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Biomedical subjects

C Mayer

Publications and source records attributed to C Mayer.

At least 91 records · Page 5Linked to original sources
PubMed1999

Genetics and specific immune response in allergy to birch pollen and food: evidence of a strong, positive association between atopy and the HLA class II allele HLA-DR7.

BACKGROUND: In some geographic areas birch pollen represents the most prominent cause for airborne allergic diseases. Up to 70% of patients allergic to birch pollen are hypersensitive to fruits, especially apples. Associations have been found, in some instances, with a sensitivity to aeroallergens and HLA class II genes. OBJECTIVES: We investigated whether susceptibility or resistance to birch pollen allergy with and without food allergy was associated with HLA class II genes. METHODS: Blood samples were obtained from 2 groups of unrelated European-born white adults: 42 atopic patients (31 of them with asthma) and 42 healthy control subjects with no personal or familial history of asthma or atopy. Their antibody responses to birch pollen, apples, grass, and weed pollens were evaluated by skin tests, RASTs, and immunoprints. Genomic DNA was extracted from PBLs. The exons of DQA1, DQB1, DRB1, and DPB1 genes were selectively amplified by using the PCR method. Genotyping was carried out by digestion of the amplified DNA products with allele-specific endonucleases (PCR-RFLP), which recognize allelic variations in the polymorphic exon. RESULTS: We found no significant differences in the frequency of DPB1 alleles between patients and control subjects. HLA class II DR4 and/or DR7 alleles were present in 42.6% of the patients and in only 2.4% of the healthy subjects. These results confirm a previous study of a group of polysensitized atopic patients, which showed that DR4 and DR7 alleles were rare in healthy control subjects and frequently observed in atopic subjects with or without concomitant asthma. CONCLUSION: We conclude that the allele HLA-DR7 is significantly involved in the presentation of apple and pollen allergens. However, we suggest that this susceptibility is more related to atopy than to specific responses to allergens.

Adult↗
PubMed1999

The role of intermolecular interactions: studies on model systems for bacterial biofilms.

The mechanical stability of biofilms and other microbial aggregates is of great importance for both the maintenance of biofilm processes and the removal of undesired biofilms. The binding forces are weak interactions such as London dispersion forces, electrostatic interactions and hydrogen bonds. In a first attempt to rank their contribution, the viscosity of solutions of extracellular polymeric substances (EPS) from a mucoid strain of Pseudomonas aeruginosa is measured. In order to distinguish the binding forces, substances are chosen which individually address the different types of bonds. Polyacrylic acid is identified as a suitable model system for EPS when molecular interactions are studied. Electrostatic interactions and hydrogen bonds are found to be the dominating forces among macromolecules within the biofilm.

Acrylic Resins↗
PubMed1999

The proenkephalin A-processing product peptide E, which encompasses two enkephalin sequences, has a much lower opioid activity than beta-endorphin.

Peptide E is a 25-amino acid peptide derived from proenkephalin A that was originally isolated from the bovine adrenal medulla. Bovine peptide E (BPE), which possesses a Met- and a Leu-enkephalin sequence at its N- and C-terminus, respectively, has been described as a highly potent and selective mu-opioid receptor agonist. Paradoxically, the frog counterpart of peptide E (FPE), which exhibits only two amino acid substitutions (Met15-->Gln and Leu25-->Met) compared with BPE, was found to be totally devoid of antinociceptive activity. To decipher this apparent discrepancy, we have decided to compare the structural and pharmacological characteristics of FPE, BPE, and the chimeric peptide [Gln15]BPE (Q15BPE). In methanol, all three peptides exhibited virtually the same conformation, the central region of each peptide (residues 10-20) being involved in a regular helix. Intracerebroventricular administration of FPE, BPE, or Q15BPE, at doses up to 1000 ng per mouse, did not induce any analgesic effects, as evaluated by the hot plate and writhing tests, whereas, in the same tests, beta-endorphin at a dose of 100 ng provoked profound analgesia. Concomitant administration of FPE, BPE, or Q15BPE (100 ng) with the aminopeptidase-N inhibitor bestatin (50 microg) or the endopeptidase 24-11 inhibitor thiorphan (10 microg) did not produce analgesic responses. Antinociceptive effects were only observed when very high doses of FPE, BPE, and Q15BPE (10000 ng per mouse) were administered. These data clearly demonstrate that, contrary to what has been previously reported, peptide E is virtually devoid of opioid activity.

