Document:

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                                                                   EXHIBIT 10.13

                   AMENDMENT TO LOAN AND SECURITY AGREEMENTS

         This Amendment to Loan and Security Agreements (the "Amendment") is
made and entered into as of the 25th day of June, 1999, by and among ARC
KENTUCKY, LLC, a Tennessee limited liability company ("ARC Kentucky"),
AMBULATORY RESOURCE CENTRES, INC., a Tennessee corporation (the "Guarantor"),
WILMINGTON SURGERY CENTER, L.P., a Tennessee limited partnership ("ARC
Wilmington") and NATIONSBANK, N.A., a national banking association and the
successor to NationsBank of Tennessee, N.A. (the "Bank").

                                   RECITALS:

         Pursuant to that certain Loan and Security Agreement dated November
16, 1998, among Guarantor, ARC Kentucky and Bank (as amended from time to time,
the "Kentucky Loan Agreement"), Bank made a loan to ARC Kentucky in the amount
of $4,312,000.00. Pursuant to that certain Loan and Security Agreement dated
May 24, 1999, among Guarantor, ARC Wilmington and Bank (as amended from time to
time, the "Wilmington Loan Agreement" and, together with the Kentucky Loan
Agreement, the "Loan Agreements"), Bank made a loan to ARC Wilmington in the
amount of $8,000,000.00. Pursuant to an Agreement and Plan of Merger dated as
of June 8, 1999 (the "Merger Agreement"), Guarantor intends to merge with
UniPhy Acquisition Sub, Inc., a wholly owned subsidiary of UniPhy Healthcare,
Inc. (the "Merger"). Lender's consent is required for the Merger, and execution
of this Amendment is one of the conditions to such consent.

         NOW, THEREFORE, ARC Kentucky, ARC Wilmington, Guarantor and Bank
hereby amend the Loan Agreements as follows:

         1.       Amended Definitions. The following definitions are hereby
deleted from each of the Loan Agreements and replaced with the following:

         "MATERIAL ADVERSE CHANGE" means a material adverse change in the
business or conditions (financial or otherwise) or in the result of operations
of the Borrower, Symbion or the Guarantor or in the value of the Collateral.

         "MATERIAL ADVERSE EFFECT" means, when referring to the taking of an
action or the omission to take an action, that such action, if taken, or
omission, would have a material adverse effect on the business, condition
(financial or otherwise) or results of operations of the Borrower, Symbion or
the Guarantor, or might materially impair the value of the Collateral.

         2.       Additional Definition. The following definition is hereby
added to the each of the Loan Agreements:

         "SYMBION" means Symbion, Inc., a Tennessee corporation.

         3.       Reporting by Symbion. The following is hereby added to each
of the Loan Agreements as Subparagraph 6.2(h)

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                  (h)      As soon as available and in any event within 45 days
         after the close of each calendar month (i) consolidated income
         statements of Symbion for such monthly period; and (ii) unaudited
         consolidated balance sheets of Symbion as of the end of such monthly
         period; - all in reasonable detail, subject to year-end audit
         adjustments and certified by the president or principal financial
         officer of Symbion to have been prepared in accordance with generally
         accepted accounting principles consistently applied, except for any
         inconsistencies explained in such certificate.

         4.       Symbion Financial Covenant. The following is hereby added to
each of the Loan Agreements as Subparagraph 6.15(h):

                  (h)      At all times, the Shareholders' Equity of Symbion,
         calculated on a consolidated basis, shall be greater than $25,000,000
         plus eighty-five percent (85%) of the aggregate amount of any new
         equity raised by Symbion after the date of this Amendment.

         5.       Additional Symbion Covenant. The following is hereby added to
each of the Loan Agreements as Paragraph 7.16:

                  7.16     Symbion Merger or Reorganization. Symbion will not
         enter into any merger, consolidation, reorganization or
         recapitalization.

         6.       Amendment to Default Provisions. In each of the Loan
Agreements, Subparagraphs 8.1(c) through 8.1(h) and Subparagraphs 8.1(j)
through 8.1(m) are amended by inserting ", Symbion" between the words
"Borrower" and "Guarantor" in each instance used in each of such subparagraphs.
In addition, Subparagraph 8.1(i) and Subparagraph 8.1(o) of each of the Loan
Agreements are each deleted in their entirety and replaced with the following:

                  (i)      A receiver or trustee shall be appointed for the
         Borrower, Symbion or Guarantor or for any substantial part of their
         respective assets, or any proceedings shall be instituted for the
         dissolution or the full or partial liquidation of the Borrower,
         Symbion or Guarantor, or the Borrower, Symbion or Guarantor shall
         discontinue business or materially change the nature of any of their
         respective businesses.

