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At least 577 records · Page 32Linked to original sources
PubMed2002

The role of parallel stent insertion in patients with esophagorespiratory fistulas.

BACKGROUND: Patients with malignant esophagorespiratory fistulas have a poor prognosis. Treatment is palliative and involves restoration of the ability to ingest food and prevention of aspiration by insertion of esophageal or tracheobronchial stents. Because insertion of a single stent may be insufficient for palliation, a series of patients who underwent parallel stent insertion were studied. METHODS: Thirteen patients with esophagorespiratory fistulas who required parallel stents were studied retrospectively. Palliation was evaluated by assessing dyspnea, dysphagia, and coughing associated with eating and/or drinking before and after insertion of stents. OBSERVATIONS: Insertion of the first stent (n = 13) resulted in complete relief of symptoms attributed to an esophagorespiratory fistula in 46% and in a reduction in symptoms in 54% of patients. The interval between insertion of the first and second stents ranged from 1 to 182 days (mean 46 days). Insertion of the second stent (n = 12) resulted in complete relief of symptoms in 42% and a reduction in symptoms in 58% of the patients. CONCLUSION: Parallel stent insertion may be indicated in patients with symptoms caused by malignant esophagorespiratory fistula.

Adult↗
PubMed2002

Clinical implications of velamentous cord insertion in triplet gestations.

OBJECTIVE: The purpose of this study was to determine the incidence of velamentous cord insertion and to evaluate the association between velamentous cord insertion and small-for-gestational age infants in triplet gestations. STUDY DESIGN: We reviewed our computerized database to identify all cases of velamentous cord insertion in triplet gestations who were delivered at our institution from January 1995 through December 1999. Triplet gestations without velamentous cord insertion who were delivered during this period were used as control subjects. Birth weights and pregnancy outcomes were obtained from medical records. Data were analyzed with descriptive statistics, analysis of variance, and chi(2) with Fisher exact test, where appropriate. RESULTS: Thirty-nine sets of triplets (117 infants) were delivered during the study period. Of these, 11 sets of triplets (28.2%) had a velamentous insertion of at least one umbilical cord. Infants with velamentous cord insertion were more likely to be small-for-gestational age than infants without velamentous cord insertion (33% vs 8%, P =.02). There were no significant differences in the rates of pregnancy complications between the two groups. CONCLUSION: Velamentous cord insertion is found frequently in triplet gestations and is significantly associated with small-for-gestational age in triplet neonates.

Cesarean Section↗
PubMed2005

Interfacial folding and membrane insertion of designed peptides studied by molecular dynamics simulations.

The mechanism of interfacial folding and membrane insertion of designed peptides is explored by using an implicit membrane generalized Born model and replica-exchange molecular dynamics. Folding/insertion simulations initiated from fully extended peptide conformations in the aqueous phase, at least 28 A away from the membrane interface, demonstrate a general mechanism for structure formation and insertion (when it occurs). The predominately hydrophobic peptides from the synthetic WALP and TMX series first become localized at the membrane-solvent interface where they form significant helical secondary structure via a helix-turn-helix motif that inserts the central hydrophobic residues into the membrane interior, and then fluctuations occur that provide a persistent helical structure throughout the peptide and it inserts with its N-terminal end moving across the membrane. More specifically, we observed that: (i) the WALP peptides (WALP16, WALP19, and WALP23) spontaneously insert in the membrane as just noted; (ii) TMX-1 also inserts spontaneously after a similar mechanism and forms a transmembrane helix with a population of approximately 50% at 300 K; and (iii) TMX-3 does not insert, but exists in a fluctuating membrane interface-bound form. These findings are in excellent agreement with available experimental data and demonstrate the potential for new implicit solvent/membrane models together with advanced simulation protocols to guide experimental programs in exploring the nature and mechanism of membrane-associated folding and insertion of biologically important peptides.

Amino Acid Motifs↗
PubMed1994

Evidence that most human Alu sequences were inserted in a process that ceased about 30 million years ago.

