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O C Yoder

Publications and source records attributed to O C Yoder.

At least 55 records · Page 3Linked to original sources
PubMed1987

Antiproliferative properties of flavone acetic acid (NSC 347512) (LM 975), a new anticancer agent.

The antiproliferative activity of flavone acetic acid (LM 975) was investigated on human adenocarcinoma cell lines (HCC-P2998, HCC-M1544, HCC-M1410, HT 29, LoVo), on a murine colon adenocarcinoma cell line (Colon 26), on murine pancreatic adenocarcinoma cells growing in primary culture (Pan 03) and on human normal fibroblasts (N1). No cytotoxic effects were found against human normal fibroblasts. LM 975 was active against murine adenocarcinoma Pan 03 and Colon 26, known to be sensitive in vivo too and, to variable extents, on human adenocarcinoma cell lines. LM 975 in vitro cytotoxic potency was relatively low. The high concentrations (1.0-1.4 mM) required to obtain a cytotoxic effect are, however, pharmacologically reasonable since they are comparable with drug plasma levels in mice or in patients treated with tolerable doses. After a relatively short LM 975 treatment (2 h) DNA, RNA and protein synthesis were inhibited in different proportions. In more sensitive cells LM 975 appeared to inhibit RNA synthesis more than DNA and protein synthesis. Inhibition of macromolecule synthesis after 2 h exposure was completely reversed in 24 h recovery. After 2 h treatment no detectable DNA breakage was found by the alkaline elution method, thus corroborating the idea that this compound does not act by causing DNA damage.

Adenocarcinoma↗
PubMed1987

Selectable genes for transformation of the fungal plant pathogen Glomerella cingulata f. sp. phaseoli (Colletotrichum lindemuthianum).

Glomerella cingulata f. sp. phaseoli (Gcp) was transformed using either of two selectable markers: the amdS + gene of Aspergillus nidulans, which encodes acetamidase and permits growth on acetamide as the sole nitrogen source and the hygBR gene of Escherichia coli which encodes hygromycin B (Hy) phosphotransferase and permits growth in the presence of the antibiotic Hy. The amdS+ gene functioned in Gcp under control of A. nidulans regulatory signals and hygBR was expressed after fusion to a promoter from Cochliobolus heterostrophus, another filamentous ascomycete. Protoplasts to be transformed were generated with the digestive enzyme complex Novozym 234 and then were exposed to plasmid DNA in the presence of 10 mM CaCl2 and polyethylene glycol. Transformation occurred by integration of single or multiple copies of either the amdS+ or hygBR plasmid into the fungal genome. There was no evidence of autonomous plasmid replication. Transformants were mitotically stable on selective and nonselective media. However, transforming DNA in hygBR transformants was observed to occasionally rearrange during nonselective growth, resulting in fewer copies of the plasmid per genome. These transformants were capable of infecting bean (Phaseolus vulgaris), the Gcp host plant, and after recovery from infected tissue were found to have retained both the transforming DNA unrearranged in their genomes and the Hy resistance phenotype. All single-conidial cultures derived from both amdS+ and hygBR transformants had the transplanted phenotype, suggesting that transformants were homokaryons.

Amidohydrolases↗
PubMed1987

Iron Specifically Protects Corn Protoplasts from T-Toxin of Cochliobolus heterostrophus.

Ferric ion reduced the damaging effects of T-toxin, a series of linear beta-polyketols produced by the pathogenic fungus Cochliobolus heterostrophus, on leaf mesophyll protoplasts from susceptible T-cytoplasm corn. Of nine metals tested, only ferric and ferrous ions had this effect. Despite the presence of 12 available oxygen atoms in each T-toxin molecule, there was no evidence for the formation of an aqueous Fe(2+)- or Fe(3+)-T-toxin complex. The protective effect of iron was eliminated by a molar excess of EDTA. Iron had no effect on the sensitivity of T-cytoplasm mitochondria to T-toxin, even at a 1000-fold molar excess, nor did it protect roots of T-cytoplasm corn seedlings from inhibition by T-toxin. The mechanism by which iron specifically protects protoplasts from T-toxin is not understood, but time lapse experiments suggest that iron acts on some intracellular site to modify T-toxin sensitivity and not on a transport system at the cell surface.

Journal Article↗
PubMed1987

Development of a fungal transformation system based on selection of sequences with promoter activity.

