Biomedical subjects

R Pérez

Publications and source records attributed to R Pérez.

At least 19 recordsLinked to original sources

PubMed2006

Toxic effects of dissolved heavy metals on Desulfovibrio vulgaris and Desulfovibrio sp. strains.

Biological treatment of metal-containing wastewaters with sulphate-reducing bacteria (SRB) is an attractive technique for the bioremediation of this kind of medium. In order to design a suitable engineering process to address this environmental problem, it is crucial to understand the inhibitory effect of dissolved heavy metals on these bacteria. Batch studies were carried out to evaluate the toxic effects of several heavy metal ions [Cr(III), Cu(II), Mn(II), Ni(II) and Zn(II)] on two cultures of SRB (Desulfovibrio vulgaris and Desulfovibrio sp.). The experimental data indicate that SRB show different responses to each metal. At the highest metal concentration tolerated for each metal, the precipitation levels for D. vulgaris were as follows: 24.7%-15 ppm Cr(III), 45%-4 ppm Cu(II), 60%-10 ppm Mn(II), 96%-8.5 ppm Ni(II) and 9%-20 ppm Zn(II). The corresponding values for Desulfovibrio sp. were: 25.5%-15 ppm Cr(III), 71%-4 ppm Cu(II), 66.2%-10 ppm Mn(II), 96.1%-8.5 ppm Ni(II) and 93%-20 ppm Zn(II). Results obtained in batch studies will be taken into account for the subsequent design of a sulphate-reducing bioreactor to reduce levels of heavy metals present in different types of contaminated media.

Cell Proliferation↗

PubMed2006

Chromosomal variation and genome size support existence of cryptic species of Triatoma dimidiata with different epidemiological importance as Chagas disease vectors.

The wide geographical distribution of Triatoma dimidiata, one of the three major vectors of Chagas disease, ranges from Mexico to northern Peru. Since this species occupies a great diversity of artificial and natural ecotopes, its eradication is extremely difficult. In order to assist control efforts, we used chromosome analyses and DNA amount as taxonomic markers to study genetic variability in populations of T. dimidiata from Mexico, Guatemala, El Salvador and Colombia. We differentiated three groups or cytotypes defined by characteristic chromosome C-banding patterns and genome size measured by flow cytometry. The three cytotypes are restricted to different geographic locations. Cytotype 1 occurs in Mexico (excluding Yucatán), Guatemala (excluding Petén), El Salvador and Colombia. Cytotype 2 occurs in Yucatán and cytotype 3 occurs in Petén. Cytotype 1, commonly associated with domestic and peridomestic environments but also inhabiting sylvatic ecotopes, is the most widespread and with major epidemiological significance. In contrast, the Yucatán cytotype inhabits wild ecotopes but increasingly enters houses, while the Petén cytotype appears exclusively sylvatic. We suggest that these cytotypes represent cryptic species of T. dimidiata with different epidemiological relevance as Chagas disease vectors. Poor ability to colonize human dwellings, together with their restricted geographic distribution, indicate that the Yucatán and Petén putative species probably have much less epidemiological significance than cytotype 1. Thus, the genetic markers we describe are powerful tools to differentiate cryptic species in T. dimidiata with different epidemiological significance, contributing to planning the most effective control measures.

Animals↗

PubMed2006

Effect of parasitism on the pharmacokinetic disposition of ivermectin in lambs.

The aim of this study was to investigate the effect of parasitism on plasma availability and pharmacokinetic behaviour of ivermectin (IVM) in lambs. Fourteen greyface Suffolk lambs (26.8 +/- 2.2 kg body weight) were selected for this study. Seven pairs of lambs were allocated into two groups in order to obtain an approximately even distribution. Group I (non-parasitized) was pre-treated by three repeated administrations of 5 mg/kg of fenbendazole (Panacur), in order to maintain a parasite-free condition. The lambs in group II (parasitized) did not receive any anthelmintic treatment and the natural infection was sustained by an oral inoculation of infective stages of nematode parasites. After the 85-day pre-treatment period both groups of animals were treated with IVM (200 microg/kg, Ivomec) by subcutaneous injection in the shoulder area. Both groups of animals were maintained under similar conditions of feeding and management. Blood samples were collected by jugular puncture at different times between 0.5 h and 25 days post-treatment. After plasma extraction and derivatization, samples were analysed by high-performance liquid chromatography with fluorescence detection. A computerized kinetic analysis was performed and data were compared using the unpaired Student's t-test. The parent molecule was detected in plasma between 30 min and either 12 (parasitized) or 20 (no parasitized) days post-IVM treatment. The area under the curve values of the parasitized group (75.2 +/- 15.5 ng x d/ml) were significantly lower that those observed in the parasite-free group (134.3 +/- 15.7 ng x d/ml). The mean residence time (MRT) of the parasitized group (2.93 +/- 0.16 days) was significantly lower than the MRT of healthy group (3.93 +/- 0.29 days). The results of this study have shown that a change in body condition followed by a parasitic infection is associated with significant changes in plasma disposition of IVM when it is administered subcutaneously to parasitized lambs. Therefore, variations in the condition induced by parasitism should be considered when these anthelmintics are used for treating parasitized animals.

