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The effect ofl-ascorbic acid on the biosynthesis of aflatoxin inAspergillus parasiticus was studied. Ascorbic acid at lower concentrations did not inhibit the growth of fungus but markedly induced aflatoxin biosynthesis. At a concentration of 1000 ppm of ascorbic acid, 4.8-fold higher levels of aflatoxin were detected. Copper did not enhance the induction of toxin synthesis by ascorbic acid when added to the growth medium. Ascorbic acid at 1000 ppm was also found to induce aflatoxin synthesis in resting mycelia. Chloroform (1% vol/vol) was found to induce aflatoxin synthesis under similar conditions. Ascorbic acid in the presence of ferrous ion can cause lipid peroxidation, which in turn is responsible for the induction of aflatoxin synthesis. During the induction of aflatoxin synthesis by ascorbic acid, the uptake of carbon source (acetate) was not affected. This observation suggests that on ascorbic acid treatment a precursor or an intermediate of aflatoxin biosynthesis is synthesized in vivo and is responsible for the higher levels of toxin without increasing the uptake of acetate. 相似文献
3.
C A Awoniyi V Chandrashekar R D Arthur B D Schanbacher A G Amador R E Falvo 《Journal of reproduction and fertility》1988,84(1):295-302
Crossbred boars were (a) immunized against GnRH conjugated to human serum globulin (200 micrograms GnRH-hSG) in Freund's adjuvant at 12 weeks of age and boosted at weeks 18 and 20 (N = 10), (b) served as controls and received hSG only in adjuvant (N = 10), or castrated at weaning (N = 10). At 24 weeks of age (immediately before slaughter), the boars were challenged with saline or pig LH (1 microgram/10 kg body weight). After slaughter, fresh testicular fragments were incubated with pig LH (0.05 and 0.2 ng/2 ml medium) to assess the effects of immunization on Leydig cell function. Pituitary contents of LH and FSH, and testicular LH receptor content were also measured. The results indicated that plasma LH and testosterone concentrations, pituitary LH content, testicular LH receptor content, testis and sex accessory organ weights were significantly reduced in GnRH-immunized boars compared to hSG-adjuvant controls. However, plasma and pituitary FSH content were not affected by high antibody titres generated against GnRH. The testicular testosterone response to exogenous LH in vivo and in vitro was significantly reduced (P less than 0.05) in GnRH-immunized boars. These results indicate that active immunization against GnRH impairs pituitary and Leydig cell functions in boars. 相似文献
4.
Partial resistance to powdery mildew (Erysiphe polygoni) in twenty one cowpea cultivars was assessed over two to three seasons under field conditions. Mildew incidence was recorded as number of leaflets affected/plant and severity as AUDPC or infection rate using Gompertz transformation. Irrespective of the parameter used to measure mildew resistance or the season, mean response of cvs V-105, V-269, V-276, V-282 and V-385 showed clear slow-mildewing, while RC-48, S-488, TVX-944-02E, V-27, V-36 and V-118 were rated as susceptible. Mildew resistance in some cultivars was negatively correlated with that for the leaf rust (Uromyces vignae). AUDPC was a more robust disease parameter than infection rate and showed a good correlation (r2= 0.79) with incidence. 相似文献
5.
Albino rat macrophages and neutrophils in the presence of immune serum adhered to and promoted killing of Brugia malayi infective larvae in vitro. At a similar cell-target ratio, macrophages were more potent than neutrophils in inducing cytotoxic response to the larvae. Eosinophils were also effective in killing but only at a high cell-target ratio. The activity in the immune serum could be absorbed to and eluted from a Protein A-Sepharose column suggesting involvement of IgG antibody in the reaction. An indirect fluorescent antibody test confirmed the presence of IgG on the surface of larvae incubated in immune serum. Infective larvae were attacked by host cells within micropore chambers 16-24 h after implantation into immunized rats. Further, a strong cytotoxic response to the larvae was seen when they were introduced intraperitoneally into immune rats indicating the role of antibody and cells in vivo. We suggest that antibody-dependent cellular cytotoxicity may represent an important mechanism of parasite killing in an immune host. 相似文献
6.
InAlysicarpus vaginalis (L.) DC. nitrogen, ascorbic acid, proline and epicuticular wax (ECW) contents were higher in the plants growing in the coastal
region whereas the protein, soluble sugars and starch contents were lower. The higher contents of proline, nitrogen and ascorbic
acid recorded in the plants of the saline habitat are a physiological adaptation to overcome the salt stress. The higher ECW
content in the plants of the saline habitat specially in the summer months seems to be an adaptation in these plants to survive
in the saline habitat.
Communicated by Z. ŠESTáK 相似文献
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Hitesh Jagani Josyula Venkata Rao Vasanth Raj Palanimuthu Raghu Chandrashekar Hariharapura Sagar Gang 《Cellular & molecular biology letters》2013,18(1):120-136
Overexpression of anti-apoptotic Bcl-2 is often observed in a wide variety of human cancers. It prevents the induction of apoptosis in neoplastic cells and contributes to resistance to chemotherapy. RNA interference has emerged as an efficient and selective technique for gene silencing. The potential to use small interfering RNA (siRNA) as a therapeutic agent for the treatment of cancer has elicited a great deal of interest. However, insufficient cellular uptake and poor stability have limited its therapeutic applications. The purpose of this study was to prepare chitosan nanoparticles via ionic gelation of chitosan by tripolyphosphate for effective delivery of siRNA to silence the anti-apoptotic Bcl-2 gene in neoplastic cells. Chitosan nanoparticles loaded with siRNA were in the size range 190 to 340 nm with a polydispersive index ranging from 0.04 to 0.2. They were able to completely bind with siRNA, provide protection against nuclease degradation, and enhance the transfection. Cell culture studies revealed that nanoparticles with entrapped siRNA could efficiently silence the antiapoptotic Bcl-2 gene. Studies on Swiss albino mice showed that siRNA could be effectively delivered through nanoparticles. There was significant decrease in the tumor volume. Blocking the expression of anti-apoptotic Bcl-2 can enhance the sensitivity of cancerous cells to anti-cancer drugs and the apoptosis rate. Therefore, nanoformulations with siRNA can be promoted as an adjuvant therapy in combination with anti-cancer drugs. 相似文献
9.
Anil K. Mantha Indu R. Chandrashekar Najma Z. Baquer Sudha M. Cowsik 《Journal of biomolecular structure & dynamics》2013,31(2):137-147
Abstract Neurokinin B (NKB), a decapeptide of mammalian origin exhibits a variety of biological activities such as regulatory functions in reproduction, pre-eclampsia and neuroprotection in Alzheimer's disease. In order to gain insight into structure-function relationship, three- dimensional structure of NKB has been investigated using CD spectropolarimetry and two-dimensional proton nuclear magnetic resonance (2D 1H-NMR) spectroscopy in aqueous and membrane mimetic solvents. Unambiguous NMR assignments of resonances have been made with the aid of correlation spectroscopy (DQF-COSY and TOCSY) experiments and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments. Distance constraints obtained from the NMR data have been used to generate a family of structures, which have been refined using restrained energy minimization and dynamics. Our data show that a helical structure is induced in NKB, in presence of perdeuterated dodecyl phosphocholine (DPC) micelles, a membrane model system. Further, the conformation adopted by NKB in presence of DPC micelles represents a structural motif typical of neurokinin-3 selective agonists. 相似文献