PubMed Health⌕ Search

Biomedical subjects

A Hefti

Publications and source records attributed to A Hefti.

At least 19 recordsLinked to original sources
PubMed2006

Effects of periodontal therapy during pregnancy on periodontal status, biologic parameters, and pregnancy outcomes: a pilot study.

BACKGROUND: Few studies have examined the potential effects of periodontal treatment during pregnancy on pregnancy outcomes, periodontal status, and inflammatory biomarkers. METHODS: A randomized, delayed-treatment, controlled pilot trial was conducted to evaluate the effects of second-trimester scaling and root planing and the use of a sonic toothbrush on the rate of preterm delivery (<37 weeks gestation). Secondary outcome measures included changes in periodontal status, levels of eight oral pathogens, levels of gingival crevicular fluid (GCF) interleukin-1beta (IL-1beta), prostaglandin E(2) (PGE(2)), 8-isoprostane (8-iso), and IL-6, and serum levels of IL-6, soluble intercellular adhesion molecule 1 (sICAM1), 8-isoprostane, soluble glycoprotein 130 (sGP130), IL-6 soluble receptor (IL-6sr), and C-reactive protein (CRP). Logistic regression models were used to test for effects of treatment on preterm delivery. Secondary outcomes were analyzed by analysis of covariance adjusting for subject baseline values. RESULTS: Periodontal intervention resulted in a significantly decreased incidence odds ratio (OR) for preterm delivery (OR = 0.26; 95% confidence interval = 0.08 to 0.85), adjusting for baseline periodontal status which was unbalanced after randomization. Pregnancy without periodontal treatment was associated with significant increases in probing depths, plaque scores, GCF IL-1beta, and GCF IL-6 levels. Intervention resulted in significant improvements in clinical status (attachment level, probing depth, plaque, gingivitis, and bleeding on probing scores) and significant decreases in levels of Prevotella nigrescens and Prevotella intermedia, serum IL-6sr, and GCF IL-1beta. CONCLUSIONS: Results from this pilot study (67 subjects) provide further evidence supporting the potential benefits of periodontal treatment on pregnancy outcomes. Treatment was safe, improved periodontal health, and prevented periodontal disease progression. Preliminary data show a 3.8-fold reduction in the rate of preterm delivery, a decrease in periodontal pathogen load, and a decrease in both GCF IL-1beta and serum markers of IL-6 response. However, further studies will be needed to substantiate these early findings.

Adult↗
PubMed2001

Confocal laser scanning microscopy and scanning electron microscopy of tissue Ti-implant interfaces.

Microscopic inspection of heterogenous three-dimensional (3D) objects such as oral implants, or implants in general, is conventionally performed either on ground sections of methyl-metacrylate-embedded material, at the cellular level by histologic analysis of the peri-implant tissue by light microscopy (LM), or at the supramolecular level by transmission electron microscopy (TEM). Alternatively, the architecture of the tissue/implant interface is visualized by scanning electron microscopy (SEM). The two approaches exclude each other because of the sample preparation.We elaborate conditions for the non-invasive analysis of tissue/implant interfaces by confocal laser scanning microscopy (CLSM) in buffer, hoping to obtain a 3D view of fluorescently labeled tissue constituents at the tissue implant interface and, through subsequent SEM, of the metal surface. The use of water-immersion objectives, originally developed for high LM under physiological conditions is essential. In an exploratory approach, the tissue/Ti-interfaces of two retrieved dental implants were analyzed. One was a step-cylinder used for orthodontic anchoring and the other was an endosseous step-screw implant retrieved after infection-related loosening prior to load. The adhering tissue fragments were fluorescently triple-labeled for actin, fibronectin, and sm-alpha-actin. Optical sections for fluorescent images and for the laser reflection map were registered concomitantly. This approach allowed the labeled structures to be located on the metal surface. Subsequently, the same implants were prepared for SEM of the tissue/implant interface, and upon removal of the adhering structures, of the underlying metal surface. Thus, specific proteins can be identified and their spatial architecture as well as that of the underlying metal surface can be visualized for one and the same implant. The immediate visualization after fluorescence labeling in buffer by means of water immersion objective lenses proved most critical.

Actins↗
PubMed2001

Adult mice deficient in actinin-associated LIM-domain protein reveal a developmental pathway for right ventricular cardiomyopathy.

Although cytoskeletal mutations are known causes of genetically based forms of dilated cardiomyopathy, the pathways that link these defects with cardiomyopathy are unclear. Here we report that the alpha-actinin-associated LIM protein (ALP; Alp in mice) has an essential role in the embryonic development of the right ventricular (RV) chamber during its exposure to high biomechanical workloads in utero. Disruption of the gene encoding Alp (Alp) is associated with RV chamber dilation and dysfunction, directly implicating alpha-actinin-associated proteins in the onset of cardiomyopathy. In vitro assays showed that Alp directly enhances the capacity of alpha-actinin to cross-link actin filaments, indicating that the loss of Alp function contributes to destabilization of actin anchorage sites in cardiac muscle. Alp also colocalizes at the intercalated disc with alpha-actinin and gamma-catenin, the latter being a known disease gene for human RV dysplasia. Taken together, these studies point to a novel developmental pathway for RV dilated cardiomyopathy via instability of alpha-actinin complexes.

Actinin↗
PubMed2000

Acoustic energy affects human gingival fibroblast proliferation but leaves protein production unchanged.

BACKGROUND, AIMS: Sonic toothbrushes are well-established in oral home care for plaque removal; however, the effects of low frequency acoustic (sonic) energy released from sonic toothbrushes to the cells of the periodontium have not been investigated. The purpose of this study was to evaluate the effects of sonic energy on human gingival fibroblast proliferation and protein production in cell culture. METHODS: Direct and indirect transfer calibration studies found the fundamental frequency of the Sonicare sonic toothbrush to be 261 hertz (Hz) with amplitudes ranging from 70 to 104 decibels (dB) in the human periodontium. Using an in vitro delivery system, which coupled a signal-wave generator with a bone transducer to mimic the energy delivered by the Sonicare toothbrush, the effects of signal, amplitude and duration were evaluated longitudinally using a gingival fibroblast cell culture model. 8 strains of fibroblasts isolated from healthy human gingiva were seeded at 30,000 cells/35 mm culture dish in minimum essential medium supplemented with 10% fetal bovine serum. To ascertain the relationship of the amplitude and the duration of sonic stimulation to cellular proliferation, gingival fibroblasts were subjected 2x daily to 261 Hz sound at various amplitudes (67-97 dB) for 0, 15, 30, 60, and 120 s on days 1, 3, 5, 7, and 10. RESULTS: It was found that either 30 or 120 s of sound exposure for 10 days of treatment had significant effects on cell proliferation in comparison to control cultures. Specifically, at day 10, 87 dB at 261 Hz for 30 s 2x daily resulted in a 25.5% increase in cell number (p<0.001), whereas 87 dB at 261 Hz for 120 s twice daily caused a 30.9% decrease in cell number (p<0.001) when compared to control cultures. When cells are stimulated under optimum acoustic conditions for 10 days, there was no difference between the treatment and control groups for collagen (p=0.897) or noncollagen (p=0.697) protein production. CONCLUSIONS: Sonic energy has been shown to both increase and decrease cellular proliferation depending on exposure time; however, during optimum sound-induced conditions for cellular proliferation, sonic energy had no effect on fibroblast protein production. These data suggest that sonic energy can affect the behavior of cells in culture. Further research into the mechanisms of these changes will provide important information for manipulating cellular behavior.

Analysis of Variance↗
PubMed1999

Ectosomes released by human neutrophils are specialized functional units.

Here we show that human polymorphonuclear leukocytes (PMN) release ectosomes independently of complement attack during their activation both in vitro and at the site of inflammation in vivo. Patterns of biotinylated proteins on the surface of PMN and on PMN-derived ectosomes indicated a specific sorting of cell surface proteins into and out of ectosomes. Ectosomes expressed clusters of complement receptor 1 (CR1), which allowed them to bind efficiently to opsonized bacteria. Myeloperoxidase and human leukocyte elastase, both stored within the azurophilic granules of PMN, were found to colocalize on ectosomes with CR1. Furthermore, myeloperoxidase colocalized with human leukocyte elastase. In contrast, not present on CR1-expressing ectosomes were CD63, a selective marker for the azurophilic granules, and CD14, which is located within the same granules and the secretory vesicles as CR1. Of the other complement regulatory proteins expressed by PMN, only CD59 colocalized with CR1, while CD55 and CD46 were almost absent. Ectosomes released by activated PMN at the site of inflammation may function as a well organized element (ecto-organelle), designed to focus antimicrobial activity onto opsonized surfaces.

Animals↗
PubMed1998

Option-3 median measurement scheme in outlier reduction.

When measurement are subject to rare but large errors, it is better to measure twice instead of once, and, if the two measurements differ too much, to take a third measurement. This is called the option-3 scheme. This paper shows that when the measurement error is the mixture of two normal random variables, use of the median of the three measurements is better than use of the average of the two closest. To reach the maximum sample size benefit, the threshold for taking the third measurement is approximately three times the measurement error standard deviation.

Humans↗
PubMed1998

Reconstitution, characterisation and mass analysis of the pentacylindrical allophycocyanin core complex from the cyanobacterium Anabaena sp. PCC 7120.

The phycobilisome (PBS) of Anabaena sp. PCC 7120 was allowed to dissociate into its constituents and the resulting allophycocyanin (AP) fraction was purified. Its reconstitution yielded a complex which according to negative stain electron microscopy and spectral analysis was identical to the native pentacylindrical PBS core domain. Each cylinder of the central tricylindric unit was comprised of four AP (alphabeta)3 disks. Mass analysis using the scanning transmission electron microscope (STEM) showed the presence of 16 AP trimers in the intact reconstitute, which had a total mass of 1966(+/-66) kDa. Composition analysis indicated an AP trimer distribution of (AP-II):(AP-LCM):(AP-B):(AP-I)=6:2:2:6, i.e. an addition of two AP-I and two AP-II complexes compared to a tricylindrical PBS core domain. Therefore, we suggest that each supplementary half-core cylinder found in pentacylindrical AP core domains is comprised of one AP-I and one AP-II trimer, in agreement with the current model. The structural significance of the 127 kDa core membrane linker polypeptide was further investigated by subjecting the AP core reconstitute to mild chymotryptic degradation. After isolation, the digested complex exhibited a tricylindrical appearance while STEM mass analysis confirmed the presence of only 12 AP complexes. Polypeptide analysis by SDS-PAGE and Edman degradation related the half-cylinder loss to cleavage of the Rep4 domain of the core membrane linker polypeptide. On the basis of these data, a general model for the assembly of the three hemidiscoidal PBS types known to date is discussed.

Amino Acid Sequence↗
PubMed1998

Cytotoxicity of endodontic materials.

An in vitro cell culture model of human gingival fibroblasts and L-929 cells was used to measure the cytotoxicity of currently used root canal sealers Endomet, CRCS, and AH26 and root-end filling materials Amalgam, Gallium GF2, Ketac Silver, mineral trioxide aggregate (MTA), and Super-EBA. Cytotoxic effects were assessed using the MTT assay for mitochondrial enzyme activity and the CV assay for cell numbers. Using inserts culture and L-929 fibroblasts. All-Bond-2 was also evaluated. The statistical analysis of results showed that CRCS was the least cytotoxic sealer followed by Endomet and AH26. Among root-end filling materials, MTA was not cytotoxic; Gallium GF2 displayed little cytotoxicity; and Ketac Silver, Super-EBA, and Amalgam showed higher levels of cytotoxicity. All Bond-2 also displayed a high degree of cytotoxicity. CRCS was the best root canal sealer and MTA the best root-end filling material. The outcome was favorable also for Gallium GF2 as a retrofilling material.

Alloys↗
PubMed1998

Severe osteolysis after third-body wear due to hydroxyapatite particles from acetabular cup coating.

One concern about the fixation of HA-coated implants is the possible disintegration of the surface, with the migration of HA granules into the joint space, producing third-body wear. We report a study of six revisions of HA-coated polyethylene RM cups at 9 to 14 years after successful primary arthroplasty. In all six hips, we found HA granules embedded in the articulating surface of the polyethylene, with abrasive wear of the cup and the metal femoral head. The cup had loosened in four hips and three showed severe osteolysis of the proximal femur. Third-body wear due to HA particles from implant coating may produce severe clinical problems with few early warning signs. Further clinical, radiological and histological observations are needed to determine the possible incidence of this late complication in the various types of coating of a variety of substrates.

Acetabulum↗
PubMed1993

Human erythrocyte band 3. Solubilization and reconstitution into two-dimensional crystals.

