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At least 487 records · Page 27Linked to original sources
PubMed2001

Biomechanical properties in titanium implants with integrated maintenance free shock absorbing elements.

Good functional properties are essential in dental implantology. Bio-kinetic elements are imitating dental resilience. In this study a new kind of implants with maintenance free shock absorbing elements will be introduced and their bio-mechanic properties reported. The mobile implant (SIS Inc., Klagenfurt, Austria) is a self-cutting conical screw implant with an integrated bio-kinetic element. The shock absorber is a central part of the implant and a titanium ring closes the shock absorbing unit within the implant. The resilience of the implant was tested by axial and horizontal loading in a special testing unit. Furthermore, a survival test of the elastic titanium ring in the most exposed cervical part of the implant was performed. The region was examined by electron microscopy after 12 million movements in the axial and horizontal direction. A progressive shock absorption was registered during horizontal and axial movements. The maximum movements were 0.06 mm in the axial and 0.16 mm in the horizontal direction. There were seen no signs of material destruction in the electron microscopic analysis. A maintenance-free bio-kinetic implant with progressive shock absorbing qualities was registered.

Biomechanical Phenomena↗
PubMed2000

[Resilience behavior of titanium implants with integrated maintenance-free biokinetic elements].

Good functional properties are essential in dental implantology. Bio-kinetics elements are imitating dental resilience. In this study a new kind of implants with maintenance-free shock-absorbing elements was introduced and their bio-mechanic properties were tested. The mobile implant (SIS Inc, Klagenfurt, Austria) is a self-cutting conical screw implant with an integrated bio-kinetic element. The shock absorber is a central part of the implant and a titanium ring obturates the shock absorbing unit in the implant. The resilience of the implant was tested by axial and excentric loading in a special testing unit. Furthermore a survival test of the elastic titanium ring in the most exposed cervical part of the implant was performed. The region was examined by scanning electron microscopy after 12 million loading cycles in the axial and radial direction. A progressive shock absorption was registered during radial and axial loading. The maximum movements were 0.06 mm in the axial and 0.16 mm in the radial direction. No signs of material destruction were seen in the electron microscopic analysis. Thus a maintenance-free bio-kinetic implant with progressive shock-absorbing qualities is presented.

Biomechanical Phenomena↗
PubMed2005

Development of an integrated CAD-FEA process for below-knee prosthetic sockets.

BACKGROUND: Computer-aided design and manufacturing has been successfully used in prosthetic applications since 1980s. It simplifies the socket rectification process and improves reproducibility but does not introduce any new principle into socket design. Integrating finite element analysis to CAD will provide a more objective assessment of socket fit and improve the chance of a successful first fitting. METHODS: Current study aims to establish a finite element model generation technique directly from geometrical information of commercial prosthetic CAD workstation. A program developed in-house automatically performs meshing of the stump geometry and assigns suitable material properties, load and boundary conditions to the model. The model was validated by comparing predicted pressure with experimentally measured values for one amputee subject. FINDINGS: The predicted pressure distribution has an root-mean-square error of 8.8 kPa compared to experimental values at 10%, 25% and 50% of the gait cycle. INTERPRETATION: Current method was able to develop a finite element model to predict interface pressure reasonably well and can be integrated with prosthetic CAD system to provide quantitative feedback to the prosthetist in an automated process.

Artificial Limbs↗
PubMed2004

Mode matching interface for efficient coupling of light into planar photonic crystals.

In order to integrate superdispersive elements based on photonic crystals, such as the superprism, with conventional integrated optics, insertion losses at the interface to the photonic crystal need to be reduced to an acceptable level. We describe a mode matching interface composed of cascaded diffraction gratings that generates the field profile of the photonic crystal Bloch mode from a slab mode. We calculate with three-dimensional finite-difference time-domain computation that by interposing such a multilayered grating between an unpatterned slab and a planar photonic crystal, the insertion efficiency is enhanced from 9% to 84%. Each diffraction grating consists of a row of holes and does not require any additional process steps from those used to fabricate the planar photonic crystal. In order to optimize the efficiency of the mode matching interface, constructive interference conditions are imposed between successive gratings and reflections from individual gratings are suppressed. We fabricate devices in silicon on insulator material and show experimental evidence of the Bloch mode structure and of the mode matching mechanism.

