Document:

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                                                                   EXHIBIT 10.13

                   SIXTH AMENDMENT TO LEASE AGREEMENT BETWEEN
                 AETNA LIFE INSURANCE COMPANY, AS LANDLORD, AND
                         LUMINEX CORPORATION, AS TENANT

                  To be attached to and form a part of Lease made the 1st day of
                  August, 1989 (which together with any amendments,
                  modifications and extensions thereof, is hereinafter called
                  the Lease), between Landlord and Tenant, covering a total of
                  32,859 square feet and located at 12212 Technology Boulevard,
                  Suites I, J and K and 12112 Technology Boulevard, Suite 200,
                  Austin, Texas, known as McNeil #4 and McNeil #5, respectively.

WITNESSETH that the Lease is hereby amended as follows:

         1. WHEREAS, Tenant needs additional space for its business purposes and
Landlord has available an area nearby effective on the Commencement Date, the
demised premises shall contain, in addition to the approximately 32,859 square
feet originally demised ("original space"), an additional area, hereinafter
called the "new space", containing approximately 18,330 square feet located at
12201 Technology Boulevard, Suite 130 (known as McNeil #3) (see Exhibit "A")
attached hereto, thus making the aggregate area of the premises approximately
51,189 square feet. The term for the new space (Suite 130 at McNeil #3) shall
end thirty-six (36) months after the Commencement Date (as defined below), and
the Term for the existing space shall end on March 31, 2002 as provided in the
Lease.

The Commencement Date for the new space is defined as thirty (30) days following
existing tenant's vacation of the "new space" and the completion of
responsibilities outlined in Paragraph 3 and Paragraph 13 of this document. The
Commencement Date is contemplated to be June 1, 2000.

         2. The Monthly Rental shall be as follows:

<TABLE>
<CAPTION>

                                MONTHLY BASE
                                 RENTAL PSF        MONTHLY BASE        MONTHLY BASE      MONTHLY BASE
                               EXISTING SPACE         RENTAL           PSF NEW SPACE      RENTAL NEW      TOTAL MONTHLY
           TERM                  (32,859 SF)      EXISTING SPACE         (18,330 SF)         SPACE         BASE RENTAL
           ----              -----------------    --------------       --------------   --------------    -------------

<S>                          <C>                  <C>                  <C>               <C>                <C>
Commencement - 3/31/02              $     0.75        $24,644.25          $     0.80        $14,664.00       $39,308.25

4/01/02 - 5/31/03                          N/A               N/A          $     0.80        $14,664.00       $14,664.00
</TABLE>

These amounts shall be in addition to property taxes, common area maintenance,
management fees, and insurance as provided in the Lease.

         3. Previous tenant or Landlord shall be responsible for servicing and
repairing, if necessary, the HVAC system by a mutually acceptable, licensed
contractor and cleaning the "new space" to broom clean condition, including but
not limited to, removal of trash and previous tenant's equipment.

         4. Landlord shall be responsible for exterior ADA compliance at the new
space.

         5. Landlord shall provide a tenant finish allowance of $54,990.00 to be
applied toward interior improvements. Tenant shall bear the entire cost of any
interior improvements to be installed by Landlord in the premises in excess of
the finish-out allowance of $54,990.00 and shall pay for such excess over the
allowance as hereinafter provided. In no event shall credit be given to Tenant
for any allowance not utilized. All improvements must comply with Trammell Crow
Company's standard specifications (see Standards and Specifications for
Office/Warehouse Buildings) and all applicable governmental regulations. Prior
to beginning construction of any such improvements, Tenant shall submit
architectural drawings of the proposed improvements to Landlord and shall obtain
Landlord's written consent to begin construction. Notwithstanding any provision
herein to the contrary, Tenant will utilize a general contractor, approved by
Landlord, to construct the interior improvements in the new space. Tenant will
have the right to access, occupy and conduct business in the new space up to,
but not exceeding, thirty (30) days prior to the Commencement Date without any
rent obligation. Tenant will construct the interior improvements in the new
space with reasonable diligence, but need not finish them prior to the
Commencement Date; such improvements may be constructed while Tenant is
occupying and conducting business in the new space. Tenant may draw the
allowance from Landlord from time to time as construction bills come due.

