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Biomedical subjects

A Calle

Publications and source records attributed to A Calle.

At least 19 recordsLinked to original sources
PubMed2006

Multi-analyte SPR immunoassays for environmental biosensing of pesticides.

Multi-analyte detection of environmentally relevant pesticides is performed by using a two-channelled surface plasmon resonance (SPR) biosensor. The special design of the SPR instrument allows the determination of several analytes (DDT, chlorpyrifos and carbaryl) via different immobilization formats. First, simultaneous pesticide monitoring is possible by flowing chlorpyrifos, carbaryl or DDT samples separately over each channel of the SPR system, wherein their corresponding recognition element was previously immobilized. The second approach is based on the multiple and combined immobilization of several analyte recognition elements on the sensing surface of one individual flow cell. In this format, the analysis time for all three pesticides varied from 40 to 60 min depending on the number of regeneration cycles. In most cases, similar detection limits were attained for the target analyte irrespective of the assay format, with sensitivity values at the nanogram per litre level (18-50 ng L(-1)). The assay reproducibility was proved through the repeated use of the same sensor surface for over more than 200 assay cycles, whereas the absence of biosensor response to non-related analytes showed the specificity and reliability of the analysis. The SPR instrument, including optics, electronics and microfluidics, is already commercialised by the company SENSIA, SL.

Antibodies↗
PubMed2006

Optical immunosensor for fast and sensitive detection of DDT and related compounds in river water samples.

A surface plasmon resonance (SPR) based immunosensor has been developed for the monitoring of environmentally persistent pollutants like DDT, its metabolites and analogues in real water samples. A reusable immunosurface is provided via the covalent attachment of the analyte derivative to a self-assembled alkanethiol monolayer formed onto the SPR gold-thin layer. The regeneration of the sensor surface allowed the performance of 270 assay cycles within an analysis time of 20 min for each assay cycle. Immunoassays based on a binding inhibition format were performed by using two monoclonal antibodies (MAbs) with different selectivity. Low limits of detection (LODs), in the sub-nanogram per litre range, were attained for DDT-selective (15 ng L-1) and DDT group-selective immunoassays (31 ng L-1). Both assays were carried out in spiked river water samples without significant effect of the matrix. SPR measurements were validated using gas-chromatography-mass spectrometry. The comparison between methods was in good agreement showing an excellent correlation coefficient (r2=0.995). The SPR analysis of DDT proved to be three times more sensitive than colorimetric ELISAs without the need of labelling and a much lower time of response. Our SPR biosensor portable platform (beta-SPR) is already commercialised by the company SENSIA, S.L. (Spain).

Antibodies↗
PubMed2006

Highly sensitive detection of biomolecules with the magneto-optic surface-plasmon-resonance sensor.

The characteristics of a novel magneto-optic surface-plasmon-resonance (MOSPR) sensor and its use for the detection of biomolecules are presented. This physical transduction principle is based on the combination of the magneto-optic activity of magnetic materials and a surface-plasmon resonance of metallic layers. Such a combination can produce a sharp enhancement of the magneto-optic effects that strongly depends on the optical properties of the surrounding medium, allowing its use for biosensing applications. Experimental characterizations of the MOSPR sensor have shown an increase in the limit of detection by a factor of 3 in changes of refractive index and in the adsorption of biomolecules compared with standard sensors. Optimization of the metallic layers and the experimental setup could result in an improvement of the limit of detection by as much as 1 order of magnitude.

Biopolymers↗
PubMed2005

Determination of carbaryl in natural water samples by a surface plasmon resonance flow-through immunosensor.

The analysis of carbaryl in natural water samples was accomplished using a portable immunosensor based on surface plasmon resonance (SPR) technology. The assay was based on a binding inhibition immunoassay format with the analyte derivative covalently immobilized on the sensor surface. An alkanethiol self-assembled monolayer (SAM) was formed onto the gold-coated sensor surface to allow the reusability of the same sensing surface during 220 regeneration cycles. Reproducibility was evaluated by performing three independent assays in triplicate on 3 different days. The batch-assay variability was also calculated using three different gold-coated sensor surfaces. The intra- and inter-day relative standard deviation were 8.6 and 15.3%, respectively, whilst a variation of 7.4% in assay sensitivity was obtained by employing different sensor chips. The lowest detection limit, calculated as the concentration providing a 10% decrease of the blank signal, was of 1.38 microg L(-1). Matrix effects were also evaluated in different water types, showing I50 values (carbaryl concentrations that produced a 50% decrease of the blank signal) within the range of carbaryl standard curves in distilled water (2.78-3.55 microg L(-1)). The carbaryl immunoassay performance was validated with respect to conventional high-performance liquid chromatography-mass spectrometry (HPLC-MS). The correlation between methods was in good agreement (r2 = 0.998, 0.999 and 0.999) for the three types of natural water samples tested. A complete assay cycle, including regeneration, is accomplished in 20 min. All measurements were carried out with the SPR sensor system (beta-SPR) commercialised by the company SENSIA, SL (Spain). The small size and low-time of response of the beta-SPR platform would allow its utilization in real contaminated locations.

