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Biomedical subjects

R A Finch

Publications and source records attributed to R A Finch.

At least 37 records · Page 2Linked to original sources
PubMed1997

Structural and functional relationships of toyocamycin on NPM-translocation.

Toyocamycin is an antitumor antibiotic which has a pyrrolo[2,3-D]pyrimidine aglycone with a -CN substituent on the 5-carbon. Treatment of HeLa cells with toyocamycin induces redistribution of the nuclear phosphoprotein nucleophosmin/B23 (NPM) from nucleoli to nucleoplasm (NPM-translocation) which can be detected by immunofluorescence. NPM-translocation is useful in showing drug effects and in detecting drug-resistant cancer cells. To study which structural features of toyocamycin are important for NPM-translocation, we used toyocamycin analogs in which the 5-position -CN was either deleted (tubercidin) or replaced with a -CONH2 (sangivamycin) or -C(NOH)NH2. HeLa cells were incubated with these analogs for 4 h and assayed for NPM-translocation by immunofluorescence. We found that the analog with the deletion of the -CN group (tubercidin) did not induce translocation while those with replacement of the -CN group with -CONH2 or -C(NOH)NH2 retained the NPM-translocation activity. When these or similar modifications were applied to 7-deazaguanosine, none of the guanosine analogs were effective. These results indicate that modifications at the 5-position of the pyrrolo[2,3-D]pyrimidine ring and a structure similar to adenine rather than guanine are essential for NPM-translocation. Since inhibition of RNA synthesis did not induce NPM-translocation, our results suggest that interference with NPM's binding in nucleoli by these analogs causes NPM-translocation.

Antibiotics, Antineoplastic↗
PubMed1996

ATP depletion affects NPM translocation and exportation of rRNA from nuclei.

Nucleophosmin/B23 (NPM) is a nucleolar phosphoprotein which shifts from nucleoli to the nucleoplasm in cells treated with certain cytotoxic agents (NPM-translocation). NPM requires GTP for localization into nucleoli (J. Biol. Chem. 268, 5823-5827, 1993). To understand more about NPM's dynamic localization, the effects of lowering ATP on NPM-translocation and rRNA synthesis were studied. When the ATP level in HeLa cells was reduced by sodium azide, NPM-translocation was blocked. Similar results were obtained when ATP was depleted by other agents, suggesting that ATP depletion was responsible for the blocking of NPM-translocation. It was found that newly synthesized rRNA accumulated in the nuclei during ATP-depletion. Significantly larger than normal nucleoli were also observed. These results indicate that NPM may be involved in the transportation of newly synthesized ribosomes.

2,4-Dinitrophenol↗
PubMed1995

GTP gamma S restores nucleophosmin (NPM) localization to nucleoli of GTP-depleted HeLa cells.

Previous studies showed that localization of nucleophosmin/B23 (NPM) to nucleoli requires adequate cellular GTP levels (Finch et al., J Biol Chem 268, 5823-5827, 1993). In order to study whether hydrolysis of GTP plays a role in NPM localization, we introduced a nonhydrolyzable GTP analog into HeLa cells. Cells were first depleted of GTP with the IMP dehydrogenase inhibitor, mycophenolic acid (MA), to induce translocation of NPM from the nucleoli to the nucleoplasm. Non-hydrolyzable GTP analogs were then introduced into cells by electroporation. We found that introduction of the non-hydrolyzable analog, GTP gamma S, was effective in restoring NPM localization to nucleoli. Cells incubated in medium containing G-nucleotides without electroporation showed no effect. To reduce the possibility that cells use guanine from degraded nucleotide to supplement GTP pools via salvage pathways, experiments were also performed in the presence of (6-mercaptopurine) 6MP, a competitive inhibitor of the salvage enzyme, HGPRT (hypoxanthine guanine phosphoribosyl transferase), in addition to MA. Under these conditions, introduction of GTP gamma S still effectively restored the localization of NPM into nucleoli. This study demonstrates that electroporation can be used effectively to introduce nucleotides into cultured cells without excessive loss of viability. Our results also indicate that the GTP dependent localization of NPM to the nucleoli may not require GTP hydrolysis.

