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                                                                   EXHIBIT 10.16

                                 PROMISSORY NOTE

$250,000                                                        DECEMBER 6, 1999
                                                         ALBUQUERQUE, NEW MEXICO

         FOR VALUE RECEIVED, the receipt and sufficiency of which is
acknowledged, CELL ROBOTICS INTERNATIONAL, INC. ("Maker"), hereby promises to
pay to HUMAGEN FERTILITY DIAGNOSTICS INC., or order ("Holder"), at the address
designated on the signature page of this Note, or at such other place as Holder
may designate by written notice to Maker, the principal sum hereinbelow
described ("Principal Amount"), (together with interest thereon, as applicable)
in the manner and at the times provided and subject to the terms and conditions
described herein.

         1.       PRINCIPAL AMOUNT.

                  The Principal Amount means the sum of Two Hundred Fifty
Thousand Dollars ($250,000).

         2.       INTEREST.

                  No interest on the Principal Amount of this Note shall accrue
unless and until Maker exercises the option set forth in paragraph 4 below. If,
due to federal or state law, interest must be paid or will be imputed, then the
rate of interest shall be the lowest rate that may accrue without causing the
imputation of interest under the Internal Revenue Code. Interest, if it accrues,
shall be computed on the basis of a three hundred sixty (360) day year and a
thirty (30) day month.

         3.       PAYMENT OF PRINCIPAL AND INTEREST.

                  Subject to paragraphs 4 and 8, below, Maker shall pay the
Principal Amount and all accrued and unpaid interest on the Principal Amount (if
any) and all other indebtedness due under this Note six (6) months from the date
of this Note, on May 6, 2000.

         4.       OPTION TO MAKE MONTHLY PAYMENTS.

                  Maker shall have the option, on or before May 6, 2000, to
elect to pay the Principal Amount and all accrued and unpaid interest on the
Principal Amount (if any) in six (6) equal monthly installments or, if Maker is
unable to pay the Principal Amount and all accrued and unpaid interest in six
(6) equal monthly installments, any longer period agreed to by Maker and Holder.
Maker may exercise this option by giving written notice of such election to
Holder on or before May 6, 2000. From and after May 6, 2000, interest on the
unpaid balance of the Principal Amount from time-to-time remaining unpaid shall
accrue at the lowest rate that interest may accrue without causing the
imputation of interest under the Internal Revenue Code.

         5.       PREPAYMENTS.

                  Maker shall have the right to prepay any portion of the
Principal Amount without prepayment penalty or premium or discount.

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         6.       MANNER OF PAYMENTS/CREDITING OF PAYMENTS.

                  Payments of any amount required hereunder shall be made in
lawful money of the United States or in such other property as Holder, in its
sole and absolute discretion, may accept, without deduction or offset, and shall
be credited first against accrued but unpaid late charges, if any, thereafter
against accrued but unpaid interest, if any, and thereafter against the unpaid
balance of the Principal Amount.

         7.       INTEREST ON DELINQUENT PAYMENTS.

                  Any payment under this Note not paid when due shall bear
interest at the same rate and method as interest is charged on the Principal
Amount from the due date until paid.

         8.       ACCELERATION UPON DEFAULT.

                  At the option of Holder, all or any part of the indebtedness
of Maker hereunder shall immediately become due and payable, irrespective of any
agreed maturity date, upon the happening of any of the following events of
default:

                  (a) If Maker shall make an assignment for the benefit of
creditors;

                  (b) If a custodian, trustee, receiver, or agent is appointed
or takes possession of substantially all of the property of Maker;

                  (c) If Maker shall be adjudicated bankrupt or insolvent or
admit in writing Maker's inability to pay Maker's debts as they become due;

                  (d) If Maker shall apply for or consent to the appointment of
a custodian, trustee, receiver, intervenor, liquidator or agent of Maker, or
commence any proceeding related to Maker under any bankruptcy or reorganization
statute, or under any arrangement, insolvency, readjustment of debt,
dissolution, or liquidation law of any jurisdiction, whether now or hereafter in
effect;

                  (e) If any petition is filed against Maker under the
Bankruptcy Code and either (A) the Bankruptcy Court orders relief against Maker,
or (B) such petition is not dismissed by the Bankruptcy Court within thirty (30)
days of the date of filing; or

                  (f) If any attachment, execution, or other writ is levied on
substantially all of the assets of Maker and remains in effect for more than
five (5) days.

Maker shall notify Holder immediately if any event of default occurs.