A novel strategy was used to develop a transformation system for the plant pathogenic fungus Cochliobolus heterostrophus. Sequences capable of driving the expression of a gene conferring resistance to the antibiotic hygromycin B in C. heterostrophus were selected from a library of genomic DNA fragments and used, with the selectable marker, as the basis for transformation. The library of random 0.5- to 2.0-kilobase-pair fragments of C. heterostrophus genomic DNA was inserted at the 5' end of a truncated, promoterless Escherichia coli hygromycin B phosphotransferase gene (hygB) whose product confers resistance to hygromycin B. C. heterostrophus protoplasts were transformed with the library and selected for resistance. Resistant colonies arose at low frequency. Each colony contained a transformation vector stably integrated into chromosomal DNA. When the transforming DNA was recovered from the genome and introduced into C. heterostrophus, resistant colonies appeared at higher frequency. We determined the sequences of two of the C. heterostrophus DNA fragments which had been inserted at the 5' end of hygB in the promoter library and found that both made translational fusions with hygB. One of the two fusions apparently adds 65 and the other at least 86 amino acids to the N-terminus of the hygB product. Plasmids containing hygB-C. heterostrophus promoter fusions can be used unaltered to drive hygB expression in several other filamentous ascomycetes. This approach to achieving transformation may have general utility, especially for organisms with relatively undeveloped genetics.

Ascomycota↗
PubMed1986

A cloned tryptophan-synthesis gene from the ascomycete Cochliobolus heterostrophus functions in Escherichia coli, yeast and Aspergillus nidulans.

A gene (TRP1) in the tryptophan biosynthetic pathway of the fungal plant pathogen Cochliobolus heterostrophus was isolated by complementation of an Escherichia coli trpF mutant which lacked phosphoribosylanthranilate isomerase (PRAI) activity. The cloned gene also complemented an E. coli trpC mutant lacking indoleglycerolphosphate synthase (IGPS) activity, a yeast trp1 mutant missing PRAI activity and an Aspergillus nidulans trpC mutant. It functioned in E. coli and A. nidulans without apparent rearrangement but in yeast only after the 5' end of the gene was deleted. The gene was subcloned on a 4.65-kb DNA fragment and the PRAI domain was localized to a 2.9-kb region. It showed homology to the A. nidulans trpC and Neurospora crassa trp-1 genes. There was one predominant transcript of C. heterostrophus TRP1, the same size (2.6-kb) as one of the two functional transcripts produced by A. nidulans trpC. The constitutive activity of the C. heterostrophus TRP1 gene was high whereas that of the A. nidulans trpC gene was low.

Aldose-Ketose Isomerases↗
PubMed1986

Flavone acetic acid: a novel agent with preclinical antitumor activity against colon adenocarcinoma 38 in mice.

Flavone acetic acid, given on Days 2 and 9 at a dose of 267 mg/kg, inhibited tumor growth completely in 60%-80% of mice with early-stage Colon Adenocarcinoma 38. The therapeutic efficacy of the flavone against this tumor was retained when the sites of tumor implantation and drug administration were separated. Flavone acetic acid also caused regression of advanced (500-mg) Colon 38 tumors, with greatest efficacy observed following administration of high individual dose rather than high total dose. Unlike many previous potential anticancer agents, only modest activity was observed for this compound against either P388 or L1210 leukemia.

Adenocarcinoma↗
PubMed1984

Investigation of the antitumor activity of new epoxide derivatives. Part I: s-Triazinetrione derivatives.

The noteworthy cytostatic activity of triglycidyl-s-triazinetrione and the planned clinical testing of this new active substance induced us to subject this class of substances to closer examination. By chemical reaction of one of the three glycidyl groups present it was possible to introduce wide variations in the properties of the compounds, whilst still retaining the active principle. A number of these substances possessed very high antitumor activity as revealed in the leukemia screening test (P 388; mouse). The influence of other substituents within the glycidyl groups affecting the reactivity of the epoxides groups was also examined.

Animals↗
PubMed1984

Investigation of the antitumor activity of new epoxide derivatives. Part II: N-glycidylated oxo-nitrogen heterocycles.

A number of N-glycidyl compounds derived from oxo-substituted nitrogen heterocycles such as diazines, triazines, diazoles, triazoles as well as condensed ring systems containing these units have been synthesised. All products were tested for their antitumor activity against leukaemia in the mouse. Almost all of the approx. 50 di- and triglycidyl compounds showed activity, whereby 5 of them exhibited an increase of lifespan of 200% and more. The most active compound was 1,2,4-triglycidyl-urazol.

Animals↗
PubMed1983

Isolation of DNA from filamentous fungi and separation into nuclear, mitochondrial, ribosomal, and plasmid components.

