Metabolic profiles of peanut (Arachis hypogaea L.) in response to Puccinia arachidis fungal infection

Background Puccinia arachidis fungus causes rust disease in the peanut plants (Arachis hypogaea L.), which leads to high yield loss. Metabolomic profiling of Arachis hypogaea was performed to identify the pathogen-induced production of metabolites involved in the defense mechanism of peanut plants. In this study, two peanut genotypes, one susceptible (JL-24) and one resistant (GPBD-4) were inoculated with Puccinia arachidis fungal pathogen. The metabolic response was assessed at the control stage (0 day without inoculation), 2 DAI (Day after inoculation), 4 DAI and 6 DAI by Gas Chromatography-Mass Spectrometry (GC-MS). Results About 61 metabolites were identified by NIST library, comprising sugars, phenols, fatty acids, carboxylic acids and sugar alcohols. Sugars and fatty acids were predominant in leaf extracts compared to other metabolites. Concentration of different metabolites such as salicylic acid, mannitol, flavonoid, 9,12-octadecadienoic acid, linolenic acid and glucopyranoside were higher in resistant genotype than in susceptible genotype during infection. Systemic acquired resistance (SAR) and hypersensitive reaction (HR) components such as oxalic acid was elevated in resistant genotype during pathogen infection. Partial least square-discriminant analysis (PLS-DA) was applied to GC-MS data for revealing metabolites profile between resistant and susceptible genotype during infection. Conclusion The phenol content and oxidative enzyme activity i.e. catalase, peroxidase and polyphenol oxidase were found to be very high at 4 DAI in resistant genotype (p-value < 0.01). This metabolic approach provides information about bioactive plant metabolites and their application in crop protection and marker-assisted plant breeding.

De novo transcriptome sequencing of drought tolerance-associated genes in little millet (Panicum sumatrense L.)

The genome size of the little millet Panicum sumatrense is unknown, although its genome is fairly diploid (2n = 4x = 36). Despite tremendous nutritional value and adaptability to adverse climatic conditions, P. sumatrense use was limited by their low palatability, coarse grain, and lack of variety of culinary preparations. Hence, understanding how to vary their usage to offer food and nutritional security in the continuously changing modern world, the proposed study was aimed to determine potential genes and metabolites implicated in drought resistance. The drought-resistant genotype of tiny millet OLM-203/Tarini was offered in pots under both relaxed and demanding circumstances. The experimental seedlings were 32 days old and had been under water stress for 23 days. A total of 7606 genes were compared between 23 and 32 days for roots and 7264 total genes were compared between 23 and 32 days for leaves, according to a research on differential expression genes (DEGs). Twenty essential genes for drought tolerance were up-or down-regulated in the control and treated roots of the OLM-203 genotype. For instance, the genes RS193 and XB34 were up-regulated in leaves while, WLIM1 was found to be down-regulated. Gene SKI35 was up-regulated in roots, whereas MPK6 and TCMOp1 were down-regulated in root samples. The roots and leaves of the tiny millet OLM-203 genotype expressed 36 up-regulated and 21 down-regulated serine transcripts, respectively. Gene annotations for leaf samples were classified as having "molecular function" (46%), "cellular component" (19%), and "biological process" (35%), while root sample gene annotations were categorized as having "biological process" (573 contigs), "molecular function" (401 contigs), and "cellular components" (166 contigs). Noteworthy, polyamines play a crucial role in drought stress tolerance in the genotype, and it was found that top ten DEGs encoding for polyamines were common in two tissues (leaf and root). Collectively, transcriptomics profiling (RNA-seq) unveiled transcriptional stability drought stress provide a new insight in underlying modus of operandi in little millet genotype "OLM-203/Tarini" in response to heat stress.

Transcriptome analysis provides insights into the stress response in cultivated peanut (Arachis hypogaea L.) subjected to drought-stress

BACKGROUND

Peanut (Arachis hypogaea L.) is one of the valuable oilseed crops grown in drought-prone areas worldwide. Drought severely limits peanut production and productivity significantly.

METHOD AND RESULTS

In order to decipher the drought tolerance mechanism in peanut under drought stress, RNA sequencing was performed in TAG - 24 (drought tolerant genotype) and JL-24 (drought susceptible genotype). Approximately 51 million raw reads were generated from four different libraries of two genotypes subjected to drought stress exerted by 20% PEG 6000 stress and control conditions, of which ~ 41 million (80.87%) filtered reads were mapped to the Arachis hypogaea L. reference genome. The transcriptome analysis detected 1,629 differentially expressed genes (DEGs), 186 genes encoding transcription factors (TFs) and 30,199 SSR among the identified DEGs. Among the differentially expressed TF encoding genes, the highest number of genes were WRKY followed by bZIP, C2H2, and MYB during drought stress. The comparative analysis between the two genotypes revealed that TAG-24 exhibits activation of certain key genes and transcriptional factors that are involved in essential biological processes. Specifically, TAG-24 showed activation of genes involved in the plant hormone signaling pathway such as PYL9, Auxin response receptor gene, and ABA. Additionally, genes related to water deprivation such as LEA protein and those involved in combating oxidative damage such as Glutathione reductase were also found to be activated in TAG-24.

