Marine estuaries act as better sink for greenhouse gases during winter in undisturbed mangrove than degraded ones in Sundarban, India.

The estuaries provide the key pathway for travelling carbon across the land-ocean interfaces and behave as both source and sink of greenhouse gases (GHGs) in water-atmosphere systems. The sink-source characteristics of estuaries for GHGs vary spatially. The primary driving factors are adjacent ecologies (agriculture, aquaculture, etc.) and proximities to the sea. To study the sink-source characteristics of estuaries for GHGs (methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2)), the water samples were collected from 53 different locations in the estuaries for estimation of dissolved GHGs concentration and air-water GHGs exchanges. The locations represent five zones (Zone I, II, III, IV and V) based on the type and degradation status of mangroves (degraded and undisturbed), anthropogenic activities, and distance from the sea. Zone I, III, V represents to the degraded mangroves far from sea, whereas, Zone II, IV surrounded by undisturbed mangroves and nearer to sea. The average dissolved CH4 concentrations were higher in the estuaries which were adjacent to degraded mangroves (154.4 nmol L-1) than undisturbed mangroves (81.7 nmol L-1). Further, the average dissolved N2O concentrations were 48% higher in the estuaries nearer to degraded mangroves than that of undisturbed ones. Among the degraded mangrove sites, the dissolved CO2 concentrations were higher at Zone I (30.1 µmol L-1) followed by Zone III and IV, whereas in undisturbed sites, it was higher in Zone IV (22.3 µmol L-1) than Zone II (17.6 µmol L-1). Among the 53 locations, 36, 51 and 33 locations acted as a sink (negative value of exchanges) for CH4, N2O and CO2, respectively. The higher sink potential for CH4 was recorded to those estuaries adjacent to undisturbed mangroves (-791.69 µmol m-2 d-1) than the degraded ones (-23.18 µmol m-2 d-1). Similarly, the average air-water N2O and CO2 exchanges were more negative in the estuaries which were nearer to undisturbed mangroves indicating higher sink potential. The pH, and salinity of the estuary water were negatively correlated with air-water CH4 and N2O exchanges, whereas those were positively correlated with CO2 exchanges. Significantly lower dissolved GHGs and air-water GHGs exchange was observed in the estuaries adjacent to the undisturbed mangrove as compared to the degraded mangrove. The reason behind higher sink behaviours of estuaries nearer to undisturbed mangroves are higher intrusion of seawater, less nutrient availability, higher salinity, low carbon contents and alkaline pH compared to estuaries adjacent to degraded mangroves and far from sea.

Rubber expansion and age-class mapping in the state of Tripura (India) 1990-2021 using multi-year and multi-sensor data.

The present study focuses on the spread of rubber monoculture in the state of Tripura during past three decades (1990-2021) in the northeast region of India which is known for its rich biodiversity, shifting cultivation, and extensive forest dynamics. Earth observation (EO) data of seven time periods from Landsat missions (1990, 1995, 2000, 2004, and 2009) and Sentinel-2 (2016 and 2021) were the main source for mapping and were supplemented with MODIS-EVI temporal spectral profiles, GEDI-derived vegetation heights (2019), and Google Earth high-resolution historical images for additional cues to support discrimination, mapping, and accuracy assessment. The methodology for rubber used its unique phenology from spectral-temporal profile and multi-year comparison of patches and their dynamics for age-class mapping. The results indicate that in the state of Tripura (geographic area 1.08 Mha), the area under rubber increased from 0.3% in 1990 to 8.9% of the geographic area in 2021. The overall classification accuracy for the maps created for the years 1990, 1995, 2000, 2004, 2009, 2016, and 2021 was 84.2%, 83.9%, 84.8%, 88.0%, 86.0%, 86.7%, and 89.5%, respectively. New areas under rubber originated from various land cover classes including open forests, shifting cultivation lands, and scrub. Recent expansion has resulted in 84.3% of rubber plantations under the 10-year age class. Implications of this transformation of the natural landscape, biodiversity and biomass, and carbon pool assessment are discussed.