Biosensing Techniques↗
PubMed2004

Nanomechanics of the formation of DNA self-assembled monolayers and hybridization on microcantilevers.

Biomolecular interactions over the surface of a microcantilever can produce its bending motion via changes of the surface stress, which is referred to nanomechanical response. Here, we have studied the interaction forces responsible for the bending motion during the formation of a self-assembled monolayer of thiolated 27-mer single-stranded DNA on the gold-coated side of a microcantilever and during the subsequent hybridization with the complementary nucleic acid. The immobilization of the single-stranded DNA probe gives a mean surface stress of 25 mN/m and a mean bending of 23 nm for microcantilevers with a length and thickness of about 200 microm and 0.8 microm, respectively. The hybridization with the complementary sequence could not be inferred from the nanomechanical response. The nanomechanical response was compared with data from well-established techniques such as surface plasmon resonance and radiolabeling, to determine the surface coverage and study the intermolecular forces between neighboring DNA molecules anchored to the microcantilever surface. From both techniques, an immobilization surface density of 3 x 10(12) molecules/cm(2) and a hybridization efficiency of 40% were determined. More importantly, label-free hybridization was clearly detected in the same conditions with a conventional sensor based on surface plasmon resonance. The results imply that the nanomechanical signal during the immobilization process arises mainly from the covalent attachment to the gold surface, and the interchain interactions between neighboring DNA molecules are weak, producing an undetectable surface stress. We conclude that detection of nucleic acid hybridization with nanomechanical sensors requires reference cantilevers to remove nonspecific signals, more sensitive microcantilever geometries, and immobilization chemistries specially addressed to enhance the surface stress variations.

Base Sequence↗
PubMed2003

Infections in diabetic foot ulcers.

Foot ulcers and infections are common in diabetic patients. A 30-month-long descriptive study was conducted in our hospital in which we analyzed microbiological isolates of all patients admitted with diabetic foot infections. The predominant flora identified were Staphylococcus aureus and coagulase-negative Staphylococcus, followed by Enterococcus spp., Streptococcus spp., and enterobacteriaceaes. In 27 positive cultures (42%) polymicrobial flora were found. There were only 5% anaerobic bacteria. There appears to be a relationship between the sample collection system and microbiological isolates.

Journal Article↗
PubMed2000

Reduction of the cesarean delivery rate in Ecuador.

OBJECTIVE: This quasi-experimental study tested a method to safely reduce the rate of cesarean delivery in Ecuador. METHOD: Hospital policy was modified to provide co-management for cesarean candidates at the major maternity hospital in Quito. Cesarean rates before (n=14743) and after (n=12351) the intervention were compared by chi-square and multiple logistic regression with other major maternity hospitals (before, n=12514; after, n=9590). Characteristics of cesarean candidates who had vaginal or cesarean deliveries in the intervention hospital were compared by chi-square (n=1584). RESULT: Cesarean rates declined by 4.5% (P<0.001) in the intervention hospital. A smaller (2.1%, P<0.01) reduction occurred in the other major public hospital in Quito where students of the co-principal investigator attempted to reduce cesarean delivery. Cesarean rates were unchanged in the public maternity hospitals of other major cities. CONCLUSION: Case co-management, a simple, locally appropriate, and inexpensive intervention, safely reduced surgical delivery, hospital stay and cost of care.

Cesarean Section↗
PubMed1999

Differential actions of the dopamine agonist bromocriptine on growth of SMtTW tumors exhibiting a prolactin and/or a somatotroph cell phenotype: relation to dopamine D2 receptor expression.

Dopamine (Da) and Da agonists are known to inhibit secretion and proliferation of normal and tumoral PRL cells, through receptors of D2 subtype. Because of the lack of an experimental model, the relationship between bromocriptine (BR) sensitivity and D2 receptor expression is poorly documented. Such a relationship was analyzed using five lineages of spontaneous transplantable rat pituitary tumors (SMtTW) exhibiting different PRL/GH phenotypes. From plasma PRL and GH concentrations of rats bearing the tumors and tumor messenger RNA contents, tumors were classified as PRL (SMtTW2), somatotroph (SMtTW10), or somatomammotroph (SMtTW5) tumors. Two lineages (SMtTW3 and SMtTW4) represented variants producing PRL and GH but with a high predominance of PRL. With the exception of SMtTW4 tumors, which were malignant, all the tumors were benign and differed in their growth rate. Hormone production and growth of tumors with a PRL or a somatomammotroph phenotype were reduced by about 90% under BR treatment, whereas somatotroph tumors and the PRL malignant tumors were totally insensitive to BR. D2 receptor messenger RNA was present in all BR-sensitive tumors and was not detected in BR-resistant tumors. In conclusion, using five lineages of SMtTW tumors that are representative of the most frequent tumors encountered in human pituitary pathology, we found a full concordance between tumor responses to BR and the expression of D2 receptor by the tumors. The identification of a tumor lineage with a malignant phenotype, secreting high amounts of PRL and presenting a resistance to BR, supports the idea that Da-resistant prolactinomas are aggressive tumors.

