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Isolation and analysis of a novel class of suppressor of Ty insertion mutations in Saccharomyces cerevisiae.

Using a new scheme for the isolation of suppressor of Ty insertion mutations (spt mutations) in yeast, we have identified six new SPT genes. Mutations in two of these genes, SPT13 and SPT14, exhibit a novel suppression pattern: suppression of complete Ty insertion mutations, but not of solo delta insertion mutations. Transcriptional analysis shows that spt13- and spt14-mediated suppression of Ty insertion mutations is the result of an elevation in the levels of adjacent gene transcription. In spite of the failure of these mutations to suppress solo delta insertion mutations, they do cause changes in transcription of at least one solo delta insertion mutation. In addition, spt13 and spt14 mutations are epistatic to mutations in certain other SPT genes that do suppress solo delta insertion mutations. These results suggest that the SPT13 and SPT14 gene products may act via sequences in both the delta and epsilon regions of Ty elements. Finally, mutations in SPT13 cause sporulation and mating defects and SPT14 is essential for growth, suggesting that these two genes have important roles in general cellular functions.

Alleles↗

Effects of a transposable element insertion on alcohol dehydrogenase expression in Drosophila melanogaster.

Variation in the DNA sequence and level of alcohol dehydrogenase (Adh) gene expression in Drosophila melanogaster have been studied to determine what types of DNA polymorphisms contribute to phenotypic variation in natural populations. The Adh gene, like many others, shows a high level of variability in both DNA sequence and quantitative level of expression. A number of transposable element insertions occur in the Adh region and one of these, a copia insertion in the 5' flanking region, is associated with unusually low Adh expression. To determine whether this insertion (called R142) causes the low expression level, the insertion was excised from the cloned R142 Adh gene and the effect was assessed by P-element transformation. Removal of this insertion causes a threefold increase in the level of ADH, clearly showing that it contributes to the naturally occurring variation in expression at this locus. Removal of all but one LTR also causes a threefold increase, indicating that the mechanism is not a simple sequence disruption. Furthermore, this copia insertion, which is located between the two Adh promoters and their upstream enhancer sequences, has differential effects on the levels of proximal and distal transcripts. Finally, a test for the possible modifying effects of two suppressor loci, su(wa) and su(f), on this insertional mutation was negative, in contrast to a previous report in the literature.

Alcohol Dehydrogenase↗

How intron splicing affects the deletion and insertion profile in Drosophila melanogaster.

Studies of "dead-on-arrival" transposable elements in Drosophila melanogaster found that deletions outnumber insertions approximately 8:1 with a median size for deletions of approximately 10 bp. These results are consistent with the deletion and insertion profiles found in most other Drosophila pseudogenes. In contrast, a recent study of D. melanogaster introns found a deletion/insertion ratio of 1.35:1, with 84% of deletions being shorter than 10 bp. This discrepancy could be explained if deletions, especially long deletions, are more frequently strongly deleterious than insertions and are eliminated disproportionately from intron sequences. To test this possibility, we use analysis and simulations to examine how deletions and insertions of different lengths affect different components of splicing and determine the distribution of deletions and insertions that preserve the original exons. We find that, consistent with our predictions, longer deletions affect splicing at a much higher rate compared to insertions and short deletions. We also explore other potential constraints in introns and show that most of these also disproportionately affect large deletions. Altogether we demonstrate that constraints in introns may explain much of the difference in the pattern of deletions and insertions observed in Drosophila introns and pseudogenes.

Animals↗

Insertion of an Alu SINE in the human homologue of the Mlvi-2 locus.

Fifty-nine human DNA samples derived from either normal tissues or hematopoietic neoplasias were examined for rearrangements in the Mlvi-2 locus, a putative oncogene. The rearranged Mlvi-2 sequences in one of them, a B cell lymphoma, were shown to result from the insertion of an approximately 300 bp DNA fragment that hybridized to a human Alu probe. DNA sequence analysis of both the rearranged and the nonrearranged allele around the site of the insertion revealed the following: a) the insert was 88.4% homologous to the consensus sequence of the Alu family of repeats and 75% homologous to the Alu related sequence in the human 7SL RNA; b) similar to other sequenced SINES, a poly(d.A) tract was present at the 3' end of this element; c) an 8 bp direct repeat was present at both ends of the inserted element; d) this repeat was present as a single copy in the unrearranged allele. We conclude from these findings that: Alu sequences can transpose and that the direct repeats flanking certain Alu SINES may be generated by the duplication of single copy cellular sequences at the site of the insertion. Furthermore the recent nature of the Alu insertion in the Mlvi-2 locus coupled to the low degree of homology of the inserted Alu to the Alu related sequence in the 7SL RNA suggest that this event did not occur via reverse transcription and reintegration of the 7SL RNA.