Advances in terrestrial and ocean dynamics studies in India.

The land, oceans, and atmosphere are tightly linked and form the most dynamic component of the climate system. Studies on terrestrial and ocean science enhance the understanding on the impacts of climate change. Across India and the world over, human-driven land use and climate changes are altering the structure, function, and extent of natural terrestrial ecosystems and in turn regional biogeochemical feedbacks. In this special issue, we present 29 manuscripts; those discuss wide-ranging aspects of terrestrial and oceanic characterization and dynamics. These contributions are based on selected presentations made at the 2nd International Workshop on Biodiversity and Climate Change (BDCC-2018) held on 24-27 February 2018 at the Indian Institute of Technology Kharagpur, India. The manuscripts are arranged in five sections such as Ecological Assessment, Plant Invasion, Carbon Dynamics, Ecosystem Characterization, and Ocean Dynamics. We realized that the utility of satellite remote sensing data has been emerging as a dominant trend in environmental monitoring and assessment studies in India.

Seasonal fluctuation in three mode of greenhouse gases emission in relation to soil labile carbon pools in degraded mangrove, Sundarban, India.

Tropical mangrove represents one of the most threatened ecosystems despite their huge contribution to ecosystem services, carbon (C) sequestration and climate change mitigation. Understanding the system in light of seasonal fluctuations on greenhouse gases (GHGs) emissions due to human interferences and the tidal effect is important for devising site-specific real-time climate change mitigation strategies. In order to capture the seasonal variations, the three modes of transport of GHGs through pneumatophore, ebullition as bubbles and water-soluble diffusion was quantified. The three unique techniques for the gas collection were used to estimate the GHGs [methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2)] emission, at three degraded-mangrove sites in Sundarban, India. We identified three degraded mangrove ecologies based on the remote sensing data of 1930 and 2013 (mangrove-covered area in Sundarban; 2387, 2136 km2, respectively). Samples were collected and analyzed for four seasons [winter (November-January), summer (February-April), pre-monsoon (May-June) and monsoon (July-October)], at three representative sites (Sadhupur, Dayapur, and Pakhiralaya). Monsoonal CH4 and CO2 fluxes (0.353 ± 0.026 and 64.5 ± 6.1 mmol m-2 d-1, respectively) were higher than winter and summer. However, the soil labile C pools showed the opposite trend i.e. more in summer followed by winter and monsoon. In contrast, the N2O fluxes were more during summer (54.2 ± 3.2 µmol m-2 d-1). The stagnant water had higher dissolved GHGs concentration compared to tidewater due to less salinity and a long time of stagnation. The mode of transport of GHGs through pneumatophore, ebullition, and water-soluble diffusion was also significantly varied with seasons, soil­carbon status and tidewater intrusion. Therefore, seasonal fluctuations of GHGs emission and tidal effect must be considered along with soil labile C pools for GHG-C budgeting and climate change mitigation in the mangrove ecosystem.

Experimental investigations of argon spark gap recovery times by developing a high voltage double pulse generator.

The voltage recovery in a spark gap for repetitive switching has been a long research interest. A two-pulse technique is used to determine the voltage recovery times of gas spark gap switch with argon gas. First pulse is applied to the spark gap to over-volt the gap and initiate the breakdown and second pulse is used to determine the recovery voltage of the gap. A pulse transformer based double pulse generator capable of generating 40 kV peak pulses with rise time of 300 ns and 1.5 µs FWHM and with a delay of 10 µs-1 s was developed. A matrix transformer topology is used to get fast rise times by reducing L(l)C(d) product in the circuit. Recovery Experiments have been conducted for 2 mm, 3 mm, and 4 mm gap length with 0-2 bars pressure for argon gas. Electrodes of a sparkgap chamber are of rogowsky profile type, made up of stainless steel material, and thickness of 15 mm are used in the recovery study. The variation in the distance and pressure effects the recovery rate of the spark gap. An intermediate plateu is observed in the spark gap recovery curves. Recovery time decreases with increase in pressure and shorter gaps in length are recovering faster than longer gaps.

