Synergystic Effect Research Articles

Synergystic effects of binary mixtures of δ-tocopherol and gallic acid derivatives on peroxidation of soybean oil-in-water emulsions

Synergystic effects of binary mixtures of δ-tocopherol and gallic acid derivatives on peroxidation of soybean oil-in-water emulsions

Synergistic, Additive and Antagonistic Interactions of Grapes' Phenolic Compounds and Organic Acids.

The antioxidant interactions between several natural phenolic and non-phenolic compounds (catechin, quercetin, rutin, resveratrol, gallic acid and ascorbic acid) and organic acids (tartaric, citric and dihydroxyfumaric acids) have been investigated through the DPPH method. Main additive and antagonistic interactions have been found for the combinations of catechin, quercetin, resveratrol and gallic acid with tartaric and citric acids; such behavoir can be due to the enhanced stability of the phenolic compounds in the acidic media. Rutin and ascorbic acid demonstrated good synergistic effects with tartaric and citric organic acids, which may rely on the polymerization processes for rutin, and change of the mechanism of action in case of ascorbic acid. In combination with dihydroxyfumaric acid, the mixtures showed dose - dependent synergistic, additive or antagonistic antioxidant interactions. Good synergystic effects have been registered for the binari mixtures of dihydroxyfumaric acid with ascorbic acid, catechin and rutin.

Nitrogen-doping boosts ∗CO utilization and H2O activation on copper for improving CO2 reduction to C2+ products

To improve the electrocatalytic transformation of carbon dioxide (CO2) to multi-carbon (C2+) products is of great importance. Here we developed a nitrogen-doped Cu catalyst, by which the maximum C2+ Faradaic efficiency can reach 72.7% in flow-cell system, with the partial current density reaching 0.62 A cm−2. The in situ Raman spectra demonstrate that the ∗CO adsorption can be strengthened on such a N-doped Cu catalyst, thus promoting the ∗CO utilization in the subsequent C–C coupling step. Simultaneously, the water activation can be well enhanced by N doping on Cu catalyst. Owing to the synergistic effects, the selectivity and activity for C2+ products over the N-deoped Cu catalyst are much improved.

Abstract 1066: PARP inhibitor rucaparib in combination with imipridones ONC201 or ONC212 demonstrates preclinical synergy against BRCA1/2-deficient breast, ovarian, and prostate cancer cells

Abstract BRCA1/2 genes encode proteins that mediate homologous recombination and repair (HRR). BRCA1/2 mutations increase risk of breast, ovarian, prostate and other cancers. BRCA1/2 mutated tumor cells are sensitive to PARP inhibitors (PARPi), that cause DNA replication fork to collapse. Approximately 40% of patients develop PARPi resistance through different mechanisms. One of the mechanisms of PARPi resistance is through P13k/Akt pathway activation. Imipridones are TRAIL-inducing compounds which are PERK-independent activators of the integrated stress response, and dual inhibitors of Akt/ERK. We hypothesized that combining imipridones with PARPi would overcome PARPi resistance due to Akt activation. PARPi also sensitize various solid tumors to recombinant TRAIL and DR5 agonist antibodies thereby further suggesting possible synergies between imipridones and PARPi. Our lab previously showed efficacy of imipridone ONC201 in BRCA-deficient cancer cells and potential synergy with olaparib (2017 AACR annual meeting abstract), without further investigating potential synergistic mechanisms. We explored combination drug synergy of rucaparib (PARP inhibitor) and imipridones (ONC212 and ONC201) in BRCA1/2-deficient breast, ovarian and prostate cancer cell lines. CellTiterGLO viability assays were performed after 72 hours to demonstrate synergistic effects of combination treatment. Western blots were performed to investigate the effect of combination treatment on the Akt pathway, as well as expression of cellular metabolic stress protein ATF4. Cytokine profiling using the Luminex 200 technology was used to study the effect of treatment on the tumor microenvironment. Combination treatment (rucaparib and ONC212, rucaparib and ONC201) in BRCA–deficient cell lines (HCC1937, PEO1, KURAMOCHI, 22RV1, LNCAP) showed synergistic reduction in cell viability. In the HCC 1937 cell line, combination studies of rucaparib-ONC212 and rucaparib-ONC201 showed a synergystic effect, as calculated by Compusyn software, combination indexes below one were observed at concentration of 0.29-37.5 of µM rucaparib with ONC201 at 1.25-5 µM and ONC212 6.25-50 nM with the best combination index of 0.7 for rucaparib-ONC201 combination and 0.31 for rucaparib-ONC212. We similarly observed synergy in other cell lines with combination treatment. Western blot analysis of rucaparib-ONC212 combination showed total Akt protein reduction and an increase in ATF4 consistent with the synergistic effects. Further studies are ongoing to characterize possible mechanisms and effects of PARP inhibitor-imipridone combination treatment on immune-mediated killing. Our findings identify novel PARP inhibitor-imipridone therapy combinations that can be further developed for treatment of BRCA1/2 deficient cancers. Citation Format: Maryam Ghandali, Kelsey E. Huntington, praveen Srinivasan, Don S. Dizon, Stephanie L. Graff, Benedito A. Carneiro, Wafik S. El-Deiry. PARP inhibitor rucaparib in combination with imipridones ONC201 or ONC212 demonstrates preclinical synergy against BRCA1/2-deficient breast, ovarian, and prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1066.