Animals↗

PubMed2006

[Acute cholestatic hepatitis after atorvastatin reintroduction].

Consumption of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA) inhibitors, known as statins, has been associated with elevated transaminase levels but rarely with acute hepatitis. Recently, several cases of acute hepatitis secondary to atorvastatin therapy have been published. We report the case of a 72-year-old man who developed acute cholestatic hepatitis after reinitiating treatment with atorvastatin at a higher dose than that previously prescribed. After treatment discontinuation, the patient made a full recovery, with normalization of clinical and laboratory findings.

Acute Disease↗

PubMed2006

[Acute rejection of kidney transplant is associated with induction of replicative senescence in CD8+ T lymphocytes].

Acute renal rejection repeatedly activates immunocompromised CD8 + T cells. Maintained activation of CD8 + T cells can induce a process of replicative senescence. In the present study, we will evaluate in CD8 lymphocytes from patients undergoing acute renal rejection characteristics of replicative senescence such as: a) low expression of CD28 molecule; b) telomere shortening and c) increase production of proinflammatory cytokines. The study was carried out in CD8 + T cells from 14 patients transplanted without clinical evidences of acute renal rejection, 14 patients kidney transplanted with clinical and anatomopathological evidences of acute renal rejection, 8 healthy controls. The results shown that in peripheral blood and renal biopsy of patients with acute renal rejection there is a significant increment of the population of T cells CD28-CD8+, with short telomere length, as compared with healthy controls and patients without acute renal rejection. The presence of senescent cells was associated with high levels of IL-10 and IFN-Y in plasma and urine. In conclusion our study suggest that the CD8 + T cells of patients with acute renal rejection suffer a process of replicative senescence.

Adult↗

PubMed2005

[Advantages and characteristics of the laparoscopic approach in the elderly].

Both the age of the population and anesthetic and surgical techniques are advancing. Currently, 40% of surgical activity is performed in patients older than 65 years, who present a higher surgical risk than younger patients. The aim of treatment in the elderly is to provide the best possible quality of life, even though this represents a surgical challenge because of associated comorbidity and reduced cardiopulmonary reserve. From the moment at which laparotomy becomes an increased stress in the elderly, laparoscopic surgery can be particularly advantageous in this population. Therefore, minimally invasive surgery may have a greater impact in these individuals than in younger patients in reducing postoperative pain, cardiorespiratory complications, hospital stay, and recovery time before resuming physical activity. The recent advances in anesthesia, together with improved patient selection and perioperative cardiac care, and the general adoption of minimally invasive access have enabled more complex gastrointestinal procedures to be performed in the elderly. The factors that could influence the development of this type of approach in the elderly, as well as the precautions that should be taken, should be further analyzed.

Aged↗

PubMed2005

Preparation of AlFe nanoparticles by mechanical alloyed technique.

Small metallic particles (1-3 nm) have been obtained using mechanical alloying techniques. Analytical techniques such as scanning electron microscopy have been used for the morphological and chemical characterization of the AlFe alloyed powders. B, Ni and Ti have been explored as reinforced elements to the initial AlFe mixture. X-ray diffraction patterns and transmission electron microscopy (TEM) techniques have been employed for the structural characterization of the small metallic particles. Theoretical simulations based on molecular dynamics have been used to interpret some of the experimental structural results. Furthermore, theoretical simulations of HREM images based on the dynamical theory of electron diffraction have also been obtained and comparisons with the experimental results have been carried out. The complementary analyses determined that the produced clusters are basically AlFe alloyed nanoparticles immersed in a matrix and with multiple defected structures.

Aluminum↗

PubMed2005

Interstitial transfer factor as adjuvant immunotherapy for experimental glioma.

