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Biomedical subjects

I Contreras

Publications and source records attributed to I Contreras.

At least 19 recordsLinked to original sources
PubMed2007

Effects of breed on follicular dynamics and oestradiol secretion during the follicular phase in sheep.

Current study evaluates effects from breed and management background on follicular dynamics and endocrine output during the follicular phase of sheep oestrous cycle. Follicular phases were synchronized with three cloprostenol doses, 10 days apart, in three groups of 10 females of different non-prolific Spanish breeds (Manchega, Rubia del Molar and Negra de Colmenar). Development of all follicles reaching antral diameters >or=2 mm was assessed by daily transrectal ultrasonographies, whereas follicular function was evaluated by measurement of plasma oestradiol concentrations. All the ovulatory follicles were present at induced luteolysis in Manchega sheep, while a 93.7% were detected in Rubia del Molar and Negra de Colmenar ewes. The mean size of these ovulatory follicles was similar between breeds at 0 h, but their growth rates were higher in Manchega ewes, reaching a larger size at oestrous detection than in Negra de Colmenar and Rubia del Molar sheep (p < 0.05). Conversely, the oestradiol levels increased with time in Rubia del Molar and Negra de Colmenar (p < 0.05); whilst remained stable in Manchega females. However, the patterns of follicular turnover were similar between breeds. These results indicate that, though differences in follicular size and size distribution, patterns of follicular turnover in sheep are affected neither by the breed nor by the background of management and selection.

Animals↗
PubMed2006

Effects of breed on kinetics of ovine FSH and ovarian response in superovulated sheep.

Embryo production is a useful tool for ex situ conservation of endangered species and breeds, despite a high variability in the ovarian response to superovulatory treatments. The current study evaluated the incidence and mechanisms of genetic factors in such variability, by determining the pharmacokinetics and pharmacodynamics of a standard treatment with ovine FSH (oFSH) in two endangered Spanish sheep breeds (Rubia del Molar, R, and Negra de Colmenar, N) in comparison to Manchega ewes (M, control group). In the first experiment, pharmacokinetics of an i.m. single dose of 1.32 mg of oFSH was evaluated in seven animals of each breed. Plasma FSH concentrations reached their maximum at 4h post-administration in all the ewes, but several of the kinetic parameters (plasma FSH concentration at 4h post-administration, maximum plasma FSH concentration, C(max), and both the area under the plasma concentration-time curve extrapolated to the infinite, AUC(inf), and to the last moment of sampling, AUC(last)) were higher in the N group. In the second trial, 10 animals of each breed were superovulated using eight decreasing doses of oFSH (3 x 1.32 mg, 2 x 1.10 mg, and 3 x 0.88 mg). The R group, when compared to N and M, showed both a higher number of corpora lutea (13.7+/-0.6 versus 10.0+/-0.4 in N and 9.8+/-0.6 in M, P<0.05 for both) and embryos (7.9+/-0.8 versus 4.3+/-0.4 in N, P<0.05, and 6.7+/-0.5 in M, n.s.). Evaluation of pharmacokinetic and dynamic parameters showed that, although there was a trend for a higher hormone availability in R sheep, mean FSH plasma concentrations were similar between breeds (0.54+/-0.08 ng/ml for R, 0.45+/-0.05 ng/ml for N and 0.35+/-0.05 ng/ml for M). However, differences were found in the number of preovulatory follicles growing in response to the FSH treatment between R (24.4+/-2.2), M (18.9+/-1.5, n.s.) and N sheep (14.1+/-1.4; P<0.01). Thus, differences in embryo yields between breeds would be related to differences in the pattern of follicular growth in response to FSH treatment.

Animals↗
PubMed2006

[Side-effects of triamcinolone in young patients].

CASE REPORTS: Intravitreal triamcinolone is being increasingly employed for the treatment of macular diseases. We report two cases of intraocular pressure elevation and cataract formation after intravitreal triamcinolone therapy, and wonder if these complications are more likely when this agent is used in young patients. Intravitreal triamcinolone was injected into both eyes of the two young patients with chronic posterior and intermediate uveitis refractory to peribulbar and oral corticosteroid therapy. Chronic cystoid macular edema improved in both patients, however the intraocular pressure increased, requiring topical antihypertensive therapy, and this was followed by accelerated cataract formation. DISCUSSION: Young age and chronic inflammation could be associated with an intraocular pressure rise and subsequent cataract development after intravitreal triamcinolone.