Synergistic Effect of Sesamin and γ-Tocotrienol on Promoting Osteoblast Differentiation via AMPK Signaling

Background: Sesamin is a rich phytochemical found in sesame seed oil that can promote osteoblast differentiation of rat BMSCs and improve rat bone structure by regulating Wnt/-Catenin pathway. Combined sesamin and γ-Tocotrienol (γ-T3) have been clarified to inhibit the proliferation of breast cancer cells, but their role in osteoporosis has not been explored. This paper aimed to discuss the synergistic effect of sesamin and γ-T3 in osteoporosis and disclose the underlying mechanism. Materials and methods: CCK-8 assay was to appraise the proliferation of hBMSCs after treated with sesamin and γ-T3. Moreover, the proteins in AMPK signaling in osteoblasts pretreated with AMPK inhibitor compound C (CC) were detected after the induction of sesamin and γ-T3. Then, CCK-8, ALP assay and ARS staining were used to analyze whether the proliferation and osteoblast differentiation of hBMSCs was via APMK pathway. RT-qPCR and western blot were conducted to quantify the levels of markers in osteoblasts. Results: It was determined that 5 g/mL sesamin and 1 μM γ-T3 exerted obvious influences on the viability of hBMSCs. Moreover, the co-treatment of sesamin and γ-T3 elevated the protein levels of related factors in AMPK pathway, which was reversed by CC. Furthermore, The proliferation and osteoblast differentiation exhibited remarkable increments upon exposure to both sesamin and γ-T3, whereas CC abolished these effects. Conclusion: In conclusion, the present study presented the first line of evidence to verify the synergystic effects of sesamin and γ-T3 on alleviating osteoporosis, and revealed their effects were realized by modulating the AMPK pathway. This paper has indicated the great potential of combined sesamin and γ-T3 in osteoporosis treatment.

In Memoriam of Jean‐Michel Savéant (1933–2020)

In Memoriam of Jean‐Michel Savéant (1933–2020)

Abstract B085: Low-sensitivity and drug-resistance to DNA-demethylating epi-drug decitabine in solid tumors: A challenge yet to overcome

