EXHIBIT 2.2

                                                                  Execution Copy


                              STOCKHOLDER AGREEMENT

      This STOCKHOLDER AGREEMENT (this "Agreement"), dated as of April 7, 2004,
is made and entered into among TELEDYNE TECHNOLOGIES INCORPORATED, a Delaware
corporation ("Parent"), MEADOW MERGER SUB INC., a Nebraska corporation and a
wholly owned subsidiary of Parent ("Merger Sub"), and the individuals listed
under the heading "STOCKHOLDERS" on the signature page hereof (each, a
"Stockholder" and collectively, the "Stockholders").

                              W I T N E S S E T H:

      WHEREAS, as of the date hereof, each Stockholder is the beneficial owner
("beneficial owner," "beneficial ownership," "beneficially," and related terms,
wherever used herein, within the meaning of Section 13(d)(1) of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and the rules and
regulations promulgated thereunder (including, without limitation, Rule 13d-3
under the Exchange Act)) of the number of common shares, par value $0.10
("Company Common Stock"), of Isco, Inc., a Nebraska corporation (the "Company"),
set forth opposite such Stockholder's name on Exhibit A hereto (the total number
of shares of Company Common Stock beneficially owned by the Stockholders, and
any other Company Common Stock or any stock option that either Stockholder may
acquire, as record or beneficial holder, whether by means of purchase, dividend,
distribution, or otherwise, prior to the termination of this Agreement, together
with all associated rights and interests, being collectively referred to as the
"Shares");

      WHEREAS, concurrently with the execution and delivery of this Agreement,
the Company, Parent, and Merger Sub are entering into an Agreement and Plan of
Merger (the "Merger Agreement") of even date herewith, which (upon the terms and
subject to the conditions set forth therein) provides for the merger of Merger
Sub with and into the Company (the "Merger"); and

      WHEREAS, as a condition to their willingness to enter into the Merger
Agreement, Parent and Merger Sub have requested the Stockholders to agree, and
in order to induce Parent and Merger Sub to enter into the Merger Agreement the
Stockholders have agreed, to enter into this Agreement.

      NOW, THEREFORE, in consideration of the foregoing premises and the
representations, warranties, covenants, and agreements hereinafter set forth,
and for other good and valuable consideration, the receipt and sufficiency of
which is hereby acknowledged, the parties hereto hereby agree as follows:

                                   ARTICLE I

                  STOCKHOLDERS' REPRESENTATIONS AND WARRANTIES

      Each Stockholder hereby represents and warrants to Parent and Merger Sub
as follows:



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      1.1 DUE ORGANIZATION AND AUTHORIZATION. Stockholder possesses the
requisite power and authority to execute, deliver, and perform this Agreement,
to appoint or cause to be appointed Merger Sub and Parent (or any nominee
thereof) as Stockholder's Proxy (as defined below), and to consummate the
transactions contemplated hereby. This Agreement has been duly executed and
delivered by Stockholder and constitutes a legal, valid, and binding obligation
of Stockholder, enforceable against Stockholder in accordance with its terms,
except as enforceability (i) may be limited by bankruptcy, insolvency,
moratorium or other similar laws affecting or relating to creditors' rights
generally and (ii) is subject to general principles of equity. There is no other
beneficial owner of any of the Shares set forth opposite Stockholder's name on
Exhibit A hereto or other beneficiary or holder of any other interest in any of
such Shares whose consent is required for the execution and delivery of this
Agreement or for the consummation by Stockholder of the transactions
contemplated hereby.

      1.2 NO CONFLICTS; REQUIRED FILINGS AND CONSENTS.

            (a) The execution and delivery of this Agreement by Stockholder do
not, and the performance of this Agreement by Stockholder will not, (i) conflict
with or violate any law applicable to Stockholder or by which Stockholder or any
of Stockholder's assets are bound or affected, or (ii) result in any breach of
or constitute a default (or an event that with notice or lapse of time or both
would become a default) under, or give to others any rights of termination,
acceleration, or cancellation of, or result in the creation of a lien or
encumbrance on any assets of Stockholder, including, without limitation, the
Shares set forth opposite Stockholder's name on Exhibit A hereto, pursuant to,
any note, bond, mortgage, indenture, contract, agreement, lease, license,
permit, franchise, or other instrument or obligation to which Stockholder is a
party or by which Stockholder or any of Stockholder's assets are bound or
affected, except in the case of clause (ii), for such matters as would not
prevent or in any way impair Stockholder's ability to perform Stockholder's
obligations under this Agreement.

