Search PubMed⌕ Search

Biomedical subjects

J Pons

Publications and source records attributed to J Pons.

At least 19 recordsLinked to original sources
PubMed2000

Multilocus enzyme analysis in aerobic and anaerobic bacteria using gel electrophoresis-nitrocellulose blotting.

An optimized multilocus enzyme electrophoresis method, which involves polyacrylamide-agarose gel electrophoresis followed by electrophoretic transfers on nitrocellulose sheets, was developed for the analysis of enzyme polymorphism in several aerobic and anaerobic bacterial species including Staphylococcus aureus, Streptococcus pneumoniae, S. agalactiae, Klebsiella pneumoniae and K. oxytoca, Clostridium bifermentans and C. sordellii, and Prevotella bivia. Serial electrophoretic transfers (during 5-15 min each) from a single polyacrylamide gel could be achieved for most enzymes studied, and allowed an increased definition of enzyme bands on nitrocellulose as compared to migration gels. Four enzymes, which could not be blotted in such conditions, could still be stained in gels after blotting. Thus, the method allowed the combined analysis of several enzymes after a single gel electrophoresis separation. The analysis of enzyme polymorphism in the various species studied raised the interest of polymorphic loci such as esterase or glutamic-oxaloacetic transaminase for epidemiologic studies. The method characterized a genetic diversity of enzyme loci of S. pneumoniae higher than previously reported, and is thus convenient for the analysis of genetic relationships between related isolates. Since the present method reduces the tediousness of multilocus enzyme electrophoresis and requires experimental conditions that are not specific for the bacterial population studied, it may be proposed for rapid population genetics analysis of a wide variety of bacteria.

Bacteria, Aerobic↗
PubMed1999

[A fatal aorto-esophageal fistula due a foreign body: a foreseeable accident?].

BACKGROUND: The ingestion of foreign bodies is the second most frequent cause of aorto-esophageal fistulization after aneurysms of the thoracic aorta. CASE REPORT: A 28-year-old man died from catastrophic hematemesis 7 days after ingesting a bone splinter. The CT scan performed 3 days before the fatal event had demonstrated a fistulous formation originating in the aorta. DISCUSSION: Aorto-esophageal fistulae develop progressively from the esophageal perforation caused by the foreign body. Clinically, there is medical chest pain, followed by arterial hematemesis and finally terminal exsanguination. Diagnosis must be achieved during the free intervals in this triad of often rapidly succeeding signs.

Adult↗
PubMed1999

[Hepatocellular carcinoma in a non-cirrhotic liver. Presentation of series of 77 operated patients].

OBJECTIVE: To present epidemiologic profile of this supposedly rare condition, its diagnostic management and the results of surgical treatment in a population of the mediterranean border. PATIENTS AND METHODS: Between 1987 and 1999, the records of patients operated on for hepatocellular carcinoma and in whom cirrhosis was not present on pathological examination of liver parenchyma were collected. Data were collected prospectively. RESULTS: Mean age was 57.6 years. There were 61 men (79%) and 16 women but sex ratio was 1/1 for patients under 50. Hepatitis B and/or C serology was positive in 22 patients (29%). At presentation, 56 patients (73%) suffered of symptoms and there was evidence of tumor at clinical examination in 30 (39%). Sensitivity of alpha-fetoprotein measurement was 55%, and 58% for preoperative percutaneous biopsy. Twelve had exploratory laparotomy only, 61 underwent partial liver resection and 4 were transplanted. Resection was presumed curative in 56 cases (73%). There was one single tumor mass in 41 cases (53%) and its mean size was 10.3 cm. Liver fibrosis was present in 24 cases (29%). After curative resection, 5-year survival rate was 46%, and favorable prognostic factors were: alpha-fetoprotein within normal range, single tumor mass or tumor size less than 10 cm. CONCLUSION: Hepatocellular carcinoma arising on noncirrhotic liver is not a rare occurrence. It is usually encountered at an advanced stage of the disease. Nonetheless, it remains extirpable in many cases with low postoperative mortality and long term results are better than those of resections for hepatocellular carcinoma on cirrhotic liver.

Actuarial Analysis↗
PubMed1999

Morbidity of major hepatic resections: a 100-case prospective study.

