Biomedical subjects

C Alfonso

Publications and source records attributed to C Alfonso.

At least 19 recordsLinked to original sources

PubMed2006

[Clinical tumoral size dissociation in acoustic neuroma: reality or measure distortion?].

INTRODUCTION: In this study we have analyzed (i) the audiometric frequencies more often affected in acoustic neuroma (AN), (ii) the percentage of patients presenting normal hearing and those with sudden hearing loss, (iii) if there is a correlation between tumor size and hearing loss, and (iv) the relationship between clinical and radiological parameters and audiological data. METHODS AND MATERIAL: Retrospective study of 81 patients undergoing surgical removal of a sporadic AN. RESULTS: The highest threshold in the tumor's ear was found at 8000 Hz, and the highest interaural difference at 4000 Hz. The percentage of patients presenting normal hearing and sudden hearing loss was 2.5% and 9%, respectively. No significant association was found between tumor size and hearing loss, preoperative facial palsy or Vth cranial nerve deficit. There was a significant association between the degree of hearing loss and Vth cranial nerve deficit, and between hearing loss and preoperative facial palsy. CONCLUSIONS: The association between hearing loss and Vth cranial nerve deficit, and between hearing loss and preoperative facial palsy is independent the size of the tumour.

Adolescent↗

PubMed2006

Solid mesenchymal hamartoma in an adult: a case report.

Mesenchymal hamartoma of the liver (MHL) is an uncommon tumour composed of architecturally abnormal bile ducts in an uncommitted myxoid stroma. Most MHL are diagnosed in childhood and few cases have been reported in adults. This report describes a case of a well defined solid mass in the right lobe of the liver in a 51 year old man. Preoperative radiological examination revealed a large completely solid mass. Biopsy showed a dense fibrous stroma with hyalinisation and some bile ducts. A provisional diagnosis of MHL was made. Surgical excision was impossible and liver transplantation was undertaken. Definitive pathology confirmed the diagnosis. Review of published reports shows this to be the fourth case of MHL treated by liver transplantation.

Hamartoma↗

PubMed2005

[Quality of life in cochlear implanted patients].

Several articles show the audiologic benefits of cochlear implants, although it is still necessary to prove their impact on quality of life. In this study, 36 Med-El processor users were included. The Glasgow Benefit Inventory (GBI) was used to measure changes in quality of life, and another questionnaire was used to evaluate the communication abilities. Eighty-six percent of the patients answered our questionnaire. The quality of life improved significantly according to the specific questionnaire. The average total benefit obtained with the GBI was +41, and the average scores related to general, social and physics benefits were +57, +16, and +3, respectively. No significant difference was found between quality of life and other parameters like insertion depth of the array, etiology or duration of the deafness.

Adolescent↗

PubMed2004

Tolerance-induced receptor selection: scope, sensitivity, locus specificity, and relationship to lymphocyte-positive selection.

Receptor editing is a mode of immunological tolerance of B lymphocytes that involves antigen-induced B-cell receptor signaling and consequent secondary immunoglobulin light chain gene recombination. This ongoing rearrangement often changes B-cell specificity for antigen, rendering the cell non-autoreactive and sparing it from deletion. We currently believe that tolerance-induced editing is limited to early stages in B-cell development and that it is a major mechanism of tolerance, with a low-affinity threshold and the potential to take place in virtually every developing B cell. The present review highlights the contributions from our laboratory over several years to elucidate these features.

Animals↗

PubMed2001

The impact of H2-DM on humoral immune responses.

