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Biomedical subjects

A Romero

Publications and source records attributed to A Romero.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Evaluation of commercial UHT milk and optimization of industrial process].

From the nutrition al point of view milk is one of the most complete food in the diet of mammals. It contains nearly all the nutrients necessary to sustain life, but milk can deteriorate very easily, either by microbiological contamination or by biochemical reactions during processing and/or storage. The objective of this research study was to design a modified UHT treatment to achieve commercial sterilization and maximize the stabilization of the heat-treated product during storage. To search for a modified UHT process, a mathematical model coupled with an optimization routine (complex method) was developed. The mathematical model considers Kinetics for the inactivation of Bacillus stearothermophilus and several quality factors. To attain the objective function, several commercial UHT milk were analyzed and for the computer search the minimization of hydroxy methyl furfural (HMF) formation was considered and also including constraints for protease and lipase inactivation. The complex optimization procedure was implemented to search for the optimum modified UHT treatment.. One of the optimum modified UHT treatments was the combination of two pre-treatment (3.16 minutes at 62.30 degrees C and 6 minutes at 75 degrees C) in addition with a UHT treatment (0.75 s at 148.8 degrees C). This treatment attains the maximum product stability with a negligible effect on composition and color formation in the treated milk (HMF formation less than 3 mg/mL).

Animals↗
PubMed1999

The 2.15 A crystal structure of CG-16, the developmentally regulated homodimeric chicken galectin.

Differential developmental regulation of expression, fine-specificity differences in ligand recognition and disparate capacity for homodimerization are characteristics of the two currently known proto-type chicken galectins. The X-ray crystal structure of the first avian galectin, the homodimeric agglutinin from chicken liver (CG-16), has been solved in the absence of ligand in two crystal forms. Although the arrangement of lectin dimers in the two crystals is different, the structure of the monomers and their association into the extended beta-sandwich that characterises the dimer are virtually identical. The fold establishes a beta-sandwich motif composed of a five-stranded and a six-stranded beta-sheet evocative of proto-type mammalian galectins. The carbohydrate-binding site is occupied by six water molecules that take the place of the sugar in the complex. They help to stabilise in the absence of the ligand the spatial arrangement of the amino acid side-chains involved in sugar recognition. Docking of N-acetyllactosamine into the binding site reveals that three of these water molecules, which are in direct contact with the protein, occupy positions equivalent to the key sugar hydroxyl groups, namely the hydroxyls at positions 4 and 6 of the galactose unit and at position 3 of the N-acetylglucosamine unit. Crystallographic data are fully consistent with the binding features in solution previously derived from chemical mapping with deoxy, fluoro and O-methyl derivatives and laser photo-CIDNP (chemically induced dynamic nuclear polarisation) studies. The possible molecular basis for the monomeric character of the chicken intestinal galectin as well as potential mechanisms of oxidative inactivation by disulphide bridging are evaluated on the basis of the given structural information concerning the CG-16 dimer interface and the cysteine residues, respectively.

Amino Acid Sequence↗
PubMed1999

Structural and functional study of a conserved region in the uncoupling protein UCP1: the three matrix loops are involved in the control of transport.

It has been reported that the region 261-269 of the uncoupling protein from brown adipose tissue mitochondria, UCP1, has an important role in the control of its proton translocating activity. Thus the deletion of residues Phe267-Lys268-Gly269 leads to the loss of the nucleotide regulation of the protein, while the complete deletion of the segment leads to the formation of a pore. The region displays sequence homology with the DNA-binding domain of the estrogen receptor. The present report analyzes the structure, by NMR and circular dichroism, of a 20 amino acid residue peptide containing the residues of interest. We demonstrate that residues 263-268 adopt an alpha-helical structure. The helix is at the N-terminal end of the sixth transmembrane domain. The functional significance of this helix has been examined by site-directed mutagenesis of the protein expressed recombinantly in yeasts. Alterations in the structure or orientation of the region leads to an impairment of the regulation, by nucleotides and fatty acids, of the transport activity. UCP1 is one member of the family formed by the carriers of the mitochondrial inner membrane. The family is characterized by a tripartite structure with three repeated segments of about 100 amino acid residues. Two of the mutations have also been performed in the first and second matrix loops and the effect on UCP1 function is very similar. We conclude that the three matrix loops contribute to the formation of the gating domain in UCP1 and propose that they form a hydrophobic pocket that accommodates the purine moiety of the bound nucleotide.

