Biomedical subjects

I Gómez

Publications and source records attributed to I Gómez.

At least 19 recordsLinked to original sources

PubMed2007

Different levodopa actions on the extracellular dopamine pools in the rat striatum.

Levodopa has been the mainstay treatment for Parkinson's disease for several decades, but the precise mechanism for its therapeutic action is still not well understood. To date, little distinction has been made between the effects of levodopa on the different brain DA pools. We studied the levodopa action on two extracellular DA pools: one was analyzed by microdialysis (often considered as indicative of volume transmission) and the other by in vivo amperometry during nigrostriatal cell stimulation (more indicative of neurotransmission). Levodopa administration induced a moderate (increased 200%) and tardy (began at 60 min) increase in the DA-pool measured by microdialysis, an effect that increased (increased 500%) and accelerated (began at 10 min) after DA-cell degeneration. Levodopa action on the DA-pool measured by amperometry was very fast (10 min) and prominent (increased 600%) in normal rats. The DA-denervated striatum showed a fast exhaustion during cell stimulation, which prevented further study of the levodopa effect on the DA amperometry-pool under this condition. This study suggests a different kinetic for levodopa action on the volume transmitter and neurotransmitter DA-pool, showing marked changes in levodopa action in the denervated striatum.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2006

Role of receptor interaction in the mode of action of insecticidal Cry and Cyt toxins produced by Bacillus thuringiensis.

Cry toxins from Bacillus thuringiensis are used for insect control. Their primary action is to lyse midgut epithelial cells. In this review we will summarize recent findings on the Cry toxin-receptor interaction and the role of receptor recognition in their mode of action. Cry toxins interact sequentially with multiple receptors. In lepidopteran insects, Cry1A monomeric toxins interact with the first receptor and this interaction triggers oligomerization of the toxins. The oligomer then interacts with second receptor inducing insertion into membrane microdomains and larval death. In the case of mosquitocidal toxins, Cry and Cyt toxins play a part. These toxins have a synergistic effect and Cyt1Aa overcomes Cry toxin resistance. Recently, it was proposed that Cyt1Aa synergizes or suppresses resistance to Cry toxins by functioning as a membrane-bound receptor for Cry toxin.

Bacillus thuringiensis↗

PubMed2006

Effect of irrigation on the survival of total coliforms in three semiarid soils after amendment with sewage sludge.

Sewage sludges are increasingly used in soil amendment programmes, although not without risk since they contain, among other potential hazards, high concentrations of total coliform bacteria. In this paper we have studied the effect of irrigation on the survival of total coliforms in three semiarid degraded soils with different agricultural practices. Fresh sewage sludge was added at 50 g kg(-1) soil, and incubated in both the presence and absence of irrigation. The absence of irrigation led to a sharp decrease in the number of total coliforms in all soils, with the bacteria disappearing in 40 days. Irrigation produced a substantial initial increase in the number of coliforms in the three soils, although after 80 days there was none growing in any of the soils. The results showed that there were significant differences in the survival of coliform bacteria due to the presence or absence of irrigation.

Agriculture↗

PubMed2006

Effect of composted sewage sludge application to soil on sweet pepper crop (Capsicum annuum var. annuum) grown under two exploitation regimes.

The aim of this study is to monitor the effect of the application of three increasing amounts of composted sewage sludge (3, 6 and 9 kg compost m(-2)) on the physico-chemical properties of a horticultural calcareous soil where sweet pepper plants (Capsicum annuum var. annuum) cv. California were grown. A comparative study of two different exploitation regimes was carried out; the first was an open-air field-grown plot and the second plot was kept under controlled conditions in a greenhouse. Changes in physical and chemical properties measured in soil and sweet pepper crop were recorded during crop growth in order to measure the evolution of these properties as a consequence of increasing compost applications. Organic matter, total nitrogen Kjeldahl and available phosphorus contents increased in soil after composted sewage sludge applications. The 9 kg compost m(-2) application promoted the appearance of deleterious effects on the properties of soil, such as salt accumulation, a significant increase in the electrical conductivity and an input of heavy metals (Pb>Cr>Cd). The 6 kg compost m(-2) application provided a supply of nutrients necessary to grow peppers plants under both exploitation regimes. Pepper fruit biomass production under greenhouse was almost 60% higher compared to that of the open-air plot. Lower contents of Ca and increased levels of Cu in fruit under greenhouse growing conditions compared to those of open-air grown peppers seemed to promote the occurrence of blossom-end rot, affecting more than 10% of the harvested fruits.

