Toxicity of endophyte-infected tall fescue alkaloids and grass metabolites on Pratylenchus scribneri.

ABSTRACT Neotyphodium coenophialum, an endophytic fungus associated with tall fescue grass, enhances host fitness and imparts pest resistance. This symbiotum is implicated in the reduction of stresses, including plant-parasitic nematodes. To substantiate this implication, toxicological effects of root extracts, polyphenolic fraction, ergot, and loline alkaloids from endophyte-infected tall fescue were investigated using Pratylenchus scribneri, a nematode pest of tall fescue. In vitro bioassays and greenhouse studies were used as tests for effects of root fractions and compounds on motility and mortality of this lesion nematode. Greenhouse studies revealed that endophyte-infected tall fescue grasses are essentially nonhosts to P. scribneri, with root populations averaging 3 to 17 nematodes/pot, compared with 4,866 and 8,450 nematodes/pot for noninfected grasses. The in vitro assay indicated that root extracts from infected tall fescues were nematistatic. Polyphenols identified in extracts included chlorogenic acid, 3,5-dicaffeoylquinic acids, caffeic acid, and two unidentified compounds, but these were not correlated with endophyte status, qualitatively or quantitatively. Tests of several ergot alkaloids revealed that ergovaline and alpha-ergocryptine were nematicidal at 5 and 50 microg/ml, respectively, while ergocornine and ergonovine were nematistatic at most concentrations. Loline (N-formylloline), the pyrrolizidine alkaloid tested, was nematicidal (50 to 200 microg/ml). The ecological benefits of the metabolites tested here should assist in defining their role in deterring this nematode species while offering some probable mechanisms of action against plant-parasitic nematodes in general.

Fumonisin concentrations and in vivo toxicity of nixtamalized Fusarium verticillioides culture material: evidence for fumonisin-matrix interactions.

The toxic potential of nixtamalized foods can be underestimated if, during cooking, reversible fumonisin-food matrix interactions reduce the amount of mycotoxin that is detected but not the amount that is bioavailable. Fusarium verticillioides culture material (CM) was nixtamalized as is (NCM) or after mixing with ground corn (NCMC). Additional portions were sham nixtamalized without (SCM) or with corn (SCMC). Nixtamalization and sham nixtamalization reduced FB(1); CM, NCM, and SCM diets contained 9.08, 2.08, and 1.19 ppm, respectively. FB(1) was further reduced in the NCMC (0.49 ppm) but not the SCMC (1.01 ppm) diets compared to their NCM and SCM counterparts. Equivalent weights of the cooked products, uncooked CM, corn (UC) or nixtamalized UC (NUC) were fed to rats for up to three weeks. Kidney lesions in the NCM-fed group were less severe than in the CM-fed, positive control group and no lesions were found in the NCMC and other groups. Group kidney sphinganine (biomarker of fumonisin exposure) concentrations decreased in the order: CM (absolute concentration (nmol/g)=600-800)>NCM (400-600)>SCM and SCMC (30-90)>NCMC, UC and NUC (<8). Together, these results suggest that mycotoxin-corn matrix interactions during nixtamalization reduce the bioavailability and toxicity of FB(1).

Cytosine arabinoside transport and metabolism in acute leukemias and T cell lymphoblastic lymphoma.

