Development and application of reverse transcription-loop mediated isothermal amplification assay for sensitive detection of groundnut bud necrosis virus infecting potato

Reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for detection of groundnut bud necrosis virus (GBNV) causing potato stem necrosis disease. The isothermal temperatures, reaction periods and concentrations of reaction mixture were optimized where, the assay worked well at 65 °C for 50 min, 6 U of WarmStart Bst 2.0 DNA polymerase, 1.4 mM dNTPs and 2.0 mM MgSO4. The optimized assay proved to be specific to GBNV with no cross reactivity to other viruses infecting potato in India. The specificity of RT-LAMP assay was found to be 100 fold more sensitive than that of RT-PCR. The developed assay was applied for the detection of GBNV from 80 potato leaf samples where 24 samples were found infected which was confirmed by RT-PCR. It was concluded that the RT-LAMP assay developed for detection of GBNV was specific, sensitive and suitable for its use in virus indexing under potato seed production programme.

RNA-seq analysis reveals an early defense response to tomato leaf curl New Delhi virus in potato cultivar Kufri Bahar

Potatoes in India are very susceptible to apical leaf curl disease, which causes severe symptoms and greater yield losses. Because the majority of potato cultivars are susceptible to the virus, it is crucial to discover sources of resistance and investigate the mechanism of resistance/susceptibility in potato cultivars. In this study, the gene expression profile of two potato cultivars, Kufri Bahar (resistant) and Kufri Pukhraj (susceptible), varying in their level of resistance to ToLCNDV, was analyzed using RNA-Seq. The Ion ProtonTM system was used to sequence eight RiboMinus RNA libraries from inoculated and uninoculated potato plants at 15 and 20 days after inoculation (DAI). The findings indicated that the majority of differentially expressed genes (DEGs) were cultivar-or time-specific. These DEGs included genes for proteins that interact with viruses, genes linked with the cell cycle, genes for proteins involved in defense, transcription and translation initiation factors, and plant hormone signaling pathway genes. Interestingly, defense responses were generated early in Kufri Bahar, at 15 DAI, which may have impeded the replication and spread of ToLCNDV. This research provides a genome-wide transcriptional analysis of two potato cultivars with variable levels of ToLCNDV resistance. At an early stage, we observed suppression of genes that interact with viral proteins, induction of genes associated with restriction of cell division, genes encoding defense proteins, AP2/ERF transcription factors, and altered expression of zinc finger protein genes, HSPs, JA, and SA pathway-related genes. Our findings add to a greater comprehension of the molecular basis of potato resistance to ToLCNDV and may aid in the development of more effective disease management techniques.

Spraying of dsRNA molecules derived from Phytophthora infestans, along with nanoclay carriers as a proof of concept for developing novel protection strategy for potato late blight

BACKGROUND

Phytophthora infestans is a late blight-causing oomycetes pathogen. It rapidly evolves and adapts to the host background and new fungicide molecules within a few years of their release, most likely because of the predominance of transposable elements in its genome. Frequent applications of fungicides cause environmental concerns. Here, we developed target-specific RNA interference (RNAi)-based molecules, along with nanoclay carriers, that when sprayed on plants are capable of effectively reducing late blight infection.

RESULTS

Targeted the genes unique to sporulation, early satge infection and the metabolism pathway stages based on in an our own microarray data. We used nanoclay as a carrier for sorbitol dehydrogenase, heat shock protein 90, translation elongation factor 1-α, phospholipase-D like 3 and glycosylphosphatidylinositol-anchored acidic serine-threonine-rich HAM34-like protein double-stranded (ds)RNAs, which were assessed by culture bioassay, detached leaf assay and spray methods, and revealed a reduction in growth, sporulation and symptom expression. Plants sprayed with multigene targeted dsRNA-nanoclay showed enhanced disease resistance (4% disease severity) and less sporulation (<1 × 10³ ) compared with plants sprayed with dsRNA alone.

CONCLUSION

The use of nanoclay with multigene targeted dsRNA was assumed to be involved in effective delivery, protection and boosting the action of RNAi as a spray-induced gene silencing approach (SIGS). A significant reduction in growth, sporulation, disease severity and decreased gene expression authenticates the effects of SIGS on late blight progression. This study demonstrated as a proof of concept the dsRNA-nanoclay SIGS approach, which could be used as an alternative to chemical fungicides and transgenic approaches to develop an environmentally friendly novel plant protection strategy for late blight. © 2022 Society of Chemical Industry.

Molecular characterization and infectivity analysis of tomato leaf curl New Delhi virus isolates infecting potato

Nucleotide sequence of complete genome of a new isolate (KAN-6) of tomato leaf curl New Delhi virus (ToLCNDV) from Kanpur, Uttar Pradesh, India was determined. Sequence analysis indicated that it shared maximum identity to ToLCNDV isolates from pumpkin and ashgourd. Infectious clones of isolate KAN-6 along with two other ToLCNDV isolates (MOD-21 & FAI-19) obtained from potato fields of Modipuram and Faizabad, India were produced and used in symptom expression studies in N. benthamiana and potato plants through agro-inoculation. These isolates produced different symptoms both in N. benthamiana and potato. Severe symptoms of yellow mottling, downward curling and stunted growth were observed in N. benthamiana plants inoculated with KAN-6. MOD-21-inoculated plants also showed downward curling, stunted growth, but yellow mottling was observed only in older leaves whereas FAI-19-inoculated plants produced only downward curling symptoms. In case of potato, typical symptoms of apical leaf curl disease were observed in cultivar Kufri Pukhraj inoculated with MOD-21 and KAN-6 that are similar to those produced by virus-infected plants in the field. However, MOD-21 produced more prominent yellow mosaic symptoms as compared to KAN-6. FAI-19 produced only restricted yellow spots in Kufri Pukhraj. Only mild symptoms appeared in KAN-6 and no symptoms were observed in MOD-21- and FAI-19-inoculated Kufri Bahar plants which is known to show lowest seed degeneration under field conditions. Analysis of genomic components indicated that these isolates had 94.8-94.9% and 87.9-97.3% identity among them in DNA A and DNA B, respectively. The results of the study indicate the association of ToLCNDV isolates of different symptomatology with apical leaf curl disease of potato. This is also a first experimental demonstration of Koch's postulate for a begomovirus associated with apical leaf curl disease of potato.Author names: Please confirm if the author names (Swarup Kumar Chakrabarti) are presented accurately and in the correct sequence (given name, middle name/initial, family name).Yes. It is correct.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02752-5.

Genetic diversity studies based on morpho-pathological and molecular variability of the Sclerotinia sclerotiorum population infecting potato (Solanum tuberosum L.)

White mould or stem rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a devastating fungal disease found in major potato cultivation areas worldwide. The aim of this study was to characterize genetic diversity in the S. sclerotiorum population from the main potato producing regions of India by means of morphological (mycelial growth, colony colour, number and distribution pattern of sclerotia) and molecular characteristics, as well as to evaluate the virulence of S. sclerotiorum isolates in potato for the first time. Among the S. sclerotiorum population analyzed, high phenotypic and genotypic diversity were observed. Using all the morphological characteristics, a dendrogram was constructed based on Gower's similarity coefficient that distributed all the isolates into three clusters at the 0.62 similarity coefficient. Carpogenic germination of apothecia revealed that larger sclerotia produced a greater number of apothecia while smaller sclerotia produced fewer apothecia. Pathogenicity test results revealed that out of 25 isolates, seven were highly aggressive, 14 were moderate and four had low aggressiveness, whilst isolates from Punjab were more pathogenic than those of Uttar Pradesh. Phylogenetic analysis of universal rice primer polymorphism showed high genetic variability within the isolates that grouped all the isolates in three evolutionary lineages in the resulting dendrogram and showed partial relationship with geographical locations of the isolates. Further, the findings suggest the occurrence of higher heterogeneity and genetic diversity among the S. sclerotiorum isolates that indicates the existence of both clonal and sexual reproduction in the pathogen population of potato producing areas in India.

