymes, and vitamins) and in bioconversion, reversible amperometric immunosensors, regeneration of enzyme electrodes, switchable biofuel cells, and artificial kidneys [359]. 

In the field of membrane dialysis the results of an evaluation study for the artificial kidney-chronic uremia programme have been reported (15 contributors). Comparative clinical studies are concerned principally with the relative merits of celiulosic and polyacrylonitrile-based membranes. New membranes based on poly(vinyl alcohol) modified in various ways and on ethylene-vinyl acetate copolymers have been described. The manufacture, and influence of manufacturing parameters, on the structure and function of membranes for artifical kidneys have been discussed. The use of assymmetric hollow fibre haemodialysers (polyamide, polyurethane, polyester) has been considered in some detail. ... 

In general, a medical device is defined as follows a medical device is an implant and equipment to be used either to achieve disease diagnosis, medical treatment, or disease prevention for human and animals, or to influence the physical structure and function of human and animals. Medical devices for humans may also be classified based on whether and how long the device is in contact with tissue or cells and on the degree of disjunction induced by the device when in a disabling situation. The term covers various categories, such as scissors and tweezers, with small risk to human function, to central venous catheters, artificial dialysis (human kidney), and pacemakers, with high risk to human function. 

With the production of artificial radioactive substances in 1934. the field of nuclear medicine was established. In 1937, the first radioactive isotope was used to treat a person with leukemia at the University of California at Berkeley. Major strides in the use of radioactivity in medicine occurred in 1946, when a radioactive iodine isotope was successfully used to diagnose thyroid function and to treat hyperthyroidism and thyroid cancer. Radioactive substances are now used to produce images of organs, such as liver, spleen, thyroid gland, kidneys, and the brain, and to detect heart disease. Today, procedures in nuclear medicine provide information about the function and structure of every organ in the body, which allows the nuclear physician to diagnose and treat diseases early. 

Capillary membranes (microporous hollow fibers) are an integral part of artificial lungs and kidneys. They represent extracorporeal applications where both the fibers and the textile structure are in direct contact with biood. For hemodialysis, mainly fibers made from cellulose, polysulfone, polymethylmethacrylate, and polyacrylonitrile are used. In oxygenators, mainly microporous hollow fibers made from polymethylpentene and silicone are used. Microporous hollow fibers can be... 

Suspension-cultured plant cells represent a somewhat artificial situation since one is interested in studying the cells of the intact plant. The structures of the walls of cells in culture and the walls of cells in the plant may conceivably differ and it is essential when studying suspension-cultured cells to keep this possibility in mind. However, the available data indicate that the walls of suspension-cultured cells are very similar in structure to the walls of intact plant tissues. Cell wall glycosyl and glycosyl-linkage compositions of pea (58) and red kidney bean (105) hypocotyl tissues show that these tissues contain walls which are very similar to the walls isolated from suspension-cultured sycamore (123) and suspension-cultured red kidney bean cells (105). In addition, it has been demonstrated that the primary walls of cambial cells which were prepared from the branches of sycamore trees are very similar to the walls of suspension-cultured sycamore cells (104). 

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