Biomedical subjects
A Santos
Publications and source records attributed to A Santos.
On the radial distribution function of a hard-sphere fluid.
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RNA interference of the salivary gland nitrophorin 2 in the triatomine bug Rhodnius prolixus (Hemiptera: Reduviidae) by dsRNA ingestion or injection.
Mass sequencing of cDNA libraries from salivary glands of triatomines has resulted in the identification of many novel genes of unknown function. The aim of the present work was to develop a functional RNA interference (RNAi) technique for Rhodnius prolixus, which could be widely used for functional genomics studies in triatomine bugs. To this end, we investigated whether double-stranded RNA (dsRNA) can inhibit gene expression of R. prolixus salivary nitrophorin 2 (NP2) and what impact this might have on anticoagulant and apyrase activity in the saliva. dsRNA was introduced by two injections or by ingestion. RT-PCR of the salivary glands showed that injections of 15 microg of NP2 dsRNA in fourth-instar nymphs reduced gene expression by 75+/-14% and that feeding 1 microg/microL of NP2 dsRNA into second-instar nymphs (approx. 13 microg in total) reduced gene expression by 42+/-10%. Phenotype analysis showed that saliva of normal bugs prolonged plasma coagulation by about four-fold when compared to saliva of knockdown bugs. These results and the light color of the salivary gland content from some insects are consistent with the knockdown findings. The findings suggest that RNAi will prove a highly valuable functional genomics technique in triatomine bugs. The finding that feeding dsRNA can induce knockdown is novel for insects.
Endoscopic treatment of acute colorectal obstruction with self-expandable metallic stents: experience in a community hospital.
BACKGROUND: The purpose of this study was to evaluate the efficacy and security of treatment with self-expandable metallic stents for acute colonic obstruction. METHODS: Retrospectively, we analyzed our experience in placing colonic stents in patients with acute colonic obstruction. Sixty-two patients with malignant colon obstruction were sent to our hospital endoscopic unit from February 1999 through September 2003. The mean age was 75.21 years. A total of 63 self-expandable metallic stents were implanted. All procedures were done under endoscopic and fluoroscopic guidance. RESULTS: Technical success was obtained in 58 patients (93.54%). Clinical improvement and resolution of the obstruction were confirmed in 56 of these 58 patients (96.55%) within 48-72 h. Sixteen complications were observed in 11 patients (19%). Twelve cases were minor complications: five patients had pain and rectal tenesmus, and there were seven cases of distal migration of the stent. Four patients (6.9%) had severe complications. Three patients underwent surgery to resolve colonic perforations and one patient developed a colovesical fistula 7 months after stent placement. The stent was used as a bridge to the elective surgery in 22 patients (37.93%). The mean time between stent placement and surgery was 7.66 days (range, 2-20). The stent was used as a definitive palliative treatment in 36 patients (62.07%). CONCLUSION: Stenting was a useful treatment of acute malignant colonic obstruction. The use of stents as a "bridge to the elective surgery" allowed the intestinal preparation, general status restoration, and a one-stage operation with resection and primary reanastomosis. We have also used the stents as a definitive palliative treatment, avoiding surgery in those patients with a very widely metastatic disease or who cannot undergo operation because of comorbid underlying conditions.
Cardiac motion analysis from ultrasound sequences using nonrigid registration: validation against Doppler tissue velocity.
Early detection of cardiac motion abnormalities is one of the main goals of quantitative cardiac image processing. This article presents a new method to compute the 2-D myocardial motion parameters from gray-scale 2-D echocardiographic sequences, making special emphasis on the validation of the proposed technique in comparison with Doppler tissue imaging. Myocardial motion is computed using a frame-to-frame nonrigid registration technique on the whole sequence. The key feature of our method is the use of an analytical representation of the myocardial displacement based on a semilocal parametric model of the deformation using Bsplines. Myocardial motion analysis is performed to obtain displacement, velocity and strain parameters. Robustness and speed are achieved by introducing a multiresolution optimization strategy. To validate the method, velocity measurements in three different regions-of-interest in the septum have been compared with those obtained with Doppler tissue velocity in healthy and pathologic subjects. Regression and Bland-Altman analysis show very good agreement between the two different approaches, with the great advantage that the new method overcomes the angle-dependency limitations of the Doppler techniques, providing both longitudinal and radial measurements.
