Stable wheat transformation obtained without selectable markers

Transgenic wheat plants without the selectable marker gene were obtained either in the presence or in the absence of selective pressure during the transformation protocol. When using hygromycin as selective agent in a co-transformation experiment involving a mixture of plasmids pGL2, containing the hpt gene, and pAI₁Gus, containing the uidA gene, 3 out of 19 transgenic wheat plants had the uidA gene alone as shown by Southern blots. The gene was transmitted to the progeny following Mendelian rules. Segregation and loss of the selectable marker gene was also found in three out of six events from other experiments where high-molecular-weight glutenin genes were expressed or over-expressed. On the other hand, in 7 experiments where no selective pressure was applied and that involved 1016 bombarded explants, 23 transgenic wheat plants were obtained. The uidA gene was stably integrated as suggested by its transmission to the progeny.these authors contributed equally to the work     

Synthesis and antimicrobial evaluation of farnesyl diphosphate mimetics

The synthesis and first antimicrobial evaluation of farnesyl diphosphate mimetics are described. Several analogues (10, 12, 13, and 20) are inhibitors of Candida albicans, Shizosaccharomyces pombe, and Saccharomyces cerevisiae. The activities of analogues 10, 12, and 13, which contain a omega-phenyl moiety and a diphosphate isostere, are not attributable to inhibition of sterol biosynthesis via squalene synthase. Two geranyl phenylsulphones (14 and 15) are potent inhibitors of Escherichia coli. Analogue 15 exhibits potent activity towards Salmonella typhimurium and Pseudomonas aeruginosa (MIC-2 microg/mL) and represents the first type of semi-synthetic terpenoid allylic sulphone active against these bacteria.     

Influence of 1 and 25 Hz, 1.5 mT magnetic fields on antitumor drug potency in a human adenocarcinoma cell line

The resistance of tumor cells to antineoplastic agents is a major obstacle during cancer chemotherapy. Many authors have observed that some exposure protocols to pulsed electromagnetic fields (PEMF) can alter the efficacy of anticancer drugs; nevertheless, the observations are not clear. We have evaluated whether a group of PEMF pulses (1.5 mT peak, repeated at 1 and 25 Hz) produces alterations of drug potency on a multidrug resistant human colon adenocarcinoma (HCA) cell line, HCA-2/1(cch). The experiments were performed including (a) exposures to drug and PEMF exposure for 1 h at the same time, (b) drug exposure for 1 h, and then exposure to PEMF for the next 2 days (2 h/day). Drugs used were vincristine (VCR), mitomycin C (MMC), and cisplatin. Cell viability was measured by the neutral red stain cytotoxicity test. The results obtained were: (a) The 1 Hz PEMF increased VCR cytotoxicity (P < 0.01), exhibiting 6.1% of survival at 47.5 microg/ml, the highest dose for which sham exposed groups showed a 19.8% of survival. For MMC at 47.5 microg/ml, the % of survival changed significantly from 19.2% in sham exposed groups to 5.3% using 25 Hz (P < 0.001). Cisplatin showed a significant reduction in the % of survival (44.2-39.1%, P < 0.05) at 25 Hz and 47.5 microg/ml, and (b) Minor significant alterations were observed after nonsimultaneous exposure of cells to PEMF and drug. The data indicate that PEMF can induce modulation of cytostatic agents in HCA-2/1(cch), with an increased effect when PEMF was applied at the same time as the drug. The type of drug, dose, frequency, and duration of PEMF exposure could influence this modulation.     

