Biomedical subjects

I Alvarez

Publications and source records attributed to I Alvarez.

At least 55 records · Page 3Linked to original sources

PubMed2000

Acute mastoiditis in children: review of the current status.

BACKGROUND: acute mastoiditis is the most common intratemporal complication of otitis media. Its management is still a challenge due to potentially serious consequences. This study was designed to evaluate the recent experience with pediatric acute mastoiditis at our institution and to determine if the incidence of this entity is changing over time. MATERIAL AND METHODS: retrospective review of records of children with acute mastoiditis treated at the hospital of the Medical School at the University of Porto, Portugal, between July 1993 and June 1998. Criteria for the diagnosis of acute mastoiditis were postauricular swelling and erythema, protrusion of the auricle, and evidence of co-existent or recent otitis media. RESULTS: 43 patients fulfilled the entry criteria. Most were boys (69%). Ages ranged from 8 months to 14 years and 4 months; infants represented 40% of the total. Acute mastoiditis was the first recognized sign of otitis media in 48% of patients. More recent years of the study saw an increase in the number of children referred with acute mastoiditis. Upon admission, 56% were under antibiotic treatment, with an average intake of 5.8 days. All patients were hospitalized; 26 cases recovered after intravenous antibiotics plus myringotomy, and the rest required an additional surgical procedure. The most common organisms recovered from cultures were Streptococcus pneumoniae and Streptococcus pyogenes. In our series, associated complications occurred in 13.9%; facial paralysis in one, and involvement of the central nervous system in five. CONCLUSIONS: pediatric acute mastoiditis continues to be a potentially dangerous infection in the antibiotic era. The incidence of this complication may be increasing recently in the community studied. Great care is required of clinicians to reach an early diagnosis in order to promote adequate management and prevent inherently severe complications.

Acute Disease↗

PubMed2000

An N-acetylated natural ligand of human histocompatibility leukocyte antigen (HLA)-B39. Classical major histocompatibility complex class I proteins bind peptides with a blocked NH(2) terminus in vivo.

Sequence-independent interactions involving the free peptidic NH(2) terminus are thought to be an essential feature of peptide binding to classical major histocompatibility complex (MHC) class I proteins. Challenging this paradigm, a natural Nalpha-acetylated ligand of human histocompatibility leukocyte antigen (HLA)-B39 was identified in this study. It matched the NH(2)-terminal sequence of two human helicases, was resistant to aminopeptidase M, and was produced with high yield from a synthetic 30 mer with the sequence of the putative parental protein by the 20S proteasome. This is the first reported natural ligand of classical MHC class I antigens that has a blocked NH(2) terminus.

Acetylation↗

PubMed2000

Influence of different factors on the inactivation of Salmonella senftenberg by pulsed electric fields.

The influence of growth phase, cell concentration, pH and conductivity of treatment medium on the inactivation of Salmonella senftenberg by high electric field pulses (HELP) was studied. Cells were more resistant to HELP treatments at the beginning of the logarithmic phase and at the stationary phase. Microbial inactivation was not a function of the initial cell concentration. At constant input voltage, electric field strength obtained in the treatment chamber depended on medium conductivity. At the same electric field strength, conductivity did not influence S. senftenberg inactivation. At the same conductivity, inactivation of S. senftenberg was bigger at neutral than acidic pH.

Electricity↗

PubMed2000

Limited diversity of peptides related to an alloreactive T cell epitope in the HLA-B27-bound peptide repertoire results from restrictions at multiple steps along the processing-loading pathway.

The influence of various factors along the processing-loading pathway in limiting the diversity of HLA-B27-bound peptides around a core protein sequence was analyzed. The C5 proteasome subunit-derived RRFFPYYV and RRFFPYYVY peptides are natural B*2705 ligands. The octamer is an allospecific CTL epitope. Digestion of a 27-mer fragment of C5 revealed that both ligands are generated from this precursor substrate with the 20S proteasome in vitro in a ratio comparable to that in the B*2705-bound peptide pool. The C5 sequence allowed to derive a nested set of six additional peptides with 8-11 residues containing the core octamer sequence and the Arg2 motif of HLA-B27, none of which was found in the B27-bound pool. Together, low proteasomal yield, disfavored TAP-binding motifs, and low affinity for B*2705 accounted for the absence of four of the six peptides. The two remaining differed from the natural octamer or nonamer ligands only by an additional N-terminal Ser residue. Their stability in complex with B*2705 was lower than the respective natural ligands, raising the possibility that N-terminal trimming might have favored a shift toward the more stable peptides. The results suggest that the B*2705-bound peptide repertoire has a highly restricted diversity around a core alloantigenic sequence. This is not explained by a single bottleneck feature, but by multiple factors, including proteasomal generation, TAP-binding motifs, MHC-binding efficiency, and perhaps optimized stability through N-terminal trimming. Tapasin-dependent restrictions, although not excluded, were not required to explain the absence in vivo of the particular peptide set in this study.

