Exhibit 99.1


                            Explanation of Responses


(1)  These securities were received upon conversion of other securities of the
     Issuer, as further described herein.

(2)  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.

(3)  The shares of Series C 8% Cumulative Redeemable Convertible Preferred Stock
     ("Series C Preferred Stock") to which this note relates (173,436 shares of
     Series C Preferred Stock) were held directly by the Investment Manager.
     Upon the closing of the initial public offering of the Issuer on February
     6, 2004 (the "IPO Closing") the Series C Preferred Stock was converted into
     Common Stock at the rate of 8.5 shares of Common Stock for each share of
     Series C Preferred Stock. In addition, upon such conversion accrued but
     unpaid dividends on such Series C Preferred Stock were paid to the holders
     thereof in such number of shares of Common Stock as if (i) such dividends
     were used to purchase Series C Preferred Stock at a valuation of $57.658
     per share and (ii) such purchased shares of Series C Preferred Stock were
     then converted into Common Stock at the 8.5 to 1 ratio.

(4)  The shares of Series D 8% Cumulative Redeemable Convertible Preferred Stock
     ("Series D Preferred Stock") and Series E 8% Cumulative Redeemable
     Convertible Preferred Stock ("Series E Preferred Stock") to which this note
     relates (74,894 shares of Series D Preferred Stock and 16,478 shares of
     Series E Preferred Stock) were held directly by Oracle Partners and Oracle
     Institutional. Upon the IPO Closing, the Series D Preferred Stock was
     converted into Common Stock at the rate of 8.61249051 shares of Common
     Stock for each share of Series D Preferred Stock. In addition, upon such
     conversion accrued but unpaid dividends on such Series D Preferred Stock
     were paid to the holders thereof in such number of shares of Common Stock
     as if (i) such dividends were used to purchase Series D Preferred Stock at
     a valuation of $66.762 per share and (ii) such purchased shares of Series D
     Preferred Stock were then converted into Common Stock at the 8.61249051 to
     1 ratio. Upon the IPO Closing, the Series E Preferred Stock was converted
     into Common Stock at the rate of 8.5 shares of Common Stock for each share
     of Series E Preferred Stock. In addition, upon such conversion accrued but
     unpaid dividends on such Series E Preferred Stock were paid to the holders
     thereof in such number of shares of Common Stock as if (i) such dividends
     were used to purchase Series E Preferred Stock at a valuation of $60.692
     per share and (ii) such purchased shares of Series E Preferred Stock were
     then converted into Common Stock at the 8.5 to 1 ratio.

(5)  The shares of Series C Preferred Stock, Series D Preferred Stock and Series
     E Preferred Stock to which this note relates were immediately exercisable
     and had no expiration date.

(6)  As the transactions reported herein involve the conversion of a derivative
     security, no information is required to be included in column 8 of Table
     II, in accordance with instruction 4(c)(iii).