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Biomedical subjects

D Fernández

Publications and source records attributed to D Fernández.

At least 37 records · Page 2Linked to original sources
PubMed1997

Study of the secretion of substance P, neurotensin and somatostatin in patients with cholelithiasis.

A comparative, case-control study on the pre- and postprandial release of three gastrointestinal peptides implicated in gallbladder motility has been carried out in humans in the attempt to determine their possible role in the pathogenesis of cholelithiasis. Fifty-seven adult patients (40 females and 17 males) with an ultrasound diagnosis of gallstones and 20 healthy subjects (9 females and 11 males) without cholelithiasis or other digestive pathology were studied. Plasma substance P, neurotensin and somatostatin were measured by means of RIA-I125 in basal fasting conditions and 30, 60 and 90 minutes after the oral intake of a semiliquid mixed meal. The levels of secretion of each hormone were compared in patients and healthy controls on an overall basis and in terms of sex, age and body weight. We found a basal and postprandial hypersecretion of substance P in patients with gallstones when compared with controls. Individuals with cholelithiasis showed a moderate decrease in neurotensin secretion after the oral meal. Somatostatin release was unchanged. In conclusion, patients with gallstones may present a functional disorder in the secretion of gastrointestinal hormones involved in gallbladder motility.

Adult↗
PubMed1996

The hydrogenase gene cluster of Rhizobium leguminosarum bv. viciae contains an additional gene (hypX), which encodes a protein with sequence similarity to the N10-formyltetrahydrofolate-dependent enzyme family and is required for nickel-dependent hydrogenase processing and activity.

Plasmid pAL618 contains the genetic determinants for H2 uptake (hup) from Rhizobium leguminosarum bv. viciae, including a cluster of 17 genes named hupSLCDEFGHIJK-hypABFCDE. A 1.7-kb segment of insert DNA located downstream of hypE has now been sequenced, thus completing the sequence of the 20441-bp insert DNA in plasmid pAL618. An open reading frame (designated hypX) encoding a protein with a calculated M(r) of 62300 that exhibits extensive sequence similarity with HoxX from Alcaligenes eutrophus (52% identity) and Bradyrhizobium japonicum (57% identity) was identified 10 bp downstream of hypE. Nodule bacteroids produced by hypX mutants in pea (Pisum sativum L.) plants grown at optimal nickel concentrations (100 microM) for hydrogenase expression, exhibited less than 5% of the wild-type levels of hydrogenase activity. These bacteroids contained wild-type levels of mRNA from hydrogenase structural genes (hupSL) but accumulated large amounts of the immature form of HupL protein. The Hup-deficient mutants were complemented for normal hydrogenase activity and nickel-dependent maturation of HupL by a hypX gene provided in trans. From expression analysis of hypX-lacZ fusion genes, it appears that hypX gene is transcribed from the FnrN-dependent hyp promoter, thus placing hypX in the hyp operon (hypBFCDEX). Comparisons of the HypX/HoxX sequences with those in databases provided unexpected insights into their function in hydrogenase synthesis. Similarities were restricted to two distinct regions in the HypX/HoxX sequences. Region I, corresponding to a sequence conserved in N10-formyltetrahydrofolate-dependent enzymes involved in transferring one-carbon units (C1), was located in the N-terminal half of the protein, whereas region II, corresponding to a sequence conserved in enzymes of the enoyl-CoA hydratase/isomerase family, was located in the C-terminal half. These similarities strongly suggest that HypX/HoxX have dual functions: binding of the C1 donor N10-formyltetrahydrofolate and transfer of the C1 to an unknown substrate, and catalysis of a reaction involving polarization of the C = O bond of an X-CO-SCoA substrate. These results also suggest the involvement of a small organic molecule, possibly synthesized with the participation of an X-CO-SCoA precursor and of formyl groups, in the synthesis of the metal-containing active centre of hydrogenase.

Amino Acid Sequence↗
PubMed1996

Membrane-bound tyrosine aminopeptidase activities in the rat brain throughout the estrous cycle.