Biodegradation, Environmental↗

PubMed2005

Co phytoavailability for tomato in amended calcareous soils.

A plot study was conducted to assess changes in Co phytoavailability for a tomato cultivar grown on an agricultural soil (a Calcic Petrocalcid) amended with sewage sludge, under controlled conditions in South-eastern Spain. The experiment consisted of three main treatment blocks: (A) without organic fertilisation, (B) with addition of 60 tha(-1) and (C) 120 tha(-1) of sewage sludge. For each block (A, B, and C), four levels of Co (0, 50, 100 and 200 mgkg(-1)) were added, as CoCl2. Diethylenetriaminepentaacetic acid, DTPA (0.005 M plus triethanolamine), ammonium acetate (1 N at pH 7), and water extractable fractions of the soils were analysed for all the plots. The time dependent Co accumulation in different parts (roots, stems, leaves, and fruits) of the tomato plants was studied. Soil Co seemed to be mainly in non-available forms, according to the low concentrations found in the water and ammonium acetate extracts, compared to DTPA. The gradient of Co accumulation in tomato plants was root > leaf > stem + branches > fruit, with a concentration in the edible parts ranging between 4 and 25 mg kg(-1). The organic amendment enhanced the plant extraction of Co, this effect being more significant with time. Plant extraction efficiency decreased with increasing Co concentration in the soils. Co in fruit showed the best correlation with all the Co extraction pools in the soil.

Calcium↗

PubMed2005

Relationship between oxidative stress parameters and atherosclerotic signs in the carotid artery of stable renal transplant patients.

Reactive oxygen species (ROS) may participate in atheroma plaque formation, which may be noninvasively diagnosed by Doppler ultrasound of carotid artery. We sought to determine the relationship between the presence of carotid artery lesions and oxidative parameters to identify factors that may influence these lesions in renal transplant patients. Fifty renal transplanted patients with stable renal function and without diabetes mellitus were studied for more than 1 year posttransplantation. Echo Doppler examination of the carotid artery was performed to assess the intimal media thickness (IMT), atheroma plaques, calcification, and stenosis. Data were collected on oxidative parameters: malondialdehyde (MDA), glutathione peroxidase (GPx), catalase, superoxide dismutase (SOD), glutathione reductase (GR), and lipid profile. The serum GPx level among patients without atheroma plaques, calcification, or stenosis was higher than in those with ultrasound signs. The LDL cholesterol fraction was lower in patients with no ultrasound signs of atherosclerotic lesions; total cholesterol values showed the same behavior. In conclusion, transplanted patients with atheromatous plaques, calcification, and carotid stenosis have a greater degree of hypercholesterolemia and lower antioxidant activity (lower GPx). Recipient age was the principal risk factor for the presence of increased IMT, atheroma plaque, calcification, and/or stenosis of carotid artery in renal transplant patients.

Adult↗

PubMed2004

Oligomerization triggers binding of a Bacillus thuringiensis Cry1Ab pore-forming toxin to aminopeptidase N receptor leading to insertion into membrane microdomains.

Bacillus thuringiensis Cry1A toxins, in contrast to other pore-forming toxins, bind two putative receptor molecules, aminopeptidase N (APN) and cadherin-like proteins. Here we show that Cry1Ab toxin binding to these two receptors depends on the toxins' oligomeric structure. Toxin monomeric structure binds to Bt-R1, a cadherin-like protein, that induces proteolytic processing and oligomerization of the toxin (Gomez, I., Sanchez, J., Miranda, R., Bravo A., Soberon, M., FEBS Lett. (2002) 513, 242-246), while the oligomeric structure binds APN, which drives the toxin into the detergent-resistant membrane (DRM) microdomains causing pore formation. Cleavage of APN by phospholipase C prevented the location of Cry1Ab oligomer and Bt-R1 in the DRM microdomains and also attenuates toxin insertion into membranes despite the presence of Bt-R1. Immunoprecipitation experiments demonstrated that initial Cry1Ab toxin binding to Bt-R1 is followed by binding to APN. Also, immunoprecipitation of Cry1Ab toxin-binding proteins using pure oligomeric or monomeric structures showed that APN was more efficiently detected in samples immunoprecipitated with the oligomeric structure, while Bt-R1 was preferentially detected in samples immunoprecipitated with the monomeric Cry1Ab. These data agrees with the 200-fold higher apparent affinity of the oligomer than that of the monomer to an APN enriched protein extract. Our data suggest that the two receptors interact sequentially with different structural species of the toxin leading to its efficient membrane insertion.