Adolescent↗
PubMed2006

[Ultrasound biomicroscopy in deep sclerectomy with a new acrylic implant].

OBJECTIVE: To describe the ultrasound biomicroscopic (UBM) characteristics seen in patients who have undergone deep phaco-sclerectomy with a new acrylic implant (Esnoper). SUBJECTS, MATERIAL AND METHODS: UBM exploration was performed 12 months after deep phaco-sclerectomy in three patients with chronic open angle glaucoma. RESULTS: One year after surgery, all three patients had intraocular pressure levels under 15 mmHg and were on no treatment. All of them had an intrascleral space in UBM, in which the hyperechogenic implant was visible. CONCLUSIONS: The new non-absorbable implant has proven to be effective in these cases. Information provided by UBM is useful and assists in understanding the mechanism of action of deep sclerectomy.

Acrylic Resins↗
PubMed2005

Genetic analysis of antibiotic-resistance determinants in multidrug-resistant Shigella strains isolated from Chilean children.

A total of 162 clinical isolates of Shigella collected from children in a semi-rural community of Chile were examined for the presence of genetic determinants of resistance to ampicillin, chloramphenicol, tetracycline, and trimethoprim. Ampicillin resistance was most frequently associated with the presence of bla(OXA) in S. flexneri and with bla(TEM) in S. sonnei. The bla(OXA) gene but not bla(TEM) was located in class 1 integrons. The dhfrIa gene encoding for resistance to trimethoprim was associated to class 2 integrons and detected exclusively in S. flexneri, whereas dhfrIIIc was found in all S. sonnei strains and in 10% of the S. flexneri isolates. Cat, coding for choramphenicol resistance, and bla(OXA) genes were located in the chromosome in all cases, whereas tetA gene, coding for tetracycline resistance, and bla(TEM), dhfrIa and dhfrIIIc genes were found either in the chromosome or in conjugative plasmids. Our results show a heterogenous distribution of antibiotic-resistance determinants between S. flexneri and S. sonnei.

Blotting, Southern↗
PubMed2004

[Utility of bronchoalveolar lavage in immunocompromised children: diagnostic yield and complications].

OBJECTIVE: Immunocompromised children are at high risk for developing pneumonia due to opportunistic pathogens. The role of bronchoalveolar lavage (BAL) in the evaluation of such patients is still controversial. MATERIAL AND METHOD: We reviewed the hospital records of immunosuppressed patients with respiratory symptoms who had undergone BAL in the pediatric department of the Hospital Clinico de la Pontificia Universidad Católica of Chile. RESULTS: Sixty-eight BAL were performed on 54 children (mean age: 7.5 years) receiving wide-spectrum antibiotic treatment. The most frequent respiratory signs and symptoms were fever (90%) and cough and respiratory distress (81%); 18% had neutropenia and 43% thrombocytopenia. A specific pathogen was identified in BAL samples for 25 patients (37%). The pathogens isolated were bacteria in 21 cases, viruses in 6, Pneumocystis carinii in 5, fungi in 4, and Mycobacterium tuberculosis in one. Fourteen (19%) of the children who underwent BAL were on mechanical ventilation. Outcome was satisfactory in all cases. Twenty-one complications were recorded, 17 of which were minor (mild hypoxemia or fever) and 4 major, requiring tracheal intubation. No deaths were recorded. CONCLUSIONS: Evaluation by fiberoptic bronchoscopy together with BAL proved to be a safe procedure with an adequate diagnostic yield that made it possible to determine the etiology of the pulmonary infiltrates seen in chest x-rays. Both positive and negative results of BAL were useful for treating the patients.

Adolescent↗
PubMed2004

[IOP spikes following contact transscleral diode laser cyclophotocoagulation].