            (b) The execution and delivery of this Agreement by Stockholder do
not, and the performance of this Agreement by Stockholder will not, require any
consent, approval, authorization or permit of, or filing with or notification
to, any governmental or regulatory authority, domestic or foreign.

      1.3 TITLE TO SHARES. Stockholder is the sole beneficial owner of the
shares of Company Common Stock set forth opposite Stockholder's name on Exhibit
A hereto, free and clear of any pledge, lien, security interest, mortgage,
claim, proxy, voting restriction or other voting trust, agreement,
understanding, or arrangement of any kind, right of first refusal or other
limitation on disposition, adverse claim of ownership, or other encumbrance of
any kind, other than restrictions imposed by securities laws or pursuant to this
Agreement. As of the date hereof, Stockholder does not own beneficially or of
record any other shares of Company Common Stock or any option to acquire any
such shares.

      1.4 INFORMATION FOR OFFER DOCUMENTS AND PROXY STATEMENT. None of the
information relating to Stockholder and Stockholder's affiliates provided in
writing to the Company by or on behalf of Stockholder or Stockholder's
affiliates specifically for inclusion in the Proxy Statement will, at the times
the Proxy Statement is filed with the U.S. Securities and Exchange Commission or
is first published, sent or given to shareholders of the Company, or at



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the time of the special meeting of shareholders to consider the Merger, contain
any untrue statement of a material fact or omit to state any material fact
required to be stated therein or necessary in order to make the statements
therein, in light of the circumstances under which they were made, not
misleading.

      1.5 ACKNOWLEDGMENT. Stockholder, on behalf of itself and Stockholder's
affiliates, acknowledges and agrees that neither it nor they shall be paid or
shall otherwise be entitled to any broker's, finder's, financial advisor's, or
other similar fee or commission in connection with the transactions contemplated
hereby or by the Merger Agreement.

                                   ARTICLE II

                             STOCKHOLDER'S COVENANTS

      Each Stockholder hereby covenants to Parent and Merger Sub as follows:

      2.1 VOTING OF SHARES. Stockholder hereby agrees that from the date hereof
until the termination of the Agreement pursuant to Section 3.1 (the "Term"), at
any meeting of the shareholders of the Company however called and in any action
by written consent of the shareholders of the Company, in each case before the
Effective Time, Stockholder shall vote (or direct the record owner of
Stockholder's Shares to vote) Stockholder's Shares (i) in favor of the Merger
and the Merger Agreement; (ii) if so directed by Parent, against any Takeover
Proposal and against any proposal for action or agreement that would result in a
breach of any covenant, representation or warranty or any other obligation or
agreement of the Company under the Merger Agreement or which could reasonably be
expected to result in any of the Company's obligations under the Merger
Agreement not being fulfilled, any change in the composition of the board of
directors of the Company (except as contemplated by the Merger Agreement), any
change in the present capitalization of the Company or any amendment to the
Company's corporate structure or business, or any other action which could
reasonably be expected to impede, interfere with, delay, postpone or materially
adversely affect the transactions contemplated by this Agreement or the Merger
Agreement or the likelihood of such transactions being consummated; and (iii) in
favor of any other matter necessary for consummation of the transactions
contemplated by the Merger Agreement which is considered at any such meeting of
shareholders or in such consent, and in connection therewith to execute any
documents which are necessary or appropriate in order to effectuate the
foregoing, including, without limitation, documents enabling Parent and Merger
Sub or their nominee(s) to vote Stockholder's Shares directly.