H2-DM (DM, previously H2-M) facilitates the exchange of peptides bound to MHC class II molecules. In this study, we have used H2-DM-deficient (DM(-/-)) mice to analyze the influence of DM in the priming of B cell responses in vivo and for Ag presentation by B cells in vitro. After immunization, IgG Abs could be raised to a T-dependent Ag, 4-hydroxy-5-nitrophenylacetyl-OVA, in DM(-/-) mice, but closer analysis revealed the IgG response to be slower, diminished in titer, and composed of low-affinity Abs. The Ab response correlated with a vast reduction in the number of germinal centers in the spleen. The presentation of multiple epitopes by H2-A(b) from distinct Ags was found to be almost exclusively DM-dependent whether B cells internalized Ags via fluid phase uptake or using membrane Ig receptors. The poor B cell response in vivo could be largely, but not completely restored by expression of a H2-Ea(d) transgene, despite the fact that Ag presentation by H2-E(d/b) molecules was found to be highly DM dependent. Hence, while substantial Ab responses can be raised in the absence of DM, this molecule is a crucial factor both for Ag processing and for the normal maturation of T-dependent humoral immune responses in vivo.

Animals↗

PubMed2001

Defective antigen processing in GILT-free mice.

Processing of proteins for major histocompatibility complex (MHC) class II-restricted presentation to CD4-positive T lymphocytes occurs after they are internalized by antigen-presenting cells (APCs). Antigenic proteins frequently contain disulfide bonds, and their reduction in the endocytic pathway facilitates processing. In humans, a gamma interferon-inducible lysosomal thiol reductase (GILT) is constitutively present in late endocytic compartments of APCs. Here, we identified the mouse homolog of GILT and generated a GILT knockout mouse. GILT facilitated the processing and presentation to antigen-specific T cells of protein antigens containing disulfide bonds. The response to hen egg lysozyme, a model antigen with a compact structure containing four disulfide bonds, was examined in detail.

Amino Acid Sequence↗

PubMed2001

Comparison of amoxicillin and azithromycin in the prevention of recurrent acute otitis media.

OBJECTIVE: To compare the outcome of patients with recurrent acute otitis media (AOM) treated either with amoxicillin or with azithromycin. METHODS: This prospective, controlled, and randomized study, compares the outcome of 71 patients with recurrent AOM treated with azithromycin (31 patients) or amoxicillin (40 patients) for the prevention of AOM. azithromycin was given at a dose of 10 mg/kg once a week, whereas amoxicillin was administered daily as a single intake of one third of the therapeutic dosage (20 mg/kg per day). All treatments were prescribed for 3 months. Both groups were homogeneous with regard to the currently accepted predisposing factors of recurrent AOM. Mean age of children was 35.3 months, and average follow-up was 11.5 months. The treatment was considered effective when the number of episodes of AOM dropped to less than 50% after the prophylaxis. RESULTS: Patients in the azithromycin group had a clinical response to prophylaxis (80.6%) comparable to those treated with amoxicillin (89.5%) (P=0.300). The incidence of adverse effects was similar in both groups. CONCLUSION: According to these results, a prophylaxis with azithromycin is as useful as amoxicillin to prevent recurrent AOM.

Acute Disease↗

PubMed2000

Interaction of the antitumor drug 9-aminoacridine with guanidinobenzoatase studied by spectroscopic methods: a possible tumor marker probe based on the fluorescence exciplex emission.

Fluorescence spectroscopy, surface-enhanced Raman spectroscopy (SERS), and analytical centrifugation are applied in this work to study the interaction of the antitumor drug 9-aminoacridine (9AA) with a trypsin-like protease, guanidinobenzoatase (GB), extracted from an Erlich tumor. As a consequence of this interaction, a strong 9AA exciplex emission can be detected at a certain drug and enzyme concentration. The 9AA exciplex emission was also studied for 9AA interacting with others serin proteases: alpha-chymotrypsin, trypsin, and penicillin G-acylase (PGA), as well as with bovine serum albumin (BSA) in order to obtain information about the active center of GB. We have found that the exciplex 9AA emission may be induced by a ring-stacking interaction between the monomeric drug, under the amino form, and an aromatic residue placed in the catalytic site of the protein. The results derived from Raman spectroscopy corroborate this interaction mechanism, as demonstrated by the existence of typical protonated amino 9AA marker bands as well as an important modification of the ring vibrations, thus indicating the existence of an interaction through ring stacking. The analytical centrifugation technique was applied to study the GB association in aqueous solution, demonstrating that the 9AA/GB interaction depends on the enzyme quaternary structure. An interaction of 9AA with an associate form of GB, which may be the actual enzyme active form, is suggested.