Base Sequence↗

On the specificity and effects on transcription of P-element insertions at the yellow locus of Drosophila melanogaster.

Fourteen P-element insertion mutants at the yellow (y) gene of D. melanogaster have been analysed by restriction mapping and DNA sequencing. The distribution of the insertion sites is nonrandom, with a preferred target site in the 5'-transcribed but non-translated leader of the gene. Transcription analysis indicates that P-elements inserted into the transcribed region of y can terminate y transcription. While the great majority of the P-element insertions into the preferred target site abolish y activity, this loss of activity is not due to disruption of the insertion site since imprecise excision events which do not restore the wild type sequence at the insertion site can restore y function. We further demonstrate that a mutant caused by a 221bp P-element insertion into the 5' transcribed but non-translated region, which show partial y activity, produces a larger mutant transcript consistent with it being a product of transcriptional readthrough. We present results which suggest that imprecise excision events which restore (or partially restore) y activity can occur by deleting P-element internal sequences which normally act to terminate y transcription.

Animals↗

Minimal pre-mRNA substrates with natural and converted sites for full-round U insertion and U deletion RNA editing in trypanosomes.

Trypanosome RNA editing by uridylate insertion or deletion cycles is a mitochondrial mRNA maturation process catalyzed by multisubunit complexes. A full-round of editing entails three consecutive steps directed by partially complementary guide RNAs: pre-mRNA cleavage, U addition or removal, and ligation. The structural and functional composition of editing complexes is intensively studied, but their molecular interactions in and around editing sites are not completely understood. In this study, we performed a systematic analysis of distal RNA requirements for full-round insertion and deletion by purified editosomes. We define minimal substrates for efficient editing of A6 and CYb model transcripts, and established a new substrate, RPS12. Important differences were observed in the composition of substrates for insertion and deletion. Furthermore, we also showed for the first time that natural sites can be artificially converted in both directions: from deletion to insertion or from insertion to deletion. Our site conversions enabled a direct comparison of the two editing kinds at common sites during substrate minimization and demonstrate that all basic determinants directing the editosome to carry out full-round insertion or deletion reside within each editing site. Surprisingly, we were able to engineer a deletion site into CYb, which exclusively undergoes insertion in nature.

Adenosine Triphosphatases↗

Evolutionary rates of insertion and deletion in noncoding nucleotide sequences of primates.

Insertions and deletions are responsible for gaps in aligned nucleotide sequences, but they have been usually ignored when the number of nucleotide substitutions was estimated. We compared six sets of nuclear and mitochondrial noncoding DNA sequences of primates and obtained the estimates of the evolutionary rate of insertion and deletion. The maximum-parsimony principle was applied to locate insertions and deletions on a given phylogenetic tree. Deletions were about twice as frequent as insertions for nuclear DNA, and single-nucleotide insertions and deletions were the most frequent in all events. The rate of insertion and deletion was found to be rather constant among branches of the phylogenetic tree, and the rate (approximately 2.0/kb/Myr) for mitochondrial DNA was found to be much higher than that (approximately 0.2/kb/Myr) for nuclear DNA. The rates of nucleotide substitution were about 10 times higher than the rate of insertion and deletion for both nuclear and mitochondrial DNA.

Animals↗

The laryngeal mask airway: a comparison between two insertion techniques.