Cytosine arabinoside (araC) has proven efficacy in acute myeloid leukemia (AML), but its place in the treatment of acute lymphoblastic leukemia (ALL) and T lymphoblastic lymphoma is uncertain. The therapeutic potential of araC has been assessed in patients with AML, ALL, and T lymphoblastic lymphoma by measuring the conversion of araC to its active metabolite, the 5'-triphosphate of araC (araCTP), in purified blasts from patients as well as in normal polymorphs and lymphocytes. In all leukemias, araCTP was the major intracellular metabolite of araC. The highest araCTP formation was in blasts from T lymphoblastic lymphoma, which formed threefold more nucleotide than myeloblasts, and in turn myeloblasts formed twofold more araCTP than lymphoblasts from ALL. The mean araCTP formation in myeloblasts was sixfold greater than polymorphs, but in contrast, lymphoblasts and lymphocytes formed low and similar amounts of this nucleotide. Reasons for the sixfold range in araCTP accumulation in the various leukemic blasts were studied. The mean size of myeloblasts was 35-70% larger than lymphoblasts when compared on the basis of protein or intracellular water content, but T lymphoblastic lymphoma blasts and lymphoblasts were the same size. Activities of deoxycytidine kinase, deoxycytidylate deaminase, and pyrimidine nucleoside monophosphate kinase were not different between any of the leukemic cell types. The number of nucleoside transport sites on blasts was estimated by measuring the equilibrium binding of [3H]nitrobenzylthioinosine (NBMPR), which binds with high affinity to the transporter. Scatchard analysis yielded mean values of 27,500 sites/cell for T lymphoblastic lymphoma blasts, 10,000 sites/cell for myeloblasts, and 2,300 sites/cell for lymphoblasts. Our previous work has shown that araC influx correlates with the maximum number of 3H-NBMPR binding sites in leukemic and normal white cells. A strong correlation was observed between the number of nucleoside transport sites per leukemic blast cell and the accumulation of intracellular araCTP from extracellular araC at 1 microM. Membrane transport of araC at the low concentrations (approximately 1 microM), which are achieved therapeutically, is a major rate-limiting step in its conversion to araCTP by leukemic blast cells. Myeloblasts form more araCTP than lymphoblasts because of both higher nucleoside transport capacity and larger cell size. The highest nucleoside transport capacity and largest conversion of araC to araCTP is in T lymphoblastic lymphoma, which suggests that araC may be effective in the treatment of this disease.

Resistance to Spodoptera frugiperda (Lepidoptera: Noctuidae) and Euxesta stigmatias (Diptera: Ulidiidae) in sweet corn derived from exogenous and endogenous genetic systems.

Field trials using Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) and Euxesta stigmatias Loew (Diptera: Ulidiidae) were conducted to evaluate resistance and potential damage interactions between these two primary corn, Zea mays L., pests against Lepidoptera-resistant corn varieties derived from both endogenous and exogenous sources. The endogenous source of resistance was maysin, a C-glycosyl flavone produced in high concentrations in varieties 'Zapalote Chico 2451' and 'Zapalote Chico sh2'. The exogenous resistance source was the Bacillus thuringiensis (Bt)11 gene that expresses Cry1A(b) insecticidal protein found in 'Attribute GSS-0966'. Damage by the two pests was compared among these resistant varieties and the susceptible 'Primetime'. Single-species tests determined that the Zapalote Chico varieties and GSS-0966 effectively reduced S. frugiperda larval damage compared with Primetime. E. stigmatias larval damage was less in the Zapalote Chico varieties than the other varieties in single-species tests. E. stigmatias damage was greater on S. frugiperda-infested versus S. frugiperda-excluded ears. Ears with S. frugiperda damage to husk, silk and kernels had greater E. stigmatias damage than ears with less S. frugiperda damage. Reversed phase high-performance liquid chromatography analysis of nonpollinated corn silk collected from field plots determined that isoorientin, maysin, and apimaysin plus 3'-methoxymaysin concentrations followed the order Zapalote Chico sh2 > Zapalote Chico 2451 > Attribute GSS-0966 = Primetime. Chlorogenic acid concentrations were greatest in Zapalote Chico 2451. The two high maysin Zapalote Chico varieties did as well against fall armyworm as the Bt-enhanced GSS-0966, and they outperformed GSS-0966 against E. stigmatias.

Identification of polynuclear aromatic hydrocarbons in cigarette smoke and their importance as tumorigens.