CONCLUSION

This genome-wide transcription map, therefore, provides a valuable tool for future transcript profiling under drought stress and enriches the genetic resources available for this important oilseed crop.

Stage specific comparative transcriptomic analysis to reveal gene networks regulating iron and zinc content in pearl millet [Pennisetum glaucum (L.) R. Br.]

Pearl millet is an important staple food crop of poor people and excels all other cereals due to its unique features of resilience to adverse climatic conditions. It is rich in micronutrients like iron and zinc and amenable for focused breeding for these micronutrients along with high yield. Hence, this is a key to alleviate malnutrition and ensure nutritional security. This study was conducted to identify and validate candidate genes governing grain iron and zinc content enabling the desired modifications in the genotypes. Transcriptome sequencing using ION S5 Next Generation Sequencer generated 43.5 million sequence reads resulting in 83,721 transcripts with N₅₀ of 597 bp and 84.35% of transcripts matched with the pearl millet genome assembly. The genotypes having high iron and zinc showed differential gene expression during different stages. Of which, 155 were up-regulated and 251 were down-regulated while during flowering stage and milking stage 349 and 378 transcripts were differentially expressed, respectively. Gene annotation and GO term showed the presence of transcripts involved in metabolic activities associated with uptake and transport of iron and zinc. Information generated will help in gaining insights into iron and zinc metabolism and develop genotypes with high yield, grain iron and zinc content.

Metabolomic Profiling of Drought-Tolerant and Susceptible Peanut (Arachis hypogaea L.) Genotypes in Response to Drought Stress

Peanut is frequently constrained by extreme environmental conditions such as drought. To reveal the involvement of metabolites, TAG 24 (drought-tolerant) and JL 24 (drought-sensitive) peanut genotypes were investigated under control and 20% PEG 6000-mediated water scarcity conditions at the seedling stage. Samples were analyzed by gas chromatography-mass spectrometry (GC-MS) to identify untargeted metabolites and targeted metabolites, i.e., polyamines and polyphenols by high-performance liquid chromatography (HPLC) and ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), respectively. The principal component analysis (PCA), partial least-squares discriminant analysis (PLS-DA), heat map, and cluster analysis were applied to the metabolomics data obtained by the GC-MS technique to determine the important metabolites for drought tolerance. Among 46 resulting metabolites, pentitol, phytol, xylonic acid, d-xylopyranose, stearic acid, and d-ribose were important drought-responsive metabolites. Agmatine and cadaverine were present in TAG 24 leaves and roots, respectively, during water-deficit conditions and believed to be the potential polyamines for drought tolerance. Polyphenols such as syringic acid and vanillic acid were produced more in the leaves of TAG 24, while catechin production was high in JL 24 during stress conditions. Seven metabolic pathways, namely, galactose metabolism, starch and sucrose metabolism, fructose and mannose metabolism, pentose and glucuronate interconversion, propanoate metabolism, amino sugar and nucleotide sugar metabolism, and biosynthesis of unsaturated fatty acids were significantly affected by water-deficit conditions. This study provides valuable information about the metabolic response of peanut to drought stress and metabolites identified, which encourages further study by transcriptome and proteomics to improve drought tolerance in peanut.

Uncloaking lncRNA-meditated gene expression as a potential regulator of CMS in cotton (Gossypium hirsutum L.)

Cytoplasmic male sterility is a well-proven mechanism for cotton hybrid production. Long non-coding RNAs belong to a class of transcriptional regulators that function in multiple biological processes. The cDNA libraries from the flower buds of the cotton CGMS, it's restorer (Rf) and maintainer lines were sequenced using high throughput NGS technique. A total of 1531 lncRNAs showed significant differential expression patterns between these three lines. Functional analysis of the co-expression network of lncRNA-mRNA using gene ontology vouchsafes that, lncRNAs play a crucial role in cytoplasmic male sterility and fertility restoration through pollen development, INO80 complex, development of anther wall tapetum, chromatin remodeling, and histone modification. Additionally, 94 lncRNAs were identified as putative precursors of 49 miRNAs. qRT-PCR affirms the concordance of expression pattern to RNA-seq data. These findings divulge the lncRNA driven miRNA-mediated regulation of gene expression profiling superintended for a better understanding of the CMS mechanisms of cotton.