Identification and fine-mapping of Xa33, a novel gene for resistance to Xanthomonas oryzae pv. oryzae.

Broadening of the genetic base for identification and transfer of genes for resistance to insect pests and diseases from wild relatives of rice is an important strategy in resistance breeding programs across the world. An accession of Oryza nivara, International Rice Germplasm Collection (IRGC) accession number 105710, was identified to exhibit high level and broad-spectrum resistance to Xanthomonas oryzae pv. oryzae. In order to study the genetics of resistance and to tag and map the resistance gene or genes present in IRGC 105710, it was crossed with the bacterial blight (BB)-susceptible varieties 'TN1' and 'Samba Mahsuri' (SM) and then backcrossed to generate backcross mapping populations. Analysis of these populations and their progeny testing revealed that a single dominant gene controls resistance in IRGC 105710. The BC(1)F(2) population derived from the cross IRGC 105710/TN1//TN1 was screened with a set of 72 polymorphic simple-sequence repeat (SSR) markers distributed across the rice genome and the resistance gene was coarse mapped on chromosome 7 between the SSR markers RM5711 and RM6728 at a genetic distance of 17.0 and 19.3 centimorgans (cM), respectively. After analysis involving 49 SSR markers located between the genomic interval spanned by RM5711 and RM6728, and BC(2)F(2) population consisting of 2,011 individuals derived from the cross IRGC 105710/TN1//TN1, the gene was fine mapped between two SSR markers (RMWR7.1 and RMWR7.6) located at a genetic distance of 0.9 and 1.2 cM, respectively, from the gene and flanking it. The linkage distances were validated in a BC(1)F(2) mapping population derived from the cross IRGC 105710/SM//2 × SM. The BB resistance gene present in the O. nivara accession was identified to be novel based on its unique map location on chromosome 7 and wider spectrum of BB resistance; this gene has been named Xa33. The genomic region between the two closely flanking SSR markers was in silico analyzed for putatively expressed candidate genes. In total, eight genes were identified in the region and a putative gene encoding serinethreonine kinase appears to be a candidate for the Xa33 gene.

Peroxyl-induced oxidative stress in aging erythrocytes of rat.

This study aims at determining the possible changes in intracellular calcium (Ca (i) (2+) ), plasma membrane calcium ATPase (PMCA) activity and phosphatidylserine (PS) along with glutathione (GSH) level in response to an oxidant challenge in vitro. Erythrocytes were isolated on Percoll and incubated with 2, 2'azobis (2-aminopropane) hydrochloride (AAPH) as well as with vitamin C preceding AAPH incubation. Membrane integrity in terms of hemolysis was negatively related to acetylcholine esterase (AChE) activity with the extent of reduction under OS being higher in the old erythrocyte than in the young. A divergent pattern was seen towards lower PMCA and higher (Ca (i) (2+) ) in the young and old cells. However, the PMCA activity in the stressed young cell was high when pre-treated with vitamin C. PS externalization in the young under OS is perhaps analogous to normal aging, with vitamin C preventing premature death. These findings suggest that young erythrocytes may benefit from vitamin C in therapies addressed towards the mechanisms underlying the reduced effects of OS.

Oxidative stress in erythrocytes: a study on the effect of antioxidant mixtures during intermittent exposures to high altitude.

The aim of our study was to compare and assess the effectiveness of antioxidant mixtures on the erythrocytes (RBC) of adult male albino rats (Wister) subjected to simulated intermittent high altitudes--5,100 m (AL(1)) and 6,700 m (AL(2))--to induce oxidative stress (OS). To achieve our objective, we pre-supplemented four sets of animals with different antioxidant mixtures [vitamin E (vit.E; 50 IU/kg BW), vitamin C (vit.C; 400 mg/kg) and L: -carnitine (400 mg/kg)] in different combinations [M1 (vit.E+vit.C), M2 (vit.C+carnitine), M3 (vit.E+carnitine) and M4 (vit.C+vit.E+carnitine)] for 30 days prior to as well during exposure to intermittent hypobaric hypoxia (IHH). Membrane instability, in terms of osmotic fragility and hemolysis, decreased in RBCs of supplemented animals. There was a significant increase in the activity of glutathione peroxidase in the RBCs of supplemented animals. We confirmed OS imposed by IHH with assays relating to lipid [thiobarbituric acid reactive substances (TBARS) and lipofuscin (LF)] and protein (carbonyl, PrC) oxidation, and found a positive correlation between PrC and hemolysis, with a decrease in both upon supplementation with M3 and M4 mixtures. Fluorescence microscopic observation showed a maximum decrease in the LF content in rats administered M4 and M1 compared to those on M2 and M3 mixtures at both altitudes. We suggest that multiple antioxidant fortifications are effective in overcoming increased OS experienced by RBCs at high altitudes.