Aminacrine↗

PubMed2000

Nonclassical MHC class II molecules.

Major histocompatibility complex (MHC) class II molecules are cell surface proteins that present peptides to CD4(+) T cells. In addition to these wellcharacterized molecules, two other class II-like proteins are produced from the class II region of the MHC, HLA-DM (DM) and HLA-DO (DO) (called H2-M, or H2-DM and H2-O in the mouse). The function of DM is well established; it promotes peptide loading of class II molecules in the endosomal/lysosomal system by catalyzing the release of CLIP peptides (derived from the class II-associated invariant chain) in exchange for more stably binding peptides. While DM is present in all class II- expressing antigen presenting cells, DO is expressed mainly in B cells. In this cell type the majority of DM molecules are not present as free heterodimers but are instead associated with DO in tight heterotetrameric complexes. The association with DM is essential for the intracellular transport of DO, and the two molecules remain associated in the endosomal system. DO can clearly modify the peptide exchange activity of DM both in vitro and in vivo, but the physiological relevance of this interaction is still only partly understood.

Animals↗

PubMed1999

Sticholysin II, a cytolysin from the sea anemone Stichodactyla helianthus, is a monomer-tetramer associating protein.

Sticholysin II (Stn-II) is a pore-forming cytolysin. Stn-II interacts with several supports for size exclusion chromatography, which results in an abnormal retardation precluding molecular mass calculations. Sedimentation equilibrium analysis has revealed that the protein is an associating system at neutral pH. The obtained data fit a monomer-tetramer equilibrium with an association constant K4c of 10(9) M(-3). The electrophoretic pattern of Stn-II treated with different cross-linking reagents, in a wide range of protein concentrations, corroborates the existence of tetrameric forms in solution. A planar configuration of the four monomers, C4 or D2 symmetry, is proposed from modelling of the cross-linking data.

Animals↗

PubMed1999

A technique to create appropriate abutment tooth contours for removable partial dentures.

A technique is presented for using light-cured composite resin to create desirable contours on abutment teeth for the retention and support of removable partial dentures. The desired tooth shape is created on a diagnostic cast, captured in a clear temporary splint material, and formed in resin on the abutment teeth with the splint acting as a matrix.

Composite Resins↗

PubMed1999

The role of H2-O and HLA-DO in major histocompatibility complex class II-restricted antigen processing and presentation.

The function of major histocompatibility complex (MHC) class II molecules is to sample exogenous antigens for presentation to CD4+ T helper cells. After synthesis in the endoplasmic reticulum, class II molecules are directed into the endosomal system by association with the invariant chain (Ii), which is sequentially cleaved, generating class II dimers loaded with Ii-derived peptides (CLIP). These class II-peptide complexes are physiological substrates for H2-M/HLA-DM, a resident of the endosomal/lysosomal system which facilitates the removal of CLIP from newly synthesised class II alpha beta dimers. Exchange of CLIP for antigenic class II-binding peptides is also promoted by the action of H2-M/HLA-DM, resulting in stable peptide-class II complexes that are transported to the cell surface for presentation to CD4+ T cells. Recent evidence suggests that this H2-M/HLA-DM-mediated 'peptide editing' is influenced by another MHC class II-encoded molecule, H2-O/HLA-DO. This non-polymorphic alpha beta heterodimer is associated with H2-M/HLA-DM during intracellular transport and within the endosomal system of B cells. H2-O/HLA-DO alters the peptide exchange function of H2-M/HLA-DM in a pH-dependent manner, so that H2-M/HLA-DM activity is limited to more acidic conditions, corresponding to lysosomal compartments. Indeed, H2-O/HLA-DO may serve to limit the presentation of antigens after fluid phase uptake by B cells, while augmenting presentation of antigens internalised via membrane Ig receptors. Such a mechanism may maintain the fidelity of the B-cell-CD4+ T-cell interaction, counteracting self reactivity arising from less stringent lymphocyte activation. Here, data evaluating the role of H2-O/HLA-DO shall be reviewed and its putative function discussed.