Transcriptome landscaping for gene mining and SSR marker development in Coriander (Coriandrum sativum L.)

Coriander (Coriandrum sativum L.) is an aromatic herb, widely used as a spice and is of great pharmaceutical interest. Despite high medicinal and economic value, there is a dearth of genomic information about profiling as well as the expressed sequence-based genic markers. In this study, transcriptome was sequenced from seeds, leaves, and flower for gene mining and identification of SSR markers. A total of 9746 SSR containing loci were identified, the most abundant type of SSR identified were the di-nucleotide repeat motifs (45.5%), followed by tri- (34.6%), tetra- (4.5%), penta- (1.5%) and hexanucleotide repeats (1%). A total of 3795 primers were designed, out of which 120 randomly selected were validated in 14 accessions of coriander cultivated in India. The current study provides useful information about preliminary transcriptome sketch and genic markers, which can be useful in breeding and genetic diversity estimation of coriander.

Transcriptome profiling and cataloging differential gene expression in floral buds of fertile and sterile lines of cotton (Gossypium hirsutum L.)

Cytoplasmic Male Sterility is maternally inherited trait in plants, characterized by failure to produce functional pollen during anther development. Anther development is modulated through the interaction of nuclear and mitochondrial genes. In the present study, differential gene expression of floral buds at the sporogenous stage (SS) and microsporocyte stage (MS) between CGMS and its fertile maintainer line of cotton plants was studied. A total of 320 significantly differentially expressed genes, including 20 down-regulated and 37 up-regulated in CGMS comparing with its maintainer line at the SS stage, as well as and 89 down-regulated and 4 up-regulated in CGMS compared to the fertile line at MS stage. Comparing the two stages in the same line, there were 6 down-regulated differentially expressed genes only induced in CGMS and 9 up-regulated differentially expressed gene only induced in its maintainer. GO analysis revealed essential genes responsible for pollen development, and cytoskeleton category show differential expression between the fertile and CGMS lines. Validation studies by qRT-PCR shows concordance with RNA-seq result. A set of novel SSRs identified in this study can be used in evaluating genetic relationships among cultivars, QTL mapping, and marker-assisted breeding. We reported aberrant expression of genes related to pollen exine formation, and synthesis of pectin lyase, myosine heavy chain, tubulin, actin-beta, heat shock protein and myeloblastosis (MYB) protein as targets for CMS in cotton. The results of this study contribute to basic information for future screening of genes and identification of molecular portraits responsible for CMS as well as to elucidate molecular mechanisms that lead to CMS in cotton.

Transcriptomic signature of drought response in pearl millet (Pennisetum glaucum (L.) and development of web-genomic resources

Pearl millet, (Pennisetum glaucum L.), an efficient (C4) crop of arid/semi-arid regions is known for hardiness. Crop is valuable for bio-fortification combating malnutrition and diabetes, higher caloric value and wider climatic resilience. Limited studies are done in pot-based experiments for drought response at gene-expression level, but field-based experiment mimicking drought by withdrawal of irrigation is still warranted. We report de novo assembly-based transcriptomic signature of drought response induced by irrigation withdrawal in pearl millet. We found 19983 differentially expressed genes, 7595 transcription factors, gene regulatory network having 45 hub genes controlling drought response. We report 34652 putative markers (4192 simple sequence repeats, 12111 SNPs and 6249 InDels). Study reveals role of purine and tryptophan metabolism in ABA accumulation mediating abiotic response in which MAPK acts as major intracellular signal sensing drought. Results were validated by qPCR of 13 randomly selected genes. We report the first web-based genomic resource ( http://webtom.cabgrid.res.in/pmdtdb/ ) which can be used for candidate genes-based SNP discovery programs and trait-based association studies. Looking at climatic change, nutritional and pharmaceutical importance of this crop, present investigation has immense value in understanding drought response in field condition. This is important in germplasm management and improvement in endeavour of pearl millet productivity.