PURPOSE: To evaluate the incidence of intraocular pressure (IOP) spikes after contact transscleral diode laser cyclophotocoagulation (cyclodiode) and to identify related risk factors. METHOD: Retrospective study of 116 eyes (110 patients) with refractory glaucoma who underwent cyclodiode. IOP measurement was obtained immediately before and one hour after cyclodiode. We defined an IOP spike as an increase equal or superior to 5 mmHg after laser treatment. We evaluated several potential pre-, intra- and post-operative factors related to the IOP spike occurrence. RESULTS: Mean IOP decreased one hour after cyclodiode 6.96 mmHg (SD: 8.36) (p<0.001). Overall, we observed 10.8% of IOP spikes. Age, sex, mean energy delivered, pop occurrence and iris colour were not associated with the postoperative IOP spike occurrence. The percentage of IOP spikes was higher in neovascular glaucoma (p=0.074). The IOP spike rate was also higher after retreatment, but the difference compared to the eyes which underwent cyclodiode for the first time was not significant. CONCLUSIONS: These preliminary results suggest that IOP spike prevention could be considered in neovascular glaucoma scheduled for cyclodiode

Aged↗
PubMed2001

The rfaH gene, which affects lipopolysaccharide synthesis in Salmonella enterica serovar Typhi, is differentially expressed during the bacterial growth phase.

We have cloned and sequenced the rfaH gene from Salmonella enterica serovar Typhi strain Ty2. The gene showed a high degree of similarity to the rfaH genes from Escherichia coli K-12 and S. enterica serovar Typhimurium. A rfaH mutant was constructed by site-directed mutagenesis. This mutant produced a rough lipopolysaccharide (LPS), with an incomplete core region. The defect in LPS expression that results from the rfaH mutation was corrected by a plasmid carrying the intact gene. The plasmid-borne rfaH gene also restored normal LPS synthesis in a rfaH mutant of E. coli. Reverse transcription-polymerase chain reaction analyses were performed to determine the effects of various environmental conditions on the expression of rfaH. The transcription of rfaH showed a growth-phase-dependent regulation, with maximal expression at the late exponential phase. Other environmental conditions, such as temperature or medium osmolarity, did not affect transcription of rfaH.

Cloning, Molecular↗
PubMed2001

Epithelial cell contact-induced alterations in Salmonella enterica serovar Typhi lipopolysaccharide are critical for bacterial internalization.

The invasion of Pseudomonas aeruginosa and Salmonella enterica serovar Typhi into epithelial cells depends on the cystic fibrosis transmembrane conductance regulator (CFTR) protein as an epithelial receptor. In the case of P. aeruginosa, the bacterial ligand for CFTR is the outer core oligosaccharide portion of the lipopolysaccharide (LPS). To determine whether serovar Typhi LPS is also a bacterial ligand mediating internalization, we used both P. aeruginosa and serovar Typhi LPS as a competitive inhibitor of serovar Typhi invasion into the epithelial cell line T84. P. aeruginosa LPS containing a complete core efficiently inhibited serovar Typhi invasion. However, neither killed wild-type Typhi cells nor purified LPS were effective inhibitors. LPS from mutant Typhi strains defective in O side-chain synthesis, but with an apparently normal core, was capable of inhibiting invasion, but LPS obtained from a deeper rough mutant strain with alterations in fast-migrating core oligosaccharide failed to inhibit invasion. Lastly, exposure of wild-type serovar Typhi to T84 cultures before heat killing resulted in a structural alteration in its LPS that allowed the heat-killed cells to inhibit invasion of wild-type serovar Typhi. These data indicate that the serovar Typhi LPS core, like the P. aeruginosa LPS core, is a ligand mediating internalization of bacteria by epithelial cells, and that exposure of this ligand on wild-type Typhi is induced by the bacteria's interaction with host cells.

Binding Sites↗
PubMed2001

Uptake of endocytic markers by rice cells: variations related to the growth phase.