Journal Article↗
PubMed1994

Shaping and positioning the nasal tip without structural disruption: a new, systematic approach.

This paper presents a new, comprehensive, and systematic approach to analysis, planning, and techniques of primary nasal tip rhinoplasty, emphasizing techniques that limit uncontrollable variables before proceeding to techniques which increase uncontrollable variables and risk secondary deformity, including (1) maintenance of structural integrity of the alar rim strips, limiting use of scoring or morselization techniques which reduce support and introduce potential secondary deformities, (2) shaping and positioning the lateral and medial crura in a reversible, nondestructive manner using permanent suture and nonvisible control graft techniques, (3) minimizing uncontrollable postoperative variables by decreasing the need for visible grafts to shape the tip complex in primary rhinoplasty, achieving the same results with existing alar structural elements, (4) integrating these concepts with specific sequences of surgical techniques--bilateral alar arch components individually positioned, then shaped and unified for symmetry, and finally positioned for rotation and projection--and (5) introducing an integrated set of surgical techniques and sequencing of tip surgery to achieve the objectives listed above in most primary and some secondary rhinoplasties. The concepts and techniques of this approach are based on the principle that preservation of structural integrity of alar complex elements (medial and lateral crural arch elements) preserves support and reduces the incidence of secondary deformities (kinking, buckling, discontinuity) that can result from shaping techniques which disrupt that integrity. If shaping and positioning of the tip can be achieved with reversible, nondestructive techniques, the need for placement of visible grafts (with their additional variables) is greatly reduced. Shaping and positioning can be performed incrementally and reversibly without jeopardizing structural integrity and support in the surgical process. Ten fresh cadaver dissections were utilized in the development of the surgical techniques. A total of 233 rhinoplasties (220 primary and 13 secondary) with 1 to 9 years of follow-up have been performed using this approach. Only two secondary procedures for tip deformity have been performed.

Cadaver↗
PubMed2004

TFExplorer: integrated analysis database for predicted transcription regulatory elements.

UNLABELLED: TFExplorer is a web-based integrated database for predicted regulatory elements in human, mouse and rat. It shows predicted binding sites of transcription factors in the promoter regions, along with their phylogenetic footprinting information. In addition, TFExplorer can search for genes that have a given sequence pattern in their promoter regions using the motif-searching method. AVAILABILITY: TFExplorer is freely available at http://mars.kribb.re.kr:8080/tfExplorer/ CONTACT: sskimb@kribb.re.kr.

Algorithms↗
PubMed1986

In vitro transcription of a human hsp 70 heat shock gene by extracts prepared from heat-shocked and non-heat-shocked human cells.

A cDNA clone homologous to HeLa cell mRNA encoding the 70 kDa human heat shock protein (hsp 70) was used to isolate a recombinant phage containing an entire human hsp 70 gene. Sequence analysis of the 5' and 3' flanking regions revealed the structural integrity of the regulatory elements. The functional integrity of this hsp 70 gene was substantiated by in vitro transcription studies with nuclear extracts. Specific run-off transcripts, synthesized by RNA polymerase II, were obtained with extracts prepared from heat-shocked cells. Extracts from non-heat-shocked cells were found inactive in hsp 70 gene transcription. However, 5' deletion mutants lacking the heat shock element (HSE) were transcribed by both heat shock and nonheat shock HeLa extracts.

Adenoviruses, Human↗
PubMed2005

[Sperm DNA integrity as diagnosis and prognosis element of male fertility].

