Energy-storing prosthetic feet.

At least six brands of energy-storing prosthetic feet (ESPF) are now commercially available in the US. These are designed to permit lower extremity amputees to participate in a wide variety of activities, such as running and jumping sports, as well as vigorous walking. Although kinesiologic studies of these devices have not been completed, clinical experience suggests that the Flex-Foot provides the highest performance, followed by the Carbon Copy II and the Seattle Foot. The S.A.F.E. Foot, the STEN Foot, and the Dynamic Foot provide less energy storage and may be suitable for less active patients or those with special needs such as walking on uneven ground. All of the ESPF except the Flex-Foot may be attached to a realigned conventional prosthesis. The Flex-Foot incorporates a pylon and foot in one unit and requires special fabrication technologies. The additional cost of most of the ESPF (compared to a Solid Ankle Cushion Heel Foot) may add little to the cost of a finished prosthesis although it provides greatly increased function. The Flex-Foot, however, is significantly more expensive. Advances in kinesiology and materials science are being applied in the design of prosthetic components that are lighter, stronger, and more resilient. Clinicians can now choose from a variety of innovative commercially available devices but have been hampered by a lack of published information. This paper will review the design philosophy, materials, and applications of ESPF, and will supplement the information available from individual manufacturers and the prosthetic literature.

Somatic cell cloning in polyester stacks.

Single somatic cells, including fibroblasts, myelomas, and hybridomas, proliferate normally when trapped between a plastic dish and a disc of polyester cloth. Contact between the overlay and the plastic for 8-16 days results in identical colony patterns on the cloth and the plate. When several cloth discs are simultaneously stacked over Chinese hamster ovary cells, three or four-high resolution colony copies can be generated from a single master dish. The colonies on the cloth can be analyzed by radiochemical methods [Esko, J. D. & Raetz, C. R. H. (1978) Proc. Natl. Acad. Sci. USA 75, 1190-1193] or by "replica plating" to a new disc. The use of polyester cloth, singly or in stacks, has several major advantages over previous techniques for somatic cell replica plating, including: (i) broad applicability to diverse cell lines such as fragile membrane mutants of Chinese hamster ovary cells and relatively nonadherent myelomas or hybridomas; (ii) the possibility of generating multiple copies of the same colony population, allowing simultaneous analysis for several enzymes or cellular components; and (iii) superior resolution and transfer efficiency in copying colony patterns from one surface to another. The remarkable capacity of animal cell colonies to proliferate upward through "polyester stacks" may reflect chemotropic movement of individual cells and opens new approaches to somatic cell genetics.

Isolation of somatic cell mutants defective in the biosynthesis of phosphatidylethanolamine.

An in situ autoradiographic assay for CDP-ethanolamine:1,2-sn-diacylglycerol ethanolamine phosphotransferase (EC 2.7.8.1) activity in Chinese hamster ovary cells was developed and used to screen approximately 10,000 individual mutagen-treated colonies attached to filter paper (Esko, J. D., and Raetz, C. R. H. (1978) Proc. Natl. Acad. Sci. U. S. A. 75, 1190-1193). A variant (strain 40.11) was isolated in which the ethanolamine phosphotransferase specific activity in vitro was 6-10-fold less than in the parent, but the level of CDP-choline:1,2-sn-diacylglycerol choline phosphotransferase (EC 2.7.8.2) activity was normal. In extracts, the mutant was also defective in the synthesis of ethanolamine plasmalogen. In vivo, the short term kinetics of labeling with [32P]phosphate or [14C]ethanolamine was correspondingly altered. However, the long tem growth rate and steady state phospholipid compositions of the mutant and parent were quite similar. These results show that the ethanolamine and choline phosphotransferases of Chinese hamster ovary cells are distinct as judged by genetic criteria, while the biosynthesis of phosphatidylethanolamine and its plasmalogen share common enzymatic component(s).