Animals↗

PubMed2002

Multiple environmental signals determine the transcriptional activation of the mycoparasitism related gene prb1 in Trichoderma atroviride.

Trichoderma atroviride parasitizes a large variety of phytopathogenic fungi. This characteristic has allowed its use as a biological control agent. The production of hydrolytic enzymes appears to be a key element in the parasitic process. Among the enzymes released by Trichoderma, the proteinase Prb1 plays a major role. We show here that the corresponding gene ( prb1) is subject to nitrogen catabolite repression. Accordingly, induction of prb1 transcription by Rhizoctonia solani cell walls and by osmotic stress requires release from a repressed condition, which is determined by nitrogen availability. Furthermore, the transcription pattern of the prb1 gene was not affected when an inhibitor of p38-Hog1, a regulator of the response to osmotic shock, was used. In contrast, a MEK1/2 (MAPK/ERK) inhibitor blocked prb1 transcription in response to nitrogen limitation, indicating that the pathway employed in the nitrogen response involves proteins similar to p42-p44. Fusion of the prb1 promoter to the gfp reporter gene allowed the detection of a novel regulatory element, providing an initial insight into the nature of the sites that control prb1 expression.

Blotting, Northern↗

PubMed2002

Prevalence of Salmonella and Campylobacter in retail chicken meat in Spain.

From February to November 1999, 198 samples of chicken meat for sale in retail outlets and supermarkets in nine provinces of Castilla and León (Spain) were analysed for the prevalence of Salmonella and Campylobacter. Salmonella was isolated from 71 (35.83%) of the samples analysed. The predominant serovars were S. enteritidis (47.88%), S. hadar (25.35%) and serotype 4,12:b:-(II) (19.71%). Other serovars such as S. mbandaka, S. derby, S. virchow and S. paratyphi B were isolated in much lower levels. Thermophilic campylobacters were isolated in 49.50% of the samples studied.

Animals↗

PubMed2002

Laparoscopic diagnosis of acute lower abdominal pain in women of reproductive age.

OBJECTIVES: To compare the accuracy of laparoscopy performed within 24 h of admission and the conventional method based on clinical observation in the etiological diagnosis of non-specific acute lower abdominal pain (NSLAP) in women of reproductive age. METHODS: A total of 110 patients who met the selection criteria and were seen from November 1997 to June 2000 at the Instituto Materno Infantil, a referral hospital for maternal and perinatal care in Bogotá, were randomly divided into two groups. The effectiveness of each method was evaluated according to number of diagnoses reached, length of in-patient stay before diagnosis, complications, and diagnostic accuracy when compared with a standard given by microbiological and histopathological findings as well as clinical course. RESULTS: The early laparoscopy group did not experience more accurate diagnoses (85% vs. 79%, P=0.61) or a greater number of complications (11% vs. 9%, P=0.48), although the patients' stay was shorter (1.3 vs. 2.3 days, P=0.008) than the stay of the conventional-diagnosis group. Sensitivity analysis showed more accurate judgements with laparoscopy in four of the five NSLAP causes, but only in two of the cases did this greater accuracy have clinical significance. CONCLUSIONS: Early laparoscopy did not show a clear benefit in women with NSLAP.

Abdomen, Acute↗

PubMed2001

Mapping the epitope in cadherin-like receptors involved in Bacillus thuringiensis Cry1A toxin interaction using phage display.

In susceptible lepidopteran insects, aminopeptidase N and cadherin-like proteins are the putative receptors for Bacillus thuringiensis (Bt) toxins. Using phage display, we identified a key epitope that is involved in toxin-receptor interaction. Three different scFv molecules that bind Cry1Ab toxin were obtained, and these scFv proteins have different amino acid sequences in the complementary determinant region 3 (CDR3). Binding analysis of these scFv molecules to different members of the Cry1A toxin family and to Escherichia coli clones expressing different Cry1A toxin domains showed that the three selected scFv molecules recognized only domain II. Heterologous binding competition of Cry1Ab toxin to midgut membrane vesicles from susceptible Manduca sexta larvae using the selected scFv molecules showed that scFv73 competed with Cry1Ab binding to the receptor. The calculated binding affinities (K(d)) of scFv73 to Cry1Aa, Cry1Ab, and Cry1Ac toxins are in the range of 20-51 nm. Sequence analysis showed this scFv73 molecule has a CDR3 significantly homologous to a region present in the cadherin-like protein from M. sexta (Bt-R(1)), Bombyx mori (Bt-R(175)), and Lymantria dispar. We demonstrated that peptides of 8 amino acids corresponding to the CDR3 from scFv73 or to the corresponding regions of Bt-R(1) or Bt-R(175) are also able to compete with the binding of Cry1Ab and Cry1Aa toxins to the Bt-R(1) or Bt-R(175) receptors. Finally, we showed that synthetic peptides homologous to Bt-R(1) and scFv73 CDR3 and the scFv73 antibody decreased the in vivo toxicity of Cry1Ab to M. sexta larvae. These results show that we have identified the amino acid region of Bt-R(1) and Bt-R(175) involved in Cry1A toxin interaction.

