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                                                                   EXHIBIT 10.30

                          SECOND REPLACEMENT REVOLVING

                                 PROMISSORY NOTE

$1,000,000                                                   Rockville, Maryland
                                                  Effective as of April 1,  1998

      FOR VALUE RECEIVED, BIORELIANCE CORPORATION, a corporation organized and
in good standing under the laws of the State of Delaware, successor in interest
to Microbiological Associates, Inc. (the "Company"), MA BIOSERVICES, INC., a
corporation organized and in good standing under the laws of the State of
Delaware ("MA BioServices"), MAGENTA CORPORATION, a corporation organized and in
good standing under the laws of the State of Delaware ("Magenta") and MAGENTA
VIRAL PRODUCTION, INC., a corporation organized and in good standing under the
laws of the State of Delaware ("Magenta Viral"; together with the Company, MA
BioServices and Magenta, each a "Borrower" and collectively, the "Borrowers"),
jointly and severally, promise to pay to the order of NATIONSBANK, N.A., a
national banking association, its successors and assigns (the "Lender"), the
principal sum of ONE MILLION DOLLARS ($1,000,000) (the "Principal Sum"), or so
much thereof as has been or may be advanced or readvanced to or for the account
of the Borrowers pursuant to the terms and conditions of the Loan Agreement (as
hereinafter defined), together with interest thereon at the rate or rates
hereinafter provided, in accordance with the following:

      1. INTEREST. Commencing as of the date hereof and continuing until
repayment in full of all sums due hereunder, the unpaid Principal Sum shall bear
interest at the LIBOR Rate (as hereinafter defined), plus the applicable LIBOR
Rate Additional Percentage (the "LIBOR Rate Option").
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            (a) For purposes hereof, the "LIBOR Rate Additional Percentage"
shall mean the percentages applicable to this Note in accordance with the
following:

                        (i) If the ratio of Funded Debt divided by EBITDA is
      equal to or greater than 2.75 to 1.0, the LIBOR Rate Additional Percentage
      shall be two percent (2.00%);

                        (ii) If the ratio of Funded Debt divided by EBITDA is
      less than 2.75 to 1.0, but equal to or greater than 2.0 to 1.0, the LIBOR
      Rate Additional Percentage shall be one and three quarters percent
      (1.75%);

                        (iii) If the ratio of Funded Debt divided by EBITDA is
      less than 2.0 to 1.0, but equal to or greater than 1.25 to 1.0 the LIBOR
      Rate Additional Percentage shall be one and one quarter percent (1.25%);
      and

                        (iv) If the ratio of Funded Debt divided by EBITDA is
      less than 1.25 to 1.0, the LIBOR Rate Additional Percentage shall be
      85/100 percent (.85%)

            (b) The initial LIBOR Rate Additional Percentage shall be 85/100
percent (.85%). Thereafter, the applicable LIBOR Rate Additional Percentage for
all Advances shall be calculated and adjusted quarterly, based on the quarterly
financial statements of the Borrowers required to be submitted to the Lender
pursuant to Section 5.1(c) of the Loan Agreement, commencing with the statements
for the quarter ending December 31, 1997. Such quarterly changes shall be
effective commencing five (5) Banking Days after submission by the Borrowers of
the required financial statements; it being understood, however, that, subject
to the provisions of the immediately following sentence, in the event the
quarterly financial statements are not submitted when due, the LIBOR Rate
Additional Percentage shall be two percent (2.00%), until such financial


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statements are submitted as required, at which time, the LIBOR Rate Additional
Percentage (for the balance of the quarterly period) shall be determined as set
forth above. If such financial statements are not submitted when due, but are
received within thirty (30) days of when due, the Lender will return to the
Borrower any additional interest collected in excess of the amount that should
have otherwise been due hereunder based on the financial statements. For
purposes of this Note, "Funded Debt" and "EBITDA" shall each be determined based
on the consolidated quarterly financial statements of the Borrowers and shall
have the meanings set forth in the Loan Agreement.