First Report of Collar and Stem Rot Caused by Rhizoctonia solani AG1-IA on Sesbania sesban in India

Sesbania sesban (L.) Merr., (family Fabaceae) commonly called as "dhaincha" in India, is a multi-purpose crop used as a cover crop, as green manure, in the paper industry as well as animal fodder. The leaves of Sesbania contain high amounts of pinitol, which acts as an anti-diabetic agent (Misra and Siddiqi 2004). During July/August from 2017 to 2019, Sesbania plants exhibiting typical Rhizoctonia-like symptoms, including collar rot, wilting, and necrotic lesions on stems were regularly observed at ICAR-Central Potato Research Institute Regional Station, Meerut, Uttar Pradesh. The disease incidence ranged between 5 and 10% in a Sesbania crop being grown on 25 ha in Sesbania-potato rotation. Ten diseased plants were collected from different fields and brought to the laboratory for diagnosis. Affected stem pieces approximately 5 mm in size were surface sterilized with 2% sodium hypochlorite, washed twice in sterilized water and air dried. Four diseased pieces per plate were inoculated on 2% water agar amended with 2% streptomycin sulfate and incubated at 28±1℃ in the dark. All four affected pieces began to produce Rhizoctonia-like colonies after 48 h of incubation and in total eight isolates were purified and stored at 4℃ for further use. The colonies of eight isolates were evaluated and all were whitish during early growth and became light brown after 72 h. Dark-brown sclerotia appeared in the random pattern on PDA after 120 h. Microscopic observations showed that all isolates had hyphal branching at right angles with slight constriction at the base of the branch, presence of dolipore septum near the branching and multinucleate individual hyphae compartments (Sneh 1991). Based on these morphological characteristics, the fungus was identified as Rhizoctonia solani. All isolates were further characterized to determine anastomosis group (AG) by pairing with a known AG tester of R. solani AG-1-IA (ITCC 7650), AG-1-IB (ITCC 5650), and AG-3 (RS-20) procured from Indian Type Culture Collection, Division of Plant Pathology, ICAR-Indian Agricultural Research Institute, New Delhi and ICAR-Central Potato Research Institute, Shimla, Himachal Pradesh, India, respectively. All eight isolates showed positive anastomosis with a known AG-1-IA tester isolate while no anastomosis was observed with other known tester isolates (Carling 1996). Furthermore, a single ~265 bp amplicon was amplified with AG-specific primer, which was specific to R. solani AG1-IA group; confirms the AG-specific identity of the isolates (Matsumoto 2002). Amplification was not observed with AG1-IB, AG3 and AG2 specific primers (Khodayari et al. 2009). The selected four isolates were molecularly characterized by amplifying the internal transcribed spacer (ITS) and ribosomal DNA (rDNA) 5.8s regions by polymerase chain reaction using ITS1 and ITS4 primer pairs (White et al. 1990). The nucleotide BLAST (BLASTn) analysis of the resulting four sequences i.e. GenBank acc. no. MT105386, MT105387, MT105388, and MT105389 supported the identification of the isolates as AG-1-IA sub-group and showed 95.12%, 98.93%, 96.79%, and 98.04%, respectively, sequence homology with known cultures of R. solani AG1-IA isolated from rice in China (KC285893), and India (MK481078). To confirm pathogenicity, Sesbania plants were grown in pots and maintained in the greenhouse at 25℃ with a 12-h-light/dark photoperiod. After 35 to 40 days of growth, the stems of ten Sesbania plant were artificially inoculated with PDA plugs containing R. solani mycelia (Jia et al. 2007) and covered with aluminium foil. Plants inoculated with noncolonized agar plugs served as control. After 96 h of incubation, all the plants inoculated presented the typical collar and stem rot symptoms. No symptoms were observed in the control plants. R. solani was re-isolated cent percent from these ten infected plants fulfilling Koch's postulates. R. solani AG1-IA has been reported to cause sheath blight and banded leaf and sheath blight diseases of rice and maize, respectively (Ogoshi 1987). To our knowledge, this is the first report of Sesbania sesban infected by R. solani AG1-IA, and serve as a host for the pathogen. The result from our findings will be helpful for planning of crop rotations in an agro-ecosystem.

Genome-wide identification and characterization of microRNAs by small RNA sequencing for low nitrogen stress in potato

Nitrogen is an important nutrient for plant growth and tuber quality of potato. Since potato crop requires high dose of N, improving nitrogen use efficiency (NUE) of plant is an inevitable approach to minimize N fertilization. The aim of this study was to identify and characterize microRNAs (miRNAs) by small RNA sequencing in potato plants grown in aeroponic under two contrasting N (high and low) regimes. A total of 119 conserved miRNAs belonging to 41 miRNAs families, and 1002 putative novel miRNAs were identified. From total, 52 and 54 conserved miRNAs, and 404 and 628 putative novel miRNAs were differentially expressed in roots and shoots, respectively under low N stress. Of total 34,135 predicted targets, the gene ontology (GO) analysis indicated that maximum targets belong to biological process followed by molecular function and cellular component. Eexpression levels of the selected miRNAs and targets were validated by real time-quantitative polymerase chain reaction (RT-qPCR) analysis. Two predicted targets of potential miRNAs (miR397 and miR398) were validated by 5' RLM-RACE (RNA ligase mediated rapid amplification of cDNA ends). In general, predicted targets are associated with stress-related, kinase, transporters and transcription factors such as universal stress protein, heat shock protein, salt-tolerance protein, calmodulin binding protein, serine-threonine protein kinsae, Cdk10/11- cyclin dependent kinase, amino acid transporter, nitrate transporter, sugar transporter, transcription factor, F-box family protein, and zinc finger protein etc. Our study highlights that miR397 and miR398 play crucial role in potato during low N stress management. Moreover, study provides insights to modulate miRNAs and their predicted targets to develop N-use efficient potato using transgenic/genome-editing tools in future.

Development of a visual detection method for Potato virus S by reverse transcription loop-mediated isothermal amplification

A reverse transcription-loop mediated isothermal amplification (RT-LAMP) assay was developed to detect the Potato virus S (PVS) in potato. Two sets of six novel primers that recognize the coat protein gene sequence of the PVS were designed and RT-LAMP assay was optimized for the parameters such as different concentrations of primers, MgSO4, betaine, dNTPs, Bst DNA polymerase, temperature and duration. The RT-LAMP was carried out under isothermal conditions without the thermal cycler using PVS infected leaf and tuber samples, LAMP specific primers with amplification at 65 °C for 60 min, and 80 °C for 5 min. The results were assessed by gel electrophoresis and visual observation of colour change using SYBR Green I dye. The detection limit of the developed RT-LAMP assay was determined and compared with a conventional reverse transcription-polymerase chain reaction (RT-PCR). RT-LAMP was found 100 times more sensitive than RT-PCR. The optimized RT-LAMP assay is robust, reliable, sensitive and convenient for the detection of the PVS in infected potato tubers including asymptomatic plants. No cross-reactions were observed with healthy plants and other potato viruses. The assay is economical and can be employed in large scale testing of potato plants against PVS under healthy seed potato production programme.

Transcriptome analysis of potato shoots, roots and stolons under nitrogen stress

Potato crop requires high dose of nitrogen (N) to produce high tuber yield. Excessive application of N causes environmental pollution and increases cost of production. Hence, knowledge about genes and regulatory elements is essential to strengthen research on N metabolism in this crop. In this study, we analysed transcriptomes (RNA-seq) in potato tissues (shoot, root and stolon) collected from plants grown in aeroponic culture under controlled conditions with varied N supplies i.e. low N (0.2 milli molar N) and high N (4 milli molar N). High quality data ranging between 3.25 to 4.93 Gb per sample were generated using Illumina NextSeq500 that resulted in 83.60-86.50% mapping of the reads to the reference potato genome. Differentially expressed genes (DEGs) were observed in the tissues based on statistically significance (p ≤ 0.05) and up-regulation with ≥ 2 log2 fold change (FC) and down-regulation with ≤ -2 log2 FC values. In shoots, of total 19730 DEGs, 761 up-regulated and 280 down-regulated significant DEGs were identified. Of total 20736 DEGs in roots, 572 (up-regulated) and 292 (down-regulated) were significant DEGs. In stolons, of total 21494 DEG, 688 and 230 DEGs were significantly up-regulated and down-regulated, respectively. Venn diagram analysis showed tissue specific and common genes. The DEGs were functionally assigned with the GO terms, in which molecular function domain was predominant in all the tissues. Further, DEGs were classified into 24 KEGG pathways, in which 5385, 5572 and 5594 DEGs were annotated in shoots, roots and stolons, respectively. The RT-qPCR analysis validated gene expression of RNA-seq data for selected genes. We identified a few potential DEGs responsive to N deficiency in potato such as glutaredoxin, Myb-like DNA-binding protein, WRKY transcription factor 16 and FLOWERING LOCUS T in shoots; high-affinity nitrate transporter, protein phosphatase-2c, glutaredoxin family protein, malate synthase, CLE7, 2-oxoglutarate-dependent dioxygenase and transcription factor in roots; and glucose-6-phosphate/phosphate translocator 2, BTB/POZ domain-containing protein, F-box family protein and aquaporin TIP1;3 in stolons, and many genes of unknown function. Our study highlights that these potential genes play very crucial roles in N stress tolerance, which could be useful in augmenting research on N metabolism in potato.

