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Biomedical subjects

F Ferreira

Publications and source records attributed to F Ferreira.

At least 109 records · Page 6Linked to original sources
PubMed1993

Creation of prosody during sentence production.

Phrase-final words tend to be lengthened and followed by a pause. The dominant view of prosodic production is that word lengthening and pausing reflect the syntax of a sentence. The author demonstrates that, instead, lengthening and pausing reflect a distinctly prosodic representation, in which phonological constituents are arranged in a hierarchical, nonrecursive structure. Prosodic structure is created without knowledge of words' phonemic content. As a result, within a single sentential position, greater word lengthening necessitates shorter pauses, but across positions, word and pause durations show a positive correlation. The author presents a model of prosodic production that describes the process of prosodic encoding and provides a quantitative specification of the relation between word lengthening and pausing. This model has implications for studies of language production, comprehension, and development.

Adult↗
PubMed1993

Eye movement control during reading: fixation measures reflect foveal but not parafoveal processing difficulty.

The main purpose of this study was to determine whether, during natural reading, the difficulty of the upcoming parafoveal word affects eye movement behaviour on the currently fixated word. A model in which visual attention is allocated in parallel over both the fixated and the upcoming parafoveal word predicts such as effect, while a sequential attention allocation model in which attention is directed first to the fixated word and then to the upcoming parafoveal word, does not. The data reported here show that neither the frequency nor the combined length, frequency and class of the upcoming word affect eye movement behaviour on the current word. These data support the sequential attention--parallel programming model of eye movement control in reading.

Adult↗
PubMed1993

Allergens from birch pollen and pollen of the European chestnut share common epitopes.

Type I allergy to pollen of the European chestnut (Castanea sativa) represents a major cause of pollinosis in (sub) Mediterranean areas. Using sera from 14 patients with established allergy to pollen of the European chestnut, 13/14 sera (92%) showed IgE-binding to a 22 kD protein, 2/14 (14%) displayed additional binding to a 14 kD protein and 1/14 (7%) bound only to the 14 kD protein of European chestnut pollen extract. Two monoclonal mouse antibodies, BIP 1 and BIP 4, directed against different epitopes of Bet v I (the major birch pollen allergen), and a rabbit antibody to recombinant birch profilin (rBet v II) were used to characterize the proteins of the European chestnut pollen. The recombinant birch pollen allergens, rBet v I and rBet v II (profilin) were employed to show common allergenic structures on proteins from both birch and European chestnut pollen by IgE-inhibition experiments. Despite the fact that the 22 kD protein displayed a higher molecular weight in comparison to the 17 kD major birch pollen allergen, Bet v I, we could demonstrate reactivity of both monoclonal antibodies, BIP 1 and BIP 4, with this protein. A complete inhibiton of IgE-binding to this 22 kD protein was shown by pre-incubating sera with purified recombinant Bet v I. In addition, the 14 kD protein could be identified by IgE-inhibition studies with recombinant Bet v II and by using a rabbit anti-profilin antibody as the profilin from pollen of the European chestnut.

Allergens↗
PubMed1993

[Combined therapy in non-insulin-dependent diabetes mellitus].

In recent years an improved understanding of potential complications associated with hyperinsulinemia has led to a growing interest in alternatives to insulin monotherapy for patients with non-insulin-dependent diabetes mellitus, who have failed on a regimen of diet and sulphonylureas. These patients typically present normal or elevated levels of insulin. This problem which has been attributed to insulin resistance, is superimposed on the peripheral hyperinsulinemia resulting from subcutaneous insulin delivery. A plethora of clinical trials have reported on the efficacy of combining therapy in limiting insulin requirements while achieving better glycemic control. This paper attempts a critical review of the pros and cons with respect to combining therapy and provides guidelines for its practical use.

Combined Modality Therapy↗
PubMed1992

Profilins constitute a novel family of functional plant pan-allergens.

