Faculty of Medicine

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Being a part of the University of Toronto Faculty of Medicine means being a part of one of the world’s largest and most productive biomedical research networks. With its history of innovation and revolutionary health advances, the faculty continues to change the course of human health.

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The radiation sensitivity of normal mouse bone marrow cells, determined by quantitative marrow transplantation into irradiated mice
(Radiation Research Society, 1960-07) McCulloch, Ernest A. ; Till, James E.
SUMMARY: 1. A technique for measuring the number of viable cells in a suspension of bone marrow by quantitative transplantation into supralethally irradiated mice has been described. 2. The technique was used to measure the radiation sensitivity of normal mouse bone marrow cells and yielded a result of 105 ± 24 rads as the D37 for marrow cells.
A direct measurement of the radiation sensitivity of normal mouse bone marrow cells
(Radiation Research Society, 1961-02) Till, James E. ; McCulloch, Ernest A.
SUMMARY: 1. A direct technique for the measurement of the number of cells in a bone marrow suspension capable of continued proliferation is described. 2. The technique was used to measure the radiation sensitivity of normal mouse bone marrow cells and yielded a Do of 115 ± 8 rads.
Cytological demonstration of the clonal nature of spleen colonies derived from transplanted mouse marrow cells
(Nature Publishing Group, 1963-02-02) Becker, Andrew J. ; McCulloch, Ernest A. ; Till, James E.
The distribution of colony-forming cells among spleen colonies
(Wiley-Liss, Inc., A Wiley Company, 1963-12) Siminovitch, Louis ; McCulloch, Ernest A. ; Till, James E.
A stochastic model of stem cell proliferation, based on the growth of spleen colony-forming cells
(National Academy of Sciences (USA), http://www.pnas.org/, 1964-01) Till, James E. ; McCulloch, Ernest A. ; Siminovitch, Louis
Spleen-colony formation in anemic mice of genotype WWv
(American Association for the Advancement of Science, 1964-05-15) McCulloch, Ernest A. ; Siminovitch, Louis ; Till, James E.
The hemopoietic cells from anemic mice of genotype WWv are less able by 200-fold to take part in colony formation in the spleen than cells from the normal littermates of genotype ww. The genetic defect shows itself in the colony-forming cells, since cells from normal littermate mice form colonies in the spleens of unirradiated mice of genotype WWv. Use of animals of genotype WWv as recipients improves the spleen-colony method by removing bias resulting from the death of irradiated recipients.
The cellular basis of the genetically determined hemopoietic defect in anemic mice of genotype Sl/Sld
(American Society of Hematology, 1965-10-01) McCulloch, Ernest A. ; Siminovitch, Louis ; Till, James E. ; Russell, Elizabeth S. ; Bernstein, Seldon E.
Summary: The proliferation and function of hemopoietic cells derived from genetically anemic Sl/Sld mice have been studied by the use of cell transplantation technics. It was found that marrow cells derived from anemic Sl/Sld or Sld/Sld mice, when implanted into heavily irradiated mice of genotype +sl/+sl, are capable of forming macroscopic spleen colonies, with approximately the same frequency as cells derived from normal +sl/+sl mice. Marrow cells derived from Sl/Sld animals were tested for their capacity to cure the anemia of W/Wv mice and were found to implant as rapidly and to have as long-lasting a beneficial effect as did marrow cells from +sl/+sl mice. The radiosensitivity of the colony-forming ability of marrow cells from Sl/Sld mice was found to be similar to that found previously for +sl/+sl marrow cells, although the anemic animals are known to be more sensitive to total-body irradiation than are their normal littermates. Marrow cells from +sl/+sl mice were found to proliferate more slowly in irradiated mice of genotype Sl/Sld than in irradiated +sl/+sl littermates, even when the anemic and the normal mice were joined in parabiosis. These observations indicate that the hemopoietic colony-forming cells in mice of genotype Sl/Sld are normal, but fail to function adequately because the tissues of mice of this genotype are unable to provide sufficient support for proliferation and differentiation of these progenitor cells.