Abstract Based on the current understanding of the epigenetic landscape, cancer methylome is highly disrupted, which makes DNA methylation an excellent target for anti-cancer cures. To date, azacytidine and its congener, decitabine (DAC) are the most successful DNA demethylating epigenetic drugs. However, scientists are yet to find the reversal of clinical resistance to these drugs. Yet another challenge remains to be the decreased efficacy of these promising therapies in the cure of solid tumors. We used a soild tumor, HCT116 colorectal cancer cell line and developed resistance against DAC. DAC-resistant HCT116 cells were used to study the epigenetic cross-talk between DNA methylation and chromatin modifications. The screening of parental and DAC-resistant HCT116 cells against inhibitors of epigenetic writers-erasers-readers unveiled increased sensitivity of resistant cells to BET inhibitor (inhibitor of reader enzymes), (+)-JQ1. BET inhibitor further mediated augmented response on cell cycle phases of resistant cells, increased anti-proliferative effects in xenograft models of resistant cells, and synergystic effects in combination with DAC in HCT116 parental cells, both in vitro and. We then sequenced the transcriptome of DAC-sensitive and -resistant HCT116 cells, and (+)-JQ1 treated-(DAC-resistant) cells, using RNA-seq. The RNA-seq data revealed the overexpression of critical oncogenes, and their binding inactivation of key tumor suppressor genes (TSGs) in resistant cells. The most significant and biologically relevant transcriptional changes were further validated by qRT-PCR, and in addition their methylation status was determined by bisulphite sequencing. We discovered that the expressions of down-regulated TSGs were driven by promoter methylation, exposing these tumor-suppressive signatures as biomarkers which might differentiate between DAC-resistance and sensitivity, whereas, overexpression of oncogenes was independent of promoter methylation. Interestingly, the expressions of up-regulated oncogenes which define cell identity, mainly those involved in signaling of inflammatory pathways (including some bromodomain-specific genes) were reversed on treatment with (+)-JQ1. Further, siRNA-mediated genetic inhibition of bromodomains in resistant cells phenocopied therapeutic inhibition by (+)-JQ1. These data unveil the chromatin “reader proteins”, as regulators of dysregulated oncogenic expressions in DAC-resistant cells. The present study provides novel insights into the epigenomic landscape of DAC-resistant colorectal cancer cells, and put forward, the alternative therapeutic regimen for DAC-resistant patients. This study was supported by Czech Ministry of Education, Youth and Sports (LO1304, LM2015091, LM2015064), Technology Agency of the Czech Republic (TE01020028) and Internal Grant Agency of Palacky University (IGA_LF_2016_019). Citation Format: Khushboo Agrawal, Petr Vojta, Rastislav Slavkosky, Ivo Frydrych, Petr Dzubak, Marian Hajduch. Low-sensitivity and drug-resistance to DNA-demethylating epi-drug decitabine in solid tumors: A challenge yet to overcome [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B085.

Abstract 5182: Chromatin reader machinery as target for overcoming resistance to DNA-demethylating epi-drug decitabine

Abstract Based on the current understanding of the epigenetic landscape, cancer methylome is highly disrupted, which makes DNA methylation an excellent target for anti-cancer cures. To date, azacytidine and its congener, decitabine (DAC) are the most successful DNA demethylating epigenetic drugs. However, scientists are yet to find the reversal of clinical resistance to these drugs. Yet another challenge remains to be the decreased efficacy of these promising therapies in the cure of solid tumors. We used a soild tumor, HCT116 colorectal cancer cell line and developed resistance against DAC. DAC-resistant HCT116 cells were used to study the epigenetic cross-talk between DNA methylation and chromatin modifications. The screening of parental and DAC-resistant HCT116 cells against inhibitors of epigenetic writers-erasers-readers unveiled increased sensitivity of resistant cells to BET inhibitor (inhibitor of reader enzymes), (+)-JQ1. BET inhibitor further mediated augmented response on cell cycle phases of resistant cells, increased anti-proliferative effects in xenograft models of resistant cells, and synergystic effects in combination with DAC in HCT116 parental cells, both in vitro and in vivo. We then sequenced the transcriptome of DAC-sensitive and -resistant HCT116 cells, and (+)-JQ1 treated-(DAC-resistant) cells, using RNA-seq. The RNA-seq data revealed the overexpression of critical oncogenes, and their binding inactivation of key tumor suppressor genes (TSGs) in resistant cells. The most significant and biologically relevant transcriptional changes were further validated by qRT-PCR, and in addition their methylation status was determined by bisulphite sequencing. We discovered that the expressions of down-regulated TSGs were driven by promoter methylation, exposing these tumor-suppressive signatures as biomarkers which might differentiate between DAC-resistance and sensitivity, whereas, overexpression of oncogenes was independent of promoter methylation. Interestingly, the expressions of up-regulated oncogenes which define cell identity, mainly those involved in signaling of inflammatory pathways (including some bromodomain-specific genes) were reversed on treatment with (+)-JQ1. Further, siRNA-mediated genetic inhibition of bromodomains in resistant cells phenocopied therapeutic inhibition by (+)-JQ1. These data unveil the chromatin “reader proteins”, as regulators of dysregulated oncogenic expressions in DAC-resistant cells. The present study provides novel insights into the epigenomic landscape of DAC-resistant colorectal cancer cells, and put forward, the alternative therapeutic regimen for DAC-resistant patients. This study was supported by Czech Ministry of Education, Youth and Sports (LO1304, LM2015091, LM2015064), Technology Agency of the Czech Republic (TE01020028) and Internal Grant Agency of Palacky University (IGA_LF_2016_019). Citation Format: Khushboo Agrawal, Petr Vojta, Rastislav Slavkosky, Ivo Frydrych, Petr Dzubak, Marian Hajduch. Chromatin reader machinery as target for overcoming resistance to DNA-demethylating epi-drug decitabine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5182.