Draft whole genome sequence of groundnut stem rot fungus Athelia rolfsii revealing genetic architect of its pathogenicity and virulence

Groundnut (Arachis hypogaea L.) is an important oil seed crop having major biotic constraint in production due to stem rot disease caused by fungus, Athelia rolfsii causing 25–80% loss in productivity. As chemical and biological combating strategies of this fungus are not very effective, thus genome sequencing can reveal virulence and pathogenicity related genes for better understanding of the host-parasite interaction. We report draft assembly of Athelia rolfsii genome of ~73 Mb having 8919 contigs. Annotation analysis revealed 16830 genes which are involved in fungicide resistance, virulence and pathogenicity along with putative effector and lethal genes. Secretome analysis revealed CAZY genes representing 1085 enzymatic genes, glycoside hydrolases, carbohydrate esterases, carbohydrate-binding modules, auxillary activities, glycosyl transferases and polysaccharide lyases. Repeat analysis revealed 11171 SSRs, LTR, GYPSY and COPIA elements. Comparative analysis with other existing ascomycotina genome predicted conserved domain family of WD40, CYP450, Pkinase and ABC transporter revealing insight of evolution of pathogenicity and virulence. This study would help in understanding pathogenicity and virulence at molecular level and development of new combating strategies. Such approach is imperative in endeavour of genome based solution in stem rot disease management leading to better productivity of groundnut crop in tropical region of world.

Assessment of phytotoxicity of anthracene in soybean (Glycine max) with a quick method of chlorophyll fluorescence

A decrease in photosynthetic efficiency may indicate the toxic effects of environmental pollutants on higher plants. Measurement of chlorophyll (Chl) a fluorescence to assess the performance of photosystem II (PSII) was used as an bioindicator of toxicity of the polycyclic aromatic hydrocarbon (PAH) anthracene (ANT) in soybean plants. The results revealed that ANT treatment caused a reduction in quantum yield of PSII, damage to the oxygen evolving complex, as well as a significant reduction in performance index of PSII. However, change in performance index was more prominent, and it seems that the performance index is a more sensitive parameter to environmental contaminants. Moreover, a change in heterogeneity of PSII was also observed. The number of active reaction centres decreased with increasing concentration of ANT, as secondary plastoquinone reducing centres were converted into non-reducing centres, and PSIIα centres were converted into PSIIβ and PSIIγ centres. The influence of ANT on PSII heterogeneity could be an important reason for reductions in the PSII performance.

Molecular epidemiology of measles in India, 2005-2010

Measles is a childhood disease that causes great morbidity and mortality in India and worldwide. Because measles surveillance in India is in its infancy, there is a paucity of countrywide data on circulating Measles virus genotypes. This study was conducted in 21 of 28 States and 2 of 7 Union Territories of India by MeaslesNetIndia, a national network of 27 centers and sentinel practitioners. MeaslesNetIndia investigated 52 measles outbreaks in geographically representative areas from 2005 through June 2010. All outbreaks were serologically confirmed by detection of antimeasles virus immunoglobulin M (IgM) antibodies in serum or oral fluid samples. Molecular studies, using World Health Organization (WHO)-recommended protocols obtained 203 N-gene, 40 H-gene, and 4 M-gene sequences during this period. Measles genotypes D4, D7, and D8 were found to be circulating in various parts of India during the study period. Further phylogenetic analysis revealed 4 lineages of Indian D8 genotypes: D8a, D8b, D8c, and D8d. This study generated a large, countrywide sequence database that can form the baseline for future molecular studies on measles virus transmission pathways in India. This study has created support and capabilities for countrywide measles molecular surveillance that must be carried forward.

Detection of Mycoplasma species in cell culture by PCR and RFLP based method: effect of BM-cyclin to cure infections

PURPOSE

A two-stage nested polymerase chain reaction (PCR) assay system was described that amplifies the 16S-23S rRNA spacer region sequences of Mycoplasma and Acholeplasma infections in cell cultures and virus stocks.

METHODS

Established cell lines and virus stocks were screened for the presence of Mycoplasma by using nested PCR using two sets of outer and inner primers, amplifies 16S-23S rRNA. PCR and restriction fragment length polymorphism (RFLP) assay was used to detect and identify most of the species-specific Mycoplasmas involved in cell cultures and virus stock contaminants. Infected cultures detected by PCR-RFLP were further treated with BM-cyclin (5 microg/mL) and passaged for three times and tested for Mycoplasma infections by PCR-RFLP.

RESULTS

Mycoplasma pirum and Mycoplasma orale infections were detected by nested PCR. Species specificity was identified by using RFLP of Vsp I, Cla I and Hin dIII restriction enzymes. Mycoplasma infections were cured by treatment with BM-cyclin. This was further confirmed by non-amplification of PCR amplimers in BM-cyclin treated vs. non-treated cultures.

CONCLUSIONS

Regular monitoring of cell cultures for Mycoplasma infections and identification of species-specific Mollicutes will identify the source of contaminations. This approach can be used for quality control of the biological reagents used in cell culture and virology laboratories.

