Deregistration Under Section 8(f) of the Investment Company Act of 1940

[File Number 811-23602] Summary: Applicant seeks an order declaring that it has ceased to be an investment company. On December 8, 2025, applicant made liquidating distributions to its shareholders based on net asset value. Expenses of $75,214.63 incurred in connection with the liquidation were paid by the applicant's investment advisor. Filing Date: The application was filed on March 26, 2026. Applicant's Address: 79 Madison Avenue, New York, New York 10016. Morgan Stanley Mortgage Securities Trust [File Number 811-04917] Summary: Applicant seeks an order declaring that it has ceased to be an investment company. The applicant has transferred its assets to Eaton Vance Mortgage Opportunities ETF, and on August 4, 2025, made a final distribution to its shareholders based on net asset value. Expenses of $607,600 incurred in connection with the reorganization were paid by the applicant'sinvestment adviser and the acquiring fund's investment adviser, and/or their affiliate. Filing Date: The application was filed on February 24, 2026. Applicant's Address: Morgan Stanley Mortgage Securities Trust c/o Morgan Stanley Investment Management Inc., 1585 Broadway, New York, New York 10036. Van Kampen Money Market Fund [File Number 811-02482] Summary: Applicant, seeks an order declaring that it has ceased to be an investment company. The applicant has transferred its assets to AIM Investment