         6. Tenant shall have the right and option to renew its Lease relative
to the "new space", 12201 Technology Boulevard, Suite 130 (McNeil 3) for one (1)
additional thirty-six (36) month term by delivering written notice thereof to
Landlord at least One Hundred Eighty (180) days prior to the expiration date of
the lease term, provided that at the time of such notice and at the end of the
lease term, Tenant is not in default hereunder. Upon the delivery of said notice
and subject to the conditions set forth in the preceding sentence, this Lease
shall be extended upon the same terms, covenants and conditions as provided in
this Lease, except that the rental payable during said extended term shall be
the prevailing market rental rate for space of comparable size, quality and
location at the commencement of such extended term (the "Market Rate"). This
right and option shall apply to the initial lease term only. In the event
Landlord and Tenant are unable to agree upon the Market Rate, Landlord and
Tenant shall each promptly appoint a real estate broker who is licensed by the
Texas Real Estate Commission (TREC) and active in the Austin industrial market,
to assist in the determination of the Market Rate, and the two

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brokers shall appoint a third broker who is also licensed by the Texas Real
Estate Commission and active in the Austin industrial market. The determination
of the Market Rate by the agreement of any two of such three brokers shall be
accepted by and shall be binding upon Landlord and Tenant as the Market Rate,
which rate shall thereafter be payable until further adjusted. Landlord and
Tenant agree to use all reasonable diligence to cause their appointed brokers to
perform in good faith and in a timely manner in order to make the determination
of the Market Rate on or before the date on which the Market Rate is to become
effective. In the event the brokers do not make such determination in a timely
manner, this Lease shall nevertheless continue in full force and effect until
such determination is made, and the rental for such period shall be payable at
the rate otherwise payable hereunder. Upon the determination of the Market Rate,
the payment of the Market Rate shall commence on the first day of the month
following the date of such determination, and in addition to such monthly
installment of rental, Tenant shall pay to Landlord the increase in rental
payable hereunder, if any, applicable to the period from the date on which the
Market Rate was scheduled to become effective to the payment of the first
installment at the Market Rate. Landlord and Tenant shall each bear the cost and
fees of their respective brokers and shall share equally the cost of the third
broker, if needed.

         7. Tenant, at its own cost and expense, shall enter into a regularly
scheduled preventive maintenance/service contract with a maintenance contractor
approved by Landlord for servicing all hot water, heating and air conditioning
systems and equipment within the Premises. The service contract must include the
replacement of filters on a regular basis and all services suggested by the
equipment manufacturer in its operations/maintenance manual and must become
effective within thirty (30) days of the date Tenant takes possession of the
Premises. Provided that Tenant maintains such service contract and is not in
default under the terms of this Lease, Landlord shall be responsible for any
repairs or replacements necessary to maintain the HVAC equipment in the new
space for a period of ninety (90) days following the Commencement Date.

         8. Tenant shall have the nonexclusive right to utilize no more than
fifty-five (55) parking spaces at the new space.

         9. Tenant's "proportionate share" of McNeil #3 is 26.8%.

         10. Subject to Landlord's written approval of the installation process
and procedure, Tenant, at its expense, shall have the right to install
telecommunication lines connecting the new space and original space.

         11. Tenant shall not use, and shall not permit any subtenant, licensee,
concessionaire, employee, agent or invitee (hereinafter collectively "Tenant's
Representatives") to use, any portion of the Premises or Building, for the
placement, storage, manufacture, disposal or handling of any hazardous materials
(hereinafter defined) unless Tenant complies with all applicable environmental
laws (federal, state or local), including, but not limited to those for
obtaining proper permits. In the event Tenant or Tenant's Representatives desire
to use or place hazardous materials on the Premises it shall notify Landlord in
writing thirty (30) days prior to such proposed use or placement, and provide
the names of the hazardous materials, procedures to insure compliance with the
applicable environmental law and such other information as Landlord may
reasonably request.

         In the event Tenant or Tenant's Representatives places, releases or
discovers any hazardous materials on the Premises or Building in violation of
applicable environmental laws, Tenant shall immediately notify Landlord of such
fact in writing within twenty-four (24) hours of the placement, release or
discovery. Tenant shall not attempt any removal, abatement or remediation of
those hazardous materials on the Premises in violation of applicable
environmental laws, without obtaining the additional written consent of
Landlord, which consent may be specifically conditioned on Landlord's right to
approve the scope, timing and techniques of any such work and the appointment of
all contractors, engineers, inspectors and consultants in connection with any
such work. Tenant shall be responsible for the cost of any removal, abatement
and remediation work of any hazardous materials placed, stored, manufactured,
disposed of or handled by Tenant or Tenant's Representatives on the Premises or
any other portion of the Building and for the cost of any removal, abatement or
remediation of any hazardous materials which might be disturbed or released as a
result of any remodeling or construction in the Premises by Tenant or Tenant's
Representatives. Such costs shall include, without limitation, the cost of any
supervision by Landlord, its employees or agents, in connection with such work.
Tenant shall comply with all environmental laws in connection with any such
removal.

