Interchangeability of genotypes and growth locations for high-quality, high-protein wheat production in Australia

The aim of this study was to assess whether the recent finding that 4 Prime Hard wheat varieties grown at southern sites provided flour of comparable quality with that from northern sites is likely to be generally applicable to other varieties, as this is especially important as new varieties are developed. The grain, dough processing, and baking properties of samples from 4 sets of lines, each grown over 2 seasons at 2 northern and 2 southern sites, was assessed. The samples included 2 sets of doubled haploid lines (one derived from Hartog × Klasic, differing only at Glu-A3, and the other Hartog × CD-87, differing at 5 glutenin loci), and 2 sets of F8 crossbred lines (from Janz/Hartog and Janz*2/Dollarbird, permitting an additional comparison of effects of allelic variation at the Glu-D1 locus). Approximately similar grain protein contents were obtained at one pair of northern and southern sites (respectively Narrabri and Ariah Park, 12–14%) and a second pair of northern and southern sites (respectively Roma and Walpeup, 14–17%, although the latter was consistently higher). The results demonstrated that the grain, dough, and baking properties of the lines were broadly similar at each protein content, and that in general, grain from the southern sites had comparable quality characteristics with that from the northern sites. However, in 1997, the Walpeup southern site suffered very dry conditions late in grain filling, and several of the grain samples were of low size and poor flour milling extraction rate and colour. In 1998, wet conditions late in the season meant that the grain at Ariah Park was lower in protein content and doughs were of lower extensibility and produced depressed loaf volumes. The variation in glutenin subunit composition also permitted the conduct of a detailed comparison of allelic influences on flour processing and baking properties at 4 sites and in 4 backgrounds. This revealed significant effects of allelic variation at Glu-B1, Glu-D1, and Glu-B3 on dough properties, with the effect of Glu-B1 differing between sets of lines.

Within-field variation in wheat quality: implications for precision agricultural management

In this study, 9 Western Australian fields sown to dryland wheat were monitored using precision agricultural techniques, in order to understand implications for processing quality of the grain. Four fields received variable inputs of N fertiliser, and 6 received variable seed rates. In most cases, there was a very large variation within-field in grain yield, protein content, and protein quality, and such variation was related to variation in soil acidity, soil nitrate, and soil organic carbon, and specific weed and pest problems in some fields, as well as variation in the inputs. Grain protein content was positively correlated with soil nitrate levels in 6 of the 7 fields for which soil analyses were carried out. For several of the larger fields, separate harvesting of zones within the fields having differences in grain protein content would have enabled a greater proportion of the grain to be in a higher return quality grade. In 7 of the 9 fields, variation in protein quality (sodium dodecyl sulfate-sedimentation volume, SDS-SV) was greater than variation in protein content. The different measures of protein quality (SDS-SV, polymeric protein (glutenin) content, and glutenin molecular weight distribution) sometimes followed similar spatial trends, but in many cases did not. Therefore, total protein estimates are probably suitable measures for predicting within-field variation in protein quality. In none of the 9 fields was there overall a negative relationship between grain yield and protein content, although limited moisture availability can affect such relationships. The results suggest that the use of precision agricultural methods to manipulate inputs such as fertiliser, lime, or seed rates to increase yield does not have a negative effect on protein content. Farmers, therefore, can use precision agricultural methods along with other approaches to maximise wheat yield and grain protein content/quality at the same time.

Albumin polymorphism and mapping of a dimeric a-amylase inhibitor in wheat

Any new protein or DNA marker is potentially useful to add detail to already constructed genetic chromosome maps and may be valuable in breeding programs wherever polymorphism exists. Non-gluten proteins represent 15–20% of total wheat grain proteins. Isoelectric focusing of wheat (Triticum aestivum L. em Thell.) proteins on ultrathin gels showed high resolution and was found to be a useful tool in the differentiation of wheat varieties. Seventeen hexaploid wheat varieties were screened to investigate polymorphism of albumin proteins using isoelectric focusing. Polymorphism was observed for albumin polypeptides of pI 5.20, 5.85, 6.25, and 7.1, and 8.0. The polymorphic protein of pI 7.1 was mapped by analysing doubled haploid populations from the intervarietal crosses, Cranbrook x Halberd and Synthetic x Opata 85. This protein locus was designated as Iha-B1.2, and is located on the short arm of chromosome 3B.

Analysis of DDT residues in soil by ELISA: an international interlaboratory study

An international interlaboratory study was conducted to determine the performance of a group of laboratories from developing and developed countries. The study used a commercial microwell ELISA on unknown samples spiked with different levels of DDT. The study design was based on Youden pairs and balanced replicates. Two soils, differing in particle size distributions, organic matter content, and cation-exchange capacities and thought to be DDT-free, were spiked at 5 DDT levels between 0.025 and 2 mg/kg. Nineteen laboratories in 17 countries took part in the collaborative trial; of these, the majority were modestly equipped laboratories in developing countries. Samples were analyzed without filtration or cleanup and using standards of pure DDT in methanol. Data were analyzed for repeatability and reproducibility, and average recoveries at the spike levels were calculated. Mean real recoveries for both soils were similar (103% for soil A and 100% for soil B), with values between 0.1 and 2 mg/kg DDT. Precision estimates were best in the linear working range of the assay (0.1-0.5 mg/kg DDT), with reproducibility relative standard deviations (RSDR) typically averaging about 38 and 46% near the upper and lower detection limits, respectively. Corresponding repeatability relative standard deviation (RSDr) values were 20-36% and 36-57%. Thus, even though much of the trial was performed under developing country conditions, performance statistics were similar to other reported results obtained with ELISAs on small molecules of agricultural importance, such as mycotoxins and pesticide and antibiotic residues.

