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                                                                   Exhibit 10.16

                            REGISTRATION RIGHTS AGREEMENT


       THIS AGREEMENT is entered into as of June 16, 1998, by and between
BIONEBRASKA, INC., a Delaware corporation (the "Company"), and MEDTRONIC, INC.,
a Minnesota corporation ("Medtronic").

                                      RECITALS:

       WHEREAS, the parties hereto have executed an Investment Agreement (the
"Investment Agreement") of even date herewith pursuant to which Medtronic is
purchasing shares of the Company's Series G Convertible Preferred Stock; and

       WHEREAS, in connection with the Investment Agreement the parties desire
to provide certain registration rights and benefits with respect to the Common
Stock (defined below) issuable upon conversion of the Series G Convertible
Preferred Stock,

       NOW, THEREFORE, in consideration of the respective covenants and
agreements contained herein, and for other valuable consideration, the receipt
and adequacy of which is hereby acknowledged, the parties hereto agree as
follows:


                                      ARTICLE I
                                     DEFINITIONS

       1.1    SPECIFIC DEFINITIONS.  As used in this Agreement, the following
terms shall have the meanings set forth or as referenced below:

       "COMMON STOCK" means the Company's Common Stock, par value $.01 per
share.

       "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended, and
the rules and regulations promulgated thereunder.

       "FORM S-3" means such form under the Securities Act in effect on the date
hereof or any successor registration form under the Securities Act subsequently
adopted by the SEC that permits inclusion or incorporation of substantial
information by reference to other documents filed by the Company with the SEC.


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       "HOLDER" means Medtronic or any person owning of record Registrable
Securities that have not been sold to the public or any assignee of record of
such Registrable Securities in accordance with Article 2.

       "PREFERRED SHARES" means the shares of Series G Convertible Preferred
Stock purchased pursuant to the Investment Agreement.

       "REGISTER," "REGISTERED," and 'REGISTRATION" mean a registration effected
by preparing and filing a registration statement in compliance with the
Securities Act, and the declaration or ordering by the SEC of effectiveness of
such registration statement.

       "REGISTRABLE SECURITIES" means (i) the Common Stock issuable or issued
upon conversion of the Preferred Shares, and (ii) any Common Stock issued as (or
issuable upon the conversion or exercise of any warrant, right, or other
security issued as) a dividend or other distribution with respect to, or in
exchange for or in replacement of, the Common Stock referenced in the preceding
clause (i).  Notwithstanding the foregoing, Registrable Securities shall not
include any securities sold by a person to the public either pursuant to a
registration statement or Rule 144 under the Securities Act or sold in a private
transaction in which the transferor's rights under Article 2 of this Agreement
are not assigned.

       "REGISTRATION EXPENSES" means all expenses incurred by the Company in
complying with Article 2 hereof, including, without limitation, all registration
and filing fees, printing expenses, fees and disbursements of counsel and
accountants for the Company, reasonable fees and disbursements of a single
special counsel for the Holders of Registrable Securities, and blue sky fees and
expenses (but excluding the compensation of regular employees of the Company,
which shall be paid in any event by the Company).

       "SEC" means the Securities and Exchange Commission.

       "SECURITIES ACT" means the Securities Act of 1933, as amended.

       "SELLING EXPENSES" means all underwriting discounts and commissions
applicable to a sale of Registrable Securities.

       1.2    DEFINITIONAL PROVISIONS.

              (a)    The words "hereof," "herein," and "hereunder" and words of
       similar import, when used in this Agreement, shall refer to this
       Agreement as a whole and not to any particular provisions of this
       Agreement.

              (b)    Terms defined in the singular shall have a comparable
       meaning when used in the plural, and vice versa.


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              (c)    References to an "Article" or a "Section" are, unless
       otherwise specified, to one of the Articles or Sections of this
       Agreement.

              (d)    The term "person" includes any individual, partnership,
       joint venture, corporation, trust, unincorporated organization or
       government or any department or agency thereof.