Tobacco consumption in relation to causes of death in an urban population of north India

BACKGROUND

Noncommunicable diseases have become a public heath problem in India concomitant with economic development, leading to increases in tobacco consumption, obesity, and changes in diet and lifestyle. Although observation suggests that tobacco consumption is a major risk factor for deaths due to circulatory, pulmonary, and malignant diseases, such studies are not available from most populations in developing countries.

SUBJECTS AND METHODS

For the period 1999-2001, we studied the randomly selected records of death of 2222 (1385 men and 837 women) decedents, aged 25-64 years, out of 3034 death records overall from the records at Municipal Corporation, Moradabad. All the families of these deceased could be contacted individually to find out the causes of death, by scientist/doctor administered, informed consented, verbal autopsy questionnaire, completed with the help of the spouse and local treating doctor practicing in the appropriate healthcare region. Social classes and tobacco intakes were assessed by a questionnaire.

RESULTS

The prevalence of tobacco consumption, including chewing + smoking, were 45% (n = 623) among men and 15% (n = 125) among women decedents. However, smoking was observed in 20% and tobacco chewing in 30% of male decedents, while only 6% of female decedents smoked and 10% chewed tobacco. Social class had no impact on tobacco consumption in men but did influence one subgroup >55 years among women, ie, among those who had the highest tobacco consumption. Tobacco intakes were significantly more common among decedents dying due to circulatory, malignant, and pulmonary diseases, compared with other causes (men 61.1%, 76.6%, pulmonary 77.3% vs 31%, P < 0.001; women 27.5%, 75.9%, pulmonary 24.6% vs 0.42%, P < 0.001) of mortality, respectively. Pulmonary causes included chronic bronchitis and asthma. Circulatory diseases (29.1%, n = 646) including heart attacks (10.0%), stroke (7.8%), valvular heart disease (7.2%, n = 160), sudden cardiac death and inflammatory cardiac disease, each (2.0%, n = 44) were the second most common causes of deaths, after infections (41.1%, n = 915). Malignant neoplasm (5.8%, n = 131), injury (14.0%, n = 313), and miscellaneous causes of deaths, including diabetes mellitus (2.2%, n = 49) were noted in 9.1%, (n = 202) of death records. Cancers of the lung (1.6%), oral cavity (1.5%), liver (1.1%), stomach (0.9%), breast (0.31%), uterus, cervix, and ovary (0.27%) were relatively common causes for deaths due to malignancy.

CONCLUSIONS

This study shows that tobacco consumption appears to be a major contributor to deaths due to circulatory diseases and malignant diseases in India. Social class status had little impact on tobacco consumption in male decedents. Rapid changes in diet and lifestyle, increases in tobacco consumption, and possibly aging of the population, appear to be strongly associated with mortality due to cardiovascular diseases and cancer in this middle-income country.

Prevalence of obesity, physical inactivity and undernutrition, a triple burden of diseases during transition in a developing economy. The Five City Study Group

OBJECTIVE AND DESIGN

The objective of the study was to find out the prevalence of overweight, obesity, undernutrition and physical activity status in the urban populations of India. Cross-sectional surveys were conducted in 6-12 urban streets in each of five cities in five different regions of India using a common study protocol and criteria of diagnosis.

SUBJECTS AND METHODS

A total of 6940 subjects (3433 women and 3507 men) aged 25 years and above were randomly selected from the cities of Moradabad (n = 2002),Trivandrum (n = 1602), Calcutta (n = 900), Nagpur (n = 894) and Bombay (n = 1542). Evaluation and validation were performed by a physician and dietitian-administered questionnaire at Moradabad. After pooling of data, all subjects were divided into various age groups for men and women. Obesity (body mass index = 30 > kg/m(2)) and overweight (BMI 2 25-29.9 kg/m(2) and > 23 kg/m(2)) as well as waist-hip ratio (> 0.85 in women and > 0.88 in men, central obesity) were calculated and physical activity status assessed by a validated questionnaire.