P1‐211: PRO‐APOPTOTIC PROTEIN PUMA REGULATES AUTOPHAGY IN AN ALZHEIMER'S DISEASE MODEL

Selective synaptic loss followed by neuronal loss underlies the pathogenesis of Alzheimer's disease (AD). Two major cell death modalities which influence the fate of a cell, under normal or anomalous conditions like neurodegeneration, are apoptosis and autophagy. Literature suggests autophagy being critical for aberrant neuronal health in AD. Pro-apoptotic protein Puma is implicated in AD and is shown to play an essential role in mitophagy in cancer cells. Our aim is to understand the role of Puma in regulating the autophagic pathway in an AD model. We performed immunohistochemistry and western blotting for autophagy profiling in 5XFAD mice brains. For time kinetics and down-regulation studies, immunocytochemistry and western blotting was done. Survivability assays were performed by nuclear counting technique. Mechanistic studies were performed by RNAi, transfection and co-immunoprecipitation. Cellular studies were performed in primary cortical neurons and pheochromocytoma (PC12) cells under amyloid-β (Aβ) treatment. Our immunohistochemistry studies suggested an increase in the levels of autophagic markers, LC3 and LAMP1, in brain slices of six month old 5XFAD mice as compared to wild type mice which was substantiated in the tissue samples by western blot. We performed a time-kinetics analysis of occurrence of autophagy and apoptosis in cortical neurons and PC12 cells under Aβ treatment for a period of 24 h and found a gradual advent of both the processes simultaneously. Interestingly, we found that inhibiting autophagy by 3-methyladenine and apoptosis by pan-caspase inhibitor had a synergystic effect on the survival of neurons suggesting a vicious crosstalk. Also, when Puma and its regulator FoxO transcription factor (both induce apoptosis in Aβ-treated neurons) were down-regulated exclusively, there were a significant decrease in autophagic initiation (LC3) and increase in its flux (p62) as opposed to Aβ treatment. Finally, our co-immunoprecipitation data showing an interaction between Puma and Beclin1 under Aβ-treated condition suggest that there may be a crosstalk between apoptosis and autophagy via Puma in AD. An extensive study on the Puma-Beclin1 gateway is under process. We conclude that pro-apoptotic protein Puma plays a major role in the initiation of autophagy and maintaining its flux in AD.

Functionalized metal-organic framework nanocomposites for dispersive solid phase extraction and enantioselective capture of chiral drug intermediates

The facile preparation, characterization and application of a novel magnetic graphene oxide- metal organic framework [Zn2(d-Cam)2(4, 4′-bpy)]n (MGO-ZnCB) as a sorbent for fast, simple and enantioselective capture of chiral drug intermediates are presented in this paper. The MGO-ZnCB nanocomposite, developed by encapsulating MGO nanoparticles into the homochiral metal organic framework of ZnCB, can integrate the advantages from each component endowing the hybrids with improved synergystic effects. The enantioselective performance of MGO-ZnCB was evaluated by dispersive magnetic nanoparticle solid phase extraction (d-MNSPE) of 1, 1′-bi-2-naphthol (BN) and 2, 2′-furoin (Furoin) racemic solutions. Due to the excellent dispersive capability, high stability, relatively larger saturation magnetization and distinct enrichment capacity of MGO-ZnCB, the d-MNSPE method provids good enantioselective separation of these compounds with enantiomeric excess (ee) values as high as 74.8% and 57.4%, respectively. The entire process with BN or Furoin can be completed within 3 min or less. After washing with methanol, the host MGO-ZnCB can be easily recycled and reused six times without any apparent loss of performance. Furthermore, the adsorbed BN and Furoin in nanodomains of the MGO-ZnCB composite were directly investigated for the first time by atomic force microscopy-infrared (AFM-IR) technique.

