Direct relationship between the level of p53 stabilization induced by rRNA synthesis-inhibiting drugs and the cell ribosome biogenesis rate.

Many drugs currently used in chemotherapy work by hindering the process of ribosome biogenesis. In tumors with functional p53, the inhibition of ribosome biogenesis may contribute to the efficacy of this treatment by inducing p53 stabilization. As the level of stabilized p53 is critical for the induction of cytotoxic effects, it seems useful to highlight those cancer cell characteristics that can predict the degree of p53 stabilization following the treatment with inhibitors of ribosome biogenesis. In the present study we exposed a series of p53 wild-type human cancer cell lines to drugs such as actinomycin D (ActD), doxorubicin, 5-fluorouracil and CX-5461, which hinder ribosomal RNA (rRNA) synthesis. We found that the amount of stabilized p53 was directly related to the level of ribosome biogenesis in cells before the drug treatment. This was due to different levels of inactivation of the ribosomal proteins-MDM2 pathway of p53 digestion. Inhibition of rRNA synthesis always caused cell cycle arrest, independent of the ribosome biogenesis rate of the cells, whereas apoptosis occurred only in cells with a high rDNA transcription rate. The level of p53 stabilization induced by drugs acting in different ways from the inhibition of ribosome biogenesis, such as hydroxyurea (HU) and nutlin-3, was independent of the level of ribosome biogenesis in cells and always lower than that occurring after the inhibition of rRNA synthesis. Interestingly, in cells with a low ribosome biogenesis rate, the combined treatment with ActD and HU exerted an additive effect on p53 stabilization. These results indicated that (i) drugs inhibiting ribosome biogenesis may be highly effective in p53 wild-type cancers with a high ribosome biogenesis rate, as they induce apoptotic cell death, and (ii) the combination of drugs capable of stabilizing p53 through different mechanisms may be useful for treating cancers with a low ribosome biogenesis rate.

A role for intracellular zinc in glioma alteration of neuronal chloride equilibrium.

Glioma patients commonly suffer from epileptic seizures. However, the mechanisms of glioma-associated epilepsy are far to be completely understood. Using glioma-neurons co-cultures, we found that tumor cells are able to deeply influence neuronal chloride homeostasis, by depolarizing the reversal potential of γ-aminobutyric acid (GABA)-evoked currents (EGABA). EGABA depolarizing shift is due to zinc-dependent reduction of neuronal KCC2 activity and requires glutamate release from glioma cells. Consistently, intracellular zinc loading rapidly depolarizes EGABA in mouse hippocampal neurons, through the Src/Trk pathway and this effect is promptly reverted upon zinc chelation. This study provides a possible molecular mechanism linking glioma invasion to excitation/inhibition imbalance and epileptic seizures, through the zinc-mediated disruption of neuronal chloride homeostasis.

Microincision cataract surgery combined with vitrectomy: a case series.

AIM: The objective of this study was to present the results of combined phacovitrectomy using 1.8 mm microincision cataract surgery (MICS) with special emphasis on the anterior segment complications in this group. METHODS: Retrospective, single-centre case series involving consecutive patients undergoing phacovitrectomy in a single centre in the United Kingdom during a 6-month period. RESULTS: A total of 52 eyes underwent combined MICS and pars plana vitrectomy. Intraoperative complications included posterior capsule rupture (n=2), minor iris trauma during phacoemulsification (n=1), iatrogenic retinal tears (n=2), and entry site break (n=1). Postoperatively two cases had significant inflammation, one of which resulted in 360° posterior synaechiea, iris bombe, and raised intraocular pressure. Other complications included mild posterior synaechiae (n=2), posterior capsular opacification (n=3), cystoid macular oedema (n=1), and hyphaema (n=1), which spontaneously resolved. There were no cases of intraocular lens decentration. Two patients who underwent surgery for retinal detachment repair subsequently redetached. Among those having surgery for macular hole, non-closure was seen in one patient and one patient developed a retinal detachment. CONCLUSION: In conclusion, sub-2 mm MICS is a safe and effective technique in dealing with vitreoretinal disorders necessitating cataract surgery at the same time.

Nonprogressive tractional inferior retinal elevation in intermediate uveitis.