RESULTS

The overall prevalence of obesity was 6.8% (7.8 vs. 6.2%, P < 0.05) and overweight 33.5% (35.0 vs. 32.0%, P < 0.05) among women and men, respectively. The highest prevalence of obesity (7.8%) and overweight (36.9%) was found among subjects aged 35 to 44 years in both sexes. The prevalence of obesity was significantly (P < 0.05) greater in Trivandrum (8.5%), Calcutta (7. 1%) and Bombay (8.3%) compared to Moradabad (6.2%) among women and in Trivandrum (7.4%) and Bombay (7.2%), compared to Nagpur (5.0%) among men. There was a significant decreasing trend in obesity (P < 0.05) and overweight (P < 0.05) with increasing age above 35-44 years in both sexes. The overall prevalence of subjects > 23 kg/m(2) was 50.8% and central obesity 52.6%. The overall prevalence of sedentary behaviour was 59.3% among women and 58.5% among men. Both sedentary behaviour and mild activity showed a significant increasing trend in women after the age of 35-44 years. In men, such a trend was observed above the age of 45 years. Sedentary behaviour was significantly (P < 0.05) greater in Trivandrum, Calcutta, and Bombay compared to Nagpur. Sedentary behaviour was significantly (P < 0.001) associated with obesity in both sexes, compared to non-obese men and women. The overall prevalence of undernutrition was 5.5% (n = 380) which was significantly more common in Moradabad, north and Nagpur, central India compared to other cities.

CONCLUSIONS

Obesity, overweight and central obesity and sedentary behaviour coexist with undernutrition, and have become a public health problem in all the five cities of India. The prevalence of obesity and sedentary behaviour was significantly greater in Trivandrum, Calcutta and Bombay compared to Moradabad and Nagpur. Sedentary behaviour was significantly associated with obesity compared to non-obese subjects in both sexes, which may be due to greater economic development in metro cities.

Development of California Public Health Goals (PHGs) for chemicals in drinking water

As part of a program for evaluation of environmental contaminants in drinking water, risk assessments are being conducted to develop Public Health Goals (PHGs) for chemicals in drinking water, based solely on public health considerations. California's Safe Drinking Water Act of 1996 mandated the development of PHGs for over 80 chemicals by 31 December 1999. The law allowed these levels to be set higher or lower than federal maximum contaminant levels (MCLs), including a level of zero if data are insufficient to determine a specific level. The estimated safe levels and toxicological rationale for the first 26 of these chemicals are described here. The chemicals include alachlor, antimony, benzo[a]pyrene, chlordane, copper, cyanide, dalapon, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 2,4-D, diethylhexylphthalate, dinoseb, endothall, ethylbenzene, fluoride, glyphosate, lead, nitrate, nitrite, oxamyl, pentachlorophenol, picloram, trichlorofluoromethane, trichlorotrifluoroethane, uranium and xylene(s). These risk assessments are to be considered by the State of California in revising and developing state MCLs for chemicals in drinking water (which must not exceed federal MCLs). The estimates are also notable for incorporation or consideration of newer guidelines and principles for risk assessment extrapolations.

Reduced T-helper cell function in mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

Antibody production to the T-dependent antigen SRBC is highly sensitive to suppression by polychlorinated dibenzo-p-dioxins. The present study provides evidence for a defect in T-helper (TH) cells in TCDD-exposed mice. Because spleen cells from nonimmune TCDD-exposed mice did not show suppressed antibody responses when adoptively transferred to irradiated hosts, we used a hapten-carrier (TNP-SRBC) system with cell separation/reconstitution techniques to determine the effects of TCDD on carrier-specific TH cells. In vitro cultures of spleen cells from SRBC-primed TCDD-treated (5 micrograms/kg) mice produced fewer anti-TNP plaque-forming cells (PFC) when immunized with TNP-SRBC, as compared to cells from primed vehicle-treated controls. A reduced anti-TNP PFC response was also observed in experiments where non-immune B-cells were induced to produce anti-TNP PFC by TH-cells obtained from carrier-primed TCDD-exposed mice, as compared to carrier-primed vehicle-exposed mice. Removal of Lyt-2+ (suppressor) T-cells in these experiments did not alter the anti-TNP PFC response. These results provide direct evidence for reduced activity of TH-cells after exposure to TCDD.

The effects of epoxidized xenobiotics on mitogen responsiveness and antibody-producing ability of murine spleen cells in vitro