         9.       NOTICE.

                  Any notice to either party under this Note shall be given by
personal delivery or by express mail, Federal Express, DHL or similar
airborne/overnight delivery service, or by mailing such notice by first class or
certified mail, return receipt requested, addressed to such party at the address
set forth below, or to such other address as either party from time to time may
designate by written notice. Notices delivered by overnight delivery service
shall be deemed delivered the next business day following consignment for such
delivery service. Mailed notices shall be deemed

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delivered and received in accordance with this provision three (3) days after
deposit in the United States mail.

         10.      USURY COMPLIANCE.

                  All agreements between Maker and Holder are expressly limited,
so that in no event or contingency whatsoever, whether by reason of the
consideration given with respect to this Note, the acceleration of maturity of
the unpaid Principal Amount and interest thereon, or otherwise, shall the amount
paid or agreed to be paid to Holder for the use, forbearance, or detention of
the indebtedness which is the subject of this Note exceed the highest lawful
rate permissible under the applicable usury laws. If, under any circumstances
whatsoever, fulfillment of any provision of this Note shall involve transcending
the highest interest rate permitted by law which a court of competent
jurisdiction deems applicable, then the obligations to be fulfilled shall be
reduced to such maximum rate, and if, under any circumstances whatsoever, Holder
shall ever receive as interest an amount that exceeds the highest lawful rate,
the amount that would be excessive interest shall be applied to the reduction of
the unpaid Principal Amount under this Note and not to the payment of interest,
or, if such excessive interest exceeds the unpaid balance of the Principal
Amount under this Note, such excess shall be refunded to maker. This provision
shall control every other provision of all agreements between Maker and Holder.

         11.      JURISDICTION; VENUE.

                  This Note shall be governed by, interpreted under and
construed and enforced in accordance with the laws of the State of New Mexico.
Any action to enforce payment of this Note shall be filed and heard solely in
Albuquerque, New Mexico.

                                       MAKER:

                                       Cell Robotics International, Inc.

                                       By: /s/ Ronald Lohrding
                                           -------------------------------------
                                           Ronald Lohrding, President & CEO
                                           2715 Broadbent Parkway, NE
                                           Albuquerque, New Mexico 87107

AGREEMENT BY HOLDER:

The undersigned agrees to the terms of this Promissory Note.

                                       Humagen Fertility Diagnostics, Inc.

                                       By: /s/ Debra Bryant
                                           -------------------------------------
                                           Debra Bryant (by facsimile)
                                           2345 Hunters Way, Unit 2
                                           Charlottesville, Virginia 22901

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     AMENDMENT TO THE DECEMBER 6, 1999 PROMISSORY NOTE BETWEEN CELL ROBOTICS

           INTERNATIONAL INC. AND HUMAGEN FERTILITY DIAGNOSTICS, INC.

----------

REPLACE PARAGRAPH 3 "PAYMENT OF PRINCIPAL AND INTEREST" WITH THE FOLLOWING NEW
PARAGRAPH:

3.       PAYMENT OF PRINCIPAL AND INTEREST

         Subject to paragraphs 4 and 8, below, Maker shall pay the Principal
Amount and all accrued and unpaid interest on the Principal Amount (if any) and
all other indebtedness due under this Note on January 15, 2001. Starting May 6,
2000, interest will accrue at a 6% (six-percent) annual rate.

IN PARAGRAPH 4 "OPTION TO MAKE MONTHLY PAYMENTS" REPLACE IN THREE PLACES THE
DATE MAY 6, 2000 WITH JANUARY 15, 2001

MAKER:                         Cell Robotics International, Inc.

                               By /s/ Ronald K. Lohrding
                                  ----------------------------------------------
                                  Ronald K. Lohrding, President and CEO
                                  2715 Broadbent Parkway NE
                                  Albuquerque, New Mexico 87107

AGREEMENT BY HOLDER:

The undersigned agrees to the amendment to the terms of the Note

                                       Humagen Fertility Diagnostics, Inc.

                               By /s/ Debra Bryant
                                  ----------------------------------------------
                                  Debra Bryant, President and CEO (by facsimile)
                                  2345 Hunters Way, Unit 2
                                  Charlottesville, Virginia 22901

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                                                                 EXHIBIT  4.4

                       ECHOSTAR COMMUNICATIONS CORPORATION
                   2001 NONEMPLOYEE DIRECTOR STOCK OPTION PLAN

I. Purpose

               The EchoStar Communications Corporation Nonemployee Director
Stock Option Plan (the "Plan") provides for the grant of Stock Options to
Nonemployee Directors of EchoStar Communications Corporation (the "Company") in
order to advance the interests of the Company through the motivation, attraction
and retention of its Nonemployee Directors.

