Exhibit 99.1


                            Explanation of Responses


(1)  These shares of Common Stock, par value $0.001 per share, of the issuer
     ("Common Stock") are held directly by Oracle Investment Management, Inc.
     (the "Investment Manager"), Oracle Partners, L.P. ("Oracle Partners") and
     Oracle Institutional Partners, L.P. ("Oracle Institutional"). Mr. Larry N.
     Feinberg ("Mr. Feinberg") is the sole shareholder and president of the
     Investment Manager and is the senior managing member of Oracle Associates,
     LLC, the general partner of Oracle Partners and Oracle Institutional (the
     "General Partner"). In accordance with instruction 4(b)(iv), the entire
     number of shares of Common Stock that may be deemed to be beneficially
     owned by Mr. Feinberg by virtue of his position with the Investment Manager
     and the General Partner is reported herein. Mr. Feinberg disclaims any
     beneficial ownership of the securities held by Oracle Partners and Oracle
     Institutional for purposes of Section 16 of the Securities Exchange Act of
     1934, except to the extent of Mr. Feinberg's pecuniary interest.