Assessing forest canopy closure in a geospatial medium to address management concerns for tropical islands--Southeast Asia.

The present study outlines an approach to classify forest density and to estimate canopy closure of the forest of the Andaman and Nicobar archipelago. The vector layers generated for the study area using satellite data was validated with the field knowledge of the surveyed ground control points. The methodology adopted in this present analysis is three-tiered. First, the density stratification into five zones using visual interpretation for the complete archipelago. In the second step, we identified two island groups from the Andaman to investigate and compare the forest strata density. The third and final step involved more of a localised phytosociological module that focused on the North Andaman Islands. The results based on the analysis of the high-resolution satellite data show that more than 75% of the mangroves are under high- to very high-density canopy class. The framework developed would serve as a significant measure to forest health and evaluate management concerns whilst addressing issues such as gap identification, conservation prioritisation and disaster management--principally to the post-tsunami assessment and analysis.

Oxidative stress and intracellular pH in the young and old erythrocytes of rat.

The effects of oxidative stress (OS) on the rat erythrocytes (RBCs) that were fractionated on the percoll/BSA gradient into young and old cells were studied to find out if the altered Na+/H+ and Cl⁻/ HCO3⁻ antiporters and in turn the intracellular pH (pHi) could act as one of the promoters of cell death. Old cells were more spherical with lesser surface area, more fragile osmotically and had lesser protein sulphydryl content than the young cells. OS was induced in RBCs by 2,20-azobis (2-amidinopropane) dihydrochloride (AAPH). AAPH increased the superoxide dismutase (SOD) activity and MDA level and, the changes between the young and old. Interestingly, vitamin C was effective in reducing MDA in the old. Further, in the old a rapid Na+-dependent acidification in the presence of AAPH and a marginal acidosis in the presence of vitamin C were evident. Old RBCs exhibited higher acidosis and vitamin C was less effective in lowering the stress-induced acidosis compared to the young. Our studies suggest that increased acidosis followed by low intracellular pH could be one of the determinant factors for the disappearance of old RBCs from circulation, and perhaps of the young too under OS.

Detection of Aspergillus spp. and aflatoxin B1 in rice in India.

Twelve hundred rice samples consisting of paddy (675) and milled rice (525) were collected from 20 states across India. These samples were assessed for Aspergillus spp. infection on selective medium and aflatoxin B(1) (AFB1) by indirect competitive ELISA. In this investigation, Aspergillus flavus contamination dominated in all the seed samples. The other major contaminants were Aspergillus niger, Aspergillus ochraceus and Aspergillus parasiticus. Out of 1200 rice samples, 67.8% showed AFB1 ranging from 0.1 to 308.0 microg/kg. All the paddy samples from Chattishgarh, Meghalaya and Tamil Nadu showed AFB1 contamination. Milled rice grains from different states showed below the permissible levels of AFB1 (average 0.5-3.5 microg/kg). Eighty-two percent of samples from open storage that were exposed to rain showed AFB1 contamination followed by one-year-old seed. Out of 1200 samples, 2% showed AFB1 contamination above the permissible limits (>30 microg/kg). This is the first comprehensive report of aflatoxin contamination in rice across 20 states in India.

In vitro models of oxidative stress in rat erythrocytes: effect of antioxidant supplements.

