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Biomedical subjects

E Díaz

Publications and source records attributed to E Díaz.

At least 19 recordsLinked to original sources
PubMed2001

Multicolour imaging of post-Golgi sorting and trafficking in live cells.

The biogenesis and maintenance of asymmetry is crucial to many cellular functions including absorption and secretion, signalling, development and morphogenesis. Here we have directly visualized the segregation and trafficking of apical (glycosyl phosphatidyl inositol-anchored) and basolateral (vesicular stomatitis virus glycoprotein) cargo in living cells using multicolour imaging of green fluorescent protein variants. Apical and basolateral cargo segregate progressively into large domains in Golgi/trans-Golgi network structures, exclude resident proteins, and exit in separate transport containers. These remain distinct and do not merge with endocytic structures suggesting that lateral segregation in the trans-Golgi network is the primary sorting event. Fusion with the plasma membrane was detected by total internal reflection microscopy and reveals differences between apical and basolateral carriers as well as new 'hot spots' for exocytosis.

Adenoviridae↗
PubMed2001

[Digestive refeeding in acute pancreatitis. When and how?].

BACKGROUND: Digestive refeeding in acute pancreatitis represent a difficult issue. It requires the resolution of intestinal ileus and carries a risk of reactivation. AIM: To evaluate criteria that may guide in early refeeding avoiding unnecessary prolonged fasting. PATIENTS AND METHODS: Thirty patients with acute pancreatitis were evaluated in a prospective trial. The severity of the pancreatitis was evaluated according to APACHE II score and Balthazar CT scan alterations. The criteria proposed to start early refeeding were absence of nausea and vomiting, decreased abdominal pain, presence of bowel sounds and lowering of serum amylase levels. Balthazar CT scan classification, was used to decide between oral or enteral refeeding. RESULTS: Eighty percent of patients had alterations in pancreatic density, necrosis or pancreatic or peripancreatic liquid collections in the CT scan (corresponding to Balthazar stages C, D, or E). Ten patients fullfilled the criteria for enteral refeeding at 8.1 +/- 3.5 days (range 3 to 15 days), and 21 patients fulfilled criteria fo enteral refeeding at 8.7 +/- 4.5 (range 4-19). No patient had a reactivation of his pancreatitis. CONCLUSIONS: Digestive refeeding can be done safely by using the criteria proposed in this study. Pancreatic necrosis or peripancreatic fluid collections do not contraindicate refeeding. Oral feeding may be employed (as the first option) in selected patients, without increasing the risk of complication, regardless of CT scan alterations of the pancreas.

Acute Disease↗
PubMed2000

Prenatal melatonin exposure affects luteinizing hormone and hypothalamic and striatal neuropeptide Y in the male rat offspring.

The present study examines the influence of prenatal melatonin on the hypothalamic and striatal neuropeptide Y (NPY) concentrations as well as on luteinizing hormone (LH) levels. Male rat offspring of control and melatonin treated mother rats were studied at different ages of the sexual development: infantile, prepubertal, pubertal and adult ages. Hypothalamic NPY levels were much higher during the juvenile than throughout the infantile period. After prenatal melatonin treatment significantly higher values since day 15 up to 35, also at 60 days of age were found, as compared with controls. Striatal NPY levels were lower than in hypothalamus. Again, NPY in the striatum from offspring of melatonin treated mother rats showed significantly higher values than the respective controls at most of the ages studied. However, prenatal melatonin exerted an inhibitory influence upon LH secretion pattern, since decreased concentrations up to 25 days of age and delayed peak values at pubertal age were observed. The present study also suggest that the effect of NPY upon LH secretion is related to sexual development, since NPY exerted opposite effect in infantile than in pubertal period and melatonin administration during intrauterine life prevented this effect.

Aging↗
PubMed2000

Transcriptional regulation of the divergent paa catabolic operons for phenylacetic acid degradation in Escherichia coli.

The expression of the divergently transcribed paaZ and paaABCDEFGHIJK catabolic operons, which are responsible for phenylacetic acid (PA) degradation in Escherichia coli, is driven by the Pz and Pa promoters, respectively. To study the transcriptional regulation of the inducible paa catabolic genes, genetic and biochemical approaches were used. Gel retardation assays showing that the PaaX regulator binds specifically to the Pa and Pz promoters were complemented with in vivo experiments that indicated a PaaX-mediated repression effect on the expression of Pa-lacZ and Pz-lacZ reporter fusions. The region within the Pa and Pz promoters that is protected by the PaaX repressor in DNase I footprinting assays contains a conserved 15-base pair imperfect palindromic sequence motif that was shown, through mutational analysis, to be indispensable for PaaX binding and repression. PA-coenzyme A (PA-CoA), but not PA, specifically inhibited binding of PaaX to the target sequences, thus confirming the first intermediate of the pathway as the true inducer and PaaX as the only bacterial regulatory protein described so far that responds to an aryl-CoA compound. Superimposed in the specific PaaX-mediated regulation is transcriptional activation by the cAMP receptor protein and the integration host factor protein. These global regulators may adjust the transcriptional output from Pa and Pz promoters to the overall growth status of the cell.