Type I allergy is a major health problem in industrialized countries where up to 15% of the population suffer from allergic symptoms (rhinitis, conjunctivitis, and asthma). Previously, we identified a cDNA clone that encoded a birch pollen allergen as profilin. Profilins constitute a ubiquitous family of proteins that control actin polymerization in eukaryotic cells; in particular, profilin participates in the acrosomal reaction of animal sperm cells. Although profilins had been unknown in plants so far, our finding led to the assumption that profilins might have similar functions in pollens during plant fertilization and therefore represent allergenic components in almost all pollens. We show that profilins are prominent allergens that can be isolated from tree pollens (Betula verrucosa, birch), from pollens of grasses (Phleum pratense, timothy grass), and weeds (Artemisia vulgaris, mugwort). About 20% of all pollen allergic patients tested (n = 65) displayed immunoglobulin E (IgE) reactivity to recombinant birch profilin that was expressed in pKK223-3. An IgE inhibition experiment performed with recombinant birch profilin and purified natural profilins from timothy grass and mugwort indicates common IgE epitopes. Moreover, all pollen profilins purified from these far distantly related plant species, and likewise the purified recombinant birch profilin, are able to elicit dose-dependent histamine release via high affinity Fc epsilon receptor of blood basophils from profilin allergic patients. The presence of profilin and possibly related proteins as crossreacting allergenic components in various plants therefore provides an explanation as to why certain allergic patients display type I allergic reactions with pollens and even food from distantly related plants. A functional pan-allergen, like profilin, available as purified recombinant protein, may be a useful diagnostic and probably therapeutic reagent.

Allergens↗
PubMed1992

Complementary DNA cloning and expression in Escherichia coli of Aln g I, the major allergen in pollen of alder (Alnus glutinosa).

Previous data showed that the major pollen allergens from trees of the order Fagales, in particular alder, birch, hazel, and hornbeam, are highly interrelated. As only the complete amino acid sequence of Bet v I, the major allergen from birch, has been known, it was of interest to obtain the primary structure of other major allergens of this group, to attribute IgE-binding properties to certain features of the amino acid sequences of those allergens. cDNA was synthesized from alder pollen mRNA, sequence-specifically amplified by polymerase chain reaction and cloned into plasmid bluescript. Comparison of the deduced amino acid sequences of Aln g I and Bet v I revealed a 86.8% homology. The Aln g I encoding cDNA was subcloned into pKK223-3 and expressed in Escherichia coli as a full-length nonfusion protein. The recombinant Aln g I bound IgE from tree pollen-allergic patients and was shown to share IgE-epitopes with Bet v I by inhibition studies with recombinant Bet v I. Computer-aided calculations predicted epitopes in both Aln g I and Bet v I at the same position; the Bet v I molecule was predicted to possess two additional epitopes near the N-terminus of the molecule.

Allergens↗
PubMed1992

Identification of common allergenic structures in hazel pollen and hazelnuts: a possible explanation for sensitivity to hazelnuts in patients allergic to tree pollen.

It is known that most patients with type I allergy to tree pollens also suffer from intolerance to nuts. To identify allergenic structures common to hazel pollen and hazelnuts, cross-reactivity of patients' IgE was investigated. With use of immunoblotting,.serum IgE from 25 patients displaying type I allergic reactions to tree pollens and intolerance to hazelnuts (group I) bound to the 17 kd major hazel pollen allergen Cor a I (100%) and to the 14 kd hazel pollen profilin (16%). IgE binding to proteins of comparable molecular weights in hazelnut extracts was found (18 kd and 14 kd), suggesting that proteins similar to Cor a I and hazel profilin might be also expressed in hazelnuts. In contrast, only four sera (22%) from 18 patients (group II) with tree pollen allergy but without any case history of nut hypersensitivity showed IgE binding to the 18 kd protein of hazelnut extract, and none of these sera exhibited IgE reactivity to the hazelnut profilin. To characterize the hazel pollen and hazelnut allergens, purified recombinant Bet v I (major birch pollen allergen) and purified recombinant Bet v II (birch profilin), respectively, were used for IgE-inhibition experiments. Binding of IgE from patients (with nut allergy) to the blotted hazelnut allergens could be blocked by preincubation of patients' sera with the recombinant proteins. Furthermore, the 18 kd protein of hazelnut extract was purified and induced specific release of histamine from basophils of a patient suffering nut hypersensitivity but not from a healthy control donor. A rabbit antibody raised against celery profilin identified the 14 kd proteins in hazel pollen and hazelnuts as profilin. Our experiments suggest a protein with IgE binding properties similar to the major allergens from pollens of hazel, Cor a I, and of birch, Bet v I, as predominant allergens in hazelnuts, and show that the plant pan-allergen profilin can be detected in both hazel pollen and hazelnut extracts.