         Tenant shall indemnify Landlord, its shareholders, directors, officers,
employees and agents and hold them harmless, from and against any loss, damage
(including, without limitation, a loss in value of the Building or damages due
to restrictions on marketing contaminated space), cost, liability or expense
(including reasonable attorneys' fees and expenses and court costs) arising out
of the placement, storage, use, manufacture, disposal, handling, removal,
abatement or remediation of any hazardous materials by Tenant or Tenant's
Representatives on the Premises or Building, or any removal, abatement or
remediation of any hazardous materials required hereunder to be performed or
paid for by Tenant, with respect to any portion of the Premises or the Building,
or arising out of any breach by Tenant of its obligations under this paragraph.

         The term "hazardous materials" as used herein shall mean (i) any
"hazardous waste" as defined by the Resource Conservation and Recovery Act of
1976 (42 U.S.C. Section 6901 et seq.), as amended

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from time to time, and regulations promulgated thereunder; (ii) any "hazardous
substance" as defined by the Comprehensive Environmental Response, Compensation
and Liability Act of 1980 (42 U.S.C. Section 9601, et seq.), as amended from
time to time, and regulations promulgated thereunder; (iii) asbestos or
polychlorinated biphenyls; (iv) any substance the presence of which on the
Building or on the Premises is prohibited or regulated by any federal, state or
local law, regulation, code or rule; and (v) any other substance which requires
special handling or notification of any federal, state or local governmental
entity in its collection, storage, treatment, or disposal.

         12. This Lease shall be subordinate to any deed of trust, mortgage, or
other security instrument (a "Mortgage"), or any ground lease, master lease, or
primary lease (a "Primary Lease"), that now or hereafter covers all or any part
of the Premises (the mortgagee under any Mortgage or the lessor under any
Primary Lease is referred to herein as "Landlord's Mortgagee"), including any
modifications, renewals or extensions of such Mortgage or Primary Lease,
provided that it is a condition to the subordination of this Lease that the
Landlord's Mortgagee execute and deliver to Tenant a non-disturbance and
attornment agreement, in recordable form, whereby such Landlord's Mortgagee
agrees that neither this Lease nor Tenant's right to possession will be
terminated so long as Tenant is not in default under this Lease (provided
Landlord's Mortgagee, or successor thereto, maintains its rights to terminate
under other provisions of the Lease, e.g., for a casualty). Notwithstanding the
foregoing, Tenant agrees that any such Landlord's Mortgagee shall have the right
at any time to subordinate such Mortgage or Primary Lease to this Lease on such
terms and subject to such conditions as Landlord's Mortgagee may deem
appropriate in its discretion. Tenant agrees upon demand to execute such further
instruments subordinating this Lease or attorning to the Landlord's Mortgagee as
Landlord may request, provided such contains non-disturbance provisions as noted
above and such other provisions which do not affect the substantive provisions
of this Lease. In the event that Tenant should fail to execute any subordination
or other agreement required by this paragraph, within twenty (20) days of
written request, it shall constitute an Event of Default, without further notice
required of Landlord.

         13. Landlord, at Landlord's expense, will repair all roof penetrations
and service and repair all existing overhead doors.

Except as herein and hereby modified and amended the Agreement of Lease shall
remain in full force and effect and all the terms, provisions, covenants and
conditions thereof are hereby ratified and confirmed.

DATED AS OF THE 25th DAY OF APRIL, 2000.

WITNESS:                            AETNA LIFE INSURANCE COMPANY:

                                    By:      Allegis Realty Investors LLC,
                                             Its Investment Advisor and Agent

  /s/ Belinda Wauson                 /s/ S. Mark Cypert
---------------------------         --------------------------------------------

                                    By:      S. Mark Cypert
                                    --------------------------------------------
                                    Title:   Director
                                    --------------------------------------------

WITNESS:                            LUMINEX CORPORATION:

  /s/ John M. Dapper                         /s/ James L. Persky
----------------------------        --------------------------------------------

                                    By:      James L. Persky
                                    --------------------------------------------
                                    Title:   Vice President
                                    --------------------------------------------<PAGE>   1
                                                                   EXHIBIT 10.17

                               LUMINEX CORPORATION
                           RESTRICTED STOCK AGREEMENT

         THIS RESTRICTED STOCK AGREEMENT (this "Agreement"), dated as of October
2, 2000, is entered into between Luminex Corporation, a Delaware corporation
(the "Company"), and Gail S. Page, an individual residing in the State of Texas
(the "Stockholder"). The Company and the Stockholder agree as follows:

         1. DEFINITIONS.

                  1.1 The terms "Cause" and "Change in Control" shall have the
respective meanings set forth in that certain Employment Agreement dated October
2, 2000 between Company and Stockholder.