Adipose Tissue↗
PubMed1999

The identification of nuclear proteins that bind the homopyrimidine strand of d(GA.TC)n DNA sequences, but not the homopurine strand.

Alternating d(GA.TC)(n)DNA sequences, which are abundant in eukaryotic genomes, can form altered DNA structures. Depending on the environmental conditions, the formation of (GA.GA) hairpins or [C+T(GA.TC)] and [GA(GA.TC)] intramolecular triplexes was observed in vitro. In vivo, the formation of these non-B-DNA structures would likely require the contribution of specific stabilizing factors. Here, we show that Friend's nuclear extracts are rich in proteins which bind the pyrimidine d(TC)(n)strand but not the purine d(GA)n strand (NOGA proteins). Upon chromatographic fractionation, four major proteins were detected (NOGA1-4) that have been purified and characterized. Purified NOGAs bind single-stranded d(TC)n with high affinity and specificity, showing no significant affinity for either d(GA)n or d(GA.TC)nDNA sequences. We also show that NOGA1, -2 and -3, which constitute the three most abundant and specific NOGA proteins, correspond to the single-stranded nucleic acid binding proteins hnRNP-L, -K and -I, respectively. These results are discussed in the context of the possible contribution of the NOGA proteins to the stabilization of the (GA.GA) and [GA(GA.TC)] conformers of the d(GA.TC)n DNA sequences.

Amino Acid Sequence↗
PubMed1999

Energetics of a hydrogen bond (charged and neutral) and of a cation-pi interaction in apoflavodoxin.

Anabaena apoflavodoxin contains a single histidine residue (H34) that interacts with two aromatic residues (F7 and Y47). The histidine and phenylalanine rings are almost coplanar and they can establish a cation-pi interaction when the histidine is protonated. The histidine and tyrosine side-chains are engaged in a hydrogen bond, which is their only contact. We analyse the energetics of these interactions using p Ka-shift analysis, double-mutant cycle analysis at two pH values, and X-ray crystallography. The H/F interaction is very weak when the histidine is neutral, but it is strengthened by 0.5 kcal mol-1on histidine protonation. Supporting this fact, the histidine p Kain a F7L mutant is 0.4 pH units lower than in wild-type. The strength of the H/Y hydrogen bond is 0.7 kcal mol-1when the histidine is charged, and it becomes stronger (1.3 kcal mol-1) when the histidine is neutral. This is consistent with our observation that the (H34)Nepsilon2-OH(Y47) distance is slightly shorter in the apoflavodoxin structure at pH 9.0 than in the previously reported structure at pH 6.0. It is also consistent with a histidine p Kavalue 0.6 pH units higher in a Y47F mutant than in the wild-type protein. We suggest that the higher stability of the neutral hydrogen bond could be due to a higher desolvation penalty of the charged hydrogen bond that would offset its more favourable enthalpy of formation. The relationship between hydrogen bond strength and the contribution of hydrogen bonds to protein stability is discussed.

Anabaena↗
PubMed1999

Molecular characterization and crystallization of Diocleinae lectins.

Molecular characterization of seven Diocleinae lectins was assessed by sequence analysis, determination of molecular masses by mass spectrometry, and analytical ultracentrifugation equilibrium sedimentation. The lectins show distinct pH-dependent dimer-tetramer equilibria, which we hypothesize are due to small primary structure differences at key positions. Lectins from Dioclea guianensis, Dioclea virgata, and Cratylia floribunda seeds have been crystallized and preliminary X-ray diffraction analyses are reported.

Amino Acid Sequence↗
PubMed1999

Hypotriglyceridaemic activity of Ficus carica leaves in experimental hypertriglyceridaemic rats.