Fraction F20, which in other studies was the most tumorigenic neutral fraction of cigarette smoke condensate (CSC), was separated by gel filtration chromatography into refined subfractions for identification of the polynuclear aromatic hydrocarbons (PAH) and for bioassay on mouse skin. Several hundred PAH were positively identified. Subfraction F55. containing most of the carcinogenic PAH as well as numerous unidentified components, was almost as tumorigenic to 7,12-dimethylbenze[a]anthracene (DMBA)-pretreated female outbred CD-1 mice as was F20. When F55 was separated into two parts, the first containing unidentified material (F55A) and the second containing the PAH (F55B), neither was significantly tumorigenic. F55B, combined with two other active fractions from the neutral and the acidic portions of CSC, exhibited a synergistic tumorigenic effect on DMBA-pretreated mice. The results supported the concept that the PAH in cigarette smoke must interact with other components in order to exert a tumorigenic effect.

Degradation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate in human leukemic myeloblasts and lymphoblasts.

The intracellular half-life for retention of the active triphosphate metabolite 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (araCTP) of 1-beta-D-arabinofuranosylcytosine was measured in vitro in blast cells from patients with acute myeloblastic leukemia, acute lymphoblastic leukemia, and T-cell lymphoblastic lymphoma. araCTP accumulation from 1 microM 1-beta-D-arabinofuranosylcytosine in leukemic blast cells was closely correlated with the nucleoside transport capacity as measured by equilibrium binding of [3H]nitrobenzylthioinosine. The half-life of araCTP retention was related to araCTP accumulation only when the level of araCTP was expressed as a percentage of total intracellular 1-beta-D-arabinofuranosylcytosine metabolites. Accumulation of 1-beta-D-arabinofuranosyluracil 5'-monophosphate was inversely related to the half-life of araCTP retention and directly related to dCMP deaminase activity in cell free extracts. No conversion of 1-beta-D-arabinofuranosyluracil to 1-beta-D-arabinofuranosyluracil 5'-monophosphate was detectable in intact cells. The end product of araCTP degradation was 1-beta-D-arabinofuranosyluracil and it is proposed that conversion of 1-beta-D-arabinofuranosylcytosine 5'-monophosphate to 1-beta-D-arabinofuranosyluracil 5'-monophosphate is a step in the degradative pathway of araCTP. However, it is the cells' nucleoside transport capacity which primarily determines the level of intracellular araCTP accumulation.

Transport and metabolism of 1-beta-D-arabinofuranosylcytosine in human ovarian adenocarcinoma cells.

1-beta-D-Arabinofuranosylcytosine (araC) is an effective drug in the i.p. therapy of ovarian carcinoma but little is known of its transport and metabolism in this tumor. Influx of araC at 1 microM into cultured human ovarian carcinoma cells (CI 80-13S) was largely inhibited by nanomolar concentrations of the nucleoside transport inhibitor, nitrobenzylthioinosine, while the residual influx (approximately 10%) was inhibited only by micromolar concentrations of nitrobenzylthioinosine. There was a two fold greater density of specific [3H]nitrobenzylthioinosine binding to the nucleoside transporters on the ovarian than on cultured human leukemic cells (RC2a). Calculated turnover rates of the nucleoside transporter for 1 microM araC were 5-fold less in ovarian than in leukemic cells. The major metabolic product of araC was 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (araCTP) which accumulated in the ovarian cells to levels half those achieved in the leukemic cells. AraC was the major product of araCTP degradation in ovarian cells consistent with a pathway (araCTP--------araCMP----araC) which is different from that previously found in leukemic cells (araCTP--------araCMP----araUMP----araU). Despite these differences, ovarian carcinoma cells show substantial accumulation of araCTP from extracellular araC.

Genetic mechanisms underlying apimaysin and maysin synthesis and corn earworm antibiosis in maize (Zea mays L.).