Amino Acid Sequence↗
PubMed1999

Allosteric properties of cyanobacterial cytochrome c oxidase: inhibition of the coupled enzyme by ATP and stimulation by ADP.

Thorough analysis of the cta operon of Synechocystis sp. PCC6803 (grown in high-concentration salt medium to enhance the expression of respiratory proteins) showed that, apart from ctaCDE and Fb genes potentially encoding subunits I, II, III, and a small pseudo-bacteria-like subunit-IV of unknown function, a large mitochondria-like cta-Fm gene and a pronounced terminator structure are additional components of the operon. The deduced cta Fm gene product shows approximately 50% and 20% sequence identity to the Saccharomyces cerevisiae and beef heart mitochondrial COIV proteins, respectively. It also shows amino acid regions (near the N terminus, on the cytosolic side) with conspicuous sequence similarities to adenylate-binding proteins such as ATP synthase beta subunit Walker A and B consensus regions or to adenylate kinase. We suggest that, similar to the situation with beef heart mitochondria, it is the mitochondria-like subunit-IV of the cyanobacterial aa3-type cytochrome-c oxidase that confers allosteric properties to the cyanobacterial enzyme, the H+/e- ratios of cytochrome c oxidation being significantly lowered by ATP (intravesicular or intraliposomal) but enhanced by ADP. Therefore, the antagonistic action of ATP and ADP was in a way that the redox reaction proper, was always significantly less affected than the coupled proton translocation. Evolutionary and ecological implications of the unusual allosteric regulation of a prokaryotic cytochrome-c oxidase is discussed.

Adenosine Diphosphate↗
PubMed1999

Bilingual-bicultural models of literacy education for deaf students: considering the claims.

As Carolyn Ewoldt (1996) points out '[M]uch has been written of late about the viability of a bilingual focus in deaf education.' While these writings are necessary to the ongoing pedagogical dialogue in the field, much of the rhetoric suffers because, rather than truly adopting a 'holistic perspective', arguments and positions focus only on selected aspects of the relevant theoretical and research information. If proponents of bilingual education for deaf children truly rely on 'research on the benefits of native sign language and from theoretical and research support coming from other disciplines' (Ewoldt, 1996, p. 5) to support their claims, then these research and theoretical supports must be examined as comprehensively, and holistically, as possible. Weaving together only a few threads of theory and research does not create the fabric for a pedagogical position that can withstand close scrutiny and analysis.In this article, we will touch on some of the major claims made in explications of bilingual models of literacy education for deaf students (Baker, 1997; Livingston, 1997; Mashie, 1995; Mason & Ewoldt, 1996). Our goal is to broaden the scope of the discussion on some of the major arguments and to encourage an expanded dialogue in this ongoing debate. It is not our aim to argue against the concept of bilingual education for deaf students nor to advocate the exclusion of native sign languages from the classroom. Rather, we support the concept of a bilingual education for deaf students with native sign languages playing a key role; however, we contend that the model as it is currently conceived requires further scrutiny and analysis.

Journal Article↗
PubMed1999

Shaping at the point of utterance: an investigation of the composing processes of the deaf student writer.

All writers face the challenge of making meaning on a blank page. They struggle to make meaning for themselves and to communicate this meaning to the potential readers of their texts. Although, in this way, the act of writing can be perceived as a solitary endeavor, the activity of writing, as one aspect of literacy development, is embedded in a sociocultural framework and must be considered not only from the perspective of an individual's mental functioning but from the social context in which it exists. What follows is a preliminary report from a larger case study examining the composing processes of four deaf student writers. This broader study aspires to the goal of sociocultural research, which is to understand the relationship between human mental functioning, on one hand and cultural historical and institutional settings, on the other (Wertsch, 1995). From such a perspective, individual mental processes and sociocultural setting are understood in terms of this relationship, and human action is understood in the context of interrelated moments. I focus on one 'moment' of the writing process that I will term, to borrow a phrase from Stephen Krashen (1977) and James Britton (1978), 'shaping at the point of utterance.' In other words, I will explore what deaf writers do as they face the 'challenge of the blank page.'

