Natural killer cell profile of two random-bred strains of athymic rats.

We have demonstrated that Rowett and NIH strains of random-bred athymic and euthymic rats exhibited significant levels of natural killer (NK) cell cytotoxicity against various murine and human tumor cell lines. Rats of both strains displayed high NK cell cytotoxicity in peritoneal exudate, peripheral blood and spleen, and lower activities in lung and liver. No activity was detected in bone marrow. In general, athymic rats manifested higher levels of NK cell cytotoxicity and higher tumor-binding potential than euthymic animals. NK cell cytotoxicity was subject to late maturation and did not decline with age. Cytotoxic cells were not removed by carbonyl iron treatment and resided in both adherent and nonadherent fraction after nylon-wool filtration, with the majority of the cytotoxicity in the latter fraction. Percoll gradient separation studies indicated that, in general, the cytotoxic cells were of large granular lymphocyte morphology and of low density. Evaluation of tumor-binding capacity and cytotoxic profile of large granular lymphocytes has shown that the majority of these cells exhibited cytotoxic potential, but only a minority of them displayed tumor-binding capacity.

Histologic classification as an indication of therapeutic response in malignant lymphoma of dogs.

In retrospective evaluation of treatment of canine malignant lymphoma, 12 of 13 dogs that had received doxorubicin alone or in combination with dacarbazine attained complete remission. Doxorubicin had been given alone, with combination chemotherapy being used only when complete remission could not be achieved and maintained with doxorubicin. The response to single or combined chemotherapy was correlated with histologic cell type of the malignant lymphoma. Histiocytic cell types did not respond to doxorubicin alone, but lymphoblastic types did respond. Combination chemotherapy was effective against histiocytic types. A mixed-cell type, which was initially responsive to doxorubicin alone, but not responsive after relapse, was observed to be histiocytic on rebiopsy.

Rescue by peripheral blood mononuclear cells in dogs from bone marrow failure after total-body irradiation.

In order to determine the minimum dose of buffy coat cells necessary to achieve hematopoietic rescue following supralethal irradiation, mongrel dogs under general anesthesia were subjected to leukacytapheresis using three different techniques of cell separation. The buffy coats were frozen with dimethylsulfoxide and stored at -196 degrees C until transfused. Sixteen dogs were irradiated with 800 rads and were supported with antibiotics and transfusions of irradiated homologous blood. They were transfused with the frozen and thawed buffy coat cells, and, if they survived, they were followed for 100 days, sacrificed, and their tissues studied. The mean yield of mononuclear cells during leukocytapheresis ranged from 4.1 +/- 2.0 X 10(9) (mean +/- SD) to 6.0 +/- 4.0 X 10(9) for the three leukacytapheresis methods; one technique was not as satisfactory as the other two. Six of the 16 dogs fully recovered with evidence of marrow rescue; however, only one had a dose of mononuclear cells less than 11.1 X 10(9). These data indicate that seven to 17 leukacytapheresis procedures would be required to reconstitute a 70 kilogram patient. These preliminary findings suggest that, because the yields of transplantable cells with current technology are not adequate, the transplantation potential of buffy coat cells exposed to mobilizing agents should be evaluated.

Late effects of 50 MeV d leads to Be neutron and cobalt-60 irradiation of rhesus monkey cervical spinal cord.

The cervical spinal cords of 30 rhesus monkeys were irradiated with 50 MeV d leads to Be neutrons or 60Co gamma rays to evaluate the dose-response relationships for radiation myelopathy. Three groups were treated with 50 MeV d leads to Be neutrons using dosage schedules of 1300 rad n gamma (Group I), 1425 rad n gamma (Group II), or 1550 rad n gamma (Group III) in nine fractions over 29 days. Three groups were irradiated with 60Co gamma rays using dosage schedules of 4620 rad (Group IV), 5390 rad (Group V), or 5940 rad (Group VI) in 22 fractions over 29 days. A significant dose-response relationship was observed for the groups treated with neutrons. Whereas none of the monkeys in Group I showed clinical evidence of neurologic dysfunction, all five animals in Group III became paralyzed. One animal in Group II developed transient neck stiffness and mild unilateral leg paresis. No definitive signs of neurologic injury were seen in any of the animals irradiated with 60Co. The histopathologic changes correlated well with the clinical observations. All of the animals in Group III exhibited moderate to severe malacia and demyelination of the white matter of the cervical spinal cord. The histologic data indicated that the RBE for five times weekly fractionation (approximately 270 rad 60Co fractions) was in the range of 4.2 to 4.6, since the malacia and demyelination in the spinal cords irradiated with 5940 rad of 60Co gamma-rays were greater than that observed in the spinal cords irradiated with 1300 rad n gamma of neutrons but less than the changes in those irradiated with 1425 rad n gamma of neutrons.

Formation and disposition of 7-hydroxymethotrexate in rabbits.

