Plasmid DNA replication and topology as visualized by two-dimensional agarose gel electrophoresis

During the last 20 years, two-dimensional agarose gel electrophoresis combined with other techniques such as Polymerase Chain Reaction, helicase assay and electron microscopy, helped to characterize plasmid DNA replication and topology. Here we describe some of the most important findings that were made using this method including the characterization of uni-directional replication, replication origin interference, DNA breakage at the forks, replication fork blockage, replication knotting, replication fork reversal, the interplay of supercoiling and catenation and other changes in DNA topology that take place as replication progresses.

A redundancy of processes that cause replication fork stalling enhances recombination at two distinct sites in yeast rDNA

DNA recombination was investigated by monitoring integration at the rDNA of a circular minichromosome containing a 35S minigene and a replication fork barrier (RFB). The effects of replication fork stalling on integration were studied in wild-type, FOB1Delta, SIR2Delta and the double mutant FOB1DeltaSIR2Delta cells. The results obtained confirmed that Sir2p represses and replication fork stalling enhances integration of the minichromosome. This integration, however, only took place at two distinct sites: the RFB and the 3' end of the 35S gene. For integration to take place at the 35S gene, replication fork stalling must occur at the 3' end of the gene in both the minichromosome and the chromosomal repeats. Integration at the RFB, on the other hand, occurred readily in FOB1Delta cells, indicating that more than a single mechanism triggers homologous recombination at this site. Altogether, these observations strongly suggest that the main role for replication fork stalling at the rDNA locus is to promote homologous recombination rather than just to prevent head-on collision of transcription and replication as originally thought.

K-->pipi amplitudes from lattice QCD with a light charm quark

We compute the leading-order low-energy constants of the DeltaS=1 effective weak Hamiltonian in the quenched approximation of QCD with up, down, strange, and charm quarks degenerate and light. They are extracted by comparing the predictions of finite-volume chiral perturbation theory with lattice QCD computations of suitable correlation functions carried out with quark masses ranging from a few MeV up to half of the physical strange mass. We observe a DeltaI=1/2 enhancement in this corner of the parameter space of the theory. Although matching with the experimental result is not observed for the DeltaI=1/2 amplitude, our computation suggests large QCD contributions to the physical DeltaI=1/2 rule in the GIM limit, and represents the first step to quantify the role of the charm-quark mass in K-->pipi amplitudes. The use of fermions with an exact chiral symmetry is an essential ingredient in our computation.

Autologous bone-marrow mononuclear cell implantation in patients with severe lower limb ischaemia: a comparison of using blood cell separator and Ficoll density gradient centrifugation

Different studies have provided evidence that implantation of bone-marrow mononuclear cells (BM-MNC) into ischaemic limbs can improve tissue vascularization. Based on these results we performed a pilot study in patients with critical lower limb ischaemia to assess efficacy and safety of implantation of autologous BM-MNC. The amount and efficacy of BM-MNC purified either by an automated method or by a manual procedure were compared. Twelve patients with severe unilateral lower limb ischaemia were entered into this study. They were randomly assigned to be injected with BM-MNC sorted on a blood cell separator or isolated by density gradient on Ficoll-Hypaque. BM-MNC were implanted into the ischaemic legs. Patients were monitored with resting ankle-brachial pressure index (ABI), arterial oxygen saturation (SaO(2)), pain-free walking time and rest pain scale evaluation. The automated and manual methods used for mononuclear cell separation gave results not significantly different. Monitored variables improved in both groups. Improvement of ischaemic condition persisted during 24 weeks follow-up. Limb salvage was achieved in five cases. Our results indicate that BM-MNC implantation into ischaemic limbs is a practical, safe and effective method that may significantly contribute to the management of patients with limb ischaemia. The Ficoll method is a simple and effective procedure for BM-MNC concentration that may be useful, mainly in hospitals without sophisticated facilities.

Human papillomavirus in men: comparison of different genital sites

OBJECTIVE

To elucidate which anatomical sites need to be sampled to detect human papillomavirus (HPV) infection in the lower male genital tract.

METHOD

In an HPV survey of Mexican soldiers (median age 24 years; range 16-50 years), a cell sample from 2 cm deep into the distal urethra (group 1; n = 168 men), or 0.5 cm deep into the meatus urethralis (group 2; n = 414 men) was collected, along with a sample from the external genitalia. The different samples were tested for 27 HPV types using a polymerase chain reaction based strip assay.

RESULTS

HPV DNA was detected more frequently in external genitalia samples (46.4%) than in the urethra (20.8%) or meatus samples (12.1%). Lack of samples from the urethra or meatus would have led to 5.1% and 1.5% false HPV negative results, respectively. The most frequently detected high risk HPV types (HPV 59, 52, 51, and 16) were similar in different sites, whereas low risk types were found rarely in urethra samples.

CONCLUSIONS

The addition of cell samples from the meatus to those from external genitalia contributed negligibly to the evaluation of the prevalence of HPV in men. HPV detection was slightly improved by the addition of urethra samples, but the gain may not justify the discomfort of the procedure in large epidemiological studies.