            (c) For purposes hereof, the "LIBOR Rate" shall mean a fluctuating
rate of interest equal to the one month rate of interest (rounded upwards, if
necessary to the nearest 1/100 of 1%) appearing on Telerate Page 3750 (or any
successor page) as the one month London interbank offered rate for deposits in
Dollars at approximately 11:00 a.m. (London time) on the second preceding
business day as adjusted from time to time in Lender's sole discretion for then
applicable reserve requirements, deposit insurance assessment rates and other
regulatory costs. If for any reason such rate is not available, the term "LIBOR
Rate" shall mean the fluctuating rate of interest equal to the one month rate of
interest (rounded upwards, if necessary to the nearest 1/100 of 1%) appearing on
Reuters Screen LIBO Page as the one month London interbank offered rate for
deposits in Dollars at approximately 11:00 a.m. (London time) on the second
preceding business day, as adjusted from time to time in Lender's sole
discretion for then applicable reserve requirements, deposit insurance
assessment rates and other regulatory costs; provided, however, if more than one
rate is specified on Reuters Screen LIBO page, the applicable rate shall be the
arithmetic mean of all such rates. "Telerate Page 3750" means the British
Bankers Association Libor Rates (determined as of 11:00 a.m. London time) that
are published by Dow Jones Telerate, Inc.


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            (d) The Borrowers shall pay to the Lender, as additional interest,
the following sums, at the time and in the manner hereinafter set forth:

                        (A) if, due to either: (i) the introduction of or any
change (including, without limitation, any change by way of imposition or
increase of reserve requirements) in or in the interpretation of any law or
regulation or (ii) the compliance by the Lender with any guideline or request
from any central bank or other governmental authority (whether or not having the
force of law), there shall be any increase in the cost to the Lender of agreeing
to make or making, funding or maintaining advances of all or a portion of the
Principal Sum, then the Borrowers shall from time to time, upon demand by the
Lender, pay to the Lender additional amounts to indemnify the Lender against any
such increased costs. A certificate as to the amount of such increased costs
submitted to the Borrowers by the Lender shall in the absence of manifest error
be conclusive. It shall be deemed, for purposes of computing any increased costs
pursuant to this Section, that (i) the making and maintaining of advances of the
Principal Sum which accrue interest based on the LIBOR Rate have been made by
the Lender from its office in London, England and (ii) the funding of each
Advance of the Principal Sum by the Lender which accrues interest based on the
LIBOR Rate has been made through the London Interbank Market. Such additional
cost shall be payable hereunder at the time and in the manner that interest is
payable hereunder for such costs incurred since the last interest payment;

                        (B) the Borrowers shall also pay to the Lender at the
time and in the manner that interest is payable hereunder for each advance, the
cost since the last interest payment date, as determined in good faith by the
Lender, of complying, in connection with such advance during such interest
period, with any reserve, special deposit or similar requirement


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(including but not limited to reserve requirements under Federal Reserve
Regulation D) imposed or deemed applicable against any assets held by or
deposits or accounts in or with or credit extended by the Lender, or the office
of the Lender in London, England, by any United States governmental authority
charged with the administration of such requirements. Each notification as to
the amount of such cost, delivered to the Borrowers by the Lender shall, in the
absence of manifest error, be conclusive as to the amount of such cost. It shall
be deemed for purposes of computing cost pursuant to the above provision that
the making and maintaining of each advance which accrues interest based on the
LIBOR Rate has been made by the Lender through its office in London, England.

            (e) In respect to any interest rate election hereunder and any
transactions contemplated hereby, the Borrowers authorize the Lender to accept,
rely upon, act upon and comply with, any verbal or written instructions,
requests, confirmations and orders of Michael R. N. Thomas or Sherry L. Rhodes
on behalf of the Borrowers. The Borrowers acknowledge and agree that the
transmission between the Borrowers and the Lender of any such instructions,
requests, confirmations and orders involves the possibility of errors,
omissions, mistakes and discrepancies and agrees to adopt such internal measures
and operational procedures to protect its interests. By reason thereof, the
Borrowers hereby assume all risk of loss and responsibility for, releases and
discharges the Lender from any and all responsibility or liability for, and
agrees to indemnify, reimburse on demand and hold the Lender harmless from, any
and all claims, actions, damages, losses, liability and expenses by reason of,
arising out of or in any way connected with or related to, (i) the Lender's
acceptance, reliance and actions upon, compliance with or observation of any
such instructions,


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requests, confirmations or orders, and (ii) any such errors, omissions, mistakes
and discrepancies, except those caused by the Lender's gross negligence or
willful misconduct.

