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S D Lyman

Publications and source records attributed to S D Lyman.

104 records · Page 6Linked to original sources
PubMed1991

Cytokine regulation of hematopoietic stem cells.

Regulation of hematopoietic stem cell proliferation and differentiation is likely to be controlled by the local concentration of both inhibitory and stimulatory cytokines. A newly described regulator of early haematopoietic cells called mast cell growth factor, stem cell factor or kit ligand (referred to here as the Sl factor) has been described. This factor is the gene product of the murine Steel locus and is the ligand for the c-kit proto-oncogene, the product of the murine W locus. The effects of Sl factor on primitive hematopoietic cells suggest that this growth factor is a major stimulator of basal hemopoiesis. Further, data indicates that Sl factor acts in synergy with virtually all of the later acting growth factors to enhance the proliferative and differentiative potential of these cells.

Animals↗
PubMed1990

Mast cell growth factor maps near the steel locus on mouse chromosome 10 and is deleted in a number of steel alleles.

Many spontaneous, chemical-induced, and radiation-induced dominant white spotting (W) and steel (Sl) mutations have been identified in the mouse. W and Sl mutations have similar phenotypic effects including deficiencies in pigment cells, germ cells, and blood cells, Numerous studies have suggested that W acts within the affected cell while Sl instead exerts its effects in the extracellular environment. Recent findings demonstrating that W encodes the c-kit proto-oncogene, a tyrosine kinase membrane receptor, have suggested that Sl encodes a ligand for c-kit. In the accompanying article we report the identification and purification of mast cell growth factor (MGF), a c-kit ligand. Here we describe the cloning of sequences encoding MGF. Furthermore, we show that Mgf maps near Sl in the distal region of mouse chromosome 10 and is deleted in a number of Sl alleles. These findings strongly support the notion that Sl encodes the mast cell growth factor.

Alleles↗
PubMed1990

Molecular cloning of mast cell growth factor, a hematopoietin that is active in both membrane bound and soluble forms.

We have previously reported the identification of a novel mast cell growth factor (MGF) that was shown to be a ligand for c-kit and is encoded by a gene that maps near the steel locus on mouse chromosome 10. We now report the cloning of cDNAs encoding the MGF protein. The MGF protein encoded by this cDNA can be expressed in a biologically active form as either a membrane bound protein or as a soluble factor. The soluble protein promotes the proliferation of MGF-responsive cell lines and, in the presence of erythropoietin, stimulates the formation of macroscopic [corrected] erythroid and multilineage hematopoietic colonies.

Amino Acid Sequence↗
PubMed1990

Human interleukin 4 receptor confers biological responsiveness and defines a novel receptor superfamily.

IL-4, a pleiotropic cytokine produced by T lymphocytes, plays an important role in immune responsiveness by regulating proliferation and differentiation of a variety of lymphoid and myeloid cells via binding to high affinity receptors. In this report we describe the isolation and functional expression of a human IL-4-R cDNA. When transfected into COS-7 cells, the cDNA encodes a 140-kD cell-surface protein. After transfection into a murine T cell line, the cDNA encodes a protein that binds human IL-4 with high affinity and can confer responsiveness to human IL-4. The predicted extracellular domain of the IL-4-R exhibits significant amino acid sequence homology with the beta subunit of the IL-2-R (p75), and the receptors for IL-6, erythropoietin, and prolactin. These receptors comprise a novel superfamily with extracellular domains characterized by four conserved cysteine residues and a double tryptophan-serine (WSXWS) motif located proximal to the transmembrane region.

Amino Acid Sequence↗
PubMed1990

A new cytokine receptor superfamily.

The amino acid sequences of several, recently cloned cytokine receptors show significant homologies, primarily in their extracellular, ligand-binding domains. With one exception, their cognate cytokines mediate biological activities on a variety of hematopoietic cell types; thus we have designated the receptors as the hematopoietic receptor superfamily.

Amino Acid Sequence↗
PubMed1989

The kinase activity of the v-fms encoded protein has a low pH optimum.