                  (o)      Any event which results in the principal executive
         management functions of Symbion and its Subsidiaries being vested in,
         and the responsibility of, less than four of Clifford G. Adlerz,
         Richard E. Francis, Kenneth C. Mitchell, Gregg A. Stanley, and William
         V. B. Webb.

The following is hereby added to each of the Loan Agreements as Subparagraph
8.1(q):

                  (q)      An event or series of events shall occur by which:

                  (1)      any "person" or "group" (within the meaning of
         Sections 13(d) and 14 (d)(2) of the Securities Exchange Act of 1934)
         shall become the "beneficial owner" (within the meaning of Rule 13d-3
         and/or Rule 13d-5 under the Securities Exchange Act of 1934, except
         that a Person shall be deemed to have "beneficial ownership" of

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         all shares that such Person has the right to acquire without
         condition, other than the passage of time, whether such right is
         exercisable immediately or only after the passage of time), directly
         or indirectly, of thirty percent (30%) or more of the combined voting
         power of all securities of Symbion entitled to vote in the election of
         directors, other than securities having such power only by reason of
         the happening of a contingency (other than the passage of time),
         excluding, however, any such person or group that is a record of
         "beneficial owner" of any such securities in any amount on the date of
         this Agreement; or

                  (2)      individuals who at the beginning of any period of
         two (2) consecutive calendar years constituted the Board of Directors
         (together with any new directors whose election by such Board of
         Directors or whose nomination for election by Symbion's shareholders
         was approved by a vote of at least two-thirds (2/3) of the members of
         the Board of Directors then still in office who either were members of
         the Board of Directors at the beginning of such period or whose
         election or nomination for election was previously so approved) shall
         cease for any reason to constitute a majority of the members of the
         Board of Directors then in office.

         7.       Ratification. Subject to the terms of this Amendment, ARC
Kentucky, ARC Wilmington and Guarantor hereby restate and ratify, as of the
date hereof, all the covenants contained in the Loan Agreements in favor of
Bank, and confirms that the terms and conditions of the Loan Agreements, as
amended hereby, remain in full force and effect and that the terms of Section 9
of the Loan Agreements shall continue to govern the respective Loan Agreements
and are hereby incorporated herein by reference and shall govern this
Amendment.

         8.       Fees and Expenses. ARC Kentucky, ARC Wilmington, Guarantor
and Symbion, jointly and severally agree to pay all reasonable fees and
expenses of Bank in connection with this Amendment (including reasonable
attorneys' fees and expenses) promptly upon receipt of an invoice.

         9.       Additional Representations. Symbion, ARC Kentucky, ARC
Wilmington and Guarantor, jointly and severally, hereby represent and warrant
to Bank as follows:

                  (a)      as of the date hereof, there is no defense against
         payment of any or all of the Obligations;

                  (b)      as of the date hereof, no Unmatured Default or Event
         of Default has occurred or is continuing under either of the Loan
         Agreements;

                  (c)      a true, correct and complete copy of the Merger
         Agreement has been delivered to Bank;

                  (d)      the representations and warranties contained in the
         Loan Agreements and the other Loan Documents are true and correct,
         except for (1) representations and warranties that expressly relate to
         an earlier date, which remain true and correct as of said earlier
         date, and (2) representations and warranties that have become untrue
         or incorrect solely because of changes permitted by the terms of the
         Loan Agreements and the other Loan Documents.

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         10.      Further Assurances. Symbion, Guarantor, ARC Kentucky and ARC
Wilmington shall perform, take, execute and deliver, and cause their respective
Subsidiaries to perform, take, execute and deliver, all such additional and
further acts, actions, instruments, documents and agreements as the Bank
reasonably may require from time to time to consummate, evidence and document
the transactions that are the subject of this Amendment and to confirm and
assure the Bank the respective rights, powers, privileges, options and remedies
of each pursuant to this Amendment, the Loan Agreements and the other Loan
Documents.

