Three-dimensional growth of large populations of cells in vitro has been observed in the interstices of a matrix consisting of collagen-coated cellu lose sponge. The growth of Walker tumor 256 in this composite matrix is com pared with that found in a matrix composed of either cellulose sponge alone or collagen sponge alone. The composite matrix is superior to either one. Collagen coated cellulose sponge may provide a simple tool for the study of social interaction of cells in the formation of organized elementary tissue structures.
The independent and unequivocal syntheses of 3a-methyl-«'s-and -irarcs-hexahydroindan and several of their deuteromethyl analogs have been achieved through stereospecific reactions. Through a Diels-Alder synthesis, a methoxycarbonyl group was locked into the «'^-configuration at the angular position of a tetrahydroindan and transformed, via the saturated angular ester, hydroxymethyl and corresponding tosylate of the latter, to the desired 3a-methyl-«s-hexahydroindan. Byemploying the appropriate combinations of lithium aluminum hydride and lithium aluminum deuteride, the mono-, diand trideuteromethyl-«s-hexahydroindans also were obtained. 3a-Methyl-
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