In addition to recently defined criteria, genetically determined inheritable traits and epidemiologic characteristics (male gender) should be taken into account when assessing PFO and related cerebrovascular risk profile. A newly defined threshold in TCCD MB count is suggested to discriminate shunts related to stroke and TIA from innocent ones.

The heterotransplantability of 22 human cell lines was studied by intravenous inoculation into newborn rats. The cell lines included nine derived from Burkitt (African) lymphoma, one from reticulum cell sarcoma, ten from leukemia, one from infectious mononucleosis and one from a normal lymph node. All were cultivated in vitro as suspension cultures. The usual inoculum for each rat was 50 or 10 or 2 million cells. At the two higher doses four of the Burkitt tumor lines (EB‐2, EB‐3, SL1, B35M), three of the leukemia lines (SK‐L2, SK‐L5, SK‐L9), the infectious mononucleosis line C566, and the cell line from a normal lymph node (SK‐LN1) propagated and caused lethal lesions in approximately half of the recipients. Inocula containing 2 million cells of lines EB‐2 or SL1 grew in a few rats but none of the other cell lines grew at this dose. Brain, eye and kidney were the most common sites of growth. Lung, adrenal, liver, and interscapular fat pad were less frequently involved, and other tissues rarely. The results are discussed in relation to the biologic significance of heterotransplantability and differences in the tissue distribution of implants of these and previously studied human cell lines.

Rats were inoculated intravenously with living J‐111 cells on the day of birth to make them immunologically tolerant to human cell antigens. The subcutaneous transplantability of 17 human cell lines was tested in these rats at age 1‐3 weeks. Eight of the cell lines were derived from Burkitt's lymphomas (EB 1, EB 2, EB 3, Kudi, Jijoye, Ogun, Raji, SL‐1) one from reticulum cell sarcoma (SK‐RCS1), 6 from leukemia (SK‐L2 SK‐L4, SK‐L6, SK‐L7, SK‐L9, SK‐L10), one from a normal lymph node (SK‐LN1), and one from infectious mononucleosis (C566). Fourteen of these cell lines, including the 2 lines derived from nonmalignant sources, grew as subcutaneous nodules in some of the recipients. The most frequent and largest nodules were produced by lines EB 2 and EB 3 from Burkitt tumors, lines SK‐L2 and SK‐L4 from acute leukemia, and the 2 lines of nonmalignant origin (SKLN1 and C566). More of the cell lines grew subcutaneously in these immunologically tolerant rats than grew on intravenous injection into newborn rats in a previously reported study.

Suspensions of human cancer cells were prepared from surgical specimens or effusions and were transplanted into rats by 2 techniques. Thirty specimens were transplanted by intravenous inoculation of single cell suspensions containing one to 5 million cells before the rats were 24 hours old. Five of these specimens produced tumor nodules in lungs and sometimes in other organs. One hundred twenty‐six specimens were transplanted by subcutaneous or intraperitoneal inoculation of a crude suspension of cells and tissue fragments into young rats which had been made tolerant by intravenous injection of human tissue‐cultured cells when they were newborn. Twenty‐six of these produced subcutaneous or intraperitoneal nodules. All takes were confirmed by histologic study.