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Reduced Resistance (reduced + resistance)

Distribution by Scientific Domains

Medical Sciences	40%
Life Sciences	40%

Selected Abstracts

Induction of apoptosis by A3 adenosine receptor agonist N6 -(3-iodobenzyl)-adenosine-5,- N -methylcarboxamide in human leukaemia cells: a possible involvement of intracellular mechanism

ACTA PHYSIOLOGICA, Issue 2 2010
P. Mlejnek
Abstract Aim:, The sensitivity of cancer cells which exhibit multi-drug resistance phenotype to A3 adenosine receptor (A3AR) agonist N6 -(3-iodobenzyl)-adenosine-5,- N -methylcarboxamide (IB-MECA) was studied. Methods:, To establish direct relationship between P-glycoprotein (P-gp, ABCB1 and MDR1) expression and IB-MECA induced cell death, a straightforward method for precise estimation of intracellular level of this A3AR agonist was developed. Results:, We subjected three human leukaemia cell lines HL-60, K562 and K562/HHT to treatment with micromolar concentrations of IB-MECA. Although all cell lines used expressed A3AR, there was a large difference in their sensitivity to IB-MECA. While HL-60 and K562 cells were almost equally sensitive, the K562/HHT cells, which exhibit a multi-drug resistance phenotype because of overexpression of P-gp, were significantly more resistant. We found that the intracellular level of IB-MECA in K562/HHT cells was approx. 10 times lower than those in HL-60 or K562 cells. Inhibitors of P-gp, including cyclosporine A (CsA) and verapamil (Vpa), increased the intracellular level of IB-MECA and reversed the resistance of K562/HHT cells to this drug. Accordingly, shRNA-mediated down-regulation of P-gp significantly increased the intracellular level of IB-MECA in K562/HHT cells which simultaneously exhibited reduced resistance to this A3AR agonist. In addition, an in vitro enzyme-based assay provided evidence that IB-MECA might serve as a substrate for P-gp. Conclusion:, Our results suggest that P-gp overexpression prevents cells from IB-MECA induced apoptosis despite the A3AR expression. Pro-apoptotic effect of IB-MECA seemed to strongly depend on its intracellular accumulation rather than on its interaction with A3AR. [source]

The nature of tobacco resistance against Botrytis cinerea depends on the infection structures of the pathogen

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2010
Mohamed El Oirdi
Summary To protect themselves, plants have evolved an armoury of defences in response to pathogens and other stress situations. These include the production of pathogenesis-related (PR) proteins and the accumulation of antimicrobial molecules such as phytoalexins. Here we report that resistance of tobacco to Botrytis cinerea is cultivar specific. Nicotiana tabacum cv. Petit Havana but not N. tabacum cv. Xanthi or cv. samsun is resistant to B. cinerea. This resistance is correlated with the accumulation of the phytoalexin scopoletin and PR proteins. We also show that this resistance depends on the type of B. cinerea stage. Nicotiana tabacum cv. Petit Havana is more resistant to spores than to mycelium of B. cinerea. This reduced resistance of N. tabacum cv. Petit Havana to the mycelium compared with spores is correlated with the suppression of PR proteins accumulation and the capacity of the mycelium, not the spores, to metabolize scopoletin. These data present an important advance in understanding the strategies used by B. cinerea to establish its disease on tobacco plants. [source]

Combined effects of wetting, drying, and microcrystalline cellulose type on the mechanical strength and disintegration of pellets