            (f) All interest payable under the terms of this Note shall be
calculated on the basis of a 360-day year and the actual number of days elapsed.

      2. PAYMENTS AND MATURITY. The unpaid Principal Sum, together with interest
thereon at the rate or rates provided above, shall be payable as follows:

            (a) Interest only on the unpaid Principal Sum shall be due and
payable monthly, commencing April 30, 1998 and on the last day of each month
thereafter to maturity; and

            (b) Unless sooner paid, the unpaid Principal Sum, together with
interest accrued and unpaid thereon, shall be due and payable in full on May 31,
1998.

      The fact that the balance hereunder may be reduced to zero from time to
time pursuant to the Loan Agreement will not affect the continuing validity of
this Note or the Loan Agreement, and the balance may be increased to the
Principal Sum after any such reduction to zero.

      3. DEFAULT INTEREST. Upon the occurrence of an Event of Default (as
hereinafter defined), the unpaid Principal Sum shall bear interest thereafter at
a rate five percent (5.0%) per annum in excess of the LIBOR Rate until such
Event of Default is cured.

      4. LATE CHARGES. If the Borrowers shall fail to make any payment under the
terms of this Note within fifteen (15) days after the date such payment is due,
the Borrowers shall pay to the Lender on demand a late charge equal to three
percent (3%) of such payment.

      5. COMMITMENT FEE. The Borrowers jointly and severally agree to pay to the
Lender on the first day of every third calendar month hereafter commencing after
the date of this Note a commitment fee (computed on the basis of a year
consisting of three hundred and sixty (360) days


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for the actual number of days elapsed) of one quarter of one percent (.25%) per
annum on the daily average of the unused amount of this Note during such period.

      6. APPLICATION AND PLACE OF PAYMENTS. All payments, made on account of
this Note shall be applied first to the payment of any late charge then due
hereunder, second to the payment of accrued and unpaid interest then due
hereunder, and the remainder, if any, shall be applied to the unpaid Principal
Sum. All payments on account of this Note shall be paid in lawful money of the
United States of America in immediately available funds during regular business
hours of the Lender at its principal office in Rockville, Maryland or at such
other times and places as the Lender may at any time and from time to time
designate in writing to the Borrowers.

      7. LOAN AGREEMENT AND OTHER LOAN DOCUMENTS. This Note is the "Line of
Credit Replacement Note" described in that certain Amended and Restated
Replacement Loan Agreement dated October 31, 1997 by and among the Borrowers and
the Lender (the Amended and Restated Replacement Loan Agreement, as thereafter
amended from time to time, is hereinafter called the "Loan Agreement"). This
Note amends and restates in its entirety that certain Replacement Revolving
Promissory Note dated October 31, 1997 in the maximum principal amount of One
Million Dollars ($1,000,000) from the Borrowers in favor of the Lender (as
amended from time to time, the "Original Note"). It is expressly agreed that the
indebtedness evidenced by the Original Note has not been extinguished or
discharged hereby. The Borrowers agree that the execution of this Agreement is
not intended to and shall not cause or result in a novation with respect to the
Original Note. The indebtedness evidenced by this Note is included within the
meaning of the term "Obligations" as defined in the Loan Agreement. The term
"Loan Documents" as used in this Note shall mean collectively this Note, the
Loan Agreement and any other instrument, agreement, or


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document previously, simultaneously, or hereafter executed and delivered by the
Borrowers and/or any other person, singularly or jointly with any other person,
evidencing, securing, guaranteeing, or in connection with the Principal Sum,
this Note and/or the Loan Agreement. All capitalized terms used herein and not
otherwise defined shall have the meanings given to such terms in the Loan
Agreement.