PURPOSE: To describe inferior peripheral retinal elevations associated with intermediate uveitis. METHODS: Retrospective review. RESULTS: Eleven eyes of 7 patients developed inferior retinal elevation secondary to intermediate uveitis. Six eyes (54.6%) were believed to have tractional retinoschisis, 2 (18.2%) had tractional retinal detachment, and the remaining 3 (27.3%) had flat retinal elevation of indeterminate type. In 10 eyes there was no evidence of progression during a mean 4-year follow-up. One eye developed extended tractional elevation with macular pucker and failed to respond to surgery. At the most recent visit, visual acuity ranged from 6/5 to NPL with a median of 6/12. CONCLUSION: Intermediate uveitis may cause inferior peripheral retinal elevation. The authors propose that preretinal and pars plana gliosis resulting from chronic pars planitis exerts traction on peripheral retina, causing elevation, but infer that such elevation removes traction and is self-limiting. Surgery should be reserved only for macula threatening lesions.

Safety of cisplatin after severe hypersensitivity reactions to carboplatin in patients with recurrent ovarian carcinoma.

BACKGROUND: Carboplatin is a milestone drug against ovarian carcinoma; it is used both in front-line and second-line chemotherapy. Hypersensitivity reactions to carboplatin may occur during the treatment as salvage therapy. The purpose of this study was to describe the feasibility of the replacing of carboplatin with cisplatin in patients presenting with severe hypersensitivity reactions to carboplatin. PATIENTS AND METHODS: Ten consecutive patients with platinum-sensitive, recurrent ovarian carcinoma, presenting with moderate/severe hypersensitivity reactions to carboplatin were treated with cisplatin 60 mg/m2 from January 2000 to December 2002. Hypersensitivity reactions consisted of respiratory distress (chest tightness, wheezing, dyspnea), urticaria/erythema with tachycardia, facial swelling and hypotension. RESULTS: The total number of cisplatin cycles given was 44 (range 2-5). The treatment with cisplatin was generally well tolerated. No serious allergic reactions occurred. A mild allergic reaction was recorded (urticaria) in only one case, after one cycle of cisplatin, and the patient was not rechallenged because of progressive disease. No reductions of chemotherapy doses were needed. CONCLUSION: To date, platinum-based regimens remain the most effective treatment in recurrent platinum-sensitive ovarian cancer with a high rate of objective responses. Although our experience is limited, we suggest that, under anesthesiologic surveillance and providing immunologic blockade, the replacement of carboplatin salvage therapy with cisplatin can be considered a safe therapeutic strategy in patients who cannot continue carboplatin due to allergic reactions.

Simulation of mercury capture by activated carbon injection in incinerator flue gas. 1. In-duct removal.

A detailed model for the in-duct mercury capture in incinerator flue gas by powdered activated carbon injection is presented. Material balances on mercury in both gaseous and adsorbed phases are carried out along the duct length and inside the activated carbon particles, taking into account mass transfer resistances and adsorption kinetics. The set of the coupled partial differential equations is transformed by means of an orthogonal collocation technique and integrated using a Runge-Kutta method with adaptive stepsize control. The model has been applied to several sorbents of practical interest, whose parameters have been evaluated from available literature data. The values and range of the operating variables have been chosen in order to simulate typical incinerators operating conditions. Results of simulations indicate that large sorbent loadings in the duct are needed to obtain high mercury removal efficiencies, due to the short residence times. As a consequence very low utilization of the sorbents is achieved in any case. To minimize the sorbent feed rate it is particularly advisable to use a reactive sorbent and to lower the operating temperature as much as possible. Improvements in the mercury capture performance can be obtained also by increasing the in-duct particles residence time and by decreasing the sorbent particles size. Model results are compared with available relevant full scale data.

Simulation of mercury capture by activated carbon injection in incinerator flue gas. 2. Fabric filter removal.

Following a companion paper focused on the in-duct mercury capture in incinerator flue gas by powdered activated carbon injection, this paper is concerned with the additional mercury capture on the fabric filter cake, relevant to baghouse equipped facilities. A detailed model is presented for this process, based on material balances on mercury in both gaseous and adsorbed phases along the growing filter cake and inside the activated carbon particles,taking into account mass transfer resistances and adsorption kinetics. Several sorbents of practical interest have been considered, whose parameters have been evaluated from available literature data. The values and range of the operating variables have been chosen in order to simulate typical incinerators operating conditions. Results of simulations indicate that, contrary to the in-duct removal process, high mercury removal efficiencies can be obtained with moderate sorbent consumption, as a consequence of the effective gas/sorbent contacting on the filter. Satisfactory utilization of the sorbents is predicted, especially at long filtration times. The sorbent feed rate can be minimized by using a reactive sorbent and by lowering the filter temperature as much as possible. Minor benefits can be obtained also by decreasing the sorbent particle size and by increasing the cleaning cycle time of the baghouse compartments. Reverse-flow baghouses were more efficient than pulse-jet baghouses, while smoother operation can be obtained by increasing the number of baghouse compartments. Model results are compared with available relevant full scale data.