Cell Nucleolus↗
PubMed1993

Nucleolar localization of nucleophosmin/B23 requires GTP.

Incubation of HeLa cells with the IMP dehydrogenase inhibitors: ribavirin (100 microM, 4 h), tiazofurin (100 microM, 4 h), selenazofurin (100 microM, 4 h), or mycophenolic acid (10 microM, 4 h) resulted in approximately 70% reduction in cellular GTP pools and shifting of nucleophosmin/B23 from nucleoli to nucleoplasm as detected by immunofluorescence (B23-translocation). Enzyme-linked immunosorbent assay and Western blot assay showed there is no loss or degradation of nucleophosmin/B23 protein during drug treatment. This translocation effect could be prevented by co-incubation with guanosine (100 microM) or reversed by addition of guanosine (100 microM) to the culture medium after B23-translocation had been induced by these inhibitors. Under these conditions of guanosine supplementation, cellular GTP pool concentrations were maintained at the control level. These results indicate that localization of nucleophosmin/B23 into the nucleolus is dependent on the cellular GTP level.

Biological Transport↗
PubMed1992

Teratogenic assessment of four solvents using the Frog Embryo Teratogenesis Assay--Xenopus (FETAX).

The Frog Embryo Teratogenesis Assay--Xenopus (FETAX) was used to assess the teratogenic potential of four solvents. Embryos of the South African clawed frog, Xenopus laevis, were exposed for 96 h to ethanol, dimethyl sulfoxide (DMSO), formamide or glycerol formal. Exposure groups were maintained using a static renewal system in which the exposure media were changed at 24-h intervals. Survival was monitored at 24-h intervals. Length, as an indicator of growth effects, and developmental malformations were determined at the end of the assay (96 h). Using this information, the 96-h LC50, the 96-h EC50 (Malformation), and the no observable effect levels (NOELs) for mortality, malformation and length were determined for each solvent. The teratogenic index [TI = 96-h LC50/96-h EC50 (Malformation)] also was calculated for each of the solvents. DMSO appeared to be the least toxic or teratogenic solvent examined, with a pooled LC50 of 1.92%, a pooled EC50 (Malformation) of 1.57% and TI values of 1.20 and 1.24 in replicate trials. Formamide appeared to be the most toxic solvent, with a pooled LC50 of 1.04%. Data trends suggested that ethanol was the most teratogenic solvent tested, with a pooled EC50 (Malformation) of 1.04% and TI values of 1.42 and 1.50. The results obtained in the present work for ethanol and DMSO were compared to previously published FETAX results for these two solvents. The present results are in close agreement with these results from other laboratories, thus providing further evidence supporting the interlaboratory reproducibility of FETAX results.

Abnormalities, Drug-Induced↗
PubMed1992

Studies of actinomycin D induced B23-translocation in P388D1 cells implanted in DBA/2 mice.

Nucleophosmin/B23 is a nucleolar phosphoprotein which redistributes from nucleoli to nucleoplasm (B23-translocation) when cells are exposed to certain anticancer drugs, particularly intercalators. The B23-translocation assay has been demonstrated in cell culture to correlate with drug effects and to detect drug-resistant cells. We now report the effect of actinomycin D on B23-translocation in P388D1 cells implanted in DBA/2 mice. B23-translocation was observed in cells after actinomycin D treatment in a dosage- and time-dependent manner. Translocation could be observed within 30 min after drug treatment. Complete B23-translocation with at least 1-day duration was achieved by a single injection of 0.25 mg/kg. Reduced dosages produced partial B23-translocation with shorter durations. These results indicate that B23-translocation may be useful in monitoring drug effects in animals.

Animals↗
PubMed1990

Chemotherapeutic characterization in mice of 2-amino-9-beta-D-ribofuranosylpurine-6-sulfinamide (sulfinosine), a novel purine nucleoside with unique antitumor properties.

