Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “insertion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources
PubMed2005

Acid-triggered membrane insertion of Pseudomonas exotoxin A involves an original mechanism based on pH-regulated tryptophan exposure.

Exposure to low endosomal pH during internalization of Pseudomonas exotoxin A (PE) triggers membrane insertion of its translocation domain. This process is a prerequisite for PE translocation to the cytosol where it inactivates protein synthesis. Although hydrophobic helices enable membrane insertion of related bacterial toxins such as diphtheria toxin, the PE translocation domain is devoid of hydrophobic stretches and the structural features triggering acid-induced membrane insertion of PE are not known. Here we have identified a molecular device that enables PE membrane insertion. This process is promoted by exposure of a key tryptophan residue. At neutral pH, this Trp is buried in a hydrophobic pocket closed by the smallest alpha-helix of the translocation domain. Upon acidification, protonation of the Asp that is the N-cap residue of the helix leads to its destabilization, enabling Trp side chain insertion into the endosome membrane. This tryptophan-based membrane insertion system is surprisingly similar to the membrane-anchoring mechanism of human annexin-V and could be used by other proteins as well.

Animals↗
PubMed2002

Cochlear implantation without mastoidectomy: the pericanal electrode insertion technique.

OBJECTIVE: A new minimally invasive cochlear implantation method with direct electrode insertion through the external auditory canal (EAC) is presented. MATERIAL AND METHODS: Surgery begins with a retroauricular skin incision. The bony surface of the mastoid plane behind the ear is dissected free and the skin of the EAC is elevated together with the posterior part of the tympanic membrane. Cochleostomy is performed through the EAC with a microdrill anterior to the round window. A rim is drilled into the postero-superior region of the bony EAC immediately above the incus towards the outer border of the EAC and connected to the retroauricular surface by a short tunnel. The implant device is placed in the usual retroauricular area. The electrode is inserted through the tunnel and rim into the tympanic cavity and pushed into the cochleostomy hole. The electrode is immobilized in the rim using glass ionomer cement and covered with bone dust. After placement of the ground electrode, the retroauricular incision is closed. The tympano-meatal flap is replaced and a dressing is put into the EAC. RESULTS: The new method has been applied thus far in 15 adults and pre-adolescent deaf patients (8 females, 7 males). A MED-EL Combi 40 + device was used in 14 patients and a Nucleus CI24M in 1. Pericanal electrode insertion was easy, with insertion depths into the cochlea of > or = 30 mm with the MED-EL and of 20 mm with the Nucleus device. There were no surgical complications, infections or electrode extrusions during postoperative observation periods ranging from 6 months to > 2 years. The functional results were comparable to those obtained with cochlear implantation via mastoidectomy. The pericanal electrode insertion technique has several advantages, the most important being that the danger of facial nerve damage is minimized and that the operating time is reduced by up to 50%. CONCLUSION: Cochlear implantation with pericanal electrode insertion is a simple, fast and particularly safe option which may replace the classical transmastoidal cochlear implantation method in adults and older children.

Adolescent↗
PubMed2004

Cochlear implantation via the round window membrane minimizes trauma to cochlear structures: a histologically controlled insertion study.

OBJECTIVE: To evaluate cochlear implant trauma to intracochlear structures when inserting the electrode via the round window membrane. MATERIAL AND METHODS: Eight fresh human temporal bones were evaluated histologically after insertion using two types of cochlear implant array. Bones underwent a special fixation and embedding procedure that allowed sectioning of undecalcified bone with the electrode in situ. Insertions depths were evaluated radiologically and histologically. RESULTS: All arrays were found in the scala tympani of the cochlea. Basal trauma could be avoided in all but one specimen. The mean depth of insertion was 382.5 degrees. Apically, only one implanted bone showed cochlear trauma exceeding lifting of the basilar membrane. CONCLUSION: Insertions through the round window membrane were shown to be atraumatic, even in basal cochlear regions. This route of insertion might be very effective for combined electric and acoustic stimulation of the auditory system.