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         IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the day and date first above written.

BANK:                                     BORROWERS:

NATIONSBANK, N.A.                         WILMINGTON SURGERY CENTER, L.P.,
                                          a Tennessee  Limited Partnership

                                          By: Ambulatory Resource Centres of
                                              Wilmington, Inc., its
                                              General Partner

BY: /s/ Walter Choppin                    BY: /s/ Jerry Eyler
    ------------------------------           ----------------------------------
TITLE: Senior Vice President              TITLE: Chief Financial Officer
      ----------------------------              -------------------------------

                                          ARC KENTUCKY, LLC

                                          BY: /s/ Jerry Eyler
                                             ----------------------------------
                                          TITLE: Chief Financial Officer
                                                -------------------------------

                                          GUARANTOR:

                                          AMBULATORY RESOURCE CENTRES, INC.

                                          BY: /s/ Jerry Eyler
                                             ----------------------------------
                                          TITLE: Chief Financial Officer
                                                -------------------------------
                                          SYMBION:

                                          SYMBION, INC.

                                          BY: /s/ Richard E. Francis, Jr.
                                              ---------------------------------
                                          TITLE: President
                                                -------------------------------

                                       5<PAGE>
                                                                   EXHIBIT 10.14

                 SECOND AMENDMENT TO LOAN AND SECURITY AGREEMENT

         THIS SECOND AMENDMENT, made this 12th day of April, 2000, is by and
among Bank of America, N.A., the successor to NationsBank, N.A. (the "Bank"),
Wilmington Surgery Center, L.P., a Tennessee limited partnership (the
"Borrower") and Symbion Ambulatory Resource Centres, Inc., a Tennessee
corporation and the successor to Ambulatory Resource Centres, Inc. (the
"Guarantor").

                                    RECITALS

         Bank has previously made a loan to the Borrower, an Affiliate of
Guarantor, pursuant to a Loan and Security Agreement dated May 24, 1999 (as
amended from time to time, the "Loan Agreement"). The Loan Agreement was amended
pursuant to an Amendment to Loan Agreements dated June 25, 1999 among Bank,
Borrower, Guarantor and ARC Kentucky, LLC. Capitalized terms not otherwise
defined in this Second Amendment shall have the meaning provided in the Loan
Agreement. Borrower has requested that Bank make certain changes to the Loan
Agreement. The Bank is willing to do so, subject, among other things, to the
execution of this Amendment and compliance with the terms hereof.

         NOW, THEREFORE, the parties to this Second Amendment hereby agree as
follows:

         Article I.        Amendment to Loan Agreement. The parties hereto amend
the Loan Agreement as follows:

                  Section 1.1. The following definitions are hereby added to
Section 1 of the Loan Agreement in appropriate alphabetical order:

                           '"COMPLIANCE DATE" means, provided no Event of
                  Default occurs between April 12, 2000 and such date and
                  provided no Unmatured Default exists at such date, the date on
                  which Borrower has delivered certificates to Bank evidencing
                  to Bank's reasonable satisfaction, for two consecutive
                  Quarterly Periods (the second of which must be a Quarterly
                  Period ending at or after September 30, 2000), that (A)
                  Borrower has complied with the covenants set forth in
                  Paragraph 6.15(b) through (e), and (B) the ratio of Borrower's
                  Cash Flow to Borrower's Debt Service has been greater than
                  1.10:1.00.

                           "COMPLIANCE QUARTER" means the second of the two
                  consecutive Quarterly Periods referenced above in the
                  definition of Compliance Date.

                           "CONSOLIDATED FUNDED DEBT" means, at any date, with
                  respect to Symbion and its Subsidiaries, all of the following
                  obligations

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                  (without duplication) as of such date: (a) all obligations for
                  borrowed money, (b) all obligations evidenced by bonds,
                  debentures, notes or other similar instruments, (c) all
                  obligations to pay the deferred purchase price of property,
                  except trade accounts payable or other short term liabilities
                  other than indebtedness for borrowed money arising in the
                  ordinary course of business, (d) all obligations as lessee
                  under capitalized leases, (e) all obligations to purchase
                  securities or other property which arise out of or in
                  connection with the sale of the same or substantially similar
                  securities or property, such as bankers acceptances or similar
                  instruments, (f) all contingent and non-contingent obligations
                  to reimburse any bank or other person in respect of amounts
                  payable or paid under a letter of credit or similar
                  instrument, (g) all debt of others secured by a lien on any
                  asset of Symbion and/or any of its Subsidiaries, whether or
                  not such debt is assumed, and (h) all Guarantee Obligations.