In preclinical investigations performed in mice, 2-amino-9-beta-D-ribofuranosyl purine-6-sulfinamide (sulfinosine), a novel derivative of 6-thioguanosine (6TGR), was active against six solid tumors and four strains of experimental leukemia. Sulfinosine penetrated the central nervous system more readily than did 6TGR and, when given repeatedly, was much more effective in the treatment of L1210 leukemia, being curative for some mice. Other findings of major interest to us were the different dosing characteristics of sulfinosine and 6TGR, the divergent efficiencies of the two drugs in generating cellular resistance, and the activity of sulfinosine against experimental leukemias refractory to 6TGR and other experimental or clinically used chemotherapeutic agents. The chemotherapeutic characterization of sulfinosine that evolved from these studies suggests that this agent may have unique properties that deserve clinical consideration. Both the dosing characteristics of the drug and its pronounced activity against thiopurine-resistant experimental leukemia favor the possibility that sulfinosine could be used to advantage in the treatment of human leukemia unresponsive to 6-mercaptopurine or 6-thioguanine.

Animals↗
PubMed1990

Oxidation of 2-amino-9-beta-D-ribofuranosylpurine-6-sulfenamide to the corresponding 6-sulfonamide facilitates changes in biologic characterization that include activity against thiopurine-refractory experimental leukemia.

Preclinical investigations in vivo revealed unexpected differences in the biological characteristics of 2-amino-9-beta-D-ribofuranosylpurine-6-sulfenamide (sulfenosine, 1) and 2-amino-9-beta-D-ribofuranosylpurine-6-sulfonamide (sulfonosine, 2), two novel but structurally related derivatives of 6-thioguanosine (6TGR). Strikingly, the addition of a fully oxidized sulfur atom at the 6 position of sulfenosine produced a purine derivative (sulfonosine) that was remarkably active against experimental leukemia resistant to treatment with either sulfenosine or 6TGR. This slight structural modification also appeared to influence solubility, scheduling capability, and oral activity as well as penetration of the central nervous system (CNS) and the onset of cellular resistance. These findings underscore the dramatic changes in biologic activity that can be produced by subtle modifications in molecular structure. We trust they may also contribute to the development of improved clinical therapy.

Animals↗
PubMed1990

Changes in diacylglycerol and membrane associated protein kinase C activity reflect the growth status of xenografted human mammary carcinoma treated with 8-Cl-cAMP.

The intracellular accumulation of cAMP inhibits the growth of transformed cells in vitro and in vivo, and exposure to various cAMP analogs produces similar results. The influence of such analogs on the growth of neoplastic cells in vivo is less well defined, and the relevance of these analogs for the phosphoinositide pathway has not been established. The present report details the inhibition of tumor growth that occurred when human mammary xenografts were treated with 8-Cl-cAMP, the subsequent rebound in tumor growth that occurred when treatment ceased, and the levels of diacylglycerol and membrane-associated protein kinase C activity that characterized tumors in different growth states. Tumor levels of diacylglycerol and particulate PKC activity appeared to be influenced not only by treatment but also by treatment withdrawal. Changes in these entities tended to coincide with tumor growth rate, being relatively suppressed during growth stasis and markedly elevated during periods of rapid growth. The data presented do not establish a causal relationship. Thus, the concomitant changes noted in tumor growth and tumor levels of either diacylglycerol and membrane-associated protein kinase C may only be coincidental. Alternatively, they may indicate that cAMP analogs inhibit tumor growth in vivo by modulating the phosphoinositide pathway.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

Synthesis and in vivo antitumor activity of 2-amino-9H-purine-6-sulfenamide, -sulfinamide, and -sulfonamide and related purine ribonucleosides.