OBJECTIVE: To assess the morbidity and its main risk factors after major hepatic resection. DESIGN: Retrospective study of prospectively collected data. SETTING: University hospital, France. SUBJECTS: 100 consecutive patients who underwent major hepatic resections, 1989-95. INTERVENTIONS: Major hepatic resection, defined as resection involving 3 or more segments according to Couinaud's classification, in all cases. MAIN OUTCOME MEASURES: All complications that affected outcome or prolonged hospital stay. Risk factors identified by univariate and multivariate analysis. RESULTS: 45 patients developed at least 1 complication and 7 died. The most common complications were: pleural effusion (n = 21), hepatic failure (n = 12), and ascites (n = 9). Univariate analysis showed that the following variables were significantly related to the morbidity: age >55 years, American Society of Anesthesiologists (ASA) grade II or more, bilirubin >80 micromol/L, alkaline phosphatase activity more than double the reference range, malignant tumours, abnormal liver parenchyma, simultaneous surgical procedures, operative time >4 hours, and perioperative blood transfusion > or =600 ml. The extent of resection did not correlate with postoperative complications. Multivariate analysis showed that volume of blood transfusion > or =600 ml and simultaneous surgical procedures were the most important independent risk factors for complicated outcome. CONCLUSIONS: The morbidity associated with major hepatic resections remains high, and the main determinants of outcome are intraoperative surgeon-related factors.

Adult↗
PubMed1999

Energetic analysis of an antigen/antibody interface: alanine scanning mutagenesis and double mutant cycles on the HyHEL-10/lysozyme interaction.

Alanine scanning mutagenesis of the HyHEL-10 paratope of the HyHEL-10/HEWL complex demonstrates that the energetically important side chains (hot spots) of both partners are in contact. A plot of deltadeltaG(HyHEL-10_mutant) vs. deltadeltaG(HEWL_mutant) for the five of six interacting side-chain hydrogen bonds is linear (Slope = 1). Only 3 of the 13 residues in the HEWL epitope contribute >4 kcal/mol to the free energy of formation of the complex when replaced by alanine, but 6 of the 12 HyHEL-10 paratope amino acids do. Double mutant cycle analysis of the single crystallographically identified salt bridge, D32H/K97, shows that there is a significant energetic penalty when either partner is replaced with a neutral side-chain amino acid, but the D32(H)N/K97M complex is as stable as the WT. The role of the disproportionately high number of Tyr residues in the CDR was evaluated by comparing the deltadeltaG values of the Tyr --> Phe vs. the corresponding Tyr --> Ala mutations. The nonpolar contacts in the light chain contribute only about one-half of the total deltadeltaG observed for the Tyr --> Ala mutation, while they are significantly more important in the heavy chain. Replacement of the N31L/K96 hydrogen bond with a salt bridge, N31D(L)/K96, destabilizes the complex by 1.4 kcal/mol. The free energy of interaction, deltadeltaG(int), obtained from double mutant cycle analysis showed that deltadeltaG(int) for any complex for which the HEWL residue probed is a major immunodeterminant is very close to the loss of free energy observed for the HyHEL-10 single mutant. Error propagation analysis of double mutant cycles shows that data of atypically high precision are required to use this method meaningfully, except where large deltadeltaG values are analyzed.

Alanine↗
PubMed1999

Open heart surgery in public and private practice.

OBJECTIVES: To compare open heart surgery services provided by public and private hospitals in Catalonia (Spain) according to case mix, procedures undergone and surgical mortality. METHODS: Data on all adult patients undergoing open heart surgery procedures were collected prospectively in a sample of public and privately owned centres for a 6.5-month period in 1994. Sociodemographic, clinical and procedural variables were collected. A predictive model stratifying patients according to their surgical mortality risk was used to adjust for differences in case mix between providers. RESULTS: Included were 1287 open heart surgery procedures. Public and private patients differed significantly in terms of gender, clinical history (e.g. hypertension, pulmonary disease, recent infarction) and procedural variables (e.g. reoperation, type of intervention). There were also statistically significant differences related to educational level, with better educated patients more likely to be treated in private centres. Crude surgical mortality rates differed between providers, although public centres operated on higher-risk patients. After adjusting for differences in case mix, the association between the type of provider and surgical mortality was not statistically significant (odds ratio 1.68; 95% CI from 0.94 to 3.0). CONCLUSIONS: Although crude mortality rates differ between public and private providers, there is a significant trend towards higher surgical risk in public centres. After adjusting for surgical risk, differences between types of provider decreased and were no longer statistically significant. The importance of other social and health-related factors, such as educational level, may explain differences between providers in their patients' surgical risk and in their performance in open heart surgery.

Aged↗
PubMed1998

[Deteriorating choledochal cyst. A case].

Choledochal cysts have an increased risk of biliary tract malignancy, induced by reflux of pancreatic juice and anomalous pancreatobiliary ductal junction. We report one case of congenital choledochal cyst in a 68-year-old female whose malignancy was revealed by history of pain and jaundice. Pancreatico-duodenectomy was performed and the patient was alive 6 months later.

Aged↗
PubMed1997

Conservation of satellite DNA in species of the genus Pimelia (Tenebrionidae, Coleoptera).