The metabolism of methotrexate in rabbits was investigated following 6 hr of infusion with [3',5',7-(3)H]methotrexate (50 mg/kg). Methotrexate and its metabolites were analyzed by an enzyme kinetic method, reverse phase high-performance liquid chromatography, and scintillation counting of radioactivity. 7-Hydroxymethotrexate was found to be a major metabolite in plasma, urine, bile and various tissues of rabbits. Cumulative production of 7-hydroxymethotrexate during the first 6 hr was 31.8% of the total dose. The peak 7-hydroxymethotrexate concentration in plasma was reached at the end of the infusion, and this concentration was higher than the methotrexate concentration. The plasma clearance of 7-hydroxymethotrexate was biphasic in nature and slower than that of methotrexate. The highest methotrexate concentration was found in kidney after 6 hr. This concentration was found to be 7.2 times greater than that in plasma. A higher ratio of 7-hydroxymethotrexate/methotrexate was found in liver, small intestine, kidney and testis when compared to plasma. Lung and kidney showed significant conversion of methotrexate to 7-hydroxymethotrexate in vitro, as did the liver.

50-MEVd leads to Be neutrons: a comparison of normal tissue tolerance in animals with clinical observations in patients.

The acute and late effects of 50 MeV neutrons were investigated by irradiating a variety of organ systems in large animals using dosage schedules similar to those that have been employed clinically. The RBEs for acute effects in pig skin and rhesus monkey oral mucosa were significantly less than the RBEs for late effects. This observation has also been noticed clinically. The RBEs for late effects in pig skin, rhesus monkey oral mucosa, and rhesus monkey kidney were consistent with values of 3.1 to 3.4 relative to approximately 200 rad 60Co fractions and approximately 2.2 to 2.6 relative to approximately 400 rad 60Co fractions. The RBE for radiation myelitis was significantly greater (4.2 to 4.6 relative to approximately 270 rad 60Co fractions). The tolerance doses for 50 MeVd leads to Be neutrons in large animals were approximately 2200 radn gamma/61/2 weeks for skin contraction, approximately 2100 radn gamma/61/2 weeks for oromucosal necrosis, approximately 1300 radn gamma/41/2 weeks for radiation myelitis, and approximately 960 radn gamma/4 weeks for radiation nephritis. These values correlate well with clinical observations at TAMVEC, since the majority of soft tissue complications in patients occurred following tissue doses in excess of 2100 radn gamma.

Transplantable tumor cell line derived from a spontaneous fibrosarcoma in a gerbil.

A cultured tumor cell line was derived from a spontaneous fibrosarcoma in a gerbil (Meriones unguiculatus). The cell line consistently produced large tumors with a high incidence of metastases in gerbils of all ages and in both sexes.

Malignant fibrous histiocytoma in dogs and cats.

Five soft tissue tumors of varied morphology in dogs and cats were classified as malignant fibrous histiocytomas on the basis of their histologic composition. All were composed of varying mixtures of histiocytes and fibroblasts and three contained large multinucleated cells. This giant cell variant of malignant fibrous histiocytoma was seen only in cats. These tumors are comparable to those described in man as malignant fibrous histiocytoma on the basis of the malignant histiocyte and its varied morphology and function.

A comparison of the effects of 50 MeVd leads to be neutron and cobalt-60 irradiation of the kidneys of rhesus monkeys.

Twenty rhesus monkeys had one kidney irradiated (after undergoing unilateral nephrectomies) with one of four doses: 960 or 1080 rads of 50 MeVd leads to Be neutrons, or 2350 or 2700 rads of 60Co. Whereas animals treated with the lower dose of neutrons or 60Co are alive with relatively normal renal function, those treated with the higher dose of neutrons died of radiation nephritis. Animals treated with the higher dose of 60Co developed radiation nephritis but survived. The physiological and histopathological changes of radiation nephritis secondary to neutron irradiation are not qualitatively different from those reported for radiation nephritis secondary to photon irradiation.

Acute and late effects of 16- and 50-MeVd leads to Be neutrons on the oral mucosa of rhesus monkeys.

Twenty-five rhesus monkeys were randomly assigned to one of five treatment schedules: 1. control group, no irradiation, 2. 60Co five times weekly, 3. 60Co twice weekly, 4. 16-MeVd leads to Be neutrons twice weekly, and 5. 50-MeVd leads to Be neutrons twice weekly. Although the acute reactions were similar in the four irradiated groups, the late sequelae were more severe in the animals irradiated twice weekly with 60Co or neutrons. All of the animals irradiated with 60Co twice weekly or with 16 MeVd leads to Be neutrons exhibited oromucosal necrosis, whereas none of those irradiated five times weekly with 60Co did. The difference in the effect of photon fractionation on early and late radiation sequelae may be related to different patterns of redistribution of surviving cells through the division cycle in tissues responsible for early and late damage.