Glioblastoma multiform (GBM) is the most common tumour of the central nervous system in humans. Unfortunately its prognosis is poor and because of the lack of efficacious therapies, immunotherapy is a potential treatment. Transfer factors (TF) are low molecular weight dialysable products extracted from immune cells which transmit the ability to express delayed-type hypersensitivity and cell mediated immunity from sensitized donors to nonimmnune recipients. In this study, we determined the efficacy of TF as immunotherapy to treat experimental glioblastoma. We used TF obtained from immunized swine. We evaluated different doses of intratumoral TF (product of 4x10(6), 8x10(5) and 1.6x10(5) cells). The best dose (product of 4x10(6) cells) of TF was also combined with carmustine for experimental therapy in rats with C6 malignant glioma. Modifications in peripheral blood T lymphocyte counts ( CD2+, CD4+, CD8+ and NK) were evaluated by flow cytometry. Cytokine expression in the tumour was assessed by RT-PCR and apoptosis was evaluated using the sub G0 method. Intratumoral TF reduced significantly the tumour size, and increased CD2+, CD4+, CD8+ and NK cell counts, it also increased the percentage of apoptotic tumour cells and the percentage of tumour tissue expressing Th1 cytokines. We observed an additive antitumoral effect when TF was combined with chemotherapy.

Animals↗

PubMed2005

[Histoplasmosis in a renal transplant patient].

The case of a Spanish kidney transplant patient who developed disseminated histoplasmosis approximately one year and a half after transplantation without having previously visited or travelled to endemic areas of histoplasmosis is presented. To our knowledge this is the first case of this disease in a kidney transplant patient in Spain without epidemiologic antecedent. The study of anti-histoplasm antibodies by complement fixation of the donor and recipient did not safely clarify the mechanism of contagion.

Histoplasmosis↗

PubMed2004

Formation of atom wires on vicinal silicon.

The feasibility of creating atomic wires on vicinal silicon surfaces via pseudomorphic step-edge decoration has been analyzed for the case of Ga on Si(112). Scanning tunneling microscopy and density functional theory calculations indicate the formation of Ga zigzag chains intersected by quasiperiodic vacancy lines or "misfit dislocations." This structure strikes a balance between the system's drive towards chemical passivation and its need for strain relaxation in the atom chains. Spatially fluctuating disorder, intrinsic to the reconstruction, originates from the two symmetry-degenerate orientations of the zigzag chains on vicinal Si.

Journal Article↗

PubMed2004

Construction of an immunotoxin with the pore forming protein StI and ior C5, a monoclonal antibody against a colon cancer cell line.

Sticholysin I (StI), a potent cytolysin isolated from the sea anemone Stichodactyla helianthus, was linked to the monoclonal antibody (mAb) ior C5. StI acts by forming hydrophilic pores in the membrane of the attacked cells leading to osmotic lysis. ior C5 is a murine IgG1, which recognizes the tumor associated antigen (TAA) ior C2. The cytolysin and the mAb were coupled by using the heterobifunctional cross-linking reagent sulfosuccinimidyl 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SMCC). Two hybrid molecules composed by one ior C5 and one or two StI molecules were obtained (named conjugated I and II, respectively). The purified conjugates were evaluated by a binding affinity assay against an ior C2-positive colon cancer cell line (SW948). Both molecules were able to recognize the antigen (Ag) in the same way that unconjugated ior C5 does. The activity of both conjugates against human erythrocytes and SW948 cells was assessed. They lost most of their hemolytic activity but their residual activity was very similar. Nevertheless, when their cytotoxicity was studied on the SW948 cell line, only conjugate II killed efficiently the cells, indicating a specific mAb-Ag interaction. In this chimeric molecule the ratio between the cytotoxic and the hemolytic activity was larger than that of the free cytolysin. This fact indicates an increase of the specificity of the toxic effect toward the SW948 cell line and consequently an increase of the difference between its hemolytic and cytotoxic doses. The results herein support the feasibility of directing StI to the surface of cancer cells expressing ior C2 Ag via the mAb ior C5.

Adenocarcinoma↗

PubMed2004

Effect of an EGF-cancer vaccine on wound healing and inflammation models.

BACKGROUND: Epidermal growth factor (EGF) and its receptor (EGF-R) are attractive targets for cancer immunotherapy. Tolerance has been broken with an EGF-vaccine and antibodies against EGF have been produced in animals and in cancer patients. EGF also plays an important role in the inflammation stage of wound healing. Because this therapeutic approach may be of importance after surgery procedures in cancer patients, we decided to investigate the possible role of the EGF-vaccine in the croton-oil-induced ear edema and in the wound healing experimental animal models. MATERIALS AND METHODS: Mice were immunized with an EGF-vaccine by intramuscular injections and serum titers against EGF were measured through ELISA techniques. Control animals received saline. RESULTS: Immunized mice produced antibodies against EGF while no antibody titers could be measured in control animals. Croton oil applied to the inner ear surface of EGF-vaccine treated mice caused a 61.3% lower ear punch weight and a 60.2% lower myeloperoxidase activity than control mice. In the EGF-vaccine treated animals, planimetry measurements and histological analysis did not led to significant impairment in tissue repair. CONCLUSIONS: The EGF-vaccination in mice decreased the normal croton-oil-induced inflammation response, without apparent impairment in tissue healing.