Cytological evidence for a relationship between normal hematopoietic colony-forming cells and cells of the lymphoid system
(The Rockefeller University Press, 1968-03-01) Wu, Alan M. ; Till, James E. ; Siminovitch, Louis ; McCulloch, Ernest A.
Physical separation of hemopoietic stem cells differing in their capacity for self-renewal
(The Rockefeller University Press, 1969-07) Worton, Ronald G. ; McCulloch, Ernest A. ; Till, James E.
Environment and mental health: the impact of new buildings on the programs and organization of a psychiatric hospital
(Wiley, 1975-05) Kelner, Merrijoy J; Haour, Mary K; Court, John PM; Voineskos, George
The reciprocal relationship between the effects of the physical environment and the programs conducted in that environment are discussed, with a particular emphasis on the effects of change in the physical environment. Participant observers were present before, during, and after the relocation of part of a provincial mental hospital from an archaic nineteenth‐century building to modern facilities on the same grounds. Data from the study, as well as historical material, are offered to illustrate some of the ways in which changed values and attitudes about mental illness are linked to modifications in physical settings where treatment is given.
A Noncatalytic Domain Conserved among Cytoplasmic Protein-Tyrosine Kinases Modifies the Kinase Function and Transforming Activity of Fujinami Sarcoma Virus P130[gag-fps]
(American Society of Microbiology, 1986-12) Sadowski, Ivan; Stone, James C.; Pawson, Tony
Proteins encoded by oncogenes such as v-fpslfes, v-src, v-yes, v-abl, and v-fgr are cytoplasmic protein tyrosine kinases which, unlike transmembrane receptors, are localized to the inside of the cell. These proteins possess two contiguous regions of sequence identity: a C-terminal catalytic domain of 260 residues with homology to other tyrosine-specific and serine-threonine-specific protein kinases, and a unique domain of approximately 100 residues which is located N terminal to the kinase region and is absent from kinases that span the plasma membrane. In-frame linker insertion mutations in Fujinami avian sarcoma virus which introduced dipeptide insertions into the most stringently conserved segment of this N-terminal domain in P130gag-fps impaired the ability of Fujinami avian sarcoma virus to transform rat-2 cells. The P130gag-fps proteins encoded by these transformation-defective mutants were deficient in protein-tyrosine kinase activity in rat cells. However v-fps polypeptides derived from the mutant Fujinami avian sarcoma virus genonles and expressed in Escherichia coli as trpE-v-fps fusion proteins displayed essentially wild-type enzymatic activity, even though they contained the mutated sites. Deletion of the N-terminal domain from wild-type and mutant v-fps bacterial proteins had little effect on autophosphorylating activity. The conserved N-terminal domain of P130gag-fps is therefore not required for catalytic activity, but can profoundly influence the adjacent kinase region. The presence of this noncatalytic domain in all known cytoplasmic tyrosine kinases of higher and lower eucaryotes argues for an important biological function. The relative inactivity of the mutant proteins in rat-2 cells compared with bacteria suggests that the noncatalytic domain may direct specific interactions of the enzymatic region with cellular components that regulate or mediate tyrosine kinase function.
v-fps protein-tyrosine kinase coordinately enhances the malignancy and growth factor responsiveness of pre-neoplastic lung fibroblasts
(Nature Publishing Group, 1988-03) Sadowski, I ; Pawson, Tony ; Lagarde, A
The v-fps oncoprotein was expressed in a pre-neoplastic, growth factor-dependent Chinese hamster lung fibroblast line (CCL39) to study its effect on growth controls and on the induction of malignancy. Two transfectants were characterized which expressed low (39FPS-8) or high (51FPS-6) levels of P130gag-f ps protein-tyrosine kinase activity. 39FPS-8 cells still arrested in quiescence when deprived of growth factors, but developed an increased sensitivity to the mitogenic actions of epidermal growth factor (20-fold) and alpha-thrombin (50-fold), although not to insulin. In contrast, 51FPS-6 cells completely escaped growth controls, divided in serum-free medium, and were insensitive to further growth factor stimulation. Both transfectants produced rapidly growing tumors in nude mice that formed pulmonary metastases from a subcutaneous site, unlike the parental cells which are non-metastatic. 51FPS-6 cells were comparatively more efficient than 39FPS-8 cells in colonizing the lungs after intravenous inoculation. The v-fps tyrosine kinase therefore induces a partial to complete relaxation of growth factor-mediated controls on the CCL39 cell cycle, with the extent of factor independence reflecting the amount of P130gag-f ps synthesized. This reduction in growth factor requirements correlates with the capacity of v-fps to confer the attributes of metastatic tumors upon preneoplastic CCL39 fibroblasts. We speculate that increased sensitivity to growth factor stimulation represents a common mechanism by which tumor cells acquire metastatic properties.