The effects of benzo(a)pyrene [B(a)P], B(a)P-4,5- and 7,8-dihydroepoxide, (+)-B(a)P-7,8-diol, (-)-B(a)P-7,8-diol, cholestan-5 alpha,6 alpha-epoxy-3 beta-ol, cholestan-5 beta,6 beta-epoxy-3 beta-ol, cholestantriol and styrene oxide, on the in vitro mitogen responses and antibody-producing ability of mouse spleen cells were evaluated. B(a)P suppressed the plaque-forming cell (PFC) response to T-cell dependent antigen sheep red blood cells (SRBC), but had no effect on the proliferative response to mitogens (phytohemagglutinin, concanavalin A and lipopolysaccharides) except a slight but significant increase to concanavalin A at lower doses. B(a)P-4,5- and 7,8-dihydroepoxides completely inhibited the proliferative response at concentrations exceeding 10(-6) M, but lower concentrations were without any effect. These two epoxides also suppressed the PFC response at concentration greater than or equal to 10(-5) M. This was accompanied by reduced cell viability. (+)-B(a)P-7,8-diol produced a dose-dependent suppression of PFC response to SRBC without altering the cell viability. The proliferative response was inhibited only at concentration greater than or equal to 10(-4) M. In contrast, (-)-B(a)P-7,8-diol has no effect on the PFC response and suppressed the proliferative response only at concentration of greater than or equal to 10(-5) M. Cholestan compounds had no effect on the plaque-forming cell response at concentrations less than or equal to 10(-5) M. The effects on the proliferative response to mitogens were inhibitory and stimulatory depending upon the dose used. Styrene oxide neither inhibited the PFC nor the proliferative responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of the Ah locus on the humoral immunotoxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin: evidence for Ah-receptor-dependent and Ah-receptor-independent mechanisms of immunosuppression

There are conflicting reports in the literature regarding the role of the Ah locus in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) immunotoxicity. The present studies have utilized two congenic strains of C57Bl/6 mice that differ only at this locus to assess its influence on TCDD-induced suppression of antibody responses. Mice were given a single oral dose of TCDD 2 days prior to challenge with sheep red blood cells (SRBC) or trinitrophenyl-lipopolysaccharide (TNP-LPS). The subsequent dose-dependent effects of TCDD on the amount of antibody produced by splenic plasma cells were measured using the hemolytic antibody isotope release assay. In addition, the relative importance of the Ah genotype of lymphoid versus nonlymphoid tissue was examined in adoptive transfer experiments. Aryl hydrocarbon hydroxylase (AHH) activity was significantly induced in Ahbb mice by a dose of 0.5 micrograms/kg TCDD and maximally induced by a dose of 2 micrograms/kg. Ahdd mice required 10-fold higher doses of TCDD to induce comparable levels of AHH. The degree of thymic involution and liver hypertrophy induced by TCDD was also influenced by the Ah genotype of the animals. Both Ahbb and Ahdd mice exhibited dose-dependent suppression of the anti-TNP response following TCDD exposure. The ID50 was 7.0 micrograms/kg in Ahbb mice and 30.8 micrograms/kg in Ahdd mice. Suppression of the antibody response to SRBC was also dependent on the Ah locus. The ID50 in Ahbb mice was 0.6 micrograms/kg TCDD. However, an apparent biphasic dose response for suppression of the anti-SRBC response in Ahdd mice suggested the involvement of an Ah-independent component of suppression as well. In adoptive transfer studies, lymphocytes were identified as an Ah-dependent component of the response. The Ah-independent component of the response was not identified, and could be either lymphoid or nonlymphoid in nature. The possibility that T helper cells represent the Ah-independent component is discussed.

In vitro effects of T-2 toxin on the mitogen responsiveness and antibody-producing ability of human lymphocytes

The effects of T-2 toxin on the in vitro mitogen responses and the antibody-producing ability of human peripheral blood lymphocytes were evaluated. T-2 toxin inhibited the mitogen response to concanavalin A (ConA) at a lower concentration (1.6 ng/ml) as compared to phytohemagglutinin (2.4 ng/ml) and pokeweed mitogen (2.4 ng/ml). Maximum inhibition was observed when the toxin was present during the first 8 h; however, the cultures were not refractory to inhibition until 48 h after culture initiation. The antibody-producing ability was inhibited by T-2 toxin concentrations of greater than or equal to 3.2 ng/ml. T-2 toxin did not induce or interfere with the generation of suppressor cells by ConA. The results of this study indicate that various lymphocyte subpopulations have different susceptibilities to T-2 toxin. The activation process associated with lymphocyte proliferation appears to be one of the most sensitive time periods.

Antibody producing ability of mouse spleen cells after subacute dietary exposure to T-2 toxin

The effects of T-2 toxin on the antibody producing ability of CD-1 mice after dietary exposure to 0, 2.5, 5 and 15 ppm of T-2 toxin for 29 days was studied. The antibody response against sheep red blood cells, a T-lymphocyte and macrophage-dependent response was suppressed at 2.5, 5 and 15 ppm of T-2 toxin exposure. In contrast, the antibody responses against dinitrophenyl-aminoethylcarbamylmethyl - Ficoll (DNP - Ficoll), a T-lymphocyte independent macrophage-dependent response, and Escherichia coli 0127 (LPS), a T-lymphocyte and macrophage-independent response, were not affected. These results suggest that the inhibitory effects of T-2 toxin on antibody-producing ability after subacute dietary exposure appear to be a direct affect on T-lymphocyte function, possibly involving the T-helper lymphocytes.