Satellite DNA has been characterized in six allopatric species from the genus Pimelia: P. interjecta, P. integra, P. variolosa and P. baetica, inhabiting Iberian Peninsula, and P. elevata and P. criba, endemic to Balearic Islands Ibiza and Mallorca, respectively. All species show the presence of a single satellite DNA of a basic monomer length of 357 bp and A+T content of 69%, comprising a considerable amount of the genome (39%-45%, corresponding to about 4.5 x 10(5) copies per haploid genome). The sequence analysis of 22 cloned repeats reveals very high intra- and interspecific sequence similarity. Phylogenetic analysis separates the satellite sequences into two clusters, each comprising clones from three species exclusively. Within the clusters, satellite clones are not grouped species-specifically, except those of P. integra where species-diagnostic nt substitutions are detected with a pattern that could be produced by gene conversion. Such high sequence conservation could be related to preservation of satellite DNA curvature, resulting in a higher order helical structure, proposed to act as a specific protein binding domain.

Animals↗
PubMed1997

Mutational analysis of the major loop of Bacillus 1,3-1,4-beta-D-glucan 4-glucanohydrolases. Effects on protein stability and substrate binding.

The carbohydrate-binding cleft of Bacillus licheniformis 1,3-1, 4-beta-D-glucan 4-glucanohydrolase is partially covered by the surface loop between residues 51 and 67, which is linked to beta-strand-(87-95) of the minor beta-sheet III of the protein core by a single disulfide bond at Cys61-Cys90. An alanine scanning mutagenesis approach has been applied to analyze the role of loop residues from Asp51 to Arg64 in substrate binding and stability by means of equilibrium urea denaturation, enzyme thermotolerance, and kinetics. The DeltaDeltaGU between oxidized and reduced forms is approximately constant for all mutants, with a contribution of 5.3 +/- 0.2 kcal.mol-1 for the disulfide bridge to protein stability. A good correlation is observed between DeltaGU values by reversible unfolding and enzyme thermotolerance. The N57A mutant, however, is more thermotolerant than the wild-type enzyme, whereas it is slightly less stable to reversible urea denaturation. Mutants with a <2-fold increase in Km correspond to mutations at residues not involved in substrate binding, for which the reduction in catalytic efficiency (kcat/Km) is proportional to the loss of stability relative to the wild-type enzyme. Y53A, N55A, F59A, and W63A, on the other hand, show a pronounced effect on catalytic efficiency, with Km > 2-fold and kcat < 5% of the wild-type values. These mutated residues are directly involved in substrate binding or in hydrophobic packing of the loop. Interestingly, the mutation M58A yields an enzyme that is more active than the wild-type enzyme (7-fold increase in kcat), but it is slightly less stable.

Bacillus↗
PubMed1997

Polymorphic curvature of satellite DNA in three subspecies of the beetle Pimelia sparsa.

The curvature of the monomeric repeats of satellite DNAs from three subspecies of the beetle Pimelia sparsa (Coleoptera, Tenebrionidae) has been analysed. Evidence of curvature was inferred from their retarded migration in native polyacrylamide gels, which was confirmed by direct electron microscopy visualisation. Sequence-comparison analysis, which included sequence alignments and modelling studies, was used to reveal the patterns of local bending and curvature. The effects of the minor-groove-binding drugs distamycin and berenil on the curvature were assayed, and analysed with respect to their (A+T)-rich sequence preferences. Since our study deals with satellite DNAs from closely related organisms (three subspecies), we correlated the differences in sequence, and also the high similarity conserved in the (A+T)-rich regions, with the changes in the patterns of curvature.

Animals↗
PubMed1996

Esophageal cancer resection in the elderly.

OBJECTIVE: Esophageal cancer is a disease whose prognosis is dismal and its surgery involves considerable risks, consequently the opportunity of esophageal resection in elderly patients with esophageal cancer is questionnable. The aim of this study was to analyze, with respect to their age, the outcome of 386 consecutive patients who underwent esophagectomy and simultaneous replacement for cancer. METHODS: A chart review of all patients with esophageal carcinoma admitted to our institution was undertaken for the period January 1979-December 1994. RESULTS: The portion of patients of 70 years of age and older (14.5%) has slightly increased during the period. Location to the lower third of the esophagus and adenocarcinoma type were prevalent in the 56 elderly patients (group I), but their postsurgical TNM staging was identical to that of the 330 younger patients (group II). Other clinical features, i.e. preoperative weight loss and the presence of co-morbid diseases, however, were comparable in the two groups. Pulmonary function, as assessed by spirometry, was significantly worse among the older patients, but blood gas determinations were not different. Operative mortality was comparable, between the two groups (10.7% vs 11.2%). Major morbidity included anastomotic leak (10.7% vs 13.6%) and pulmonary complications (17.9% vs 20.6%) in both groups. Excellent palliation of dysphagia was achieved in 92% of the 50 group I patients who survived the operation. Long-term survival was not different in elderly patients (5-year rate: 17%) when compared with that of younger patients (18.9%). CONCLUSION: These data suggest that esophagectomy can be performed safely in selected septuagenarian patients, thus allowing a substantial survival with excellent functional status in a portion of these patients.