                           "DE NOVO LOSSES" means, at any date, the aggregate,
                  cumulative losses of each Subsidiary operating a surgery
                  center which has been accepting patients for less than nine
                  (9) months.

                           "EXCESS CASH" means, at any date, for any Person,
                  such Person's cash on hand less the amount of the Required
                  Cash Availability at such date.

                           "NON-RECOURSE DEBT" means, at any date, that portion
                  of Consolidated Funded Debt which is not a corporate
                  obligation of Symbion, and is included within the definition
                  of Consolidated Funded Debt solely because it is Indebtedness
                  of a Subsidiary.

                           "QUARTERLY COMPLIANCE DATE" means the last day of the
                  second consecutive Quarterly Period referenced above in the
                  definition of Compliance Date.

                           "REQUIRED CASH AVAILABILITY" means, at any date, for
                  any Person, an amount equal to such Person's anticipated
                  operating expenses for the succeeding two weeks.'

                  Section 1.2 Section 6.15 of the Loan Agreement is hereby
deleted in its entirety and replaced with the following:

                           "6.15 Financial Ratios. The Borrower will maintain or
                  cause to be maintained, the following financial ratios and
                  covenants:

                           (a)   for each Quarterly Period, (i) beginning with
                  the Quarterly Period ending March 31, 2000, a ratio of
                  Borrower's Cash Flow to the sum of Borrower's Debt Service
                  minus $26,786, of not less

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                  than 1.05:1.00, and (ii) beginning with the first Quarterly
                  Period ending after the Compliance Quarter, a ratio of
                  Borrower's Cash Flow to the sum of Borrower's Debt Service of
                  not less than 1.10:1.00;

                           (b) At all times, Borrower's cash on hand shall be
                  greater than Borrower's Required Cash Availability. Promptly
                  following a request from Bank, Borrower shall provide evidence
                  reasonably satisfactory to Bank to document compliance with
                  this covenant;

                           (c) At all times, the sum of Borrower's Shareholder's
                  Equity plus the outstanding principal balance of all
                  Indebtedness for money borrowed from Guarantor by Borrower
                  shall be greater than $4,000,000;

                           (d) At all times, the Shareholders' Equity of
                  Symbion, calculated on a consolidated basis, shall be greater
                  than $25,000,000 plus eighty-five percent (85%) of (i) the
                  aggregate amount of any new equity raised by Symbion after
                  June 25, 1999 and (ii) the aggregate, cumulative, positive Net
                  Income of Symbion (without any credit or deduction in the
                  event Net Income is a negative number) after June 25, 1999;

                           (e) At the end of each Quarterly Period, beginning
                  with the Quarterly Period ending September 30, 1999 and
                  continuing through and including the Quarterly Period ending
                  September 30, 2000, the ratio of (i) the sum of (A) Symbion's
                  Consolidated Funded Debt less (B) Symbion's Excess Cash to
                  (ii) the sum of (X) EBITDA for such Quarterly Period, plus (Y)
                  the lesser of (1) $125,000 or (2) the De Novo Losses at such
                  date, giving Pro-Forma Effect to any Acquisition made and any
                  Indebtedness incurred therewith as of the date of
                  determination, shall be less than 3.75:1.00; and

                           (f) At the end of each Quarterly Period beginning
                  with the Quarterly Period ending December 31, 2000 and
                  continuing through each Quarterly Period ending thereafter,
                  the ratio of (i) the sum of (A) Symbion's Consolidated Funded
                  Debt less (B) Symbion's Excess Cash to (ii) Symbion's
                  consolidated EBITDA for such Quarterly Period, giving
                  Pro-Forma Effect to any Acquisition made and any Indebtedness
                  incurred therewith as of the date of determination, shall be
                  less than 3.50:1.00; provided, however, if the result of such
                  ratio is greater than or equal to 3.50:1.00 and less than
                  3.75:1.00, the Borrower shall be in compliance with this
                  covenant for such Quarterly Period if the ratio of (i) the sum
                  of (A) Symbion's Consolidated Funded Debt less (B) Symbion's
                  Excess Cash less (C) Symbion's Non-Recourse Debt to (ii)
                  Symbion's consolidated EBITDA for such Quarterly Period,

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                  giving Pro-Forma Effect to any Acquisition made and any
                  Indebtedness incurred therewith as of the date of
                  determination, shall be less than 3.50:1.00."