UNLABELLED: The purpose of the study was to compare the ease of insertion of the laryngeal mask airway using the standard uninflated approach or with a fully inflated cuff. Two hundred consecutive patients undergoing anesthesia using a laryngeal mask airway were randomized to have the laryngeal mask inserted using either method. Successful insertion was judged primarily by the clinical function of the airway. The number of insertion attempts to achieve a satisfactory airway and whether an alternative technique was required for success were recorded. On removal of the laryngeal mask, a blind observer noted the presence or absence of blood. Just before leaving the recovery room, each patient was asked whether they had a sore throat. Insertion technique made no difference with regard to first attempt success. However, the presence of blood on the removed masks (P < 0.01) and sore throat (P < 0.01) were less frequent in the inflated cuff group. We conclude that the inflated cuff insertion technique is an acceptable alternative to the standard approach and has the advantage of reducing the incidence of minor pharyngeal mucosal trauma, as evidenced by mucosal bleeding and sore throat. IMPLICATIONS: Insertion of the laryngeal mask airway with the cuff fully inflated is equally successful to the standard uninflated approach in experienced hands. The inflated technique was associated with less minor pharyngeal mucosal trauma and, consequently, a lower incidence of postoperative sore throat. This implies that the inflated technique would be acceptable to the general population of laryngeal mask users.

Anesthesia↗

Influence of nitrous oxide on minimum alveolar concentration of sevoflurane for laryngeal mask insertion in children.

BACKGROUND: Inhalational induction with sevoflurane and nitrous oxide is frequently used for Laryngeal Mask Airway (LMA; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) insertion in children. The authors determined the influence of nitrous oxide on the minimum alveolar concentration (MAC) of sevoflurane for LMA insertion. METHODS: One hundred twenty unpremedicated children (age, 1-9 yr; American Society of Anesthesiologists physical status I) were randomly assigned to receive 1 of 15 end-tidal concentrations of nitrous oxide and sevoflurane for inhalational induction via a facemask: 0% nitrous oxide with 1.2, 1.4, 1.6, 1.8, or 2.0% sevoflurane; 33% nitrous oxide with 0.8, 1.0, 1.2, 1.4, or 1.6% sevoflurane; or 67% nitrous oxide with 0.4, 0.6, 0.8, 1.0, or 1.2% sevoflurane. The LMA was inserted after steady state end-tidal anesthetic concentrations had been maintained for 15 min. The response to insertion was recorded by three independent blinded observers. The interaction between nitrous oxide and sevoflurane was determined using logistic regression analysis. RESULTS: The MAC of sevoflurane for LMA insertion (95% confidence limit) was 1.57% (1.42-1.72%), and the concentration of sevoflurane required to prevent movement in 95% of children was 1.99% (1.81-2.57%). The addition of 33% and 67% nitrous oxide linearly decreased the MAC of sevoflurane for LMA insertion by 22% and 49%, respectively (P < 0.001). The interaction coefficient between nitrous oxide and sevoflurane did not differ from zero (P = 0.7843), indicating that the relation was additive. CONCLUSIONS: Nitrous oxide and sevoflurane suppress the responses to LMA insertion in a linear and additive fashion in children.

Algorithms↗

Laryngeal mask airway insertion by anesthetists and nonanesthetists wearing unconventional protective gear: a prospective, randomized, crossover study in humans.

BACKGROUND: Mass casualty situations impose special difficulties in airway management, even for experienced caregivers. The laryngeal mask airway is part of the difficult airway algorithm. The authors evaluated the success rate and the time to secure airways by mask by anesthetists, surgeons, and novices when wearing either surgical attire or full antichemical protective gear that included butyl rubber gloves and a filtering antigas mask. METHODS: Twenty anesthetists and 22 surgeons with 2-5 yr of residency inserted a laryngeal mask airway in 84 anesthetized patients, and 6 novices repetitively inserted masks in 57 patients under both conditions in a prospective, randomized, crossover manner. The duration of insertion was measured from the time the device was first grasped until a normal capnography recording was obtained. RESULTS: Anesthetists needed 39 +/- 14 s to insert the masks when wearing surgical attire and 40 +/- 12 s with protective gear. In contrast, surgery residents needed 64 +/- 40 and 102 +/- 40 s (P = 0.0001), respectively. Anesthetists inserted masks in a single attempt, whereas the surgeons needed up to four attempts with no hypoxia or failure associated. The initial attire-wearing novices' insertions took as long as the surgeons'; three of them then reached the mean performance time of the anesthetists after four (protective gear) and two (surgical attire) trials, with only one occurrence of hypoxia and a failure rate similar to that of the surgeons. CONCLUSIONS: Anesthesia residents insert laryngeal mask airways at a similar speed when wearing surgical attire or limiting antichemical protective gear and two to three times faster than surgical residents or novices wearing either outfit. Novices initially perform at the level of surgical residents, but their learning curve was quick under both conditions.