Cochlea↗
PubMed1998

Somatic hypermutation introduces insertions and deletions into immunoglobulin V genes.

During a germinal center reaction, random mutations are introduced into immunoglobulin V genes to increase the affinity of antibody molecules and to further diversify the B cell repertoire. Antigen-directed selection of B cell clones that generate high affinity surface Ig results in the affinity maturation of the antibody response. The mutations of Ig genes are typically basepair substitutions, although DNA insertions and deletions have been reported to occur at a low frequency. In this study, we describe five insertion and four deletion events in otherwise somatically mutated VH gene cDNA molecules. Two of these insertions and all four deletions were obtained through the sequencing of 395 cDNA clones (approximately 110,000 nucleotides) from CD38+IgD- germinal center, and CD38-IgD- memory B cell populations from a single human tonsil. No germline genes that could have encoded these six cDNA clones were found after an extensive characterization of the genomic VH4 repertoire of the tonsil donor. These six insertions or deletions and three additional insertion events isolated from other sources occurred as triplets or multiples thereof, leaving the transcripts in frame. Additionally, 8 of 9 of these events occurred in the CDR1 or CDR2, following a pattern consistent with selection, and making it unlikely that these events were artifacts of the experimental system. The lack of similar instances in unmutated IgD+CD38- follicular mantle cDNA clones statistically associates these events to the somatic hypermutation process (P = 0.014). Close scrutiny of the 9 insertion/deletion events reported here, and of 25 additional insertions or deletions collected from the literature, suggest that secondary structural elements in the DNA sequences capable of producing loop intermediates may be a prerequisite in most instances. Furthermore, these events most frequently involve sequence motifs resembling known intrinsic hotspots of somatic hypermutation. These insertion/deletion events are consistent with models of somatic hypermutation involving an unstable polymerase enzyme complex lacking proofreading capabilities, and suggest a downregulation or alteration of DNA repair at the V locus during the hypermutation process.

Amino Acid Sequence↗
PubMed2005

Effect of insertion depth on helical antenna performance in a muscle-equivalent phantom.

Barrett's oesophagus is considered to increase the risk of cancer 30 fold. A set of helical microwave antennas was designed to investigate their potential use in the thermal therapy of Barrett's oesophagus. For treatment, a balloon filled with muscle-equivalent material encapsulates the antenna. The effects of insertion depth and coil-spacing on the thermal distribution produced by the antennas (20-35 mm) were characterized. The 35 mm helical antenna, with a coil-spacing of 3.6 mm resulted in uniform heating for an insertion depth of 40 mm. It was observed that the resultant temperature distribution produced, by the antennas, was dependent on the insertion depth within the phantom. For all antennas studied, deeper insertion resulted in two high intensity regions, approximately 1/4 and 3/4 along the antenna length. In contrast, shallow insertion resulted in predominant tip heating with undesirable heating at the phantom entry point. However, by manipulating the coil-spacing of the helix, uniform temperature profiles were achieved for a range of insertion depths.

Barrett Esophagus↗
PubMed2004

Changes in arterial oxygen saturation before and after enteral feeding tube insertion in dysphagic stroke patients.

OBJECTIVE: to determine whether insertion of nasogastric or percutaneous endoscopic gastrostomy feeding tubes is associated with hypoxaemia. METHODS: dysphagic stroke patients had their arterial oxygen saturation measured by pulse oximetry continuously for 10 minutes before, during and after tube insertion. RESULTS: in 14 patients nasogastric tube insertion had little effect on oxygen saturation. Six patients maintained oxygen saturation during percutaneous endoscopic gastrostomy insertion (whilst on 2 litres oxygen/min) but had a significantly lower median oxygen saturation (P = 0.03) after the procedure (when oxygen was discontinued) and four of these had oxygen saturation of < or =90%. CONCLUSIONS: in this small group of stroke patients, difficult insertions of nasogastric and percutaneous endoscopic gastrostomy tubes were associated with moderate hypoxaemia. Clinicians should be aware of the potential impact of tube insertion and ensure patients are appropriately monitored and if necessary receive supplemental oxygen, after as well as during the procedure.