A model of hypertriglyceridaemia in rats is described, which was used to investigate the hypolipidaemic effect of an intraperitoneal (i./p.) administration of a Ficus carica leaf decoction. Hypertriglyceridaemia was induced in rats following the protocol: a fasting period of 22 h, 2 h of oral (p.o.) administration of 20% emulsion of longchain triglycerides (LCT emulsion), both repeated once. The plasma triglyceride and total cholesterol levels obtained 2 h after the protocol were 5.7 +/- 2.5 mmol/L (p < 0.0001 vs basal levels) and 1.7 +/- 0.3 mmol/L, respectively, n = 10. The new model was used to test the hypotriglyceridaemic effect of a single dose of Ficus carica (fig tree) leaf decoction administered i./p. (50 g dry wt/kg body wt). After the i.p. injection of serum saline (control group, n = 10) or Ficus carica extract (group A, n = 10), plasma triglyceride levels in the control group and group A were 5.9 +/- 2.9 mmol/L and 5.5 +/- 2.9 mmol/L just after the LCT emulsion protocol; 4.7 +/- 2.7 mmol/L and 0.9 +/- 0.4 mmol/L, p < 0.005, 60 min after the LCT protocol; and 3.6 +/- 2.9 mmol/L and 1.0 +/- 0.4 mmol/L, p < 0.05, 90 min after the LCT protocol. The plasma total cholesterol levels, which were not modified in our experimental model, showed no significant differences in relation to baseline levels in the presence or absence of Ficus carica treatment either. The clearly positive results suggest the presence in the fig leaf decoction of a compound or compounds that influence lipid catabolism.

Animals↗
PubMed1999

CO2 as a contrast medium in endoluminal treatment of high flow vascular malformations.

PURPOSE: To evaluate the diagnostic usefulness of CO2 as a radiologic contrast medium in pre and post-embolization of hemodynamically active vascular malformations. MATERIAL AND METHODS: Eight pre-and post-embolization angiographies were performed on five patients with hemodynamically active vascular malformations. In all cases sequentially iodinated contrast medium and CO2 were used. Procedures were performed using Philips Integris V equipped with specific software to process images obtained with CO2 as contrast medium and with a purpose-built gas injector pump. The images were assessed by three interventional radiologists who evaluated the findings by consensus. They were asked whether uptake of the malformations were better, worse or the same with iodinated contrast and CO2. The images were judged according to the following characteristics; quality, the filling in of the contrast in afferent artery of the HAVM, caliber and number of vessels and existence of pathologic communications in HAVM. These characteristics were assessed in all the patients of the study, both before and after embolization. RESULTS: The CO2 angiographic results were compared to those obtained using iodinated contrast material. Iodinated contrast provided superior image quality in all performed studies. The filling of arterial afference of HAVM was well defined with both contrast media. In all performed cases with CO2, the malformations showed more vessels. No inmediate nor subsequent complications developed with CO2 injections, except in one female patient, who presented an intense sensation of cramps in the lower limbs. CONCLUSION: CO2 is a useful diagnostic and assessment tool before and especially during the embolization of hemodynamically active vascular malformations. It improves quantification and uptake of the malformation's vascular architecture, detecting collateral circulation and arteriovenous shunts. It also detects residual post-embolization disease when iodinated contrast agent is unsuccessful.

Adolescent↗
PubMed1999

Does frequent replenishment with fresh monoenoic oils permit the frying of potatoes indefinitely?

