Identification of immunogenic maize proteins in a casein hydrolysate formula

Cow's milk‐based formulas used for infants with cow's milk allergy are based on hydrolyzed proteins. The formulas that are successful in preventing allergic responses are extensively hydrolyzed. Nevertheless, reactions to such formulas are occasionally reported, and protein material of higher molecular weight than expected has been detected by binding immunoglobulin E (IgE) from patients' sera. This paper presents the identification of high‐molecular‐weight material in the extensively hydrolyzed casein formula, Nutramigen. The material was concentrated by simple centrifugation. The proteins in the pellet were separated by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), and protein‐containing bands were analyzed by protein sequencing after electroblotting. The proteins were identified as maize zeins, which are water‐insoluble proteins of apparent M_r 20 000 and 23 000, presumably originating from the maize starch in Nutramigen. Rabbits immunized with this formula developed antibodies against zeins but not against milk proteins. The maize zeins are probably identical to the recently reported components in Nutramigen ( 1 ), detected by binding of IgE from milk allergic patients, but not correlated to clinical allergic reactivity. The clinical relevance of maize proteins in Nutramigen remains to be established.     

Sphinganine/Sphingosine ratio in plasma and urine as a possible biomarker for fumonisin exposure in humans in rural areas of Africa

This study was conducted in the Transkei region of the Eastern Cape and KwaZulu-Natal province, South Africa and in the Bomet district, western Kenya. The sphinganine (Sa)/sphingosine (So) ratios in the plasma and urine of male and female volunteers consuming a staple diet of home-grown maize in Transkei, were 0.34±0.36 (mean±standard deviation) (n=154) and 0.41±0.72 (n=153), respectively and in plasma samples from KwaZulu-Natal it was 0.44±0.23 (n=26). In Kenya, the ratios in plasma and urine were 0.28±0.07 (n=29) and 0.34±0.20 (n=27), respectively. Mean total fumonisin level in home-grown maize, randomly collected in Transkei from the same region where the human volunteers lived, was 580 ng/g (n=40), as compared to the KwaZulu-Natal province, where no fumonisin (n=17) were detected (<10 ng/g) in the home-grown maize. In Kenya, only one of seven samples was contaminated with 60 ng/g fumonisins. No significant differences were found in the Sa/So ratios between males and females within the regions nor between the different regions (P>0.05). It is possible that the ratio is not sensitive enough to act as a biomarker for fumonisin exposure in humans at these levels of contamination in maize. This is the first report on Sa/So ratios determined in rural populations in Africa consuming home-grown maize as their staple diet.     

Infant food from quality protein maize and chickpea: Optimization for preparing and nutritional properties

The present study had two objectives: to determine the best combination of nixtamalized maize flour (NMF) from quality protein maize and extruded chickpea flour (ECF) for producing an infant food, and to evaluate the nutritional properties of the optimized NMF/ECF mixture and the infant food. Response surface methodology (RSM) was applied to determine the best combination of NMF/ECF; the experimental design (Lattice simplex) generated 11 assays. Mixtures from each assay were evaluated for true protein and available lysine. Each one of 11 mixtures was used for preparing 11 infant foods that were sensory evaluated for acceptability. A common optimum value for the three response variables was obtained utilizing the desirability method. The best combination of NMF/ECF for producing an infant food was NMF?=?26.7%/ECF?=?73.3%; this optimized mixture had a global desirability of 0.87; it contained 19.72% dry matter (DM) proteins, 6.10% (DM) lipids, 71.45% (DM) carbohydrates, and 2.83% (DM) minerals; its essential amino acids profile covered the amino acids requirements for children 10–12?years old. The infant food prepared from optimized mixture had an in vitro protein digestibility of 87.9%, and a calculated protein efficiency ratio of 1.86. Infant food could be used to support the growth of infants in developing countries.     