Adult↗

Correlations between screw hole preparation, torque of insertion, and pullout strength for spinal screws.

The bone-screw interface is critical in the use of spinal instrumentation. The purpose of these experiments described here was twofold. First, to determine whether a correlation existed between torque generated during screw insertion and the pullout strength. Second, to determine how differing surgical methods of screw hole preparation influenced torque of insertion and screw pullout strength. A series of experiments were carried out in which screws were inserted into synthetic bone (experiment 1) and into calf vertebrae (experiment 2). The method of screw hole preparation (i.e., diameter of entrance hole and pilot hole) was varied while the resulting torque of insertion and the pullout strength of the screw was measured in each case. A torque screwdriver was used to measure the torque of insertion of the screws. Screw pullout strength was measured using a materials testing machine. Two important results emerged from these experiments. First, a higher torque of insertion correlated with a higher screw pullout force. This correlation may be useful intraoperatively in evaluating fixation. Second, torque of insertion and pullout force were more influenced by cortex over-drill diameter than pilot hole diameter. These experiments show the importance of the dorsal cortex in pedicle screw fixation.

Animals↗

Inflammation at the insertion site is not predictive of catheter-related bloodstream infection with short-term, noncuffed central venous catheters.

BACKGROUND: Noncuffed, percutaneously inserted central venous catheters (CVCs) are widely used and cause at least 250,000 bloodstream infections (BSIs) in U.S. hospitals each year. We report a prospective study to determine whether inflammation at the insertion site is predictive of CVC-related BSI. METHODS: Percutaneously inserted, noncuffed CVCs inserted into the subclavian, internal jugular, or femoral vein in two randomized trials during 1998-2000 were prospectively studied; most patients were in an intensive care unit. The condition of the insertion site was evaluated daily by research nurses, quantifying pain (0, 1), erythema (0-2), swelling (0, 1), and purulence (0, 1); the lowest possible overall inflammation score was 0 and the highest was 5. CVC-related BSI was confirmed in each case by demonstrating concordance between isolates from the catheter segment and from blood cultures by restriction-fragment DNA subtyping. RESULTS: Among 1,263 CVCs prospectively studied, 333 (26.3%) were colonized at removal; of these, 35 catheters (2.7%) caused BSIs (5.9 per 1000 CVC days). BSIs were caused by coagulase-negative staphylococci (n = 27), enterococci (n = 4), enteric Gram-negative bacilli (n = 3), or (n = 1). Most insertion sites showed little or no inflammation at the time of removal. There were no significant differences among mean scores for each inflammatory variable examined or overall score among colonized CVCs (0.1 +/- 0.1), catheters causing CVC-related BSI (0.2 +/- 0.4), and noncolonized CVCs (0.1 +/- 0.1). The sensitivity of local inflammation for diagnosis of CVC-related BSI was dismal (0-3%). CONCLUSION: Local inflammation is uncommon with infected CVCs, probably because most catheter-associated infections are currently caused by coagulase-negative staphylococci, a pathogen that incites little local or systemic inflammation. Whereas overt inflammation of the insertion site should raise suspicion of CVC-related BSI caused by or Gram-negative bacilli, especially if the patient has fever or other signs of sepsis, in general, site appearance cannot be relied on to identify catheter colonization or CVC-related BSI.

Catheterization, Central Venous↗

Catheter infection risk related to the distance between insertion site and burned area.

