Biomedical subjects
Publications and source records attributed to L Sachs.
The apparent association constant (K-a) of cAMP to the binding proteins from resistant and nonresistant cells was 7.4 times 10-7 M-1 and 8.2 times 10-7 M-1, respectively, and the specific activity of cAMP BINDING TO THESE PROTEINS WAS SIMILAR FOR BOTH TYPES OF CELLS.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
D+ but not D- myeloid leukemic cells can be induced by the appropriate conditioned medium or by serum from endotoxin treated mice, to undergo cell migration in agar, cell attachment to the surface of a Petri dish and differentiation to mature macrophages and granulocytes. Inhibition of cell multiplication by cytosine arabinoside, hydroxyurea, mitomycin C, thymidine, 5-bromodeoxyuridine, 5-iododeoxyuridine, 5-fluorodeoxyuridine or actinomycin D, but not by vinblastine or cycloheximide, induced cell migration, cell attachment to the Petri dish and the formation of macrophages in D+ cells. There was no induction of cell migration or formation of macrophages and a much lower induction of cell attachment in D- cells. The induction of these changes in D+ cells required protein synthesis and the inhibitors showed the same toxicity for D+ and D- cells. The results indicate, that the inhibitors induced specific surface membrane changes in D+ but not in D- cells.
There are three types of myeloid leukemic cells, IR+D, IR+D- and IR-D-. IR+D+ cells were induced to differentiate to granulocytes in mass culture in liquid medium by conditioned medium (CM) from cultures of lungs from mice injected with endotoxin. About 90% of the leukemic cells were induced to differentiate, 50% to mature granulocytes and 40% to intermediate stages. An efficient induction of granulocyte differentiation was also obtained with CM from primary cultures of rat embryo or human spleen and there was a lower activity with CM from various other sources. IR+D- cells were induced to differentiate to about 20% cells with intermediate stages but not to mature granulocytes; IR-D- cells could not be induced to differentiate to intermediate or mature stages. IR+D+ cells were induced to form intermediate stages of granulocyte differentiation, to phagocytose and to attach to the surface of the Petri dish, three days after incubation with CM. Optimum induction of mature granulocytes required six more days incubation with CM. Mature granulocytes induced from leukemic cells showed cytochemical properties and a morphology in the electron microscope similar to that of normal mature granulocytes. These induced granulocytes did not form leukemiac in animals or colonies in agar. The granulocytes induced from the myeloid leukemic cells, therefore, behaved like normal mature granulocytes.
Glucose utilization, energy metabolism and associated membrane changes, have been studied in D+ myeloid leukemic cells that can be induced to undergo cell differentiation to mature granulocytes by incubation with the appropriate conditioned medium (CM) and in D- myeloid leukemic cells that cannot be induced to differentiate to mature cells. Before incubation with CM, glycolysis and the glycolytic production of ATP were lower and the activity of the pentose cycle was higher in D+ than in D- cells. ATP depletion induced a higher degree of agglutination by concanavalin A in D- than in D+ cells, indicating a difference in their surface membrane. There were no detectable differences in the transport of glucose and the synthesis of sterols and fatty acids. After incubation with CM, the D+ cells, like normal granulocytes, showed a higher glycolysis, produced their ATP more through glycolysis than oxidative phosphorylation, became less dependent on the exogenous supply of glucose and oxygen and had a lower rate of sterol and fatty acid synthesis. The differentiating D+ cells also showed a change in their surface membrane resulting in an increased agglutinability without a change in ATP content and a stimulation of the pentose cycle by concanavalin A. These properties, which were not acquired by D- cells, were found before most of the D+ cells had differentiated to mature granulocytes. The data indicate, that the block in the ability of the D- cells to differentiate and the acquistion of the metabolic properties of normal granulocytes by differentiating D+ cells, were associated with differences in the organization of the cell surface membrane.