Puromycin sensitive and insensitive membrane-bound aminopeptidase activity levels during the estrous cycle in several brain areas have been described in this research. We have found the highest aminopeptidase M activity levels during the proetrous stage in the hypothalamus, the amygdala and the pituitary gland. Since this enzyme has been involved in opioid peptide metabolism, it is suggested that aminopeptidase M could play a part in the decrease in the inhibitory influence of the endogenous opioids peptides that participate in the LH surge.

Aminopeptidases↗
PubMed1996

[Evaluation of a Dot ELISA for the detection of a Rotavirus antigen].

An evaluation of a Dot ELISA made by the Center of Genetic Engineering and Biotechnology for detecting Rotavirus antigen, was carried out. 100 feces samples were analyzed by this technique and the results were compared with those obtained with polyacrylamide gel electrophoresis, technique traditionally used in the Rotavirus diagnosis. It was obtained a high coincidence, specificity and sensitivity among them.

Antigens, Viral↗
PubMed1995

Acid, basic and neutral soluble and membrane-bound aminopeptidase activities after lidocaine administration in discrete areas of the rat brain.

It has been suggested that aminopeptidase activity could play an important role in the regulation and biotransformation of several neuroactive peptides. Lidocaine is a local anesthetic widely used in therapeutics and as antiarrhythmic agent. However, information concerning possible alterations in the neuropeptide metabolism after treatment with this anesthetic is lacking. This being the case, in the present paper we have studied the activities of three aminopeptidases (Asp-, Leu- and Lys-aminopeptidase) in several brain areas after lidocaine administration. The study includes the activities of the soluble and membrane-bound forms. Soluble neutral and basic aminopeptidase activities show significant decreases after lidocaine administration in the frontal cortex. Soluble Lys-aminopeptidase also shows a significant decrease in the pituitary gland. On the other hand, membrane-bound Leu-aminopeptidase activity shows significant decreases not only in the frontal, but also in the parietal cortex and in the thalamus. These data might suggest that the neuropeptide transmission and/or modulation could be activated by lidocaine.

Aminopeptidases↗
PubMed1994

Rapid detection of rotavirus in faeces using a dipstick system with monoclonal antibodies and colloidal gold as marker.

Rotavirus (RV) is known to be the most common cause of severe diarrhoea in infants and young children, each year leading to an estimated 800,000-900,000 deaths. RV also infects bovines and other species, with high morbidity and mortality. A rapid and simple 'naked-eye' dipstick system was developed to detect human RV in faeces, using nitrocellulose as solid phase, two monoclonal antibodies, and colloidal gold as marker. The system detects 10(4) viral particles (1-2 ng)/g of faeces. For human RV the specificity and sensitivity were 100% when compared with a commercial latex system, and 99% and 98%, respectively, when correlated with traditional RNA-PAGE, and 100% and 98% compared to an ELISA system.

Animals↗
PubMed1994

Brain Lys-aminopeptidase activity. Changes during cycle and pregnancy.

Lys-aminopeptidase activity levels during the estrous cycle (estrous and proestrous, in the morning and afternoon) and the pregnancy (2nd, 7th, 14th and 20th day postinsemination and the parturition day), in several areas of the rat brain, were studied in this research. The selected brain regions were the frontal, parietal and occipital cortices, olphactory bulbus, thalamus, hypothalamus, hippocampus, amygdala, striatum and pituitary gland. The most significant changes were shown in the hypothalamus and the pituitary gland. Thus, in these areas, the higher cyclic enzyme levels were found in the proestrous stage. During pregnancy, there was a rise on the 7th and 14th days, with a decrease on the 20th day. Also, similar changes in the occipital cortex, striatum, hippocampus and amygdala were appreciated, but fewer than those observed in the hypothalamus and the pituitary. In conclusion, the activity of the aminopeptidase under study fluctuates during the estrous cycle and during pregnancy, as well as in the hypothalamic-pituitary axis and also in several extrahypothalamic areas of the rat brain.

Aminopeptidases↗
PubMed1994

Effect of acute lithium administration on pyroglutamyl-aminopeptidase I activity in several brain areas of the rat.