Recent progress in reproductive biology has improved comprehension physiology of the spermatozoa and on the fertilization mechanisms. This new knowledge has carried out the elaboration of tests on male fertility based on sperm genomic integrity. This review presents some of these techniques and brings a reflexion element on the application and use of sperm DNA integrity in the investigation of male fertility. The single cell gel electrophoresis (COMET assay), Sperm Chromatin Structure Assay (SCSA), In Situ Nick Translation (NT: Nick Translation) and Terminal Uridine Nick-End Labelling (TUNEL assay) are actually the most currently used techniques for the measure of sperm DNA integrity in research clinic. From a certain point of view, TUNEL assay, SCSA, COMET assay and NT assay are complementary. The TUNEL and COMET can measure single and double strand breaks of DNA, the SCSA can detect the abnormalities in the chromatin compaction and the NT assay can detect the single strand breaks of DNA. The exact origin of sperm DNA fragmentation is not established yet. However, several mechanisms have been proposed: defect in the chromatin compaction during spermiogenesis; reactive oxygen species production by immature spermatozoa; apoptosis during spermatogenesis. It becomes important to consider the possible consequences of the oocyte fertilization by a spermatozoon having a high degree of DNA fragmentation. The use in routine of some of these tests must however pass by a standardization of the inter laboratory protocols and obviously, by the establishment of both in vivo and in vitro discriminating threshold values in order for these tests to present a good predictive value for pregnancy outcome.

Comet Assay↗
PubMed2005

Transfer RNA gene-targeted integration: an adaptation of retrotransposable elements to survive in the compact Dictyostelium discoideum genome.

Almost every organism carries along a multitude of molecular parasites known as transposable elements (TEs). TEs influence their host genomes in many ways by expanding genome size and complexity, rearranging genomic DNA, mutagenizing host genes, and altering transcription levels of nearby genes. The eukaryotic microorganism Dictyostelium discoideum is attractive for the study of fundamental biological phenomena such as intercellular communication, formation of multicellularity, cell differentiation, and morphogenesis. D. discoideum has a highly compacted, haploid genome with less than 1 kb of genomic DNA separating coding regions. Nevertheless, the D. discoideum genome is loaded with 10% of TEs that managed to settle and survive in this inhospitable environment. In depth analysis of D. discoideum genome project data has provided intriguing insights into the evolutionary challenges that mobile elements face when they invade compact genomes. Two different mechanisms are used by D. discoideum TEs to avoid disruption of host genes upon retrotransposition. Several TEs have invented the specific targeting of tRNA gene-flanking regions as a means to avoid integration into coding regions. These elements have been dispersed on all chromosomes, closely following the distribution of tRNA genes. By contrast, TEs that lack bona fide integration specificities show a strong bias to nested integration, thus forming large TE clusters at certain chromosomal loci that are hardly resolved by bioinformatics approaches. We summarize our current view of D. discoideum TEs and present new data from the analysis of the complete sequences of D. discoideum chromosomes 1 and 2, which comprise more than one third of the total genome.

Animals↗
PubMed2004

A wide-range integrative yeast expression vector system based on Arxula adeninivorans-derived elements.

An Arxula adeninivorans integration vector was applied to a range of alternative yeast species including Saccharomyces cerevisiae, Debaryomyces hansenii, Debaryomyces polymorphus, Hansenula polymorpha and Pichia pastoris. The vector harbours a conserved A. adeninivorans-derived 25S rDNA sequence for targeting, the A. adeninivorans-derived TEF1 promoter for expression control of the reporter sequence, and the Escherichia coli-derived hph gene conferring resistance against hygromycin B for selection of recombinants. Heterologous gene expression was assessed using a green fluorescent protein (GFP) reporter gene. The plasmid was found to be integrated into the genome of the various hosts tested; recombinant strains of all species exhibited heterologous gene expressions of a similar high level.

Cloning, Molecular↗
PubMed2006

Identification and characterization of novel polymorphic LINE-1 insertions through comparison of two human genome sequence assemblies.

Mobile elements represent a relatively new class of markers for the study of human evolution. Long interspersed elements (LINEs) belong to a group of retrotransposons comprising approximately 21% of the human genome. Young LINE-1 (L1) elements that have integrated recently into the human genome can be polymorphic for insertion presence/absence in different human populations at particular chromosomal locations. To identify putative novel L1 insertion polymorphisms, we computationally compared two draft assemblies of the whole human genome (Public and Celera Human Genome assemblies). We identified a total of 148 potential polymorphic L1 insertion loci, among which 73 were candidates for novel polymorphic loci. Based on additional analyses we selected 34 loci for further experimental studies. PCR-based assays and DNA sequence analysis were performed for these 34 loci in 80 unrelated individuals from four diverse human populations: African-American, Asian, Caucasian, and South American. All but two of the selected loci were confirmed as polymorphic in our human population panel. Approximately 47% of the analyzed loci integrated into other repetitive elements, most commonly older L1s. One of the insertions was accompanied by a BC200 sequence. Collectively, these mobile elements represent a valuable source of genomic polymorphism for the study of human population genetics. Our results also suggest that the exhaustive identification of L1 insertion polymorphisms is far from complete, and new whole genome sequences are valuable sources for finding novel retrotransposon insertion polymorphisms.

Alleles↗
PubMed1999

Evidence that Tn5565, which includes the enterotoxin gene in Clostridium perfringens, can have a circular form which may be a transposition intermediate.

The Clostridium perfringens enterotoxin gene is on a transposon-like element, Tn5565, integrated in the chromosome in human food poisoning strains. The flanking IS elements, IS1470 A and B, are related to IS30. The IS element found in the transposon, IS1469, is related to IS200 and has been found upstream of cpe in all Type A strains. PCR and sequencing studies from cell extracts and plasmid isolations of C. perfringens indicate that Tn5565 can form a circular form with the tandem repeat (IS1470)2, similar to the transposition intermediates described for a number of IS elements.

Base Sequence↗
PubMed1991

Revised genomic consensus for the hypermethylated CpG island region of the human L1 transposon and integration sites of full length L1 elements from recombinant clones made using methylation-tolerant host strains.

Efficient recovery of clones from the 5' end of the human L1 dispersed repetitive elements necessitates the use of deletion mcr- host strains since this region contains a CpG island which is hypermethylated in vivo. Clones recovered with conventional mcr+ hosts seem to have been derived preferentially from L1 members which have accumulated mutations that have removed sites of methylation. We present a revised consensus from the 5' presumptive control region of these elements. This revised consensus contains a consensus RNA polymerase III promoter which would permit the synthesis of transcripts from the 5' end of full length L1 elements. Such potential transcripts are likely to exhibit a high degree of secondary structure. In addition, we have determined the flanking sequences for 6 full length L1 elements. The majority of full length L1 clones show no convincing evidence for target site duplication in the insertion site as commonly observed with truncated L1 elements. These data would be consistent with two mechanisms of integration of transposing L1 elements with different mechanisms predominating for full length and truncated elements.

Base Sequence↗
PubMed1994

Characterization of a human locus in transition.

The spermatid-specific nucleoprotamine genes PRM1 and PRM2 and the transition protein gene TNP2 are clustered at a single site on human chromosome 16p13.2. To begin to understand the mechanism governing their genesis and coordinate regulation the primary sequence of this approximately 40.6 kilobase region was determined. This cluster of genes is embedded within a series of repetitive elements, including numerous Alu elements distributed at a frequency of > 1 Alu element/kilobase. Multiple Alu elements have integrated into separate truncated L1 sequences within this region. Many of these Alu elements are tandemly inserted or clustered. The role of repetitive elements in the genomic organization and evolution of this gene cluster is discussed. Computer-assisted sequence analysis revealed the presence of structural sequence elements often associated with the boundary regions of active transcriptional domains. Further analysis identified a CpG island at the 3' end of this segment of chromosome 16 and other candidate coding segments within this region indicative of an additional linked gene. These sequence landmarks are commensurate with the complexity of the region.

Base Sequence↗
PubMed1998

Vibrotactile pattern isolation/integration.