Fractionation of heavy metals in sludge from anaerobic wastewater stabilization ponds in southern Spain.
The analysis of heavy metals is a very important task to assess the potential environmental and health risk associated with the sludge coming from wastewater treatment plants (WWTPs). However, it is necessary to apply sequential extraction techniques to obtain suitable information about their bioavailability or toxicity. In this paper, a sequential extraction scheme according to the Standard, Measurements and Testing Programme of the European Commission was applied to sludge samples collected from ten anaerobic wastewater stabilization ponds (WSPs) located in southern Spain. Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Ti and Zn were determined in the sludge extracts by inductively coupled plasma atomic emission spectrometry. In relation to current international legislation for the use of sludge for agricultural purposes, none of the metal concentrations exceeded maximum permitted levels. Overall, heavy metals were mainly associated with the two less-available fractions (34% oxidizable metal and 55% residual metal). Only Mn and Zn showed the highest share of the available (exchangeable and reducible) fractions (25-48%).
Prebiotics and their long-term influence on the microbial populations of the mouse bowel.
Various prebiotics were orally administered to mice and the evolution of different microbial populations was studied. The administration of prebiotics significantly increased lactobacilli and bifidobacteria in the large bowel content. Ingestion of prebiotics specifically lowered microbial populations of sulphite-reducing clostridia. Xylo-oligosaccharides (XOS) increased lactobacilli by 10 fold and produced the highest counts of bifidobacteria. In XOS-treated mice, levels of sulphite-reducing clostridia decreased significantly. Prebiotics slightly reduced the amount of aerobic bacteria and significantly increased the number of anaerobes in both the small and the large bowel. These effects of prebiotics were reverted by the basal diet.
Demixing can occur in binary hard-sphere mixtures with negative nonadditivity.
A binary fluid mixture of nonadditive hard spheres characterized by a size ratio gamma = sigma(2)/sigma(1) < 1 and a nonadditivity parameter Delta = 2 sigma(12)/(sigma(1) + sigma(2)) - 1 is considered in infinitely many dimensions. From the equation of state in the second virial approximation (which is exact in the limit d--> infinity) a demixing transition with a critical consolute point at a packing fraction scaling as eta approximately d2(-d) is found, even for slightly negative nonadditivity, if Delta >-1/8 (ln gamma)(2). Arguments concerning the stability of the demixing with respect to freezing are provided.
Pair correlation function of short-ranged square-well fluids.
We have performed extensive Monte Carlo simulations in the canonical (NVT) ensemble of the pair correlation function for square-well fluids with well widths lambda-1 ranging from 0.1 to 1.0, in units of the diameter sigma of the particles. For each one of these widths, several densities rho and temperatures T in the ranges 0.1< or =rhosigma(3)< or =0.8 and T(c)(lambda) less or approximately T less or approximately 3T(c)(lambda), where T(c)(lambda) is the critical temperature, have been considered. The simulation data are used to examine the performance of two analytical theories in predicting the structure of these fluids: the perturbation theory proposed by Tang and Lu [Y. Tang and B. C.-Y. Lu, J. Chem. Phys. 100, 3079 (1994); 100, 6665 (1994)] and the nonperturbative model proposed by two of us [S. B. Yuste and A. Santos, J. Chem. Phys. 101 2355 (1994)]. It is observed that both theories complement each other, as the latter theory works well for short ranges and/or moderate densities, while the former theory works for long ranges and high densities.
The mitochondrial respiratory complex I is a target for 15-deoxy-delta12,14-prostaglandin J2 action.
The prostaglandin J2 derivative 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) is a very active compound with important effects on inflammation, apoptosis, and cell growth processes. To exert this broad range of effects, 15d-PGJ2 binds and alters the activity of diverse proteins, which consequently are postulated to be mediators of its action. Among them are the transcription factors peroxisome proliferator-activated receptor gamma and nuclear factor kappaB, which are thought to play an essential role in the antitumorigenic and anti-inflammatory actions of 15d-PGJ2. Here, we show that 15d-PGJ2, at micromolar concentrations, efficiently blocks state 3 oxygen consumption in intact nonsynaptic mitochondria isolated from rat cerebral cortex. This effect is attributable to the inhibition by this prostaglandin of the activity of the enzyme NADH-ubiquinone reductase (complex I) of the mitochondrial respiratory chain. In addition to this, 15d-PGJ2 dramatically increases the rate of reactive oxygen species generation by complex I. The inhibition by 15d-PGJ2 of complex I activity was abolished by dithiothreitol, which raises the possibility that adduct formation with a critical component of complex I accounts for the inhibitory effect of this prostaglandin. These results clearly identified mitochondrial complex I as a new target for 15d-PGJ2 actions.