      2.2 PROXY. Stockholder hereby revokes all prior proxies or powers of
attorney with respect to any and all of Stockholder's Shares. During the Term,
Stockholder hereby constitutes and appoints Parent and Merger Sub, or any
nominee designated by Parent and Merger Sub, with full power of substitution and
resubstitution at any time during the Term, as Stockholder's true and lawful
attorney and proxy ("Proxy"), for and in its name, place, and stead, in the
Proxy's discretion, to demand that the Secretary of the Company call a special
meeting of the shareholders of the Company for the purpose of considering any
matter referred to in Section 2.1 and to vote each Share held by Stockholder as
Stockholder's Proxy in respect of any such matter, at every annual, special,
adjourned, or postponed meeting of the shareholders of the



                                      -3-

Company, including, without limitation, the right to sign its name as
Stockholder (or to direct the record owner to sign its name as Stockholder) to
any consent, certificate, or other document relating to the Company that the law
of the State of Nebraska might permit or require. THE FOREGOING PROXY AND POWER
OF ATTORNEY ARE IRREVOCABLE AND COUPLED WITH AN INTEREST THROUGHOUT THE TERM.
Stockholder will take such further action and execute such other documents as
may be necessary to effectuate the intent of this Section 2.2.

      2.3 RESTRICTIONS ON TRANSFER, PROXIES AND NON-INTERFERENCE.

            (a) Stockholder hereby agrees, until the termination of this
Agreement pursuant to Section 3.1 not to (i) sell, transfer, pledge, encumber,
assign or otherwise dispose of, or enter into any contract, option or other
arrangement or understanding with respect to the sale, transfer, pledge,
encumbrance, assignment or other disposition of, any of Stockholder's Shares,
(ii) grant any proxies, deposit any of Stockholder's Shares into a voting trust
or enter into a voting agreement with respect to any of Stockholder's Shares, or
(iii) take any action that would make any representation or warranty of
Stockholder contained herein untrue or incorrect in any material respect or have
the effect of preventing, impairing, or disabling Stockholder from timely and
promptly performing Stockholder's obligations under this Agreement.

            (b) Stockholder hereby agrees, if so requested by Parent, (i) that
the Shares held by Stockholder shall bear a legend stating that they are subject
to this Agreement and to an irrevocable proxy and (ii) that, subject to the
terms of Section 2.3(a), such Stockholder shall not sell, transfer, pledge,
encumber, assign or otherwise dispose of, or enter into any contract, option or
other arrangement or understanding with respect to the sale, transfer, pledge,
encumbrance, assignment or other disposition of, any of Stockholder's Shares
without first having the aforementioned legend affixed to the certificates
representing such Shares.

      2.4 NO SOLICITATION. Stockholder covenants and agrees that, during the
Term, it shall not, directly or indirectly, solicit, initiate, knowingly
encourage, or take any other action designed to facilitate any inquiries or the
making of any proposal from any Person (other than from Parent or Merger Sub)
relating to any transaction that constitutes a Takeover Proposal. Stockholder
further covenants and agrees that, during the Term, it shall not participate in
any discussions or negotiations (except with Parent or Merger Sub) regarding, or
furnish to any Person (other than Parent or Merger Sub or if required by law or
compelled by subpoena or similar legal process) any information with respect to,
or otherwise cooperate in any way with, or assist or participate in or
facilitate or encourage, any effort or attempt by any Person (other than Parent
and Merger Sub) to make or effect, any transaction that may constitute a
Takeover Proposal. Stockholder immediately shall cease and cause to be
terminated any existing discussions or negotiations of Stockholder and
Stockholder's agents or other representatives with any Person (other than Parent
and Merger Sub) with respect to any of the foregoing. Stockholder shall notify
Parent and Merger Sub promptly of any specific proposal or offer made to
Stockholder relating to a Takeover Proposal, or any substantive inquiry or
contact made to Stockholder specifically relating to a Takeover Proposal, and
shall, in any such notice to Parent and Merger Sub, indicate in reasonable
detail the identity of the Person making such proposal, offer, inquiry, or
contact and the material terms and conditions of such proposal, offer, inquiry,
or contact. Notwithstanding the foregoing, Dr. Allington may, in his capacity as
an officer of the



                                      -4-

Company or a member of the Board of Directors of the Company, take such actions,
if any, as are permitted by Section 5.2 of the Merger Agreement.