Amino Acid Sequence↗

PubMed2000

HLA-B27 and immunogenetics of spondyloarthropathies.

The arthritogenic peptide hypothesis has inspired research aimed at defining the peptide-presenting properties of HLA-B27 subtypes and their relation to ankylosing spondylitis. Various studies have shed new light on the influence of HLA-B27 polymorphism in modulating peptide binding and T-cell antigen presentation. Moreover, multiple factors along the antigen processing-loading pathway, including tapasin, contribute to shaping the HLA-B27 repertoire. Other studies have revealed significant peptide-binding similarities between HLA-B27 and subtypes of HLA-B39, supporting a role of this antigen in spondyloarthropathy. A putative pathogenetic role of the HLA-B27 heavy chain, initially suggested from studies in transgenic mice, is claimed on the basis of novel, yet circumstantial, evidence concerning an apparently unusual capacity of the heavy chain to form stable homodimers or misfold after biosynthesis. Finally, it appears that arthritogenic infections might downregulate HLA-B27 expression, favoring bacterial survival. The specificity and mechanism of this phenomenon are yet to be defined.

Alleles↗

PubMed2000

Pharmacology of cizolirtine: a new analgesic agent.

Cizolirtine citrate (E-4018) is a new analgesic agent with antinociceptive activity against phenylquinone (ED50 33.7 mg/kg) and acetic acid (ED50 24.4 mg/kg) in mice, against acetic acid in rats (ED50 21.3 mg/kg) and in the plantar test (ED50 26.8 mg/kg). It demonstrated antinociceptive activity in the tail-pinch and tail-flick tests (ED50s of 68.0 and 46.0 mg/kg, respectively), in both phases of the formalin test (ED50 13.8 and 2.31 mg/kg), and in the capsaicin test (ED50 7.14 mg/kg). Cizolirtine does not inhibit prostaglandin biosynthesis, it is not a ligand for opioid receptors, it does not have antiinflammatory or ulcerogenic activity, it has some antipyretic activity and shows no affinity for alpha 2-adrenergic receptors, but its analgesic effect was modified by idazoxan and by desipramine. Recent studies have shown that the analgesic effect of cizolirtine could be related, at least partially, to an inhibition of spinal substance P release.

Analgesics↗

PubMed2000

Heat resistance of Alicyclobacillus acidocaldarius in water, various buffers, and orange juice.

The effect of the pH or the composition of the heating medium and of the sporulation temperature on the heat resistance of spores of a thermoacidophilic spore-forming microorganism isolated from a dairy beverage containing orange fruit concentrate was investigated. The species was identified as Alicyclobacillus acidocaldarius. The spores showed the same heat resistance in citrate-phosphate buffers of pH 4 and 7, in distilled water, and in orange juice at any of the temperatures tested (D120 degrees C = 0.1 min and z = 7 degrees C). A raise in 20 degrees C in the sporulation temperature (from 45 to 65 degrees C) increased the heat resistance eightfold (from D110 degrees C = 0.48 min when sporulated at 45 degrees C to 3.9 min when sporulated at 65 degrees C). The z-values remained constant for all sporulation temperatures. The spores of this strain of A. acidocaldarius were very heat resistant and could easily survive any heat treatment currently applied to pasteurize fruit juices.

Bacillaceae↗

PubMed2000

Kidney transplants in Uruguay.

Explore the source record for details and available documents.

Adolescent↗

PubMed1999

A molecular insight on the association of HLA-B27 with spondyloarthropathies.

This article focuses on molecular studies concerning HLA-B27 and their relevance for its pathogenetic role in spondyloarthropathy. The peptide binding and T-cell antigen presenting properties of HLA-B27 are discussed, mainly in connection with differential subtype association to ankylosing spondylitis. Molecular studies in transgenic rodents are also considered, with an emphasis on their relevance to the various pathogenetic mechanisms. Recent studies on the putative role of HLA-B27 in bacteria-host interactions are also discussed, as they suggest another level of implication of HLA-B27 in disease whose molecular basis is obscure.