Animals↗
PubMed1996

The effect of chronic intestinal parasitic infection on maternal and perinatal outcome.

OBJECTIVE: The main objective of this prospective cohort study was to investigate the prevalence, risk factors and maternal-perinatal consequences of chronic asymptomatic intestinal parasitic infection during pregnancy. METHODS: Prenatal patients (n=91) attending a public clinic in Quito, Ecuador, were followed during the third trimester. Intestinal parasitic, nutritional status, sociodemographic/sanitation indicators and fetal outcome data were collected and analyzed using multivariate ANOVA and regression techniques. RESULTS: Most subjects (93%) were infected with at least one species of pathogenic intestinal parasite: 88% with Entamoeba histolytica. Greater parasite burdens were associated with poorer maternal iron status and reduced fetal growth. In particular, a high E. histolytica load was associated with decreased maternal serum hemoglobin (P=0.002) and hematocrit levels (P=0.01), iron deficiency anemia (P=0.026), and indicators of diminished intrauterine growth including a decreased ponderal index (P=0.04), mid-arm circumference (P=0.01), and mid-arm/head circumference ratio (P=0.003). CONCLUSION: Asymptomatic intestinal parasitic infection represents a hidden risk factor for maternal iron deficiency anemia and fetal growth retardation.

Adult↗
PubMed1996

Cyclic guanosine 3',5' monophosphate concentrations in pre-eclampsia: effects of hydralazine.

OBJECTIVE: To elucidate the role of the L-arginine:nitric oxide pathway in pregnancy and pre-eclampsia. PARTICIPANTS: Pregnant women (nulliparous, age <25 years). Normotensive pregnancy (n=22) was defined when blood pressure remained at levels of <120/80 mmHg and there was no proteinuria. Women with pre-eclampsia (n=22) had blood pressure measurements of >140/90 mmHg and proteinuria of >300 mg/l. Nonpregnant normotensive women (n=22) were studied as controls. STUDY DESIGN: Blood samples were taken for measurements of ionised calcium, atrial natriuretic factor, cyclic guanosine 3'5' monophosphate (GMP),arginine and asymmetric dimethylarginine. Urine samples were collected for determination of cyclic GMP excretion. Cyclic GMP concentrations were also determined in 12 women with severe pre-eclampsia before and after treatment with hydralazine. RESULTS: L-arginine, asymmetric dimethylarginine and atrial natriuretic factor were not different in any group. Cyclic GMP concentrations in plasma [0.94 (SD 0.23) nM] as well as in urine [50.1 (SD 15.7) microM] were increased significantly (P<0.05) in normal pregnancy compared to nonpregnant controls [plasma mean 0.46 (SD 0.12) nM and urine mean 18.4 (SD 10.3) microM], but not in the pre-eclampsia group [plasma mean 0.48 (SD 0.10) nM and urine mean 24.1 (SD 14.5) microM]. Concentrations of cyclic GMP in plasma and urine increased significantly (P<0.05) in women treated with hydralazine. CONCLUSIONS: The differences in cyclic GMP concentrations may reflect differences in nitric oxide production. Hydralazine increases cyclic GMP concentrations in severely pre-eclamptic women. This action could explain the antihypertensive effect of hydralazine.

Adult↗
PubMed1996

Cell-to-cell communication in the anterior pituitary: evidence for gap junction-mediated exchanges between endocrine cells and folliculostellate cells.

The ability of rat anterior pituitary cells to communicate through gap junctions (GJ) was studied using a fluorescent molecule, Lucifer Yellow (LY), which freely passes through GJ channels. The probe was introduced into the cell cytoplasm by using either the cut-end loading method on intact tissue, or cell microinjection on cultured cells. The identification of communicating cells was performed by immunofluorescence labeling of specific hormones in endocrine cells and of S100 protein in folliculostellate (FS) cells. Rat anterior pituitary cells in their physiological organization, i.e. in the intact tissue, exhibited a high level of coupling through GJ. LY-labeled cells were found up to 300-microns apart from its site of introduction. The communicating cells were primarily PRL cells, GH cells, and FS cells. Only a few LH, TSH, and ACTH cells were labeled with LY. Anterior pituitary cells, isolated from the rat tissue by mild protease treatment and cultured for 3 days, reestablished functional GJ as demonstrated by microinjection of LY into individual cells. By immunolabeling of specific hormones and/or S100 protein, we found a GJ coupling between FS cells, and between FS cells and endocrine cells, including PRL cells. The communication between FS cells was by far the most frequent. In conclusion, we demonstrate the presence of functional GJ between anterior pituitary cells of the same type and between anterior pituitary cells having distinct differentiated functions.