A number of 6-sulfenamide, 6-sulfinamide, and 6-sulfonamide derivatives of 2-aminopurine and certain related purine ribonucleosides have been synthesized and evaluated for antileukemic activity in mice. Amination of 6-mercaptopurine ribonucleoside (7a) and 6-thioguanosine (7b) with chloramine solution gave 9-beta-D-ribofuranosylpurine-6-sulfenamide (8a) and 2-amino-9-beta-D-ribofuranosylpurine-6-sulfenamide (sulfenosine, 8b), respectively. Selective oxidation of 8a and 8b with 3-chloroperoxybenzoic acid (MCPBA) gave (R,S)-9-beta-D-ribofuranosylpurine-6-sulfinamide (9a) and (R,S)-2-amino-9-beta-D-ribofuranosylpurine-6-sulfinamide (sulfinosine, 9b), respectively. However, oxidation of 8a and 8b with excess of MCPBA gave 9-beta-D-ribofuranosylpurine-6-sulfonamide (10a) and 2-amino-9-beta-D-ribofuranosylpurine-6-sulfonamide (sulfonosine, 10b), respectively. Similarly, amination of 5'-deoxy-6-thioguanosine (7c) afforded the 6-sulfenamide derivative (8c), which on controlled oxidation gave (R,S)-2-amino-9-(5-deoxy-beta-D-ribofuranosyl)purine-6-sulfinamide (9c) and the corresponding 6-sulfonamide derivative (10c). Treatment of 6-thioguanine (12) with aqueous chloramine solution gave 2-amino-9H-purine-6-sulfenamide (13). Oxidation of 13 with 1 molar equiv of MCPBA afforded (R,S)-2-amino-9H-purine-6-sulfinamide (14), whereas the use of 4 molar equiv of MCPBA furnished 2-amino-9H-purine-6-sulfonamide (15). The resolution of R and S diastereomers of sulfinosine (9b) was accomplished by HPLC techniques. The structures of (R)-9b and 10b were assigned by single-crystal X-ray diffraction studies. (R)-9b exists in the crystal structure in four crystallographically independent conformations. Of the 18 compounds evaluated, 13 exhibited very significant anti-L1210 activity in mice. Sulfenosine (8b) at 22 mg/kg per day X 1 showed a T/C of 170, whereas sulfinosine (9b) at 173 mg/kg per day X 1 showed a T/C of 167 against L1210 leukemia. The 5'-deoxy analogue of sulfinosine (9c) at 104 mg/kg per day also showed a T/C of 172. A single treatment with 8b, 9b, and 9c reduced body burdens of viable L1210 cells by more than 99.8%.

2-Aminopurine↗
PubMed1990

1,2,4-Diazaphosphole nucleosides. Synthesis, structure, and antitumor activity of nucleosides with a lambda 3 phosphorus atom.

Glycosylation of 1,2,4 lambda 3-diazaphosphole (4) under Lewis acid catalyzed conditions gave 1-alpha-D-ribofuranosyl-1,2,4 lambda 3-diazaphosphole (5) as the only product. Ethyl 1,2,4 lambda 3-diazaphosphole-3-carboxylate (10) was synthesized by the cyclocondensation of ethyl (chlorophosphinidene)(trimethylsilyl)acetate (8) with (trimethylsilyl)diazomethane and subsequent desilylation with tetra-n-butylammonium fluoride. Reaction of 10 with methanolic ammonia at 80 degrees C gave 1,2,4 lambda 3-diazaphosphole-3-carboxamide. Glycosylation of 10 using trimethylsilyl triflate catalyst followed by ammonlysis gave the ribavirin (1) analogue 1-beta-D-ribofuranosyl-1,2,4 lambda 3-diazaphosphole-3-carboxamide (11). Acetylation of 11 and subsequent treatment with phosphorus pentasulfide gave 2',3',5'-tri-O-acetyl-1-beta-D-ribofuranosyl-1,2,4 lambda 3-diazaphosphole-3- thiocarboxamide (13). Deprotection with methanolic ammonia gave 1-beta-D-ribofuranosyl-1,2,4 lambda 3-diazaphosphole-3-thiocarboxamide (14). Compound 14 gave a 25% increase in life span (ILS) against L1210 in female BDF1 mice. The anomeric configuration and site of glycosylation of 5 and 13 were established by single-crystal X-ray crystallography.

Animals↗
PubMed1990

Synthesis and antitumor evaluation in mice of certain 7-deazapurine (pyrrolo[2,3-d]pyrimidine) and 3-deazapurine (imidazo[4,5-c]pyridine) nucleosides structurally related to sulfenosine, sulfinosine, and sulfonosine.