Reactive oxygen species,antioxidant mechanisms and serum cytokine levels in cancer patients: impact of an antioxidant treatment

Objective. So far, it is not well established whether oxidative stress found in cancer patients results from an increased production of oxidants in the body or from a failure of physiological antioxidant systems. To further investigate this question we have assessed the blood levels of reactive oxygen species as a marker of free radicals producing oxidative stress and the most relevant of the physiological body enzymes counteracting reactive oxygen species, namely glutathione peroxidase and superoxide dismutase. Serum levels of proinflammatory cytokines and IL‐2 were also investigated. All these parameters were studied in relation to the clinically most important index of disease progression, namely Performance Status (ECOG PS). We also tested the reducing ability of different antioxidant agents on reactive oxygen species levels by measuring the increase in glutathione peroxidase activity, and the reduction of serum levels of IL‐6 and TNF. Design, setting and subjects. We carried out an open non randomized study on 28 advanced stage cancer patients (stage III, 10.7%, and stage IV, 89.3%) with tumours at different (8) sites: all were hospitalized in the Medical Oncology Dept, University of Cagliari Interventions. The patients were divided into 5 groups and a different antioxidant treatment was administered to each group. The selected antioxidants were: alpha lipoic acid 200 mg/day orally, N‐acetylcysteine 1800 mg/day i.v. or carboxycysteine‐lysine salt 2.7 g/day orally, amifostine 375 mg/day i.v., reduced glutathione 600 mg/day i.v., vitamin A 30000 IU/day orally plus vitamin E 70 mg/day orally plus Vitamin C 500 mg/day orally. The antioxidant treatment was administered for 10 consecutive days. Results. Our results show that all but one of the antioxidants tested were effective in reducing reactive oxygen species levels and 2 of them (cysteine‐containing compounds and amifostine) had the additional effect of increasing glutathione peroxidase activity. Comprehensively, the “antioxidant treatment” was found to have an effect both on reactive oxygen species levels and glutathione peroxidase activity. The antioxidant treatment also reduced serum levels of IL‐6 and TNF. Patients in both ECOG PS 0‐1 and ECOG PS 2‐3 responded to antioxidant treatment.     

Potent inhibition of DNA unwinding and ATPase activities of pea DNA helicase 45 by DNA-binding agents

Pea DNA helicase 45 (PDH45) is an ATP-dependent DNA unwinding enzyme, with intrinsic DNA-dependent ATPase activity [Plant J. 24 (2000) 219]. We have determined the effect of various DNA-binding agents, such as daunorubicin, ethidium bromide, ellipticine, cisplatin, nogalamycin, actinomycin C1, and camptothecin on the DNA unwinding and ATPase activities of the plant nuclear DNA helicase PDH45. The results show that all the agents except actinomycin C1, and camptothecin inhibited the helicase (apparent K(i) values ranging from 1.5 to 7.0 microM) and ATPase (apparent K(i) values ranging from 2.5 to 11.9 microM) activities. This is the first study to show the effect of various DNA-binding agents on the plant nuclear helicase and also first to demonstrate inhibition of any helicase by cisplatin. Another striking finding that the actinomycin C1 and ellipticine act differentially on PDH45 as compared to pea chloroplast helicase suggests that the mechanism of DNA unwinding could be different in nucleus and chloroplast. These results suggest that the intercalation of the inhibitors into duplex DNA generates a complex that impedes translocation of PDH45, resulting in both the inhibitions of unwinding activity and ATP hydrolysis. This study would be useful to obtain a better understanding of the mechanism of plant nuclear DNA helicase unwinding and the mechanism by which these agents can disturb genome integrity.     

Resistance to thapsigargin-induced intracellular calcium mobilization in a multidrug resistant tumour cell line

A multidrug resistant (MDR) cell line, derived from the human leukaemic cell K562 and selected for its resistance to Vincristine, was shown to be resistant to Thapsigargin (TG). A concentration of 50 nM TG was toxic to K562 cells whereas the MDR cell line, known as Lucena I cells, survived unaffected for up to seven days in culture. Similarly, no intracellular Ca²⁺ mobilization was observed in the MDR cell line treated with TG. This effect was not a result of TG extrusion by P glycoprotein (Pgp), as no mobilization was observed even in the presence of the Pgp inhibitors Verapamil (5 M) and Cyclosporin A (0.16 M). In the present study, both cell lines expressed comparable levels of Bcl-2 making it unlikely that Bcl-2 was involved in this process. Similarly, no overexpression of the endoplasmic reticulum Ca²⁺ ATPase (SERCA) could be detected in the MDR cell line and Ca²⁺ uptake by vesicles of the two cell types were equally sensitive to TG. These results confirm that MDR cells do not mobilize Ca²⁺ in the presence of TG but go against the possibility that this might be due to TG extrusion or to the overexpression of a resistant SERCA isoform.     