The frying life of two monoenoic oils, extra virgin olive oil (EVOO) and high oleic acid sunflower oil (HOSO), used to fry potatoes following a domestic frying model, by replenishing the oil in the fryer with fresh oil after each use to maintain the oil volume/fresh potato ratio, was studied by measuring polar content (PC) and triglyceride oligomer (TO) content. A combination of column and high-performance size-exclusion chromatography was used. Changes in the PC and TO content of both oils according to the number of frying uses were adjusted to linear, logarithmic, and power equations. While all three equations reflected the alterations quite accurately (p < 0.001), the logarithmic and power equations defined them best. Frequent replenishment of both frying oils with fresh oil produced a stabilization of PC and TO levels after 20-40 uses. According to the linear adjustment equation, 321 +/- 33 frying operations with EVOO and 290 +/- 40 with HOSO would be needed to raise PC to 25%. To reach the 10% TO level set for discarding oil used in frying, EVOO and HOSO would have to be used 319 +/- 35 and 241 +/- 37 times, respectively. Using the power adjustment, however, the theoretical frying life of both oils would be much higher (at least 4460 frying uses before reaching a 25% PC and 538-1552 uses for the EVOO and 249-1319 uses for the HOSO to reach a 10% TO level). The frying life of EVOO and HOSO would be extended almost indefinitely (at least 170 000 uses) when the logarithmic adjustment was applied. These data suggest that frequent replenishment of used monoenoic oil with fresh oil permits one to fry sets of fresh potatoes a very high number of occasions.

Chromatography, High Pressure Liquid↗
PubMed1999

Vinorelbine and paclitaxel as first-line chemotherapy in metastatic breast cancer.

PURPOSE: To evaluate the efficacy and toxicity of a combination of vinorelbine (VNB) and paclitaxel (PTX) as first-line chemotherapy in metastatic breast carcinoma (MBC). PATIENTS AND METHODS: Between August 1995 and August 1997, 49 patients with untreated MBC received a regimen that consisted of VNB 30 mg/m2 in a 20-minute intravenous (IV) infusion on days 1 and 8 and PTX 135 mg/m2 in a 3-hour IV infusion (starting 1 hour after VNB) on day 1. Cycles were repeated every 28 days. The median age of the patients was 52 years, and 59% of patients were postmenopausal. Median performance status was 1. Dominant sites of disease were soft tissue in 6%, bone in 29%, and viscera in 65%. RESULTS: Objective responses were recorded in 27 of 45 assessable patients (60%; 95% confidence interval, 46% to 74%). Complete remissions occurred in three patients (7%), and partial remissions occurred in 24 patients (53%). No change was recorded in 12 patients (27%), and progressive disease occurred in six patients (13%). The median time to treatment failure was 7 months, and median survival duration was 17 months. The limiting toxicity was myelosuppression, mainly leukopenia in 49 patients (100%) (grade 1 to grade 2, four patients; grade 3, 30 patients; and grade 4, 15 patients). Neutropenia was observed in 100% of patients (grade 1 to grade 2, three patients; grade 3, 11 patients; grade 4, 35 patients). Two treatment-related deaths due to febrile neutropenia were observed in patients with massive liver involvement. Peripheral neurotoxicity developed in 33 patients (67%) (grade 1, 25 patients; grade 2, eight patients); there were no grade 3 or grade 4 episodes. CONCLUSION: The combination of VNB-PTX showed significant activity as first-line chemotherapy for patients with MBC. Myelosuppression was the dose-limiting side effect, whereas neurotoxicity was mild to moderate.

Adult↗
PubMed1999

[Hypothyroidism in patients treated for laryngeal cancer: preliminary results].

OBJECTIVE: The reported incidence of hypothyroidism following surgery and/or irradiation for laryngeal cancer varies widely and the condition often is misdiagnosed. This study examines the incidence of thyroid dysfunction in patients with laryngeal cancer. MATERIAL AND METHODS: Thyroid function tests were carried out in 75 patients with stage III and IV laryngeal carcinoma who were treated in our center with surgery (13 cases), radiotherapy (13 cases), or surgery and radiotherapy (49 cases) at least 18 months earlier. The clinical and histological variables recorded included T4 and TSH concentrations. Univariate and multivariate analysis was carried out with the BMDP program from UCLA (1995 version) to examine the relationship between hypothyroidism and clinical and pathological factors. RESULTS: Twenty-nine patients (38.6%) had high TSH or low T4 concentrations and were diagnosed as having hypothyroidism. Hypothyroidism was significantly related with date of surgery (before 1993) and the treatment used on the neck. Thyroid function was rarely affected in patients who underwent functional neck dissection, but radical neck dissection and irradiation of the neck always were followed by hypothyroidism. CONCLUSIONS: Thyroid testing should be performed routinely in the follow-up of laryngeal cancer. Many psychological symptoms attributed to total laryngectomy may be due to hypothyroidism, an easily treated condition.