Rapid antibody-based field test to distinguish between Helicoverpa armigera (Lepidoptera: Noctuidae) and Helicoverpa punctigera (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) are the two most important insect pests of cotton production in Australia and require application of insecticides to control them. H. armigera has developed resistance to several insecticides but H. punctigera has not. Cost-effective management of insecticide resistance requires that growers be able to determine the proportion of H. armigera eggs or young larvae present on their crop before applying insecticides. This is impossible visually. We generated two monoclonal antibodies that reacted with the insect protein "lipophorin" and were capable of discriminating individuals of the two species at all life-stages. The antibodies were incorporated into a rapid test kit that was tested under field conditions over two growing seasons. Results obtained with the kit agreed closely with those obtained by rearing larvae through to second instar.

Development of immunoassays for tyramine and tryptamine toxins of Phalaris aquatica L

The leaves of the perennial pasture grass Phalaris aquatica L. (phalaris) contain two groups of known toxins, indole alkaloids, primarily dimethyltryptamines and N-methyltyramines, which cause illnesses in grazing animals, especially sheep. Using amino-reactive and phenolic hydroxyl-reactive homobifunctional reagents, simple methods were devised for coupling toxins representative of those in phalaris to carrier proteins and enzymes for ELISA development. ELISAs were produced for both groups of toxins. Dimethyltryptamines were most sensitively detected [lower limit of detection (LLD) of 1 microg/L for bufotenine] using rabbit anti-bufotenine antibodies, coupled to ovalbumin using divinyl sulfone, with detection using a peroxidase conjugate prepared using the same hapten coupled with 1, 4-butanediol diglycidyl ether. The assay cross-reacted with other toxins of the same class (N,N-dimethyltryptamine and N, N-dimethyl-5-methoxytryptamine) but not with the structurally related amino acids histidine and tryptophan. The most sensitive N-methyltyramine assay (LLD of 1 microg/mL for N-methyltyramine) utilized antisera to tyramine with N-methyltyramine coupled to peroxidase. Significant cross-reaction was seen with the low-grade toxin hordenine, but detection of tyramine was poorer, whereas the amino acid tyrosine was not detected. These assays could be applied to the analysis of simple extracts of Phalaris leaves with minimal interference. A good correspondence was observed between toxin levels by ELISA and estimates from a more tedious thin-layer chromatography method. The method has now been incorporated in a Phalaris breeding program.

Immunoassay for wheat processing quality: utilization of a sandwich assay incorporating an immobilized single-chain fragment

A single-chain fragment (scFv) was engineered from a monoclonal antibody to high molecular weight glutenin subunits (HMW-GS), wheat flour polypeptides that play a major role in determining the mixing- and extension strength-related properties of dough and its subsequent baking performance. The scFv was expressed in a thioredoxin mutant Escherichia coli strain that allows disulfide bond formation in the cytoplasm and incorporated into a diagnostic test for wheat quality. Although the scFv lacks the more highly conserved antibody constant regions usually involved with immobilization, it was able to be directly immobilized to a polystyrene microwell solid phase without chemical or covalent modification of the protein or solid phase and utilized as a capture antibody in a double-antibody (two-site) immunoassay. In the sandwich assay, increasing HMW-GS concentrations produced increasing assay color, and highly significant correlations were obtained between optical densities obtained in the ELISA using the scFv and the content of large glutenin polymers in flours as well as measures of dough strength as measured by resistance to dough extension in rheological testing. The assay using the scFv was able to be carried out at lower flour sample extract dilutions than that required for a similar assay utilizing a monoclonal capture antibody. This research shows that engineered antibody fragments can be utilized to provide superior assay performance in two-site ELISAs over monoclonal antibodies and is the first application of an engineered antibody to the analysis of food processing quality.

Development of a compound-specific ELISA for flufenoxuron and an improved class-specific assay for benzoylphenylurea insect growth regulators

This study describes immunochemical approaches for the compound-specific detection of flufenoxuron and class-specific detection of benzoylphenylurea (BPU) insecticides. With the aim of developing a highly specific immunoassay for flufenoxuron, a hapten was synthesized by introducing a spacer arm at the 2,6-difluoro substituent aromatic ring of a flufenoxuron derivative. An IC(50) value of 2.4 ppb was obtained for flufenoxuron, with detection of the other four BPUs being more than 4000-fold less sensitive. For the development of class-specific ELISA for five BPUs, a new approach was used for the hapten preparation in which a butanoic acid linkage was introduced into the 3,5-dichloro-substituted aniline ring of chlorfluazuron analogue. Although the resultant ELISA still exhibited slightly differing cross-reactions for these five BPUs, this method had broader specificity than the previously reported polyclonal antibody-based ELISA. Spike and recovery studies for five BPUs in soil and water indicated that both the compound- and class-specific ELISAs were able to quantitatively detect BPU residues in soil and water. This study also provided additional insights into the influence of the immunizing hapten structure on the specificities of the antibodies obtained.

Development of Immunoassays for Type II Synthetic Pyrethroids. 1. Hapten Design and Application to Heterologous and Homologous Assays