Journal Article↗
PubMed1999

Protein and allergen analysis of latex mattresses.

BACKGROUND: Latex allergy is a well-recognized health problem. The wide use of latex in daily life raised the question whether latex articles could be a source of allergens. The present study was carried out to analyse various latex mattresses for protein and allergen characterization. METHODS: Five latex foam mattresses were reduced to powder and proteins were extracted using either water or urea. The protein content of the extracts was analyzed by SDS-PAGE, IEF, 2-D gel electrophoresis and amino acid sequence analysis. The presence of specific IgE, directed toward mattress proteins found in human sera of latex-allergic patients, was tested using ELISA and immunoprints. RESULTS: The results showed that no protein or allergen could be extracted from synthetic foam. However, depending on the type of mattress and extraction procedure, various quantities of proteins could be extracted from mattresses containing natural latex. The ELISA levels of various latex-allergic patients were always more significant against urea extracts than against water extracts, except for one mattress. The protein and allergen patterns were qualitatively similar for all mattresses containing natural latex. Hev b 1 was identified by N-terminal amino acid sequence analysis. CONCLUSION: Because the natural rubber of the mattresses contains latex allergens, these allergens are a potential source of sensitization and could constitute a risk, at least to allergic individuals.

Allergens↗
PubMed1999

Expression of vascular endothelial growth factor receptor-3 and podoplanin suggests a lymphatic endothelial cell origin of Kaposi's sarcoma tumor cells.

Despite intensive research over the past decade, the exact lineage relationship of Kaposi's sarcoma (KS) tumor cells has not yet been settled. In the present study, we investigated the expression of two markers for lymphatic endothelial cells (EC), ie, vascular endothelial growth factor receptor-3 (VEGFR-3) and podoplanin, in AIDS and classic KS. Both markers were strongly expressed by cells lining irregular vascular spaces in early KS lesions and by tumor cells in advanced KS. Double-staining experiments by confocal laser microscopy established that VEGFR-3-positive and podoplanin-positive cell populations were identical and uniformly expressed CD31. By contrast, these cells were negative for CD45, CD68, and PAL-E, excluding their hemopoietic and blood vessel endothelial cell nature. Podoplanin expression in primary KS tumor lysates was confirmed by Western blot analysis. Both splice variants of VEGFR-3 were found in KS-tumor-derived RNA by RT-PCR. In contrast to KS tumor cells in situ, no expression of VEGFR-3 and podoplanin was detected in any of four KS-derived spindle cell cultures and in one KS-derived autonomously growing cell line (KS Y-1). Our findings that KS tumor cells express two lymphatic EC markers in situ strongly suggest that they are related to or even derived from the lymphatic EC lineage. Lack of these antigens on cultured cells derived from KS lesions indicates that they might not represent tumor cells that grow in tissue culture, but rather other cell types present in KS lesions.

Blotting, Western↗
PubMed1999

Neuroligand-mediated calcium signaling in cultured human schwannoma cells.