Carcinoma, Squamous Cell↗
PubMed1999

Experimental hypertriglyceridaemia and hypercholesterolaemia in rats.

Lipid disorders and cardiovascular diseases have been related in many studies. We here studied the influence of acute ingestion of a long chain triglyceride (LCT) emulsion (rich in triglycerides) on plasma triglyceride (TG) and total cholesterol (TC) levels in laboratory animals (Wistar rats), comparing it with the induction of hypertriglyceridaemia and hypercholesterolaemia by Triton WR-1339 injection. The results show that Triton would be suitable for inducing hypercholesterolaemia but not hypertriglyceridaemias similar to those in humans. The LCT emulsion intake, however, provoked transitory hyperlipaemia with values similar to those often found in hyperlipaemic subjects, and would thus be suitable for testing possible antilipaemic treatments. Our study also presents a model of hypertriglyceridaemia, hypercholesterolaemia and obesity in experimental animals, provoked by a chronic intake of an LCT emulsion. This model may be useful in investigating the mechanisms of the pathogenesis of atherosclerosis and the pharmacological treatment of obesity and dyslipaemias.

Animals↗
PubMed1998

Binding of mannose-6-phosphate and heparin by boar seminal plasma PSP-II, a member of the spermadhesin protein family.

PSP-I/PSP-II, a heterodimer of glycosylated spermadhesins, is the major component of boar seminal plasma. Similarly to other spermadhesins, the PSP-II subunit is a lectin which displays heparin- and zona pellucida glycoprotein-binding activities. We have investigated the ligand binding capabilities of the heterodimer and the isolated subunits using several polysaccharides, glycoproteins, and phospholipids. PSP-II binds the sulfated polysaccharides heparin and fucoidan in a dose-dependent and seemingly-specific manner. In addition, PSP-II binds oligosaccharides containing exposed mannose-6-phosphate monoester groups and the binding is selectively inhibited by mannose-6-phosphate and glucose-6-phosphate. Inhibition experiments indicate that binding of PSP-II to sulfated polysaccharides and mannose-6-phosphate-containing oligosaccharides involves distinct but possibly overlapping binding sites. Heterodimer formation with PSP-I abolishes both the heparin and the mannose-6-phosphate binding capabilities, suggesting that the corresponding sites may be located at the dimer interface. Using the crystal structure of PSP-I/PSP-II heterodimer as a template, we have explored possible binding sites which satisfy the observed binding characteristics. In the proposed models, PSP-II Arg43 appears to play a pivotal role in both heparin- and mannose-6-phosphate-complexation as well as in heterodimer formation.

Animals↗
PubMed1998

The 2.15 A crystal structure of a triple mutant plastocyanin from the cyanobacterium Synechocystis sp. PCC 6803.

The crystal structure of the triple mutant A42D/D47P/A63L plastocyanin from the cyanobacterium Synechocystis sp. PCC 6803 has been determined by Patterson search methods using the known structure of the poplar protein. Crystals of the triple mutant A42D/D47P/A63L, which are stable for days in its oxidized form, were grown from ammonium sulfate, with the cell constants a = b = 34.3 A and c = 111.8 A belonging to space group P3(2)21. The structure was refined using restrained crystallographic refinement to an R-factor of 16.7% for 4070 independent reflections between 8.0 and 2.15 A with intensities greater than 2 sigma (I), with root mean square deviations of 0.013 A and 1.63 degrees from ideal bond lengths and bond angles, respectively. The final model comprises 727 non-hydrogen protein atoms within 98 residues, 75 water molecules and a single copper ion. The overall tertiary fold of Synechocystis plastocyanin consists of a compact ellipsoidal beta-sandwich structure made up of two beta-sheets embracing a hydrophobic core. Each sheet contains parallel and antiparallel beta-strands. In addition to the beta-sheets, the structure contains an alpha-helix from Pro47 to Lys54 that follows beta-strand 4. The three-dimensional structure of Synechocystis plastocyanin is thus similar to those reported for the copper protein isolated from eukaryotic organisms and, in particular, from the cyanobacterium Anabaena variabilis, the only cyanobacterial plastocyanin structure available so far. The molecule holds an hydrophobic region surrounding His87, as do other plastocyanins, but the lack of negatively charged residues at the putative distant remote site surrounding Tyr83 could explain why the Synechocystis protein exhibits a collisional reaction mechanism for electron transfer to photosystem I (PSI), which involves no formation of the transient plastocyanin-PSI complex kinetically observed in green algae and higher plants.

