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At least 487 records · Page 27Linked to original sources
PubMed2003

Improved accuracy of computer-assisted cervical pedicle screw insertion.

OBJECT: The authors introduce a unique computer-assisted cervical pedicle screw (CPS) insertion technique used in conjunction with specially modified original pedicle screw insertion instruments. The accuracy of screw placement as well as surgery-related outcome and complication rates were compared between two groups of patients: those in whom a computer-assisted and those in whom a conventional manual insertion technique was used. METHODS: The screw insertion guiding system consisted of a modified awl, probe, tap and a screwdriver specially designed for a computer-assisted CPS insertion. Using this system, real-time instrument/screw tip information was three dimensionally identified in each step of screw insertion. Seventeen patients underwent CPS fixation in which a computer-assisted surgical navigation system was used. The cervical disorders consisted of spondylotic myelopathy with segmental instability or kyphosis, metastatic spinal tumor, rheumatoid spine, and postlaminectomy kyphosis. The rate of pedicle wall perforation was significantly lower in the computer-assisted group than that in the other group (1.2 and 6.7%, respectively; p < 0.05). The screw trajectory in the horizontal plane was significantly closer to the anatomical pedicle axis in the computer-assisted group compared with the manual insertion group (p < 0.05). This factor significantly reduced the incidence of screw perforation laterally. Complications such as neural damage or vascular injury were not demonstrated in the computer-assisted group (compared with 2% in the manual insertion treatment group). The overall surgery-related outcome was satisfactory. CONCLUSIONS: In contrast to the previously reported computer-assisted technique, our CPS insertion technique provides real-time three-dimensional instrument/screw tip information. This serves as a powerful tool for safe and accurate pedicle screw placement in the cervical spine.

Adolescent↗
PubMed1999

Depth and quality of electrode insertion: a radiologic and pitch scaling assessment of two cochlear implant systems.

OBJECTIVE: To compare the depth of electrode insertion in two types of cochlear implants, and to assess the ability of the implantees in each group to place-pitch during random electrical stimulation. STUDY DESIGN: This was a prospective clinical study. SETTING: This study was performed at an implant program within a university teaching hospital. PATIENTS: Five consecutive patients with the Clarion (Advanced Bionics, Symlar, CA, U.S.A.) device and 5 with the Nucleus-22 (Cochlear Corporation, Sydney, Australia) implants were enrolled. All 10 implantees had fully active and functioning electrodes. INTERVENTIONS: The depth of insertion was determined using plain anteroposterior skull film and high resolution computed tomography (CT). The quality of electrode insertion was assessed by pitch scaling; electrodes were randomly stimulated to generate subjective pitch responses. OUTCOME MEASURES: The depth of electrode insertion was measured radiographically as degrees of angular rotation within the cochlea. For pitch scaling, the averaged responses to electrical stimulation was plotted against the "place" of the electrodes along the array. Pitch range, plateauing, and reversal of pitches were also noted. Insertion depth was correlated with the result of pitch scaling and open-set speech discrimination at 3 months. RESULTS: The mean insertion depth was 406 degrees for the Clarion device and 254 degrees for the Nucleus device. CT was used to confirm the intracochlear placement of the electrodes and their relationships to the cochleostomy site. It did not confer more information than the plain films unless kinking had occurred. Pitch perception was consistent with the tonotopic organization of the cochlea. The Nucleus-22 recipients displayed a broader range of pitches with less plateaus and reversals than the Clarion implants. The depth of insertion did not compare well with the outcome of pitch scaling or with open-set speech discrimination scores in either group of implantees. CONCLUSION: The preformed spiral array of the Clarion device allowed deeper electrode insertion compared to the Nucleus-22 device. However, depth of insertion did not translate into better pitch placement.

Adult↗
PubMed2001

Bending stiffness, torsional stability, and insertion force of cementless femoral stems.

