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                                                                     EXHIBIT 4.2



                            CERTIFICATE OF AMENDMENT

                                       TO

                          CERTIFICATE OF INCORPORATION

                                       OF

                          ACCUMED INTERNATIONAL, INC.


         The undersigned, the President and Secretary of AccuMed International,
Inc., a Delaware corporation (the "Corporation"), do hereby certify as follows:

         1.  The Board of Directors of AccuMed International, Inc. duly adopted
a resolution, in accordance with Section 242 of the General Corporation Law of
the State of Delaware, to amend the Certificate of Incorporation of AccuMed
International, Inc. to increase the authorized shares of Common Stock from
30,000,000 shares to 50,000,000 shares, and declaring the advisability thereof.

         2.  At the Combined Annual and Special Meeting of Stockholders held on
May 23, 1997, dully called and held in accordance with the provisions of
Section 222 of the General Corporation Law of the State of Delaware, a majority
of the shares of the outstanding stock entitled to vote thereon, and a majority
of the outstanding stock of each class entitled to vote thereon as a class,
were voted in favor of such amendment in accordance with Section 242 of the
General Corporation Law of the State of Delaware.
         3.  Article FOURTH of the Certificate of Incorporation of the
             Corporation is hereby amended to read in its entirety as follows:

                 FOURTH.  The total number of shares of all classes of capital
         stock which the Corporation shall have authority to issue is
         55,000,000 shares, divided into two classes as follows:

                           5,000,000 shares of Preferred Stock of the par value
                           of $0.01 per share ("Preferred Stock"); and





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                           50,000,000 shares of Common Stock of the par value of
                           $0.01 per share ("Common Stock").

                 The designations, powers, preferences and rights, and the
         qualifications, limitations or restrictions of the above classes of
         stock are as follows:

                                   DIVISION I

                                PREFERRED STOCK

                 1.       The board of directors is expressly authorized at any
         time, and from time to time, to issue shares of Preferred Stock in one
         or more series, and for such consideration as the board of directors
         may determine, with such voting powers, full or limited but not to
         exceed one vote per share, or without voting powers, and with such
         designations, preferences and relative, participating, optional or
         other special rights, and qualifications, limitations or restrictions
         thereof, as shall be stated in the resolution or resolutions providing
         for the issue thereof, and as are not stated in this Certificate of
         Incorporation, or any amendment thereto.  All shares of any one series
         shall be of equal rank and identical in all respects.

                 2.       No dividend shall be paid or declared on any
         particular series of Preferred Stock unless dividends shall be paid or
         declared pro rata on all shares of Preferred Stock at the time
         outstanding of each other series which ranks equally as to dividends
         with such particular series.

                 3.       Unless and except to the extent otherwise required by
         law or provided in the resolution or resolutions of the board of
         directors creating any series of Preferred Stock pursuant to this
         Division I, the holders of the Preferred Stock shall have no voting
         power with respect to any matter whatsoever.  In no event shall the
         Preferred Stock be entitled to more than one vote in respect of each
         share of stock.  Subject to the protective conditions or restrictions
         of any outstanding series of Preferred Stock, any amendment to this
         Certificate of Incorporation which shall increase or decrease the
         authorized capital stock of any class or classes may be adopted by the
         affirmative vote of the holders of a majority of the outstanding
         shares of the voting stock of the Corporation.

                 4.       Shares of Preferred Stock redeemed, converted,
         exchanged, purchased, retired or surrendered to the Corporation, or
         which have been issued and reacquired in any manner, shall, upon
         compliance with any applicable provisions of the GCL, have the status
         of authorized and unissued shares of Preferred Stock and may be
         reissued by the board of directors as part of the series





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         of which they were originally a part or may be reclassified into and
         reissued as part of a new series or as a part of any other series, all
         subject to the protective conditions or restrictions of any
         outstanding series of Preferred Stock.

                                  DIVISION II

                                  COMMON STOCK

                 1.       DIVIDENDS.  Subject to the preferential dividend
         rights, if any, applicable to shares of the Preferred Stock and
         subject to applicable requirements, if any, with respect to the
         setting aside of sums for purchase, retirement or sinking funds for
         the Preferred Stock, the holders of the Common Stock shall be entitled
         to receive to the extent permitted by law, such dividends as may be
         declared from time to time by the board of directors.

                 2.       LIQUIDATION.  In the event of the voluntary or
                 involuntary liquidation, dissolution, distribution of assets
                 or winding up of the Corporation, after distribution in full
                 of the preferential amounts, if any, to be distributed to the
                 holders of shares of the Preferred Stock, holders of the
                 Common Stock shall be entitled to receive all the remaining
                 assets of the Corporation of whatever kind available for
                 distribution to stockholders ratably in proportion to the
                 number of shares of Common Stock held by them respectively.

                 3.       VOTING RIGHTS.  Except as may be otherwise required
                 by law or this Certificate of Incorporation, each holder of
                 the Common Stock shall have one vote in respect of each share
                 of stock held by him or her of record on the books of the
                 Corporation on all matters voted upon by the stockholders.


                                  DIVISION III

                           ELIMINATION OF PREEMPTIVE
                                     RIGHTS

                 No holder of stock of any class of the Corporation shall be
         entitled as a matter of right to purchase or subscribe for any part of
         any unissued stock of any class, or of any additional stock of any
         class or capital stock of the Corporation, or of any bonds,
         certificates of indebtedness, debentures, or other securities
         convertible into stock of the Corporation, now or hereafter
         authorized, but any such stock or other securities convertible into
         stock may be issued and disposed of pursuant to resolution by the
         board of directors to such persons, firms,





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         corporations or associations and upon such terms and for such
         consideration (not less than the par value or stated value thereof) as
         the board of directors in the exercise of its discretion may determine
         and as may be permitted by law without action by the stockholders.


         IN WITNESS WHEREOF, we have signed this Certificate this 23rd day of
May 1997.

                                    ACCUMED INTERNATIONAL, INC.



                                    By: /s/ PETER P. GOMBRICH       
                                    Peter P. Gombrich, President



ATTEST:



/s/ JOYCE L. WALLACH
- ------------------------------
Joyce L. Wallach
Secretary















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