Amino Acid Sequence↗
PubMed1998

Glycine-enhanced inhibition of rat liver nucleotide pyrophosphatase/phosphodiesterase-I by EDTA: a full account of the reported inhibition by commercial preparations of acidic fibroblast growth factor (FGF-1).

The earlier reported inhibition of rat liver nucleotide pyrophosphatase/phosphodiesterase I (EC 3.1.6.9/EC 3.1.4.1; NPP/PDE) by culture-grade acidic fibroblast growth factor (FGF-1) correlates with a low-Mr contaminant. 1H-NMR analyses revealed EDTA in the total-volume fractions of a gel-filtration experiment, where all the inhibitory activity of the FGF-1 preparation was recovered. NPP/PDE inhibition by EDTA (and by unfractionated FGF-1 or the EDTA-containing fractions) was time-dependent, blocked by the substrate p-nitrophenyl-dTMP, and strongly enhanced by glycine. The use of glycine buffers in earlier work was critical to the apparent inhibition by FGF-1. The results point to a conformational change favored by glycine that may be relevant to the biological role of NPP/PDE.

Animals↗
PubMed1998

Structure of proline iminopeptidase from Xanthomonas campestris pv. citri: a prototype for the prolyl oligopeptidase family.

The proline iminopeptidase from Xanthomonas campestris pv. citri is a serine peptidase that catalyses the removal of N-terminal proline residues from peptides with high specificity. We have solved its three-dimensional structure by multiple isomorphous replacement and refined it to a crystallographic R-factor of 19.2% using X-ray data to 2.7 A resolution. The protein is folded into two contiguous domains. The larger domain shows the general topology of the alpha/beta hydrolase fold, with a central eight-stranded beta-sheet flanked by two helices and the 11 N-terminal residues on one side, and by four helices on the other side. The smaller domain is placed on top of the larger domain and essentially consists of six helices. The active site, located at the end of a deep pocket at the interface between both domains, includes a catalytic triad of Ser110, Asp266 and His294. Cys269, located at the bottom of the active site very close to the catalytic triad, presumably accounts for the inhibition by thiol-specific reagents. The overall topology of this iminopeptidase is very similar to that of yeast serine carboxypeptidase. The striking secondary structure similarity to human lymphocytic prolyl oligopeptidase and dipeptidyl peptidase IV makes this proline iminopeptidase structure a suitable model for the three-dimensional structure of other peptidases of this family.

Amino Acid Sequence↗
PubMed1998

Transcatheter embolization of symptomatic hepatic venous malformations.

The aim of this study was to evaluate our results in treatment and management of symptomatic hepatic venous malformations using transcatheter embolization therapy. From 1991 to 1997 five venous malformations were embolized in one man and four women ranging in age from 31 to 50 years. All patients presented nonspecific abdominal pain and were assessed in the general surgery unit. Percutaneous embolization was recommended. In all cases polyvinyl alcohol was used to embolize the afferent arterioles. Clinical and echographic control follow-up was carried out on an outpatient basis in our Vascular and Interventional Radiology Unit. Embolization was possible in all cases. No complications developed during the procedure, except in one case where the subject suffered a spasm of the hepatic artery. Mean follow-up time was 42 months (6-73 months). Four patients remained asymptomatic during the entire follow-up period, whereas one patient required reembolization. In our experience, transcatheter embolization of hepatic venous malformations is a noninvasive technique which requires few admissions and presents few complications. With further use, it could become the treatment of choice in symptomatic hepatic venous malformations as an alternative to surgery.

Adult↗