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Lymphocytes were isolated from the peripheral blood of 21 normal persons and 66 patients with chronic lymphocytic leukemia (CLL), CLL in remission, Hodgkin's disease, Hodgkin's disease in remission, various other tumors, or cardiovascular diseases; The lymphocytes were studied for cap formation and agglutinability by concanavalin A, and for cell attachment to the surface of a petri dish. The frequency of cap formation was lowest in lymphocytes from patients with untreated Hodgkin's disease (2.1 plus or minus 0.8%), next lowest in lymphocytes from patients with CLL who were or were not under treatment (7,0 plus or minus 1;3%), and also low in Hodgkin's disease in remission (10.6 plus or minus 1.2%). The frequencies of cap formation by lymphocytes from patients with various other tumors (19.1 plus or minus 2.5%), with CLL in remission (24.0 plus or minus 0.9%), and with nonmalignant diseases (26.0 plus or minus 2.2%) were more similar to the frequency found in lymphocytes from normal persons (29.4 plus or minus 2.8%). Lymphocytes from all the patients, including those in remission, showed a higher degree of agglutinability by concanavalin A than lymphocytes from normal persons. Cell attachment to a petri dish was highest with CLL, next highest with CLL in remission, and low for normal persons and all the other patients. Lymphocytes from normal persons that consisted predominantly of thymus-derived cells gave similar results to isolated normal bone marrow-derived cells. The results indicate that there were different changes in the surface membrane of lymphocytes from patients with CLL, CLL in remission, Hodgkin's disease, and Hodgkin's disease in remission, and that the patients in clinical remission still showed abnormalities in their lymphocytes.
The cell-to-cell binding induced by concanavalin A (Con A) and the lectins from wheatgerm, soybean, and waxbean has been analyzed by measuring the ability of single cells to bind to lectin-coated cells immobilized on nylon fibers. The cells used were lymphoma, myeloid leukemia, and normal fibroblast cells. With all lectins, cell-to-cell binding was inhibited if both cells were prefixed with glutaraldehyde. However, in most cases cell-to-cell binding was enhanced when only the lectin-coated cell was prefixed. With normal fibroblasts, treatment of either one or both cells with trypsin enhanced the cell-to-cell binding induced by Con A and the wheatgerm lectin. Neuraminidase, which increases the number of receptors for soybean agglutinin, increased cell-to-cell binding only if both cells were treated. Although cell-to-cell binding induced by the lectins from soybean and wheatgerm could be partially reversed by the appropriate competitive saccharide inhibitor, binding induced by Con A could not be reversed. The experiments indicate that cell-to-cell binding induced by a lectin can be prevented by an insufficient density of receptors for the lectin, insufficient receptor mobility, or induced clustering of receptors. These effects can explain the differences in cell-to-cell binding and agglutination observed with different cell types and lectins. They also suggest that cell-to-cell binding induced by different lectins with a variety of cell types is initiated by a mechanism involving the alignment of complementary receptors on the colliding cells for the formation of multiple cell-to-lectin-to-cell bridges.