The protein encoded by v-fms, the oncogene of the Susan McDonough strain of feline sarcoma virus, is a member of the protein tyrosine kinase family. The kinase activity of the v-fms encoded protein has been reported to be low compared to other members of this enzyme family. We found that the optimal pH in vitro for the autophosphorylation of the immunoprecipitated v-fms encoded protein kinase activity was about pH 5.0; the activity at this pH was 15-fold higher than at the pH (7.4) used in standard kinase assays. The low pH optimum of the kinase activity of the v-fms encoded protein was observed when this protein was immunoprecipitated with each of four independent polyclonal antisera. v-fms proteins from transfected rat, mink or hamster cells all showed the same pH optimum for the kinase activity, as did the protein encoded by the feline c-fms gene. Autophosphorylation of v-fms in vitro at pH 5.0 occurred exclusively on tyrosine residues. Enolase was a substrate for the v-fms encoded protein kinase, and the pH profile for phosphorylation of this substrate in vitro paralleled that seen for the autophosphorylation of v-fms encoded proteins. The discovery of the low pH optimum of the kinase activity exhibited by v-fms proteins may be useful for further characterization of this activity in vitro, as well as for phenotypic classification of other members of the protein tyrosine kinase family.

Hydrogen-Ion Concentration↗
PubMed1988

Colony stimulating factor-1 induced growth stimulation of v-fms transformed fibroblasts.

The v-fms oncogene, which is capable of transforming fibroblasts, was derived by recombination of a feline leukemia virus with a cellular gene (c-fms) that encodes the receptor for colony stimulating factor 1 (CSF-1). We examined the capacity of recombinant human CSF-1 (produced in a yeast expression system) to stimulate the growth of v-fms transformed rat fibroblasts. Recombinant human CSF-1 bound to v-fms transformed fibroblasts with high affinity (apparent Kd = 6.0 x 10(-10) M); only non-specific binding was observed on control cells. The number of colonies formed in soft agar by v-fms transformed cells was increased by CSF-1 treatment in a dose-dependent manner; a nine fold increase in the number of colonies was seen in the presence of 10(-8) M CSF-1. CSF-1 did not stimulate the growth of either non-transformed cell lines, a non-transformed cell line that expresses a mutated v-fms protein on the cell surface, or cells transformed by the v-fgr oncogene. The growth stimulating effect of CSF-1 on v-fms transformed cells was also seen in monolayer culture. The v-fms transformed cells treated with CSF-1 had a more refractile, rounded morphology than non-treated cells; no morphology change was observed in CSF-1 treated control cells. CSF-1 treatment also increased both the number and size of foci that arose from fibroblasts following transfection with the v-fms oncogene. These data show that the altered CSF-1 receptor encoded by the v-fms oncogene retains a capacity to bind, and be stimulated by, human CSF-1.

Animals↗
PubMed1987

Analysis of functional domains of the v-fms-encoded protein of Susan McDonough strain feline sarcoma virus by linker insertion mutagenesis.

The Susan McDonough strain of feline sarcoma virus contains an oncogene, v-fms, which is capable of transforming fibroblasts in vitro. The mature protein product of the v-fms gene (gp140fms) is found on the surface of transformed cells; this glycoprotein has external, transmembrane, and cytoplasmic domains. To assess the functional role of these domains in transformation, we constructed a series of nine linker insertion mutations throughout the v-fms gene by using a dodecameric BamHI linker. The biological effects of these mutations on the function and intracellular localization of v-fms-encoded proteins were determined by transfecting the mutated DNA into Rat-2 cells. Most of the mutations within the external domain of the v-fms-encoded protein eliminated focus formation on Rat-2 cells; three of these mutations interfered with the glycosylation of the v-fms protein and interfered with formation of the mature gp140fms. One mutation in the external domain led to cell surface expression of v-fms protein even in the absence of complete glycosylational processing. Cell surface expression of mutated v-fms protein is probably necessary, but is not sufficient, for cell transformation since mutant v-fms protein was found on the surface of several nontransformed cell lines. Mutations that were introduced within the external domain had little effect on in vitro kinase activity, whereas mutations within the cytoplasmic domain all had strong inhibitory effects on this activity.

Cell Compartmentation↗
PubMed1985

Metabolism of tamoxifen and its uterotrophic activity.