In cementless total hip arthroplasty, increased femoral stem flexibility and decreased fracture propensity are desirable characteristics. The slotting and tapering of the stem have been introduced to achieve this. These features should not, however, be allowed to interfere with the ability of the distal stem to provide initial mechanical stability, especially under rotation. This study was done to investigate the ability of slotted and tapered stem designs to reduce stiffness and insertion force while still maintaining adequate torsional strength. The torsional strength, maximum insertion force, and insertional work of straight, slotted, and taper stems were measured by inserting each type into rigid polyurethane foam and torque testing to failure. Bending stiffness of each stem design was calculated using numerical methods. When compared to a straight stem, a unislot stem has similar torsional strength, maximum insertional force, and work of insertion. The bending stiffness is decreased by 19% to 82% depending on the bending direction. A trislot design decreased torque strength by 29%, maximal insertion force by 36%, and work by 11%. Bending stiffness was decreased by 74% and was not dependent on bending direction. A 0.5-mm taper decreased torque strength by 11% and insertional work by 14%. No difference was seen in maximum insertional force. We conclude that the design features studied (slots and taper) are effective in decreasing stem stiffness and reducing fracture propensity.

Analysis of Variance↗
PubMedDate not supplied

Marginal adaptation of ceramic inserts after cementation.

The advantage of using ceramic inserts is to prevent major drawbacks of composite resins such as polymerization shrinkage, wear and microleakage. This in vitro study evaluated the marginal adaptation of two approximal ceramic insert systems after cementation to the cavities opened with ultrasonic tips. Proximal cavities with margins in enamel were prepared in 20 intact molars using ultrasonic tips (SONICSYS approx tips [microtorpedo size #2 and #3]; Siplus Instrument approximal [U-shaped]). Inserts of similar sizes (n=10) from two systems corresponding to the ultrasonic tips were placed in the cavities (SONICSYS Inlay; SDS-Inlay system), one on the mesial side and the other on the distal side of the same molar. Following cementation and thermocycling (5000 cycles, between 5-55 degrees C), cement thickness was measured at the buccal, lingual walls and pulpal floors of the proximal boxes under light microscope (x150). The mean cement thickness values recorded for SONICSYS inserts #2 (25 microm) was not significantly different (p>0.05) from that of SDS inserts of similar size (26 microm). There was a significant difference (p<0.05) in cement thickness values between SONICSYS #3 inserts (34 microm) and SDS inserts of similar size (23 microm). Comparison of mean values between the ceramic insert systems examined revealed that marginal adaptation was better at the buccal and lingual proximal walls than those at the pulpal floor in the SDS system, however, there was no difference for SONICSYS at both sizes. Ceramic inserts placed in cavities prepared with ultrasonic tips provide clinically acceptable marginal quality.

Acid Etching, Dental↗
PubMed2002

Intraoperative insertion of Greenfield filters: lessons learned in a personal series of 152 cases.

The objective of this study was to define outcomes of 151 patients who underwent insertion of 152 Greenfield filters in the operating room by general and vascular surgery residents with supervision by one attending vascular surgeon. Each patient was taken to the operating room for inferior vena cava (IVC) interruption immediately after a vena cavagram was performed. One patient required a subsequent return to the operating room after developing paradoxical arterial embolism from a large venous thromboembolism which was trapped by and spanned both sides of the first IVC filter. In this case a second suprarenal filter was placed at the time of arterial embolectomy. In each of these 152 cases intraoperative venacavography was performed using a mobile C-arm. Complications such as hemothorax, filter misplacement, and vena cava perforation were identified. Late survival was defined using the Social Security Death Index. Of the 151 patients undergoing intraoperative insertion of Greenfield filters there was one hemothorax from attempts at acquiring venous access via percutaneous puncture of the internal jugular vein. This required transfusion but not thoracotomy, and IVC interruption was achieved. A separate patient had insertion of a Greenfield filter into a gonadal vein which required placement of a second filter into the IVC. There was one IVC perforation from a transfemoral filter insertion which required placement of a second filter above this perforation and laparotomy to retrieve the filter and repair the IVC. In one more patient the IVC filter initially failed to open, and a second filter was placed above the first filter. In this experience the misplacement rate was 0.7 per cent and the serious complication rate was 1.3 per cent. None of the patients was adversely affected per se by transfer to the operating room for Greenfield filter insertion. No patient died from filter insertion, but in two cases serious associated complications contributed to the adverse outcomes in these already terminally ill patients. Overall 30-day mortality rate was 6.6 per cent. Late survival was defined as follows: survival at one year after filter insertion was 75 per cent, at 2 years 63 per cent, at 3 years 60 per cent, at 4 years 57 per cent, and at 5 years 54 per cent. Mean survival after filter placement was 4.96 years. We conclude that Greenfield filters can be inserted in the operating room by general and vascular surgery residents with attending supervision with reasonable safety and with a low rate of filter misplacement. The caval perforation and gonadal vein filter misplacement could both have been avoided by use of an over-the-wire filter deployment system, which at the time of these specific complications was not available. Vena cava filter insertion should remain within the scope of practice of surgeons and can be done with reasonable safety under C-arm guidance in the operating room. Use of over-the-wire systems could have helped reduce the likelihood of all but one of the filter-related complications experienced in this series.