Immunoassays differing in selectivities for pyrethroid insecticides have been developed for the detection of type II pyrethroids, including deltamethrin, cypermethrin, and lambda-cyhalothrin. Two approaches were employed in hapten synthesis to raise antibodies with different cross-reactions: (1) use of three spacer attachment points to offset different parts of molecules from the points of attachment and (2) use of linkers with and without bulky groups in the enzyme conjugate to reduce antibody affinities for the spacer arm in the immunoassay. The first approach resulted in the preparation of three series of haptens with a spacer attached (1) at the aromatic moiety of pyrethroid, (2) through the middle of the molecule, and (3) at the cyclopropane moiety. Haptens based on the derivatives of the pyrethroid metabolites were also prepared. The second approach involved the use of a linker with a bulky (cyclohexane ring) functionality for preparation of an enzyme conjugate. While most combinations of antibody and conjugate could be used in immunoassays for detection of deltamethrin in the 10-100 µg/L range, in most cases the limits of detection of the assays (for total isomers of a particular target pyrethroid) were lowered 10-50 fold by treatment of the pyrethroid standards with dilute alkali to produce a different isomer mix. Fifteen antisera prepared using 8 haptens were each screened with 14 peroxidase conjugates, and 26 antibody/conjugate combinations were selected for further study on the basis of the assay sensitivity, dynamic behavior, and specificity for deltamethrin, cypermethrin, and cyhalothrin. These immunoassays provided 50% inhibition of antibody binding (IC(50)) values between 1.5 and 4.2 µg/L of isomerized total deltamethrin and limits of detection of 0.2-0.7 µg/L. The most sensitive immunoassay for total deltamethrin was obtained using cypermethric acid-KLH as the immunogen and a conjugate based on a derivative of cypermethrin coupled through the middle of the molecule to peroxidase. These provided an IC(50) of 2 µg/L and a limit of detection of 0.2 µg/L of isomerized total deltamethrin. However, no particular hapten design produced antisera of clearly superior sensitivity or specificity for deltamethrin. Differing cross-reactions with the closely related pyrethroids, deltamethrin, cypermethrin, and cyhalothrin, were obtained, and for several antibodies the cross-reaction as well as the limits of detection could be altered by varying the conjugate combinations. Each of the 12 antibody/enzyme conjugate combinations that sensitively detected deltamethrin were very stereospecific, detecting the alphaS, 1R cis, (DM1), and alphaR, 1R cis (DM2) isomers only; the assay sensitivity was greater for the latter isomer.

Development of Immunoassays for Type II Synthetic Pyrethroids. 2. Assay Specificity and Application to Water, Soil, and Grain

Cross-reactions of a panel of immunoassays developed for type II (alpha-cyano-) synthetic pyrethroids were evaluated with type I and II compounds. Cross-reactions of both groups were affected by alkali treatment. The treatment typically increased sensitivities of type II compounds, and decreased cross-reactions of type I compounds. After isomerization, each of the 12 combinations studied provided more sensitive detection of deltamethrin than the other compounds, even in the case of antisera and enzyme conjugates based on cypermethrin, cyhalothrin, or their fragments. Several immunoassays were selective for deltamethrin. Assays with the broadest specificities detected type I and II compounds with IC(50) values of 20-400 µg/L. None of the assays detected compounds lacking a cyclopropane ring (fenvalerate, fluvalinate). Spike and recovery studies for deltamethrin in water, soil, and wheat grain indicated that the selected immunoassays quantified it with high precision and good recoveries. Good correlations between immunoassay and gas chromatography/mass spectrometry data were also obtained for incurred residues of deltamethrin and bifenthrin extracts of water and soil samples.

A rapid antibody-based test for Sec-2, a marker for the short arm of chromosome 2 of rye (2RS)

A simple monoclonal antibody-based screening test has been developed for the presence of translocations of the short arm of chromosome 2 of rye (2RS) with wheat chromosome 2B. 2RS encodes a set of about three polypeptides known as Mr 75 000 gamma-secalins. Use of the antibody test for these secalins enabled screening of several hundred seeds per day. The antibody could readily distinguish 2BL–2RS translocations and 2R substitutions from 1BL–1RS translocations or nontranslocation wheats. Use of the antibody in analysis of segregating progeny for Sec-2 in several wheat backgrounds was successful. Results with a selection of the seed population were checked using protein gel electrophoresis, with 100% correct confirmation. Key words : rye, wheat, seed proteins, translocation, diagnostic test.

Cloning of a wheat 15-kDa grain softness protein (GSP). GSP is a mixture of puroindoline-like polypeptides

The wheat starch 15-kDa protein (called grain softness protein or GSP) consists of a major polypeptide and several minor polypeptides. An antiserum raised against GSP was used to screen a wheat cDNA library. A cDNA family encoding approximately 15-kDa proteins that included a heptapeptide sequence previously isolated from protease digests of GSP was identified. A partial cDNA was used in a prokaryotic expression system to produce a fusion protein which reacted strongly against the original anti-GSP serum. A new antiserum raised against the fusion protein produced a weak reaction against a 15-kDa polypeptide extracted from wheat seeds. The results suggest that the proteins encoded by the cDNA family form a minor component of the mixture of 15-kDa polypeptides defined as GSP. RNA complementary to the cDNAs could be extracted from both soft and hard wheat grains from about half-way through grain filling. The encoded proteins are novel members of the 2S superfamily of seed proteins, a diverse family of proteins which maintain a characteristic framework of cysteine residues. The deduced proteins show the highest similarity to the oat 16-kDa avenin and to wheat puroindoline (a lipid-binding 15-kDa protein from wheat). Review of previously published data shows that puroindoline is also closely related to the major polypeptide of GSP, suggesting that the lipid-binding properties of GSP polypeptides may influence grain softness.

Studies of in vitro gamma-interferon production in coeliac disease as a response to gliadin peptides

The effects of certain fractions of a peptic-tryptic-pancreatinic (PTP) digest of wheat gliadin and of synthetic peptides on the production of gamma interferon (gamma-IFN) in cultures of whole blood from adult patients with coeliac disease (CD) have been studied using a sandwich enzyme immunoassay. The most active peptides were fraction 9, its two principal sub-fractions (sub-fractions 1 and 2) and a synthetic peptide of sequence RPQQPYPQPQPQ (peptide V) corresponding to the principal peptide obtained from reversed-phase HPLC of fraction 9. Results with blood from the control group of subjects also indicated some response to these antigens, in most cases at similar levels to those observed with the coeliacs. Fraction 1 of the PTP digest and the other nine synthetic peptides tested were inactive with both coeliacs and controls. These results are in agreement with the results of in vivo and in vitro toxicity tests. They provide evidence of a link between toxicity and cell-mediated immune response in CD, and suggest that peptide V represents one of the active parts of the gliadin molecule.