                                      ARTICLE 2
                                 REGISTRATION RIGHTS

       2.1    DEMAND REGISTRATIONS.

              (a)    Subject to the conditions of this Section 2.1, if the
       Company shall receive at any time after the date hereof a written request
       from Medtronic or other Holder(s) of at least 50 percent of the
       Registrable Securities then outstanding that the Company file a
       registration statement under the Securities Act covering the registration
       of Registrable Securities having a proposed aggregate offering price to
       the public of at least $1,000,000, then the Company shall, within 30 days
       after the receipt thereof, give written notice of such request to all
       Holders and, subject to the limitations of Section 2. 1 (b), effect, as
       soon as practicable, the registration under the Securities Act of all
       Registrable Securities that the Holders request to be registered.

              (b)    If the Holder requesting such registration intends to
       distribute the Registrable Securities covered by its request by means of
       an underwriting, the Holder shall so advise the Company as a part of its
       request made pursuant to this Section 2.1 and the Company shall include
       such information in the written notice referred to in Section 2.1(a).  In
       such event, the right of any Holder to include such Holder's Registrable
       Securities in such registration shall be conditioned upon such Holder's
       participation in such underwriting and the inclusion of such Holder's
       Registrable Securities in the underwriting (unless otherwise mutually
       agreed by a majority in interest of the Holders) to the extent provided
       herein.  All Holders proposing to distribute their securities through
       such underwriting shall enter into an underwriting agreement in customary
       form with the underwriter or underwriters selected for such underwriting
       by the Holder that initially requested the registration (which
       underwriter or underwriters shall be reasonably acceptable to the
       Company).

              (c)    The Company shall not be obligated to effect more than two
       registrations pursuant to this Section 2.1.  Further, the Company shall
       not be obligated to take any action to effect any registration pursuant
       to this Section 2.1 until the earliest to occur of, (i) the date that is
       three years after the date hereof, (ii) the first date as of which any
       other shareholder of the Company exercises a demand registration, or
       (iii) 180 days after the effective date of the registration statement
       pertaining to the first underwritten public


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       offering of securities of the Company for its own account.
       Further, the Company shall not be obligated to effect a demand
       registration pursuant to this Section 2.1 if the Company furnishes
       to the Holders a certificate signed by the Chief Executive Officer
       stating that, in the good faith judgment of the Board, it would be
       seriously detrimental to the Company and its shareholders for such
       registration to be effected at such time, in which event the
       Company shall have the right to defer the filing of the
       registration statement for a period of not more than 120 days after
       receipt of the request of the Holder or Holders under this
       Section 2.1.  The Company shall give written notice to the Holders of
       any demand made by other holders of securities of the Company for
       registration of such securities.


       2.2    PIGGYBACK REGISTRATIONS.

              (a)    The Company shall notify all Holders of Registrable
       Securities in writing at least 30 days prior to the filing of any
       registration statement under the Securities Act for purposes of a public
       offering of securities of the Company (including, but not limited to,
       registration statements relating to secondary offerings of securities of
       the Company, but excluding registration statements relating to employee
       benefit plans and corporate reorganizations) and will afford each such
       Holder an opportunity to include in such registration statement all or
       part of such Registrable Securities of such Holder.  Each Holder desiring
       to include in any such registration statement all or any part of such
       Holder's Registrable Securities shall, within 20 days after receipt of
       the above-described notice from the Company, so notify the Company in
       writing.  Such notice shall state the intended method of disposition of
       the Registrable Securities by such Holder.  If a Holder of Registrable
       Securities decides not to include any or all of such Holder's Registrable
       Securities in any registration statement thereafter filed by the Company,
       such Holder shall nevertheless continue to have the right to include any
       Registrable Securities in any subsequent registration statement or
       registration statements as may be filed by the Company with respect to
       offerings of its securities, all upon the terms and conditions set forth
       herein.

              (b)    If the registration statement under which the Company gives
       notice under this Section 2.2 is for an underwritten offering, the
       Company shall so advise the Holders of Registrable Securities.  In such
       event, the right of any such Holder to be included in a registration
       pursuant to this Section 2.2 shall be conditioned upon such Holder's
       participation in such underwriting and the inclusion of such Holder's
       Registrable Securities in the underwriting to the extent provided herein.
       All Holders proposing to distribute their Registrable Securities through
       such underwriting shall enter into an underwriting agreement in customary
       form with the underwriter or underwriters selected for such underwriting.
       Notwithstanding any other provisions of this Agreement, if the
       underwriter determines in good faith that marketing factors require a
       limitation of the number of shares to be underwritten, the number of
       shares that may be included in the underwriting shall be allocated,
       first, to the Company and, second, to the Holders and any


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       other selling shareholders on a pro rata basis based on the total
       number of securities held by such Holders and other selling
       shareholders and requested to be included in such registration.