Adult↗
PubMedDate not supplied

Effect of cooled composite inserts in the sealing ability of resin composite restorations placed at intraoral temperatures: an in vitro study.

Polymerization shrinkage causes microleakage of resin composite restorations. New materials and operative techniques should be developed in order to reduce polymerization shrinkage. This research studied the effects of cooled composite inserts and room-temperature composite inserts in the sealing ability of resin composite restorations placed at intraoral temperatures. Forty-eight extracted human molars (providing a total of 155 sections) were kept at intraoral temperatures, and Class V cavities were restored with an ormocer-based resin composite (Admira, Voco). Three restorative techniques were used: conventional bulk insertion (Group I or control group) (n = 53 sections), room-temperature resin composite inserts (Group II) (n = 52) and cooled resin composite inserts (Group III) (n = 50). Microleakage and penetrating microleakage were studied under the microscope. Cooled composite inserts reduce microleakage at the gingival margins with respect to Groups I (p = 0.002) and II (p = 0.014). When small-size cooled composite inserts were used, the sealing ability at the gingival margins of Class V composite restorations was improved with respect to the bulk insertion technique and the room-temperature composite inserts technique.

Body Temperature↗
PubMed1992

Differential irreversible insertion of protein kinase C into phospholipid vesicles by phorbol esters and related activators.

Incubation of protein kinase C (PKC) alpha with phorbol 12,13-dibutyrate and phospholipid vesicles promoted a time-dependent irreversible insertion of the enzyme into the vesicles and the generation of a calcium-independent kinase activity. Calcium neither caused insertion nor influenced the insertion induced by the phorbol ester. The effect was strongly dependent on the phosphatidylserine concentration in the vesicle and could also be supported by other anionic phospholipids. An analysis of the structure-activity relations of PKC activators for the calcium-independent kinase activity revealed marked relative differences in potencies for binding and for insertion. Compounds such as phorbol 13-myristate 12-acetate and mezerein were very efficient at inducing insertion. In contrast, 12-deoxyphorbol esters and diacylglycerol were relatively inefficient at inducing insertion, requiring higher concentrations than expected from their binding affinities. The insertion of PKC alpha depended substantially on the length of the aliphatic esters in the 12- and 13-positions of the phorbol derivatives, and once again, potencies for insertion and binding were not directly proportional. Our findings suggest two different sites for ligand interaction on the molecule of PKC alpha with different structure-activity requirements. We speculate that the differential ability of compounds to promote insertion could contribute to the documented marked differences in the biological behavior of PKC activators.

Animals↗
PubMed2003

Insertion distance of neonatal intercostal catheters using a 10 French Argyle trocar thoracic catheter.

OBJECTIVE: We believed that intercostal catheters were often inserted too far into the thoracic cavity in neonatal patients. The aim of this study was to determine the average distance from the catheter tip to the midline, of intercostal catheters inserted in our neonatal unit and the incidence of catheters that were inserted too far into the thoracic cavity. METHODS: During a two year period we examined the chest X-rays of all infants who had an intercostal catheter inserted using an Argyle 10 French trocar thoracic catheter for drainage of a pneumothorax. For each initial chest X-ray following the insertion of the intercostal catheter we measured the horizontal distance in mm from catheter tip to the midline. The tip to midline distance was zero if the tip was at the midline and negative if it crossed the midline. To standardise the tip to midline distance for different size infants we measured the distance in 'inter-vertebral' units. RESULTS: During the two year period, 13 of 24 intercostal catheters (54%) crossed the midline (i.e. were inserted too far). The mean (+/- SD) tip to midline distance was -1.29 (+/- 13.9) mm with a range varying between -40 to 34 mm with a calculated 'inter-vertebral' units mean (+/- SD) tip to midline distance of -0.32 (+/- 1.9) range -4.6 to 4.0. CONCLUSIONS: Fifty four percent of the intercostal catheters inserted in our unit were inserted too far. As the distance markings on the Argyle intercostal catheters are marked from the last side-hole rather than from the tip of the catheter, Argyle intercostal catheters may be inadvertently inserted two centimetres further than they should be.