II. Non-Incentive Stock Options

               The Stock Options granted under the Plan shall be nonstatutory
stock options ("NSOs") which are intended to be options that do not quality as
"incentive stock options" under Section 422 of the Internal Revenue Code of
1986, as amended (the "Code").

III. Administration

         A.       Committee. The Plan shall be administered by the Board of
                  Directors of the Company (the "Board") or by a committee of
                  two or more directors (the "Committee"). The Committee or the
                  Board, as the case may be, shall have full authority to
                  administer the Plan, including authority to interpret and
                  construe any provision of the Plan and any Stock Option
                  granted thereunder, and to adopt such rules and regulations
                  for administering the Plan as it may deem necessary in order
                  to comply with the requirements of the Code or in order to
                  conform to any regulations or to any change in any law or
                  regulation applicable thereto. The Board may reserve to itself
                  any of the authority granted to the Committee as set forth
                  herein, and it may perform and discharge all of the functions
                  and responsibilities of the Committee at any time that a duly
                  constituted Committee is not appointed and serving. All
                  references in this Plan to the "Committee" shall be deemed to
                  refer to the Board of Directors whenever the Board is
                  discharging the powers and responsibilities of the Committee.

         B.       Actions of Committee. All actions taken and all
                  interpretations and determinations made by the Committee in
                  good faith (including determinations of Fair Market Value)
                  shall be final and binding upon all Participants, the Company
                  and all other interested persons. No member of the Committee
                  shall be personally liable for any action, determination or
                  interpretation made in good faith with respect to the Plan,
                  and all members of the Committee shall, in addition to their
                  rights as directors, be fully protected by the Company with
                  respect to any such action, determination or interpretation.

IV. Definitions

         A.       "Stock Option." A Stock Option is the right granted under the
                  Plan to a Nonemployee Director to purchase, at such time or
                  times and at such price or prices ("Option Price") as are
                  determined pursuant to the Plan, the number of shares of
                  Common Stock set forth in the Plan.

         B.       "Common Stock." A share of Common Stock means a share of
                  authorized but unissued or reacquired Class A Common Stock
                  (par value $.01 per share) of the Company.

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         C.       "Fair Market Value." If the Common Stock is not traded
                  publicly, the Fair Market Value of a share of Common Stock on
                  any date shall be determined, in good faith, by the Board or
                  the Committee after such consultation with outside legal,
                  accounting and other experts as the Board or the Committee may
                  deem advisable, and the Board or the Committee shall maintain
                  a written record of its method of determining such value. If
                  the Common Stock is traded publicly, the Fair Market Value of
                  a share of Common Stock on any date shall be the average of
                  the representative closing bid and asked prices, as quoted by
                  the National Association of Securities Dealers through NASDAQ
                  (its automated system for reporting quotes), for the date in
                  question or, if the Common Stock is listed on the NASDAQ
                  National Market System or is listed on a national stock
                  exchange, the officially quoted closing price on NASDAQ or
                  such exchange, as the case may be, on the date in question.

         D.       "Nonemployee Director." A Nonemployee Director is a director
                  of the Company who is not also an employee of the Company.

         E.       "Participant." A participant is a Nonemployee Director to whom
                  a Stock Option is granted.

V. Option Grants

         A.       Number of Shares. Upon the initial election or appointment of
                  a Nonemployee Director to the Board, the Nonemployee Director
                  shall be granted Stock Options to purchase ten thousand
                  (10,000) shares of Common Stock (subject to adjustment
                  pursuant to Section VI.B. hereof) effective as of the last day
                  of the calendar quarter in which such person is elected or
                  appointed to the Board of Directors. The Committee in its
                  discretion shall have the ability to make further grants to
                  Participants, provided that no Nonemployee Director may be
                  awarded Stock Options to purchase more than ten thousand
                  (10,000) shares of Common Stock (subject to adjustment
                  pursuant to Section VI.B. hereof) in any twelve month period.

         B.       Price. The purchase price per share of Common Stock for the
                  shares to be purchased pursuant to the exercise of any Stock
                  Option shall be 100% of the Fair Market Value of a share of
                  Common Stock as of the last day of the calendar quarter in
                  which the Nonemployee Director receiving the Stock Option is
                  elected, appointed or reelected to the Board of Directors, as
                  the case may be.