Non-catalytic domains of cytoplasmic protein-tyrosine kinases: regulatory elements in signal transduction
(Nature Publishing Group, 1988-11) Pawson, Tony
Novel protein-tyrosine kinase cDNAs related to fps/fes and eph cloned using anti-phosphotyrosine antibody
(Nature Publishing Gro, 1988-12) Letwin, K ; Yee, SP ; Pawson, Tony
A rat brain lambda gt11 cDNA expression library was screened with anti-phosphotyrosine antibody to identify recombinant clones that encode enzymatically active protein-tyrosine kinases. The inserts of two bacteriophage that gave positive signals were sequenced. Both translation products possess sequence motifs characteristic of protein-tyrosine kinases. However, each polypeptide is distinct from previously described members of the tyrosine kinase family. The predicted product of the lambda B1 clone contains a catalytic domain and C-terminal tail most closely related to the eph gene product, a presumed transmembrane receptor-like protein-tyrosine kinase. The clone lambda B2 encodes a partial SH2 domain and a kinase domain similar in organization and sequence to the fps/fes cytoplasmic protein-tyrosine kinase. These new protein-tyrosine kinases (elk and flk) are apparently members of subfamilies for which eph and fps/fes are prototypes. elk is predominantly expressed in brain, while flk RNA is widely distributed and most abundant in testes. The preferential isolation of cDNAs for previously uncharacterized protein-tyrosine kinases in a screen based on catalytic activity suggests that additional members of the protein-tyrosine kinase family remain to be identified.
Mutational analysis of a phosphotransfer motif essential for v-fps tyrosine kinase activity
(Nature Publishing Group, 1988-12) Moran, MF ; Koch, CA ; Sadowski, I ; Pawson, Tony
The catalytic domains of protein-tyrosine kinases such as the P130gag-fps oncoprotein contain the sequence HRDLAARN, followed thirteen residues C-terminal by DFG (P130gag-fps residues 1041-1048 and 1061-1063). These residues define a structural motif conserved among eucaryotic protein kinases (-RD----N, DFG) and shared with several procaryotic 3'aminoglycoside phosphotransferases (H-D----N, D-G). Functional analysis of mutant v-fps proteins employing bacterial and mammalian expression systems indicated that this motif is critical for P130gag-fps kinase activity and oncogenicity. In particular, conservative substitutions of the two invariant aspartates (asp1043, asp1061) with glutamate or asparagine completely eliminated enzymatic activity, suggesting that these residues are essential for catalysis. In contrast, substitution of arg1042 with glutamate decreased but did not eliminate v-fps kinase activity in bacteria. The effects of these and other amino acid substitutions within the phosphotransfer motif and at the nearby autophosphorylation site (tyr1073) of P130gag-fps indicate that these conserved residues are intrinsically essential to the execution or regulation of catalytic activity, and suggest that tight spatial constraints operate within the active centre of the v-fps tyrosine kinase domain.