7-Deaza (pyrrolo[2,3-d]pyrimidine) and 3-deaza (imidazo[4,5-c]pyridine) congeners of sulfenosine (5a and 9), sulfinosine (6a and 10), and sulfonosine (7a) have been prepared and evaluated for their antileukemic activity in mice. Amination of 2-amino-7-beta-D-ribofuranosylpyrrolo[2,3-d]pyrimidine-4(3H)-th ion e (4a) and its 2'-deoxy analogue (4c) with a chloramine solution gave the corresponding 4-sulfenamides (5a and 5c, respectively), which on selective oxidation with m-chloroperoxybenzoic acid (MCPBA) gave the respective diastereomeric 2-amino-7-beta-D-ribofuranosyl-pyrrolo[2,3-d]pyrimidine-4-sulfinamide (7-deazasulfinosine, 6a) and its 2'-deoxy derivative (6c). A similar amination of 7-(2-deoxy-beta-D-erythro-pentofuranosyl)pyrrolo[2,3-d]pyrimidine-4(3H)- thione (4b) gave the corresponding 4-sulfenamide derivative (5b). Oxidation of 5b with 1 molar equiv of MCPBA furnished (R,S)-7-(2-deoxy-beta-D-erythro-pentofuranosyl)pyrrolo[2,3-d]pyrimidine- 4- sulfinamide (6b), whereas use of excess of MCPBA afforded the corresponding sulfonamide derivative (7b). Treatment of 3-deaza-6-thioguanosine (8) with a chloramine solution gave 3-deazasulfenosine (6-amino-1-beta-D- ribofuranosylimidazo[4,5-c]pyridine-4-sulfenamide, 9). Controlled oxidation of 9 with MCPBA afforded 3-deazasulfinosine (10). As gauged by increases in the mean postinoculation life spans of L1210 inoculated mice, none of these nucleosides exhibited biologically significant activity (T/C greater than or equal to 125). Even so, antileukemic activity appeared to be influenced, albeit not uniformly, by structural modifications in the base and carbohydrate moieties of sulfenosine and sulfinosine. Thus, while several of the compounds were lacking in cytotoxic activity, eight others (4c, 5a, 5c, 6a, 6b, 7b, 9, and 10) were estimated to have reduced body burdens of viable L1210 cells by 16-77%.

Animals↗
PubMed1989

Inhibition of phosphoribosylpyrophosphate synthetase by 4-methoxy-(MRPP) and 4-amino-8-(D-ribofuranosylamino) pyrimido[5,4-d]pyrimidine (ARPP).

The basis for the antitumor activities of the exocyclic amino nucleosides 4-amino-(ARPP) and 4-methoxy-8-(D-ribofuranosylamino)pyrimido[5,4-d]pyrimidine (MRPP) was investigated. The primary target of these nucleosides appeared to be 5-phospho-alpha-D-ribofuranose-1-pyrophosphate (PRPP) synthetase. MRPP-5'-monophosphate was a competitive inhibitor (Ki = 40 microM) of the activation of this enzyme by the cofactor inorganic phosphate (K alpha = 2.2 mM). Consequently, ARPP and MRPP treatment of WI-L2 cultures rapidly inhibited both de novo pyrimidine and purine synthesis as well as the nucleotide salvage reactions dependent on PRPP, ARPP or MRPP treatment completely prevented [14C]bicarbonate incorporation into acid-soluble pyrimidine and purine nucleotides. The rate of salvage of [8-14C]hypoxanthine to form IMP was decreased by 85%. Treatment of cells with these agents caused a 50% reduction in the steady-state level of PRPP. When the capacity of the treated cells for sustained synthesis of PRPP was examined by adenine incorporation, the rate of adenine uptake was inhibited by greater than 50%. In vivo treatment of BDF1 mice with a single dose of ARPP (173 mg/kg) or MRPP (62 mg/kg) extended the mean life span of the mice, which had been inoculated intraperitoneally 1 day earlier with 1 x 10(6) L1210 murine leukemia cells, by 62 and 82% respectively. These studies indicate that MRPP and ARPP inhibit PRPP synthetase, and that PRPP synthetase may be a viable target in the development of certain antitumor agents.