Comparison of colorimetric methods for determination of phytic acid content in raw and oil extracted flour samples of maize

There are different colorimetric methods, with various analysis principles and phases, for the estimation of phytic acid content in agricultural products. Maize genotypes may possess a wide range of oil content, which is considered as a factor affecting the results of phytic acid analyses. Elaborative studies are needed to examine these methods to clarify the effect of oil content on the results, especially in the sample sets with varying oil concentrations. We utilized 4 different colorimetric methods; namely, AOAC, Wade, Chen and Haug-Lantzsch (H-L), to estimate phytic acid content in 19 maize genotypes, classified as having high (>7 %, n = 7) normal (3–5 %, n = 6) and low (<3 %, n = 6) oil content. Phytic acid determination was carried out on 2 groups of flour samples (raw: E1, and oil extracted: E2) using 3 replications. The results indicated that analysis methods yielded rather different phytic acid values. They also differed significantly in time and cost, with the Chen method being the cheapest and Haug-Lantzsch (H-L) the quickest. Oil extraction had significant effects on phytic acid results, and these effects varied across the analysis methods and the oil content of the genotypes. Our data suggest that either novel or improved colorimetric methods are necessary when analyzing phytic acid in special maize genotypes, considering the dissimilarity of the results from the current methods.     

Prevalence of oral pathologic findings in an ancient pre-Columbian archeologic site in the Atacama Desert

Objective:  To determine the prevalence of oral pathologic findings in an ancient culture that inhabited the Atacama Desert.
Materials and methods:  A systematic examination was performed on the remains of 83 individuals unearthed from a prehistoric burial ground. A total of 57 skeletal remains achieved appropriate inclusion criteria, from which estimated age at death, gender, ante- and postmortem tooth loss, prevalence and location of caries, apical periodontitis sequela, alveolar bone resorption and attrition were recorded.
Results:  From the analyzed skeletal remains (13 male, 22 female and 22 not identifiable), the mean age estimated was 29.9 ± 13.8 years. A total of 89.4% of them presented permanent dentition with a mean ante-mortem tooth loss of 9.0 teeth and a postmortem mean tooth loss of 14.4 teeth per subject. In all, 46.4% of the postmortem remaining permanent teeth ( n  = 237) showed caries lesions. Interproximal caries was most frequently observed (31.5%), followed by occlusal (25.9%) and cervical caries (19.4%). Root remnants were found in 23.1% of the cases. In addition, 58.0% of the adults presented attrition, 26.0% signs of apical periodontitis and 44.0% loss of alveolar bone support >5 mm.
Conclusion:  The remains of jaws and teeth of the individuals examined in this study presented sequelae of severe oral health damage due to caries and periodontal disease.     

Ochratoxin A contamination of food from Croatia

Ochratoxin A (OTA) is a mycotoxin with nephrotoxic, genotoxic and carcinogenic properties produced by Penicillium and Aspergillus moulds under different climatic conditions. Humans and animals are exposed to this compound mainly via ingestion of contaminated food. In Croatia, research on mycotoxins focused on OTA when the mycotoxin theory of endemic nephropathy (EN) was postulated. Ochratoxin A was more frequent and at higher concentration in foods from EN than those from the control regions. Subsequently, OTA concentrations were determined in some commodities intended for human consumption such as maize, wheat, beans and wine. Samples from all parts of Croatia were analyzed and OTA was found in all types of commodities. It was frequently found together with other mycotoxins (fumonisin B(1), fumonisin B(2) and zearalenone). In general, OTA concentration in foods from Croatia is low, but the frequency of positive samples shows considerable variations from year to year depending also on sampling location. Although low levels of OTA were found in a large proportion of analyzed food samples, its persistent co-occurrence with other significant mycotoxins should raise serious public health concerns as there interactions may be synergistic or additive in causing toxicity in humans and animals. There is need to establish control measures through which such contaminations in foods can be managed.     

From the Cover: PHS1 regulates meiotic recombination and homologous chromosome pairing by controlling the transport of RAD50 to the nucleus

