Effect of dibutyryl cyclic adenosine 5'-monophosphate on protein synthesis in L5178Y cells after hyperthermia

Protein synthesis in the L5178Y mouse lymphoma cell line was stimulated after short-duration heat shock by the addition of dibutyryl cyclic AMP. The stimulation was concentration-dependent (range, 0.01-1.0 mM) and was enhanced by preincubation of the cells in the presence of the cyclic nucleotide before the heat shock. Actinomycin, which blocks the recovery of protein synthesis activity after heat shock, did not block the cyclic AMP stimulation.

Canine transmissible venereal sarcoma: electron microscopic changes with time after transplantation

The structure of canine transmissible venereal sarcoma (CTVS) has been examined from 14 to 71 days after implantation. During early growth, the tumour appears to be composed primarily of loosely arranged, round cells and a few fibroblast-like cells. As the tumour mass increases, the round cells become tightly packed with highly interdigitating plasma membranes. The number of irregularly shaped round cells and fibroblast-like cells increases with increasing tumour mass. Collagen and reticular fibres can be found in early tumours, frequently in association with the round cells, and in regions devoid of fibroblast-like cells. During tumour regression, cellular degradation is evident in fibroblast-like and irregularly shaped cells as well as round cells. The data suggest that transformation may occur in the course of tumour growth, causing morphological change from round to fibroblast-like cells, and that CTVS is an undifferentiated round-cell sarcoma capable of differentiation in a fibroblastic direction. Also present, primarily in tumour cells from newborn dogs, are cytoplasmic lamellar arrays and crystalline virus-like structures, both previously described in other forms of tumor cells.

Spontaneous eosinophil-erythrocyte rosette formation

Eosinophils of dogs form rosettes with washed human erythrocytes in a manner very similar to that of thymus-derived (T) lymphocytes. Identification of rosette-forming eosinophils was made by both light and electron microscopic study of eosinophils infiltrating into the canine transmissible venereal sarcoma.

Amino acid metabolism of myeloma cells in culture

The growth of myeloma cells in Leibovitz medium supplemented with 20% serum was limited by the depletion of glutamine. A simple modification of the Leibovitz medium by increasing the concentrations of glutamine, lysine, isoleucine, leucine, sodium pyruvate, galactose, and vitamins resulted in over 100% increase in cell growth yield. The total myeloma protein produced by the cells was increased by approximately 90% in modified Leibovitz media. Analysis of spent culture media for 19 amino acids showed that the concentrations of 8 amino acids were reduced; those of 5 amino acids were increased and the other 6 did not change significantly.

Rosette formation of human erythrocytes on canine transmissible venereal sarcoma cells

Human erythrocytes have been shown to form spontaneous rosettes on nonlymphoid canine transmissible venereal sarcoma cells. The tumor cell would attach on glass surface, and morphologic studies by both electron microscopy and light microscopy on Giemsa-stained rosetting tumor cells showed that they could be differentiated from the rosetting T lymphocytes in the tumor.

Quantitative study of lymphoreticular infiltration into canine transmissible venereal sarcoma

Lymphoreticular cell (LRC) infiltration into tumour masses at different stages of growth after transplantation was studied in canine transmissible venereal sarcoma (CTVS). The percent viable LRC of total viable cells in tumour suspensions shows an inverse correlation with the logs of tumour mass of adult dogs (R = -0.475, phi = 28, P less than 0.01), which suggests that the degree of LRC infiltration is a measure of the host immune response. However, an estimate of the surface area (S.A.) of the tumour rather well perfused with blood elements based on the formula S.A. = 5.43 (tumour mass in g)2/3 showed that the LRC mass present in a tumour was a function of its surface area. Thus, the inverse correlation of the percent viable LRC's in a viable tumour cell suspension to the log of the CTVS mass might not necessarily indicate that the infiltrated LRC's were active as immune effector cells. The correlation does show that, as the CTVS size increases, the volume of the necrotic center increases more rapidly than the volume perfused with blood and, therefore, the percent viable LRC's in CTVS decreases with CTVS size increase.