         C.       Terms. Each Stock Option shall be evidence by a written
                  agreement ("Option Agreement") containing such terms and
                  provisions as the Committee may determine, subject to the
                  provisions of the Plan.

VI. Shares of Common Stock Subject to the Plan

         A.       Maximum Number. The maximum aggregate number of shares of
                  Common Stock that may be made subject to Stock Options shall
                  be 250,000 authorized but unissued shares. If any shares of
                  Common Stock subject to Stock Options are not purchased or
                  otherwise paid for before such Stock Options expire, such
                  shares may again be made subject to Stock Options.

         B.       Capital Changes. In the event any changes are made to the
                  shares of Common Stock (whether by reason or merger,
                  consolidation, reorganization, recapitalization, stock
                  dividend in excess of ten percent (10%) at any single time,
                  stock split, combination of shares, exchange of shares, change
                  in corporate structure or otherwise), appropriate adjustments
                  shall be made in: (i) the number of shares of Common Stock
                  theretofore made subject to Stock Options, and in the purchase
                  price of said shares; and (ii) the aggregate number of shares
                  which may be made subject to Stock Options. If any of the
                  foregoing adjustments shall result in a fractional share, the
                  fraction shall be disregarded, and the Company shall have no
                  obligation to make any cash or other payment with respect to
                  such a fractional share.

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VII. Exercise of Stock Options

         A.       Time of Exercise. Subject to the provisions of the Plan, the
                  Committee, in its discretion, shall determine the time when a
                  Stock Option, or a portion of a Stock Option, shall become
                  exercisable, and the time when a Stock Option, or a portion of
                  a Stock Option, shall expire. Such time or times shall be set
                  forth in the Option Agreement evidencing such Stock Option. A
                  Stock Option shall expire, to the extent not exercised, no
                  later than five years after the date on which it was granted.
                  The Committee may accelerate the vesting of any Participant's
                  Stock Option by giving written notice to the Participant. Upon
                  receipt of such notice, the Participant and the Company shall
                  amend the Option Agreement to reflect the new vesting
                  schedule. The acceleration of the exercise period of a Stock
                  Option shall not affect the expiration date of that Stock
                  Option.

         B.       Six-Month Holding Period. The shares of Common Stock issued
                  upon the exercise of a Stock Option may not be sold or
                  otherwise disposed of within six months after the date of the
                  grant of the Stock Option.

         C.       Exchange of Outstanding Stock. The Committee, in its sole
                  discretion, may permit a Participant to surrender to the
                  Company shares of Common Stock previously acquired by the
                  Participant as part or full payment for the exercise of a
                  Stock Option. Such surrendered shares shall be valued at their
                  Fair Market Value on the date of exercise.

         D.       Use of Promissory Note. The Committee may, in its sole
                  discretion, impose terms and conditions, including conditions
                  relating to the manner and timing of payments, on the exercise
                  of Stock Options. Such terms and conditions may include, but
                  are not limited to, permitting a Participant to deliver to the
                  Company his promissory note as full or partial payment for the
                  exercise of a Stock Option.

         E.       Stock Restriction Agreement. The Committee may provide that
                  shares of Common Stock issuable upon the exercise of a Stock
                  Option shall, under certain conditions, be subject to
                  restrictions whereby the Company has a right of first refusal
                  with respect to such shares or a right or obligation to
                  repurchase all or a portion of such shares, which restrictions
                  may survive a Participant's term as a director of the Company.
                  The acceleration of time or times at which a Stock Option
                  becomes exercisable may be conditioned upon the Participant's
                  agreement to such restrictions.

         F.       Termination of Director Status Before Exercise. If a
                  Participant's term as a director of the Company shall
                  terminate for any reason other than the Participant's
                  disability, any Stock Option then held by the Participant, to
                  the extent then exercisable under the applicable Option
                  Agreement(s), shall remain exercisable after the termination
                  of his director status for a period of three months (but in no
                  event beyond five years from the date of grant of the Stock
                  Option). If the Participant's director status is terminated
                  because the Participant is disabled within the meaning of
                  Section 22(e)(3) of the Code, any Stock Option then held by
                  the Participant, to the extent then exercisable under the
                  applicable Option Agreement(s), shall remain exercisable after
                  the termination of his employment for a period of twelve
                  months (but in no event beyond five years from the date of
                  grant of the Stock Option). If the Stock Option is not
                  exercised during the applicable period, it shall be deemed to
                  have been forfeited and of no further force or effect.