Development and application of fluorescent loop mediated isothermal amplification technique to detect Phytophthora infestans from potato tubers targeting ITS-1 region

The goal of this study was to develop a fluorescent based loop-mediated isothermal amplification (LAMP) assay for a simple, sensitive and visual detection of P. infestans from tubers targeting a novel internal transcribed spacer 1 (ITS-1) region of ribosomal DNA. The ITS-1 LAMP primers were designed using the Primer Explorer V4 software. The optimization of LAMP reaction conditions and reagents concentrations were carried out with time, temperature, MgSO₄, dNTPs and WarmStart Bst DNA polymerase. The amplified products were analysed using SYBR Green I dye and by agarose gel electrophoresis. We optimized reaction conditions included reagent mix, incubated at 65 °C for 60 min. The target specificity of primers was assessed with PCR, restriction digestion and sequence analysis. The developed LAMP assay was evaluated for its analytical specificity, sensitivity and validation in field tuber samples. The analytical specificity of LAMP primers indicates positive reaction with P. infestans and closely related species except P. erythosepctica. We were able to detect down to 1 pg/µl of DNA using the newly developed LAMP primers whereas the minimal amount detectable for conventional PCR was 0.1 ng/µl. Further, the samples with positive reaction developed a characteristic fluorescent green color. The detection of LAMP assay for inoculum of P. infestans was determined in the artificially inoculated leaves and tubers. In 98 field tuber samples, 54 (55.10%) were confirmed as positive by LAMP while 39 (39.79%) positive by PCR. The LAMP assay developed in this study has a potential to be a beneficial tool in early detection of P. infestans in low cost laboratory. Because the LAMP assay performed well in aspects of sensitivity, repeatability, target specificity, reliability, and visibility, it is suitable for detection of P. infestans in infected potato tubers.

Curcumin Downregulates GSK3 and Cdk5 in Scopolamine-Induced Alzheimer's Disease Rats Abrogating Aβ40/42 and Tau Hyperphosphorylation

Alzheimer's disease (AD) is the most common form of dementia. Extracellular amyloid-β (Aβ) aggregation and tau hyperphosphorylation are the key drivers of AD. Glycogen synthase kinase 3 (GSK3) and cyclin dependent kinase 5 (Cdk5) have been known as leading applicants arbitrating abnormal tau hyperphosphorylation. Thus, we evaluated the efficacy and underlying mechanism of action of curcumin in scopolamine-induced AD rats in our study. We found that curcumin-treated AD rats markedly reduced the levels of Aβ₄₀ and Aβ₄₂ in the brain and in the plasma in comparison to untreated AD rats. Moreover, the levels of phosphorylated tau at Ser396 (PHF13), Ser202/Thr205 (AT8), and Aβ_40/42 (MOAB2) were decreased significantly in AD rats treated with curcumin. Phospho-GSK3β (Tyr216), the active form of GSK3β, and total GSK3β were significantly decreased in AD rats treated with curcumin. Furthermore, Cdk5 and its activators p35 and p25 were significantly decreased in curcumin-treated AD rats. The reduced levels of Cdk5, p35, p25, and GSK3β in curcumin-treated AD rats may result decreased Aβ aggregation and tau hyperphosphorylation, thus ameliorating AD. Impaired spatial memory and locomotor activity in AD rats were partially reversed by curcumin. Therefore, curcumin, as a natural compound present in turmeric, may be a more effective therapeutic agent in the treatment of AD in humans.

Analysis of allelic variation in wild potato (Solanum) species by simple sequence repeat (SSR) markers

Allelic variation in wild potato (Solanum) species was analysed using 14 simple sequence repeat (SSR) markers. SSR allelic profiles showed high polymorphism and distinctness among the wild species. A total of 109 alleles of 14 polymorphic SSR markers were scored in 82 accessions belonging to 22 wild potato species. Allele size ranged from a minimum of 104 bp (STI0030) to a maximum of 304 bp (STM5114). Number of SSR alleles per marker ranged from 4 (STM5127/STM1053) to 13 (STM0019), whereas PIC value varied between 0.66 (STM1053) and 0.91 (STM0019). Cluster analysis using SSR allelic profiles of 82 accessions grouped showed 5 major clusters (I-V) based on the Dice similarity coefficient using neighbour-joining clustering method. Distinct allelic variations were observed among the accessions irrespective of the origin country, series and species. Our study suggests that SSR-based molecular characterization of wild potato species is accession specific and development of an allelic dataset for all the accessions would strengthen their utilization in potato research in future.

Curcumin Ameliorates the Impaired Insulin Signaling Involved in the Pathogenesis of Alzheimer's Disease in Rats

To date, dysregulation of the insulin signaling pathway in the brain has not been demonstrated unequivocally in Alzheimer's disease (AD). The purpose of the study was to examine the possible dysregulation of insulin signaling pathway in an AD rat model. Furthermore, the present study investigated the effect of Donepezil and Curcumin on insulin signaling, insulin, and glucose levels in AD rat brain. The rats were induced to develop AD by intraperitoneal administration of Scopolamine. We found that glucose levels in plasma and brain were decreased in AD rats, whereas the insulin levels was increased in plasma but decreased in brain in AD rats. In addition, insulin signaling proteins IR-β, IGF-1, IRS-1, IRS-2 p-Akt (Ser473), and Akt were markedly reduced in the AD rats. Furthermore, GLUT3 and GLUT4 levels in the brain were markedly reduced in AD rats. All these data were compared to Saline-treated control rats. Curcumin significantly increased glucose levels in plasma and in brain. However, insulin levels was decreased in plasma and was increased in AD rats' brain. Moreover, GLUT3 and GLUT4 levels were significantly increased in Curcumin-treated AD rats. All these data were compared to Scopolamine- induced AD rats. Thus amelioration of impaired insulin signaling and improved glucose regulation in AD rats by Curcumin may be beneficial in the management of AD.

Complete mitogenome mapping of potato late blight pathogen, Phytophthora infestans A2 mating type

Complete mitochondrial genome of Phytophthora infestans, A₂ mating type (MT) with a size of ≅37,767 bp was sequenced. A total of 53 protein-coding genes are predicted on both strands, including 25 tRNA, 2 rRNA, and 18 respiratory proteins. Gene order of A₂MT was consistent with that established in A₁, despite high level of polymorphism in both coding and non-coding regions. The mtDNA of A₂MT was found to have 99.5% and 99.4% homology with Ia and Ib, whereas 94.7% and 94.3% with IIa and IIb, respectively. Study of repeats revealed a dinucleotide (AT)₉ specific to A₁ and homology of cox1 gene sequence revealed the relationship among 50 Phytophthora species.

Genome sequencing of four strains of Phylotype I, II and IV of Ralstonia solanacearum that cause potato bacterial wilt in India

Ralstonia solanacearum is a heterogeneous species complex causing bacterial wilts in more than 450 plant species distributed in 54 families. The complexity of the genome and the wide diversity existing within the species has led to the concept of R. solanacearum species complex (RsSC). Here we report the genome sequence of the four strains (RS2, RS25, RS48 and RS75) belonging to three of the four phylotypes of R. solanacearum that cause potato bacterial wilt in India. The genome sequence data would be a valuable resource for the evolutionary, epidemiological studies and quarantine of this phytopathogen.

Uniplex and duplex PCR detection of geminivirus associated with potato apical leaf curl disease in India

Apical leaf curl disease has emerged as a new disease in potato during the last decade in India due to a change in planting date and an increased whitefly population. Its incidence is on the rise threatening the cultivation of potato across the country. Hence, a PCR assay was developed for the detection of Tomato leaf curl New Delhi virus-potato (ToLCNDV-Potato) which is the causal agent of apical leaf curl disease in potato. Primers specific to the coat protein (AV1) and replicase (AC1) gene regions were designed and used for standardization of the PCR. Some of the primers (LCVCPF1/LCVCPR1, LCVREPF2/LCVREPR2, LCrep1F/LCrep2R) could detect the virus in 2.4-0.24pg of total DNA of infected plant. A duplex PCR assay was optimized with the selected coat protein gene specific primers and primers specific to potato urease gene, a housekeeping gene served as an internal check. The suitability of these primers was examined for detection of the virus in 80 potato apical leaf curl disease samples from 11 different potato growing states of India and also from micro-plants grown in tissue culture. The selected coat protein primer pair (LCVCPF1/LCVCPR1) was found to be conserved in all 80 isolates except for a few isolates, which had a single nucleotide substitution in the forward primer sequence. These substitutions did not interfere with amplification of the coat protein gene. The primers could detect the virus using a print-capture PCR assay both in the presence and absence of an internal control. These results indicate the robustness of the PCR assay for virus indexing of mother stocks in the seed production system.