A prospective observational study of central venous catheters (CVC) was carried out in order to determine if a CVC inserted near an open burn wound increases catheter infection risk in burned patients. The study was carried out during a 12-month period (1998-1999) at the Benaim Foundation's Burn Unit in Buenos Aires (C.E.P.A.Q.). Eighty-three CVCs were inserted in 20 burned patients during the study period. Twenty-six catheters were inserted near an open wound (NOW) and 57 far from an open wound (FOW). NOW CVCs were considered when 25 cm2 surrounding the catheter's insertion site overlapped the wound. Colonization rates were 84% (22/26 CVCs) in those inserted NOW and 47% (27/57 CVCs) in FOW (P = 0.001). Colonization relative risk of NOW-CVCs was 1.79 (95% confidence interval, 1.3-2.46). Bacteremia rates were 27% (7/26 CVCs) in CVCs inserted NOW and 6% (3/57 CVCs) in FOW (P = 0.004). Bacteremic risk of NOW-CVCs was 5.12 (95% confidence interval, 1.44-18.22). Colonization rates were higher and sooner in NOW-CVCs than in FOW-CVCs. We suggest that insertion of catheters near an open burn wound should be avoided and, if inevitable, should not be left in place for period exceeding 3 days.

Adolescent↗

A review of risk factors for catheter-related bloodstream infection caused by percutaneously inserted, noncuffed central venous catheters: implications for preventive strategies.

Strategies for preventing central venous catheter (CVC)-related bloodstream infection are most likely to be effective if guided by an understanding of the risk factors associated with these infections. In this critical review of published studies of risk factors for CVC-related bloodstream infection that were prospective and used multivariable techniques of data analysis or that were randomized trials of a preventive measure, a significantly increased risk of catheter-related bloodstream infection was associated with inexperience of the operator and nurse-to-patient ratio in the intensive care unit, catheter insertion with less than maximal sterile barriers, placement of a CVC in the internal jugular or femoral vein rather than subclavian vein, placement in an old site by guidewire exchange, heavy colonization of the insertion site or contamination of a catheter hub, and duration of CVC placement > 7 days. Prospective studies or randomized trials of control measures focusing on these risk factors have been shown to reduce risk significantly: formal training in CVC insertion and care, use of maximal sterile barriers at insertion, use of chlorhexidine rather than povidone-iodine for cutaneous antisepsis, applying a topical anti-infective cream or ointment or a chlorhexidine-impregnated dressing to the insertion site, and the use of novel catheters with an anti-infective surface or a contamination resistant hub. Better prospective studies of sufficient size to address all potential risk factors, including insertion site and hub colonization, insertion technique, and details of follow-up care, would enhance our understanding of the pathogenesis of CVC-related bloodstream infection and guide efforts to develop more effective strategies for prevention.

Asepsis↗

Reducing venipuncture and intravenous insertion pain with eutectic mixture of local anesthetic: a meta-analysis.

BACKGROUND: The eutectic mixture of local anesthetics (EMLA), by producing dermal anesthesia through contact with intact skin, has become a major indication for the reduction of pain experienced during venipuncture (VE) and intravenous (IV) insertion. OBJECTIVES: The purpose of the study was to determine the mean effect sizes and moderators of EMLA cream application in reducing VE and IV insertion pain. METHOD: A meta-analysis of 20 studies was conducted to determine the magnitude of the effect of EMLA cream on VE and IV insertion pain. Effect sizes were calculated three ways: weighted, unweighted, and weighted by quality index score. Potential moderating variables of sample age, premedication, therapist control, insertion site, application duration, research design, pain scale, and funding, were investigated for their influence on EMLA's effect. RESULTS: EMLA cream had a large significant effect on VE pain (d = 1.05) with a 95% confidence interval from.92 to 1.34 and a large significant effect on IV insertion pain (d = 1.04) with a 95% confidence interval from.84 to 1.46. Subject age (child versus adult), type of pain scale, number of therapists, location of insertion site, premedication, funding, or study design did not appear to act as effect modifiers. CONCLUSIONS: EMLA cream can significantly decrease VE and IV insertion pain in 85% of the population.

Anesthetics, Combined↗

Breast reconstruction with latissimus dorsi flap: improved aesthetic results after transection of its humeral insertion.