The present study was designed to induce oxidative stress in lipid and aqueous phases through azo bis(2-amidinopropane)dihydrochloride (AAPH), 2,2'-azobis 2,4-dimethylvaleronitrile (ADVN) and hydrogen peroxide (H(2)O(2)) either alone or in combination with vitamin C or vitamin El and to assess the vulnerability of rat erythrocytes to oxidative stress. While AAPH acted equally on cell membrane and cytosol, ADVN increased OS in the membrane. The extent of hemolysis and increased membrane fragility caused was more in the case of azo compounds than of H(2)O(2). While vitamin E (2mM) reduced oxidative stress in the membrane, vitamin C (60mM) was more effective in the lysates. The concentration of malondialdehyde and advanced oxidation protein products was lowered by antioxidants. The level of lipofuscin, a product of lipid peroxidation was also increased by ADVN and H(2)O(2). Antioxidants, did, however, reduce the accumulation of protein carbonyl content in cells exposed to azo compounds although they were ineffective in inhibiting oxidation of membrane band 3 protein and sulphydryl content. Taken together, our study demonstrated the antioxidative property of vitamin E and vitamin C in reducing oxidative stress in aqueous as well as lipid phases of erythrocytes and further suggested the feasibility of in vitro models in evaluating the mechanisms of oxidative injury.

Secalonic acid D blocks embryonic palatal mesenchymal cell-cycle by altering the activity of CDK2 and the expression of p21 and cyclin E.

BACKGROUND: The mycotoxin, secalonic acid D (SAD), a known animal and potential human cleft palate (CP)-inducing agent, is produced by Pencillium oxalicum in corn. SAD selectively inhibits proliferation of murine embryonic palatal mesenchymal (MEPM) cells leading to a reduction in cell numbers. These effects can explain the reduction in shelf size and the resulting CP seen in the offspring of SAD-exposed mice. Ability of SAD to inhibit proliferation as well as to block the progression of cells from G1- to S-phase of the cell-cycle were also shown in the human embryonic palatal mesenchymal (HEPM) cells suggesting the potential CP-inducing effect of SAD in human beings METHODS: Gestation day (GD) 12 mouse embryos and HEPM cells were used to test the hypothesis that the cell-cycle block induced by SAD results from a disruption of stage-specific regulatory components both in vivo and in vitro. The effects of SAD on the activity of various cyclin dependent kinases (CDK) and on the levels of various positive (cyclins and CDK) and negative (CDK inhibitors p15, 16, 18, 19, 21, 27, 57) cell-cycle regulators were assessed by performing kinase assays and immunoblots, respectively. RESULTS: In the murine embryonic palates, SAD specifically inhibited G1/S-phase-specific CDK2 activity, reduced the level of cyclin E and tended to increase the level of the CIP/kip CDK inhibitor, p21. In the HEPM cell cultures, exposure to IC50 of SAD significantly affected all of the above targets. In addition, a reduction in the levels/activity of CDK 4/6, a reduction in the levels of cyclins D1, D2, D3, E, A, and all INK4 family proteins, and an increase in the level of the CIP/kip CDK inhibitor, p57, were also seen. CONCLUSIONS: These results suggest that the S-phase-specific cell-cycle proteins CDK2, cyclin E and possibly p21 are the common targets of SAD in murine palatal shelves in vivo and in human embryonic palatal mesenchymal cells in vitro and may be relevant to the pathogenesis of SAD-induced CP.

Inhibition of human embryonic palatal mesenchymal cell cycle by secalonic acid D: a probable mechanism of its cleft palate induction.

