EXHIBIT 10.51
FOURTH AMENDMENT
This Fourth Amendment (the "4th Amendment") is made and entered into as of this 27th day of December 1999
by and between NATIONAL DIAGNOSTICS, INC., an Florida corporation ("NDI") and American
Enterprise.com, Corp., formerly known as American Enterprise Solutions, Inc., a Florida corporation ("AESI").
RECITALS
WHEREAS, NDI and AESI have entered into that certain Merger Agreement dated February 23, 1998 as
amended by that certain First Amendment dated March 17, 1998 and that certain Second Amendment dated
April 29, 1998 and that Third Amendment dated July 24, 1998 (the "Agreement") pursuant to which it is
contemplated with AESI will be merged (the "Merger") with and into NDI under the terms and conditions
specified in the Agreement; and
WHEREAS, Section 4.1 of the Agreement currently provides, among other things, that the Closing of the Merger
shall occur on July 31, 1998, or as soon as practicable after all conditions to Closing shall have been satisfied or
waived, or at such other time and date as NDI and AESI may mutually agree; and
WHEREAS, AESI and NDI have mutually agreed that the date of Closing the Merger shall be on or before
December 31, 2000, or as soon as practicable after all conditions to Closing shall have been satisfied or waived,
or at such other time and date as NDI and AESI may mutually agree; and
WHEREAS, Section 13.1(ii) of the Agreement currently provides, among other things, that AESI (acting through
its board of directors) shall have the right to terminate the Agreement if the Closing shall not have occurred by
December 31, 1998; and
WHEREAS, AESI and NDI have mutually agreed that Section 13.1(ii) of the Agreement should be amended to
reflect the fact that AESI (acting through its board of directors) shall have the right to terminate the Agreement if
the Closing has not occurred by December 31, 2000.
NOW, THEREFORE, in consideration of the premises set forth herein, and for other good and valuable
consideration, the receipt and