Acetyl Coenzyme A↗
PubMed2000

Antifungal monoterpene production in elicited cell suspension cultures of Piqueria trinervia.

Cell suspension cultures of the traditional medicinal plant Piqueria trinervia Cav., which synthesizes monoterpene piquerol A, were established. A defense response was induced in the cultures when eight homogenized fungi isolated from wild populations of P. trinervia were added. Piquerol A was not produced in the elicited system, while four other substances were synthesized de novo. They were excreted into the medium and inhibited in vitro fungal growth. The most abundant substance produced in this system was a new monoterpene: 2-methylene-7,7-dimethylbicyclo (3,3,1) heptane-4,6-diol. Monoterpenes in the cell suspension culture reported here were produced via two metabolic channels: the first acted constitutively and expressed in liquid and solid cultures, the second is inducible in response to several pathogens and elicitor substances.

Antifungal Agents↗
PubMed2000

Bacterial promoters triggering biodegradation of aromatic pollutants.

Unraveling the complex transcriptional regulation of bacterial catabolism of aromatic pollutants is a prerequisite for engineering efficient biological systems for many biotechnological applications. A first level of regulation relies on specific regulator-promoter pairs. There have been new insights into the molecular mechanisms that regulatory proteins use to sense a given signal and to activate transcription initiation from the cognate promoters. A second level of regulation allows adjustment of the expression of the particular catabolic operons in response to the global environmental conditions of the cells, and recent findings provide some clues about the mechanisms underlying such complex regulatory checkpoints.

Biodegradation, Environmental↗
PubMed2000

2D NMR analysis of highly restricted internal rotation in 2-methylthio-3H-4-p-bromophenyl)-7-[(ortho- and para-substituted)-phenylthio]-1, 5-benzodiazepines.

The complete assignments of twelve 4-aryl-7-thioaryl-1,5-benzodiazepines 1H and 13C spectra, performed with the use of high resolution variable solvent and temperature 1D and 2D techniques (e.g. HOMOCOSY, NOESY, HMQC and HMBC), lead to the determination of conformational equilibria between two rotamers having the aromatic ring of the thioaryl oriented in a perpendicular or helical orientation toward the benzodiazepine ring. The restricted rotation was evaluated from the population of these conformers.

Benzodiazepines↗
PubMed2000

13C and 1H NMR of 2,6-diaryl-1-hydroxy piperidin-4-one oximes; substituent effects on cis/trans ratio and conformational equilibria.

The reaction of substituted diarylidene acetones with hydroxylamine hydrochloride affords isomeric N-hydroxy diaryl piperidinone oximes as main products. The structures as well as conformational equilibria of these products were established by 1H and 13C NMR spectroscopy and further studied by variable temperature NMR. It was found that the cis/trans ratio of 2,6-substituted piperidine derivatives depended on the position of the substituent on the aromatic ring.

Acetone↗
PubMed2000

A gene containment strategy based on a restriction-modification system.

Engineering barriers to the spread of specific genes are of great interest both to increase the predictability of recombinant microorganisms used for environmental applications and to study the role of gene transfer in the adaptation of microbial communities to changing environments. We report here a new gene containment circuit based on a toxin-antidote pair that targets the cell DNA, i.e. the type II EcoRI restriction-modification system. The set-up involved linkage of the ecoRIR lethal gene encoding the EcoRI endonuclease (toxin) to the contained character in a plasmid and chromosomal insertion of the ecoRIM gene encoding the cognate EcoRI methylase (antidote) that protects the target DNA from restriction. Transfer of the contained character to a recipient cell lacking the antidote caused EcoRI-mediated chromosomal breaks, leading to cell death, thereby preventing gene spread. Using transformation and conjugation as mechanisms of DNA transfer and different environmentally relevant bacteria as recipients, we have shown that the potentially universal EcoRI-based containment system decreases gene transfer frequencies by more than four orders of magnitude. Analyses of the survivors escaping killing revealed a number of possible inactivation mechanisms.

Base Sequence↗
PubMed2000

Enhancing desulphurization by engineering a flavin reductase-encoding gene cassette in recombinant biocatalysts.