Intracellular Ca2+ release regulates proliferation of nonexcitable cells, however, it is not known whether and which neuroligands modulate the free intracellular Ca2+ concentration in human schwannoma cells. Confocal laser scanning microscopy was used for the study of neuroligand-induced Ca2+ signaling in cultured human schwannoma cells loaded with the Ca2+-sensitive fluorescent dyes Calcium Green-1 and Fura Red. Intracellular Ca2+ transients were observed during bath application of ATP (90% of cells tested), endothelin (60%), and norepinephrine (20%); histamine, serotonin, glutamate, and bradykinin did not have this effect. Two types of P2Y nucleotide receptor subtypes involved in ATP-induced Ca2+ transients could be separated by application of different P2Y receptor agonists and cross desensitization experiments: P2Y1 (rank order of potency: 2-MeSADP > 2-MeSATP > ADP > ATP) and P2Y2 (sensitive to UTP and ATP). Endothelin-induced Ca2+ signaling was also seen during application of [Ala(1,3,11,15)]ET-1; this suggests the presence of an ET(B) receptor subtype. The results indicate that the presence of receptors linked to neuroligand-triggered Ca2+ signaling does not seem to be abnormal in a human Schwann cell tumor, i.e. schwannoma cells retain this characteristic of peripheral glia.

Adenosine Diphosphate↗
PubMed1998

Nickel subsulfide is genotoxic in vitro but shows no mutagenic potential in respiratory tract tissues of BigBlue rats and Muta Mouse mice in vivo after inhalation.

Carcinogenic nickel compounds are known to induce promutagenic DNA lesions such as DNA strand breaks and DNA adducts in cultured mammalian cells. In standard mutation assays, in contrast, they were found to be either inactive or weakly active. In our in vitro mutation studies in a lacI transgenic embryonic fibroblast cell line, nickel subsulfide (Ni3S2) increased mutation frequency up to 4. 5-fold. We subsequently applied the comet assay and transgenic rodent mutation assays to investigate the DNA damaging effect and mutagenic potential of nickel subsulfide in target cells of carcinogenesis. A 2-h in vitro treatment of freshly isolated mouse nasal mucosa and lung cells with nickel subsulfide clearly induced DNA fragmentation in a concentration dependent manner. The strong effect was not seen in the same cell types following inhalative treatment of mice and rats, leading only in the mouse nasal mucosa to high DNA damage. When the same inhalative treatment was applied to lacZ and lacI transgenic mice and rats, the spontaneous mutation frequency of these target genes in the respiratory tissues was not increased. These results support a recently proposed non-genotoxic model of nickel carcinogenesis, which acts through gene silencing via DNA methylation and chromatin condensation. This model may also explain our in vitro mutation data in the lacI transgenic cell line, in which nickel subsulfide increased mutation frequency, but in about one-third of the mutants, molecular analysis did not reveal any DNA sequence change in the coding region of the lacI gene despite of the phenotypic loss of its function.

Administration, Inhalation↗
PubMed1998

Interaction of ribosomal L1 proteins from mesophilic and thermophilic Archaea and Bacteria with specific L1-binding sites on 23S rRNA and mRNA.

In Bacteria and Archaea (formerly Archaebacteria) ribosomal protein L1 has a dual function, as a primary rRNA-binding protein and as a translational repressor which binds to its own mRNA. The L1-binding site on the mRNA exhibits high similarity in both sequence and secondary structure to the binding site for L1 on the 23 S rRNA. A sensitive membrane-filter-binding assay has been used to examine the interactions between ribosomal L1 proteins from different archaeal and bacterial species, and 23S rRNA and mRNA fragments from Methanococcus vannielii containing the MvaL1-binding site. Under standard conditions (0 degrees C, pH 7.5, 20 mM Mg2+, 500 mM KCl), the apparent dissociation constant Kd of the homologous MvaL1-23S rRNA complex is 5 nM, the apparent dissociation constant Kd of the MvaL1-mRNA complex is 0.15 degrees M. L1 proteins from Escherichia coli (EcoL1) and from the thermophilic Bacterium Thermus thermophilus (TthL1), and from the thermophilic Archaea Methanococcus thermolithotrophicus (MthL1), Methanococcus jannaschii (MjaL1), and Sulfolobus solfataricus (SsoL1) were tested for their affinity to the specific L1-binding sites on the 23 S rRNA and mRNA. In general, the affinity of L1 proteins from thermophilic species to the binding sites on both 23 S rRNA and mRNA is about one order of magnitude higher than that of their mesophilic counterparts. This stronger protein-RNA interaction might make a substantial contribution to the thermal tolerance of ribosomes in thermophilic organisms.

Archaea↗
PubMed1998

[Primary pulmonary plasmacytoma. Case report of a rare lung tumor].

HISTORY AND CLINICAL FINDINGS: A 45-year old man, suffering from dry cough without haemoptysis, was admitted for evaluation of pulmonary changes of uncertain aetiology. A chest radiograph and computed tomography (CT) had shown a large space-occupying lesion in the left hilus. His general condition was poor and he had resting dyspnoea and stridor. On auscultation of the lung there were decreased breath sounds and dry rales over the left and vesicular breathing over the right lung. INVESTIGATIONS: CT revealed a 7.0 x 6.0 cm space-occupying lesion in the left hilus and ipsilaterally a tumour in the dorsolateral lower lobe surrounding the left lower lobe bronchus. Initial bronchoscopy showed this bronchus to be involved in the tumour process. Biopsy demonstrated monomorphic proliferating plasma cells which on immunochemical testing showed selective staining to lambda-light chains and immunoglobulin G. The first serum electrophoresis was unremarkable, but a later repeat discovered a small amount of paraprotein for IgG-lambda type. Bence-Jones protein was demonstrated in the urine. On the basis of these findings an extramedullary plasmacytoma of the lung (PPP) was diagnosed. TREATMENT AND COURSE: At first the patient was given i.v. chemotherapy, and to prevent a threatening bronchial occlusion oral dexamethasone was given. Pericardial effusion and recurrent retention pneumonia developed. 6 month after onset of symptoms radiotherapy was begun and the tumour became markedly smaller. CONCLUSION: PPP should be included in the differential diagnosis of pulmonary space-occupying lesions even when initial serum protein electrophoresis is negative for monoclonal paraproteinaemia. Pericardial effusion may be caused by pulmonary involvement of the plasma cell tumours.

Biopsy↗
PubMed1998

Chemoafferent degeneration and carotid body hypoplasia following chronic hyperoxia in newborn rats.

1. To define the role of environmental oxygen in regulating postnatal maturation of the carotid body afferent pathway, light and electron microscopic methods were used to compare chemoafferent neurone survival and carotid body development in newborn rats reared from birth in normoxia (21 % O2) or chronic hyperoxia (60 % O2). 2. Four weeks of chronic hyperoxia resulted in a significant 41 % decrease in the number of unmyelinated axons in the carotid sinus nerve, compared with age-matched normoxic controls. In contrast, the number of myelinated axons was unaffected by hyperoxic exposure. 3. Chemoafferent neurones, located in the glossopharyngeal petrosal ganglion, already exhibited degenerative changes following 1 week of hyperoxia from birth, indicating that even a relatively short hyperoxic exposure was sufficient to derange normal chemoafferent development. In contrast, no such changes were observed in the vagal nodose ganglion, demonstrating that the effect of high oxygen levels was specific to sensory neurones in the carotid body afferent pathway. Moreover, petrosal ganglion neurones were sensitive to hyperoxic exposure only during the early postnatal period. 4. Chemoafferent degeneration in chronically hyperoxic animals was accompanied by marked hypoplasia of the carotid body. In view of previous findings from our laboratory that chemoafferent neurones require trophic support from the carotid body for survival after birth, we propose that chemoafferent degeneration following chronic hyperoxia is due specifically to the loss of target tissue in the carotid body.

Afferent Pathways↗
PubMed1998

The radioprotective potential of the Bowman-Birk protease inhibitor is independent of its secondary structure.

The Bowman-Birk protease inhibitor (BBI), a serine-protease inhibitor, has been reported to exert both anticarcinogenic and radioprotective activity. In this work we examined whether this effect is mediated through inhibition of serine-proteases of the trypsin-chymotrypsin type. Using linearized forms of BBI, evidence will be provided that the secondary structure, obligatory for the protease inhibitory function, is not necessary for the radioprotective effect. Detailed analysis indicated that the radioprotective effect is correlated with the chymotrypsin-inhibitory region of the molecule. Using a synthetic nonapeptide lacking protease inhibitor activity, the radioprotective effect of the total BBI molecule could be mimicked, indicating that the radioprotective effect is independent of the protease inhibitor function.