Lithium (CAS 7439-93-2) is widely accepted as an effective treatment in acute mania. A considerable body of literature exists on the effects of lithium on the central nervous system. However, the neurochemical mechanism of the ion action remains still relatively obscure. In the present work, the effect of acute lithium administration on pyroglutamyl-aminopeptidase I activity in discrete areas of the rat brain, including the hypothalamic-pituitary axis, is described. Increases of the enzyme activity in the striatum and the hypothalamus after lithium treatment were observed. It is suggested that this enzyme activity plays a part in the lithium action mechanism, possibly through the regulation of the activity of TRH (Thyrotropin Releasing Hormone) and/or histidyl-proline diketopiperazine.

Animals↗
PubMed1993

Brain soluble and membrane-bound Tyr-aminopeptidase activities during the stages of estrous and proestrous in the female rat.

Brain Tyr-aminopeptidase activity levels during two stages of the rat estrous cycle (estrous and proestrous), are described in this research. The study includes the activities of the soluble and the membrane-bound forms. Soluble Tyr-aminopeptidase activity shows a significant increase during the proestrous stage in the hypothalamus. The complete membrane-bound activity did not significantly change at any point. However, a significant rise was found in the membrane-bound puromycin insensitive aminopeptidase activity in the hypothalamus and the pituitary gland during the proestrous phase.

Aminopeptidases↗
PubMed1993

[Comparative study of famotidine vs ranitidine in critically ill patients in mechanical ventilation].

Stress ulcers are frequent in critically ill patients. Gastric mucosa protection with antacids, H2 blockers or sucralphate decrease the incidence of stress ulcers and upper gastrointestinal bleeding but may have adverse effects. The present study compares the efficacy of continuous infusions of famotidine on gastric pH control and bleeding prevention in critically ill patients receiving mechanical ventilation. Fifty six patients (aged 55 +/- 22 years, 26 male) were randomly assigned to receive famotidine 40 mg/day (n = 27) or ranitidine 150 mg/day (n = 29) during 5 days. Gastric pH was measured every 6 hours and when it was below 5, aluminum hydroxide (30 ml every 2 hours) was administered to obtain values over 5. Patients receiving famotidine had higher mean gastric pH (6.3 +/- 0.2 and 93% of measurements over 5 vs 5.8 +/- 0.6 and 83% of measurements over 5 (p < 0.05), and required lower amounts of aluminum hydroxide (1.880 vs 2.770 ml). No patient had evidence of gastrointestinal bleeding and one had a mild psychomotor agitation. No other adverse reactions were observed. It is concluded that famotidine was more effective than ranitidine on gastric pH control in mechanically ventilated critically ill patients.

Acute Disease↗
PubMed1991

[Starch-induced granulomatous peritonitis].

A case of granulomatous peritonitis produced by starch is presented. This is a rare pathology caused by abdominal contamination with starch from surgical gloves during an operation. The symptoms can be very similar to acute abdomen, therefore, it is sometimes necessary to carry out a second operation in order to confirm the diagnosis. A peritoneal biopsy or cytology of the ascitic liquid usually provides the correct diagnosis as the typical starch granules show up. With non-steroid analgesics, or steroids in some cases, the process can controlled.

Abdomen, Acute↗
PubMed1990

In vivo experimental assessment of polytetrafluoroethylene trileaflet heart valve prosthesis.

This report summarizes the results of a series of experimental implantations of polytetrafluoroethylene valves in sheep. Twelve prostheses were implanted in the tricuspid position in weanling (3- to 4-month-old, 26 +/- 3 kg) sheep. The valve sizes were 23 mm (eight animals) and 25 mm (four animals). There were two early deaths, and the 10 survivors were killed in a stepwise manner to get a mineralization profile of the valve. There was one episode of acute thrombosis but no evidence of pulmonary thromboemboli in any animal. In all cases the leaflets were thin and unretracted, but in half of them one cusp or more were stiffened. One valve displayed a fixed outward eversion of the free margin of two leaflets. Macroscopic calcification was detected in seven specimens and always involved the commissural areas. Radiologic studies confirmed this calcium topography and revealed only one case of severe and diffuse mineralization. In most cases the cusps showed a grossly visible pannus that was thinner and less extensive than usually seen in bioprostheses. Examination with light microscopy disclosed a complete lack of infiltrating cells within the cuspal material (made of compact polytetrafluoroethylene). However, those parts of the prostheses made of expanded polytetrafluoroethylene (the material covering the valve frame and the sutures) did show infiltration by host cells and calcium. Mineralized lesions were of extrinsic type, involving fibrin and fibroelastic host tissue accumulated in the inflow aspect of the commissures. Examination with transmission electron microscopy disclosed electron-dense masses surrounded by an electron-lucent granular homogeneous material in areas of mineralization. The time-course evolution of the tissue calcium content shows a moderate mineralization rate (0.46 +/- 0.31 mg/gm of dry-weight material per week of follow-up) and a marginally significant positive correlation between calcium content and follow-up. Our results suggest that the polytetrafluoroethylene valves have a moderate overall calcification rate and that calcium deposits appear to be always related to the commissural region and to the presence of expanded polytetrafluoroethylene.