Allergens↗
PubMed1992

Association between IgE response against Bet v I, the major allergen of birch pollen, and HLA-DRB alleles.

The association of the human IgE response against Bet v I, the major allergen of birch pollen, and the HLA-DR and DQ phenotype was studied. Birch pollen allergic patients showed a typical case history, positive skin-prick test, and positive RAST with birch pollen extracts. They were divided into two groups. Group I (n = 37) consisted of individuals generating IgE antibodies that selectively reacted with Bet v I. Their serum IgE did not react with minor allergens from birch pollen as tested by immunoblot analysis, nor did they show a response against allergens from a panel of grass and other tree pollen or perennial allergens from animals and fungi as determined by skin-prick test. Patients belonging to group II (n = 34) possessed IgE reacting with Bet v I plus one or more additional allergens. The control group consisted of 637 healthy blood donors. Comparison of the frequencies of RFLP-defined HLA-DR and DQ alleles in patients and the control group revealed that the distribution of DRB3 alleles in group I patients differed significantly from that in the control group: A higher frequency of the DRw52a/c alleles in comparison to the control group (pcorr less than 0.02) was observed. In addition, alleles defined by nucleotide sequences coding for the amino acid sequence tyrosine-phenylalanine-histidine at positions 30-32 of the beta chain of DR molecules were found with a higher frequency in patient group I (pcorr less than 0.02), too. These alleles comprise DRw52a/c and some DRB1 alleles.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1992

[Persistent ductus arteriosus in the adult--report of a case].

The authors describe a case of congenital heart disease no longer frequent in adults, due to an early diagnosis and surgical treatment. The patent ductus arteriosus in adults who received no therapy can present several forms of evolution, depending on its own hemodynamic profile. The present case is an example of a congenital heart disease not diagnosed during the childhood, that developed pulmonary hypertension and congestive heart failure. These clinical situations have a bad prognosis and place this patient in a group of high surgical risk. Thus, surgery is not advisable considering the bad prognosis and early high mortality rate.

Age Factors↗
PubMed1991

Structural studies of the extracellular polysaccharide elaborated by Azotobacter vinelandii strain 1484.

The structure of the extracellular polysaccharide from Azotobacter vinelandii strain 1484 has been investigated, specific degradations and n.m.r. spectroscopy being the main methods used. It is concluded that the polysaccharide is composed of tetrasaccharide repeating-units having the following structure, [sequence: see text] in which Sug is 3-deoxy-D-threo-hexulosonic acid. The polysaccharide also contains a non-stoichiometric amount of O-acetyl groups, distributed over at least two positions.

Azotobacter↗
PubMed1990

Effects of foveal processing difficulty on the perceptual span in reading: implications for attention and eye movement control.

Two experiments were conducted to examine the effects of foveal processing difficulty on the perceptual span in reading. Subjects read sentences while their eye movements were recorded. By changing the text contingent on the reader's current point of fixation, foveal processing difficulty and the availability of parafoveal word information were independently manipulated. In Experiment 1, foveal processing difficulty was manipulated by lexical frequency, and in Experiment 2 foveal difficulty was manipulated by syntactic complexity. In both experiments, less parafoveal information was acquired when processing in the fovea was difficult. We conclude that the perceptual span is variable and attentionally constrained. We also discuss the implications of the results for current models of the relation between covert visual-spatial attention and eye movement control in reading.

Adult↗
PubMed1990

Use of verb information in syntactic parsing: evidence from eye movements and word-by-word self-paced reading.

We investigated whether readers use verb information to aid in their initial parsing of temporarily ambiguous sentences. In the first experiment, subjects' eye movements were recorded. In the second and third experiments, subjects read sentences by using a noncumulative and cumulative word-by-word self-paced paradigm, respectively. The results of the first two experiments supported Frazier and Rayner's (1982) garden-path model of sentence comprehension: Verb information did not influence the initial operation of the parser. The third experiment indicated that the cumulative version of the self-paced paradigm is not appropriate for studying on-line parsing. We conclude that verb information is not used by the parser to modify its initial parsing strategies, although it may be used to guide subsequent reanalysis.

Adult↗
PubMedDate not supplied

The importance of recombinant allergens for diagnosis and therapy of IgE-mediated allergies.

