REACTIVATION OF EXTRACTED SPERM CELL MODELS 253 



fen ing to glycerol-extracted muscle preparations. Perhaps a more cor- 

 rect term would be reconstituted cells or fibers as suggested by 

 Hayashi. Nevertheless, the distinction should be clear between ex- 

 tracted sperm cell models as described here and the conceptual models 

 of contraction envisaged by Pringle (1960), for example, or the actual 

 mechanical models of spermatozoa fabricated by Sir Geoffrey Taylor 

 (1952). 



To Hoffmann-Berling (1955a) goes the credit for having first ap- 

 plied the extracted cell procedure to nonmuscular systems, including 

 spermatozoa. Glycerol-KCl-extracted sperm of the locust, Tachycines, 

 were found, after storage, to respond to adenosine triphosphate 

 (ATP), in the proper ionic milieu, by assuming a vigorous and con- 

 tinuing rhythmic motility. Since that time, ATP-sensitive model sys- 

 tems have been described for a variety of flagella, cilia, interkinetic 

 and mitotic fibroblasts, sarcoma cells, vorticellid myonemes, Para- 

 mecium trichocysts and T 2 bacteriophage (Hoffmann-Berling, 1955b, 

 1958a, b, 1959; Brokaw, 1961; Alexandrov and Arronet, 1956; Levine, 

 1956; Kinoshita, 1958, 1959; Kozloff and Lute, 1959; Bishop and 

 Hoffmann-Berling, 1959). 



Since the methods of extraction of sperm models have been ade- 

 quately presented elsewhere (Hoffmann-Berling, 1955a,b; Kinoshita, 

 1958; Bishop, 1958a; Bishop and Hoffmann-Berling, 1959), the sub- 

 ject may well be omitted here. Attention should be directed, how- 

 ever, to the possible role and significance of glycerol in the actual 

 extraction process. In order that sperm models may be preserved in a 

 reactivatable state at subzero temperatures, they must be bathed in 

 an approximately 50% glycerol-saline medium, comparable to the 

 muscle extraction medium advocated by Szent-Gyorgyi. Mammalian 

 spermatozoa, however, can be satisfactorily extracted at 20°C without 

 glycerol and subsequently reactivated with ATP (Bishop and Hoff- 

 mann-Berling, 1959). Studies on these cells indicate that glycerol is 

 more important in the stabilization and preservation of the con- 

 tractile protein system than in the extraction process per se. 



In order to ensure complete extraction, certain criteria were es- 

 tablished for these preparations. When properly treated, extracted 

 mammalian sperm showed neither respiratory activity (oxygen con- 

 sumption) nor glycolysis (lactate formation); reactivation was in- 

 ducible only by nucleotides at reasonable concentrations; deteriora- 