The primate Alu interspersed repeats can be subdivided into classes on the basis of shared nucleotides at a set of diagnostic positions. Each of the classes of Alu sequences is apparently the result of past retrotransposition of transcripts of highly conserved class-specific source genes that differed from each other at the diagnostic positions. The nucleotides at the majority of positions are identical among the source genes and therefore were identical among all of the Alu sequences at the time of their insertion. These CONSBI (conserved before insertion) positions are useful because the changes that have occurred after insertion are recognizable and the divergence resulting from nucleotide substitutions, insertions, and deletions is informative. The divergence of Alu sequences at the CONSBI positions is a measure of the time since a class was inserted. The greatest majority of Alu sequences are in one class (identified as class II), and it is particularly suitable for such examination, since nearly full-length sequences are now known for nearly a thousand members of this class. The average divergence of class II members indicates that the class has an average age of about 40 million years. The distribution in divergence of class II accurately fits a sum of two Poisson distributions. The implication is that class II Alu sequences were derived from two massive past events of insertion of many Alu sequences. In this model the younger subset of class II sequences (corresponding to about 300,000 copies in the genome) has an average divergence of 5% at CONSBI positions. The older set of class II sequences (corresponding to about 150,000 genomic copies) has a 9% average divergence. Based on the drift rate of primate DNA sequences, the events of insertion probably occurred 30-50 million years ago. The goodness of the fit to the Poisson distribution indicates that no significant number of members of class II have been inserted since 30 million years ago.

Animals↗
PubMed1996

DNA sequence insertion and evolutionary variation in gene regulation.

Current evidence on the long-term evolutionary effect of insertion of sequence elements into gene regions is reviewed, restricted to cases where a sequence derived from a past insertion participates in the regulation of expression of a useful gene. Ten such examples in eukaryotes demonstrate that segments of repetitive DNA or mobile elements have been inserted in the past in gene regions, have been preserved, sometimes modified by selection, and now affect control of transcription of the adjacent gene. Included are only examples in which transcription control was modified by the insert. Several cases in which merely transcription initiation occurred in the insert were set aside. Two of the examples involved the long terminal repeats of mammalian endogenous retroviruses. Another two examples were control of transcription by repeated sequence inserts in sea urchin genomes. There are now six published examples in which Alu sequences were inserted long ago into human gene regions, were modified, and now are central in control/enhancement of transcription. The number of published examples of Alu sequences affecting gene control has grown threefold in the last year and is likely to continue growing. Taken together, all of these examples show that the insertion of sequence elements in the genome has been a significant source of regulatory variation in evolution.

Animals↗
PubMed1996

Efficient insertion of odd-numbered transmembrane segments of the tetracycline resistance protein requires even-numbered segments.

Functional membrane insertion elements in the pBR322 tetracycline resistance protein were identified by comparing the ability of odd-numbered transmembrane segments and their attached periplasmic loops to insert into the membrane individually or when combined with the next even-numbered segment in the tetracycline resistance protein sequence. The efficiency with which individual odd-numbered segments and periplasmic loops inserted was probed by treating proteins truncated at the distal ends of periplasmic loops P2-P6 with carboxypeptidases and endoproteases in inside-out membrane vesicles. Insertion of odd-numbered segments and attached loops is inefficient when they occupy a C-terminal position in the protein. The C-terminal odd-numbered segment and loop sequences of 34-54% of the molecules of periplasmic loop truncation mutants could be removed by carboxypeptidase Y. In contrast, odd-numbered segments and loops insert efficiently if the next even-numbered segment in the sequence is present. In such cytoplasmic loop truncation mutants, only the cytoplasmic tail sequences of the proteins could be removed by carboxypeptidases. Remarkably, insertion of individual odd-numbered segments and loops is inefficient even though free energies for insertion of these sequences are highly favorable. The results indicate that pairs of adjacent segments, possibly "helical hairpins," are necessary for efficient membrane insertion of the tetracycline resistance protein.

Amino Acid Sequence↗
PubMed1999

Insertion of atToc34 into the chloroplastic outer membrane is assisted by at least two proteinaceous components in the import system.