C-glycosyl flavones in maize silks confer resistance (i.e., antibiosis) to corn earworm (Helicoverpa zea [Boddie]) larvae and are distinguished by their B-ring substitutions, with maysin and apimaysin being the di- and monohydroxy B-ring forms, respectively. Herein, we examine the genetic mechanisms underlying the synthesis of maysin and apimaysin and the corresponding effects on corn earworm larval growth. Using an F2 population, we found a quantitative trait locus (QTL), rem1, which accounted for 55.3% of the phenotypic variance for maysin, and a QTL, pr1, which explained 64.7% of the phenotypic variance for apimaysin. The maysin QTL did not affect apimaysin synthesis, and the apimaysin QTL did not affect maysin synthesis, suggesting that the synthesis of these closely related compounds occurs independently. The two QTLs, rem1 and pr1, were involved in a significant epistatic interaction for total flavones, suggesting that a ceiling exists governing the total possible amount of C-glycosyl flavone. The maysin and apimaysin QTLs were significant QTLs for corn earworm antibiosis, accounting for 14. 1% (rem1) and 14.7% (pr1) of the phenotypic variation. An additional QTL, represented by umc85 on the short arm of chromosome 6, affected antibiosis (R2 = 15.2%), but did not affect the synthesis of the C-glycosyl flavones.

Assessment of proliferative responses to granulocyte-macrophage colony-stimulating factor (GM-CSF) in acute myeloid leukaemia using a fluorescent ligand for the nucleoside transporter.

Nucleoside transporter expression has been linked to proliferation in a variety of haemopoietic cell types. Granulocyte-macrophage colony-stimulating factor (GM-CSF) was given for 72 h before commencing chemotherapy in 15 patients with relapsed or refractory acute myeloid leukaemia (AML) and in 11 patients serial bone marrows were taken for measurement of [3H]thymidine labelling index, Ki-67 positivity and maximal binding of 5-(SAENTA-x8)-fluorescein, a flow cytometry ligand which enumerates nucleoside transporter sites. GM-CSF caused proliferation of marrow myeloblasts in eight of 11 patients, while in three patients there was no change in proliferative indices. The expression of nucleoside transporters increased up to 4-fold in the myeloblasts from the patients showing a proliferative response to GM-CSF but there was no increase in transporters on the myeloblasts from the three non-responding patients. A close correlation was found between the fold increase in nucleoside transporter expression and the fold increase in labelling index of marrow myeloblasts (r = 0.86, n = 9, p < 0.01). In one patient with acute megakaryoblastic leukemia, GM-CSF caused parallel increases in labelling index, Ki-67 positivity and numbers of nucleoside transporters on peripheral blood blast cells. Thus induction of proliferation by cytokine increases the expression of nucleoside transporters on leukaemic myeloblasts studied in serial samples from the same source (bone marrow or blood). The suitability of 5-(SAENTA-x8)-fluorescein for two colour flow cytometric analysis allows the rapid enumeration of nucleoside transporters in the myeloblast compartment of heterogeneous marrow samples.

Circulating ghrelin is sensitive to changes in body weight during a diet and exercise program in normal-weight young women.

Ghrelin is directly involved with short-term regulation of energy balance. Although circulating levels of ghrelin are elevated in anorexia nervosa and reduced in obesity, the role of ghrelin in regulating long-term energy balance in healthy women has not been investigated. We examined the effects of a 3-month energy deficit-imposing diet and exercise intervention on circulating ghrelin in normal-weight, healthy women. Body composition, resting metabolic rate, and serum ghrelin were measured at pre-, mid-, and postintervention in controls (n = 7), who performed no exercise, and exercising women who remained weight stable (n = 5) or lost weight (n = 10). Exercise training occurred five times per week, and subjects were fed a specific diet. Ghrelin significantly increased over time (770 +/- 296 to 1322 +/- 664 pmol/liter) in the weight-loss group compared with the controls and the weight-stable group (P < 0.05). Changes in ghrelin were negatively correlated with changes in body weight (r = -0.61; P < 0.05). Body fat, body weight, and resting metabolic rate significantly decreased in the weight-loss group before the increase in ghrelin. These findings suggest that ghrelin responds in a compensatory manner to changes in energy homeostasis in healthy young women, and that ghrelin exhibits particular sensitivity to changes in body weight.

The P2Z-purinoceptor of human lymphocytes: actions of nucleotide agonists and irreversible inhibition by oxidized ATP.