Adenocarcinoma↗
PubMed1995

Crystal structure of Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase at 1.8 A resolution.

The crystal structure of the 1,3-1,4-beta-D-glucan 4-glucanohydrolase from Bacillus licheniformis is solved at a resolution of 1.8 A and refined to R = 16.5%. The protein has a similar beta-sandwich structure as the homologous enzyme from Bacillus macerans and the hybrid H(A16-M). This demonstrates that the jellyroll fold of these proteins is remarkably rigid and only weakly influenced by crystal contacts. The crystal structure permits to extend mechanistic considerations derived for the B. licheniformis enzyme to the entire class of bacterial 1,3-1,4-beta-D-glucan 4-glucanohydrolases.

Bacillus↗
PubMed1995

Contribution of a disulfide bridge to the stability of 1,3-1,4-beta-D-glucan 4-glucanohydrolase from Bacillus licheniformis.

Bacillus 1,3-1,4-beta-glucanases possess a highly conserved disulfide bridge connecting a beta-strand with a solvent-exposed loop lying on top of the extended binding site cleft. The contribution of the disulfide bond and of both individual cysteines (Cys61 and Cys90) in the Bacillus licheniformis enzyme to stability and activity has been evaluated by protein engineering methods. Reduction of the disulfide bond has no effect on kinetic parameters, has only a minor effect on the activity-temperature profile at high temperatures, and destabilizes the protein by less than 0.7 kcal/mol as measured by equilibrium urea denaturation at 37 degrees C. Replacing either of the Cys residues with Ala destabilizes the protein and lowers the specific activity. C90A retains 70% of wild-type (wt) activity (in terms of Vmax), whereas C61A and the double mutant C61A-C90A have 10% of wt Vmax. A larger change in free energy of unfolding is seen by equilibrium urea denaturation for the C61A mutation (loop residue, 3.2 kcal/mol relative to reduced wt) as compared with the C90A mutation (beta-strand residue, 1.8 kcal/mol relative to reduced wt), while the double mutant C61A-C90A is approximately 0.8 kcal/mol less stable than the single C61A mutant. The effects on stability are interpreted as a result of the change in hydrophobic packing that occurs upon removal of the sulfur atoms in the Cys to Ala mutations.

Bacillus↗
PubMed1994

Identification of active site carboxylic residues in Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase by site-directed mutagenesis.

Active site residues of 1,3-1,4-beta-D-glucan 4-glucanohydrolase (EC 3.2.1.73) from Bacillus licheniformis have been identified by site-directed mutagenesis. Previous work revealed that Glu-134 was essential for enzymatic activity, and it was proposed as the catalytic nucleophile by affinity labeling of the highly homologous Bacillus amyloliquefaciens enzyme. To search for the general acid catalyst, the Asp and Glu residues conserved among the Bacillus isozymes have been mutated to Asn and Gln, respectively. Out of the 14 positions studied, only the E138Q mutation yielded an inactive enzyme, whereas the E134Q and D136N mutants retained less than 0.5% of the wild type activity. Based on the three-dimensional structure of a hybrid B. amyloliquefaciens-Bacillus macerans 1,3-1,4-beta-D-glucan 4-glucanohydrolase, Glu-134, Asp-136, and Glu-138 are the only carboxylic acid residues that are properly located into the active site cleft to participate in catalysis. Glu-138 appears as the most likely candidate to function as the general acid catalyst, while Asp-136 may affect the pK alpha of the catalytic residues.

Amino Acid Sequence↗
PubMed1993

Localization of tandemly repeated DNA sequences in beetle chromosomes by fluorescent in situ hybridization.

In situ hybridization to chromosomes and nuclei of Tenebrio molitor shows the massive presence of a species-specific satellite DNA in all chromosomes and six sites of rDNA in mitotic chromosomes. These sites are located in two autosomal pairs and in the X and Y chromosomes. In a related species, Misolampus goudoti, in which two different families of highly repetitive DNA have been previously characterized, one family is located in centromeric regions of all chromosomes with the exception of chromosome Y, while the other repeated DNA family is present both in centromeric and distal regions of all chromosomes. rRNA genes in this species are present in a medium-sized autosomal pair only. These results show that molecular cytogenetics can be applied to coleopteran chromosomes and open the way for a physical mapping of DNA sequences in these organisms. The results also provide insights into the type of meiotic association of the X and Y chromosomes in Coleoptera and the distribution of repeated DNAs within the genome of these insects.

Animals↗