Roux-en-Y gastric bypass reduces plasma cholesterol in diet-induced obese mice by affecting trans-intestinal cholesterol excretion and intestinal cholesterol absorption.

Bariatric surgery appears as the most efficient therapeutic alternative in morbidly obese patients. In addition to its efficiency to decrease body weight, it also improves metabolic complications associated to morbid obesity, including dyslipidemia. Although the cholesterol-lowering effect varies with the bariatric procedures, the underlying molecular mechanisms remain poorly defined. This study aims to assess the consequence of both restrictive (sleeve gastrectomy; SG) and malabsorptive (Roux-en-Y gastric bypass; RYGB) procedures on cholesterol metabolism in mice. Ten-week-old C57BL6/J males were fed with a high-fat diet for 8-14 weeks before sleeve or RYGB surgery. SG has a modest and transient effect on plasma cholesterol levels, linked to a reduction in food intake. In contrast, modified RYGB led to a sustained ≈35% reduction in plasma cholesterol concentrations with a drastic increase in fecal cholesterol output. Mechanistically, RYGB exerts a synergystic effect on cholesterol metabolism by inducing the trans-intestinal cholesterol efflux and reducing the intestinal cholesterol absorption. In mice, RYGB, but not sleeve, strongly favors plasma cholesterol elimination by concomitantly increasing trans-intestinal cholesterol excretion and by decreasing intestinal cholesterol absorption. Our models open new perspective for deciphering the hypocholesterolemic effects of bariatric procedures.

Synergystic Effect of Using Blends of Oxygenates and Amines as Straight-Run Gasoline Additives

The effectiveness of using binary and ternary composites of alcohols and nonaromatic amines as antiknock additives to straight-run gasoline was studied. Their synergystic effect was ascertained. Gum formability of fuels with such additives was studied. It is shown that the increase in gum formability does not obey the additivity law.

The synergystic effects of omega-3 fatty acids against 5-fluorouracil-induced mucosal impairment in mice

Anti-cancer pharmaceuticals frequently have adverse side effects on patients such as gastrointestinal involvement limiting their clinical applications. These effects may be controlled by nutritional interventions, however, there are few studies that have shown any mechanistic effects. In this study, we examined effects of diet enhanced with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on 5-fluorouracil (5-FU)-induced intestinal impairment and immunity in mice. C57Bl6 mice were randomized to control diet, control diet + EPA, control + DHA, control + fish oil, or diet enchanced with DHA/EPA. After seven days of each respective diet, mice, excluding those in the sham group, were treated with 10 mg/kg/day 5-FU for 7 days. The effects of 5-FU-induced impairment in the small intestine were assessed using cytokine concentrations in serum and tissue, secretory immunoglobulin (Ig) A, diamine oxidase (DAO) activity, the length of the small intestine, and the expression of apoptosis signaling genes. The EPA/DHA-enhanced diet resulted in the most beneficial, synergystic and protective effect against 5-FU induced weight loss. Protection against inflammation, impaired intestinal function, and immunity of the small intestine were also observed. Individually, a DHA-enriched diet demonstrated a protective effect against 5-FU damage with longer small intestine mucosal and crypt lengths, greater DAO activity, and higher IgA concentrations, whereas the EPA-enriched diet resulted in decreased inflammatory cytokine concentrations in both plasma and small intestine and expression of apoptosis target genes. In conclusion, a diet enhanced with EPA and DHA results in synergism protecting against the detrimental effects of 5-FU and limiting chemotherapy induced mucosal impairment.