Animals↗

PubMed2004

Development of a new disease-specific quality-of-life questionnaire to adults living with haemophilia.

A haemophilia-specific health-related quality-of-life questionnaire (named 'Hemofilia-QoL') was developed to assess quality-of-life in adults with haemophilia, and was psychometrically tested. Seventy-three interviews with haemophilia patients and health care professionals were used to generate the items included in the questionnaire, and expert ratings on the items formulated were used to screen them for potential omission. This was followed by psychometric testing in a sample of 35 patients. Preliminary psychometric testing of the revised questionnaire version, which contains 10 domains (physical health, physical role, joint damage, pain, treatment satisfaction, emotional role, mental health, social support), showed acceptable reliability (alpha = 0.94 for the Hemofilia-QoL total score) and validity, and this will be examined in a subsequent study with a larger patient sample.

Adolescent↗

PubMed2004

Antimicrobial activity of enterocin EJ97 against 'Bacillus macroides/Bacillus maroccanus' isolated from zucchini purée.

AIMS: Activity of the bacteriocin EJ97 produced by Enterococcus faecalis EJ97 against strains of 'Bacillus macroides/B. maroccanus' isolated from spoiled zucchini purée was investigated. METHODS AND RESULTS: The influence of several factors like bacteriocin concentration, incubation temperature, pH, growth medium and chemical perservatives on bacteriocin activity was investigated. Enterocin EJ97 [2 arbitrary units (AU) per millilitre] had a marked bactericidal effect on strain INRA P53-2 after 4 h of incubation at 37 degrees C, 24 h at 15 degrees C or 48 h at 4 degrees C. Activity was markedly reduced at pH values of 5.0 and 9.0, but was potentiated by sodium nitrite, sodium benzoate, sodium lactate and sodium tripolyphosphate. Inhibition of strain INRA P53-2 in a commercial vegetable purée required a 10-fold higher bacteriocin concentration. Strain EJ97 was able to grow and produce bacteriocin on vegetable purée, but no inhibition of strain INRA P53-2 was detected. CONCLUSIONS: The concentration-dependent bactericidal activity of enterocin EJ97 against strain INRA P53-2 was higher at 37 degrees C and neutral pH, and was potentiated by chemical preservatives. Although enterocin EJ97 was less active in vegetable purée, the concentrations providing bactericidal activity in this food matrix are practical for commercial use. SIGNIFICANCE AND IMPACT OF THE STUDY: Enterocin EJ97 may have a potential for use in the prevention of food spoilage caused by 'B. macroides/B. maroccanus'.

Anti-Bacterial Agents↗

PubMed2004

Human platelet antigen systems in allogeneic peripheral blood progenitor cell transplantation: effect of human platelet antigen mismatch on platelet engraftment and graft-versus-host disease.

BACKGROUND: Alloimmune incompatibility in allo-geneic stem cell transplantation (ASCT), pregnancy, and blood transfusion might trigger an immune response with clinical consequences. Human PLT antigens (HPAs), which play a significant role in pregnancy or blood transfusion-associated alloimmune thrombocytopenia, are also expressed on the surface of tissues affected by GVHD. Thus, HPA mismatch in HLA-identical ASCT could play a potential role in PLT engraftment and GVHD. STUDY DESIGN AND METHODS: We studied the HPA-1, -2, and -5 genotypes in Caucasian donors and patients involved in 77 HLA-identical ASCTs. We evaluated the association of HPA compatibility with clinical outcome, analyzing the relevance of host-versus-donor HPA incompatibility in PLT engraftment and donor-versus-host HPA incompatibility in GVHD. RESULTS: PLT engraftment and transfusion require-ments were similar in HPA-compatible and HPA-incompatible ASCT. Cases with severe thrombocytopenia or significant delayed PLT engraftment did not display host-versus-donor HPA incompatibility. Moreover, the incidence of GVHD did not correlate with HPA compatibility. CONCLUSION: Our results support no role for these antigens in immune complications of ASCT: PLT engraftment, requirement of PLT transfusions, and GVHD.

Adolescent↗

PubMed2003

Phonon softening, chaotic motion, and order-disorder transition in Sn/Ge(111).

