A comparison of screening methods in two early phase oral leukoplakia clinical trials.

OBJECTIVES/INTRODUCTION: Clinical trial accrual for oral dysplasia is difficult in the United States and elsewhere. Patients with dysplastic oral leukoplakia progress to frank invasive carcinoma at a rate of 5-37% over 5 years. We compared two clinical trial screening efforts to hopefully devise better accrual strategies to these types of clinical trials. METHODS: For the first trial, we identified 244 patients with dysplastic oral leukoplakia in our university database and a media campaign. Patients were notified and screened by examination and biopsy. For the second clinical trial, we established a preneoplastic lesions clinic and teaching and communications network with regional oral healthcare professionals. RESULTS: Only one of 244 patients accrued to the first clinical trial through an organized screening effort based on database/medical records review. The second clinical trial accrued 16/30 screened patients through redirected efforts in teaching, communications, and a preneoplastic lesions clinic. CONCLUSION: We conclude that significant difficulties resulted from medical record/database review of leukoplakia patients as a screening method for leukoplakia clinical trial entry. We feel that persistent direct contact and education of healthcare professionals who are likely to examine leukoplakia patients improved accrual to the second clinical trial.

Phenotypic versus marker-assisted selection for stalk strength and second-generation European corn borer resistance in maize.

Maize ( Zea mays L.) stalk lodging is breakage of the stalk at or below the ear, which may result in loss of the ear at harvest. Stalk lodging is often intensified by the stalk tunneling action of the second-generation of the European corn borer (2-ECB) [Ostrinia nubilalis (Hübner)]. Rind penetrometer resistance (RPR) has been used to measure stalk strength and improve stalk lodging resistance, and quantitative trait loci (QTL) have been identified for both RPR and 2-ECB damage. Phenotypic recurrent selection (PS) increases the frequency of favorable alleles over cycles of selection. Several studies have indicated that marker-assisted selection (MAS) is also a potentially valuable selection tool. The objective of this study was to compare the efficiency of PS versus MAS for RPR and 2-ECB. Marker-assisted selection for high and low RPR was effective in the three populations studied. Phenotypic selection for both high and low RPR was more effective than MAS in two of the populations. However, in a third population, MAS for high RPR using QTL effects from the same population was more effective than PS, and using QTL effects from a separate population was just as effective as PS. Marker-assisted selection for resistance and susceptibility to 2-ECB using QTL effects from the same population was effective in increasing susceptibility, but not in increasing resistance. Marker-assisted selection using QTL effects from a separate population was effective in both directions of selection. Thus, MAS was effective in selecting for both resistance and susceptibility to 2-ECB. These results demonstrated that MAS can be an effective selection tool for both RPR and 2-ECB resistance. These results also validate the locations and effects of QTL for RPR and 2-ECB resistance identified in earlier studies.

Performance of transgenic corn hybrids in Missouri for insect control and yield.

The efficacy of Bacillus thuringiensis-transformed corn (Zea mays L.) hybrids compared with comparable nontransformed corn hybrids for controlling first- and second-generation European corn borer, Ostrinia nubilalis (Hübner), and second-generation southwestern corn borer, Diatraea grandiosella Dyar, was determined. Yield comparisons were obtained from the same plots of corn hybrids. Both generations of European and the second-generation of southwestern corn borer were effectively controlled, but the Bt hybrids varied in degree of control. Hybrids from Ciba Seeds, DEKALB, and Mycogen had more European corn borer tunneling than those from Novartis or Cargill, and this was generally ascribed to different transgenic events. The Bt-transformed hybrids had virtually no leaf-feeding damage and less tunneling than the non-Bt corn hybrids. Some Bt corn hybrids had no tunneling, whereas other Bt hybrids had a small amount of tunneling. All of the non-Bt hybrids had significant leaf-feeding damage and stalk tunneling from both insects. Only three live European corn borer larvae (stunted) were found in the Bt corn hybrids while splitting stalks to assess tunnel length. When insect damage was significant, and in some evaluations where damage was not significant, differences in yields among hybrids were observed. No significant insect population differences were observed for five genera of beneficial insects for Bt versus non-Bt corn hybrids. Corn hybrids that have been transformed with the Bt gene provide an effective means of control for corn borers and efforts to reduce the likelihood of development of borer resistance are warranted.

Dosage effects on morphological and quantitative traits in maize aneuploids.

Dosage effects generated by either loss or gain of a chromosome segment were used to identify chromosome regions associated with morphological and quantitative characters in maize (Zea mays L.). Using B-A translocation stocks introgressed into a B73Ht background, a chromosome arm dosage series in a Mo17Ht x B73Ht F1 hybrid background was created for 18 of the 20 chromosome arms. The dosage series was then evaluated for 12 quantitatively inherited characters to associate specific phenotypic changes in a trait with a specific chromosome arm. Not only did our results show the familiar aneuploid syndrome phenomenon, but differential dosage effects among particular chromosome arms were demonstrated. All the quantitative traits measured and all the chromosome arms examined in this study were responsive to changes in chromosome arm dosage. The possible bases behind those differences and their utility in identifying quantitative trait loci, as well as the genetic relationships among the group of quantitatively inherited characters studied, are considered. Key words : corn, chromosome arm, B-A translocations, dosage analysis.