       2.3    FORM S-3 REGISTRATIONS.  If the Company receives from any Holder
or Holders of Registrable Securities a written request or requests that the
Company effect the registration under the Securities Act of all or a part of the
Registrable Securities owned by such Holder or Holders by the filing with the
SEC of a registration statement on Form S-3 covering such Registrable
Securities, the Company will:

              (a)    promptly give written notice of the proposed registration
       to all other Holders of Registrable Securities; and

              (b)    as soon as practicable, effect such registration and,
       in connection therewith, make all such related qualifications and
       compliances as would permit or facilitate the sale and distribution
       of all or such portion of such Holder's or Holders' Registrable
       Securities as are specified in such request, together with all or
       such portion of the Registrable Securities of any other Holder or
       Holders joining in such request as are specified in a written
       request given within 15 days after receipt of such written notice
       from the Company; provided, however, that the Company shall not be
       obligated to effect any such registration, qualification, or
       compliance pursuant to this Section 2.3: (i) if Form S-3 under the
       Securities Act is not available for such offering by the Holders,
       (ii) if the Holders, together with the holders of any other
       securities of the Company entitled to inclusion in such
       registration, propose to sell Registrable Securities and such other
       securities (if any) at an aggregate price to the public of less
       than $500,000, (iii) if the Company shall furnish to the Holders a
       certificate signed by the Chief Executive Officer stating that, in
       the good faith judgment of the Board, it would be seriously
       detrimental to the Company and its shareholders for such
       registration to be effected at such time, in which event the
       Company shall have the right to defer the filing of the Form S-3
       registration statement for a period of not more than 120 days after
       receipt of the request of the Holder or Holders under this Section
       2.3, (iv) in a given six-month period, the Company has effected one
       such registration during such period, (v) the registration request
       occurs within six months following the effective date of a
       registration initiated by the Company, or (vi) if one of the
       following has not occurred at the time of such request: (a) three
       years have elapsed since the effective date of this Agreement, (b)
       no other investor has exercised its right to demand registration,
       or (c) 180 days have not elapsed since the closing of the Company's
       initial public offering.

              (c)    Subject to the foregoing, the Company shall file a Form S-3
       registration statement covering the Registrable Securities and other
       securities so requested to be registered as soon as practicable after
       receipt of the request or requests of the Holders.


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<PAGE>

       2.4    EXPENSES OF REGISTRATION.  All Registration Expenses incurred in
connection with any registration, qualification, or compliance pursuant to
Section 2.1 or any registration under Section 2.2 or 2.3 shall be borne by the
Company.  All Selling Expenses incurred in connection with any such registration
shall be borne by the Holders of the securities so registered pro rata on the
basis of the number of shares so registered.  The Company shall not, however, be
required to pay for expenses of any registration proceeding begun pursuant to
Section 2.1 or 2.3, the request of which has been subsequently withdrawn by the
Holders, unless (a) the withdrawal is based upon material adverse information
concerning the Company of which the Company was aware but the Holders were not
aware at the time of such request or (b) the Holders of a majority of
Registrable Securities agree to forfeit their right to one requested
registration pursuant to Section 2.1 (in which event such right shall be
forfeited by all Holders).  If the Holders are required to pay the Registration
Expenses, such expenses shall be borne by the Holders of securities (including
Registrable Securities) requesting such registration in proportion to the number
of shares for which registration was requested.  If the Company is required to
pay the Registration Expenses of a withdrawn offering pursuant to this Section
2.4, then the Holders shall not forfeit their rights pursuant to Section 2.1 to
a demand registration.