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2009
Maria Balaxi
Abstract Effects of wetting and drying conditions on micromeritic, mechanical and disintegration properties of microcrystalline cellulose (MCC) pellets were evaluated. Extrusion/spheronization and three drying methods (fluidized bed, microwaves, and freeze drying) were applied using two wetting liquids (water or water-isopropanol 60:40 w/w) and three MCC types: (standard, silicified, and modified). Additionally, the effects of drying method were compared on highly porous pellets prepared by the incorporation and extraction of pore former (NaCl). It was found that the drying method has the greatest effect on the pellet size and porosity followed by the wetting liquid. The modification of MCC resulted in reduced water retention ability, implying hornification, increased porosity, reduced resistance to deformation and tensile strength of pellets. The disintegration time also decreased markedly due to the modification but only in the low porosity range <37%. Silicification increased greatly the disintegration time of the low porosity pellets (<14%). Combination of water-isopropanol, freeze drying and modified MCC gave the greatest increase in pellet size and porosity. The increase in pellet porosity caused exponential reduction in the resistance to deformation, tensile strength and disintegration time, as expected. Compared to fluidized bed, the freeze drying resulted in 20,30% higher porosity for pellets prepared without pore former and 6% for those with pore former, indicating the possibility of preparing highly porous pellets by employing freeze drying. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:676,689, 2009 [source]

Green tea extract weakens the antibacterial effect of amoxicillin in methicillin-resistant Staphylococcus aureus infected mice

PHYTOTHERAPY RESEARCH, Issue 1 2010
Qing Peng
Abstract Tea (Camellia sinensis) has been known for its modulation of resistance of methicillin-resistant Staphylococcus aureus (MRSA) to ,-lactam antibiotics in vitro. This study aimed to confirm the in vitro effect of green tea extracts with ,-lactams and to determine whether green tea extracts can reduce the minimum inhibitory concentrations (MICs) of amoxicillin in MRSA-infected mice. The catechins in the test tea that account for the reduced resistance to ,-lactams were quantitatively determined by high-performance liquid chromatography. The MICs of the ampicillin, cefazolin, amoxicillin, oxacillin, tea extract alone and tea extract in combination with ,-lactams were determined. Proportions of tea extracts and amoxicillin-tea extract combinations were administered to groups of mice enterally. The in vitro experiment showed that the MICs of four ,-lactams were greatly decreased in the presence of 0.25% tea extract. However, in an in vivo experiment, amoxicillin in combination with 5% tea extract conferred a higher ED50 than that of antibiotic alone. Green tea extract, alone or in combination with amoxicillin, does not have protective benefits in MRSA-infected mice. This study concluded that tea extract weakened the antibacterial effect of amoxicillin in MRSA infected mice. Tea drinking is not recommended in combination with amoxicillin treatment. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Effect of leptin on activation and cytokine synthesis in peripheral blood lymphocytes of malnourished infected children

CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 3 2007
L. Rodríguez
Summary Malnutrition compromises immune function, resulting in reduced resistance to infection. Recent animal and human studies have suggested that leptin is capable of modulating the immune response and that its levels, which are regulated by nutritional status, fall rapidly during starvation. Leptin deficiency is associated with impaired cell-mediated immunity, an increased incidence of infectious disease and an associated increase in mortality. The purpose of this study was to examine the effect of leptin on activation and cytokine production in peripheral blood T cells from malnourished children. The data obtained in the present study demonstrate that leptin produced an increase in the percentage of CD4+ and CD8+ cells producing interleukin (IL)-2 and interferon (IFN)-, in 24-h cultures. Moreover, leptin decreased the percentage of CD4+ and CD8+ cells producing IL-4 and IL-10, and enhanced activation of circulating T cells when co-stimulated by phorbol 12-myristate 13 acetate (PMA),ionomycin. Leptin enhanced the expression of activation markers CD69 and CD25 in both CD4+ and CD8+ cells after 5 h of stimulation. In conclusion, the results obtained show that leptin modulates CD4+ and CD8+ cell activation towards a T helper 1 (Th1) phenotype by stimulating the synthesis of IL-2 and IFN-,. In contrast, leptin decreases IL-4 and IL-10 production. Moreover, leptin enhanced the expression of CD69 and CD25 on CD4+ and CD8+ cells after stimulation with PMA,ionomycin. [source]