Genetic variation in dosage effects in maize aneuploids.

In maize (Zea mays L.), the consequences of aneuploidy have been well documented, however, genetic variation in the responses to aneuploidy has not been examined. Using simple B-A translocation stocks to generate a dosage series involving segments from 14 chromosome arms, we tested for the presence of genetic variation for dosage responses in maize by examining reciprocal and maternal genotype effects on the dosage responses. Reciprocal effects examined whether there were differences between two distinctly different inbred backgrounds, Mo17Ht and B73Ht, in how they responded to loss or gain of a B73Ht segment in the Mo17Ht x B73Ht (TB) F1 cross versus a Mo17Ht segment in the B73Ht x Mo17Ht (TB) F1 cross. Maternal genotype effects questioned whether different inbred backgrounds, Sc41R, T8, and either Mo17Ht or B73Ht (depending on the male), when used as females responded differently to the loss or gain of a chromosome arm segment from the same male (either B73Ht TB or Mo17Ht TB) in an F1 cross. Numerous examples of reciprocal and maternal genetic effects were identified in this study. Most of the genetic effects were due to differences in magnitude of response rather than direction; however, tassel-branch number involving the 5S chromosome segment in the B73Ht male background and the 7L chromosome segment in the Mo17Ht male background showed a trend toward the maternal genotype effects being due to differences in the direction of the response. Key words : quantitative traits, corn, B-A translocations, dosage analysis.

Expression of A/B zeins in single and double maize endosperm mutants.

Zeins, the major endosperm proteins in maize (Zea mays L.), are deficient in the essential amino acids lysine and tryptophan. Some mutant genes, like opaque-2 (o2) and floury-2 (fl2), reduce the levels of A- and B-zeins, thereby improving maize's nutritional value. Other mutants, such as amylose-extender (ae), floury-1 (fl1), soft starch (h), dull-1 (du), shrunken-1 (sh1), sugary-1 (su1), sugary-2 (su2), and waxy (wx), primarily affect starch composition, but also alter zein composition. We undertook this study to examine the effects of some of these mutant genes on A/B-zein composition and to study the interactions of these genes in double-mutant combinations. Endosperm prolamins were extracted from inbred B37, ten near-isogenic single mutants (ae, du, fl1, fl2, h, o2, sh1, su1, su2, and wx), and most double-mutant combinations. Zeins in these extracts were fractionated by reversed-phase highperformance liquid chromatography (RP-HPLC) into 22-24 peaks. Of the resulting 22 major peaks the areas of 16 (per milligram endosperm) were significantly affected by individual mutant genes relative to the zein composition of the normal inbred. In combination these genes exhibited significant epistatic interactions in regulating the expression of individual A/B zeins. Epistatic interactions were judged to be significant when the amount of a peak in a double mutant differed from the averages for the peak in the two respective single mutants. The o2 gene, alone and in combination with other mutant genes, significantly decreased the amounts of many individual zeins. The effect of the o2 gene was the greatest of all the genes examined. Various clustering techniques were used to see if mutant effects could be grouped; among these was principal component analysis, a multivariate statistical technique that analyzes all peak sizes simultaneously. Three-dimensional scatter graphs were constructed based on the first three principal components. For the single mutants, these showed no relationships to gene actions; for the double mutants, however, this technique showed that four single mutants, o2, sh1, su1 and su2, had the greatest effects on zein composition when combined with each other and with the remaining six single mutants.

Expression of alcohol-soluble endosperm proteins in maize single and double mutants.

Many maize (Zea mays L.) mutant genes exist. Some affect protein content or composition, while others modify carbohydrates or kernel phenotype. In doublemutant lines, two mutant genes are present. We know little about interactions of such genes, however. We therefore examined a normal maize inbred, B37, 10 near-isogenic single mutants and 46 double mutants to analyze quantitative effects on alcohol-soluble endosperm proteins. Proteins were extracted with 70% ethanol0.5% sodium acetate-5% mercaptoethanol, and fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC). Early peaks were alcohol-soluble glutelin (ASG) subunits, while late peaks contained zein. Results were quantified and statistically analyzed. In many double mutants, protein compositions differed significantly from averages of compositions of corresponding single mutants. For example, a high-methionine, water-insoluble ASG is absent when the opaque-2 (o2) gene combines with shrunken-1 (sh1) or surgary-1 (su1). Another water-insoluble ASG nearly doubled when floury-2 (fl2) andsu1 combined. A high-proline, high-histidine, water-soluble ASG nearly doubled in combinations offl2 witho2,su1 and sugary-2 (su2). Zein was about half its expected value wheno2 combined with amylose-extender (ae), floury-1 (fl1), soft-starch (h),sh1 andsu1. Thus, rapid protein extraction and quantitative RP-HPLC showed major new epistatic and synergistic effects of several mutant genes on protein composition. Unexpectedly, these effects often involve genes that primarily affect starch composition or kernel phenotype. Alcohol-soluble proteins often vary in amount, as ino2 lines. They also differ in nutritional value. Thus, RP-HPLC analysis of these proteins can identify nutritionally superior genotypes, and may help explain the basis of such quality.