      8. EVENTS OF DEFAULT. The occurrence of any one or more of the following
events shall constitute an event of default (individually, an "Event of Default"
and collectively, the "Events of Default") under the terms of this Note:

            (a) The failure of the Borrowers to pay to the Lender when due any
and all amounts payable by the Borrowers to the Lender and such failure remains
uncured for five (5) days after written notice thereof; or

            (b) The occurrence of an event of default (as defined therein) under
the terms and conditions of any of the other Loan Documents.

      9. REMEDIES. Upon the occurrence of an Event of Default, at the option of
the Lender, all amounts payable by the Borrowers to the Lender under the terms
of this Note shall immediately become due and payable by the Borrowers to the
Lender without notice to the Borrowers or any other person, and the Lender shall
have all of the rights, powers, and remedies available under the terms of this
Note, any of the other Loan Documents and all applicable laws. The Borrowers and
all endorsers, guarantors, and other parties who may now or in the future be
primarily or secondarily liable for the payment of the indebtedness evidenced by
this Note hereby severally waive presentment, protest and demand, notice of
protest, notice of demand and of dishonor and non-payment of this Note and
expressly agree that this Note or any payment hereunder may be extended


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from time to time without in any way affecting the liability of the Borrowers,
guarantors and endorsers.

      Until such time as the Lender is not committed to extend further credit to
the Borrowers and all Obligations of the Borrowers to the Lender have been
indefeasibly paid in full in cash, and subject to and not in limitation of the
provisions set forth in the next following paragraph below, no Borrower shall
have any right of subrogation (whether contractual, arising under the Bankruptcy
Code or otherwise), reimbursement or contribution from any Borrower or any
guarantor, nor any right of recourse to its security for any of the debts and
obligations of any Borrower which are the subject of this Note. Except as
otherwise expressly permitted by the Loan Agreement, any and all present and
future debts and obligations of any Borrower to any other Borrower are hereby
subordinated to the full payment and performance of all present and future debts
and obligations to the Lender under this Note and the Loan Agreement and the
Loan Documents, provided, however, notwithstanding anything set forth in this
Note to the contrary, prior to the occurrence of a payment Default, the
Borrowers shall be permitted to make payments on account of any of such present
and future debts and obligations from time to time in accordance with the terms
thereof.

      Each Borrower further agrees that, if any payment made by any Borrower or
any other person is applied to this Note and is at any time annulled, set aside,
rescinded, invalidated, declared to be fraudulent or preferential or otherwise
required to be refunded or repaid, or the proceeds of any property hereafter
securing this Note is required to be returned by the Lender to any Borrower, its
estate, trustee, receiver or any other party, including, without limitation,
such Borrower, under any bankruptcy law, state or federal law, common law or
equitable cause, then, to the extent of such payment or repayment, such
Borrower's liability hereunder (and any lien, security interest or other


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collateral securing such liability) shall be and remain in full force and
effect, as fully as if such payment had never been made, or, if prior thereto
any such lien, security interest or other collateral hereafter securing such
Borrower's liability hereunder shall have been released or terminated by virtue
of such cancellation or surrender, this Note (and such lien, security interest
or other collateral) shall be reinstated in full force and effect, and such
prior cancellation or surrender shall not diminish, release, discharge, impair
or otherwise affect the obligations of such Borrower in respect of the amount of
such payment (or any lien, security interest or other collateral securing such
obligation).

      The JOINT AND SEVERAL obligations of each Borrower under this Note shall
be absolute, irrevocable and unconditional and shall remain in full force and
effect until the outstanding principal of and interest on this Note and all
other Obligations or amounts due hereunder and under the Loan Agreement and the
Loan Documents shall have been indefeasibly paid in full in cash in accordance
with the terms thereof and this Note shall have been canceled.