Aged↗
PubMed1998

Haemodynamic and electroencephalographic response to insertion of a cuffed oropharyngeal airway: comparison with the laryngeal mask airway.

We have compared the cuffed oropharyngeal airway (COPA), a modified Guedel airway device with a specially designed cuff at its distal end, with the laryngeal mask airway (LMA), on haemodynamic and electroencephalographic (EEG) responses to insertion. In addition, we examined the haemodynamic and EEG changes during initiation of the effect-compartment controlled infusion. We studied 35 female patients undergoing ambulatory gynaecological surgery allocated randomly to received an LMA or COPA to manage the airway. After premedication with midazolam 0.03 mg kg-1 i.v. and low-dose alfentanil (0.01 mg kg-1), anaesthesia was induced and maintained with propofol, using an effect-compartment controlled infusion set at an effect-site concentration of 4 micrograms ml-1. After intercompartmental equilibration, the LMA (group I) or COPA (group II) was inserted and haemodynamic (arterial pressure, heart rate) and EEG (bispectral index (BIS)) responses to insertion studied. The effect-compartment controlled infusion of propofol caused only mild haemodynamic changes during induction. Changes in arterial pressure and heart rate after insertion were similar in both groups and not significantly different from baseline values before insertion. Changes in BIS after insertion were minor and similar between groups.

Ambulatory Surgical Procedures↗
PubMed1999

Prediction of movement at laryngeal mask airway insertion: comparison of auditory evoked potential index, bispectral index, spectral edge frequency and median frequency.

We have studied 46 patients to compare the efficacy of the auditory evoked potential (AEP) index, bispectral index (BIS), 95% spectral edge frequency (SEF) and median frequency (MF) in predicting movement in response to insertion of the laryngeal mask airway (LMA). Anaesthesia was induced with target-controlled infusions of propofol and alfentanil. After loss of eyelash reflex and adequate jaw relaxation, the LMA was inserted without the assistance of a laryngoscope or neuromuscular blocker. Patients who showed any visible spontaneous muscle movement within 1 min of LMA insertion were defined as movers. Values in movers and non-movers at 30 s before LMA insertion were analysed. Only AEP index discriminated between movers and non-movers with a prediction probability of 0.872. BIS, SEF and MF could not predict movement at LMA insertion. AEP index was the most reliable predictor of movement in response to LMA insertion.

Adolescent↗
PubMed2006

Length of insertion for pulmonary artery catheters to locate different cardiac chambers in patients undergoing cardiac surgery.

BACKGROUND: Although, guidelines related to length of insertion of a pulmonary artery catheter to reach a particular cardiac chamber are available, these are not backed by clinical studies. We measured the length of insertion of pulmonary artery catheters to locate the right ventricle, pulmonary artery and pulmonary capillary wedge positions in 300 adult patients undergoing elective cardiac surgery. METHODS: The pulmonary artery catheters were inserted using a standard technique through the right internal jugular vein. The right ventricle, pulmonary artery and wedge position of the catheter were confirmed by the characteristic waveforms, and the length of insertion to these points was measured. RESULTS: The right ventricle was reached at 24.6 (3) cm (95% CI 24.2-24.9 cm), pulmonary artery at 36 (4) cm (95% CI 35.6-36.5 cm) and wedge position at 42.8 (5.7) cm (95% CI 42.2-43.5 cm). The length of catheter to reach the right ventricle, pulmonary artery and wedge position was significantly more in patients undergoing valve surgery as compared with those undergoing coronary artery bypass grafting [26 (3.8) and 24 (2.5) cm; 38.5 (4.6) and 35 (3.2) cm; and 47.8 (6.9) and 41.2 (4.1) cm, respectively, P<0.001]. The length of insertion to reach pulmonary artery and pulmonary capillary wedge position was directly related to height of the patient (Pearson's correlation 0.157 and 0.15, respectively). CONCLUSIONS: We have provided the norms related to length of insertion of pulmonary artery catheter, which should be useful in accurate placement of the catheter and minimize complications related to coiling of the catheter.