Influence of drying of biosludge on organochlorine compounds from pulp and paper industry

Pulp and paper industry is one of the major sources of man-made generation of organochlorine compounds. During biological treatment of wastewater, part of organochlorine compounds is discharged with treated effluent and part is retained on biomass and disposed of as waste activated sludge. Due to presence of these compounds, the disposal of biosludge from pulp and paper industry has become an issue. The estimation of adsorbable organic halogen (AOX) compounds after drying and grinding resulted in 49% lower concentration of AOX due to stripping of purgeable compounds. These purgeable compounds are not released at 60 degrees C in aqueous medium during estimation of purgeable organic halogen (POX) compounds. Dispersion of sludge by sonication overcomes the loss of POX compounds and results in higher concentration ofAOX compounds. The drying of biosludge samples at 45, 100 degrees C and in presence of sun light resulted in 20.1, 49.0 and 29.6% removal of purgeable AOX compounds, respectively. The lab scale sorption study using dichloromethane (as volatile organochlorine compound) reveal that biosludge from pulp and paper industry is a good adsorbent of volatile organochlorine compounds and results in poor release of these compounds during estimation of POX compounds.

12-Lipoxygenase Products Reduce Insulin Secretion and {beta}-Cell Viability in Human Islets

CONTEXT

Inflammation is increasingly recognized as an important contributing factor in diabetes mellitus. Lipoxygenases (LOs) produce active lipids that promote inflammatory damage by catalyzing the oxidation of linoleic and arachidonic acid, and LO is expressed in rodent and human islets. Little is known about the differential effect of the various hydroxyeicosatetraenoic acids (HETEs) that result from LO activity in human islets.

OBJECTIVE

We compared the effects of 12-LO products on human islet viability and function.

DESIGN

Human islets were treated with stable compounds derived from LOs: 12(S)-HETE, 15HETE, 12HPETE, and 12RHETE and then examined for insulin secretion and islet viability. The p38-MAPK (p38) and JNK stress-activated pathways were investigated as mechanisms of 12-LO-mediated islet inhibition in rodent and human islets.

RESULTS

Insulin secretion was consistently reduced by 12(S)-HETE and 12HPETE. 12(S)-HETE at 1 nm reduced viability activity by 32% measured by MTT assay and increased cell death by 50% at 100 nm in human islets. These effects were partially reversed with lisofylline, a small-molecule antiinflammatory compound that protects mitochondrial function. 12(S)-HETE increased phosphorylated p38-MAPK (pp38) protein activity in human islets. Injecting 12-LO siRNA into C57BL/6 mice reduced 12-LO and pp38-MAPK protein levels in mouse islets. The addition of proinflammatory cytokines increased pp38 levels in normal mouse islets but not in siRNA-treated islets.

CONCLUSIONS

These data suggest that 12(S)-HETE reduces insulin secretion and increases cell death in human islets. The 12-LO pathway is present in human islets, and expression is up-regulated by inflammatory cytokines. Reduction of 12-LO activity could thus provide a new therapeutic approach to protect human beta-cells from inflammatory injury.

Effect of ozonation on activated sludge from pulp and paper industry

Aerobic biological treatment with activated sludge is the predominant process all over the world for treatment of pulp and paper industry wastewater. 50-70% of the biodegradable organic material is oxidized to CO₂ and the rest is converted to bacterial biomass, typically termed as excess sludge or waste activated sludge (WAS). Handling and disposal of WAS in general and in particular from the pulp and paper industry face different processing difficulties, regulatory stringency due to organochlorine contamination and reluctance of people for reuse. With an objective of reducing the net disposable biomass, ozonation of WAS from a pulp and paper mill and from a laboratory scale batch activated sludge process operated with the wastewater and bacterial seed of the same pulp and paper mill have been carried out. With the mill sludge having predominant filamentous organisms 18% MLSS was reduced at an ozone dosage of 55 mg O₃/g dry MLSS solid (DS) resulting in 2.5 times COD increase. With the laboratory sludge which is well structured and flocculating, only 6% MLSS was reduced at an ozone dosage of 55 mg O₃/g DS. Ozonation mineralizes 26% and 20% AOX compounds embedded in the secondary sludge in the mill and laboratory sludge respectively at an ozone dosage of 55 mg O₃/g DS. During ozonation, absorbed/adsorbed lignin on biomass was released which resulted in increased colour concentration. Ozonation can be a potential oxidative pretreatment process for reducing the WAS and paving the way for cost effective overall treatment of WAS.

Assessment of genetic fidelity of micropropagated apple rootstock plants, EMLA 111, using RAPD markers

EMLA 111(East Malling Long Ashton), a clonal rootstock of apple (Malus pumila Mill.) was micropropagated using axillary bud and shoot apices. The present work was carried out to assess the genetic fidelity of micropropagated plants using random amplified polymorphic DNA (RAPD). Ten arbitrary decamer primers have been used to amplify genomic DNA from in vitro raised field material and mother plant. A total of 57 amplified products were obtained, out of which 53 were monomorphic across the mother tree and its tissue culture raised progenies. Of the ten primers used, 8 showed RAPD profiles which were identical to the mother plant. Similarity matrix based on Jaccard's coefficient revealed that pairwise value between the mother plant and its tissue cultured plants ranged from 0.93 to 1.00 and among tissue cultured plants, it was 0.92 to 1.00, thus indicating a high degree of genetic fidelity.

Multiple displacement amplification as a pre-polymerase chain reaction (pre-PCR) to detect ultra low population of Ralstonia solanacearum (Smith 1896) Yabuchi et al. (1996)

AIMS

To develop a reliable and sensitive protocol for detection of Ralstonia solanacearum using MDA-PCR (Multiple displacement amplification-PCR amplification).

METHODS AND RESULTS

MDA-PCR technique was performed on pure cell lysates as well as soil samples. Pure cell lysate as well as that of soil DNA was used as template in MDA reaction. MDA of template DNA was carried out in the presence of sample buffer, reaction buffer and enzyme mix (Phi 29 DNA polymerase and random hexamers). The MDA amplified DNA was used for PCR amplification using R. solanacearum -specific PCR primers. MDA-PCR could detect as low as 1 colony forming unit (CFU ml(-1)) of bacteria within 8 h including DNA isolation.

CONCLUSION

MDA followed by standard PCR facilitated the detection of pathogen from very low count samples. The method is of great importance in managing the brown rot disease of potato.

SIGNIFICANCE AND IMPACT OF STUDY

The ultrasensitive detection technique developed in the present study is sensitive and speedy enough to be included into integrated wilt disease control programmes.

Genotypic diversity in a localized population of Ralstonia solanacearum as revealed by random amplified polymorphic DNA markers

AIMS

To assess genotypic diversity within Ralstonia solanacearum isolates of a single field.

METHODS AND RESULTS

A total of 44 field isolates and 22 in vitro generated clones of R. solanacearum were studied for genotypic diversity by random amplified polymorphic DNA (RAPD) technique. Genomic DNA of these isolates and clones was extracted by proteinase-K-SDS lysis mini-prep method. RAPD analysis was done with 30 decamer primers. The data were analysed using NTSYSpc 2.02h software. Forty-two out of 44 field isolates and all the clonal isolates were identified as distinct genotypes at 70% similarity level.

CONCLUSION

Very high level of genome variability was observed within the field and clonal isolates of R. solanacearum. This might be a reason for the wide host range of this bacterium and for quick breakdown of wilt resistance in host plants.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results suggest that it would be difficult to design specific diagnostic protocol for R. solanacearum even for a localized population and to breed cultivars with broad-spectrum resistance.

Expression of the cry9Aa2 B.t. gene in tobacco chloroplasts confers resistance to potato tuber moth

We report here the control of potato tuber moth (Phthorimaea operculella) by incorporating a truncated Bacillus thuringiensis cry9Aa2 gene in the plastid genome. Plasmids pSKC84 and pSKC85 are derivatives of a new polycistronic plastid transformation vector, pPRV312L, that carries spectinomycin resistance (aadA) as a selective marker and targets insertions in the trnI-trnA intergenic region. The Cry9Aa2 N-terminal region (82.1 kDa; 734 amino acids) was expressed in a cassette, which consists of 49 nucleotides of the cry9Aa2 leader and the 3'-untranslated region of the plastid rbcL gene (TrbcL), and relies on readthrough transcription from the plastid rRNA operon. In a tobacco leaf bioassay, expression of Cry9Aa2 conferred resistance to potato tuber moth. In accordance, the Cry9Aa2 insecticidal protein accumulated to high levels, approximately 10% of the total soluble cellular protein and approximately 20% in the membrane fraction. However, high-level Cry9Aa2 expression significantly delayed plant development. Thus, a practical system to control potato tuber moth by Cry9Aa2 expression calls for down-regulation of its expression.

