G. A. Heidt,¹ H. H. Conaway,² C. Frith,³ H. E. Farris<sup>4

1</sup>Department of Biology, University of Arkansas at Little Rock, Little Rock, Arkansas 72204, USA
²Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA
³Veterans Administration Hospital, Little Rock, Arkansas 72201, USA
⁴Division of Laboratory Animal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA