Search PubMed⌕ Search

Biomedical subjects

E Muller

Publications and source records attributed to E Muller.

At least 37 records · Page 2Linked to original sources
PubMed2000

A simple and fast TEM preparation method utilizing the pre-orientation in plate-like, needle-shaped and tubular materials

In order to observe anisotropically grown crystalline materials perpendicular to a certain preferred orientation, a standard cross-sectional TEM preparation method has been modified. The material is embedded in an organic epoxy resin between two Si-wafers. Plates, needles and tubes lay flat inside the resulting sandwich, which is then cut into slices perpendicular to the wafers. The slices are thinned by mechanical abrading and, finally, by ion milling. Crystals located near the central hole are electron-transparent, and their orientation often allows for an observation along the desired direction. The usefulness of this procedure is demonstrated on the examples of high-Tc superconductors and vanadium oxide nanotubes.

Journal Article↗
PubMed2000

Immediate loading of titanium hexed screw-type implants in the edentulous patient: case report.

Histologic and histomorphometric studies in both animals and humans have shown that more rapid and greater bone-to-implant contact can be achieved with implants that incorporate certain surface characteristics compared with the original machined-surface implants. Such findings are significant because various implant designs may allow the fixtures to sufficiently resist functional loading sooner than originally thought. The case report presented here indicates that immediate loading of hexed titanium screw-type implants in the anterior mandible can lead to successful osseointegration and clinical outcome. The number of implants placed, their distribution, and the type of rigid connection are critical considerations for immediate loading. A bone height that can accommodate dental implants > or = 10 mm long is recommended. Biomechanically, the implants to be immediately loaded must be stable and resistant to macromovement to ensure good osseointegration.

Dental Implants↗
PubMed1999

Supportive periodontal therapy in South America. A retrospective multi-practice study on compliance.

BACKGROUND: Supportive periodontal therapy is needed for the success of periodontal therapy but there is little information about the extent of patient cooperation. It is known, however, that cooperation is poor and a matter of concern. METHODS: The present study is part of a more extensive study including information from 5,041 patient records from private periodontal practices in Brazil, Venezuela, Chile, and Argentina. Patient cooperation was measured according to gender, age, type of therapy (surgical or non-surgical), maintenance period (first year, 5 years, 10 years, 15 years, and 20 years), and level of cooperation (non-compliant, regular or irregular) for each of the 4 practices. RESULTS: We observed a great variation in the behavior of the patients from different practices, suggesting that studies on compliance cannot be generalized because differences in culture, economic conditions, knowledge of oral hygiene, and even the philosophy of treatment should be considered. The most significant data were sometimes similar for 2 or 3 of the countries but never for all 4 practices. CONCLUSIONS: Compliance is a very complex matter and findings from individual studies cannot be generalized.

Adult↗
PubMed1999

[Cytological screening of uterine cervical cancer by samples in liquid medium (CytoRich). Preliminary study of a series of 111 292 patients].

We report on the preliminary results of a series of 111,292 patients who benefited from a liquid medium sample (CytoRich) for cervical cancer screening. The number of dubious or limited smears was reduced by 0.03% and 0.53% respectively. The junction zone was better explored, and metaplastic changes were observed in 35.71% of the cases. This method improved the identification of low-grade lesions by +56% (2751/111,292; 2.47%) and of high-grade lesions by +75% (860/111,292; 0.77%), with a reduction in the number of ASCUS/AGUS by -44% (2065/111,292; 1.85%). This preliminary study confirms the results already published. The results demonstrating cytohistological correlation should prove to be a decisive factor, enabling the testing of the sensitivity and specificity of this technique. It will then be possible to envisage a future 'new paradigm' for screening cervical cancer as the result of a liquid medium sample, computer-assisted screening and HPV viral identification by Hybrid capture II.

Cervix Uteri↗
PubMed1998

Mechanism of salicylate-mediated inhibition of biofilm in Staphylococcus epidermidis.

The inclusion of 5 mM salicylic acid (SAL) in medium inhibited both growth and biofilm production by Staphylococcus epidermidis by up to 55%. The inhibition was not due primarily to chelation of cations. Excess divalent cations restored growth and biofilm production in chelated medium and in medium containing EDTA but not in medium containing SAL. ELISA analyses demonstrated that SAL inhibited production of teichoic acid, slime-associated proteins, and type 1 antigen by as much as 95%. However, it inhibited polysaccharide/adhesin production by only 50%--a figure paralleling the reduction in growth. The equivalent inhibitory effects of SAL on a pair of isogenic strains, one of which was a polysaccharide/adhesin-deficient mutant, confirmed that the primary effect of SAL was a reduction in the production of biofilm components rather than a reduction in the retention of these components in the slime layer prior to assembly into a biofilm.

Adhesins, Bacterial↗
PubMed1998

Staphylococcus hominis subsp. novobiosepticus subsp. nov., a novel trehalose- and N-acetyl-D-glucosamine-negative, novobiocin- and multiple-antibiotic-resistant subspecies isolated from human blood cultures.

A new subspecies, Staphylococcus hominis subsp. novobiosepticus, isolated from human blood cultures, a wound, a breast abscess and a catheter tip, is described on the basis of a study of 26 strains isolated between 1989 and 1996. DNA-DNA reassociation reactions, conducted under stringent conditions, and macrorestriction pattern analysis demonstrated that these strains are closely related to previously characterized S. hominis strains isolated from human skin and clinical specimens, but are significantly divergent. S. hominis subsp. novobiosepticus can be distinguished from S. hominis (now named S. hominis subsp. hominis) by its combined characteristics of novobiocin resistance and failure to produce acid aerobically from D-trehalose and N-acetyl-D-glucosamine. Furthermore, all 26 strains of the new subspecies are resistant to nalidixic acid, penicillin G, oxacillin, kanamycin and streptomycin, and were either resistant or had intermediate resistance to methicillin and gentamicin. Most strains were also resistant to erythromycin, clindamycin, chloramphenicol, trimethoprim/sulfamethoxazole and ciprofloxacin. Based on a comparison of the sequences of a 1001 bp mecA amplification product from reference methicillin-resistant staphylococci, the mecA gene present in S. hominis subsp. novobiosepticus was identified as homologue A, commonly found in S. aureus and many coagulase-negative staphylococcal species. The type strain of S. hominis subsp. novobiosepticus is ATCC 700236T. Descriptions of S. hominis subsp. novobiosepticus subsp. nov and S. hominis subsp. hominis are given and the description of S. hominis is emended.

Acetylglucosamine↗
PubMed1998

The ica locus of Staphylococcus epidermidis encodes production of the capsular polysaccharide/adhesin.

Clinical isolates of coagulase-negative staphylococci often elaborate a biofilm involved in adherence to medical devices and resistance to host defenses. The biofilm contains the capsular polysaccharide/adhesin (PS/A), which mediates cell adherence to biomaterials, and another antigen, termed polysaccharide intercellular adhesin (PIA), which is thought to mediate bacterial accumulation into cellular aggregates. PIA is a polymer of beta-1, 6-linked N-acetyl glucosamine residues with a molecular mass of <30, 000 kDa. We found that recombinant Staphylococcus carnosus and Staphylococcus aureus carrying a plasmid with genes of the ica locus, which was reported to encode the biosynthetic proteins for production of PIA, were also able to synthesize PS/A. PS/A and a chemically and immunologically identical polysaccharide isolated from S. carnosus carrying the ica genes on plasmid pCN27 were found to be high-molecular-mass (>250,000 kDa), acid-stable polymers of beta-1,6-linked glucosamine substituted on the amino group primarily with succinate, although some preparations also contained acetate. Moreover, all recombinant staphylococcal strains with the ica genes had the biologic properties previously attributed to PS/A. ica-positive strains readily formed an in vitro biofilm on plastic, adhered 3- to 10-fold more to catheters during a 30-min assay compared with control strains carrying only the cloning vector, adsorbed out antibodies to PS/A from immune serum, and elaborated a capsule visualized by immunoelectron microscopy with antisera to PS/A. These properties were also seen with PS/A-producing strains of Staphylococcus epidermidis, but not with transposon mutants lacking PS/A. An antiserum raised to PIA contained high-titer antibody to PS/A that was readily adsorbed out by PS/A-positive strains of S. epidermidis and recombinant strains of staphylococci carrying the ica genes. We conclude that the ica locus encodes production of PS/A and that the properties of S. epidermidis associated with initial bacterial adherence, biofilm formation, and intercellular adhesion can be correlated with elaboration of PS/A.

Adhesins, Bacterial↗
PubMed1998

Redesigning nucleic acids.

A research program has applied the tools of synthetic organic chemistry to systematically modify the structure of DNA and RNA oligonucleotides to learn more about the chemical principles underlying their ability to store and transmit genetic information. Oligonucleotides (as opposed to nucleosides) have long been overlooked by synthetic organic chemists as targets for structural modification. Synthetic chemistry has now yielded oligonucleotides with 12 replicatable letters, modified backbones, and new insight into why Nature chose the oligonucleotide structures that she did.

Catalysis↗
PubMed1997

A heterodimer of thioredoxin and I(B)2 cooperates with Sec18p (NSF) to promote yeast vacuole inheritance.

Early in S phase, the vacuole (lysosome) of Saccharomyces cerevisiae projects a stream of vesicles and membranous tubules into the bud where they fuse and establish the daughter vacuole. This inheritance reaction can be studied in vitro with isolated vacuoles. Rapid and efficient homotypic fusion between salt-washed vacuoles requires the addition of only two purified soluble proteins, Sec18p (NSF) and LMA1, a novel heterodimer with a thioredoxin subunit. We now report the identity of the second subunit of LMA1 as I(B)2, a previously identified cytosolic inhibitor of vacuolar proteinase B. Both subunits are needed for efficient vacuole inheritance in vivo and for the LMA1 activity in cell extracts. Each subunit acts via a novel mechanism, as the thioredoxin subunit is not acting through redox chemistry and LMA1 is still needed for the fusion of vacuoles which do not contain proteinase B. Both Sec18p and LMA1 act at an early stage of the in vitro reaction. Though LMA1 does not stimulate Sec18p-mediated Sec17p release, LMA1 cannot fulfill its function before Sec18p. Upon Sec17p/Sec18p action, vacuoles become labile but are rapidly stabilized by LMA1. The action of LMA1 and Sec18p is thus coupled and ordered. These data establish LMA1 as a novel factor in trafficking of yeast vacuoles.

Adenosine Triphosphatases↗
PubMed1997

Classification of plant trypanosomatids (Phytomonas spp.): parity between random-primer DNA typing and multilocus enzyme electrophoresis.

The genetic polymorphism of 30 isolates of plant trypanosomatids colloquially referred to as plant trypanosomes was assayed by means of RAPD. The principle objectives of this study were to assess the discriminative power of RAPD analysis for studying plant trypanosomes and to determine whether the results obtained were comparable with those from a previous isoenzyme (MLEE) study. The principle groups of plant trypanosomes identified previously by isoenzyme analysis--intraphloemic trypanosomes, intralaticiferous trypanosomes and trypanosomes isolated from fruits--were also clearly separated by the RAPD technique. Moreover, the results showed a fair parity between MLEE and RAPD data (coefficient of correlation = 0.84) and the two techniques have comparable discriminative ability. Most of the separation revealed by the two techniques between the clusters was associated with major biological properties. However, the RAPD technique gave a more coherent separation than MLEE because the intraphloemic isolates, which were biologically similar in terms of their specific localization in the sieve tubes of the plant, were found to be in closer groups by the RAPD. For both techniques, the existence of the main clusters was correlated with the existence of synapomorphic characters, which could be used as powerful tools in taxonomy and epidemiology.

Animals↗
PubMed1996

Factors affecting Staphylococcus epidermidis adhesion to contact lenses.

BACKGROUND: Staphylococcus epidermidis is a major causative agent of infectious keratitis associated with contact lens wear. Adhesion of this bacterium to contact lenses may contribute to the pathogenesis of infection and could be influenced by lens surface properties, packaging/storage solutions, and vary among different strains according to the level or type of adhesins expressed. METHODS: Adhesion of six clinical isolates of S. epidermidis to three different contact lens materials was tested. Adhesion assays were performed on lenses immediately after removal from their packages, and also after lenses were soaked in sterile phosphate buffered saline (PBS) for 7 days to dilute the packaging solution. RESULTS: For lenses tested immediately upon removal from their packaging, adhesion to polymacon (in PBS with 0.1% polyvinyl alcohol) was significantly greater than to etafilcon A (in borate buffered saline) and vifilcon A (in PBS). After soaking, adhesion to polymacon lenses was significantly less than to the other lens materials. This pattern was consistent for all strains, although major differences in baseline adhesion levels existed between strains, with exopolysaccharide (slime)-positive bacteria being more adherent to lenses. CONCLUSIONS: Properties of contact lens materials were not the sole determinant of viable S. epidermidis adhesion to lenses. Strain variability, including levels of exopolysaccharide expression, and the solution used for lens immersion also influenced adhesion.

Bacterial Adhesion↗
PubMed1996

Molecular genetic and immunohistochemical analysis of the tumor suppressor genes Rb and p53 in palmar and aggressive fibromatosis.

This pilot project analyzed the tumor suppressor genes p53 and Rb in 13 cases of aggressive fibromatoses and six cases of palmar fibromatoses (Dupuytren contracture). Immunohistochemistry, reverse transcription polymerase chain reaction, polymerase chain reaction followed by single-strand confirmation polymorphism analysis, and Southern blot to detect gene rearrangements were used. No abnormalities were detected in p53. The aggressive fibromatoses demonstrated a lack of Rb immunohistochemical staining and decreased mRNA for Rb. No structural mutation in the coding sequence of the Rb gene was detected. The decreased level of Rb gene expression, despite a normal coding sequence, may indicate increased proliferation and may suggest potential treatment schemes.

Blotting, Southern↗
PubMed1996

Acquisition of iron from host proteins by the group A streptococcus.

To identify mammalian iron-binding proteins that can serve as iron sources for Streptococcus pyogenes, the group A streptococcus (GAS), we used a plate assay. Ferritin, hemin, hemoglobin, myoglobin, and catalase can support growth of GAS on iron-depleted medium. However, growth was not detected when iron was provided as iron-saturated transferrin or lactoferrin or bound to cytochrome c. Therefore, it appears that GAS can use the intracellular iron sources available in the human body, which is consistent with its ability to cause tissue destruction during infection.

Animals↗
PubMed1995

The pathogenic role of Staphylococcus epidermidis capsular polysaccharide/adhesin in a low-inoculum rabbit model of prosthetic valve endocarditis.

BACKGROUND: The capsular polysaccharide/adhesin (PS/A) antigen of Staphylococcus epidermidis was required to produce endocarditis in a rabbit model in which infection resulted from hematogenous spread of bacteria from a contaminated catheter in the jugular vein. However, many prosthetic valve endocarditis (PVE) infections probably result from direct contamination of the valve with small numbers of bacteria during surgery. The role of PS/A in this situation was evaluated by modifying a rabbit model of endocarditis to partially mimic PVE. METHODS AND RESULTS: A Teflon catheter was contaminated with graded inocula of either PS/A-positive S epidermidis strain M187sp11 or the PS/A-negative, isogenic strain M187sn3 and inserted into the left ventricle through the aortic valve. The PS/A-positive strain had a 50% infectious dose of 1.1 x 10(2) cfu (95% CI, 3.3 to 3.7 x 10(3)) compared with 8.5 x 10(4) cfu of the PS/A-negative strain (95% CI, 8.6 x 10(3) to 8.5 x 10(5)). The odds for developing endocarditis were estimated to be 42 times higher for any given inoculum level of the PS/A-positive strain (P = .1). When the PS/A-positive strain was adherent to a catheter surface it survived in rabbit blood, whereas under the same conditions the PS/A-negative strain was killed approximately 90% in 1 hour. CONCLUSIONS: Direct contamination of an intraventricular foreign body by low levels of PS/A-positive S epidermidis results in endocarditis in rabbits, but at suitably high doses PS/A-negative strains have sufficient virulence to infect cardiac vegetations. PS/A enhances but is not absolutely required for bacterial virulence in a rabbit model of PVE.

Animals↗
PubMed1995

Potentiation of Staphylococcus epidermidis catheter-related bacteremia by lipid infusions.

Lipid infusions given to low-birth-weight neonates are associated with coagulase-negative staphylococcal bacteremia. A rabbit model of catheter-related Staphylococcus epidermidis bacteremia was used to compare infection rates between animals receiving 20% lipid infusions with those receiving 10% glucose infusions. Bacterial growth was detected in 43 (66%) of 65 blood cultures obtained during lipid infusions but only 6 (7%) of 91 blood cultures obtained during glucose infusions (P < .001). S. epidermidis was cultured from 7 of 9 catheters recovered from lipid-infused rabbits but from only 3 of 13 catheters from glucose-infused rabbits (P = .016). Lipid but not glucose solutions containing low levels of protein (0.1%-1.0%) supported the survival and growth of S. epidermidis. These results suggest that lipids contribute to the survival and growth of S. epidermidis on contaminated catheters, enhancing the potential of these organisms to disseminate and cause bacteremia.

Animals↗