Genetic diversity and differentiation of Indian isolates of Phytophthora infestans as revealed by RAPD analysis

Sixty-seven isolates of Phytophthora infestans collected from Himalayan hill regions and subtropical planes of India were characterized by RAPD markers to assess diversity and differentiation based on location of origin. Ten random decamer primers generated 161 polymorphic fragments. Association of P. infestans isolates on the dendrogram and PCO plot revealed two clear grouping based on geographical location of origin-hill isolates and plane isolates. Quantification of diversity by Shannon index of diversity analysis demonstrated that most of the diversity was present with a particular population (hill or plane) of P. infestans isolates, with 85% variation being within and 15% being between hill and plane isolates. Subtropical plane isolates of P. infestans exhibited higher variability compared to hill isolates and they were more dispersed on the PCO plot. No clear differentiation of isolates based on mating type was reflected on the dendrogram and PCO plot.

Phylogenetic analysis of 5'-UTR and P1 protein of Indian common strain of potato virus Y reveals its possible introduction in India

The 5' untranslated region (UTR) and P1 region of the Indian strain of potato virus Y ordinary strain (PVYO) was cloned and sequenced for the first time. Database searches and multiple sequence alignment showed the highest sequence similarity with the PVYO strains of European origin. Based on the phylogenetic analysis and multiple sequence alignment, the possible evolution of PVYN from PVYO is predicted. PVYO strains from China and India were perhaps introduced into these countries from a similar geographical location. All major PVY strains available in the database can be classified into two major subgroups of North American and European origin. The Chinese and Indian PVYO strains fall within the European union subgroup suggesting a long association since potato was introduced from Europe into these countries by two separate independent events. The possible function of P1 protein in plant virus replication is suggested due to in-silico prediction of nuclear localization signal (NLS) and other phosphorylation regulatory domains at the vicinity of the NLS.

Cloning and sequencing of coat protein gene of an Indian potato leaf roll virus (PLRV) isolate and its similarity with other members of Luteoviridae

An Indian strain of potato leaf roll virus (PLRV) was purified to generate complementary DNA corresponding to the coat protein (CP) gene. Virus cDNA was synthesized from purified viral RNA using oligo (dT)-anchor primer and virus specific primers. The viral sequence encoding the coat protein was specifically amplified by polymerase chain reaction (PCR), using specific primers bordering the CP gene. The unique amplified product thus obtained was A-T cloned into the pGEM-T Easy vector and the authenticity of the cloned gene verified by dot blot hybridization and sequence analysis. Run-way-transcripts of the cloned CP gene could detect PLRV in tissue imprints and tissue dilution. The nucleotide sequences and the deduced amino acid sequences were compared with the other PLRV isolates and found to be 97-99% identical at both the nucleotide and amino acid sequence level of other isolates. Multiple sequence alignment of deduced amino acid sequences revealed considerable homology to other luteoviruses. A nuclear localization signal located close to the N-terminus of the CP gene was predicted. This is the first report of PLRV coat protein sequence from an Indian strain.

Characterization of genetic diversity of some serovars of Bacillus thuringiensis by RAPD

RAPD based fingerprinting of 21 serovars of Bacillus thuringiensis (Bt) representing different serotypes was performed using 19 random decamer primers. A total of 172 polymorphic fragments, ranging in size from 161-2789 bp, were amplified from 13 of the 19 primers. Pairwise genetic similarity analysis revealed very low similarity values, ranging from 3-68%, among the serovars of Bt, indicating high genetic divergence. Nineteen serovars of Bt fell in two major clusters and remaining two formed solitary clusters in the dendogram. Clustering of Bt strains established genetic relatedness between serovars and serotypes. It has been suggested that RAPD analysis can be used for genotypic characterization of Bt to complement flagellar serotyping.

Effects of different nickel compounds on the transport of para-aminohippurate ion by rat renal cortical slices

In vitro rat renal cortical slice uptake of para-aminohippurate ion (PAH) expressed as tissue slice-to-medium ratio was used as a model to predict nephrotoxicity of different nickel compounds. Pretreatment with nickel compounds for a period of up to 4 h was followed by an incubation with 74 microM PAH for 2 h. The PAH uptake by renal cortical slices was reduced by nickel compounds in both concentration- and time-dependent manner. Furthermore, the extent of such reduction of PAH uptake was found to depend on the chemical form (speciation) of nickel. Thus, slice-to-medium ratios were 41, 49, 48, and 66% of control values after a 4-h pretreatment with 0.378 mM nickel carbonate hydroxide, 1.5 mM nickel subsulfide, 4 mM nickel sulfate and 2.98 mM nickel oxide, respectively. Such an inhibition of PAH transport was not due to cytotoxicity. The results suggest that the nephrotoxic potency decreases in the following order: nickel carbonate hydroxide>nickel subsulfide>nickel sulfate>nickel oxide. Treatment of renal cortical slices with high concentrations of either mannitol, a hydroxyl radical scavenger, or glutathione significantly reduced the inhibition of PAH uptake by soluble form of nickel subsulfide, with concomitant reduction of nickel ion uptake by cortical slices. But no such oxidative stress seems to be involved in nickel carbonate hydroxide-induced inhibition of PAH uptake.

Visceral afferent hypersensitivity in irritable bowel syndrome--evaluation by cerebral evoked potential after rectal stimulation

OBJECTIVES

Gut hypersensitivity has been shown to be present in irritable bowel syndrome. The current study sought to determine the involvement or hypersensitivity of the gut afferents, objectively, by recording cerebral evoked potential after rectal stimulation.

METHODS

In 13 patients with irritable bowel syndrome and nine healthy controls, rectal perception thresholds to electrical stimulation were measured, and cerebral evoked potentials were recorded from 2 cm behind vertex (Cz') after rectal stimulation electrically (frequency 1 Hz, duration 0.5 ms) at an intensity 50% above perception threshold and with filter setting 1-250 Hz.

RESULTS

Perception thresholds to rectal electrical stimuli in patients with irritable bowel syndrome were lower than controls (p < 0.05). Rectal stimulation led to recognizable and reproducible cerebral evoked potentials. P1, N1, P2 latencies in patients with irritable bowel syndrome were shorter than that in controls (p < 0.05). P1/N1 amplitude was greater in patients with irritable bowel syndrome than in controls (p < 0.05).

CONCLUSIONS

The shorter latency and increased amplitude of cerebral evoked potential after rectal stimulation in patients with irritable bowel syndrome compared to controls provide objective evidence supporting visceral afferent hypersensitivity as the underlying mechanism in irritable bowel syndrome.

Caffeine potentiation of allyl alcohol-induced hepatotoxicity. II. In vitro study

We examined the effects of caffeine (C) on allyl alcohol (AA)- and acrolein (A)-induced hepatotoxicity on freshly-isolated, rat hepatocytes obtained from livers of adult, male, Sprague-Dawley rats. Isolated rat hepatocytes in suspension were incubated in each test with one of the following: 0, 1.0, or 2.5 mM of AA alone; or with 0, 2.5, or 5 mM of C alone; or a combination of AA and C at the same range of concentrations as used alone, for 15, 30, 60, 90, and 120 minutes at 37 degrees C. A dose- and time-dependent potentiation of cytotoxicity as measured by cellular viability (using trypan blue exclusion) were observed. The AA (2.5 mM)-induced lactate dehydrogenase (LDH) leakage observed after 60 minutes incubation was completely prevented when pretreated for 15 minutes with 4-methylpyrazole (MP) (0.5 mM). Such pretreatment, even with a double dose of 4-MP, only partially, and not significantly, prevented LDH leakage when the hepatocytes were incubated with a mixture of 2.5 mM AA and 5 mM C. The depletion of hepatocyte nonprotein sulfhydryl (NPSH) content caused by AA was further enhanced in the presence of C, as early as 15 minutes after their exposure. The AA-induced increase in lipid peroxidation was also potentiated by C; however, potentiation started later, and only after sufficient depletion of NPSH (mostly glutathione) occurred resulting from the presence of AA plus C. A significant loss of protein sulfhydryls in rat hepatocytes could be noted following a 60-minute incubation period with either AA (1 mM) or AA (1 mM) plus C (5 mM). Similarly, C produced a dose-and time-dependent potentiation of A-induced liver cytotoxicity, which was preceded by severe loss of NPSH content within 15 minutes of exposure, whereas the potentiation of lipid peroxidation (LPO) resulting from A plus C was found to be a relatively late event, as with AA plus C. Furthermore, combined treatment with AA and C produced a significantly higher cytotoxicity (as measured by cellular viability) than that due to the combined treatment with A plus C based on equimolar concentration. These results suggest that two increased bioactivation pathways of AA involving the P-450 mixed-function oxidase system resulting from C may be involved in the potentiation of AA hepatotoxicity.