Isolation and characterization of wheat triticin cDNA revealing a unique lysine-rich repetitive domain

Polyclonal antibodies were raised against a purified 22 kDa triticin polypeptide (delta) and were used to screen a wheat seed cDNA library in the Escherichia coli expression vector lambda gt11. The isolated cDNA clones were grouped into three families based on their cross-hybridization reactions in DNA dot-blot studies. Southern blots of genomic DNAs extracted from ditelocentric and nullisomic-tetrasomic lines of Chinese Spring wheat, probes with the excised cDNA inserts, indicated that one of the three families (9 clones) had triticin clones. This was finally confirmed by comparing the predicted amino acid sequences of two of these clones (lambda Tri-12, lambda Tri-25) with the published tryptic peptide sequences of triticin. The Southern blots also showed that there is at least one triticin gene located on the short arm of each of the homoeologous group 1 chromosomes (1A, 1B, 1D), although till now no triticin protein product has been identified for the chromosome 1B. The nucleotide sequence of the largest triticin cDNA clone lambda Tri-25 (1567 bp) is presented here, and its predicted amino acid sequence shows strong homology with the legumin-like proteins of oats (12S globulin), rice (glutelin) and legume seeds. A unique feature of the triticin sequence is that it contains a lysine-rich repetitive domain, inserted in the hypervariable region of the typical legumin-like genes. Northern blotting of total RNA extracted from different stages of the developing wheat seed revealed that the triticin gene expression is switched on 5-10 days after anthesis (DAA). There was a steady increase in the level of triticin mRNA until 20 DAA, after which it started decreasing. The maximum mRNA accumulation occurred between 17 and 20 DAA. These observations conform closely with the published data on triticin protein accumulation during grain development.

Synthesis of Organothiophosphate Antigens for the Development of Specific Immunoassays

By use of t-butyl 3-[ chloro ( methoxy ) phosphorothioylamino ] propanoate (1), a general method was developed that allowed the preparation of analogues of specific organothiophosphates ; these analogues are suitable for use as haptens in the development of tests for detection of the individual organophosphates. The bifunctional reagent (1) was conveniently prepared from readily available starting materials.

Co-existence of coeliac disease and insulin-dependent diabetes mellitus in children: screening sera using an ELISA test for gliadin antibody

The prevalence of coeliac disease in children with insulin-dependent diabetes mellitus was investigated using a screening test of serum for antigliadin antibody by ELISA. One hundred and eighty (180) unselected diabetic children were screened for IgA and IgG class antigliadin antibodies (AGA); children with either grossly elevated or slightly elevated AGA had small bowel biopsies. The four children with the highest IgA AGA had total villous atrophy. These four children were considered to have unsuspected coeliac disease. The prevalence of coeliac disease in this group of children was one in 45. Anti-gliadin IgA and IgG tests are suitable for screening children at high risk of having coeliac disease.

Differentiation of coeliac disease and other malabsorption diseases using specific serum antigliadin IgG subclass profiles and IgA1 levels

The differential diagnostic potential of serum gliadin-specific IgG subclass antibodies was assessed by comparing the antigliadin IgG1, 2, 3, 4 profile at different stages of coeliac disease with that of gastro-intestinal infection and also conditions associated with increased intestinal permeability. The IgG subclass profile of untreated coeliac disease was found to be the same as in healthy controls (IgG1 approximately IgG2 > IgG3 > IgG4), with only the magnitude of the individual subclass responses being increased in coeliac patients. Coeliac adults and children on gluten-free diets had different antigliadin IgG subclass profiles with IgG2 being elevated. Increased intestinal permeability or recent gastro-intestinal infection did not alter the antigliadin subclass profile from that observed in healthy individuals. Assessment of the diagnostic potential of antigliadin IgA1 and IgG1-4 measurements in screening for coeliac disease demonstrated that measurement of subclasses of gliadin-specific IgA and IgG was less sensitive and specific compared with the combined use of total antigliadin IgA and IgG. Therefore it is suggested that IgG subclasses should not be used for routine screening for coeliac disease.

Cellular and humoral responses in coeliac disease. 2. Protein extracts from different cereals

The humoral and cellular immune responses to grain protein extracts from coeliac-toxic and non-toxic cereals were compared by use of a number of ELISA and immunoblotting methods and the indirect leucocyte migration inhibition factor (LMIF) assay. Both adult and child coeliacs had elevated levels of serum antibody to proteins from the coeliac-toxic cereals, namely bread wheat, durum wheat, rye and barley and low levels of proteins from other cereals. Using protein blotting techniques, antibody binding was greatest to gliadins/low mol mass glutenin subunits and homologous prolamins from rye and barley, consistent with the ELISA findings. Competition ELISA and preabsorption tests indicated that antibody reaction to maize storage proteins did not simply result from cross-reaction of antigliadin antibodies. In LMIF assays, only the wheat extracts had activity in coeliac patients. This is most likely partly due to loss of some of T-cell epitopes from the extraction technique required for these proteins, as well as the relatively small effects seen for even very active fractions in the LMIF assay.