                  1.2 "Person" means any individual, corporation, partnership,
limited liability company, joint venture, association, joint stock company,
trust, unincorporated organization or government or any agency or political
subdivision thereof.

         2. ACQUISITION OF RESTRICTED STOCK. Concurrently with the execution and
delivery hereof, the Company has issued to the Stockholder 15,000 shares of the
Company's common stock, par value $.001 per share ("Common Stock"). The Company
and the Stockholder have determined that it would be in their best interests to
impose certain rights and obligations upon the Company, the Stockholder and her
legal representatives, as the case may be, with respect to such 15,000 shares of
Common Stock (as adjusted for stock splits, dividends and the like, the
"Shares").

         3. RESTRICTION PERIOD. During the period (the "Restriction Period")
commencing as of the date hereof (the "Commencement Date") and ending on April
2, 2002, the Shares shall be subject to the restrictions described in Section 4
of this Agreement (the "Restrictions"). The Shares subject to the Restrictions
at any given time are called the "Restricted Shares."

         4. RESTRICTIONS. The Restricted Shares shall be represented by one or
more stock certificates registered in the name of the Stockholder. The
Stockholder shall have the right to receive dividends on the Restricted Shares,
to vote the Restricted Shares and to enjoy all other stockholder rights with
respect thereto, except that (i) the Stockholder shall not be entitled to
possession of the stock certificate representing the Restricted Shares, (ii) the
Company shall retain custody of the stock certificate(s) representing the
Restricted Shares, (iii) the Stockholder may not, other than as permitted under
Section 9.2, sell, transfer, pledge, exchange, hypothecate or otherwise dispose
of the Restricted Shares and (iv) the Restricted Shares are subject to potential
forfeiture as provided in Section 5 of this Agreement.

         5. FORFEITURE. Any Restricted Shares (and all voting and other rights
associated with such Restricted Shares) shall be forfeited to the Company in the
event (i) such Restricted Shares are transferred by operation of law to any
Person other than the Company or in accordance with Section 9.2 for any reason
(including without limitation the bankruptcy of the Stockholder and seizure and
sale by legal process), or (ii) the Stockholder's employment with the Company is
terminated prior

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to the end of the Restriction Period, unless such termination of employment is
due to the Stockholder's death or the termination of the Stockholder's
employment by the Company without Cause. The Company shall not be obligated to
pay the Stockholder any amount for the forfeiture of any Restricted Shares. The
Stockholder shall be entitled to retain all Shares to which the Restrictions
have ceased to apply.

         6. LAPSE OF RESTRICTIONS. The Restrictions shall lapse (i) on October
2, 2001 with respect to 7,500 Shares and (ii) on April 2, 2002 with respect to
the remaining 7,500 Shares. Notwithstanding the foregoing, in the event of (i)
the death of the Stockholder, (ii) the termination of the Stockholder's
employment by the Company without Cause or (iii) a Change in Control, the
Restrictions shall lapse with respect to all of the Shares held by the
Stockholder, and shall no longer be subject to forfeiture to the Company
pursuant to Section 5 of this Agreement.

         7. RESTRICTIONS ON CORRESPONDING SECURITIES AND ASSETS. Any other
securities or assets (other than ordinary cash dividends) that are received by
the Stockholder with respect to any of the Restricted Shares shall be subject to
the Restrictions to the same extent and for so long as such Restricted Shares to
which such securities or other assets are attributable remain subject to the
Restrictions.

         8. DELIVERY OF CERTIFICATES UPON LAPSE OF RESTRICTIONS. Promptly
following the lapse of the Restrictions as to any of the Shares, the Company
will deliver the stock certificate or certificate representing such Shares with
respect to which the Restrictions have lapsed to the Stockholder or her legal
representative.

         9. CERTAIN RESTRICTIONS ON TRANSFERABILITY OF SHARES BY THE
STOCKHOLDER. The following restrictions shall apply to all Restricted Shares,
whether or not issued or outstanding at the date of this Agreement.

                  9.1 Restriction on Transfers in Violation of the Securities
Act. Notwithstanding any provision to the contrary contained herein, in no event
shall the Stockholder make any disposition of the Shares, including a
disposition by pledge, if such disposition might reasonably be expected to
result in a violation of the Securities Act of 1933, as amended (the "Securities
Act"), or any applicable state's securities laws. Unless the Company agrees
otherwise, the Stockholder shall be required to provide an opinion of counsel
acceptable to the Company with regard to such intended disposition.