1. Extracellular adenosine triphosphate (ATP) is known to open a receptor-operated ion channel (P2Z class) in human lymphocytes which conducts a range of cationic permeants. The activity of a range of different agonists and inhibitors towards the P2Z-purinoceptor was investigated by measuring the agonist-induced influx of Ba2+ into fura-2 loaded lymphocytes. 2. The most potent agonist was 2' & 3'-0-(4-benzoylbenzoyl)-ATP (benzoylbenzoic ATP) which gave 2 fold greater maximum Ba2+ influx and had a 10 fold lower EC50 than for ATP. The rank order of agonist potency in K(+)-media was benzoylbenzoic ATP >> ATP = 2-methylthio ATP = 2-chloro ATP > ATP-gamma-S. ADP, UTP and alpha,beta-methylene ATP were unable to stimulate Ba2+ influx. 3. Extracellular Na+ inhibited the increment of Ba2+ influx induced by all concentrations of ATP, 2-methylthio ATP, 2-chloroATP and ATP-gamma-S. This inhibitory effect of extracellular Na+ is also reflected in the different EC50s for benzoylbenzoic ATP (8 microM in K(+)-media, 18 microM in Na(+)-media) but the maximal response to this agonist was the same in the presence or absence of Na+. 4. Treatment of lymphocytes with 2,3 dialdehyde ATP (oxidized ATP0 at 300 microM for 60 min gave total and irreversible inhibition of ATP-induced Ba2+ influx. 5'-p-Fluorosulphonyl benzoyladenosine (FSBA) also was an irreversible inhibitor but the maximal inhibition achieved was 90%. 5. It is concluded that the P2z-purinoceptor of human lymphocytes has a rank order of agonist potency which clearly distinguishes it from other P2-receptors and that oxidized ATP is a convenient irreversible inhibitor for the P2Z-purinoceptor.

Saturation of intracellular cytosine arabinoside triphosphate accumulation in human leukemic blast cells.

Accumulation of cytosine arabinoside triphosphate (araCTP) from a range of cytosine arabinoside (araC) concentrations (1-50 microM) was measured during incubations of leukemic cells freshly isolated from patients with acute leukemia. In all but one patient, increments in extracellular araC above 10 microM did not increase intracellular araCTP levels. This maximal level of araCTP accumulation ranged from 254 to 1607 pmol/10(7) cells attained after 1 h incubation and did not correlate with either the number of nucleoside transporters on the cell membrane or the Vmax of araC phosphorylation in cell free extracts. Extremely low araCTP accumulation (103 pmol/10(7) cells/h at 50 microM araC) was observed in an AML patient with the unusual finding of micromyeloblasts. These cells also had very low numbers of nucleoside transport sites (less than 500 sites/cell) and were mitotically inactive. The unique feature of the myeloblasts from this patient was that intracellular araCTP accumulation showed a linear dependence on extracellular araC up to 50 microM with no evidence of saturation.

Evaluation of a pulse oximeter and customized probe for pulp vitality testing.

Current routine methods for assessment of pulp vitality rely on stimulation of A-delta nerve fibers and give no direct indication of blood flow within the pulp. Recent papers have suggested that pulse oximeters may be used to diagnose pulp vitality by detection of blood flow. In this study, an optimized pulse oximeter probe for teeth was designed, built and tested using the Biox 3740 Oximeter (Ohmeda, Louisville, CO). Following preliminary in vitro tests, the probe was tested clinically. Pulse waveforms from maxillary and mandibular anterior teeth were noted. Simultaneous readings from the subjects' finger were used as controls. Pulse wave readings from the teeth were found to be synchronous with the finger probe, but not consistently. It was easier to maintain continuous readings from mandibular incisors than from maxillary incisors. The average percentage synchronization with the pulse was 28.95% for maxillary incisors and 50.28% for mandibular incisors. This difference was significant (p = 0.05). The overall accuracy of the commercial instrument was disappointing, and in its present form it was not considered to have clinical value.

Changes and challenges in rural graduate medical education: the Family Medicine Spokane Rural Training Track experience in Colville, Wash.