                  Section 1.3. The following is hereby added to the Loan
Agreement as Section 6.17:

                           "6.17 Cash Collateral. On or before April 21, 2000
                  Borrower shall purchase a certificate of deposit issued by
                  Bank in the amount of not less than $750,000, and Borrower
                  shall maintain such certificate of deposit until no longer
                  required to do so pursuant to this Paragraph 6.17. Borrower
                  hereby acknowledges that Bank shall be entitled to exercise
                  full rights of setoff with respect to the certificate of
                  deposit. Provided no Event of Default occurs between April 12,
                  2000 and the Compliance Date and provided no Unmatured Default
                  exists at the Compliance Date, upon the Compliance Date,
                  Borrower shall no longer be required to maintain the
                  certificate of deposit, and this Paragraph 6.17 shall be
                  inapplicable and such funds shall be returned to Borrower in
                  full. Until the Compliance Date, Borrower shall not make any
                  payment of principal or interest owed on any indebtedness of
                  Borrower to Guarantor, Symbion or any other Affiliate of
                  Borrower."

                  Section 1.4. The following is hereby added to the Loan
Agreement as Section 6.18:

                           "6.18 Symbion Financing. If, after April 12, 2000,
                  Symbion enters into any financing arrangement which imposes
                  covenants upon Symbion that are more restrictive than, or in
                  addition to, the covenants imposed by the Loan Agreement,
                  Borrower will promptly notify Bank, and Borrower, Guarantor
                  and Symbion will promptly execute any documentation reasonably
                  requested by Bank to add such covenants to the Loan
                  Agreement."

         Article II.       General.

                  Section 2.1 Loan Agreement. Except as amended hereby, the
provisions of the Loan Agreement shall remain in full force and effect.
References in the Loan Agreement and the other Loan Documents shall be
references to the Loan Agreement as amended by this Second Amendment.

                  Section 2.2 Symbion Indebtedness. If Symbion enters into any
financing arrangement after April 12, 2000 which imposes covenants upon Symbion
that are more restrictive than, or in addition to, the covenants imposed by the
Loan Agreement, such covenants shall be incorporated by reference into the Loan
Agreement, unless, within ten (10) days after Symbion enters into such financing

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arrangement, Borrower, Guarantor and Symbion execute the documentation
referenced in Section 1.5 of this Second Amendment.

                  Section 2.3 Governing Law. This Second Amendment shall be
governed by and construed in accordance with the laws of the State of Tennessee
without reference to its choice of law rules.

                  Section 2.4 Execution in Counterparts. This Second Amendment
may be executed in one or more counterparts, each of which shall be considered
an original instrument, but all of which shall be considered one and the same
agreement, and shall become binding when one or more counterparts have been
signed by each of the parties and delivered to each of the parties.

                  Section 2.5 Representations. Borrower hereby makes the
following representations and warranties:

                           (a) as of the date hereof, Borrower has no defense
                  against payment of any or all of the Obligations;

                           (b) as of the date hereof, no Event of Default or
                  Unmatured Default has occurred or is continuing (after giving
                  effect to this Amendment).

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         IN WITNESS WHEREOF, the parties hereto have duly executed this
Agreement as of the day and year first above written.

BANK OF AMERICA, N.A.               WILMINGTON SURGERY CENTER, L.P.,
                                    a Tennessee limited partnership

                                    By: Ambulatory Resource Centers of
                                        Wilmington, Inc., its General Partner

BY: /s/ Elizabeth L. Knox           BY:/s/ Charles T. Neal
    ------------------------           -------------------

TITLE: Senior Vice President        TITLE: President and Chief Executive Officer
       ---------------------              --------------------------------------

                                    SYMBION AMBULATORY RESOURCE
                                    CENTRES, INC.

                                    BY: /s/ Charles T. Neal

                                    TITLE: President and Chief Executive Officer
                                          --------------------------------------

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