A general procedure for purifying and efficiently separating four types of DNA from filamentous fungi has been developed. The protocol involves (i) disruption of mycelial cells by blending in liquid nitrogen followed by suspension of cell contents in buffer containing high concentrations of protease and EDTA; (ii) deproteinization with phenol; (iii) cesium chloride/bisbenzimide density gradient centrifugation to separate nuclear DNA, mitochondrial DNA, and ribosomal DNA; and (iv) agarose gel electrophoresis to identify and purify plasmid DNA, if present. All DNAs are suitable for digestion with restriction endonucleases, ligation, and cloning in Escherichia coli, and DNAs from step three are recovered in high-molecular-weight form. The procedure has been used successfully with several dozen isolates of the plant pathogenic fungus Cochliobolus heterostrophus (including both laboratory strains and isolates collected directly from the field), and has been found to be equally suitable for C. carbonum, Neurospora crassa, N. tetrasperma, and Nectria haematococca.

Cell Nucleus↗
PubMed1979

Reduction of Adenosine Triphosphate Levels in Susceptible Maize Mesophyll Protoplasts by Helminthosporium maydis Race T Toxin.

Helminthosporium maydis race T (HMT) toxin caused a reduction in the steady-state ATP levels when leaf mesophyll protoplasts isolated from maize containing Texas male-sterile (T) but not male-fertile (N) cytoplasm were incubated in the dark. At a toxin concentration 10 times the mean effectived dose for inhibition of root growth, the ATP levels began to fall in 30 to 90 seconds, fell by 50% in about 4 minutes, and reached 23% of the original levels in 100 minutes. This is faster than any previously observed response of whole cells or tissues to HMT toxin. In protoplasts incubated in the light, ATP levels were 25% higher than in the dark and were either unaffected or only slightly diminished by toxin. 3-(3,4-Dichlorophenyl)-1, 1-dimethylurea (DCMU), an inhibitor of photosynthetic electron transport, overcame the effect of light on both toxin-treated and control protoplasts. Oligomycin, an inhibitor of mitochondrial ATP synthesis, mimicked the effects of toxin in the dark, in the light, and in the light plus DCMU, but it was not specific for T cytoplasm. During the first 24 hours of culture, ATP levels in control protoplasts increased in both the light and dark. In the dark, ATP was not detectable after 24-hour incubation in the presence of toxin, whereas in the light a substantial amount of ATP remained. Our results are compatible with the hypothesis that mitochondria in vivo are inhibited by HMT toxin. Other responses of cells and tissues to toxin can be explained in terms of reduced ATP levels.

Journal Article↗
PubMed1978

Cytoplasm-specific Effects of Helminthosporium maydis Race T Toxin on Survival of Corn Mesophyll Protoplasts.

High yields of mesophyll protoplasts were obtained from leaves of corn (Zea mays L., inbred W64A). Many protoplasts survived a week in the dark in a simple osmoticum. Culture filtrate from Helminthosporium maydis race T at dilutions of 1:10,000 to 1:20,000 destroyed protoplasts with Texas male-sterile (T) cytoplasm. Substantial damage to protoplasts with nonmale-sterile (N) cytoplasm occurred only at a 1:20 dilution. High concentrations of partially purified H. maydis race T (HMT) toxin (32.5-130 mug dry weight/ml) did not reduce survival of protoplasts with N cytoplasm or C or S male-sterile cytoplasms after 6 days of exposure. Protoplasts with T or TRf (fertility restored) cytoplasm collapsed within 1 to 3 days after treatment with 0.13 mug of HMT toxin/ml, which was one-fifth the level causing 50% inhibition of T cytoplasm seedling root growth. Protoplasts with T cytoplasm which were washed after 30 minutes or more of exposure to HMT toxin also collapsed within a few days. Cultured W64A T protoplasts and freshly isolated protoplasts from inbreds C103 and Mo17 with T cytoplasm were less sensitive to HMT toxin than freshly isolated W64A T protoplasts. Toxin-treated protoplasts survived longer in the light than in the dark. The sensitivity and specificity of the system described will facilitate physiological, ultrastructural, and genetic studies of toxin action.

Journal Article↗
PubMed1977

Ultrastructural effects of Helminthosporium maydis race T toxin on mitochondria of corn roots and protoplasts.

Zea mays inbred W64A in Texas (T, toxin sensitive) male sterile and non-male sterile (N, toxin resistant) cytoplasms were utilized. Roots of freshly germinated seeds were treated for 15 min of 2 hr with culture filtrate from liquid grown Helminthosporium maydis Race T, or with a chloroform extractable purified fraction from the culture filtrate. In the susceptible W64A T line, toxin treatment, both crude and purified, caused swelling and loss of matrix densiy in mitochondria of root cap and vacuolated cells in the region of elongation. One hour treatment with the chloroform extractable toxin fraction caused similar effects or mitochondria of isolated leaf protoplasts. This is the first report of such rapid in vivo effects of HmT toxin on mitochondria. Difficulty in obtaining consistent preservation of meristem mitochondria precluded drawing firm conclusions concerning that region of the root. In the resistant W64A N line, protoplast and root mitochondria were unaffected by the toxin.