Rural community-based graduate medical education programs in family practice are considered wise investments in America's future because they generate highly trained physicians who typically settle and practice in rural communities. In recent years, however, federal funding cutbacks and revised accreditation requirements have threatened the viability of these programs. In Colville, Wash., Mount Carmel Hospital has responded by agreeing to continue its collaboration with the Northeast Washington Medical Group to fully fund the cost of the Family Medicine Spokane Rural Training Track family practice residency program.

Effect of level of endophyte infection, nitrogen fertilization rate, grazing period, and paddock exchange on some chemical properties of four bovine tissues.

Three grazing experiments were conducted to determine the effect of level of endophyte infection, rate of N fertilization of tall fescue grass, grazing period, and paddock exchange on selected chemical properties of four bovine carcass tissues. Samples of semitendinosus and longissimus muscle and of subcutaneous and perinephric adipose tissue were excised from the left side of each carcass. In Exp. 1, percentage of stearic acid was higher (P less than .05) and percentages of palmitoleic and oleic acid were lower (P less than .05) in all tissues from steers grazed on LELN Au-Triumph fescue than in tissues from steers grazed on LELN KY-31 fescue. Grazing periods of 175 or 245 d or paddock exchange (Exp. 2) had no significant effect on proximate composition of semitendinosus and longissimus muscles; however, moisture content was higher (P less than .05) in the semitendinosus muscle from steers grazed on 100% (100E) endophyte-infected KY-31 fescue. Forage treatment, grazing period, and paddock exchange (Exp. 2 and 3) had no significant effect on percentage of saturated fatty acids in the subcutaneous, semitendinosus, and longissimus tissue samples. In Exp. 2 and 3, percentages of saturated fatty acids were higher (P less than .05) in subcutaneous and perinephric adipose tissue samples from steers grazed on 100E than in samples from steers grazed on zero endophyte (OE) fescue.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrent selection for corn earworm (Lepidoptera: Noctuidae) resistance in three closely related corn southern synthetics.

Plant resistance offers a good alternative to pesticides for protecting corn (Zea mays L.) from attack by corn earworm, Helicoverpa zea (Boddie). The GT-CEW-RS8 synthetic is a breeding population with some resistance to corn earworm, but based on variability for this trait, further improvement was possible in this population. S1 recurrent selection for corn earworm resistance was conducted to improve three synthetics derived from GT-CEW-RS8. The objective of this research was to study the effectiveness of these selection programs to increase insect resistance and maintain agronomic performance. Cycles of selection for each population were evaluated under four environments. Significant gains in resistance were realized, but all three synthetics derived from GT-CEW-RS8 showed a negative response for yield. However, yield losses were not very dramatic for 66RM4 and inbreeding depression would not affect the yield performance in hybrid combination. Selection for yield done simultaneously with selection for reducing ear damage by corn earworm and husk tightness could assist in avoiding decreased yield.

Lost P1 allele in sh2 sweet corn: quantitative effects of p1 and a1 genes on concentrations of maysin, apimaysin, methoxymaysin, and chlorogenic acid in maize silk.

In the United States, insecticide is used extensively in the production of sweet corn due to consumer demand for zero damage to ears and to a sweet corn genetic base with little or no resistance to ear-feeding insects. Growers in the southern United States depend on scheduled pesticide applications to control ear-feeding insects. In a study of quantitative genetic control over silk maysin, AM-maysin (apimaysin and methoxymaysin), and chlorogenic acid contents in an F2 population derived from GE37 (dent corn, P1A1) and 565 (sh2 sweet corn, p1a1), we demonstrate that the P1 allele from field corn, which was selected against in the development of sweet corn, has a strong epistatic interaction with the a1 allele in sh2 sweet corn. We detected that the p1 gene has significant effects (P < 0.0001) not only on silk maysin concentrations but also on AM-maysin, and chlorogenic acid concentrations. The a1 gene also has significant (P < 0.0005) effects on these silk antibiotic chemicals. Successful selection from the fourth and fifth selfed backcrosses for high-maysin individuals of sweet corn homozygous for the recessive a1 allele (tightly linked to sh2) and the dominant P1 allele has been demonstrated. These selected lines have much higher (2 to 3 times) concentrations of silk maysin and other chemicals (AM-maysin and chlorogenic acid) than the donor parent GE37 and could enhance sweet corn resistance to corn earworm and reduce the number of applications of insecticide required to produce sweet corn.