Animals↗

PubMed1999

Relationship of human papillomavirus to ploidy in squamous cell carcinomas of the head and neck.

To establish the relationship between the presence of human papillomavirus (HPV) gene sequences and the development of genetic abnormalities, 31 squamous cell carcinomas of the head and neck were studied for the presence of HPV types 6b and 16 and the DNA content by flow cytometry. Eighteen (58%) cases were aneuploid. HPV DNA was present in seven (22.5%) tumors. Five of them were positive for the HPV type 6b and two for the HPV type 16. Aneuploidy was correlated with poorly differentiated tumors. No correlation was found between the presence of HPV, DNA content, or tumor differentiation. Consequently, the presence of HPV gene sequences does not seem to be related to a higher incidence of genetic abnormalities in squamous cell carcinomas of the head and neck.

Adult↗

PubMed1999

Ionization, electron attachment, and drift in CHF3.

Using a pulsed Townsend technique, we have measured the effective ionization coefficient and the electron drift velocities in CHF(3). The density-normalized electric field intensity E/N ranged from 4 to 250 townsends (Td) (1 Td=10(-17) V cm(2)). The E/N value at which the effective ionization coefficient becomes zero was estimated to be 66 Td. For E/N<20 Td, the electron attachment coefficients are practically constant, and are compatible to within about +/-70% with previously measured values at thermal energies and above.

Journal Article↗

PubMed1999

Glutathione protection against hydrogen peroxide, tert-butyl hydroperoxide and diamide cytotoxicity in rat hepatoma-derived Fa32 cells.

1. Several ozonides, peroxides and aldehydes are formed during ozone therapy, recently introduced in medicine. tert-Butyl hydroperoxide (t-BHP), H2O2 and diamide were investigated as model substrate in rat hepatoma-derived Fa32 cells. 2. The cytotoxicity was measured by the neutral red uptake inhibition assay after 1 h or 24 h treatment. The relative toxicities were quantified by the determination of the NI50. This is the concentration of test compound required to induce an inhibition of 50% in neutral red uptake as compared to the control cells. All test chemicals were more toxic after 24 h than after 1 h. 3. The influence of the glutathione (GSH) alteration on the cytotoxicity was measured by treating the cells with 2-oxo-4-thiazolidine carboxylic acid (OTC) or L-buthionine sulfoximine (BSO). OTC increased the endogenous GSH content in the cells. BSO pretreatment strongly decreased the NI50 of the three chemicals. OTC pretreatment increased the NI50 of H2O2 but not of t-BHP and diamide. This can be explained by the strong GSH-depletion after 1 h by t-BHP and diamide, which contrasted with a weak GSH-depletion by H2O2 after the same time period. 4. The three test chemicals increased the endogenous GSH content after 24 h. t-BHP and H2O2, but not diamide, increased the total GSH transferase (GST) activity. Several alterations of the GST subunits were observed. Most striking was the increase of class alpha GST subunits, also for diamide. 5. Since H2O2 and t-BHP are ozone metabolites thought to be responsible for the therapeutic effects of well-dosed ozone, the results show that Fa32 cells can be used as a valuable alternative model system for studying the effects encountered in human ozone therapy.

Animals↗

PubMed1998

[Treatment of low-grade gastric MALT lymphoma with Helicobacter pylori eradication. Follow-up of the histological and molecular response].

BACKGROUND: Low grade gastric MALT lymphoma is associated to infection with Helicobacter pylori. Also, H. pylori eradication can produce histologic regression of the lymphoma. PATIENTS AND METHODS: This study reports the follow-up of a prospective series of 11 patients with low grade gastric MALT lymphoma, stage I, treated with eradicative therapy for H. pylori. After treatment, patients were followed up with sequential endoscopies to asses the histological and molecular regression of the lymphoma, using a score of the histological lesions and the amplification of the IgH gene with PCR analysis. RESULTS: Helicobacter pylori was eradicated in all patients. In 10(90.9%) histological regression of the lymphoma was demonstrated, in 6 of them in the first control after treatment. In the 10 patients with histological response, PCR analysis demonstrated a polyclonal rearrangement of the IgH gene in 6 (60%) and a clonal band in 4 (40%), that eventually disappeared at 12 (SD 4) months after treatment. In 4 patients with a previous polyclonal rearrangement, a clonal band was occasionally detected in any sequential controls; in 2 of these cases the clonal band disappeared 5 and 7 months after treatment and in the remaining 2 its evolution is not yet known. Nine patients have been followed up and are in remission 18 (SD 8) months after treatment. CONCLUSIONS: Eradication of H. pylori can produce histologic regression in stage I low grade gastric MALT lymphoma, and should be the first therapeutic option. Despite histological regression of the lymphoma, PCR analysis can detect a clonal rearrangement of the IgH gene in 40% of the cases, but its significance remains unknown. Sequential and prolonged follow-up is essential to assess whether this lymphoma can be actually cured with eradication therapy for H. pylori.