Equation of state of nonadditive d-dimensional hard-sphere mixtures.
An equation of state for a multicomponent mixture of nonadditive hard spheres in d dimensions is proposed. It yields a rather simple density dependence and constitutes a natural extension of the equation of state for additive hard spheres proposed by us [A. Santos, S. B. Yuste, and M. Lopez de Haro, Mol. Phys. 96, 1 (1999)]. The proposal relies on the known exact second and third virial coefficients and requires as input the compressibility factor of the one-component system. A comparison is carried out both with another recent theoretical proposal based on a similar philosophy and with the available exact results and simulation data in d=1, 2, and 3. Good general agreement with the reported values of the virial coefficients and of the compressibility factor of binary mixtures is observed, especially for high asymmetries and/or positive nonadditivities.
Feasibility study of the use of similarity maps in the evaluation of oncological dynamic positron emission tomography images.
A preliminary study is presented on the potential role of similarity mapping (SM) in the evaluation of oncological dynamic 18F-fluorodeoxyglucose positron emission tomography studies, mainly in lesion localisation and detectability. Similarity maps were calculated using previously described (correlation coefficient (COR) and normalised correlation coefficient (NCOR)) and newly introduced similarity measures (sum of squares coefficient (SSQ), squared sum coefficient (SQS), sum of cubes coefficient (SC) and cubed sum coefficient (CS)). The results were evaluated using simulated and clinical data. The study revealed that the best-suited similarity measure for such applications was the CS similarity coefficient, which provided the best parametric images, delineating structures of interest and supporting the visual interpretation of data sets. It was shown that SM and standardised uptake value (SUV) images had comparable diagnostic performance, although SM was able to offer additional time-related information in a single image. For the case of colorectal recurrences (17 cases), the measured contrast values for the CS and SUV images were 2.36 +/- 0.47 and 4.12 +/- 0.42, respectively, whereas, for three cases of giant cell tumours, these values were 11.6 +/- 2.1 and 11.9 +/- 1.8, respectively.
[Squamous cell carcinoma in bladder extrophy].
Bladder extrophy is a rare congenital malformation that nowadays is surgically corrected in neonatal period. We present a case report of a 71-year-old male with a verrucous squamous cell carcinoma arising in a classical uncorrected form of bladder extrophy.
Influence of cadmium on the performance of an activated SBR sludge treatment.
High concentration of heavy metals is a toxic factor for most microorganisms. As a result, such metals give rise to severe disruption in wastewater treatment operations. It has been noticed, however, that biological systems may adapt to heavy metals when their concentration is limited. In fact, such systems can even produce some degree of metal elimination provided that an optimal exposure tempo is guaranteed. On the other hand, irreversible damage may occur when metal concentration is sufficiently high. It is the aim of the present study to report on the inhibiting effects due to Cadmium on the activated sludge treatment method. To that end, different Cd concentrations were tested (ranging from 0.25 to 14 mg l(-1)) in a Sequential Biological Reactor, using synthetic wastewater without recirculation. The feed water providing 325 mg l(-1) COD and 30 mg l(-1) NH4+ -N. The process was screened by checking elimination percentages for COD and ammonia, as well as the evolution of ciliate protozoa. In addition, research was carried out on Cd assimilation by the activated sludge system by means of measuring in the mixed liquor and in the effluent. Results showed a marked decrease in purification efficiency when Cd-concentration rose over 14 mg l(-1), in which case COD elimination dropped from 98% to 41% while ammonia elimination went down from 98% to 32%. The Sludge Biotic Index decreases to 0 at Cd concentrations above 10 mg l(-1).
A feasibility study of a personalized, internet-based compliance system for chronic disease management.