Influence of caffeine on allyl alcohol-induced hepatotoxicity in rats. I. In vivo study

Cotreatment of rats with a low hepatotoxic dose (30.7 mg/kg, i.p.) of allyl alcohol (AA) and a higher, but nontoxic, dose (150 mg/kg, oral) of caffeine (CF) potentiated the hepatotoxicity of AA. This was verified by significantly higher levels of plasma alanine aminotransferase (ALT) activity and histopathologically greater severity of lesions in the periportal hepatocytes than those due to AA alone. Treatment of rats with 4-methylpyrazole (4-MP) (0.5 mmol/kg, i.p.) (an inhibitor liver alcohol dehydrogenase) for 30 minutes, followed by similar cotreatment with AA and CF, completely prevented the elevation of plasma levels of ALT and histological damage induced by cotreatment with CF and AA 24 hours following their administration. Severe liver damage induced by cotreatment with CF and AA was further, markedly enhanced by phenobarbital pretreatment (80 mg/kg, i.p., 3 days). Thus, extensive necrosis of periportal hepatocytes was noted, as well as edema and accumulation of inflammatory cells in the necrotic foci caused by such pretreatment. The depression of hepatic nonprotein sulfhydryls resulting from CF plus AA was much more severe than that caused by AA or CF alone and appeared as early as 30 minutes after administration. However, much less marked depletion of protein thiols was observed following similar treatments. Significant increase in lipid peroxidation (as measured by melondialdehyde [MDA] formation) was also observed in rat liver but only 24 hours after administration. The production ofMDA in the rat liver was significantly higher after administration of AA plus CF than after administration of AA alone. Pretreatment of rats with phenobarbital further significantly enhanced the formation of 2,4-dinitrophenylhydrazine (DNP)-reactive metabolite(s) (measured as DNP-acrolein adduct equivalents) in rat liver induced by AA (30.7 mg/kg) plus CF (150 mg/kg) within 1 hour following such treatment. Cotreatment with AA and a higher dose of CF resulted in significantly higher excretion of urinary thioethers or mercapturic acids than in rats treated with AA alone. Thus, these data suggest that an increased bioactivation pathway of acrolein involving a P450 mixed-function oxidase system caused by CF may be involved in such potentiating effects of CF on AA-induced hepatotoxicity in rats.

DNA-protein crosslinks induced by nickel compounds in isolated rat lymphocytes: role of reactive oxygen species and specific amino acids

Isolated rat lymphocytes in salts-glucose medium (pH 7.2) were incubated with nickel chloride, nickel acetate, nickel sulfate, and a soluble form of nickel subsulfide (0-2 mM) at 37 degrees C for 2 h. The soluble form of nickel subsulfide induced a significant increase in DNA-protein crosslinks (DPXLs) (111%) beginning at 0.5 mM and a maximum increase of 700% from that of the control value was reached at a 2 mM concentration, whereas nickel sulfate produced only a 65% increase of such crosslinks at the 2 mM concentration only. No significant reduction in viability of rat lymphocytes (as measured by trypan blue exclusion) due to these nickel compounds was observed at any concentration used. Time-course studies of DPXLs and cellular viability due to 2 mM nickel subsulfide indicate that DPXL formation may not be due in part to cellular necrosis. Coincubation of nickel subsulfide (2 mM) with l-histidine (16 mM), l-cysteine (4 or 8 mM), or l-aspartic acid (24 mM) significantly reduced the DPXLs induced by 2 mM nickel subsulfide. But Mg(2+) even at 24 mM failed to antagonize nickel subsulfide-induced increase in DPXLs. High concentrations of these amino acids significantly decreased the accumulation of Ni(2+) from nickel subsulfide in lymphocytes, suggesting that such reduction of cellular uptake of Ni(2+) by these amino acids is partly responsible for the potent protective effects of these amino acids against such genotoxicity of nickel subsulfide. In vitro exposure of lymphocytes to nickel subsulfide (0-2 mM) increased the formation of reactive oxygen species (ROS) in a concentration-dependent manner. Furthermore, coincubation of 2 mM nickel subsulfide with catalase, dimethylthiourea, mannitol, or vitamin C at 37 degrees C for 2 h resulted in a significant decrease of nickel subsulfide-induced formation of DPXLs, suggesting that nickel subsulfide-induced DPXLs formation in isolated rat lymphocytes is caused by the formation of ROS. The amino acid treatment also abrogated Ni(3)S(2)-induced generation of ROS. Deferoxamine (a highly specific iron chelator) treatment prevented nickel subsulfide-induced DNA-protein crosslink formation, suggesting that Ni(2+)-induced DPXL formation in rat lymphocytes is caused by the induction of Fenton/Haber-Weiss reaction, generating hydroxyl radicals. The potent protective effects of these specific amino acids against nickel subsulfide-induced DPXL formation in isolated rat lymphocytes may be due in part to impaired cellular uptake of Ni(2+), inhibition of the binding of Ni(2+) to deproteinized DNA, and a reduction in reactive oxygen species.

SarA represses agr operon expression in a purified in vitro Staphylococcus aureus transcription system

Mutation and genetic complementation studies suggested that two chromosomal loci, agr and sar, are involved in the upregulation of several exotoxin genes and the downregulation of a number of surface protein genes in a growth phase-dependent manner in Staphylococcus aureus. We purified recombinant T7-tagged SarA from Escherichia coli and determined its effect on transcription from several S. aureus promoters by using purified RNA polymerase reconstituted with either sigma(A) or sigma(B) from S. aureus. Of the seven sigma(A)-dependent promoters that we tested, SarA repressed transcription from agrP2, agrP3, cna, sarP1, and sea promoters and did not affect sec and znt promoters. Furthermore, SarA had no effect on transcription from the sigma(B)-dependent sarP3 promoter. In vitro experimental data presented in this report suggest that SarA expression is autoregulated.

Effects of protein-deficient nutrition during rat pregnancy and development on developmental hindlimb crossing due to methylmercury intoxication

Pregnant rats were fed either a control (20% protein) or low (3.5%) protein diet during gestation and lactation. The pups were separated from their mothers on postnatal day 21, and were given the same diet as their corresponding mothers. The groups of pups from each diet group were treated on either postnatal day 21 or postnatal day 60 with 7.5 mg methylmercury chloride (MeHgCl) per kg b.w. once daily by gavage for 10 consecutive days, and the development of ataxia (hind-limb crossing) was monitored. The offspring from mothers on the protein-deficient diet were found to be more sensitive to MeHg-induced ataxia than those on the protein-sufficient diet. The former accumulated more mercury in different brain regions than the latter. The rates of protein synthesis in different brain regions of the offspring fed the protein-deficient diet were significantly reduced compared with the rates in those fed the protein-sufficient diet. However, MeHg treatment did not significantly modify the rates of such protein synthesis further in protein-deficient rats. Thus, a significantly much higher inhibition of the intrinsic rates of protein synthesis in different brain regions due to severe protein deficiency, as observed in this study, may be partly responsible for the increased susceptibility of developing rats fed a protein-deficient diet to MeHg-induced ataxia, or hindlimb crossing, although other factor(s) might also be involved.

Altered regulation of dopaminergic activity and impairment in motor function in rats after subchronic exposure to styrene

Animal and human studies suggest a dopamine-mediated effect of styrene neurotoxicity. However, the results reported to date are incomplete and not consistent. As such, the mechanism of its neurotoxicity is still unclear. The present study has, therefore, reexamined the central dopaminergic system in relation to some neurobehavioral effects in rats following subchronic exposure to styrene. Groups of adult male Sprague-Dawley rats received 0, 0.25, or 0.5 g styrene per kg b.wt. by gavage for 13 consecutive weeks. Twenty-four hours after cessation of such treatment with the higher dose (0.5 g/kg), the contents of dopamine (DA) and its metabolites were significantly reduced in the corpus striatum, hypothalamus, and lateral olfactory tract regions. In vitro styrene showed a significant increase in DA release from rat striatal synaptosomes similar to that of tyramine. Significant loss of motor function was observed on days 56, 70, and 84 during the styrene treatment with the higher dose, and lasted over a month after such treatment. However, the treated animals recovered their motor function within 45-60 days after cessation of such treatment, along with the recovery of normal levels of dopamine and its metabolites. Furthermore, styrene-induced initial impairments in measures of dopaminergic activity cannot be attributed to altered regulation of tyrosine hydroxylase activity. Specific [3H]-spiroperidol binding was also unaltered 7 or 15 days after subchronic treatment with styrene. These data imply that despite the dopaminergic neuronal loss due to styrene, dopaminergic transmission was not reduced to a level that would result in an overall development of dopamine receptor supersensitivity in the striatum. Collectively, these studies indicate that the subchronic neurotoxic action of styrene may be primarily presynaptic in nature and may involve impaired regulation of DA content and stimulation of DA release.