      2.5 MUTUALITY. Each Stockholder agrees that the terms of this Agreement
shall apply to any interest, spousal or otherwise, of such Stockholder in the
Shares described in this Agreement as being owned by the other Stockholder. The
representations, warranties, and covenants of the Stockholders made in this
Agreement are joint and several.

                                  ARTICLE III

                                  MISCELLANEOUS

      3.1 TERMINATION. This Agreement shall terminate and be of no further force
and effect: (a) upon the giving of notice in writing by Parent, automatically
and without any required further action of the parties hereto or (b)
automatically and without any required action of the parties hereto upon the
earliest to occur of

            (i)   the Effective Time,

            (ii)  any amendment of the Merger Agreement without the written
                  consent of both Stockholders that (x) provides for a reduction
                  in the Merger Consideration below $16.00 per Share or (y)
                  changes the form of the Merger Consideration to other than
                  cash

            (iii) any termination of the Merger Agreement pursuant to its terms,
                  and

            (iv)  the one year anniversary of the date of this Agreement.

The termination of this Agreement shall not relieve any party hereto from any
liability for any breach of this Agreement prior to termination.

      3.2 DEFINITIONS. Terms used but not otherwise defined in this Agreement
shall have the respective meanings ascribed to such terms in the Merger
Agreement, as it may be amended from time to time.

      3.3 EXPENSES. All costs and expenses incurred in connection with the
transactions contemplated by this Agreement shall be paid by the party incurring
such costs and expenses.

      3.4 NOTICES. All notices and other communications hereunder shall be in
writing and shall be deemed to have been duly given (i) upon hand delivery, (ii)
upon confirmation of receipt of facsimile transmission, or (iii) upon confirmed
delivery by a standard overnight courier, to the following address or to such
other address that a party hereto might later specify by like notice:





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            (a)   If to Parent or Merger Sub, to:

                  Teledyne Technologies Incorporated
                  12333 West Olympic Boulevard
                  Los Angeles, CA 90064
                  Attention: John T. Kuelbs
                  Telecopier No.: (310) 893-1610

                  with a copy to:

                  Munger, Tolles & Olson LLP
                  Attention: Robert Denham and Brian Daly
                  355 South Grand Avenue, 35th Floor
                  Los Angeles, California 90071-1560
                  Telecopy: (213) 687-3702

            (b)   If to Stockholder, to:

                  Dr. Robert W. Allington
                  c/o Isco, Inc.
                  4700 Superior Street
                  Lincoln, Nebraska 68504
                  Telecopier No.: (402) 465-3905

                  with a copy to:

                  Baird, Holm, McEachen, Pedersen, Hamann & Strasheim LLP
                  Attention: John S. Zeilinger
                  1500 Woodmen Tower
                  Omaha, Nebraska 68102-2068
                  Telecopier No.: (402) 231-8556

      3.5 SEVERABILITY. In the event that any provision in this Agreement is
held invalid, illegal, or unenforceable in a jurisdiction, such provision shall
be modified or deleted as to the jurisdiction involved but only to the extent
necessary to render the same valid, legal, and enforceable. The validity,
legality, and enforceability of the remaining provisions hereof shall not in any
way be affected or impaired thereby nor shall the validity, legality, or
enforceability of such provision be affected thereby in any other jurisdiction.

      3.6 ENTIRE AGREEMENT. This Agreement constitutes the entire agreement
among the parties hereto with respect to the subject matter hereof and
supersedes all prior agreements and understandings, both written and oral, among
the parties hereto, or any of them, with respect thereto.

      3.7 ASSIGNMENT. No party hereto may assign or delegate this Agreement or
any right, interest, or obligation hereunder; provided, however, that Parent or
Merger Sub, in its sole discretion, may assign or delegate its rights and
obligations hereunder to any direct or indirect wholly owned subsidiary of
Parent without obtaining the consent of any other party



                                      -6-

hereto; and provided, further, that any such assignment or delegation shall not
relieve Parent or Merger Sub from liability hereunder.