Tamoxifen is an estrogen agonist in mouse uterus, a partial estrogen agonist/antagonist in rat uterus, and a pure estrogen antagonist in chicken oviduct. Tamoxifen metabolism was examined both in vitro and in vivo to determine if differences in the species response to this drug resulted from the differential formation of metabolites with estrogenic or antiestrogenic activity. Animals were given a subcutaneous injection of [3H]tamoxifen, and 4 or 24 hr later tamoxifen and its metabolites were extracted from tissues and separated by TLC. The profiles of metabolites extracted from the livers of these species were qualitatively similar; the principle metabolite was 4-hydroxytamoxifen, which comprised 27, 14, and 16% of the radioactivity from mouse, rat, and chicken livers, respectively, at 24 hr. Tamoxifen, however, was the principal compound extracted from all three livers. Metabolites extracted from mouse and rat uteri were the same ones obtained from liver, although their abundance (relative to tamoxifen) was much lower in uteri than in liver. Metabolite E and bisphenol, two tamoxifen derivatives that we believed might account for the uterotrophic effect of tamoxifen in the mouse, were found not to be formed in either liver or uterus. Tamoxifen metabolism was also studied in vitro using liver microsomes from these same species; The same metabolites were formed in vitro as in vivo, although their relative abundances were lower in vitro. No clear-cut differences in metabolism were seen that would account for the disparate pharmacological effects of tamoxifen in these species.

Animals↗
PubMed1985

Possible mechanisms for the agonist actions of tamoxifen and the antagonist actions of MER-25 (ethamoxytriphetol) in the mouse uterus.

Experiments were conducted to determine why tamoxifen, a non-steroidal antiestrogen, is uterotrophic in mice, whereas MER-25 (ethamoxytriphetol), a structurally related compound, is antiuterotrophic. Initial experiments indicated that the pituitary was not required for a uterotrophic response in mice to either estradiol (E2), tamoxifen (TAM), or 4-hydroxytamoxifen (4-OH-TAM) MER-25 was not uterotrophic in mice but was capable of completely inhibiting the uterotrophic responses of mice to estrogens (E2) as well as antiestrogens (TAM and 4-OH-TAM); this inhibition was reversible by increasing the dose of the antiestrogen (TAM). The relative binding affinities (RBA) of TAM, 4-OH-TAM, and MER-25 to mouse uterus estrogen receptor (ER) and mouse liver antiestrogen binding sites (AEBS) were compared to determine whether either (or both) of these sites mediate the biological effects of these compounds. E2 is arbitrarily assigned an RBA of 100 for ER; similarly, TAM is assigned an RBA of 100 for AEBS. MER-25 bound to AEBS with an RBA of 8.9 and to ER with an RBA of less than 0.06; in contrast, TAM and 4-OH-TAM bound to AEBS with RBAs of 100 and 53, respectively, and to ER with RBAs of 2 and 131, respectively. Five other compounds that had similar RBAs as MER-25 for AEBs (RBAs in the range 4-9) and for ER (RBAs less than 0.06) were tested for their antiuterotrophic activities in vivo against both estrogen (E2) and antiestrogen (TAM) in ovariectomized mice. None of these compounds were antiuterotrophic against either estradiol or tamoxifen (P less than 0.01), nor were any of the compounds uterotrophic in mice. These data suggest that differences in the biological actions of tamoxifen and MER-25 in mice are not mediated through AEBS and are most likely due to differences in their interactions with ER.

Animals↗
PubMed1985

Rat uterine growth and induction of progesterone receptor without estrogen receptor translocation.