Toc34 is a member of the outer membrane translocon complex that mediates the initial stage of protein import into chloroplasts. Toc34, like most outer membrane proteins, is synthesized in the cytosol at its mature size without a cleavable transit peptide. The majority of outer membrane proteins do not require thermolysin-sensitive components on the chloroplastic surface or ATP for their insertion into the outer membrane. However, different results have been obtained concerning the factors required for Toc34 insertion into the outer membrane. Using an Arabidopsis homologue of pea Toc34, atToc34, we show that the insertion of atToc34 was greatly reduced by thermolysin pretreatment of chloroplasts as assayed either by protease digestion or by alkaline extraction. The insertion was also dependent on the presence of ATP or GTP. A mutant of atToc34 with the GTP-binding domain deleted still required ATP for optimal insertion, indicating that ATP was used by other protein components in the import system. The ATP-supported insertion was observed even in thermolysin-pretreated chloroplasts, suggesting that the protein component responsible for ATP-stimulated insertion is a different protein from the thermolysin-sensitive component that assists atToc34 insertion.

Adenosine Triphosphate↗
PubMed2001

Insertion of mitochondrial DNA-encoded F1F0-ATPase subunit 8 across the mitochondrial inner membrane in vitro.

Cytochrome oxidase subunits I, II, and III, the mitochondrial DNA-encoded proteins, are inserted across the inner membrane by the Oxa1p-containing translocator in a membrane potential-dependent manner. Oxa1p is also involved in the insertion of the cytoplasmically synthesized precursor of Oxa1p itself into the inner membrane from the matrix via the conservative sorting pathway. The mechanism of insertion of the other mitochondrially synthesized proteins, however, is unexplored. The insertion of the mitochondrial DNA-encoded subunit 8 of F(1)F(0)-ATPase (Su8) across the inner membrane was analyzed in vitro using the inverted inner membrane vesicles and the Escherichia coli lysate-synthesized substrate. This assay revealed that the N-terminal segment of Su8 inserted across the membrane to the intermembrane space and assumed the correct trans-cis topology depending on the mitochondrial matrix fraction. This translocation reaction was similar to those of Sec-independent, direct insertion pathways of E. coli and chloroplast thylakoid membranes. (i) It required neither nucleotide triphosphates nor membrane potential, and hydrophobic forces drove the process. (ii) It did not require protease-sensitive membrane components facing the matrix space. (iii) It could be inserted across liposomes in the correct topology in a matrix fraction-dependent manner. Thus, a novel mechanism conserved in bacteria and chloroplasts also functions in the insertion of Su8 across the mitochondrial inner membrane.

Amino Acid Sequence↗
PubMed2001

Distinct Albino3-dependent and -independent pathways for thylakoid membrane protein insertion.

The homologous proteins Oxa1, YidC, and Alb3 mediate the insertion of membrane proteins in mitochondria, bacteria, and chloroplast thylakoids, respectively. Depletion of YidC in Escherichia coli affects the integration of every membrane protein studied, and Alb3 has been shown previously to be required for the insertion of a signal recognition particle (SRP)-dependent protein, Lhcb1, in thylakoids. In this study we have analyzed the "global" role of Alb3 in the insertion of thylakoid membrane proteins. We show that insertion of two chlorophyll-binding proteins, Lhcb4.1 and Lhcb5, is almost totally blocked by preincubation of thylakoids with anti-Alb3 antibodies, indicating a requirement for Alb3 in the insertion pathway. Insertion of the related PsbS protein, on the other hand, is unaffected by Alb3 antibodies, and insertion of a group of SRP-independent, signal peptide-bearing proteins, PsbX, PsbW, and PsbY, is likewise completely unaffected. Proteinase K is furthermore able to completely degrade Alb3, but this treatment does not affect the insertion of these proteins. Among the thylakoid proteins studied here, Alb3 requirement correlates strictly with a requirement for stromal factors and nucleoside triphosphates. However, the majority of proteins tested do not require Alb3 or any other known form of translocation apparatus.

Arabidopsis Proteins↗
PubMed2005

In vivo regulation of acetylcholinesterase insertion at the neuromuscular junction.