Cellular and humoral responses in coeliac disease. 1. Wheat protein fractions

The humoral and cellular immune response of coeliac individuals to various wheat protein fractions was studied using serum antibody ELISA assays and the indirect leucocyte migration inhibition factor (LMIF) assays. Greater migration inhibition factor activity was seen in coeliacs on a gluten-free-diet having low serum antibody titres, and using purified T-cells instead of total peripheral blood mononucleocytes. Gliadin was the most active fraction in both assays. Raised antibodies to low-molecular weight and high-molecular weight glutenin polypeptides was observed, though these proteins had little migration inhibition factor activity. No cellular or humoral response was seen to albumins or globulins. Proteins associated with the granules of well-washed wheat starch are distinct from gluten proteins and had little T-cell activity, correlating with clinical observations that properly prepared wheat starch is devoid of coeliac toxicity. The greater specificity of the humoral response for individual wheat protein fractions in this study, compared with the earlier reports, likely results from cross-contamination in the earlier work of each fraction with gliadin.

A reliable screening test for coeliac disease: enzyme-linked immunosorbent assay to detect anti-gliadin antibodies in serum

A simple, rapid, highly reproducible enzyme-linked immunosorbent assay detecting anti-gliadin antibodies in serum to screen for coeliac disease (CD) is described. By combining the results of anti-gliadin IgA and IgG determinations the overall sensitivity of the assay was found to be 100% and the specificity 96% for children and 99% for adults. Significantly elevated antigliadin IgA and IgG antibodies were detected in all 20 children and all 25 adults with untreated CD. False positive results were found in 1/79 histologically normal control and 5/86 disease control children, while for adults false positive rates were 0/74 and 1/34 for the healthy and disease control groups, respectively. Anti-gliadin IgA and IgG was measured in serum samples from 52 coeliac patients (11 children and 41 adults) treated with a gluten-free diet (GFD). Each of the children and 28 of the adults who followed a strict GFD had significantly lower IgA and IgG levels than untreated CD patients. The serum anti-gliadin IgA and IgG levels of the 13 adults not complying with a GFD were similar to those found for untreated CD patients. This assay is recommended as a screening test for CD as well as a tool for follow-up of treated patients.

Chromosomal control of wheat gliadin protein epitopes: analysis with specific monoclonal antibodies

The genetic relationships between small clusters of monomeric alcohol-soluble wheat (Triticum aestivum L.) grain storage proteins (gliadins) were studied using a panel of monoclonal antibodies and immunoblotting, ELISA, and RIA methods. Use of Chinese Spring nullisomic-tetrasomic lines showed that several narrow-specificity antibodies bound specifically to gliadins encoded by genes located on a single chromosome. In at least one case, antibodies bound to genetic "blocks" of gliadins, indicating that these block members have structural homology. However, often not all gliadins of a block were recognized by an antibody. For broad-specificity antibodies and some narrow-specificity antibodies, structural genes on several chromosomes were important. Studies with several primitive wheat species indicated that, while antibodies usually bound gliadins from the same genome in bread and primitive wheats, antibodies sometimes bound proteins of quite differing mobilities in the two wheat types. Use of antibodies to identify gliadin blocks is simpler than block analysis based on performing crosses, and should be of value in monitoring genotype/end-use quality relationships.

Chemistry, coeliac-toxicity and detection of gluten and related prolamins in foods

Some recent advances in the understanding of the chemistry of gluten proteins and its relationship to the toxicity of different fractions in coeliac disease (gluten intolerance) is reviewed. Most recent studies on gluten toxicity have used in vitro analyses of cellular immune activation by gluten fractions and peptides. Our work indicates that gliadin is the most active of the different protein families found within the wheat grain and that a specific peptide sequence located in the amino terminus domain of alpha-gliadin and containing the sequence proline-serine-glutamine-glutamine was most active. Improvement in the dietary management of coeliac disease is possible by use of test kits for the detection of gluten in foods. Both laboratory kits and home test kits (suitable for use by individual coeliacs) are available and reliably detect gluten from wheat, rye and barley even after cooking or baking.

Enzyme immunoassay for determination of gluten in foods: collaborative study

A collaborative study was performed in 15 laboratories to validate a monoclonal antibody-based enzyme immunoassay (EIA) for determination of gluten in foods. The study included 13 samples: maize starch, "gluten-free" baking mixes, wheat flours, cookies, cooked meats, and a soup. Gluten was present in these samples at either zero or 0.02 to 10% by weight, i.e., over almost 3 orders of magnitude. The mean assay values for the foods varied from 88 to 105% of the actual amounts. The assay was quantitative for cereal products and the soup with repeatability (RDS-r, relative standard deviation) and reproducibility (RSD-R) of 16-22% and 24-33%, respectively. The assay was semiquantitative for the processed meat products (RSD-r 14 and 26% and RSD-R 46 and 56%), probably because gluten was unevenly distributed in the small (1 g) samples that were analyzed. The ELISA method produced no false positive results, and false negatives obtained with tannin-containing foods could be avoided by use of a modified sample extractant. None of the collaborators reported problems in following the protocol. The method has been adopted official first action by AOAC for determination of wheat gluten in foods.

Self-management of dietary compliance in coeliac disease by means of ELISA "home test" to detect gluten

To improve compliance with a gluten-free diet in coeliac disease a simple prototype test kit was developed to detect gluten in foods for use at home. The test is based on monoclonal antibodies to heat-stable gluten proteins which crossreact appropriately with barley and rye proteins. It is suitable for use with a wide range of raw or cooked foods. The food is extracted with dilute hydrochloric acid and 1 drop of the extract transferred to an antibody-coated tube; enzyme-labelled gluten detection antibody is added and after 3 min the tube is washed and colour developer is added. The reaction is stopped after 2 min, stabilising the blue colour. The home kit was compared with a quantitative laboratory kit, and the qualitative agreement was very good. The kit could distinguish foods with trace gluten contents (acceptable for a "gluten-free" diet) from those with a slightly higher but unacceptable gluten content. In a trial of the prototype kit by 47 coeliac disease patients of diverse ages and educational backgrounds, 93% of tests correctly identified foods as acceptable or unacceptable.