The phonon dynamics of the Sn/Ge(111) interface is studied using high-resolution helium atom scattering and first-principles calculations. At room temperature we observe a phonon softening at the Kmacr; point in the (sqrt[3]xsqrt[3])R30 degrees phase, associated with the stabilization of a (3x3) phase at low temperature. That phonon band is split into three branches in the (3x3) phase. We analyze the character of these phonons and find out that the low- and room-temperature modes are connected via a chaotic motion of the Sn atoms. The system is shown to present an order-disorder transition.

Journal Article↗

PubMed2003

Nonlinear characterization with burst excitation of 1-3 piezocomposite transducers.

Ultrasonic transducers made with 1-3 connectivity piezocomposites are frequently used in Medical applications and nondestructive testing. When the transducer is used for special applications as, for instance air-coupled transmission, it is necessary to compensate for the high difference of acoustic impedance between transducer and medium using high amplitude pulses to generate high acoustic signal. Thus, the nonlinear behavior of the transducer must be taken into account in similar application conditions. The newly developed method, which performs the nonlinear characterization with burst signal excitation near the thickness resonance frequency, is based on the measure of the current as well as the vibration velocity of the piezocomposite transducer. The current of the stationary response is measured before the end of the burst signal excitation. Burst excitation enables us to measure the nonlinear characterization without producing overheating in the transducers. The amplitude level dependence of mechanical losses tandelta(m) and the stiffness increases |Deltac/c(0)| have been studied, as well as the velocity dependence of a point of the transducer, measured with a laser vibrometer. In this method, the power level applied to the transducers can be higher than other nonlinear measurement methods, providing measurements of high accuracy.

Equipment Design↗

PubMed2003

Comparative study of the efficacy of an induction dose of interferon-alpha2b with ribavirin compared with standard combined treatment in naive patients with chronic hepatitis C.

The efficacy and secondary effects of an induction dose of interferon-alpha2b (IFN-alpha2b) with ribavirin compared with standard combined treatment in naive patients with chronic hepatitis C infection were compared. A prospective study was undertaken between March 1998 and November 2001 in which 84 Spanish hospitals took part. Six hundred and fourteen naive patients (age range 18-65 years) diagnosed with chronic hepatitis C virus (HCV) infection and without cirrhosis or co-infection by other viruses, were included. Patients were divided into two groups. Group A (n = 304) received induction treatment with a daily dose of 5 MU of IFN-alpha2b for 4 weeks, followed by 5 MU three times a week with ribavirin (1000-1200 mg/day, according to weight) until completing 1 year of treatment. Group B (n = 310) received the standard dose of IFN-alpha2b of 3 MU three times per week for 48 weeks together with ribavirin (1000-1200 mg/day, according to weight). Both groups were completely comparable according to age, gender, body weight, transaminase levels, genotype, viral load and hepatic inflammatory activity (Knodell Index). No control group was included for ethical reasons. Pegylated interferon was not available at the time of the study. Serum baseline samples were collected for the determination of genotype. Samples were also collected at baseline, weeks 4, 12, 24, 48 and 72, in order to detect and quantify HCV-RNA. The efficacy of treatment was evaluated by means of sustained viral response (SVR) characterized by persistent negativity of HCV-RNA at the end of the follow-up period. At week 4, the response to treatment was greater in group A (49.6%) compared with group B (34.5%) (P = 0.0002), and was maintained until week 12 (64.1% compared with 55.8% respectively) (P = 0.03). These differences disappeared at week 24, when group A (69%) was compared with group B (65%) (NS). At week 48, the response rate for group A was 50.6% compared with group B 47.4% (NS), and at week 72, the SVR in group A was 46% compared with 40.3% for group B (NS). The global SVR was 43.1%. On analysing the response to treatment according to genotype and viral load, we found that the induction treatment was slightly superior in patients with genotype 1 and an elevated viral load (>2 x 10(6) copies/ml). They achieved a SVR in group A of 39.1% compared with 25.5% in group B (P < 0.05). However, this slight improvement obtained in group A, was achieved at the expense of a greater percentage of dropouts compared with group B (6.4% vs 2.2%, P < 0.01); a greater rate of side effects (58.5 vs 36.7%, P < 0.05) and also a greater percentage of neutropenia (3.1% vs 0.9%, P < 0.05). The induction treatment presented a better initial response, but this was not maintained at the end of treatment, and did not improve the results obtained with the standard treatment. Although the patients with genotype 1 and elevated viral load had a better response with the induction treatment, this was accompanied by a greater percentage of dropouts and secondary effects. It would be interesting to repeat this type of study in the future, using pegylated interferon.

Adolescent↗