Various polyoxyethylene alkylethers were used to extract integral proteins from human erythrocyte membranes. The solubilization power of these detergents and the oligomerization of solubilized band 3 were studied. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed that short-chain detergents induced oligomers larger than the band 3 dimer. In contrast, after solubilization with long-chain detergents, the predominant band on SDS-containing gels was the monomeric band 3. Oligomerization in short-chain detergents occurred preferentially at room temperature whereas monomeric band 3 prevailed at 4 degrees C. Consistent with these results, negative stain electron microscopy of solubilized isolated band 3 showed larger complexes with short-chain detergents than with long-chain detergents. Cu2+/o-phenanthroline-induced crosslinking had no effect on size or shape of band 3 particles. Despite their rather heterogeneous dimensions, octylpolyoxyethylene-solubilized band 3 complexes assembled into two-dimensional trigonal lattices (a = b = 11 (+/- 0.5) nm) in the presence of dimyristoyl phosphatidylcholine. The unit cell exhibited a pronounced stain-filled region surrounded by three elongated morphological subunits. Each subunit most likely represents a band 3 dimer. Freeze-drying/metal-shadowing of reconstituted lattices revealed one large elevation per unit cell protruding from an otherwise smooth surface.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1992

Analysis of the structure of photosystem I in cyanobacterial thylakoid membranes.

Using electron microscopy of negatively stained specimens, we have investigated the shape and degree of association of photosystem (PS) I complexes in cyanobacterial thylakoid membranes. When incubated at high concentrations of magnesium chloride (greater than 0.15 M), the PSI complexes form small ordered arrays in the membrane composed of monomeric complexes in a P1 square lattice of dimensions a = b = 11 nm. Averaged projections of the complex resemble those found for the purified PSI reaction centre after reconstitution (Ford, R.C, Hefti, A. and Engel, A. (1990) EMBO J. 9, 3067-3075). Some small differences in its shape are discussed, with particular reference to the differences in the polypeptide composition of the 2 preparations. We find that the complex remains in the monomeric form in the thylakoid membrane under all the conditions tested.

Cyanobacteria↗
PubMed1992

2D crystallization: from art to science.

The techniques as well as the principles of the 2D crystallization of membrane and water-soluble proteins for electron crystallography are reviewed. First, the biophysics of the interactions between proteins, lipids and detergents is surveyed. Second, crystallization of membrane proteins in situ and by reconstitution methods is discussed, and the various factors involved are addressed. Third, we elaborate on the 2D crystallization of water-soluble proteins, both in solution and at interfaces, such as lipid monolayers, mica, carbon film or mercury surfaces. Finally, techniques and instrumentations that are required for 2D crystallization are described.

Aluminum Silicates↗
PubMed1991

In vitro assembly of gap junctions.

Gap junction structures were assembled in vitro from octyl-beta-D-glucopyranoside-solubilized components of lens fiber cell membranes. Individual pore structures (connexons), short double-membrane structures, and other amorphous material were evident in the solubilized mixture. Following the removal of the detergent by dialysis, these connexons associated to form single- and double-layered, two-dimensional hexagonal arrays (unit cell size a = b = 8.5 nm). The formation of larger arrays was dependent on the lipid-to-protein ratio and the presence of Mg2+ ions. Crystallographic analysis of electron micrographs revealed that lens junctional connexons consisted of six subunits surrounding a stain-filled channel. Upon further detergent treatment, in vitro assembled gap junctions were insoluble and formed three-dimensional stacks while other components were solubilized. SDS-PAGE and mass data from scanning transmission electron microscopy strongly suggest that a 38-kDa polypeptide, which is a processed form of the lens specific gap junction protein MP70, is a major component of the arrays. The in vitro assembly of gap junctions opens new avenues for the structural analysis of gap junctions and for the study of the intermolecular interactions of connexons during junctional assembly.

Animals↗
PubMed1990

Ordered arrays of the photosystem I reaction centre after reconstitution: projections and surface reliefs of the complex at 2 nm resolution.

We present an electron microscopical analysis of the photosystem I reaction centre, the membrane complex involved in the second light-driven step of photosynthetic electron transfer in plants and cyanobacteria. To this end, ordered two-dimensional arrays were reconstituted from detergent solubilized photosystem I reaction centres and phospholipids, and studied by electron microscopy and digital image processing. Small (P1) and large (P3) hexagonal lattices obtained with reaction centres of the thermophilic cyanobacterium Phormidium laminosum had unit cell sizes of a = b = 8.8 nm and 15.8 nm, respectively. Reaction centres of a second thermophilic strain, Synechococcus sp. OD24, gave square lattices (a = b = 14.5 nm; P2(1)). Irrespective of the packing arrangement, projections of negatively stained photosystem I complexes showed elongated asymmetric shapes with a large domain at one end which was tilted with respect to a small domain forming the tip of the other end. Such features were also found in averaged projections of solubilized reaction centre trimers. Surface reliefs reconstructed from freeze-dried metal-shadowed P2(1) lattices revealed that reaction centres had a ridge of 2.5 nm height projecting from one side of the membrane while their other side was rather flat and exhibited a shallow, central indentation.

Cyanobacteria↗