Endocytosis is now considered a basic cellular process common to plant cells. Although both non-specific and receptor-mediated endocytosis appear to take place in plant cells, the physiological role of the latter remains unclear. We have investigated the endocytic process in rice cell suspensions using two biotinylated proteins, peroxidase and bovine serum albumin (bHRP and bBSA), as markers. First, we show that markers are internalized by rice cells and appear in intracellular membranes. The uptake of the two markers is temperature dependent, saturable with time and markers dose and it is competed by free biotin. Thus, it shows the properties of a receptor-mediated process. We also show that uptake of markers is strongly influenced by growth phase as optimal uptake occurs during the lag phase, but the initiation of the exponential growth phase decreases uptake drastically. Arrest of the cell cycle by starvation of either a nutrient (phosphate) or a growth regulator (2,4-dichlorophenoxyacetic acid), both components of the culture medium, does not modify the rate of bBSA uptake. Subsequent readdition of these components results in growth recovery and a dramatic decrease in bBSA uptake. On the other hand, nocodazole treatment, a method to arrest the cell cycle by microtubule depolymerization, inhibited bBSA uptake. The possible causes for this arrest of endocytosis are discussed.

Biomarkers↗
PubMed2000

Estrogen replacement therapy and the prevention of coronary heart disease in postmenopausal women.

The use of estrogen replacement therapy (ERT) for the prevention of coronary heart disease (CHD) is discussed. Cardiovascular disease is the number one cause of death in women. It is believed that the loss of estradiol production at menopause increases the risk of CHD. Theoretically, ERT should decrease CHD risk in postmenopausal women by maintaining at premenopausal levels the metabolic factors that affect CHD. Many mechanistic studies of the effects of estrogen on lipoproteins, hemostasis, carbohydrate metabolism, and vessel wall tone and reactivity support a cardioprotective role for estrogen. In addition, observational studies have found that ERT, with or without progesterone, significantly reduces the risk of CHD. However, mechanistic and observational studies can establish only an association, not a cause-and-effect relationship. Furthermore, bias may influence the risk estimates. The Heart and Estrogen/Progestin Replacement Study (HERS), published in 1998, was the first large, randomized, controlled trial to evaluate the efficacy of estrogen and progesterone replacement therapy in reducing CHD risk. Overall, the study found that continuous hormone replacement therapy (HRT) in women with CHD did not reduce cardiovascular risk at an average of 4.1 years of follow-up. In addition, there was an early increase in the risk of thromboembolic events. Although many mechanistic and observational studies suggest that ERT reduces the risk of morbidity and mortality from CHD in postmenopausal women, the only large, randomized, controlled study of this question to date failed to confirm this. Until data from ongoing studies are available, health care providers must reconsider prescribing ERT or HRT solely for the secondary prevention of CHD.

Coronary Disease↗
PubMed2000

Characterization of Cop I coat proteins in plant cells.

Membrane traffic in eukaryotic cells is mediated by COP (coat protein)-coated vesicles. Their existence in plant cells has not yet been unequivocally demonstrated, although coated vesicles (probably with a COP coat) can be seen by electron microscopy. At the gene level, plant cells seem to contain all the components necessary to form COP-coated vesicles. In this paper, we have used antibodies raised against mammalian COPI coat proteins to detect putative homologues in rice (Oryza sativa) cells. Using these antibodies, we have found that rice cells contain alpha-, beta-, beta'-, and gamma-COP, as well as ADP-ribosylation factor (ARF) 1 protein. In addition, we show that antibodies against mammalian beta'-COP can immunoprecipitate not only beta'-COP but also alpha-, beta-, and gamma-COP, suggesting that COPI components in rice cells exist as a complex (or coatomer) in the cytosol, as in mammalian cells. Finally, we show that COP binding to membranes is GTP-dependent, and that ARF1 also binds to membranes in a GTP-dependent manner.

ADP-Ribosylation Factor 1↗
PubMed2000

Effect of Salmonella typhi wild type and O-antigen mutants on human natural killer cell activity.