                  9.2 Permitted Transfers. The Stockholder may transfer all or
any part of the Shares, to (i) the members of the immediate family of the
Stockholder (including lineal descendants) or one or more trusts or partnerships
for the benefit of the Stockholder and/or members of the immediate family of the
Stockholder (including lineal descendants); or (ii) the estate of the
Stockholder or to any heir, executor, administrator or lineal descendant of the
Stockholder; provided that prior to any such transfer either the Stockholder or
the transferee delivers to the Company a written instrument in accordance with
Section 10 and an opinion of counsel reasonably satisfactory to the Company in
accordance with Section 9.1 to the effect that the transfer is exempt from

                                      -2-
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registration under the Securities Act. In the event of a transfer under this
Section 9.2, such transferee(s) shall be deemed a Stockholder for purposes of
this Agreement.

         10. ADDITIONAL ISSUANCES. It shall be a condition to the transfer of
any Restricted Shares by the Stockholder to any Person that the recipient of
such Restricted Shares shall become a signatory to this Agreement by executing
an Addendum Agreement in the form and substance satisfactory to the Company.

         11. LEGENDS ON CERTIFICATES. The reverse side of each certificate
reflecting ownership of the Restricted Shares subject to the Restrictions under
Section 4 shall bear the following legend:

         The shares represented hereby and the sale, assignment, transfer, gift,
         bequest, pledge or other disposition thereof are subject to certain
         restrictions contained in a Restricted Stock Agreement dated effective
         as of October 2, 2000, among the Company and the holder hereof. A copy
         of such Agreement and all applicable amendments thereto will be
         furnished by the Company to the holder hereof without charge upon
         written request to the Company at its principal place of business or
         registered office.

         12. NOTICES. Any notice required or permitted under this Agreement
shall be in writing and shall be deemed to be delivered (i) upon physical
delivery (if hand delivered); (ii) three business days after deposit in the
United States mail (if mailed), postage prepaid, certified or registered mail,
return receipt requested, addressed as set forth below or (iii) the day such
notice is sent via confirmed electronic mail or facsimile as set forth below:

         Company:                           Luminex Corporation
                                            12212 Technology Boulevard
                                            Austin, Texas 78727
                                            Attention:  General Counsel
                                            Fax:  (512) 219-63295
                                            E-mail: mlb@luminexcorp.com

         Stockholder:                       Gail S. Page
                                            Luminex Corporation
                                            12212 Technology Boulevard
                                            Austin, Texas 78727
                                            Fax:  (512) 219-5195
                                            E-mail: gpage@luminexcorp.com

Notice given in any other manner shall be effective when received. The address
for notice may be changed by notice given in accordance with this provision. If
notice is required to be delivered to any party to this Agreement, a copy of
such notice shall be delivered to all other parties to this Agreement.

                                      -3-
<PAGE>   4

         13. WAIVER. No waiver of any provision of this Agreement shall
constitute a waiver of any other provision of this Agreement, nor shall such
waiver constitute a waiver of any subsequent breach of such provision.

         14. BINDING EFFECT. This Agreement shall be binding upon and shall
inure to the benefit of the Stockholder and their heirs, executors,
administrators and legal representatives and upon the Company and its successors
and assigns.

         15. GOVERNING LAW. The validity, construction, and enforcement of this
Agreement shall be governed by the laws of the State of Delaware, without regard
for any principles of conflict of laws.

         16. SEVERABILITY. If any provision of this Agreement is declared
unenforceable by a court of last resort, such declaration shall not affect the
validity of any other provision of this Agreement.

         17. CONSTRUCTION. The headings contained in this Agreement are for
reference purposes only and shall not affect this Agreement in any manner
whatsoever. Wherever required by the context, any gender shall include any other
gender, the singular shall include the plural, and the plural shall include the
singular.

         The parties have executed this Agreement effective as of October 2,
2000.

LUMINEX CORPORATION

By:   /s/ MICHAEL L. BENGTSON                     /s/ GAIL S. PAGE
      --------------------------                  ------------------------------

Name:     Michael L. Bengtson
      --------------------------                  Gail S. Page

Title:  Executive Vice President
        ------------------------

         The undersigned, the spouse of the Stockholder, hereby joins in the
execution and delivery of this Agreement to evidence his consent and approval
to, and agreement to be bound by, all the terms and provisions hereof.

          /s/ DAN PAGE
         --------------------------------------
         Dan Page

                                      -4-

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