Effects of prostaglandins E1, E2, and F2alpha on the growth of leukaemia cells in culture

Prostaglandins E1, E2, and F2alpha (PGE1, PGE2, and PGF2alpha) were shown to inhibit the growth of mouse leukaemia lymphoblasts L5178Y in culture. The effects of PGE1 and PGE2 were greater than that of PGF2alpha. PGE1 and PGE2, at the concentration of 100 mug per ml showed significant inhibitory effects on the rates of incorporation of tritiated thymidine, uridine and leucine. At concentrations of 50 and 25 mug per ml, there was significant inhibition of thymidine and uridine incorporation, but not of leucine, PGF2alpha showed significant inhibition of thymidine and uridine incorporation but not leucine incorporation, in all 3 concentrations studied (100, 50, and 25 mug/ml). The ability of the cells to form colonies in soft agar was significantly inhibited by PGE1 and PGE2 at concentrations as low as 1–8 mug/ml. For F2alpha, however, a concentration as high as 56mug/ml was required to show inhibitory effect, but at 1–8 mug/ml it was found to be stimulatory.

Stimulatory effect of 3', 5'-adenosine monophosphate on protein synthesis in heat-shocked murine leukemia lymphoblasts

The murine leukemia lymphoblast line L5178Y was tested for its early molecular response to the presence of dibutyryl cyclic AMP. Protein synthesis was reversibly inhibited by short durations of hyperthermia, and against this reduced background of protein synthetic activity, early leucine incorporation (30-120 min) was markedly and consistently stimulated by the presence of the cyclic nucleotide. The effect became one of inhibition with extended times of incubation (longer than 120 min).

Inhibitory effects of phytohemagglutinin on growth of leukemia lymphoblasts L5178Y in vitro and in vivo

Phytohemagglutinin (PHA) inhibited the growth of mouse leukemia lymphoblasts L5178Y in culture. RNA synthesis was repressed significantly within the first hour, and the rates of DNA and protein synthesis were significantly decreased within the second hour; maximum inhibition occurred after 24 hours. The ability of the cells to form colonies in soft agar was limited to a greater extent at much lower PHA concentrations. The cells lost their tumorigenicity in syngeneic DBA/2 mice after 4 hours of PHA treatment, when the viability was not appreciably decreased. The cultures of a PHA-resistant strain derived from a resistant colony cloned from the PHA-containing soft agar plate showed increased resistance toward PHA. A fourfold increase in PHA concentration was needed for the same rate of inhibition of the original cell line to be attained.

Canine cyclic haematopoiesis: marrow transplantation between littermates

Dogs affected with cyclic haematopoiesis (CH) and experiencing recurrent 12-day cycles of neutropenia were supralethally irradiated and transplanted with marrow from their normal littermates. Following transplantation of the normal marrow, dogs with CH experienced no further cycles of neutropenia. Platelet and reticulocyte numbers also ceased to fluctuate cyclically in these dogs. The marrows of dogs with CH were transplanted into unaffected supralethally irradiated littermates. Prompt engraftment occurred in the recipient dogs with subsequent cyclic rises and falls of the numbers of platelets, reticulocytes and neutrophils. In the post-transplant period, immunosuppressant drugs were not used in three of the recipients and the fourth received only a single 5 mg dose of methotrexate.

Canine cyclic neutropenia: Erythropoietin and platelet cycles after bone marrow transplantation

The marrow of a dog affected with cyclic neutropenia (CN) was transplanted into an unaffected supralethally irradiated litermate. Prompt engraftment occurred, and cyclic rises and falls in numbers of platelets, reticulocytes, and granulocytes were noted in the recipient soon after engraftment. Prior to transplantation and under hypoxic conditions, the donor had serum erythropoietin (ESF) peak levels at 11-12-day intervals. Following transplatation and under hypoxic conditions, cyclic peaks of ESF occurred in the transplanted dog.

Inhibitory effects of anticellular antibodies on colony formation of mouse leukemia L5178YR cells in soft agar

Heat-inactivated antiserum in the absence of complement inhibits colony formation of mouse leukemia L5178YR cells in soft agar. Cells derived from resistant clones in these plates showed the same sensitivity to antiserum as the parent population. Agglutination of the cells was prevented by placing the antiserum dilutions over the cell-containing agar layer. This clearly indicates that cell agglutination by antiserum is not necessarily the essential cause of growth inhibition.