Purification and characterization of an extracellular alkaline serine protease from Aspergillus terreus (IJIRA 6.2)

An extracellular alkaline serine protease has been purified from Aspergillus terreus (IJIRA 6.2). The purification procedure involved chromatography on DEAE-Sephadex A25, phosphocellulose, hydroxyapatite, casein-Sepharose, gel filtration on Sephacryl-S-300 and by glycerol density gradient centrifugation. The enzyme was further purified to apparent homogeneity through a combination of electrophoresis in polyacrylamide gel containing 0.1% sodium dodecyl sulfate (SDS) with or without protease substrate (gelatin) and subsequent regeneration of its activity in situ by removal of SDS. The active enzyme was visualized in a zymogram or on the basis of protease activity exhibited on an X-ray film. The protein in the unstained segment of the gel was electroeluted. The eluted protein with protease activity exhibited a molecular mass of 37,000-daltons on electrophoresis in SDS-polyacrylamide gel. A sedimentation coefficient of 3.2S was obtained by glycerol density gradient contrifugation. Maximum activity of protease was observed at pH 8.5 and at 37 degrees C. Purified protease was active between pH 5.5 and 9.5 and was found to be stable up to 60 degrees C. With Na-caseinate, the K(m) of the purified protease was found to be 0.055 mM. Antipain, phenylmethane sulfonyl fluoride, and chymostatin served as non-competitive inhibitors. Substrate specificity was determined by using a synthetic chromogenic peptide containing N-P-Tosyl-Gly-Pro-Arg-p-nitroanilide. Results showed that the protease cleaved the peptide on the -COOH end of arginine residue.

Correlation among Quasi-Periodic Oscillation Frequencies and Quiescent-State Duration in Black Hole Candidate GRS 1915+105

We discover a definite correlation between the frequency of the quasi-periodic oscillations (QPOs) in quiescent states and the duration of the quiescent state of the transient X-ray source GRS 1915+105. We find that while the QPO frequency can be explained by the oscillation of shocks in accretion flows, the switching of burst to quiescent states (and vice versa) and their duration can be explained by assuming an outflow from the postshock region. The duration of the quiescent state is inversely related to the QPO frequency. We derive this relation. We also find the correlation between the observed low ( approximately 0.001-0.01 Hz) and the intermediate (1-10 Hz) QPO frequencies. Our analytical solutions are verified by analyzing several days of public domain data from the Rossi X-Ray Timing Explorer.

Role of oxidative stress in nickel chloride-induced cell injury in rat renal cortical slices

Nickel chloride (NiCl2) induced lactate dehydrogenase (LDH) release and lipid peroxidation (LPO) in rat renal cortical slices in vitro in a concentration- (0-2 mM) and time- (0-4 hr) dependent manner, with initial significant LDH release occurring as early as 1 hr, whereas significant increase in LPO started 3 hr after exposure, suggesting that LPO results from renal cell injury. Both NiCl2-induced LDH release and LPO were prevented significantly by glutathione and dithiothreitol, suggesting that NiCl2-induced renal cell injury is dependent on thiols. However, such injury is not dependent solely on thiols, because (a) these thiols failed to inhibit completely the uptake of Ni2+ by the renal cortex, and (b) diethylmaleate pretreatment failed to increase NiCl2-induced cell injury further. Superoxide dismutase partially reduced the NiCl2-induced LDH release without affecting LPO and glutathione, whereas catalase did not affect such LDH release and LPO. Dimethylthiourea and DMSO completely prevented NiCl2-induced LPO, but only partially reduced LDH release. Deferoxamine prevented NiCl2-induced renal cell injury without affecting LPO and without significantly reducing Ni2+ uptake by the renal cortex, suggesting that nickel chelation is not important in such prevention of injury. NiCl2-induced inhibition of para-aminohippurate uptake was prevented significantly by thiols, deferoxamine, and dimethylthiourea. NiCl2-induced loss of cellular glutathione content was prevented significantly by thiols and deferoxamine, but not by superoxide dismutase and dimethylthiourea. These results suggest that LPO was not related to NiCl2-induced lethal renal cell injury, whereas such injury may be caused by the induction of the Fenton reaction, generating hydroxyl radicals.

Biphasic biomethanation of wood-hydrolysate effluent

The dissolving pulp industry, spread throughout the world, is the principal source of wood-hydrolysate effluent rich in hemicelluloses. This effluent is the major source of pollution in the industry. COD and BOD5 values of the effluent range from 60,000 to 103,000 and 42,000 to 78,000 mg/l respectively. Biomethanation of this effluent is the best possible treatment option for reducing the COD load and recovering the bioenergy embedded in the effluent. This paper deals with the study on the biphasic biomethanation of the wood-hydrolysate in upflow acidogenic reactor coupled with anaerobic filter methanogenic reactor. The two reactors were operated at organic loading rates of 69.6 and 30.1 g COD/l/d respectively. The overall COD, hemicelluloses and lignin reductions, and methane generation were observed to be 88%, 92%, 82% and 6.5 l/l reactor volume/d respectively. The relative size of the biphasic, anaerobic filter (mono-phasic) and upflow anaerobic sludge blanket (mono-phasic) reactors is found to be 1:1.6:2.03 respectively.

Toxicity and bioaccumulation of nickel sulfate in Sprague-Dawley rats following 13 weeks of subchronic exposure

Adult male Sprague-Dawley rats were given 0, 0.02, 0.05, and 0.1% nickel sulfate (NiSO4-6H2O) or 0, 44.7, 111.75, and 223.5 mg Ni/L, respectively, in their drinking water for 13 wk. Twenty-four hours following the end of such treatment, all animals survived and no apparent clinical signs of toxicity were noted. The final mean body weights of various nickel sulfate-treated rats were not significantly decreased except for the 0.1% nickel sulfate treated group when compared to those in the control. The absolute and relative organ weights were either increased or decreased or remained unchanged, depending on the organ and the dose of nickel sulfate. Total plasma proteins, plasma albumin and globulins, and plasma glutamic pyruvic transaminase activity were all significantly decreased in 0.1% nickel sulfate-treated rats. Lymphocyte subpopulations (T and B cells) were induced at lower dose levels, but suppressed at the highest (0.1%) dose group. A significant decrease in urine volume and an increase in BUN were observed at the highest dose group. Biochemical analysis of bronchoalveolar lavage fluid and lung tissue showed some lung damage, whereas no damage to the testis or DNA in liver and kidneys were found. No gross or microscopic changes were seen in any of the various tissues examined. The relative order of bioaccumulation of nickel in different organs of rats when treated at 0.1% nickel sulfate (223.5 mg Ni/L) was kidneys > testes > lung = brain > spleen > heart = liver. But with regard to order of toxicity, both immune and pulmonary systems were found to be very sensitive targets, followed by kidney.

Styrene and styrene oxide affect the transport of dopamine in purified rat striatal synaptic vesicles

Animal and human studies suggest a dopamine-mediated effect of styrene neurotoxicity. To date, mechanisms of cerebral membrane transport of neurotransmitter amines in the presence of styrene in relation to its neurotoxicity have not been addressed properly. So, the present study has examined to test the hypothesis that dopaminergic malfunction in vesicular transport is a critical component in styrene-induced neurotoxicity in rats. Both styrene and its intermediate reactive metabolite, styrene oxide antagonized the in vitro striatal binding of [3H] tyramine, a putative marker of the vesicular transporter for dopamine. Both styrene and styrene oxide potently inhibited the uptake of [3H] dopamine in purified synaptic vesicles prepared from rat brain striata, in a dose-related manner, with inhibitory constants (Ki) 2.5 and 2.2 microM respectively. However, neither styrene nor styrene oxide significantly increased the basal efflux of [3H] dopamine that has been preloaded into striatal vesicles in vitro. On the other hand, both styrene and styrene oxide have failed to significantly inhibit the uptake of either [3H] norepinephrine, or [3H] serotonin into striatal synaptic vesicles. It is concluded that both styrene and styrene oxide are capable of producing impairments in dopaminergic transport in purified striatal synaptic vesicles, an effect which may be a critical component in styrene-induced neurotoxicity.