This paper describes a feasibility study on an Internet-based compliance system to provide personalized care for patients suffering from chronic diseases. Relevant medical trials from three different European countries provided preliminary evidence of the feasibility of the system and its efficacy in helping patients to manage their diseases at home. The study discusses further improvements not only for the C-Monitor system, but also for other Internet-based health-care services.
Management of gingival recession by the use of an acellular dermal graft material: a 12-case series.
BACKGROUND: Different soft tissue defects can be treated by a variety of surgical procedures. Most of these techniques require the palatal area as a donor site. Recently, an acellular dermal graft has become available that can substitute for palatal donor tissue. METHODS: This study describes the surgical technique for gingival augmentation and root coverage and the results of 12 clinical cases. A comparison between the three most popular mucogingival procedures for root coverage is also presented. RESULTS: The results of the 12 patients and the 26 denuded surfaces have shown that we can obtain a mean root coverage of 74% with the acellular dermal graft. Thirteen out of the 26 denuded surfaces had complete root coverage. The average increase in keratinized tissue was 1.19 mm. It seems that the long-term results of the cases are stable. CONCLUSION: The proposed technique of root coverage with an acellular dermal graft can be a good alternative to soft tissue grafts for root coverage, and it should be part of our periodontal plastic surgery armamentarium.
Rarity of DNA sequence alterations in the promoter region of the human androgen receptor gene.
The human androgen receptor (AR) gene promoter lies in a GC-rich region containing two principal sites of transcription initiation and a putative Sp1 protein-binding site, without typical "TATA" and "CAAT" boxes. It has been suggested that mutations within the 5'untranslated region (5'UTR) may contribute to the development of prostate cancer by changing the rates of gene transcription and/or translation. In order to investigate this question, the aim of the present study was to search for the presence of mutations or polymorphisms at the AR-5'UTR in 92 prostate cancer patients, where histological diagnosis of adenocarcinoma was established in specimens obtained from transurethral resection or after prostatectomy. The AR-5'UTR was amplified by PCR from genomic DNA samples of the patients and of 100 healthy male blood donors, included as controls. Conformation-sensitive gel electrophoresis was used for DNA sequence alteration screening. Only one band shift was detected in one individual from the blood donor group. Sequencing revealed a new single nucleotide deletion (T) in the most conserved portion of the promoter region at position +36 downstream from the transcription initiation site I. Although the effect of this specific mutation remains unknown, its rarity reveals the high degree of sequence conservation of the human androgen promoter region. Moreover, the absence of detectable variation within the critical 5'UTR in prostate cancer patients indicates a low probability of its involvement in prostate cancer etiology.
No topoisomerase I alteration in a neuroblastoma model with in vivo acquired resistance to irinotecan.
CPT-11 (irinotecan) is a DNA-topoisomerase I inhibitor with preclinical activity against neuroblastoma (NB) xenografts. The aim was to establish in vivo an NB xenograft resistant to CPT-11 in order to study the resistance mechanisms acquired in a therapeutic setting. IGR-NB8 is an immature NB xenograft with MYCN amplification and 1p deletion, which is sensitive to CPT-11. Athymic mice bearing advanced-stage subcutaneous tumours were treated with CPT-11 (27 mg kg(-1) day(-1) x 5) every 21 days (1 cycle) for a maximum of four cycles. After tumour regrowth, a new in vivo passage was performed and the CPT-11 treatment was repeated. After the third passage, a resistant xenograft was obtained (IGRNB8-R). The tumour growth delay (TGD) was reduced from 115 at passage 1 to 40 at passage 4 and no complete or partial regression was observed. After further exposure to the drug, up to 28 passages, the resistant xenograft was definitively established with a TGD from 17 at passage 28. Resistant tumours reverted to sensitive tumours after 15 passages without treatment. IGR-NB8-R remained sensitive to cyclophosphamide and cisplatin and cross-resistance was observed with the topoisomerase I inhibitor topotecan. No quantitative or qualitative topoisomerase I modifications were observed. The level of expression of multidrug resistance 1 (MDR1), MDR-associated protein 1 (MRP1) and, breast cancer resistance protein, three members of the ATP-binding cassette transporter family was not modified over passages. Our results suggest a novel resistance mechanism, probably not involving the mechanisms usually observed in vitro.