OBJECTIVE: To assess the mechanism(s) of cleft palate induction by secalonic acid D (SAD) in human embryonic palatal mesenchymal (HEPM) cells and compare them with those evaluated in the murine embryonic palate. DESIGN: Effect of SAD on HEPM cell proliferation was studied by obtaining dose response curves for cell numbers, uptake of 3H-thymidine and the expression of proliferating cell nuclear antigen (PCNA). Effects of SAD on cell cycle were assessed by flowcytometry. Cell-labeling with 3H-glucosamine and immunoblot analysis were conducted to study SAD effects on the synthesis of glycosaminogycans (GAG) and the expression of fibronectin and tenascin, respectively. RESULTS: SAD induced a concentration-dependent decrease in HEPM cell number and 3H-thymidine uptake beginning at 0.1 microg of SAD/ml. Expression of PCNA and progression of cell cycle from G1 to S phase were inhibited following SAD exposure. Cell viability was significantly reduced only at 7.5 microg/ml of SAD or higher indicating that the reduction in cell numbers by SAD at lower concentrations is likely due to reduced proliferation and at higher concentrations due to both reduced proliferation and cell death. Synthesis of extra cellular matrix components (GAGs, fibronectin or tenascin) by HEPM cells, however, was not inhibited by SAD. CONCLUSION: The results of these studies confirmed those of our previous studies with mice and the MEPM cells that SAD may induce cleft palate by reducing numbers of palatal mesenchymal cells by inhibition of their proliferation thereby leading to a reduction in the size of the developing palate shelves.

Isozyme polymorphism and virulence of Indian isolates of the rice sheath blight fungus.

Inadequate information about the genetic structure of the polyphagous Rhizoctonia solani has made sheath blight resistance breeding a difficult task. To assess the variability in the Indian populations of sheath blight fungus, 18 isolates were collected from different rice growing regions of India and analyzed for virulence and electrophoretic profiles of 13 isozymes. The virulence spectrum of all 18 isolates was examined on susceptible IR50 and tolerant Swarnadhan varieties, based on which the isolates could be grouped as highly virulent, moderately virulent or avirulent. A total of 11 enzyme systems with 153 electrophoretic phenotypes were applied to characterize the genetic variation among the isolates. Cluster analyses based on isozyme patterns resulted in one major cluster comprising 16 virulent isolates, with two avirulent isolates loosely linked to this at 0.13 similarity. Isozyme systems of esterases (both alpha and beta) and 6-phosphogluconic dehydrogenase could be used to fingerprint the individual isolates.

Polyhydroxyalkanoates: an overview.

Polyhydroxyalkanoates have gained major importance due to their structural diversity and close analogy to plastics. These are gaining more and more importance world over. Different sources (natural isolates, recombinant bacteria, plants) and other methods are being investigated to exert more control over the quality, quantity and economics of poly(3-hydroxybutyrate) (PHB) production. Their biodegradability makes them extremely desirable substitutes for synthetic plastics. The PHB biosynthetic genes phbA, phbB and phbC are clustered and organized in one phbCAB operon. The PHB pathway is highly divergent in the bacterial genera with regard to orientation and clustering of genes involved. Inspite of this the enzymes display a high degree of sequence conservation. But how similar are the mechanisms of regulation of these divergent operons is as yet unknown. Structural studies will further improve our understanding of the mechanism of action of these enzymes and aid us in improving and selecting better candidates for increased production. Metabolic engineering thereafter promises to bring a feasible solution for the production of "green plastic".

Enhanced production of itaconic acid from corn starch and market refuse fruits by genetically manipulated Aspergillus terreus SKR10.

A potent itaconic acid producing strain, Aspergillus terreus SKR10, was isolated from horticulture waste. Market refuse, apple and banana, were explored as novel substrates for itaconic acid production with yields of 20+/-2.0 and 20.0+/-1.0 g l(-1), respectively. Itaconic acid yields of 28.5+/-2.2 and 31.0+/-1.7 g l(-1) were obtained with acid and alpha-amylase hydrolyzed corn starch. The efficiency of itaconic acid production by this wild type strain was improved by ultraviolet, chemical and mixed mutagenic treatments. Two high itaconic acid yielding mutants, N45 and UNCS1 were obtained by gradient plating. These two mutants were capable of producing twice the yield of itaconic acid as the parent strain.

Ca(2+)-calmodulin antagonist chlorpromazine and poly(ADP-ribose) polymerase modulators 4-aminobenzamide and nicotinamide influence hepatic expression of BCL-XL and P53 and protect against acetaminophen-induced programmed and unprogrammed cell death in mice.