Adolescent↗
PubMed1983

Specificity of transposon Tn5 insertion.

Genetic mapping studies had shown that the bacterial transposon Tn5 can insert into many sites in a gene, but that some sites are preferred. To begin understanding Tn5's insertion specificity at the molecular level, we selected transpositions of Tn5 from the Escherichia coli chromosome to the plasmid pBR322 and analyzed the resultant pBR322::Tn5 plasmids by restriction endonuclease digestion and DNA sequencing. Seventy-five insertions in the tet gene were found at 28 sites including one major hotspot (with 21 insertions) and four lesser hotspots (with four to ten insertions each). All five hotspots are within the first 300 of the 1250-base pair (bp) tet gene. In contrast, 31 independent insertions in the amp gene were found in at least 27 distinct sites.--Tn5 generates 9 bp target sequence duplications when it transposes. Such transposon-induced duplications are generally taken to indicate that cleavages of complementary target DNA strands are made 9 bp apart during transposition. DNA sequence analysis indicated that GC base pairs occupy positions 1 and 9 in the duplications at each of the five hotspots examined, suggesting a GC-cutting preference during Tn5 transposition.

Base Sequence↗
PubMed1984

Crosses between insertion and point mutations in lambda gene cI: stimulation of neighboring recombination by heterology.

Intragenic recombination between lambda cI point mutations and insertions was studied in four-factor crosses. In crosses between two point mutations, there is a linear relationship between recombination frequency and distance. However, in crosses between an insertion and point mutations, there is additional recombination in the regions 200 base pairs to the right and to the left of the insertion. The recombinational stimulation occurred with IS insertions and also with insertions consisting of HindIII fragments of SV40 and with a deletion that removes part of cI. This indicated that the stimulation was a result of heterology per se rather than of information encoded by the insertions. Either Rec or Red functions are sufficient for enhanced recombination near a heterology. The stimulation is attributed to more frequent resolution of recombinational intermediates in the neighborhood of a heterology. "Stalling" of migrating branches or invading strands at a heterology may increase the probability of local DNA cleavage.

Bacteriophage lambda↗
PubMed1990

Mobile element insertions causing mutations in the Drosophila suppressor of sable locus occur in DNase I hypersensitive subregions of 5'-transcribed nontranslated sequences.

The locations of 16 mobile element insertions causing mutations at the Drosophila suppressor of sable [su(s)] locus were determined by restriction mapping and DNA sequencing of the junction sites. The transposons causing the mutations are: P element (5 alleles), gypsy (3 alleles), 17.6, HMS Beagle, springer, Delta 88, prygun, Stalker, and a new mobile element which was named roamer (2 alleles). Four P element insertions occur in 5' nontranslated leader sequences, while the fifth P element and all 11 non-P elements inserted into the 2053 nucleotide, 5'-most intron that is spliced from the 5' nontranslated leader approximately 100 nucleotides upstream of the translation start. Fifteen of the 16 mobile elements inserted within a approximately 1900 nucleotide region that contains seven 100-200-nucleotide long DNase I-hypersensitive subregions that alternate with DNase I-resistant intervals of similar lengths. The locations of these 15 insertion sites correlate well with the roughly estimated locations of five of the DNase I-hypersensitive subregions. These findings suggest that the features of chromatin structure that accompany gene activation may also make the DNA susceptible to insertion of mobile elements.

Animals↗
PubMed2004

Prognostic significance of a short sequence insertion in the MCL-1 promoter in chronic lymphocytic leukemia.