Amino Acid Sequence↗

PubMed2001

PCR detection of Helicobacter pylori in string-absorbed gastric juice.

Molecular methods for detection of Helicobacter pylori infection have been shown to be highly sensitive in gastric biopsies and cultures. The objective of this work was to compare PCR detection of H. pylori DNA in string-absorbed gastric juice and in gastric biopsies. The study was performed in 47 dyspeptic adult patients undergoing endoscopy, and infection was detected by amplification of a segment of H. pylori ureA gene. Of the 29 patients positive in biopsy analysis, 23 (79%) were also positive in the gastric string. PCR analysis of gastric strings is a sensitive and safe procedure to detect H. pylori when endoscopy is not indicated, and may be of great clinical and epidemiological usefulness in determining effectiveness of eradication therapies, typing virulence genes and detecting antibiotic resistance mutations.

Adult↗

PubMed2001

Comparison of PCR and common clinical tests for the diagnosis of H. pylori in dyspeptic patients.

Helicobacter pylori has been recognized as a major gastric pathogen. The objective of this study was to assess the diagnostic value of common clinical tests to detect H. pylori infection, by comparison with PCR. Serum and gastric biopsy specimens from 106 dyspeptic patients were examined. Serology was performed with Pyloriset Dry test, and biopsies were examined histologically, for rapid urease activity and PCR amplification of an ureA gene segment of H. pylori. PCR primers were specific for H. pylori and required at least 1.47 pg of H. pylori DNA, corresponding to about 800 bacterial cells. According to serology, histology, rapid urease, and PCR, positive results were respectively found in 56%, 86%, 64%, and 85% of dyspeptic patients, primarily with gastritis. Relative to PCR, the sensitivity (and specificity) was 55% (38%) for serology, 86% (13%) for histology, 70% (69%) for urease. When combining histology and urease, Bayesian analysis of data indicated no advantage of using combined methods over rapid urease test alone. Histology should not any longer be considered a gold standard test for Helicobacter pylori. Urea breath test still seems the first option for non invasive diagnostic. If an invasive diagnostic is justified, highly specific and sensitive molecular methods should be used to examine specimens.

Bayes Theorem↗

PubMed2001

Reclamation of a burned forest soil with municipal waste compost: macronutrient dynamic and improved vegetation cover recovery.

The reclamation of burned soils in Mediterranean environments is of paramount importance in order to increase the levels of soil protection and minimise erosion and soil loss. The changes produced in the content of total organic carbon (TOC), N (Kjeldahl) and available P, K, Ca and Mg by the addition of different doses of a municipal solid waste compost to a burned soil were evaluated during one year. The effect of organic amendment on the improvement in the vegetation cover after one year was also evaluated. The organic amendment, particularly at a high dose, increased the TOC and N-Kjeldahl content of the soil in a closely related way. The levels of available K in soil were also enhanced by the organic amendment. Although the effects on all three parameters tended to decrease with time, their values in the amended soils were higher than in the control soil, which clearly indicates the improvement in the chemical quality of the soil brought about by the organic amendment. The available P content did not seem to be influenced by organic treatment, while available Mg levels were higher than in the control during the first 4 months following organic amendment. The application of compost to the burned soil improved its fertility and favoured rapid vegetal recovery, thus minimising the risk of soil erosion.

Biomass↗

PubMed2000

Evidence for intermolecular interaction as a necessary step for pore-formation activity and toxicity of Bacillus thuringiensis Cry1Ab toxin.