The rat uterus responds to estradiol (E2) and E2 benzoate stimulation with an increase in progesterone receptor production and with growth. These responses were also elicited to varying degrees by a series of estrogenic (ICI 77,949 and ICI 47,699) and antiestrogenic triphenylethylene derivatives [tamoxifen (TAM), 4-hydroxy-TAM (4-OH-TAM), and 4-CH3-TAM]. These compounds have a range of affinities for the estrogen receptor (ER) and are able to compete with [3H]E2 binding in the uterus in vivo. Within 1-2 h of a sc injection of high affinity ligands (E2, E2B, and 4-OH-TAM), there was decrease in cytosol ER. This decrease was also observed with TAM, which is metabolized to 4-OH-TAM in vivo. In contrast, there was no decrease in cytosolic ER in animals treated with low affinity compounds (ICI 77,949, ICI 47,699, and 4-CH3-TAM) at any time before the onset of an estrogenic response. Furthermore, the nuclear ER increased after administration of a high affinity ligand (E2), as measured by exchange assay, but no increase in nuclear ER was observed after administration of low affinity ligands (ICI 77,949 and 4-CH3-TAM), although estrogenic responses were produced. From these data we have suggested a functional model to explain ER-mediated events in the rat uterus that supports the recent proposal that unoccupied ER is located in the nuclear compartment. In this model, the majority of unoccupied ER may reside in the nucleus in vivo; however, when the cells are disrupted in vitro, the unoccupied receptor or dissociation of low affinity ligand-ER complex causes unoccupied receptor to fall out of the nucleus and be incorporated into the cytosolic fraction. The high affinity ligand-ER complexes are retained in the nucleus. This would suggest that the apparent translocation of the ER from the cytoplasm to the nucleus may be an artifact. The data may reflect differential extraction of unoccupied receptors from the nucleus rather than transfer of receptor complexes to the nucleus.

Animals↗
PubMed1983

Effect of the brachymorphic trait in mice on xenobiotic sulfate ester formation.

Mice carrying the recessive mutation brachymorphic have been shown previously to have a reduced capacity to synthesize 3'-phosphoadenosine-5'-phosphosulfate (PAPS), the required coenzyme in sulfation reactions [K. Sugahara and N. Schwartz, Proc. natn. Acad. Sci. U.S.A. 76, 6615 (1979)]. The capacity of the liver cytosol fractions from brachymorphic (bm/bm) mice or their phenotypically normal littermates (+/+ or +/bm) to catalyze the formation of sulfate esters of [3H]estrone and [14C]p-nitrophenol in vitro was determined. When PAPS was added to the reaction, the rates of sulfate ester formation catalyzed by the two cytosol fractions were similar. In contrast, when PAPS was generated in situ from ATP and SO(4)2-, the rates of sulfate ester formation catalyzed by the brachymorphic cytosol were only 4-22% of the rates catalyzed by the cytosol fraction from normal mice. The hepatic cytosol fraction from brachymorphic mice incorporated less 35SO(4)2- into PAPS than that catalyzed by cytosol of normal mice. [14C]p-Nitrophenol (1.5 mumoles/kg) was eliminated from brachymorphic and normal mice as urinary conjugates; in normal mice, 73% of the urinary radioactivity was p-nitrophenyl sulfate, while in the brachymorphic mice only 33% of the urinary excretion was the sulfate ester. Brachymorphic mice have a reduced capacity for synthesizing sulfate esters of xenobiotics in vitro and in vivo, which is attributable to their reduced synthesis of PAPS.

Adenine Nucleotides↗
PubMed1980

Genetic polymorphism of microsomal epoxide hydrolase activity in the mouse.

Hepatic microsomal epoxide hydrolase activity (EC 3.3.2.3), assayed using styrene oxide as the substrate, has a pH optimum of 9.5 from C57BL/6J mice and a pH optimum of 8.7 from DBA/2J mice. In cross and back-cross matings between C57BL/6J and DBA/2J mice, this phenotypic difference in epoxide hydrolase activity is inherited as a single autosomal trait, with co-dominant expression in heterozygotes. Heating liver microsomes from C57Bl/6J mice at 62 degrees C for 30 min produced a slight decrease in enzyme activity, whereas the same treatment of DBA/2J microsomes reduced enzyme activity to less than 3% of its initial value. Twenty-six inbred strains of mice were examined and separated into two phenotypic classes on the basis of differences in pH optima and heat sensitivity of microsomal epoxide hyrolase activity. Eph-1 is proposed as the locus symbol of the structural gene for microsomal epoxide hydrolase, with superscripts b and d designating the alleles carried by C57BL/6J and DBA/2J mice, respectively. Using 24 recombinant inbred strains derived from C57BL/6J and DBA/2J mice, Eph-1 was found to be linked to two loci on Chromosome 1.

Animals↗