The ability of cells to bind to nylon fibers coated with lectin molecules interspaced with varying numbers of albumin molecules has been analyzed. The cells used were lymphoma cells, normal lymphocytes, myeloid leukemia cells, and normal and transformed fibroblasts, and the fibers were coated with different densities of concanavalin A or the lectins from soybean or wheat germ. Cells fixed with glutaraldehyde did not bind to lectin-coated fibers. The number of cells bound to fibers could be increased by increasing the density of lectin molecules on the fiber, the density of specific receptors on the cell, or the mobility of the receptors. It is suggested that binding of cells to fibers involves alignment and binding of specific cell surface receptors with lectin molecules immobilized on the fibers, and that this alignment requires short-range rapid lateral mobility (RLM) of the receptors. The titration of cell binding to fibers coated with different densities of lectin and albumin has been used to measure the relative RLM of unoccupied cell surface receptors for the lectin. The results indicate a relationship of RLM to lectin-induced cell-to-cell binding. The RLM or receptors for concanavalin A (Con A) was generally found to be higher than that of receptors for the lectins from wheat germ or soybean. Receptor RLM could be decreased by use of metabolic inhibitors or by lowering the temperature. Receptors for Con A had a lower RLM on normal fibroblasts than on SV40-transformed fibroblasts, and trypsinization of normal fibroblasts increased Con A receptor RLM. Normal lymphocytes, lymphoma cells, and lines of myeloid leukemia cells that can be induced to differentiate had a high receptor RLM, whereas lines of myeloid leukemia cells that could not be induced to differentiate had a low receptor RLM. These results suggest that the RLM of Con A receptors is related to the transformation of fibroblasts and the ability of myeloid leukemia cells to undergo differentiation
Translation in vitro of messenger RNA obtained from preparations of active polysomes isolated from the epidermal basal, spinous, and granular cells of the newborn rat has provided evidence that in the context of differentiation in this tissue, control of protein synthesis is exerted at the level of transcription. The data supporting this hypothesis are reviewed.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The early development of parthenogenetically activated oocytes had been studied in C57BL X CBA-T6T6 (F1T6) translocation heterozygote mice and C57BL X CBA-LAC (F1LAC) mice. All F1T6 oocytes had either a quadrivalent or a univalent-trivalent configuration at meiosis I; no such chromosome configurations were observed in the F1LAC oocytes. At ovulation 36-5% of the F1T6 oocytes had 19 or 21 chromosomes, whereas 97% of the F1LAC had the normal haploid chromosome number of 20. After parthenogenetic activation, chromosome counts at metaphase of the first cleavage mitosis were made of the eggs with a single pronucleus following extrusion of the second polar body. These activated eggs had similar frequencies of 19, 20 and 21 chromosomes as had the oocytes at ovulation. The activated 1-cell eggs were transferred to the oviducts of pseudopregnant recipients and the embryos recovered 3 days later. At this stage of development, most of the F1T6 embryos with 19 chromosomes were no longer found, but the frequency of 21-chromosome embryos was similar to the frequency of 21-chromosome oocytes and activated eggs. There was a similar mean number of cells in the embryos with 20 and 21 chromosomes. The results indicate that nearly all the embryos with 19 chromosomes failed to develop, probably beyond the 2-cell stage, whereas oocytes with 21 chromosomes had a similar development of oocytes with 20 chromosomes up to the morula stage.
Explore the source record for details and available documents.
The metabolism of benzo (a) pyrene (BP) in normal golden hamster and BHK cells in culture was increased by treating the cells with dibutyryl cyclic AMP (dcAMP), prostaglandin E1, theophylline or aminophylline. The largest increase, 6-fold for the normal cells and 20-fold for the BHK cells, was obtained by treatment with both dcAMP and aminophylline. Treatment with aminophylline also stimulated the metabolism of 20-methylcholanthrene and 7,12-dimethylbenz (a) anthracene. The increased metabolism of these three carcinogeneic polycyclic hydrocarbons was associated with an increased cytotoxicity. Treatment with aminophylline increased the cytotoxicity of five other potent and weak carcinogenic polycyclic hydrocarbons, but not of two non-carcinogenic polycyclic hydrocarbons. The amount of BP metabolism in 27 different cell types from various mammals, including humans, ranged from less than 0.1 mug to 2.3 mug metabolized BP per 10-6 cells. Treatment of these different cell types with aminophylline gave either an increase in BP metabolism, an induction of metabolism in cells that did not metabolize without aminophylline, or no induction after treatment with aminophylline and dcAMP. The existence of responding and non-responding cell lines indicates that the regulation of the level of polycyclic hydrocarbon metabolism by dcAMP is genetically controlled. The induction of metabolism in cells that did not metabolize without aminophylline resulted in the conversion of cell resistance to cell susceptibility to the cytotoxic effect of BP. Treatment with dcAMP and aminophylline can therefore be used to increase the sensitivity of screening tests for chemical carcinogens.