Antineoplastic Agents↗
PubMed1998

Differences in the sensitivity to purinergic stimulation of myelinating and non-myelinating Schwann cells in peripheral human and rat nerve.

Schwann cells of the peripheral nervous system are distinguished by morphological and functional criteria in myelinating and non-myelinating subtypes. We and others have previously reported that Schwann cells in isolated peripheral human and rat nerve respond to extracellular application of ATP with a rise in the intracellular free calcium concentration [Ca2+]i. In the present study, the receptors mediating these Ca2+ transients have been investigated in myelinating and non-myelinating Schwann cells of intact fascicles of isolated human sural nerves, rat ventral roots, and rat vagus nerves. Microfluorometry and confocal laser scanning was used on preparations stained with the Ca2+-sensitive dyes Calcium Green-1 and Fura Red. In myelinating Schwann cells of human and rat nerves, the ATP-induced rise of [Ca2+]i resulted from the activation of a P2Y2 purinoceptor subtype (rank order of potency: UTP > or = ATP >> 2-MeSATP = ADP). In contrast, in non-myelinating Schwann cells, Ca2+ transients were produced by activation of a P2Y1 purinoceptor subtype (rank order of potency: 2-MeSATP > ATP > ADP >> UTP). The P1 agonist adenosine and alpha,alpha-meATP did not evoke Ca2+ signals. Ca2+ transients in both types of Schwann cells were found to be due to Ca2+ release from cyclopiazonic acid-sensitive intracellular stores. However, inhibition by suramin was only found in non-myelinating Schwann cells. These findings indicate that mammalian Schwann cells express phenotype-specific P2Y receptor subtypes.

Adenosine Triphosphate↗
PubMed1998

Influence of the secondary structure on the pore forming properties of synthetic alamethicin analogs: NMR and molecular modelling studies.

Synthetic alamethicin analogs, in which all Aib residues had been replaced by Leu (L2) then proline 14 replaced by an alanine (L5), were studied in SDS micelles using circular dichroism and NMR spectroscopy. Nuclear Overhauser effects were used as constraints for molecular modelling. The structures determined for both peptides in SDS micelles were compared with those previously obtained in methanol in order to establish a secondary structure/ionophore activity relationship. Our results indicated that a shortening of peptide helices could be responsible for the observed decrease in ion channel lifetimes. However, the length of helices may not by itself explain the drastic destabilization of channels when Pro14 of alamethicin is replaced by Ala in L5. Indeed analysis of the helical wheel of L5 reveals heterogeneity in the amphipathicity depending on the medium. Thus, loss of amphipathicity seems to underly the observed destabilization of channels.

Alamethicin↗
PubMed1998

[Artifactual disorders--between deception and self-mutilation. Experiences in consultation psychiatry at a university clinic].

During a 18-year-period 93 patients (f = 76, m = 17) with a factitious disorder were identified in the psychiatric consultation service of a university hospital (incidence: 0.62%). 50% of women were working in medical professions whereas only 6% of men. Chronic courses of illness were prevailing, but at least one quarter of female patients showed an intermittent type. There was a classical Munchhausen syndrome in 11% of patients. Depressive and anxiety disorders (10%, 4%) were to be respected as psychiatric comorbidity. Ca 25% of the patients suffered from a somatic illness in addition to the factitious disorder, and one third of the women had symptoms of psychosomatic, especially of eating disorders. Previous somatoform disorders, deliberate self harm and attempts of suicide were to be noted in the psychiatric history of many patients. There were frequent traumatizing events (foster home, disturbing family disharmony, physical and sexual abuse, early losses, serious illnesses) in the early biography. Various psychosocial stressors could be identified in the actual eliciting situation. The results are discussed in respect of epidemiology, development and clinical phenomenology of factitious disorders, psychodynamics and psychopathology of deception and self harm, and therapeutic options in the psychiatric consultation service.

Adult↗