The efficiency of synaptic transmission between nerve and muscle depends on the number and density of acetylcholinesterase molecules (AChE) at the neuromuscular junction. However, little is known about the way this density is maintained and regulated in vivo. By using time lapse and quantitative fluorescence imaging assays in living mice, we demonstrated that insertion of new AChEs occurs within hours of saturating pre-existing AChEs with fasciculin2, a snake toxin that selectively labels AChE. In the absence of muscle postsynaptic activity or evoked nerve presynaptic neurotransmitter release, AChE insertion was decreased significantly, whereas direct stimulation of the muscle completely restored AChE insertion to control levels. This activity-dependent AChE insertion is mediated by intracellular calcium. In muscle stimulated in the presence of a Ca2+ channel blocker or calcium-permeable Ca2+ chelator, AChE insertion into synapses was significantly decreased, whereas ryanodine or ionophore A12387 treatment of blocked and unstimulated synapses significantly increased AChE insertion. These results demonstrated that synaptic activity is critical for AChE insertion and indicated that a rise in intracellular calcium either through voltage-gated calcium channels or from intracellular stores is critical for proper AChE insertion into the adult synapse.

Acetylcholinesterase↗
PubMed2005

Membrane insertion of Escherichia coli alpha-hemolysin is independent from membrane lysis.

Escherichia coli alpha-hemolysin (HlyA) is a protein exotoxin that binds and lyses eukaryotic cell and model membranes in the presence of calcium. Previous studies have been able to distinguish between reversible toxin binding to the membrane and irreversible insertion into the lipid matrix. Membrane lysis occurs as the combined effect of protein insertion plus a transient perturbation of the membrane bilayer structure. In the past, insertion and bilayer perturbation have not been experimentally dissected. This has now been achieved by studying HlyA penetration into lipid monolayers at the air-water interface, in which three-dimensional effects (of the kind required to break down the bilayer permeability barrier) cannot occur. The study of native HlyA, together with the nonlytic precursor pro-HlyA, and of different mutants demonstrates that although some nonlytic variants (e.g. pro-HlyA) exhibit very low levels of insertion, others (e.g. the nonlytic mutant HlyA H859N) insert even more strongly than the lytic wild type. These results show that insertion does not necessarily lead to membrane lysis, i.e. that insertion and lysis are not "coupled" phenomena. Millimolar levels of Ca(2+), which are essential for the lytic activity, cause an extra degree of insertion but only in the case of the lytic forms of HlyA.

Adsorption↗
PubMed1998

Cutaneous microdialysis in man: effects of needle insertion trauma and anaesthesia on skin perfusion, erythema and skin thickness.

Cutaneous microdialysis is a method of measuring endogenous and exogenous compounds in the dermal interstitial fluid. The microdialysis probe is inserted in the dermis using a guide cannula. The insertion trauma was studied in dorsal forearm skin in a total of 28 human healthy volunteers. Twenty-four volunteers received local anaesthesia (Xylocain 10 mg/ml) in both forearms and a microdialysis probe was inserted in one of the arms. In 12 volunteers the insertion trauma and the effect of anaesthesia on skin blood flow and erythema were studied by laser Doppler perfusion imaging, Minolta Chromameter CR 200 and Dermaspectrometer. In the other 12 subjects trauma-induced oedema and effects on skin thickness were studied by ultrasound imaging. In addition, a microdialysis probe was inserted without prior anaesthesia in 4 volunteers, and the effects on skin blood flow and erythema were investigated. Significant increases in skin blood flow, erythema and skin thickness were found after insertion of the microdialysis probe. Local anaesthesia prior to the insertion reduced the effects of trauma. Probe depth in dermis did not influence the effects of trauma. At least 90-120 min is required after insertion in order to allow the vascular reaction to needle trauma to return to the baseline range.

Administration, Cutaneous↗
PubMed2005

Interface evaluation after manual and ultrasonic insertion of standardized class I inlays using composite resin materials of different viscosity.