Adult↗

PubMed1998

Lysine-rich gamma-zeins are secreted in transgenic Arabidopsis plants.

We have previously shown that the maize (Zea mays L.) storage prolamine gamma-zein, accumulates in endoplasmic reticulum-derived protein bodies in transgenic plants of Arabidopsis thaliana (L.) ecotype R + P. The retention of gamma-zein in the endoplasmic reticulum was found to be mediated by structural features contained in the polypeptide, an N-terminal proline-rich and a C-terminal cysteine-rich domain which were necessary for the correct retention and assembly of gamma-zein within protein bodies (M.I. Geli et al., 1994, Plant Cell 6: 1911-1922). In the present work we incorporated in the gamma-zein gene lysine-rich coding sequences which were positioned after the N-terminal proline-rich domain and at five amino-acid residues from the C-terminus. The targeting of lysine-rich gamma-zeins was analyzed by expression of chimeric genes regulated by the cauliflower mosaic virus (CaMV) 35S promoter in transgenic Arabidopsis plants. The lysine-rich gamma-zeins were detected by immunoblotting and we found that these proteins were modified posttranslationally to reach their mature form. Subcellular fractionation and immunocytochemical studies demonstrated that glycosylated lysine-rich gamma-zeins were secreted to the cell wall of transgenic Arabidopsis leaf cells.

Arabidopsis↗

PubMed1998

Technetium-99m-labeled anti-EGF-receptor antibody in patients with tumor of epithelial origin: I. Biodistribution and dosimetry for radioimmunotherapy.

UNLABELLED: Accurate estimation of biodistribution and absorbed dose to normal organs and tumors is important for immunoscintigraphic studies and radioimmunotherapy treatment planning. METHODS: Four patients (3 men, 1 woman; mean age 54.8 +/- 9.2 yr; range 42-64 yr) were administered 3 mg of anti-human epidermal growth factor receptor (anti-hEGF-r) antibody (ior egf/r3), radiolabeled with 99mTc activity of 39.5 +/- 1.1 mCi (range 38.5 mCi-40.7 mCi) by intravenous bolus infusion. After administration, blood and urine samples were collected from three patients up to 24 hr after injection. Whole-body anterior and posterior scans were obtained at 5 min and 1, 3, 5 and 24 hr after injection. Using a computer program, regions of interest were drawn over the heart, liver, spleen, bladder and tumor to measure the activity in the source organs at each scanning time. Time-activity curves for each source organ were then fitted to monoexponential or biexponential functions by nonlinear least squares regression using the flexible polyhedrals method, which adequately fit our data with the correlation coefficient of 0.985 +/- 0.013, and were integrated to determine organ residence times. The mean absorbed doses to the whole body and various normal organs were then estimated from residence times and from blood and urine samples using the methods developed by the Medical Internal Radiation Dose Committee. The effective dose equivalent and effective dose were calculated as prescribed in ICRP Publication Nos. 30 and 60. RESULTS: Plasma disappearance curves of 99mTc-labeled anti-hEGF-r antibody were best-fit by a two-compartment model in all patients with a distribution half-life (t(1/2alpha)) of 0.207 hr +/- 0.059 hr (mean +/- s.d., n = 3) and an elimination half-life (t(1/2beta)) of 13.9 hr +/- 2.2 hr. Among the various organs, significant accumulation of the radiolabeled antibody was found in the liver (48.5% +/- 4.4%, mean +/- s.d.), heart (3.50% +/- 0.17%) and spleen (3.1% +/- 1.8%) at 5 min postadministration. These values were reduced to 3.2% +/- 0.4%, 0.1% +/- 0.01% and 0.1% +/- 0.1%, respectively, at 24 hr. Mean cumulative urinary excretion of 99mTc-labeled anti-hEGF-r antibody was 4.6% +/- 0.6% at 24 hr postinjection. Estimates of radiation absorbed dose to normal organs in rad/mCi administered (mean +/- s.d., n = 4) were: whole body 0.017 +/- 0.002; gallbladder wall 0.074 +/- 0.007; spleen 0.136 +/- 0.076; and liver 0.267 +/- 0.036. The effective dose equivalent and effective dose estimates for adults were 0.041 +/- 0.008 rem/mCi and 0.027 +/- 0.004 rem/mCi administered. CONCLUSION: This feasibility study indicates that 99mTc-labeled anti-hEGF-r antibody (ior egf/r3) can be used safely; this analysis provides a dosimetric framework for future studies. This monoclonal antibody, labeled with 188Re, could possibly permit a successful regional radioimmunotherapy of tumors of epithelial origin.