Identification of reactive synthetic gliadin peptides specific for coeliac disease

Gluten intolerance (coeliac disease) is characterised by the development of a small intestinal lesion following exposure to the gliadin fraction after consumption of wheat and related cereals. Cellular immune mechanisms are thought to be responsible for gliadin toxicity, but the toxic sequence/s within gliadin have not been clearly established. A panel of synthetic gliadin peptides was tested using peripheral blood mononuclear cells from coeliac patients and two assays for cell-mediated immunity. Using the indirect leucocyte migration inhibition factor and the macrophage procoagulant activity assays, gliadin peptides which were located in the aminoterminal or the proline-rich domain of the alpha/beta gliadin molecule were coeliac-active. Peptides predicted by T cell algorithms or on the basis of homology to adenovirus Ad12 Elb protein and which were located in the proline-poor gliadin domains were inactive. Protein sequence studies which indicate significant homology in the proline-poor gliadin domains with a number of non-coeliac-toxic seed proteins also supported the hypothesis that the proline-rich domains may be more important in the pathogenesis of coeliac disease.

Macrophage procoagulant activity as an assay of cellular hypersensitivity to gluten peptides in coeliac disease

Gluten and casein digests were tested for their ability to induce a cellular immune response on peripheral blood mononuclear cells (PBM) obtained from coeliac patients as well as healthy volunteers and disease control patients using the macrophage procoagulant assay. PBM from coeliac patients who had been on a gluten-free diet for less than 2 years responded strongly to gluten peptides, while coeliac patients at diagnosis or who had maintained a strict gluten-free diet for longer than 5 years showed weaker responses. PBM from healthy volunteers did not respond to gluten or casein peptides, whereas those from patients with Crohn's disease displayed weak reactivity to gluten and casein peptides. Our study using the macrophage procoagulant assay confirms previous findings that lymphoid cells from patients with coeliac disease exhibit a specific cellular immune response to gluten. This assay represents an alternative measure for cell-mediated immunity and is technically much simpler than the previously described leucocyte migration inhibition assay. Macrophage procoagulant activity is measured using a simple plasma recalcification time assay or spectrophotometrically using commercially available chromogenic substrates.

Antibody response reveal differences in oral tolerance to wheat and maize grain protein fractions

The influence of diet on humoral immune responses to gluten- and maize-derived proteins was examined using ELISA and protein blotting techniques. Mice raised on the maize-based (gluten-free) diet responded well to parenteral immunization with each of six gluten-derived protein preparations (whole gliadin, two omega-gliadin fractions, wheat salt-soluble proteins, a peptic-tryptic digest and a subtilisin digest of gluten), as serum antibody levels increased at least 300-fold in each case. In contrast, mice raised on the wheat-based diet responded poorly to immunization with either whole gliadin or omega-gliadin and were virtually non-responsive to enzymic digest of gluten. Diet had little effect on the magnitude of the antibody response to wheat salt-soluble proteins, with both groups showing a 300-fold increase in titre. Similarly, tolerance to alpha-zeins, the alcohol-soluble proteins of maize, did not occur on either diet. However, some oral tolerance was observed to maize glutelin. The specificity of the various antibody responses was then analysed by immunoblotting. Following immunization with gluten proteins or digests, antibodies from the maize-fed mice bound more or less equally to each of the main gliadin bands and to the glutenins while the mice on the wheat-based diet had antibody specific for omega-gliadin proteins. Serum antibodies from the maize-fed mice, immunized with either alpha-zein or maize glutelin, showed even labelling of the major maize endosperm proteins while antibodies from mice on the wheat diet showed strong labelling of the Mr 27,000 and 58,000 bands. These results show that diet influenced the specificity, as well as the magnitude of serum antibody responses to cereal proteins. In addition, oral tolerance appeared to affect the humoral response to some cereal proteins more than others. Both of these findings have important implications for our understanding of coeliac disease.

Anti-gliadin antibody specificity for gluten-derived peptides toxic to coeliac patients

The specificities of serum and intestinal antibodies from coeliac and normal individuals towards gluten-derived peptides, known to be toxic in coeliac disease, has been investigated. Though untreated coeliacs had high serum antibody levels towards gliadin and some gluten-derived peptides, antibody specificities to various toxic gluten-derived peptides were similar to normal patients. Further, no significant binding in any patient group was found to the alpha-gliadin-derived peptides B1342 (Wieser, Belitz & Ashkenazi, 1984) or the 12 amino-acid A-gliadin peptide (Kagnoff, 1985). There appears to be no direct relationship between the toxicities and the antigenic reactivity of gluten-derived peptides. Thus, the intestinal damage in coeliac disease is probably not primarily caused by antibody-dependent mechanisms. The specificities of several monoclonal antibodies which bound to wheat prolamins as well as prolamins from other coeliac-toxic cereals have also been investigated with these toxic gluten-derived peptides, in order to identify possible common epitopes. No monoclonal antibody tested bound the B1342 and 12-amino-acid A-gliadin peptide. However the monoclonal antibodies which were specific for the coeliac-toxic cereal prolamins did show the strongest binding to other coeliac-toxic gluten-derived peptides.

Identification of legumin-like proteins in wheat

We have obtained several amino acid sequences from purified polypeptides of a wheat endosperm storage globulin previously described as 'triplet' protein. The amino acid sequence data supported by immunochemical analysis using anti-oat 12S globulin antibodies, provide definitive evidence that the triplet protein is homologous to pea legumin and related seed storage proteins of oats, rice and several dicotyledonous species. Thus, it is now proposed that the triplet protein of wheat be renamed 'triticin'. The oat globulin antibodies also cross-reacted strongly with the high-molecular-weight (HMW) glutenin subunits which have been implicated in bread-making quality.