Animals↗

PubMed1999

[Effect of amiloride and its derivative dichlorobenzamil on guinea pig atria: interaction with other inotropic mechanisms].

The inotropic and chronotropic effects of Amiloride (AMI) and Dichloro-benzamil Amiloride (DBC-AMI) were studied on the guinea pig isolated atria, also, the interaction between these drugs and Beta-methyl-Digoxin (BM-DIGO), epinephrine and low extracellular potassium (1 mM). AMI (10(-3) M) has a negative chronotropic and positive inotropic effects, not dependent on the autonomic system. DCB-AMI has a bimodal effect on the contractile force: increases it at low concentrations but causes a decrease at concentrations higher than 10(-6) M. The effect of AMI on the sinus frequency is unchanged by BM-DIGO. AMI (10(-3) M) decreases the inotropic effect of BM-DIGO and increases the toxic concentration of this drug on isolated tissues. The dose-response curve to epinephrine was not changed by AMI. Similar results were obtained using DCB-AMI (2 x 10(-7) M). The positive inotropic effect obtained by low extracellular potassium (1 mM) was not altered by AMI. The activity of the Mg(++)-dependent, Na+/K+ ATPase measured in the microsomal fraction obtained from guinea pig heart was diminished (10%) by AMI (10(-3) M). The drug did not affect the inhibition of the enzyme induced by ouabain. In conclusion, our experiments show multiple effects of AMI and DCB-AMI on the guinea pig heart. The inhibition of the Na+/Ca++ exchange explains them only partially. A slow channel blocking effect appears fundamental to interpret our results.

Amiloride↗

PubMed1997

AFLP Linkage Map of the Oomycete Phytophthora infestans

Here we present the first comprehensive genetic linkage map of the heterothallic oomycetous plant pathogen Phytophthora infestans. The map is based on polymorphic DNA markers generated by the DNA fingerprinting technique AFLP (Vos et al., 1995, Nucleic Acids Res. 23: 4407-4414). AFLP fingerprints were made from single zoospore progeny and 73 F1 progeny from two field isolates of P. infestans. The parental isolates appeared to be homokaryotic and diploid, their AFLP patterns were mitotically stable, and segregation ratios in the F1 progeny were largely Mendelian. In addition to 183 AFLP markers, 7 RFLP markers and the mating type locus were mapped. The linkage map comprises 10 major and 7 minor linkage groups covering a total of 827 cM. The major linkage groups are composed of markers derived from both parents, whereas the minor linkage groups contain markers from either the A1 or the A2 mating type parent. Non-Mendelian segregation ratios were found for the mating type locus and for 13 AFLP markers, all of which are located on the same linkage group as the mating type locus. Copyright 1997 Academic Press

Journal Article↗

PubMed1996

Anterior extraoral surgery to the upper cervical spine.

STUDY DESIGN: A series of 10 patients surgically treated with prevascular or retrovascular extraoral retropharyngeal approach to the upper cervical spine is examined. OBJECTIVES: In orthopedic surgery, retropharyngeal approach may replace the transoral surgery, obviating the risks of infection and the uncomfortable postoperative course of cases in which median labiomandibular glossotomy was used to accomplish complex bone reconstruction. SUMMARY OF THE BACKGROUND DATA: The transoral approach is reported in literature as the classical anterior access to the upper cervical spine that provides direct exposure for anterior decompression of the spinal cord. The risks, the surgical limits, and the postoperative difficulties of transmucosal access suggest the use of an anterior extraoral retropharyngeal approach in orthopedic surgery. METHODS: The series includes four neoplastic lesions (osteoma, aneurismal bone cyst, giant cell tumor, solitary metastasis), three retropharyngeal ossifications resulting from diffuse idiopathic skeletal hyperostosis, and a single case of os odontoideum, craniocervical malformation, and postlaminectomy kyphosis. RESULTS: At follow-up evaluation, all patients achieved a satisfactory outcome, with good clinical and radiographic results; nasotracheal intubation obviated the need for tracheostomy. The wide surgical exposure allowed reconstruction with iliac strut bone grafts and internal fixation in six patients, avoiding the need of a halo device. The only complications were four instances of transient palsies of the marginal mandibular branch of the facial nerve. CONCLUSIONS: In the anterior surgery of the upper cervical spine, the prevascular approach allows a wide surgical exposure, with visualization similar to that obtained with median labiomandibular glossotomy. The retrovascular approach is indicated in selected cases, such as tumor adjacent to the vertebral artery and C1-C2 arthrodesis with bilateral transarticular screws according to Barbour.

