Search PubMed⌕ Search

Biomedical subjects

D R Spriggs

Publications and source records attributed to D R Spriggs.

At least 91 records · Page 5Linked to original sources
PubMed1985

Inhibition of murine erythroleukemia cell differentiation by 3-deazaadenosine.

Recent studies have demonstrated that 5'-methylthioadenosine, an inhibitor of S-adenosylhomocysteine (AdoHcy) hydrolase, blocks induction of murine erythroleukemia cell (MEL) differentiation. The nucleoside analogue 3-deazaadenosine (c3Ado) is both an efficient substrate and a potent inhibitor of AdoHcy hydrolase. The present study was undertaken to determine whether c3Ado would similarly inhibit MEL differentiation. The results demonstrate that c3Ado inhibits induction of MEL differentiation by dimethyl sulfoxide, hexamethylene bisacetamide, butyric acid, and diazapam. c3Ado blocks the appearance of the differentiated MEL phenotype by inhibiting both MEL heme synthesis and transcription of alpha- and beta-globin RNA. The inhibitory effect of c3Ado on MEL differentiation is concentration dependent, reversible, and potentiated by L-homocysteine thiolactone. Furthermore the AdoHcy/AdoMet ratio increases nearly 3.5-fold after 24 h of treatment with 50 microM c3Ado. In contrast, this c3Ado effect is not associated with polyamine depletion or cytostasis. These findings indicate that c3Ado blocks the induction of MEL differentiation at a transcriptional level and that this effect may be related to inhibition of AdoHcy hydrolase.

Adenosine↗
PubMed1985

Cellular and clinical pharmacology of low-dose ara-C.

Although the mechanism of action responsible for the effects of low-dose ara-C remains unclear, certain insights are available concerning the interaction of this agent with DNA. Ara-C incorporates into DNA, and the extent of (ara-C)DNA formation correlates significantly with loss of clonogenic survival. The inhibition of DNA replication by ara-C also results in DNA fragmentation and terminal differentiation of leukemic cells. Other studies have demonstrated that inhibition of DNA replication by ara-C results in an aberrant form of DNA synthesis with certain segments of DNA being replicated more than once within a single cell cycle. The additional copies of certain segments of DNA could lead to the accumulation of DNA fragments and alterations in gene expression. It is of interest that other inhibitors of S-phase DNA replication such as aphidicolin and hydroxyurea can also induce similar phenotypic changes in HL-60 and K562 leukemia cells. Although the in vitro data support the concept that ara-C is capable of inducing leukemic cell differentiation, there is no evidence to suggest that this agent induces differentiation of human leukemic cells in vivo. Drug levels achieved by administration of low-dose ara-C (42-64 nmol/L) result in the incorporation of ara-C into bone marrow mononuclear preparations from patients with preleukemia syndromes. This concentration of ara-C (5 X 10(-8) mol/L) slows DNA replication of human leukemic cells in vitro. Thus, the clinical use of low doses of ara-C that achieve plasma concentrations of 10(-8) to 10(-7) mol/L could theoretically induce maturational effects by partially inhibiting DNA synthesis. At the present time we have no available data to support this contention. On the basis of chromosomal analyses, low-dose ara-C apparently maintains sufficient drug levels to suppress more "malignant" clones, but even "clonal" selection may represent elimination of leukemic cells by either cytotoxicity or induction of terminal differentiation. Further studies will be necessary to define the mechanism of action of low-dose ara-C in preleukemia.

Adult↗
PubMed1985

Continuous infusion of high-dose 1-beta-D-arabinofuranosylcytosine: a phase I and pharmacological study.

High doses of 1-beta-D-arabinofuranosylcytosine, administered as a continuous i.v. infusion, were evaluated in a Phase I trial in 14 patients with advanced solid tumors. 1-beta-D-Arabinofuranosylcytosine was given at 250 mg/sq m/h for infusions of 12 to 36 h. The mean steady state 1-beta-D-arabinofuranosylcytosine plasma level was 19.6 microM with a range of 9 to 59 microM. The principal toxicity was myelosuppression. An infusion of 18 h was well tolerated by most patients. A Phase II dose of 250 mg/sq m/h for 24 h can be used if platelet support is available. This dose schedule may be useful in the treatment of hematological disorders or in clinical combinations with DNA-damaging agents in the treatment of solid tumors.

Adult↗
PubMed1983

Hemagglutinin variants of reovirus type 3 have altered central nervous system tropism.

Variants of the Dearing strain of reovirus type 3 with antigenically altered hemagglutinin proteins are much less neurovirulent than the parental virus. When injected intracerebrally into mice these variants infected a subset of the brain neurons that were infected by the parental virus. When injected intraperitoneally, the variants did not spread to the brain. These results indicate that minor modifications of the reovirus hemagglutinin dramatically alter the ability of the virus to spread into and injure the central nervous system.

Animals↗
PubMed1983

Topological analysis of the reovirus type 3 hemagglutinin.

We previously showed that the reovirus type 3 hemagglutinin (HA) has distinct functional domains. For example, we identified one group of anti-HA monoclonal antibodies which only inhibited virus-mediated hemagglutination and another group which exclusively neutralized reovirus infectivity. Using competition radioimmunoassays, we now report that these functionally discrete domains on the reovirus type 3 HA correspond to discrete antigenic regions of the protein.

Antibodies, Monoclonal↗
PubMed1983

Specific plasma membrane receptors for reovirus on rat pituitary cells in culture.