We investigated the effect of glutaraldehyde-fixed Salmonella typhi Ty2 (Vi(-)) wild-type (World Health Organization's vaccine strain) and mutant strains MEI028 (rough, O-antigen(-)) and MEI012 [smooth (O-antigen(+)95%), immunomagnetically isolated NK cell preparations. Incubation of PBMC with each and every one of the S. typhi strains studied consistently and significantly, increased this cellular immune function, as well as the supernatant level of the various cytokines tested e.g. IFN-gamma, TNF-alpha, IL-10 and IL-12 (ELISA). In similar experiments, a significant increase in the cytolytic activity of HPNK cells was elicited by S. typhi Ty2 but not by mutant strain MEI028; neither of the cytokines assayed (IFN-gamma and TNF-alpha) was detected in the supernatant. Our results suggest that S. typhi O-antigen plays an essential role in a mechanism resulting in the direct activation of NK cell activity in HPNK cell preparations. However, the relative quantitative significance of this antigen in the direct stimulation of NK cell cytotoxicity expression in PBMC samples is less clear, as it appears that in this case bacterial-induced monocyte-released cytokines plays a most important role. Incubation with S. typhi Ty2 or MEI028 elicited significant expression of CD69, an early marker of NK cell activation, in PBMC but not in HPNK cell samples (flow cytometry); in similar experiments, the expression of CD16/56 and activation marker CD25 remained essentially unchanged.

Adult↗
PubMed1997

Effects of aspirin or basic amino acids on collagen cross-links and complications in NIDDM.

OBJECTIVE: To determine if long-term therapy with aspirin or basic amino acids for subjects with NIDDM reduces the severity of clinical complications and/or reduces tissue levels of markers of glycooxidative damage. RESEARCH DESIGN AND METHODS: Subjects with NIDDM were administered either aspirin (100 mg/day) or a combination of basic amino acids consisting of L-arginine (2 g/day) plus L-lysine (0.5 g/day) for 1 year. The study was double-blind and placebo-controlled. The presence and severity of retinopathy, nephropathy, and neuropathy were assessed in all subjects at 4-month intervals, as were serum blood glucose, glycohemoglobin levels, and presence of albuminuria. Collagen cross-linking and collagen glycation were measured in skin collagen obtained by biopsy at the beginning and the end of the study. Skin biopsies were also obtained from age-matched control subjects. RESULTS: Skin samples obtained from NIDDM subjects at the beginning of the study had significantly increased levels of glucitolyllysine, pentosidine, and hydroxypyridinium, as compared with age-matched control subjects. Pentosidine levels were significantly correlated with severity of retinopathy and neuropathy, but not nephropathy. Subjects receiving aspirin, but not amino acids or placebo, had significantly decreased levels of skin pentosidine after 1 year of therapy. CONCLUSIONS: It is concluded that 1) low-dose aspirin may reduce glycooxidative damage in people with NIDDM, and 2) treatment may need to continue for more than 1 year before clinical status improves.

Analysis of Variance↗
PubMed1996

Utility of Albicans ID plate for rapid identification of Candida albicans in clinical samples. Rapid identification of Candida albicans.

Albicans ID (bioMérieux, Marcy l'Etoile, France) is a ready-to-use medium that contains a chromogenic substrate that allows rapid detection and specific identification of Candida albicans. We have evaluated its clinical performance by culturing 846 clinical specimens from pregnant women and neonates. A 99.2% sensitivity and a 100% specificity were observed in the identification of C. albicans isolates from primary culture.

Bacteriological Techniques↗
PubMed1995

Heterologous expression of Escherichia coli porin genes in Salmonella typhi Ty2: regulation by medium osmolarity, temperature and oxygen availability.

Electrophoretic analysis of outer membrane proteins showed that Salmonella typhi OmpC expression is not reciprocally regulated relative to OmpF as described for Escherichia coli and S. typhimurium. When bacteria were grown in minimal media, both OmpC and OmpF were repressed as the osmolarity increased. However, in Luria broth, expression of OmpC was slightly induced by osmolarity up to 0.3 osmM. Plasmids bearing E. coli ompC-lacZ or ompF-lacZ gene fusions were studied for their expression in S. typhi and E. coli. Under anaerobic growth conditions, expression of ompC-lacZ in S. typhi was maximal at 0.16 osmM, while in E. coli expression was maximal at 0.7 osmM. ompF-lacZ expression was similarly repressed by medium osmolarity and anaerobiosis in both species. In contrast, a drastic difference in the regulation of OmpF by temperature was observed; at 37 degrees C ompF-lacZ expression was repressed in E. coli, while in S. typhi it was induced.

Bacterial Outer Membrane Proteins↗