Temporal integration has been cited as a major factor in temporal masking. Two experiments were designed to examine the conditions under which temporal integration may aid or hinder the perception of vibrotactile spatial patterns. In Experiment 1, the subject's task was to discriminate between pairs of patterns. Each pattern was composed of two temporally separated pattern elements. When the task required the subjects to perceive the individual pattern elements, performance improved with temporal isolation--that is, performance improved as the temporal separation between the elements increased. In a second task, when the discrimination could be based on either the overall pattern shape or the pattern elements, temporal integration appeared to improve performance--that is, performance improved as the temporal separation decreased. In Experiment 2, an identification task was used. Several factors appeared to determine whether temporal integration aided or hindered pattern identification. When pattern elements similar to those in Experiment 1 were tested, performance improved with increasing temporal separation (isolation). A single function was fit to the discrimination (isolation) and identification (isolation) results. Whether temporal integration aids or hinders pattern perception appears to depend on pattern shape, the pattern elements, and the nature of the task.

Female↗
PubMed1996

Molecular characterization of the Anopheles gambiae 2L telomeric region via an integrated transgene.

A Drosophila P-element derivative (pUChsneo) integrated into the telomeric region of the left arm of the second chromosome of Anopheles gambiae was used to clone the proximally flanking An. gambiae sequences. Molecular analyses revealed that the pUChsneo construct was partially duplicated and had integrated into a subterminal minisatellite. This satellite has a repeat unit of 820 bp and is located exclusively at the tip of 2L. No sequence similarity to subterminal minisatellites from other dipterans was detected, but some structural features such as tandem subrepeats are shared. The end of the chromosome was mapped with respect to restriction sites in pUChsneo at approximately generation 100 after the integration event. Considering inevitable terminal nucleotide loss due to incomplete DNA replication, we conclude that the chromosome end must have undergone a dramatic elongation process since it was mapped in generation 23.

Animals↗
PubMed1991

Stereospecific alignment of the X and Y elements is required for major histocompatibility complex class II DRA promoter function.

The regulatory mechanisms controlling expression of the major histocompatibility complex (MHC) class II genes involve several cis-acting DNA elements, including the X and Y boxes. These two elements are conserved within all murine and human class II genes and are required for accurate and efficient transcription from MHC class II promoters. Interestingly, the distance between the X and Y elements is also evolutionarily conserved at 18 to 20 bp. To investigate the function of the invariant spacing in the human MHC class II gene, HLA-DRA, we constructed a series of spacing mutants which alters the distance between the X and Y elements by integral and half-integral turns of the DNA helix. Transient transfection of the spacing constructs into Raji cells revealed that inserting integral turns of the DNA helix (+20 and +10 bp) did not reduce promoter activity, while inserting or deleting half-integral turns of the DNA helix (+15, +5, and -5 bp) drastically reduced promoter activity. The loss of promoter function in these half-integral turn constructs was due neither to the inability of the X and Y elements to bind proteins nor to improper binding of the X- and Y-box-binding proteins. These data indicate that the X and Y elements must be aligned on the same side of the DNA helix to ensure normal function. This requirement for stereospecific alignment strongly suggests that the X- and Y-box-binding proteins either interact directly or are components of a larger transcription complex which assembles on one face of the DNA double helix.

Animals↗
PubMedDate not supplied

[Intramolecular dynamics of human erythrocyte membrane proteins upon modification of spectrin by tryptophan phosphorescence].

The slow (millisecond) protein internal dynamics of isolated human erythrocyte membranes in suspension without treatment, after deleting 95% of spectrin, after spectrin thermal denaturation upon acidification of medium in the pH range 6.0-4.0, and spectrin extracted in solution from membranes has been studied by room-temperature tryptophan phosphorescence. It has been established that integral proteins and spectrin differ in structural and dynamic state. Millisecond movements of structural elements of integral proteins are more restricted compared with those of spectrin. The removal of spectrin from the membrane led to an increase in slow fluctuations of integral protein structure. This indicates that spectrin participates in the control of the structural and dynamic state of erythrocyte membrane proteins. As medium was acidified in the pH range 6.0-4.0, the protein slow internal dynamics of membranes in native state decreased, which was explained by spectrin pH aggregation. After thermal denaturation of spectrin, no pH-induced increase of membrane protein structure rigidity was observed.

Blood Proteins↗