Animals↗
PubMed1988

Degenerative pathologic findings after long-term implantation of bovine pericardial bioprosthetic heart valves.

Degeneration of bioprosthetic heart valves constitutes the most important limitation to their long-term durability and the factor that avoids a wider clinical use of these devices. We studied 26 degenerated bovine pericardial valves that belong to a series of 55 prostheses explanted for various reasons. Age of the patients at implantation of the valve and other factors predisposing to primary tissue failure did not seem to significantly influence the results obtained. Mean implantation time was longer for aortic than for mitral valves (p less than 0.05). Also, the mode of failure was different for mitral and aortic prostheses. Tearing of one or more leaflets without mineralization was more frequent (p less than 0.0025) among mitral than among aortic specimens. Coverage of the valve cusps by a macroscopically visible host sheath was more extensive on the outflow than on the inflow aspect (p less than 0.0015 aortic valves; p less than 0.015 mitral valves). On radiological examination the majority of valves had diffuse and severe mineralized lesions. Collagen degeneration was the most frequent histologic lesion to be found in both mineralized and calcium-free valves. Calcification was also frequent and appeared as mineral deposits that extended between different collagen planes. Scanning electron microscopy revealed the almost complete lack of "endothelium-like" cover on any of the valves and exposure of the underlying fibrous components of the pericardial tissue in areas subjected to abrasion. Transmission electron microscopy confirmed the collagen degeneration and disclosed electron-dense microparticles (probably mineralized) both in the extracellular space and within degenerated host connective tissue cells.

Adult↗
PubMed1987

The behavior of pericardial versus porcine valve xenografts in the growing sheep model.

The comparative long-term behavior of the pericardial versus the porcine bioprostheses is not yet known. The need for long follow-up times to answer this question makes the growing sheep model an attractive alternative, given its ability to induce early valve degeneration. Sixty-three sheep, 12 to 16 weeks old, were operated on and received 39 porcine (11 Xenomedica, 10 Carpentier-Edwards S, nine Hancock I standard, and nine Hancock I T6-treated) and 24 pericardial (14 Mitroflow and 10 Ionescu-Shiley low profile) prostheses of clinical quality in the tricuspid position. Of the 52 operative survivors (32 received porcine valves and 20 received pericardial bioprostheses), six animals (five pericardial and one porcine) were eliminated because of bioprosthetic infection. Late sudden death before the scheduled killing occurred significantly more often (p less than 0.0001) in the pericardial (8/15 or 53%) than in the porcine group (1/31 or 3%). Calcium content of the explanted valves was significantly correlated with time in the pericardial group and the Xenomedica porcine prostheses (p less than 0.05) but not in the Hancock I and Carpentier-Edwards S valves, where it was only marginally significant (0.1 greater than p greater than 0.05). Linear regression analysis of tissue calcium content showed a similar slope for the pericardial group and Xenomedica porcine valves, in comparison with the remaining porcine valves. Comparison between the two lines using covariance analysis demonstrated a statistically significant difference between them, which shows that the pericardial and Xenomedica porcine valves appear to reach higher levels of calcification in a shorter follow-up time than the Hancock I, standard and T6-treated, and the Carpentier-Edwards S valve in this animal model.

Animals↗