Recombination and pairing of homologous chromosomes are critical for bivalent formation in meiotic prophase. In many organisms, including yeast, mammals, and plants, pairing and recombination are intimately interconnected. The POOR HOMOLOGOUS SYNAPSIS1 (PHS1) gene acts in coordination of chromosome pairing and early recombination steps in plants, ensuring pairing fidelity and proper repair of meiotic DNA double-strand-breaks. In phs1 mutants, chromosomes exhibit early recombination defects and frequently associate with non-homologous partners, instead of pairing with their proper homologs. Here, we show that the product of the PHS1 gene is a cytoplasmic protein that functions by controlling transport of RAD50 from cytoplasm to the nucleus. RAD50 is a component of the MRN protein complex that processes meiotic double-strand-breaks to produce single-stranded DNA ends, which act in the homology search and recombination. We demonstrate that PHS1 plays the same role in homologous pairing in both Arabidopsis and maize, whose genomes differ dramatically in size and repetitive element content. This suggests that PHS1 affects pairing of the gene-rich fraction of the genome rather than preventing pairing between repetitive DNA elements. We propose that PHS1 is part of a system that regulates the progression of meiotic prophase by controlling entry of meiotic proteins into the nucleus. We also document that in phs1 mutants in Arabidopsis, centromeres interact before pairing commences along chromosome arms. Centromere coupling was previously observed in yeast and polyploid wheat while our data suggest that it may be a more common feature of meiosis.     

Spatial patterns of aflatoxin levels in relation to ear-feeding insect damage in pre-harvest corn

Key impediments to increased corn yield and quality in the southeastern US coastal plain region are damage by ear-feeding insects and aflatoxin contamination caused by infection of Aspergillus flavus. Key ear-feeding insects are corn earworm, Helicoverpa zea, fall armyworm, Spodoptera frugiperda, maize weevil, Sitophilus zeamais, and brown stink bug, Euschistus servus. In 2006 and 2007, aflatoxin contamination and insect damage were sampled before harvest in three 0.4-hectare corn fields using a grid sampling method. The feeding damage by each of ear/kernel-feeding insects (i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs), and maize weevil population were assessed at each grid point with five ears. The spatial distribution pattern of aflatoxin contamination was also assessed using the corn samples collected at each sampling point. Aflatoxin level was correlated to the number of maize weevils and stink bug-discolored kernels, but not closely correlated to either husk coverage or corn earworm damage. Contour maps of the maize weevil populations, stink bug-damaged kernels, and aflatoxin levels exhibited an aggregated distribution pattern with a strong edge effect on all three parameters. The separation of silk- and cob-feeding insects from kernel-feeding insects, as well as chewing (i.e., the corn earworm and maize weevil) and piercing-sucking insects (i.e., the stink bugs) and their damage in relation to aflatoxin accumulation is economically important. Both theoretic and applied ramifications of this study were discussed by proposing a hypothesis on the underlying mechanisms of the aggregated distribution patterns and strong edge effect of insect damage and aflatoxin contamination, and by discussing possible management tactics for aflatoxin reduction by proper management of kernel-feeding insects. Future directions on basic and applied research related to aflatoxin contamination are also discussed.     

Synthesis of the protected repeat sequence of glutelin-2 of maize,Boc-Val-His-Leu-Pro-Pro-Pro-OH,via nucleophilic cleavage from an Nbb-resin

The protected hexapeptide Boc-Val-His-Leu-Pro-Pro-Pro-OH, the N-terminal protected repeat sequence of glutelin-2 of maize, has been synthesized on a bromomethyl-Nbb-resin. After cleavage of the peptide-resin bond by two 3-min treatments with dioxane/methanol/4n NaOH (30:9:1), gel filtration followed by anion-exchange chromatography allowed the isolation of the target peptide (37% yield) and its methyl ester derivative (52% yield). Cleavage with dioxane/2-dimethylaminoethanol/4n NaOH (30:9:1) has been found to be a simple and effective alternative to the photolysis of the peptide-Nbb-resin bond. After two 15-min treatments with this reagent the protected hexapeptide was isolated by chromatography without apparent epimerization.     

玉米加工产品中转基因成分的定量检测

[目的]建立检测玉米加工产品中转基因成分的实时荧光定量PCR技术。[方法]根据转基因Bt176玉米中的外源基因和内源基因设计的引物和TaqMan荧光探针,使用实时定量PCR技术对转基因成分含量进行了定量检测,建立了Bt176玉米参照样品的外源基因和内源基因Ct值之差与转基因成分含量之间的标准曲线和线性回归方程,并对采自市场的未知样品进行了检测。[结果]在1份玉米粒样品中检测到了Bt176玉米转基因成分。检测灵敏度达到0.01%。[结论]实时荧光定量PCR技术检测方法是灵敏和准确的,可以广泛地应用到转基因作物及其加工产品的转基因成分检测中。