Adolescent↗

PubMed1995

Purification of a heat-stable chitin deacetylase from Aspergillus nidulans and its role in cell wall degradation.

An extracellular chitin deacetylase activity has been purified to homogeneity from autolyzed cultures of Aspergillus nidulans. This enzyme is an acidic glycoprotein with a pI of 2.75 and a 28% (wt/wt) carbohydrate content. The apparent M(r) of the enzyme estimated by SDS/PAGE and Superose 12 (f.p.l.c.) was around 27,000. The enzyme had an optimum pH at 7.0 and was stable in the pH range 4.0-7.5. Its optimum temperature of reaction was 50 degrees C, and it was stable from 30 degrees to 100 degrees C after 1 h of preincubation. The enzyme hydrolyzed glycol chitin and oligomers of N-acetylglucosamine and to a lesser extent chitin, colloidal chitin, carboxymethylchitin, and an alpha-1-->3, 1-->6-N-acetylgalactosamine-galactan among other substances with amido groups, but the enzyme did not hydrolyze peptide bonds. The role of this enzyme could be deacetylation of chitin oligosaccharides during autolysis, after action of endochitinase on cell walls.

Amidohydrolases↗

PubMed1994

Processing of viable group A streptococci leads to major histocompatibility complex class II presentation of T cell epitopes from the major protective antigen.

We have previously mapped major histocompatibility complex (MHC) class II-restricted T cell epitopes of the surface M protein of type 5 group A streptococci (M5) and show here that two out of four epitopes investigated were efficiently processed during incubation of viable streptococci with spleen cells for presentation to M5-specific murine T cell clones. Viable streptococci were processed more efficiently than heat-killed bacteria suggesting that secreted virulence factors of streptococci do not obstruct processing of streptococcal antigens in the dose range used. Epitopes from different regions of M5 could be ranked according to the efficiency with which they were processed, which may contribute to their relative immunodominance. It was further demonstrated that T cell clones specific for M5 308-319, an epitope from the M type conserved carboxy-terminal half of M5, cross-reacted between M5, M6 and M12, but not M49, streptococci. Helper T cell epitopes which are shared between streptococcal M types and are presented by MHC class II molecules on antigen-presenting cells after processing of viable streptococci could be particularly useful in the design of multivalent streptococcal vaccines.

Amino Acid Sequence↗

PubMed1992

Purification of a new galactanase from Penicillium oxalicum catalysing the hydrolysis of beta-(1----5)-galactofuran linkages.

An endo beta-(1----5)-galactofuranase from Penicillium oxalicum has been purified 91-fold. The enzyme is a basic glycoprotein with a pI 7.9 and 20% (w/w) carbohydrate content, galactose being the principal sugar. The apparent Mr of the enzyme estimated by denaturing gel electrophoresis was 77,000. The optimum pH was 5.0, and the enzyme was stable over the pH range 4.0-7.5. This enzyme hydrolyses specifically (1----5)-linked beta-D-galactofuranose residues in homo- and heterogalactans, but did not hydrolyse o-nitrophenyl galactose and beta-(1----5)-galactofuranbiose. Km and Vmax. values were 1.2 mg.ml-1 and 0.55 mumol.h-1 respectively when Eupenicillium crustaceum beta-(1----5)-galactofuran was used as substrate. The enzyme showed high affinity for different separation gels and proteins. The enzyme specificity and its mode of action showed that it could be an useful tool for analysing the fine structure of polysaccharides.

Carbohydrate Conformation↗