Molecular determinants of Akt-induced keratinocyte transformation

The PI3K/PTEN/Akt signaling pathway has emerged in recent years as a main player in human cancers, increasing proliferation and decreasing apoptosis of transformed cells, and thus becoming a potential target for therapeutic intervention. Our previous data have demonstrated that Akt-mediated signaling is of a key relevance in the mouse skin carcinogenesis system, one of the best-known models of experimental carcinogenesis. Here, we investigated the involvement of several pathways as mediators of Akt-induced increased proliferation and tumorigenesis in keratinocytes. Tumors produced by subcutaneous injection of Akt-transformed keratinocytes showed increased Foxo3a phosphorylation, but no major alterations in p21(Cip1/WAF1), p27(Kip1) or mdm2 expression and/or localization. In contrast, we found increased expression and nuclear localization of DeltaNp63, beta-catenin and Lef1. Concomitantly, we also found increased expression of c-myc and CycD1, targets of the beta-catenin/Tcf pathway. Such increase is associated with increased phosphorylation and stabilization of c-myc protein as well as increased translation of c-myc and CycD1 due to mTOR activation. Using immunohistochemistry approaches in samples of oral dysplasias and human head and neck squamous cell carcinomas, we confirmed that increased Akt activation significantly correlates with increased DeltaNp63 and CycD expression, c-myc phosphorylation and nuclear accumulation of beta-catenin. Collectively, these results demonstrate that Akt is able to transform keratinocytes by specific mechanisms involving transcriptional and post-transcriptional processes.

The effect of selection for growth rate and slaughter age on carcass composition and meat quality traits in rabbits1

The effect of selection for growth rate on carcass and meat quality was assessed by comparing selected and control populations of rabbits measured at the same stage of maturity and slaughtered at 9 and 13 wk of age. Embryos belonging to Generation 7 were frozen, thawed, and implanted in does to produce the control group. The control group was formed from the offspring of the embryos belonging to the Generation 7. Selected animals belonging to Generation 18 (S) were compared with contemporary animals of the control group (C). Carcasses were dissected and measured according to World Rabbit Science Association recommended practices. When animals were compared at similar degrees of maturity, selection for growth rate did not produce a negative effect on carcass and meat quality. There was no increase in fat content of the carcass, and there was an improvement of the meat:bone ratio with selection, with a difference between C and S groups of -0.42. However, the carcasses of S animals have 1.45% lower water-holding capacity. Carcass quality changed markedly with animal age. Heavy rabbit carcasses had lower organ percents and a higher loin percent. Dissectible and i.m. fat content were higher in older rabbits, with older animals having 0.97 and 0.79% more dissectible and i.m. fat content, respectively. Meat quality traits improved with age of slaughter, although there was an increase in glycolytic metabolism. Results from this study indicate that selection for growth rate has little effect in carcass and meat quality when rabbits are measured at the same stage of maturity.

Surgical treatment of intracranial hypertension in encephalic cryptococcosis

The incidence of cryptococcosis has risen sharply together with the growing number of patients with Acquired Immunodeficiency Syndrome (AIDS). Cryptococcal meningitis is nowadays the most common intracranial non-viral infection in such cases. One of its most serious complications is intracranial hypertension (ICH), a situation that can lead either to early death, or disabling sequelae. The authors analyse a series of 10 cases of encephalic cryptococcosis with ICH, and describe the clinical course, diagnosis, medical and surgical treatment, and evolution. The physiopathology of ICH in these patients is discussed, proposing placement of a ventriculo-peritoneal shunt as the primary and emergency treatment, even when ventricular enlargement might be absent. Although the present series is certainly small, from the preceding discussion and according to an extensive bibliographical review, our conclusion is that patients with encephalic cryptococcosis and uncontrollable ICH should receive surgical treatment, consisting of an emergency diversion of the CSF, because serial lumbar punctures are not enough to improve the clinical course, that if left to its natural evolution would lead to a fatal outcome in a short time. In spite of the fact that CSF shunts were carried out on immunocompromised patients, no superinfections occurred.

Carbon felt electrode design: application to phenol electrochemical determination by direct oxidation

In this paper, electrochemical behaviour of phenol in a carbon felt electrode is studied. An adsorption process on electrode surface that inhibits polymer formation after oxidation of phenol was confirmed. In this work we propose a phenol determination method based on direct electrochemical oxidation on carbon felt electrodes after an accumulation process.

Development of cost-effective Hordeum chilense DNA markers: molecular aids for marker-assisted cereal breeding

Hordeum chilense is a potential source of useful genes for wheat breeding. The use of this wild species to increase genetic variation in wheat will be greatly facilitated by marker-assisted introgression. In recent years, the search for the most suitable DNA marker system for tagging H. chilense genomic regions in a wheat background has lead to the development of RAPD and SCAR markers for this species. RAPDs represent an easy way of quickly generating suitable introgression markers, but their use is limited in heterogeneous wheat genetic backgrounds. SCARs are more specific assays, suitable for automatation or multiplexing. Direct sequencing of RAPD products is a cost-effective approach that reduces labour and costs for SCAR development. The use of SSR and STS primers originally developed for wheat and barley are additional sources of genetic markers. Practical applications of the different marker approaches for obtaining derived introgression products are described.

Differential expression of Ran GTPase during HMBA-induced differentiation in murine erythroleukemia cells

Murine erythroleukemia (MEL) cells undergo erythroid differentiation in vitro when treated with hexamethylene bisacetamide (HMBA). To identify genes involved in the commitment of MEL cells to differentiate, we screened a cDNA library constructed from HMBA-induced cells by differential hybridization and isolated GTPase Ran as a down-regulated gene. We observed that Ran was expressed in a biphasic mode. Following a decrease in mRNA level during the initial hours of induction, Ran re-expressed at 24-48 h, and gradually declined again. To investigate the role of Ran during MEL differentiation we constructed MEL transfectants capable to express or block Ran mRNA production constitutively. No effects were observed on cell growth and proliferation. Blockage of Ran, however, interfered with MEL cell differentiation resulting in a decrease of cell survival in the committed population.