BACKGROUND: Mcl-1 protein contributes to the longevity of chronic lymphocytic leukemia (CLL) B cells, and its higher expression has been associated with resistance to chemotherapy. We sought structural changes in the MCL-1 gene in CLL patients and associated these with clinical parameters of the disease. METHODS: The MCL-1 gene from peripheral blood lymphocytes from 58 CLL patients and 18 control subjects and from the RL and BC-3 lymphoma cell lines was sequenced. Mcl-1 mRNA expression (in 20 consecutive patients and four control subjects) was analyzed by RNase protection assay, and Mcl-1 protein expression (in 18 consecutive patients and four controls) was analyzed by western blotting. Genetic changes in MCL-1 were associated with biochemical and clinical characteristics, including expression of CD38, a negative prognostic factor. Cox proportional hazards modeling was used to determine the prognostic importance of changes in the MCL-1 gene, and the Kaplan-Meier method was used to analyze patient survival. All statistical tests were two sided. RESULTS: A 6- or 18-nucleotide sequence insertion was found in the same site in the MCL-1 promoter in 17 of 58 patients and in BC-3 cells; it was absent in all control subjects and in RL cells. Of 21 CD38-negative patients, 10 had a promoter insertion; of 17 CD38-positive patients, one had a promoter insertion (P =.0099). Patients with a promoter insertion had higher mRNA (median = 26.8 relative units, interquartile range [IQR] = 14.9 to 35.2, versus median = 8.8 relative units, IQR = 3.9 to 15.7, P =.030, U-test) and protein (median = 0.84 relative units, IQR = 0.81 to 1.0 versus median = 0.47, IQR = 0.32 to 0.70, P =.021, U-test) expression, more rapid disease progression (P =.012), poorer response to chemotherapy (P =.001), and shorter overall (P =.0088) and disease-specific (P <.001) survival than patients with a normal promoter. The presence of an MCL-1 promoter insertion had prognostic significance in a Cox model (P =.001). CONCLUSIONS: The MCL-1 promoter insertion may identify a high-risk group of CD38-negative CLL patients.

Adult↗
PubMed2006

Impact of the excision of an ancient repeat insertion on Rickettsia conorii guanylate kinase activity.

The genomic sequencing of Rickettsia conorii revealed a new family of Rickettsia-specific palindromic elements (RPEs) capable of in-frame insertion in preexisting open reading frames (ORFs). Many of these altered ORFs correspond to proteins with well-characterized or essential functions in other microorganisms. Previous experiments indicated that RPE-containing genes are normally transcribed and that no excision of the repeat occurs at the mRNA level. Using mass spectrometry, we now confirmed the retention of the RPE-derived amino acid residues in 4 proteins successfully expressed in Escherichia coli, raising the general question of the consequences of this common insertion event on the fitness of Rickettsia enzymes. The predicted guanylate kinase activity of the R. conorii gmk gene product was measured both on the RPE-containing and RPE-excised recombinant proteins. We show that the 2 proteins are active but exhibit substantial differences in their affinity for adenosine triphosphate, guanosine monophosphate, and catalytic constants. The distribution of the RPEgmk insert among Rickettsia species indicates that the insertion event is ancient and occurred after the divergence of Rickettsia felis and R. conorii but before that of Rickettsia helvetica and R. conorii. We found no evidence that the gmk gene fixed adaptive changes to compensate the RPE peptide insertion. Furthermore, the analysis of the rates of divergence in 23 RPE-containing genes indicates that coding RPE repeats tend to evolve under weak selective constraint, at a rate similar to intergenic noncoding RPE sequences. Altogether, these results suggest that the insertion of RPE-encoded "selfish peptides," although respecting the original fold and activity of the host proteins, might be slightly detrimental to the enzyme efficiency within limits tolerable for slow-growing intracellular parasites such as Rickettsia.

Amino Acid Sequence↗
PubMed1984

Ribosomal DNA genes of Bombyx mori: a minor fraction of the repeating units contain insertions.

We have analyzed multiple recombinant DNA clones containing ribosomal RNA repeat units of the silkmoth, Bombyx mori. In combination with genomic DNA blots, analysis of these clones indicated that the rDNA repeat of B. mori is 10.8 kilobase pair in length and tandemly repeated in the genome, as reported by Manning et al. (18). However, contrary to that report, approximately 12% of the rDNA cistrons are interrupted by insertions of non-ribosomal DNA. Two classes of DNA insertions were identified. In one class the insertions are positioned in a region of the 28S coding sequence similar to that of the predominant rDNA insertions found in a variety of Dipteran and Tetrahymena species. In the second class, probable insertions are found close to the 3' terminus of the 28S coding sequence. Restriction enzyme analysis indicates that the two classes of insertions are not related.