Specific cellular and host tropism is a characteristic property of many viruses mediated by the interaction of viral attachment proteins with components of the plasma membrane of the cell. We have studied the binding of virus to cells quantitatively by using type 3 reovirus labeled with 125I and GH4C1 pituitary cells in culture. Binding was rapid at both 4 degrees and 15 degrees C and was stable over a 9-h period. Unlabeled virus inhibited binding of the labeled virus in a dose-dependent manner. Scatchard analysis revealed 4,200 viral binding sites/cell with an apparent affinity of 1.2 X 10(-11) M. Also, binding of type 3 reovirus was inhibited by antibodies directed against the viral hemagglutinin and partially inhibited by type 2 reovirus, but was unaffected by type 1 reovirus or a variety of other ligands that bind to receptors on GH4C1 cells. These data indicate that reovirus binds to a high affinity, specific receptor on target cells, which may control its tropism and ultimate disease expression.

Animals↗
PubMed1982

Identification of a hemagglutinin-specific idiotype associated with reovirus recognition shared by lymphoid and neural cells.

A xenogeneic antiserum raised to antireovirus immunoglobulin was used to define an idiotypic determinant present on antibodies to reovirus type 3 hemagglutinin. The same idiotype was identified on nonimmune lymphoid cells and on neuronal cells that specifically bind the hemagglutinin of type 3 reovirus. This idiotypic determinant, called Id3, is shared by (a) a monoclonal antibody to the neutralization site of hemagglutinin from type 3 reovirus; (b) BALB/c serum antibodies to the hemagglutinin of reovirus type 3; (c) R1.1, a murine thymoma cell line that binds reovirus type 3; (d) primary cultures of murine neuronal cells. The presence of an idiotype shared by antihemagglutinin antibodies and by structures on nonlymphoid cells suggests a general relationship between disparate receptors that recognize a common determinant. Furthermore, this suggests a novel approach for the study of viral receptor interactions and for analysis of mechanisms of autoimmune responses.

Animals↗
PubMed1982

Identification of idiotypic receptors on reovirus-specific cytolytic T cells.

Cytolytic T lymphocytes (Tc) specific for cells infected with reovirus type 3 were shown to lyse an uninfected B-cell hybridoma line (designated 87.92.6). This hybridoma expresses and secretes an anti-idiotypic antibody that reacts with a monoclonal antibody (termed G-5). G-5 recognizes a domain on the hemagglutinin of the reovirus that is relevant to virus tropism. The Tc cell response was H-2 restricted and could be inhibited by G-5. As shown by limiting dilution analysis, identical clones lysed reovirus-infected and anti-idiotype-bearing target cells. Tc cells induced by a variant of wild-type reovirus type 3 (immunologically selected by resistance to neutralization by G-5) were unable to recognize the anti-idiotype-bearing cells although they lysed reovirus type 3-infected tumor cells. We conclude that Tc cells must bear determinants that bind anti-idiotype molecules and, furthermore, that B cells and cytolytic T cells can share these idiotypic determinants.

Animals↗
PubMed1982

Host immune response to reovirus: CTL recognize the major neutralization domain of the viral hemagglutinin.

Previous studies have demonstrated the importance of the hemagglutinin (HA) of reovirus in determining virus-specific immune responses. In this study, we have used anti-HA monoclonal antibodies and reoviruses with antigenically altered HA proteins to further analyze the CTL response against the HA. We showed that reovirus-specific CTL primarily recognize one distinct antigenic domain on the HA. These results emphasize the fine specificity of the T cell receptor that recognizes viral determinants. The CTL response is directed against the region of the HA that is also responsible for neurotropism and binding to neutralizing antibody.

Animals↗
PubMed1980

BALB/c myeloma retroviruses: peptide mapping and immunological analysis of the pp12 structural protein.

We have compared the pp12 structural protein of the MO-21 and FL-1 BALB/c myeloma retroviruses with the pp12 of several prototype retroviruses. Chymotryptic peptide maps of 125I-labeled, immune-precipitated pp12 proteins revealed that the MO-21 and FL-1 proteins can be distinguished from one another. The MO-21 pp12 most closely resembled the NIH-xenotrophic virus pp12, and the FL-1 pp12 most closely resembled the pp12 of BV-2 and WN 1802 B. Competition radioimmunoassay studies showed that the MO-21 and FL-1 pp12 proteins are also antigenically distinct from one another and that both contain pp12 antigenic determinants of a xenotropic virus. These data support our proposal that these two BALB/c viruses contain a gag gene that was generated by recombination between endogenous eco- and xenotropic viral sequences.

Animals↗
PubMed1980

BALB/c myeloma retroviruses have mink cell focus-inducing activity.

We have determined the in vitro host range of the cloned MO-21 and FL-1 murine myeloma retroviruses grown in SC-1 cells that were originally isolated from cloned MOPC-21 and FLOPC-1 BALB/c plasmacytoma cell lines. These viruses are able to replicate in murine (BALB/3T3, NIH/3T3) as well as numerous heterologous cell lines. These myeloma retroviruses also exhibit mink cell focus-inducing activity. MO-21 and FL-1 shared interference patterns with each other, but their replication was not interfered with by ecotropic, xenotropic, or amphotropic viruses. The lack of cross-interference with ecotropic or xenotropic viruses distinguishes these isolates from other mink cell focus-inducing viruses.

Animals↗