OBJECTIVE: The aim of the present study was to investigate the effect of manual and ultrasonic insertion of standardized class I inlays (Cerana) using three composite resin materials of different viscosity (Tetric Flow, Tetric, and Tetric Ceram) on time to seat inlays, film thickness, and filler distribution within the materials. METHODS: In a preliminary test, mean loads for manual and ultrasonic insertion were measured using the high viscosity composite resin material (Tetric Ceram). These loads were then applied with all composite resin materials to evaluate the times required to seat the inlays. In addition, film thickness was assessed using scanning electron microscopy, and filler distribution (wt% silicon, barium, ytterbium) was monitored using energy-dispersive spectroscopy. RESULTS: Ultrasonic insertion significantly reduced mean load applied to seat inlays (6.4+/-1.4 N; mean+/-SD) as compared to manual insertion (18.9+/-3.1 N; p < 0.001). Using an ultrasonic device, times for insertion values were significantly lower in the high and medium viscosity composite resin material groups compared to manual insertion (p < 0.05). The widest film thickness was recorded for the high viscosity composite resin material in combination with manual insertion (p < 0.05). However, when ultrasound was applied, there was no difference in film thickness between the three materials at any levels. Furthermore, the analysis of filler distribution revealed no significant differences between groups. CONCLUSION: Highly filled viscous composite resin materials may be used in combination with the ultrasonic insertion technique without untoward effects on film thickness or filler distribution.

Barium↗
PubMed1997

Re-insertion of a progesterone-containing intravaginal device to synchronise returns to oestrus in dairy heifers.

Recommendations for oestrus synchronisation of dairy heifers using progesterone-containing intravaginal devices suggest re-insertion of used devices 16 days after first insemination for a period of 5 days to allow a second opportunity for artificial insemination. Controlled studies on the effectiveness of re-using intravaginal devices to synchronise returns to oestrus in non-pregnant dairy heifers are lacking. A clinical trial was conducted involving 750 Friesian heifers in 13 herds. After an initial synchronisation programme, the used intravaginal devices were re-inserted 14 or 16 days after first insemination into half of the heifers in each herd for a period of 5 days. After the first synchronisation programme, 47.5% of heifers remained non-pregnant. Re-insertion of used intravaginal devices for 5 days significantly increased the number of non-pregnant heifers detected in oestrus and inseminated by 48 hours after device removal compared to heifers in which devices were not re-inserted (45.2% v. 27.3%, p < 0.05, in herds where intravaginal devices were re-inserted on day 14; 48.8% v. 13.6%, p < 0.05, in herds where intravaginal devices were re-inserted on day 16). Re-insertion at 14 or 16 days after first insemination was equally effective in increasing visible returns to service. However, the number of non-pregnant heifers synchronised for a second round of artificial insemination was less than expected. Conception rate to the re-synchronised oestrus was unaffected by the treatment. It is concluded that the additional procedures of CIDR re-insertion, removal, tailpainting and insemination involved in there-synchrony programme, and the relatively low in-calf rate to the re-synchronised round of insemination, reduced the potential benefits of re-synchronisation.

Journal Article↗
PubMedDate not supplied

Safe techniques for inserting the hickman catheter in pediatric patients.

The placement of the Hickman catheter in the central veins is thought to be an effective method for providing venous access in various clinical situations in children. The catheter is usually inserted by the percutaneous approach, but in some cases various troublesome complications can occur, such as sheath introducer kinking or damage, in addition to other major ones. Therefore, some modified techniques, using vascular dilators, both to dilate the route and to avoid such complications, have been developed and investigated to obtain a smooth and safe percutaneous insertion of the Hickman catheter in children. A total of 41 Hickman catheters were inserted by the percutaneous method in 41 pediatric patients from 1996 to 2004 in our department. Sixteen catheters were inserted by means of a standard method, using the manufacturer's insertion kit, and 25 catheters were inserted by means of a modified method, namely, using various sized vascular dilators. The length of time for the procedure, the complication rate, and the changes in the serum C-reactive reaction (CRP) levels were then compared between the standard and the modified methods. Those parameters were also compared between a right-side and left-side approach using both methods, to clarify which side was better for the insertion of this catheter. The length of time for the catheter replacement procedure in the standard group was significantly longer than that in modified one. The occurrence rate for both the kinking and small damage to the sheath introducer in the standard group was higher than that in the modified one. The peak of serum CRP in the modified group was significantly lower than that in the standard one. When comparing a right-side and left-side approach, 7 catheters out of 16 were inserted by the right-side approach in the standard group, while 10 catheters out of 25 were done by the right-side approach in the modified group. The length of time for the procedure for the left-side approach was significantly shorter than that for the right-side one in both groups. No difference in technical complications was observed between the two different approaches in the modified group, while complications when using the right-side approach often occurred in the standard group. The peak of serum CRP in the left-side approach was lower than that in the right-side one in both groups. The use of the modified percutaneous method, using various sized vascular dilators and the left-side approach, was therefore found to be useful for the safe and smooth placement of the Hickman catheter in children.