Animals↗
PubMed1992

[Incidence and surgical treatment of extrahepatic abdominal hydatidosis].

From 1974 to May 1991, 417 patients with abdominal hydatid cyst disease were surgically treated. Twenty-eight patients had extrahepatic abdominal cyst disease (6.7%). Six patients had only extrahepatic disease where as 22 had associated hepatic and extrahepatic cysts. Most frequent sites were the peritoneum (52.7%), the spleen (22%) and pelvis (11%). Fourteen out of the 14 CT scans performed, detected the extrahepatic cysts. The preferred surgical technique was total closed cystectomy (in hepatic and extrahepatic cysts). Resection of the organ affected (8 splenectomies, 1 nephrectomy, 1 partial vertebral resection, 1 orchiectomy and 1 salpingo-oophorectomy) was also performed. There was no mortality and morbidity was 32.1%: 3 intraabdominal abscesses, 1 intraabdominal haemorrhage, 4 biliary fistulae and 1 partial necrosis of the large bowel. Only 3 patients (neither were treated with mebendazole) were reoperated on for recurrent peritoneal hydatic cyst.

Abdomen↗
PubMed1987

Mechanical properties and biocompatibility of two polyepoxy matrices: DGEBA-DDM and DGEBA-IPD.

The aim of this paper was to study the biocompatibility and mechanical properties of materials for orthopaedic and odontologic surgical use. The products used were obtained by polycondensation of a diepoxy resin (DGEBA) with two curing agents (DDM or IPD). The materials present a slight swelling in liquid medium and their thermomechanical properties are hardly affected after 12 month implantation. The absence of molecular desorption in isotonic liquid and human serum confirms their hydrolytic stability and thus their inertia. These materials do not give rise to an intolerance reaction by neighbouring tissues during implantation time (1 d to 12 month).

Aniline Compounds↗
PubMed1987

Interactions between fibroblasts and a reconstituted basement membrane matrix.

A gel-like reconstituted basement membrane matrix containing type IV collagen, laminin, entactin, nidogen, and heparan sulfate proteoglycan was used to examine the interactions between normal calf skin fibroblasts and basement membranes. Within 6 h after seeding, fibroblasts initiated a migration that resulted in the formation of a cellular network after 1 day of culture on top of the gel. Electron microscopy revealed that fibroblasts were able to remodel the basement membrane matrix by penetrating into the gel (from day 3), depositing fibronectin and collagen fibers, and retracting this extracellular matrix. Fibroblasts cultured on the Engelbreth-Holm-Swarm reconstituted basement membrane matrix displayed ultrastructural features characterized by a poor synthetic apparatus (rough endoplasmic reticulum and Golgi vesicles), a large cytoskeleton, and intracytoplasmic vesicles containing laminin. Thus the reconstituted basement membrane matrix is remodeled by skin fibroblasts, and reciprocally their ultrastructural morphologic features are affected by this matrix.

Animals↗
PubMed1987

Iron status in Ecuadorian pregnant women living at 2,800 m altitude: relationship with infant iron status.

An evaluation of iron status was performed in 84 pregnant women at delivery (and in cord blood from their newborn) and in a control group of 32 menstruating women living in Quito (2800 m altitude). Anemia as defined according to the WHO references adjusted to altitude was observed in 46% of pregnant women. Iron deficiency was defined as the combination of a low serum ferritin level (12 micrograms/l or less) and a low transferrin saturation percentage (less than 16%). A moderate elevation in the serum ferritin concentration (between 13 and 50 micrograms/l) associated with low transferrin saturation indicated iron deficiency in an inflammatory context. Iron deficiency was present in 46% of pregnant women. Anemia was associated with iron deficiency in 59% of cases. A correlation between maternal and cord blood hemoglobin was found and some iron parameters in cord blood were related to maternal iron status, and especially to maternal iron stores assessed by serum ferritin concentration.

Altitude↗
PubMed1986

Ultrastructure of multilayered cultures of human gingival epithelial cells: attachment to enamel surfaces in vitro.

Human gingival cells were collected using an enzymatic procedure and seeded on a feeder layer of irradiated mouse 3T3 fibroblasts. Epithelial cells generate stratified colonies ultimately forming an epithelium which was studied using electron microscopy. When this epithelium-like structure was dispased and transferred to enamel surfaces, the relationship between basal cells and enamel corresponded to half-desmosomes and a discontinuous extracellular matrix.

Adult↗