Immunological responsiveness of mouse spleen cells after in vivo or in vitro exposure to 3-acetyldeoxynivalenol

The effects of 3-acetyldeoxynivalenol (3-AcDON) on mitogen-induced lymphocyte proliferation and antibody production were studied in male CD-1 mice exposed to 0, 2.5, 5 or 10 ppm 3-AcDON in the diet for 35 days. Mitogen-induced lymphocyte proliferation and T-cell-independent antibody responses to dinitrophenyl-ficoll or Escherichia coli were not altered by dietary exposure to 3-AcDON. The T-cell-dependent antibody response to sheep red blood cells was increased in the group fed 10 ppm 3-AcDON. In vitro, 3-AcDON inhibited lymphocyte proliferation in a dose-dependent manner. Inhibition was observed when the toxin was present during the first 8 hr in phytohaemagglutinin-stimulated cultures and during the first 24 hr in lipopolysaccharide-stimulated cultures. This suggests that 3-AcDON blocks an early step in lymphocyte activation. This inhibition was not restored by thiol reducing agents (dithiothreitol, L-cysteine or 2-mercaptoethanol). Similarly, the addition of lymphokines, including interleukin-1 or interleukin-2, did not alter the inhibitory effects of 3-AcDON. These results suggest that the in vitro effects of 3-AcDON may not reflect its in vivo immunotoxicity. However, 3-AcDON may serve as a chemical probe for examining the activation process of lymphocyte proliferation.

The effect of cadmium on antibody responses to antigens with different cellular requirements

Six week old BDF1 or CD-1 female mice were exposed to cadmium chloride in the drinking water at concentrations ranging from 0 to 50 ppm cadmium for 3 weeks. The in vivo antibody response against dinitrophenyl-aminoethylcarbamylmethyl-Ficoll (DNP-Ficoll), a T-lymphocyte independent, macrophage dependent response, was enhanced by cadmium. Similarly, the in vivo antibody response against Escherichia coli 0127 (LPS), a T-lymphocyte and macrophage independent response, was also enhanced by cadmium. In contrast, the in vitro antibody response against sheep red blood cells (SRBC), a T-lymphocyte and macrophage dependent response, was suppressed in spleen cell cultures that contained cadmium-exposed non-adherent cells (lymphocytes). Cultures containing cadmium-exposed adherent cells (macrophages) were not suppressed by cadmium. These results suggest that the immunosuppressive effects of cadmium as it relates to humoral immunity involve T-lymphocyte function rather than macrophage or B-lymphocyte activity. The enhanced T-lymphocyte independent antibody responses which accompany suppressed T-lymphocyte-dependent responses following cadmium exposure are an indication of compensatory mechanisms that are associated with the immune system.

In vitro effects of 3-acetyl-deoxynivalenol on the immune response of human peripheral blood lymphocytes

The effects of 3-acetyl-deoxynivalenol (3-AcDON) on the in vitro mitogen responses and the antibody producing ability of human peripheral blood lymphocytes were evaluated. 3-AcDON inhibited the proliferative response to pokeweed mitogen and concanavalin A at a lower concentration (100 ng/ml) as compared to phytohemagglutinin (200 ng/ml). The antibody producing ability was inhibited by 3-AcDON concentrations of greater than or equal to 200 ng/ml. Higher concentrations of 3-AcDON (greater than or equal to 300 ng/ml) produced severe suppression of plaque forming cell response in vitro and reduced the total yield of lymphocytes without altering cell viability. The results of this study indicate that 3-AcDON produces immunosuppressive effects in a dose dependent manner in vitro.

Subacute toxicity of dietary 3-acetyldeoxynivalenol in mice

3-Acetyldeoxynivalenol was incorporated into a semisynthetic diet at levels of 2.5, 5, 10 or 20 ppm and fed to mice for up to 48 days. Body weights and feed consumption were determined, and blood samples for hematological evaluation were taken. Selected tissues were examined microscopically and the humoral immune response was assessed using the Jerne plaque assay. 3-Acetyldeoxynivalenol caused a dose-related depressed feed consumption within the first seven days and reduced body weight until day 14 when fed at levels up to 10 ppm. When fed at a level of 20 ppm, an initial depression in body weight gain and a general malaise were followed by a return to normal. At necropsy, no macroscopic or microscopic lesions could be found. The immune response was not significantly affected after seven or 14 days, but at 21 days, a dose-dependent enhanced response was observed. The findings indicate that, after an initial period of reduced feed intake, animals are apparently able to overcome the toxic effects of 3-acetyldeoxynivalenol.