Journal Article↗
PubMed1986

Is percutaneous insertion of the intra-aortic balloon pump through the femoral artery the safest technique?

Between Jan. 1, 1979, and Sept. 30, 1983, 423 intra-aortic balloon pumps (IABPs) were successfully inserted into 400 patients; IABPs could not be inserted in 36 patients (success rate 91.7%). Before 1980 all balloons were inserted surgically through a graft and by 1983 virtually all IABPs were inserted by percutaneous techniques. Infectious complications occurred in 12.3% of IABPs inserted by the open technique and 1.5% of IABPs inserted percutaneously (p less than 0.001). Major ischemic complications were not significantly different between the two groups when all of the patients were analyzed together (p greater than 0.5) and when only the surviving patients were analyzed (p greater than 0.75). However, ischemic complications occurred in 32.9% of women in the study and only 19.7% of the men (p less than 0.005). The percutaneous insertion of the IABP is recommended as the technique of choice because of the ease of insertion, lack of infectious complications, and similar rate of major ischemic complications when compared with IABPs inserted by open surgical means through a graft anastomosed to the common femoral artery.

Coronary Disease↗
PubMed1979

[Variations in the muscular insertion, the course and elasticity of the muscles in people suffering from squint (author's transl)].

Variations in the area of the insertions of the rectus muscles are quite often observed. We have been paying more attention to these changes during the past year, and therefore we measured the distance of insertion from the corneal limbus during 310 squint operations. Furthermore we noted the width of the tendon at the insertion, atypical forms of insertions and finally we tried to evaluate the factor of muscular elasticity. The findings are as follows: 1. The arithmetical mean of the distance of insertion from the limbus was slightly less than cited in literature on this subject. It was not unusual to find variations of up to 4mm, even between the same muscles of both eyes. This seems to have little influence on the primary position and on the success of surgical interventions; when they do not exceed the measures cited in our paper. The relatively great area of contact will balance these variations. 2. We could not find a correlation between anomalies of refraction and the distance of insertions of the limbus. The insertions of higher degree hyperopia was not closer to the limbus. 3. The arithmetical mean of the width of tendon conformed to the values as shown in the literature. A range up to 8 mm for the medial rectus, up to 5,5 mm for the lateral rectus and up to 2,5 mm for the vertical rectus were observed. 4. We could see variations of the insertions: upward and downward and furthermore different lines of insertions: arched and step-like. These anomalies were found 52 times among the 310 muscles measured. 5. An increased muscular rigidity was felt in 56 medial rectus and in 13 lateral rectus muscels. In 21 cases the course of the horizontal muscles was atypical, i.e., they ran from below diagonally out of the orbita.

Child, Preschool↗
PubMed1995

Shock-absorbing effect of shoe insert materials commonly used in management of lower extremity disorders.

The efficacy of 3 shock-absorbing materials was compared by determining impact characteristics with a drop test method and also by testing the effect of each material when used as a shoe insert in 16 asymptomatic subjects. Peak vertical ground reaction force (F1, F2, F3) and temporal force factors (T1, T2, T3) were obtained with a force plate at a high-frequency sampling rate. Impact force, impact time, impact slope, and impact energy were determined. A standard weight was dropped from 3 heights on each material covering the force plate while reduction of peak force was compared. Impact force was attenuated most effectively by Insert 3 (polymeric foam rubber) and averaged 11% less than that in shoes without inserts. Impact time was increased for all 3 inserts. Impact slope and impact energy were reduced significantly in Insert 3. There was a significant difference in peak vertical force F1 for all 3 inserts, in vertical force F2 for Insert 2 (viscoelastic polymeric material), and in vertical force F3 for Insert 2. Drop-test studies showed that at all ball heights, the highest mean peak force was observed consistently in Insert 2.