Synergystic Effect of Temperature and Electric Field Intensity in Escherichia coli Inactivation

Electric Fields are increasingly used to manipulate bacteria. However, there is no systematic and definitive study on how the different electric parameters change bacteria viability. Here we present a study on the effects of electric field intensity and temperature to bacterial cultures. Escherichia coli colonies have been exposed to different electric field intensities at 1MHz during 5 minutes by means of a microfluidic device specially designed for the experiment. From the analysis of the results it is possible to see that Escherichia coli survival rate diminishes when applying field intensities as low as 220V during 5 minutes. Death rates also increase when stronger fields are applied. However, viability of survived bacteria is maintained. Additionally, temperature shows a synergistic effect with voltage. When temperature was increased, results showed a stronger sensitivity of cells to the electric field. Moreover, the expression patterns of Outer Membrane Protein A and Ribosomal Proteins differ in control and treated samples, suggesting changes in bacterial metabolism and structure.

The effect of salt stress on Arabidopsis thaliana and Phelipanche ramosa interaction

SummarySalinity and Orobanche or Phelipanche spp. infection are important crop stress factors in agricultural areas. In this study, we investigated the effect of salt stress on Phelipanche ramosa seed germination and its attachment onto Arabidopsis thaliana roots. We also evaluated the effect of both stresses on the expression of genes regulated by abiotic and biotic stresses. According to our results, high concentration of NaCl delayed P. ramosa seed germination in the presence of a strigolactone analogue (GR24). A similar pattern was observed in the presence of A. thaliana plants. Furthermore, we found that salt‐treated A. thaliana seedlings were more sensitive to P. ramosa attachment compared with the untreated plants, indicating that there was a positive correlation between salt sensitivity and the ability of P. ramosa to infect A. thaliana plants. At the molecular level, a synergystic effect of both salt and P. ramosa stresses was observed on the cold‐regulated (COR) gene expression profile of treated A. thaliana seedlings. Our data clarify the interaction between parasitic plants and their hosts under abiotic stress conditions.

Isothermal Cold‐Crystallization of PLA/PBAT Blends With and Without the Addition of Acetyl Tributyl Citrate

AbstractThe isothermal cold‐crystallization kinetics of the PLA phase is studied by DSC and the crystallization from the melt by PLOM. Even though the blends exhibit two phases by SEM, several pieces of evidence indicate that partial miscibility may be present in these blends: small changes in both Tg and Tm of the PLA phase; a dependence of the spherulitic growth rate on blend composition and the oclusion of PBAT droplets inside PLA spherulites. Acetyl tributyl citrate is able to plasticize both phases in the blends, but it displays a preference to dissolve within the PBAT rich phase. There is a synergystic effect on the increase in the overall crystallization rate of the PLA rich phase when both ATBC and PBAT are present in the blend.

Irradiation of structural materials in contact with lead bismuth eutectic in the high flux reactor

In the framework of the materials domain DEMETRA in the European Transmutation research and development project EUROTRANS, irradiation experiment IBIS has been performed in the High Flux Reactor in Petten. The objective was to investigate the synergystic effects of irradiation and lead bismuth eutectic exposure on the mechanical properties of structural materials and welds. In this experiment ferritic martensitic 9 Cr steel, austenitic 316L stainless steel and their welds have been irradiated for 250 Full Power Days up to a dose level of 2 dpa. Irradiation temperatures have been kept constant at 300 °C and 500 °C. During the post-irradiation test phase, tensile tests performed on the specimens irradiated at 300 °C have shown that the irradiation hardening of ferritic martensitic 9 Cr steel at 1.3 dpa is 254 MPa, which is in line with the irradiation hardening obtained for ferritic martensitic Eurofer97 steel investigated in the fusion program. This result indicates that no LBE interaction at this irradiation temperature is present. A visual inspection is performed on the specimens irradiated in contact with LBE at 500 °C and have shown blackening on the surface of the specimens and remains of LBE that makes a special cleaning procedure necessary before post-irradiation mechanical testing.

Relationships between Actin Regulatory Mechanisms and Measurable State Variables

In this report we extend our recent mathematical formulation of the actin cycle model [Bindschadler et al. Biophys. J. 86 (2004) 2720] to predict the influence of key regulatory mechanisms on network-scale state variables estimable in live cell experiments. Specifically, we examine the influence of regulation by cofilin, profilin, capping protein and proteins that adjust filament number through nucleation and/or filament severing, on the higher order variables of average filament length, polymer fraction, and filament turnover rate. Importantly, we find that severing/nucleation, the acceleration of ADP-subunit disassembly by cofilin, and the catalytic and shuttle functions of profilin have 'signature' effects on the higher order state variables. In this way, measurement of the state variables in live cells can allow inference of regulatory mechanism(s) underlying changes in cell state. Our results compare favorably to published data for endothelial cells undergoing a transition from non-motile confluent cells to highly motile subconfluent cells. The extension of our model to higher order state variables allows us to investigate other important issues such as the distinction between basic and higher order measures of filament dynamics, the influence of thymosin beta4 on network state variables, the interplay between thymosin beta4 and profilin, and the synergystic effects of cofilin and profilin.