Based on the observation of large conductance states formed by Bacillus thuringiensis Cry toxins in synthetic planar lipid bilayers and the estimation of a pore size of 10-20 A, it has been proposed that the pore could be formed by an oligomer containing four to six Cry toxin monomers. However, there is a lack of information regarding the insertion of Cry toxins into the membrane and oligomer formation. Here we provide direct evidence showing that the intermolecular interaction between Cry1Ab toxin monomers is a necessary step for pore formation and toxicity. Two Cry1Ab mutant proteins affected in different steps of their mode of action (F371A in receptor binding and H168F in pore formation) were affected in toxicity against Manduca sexta larvae. Binding analysis showed that F371A protein bound more efficiently to M. sexta brush border membrane vesicles when mixed with H168F in a one to one ratio. These mutant proteins also recovered pore-formation activity, measured with a fluorescent dye with isolated brush border membrane vesicles, and toxicity against M. sexta larvae when mixed, showing that monomers affected in different steps of their mode of action can form functional hetero-oligomers.

Animals↗

PubMed2000

Antigenicity of chimeric synthetic peptides based on HTLV-1 antigens and the impact of epitope orientation.

The present study evaluated four chimeric synthetic peptides incorporating immunodominant sequences from HTLV-1 virus. Monomeric peptides M1, M2, and M3 represent sequences from core (p19) and envelope (gp46) of the virus. The peptide M1 is a p19 (105-124) sequence, the peptide M2 is a gp46 (190-207) sequence, and the peptide M3 is a gp 46 sequence with substitution of proline at position 192 by serine. Those peptides were arranged in such a way that permits one to obtain different combinations of chimeric peptides (M1-M2, M2-M1, M1-M3, and M3-M1). Two glycine residues were used as arm spacers for separating the two sequences. The antigenicity of these peptides was evaluated in an ultramicroenzyme-linked immunosorbent assay (UMELISA) using sera of human T cell leukemia virus type I (HTLV-I)-infected individuals (n = 24), while specificity was evaluated with anti-HTLV-II-positive samples (n = 11) and healthy blood donors (n = 25). The results were compared to plates coated with monomeric peptides M1, M2, and M3. The chimeric peptide orientation (M1-M2) and the proline at position 192 of the gp46 peptide showed higher sensitivity.

Amino Acid Sequence↗

PubMed2000

Chimeric synthetic peptide as antigen for immunodiagnosis of HIV-1 infection.

One chimeric peptide incorporating antigenic sequences from the gp41 transmembrane region (peptide H-18) and the gp120 envelope region (peptide H-15) corresponding to amino acids (587-617) on gp41 and (495-516) on gp120 of human immunodeficiency virus (HIV 1) was synthesized. Both sequences were separated by two glycine residues. This peptide was evaluated as antigen in an ultramicro-enzyme-linked immunosorbent assay (UMELISA) with samples derived from HIV-1 (n = 30) with different titers of antibodies and healthy blood donors (n = 30). The results were compared to plates coated with monomeric peptides and to plates coated with two monomeric peptides together. Results demonstrated that monomeric peptides gp41 (H-18) and gp120 (H-15) were good as antigens with samples that present antibodies to these regions. The chimeric peptide was the most antigenic. Those results may be related to the peptide structure, adsorption to the solid surface, and epitope accessibility to the antibodies. This chimeric peptide would be very useful for HIV-1 diagnostics.

AIDS Serodiagnosis↗

PubMed1999

The gene for mitochondrial ribosomal protein S14 has been transferred to the nucleus in Arabidopsis thaliana.

The transfer of genetic information from the mitochondrion to the nucleus is thought to be still underway in higher plants. The mitochondrial genome of Arabidopsis thaliana contains only one rps14 pseudogene. In this paper we show that the functional gene encoding mitochondrial ribosomal protein S14 has been translocated to the nucleus. This gene transfer is a recent evolutionary event, which occurred within Cruciferae, probably after the divergence of Arabidopsis and Brassica napus. A 5' extension of the rps14 reading frame encodes a presequence which, in vitro, targets the polypeptide to isolated mitochondria and is cleaved off during or after import. No intron was found at the junction of the targeting presequence with the mitochondrially derived sequence, which are directly connected. By contrast, a 90-bp intron, which is removed by splicing to give a mature poly(A)+ mRNA of 0.9 kb, is located in the 3' non-coding region. To our knowledge, this is the first report of an intron in such a position in a functional transferred gene in higher plants, and suggests that exon shuffling may have been involved in the acquisition of elements necessary for expression in the nucleus. Putative roles of this intron in polyadenylation and enhancement of gene expression are discussed.

Amino Acid Sequence↗