Animals↗
PubMed1986

Expression of ribosomal insertion in Drosophila: sensitivity to intercalating drugs.

Ribosomal insertions in Drosophila are transcribed at very low levels. The abundance of the most prominent 0.8 kb type 1 insertion transcript increased up to 60-fold when cultured cells were exposed to the DNA intercalating drug chloroquine. After injection of insertion-containing rDNA in circular form into Xenopus laevis oocytes an apparently identical 0.8 kb insertion transcript was synthesized, and its accumulation was stimulated several fold by coinjection of chloroquine or ethidium bromide. We suggest that ribosomal insertions are assembled in a chromatin conformation that lacks unconstrained torsional stress, accounting for the inactivity of these DNA regions; introduction of stress by intercalation results in activation of transcription from the insertion sequences.

Animals↗
PubMed2005

Selenocysteine insertion directed by the 3'-UTR SECIS element in Escherichia coli.

Co-translational insertion of selenocysteine (Sec) into proteins in response to UGA codons is directed by selenocysteine insertion sequence (SECIS) elements. In known bacterial selenoprotein genes, SECIS elements are located in the coding regions immediately downstream of UGA codons. Here, we report that a distant SECIS element can also function in Sec insertion in bacteria provided that it is spatially close to the UGA codon. We expressed a mammalian phospholipid hydroperoxide glutathione peroxidase in Escherichia coli from a construct in which a natural E.coli SECIS element was located in the 3'-untranslated region (3'-UTR) and adjacent to a sequence complementary to the region downstream of the Sec UGA codon. Although the major readthrough event at the UGA codon was insertion of tryptophan, Sec was also incorporated and its insertion was dependent on the functional SECIS element in the UTR, base-pairing potential of the SECIS flanking region and the Sec UGA codon. These data provide important implications into evolution of SECIS elements and development of a system for heterologous expression of selenoproteins and show that in addition to the primary sequence arrangement between UGA codons and SECIS elements, their proximity within the tertiary structure can support Sec insertion in bacteria.

3' Untranslated Regions↗
PubMed2004

Venography at insertion of tunnelled internal jugular vein dialysis catheters reveals significant occult stenosis.

BACKGROUND: Tunnelled catheters are widely used to provide vascular access for haemodialysis. Percutaneous insertion of these catheters requires large calibre tissue dilators with the potential to cause trauma to central veins, particularly if anatomical abnormalities are present. METHODS: We evaluated the use of venography to identify central vein anatomical abnormalities in 69 consecutive patients undergoing percutaneous placement of tunnelled right internal jugular vein catheters. The internal jugular vein was entered under ultrasound guidance and venography was performed prior to insertion of a guide-wire. Images were evaluated on-screen by the operator and a decision made regarding the need for additional fluoroscopy during insertion of the catheter. RESULTS: In 29 cases (42%), venography showed evidence of unexpected stenosis and/or angulation of the central veins of sufficient severity to warrant additional fluoroscopy during insertion of the dilators, or abandonment of the procedure. Patients who had previously had tunnelled internal jugular catheters had more than double the incidence of such abnormalities than those who had not [15/23 (65%) vs 14/46 (30%); P = 0.009]. In two patients the procedure was abandoned due to severe stenosis. No patient suffered central vein trauma or pneumothorax. There were no adverse reactions to contrast injection. CONCLUSIONS: Venography performed immediately prior to tunnelled internal jugular dialysis catheter insertion detects unexpected, clinically significant anatomical abnormalities of the central veins in a substantial proportion of patients, particularly those with a history of previous tunnelled catheter insertion. We suggest that the use of venography may help to minimize the risk of complications from this procedure.

Aged↗