      10. EXPENSES. The Borrowers, jointly and severally, promise to pay to the
Lender on demand by the Lender all reasonable costs and expenses incurred by the
Lender in connection with the collection and enforcement of this Note,
including, without limitation, reasonable attorneys' fees and expenses and all
court costs.

      11. NOTICES. Any notice, request, or demand to or upon the Borrowers or
the Lender shall be deemed to have been properly given or made when delivered in
accordance with Section 9.1 of the Loan Agreement.

      12. MISCELLANEOUS. Each right, power, and remedy of the Lender as provided
for in this Note or any of the other Loan Documents, or now or hereafter
existing under any applicable law or otherwise shall be cumulative and
concurrent and shall be in addition to every other right, power,


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or remedy provided for in this Note or any of the other Loan Documents or now or
hereafter existing under any applicable law, and the exercise or beginning of
the exercise by the Lender of any one or more of such rights, powers, or
remedies shall not preclude the simultaneous or later exercise by the Lender of
any or all such other rights, powers, or remedies. No failure or delay by the
Lender to insist upon the strict performance of any term, condition, covenant,
or agreement of this Note or any of the other Loan Documents, or to exercise any
right, power, or remedy consequent upon a breach thereof, shall constitute a
waiver of any such term, condition, covenant, or agreement or of any such
breach, or preclude the Lender from exercising any such right, power, or remedy
at a later time or times. By accepting payment after the due date of any amount
payable under the terms of this Note, the Lender shall not be deemed to waive
the right either to require prompt payment when due of all other amounts payable
under the terms of this Note or to declare an Event of Default for the failure
to effect such prompt payment of any such other amount. No course of dealing or
conduct shall be effective to amend, modify, waive, release, or change any
provisions of this Note.

      13. PARTIAL INVALIDITY. In the event any provision of this Note (or any
part of any provision) is held by a court of competent jurisdiction to be
invalid, illegal, or unenforceable in any respect, such invalidity, illegality,
or unenforceability shall not affect any other provision (or remaining part of
the affected provision) of this Note; but this Note shall be construed as if
such invalid, illegal, or unenforceable provision (or part thereof) had not been
contained in this Note, but only to the extent it is invalid, illegal, or
unenforceable.

      14. CAPTIONS. The captions herein set forth are for convenience only and
shall not be deemed to define, limit, or describe the scope or intent of this
Note.



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      15. APPLICABLE LAW. Each of the Borrowers acknowledges and agrees that
this Note shall be governed by the laws of the State of Maryland, even though
for the convenience and at the request of the Borrowers, this Note may be
executed elsewhere.

      16. ARBITRATION. ANY CONTROVERSY OR CLAIM BETWEEN OR AMONG THE PARTIES
HERETO INCLUDING BUT NOT LIMITED TO THOSE ARISING OUT OF THIS NOTE, THE LOAN
DOCUMENTS OR ANY RELATED INSTRUMENTS, AGREEMENTS OR DOCUMENTS, INCLUDING ANY
CLAIM BASED ON OR ARISING FROM AN ALLEGED TORT, SHALL BE DETERMINED BY BINDING
ARBITRATION IN ACCORDANCE WITH THE FEDERAL ARBITRATION ACT (OR IF NOT
APPLICABLE, THE APPLICABLE STATE LAW), THE RULES OF PRACTICE AND PROCEDURE FOR
ARBITRATION OF COMMERCIAL DISPUTES OF ENDISPUTE, INC., D/B/A J.A.M.S./ENDISPUTE
("J.A.M.S.") AND THE "SPECIAL RULES" SET FORTH BELOW. IN THE EVENT OF AN
INCONSISTENCY, THE SPECIAL RULES SHALL CONTROL. JUDGMENT UPON ANY ARBITRATION
AWARD MAY BE ENTERED IN ANY COURT HAVING JURISDICTION. ANY PARTY TO THIS NOTE,
AGREEMENT OR DOCUMENT MAY BRING ANY ACTION, INCLUDING A SUMMARY OR EXPEDITED
PROCEEDING, TO COMPEL ARBITRATION OF ANY CONTROVERSY OR CLAIM TO WHICH THIS
NOTE, AGREEMENT OR DOCUMENT RELATES IN ANY COURT HAVING JURISDICTION OVER SUCH
ACTION.