Phosphorylation of GAP and GAP-associated proteins by transforming and mitogenic tyrosine kinases
(Nature Publishing Group, 1990-01) Ellis, C ; Moran, M ; McCormick, F ; Pawson, Tony
The critical pathways through which protein-tyrosine kinases induce cellular proliferation and malignant transformation are not well defined. As microinjection of antibodies against p21ras can block the biological effects of both normal and oncogenic tyrosine kinases, it is likely that they require functional p21ras to transmit their mitogenic signals. No biochemical link has been established, however, between tyrosine kinases and p21ras. We have identified a non-catalytic domain of cytoplasmic tyrosine kinases, SH2, that regulates the activity and specificity of the kinase domain. The presence of two adjacent SH2 domains in the p21ras GTPase-activating protein (GAP) indicates that GAP might interact directly with tyrosine kinases. Here we show that GAP, and two co-precipitating proteins of relative molecular masses 62,000 and 190,000 (p62 and p190) are phosphorylated on tyrosine in cells that have been transformed by cytoplasmic and receptor-like tyrosine kinases. The phosphorylation of these polypeptides correlates with transformation in cells expressing inducible forms of the v-src or v-fps encoded tyrosine kinases. Furthermore, GAP, p62 and p190 are also rapidly phosphorylated on tyrosine in fibroblasts stimulated with epidermal growth factor. Our results suggest a mechanism by which tyrosine kinases might modify p21ras function, and implicate GAP and its associated proteins as targets of both oncoproteins and normal growth factor receptors with tyrosine kinase activity. These data support the idea that SH2 sequences direct the interactions of cytoplasmic proteins involved in signal transduction.
p185neu is phosphorylated on tyrosine in human primary breast tumors which overexpress neu/erbB-2
(Nature Publishing Group, 1990-06) Wildenhain, Y ; Pawson, Tony ; Blackstein, ME ; Andrulis, IL
A series of primary human breast tumors was analysed by immunoblotting with anti-neu antibodies. Overproduction of the neu protein-tyrosine kinase, p185neu, was observed in 23 of 56 malignant tumor samples. 29 of these tumors were also immunoblotted with antiphosphotyrosine antibodies. A single prominent phosphotyrosine-containing protein, which co-migrated with p185neu was identified in 11 of the 29 tumors examined. There was an exact concordance between the tumors with a 185kDa phosphotyrosine-containing protein, and those with elevated p185neu. These results indicate that overexpressed p185neu in primary human breast cancer is phosphorylated on tyrosine, most likely by autophosphorylation, and by inference is enzymatically activated as a protein-tyrosine kinase. Aberrant tyrosine phosphorylation may therefore be important in the development of a substantial fraction of breast cancers.
Binding of SH2 Domains of Phospholipase Cγ1, GAP, and Src to Activated Growth Factor Receptors
(American Association for the Advancement of Science, 1990-11-16) Anderson, Deborah ; Koch, C. Anne ; Grey, Laura ; Ellis, Christine ; Moran, Michael ; Pawson, Tony
Phospholipase Cγ1 (PLCγl) and p21ras guanosine triphosphatase (GTPase) activating protein (GAP) bind to and are phosphorylated by activated growth factor receptors. Both PLCγl and GAP contain two adjacent copies of the noncatalytic Src homology 2 (SH2) domain. The SH2 domains of PLCγl synthesized individually in bacteria formed high affinity complexes with the epidermal growth factor (EGF)- or platelet derived growth factor (PDGF)-receptors in cell lysates, and bound synergistically to activated receptors when expressed together as one bacterial protein. In vitro complex formation was dependent on prior growth factor stimulation and was competed by intracellular PLCγl. Similar results were obtained for binding of GAP SH2 domains to the PDGF-receptor. The isolated SH2 domains of other signaling proteins, such as p60src and Crk, also bound activated PDGF-receptors in vitro. SH2 domains, therefore, provide a common mechanism by which enzymatically diverse regulatory proteins can physically associate with the same activated receptors and thereby couple growth factor stimulation to intracellular signal transduction pathways.
Failure of chronic hyperinsulinemia to suppress pancreatic glucagon in vivo in the rat
(National Research Council Canada, 1991) Brubaker, Patricia L.; Kazumi, T.; Hirano, T.; Vranic, M.; Steiner, G.
Central mechanisms of vascular headaches
(National Research Council Canada, 1991) Dostrovsky, J. O.; Davis, K. D.; Kawakita, K.

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