DNA-Protein crosslinks induced by nickel compounds in isolated rat renal cortical cells and its antagonism by specific amino acids and magnesium ion

Suspensions of isolated renal cortical cells in modified Krebs-Henseleit buffer (pH 7.4) were incubated with nickel chloride, nickel acetate, nickel sulfate, and nickel subsulfide (0-2 mM) at 37 degreesC for 2 h. A significant increase (63%) in DNA-protein crosslinks was observed at 2 mM nickel sulfate, whereas nickel subsulfide induced a significant increase in such crosslinks beginning at 0.5 mM concentration and a maximum increase of 200% of the control value reached at 2 mM concentration. No significant reduction in viability of renal cortical cells (as measured by trypan blue exclusion) was observed due to these nickel compounds at any concentration used. In the second series of experiments, coincubation of nickel subsulfide (2 mM) with l-histidine (8 or 16 mM), l-cysteine (4 or 8 mM), or l-aspartic acid (8 or 24 mM) significantly reduced the DNA-protein crosslinks induced by 2 mM nickel subsulfide. Similarly Mg2+ (24 mM), but not Ca2+ (24 mM), was able to antagonize nickel subsulfide-induced increase in DNA-protein crosslinks. High extracellular levels of Mg2+ and these amino acids significantly decreased the accumulation of Ni2+ from nickel subsulfide in renal cortical cells. Furthermore, these amino acids at high concentrations significantly inhibited the binding of Ni2+ from nickel subsulfide to deproteinized DNA from renal cortical cells, whereas such inhibition due to Mg2+ was close to significant (0.1 > p > 0.05). In vitro exposures of renal cortical cells to nickel subsulfide (0-2 mM) increased the formation of reactive oxygen species in concentration-dependent manner. Furthermore, coincubation of 2 mM nickel subsulfide with either catalase, dimethylthiourea, mannitol, or vitamin C at 37 degreesC for 2 h resulted in a significant decrease of nickel subsulfide-induced formation of DNA-protein crosslinks, suggesting that nickel subsulfide-induced DNA-protein crosslink formation in isolated rat renal cortical cells is caused by the formation of reactive oxygen species. The potent protective effects of these specific amino acids and Mg2+ against nickel subsulfide-induced DNA-protein crosslink formation in isolated renal cortical cells are due to reduction of cellular uptake of Ni2+ and inhibition of the binding of Ni2+ to deproteinized DNA.

S-[(1 and 2)-phenyl-2-hydroxyethyl]cysteine-induced alterations in renal mitochondrial function in male Fischer-344 rats

Previous studies from our laboratory have shown that mitochondrial dysfunction may be an important early event in S-[(1 and 2)-phenyl-2-hydroxyethyl]cysteine (PHEC)-induced cytotoxicity in isolated rat renal proximal tubules. The present study has therefore examined in more detail PHEC-induced mitochondrial dysfunction, both in vivo and in vitro, using isolated renal cortical mitochondria. Renal cortical mitochondria isolated from PHEC-treated rats in vivo showed depressed effects on the mitochondrial respiration and oxidative phosphorylation in both a dose (0, 250, and 500 micromol/kg iv)- and time (0-24 h)-dependent manner in the presence of both succinate (Site 2) and malate plus alpha-ketoglutarate (Site 1) as respiratory substrates, with initial significant depression occurring as early as 4 h following treatment with 500 micromol PHEC/kg. Similar mitochondrial dysfunctions were observed in vitro in concentration- and time-dependent manners with both respiratory substrates. PHEC also caused a marked dose-dependent inhibition of mitochondrial succinate dehydrogenase and NADH cytochrome c reductase activities both in vivo and in vitro, with initial inhibition occurring as early as 4 h after in vivo administration and 45 min after exposure to PHEC in vitro, while the NADH dehydrogenase activity was not considerably inhibited. The mitochondrial ATPase activity was significantly decreased 4 and 24 h following treatment with PHEC (500 micromol/kg). These results suggest that PHEC exerts its inhibitory effect on the mitochondrial respiration and oxidative phosphorylation through the action on the mitochondrial electron transport chain. PHEC significantly reduced the activity of adenine nucleotide translocase as well as the net uptake of substrates by mitochondria without affecting their efflux within 2-4 h after its injection (500 micromol/kg). On the other hand, significant renal damage, as assessed by morphological study, appeared as early as 24 h following such treatment. The observation of similar effects after both in vivo and in vitro exposures may suggest that the effect on mitochondria may have a pathogenic role in PHEC-induced renal injury in rats. PHEC produces mitochondrial toxicity that results from an inactivation of mitochondrial anionic substrate transporters as well as from an inhibition of activities of adenine nucleotide translocase and dehydrogenases.

Modulation of monoamine oxidase activity in different brain regions and platelets following exposure of rats to methylmercury

Monoamine oxidase (MAO; EC 1.4.3.4) is known to have an important role in the regulation of biogenic amines in the brain and peripheral tissues. It is also known that circulating platelets represent an excellent model for an easy assessment of the effect of MAO-B inhibitors in extracerebral tissue. The present study was carried out to determine the effects of methylmercury (MeHg) on the activity of MAO in synaptosomes of different brain regions of male Sprague-Dawley rats as well as in rat blood platelets both in vitro and in vivo. MeHg pretreatment inhibited the activity of MAO in the synaptosomes of the cortex, hypothalamus, hippocampus, striatum, cerebellum, and brain stem in a concentration-dependent (0-10 microM) manner. The threshold concentration of MeHg for such inhibition in different brain synaptosomes was found to be the same (i.e., 1 microM) except for in the rat striatum it was 2.5 microM, and the IC50 value for MeHg was found to be around 2.1 microM. Significant inhibition of the MAO activity was also observed in synaptosomes of the cortex, cerebellum, hypothalamus, and hippocampus as well as in platelets of rats 24 h after treatment by gavage with a total cumulative dose of 35 mg/kg (5 mg/kg/day for 7 days). The decrease of such activity was found to be at maximum in different brain synaptosomes and platelets 24 h following treatment with a cumulative total dose of 75 mg/kg (7.5 mg/kg/day for 10 days); the treated animals showed signs of ataxia under these conditions. The data have further shown that methylmercury is capable of inhibiting the MAO activity in different brain synaptosomes to different degrees but without showing any specificity towards any specific brain region. The present in vivo results suggest that the platelet MAO activity may be used as a potential biomarker of early neurotoxicity due to repeated exposure to MeHg in rats.

S-[(1 and 2)-phenyl-2-hydroxyethyl]-cysteine-induced cytotoxicity to rat renal proximal tubules

S-[(1 and 2)-phenyl-2-hydroxyethyl]-glutathione is nephrotoxic in rats through its metabolic conversion to corresponding cysteine-S-conjugate, e.g., S-[(1 and 2)-phenyl-2-hydroxyethyl]-cysteine (PHEC). The present study was carried out to determine the mechanism of PHEC-induced toxicity in isolated rat renal proximal tubules. PHEC decreased tubule viability in concentration (0-2 mM)- and time (0-3 hr)-dependent manner, with initial decreases occurring 2 hr after exposure. Tubule basal and nystatin-stimulated oxygen consumption decreased before cell death following exposure to 0.5 and 1 mM PHEC. Assessment of direct mitochondrial function within the proximal tubules showed that respiration was reduced in the absence and presence of a phosphate acceptor using site II (succinate) and site I (malate/glutamate) respiratory substrates 30 and 45 min after exposure to 0.5 and 1 mM PHEC. Exposure of proximal tubules to 1 mM PHEC caused a time-dependent decline of mitochondrial membrane potential (as measured by the uptake of the cationic fluorescent dye, rhodamine 123 by the proximal tubules) and depletion of ATP content with initial decrease occurring as early as 30 min after the exposure. Glutathione depletion and lipid peroxidation occurred within 90 min clearly preceding cell death after exposure to 0.5 and 1 mM PHEC. Pretreatment with 1 mM deferoxamine prevented PHEC-induced lipid peroxidation but did not prevent PHEC-induced cytotoxicity, whereas deferoxamine pretreatment prevented lipid peroxidation, mitochondrial dysfunction, and cytotoxicity after exposure to 0.5 mM tertiary-butyl hydroperoxide, suggesting that iron-mediated lipid peroxidation does not contribute to PHEC-induced proximal tubule cell death. Pretreatment of renal proximal tubules with 10 mM fructose failed to prevent the change in mitochondrial membrane potential, the ATP depletion and cytotoxicity caused by 1 mM PHEC, indicating that the glycolytic pathway is not important in renal proximal tubule respiration and cell injury. Pretreatment of renal tubules with aminooxyacetic acid failed to prevent the mitochondrial dysfunction induced by 1 mM PHEC, indicating an absence of further metabolism of PHEC by a beta-lyase-dependent pathway. It is therefore proposed that the alteration of mitochondrial functions and the consequent loss of cellular energy supplies can represent the mechanisms by which PHEC expressed its acute cytotoxicity.