      (A) SPECIAL RULES. THE ARBITRATION SHALL BE CONDUCTED IN MONTGOMERY
COUNTY, MARYLAND AND ADMINISTERED BY J.A.M.S. WHO WILL APPOINT AN ARBITRATOR. IF
J.A.M.S. IS UNABLE OR LEGALLY PRECLUDED FROM


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ADMINISTERING THE ARBITRATION, THEN THE AMERICAN ARBITRATION ASSOCIATION WILL
SERVE. ALL ARBITRATION HEARINGS WILL BE COMMENCED WITHIN NINETY (90) DAYS OF THE
DEMAND FOR ARBITRATION; FURTHER, THE ARBITRATOR SHALL ONLY, UPON A SHOWING OF
CAUSE, BE PERMITTED TO EXTEND THE COMMENCING OF SUCH HEARING FOR AN ADDITIONAL
SIXTY (60) DAYS.

      (B) RESERVATION OF RIGHTS. NOTHING IN THIS NOTE, AGREEMENT OR DOCUMENT
SHALL BE DEEMED TO: (I) LIMIT THE APPLICABILITY OF ANY OTHERWISE APPLICABLE
STATUTES OF LIMITATION OR REPOSE AND ANY WAIVERS CONTAINED IN THIS NOTE,
AGREEMENT OR DOCUMENT; OR (II) BE A WAIVER BY THE LENDER OF THE PROTECTION
AFFORDED TO IT BY 12 U.S.C. SECTION 91 OR ANY SUBSTANTIALLY EQUIVALENT STATE
LAW; OR (III) LIMIT THE RIGHT OF THE LENDER: (A) TO EXERCISE SELF HELP REMEDIES
( BUT NOT INCLUDING SETOFF), OR (B) TO FORECLOSE AGAINST ANY REAL OR PERSONAL
PROPERTY COLLATERAL, OR (C) TO OBTAIN FROM A COURT PROVISIONAL OR ANCILLARY
REMEDIES SUCH AS (BUT NOT LIMITED TO) INJUNCTIVE RELIEF, WRIT OF POSSESSION OR
THE APPOINTMENT OF A RECEIVER. THE LENDER MAY EXERCISE SUCH SELF HELP RIGHTS,
FORECLOSE UPON SUCH PROPERTY, OR OBTAIN SUCH PROVISIONAL OR ANCILLARY REMEDIES
BEFORE, DURING OR AFTER THE PENDENCY OF ANY ARBITRATION PROCEEDING BROUGHT
PURSUANT TO THIS NOTE, AGREEMENT OR DOCUMENT. NEITHER THE EXERCISE OF SELF HELP
REMEDIES NOR THE


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INSTITUTION OR MAINTENANCE OF ANY ACTION FOR FORECLOSURE OR FOR PROVISIONAL OR
ANCILLARY REMEDIES SHALL CONSTITUTE A WAIVER OF THE RIGHT OF ANY PARTY,
INCLUDING THE CLAIMANT IN SUCH ACTION, TO ARBITRATE THE MERITS OF THE
CONTROVERSY OR CLAIM OCCASIONING RESORT TO SUCH REMEDIES.

      IN WITNESS WHEREOF, the Borrowers have caused this Note to be executed
under seal by their duly authorized officers as of the date first written above.

WITNESS/ATTEST:                           BIORELIANCE CORPORATION

______________________________            By:__________________________(SEAL)
                                             Name:
                                             Title:

WITNESS/ATTEST:                           MA BIOSERVICES, INC.

______________________________            By:__________________________(SEAL)
                                             Name:
                                             Title:

WITNESS/ATTEST:                           MAGENTA CORPORATION

______________________________            By:__________________________(SEAL)
                                             Name:
                                             Title:

WITNESS/ATTEST:                           MAGENTA VIRAL PRODUCTION, INC.

______________________________            By:__________________________(SEAL)
                                             Name:
                                             Title:


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