Does transecting the tendinous insertion of the latissimus dorsi on the humerus improve aesthetic results and avoid the displeasing bulge in the armpit that sometimes occurs when the latissimus dorsi is used for breast reconstruction? In a prospective study, 60 patients who were having breast cancer surgery and simultaneous breast reconstruction using the latissimus dorsi flap were randomized for cutting (n = 29) or leaving intact (n = 31) the tendinous muscle insertion on the humerus. The cosmetic outcome was evaluated by patients and surgeons 6 to 12 months postoperatively. Patients reported good cosmetic results in 29 of 31 cases with the humeral insertion left intact and in 26 of 29 cases when the tendon was cut (p = 0.59), as compared with 21 of 31 cases versus 25 of 29 cases (p = 0.091), according to the surgeon's evaluation. A lateral bulge was more frequently observed by the surgeons in the group with intact insertion (10 of 31 patients), as compared with the group with a transected humeral insertion (2 of 29 patients). Discomfort caused by this bulge was reported by 19 of 31 patients with intact insertion, but only 3 of 29 patients with the tendon cut (p < 0.0001). The additional transection of the tendon was not associated with any complications. The additional transection of the tendinous humeral insertion of the latissimus dorsi muscle improves aesthetic results and avoids a displeasing bulge in the axilla when the latissimus dorsi flap is used for breast reconstruction.

Breast Neoplasms↗

Characteristics of pedicle screw loading. Effect of sagittal insertion angle on intrapedicular bending moments.

STUDY DESIGN: A bending analysis of pedicle screws inserted into vertebral body analogues. Intravertebral and intrapedicular pedicle screw bending moments were studied as a function of sagittal insertion angle. OBJECTIVES: To determine how the pedicle screw bending moment is affected by changes in the insertion angle. SUMMARY OF BACKGROUND DATA: There is a significant incidence of failure when pedicle screws are used to instrument unstable spinal segments. Extrinsic factors that affect screw bending failure have been poorly characterized. Previous work has demonstrated that intrapedicular pedicle screw bending moments are significantly affected by the sagittal location and depth of pedicle screw placement. METHODS: Pedicle screw transducers were inserted in analogue vertebrae at one of three orientations: 7 degrees cephalad (toward the superior endplate), 7 degrees caudal (toward the inferior endplate), or parallel to the superior endplate (control). An axial load was applied to the superior endplate of the vertebra, and screw bending moments were recorded directly from the transducers. RESULTS: Screws angled 7 degrees cephalad developed significantly greater mean intrapedicular bending moments compared with screws inserted caudal or control screws. There was no significant difference in bending moments realized within the vertebral body for the three screw positions. CONCLUSIONS: Angulating pedicle screws toward the superior endplate increased bending moments within the pedicle. If attention to optimal screw insertion technique can reduce bending moments and potential for screw failure without increasing morbidity, surgical risk, or operative time, then proper insertion technique takes on new importance.

Bone Screws↗

Accuracy of atlantoaxial transarticular screw insertion.

STUDY DESIGN: The accuracy and safety of atlantoaxial transarticular screw insertion were evaluated in clinical cases. OBJECTIVES: To evaluate the accuracy and safety of atlantoaxial transarticular screw insertion under lateral fluoroscopic monitoring without opening the joint. SUMMARY OF BACKGROUND DATA: Atlantoaxial transarticular screw fixation has been reported to be biomechanically superior to posterior atlantoaxial wiring techniques. Several clinical series have been reported in the literature. In some reports, the risk of screw insertion in this technique has been pointed out. MATERIALS AND METHODS: Fifty-six consecutive patients with atlantoaxial instability were treated by transarticular screw fixation. One hundred twelve screw insertions in these 56 patients were assessed by surgical record and computed tomographic examination. One screw could not be inserted because of the difficulty of adequate placement during operation; 111 screws were therefore inserted. Adequate position was defined as when the screw perforated the lateral atlantoaxial joint. RESULTS: In this series, neither vertebral artery injury nor spinal cord injury was experienced clinically. One guide wire was broken during drilling with a cannulated drill. Computed tomographic examination demonstrated that 106 screws perforated the atlantoaxial joint. Therefore, 95.5% of screws were adequately positioned. There were two screws positioned lateral to the joint, two medially, and one anteroinferiorly to the joint. CONCLUSIONS: Atlantoaxial transarticular screw insertion using image intensifier without opening the lateral joint was performed safely, but not accurately, in all cases.

Adolescent↗