Acetaminophen (AAP), the analgesic hepatotoxicant, is a powerful inducer of oxidative stress, DNA fragmentation, and apoptosis. The anti-apoptotic oncogene bcl-XL, and the pro-apoptotic oncogene p53 are two key regulators of cell cycle progression and/or apoptosis subsequent to DNA damage in vitro and in vivo. This study investigated the effect of AAP on the expression of these oncogenes and whether agents that modulate DNA fragmentation (chlorpromazine, CPZ) and DNA repair through poly(ADP-Ribose) polymerase (PARP) activity (4-AB: 4-aminobenzamide) can protect against AAP-induced hepatotoxicity by inhibiting oxidative stress, DNA fragmentation, and/or by altering the expression of bcl-XL and p53. In addition, the protective effect of supplemental nicotinamide (NICO), known to be depleted in cells with high PARP activity during DNA repair, is similarly evaluated. Male ICR mice (3 months old) were administered vehicle alone; nontoxic doses of 4-AB (400 mg/kg, ip), NICO (250 mg/kg, ip) or CPZ (25 mg/kg, ip), hepatotoxic dose of AAP alone (500 mg/kg, ip), or AAP plus one of the protective agents 1 h later. All animals were sacrificed 24 h following AAP administration. Serum alanine aminotransferase activity (ALT), hepatic histopathology and lipid peroxidation, DNA damage, and expression of bcl-XL and p53 (western blot analysis) were compared in various groups. All of the three agents significantly prevented AAP-induced liver injury, lipid peroxidation, DNA damage, and associated apoptotic and necrotic cell deaths, 4-AB being the most effective and NICO the least. Compared to control, there was a considerable decrease in bcl-XL expression, and an increase in p53 expression in AAP-exposed livers. The effect of AAP on bcl-XL was antagonized and that on p53 was synergized by the PARP-modulator 4-AB as well as NICO, whereas the endonuclease inhibitor CPZ was without effect on either bcl-XL or p53 expression. These results suggest that the hepatotoxic effect of AAP involves multiple mechanisms including oxidative stress, upregulation of endonuclease (or caspase-activated DNAse) and alteration of pro- and anti-apoptotic oncogenes. The observed antagonism of AAP-induced hepatocellular apoptosis and/or necrosis by modulators of multiple processes including DNA repair suggests the likelihood that a more effective therapy against AAP intoxication should involve a combination of antidotes.

Secalonic acid D alters the nature of and inhibits the binding of the transcription factors to the phorbol 12-O-tetradecanoate-13 acetate-response element in the developing murine secondary palate.

Secalonic acid D (SAD), a mycotoxin produced by Penicillium oxalicum in corn, induces cleft palate (CP) in the offspring of exposed dams. Results of recent studies suggest that protein kinase C (PKC) inhibition by SAD may be relevant to its CP-induction. Downstream effects of PKC are determined by the nature of transcription factors (TF) that form the activator protein-1 (AP-1) and the binding of AP-1 (and other TF) to the phorbol 12-O-tetradecanoate-13 acetate-response element (TRE) to form AP-1-TRE complex, neither of which have been studied in the palate. The aims of the present study were to identify the components of the murine palatal AP-1-TRE complex during development and to uncover the effects of SAD on this complex. Western blots and gel mobility shift assays of control palatal nuclear extracts revealed that, although all relevant TF are present in the palate throughout development, only cyclic-AMP response element (CRE) binding protein (CREB) and CRE-modulator protein-1 (CREM-1) and activating transcription factor-1 bound to TRE on Gestation Day (GD) 12. The pattern shifted to c-Jun and c-Fos (known AP-1 components) on GD 13 and 14. In SAD-treated offspring, however, CREM-1 alone; c-Jun, c-Fos, and CREB; and c-Jun and c-Fos bound to TRE on GD 12, 13, and 14, respectively. Binding of TF to TRE was inhibited by SAD on both GD 12 and 13. These results suggest that a dynamic shift in the binding of TF to TRE from PKA- to PKC-responsive TF occurs during palate development and that teratogens such as SAD can alter both the nature and extent of TF binding to TRE.