Drug Resistance↗
PubMed1977

Evaluation of a Chemical Method for Assay of Helminthosporium maydis Race T Toxin.

A chemical test reported by Karr et al. (Plant Physiol. 55:727) to assay for host-specific toxin produced by Helminthosporium maydis race T was evaluated. Preparations from culture filtrates of both race T isolates, containing host-specific toxin, and similar preparations from race O isolates, containing no detectable host-specific toxin, gave positive reactions in the chemical assay. Also, preparations containing active or inactive toxin gave equal responses in this test. The procedure does not provide a reliable method for assaying H. maydis race T toxin.

Journal Article↗
PubMed1973

Anaerobic nitrite production by plant cells and tissues: evidence for two nitrate pools.

Tobacco (Nicotiana tabacum L. cv. Xanthi) XD cells containing nitrate and nitrate reductase stopped producing nitrite after approximately 1 hour when incubated under anaerobic conditions. The cessation of nitrite production was not due to an inactivation of the nitrate reducing system. This was shown by the ability of the cells to resume anaerobic nitrite production at a rate similar to the initial rate of nitrite production upon exposure to nitrate, monohydroxy alcohols or pyrazole. Cessation of nitrite production also could not be attributed to leakage of nitrate from the cells. Although some nitrate did leak from the cells, most of the nitrate was still in the cells by the time anaerobic nitrite production ceased. We infer the existence of a small metabolic pool and a large storage pool of nitrate, such that nitrite production ceases when the metabolic pool is depleted of nitrate. The metabolic pool of nitrate in tobacco cells decreased 170-fold as the culture aged from 3 to 5 days. However, total cellular nitrate during this period remained relatively constant.Anaerobic nitrite production by barley (Hordeum vulgare) aleurone layers and corn (Zea mays) leaf sections also ceased after only a small fraction of endogenous nitrate was reduced and resumed again upon addition of exogenous nitrate. In contrast to that found with tobacco cells, the metabolic pool of nitrate in corn leaf sections remained constant with age, while total endogenous nitrate increased. These results were interpreted to mean that higher plants in general contain metabolic and storage pools of nitrate, the properties of which vary with species and physiological variables.

Journal Article↗
PubMed1973

Effects of Helminthosporium carbonum Toxin on Nitrate Uptake and Reduction by Corn Tissues.

Susceptible corn tissues exposed to the host-specific toxin of Helminthosporium carbonum race 1 reduced more nitrate to nitrite than did control tissues, as measured by an in vivo method. There were no differences in nitrate reductase activities extracted from treated and control tissues and assayed by an in vitro method. Toxin-treated susceptible roots removed nitrate from solution and accumulated it in the tissues twice as fast as did control roots. Uptake by resistant roots was stimulated also, provided approximately 100 times higher concentrations of toxin were used. Toxin-stimulated nitrate uptake occurred in the presence of tungstate, which eliminates nitrate reductase activity. Toxin did not cause leakage of nitrate from roots under these conditions. Thus, toxin-enhanced nitrate accumulation was caused by increased nitrate uptake rather than by decreased nitrate metabolism or decreased nitrate leakage. The data indicate that toxin increases the rate of nitrate reduction in vivo by increasing the availability of substrate, not by stimulation of enzyme synthesis.

Journal Article↗
PubMed1973

Effects of Helminthosporium carbonum Toxin on Absorption of Solutes by Corn Roots.

Susceptible corn roots exposed to the host-selective toxin of Helminthosporium carbonum took up and retained more NO(3) (-), Na(+), Cl(-), 3-o-methylglucose, and leucine than did control roots. Stimulatory effects on uptake were more pronounced with freshly cut roots than with roots that were washed and aged. Solutes were accumulated against a concentration gradient, and toxin-treated tissues developed a steeper gradient than did control tissues. Toxin affected both the low and high affinity uptake systems for Na(+) and Cl(-). Toxin did not affect uptake of Na(2) (-), K(+), Ca(2+), phosphate ion (H(2)PO(4) (-) and HPO(4) (-)), SO(4) (-), and glutamic acid. No toxin-induced leakage of any solute tested was detected within 5 to 6 hr after initial exposure to toxin. The data suggest that toxin from H. carbonum does not cause the general plasma membrane derangement caused by other host-selective toxins. Instead, H. carbonum toxin may cause specific changes in characteristics of the plasmalemma, which result in increased uptake of certain solutes.

Journal Article↗