Biological desulphurization of petroleum feedstocks and products may offer an attractive alternative to reduce sulphur oxide emissions that cause serious environmental pollution. Dibenzothiophene (DBT) desulphurization via the Dsz pathway of Rhodococcus erythropolis IGTS8 is an energetically expensive process that consumes reducing equivalents. We have shown in this work that the HpaC oxidoreductase from Escherichia coli W is able to supply the required FMNH2 to the Dsz monooxygenases. The cloning and expression of the hpaC gene in Pseudomonas strains bearing the dszABC gene cluster significantly enhanced DBT desulphurization efficacy of the recombinant biocatalysts in a resting-cell process, thus indicating that overexpression of a heterologous flavin reductase in the host cell is critical for a high rate of sulphur removal in vivo. The hpaC and dszABC genes have been engineered as a single transcription unit under control of broadhost-range regulatory signals in a mobilizable DNA cassette that can be used to confer a DBT desulphurization phenotype to a wide variety of bacteria regardless of the expression of putative housekeeping flavin reductases within the host cells. This cassette will be very useful in exploring the biotechnological potential of novel biocatalysts for developing an efficient desulphurization process.

Air Pollutants↗
PubMed2000

Functional analysis of the small component of the 4-hydroxyphenylacetate 3-monooxygenase of Escherichia coli W: a prototype of a new Flavin:NAD(P)H reductase subfamily.

Escherichia coli W uses the aromatic compound 4-hydroxyphenylacetate (4-HPA) as a sole source of carbon and energy for growth. The monooxygenase which converts 4-HPA into 3,4-dihydroxyphenylacetate, the first intermediate of the pathway, consists of two components, HpaB (58.7 kDa) and HpaC (18.6 kDa), encoded by the hpaB and hpaC genes, respectively, that form a single transcription unit. Overproduction of the small HpaC component in E. coli K-12 cells has facilitated the purification of the protein, which was revealed to be a homodimer that catalyzes the reduction of free flavins by NADH in preference to NADPH. Subsequently, the reduced flavins diffuse to the large HpaB component or to other electron acceptors such as cytochrome c and ferric ion. Amino acid sequence comparisons revealed that the HpaC reductase could be considered the prototype of a new subfamily of flavin:NAD(P)H reductases. The construction of a fusion protein between the large HpaB oxygenase component and the choline-binding domain of the major autolysin of Streptococcus pneumoniae allowed us to develop a rapid method to efficiently purify this highly unstable enzyme as a chimeric CH-HpaB protein, which exhibited a 4-HPA hydroxylating activity only when it was supplemented with the HpaC reductase. These results suggest the 4-HPA 3-monooxygenase of E. coli W as a representative member of a novel two-component flavin-diffusible monooxygenase (TC-FDM) family. Relevant features on the evolution and structure-function relationships of these TC-FDM proteins are discussed.

Amino Acid Sequence↗
PubMed2000

[Relationship between leptin and insulin blood levels in obese and lean Chilean women].

BACKGROUND: Leptin, a product of ob gene and insulin blood levels, are proportional to the amount of adipose tissue. Insulin could have an independent regulatory effect on leptin secretion. AIM: To assess the relationship between serum leptin and plasma insulin levels in obese and lean Chilean women. MATERIAL AND METHODS: One hundred forty five women, aged 20 to 60 years old, were studied. Weight, height, waist and hip circumference, fasting blood glucose, insulin and leptin levels were measured. Insulin resistance was assessed using the homeostasis model assessment. The relationship between different variables was determined using multiple linear regression, variance analysis and non parametric correlation. RESULTS: Leptin serum concentrations were positively correlated with body mass index, insulin plasma levels and degree of insulin resistance. The association of leptin with insulin was independent of body mass index and persisted after adjustments by body fat distribution and age. CONCLUSIONS: Insulin and insulin resistance are associated to high blood leptin levels and this association is independent of the degree of adiposity and body fat distribution.

Adult↗
PubMed2000

[Obesity and fatty acids in the etiology of insulin resistance].

Fatty acids, obesity and insulin resistance relationship are discussed. In the last decades fatty acids (FA) have been implicated in the etiology of insulin resistance. Initially, this process was related to FA inhibitory effects on glucose uptake mediated by the FA oxidation metabolites. This mechanism known as the Randle cycle has been presently discarded based on recent evidence for FA effects on glucose metabolism. Now is known that cytosolic lipid content and FA molecular structure determines higher or lower storage and oxidation capacity. Another factor is given by Tumor Necrosis Factor-alpha, which is overexpressed in animal and human obesity, producing insulin signaling and glucose uptake inhibition. This paper discuss the role played by FA and obesity on insulin resistance, mainly in relation to FA effects on glucose metabolism in the liver, muscle and adipose tissues. In the obesity condition adipose tissue releases higher levels of free FA which in turn stimulates hepatic glucose production. Adipose tissue also, increase TNF-alpha secretion impairing glucose utilization and insulin signaling. In muscle, cytosolic lipid content activate a Protein Kinase that inhibits the insulin signaling and reduce GLUT-4 translocation. The study of cellular and metabolic changes associated to weight gain and its relationship with insulin resistance etiology are encouraged.