Alpha-synuclein up-regulation in substantia nigra dopaminergic neurons following administration of the parkinsonian toxin MPTP

Mutations in alpha-synuclein cause a form of familial Parkinson's disease (PD), and wild-type alpha-synuclein is a major component of the intraneuronal inclusions called Lewy bodies, a pathological hallmark of PD. These observations suggest a pathogenic role for alpha-synuclein in PD. Thus far, however, little is known about the importance of alpha-synuclein in the nigral dopaminergic pathway in either normal or pathological situations. Herein, we studied this question by assessing the expression of synuclein-1, the rodent homologue of human alpha-synuclein, in both normal and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mice. In normal mice, detectable levels of synuclein mRNA and protein were seen in all brain regions studied and especially in ventral midbrain. In the latter, there was a dense synuclein-positive nerve fiber network, which predominated over the substantia nigra, and only few scattered synuclein-positive neurons. After a regimen of MPTP that kills dopaminergic neurons by apoptosis, synuclein mRNA and protein levels were increased significantly in midbrain extracts; the time course of these changes paralleled that of MPTP-induced dopaminergic neurodegeneration. In these MPTP-injected mice, there was also a dramatic increase in the number of synuclein-immunoreactive neurons exclusively in the substantia nigra pars compacta; all synuclein-positive neurons were tyrosine hydroxylase-positive, but none coexpressed apoptotic features. These data indicate that synuclein is highly expressed in the nigrostriatal pathway of normal mice and that it is up-regulated following MPTP-induced injury. In light of the synuclein alterations, it can be suggested that, by targeting this protein, one may modulate MPTP neurotoxicity and, consequently, open new therapeutic avenues for PD.     

The endogenous amine 1-methyl-1,2,3,4- tetrahydroisoquinoline prevents the inhibition of complex I of the respiratory chain produced by MPP(+)

The endogenous monoamine 1-methyl-1,2,3,4-tetrahydroisoquinoline has been shown to prevent the neurotoxic effect of MPP(+) and other endogenous neurotoxins, which produce a parkinsonian-like syndrome in humans. We have tested its potential protective effect in vivo by measuring the protection of 1-methyl-1,2,3,4-tetrahydroisoquinoline in the neurotoxicity elicited by MPP(+) in rat striatum by tyrosine hydroxylase immunocytochemistry. Because we know that cellular damage caused by MPP(+) is primarily the result of mitochondrial respiratory inhibition at the complex I level, we have extended the study further to understand this protective mechanism. We found that the inhibitory effect on the mitochondrial respiration rate induced by MPP(+) in isolated rat liver mitochondria and striatal synaptosomes was prevented by addition of 1-methyl-1,2,3,4-tetrahydroisoquinoline. This compound has no antioxidant capacity; therefore, this property is not involved in its protective effect. Thus, we postulate that the preventive effect that 1-methyl-1,2,3,4-tetrahydroisoquinoline has on mitochondrial inhibition for MPP(+) could be due to a "shielding effect," protecting the energetic machinery, thus preventing energetic failure. These results suggest that this endogenous amine may protect against the effect of several parkinsonism-inducing compounds that are associated with progressive impairment of the mitochondrial function.     

超顺磁性造影剂的研究进展

超顺磁性造影剂是一种新型的磁共振造影剂,对肝脾等部位的成像效果显著,已成为国内外研究的热点之一。本文对超顺磁性造影剂的增强原理和制备方法进行了总结及评论。