Restriction fragment length polymorphism markers associated with silk maysin, antibiosis to corn earworm (Lepidoptera: Noctuidae) larvae, in a dent and sweet corn cross.

Maysin, a C-glycosylflavone in maize silk, has insecticidal activity against corn earworm, Helicoverpa zea (Boddie), larvae. Sweet corn, Zea mays L., is a vulnerable crop to ear-feeding insects and requires pesticide protection from ear damage. This study was conducted to identify maize chromosome regions associated with silk maysin concentration and eventually to transfer and develop high silk maysin sweet corn lines with marker-assisted selection (MAS). Using an F2 population derived from SC102 (high maysin dent corn) and B31857 (low maysin sh2 sweet corn), we detected two major quantitative trait loci (QTL). It was estimated that 25.6% of the silk maysin variance was associated with segregation in the genomic region of npi286 (flanking to p1) on chromosome 1S. We also demonstrated that a1 on chromosome 3L had major contribution to silk maysin (accounted for 15.7% of the variance). Locus a1 has a recessive gene action for high maysin with the presence of functional p1 allele. Markers umc66a (near c2) and umc105a on chromosome 9S also were detected in this analysis with minor contribution. A multiple-locus model, which included npi286, a1, csu3 (Bin 1.05), umc245 (Bin 7.05), agrr21 (Bin 8.09), umc105a, and the epistatic interactions npi286 x a1, a1 x agrr21, csu3 x umc245, and umc105a x umc245, accounted for 76.3% of the total silk maysin variance. Tester crosses showed that at the a1 locus, SC102 has functional A1 alleles and B31857 has homozygous recessive a1 alleles. Individuals of (SC102 x B31857) x B31857 were examined with MAS and plants with p1 allele from SC102 and homozygous a1 alleles from B31857 had consistent high silk maysin. Marker-assisted selection seems to be a suitable method to transfer silk maysin to sweet corn lines to reduce pesticide application.

Stability of the mycotoxin deoxynivalenol (DON) during the production of flour-based foods and wheat flake cereal.

Deoxynivalenol (DON) is a mycotoxin found in cereal grains and cereal-based foods. DON concentrations in finished products are reduced under some processing conditions, but not others. DON concentrations in flour, wheat and selected foods made from them under commercially relevant conditions were compared by GC with electron capture detection. Average concentrations (n = 9/item) in cookies, crackers and pretzels ranged from 61% (cookies) to 111% (pretzels) compared with flour (100% = 0.46 µg g⁻¹). Lesser amounts were found in donuts and bread: their respective DON concentrations were 44% and 30% that of flour. Mass balance estimates for DON (µg g⁻¹ flour equivalents) ranged from 50% (bread = 0.23 µg g⁻¹ flour equivalents) to 120% (donuts), indicating that dilution by recipe ingredients contributed to DON reductions in bread and accounted for all of the apparent reduction in donuts. Mass balance estimates averaged 76% (crackers) to 107% (pretzels) for the other flour products. DON concentrations were higher in cereal flakes (0.55 µg g⁻¹ in the finished product and 0.58 µmg g⁻¹ on a mass balance basis) than in wheat (0.40 µg g⁻¹), suggesting that DON concentrations might increase during processing of wheat cereals under some conditions. In summary, DON concentrations of finished food products were reduced ≥ 50% only in bread and donuts. Reduction in bread resulted from a combination of DON 'loss' and dilution by recipe ingredients whereas the reduction in donuts was due entirely to dilution. These results are further evidence of DON stability during the preparation of popular flour or wheat-based products.