Genes from mycoparasitic fungi as a source for improving plant resistance to fungal pathogens.

Disease resistance in transgenic plants has been improved, for the first time, by the insertion of a gene from a biocontrol fungus. The gene encoding a strongly antifungal endochitinase from the mycoparasitic fungus Trichoderma harzianum was transferred to tobacco and potato. High expression levels of the fungal gene were obtained in different plant tissues, which had no visible effect on plant growth and development. Substantial differences in endochitinase activity were detected among transformants. Selected transgenic lines were highly tolerant or completely resistant to the foliar pathogens Alternaria alternata, A. solani, Botrytis cinerea, and the soilborne pathogen Rhizoctonia solani. The high level and the broad spectrum of resistance obtained with a single chitinase gene from Trichoderma overcome the limited efficacy of transgenic expression in plants of chitinase genes from plants and bacteria. These results demonstrate a rich source of genes from biocontrol fungi that can be used to control diseases in plants.

Potential of genes and gene products from Trichoderma sp. and Gliocladium sp. for the development of biological pesticides.

Fungal cell wall degrading enzymes produced by the biocontrol fungi Trichoderma harzianum and Gliocladium virens are strong inhibitors of spore germination and hyphal elongation of a number of phytopathogenic fungi. The purified enzymes include chitinolytic enzymes with different modes of action or different substrate specificity and glucanolytic enzymes with exo-activity. A variety of synergistic interactions were found when different enzymes were combined or associated with biotic or abiotic antifungal agents. The levels of inhibition obtained by using enzyme combinations were, in some cases, comparable with commercial fungicides. Moreover, the antifungal interaction between enzymes and common fungicides allowed the reduction of the chemical doses up to 200-fold. Chitinolytic and glucanolytic enzymes from T. harzianum were able to improve substantially the antifungal ability of a biocontrol strain of Enterobacter cloacae. DNA fragments containing genes encoding for different chitinolytic enzymes were isolated from a cDNA library of T. harzianum and cloned for mechanistic studies and biocontrol purposes. Our results provide additional information on the role of lytic enzymes in processes of biocontrol and strongly suggest the use of lytic enzymes and their genes for biological control of plant diseases.

Parallel formation and synergism of hydrolytic enzymes and peptaibol antibiotics, molecular mechanisms involved in the antagonistic action of Trichoderma harzianum against phytopathogenic fungi.

Chitinase, beta-1,3-glucanase, and protease activities were formed when Trichoderma harzianum mycelia, grown on glucose as the sole carbon source, were transferred to fresh medium containing cell walls of Botrytis cinerea. Chitobiohydrolase, endochitinase, and beta-1,3-glucanase activities were immunologically detected in culture supernatants by Western blotting (immunoblotting), and the first two were quantified by enzyme-linked immunosorbent assay. Under the same conditions, exogenously added [U-14C]valine was incorporated in acetone-soluble compounds with an apparent M(r) of < 2,000. These compounds comigrated with the peptaibols trichorzianines A1 and B1 in thin-layer chromatography and released [U-14C]valine after incubation in 6N HCl. Incorporation of radioactive valine into this material was stimulated by the exogenous supply of alpha-aminoisobutyric acid, a rare amino acid which is a major constituent of peptaibols. The obtained culture supernatants inhibited spore germination as well as hyphal elongation of B. cinerea. Culture supernatants from mycelia placed in fresh medium without cell walls of B. cinerea did not show hydrolase activities, incorporation of [U-14C]valine into peptaibol-like compounds, and inhibition of fungal growth. Purified trichorzianines A1 and B1 as well as purified chitobiohydrolase, endochitinase, or beta-1,3-glucanase inhibited spore germination and hyphal elongation, but at concentrations higher than those observed in the culture supernatants. However, when the enzymes and the peptaibols were tested together, an antifungal synergistic interaction was observed and the 50% effective dose values obtained were in the range of those determined in the culture supernatants. Therefore, the parallel formation and synergism of hydrolytic enzymes and antibiotics may have an important role in the antagonistic action of T. harzianum against fungal phytopathogens.