Variation of serum and intestinal gluten antibody specificities in coeliac disease

Protein blotting techniques were used to investigate the gluten specificity of IgA and IgG antibodies in sera and intestinal aspirates from patients with coeliac disease and normal controls. Initially, discontinuous SDS polyacrylamide gel electrophoresis was used to separate the flour proteins. All normal and coeliac sera contained antibodies which bound to various of the gliadin proteins. In only a few sera was binding found to the high molecular weight glutenin subunits, while none was detected to the salt-soluble wheat proteins. Polyacrylamide gradient gel electrophoresis was then used to further separate the gliadin proteins. Almost all normal sera examined showed similar gliadin specificity, binding uniformly to all gliadin groups. While approximately a quarter of the coeliac sera showed even binding to all of the gliadin proteins, the majority showed antibody binding intensely to discrete groups of gliadin bands. We were unable to identify any gliadin band(s) which only bound antibodies from coeliac patients in comparison with normal subjects. The specificities of IgG and IgA serum antibodies were identical for each patient examined, but some differences between serum and intestinal IgA specificities were found for certain patients.

Adenosine agonists reduce voltage-dependent calcium conductance of mouse sensory neurones in cell culture

Adenosine and several of its analogues produced a concentration-dependent shortening of calcium-dependent action potential (c.a.p.) duration of mouse dorsal root ganglion (d.r.g.) neurones in dissociated cell culture. The following rank order of potency was obtained: N6-(L-phenylisopropyl)adenosine greater than N6-(D-phenylisopropyl)adenosine greater than N6-cyclohexyladenosine greater than 2-chloroadenosine much greater than 1-methylisoguanosine greater than adenosine. Effects of adenosine agonists on c.a.p. duration were blocked by methylxanthine adenosine antagonists. Adenosine monophosphate (AMP) and cyclic AMP shortened c.a.p.s in d.r.g. neurones, while ATP also depolarized cells. Voltage-clamp analysis revealed that the effect arose from reduction of a voltage-dependent calcium conductance. Adenosine agonists reduced depolarization-evoked inward currents but did not alter membrane conductance following blockade of calcium channels by cadmium. Additionally, adenosine reduced the instantaneous current-voltage slope (chord conductance) during step commands that produced maximal activation of voltage-dependent calcium conductance. If effects of adenosine on neuronal somata and synaptic terminals are similar, adenosine agonists may inhibit neurotransmitter release in the central nervous system by inhibiting a voltage-dependent calcium conductance. Since effects of adenosine agonists did not correspond with their relative potencies as modulators of adenylate cyclase activity or inhibitors of neurotransmitter release in peripheral tissues, a novel adenosine receptor may be involved in regulation of this conductance.

Anticonvulsant drug mechanisms of action

The effects of clinically used anticonvulsant drugs on high-frequency sustained repetitive firing (SRF) of action potentials and on postsynaptic responses to iontophoretically applied gamma-aminobutyric acid (GABA) have been compared to establish a classification of anticonvulsant drugs based on cellular mechanisms of action. By using concentrations in the range of therapeutic cerebrospinal fluid values in humans, drugs have been separated into three categories: Phenytoin, carbamazepine, and valproic acid limited SRF, but did not alter GABA responses. Phenobarbital, clonazepam, and diazepam augmented GABA responses and limited SRF only at concentrations above the therapeutic range in ambulatory patients but that are achieved in the acute treatment of status epilepticus. Ethosuximide failed to affect SRF or GABA responses even at supratherapeutic concentrations. Ability of an anticonvulsant to limit SRF correlated well with efficacy against generalized tonic-clonic seizures clinically and against maximal electroshock seizures in experimental animals. Augmentation of GABA responses and lack of limitation of SRF correlated with efficacy against generalized absence seizures in humans and against pentylenetetrazol-induced seizures in animals. However, ethosuximide must act against generalized absence seizures and against pentylenetetrazol-induced seizures by a third, as yet unknown, mechanism. Other actions occurring at supratherapeutic concentrations correlated with clinical toxicity.

Diazepam and its anomalous p-chloro-derivative Ro 5-4864: comparative effects on mouse neurons in cell culture

The actions of diazepam and its p-chloro-derivative Ro 5-4864 were compared on mouse spinal cord and dorsal root ganglion neurons in cell culture. Diazepam enhanced but Ro 5-4864 reduced iontophoretic GABA responses in a concentration-dependent manner. Both diazepam and Ro 5-4864 limited sustained, high frequency repetitive firing of spinal cord neurons but diazepam was more potent. Ro 5-4864 was, however, more potent than diazepam in inhibiting spontaneous neuronal activity of spinal cord neurons and reducing the duration of calcium-dependent action potentials of dorsal root ganglion neurons. The differing actions of diazepam and Ro 5-4864 may account for the contrasting pharmacological spectra of the two benzodiazepines.

Multiple actions of convulsant barbiturates on mouse neurons in cell culture

The convulsant barbiturate 5-(2-cyclohexylidene-ethyl)-5-ethyl barbituric acid (CHEB) depolarized most (greater than 90%) mouse spinal cord (SC) neurons in primary dissociated cell culture in a concentration-dependent fashion with threshold effects at 10 to 50 nM. Dorsal root ganglion (DRG) neurons were also depolarized by CHEB, but only about 50% of the neurons responded. The threshold concentration for depolarization of DRG neurons was several hundred-fold higher than for SC neurons. CHEB depolarizations may be mediated by an increase in a cation conductance which is calcium-dependent because CHEB depolarizations had an extrapolated reversal potential near 0 mV, were insensitive to intracellular anion (chloride ion) injection, were absent after removal of extracellular calcium ions and were reduced by cadmium ions. In contrast, the nonconvulsant barbiturates, pentobarbital and phenobarbital, did not produce membrane depolarization. However, at concentrations of CHEB somewhat higher than those which directly depolarized cells, CHEB resembled pentobarbital and phenobarbital because it reduced the spontaneous activity of SC neurons and shortened calcium-dependent action potentials of DRG neurons. Two other convulsant barbiturates, trans-5-ethyl-5-(3'-methyl-but-2'-enyl) barbituric acid and trans-5-ethyl-5-(1',3'-dimethyl-but-1'-enyl) barbituric acid, also produced membrane depolarization, reduced spontaneous activity and shortened calcium-dependent action potentials. Another convulsant barbiturate, S(+)-1-methyl-5-phenyl-5-propyl barbituric acid, did not alter membrane potential or conductance of SC neurons, suggesting that mechanistic subclasses of convulsant barbiturates exist.(ABSTRACT TRUNCATED AT 250 WORDS)