Adult↗

PubMed1998

Histomorphometric changes after small bowel transplantation.

AIM: Rejection results in destruction of the intestinal mucosa. This is the major cause of morbidity and morbility in human allografts. The aim of this study was to investigate histomorphometric changes in both the graft and recipient intestinal mucosa after experimental orthotopic small bowel transplantation. EXPERIMENTAL DESIGN: Using the pig model, 21 large-white pigs underwent: laparotomy (n = 7) (control group); orthotopic small bowel transplantation without immunosuppression (n = 7); and orthotopic small bowel transplantation with cyclosporine A (n = 7). RESULTS: 1) Significant reduction of total mucosal thickness (villi plus crypt) (p < 0.05) in both the graft and recipient mucosa; 2) Attenuation of this effect by administration of cyclosporine A, which reduced the loss of mucosal thickness mainly at the expense of crypt hipertrophy. CONCLUSIONS: These findings suggest that villi and crypt length measurements may be a reliable method for monitoring rejection after small bowel transplantation.

Animals↗

PubMed1997

A ColE1-type plasmid from Salmonella enteritidis encodes a DNA cytosine methyltransferase.

The multicopy plasmid pFM366 was isolated from a virulent Salmonella enteritidis strain and was found to code for DNA methylase activity (Ibáñez and Rotger, 1993). The present work was aimed at characterizing the genetic organization and functional features of this 5.6 kb plasmid. We found pFM366 almost identical to the plasmid P4 isolated from Shigella sonnei, that encodes the SsoII restriction-modification system (Karyagina et al., 1993), and related to other ColE1-type plasmids. Examination of these plasmids revealed a common organization which suggests they were the result of similar recombinational events. The cytosine methylase of pFM366 is nearly identical to M. SsoII, whereas the gene encoding the restrictase homologous to R. SsoII is truncated and its product is inactive. The expression of the cytosine methylase encoded by pFM366 is strongly affected by deletion of regions located upstream and downstream of its ORF, and is negatively controlled by the rpoS gene in Escherichia coli. The methylase activity encoded by pFM366 induces the SOS response, which could be responsible for the observed delay in the growth of E. coli.

Amino Acid Sequence↗

PubMed1997

Lysine-rich modified gamma-zeins accumulate in protein bodies of transiently transformed maize endosperms.

During maize seed development, endosperm cells synthesize large amounts of storage proteins, alpha-, beta-, and gamma-zeins, which accumulate within endoplasmic reticulum (ER)-derived protein bodies. The absence of lysine in all zein polypeptides results in an imbalance in the amino acid composition of maize seeds. We modified the maize gamma-zein gene through the introduction of lysine-rich (Pro-Lys)n coding sequences at different sites of the gamma-zein coding sequence. Maize endosperms were transiently transformed by biolistic bombardment with Lys-rich gamma-zein constructs under the control of the 1.7 kb gamma-zein seed-specific promoter and the cauliflower mosaic virus (CaMV) 35S promoter. When (Pro-Lys)n sequences were inserted contiguous to or in substitution of the Pro-Xaa region of the gamma-zein, high levels of protein were observed. In contrast, when (Pro-Lys)n sequences were inserted five residues from the C-terminal, the transcript was present but modified protein was not detected. These results suggest that only an appropriate positioning of Lys-rich inserts leads to the modified molecule displaying correct folding and stability. Subcellular localization analyses and immunoelectron microscopy studies on isolated protein bodies demonstrated that modified gamma-zeins accumulate within these organelles and co-localized with endogenous alpha- and gamma-zeins. The studies reported here show the feasibility of manipulating the gamma-zein gene in order to obtain stable and correctly targeted Lys-rich zeins in maize seeds.

Cloning, Molecular↗