Adolescent↗
PubMed2006

Preventing catheter-associated bloodstream infections: a survey of policies for insertion and care of central venous catheters from hospitals in the prevention epicenter program.

OBJECTIVE: To determine the extent to which evidence-based practices for the prevention of central venous catheter (CVC)-associated bloodstream infections are incorporated into the policies and practices of academic intensive care units (ICUs) in the United States and to determine variations in the policies on CVC insertion, use, and care. DESIGN: A 9-page written survey of practices and policies for nontunneled CVC insertion and care. SETTING: ICUs in 10 academic tertiary-care hospitals. PARTICIPANTS: ICU medical directors and nurse managers. RESULTS: Twenty-five ICUs were surveyed (1-6 ICUs per hospital). In 80% of the units, 5 separate groups of clinicians inserted 24%-50% of all nontunneled CVCs. In 56% of the units, placement of more than two-thirds of nontunneled CVCs was performed in a single location in the hospital. Twenty units (80%) had written policies for CVC insertion. Twenty-eight percent of units had a policy requiring maximal sterile-barrier precautions when CVCs were placed, and 52% of the units had formal educational programs with regard to CVC insertion. Eighty percent of the units had a policy requiring staff to perform hand hygiene before inserting CVCs, but only 36% and 60% of the units required hand hygiene before accessing a CVC and treating the exit site, respectively. CONCLUSION: ICU policy regarding the insertion and care of CVCs varies considerably from hospital to hospital. ICUs may be able to improve patient outcome if evidence-based guidelines for CVC insertion and care are implemented.

Academic Medical Centers↗
PubMed1988

Why do unrelated insertion sequences occur together in the genome of Escherichia coli?

Natural isolates of Escherichia coli are polymorphic for the presence or absence of insertion sequences. Among the ECOR reference collection of 71 natural isolates studied for the number of copies of the insertion sequences IS1, IS2, IS3, IS4, IS5 and IS30, the number of strains containing no copies of the insertion sequences were 11, 28, 23, 43, 46 and 36, respectively. Significant correlations occur in the ECOR strains in the presence or absence of unrelated insertion sequences in the chromosome and plasmid complements. Strains containing any insertion sequence are more likely to contain additional, unrelated insertion sequences than would be expected by chance. We suggest that the positive correlations result from horizontal transfer mediated by plasmids. A branching-process model for the plasmid-mediated transmission of insertion sequences among hosts yields such a correlation, even in the absence of interactions affecting transposition or fitness. The predictions of the model are quantitatively in agreement with the observed correlations among insertion sequences.

DNA Transposable Elements↗
PubMed1992

Insertion of the B2 sequence into intron 13 is the only defect of the H-2k C4 gene which causes low C4 production.

The serum level of the fourth component of complement (C4) in mice bearing H-2k haplotype is only 1/10 of that of non-H-2k mice. H-2k bearing mice, but not non-H-2k bearing mice, have an insertion of the B2 sequence into intron 13 of the C4 gene, and aberrant C4 mRNA in liver apparently generated by abnormal RNA splicing caused by the insertion of the B2 sequence. To test the possible causal relationship between the B2 insertion and low C4 production in H-2k mice directly, we constructed the H-2k C4 gene without the B2 insertion and the H-2w7 (non-H-2k) C4 gene with the B2 insertion by exchanging a part of intron 13 between these two genes. Transfection of the intact H-2w7 C4 gene or the chimeric H-2k gene without the B2 insertion into HepG2 cells resulted in the production of only normal C4 mRNA at the normal level. On the other hand, the intact H-2k C4 gene or the chimeric H-2w7 C4 gene with the B2 insertion directed production of both aberrant and a decreased amount of normal C4 mRNA. These results demonstrated that the insertion of B2 sequence into intron 13 of the C4 gene is the only determinant of low C4 production by H-2k mice through aberrant RNA processing.

Animals↗