       2.5    OBLIGATIONS OF THE COMPANY.  Whenever required to effect the
registration of any Registrable Securities, the Company shall, as expeditiously
as reasonably possible:

              (a)    Prepare and file with the SEC a registration statement, on
       such form as is then available to the Company in connection with such
       registration, with respect to such Registrable Securities and use its
       best efforts to cause such registration statement to become effective
       and, upon the request of the Holders of a majority of the Registrable
       Securities registered thereunder, keep such registration statement
       effective for up to nine months.

              (b)    Prepare and file with the SEC such amendments and
       supplements to such registration statement and the prospectus used in
       connection with such registration statement as may be necessary to comply
       with the provisions of the Securities Act with respect to the disposition
       of all securities covered by such registration statement.

              (c)    Furnish to the Holders such number of copies of a
       prospectus, including a preliminary prospectus, in conformity with the
       requirements of the Securities Act, and such other documents as they may
       reasonably request in order to facilitate the disposition of Registrable
       Securities owned by them.

              (d)    Use its best efforts to register or qualify the securities
       covered by such registration statement under such other securities or
       blue sky laws of such jurisdictions as shall be reasonably requested by
       the Holders within 20 days following the original filing of such
       registration statement, provided that the Company shall not be required
       in connection therewith or as a condition thereto to qualify to do
       business or to file a general consent to service of process in any such
       states or jurisdictions.


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              (e)    In the event of any underwritten public offering,
       enter into and perform its obligations under an underwriting
       agreement, in usual and customary form, with the managing
       underwriter(s) of such offering.  Each Holder participating in such
       underwriting shall also enter into and perform its obligations
       under such an agreement.

              (f)    Notify each Holder of Registrable Securities covered by
       such registration statement at any time when a prospectus relating
       thereto is required to be delivered under the Securities Act of the
       occurrence of any event as a result of which the prospectus included in
       such registration statement, as then in effect, includes an untrue
       statement of a material fact or omits to state a material fact required
       to be stated therein or necessary to make the statements contained
       therein not misleading in the light of the circumstances then existing.

              (g)    Furnish, at the request of a majority of the Holders
       participating in the registration, on the date that such Registrable
       Securities are delivered to the underwriters for sale, if such securities
       are being sold through underwriters, or, if such securities are not being
       sold through underwriters, on the date that the registration statement
       with respect to such securities becomes effective, (i) an opinion, dated
       as of such date, of the counsel representing the Company for the purposes
       of such registration, in form and substance as is customarily given to
       underwriters in an underwritten public offering and reasonably
       satisfactory to a majority in interest of the Holders requesting
       registration, addressed to the underwriters, if any, and to the Holders
       requesting registration of Registrable Securities, and (ii) a letter
       dated as of such date, from the independent certified public accountants
       of the Company, in form and substance as is customarily given by
       independent certified public accountants to underwriters in an
       underwritten public offering and reasonably satisfactory to a majority in
       interest of the Holders requesting registration, addressed to the
       underwriters, if any, and to the Holders requesting registration of
       Registrable Securities.

       2.6    TERMINATION OF REGISTRATION RIGHTS.  All registration rights
granted under this Article 2 shall terminate and be of no further force and
effect on the date that Medtronic would be able to sell all of its remaining
Registrable Securities, without limitation, under Rule 144(k) of the Securities
Act.

       2.7    DELAY OF REGISTRATION.  No Holder shall have any right to obtain
or seek an injunction restraining or otherwise delaying any such registration as
the result of any controversy that might arise with respect to the
interpretation or implementation of this Article 2.

       2.8    INDEMNIFICATION.  If any Registrable Securities are included in a
registration statement under Section 2.1, 2.2, or 2.3:


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              (a)    To the extent permitted by law, the Company will indemnify
       and hold harmless each Holder, the partners, officers, and directors of
       each Holder, and each person, if any, who controls such Holder within the
       meaning of the Securities Act or the Exchange Act, and each underwriter,
       if any, and each person, if any, who controls any underwriter within the
       meaning of the Securities Act or the Exchange Act, against any losses,
       claims, damages, or liabilities (joint or several) to which they may
       become subject under the Securities Act, the Exchange Act, or other
       federal or state law, insofar as such losses, claims, damages, or
       liabilities (or actions in respect thereof) arise out of or are based
       upon any of the following statements, omissions, or violations
       (collectively a "Violation") by the Company:  (i) any untrue statement or
       alleged untrue statement of a material fact contained in such
       registration statement, including any preliminary prospectus or final
       prospectus contained therein or any amendments or supplements thereto,
       (ii) the omission or alleged omission to state therein a material fact
       required to be stated therein, or necessary to make the statements
       therein not misleading, or (iii) any violation or alleged violation by
       the Company of the Securities Act, the Exchange Act, any state securities
       law or any rule or regulation promulgated under the Securities Act, the
       Exchange Act, or any state securities law in connection with the offering
       covered by such registration statement; and the Company will reimburse
       each such Holder, partner, officer, director, underwriter, and
       controlling person for any legal or other expenses reasonably incurred by
       them in connection with investigating or defending any such loss, claim,
       damage, liability, or action; provided, however, that the indemnity
       agreement contained in this Section 2.8(a) shall not apply to amounts
       paid in settlement of any such loss, claim, damage, liability, or action
       if such settlement is effected without the consent of the Company (which
       consent shall not be unreasonably withheld), nor shall the Company be
       liable in any such case for any such loss, claim, damage, liability, or
       action to the extent that it arises out of or is based upon a Violation
       that occurs in reliance upon and in conformity with written information
       furnished expressly for use in connection with such registration by such
       Holder, partner, officer, director, or controlling person of such Holder.

              (b)    To the extent permitted by law, each selling Holder will
       indemnify and hold harmless the Company, each of its officers and
       directors, each person, if any, who controls the Company within the
       meaning of the Securities Act, and each underwriter, if any, and each
       person, if any, who controls any underwriter within the meaning of the
       Securities Act or the Exchange Act, and any other Holder selling
       securities under such registration statement or any of such other
       Holder's partners, directors, or officers or any person who controls such
       Holder, against any losses, claims, damages, or liabilities (joint or
       several) to which the Company or any such director, officer, underwriter,
       controlling person, or other such Holder, or partner, director, officer,
       or controlling person of such other Holder may become subject under the
       Securities Act, the Exchange Act, or other federal or state law, insofar
       as such losses, claims, damages, or liabilities (or actions in respect
       thereto) arise out of or are based upon any Violation, in each case to
       the extent (and only to the extent) that such Violation occurs in
       reliance upon and in conformity

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       with written information furnished by such Holder and stated to be
       specifically for use in connection with such registration; and each
       such Holder will reimburse any legal or other expenses reasonably
       incurred by the Company or any such director, officer, underwriter,
       controlling person, or other Holder, or partner, officer, director,
       or controlling person of such other Holder in connection with
       investigating or defending any such loss, claim, damage, liability,
       or action if it is judicially determined that there was such a
       Violation; provided, however, that the indemnity agreement
       contained in this Section 2.8(b) shall not apply to amounts paid in
       settlement of any such loss, claim, damage, liability, or action if
       such settlement is effected without the consent of the Holder,
       which consent shall not be unreasonably withheld; provided,
       further, that in no event shall any indemnity under this
       Section 2.8(b) exceed the proceeds from the offering received by such
       Holder unless the Violation is the result of fraud on the part of
       such Holder.

              (c)    Promptly after receipt by an indemnified party under this
       Section 2.8 of notice of the commencement of any action (including any
       governmental action), such indemnified party will, if a claim in respect
       thereof is to be made against any indemnifying party under this Section
       2.8, deliver to the indemnifying party a written notice of the
       commencement thereof, and the indemnifying party shall have the right to
       participate in, and, to the extent the indemnifying party so desires,
       jointly with any other indemnifying party similarly noticed, to assume
       the defense thereof with counsel mutually satisfactory to the parties;
       provided, however, that an indemnified party shall have the right to
       retain its own counsel, with the fees and expenses to be paid by the
       indemnifying party (or, if there is more than one indemnified party, the
       indemnifying party shall pay the fees and expenses of one counsel for any
       and all indemnified parties, to be mutually agreed upon by such
       indemnified parties), if representation of such indemnified party by the
       counsel retained by the indemnifying party would be inappropriate due to
       actual or potential differing interests between such indemnified party
       and any other party represented by such counsel in such proceeding.  The
       failure to deliver written notice to the indemnifying party within a
       reasonable time of the commencement of any such action, if materially
       prejudicial to its ability to defend such action, shall relieve such
       indemnifying party of any liability to the indemnified party under this
       Section 2.8, but the omission so to deliver written notice to the
       indemnifying party will not relieve it of any liability that it may have
       to any indemnified party otherwise than under this Section 2.8.