Hsp90 Inhibitors Induce Apoptosis in Human Leukemia Cells.

The 90-Kda heat shock protein (Hsp90), together with a number of other chaperones are involved in normal cellular differentiation and cancerogenesis. Hsp90 is implicated in the conformational maturation of a large variety of protein kinases. We have shown its overexpression in a series of 116 acute myeloid leukemias (AML). Geldanamycin and its analogue 17-AAG selectively block the activities of Hsp90, but do not interact with other members of the Hsp family. The objective of the study was to test the effect of 17-AAG on cell lines (Jurkat, U-937, HL60, HL60R : resistant to daunorubicin (DNR), and KG1a) and on 24 AML samples tested positive for Hsp90 (14 strongly positive and 10 moderately positive). CD34+ cells from bone marrow donors were used as controls. Cells were maintained in liquid culture in the presence or absence of 17-AAG. Moreover hematopoietic and leukemic progenitor assays were performed in semi-solid media containing or not 17-AAG. CD34+ cells were non affected by 17-AAG. Jurkat, U937, HL60 were partially sensitive to 17-AAG. Addition of low dose DNR to 17-AAG induced an apoptotic death in 48 hours in all samples, including HL60R. KG1a (exhibiting high HSP90 levels) was more sensitive to 17-AAG alone with a death rate of 100% at higher doses. A similar effect was observed in AML samples : 17-AAG induced cell death in all 14 cases highly positive for HSP90, but a partial death in 5 cases, and no death in 5 cases mildly positive for HSP90. DNR increased apoptosis in only 5/10 of these cases. The other 5 patients were also positive for bcl-2. When they were first incubated with 17-AAG and then treated with bcl-2 antisens oligodeoxynucleotides (bcl-2AS), a complete apoptosis was obtained. So, in the 10 samples with moderate HSP90 expression a synergystic effect was found when a combination of 17-AAG with either chemotherapy or bcl -2AS was used. While normal progenitors were not affected by 17-AAG, leukemic progenitors were completed inhibited in the 14 patients who responded to 17-AAG in liquid culture. This apoptosis was caspase -3 dependant. Finally, we investigated the implication of the ERK signal pathway in Jurkat line and in 14/24 17-AAG responder samples using an ERK inhibitor (PD98059). When this inhibitor was added prior to 17-AAD and DNR, the apoptotic effect was completely inhibited. So, ERK signal pathway may interfere with the Hsp90 function. In conclusion, these results raise the possibility that Hsp90 antagonists represent a novel antileukemic strategy in sequential addition to conventional chemotherapy

Factors Contributing to the Marginalization of Shifting Cultivation in North-East India: Micro-Scale Issues

Shifting cultivation, locally known as jhum, is the predominant agricultural practice for most communities inhabiting the uplands of north-east India. The negative impacts of the practice on forest and biological resources, soil erosion and land degradation have been a serious concern for several decades now to administrators and planners as well as to the academic community. In the current context, the practice has undergone drastic changes and has become increasingly unviable, gradually leading to the marginalization of farmers practising it. Although shifting cultivation in this area has been the focus of intensive studies, particularly in terms of the underlying ecological dynamics, few have attempted to analyse the factors contributing to the marginalization of the practice. This paper examines micro-scale issues that contribute to reducing productivity (and hence marginalization), and which are of immediate concern to the shifting cultivator. The paper focuses on fundamental issues influencing the reduction in fallow cycle lengths, the impact of rural–urban migration on labour requirements for agriculture, the consequences of inadequate employment and cash generation facilities on labour availability and crop productivity, as well as government efforts to promote agricultural productivity in these areas. The main focus of the paper is on the impact of each of these factors and their synergystic effect on the marginalization of shifting cultivation.