In the past 10 years, a considerable number of cDNAs coding for allergens have been isolated and expressed. Intensive investigations showed that recombinant allergens and their respective natural counterparts possess comparable properties with respect to structure, function and interaction with the immune system. Recent studies documented that in vitro as well as in vivo diagnosis of IgE-mediated allergic diseases can be successfully improved by the application of recombinant allergens. In addition, new strategies for a safer specific immunotherapy (SIT) have been developed based on the knowledge of the primary structures of allergens. Naturally occurring isoforms of allergens as well as recombinant allergens with modified amino acid sequences show very low IgE binding capacity but strong T cell-stimulatory activity and represent possible candidates. In case of Bet v 1, the major birch pollen allergen, isoforms d, g and l and a Bet v 1a mutant, produced by site-directed mutagenesis resulting in 6 amino acid exchanges, fulfilled the above mentioned criteria. In a third approach, two adjacent peptides covering the entire Bet v 1a sequence were produced in an Escherichia coli expression system. These peptides contained most of the relevant T cell epitopes, but lost their IgE binding capacity and, thus, their ability to activate mast cells and basophils of sensitized patients. Our results suggest that allergen variants (isoforms, mutants, T cell epitope-containing peptides) may be used as 'hypoallergenic agents' in SIT.

Allergens↗
PubMedDate not supplied

The influence of CpG motifs on a protein or DNA-based Th2-type immune response against major pollen allergens Bet v 1a, Phl p 2 and Escherichia coli-derived beta-galactosidase.

BACKGROUND: DNA immunization and protein immunization with CpG motifs as adjuvants represent promising approaches in allergen-specific immunotherapy. OBJECTIVE: We investigated the effect of coinjection or prepriming with CpG-ODN on Th2-type responses induced by gene gun and protein immunization. METHODS: BALB/c mice were immunized with the gene gun using plasmid DNA containing the cDNAs coding for the genes of Bet v 1a, Phl p 2 and beta-galactosidase or with the purified Al(OH)(3)-adsorbed proteins. In addition, CpG-ODN were applied by coinjection or by prepriming treatment. Antibody and cytokine responses were measured by ELISA, proliferative and cytotoxic responses were determined by standard labeling procedures. Furthermore, the allergenic activity of sera was measured by passive cutaneous anaphylaxis. RESULTS: Gene gun immunization and protein immunization induced a clear Th2-type response for all antigens. The Th1-promoting effect of CpG-ODN coinjection together with gene gun immunization was restricted to beta-galactosidase as indicated by the increase of IgG2a and a marked expression of IFN-gamma. CpG motifs also increased the specific cytotoxic response against beta-galactosidase. Prepriming with CpG-ODN and gene gun or protein immunization with Bet v 1a exhibited no significant difference to the non-CpG control group. However, sera from mice preprimed with CpG-ODN induced no anaphylaxis with gene gun immunization, but with protein immunization. CONCLUSIONS: The effect of CpG motifs in vivo depends on a variety of parameters like the nature of the antigen and the immunization modality. Furthermore, our studies indicate that a combination of CpG + DNA immunization may be more effective in antagonizing Th2 responses than the combination of CpG + protein immunization.

Adjuvants, Immunologic↗
PubMedDate not supplied

Humoral immune responses to recombinant tree pollen allergens (Bet v I and Bet v II) in mice: construction of a live oral allergy vaccine.

Recombinant tree pollen allergens (recombinant Bet v I and recombinant birch profilin, Bet v II) were purified and used to immunize BALB/c and B6D2F1 mice with Al(OH)3 to elicit a specific IgE response. Serum from immunized mice was then used to detect immunoblotted natural tree pollen allergens. The onset of the humoral immune response was monitored using antimouse IgE, IgG1, IgG2a/b, IgG3 and IgA. In both strains, a specific and long-lasting IgE response could be elicited with both recombinant allergens. Mice immunized continuously with recombinant Bet v I + Al(OH)3 showed a significant decrease of specific IgE antibodies indicating that continuous application of allergens can reduce specific IgE responses. The possibility of inducing a different type of immune responses is indicated by the fact that mice fed with Bet v I expressed in apathogenic Salmonella strains showed a Th1 immune response to Bet v I accompanied by specific IgG2a/b without detectable IgG1 or IgE. Recombinant allergens can hence be used to decrease or even modulate specific IgE responses in vivo.

Adjuvants, Immunologic↗