              (d)    If the indemnification provided for in this Section 2.8 is
       held by a court of competent jurisdiction to be unavailable to an
       indemnified party with respect to any losses, claims, damages, or
       liabilities referred to herein, the indemnifying party, in lieu of
       indemnifying such indemnified party thereunder, shall to the extent
       permitted by applicable law contribute to the amount paid or payable by
       such indemnified party as a result of such loss, claim, damage, or
       liability in such proportion as is appropriate to reflect the relative
       fault of the indemnifying party on the one hand and of the indemnified
       party on the other in connection with the Violation(s) that resulted in
       such loss, claim,

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       damage, or liability, as well as any other relevant equitable
       considerations.  The relative fault of the indemnifying party and of the
       indemnified party shall be determined by a court of law by reference to,
       among other things, whether the untrue or alleged untrue statement of a
       material fact or the omission to state a material fact relates to
       information supplied by the indemnifying party or by the
       indemnified party and the parties' relative intent, knowledge,
       access to information, and opportunity to correct or prevent such
       statement or omission.

              (e)    The foregoing indemnity agreements of the Company and
       Holders are subject to the condition that, insofar as they relate to any
       Violation made in a preliminary prospectus but eliminated or remedied in
       the amended prospectus on file with the SEC at the time the registration
       statement in question becomes effective or the final prospectus is filed
       with the SEC pursuant to SEC Rule 424(b), such indemnity agreement shall
       not inure to the benefit of any person if a copy of such final prospectus
       was furnished to the indemnified party and was not furnished to the
       person asserting the loss, liability, claim, or damage at or prior to the
       time such action is required by the Securities Act.

              (f)    The obligations of the Company and Holders under this
       Section 2.8 shall survive the completion of any offering of Registrable
       Securities in a registration statement, and otherwise.

       2.9    ASSIGNMENT OF REGISTRATION RIGHTS.  The rights to cause the
Company to register Registrable Securities pursuant to this Article 2 may be
assigned by a Holder to a transferee or assignee of Registrable Securities;
provided, however, that no such transferee or assignee shall be entitled to
registration rights under this Article 2 hereof unless it acquires Registrable
Securities that represent at least 25 percent of the then-outstanding
Registrable Securities (as adjusted for stock splits and combinations) and the
Company shall, within 20 days after such transfer, be furnished with written
notice of the name and address of such transferee or assignee and the securities
with respect to which such registration rights are being assigned; provided,
however, that a Holder's failure to provide such notice to the Company shall not
in any way impair a Holder's right to make an assignment under this Section 2.9,
but until such notice is provided, the Company may continue to treat the
original Holder (and not the Holder's assignee) as the Holder of the
registration rights.  Notwithstanding the foregoing, rights to cause the Company
to register securities may be assigned to any person or entity who is a
subsidiary, parent, general partner, or limited partner of a Holder regardless
of the number of securities transferred to such person or entity.

       2.10   AMENDMENT OF REGISTRATION RIGHTS.  Any provision of this Article 2
may be amended and the observance thereof may be waived (either generally or in
a particular instance and either retroactively or prospectively) only with the
written consent of the Company and the Holders of Registrable Securities
representing at least 75% of the total of the then Registrable Securities.  Any
amendment or waiver effected in accordance with this Section 2.0 shall be


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<PAGE>

binding upon each Holder and the Company.  By acceptance of any benefits under
this Article 2, Holders of Registrable Securities hereby agree to be bound by
the provisions hereunder.

       2.11   LIMITATION ON SUBSEQUENT REGISTRATION RIGHTS.  If the Company
grants to any other person or persons registration rights that are more
favorable in any respect than the rights granted to the Holders hereunder, the
Holders shall immediately be granted the same rights, and this Agreement shall
be amended or deemed amended to include such more favorable rights.