Pyrazolo[3,4-d]pyrimidines as adenosine antagonists

A large number of nitrogen heterocycles structurally related to caffeine and theophylline have been tested for activity as adenosine antagonists. Preliminary screening, utilizing displacement of [3H]N6-phenylisopropyladenosine (PIA) binding to rat brain membranes, identified several pyrazolo[3,4-d]pyrimidines with potential antagonist activity. These were then tested for their ability to antagonize adenosine-stimulated adenylate cyclase of guinea-pig slices and to block adenosine receptors which mediate presynaptic inhibition of transmitter release from cholinergic nerves in guinea-pig ileum. Of several compounds found to have antagonist activity, one of these, 4,6-bis-alpha- carbamoylethylthio -1-phenylpyrazolo[3,4-d]pyrimidine ( DJB -KK) was approximately an order of magnitude more potent than theophylline in both tests. GTP greatly reduces the potency of purine agonists, but not antagonists, as inhibitors of [3H] PIA binding; the potency of the pyrazolo[3,4-d]pyrimidine compounds was not altered by GTP. The compounds have no significant activity against [3H]adenosine uptake or on the binding of ligands to muscarinic cholinergic, beta-adrenergic, GABA or L-glutamate receptors.

Benzodiazepine receptor ligand actions on GABA responses. Benzodiazepines, CL 218872, zopiclone

The effects on GABA (4-aminobutyric acid) responses of several benzodiazepine and nonbenzodiazepine benzodiazepine receptor ligands were examined using mouse spinal cord neurons in dissociated cell culture. Diazepam, clonazepam and nitrazepam enhanced GABA responses potently at low nanomolar concentrations. Diazepam and clonazepam were most potent with significant enhancement at 1 nM and peak enhancement of 80.7 and 50.2% at 10 nM respectively. Nitrazepam was least potent with no significant enhancement at 1 nM and enhancement of only 20.7% at 10 nM. The benzodiazepine antagonist, Ro 15-1788, blocked enhancement by diazepam but also weakly enhanced GABA responses at low micromolar concentrations, suggesting partial agonist activity. The convulsant benzodiazepine, Ro 5-4864, did not enhance GABA responses at any concentration tested but antagonized GABA responses at 1 microM and above. Diazepam shifted GABA dose-response curves to the left by decreasing the apparent KD but without altering the apparent Vmax (Lineweaver-Burk analysis). Two nonbenzodiazepine anxiolytic/anticonvulsants, CL 218872 and zopiclone, were weak enhancers of GABA responses at high nanomolar concentrations. These results with benzodiazepines, CL 218872 and zopiclone are consistent with their anxiolytic and anticonvulsant profile in vivo and with studies of their effects upon low affinity GABA binding in vitro.

Benzodiazepine receptor ligand actions on GABA responses. Beta-carbolines, purines

The effects of several beta-carboline and purine ligands for benzodiazepine receptors were studied upon GABA (4-aminobutyric acid) responses and upon diazepam enhancement of GABA responses, using mouse spinal cord neurons in dissociated cell culture. While the potent convulsant beta-carboline DMCM (methyl-6,7-dimethyoxy-4-ethyl-carboline-3-carboxylate), reduced GABA responses, methyl-carboline-3-carboxylate (beta CCMe) and the corresponding ethyl ester (beta CCEt) did not alter GABA responses. The propyl ester (beta CCPr) enhanced GABA responses in a concentration-dependent fashion, while both beta CCMe and beta CCPr blocked diazepam enhancement of GABA responses. beta CCPr may thus have partial agonist activity. Two purines with moderate benzodiazepine receptor affinity, 1-methylisoguanosine (MeIG) and 6-dimethylaminopurine (DMAP), weakly enhanced GABA responses. MeIG also significantly antagonized diazepam enhancement of GABA responses. Inosine and hypoxanthine had no apparent actions upon GABA responses or upon diazepam enhancement of such responses. The results with beta-carbolines are consistent with their behavioural profile in vivo and with neurochemical studies of their effects upon GABA-benzodiazepine receptor complexes. Furthermore, certain purines are also able to interact with these complexes.

Diazepam enhances the action but not the binding of the GABA analog, THIP

GABA (4-aminobutyric acid) and its bicyclic analog THIP (4,5,6,7-tetrahydroisoxazolo-[4,5-c]-pyridin-3-ol) produced membrane hyperpolarization and increased chloride ion conductance of mouse spinal cord neurons in cell culture. Above 1 nM diazepam enhanced the actions of both GABA and THIP with similar potency and efficacy. Diazepam has been shown to enhance the binding of [3H]GABA to rat brain membranes over similar concentration ranges, with the EC50 values for enhancement of [3H]GABA binding and increase in membrane conductance being similar. In contrast, binding of [3H]THIP has been shown to be unaltered by diazepam under a variety of conditions. The possible reasons for such a discrepancy between these electrophysiological and neurochemical results with THIP are discussed.