         G.       Disposition of Forfeited Stock Options. Any shares of Common
                  Stock subject to Stock Options forfeited by a Participant
                  shall not thereafter be eligible for purchase by Participant
                  but may be made subject to Stock Options granted to other
                  Participants.

VIII. No Effect Upon Stockholder Rights

               Nothing in this Plan shall interfere in any way with the right of
the stockholders of the Company to remove the Participant from the Board
pursuant to the Nevada General Corporation Law and the Company's Certificate of
Incorporation and Bylaws.

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IX. No Rights as a Stockholder

               A Participant shall have no rights as a stockholder with respect
to any shares of Common Stock subject to a Stock Option. Except as provided in
Section VI.B., no adjustment shall be made in the number of shares of Commons
Stock issued to a Participant, or in any other rights of the Participant upon
exercise of a Stock Option by reason of any dividend, distribution or other
right granted to stockholders for which the record date is prior to the date of
exercise of the Participant's Stock Option.

X. Assignability

               No Stock Option granted under this Plan, nor any other rights
acquired by a Participant under this Plan, shall be assignable or transferable
by a Participant, other than by will or the laws of descent and distribution or
pursuant to a qualified domestic relations order as defined by the Code, Title I
of the Employee Retirement Income Security Act ("ERISA"), or the rules
thereunder. In the event of the Participant's death, the Stock Option may be
exercised by the Personal Representative of the Participant's estate or, if no
Personal Representative has been appointed, by the successor or successors in
interest determined under the Participant's will or under the applicable laws of
descent and distribution.

XI. Merger or Liquidation of the Company

               If the Company or its stockholders enter into an agreement to
dispose of all, or substantially all, of the assets or outstanding capital stock
of the Company by means of a sale or liquidation, or a merger or reorganization
in which the Company is not the surviving corporation, all Stock Options
outstanding under the Plan as of the day before the consummation of such sale,
liquidation, merger or reorganization, to the extent not exercised, shall for
all purposes under this Plan become exercisable in full as of such date even
though the dates of exercise established pursuant to Section VII.A. have not yet
occurred, unless the Board shall have prescribed other terms and conditions to
the exercise of the Stock Options, or otherwise modified the Stock Options.

XII. Amendment

               The Board may, from time to time, alter, amend, suspend or
discontinue the Plan, including where applicable, any modifications or
amendments as it shall deem advisable in order to conform to any regulation or
to any change in any law or regulation applicable thereto; provided, however,
that no such action shall adversely affect the rights and obligations with
respect to Stock Options at any time outstanding under the Plan; and provided
further that no such action shall, without the approval for the stockholders of
the Company, (i) materially increase the maximum number of shares of Common
Stock that may be made subject to Stock Options (unless necessary to effect the
adjustments required by Section VI.B.), or (ii) materially modify the
requirements as to eligibility for participation in the Plan. Subject to the
foregoing, the provisions of Article V of the Plan which set forth the number of
shares of Common Stock for which Stock Options shall be granted, the timing of
Stock Option grants and the Stock Option exercise price shall not be amended
more than once every six (6) months other than to comport with changes in the
Code, ERISA, or the rules thereunder.

XIII. Registration of Optioned Shares

               The Stock Options shall not be exercisable unless the purchase of
such optioned shares is pursuant to an applicable effective registration
statement under the Securities Act of 1933, as amended (the "Act"), or unless,
in the opinion of counsel to the Company, the proposed purchase of such optioned
shares would be exempt from the registration requirements of the Act and from
the registration or qualification requirements of applicable state securities
laws.

XIV. Brokerage Arrangements

               The Committee, in its discretion, may enter into arrangements
with one or more banks, brokers or other financial institutions to facilitate
the disposition of share secured upon exercise of Stock Options including,
without limitation, arrangements for the simultaneous exercise of Stock Options
and sale of the shares acquired upon such exercise.

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XV. Nonexclusivity of the Plan

               Neither the adoption of the Plan by the Board nor the submission
of the Plan to stockholders of the Company for approval shall be construed as
creating any limitations on the power of authority of the Board to adopt such
other or additional compensation arrangements of whatever nature as the Board
may deem necessary or desirable or preclude or limit the continuation of any
other plan, practice or arrangement for the payment of compensation or fringe
benefits to Nonemployee Directors, which the Company now has lawfully put into
effect.

XVI. Effective Date

               This Plan was adopted by the Board of Directors and became
effective on June 12, 2001.

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