Adenosine Deaminase↗
PubMed1989

Inhibition of growth and modulation of gene expression in human lung carcinoma in athymic mice by site-selective 8-Cl-cyclic adenosine monophosphate.

Site-selective cyclic AMP (cAMP) analogues inhibit growth and induce changes in morphology in a spectrum of human cancer cell lines (D. Katsaros et al., FEBS Lett., 223:97, 1987). The cellular events underlying such effects of cAMP analogues include differential regulation of type I versus type II cAMP-dependent protein kinase isozymes (S. Ally et al., Proc. Natl. Acad. Sci. USA, 85: 6319, 1988). Infusion (i.p.) of 8-Cl-cAMP, the most potent site-selective cAMP analogue, for 7 days produced regression of LX-1 lung carcinoma in athymic mice in a dose-dependent manner. The tumor regression correlated with the changing levels of cAMP receptor proteins, RI alpha and RII beta, the regulatory subunits of cAMP-dependent protein kinase type I and type II, respectively. By photoaffinity labeling with 8-N3-[32P]cAMP and immunoblotting with a monospecific anti-RII antibody, RI alpha (Mr 49,000) and RII beta (Mr 51,000) were identified in the untreated control tumors. 8-Cl-cAMP treatment induced a rapid increase of both RI alpha and RII beta in tumor cytosols and translocation (within 1 h) of only RII beta from the cytosol to the nucleus. RII beta in both cytosols and nuclei remained elevated during 8-Cl-cAMP treatment, whereas RI alpha in the cytosols gradually decreased with time of treatment after its initial transient increase. Northern blot analyses demonstrated that the RII beta mRNA level increased within 6 h of 8-Cl-cAMP treatment and remained elevated during treatment, whereas the RI alpha mRNA level decreased to below that of the untreated control tumor level after its transient increase during 1-6 h of treatment. 8-Cl-cAMP treatment also caused a sharp decrease in both N-ras and c-myc mRNA levels. These results suggest that the fundamental basis for the antineoplastic activity of 8-Cl-cAMP may reside in the restoration of normal gene regulation in neoplasms in which cAMP receptor proteins play a role.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1981

Hypernatremia during lithium and ticarcillin therapy.

A patient being treated for leukemia received lithium carbonate and ticarcillin for sepsis, and polyuria and severe hypernatremia developed. Although useful in neutropenic patients, the simultaneous use of these drugs may result in life-threatening hypernatremia.

Aged↗
PubMed1981

Hordeum and Secale mitotic genomes lie apart in a hybrid.

In both unpretreated root tip metaphases and pretreated mitoses of Hordeum vulgare L. cv. Sultan x Secale africanum Stapf F1 hybrids, Hordeum chromosomes tended to be nearer the centre of the mitosis than Secale chromosomes. This was clear in 4 serially sectioned cells examined in the electron microscope. In Feulgen squashes of 38 of 40 cells studied in the light microscope, the mean distances in each cell from the mean centromere position for the cell was less for Hordeum centromeres than for Scale centromeres. Such spatial separation of parent genomes might prevent pairing of homoeologues in hybrids.

Centromere↗
PubMed1980

Chemical carcinogen in vitro testing: a method for sizing cell nuclei in the nuclear enlargement assay.

The observation that cells often respond to carcinogens by nuclear enlargement has suggested that this property might be useful to develop a short-term screening test for such compounds. Previous methods for detecting nuclear size increases have used an image analyzer system to detect nuclear changes in individual cells. This paper details a more rapid method for obtaining nuclei by use of a stromalyzing procedure following by analysis of nuclear volumes, using a Coulter Counter Channelyzer. This new and simplified nuclear sizing method should facilitate the use of the assay as a possible carcinogenesis screen by permitting rapid and efficient testing of large numbers of compounds.

Carcinogens↗