Animals↗
PubMed1999

RegulonDB (version 2.0): a database on transcriptional regulation in Escherichia coli.

RegulonDB version 2.0, a database on transcriptional regulation and operon organization in Escherichia coli, is now available on the web at the following URL: http://www.cifn.unam. mx/Computational_Biology/regulondb/. In this paper we describe the main computational changes to the database, which include migrating the database to Sybase, providing graphical descriptions of the internal organization of operons and regulons, and direct links to MEDLINE references. The web interface offers searching either by mechanisms of regulation or by operon organization. The results of a search (operon organization, or site collection) are displayed as hypertext, and can also be displayed graphically. In terms of its contents, RegulonDB contains a large number of operons, as well as the absolute position in the completed genome sequence of sites, promoters, and individual genes of E.coli.

Databases, Factual↗
PubMed1999

Persistent neuronal density changes related to the establishment of a motor memory.

Rats were trained in a lateralized reaching motor task during either an 'early' (22-31 days old) or a 'late' (62-71 days old) postnatal period. The 'late' group showed significant neuronal density reduction in cortical layers II-III of the contralateral motor forelimb representation. The 'early' group evidenced a similar localized contralateral effect that persisted after a subsequent period without training. Furthermore, in this group, a bilateral overall decrease in neuronal density was found throughout the motor cortex. This bilateral experience and age-dependent effect is conceivably related to a critical period of motor cortical development. The localized reduction of neuronal density strongly indicates a morphological expression of the motor engram. Our present study supports the concept that the acquisition and retention of motor learning involves the persistence of structural changes in the brain.

Animals↗
PubMed1999

Short-term effects of marathon running in master runners: no evidence of myocardial injury.

The purpose of this investigation was to analyze the short-term effects of marathon running on serum levels of cardiac markers in a group of master runners (> 60 yrs). Ten marathoners (9 male and 1 female; 63+/-4 yrs) were enrolled in the study. All of them completed the Madrid Marathon (1998). Venous blood was drawn from each subject three times during the study (48 h before the race, immediately after the race, and 24 h post-competition) for the determination of the several biochemical markers, such as total creatine kinase catalytic activity (total CK), mass concentration of creatine kinase isoenzyme MB (CK-MB mass), and cardiac troponin I (Tnl-c). The most important finding was that in each sample (pre- or post-race) serum Tnl-c was below the commonly accepted level of 0.1 ng x m(-1) indicative of myocardial injury. Although further research is needed using more complete methodology, our results suggest that marathon running does not have an acute deleterious effect on the hearts of the elderly.

Aged↗
PubMed1999

Effect of exogenous melatonin on neuroendocrine-reproductive function of middle-aged female rats.

The possible role of melatonin in the regulation of the reproductive system of female rats during ageing was investigated in middle-aged female rats showing irregular duration of the oestrous cycle (n = 30). Blood samples were obtained by jugular venepuncture during the oestrous cycle in control rats. After this experiment was completed, the female rats were treated with melatonin for 2 months and blood samples were obtained at different stages of the oestrous cycle. Plasma LH, FSH and prolactin concentrations were significantly increased in the afternoon of the day of pro-oestrus after melatonin treatment compared with control rats. Moreover, FSH concentrations too were significantly increased on the morning of pro-oestrus and oestrus in melatonin treated rats compared with control rats. Similarly, oestradiol concentrations were significantly higher on the morning of pro-oestrus in melatonin treated rats compared with controls. Another group of rats showing irregular duration of the oestrous cycle was used to study the possible effect of melatonin treatment on the timing of pro-oestrous surges of LH and FSH. The results showed that LH and FSH peak values occurred at 5 h after melatonin treatment. Pituitary responsiveness to LHRH in a 90 min test was also studied in middle-aged rats showing irregular duration of the oestrous cycle that had been injected for 1 month with either melatonin or saline. Prolactin response was unaffected by exogenous melatonin, but a stimulatory effect of melatonin on LH and FSH pituitary responsiveness to LHRH was observed. The results indicate an improved function of the neuroendocrine-reproductive axis in middle-aged rats after melatonin treatment.

Aging↗