       2.12   REGISTRATION RIGHTS SEPARATE FROM OTHER REGISTRATION RIGHTS.  The
registration rights granted to any Holder hereunder shall be deemed to be
separate and distinct from any other registration rights (the "Other
Registration Rights") granted by the Company to any such Holders or any other
holder of the Company's securities.  In addition, any registration of
Registrable Securities pursuant to the rights granted hereunder shall not affect
the rights of any Holder or any other person under the Other Registration
Rights, and any registration of the Company's securities under the Other
Registration Rights shall not affect the rights of any Holder of Registrable
Securities hereunder.


                                      ARTICLE 3
                                   OTHER PROVISIONS

       3.1    COMPLETE AGREEMENT.  This Agreement constitutes the entire
agreement between the parties hereto with respect to the subject matter hereof

       3.2    WAIVER, DISCHARGE, AMENDMENT, ETC.  The failure of any party
hereto to enforce at any time any of the provisions of this Agreement shall not,
absent an express written waiver signed by the party making such waiver
specifying the provision being waived, be construed to be a waiver of any such
provision, nor in any way to affect the validity of this Agreement or any part
hereof or the right of the party thereafter to enforce each and every such
provision.  No waiver of any breach of this Agreement shall be held to be a
waiver of any other or subsequent breach.

       3.3    NOTICES.  All notices or other communications to a party required
or permitted hereunder shall be in writing and shall be delivered personally or
by telecopy (receipt confirmed) to such party (or, in the case of an entity, to
an executive officer of such party) or shall be sent by a reputable express
delivery service or by certified mail, postage prepaid with return receipt
requested, addressed as follows:

       if to Medtronic to:

              Medtronic, Inc.
              Corporate Center
              7000 Central Avenue N.E.


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              Minneapolis, Minnesota 55432

              with separate copies thereof addressed to:

              Attention:    General Counsel
              Fax:          (612) 572-5459

              Attention:    Vice President, Corporate Development
                            and Associate General Counsel
              Fax:          (612) 572-5404

       if to another Holder, at such Holder's address as such Holder shall have
       specified to the Company in writing;

       if to the Company to:

              BioNebraska, Inc.
              3820 NW 46th Street
              Lincoln, Nebraska 68524
              Attention:    Thomas R. Coolidge,
                            Chairman of the Board and CEO

Any party may change the above-specified recipient and/or mailing address by
notice to all other parties given in the manner herein prescribed.  All notices
shall be deemed given on the day when actually delivered as provided above (if
delivered personally or by telecopy) or on the day shown on the return receipt
(if delivered by mail or delivery service).

       3.4    GOVERNING LAW.  This Agreement shall be governed by and
interpreted in accordance with the laws of the State of Minnesota, including all
matters of construction, validity, performance, and enforcement, without giving
effect to principles of conflict of laws.

       3.5    TITLES AND HEADINGS; CONSTRUCTION.  The titles and headings to the
Articles and Sections herein are inserted for the convenience of reference only
and are not intended to be a part of or to affect the meaning or interpretation
of this Agreement.  This Agreement shall be construed without regard to any
presumption or other rule requiring construction hereof against the party
causing this Agreement to be drafted.

       3.6    BENEFIT.  Nothing in this Agreement, expressed or implied, is
intended to confer on any person other than the parties hereto or their
respective successors or assigns, any rights, remedies, obligations, or
liabilities under or by reason of this Agreement.


                                       12

<PAGE>

       3.7    COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed as original and all of which
together shall constitute one instrument, and may be delivered in person or by
facsimile transmission.

       IN WITNESS WHEREOF, each of the parties has caused this Agreement to be
executed as of the date first written above.

                                          BIONEBRASKA, INC.


                                          By: /s/ Thomas R. Coolidge
                                              ---------------------------------
                                          Name:  Thomas R. Coolidge
                                          Title: Chairman of the Board and Chief
                                                 Executive Officer


                                          MEDTRONIC, INC.


                                          By:    /s/ Michael D. Ellwein
                                                -------------------------------
                                          Name: Michael D. Ellwein
                                                -------------------------------
                                          Title:   Vice President
                                                -------------------------------

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