      3.8 NO THIRD-PARTY BENEFICIARIES. This Agreement shall be binding upon,
inure solely to the benefit of, and be enforceable by only the parties hereto,
their respective successors, and their permitted assigns, and nothing in this
Agreement, express or implied, is intended to or shall confer upon any Person,
other than the parties hereto, their respective successors, and permitted
assigns, any rights, remedies, obligations, or liabilities of any nature
whatsoever.

      3.9 WAIVER OF APPRAISAL RIGHTS. Stockholder hereby waives any rights of
appraisal or rights to dissent from the Merger.

      3.10 FURTHER ASSURANCE. Each party hereto shall execute and deliver such
additional documents and take all such further action as may be necessary or
desirable to consummate and make effective, in the most expeditious manner
practicable, the transactions contemplated by this Agreement.

      3.11 CERTAIN EVENTS. Stockholder agrees that this Agreement and the
obligations hereunder shall attach to Stockholder's Shares and shall be binding
upon any Person to which legal or beneficial ownership of such Shares shall
pass, whether by operation of law or otherwise. Notwithstanding any transfer of
Shares, the transferor shall remain liable for the performance of all
obligations under this Agreement.

      3.12 NO WAIVER. The failure of any party hereto to exercise any right,
power, or remedy provided under this Agreement or otherwise available at law or
in equity, the failure of any party hereto to insist upon compliance by any
other party hereto with its respective obligations hereunder, or the existence
of any custom or practice of the parties hereto at variance with the terms
hereof shall not constitute a waiver by such party of its right to exercise any
such or other right, power, or remedy or to demand such compliance.

      3.13 SPECIFIC PERFORMANCE. The parties hereto acknowledge that irreparable
damage would occur in the event that any of the provisions of this Agreement
were not performed in accordance with their specific terms or were otherwise
breached. Accordingly, the parties hereto agree that an aggrieved party shall be
entitled to injunctive relief to prevent breaches of this Agreement and to
enforce specifically the terms and provisions hereof in any court having
jurisdiction, this being in addition to any other right or remedy to which such
party may be entitled under this Agreement at law, or in equity.

      3.14 GOVERNING LAW. This Agreement shall be governed by, and construed in
accordance with, the laws of the State of Delaware, without giving effect to
provisions thereof relating to conflicts of law.

      3.15 HEADINGS. The descriptive headings in this Agreement were included
for convenience of reference only and shall not affect in any way the meaning or
interpretation of this Agreement.



                                      -7-

      3.16 COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument. Facsimile transmission of
any signed original document and/or retransmission of any signed facsimile
transmission will be deemed the same as delivery of an original. At the request
of another party hereto, each party hereto will confirm facsimile transmission
by signing a duplicate original document.

                  [Remainder of page intentionally left blank.]





                                      -8-

                                                                  Execution Copy


      IN WITNESS WHEREOF, the parties hereto have each caused this Agreement to
be executed in a manner sufficient to bind them as of the date first written
above.

                           TELEDYNE TECHNOLOGIES INCORPORATED

                           By:      /s/ Robert Mehrabian
                              --------------------------------------------
                                 Name: Robert Mehrabian
                                 Title: Chairman, President and
                                        Chief Executive Officer

                           MEADOW MERGER SUB INC.


                           By:     /s/ Melanie S. Cibik
                              --------------------------------------------
                                 Name: Melanie Cibik
                                 Title: Vice President and Assistant Secretary

                           STOCKHOLDERS:

                                   /s/ Robert W. Allington
                           ----------------------------------------------
                                     ROBERT W. ALLINGTON

                                     /s/ Mary L. Allington
                           ----------------------------------------------
                                       MARY L. ALLINGTON

                                     -S-1-

                                    EXHIBIT A



                                                          No. of Shares of
Name of Beneficial and Record Owner                     Company Common Stock
- -----------------------------------                     --------------------
                                                

Robert W. Allington                                -   2,636,104 Shares

                                                   -   264.8277 Shares under
                                                       the Retirement Plu$ Plan

                                                   -   42,491 Shares
                                                       exercisable pursuant to
                                                       options granted under
                                                       the Isco, Inc. 1996
                                                       Stock Option Plan (of
                                                       which 18,679 shares are
                                                       currently vested)

Mary L. Allington                                  -   100,000 Shares