Biomechanical Phenomena↗
PubMed1994

Histologic characteristics of the lateral pterygoid muscle insertion to the temporomandibular joint.

This study used low-power light microscopy to examine the histologic organization of the lateral pterygoid muscle interface with the temporomandibular joint. The sample included parasagittal sections of 20 intact temporomandibular joints from young adults (mean age 26.2 years) at autopsy. The lateral pterygoid muscle showed no consistent divisions into separate anatomic muscle heads at the insertion. The muscle fibers attached to the pterygoid fovea of the condyle immediately inferior to the articular surface in all cases. Some additional fibers inserted superiorly into the more anterior part of the articular disc in a minority of cases (31%). Fibers inserting into the disc represented only 2.4% to 6% of the total superior-inferior length of the muscle insertion. It is hypothesized that the muscular force exerted by these few fibers inserting into the disc would not be sufficient to displace the disc anteriorly to the condyle. There were two histologic types of insertion of the lateral pterygoid muscle to the condyle. The superior part of the insertion was characterized by an identifiable tendon inserting through fibrocartilage. In the inferior part of the insertion, the muscle attached to periosteum without an obvious tendon. The presence of this tendon must be recognized in interpretation of soft tissue temporomandibular joint imaging.

Adolescent↗
PubMed1993

The role of velamentous cord insertion in the etiology of twin-twin transfusion syndrome.

OBJECTIVE: To evaluate the prevalence of velamentous cord insertion in twin-twin transfusion using the hypothesis that such insertions may contribute to the etiology of the condition. METHODS: All cases of placentas referred for pathologic evaluation at the University of California at San Francisco from 1984-1992 were reviewed for the citation of diamniotic-monochorionic placentation, including the presence of velamentous cord insertions. Maternal and infant records were studied for findings consistent with twin-twin transfusion syndrome. RESULTS: Thirty-eight cases of monochorionic-diamniotic twins were identified, 11 of which showed twin-twin transfusion syndrome. The prevalence of velamentous cord insertion in the transfusion syndrome subset was 63.6%, compared with 18.5% in those without (significant difference at P < .01). Twin-twin transfusion syndrome pregnancies with velamentous insertions were delivered at a significantly earlier gestational age; they also had fewer surviving infants and were more likely to have been treated prenatally than transfusion syndrome pregnancies without velamentous insertion, although these latter two findings were not significantly different. CONCLUSIONS: Velamentous cord insertions are more common in twin-twin transfusion syndrome pregnancies and may contribute to the development of profound disparity in fluid volume because the membranously inserted cord can be easily compressed, reducing blood flow to one twin. Large-volume amniocentesis may reduce this compressive force on the cord insertion, thus explaining the success of this mode of intervention.

Female↗
PubMed1996

[The study of insertion sequence IS2. II. Polarity effect of the mutant and DNA sequence analysis].

Insertion Sequence IS2 brought about polarity effect when it was inserted into a transcription. In study I, we found that the into polarity effects were different whether IS2 was inserted into the left side or into the right side. In this study, further research also showed that the polarity effects were very different when different IS2 was inserted into the left side. The analysis on IS2 DNA sequence showed that when the direction of IS2 ORF was the same as the transcription direction of the inserted transcription, known as a left insertion, the polarity effect was weaker. When the direction of IS2 ORF was opposite to the transcription direction of the inserted transcription, known as a right insertion, the polarity effect was stronger. When a stop codon was produced in IS2 due to base mutation, the polarity effect of a left insertion was increased.

Base Sequence↗
PubMed1998

Insertion of internal jugular temporary hemodialysis cannulae by direct ultrasound guidance--a prospective comparison of experienced and inexperienced operators.

OBJECTIVE: Previous studies have shown that inexperienced operators have a lower success rate than experienced operators for insertion of internal jugular cannulae using the anatomical landmark technique. The object of this study was to determine the rate of successful insertion, incidence of immediate complications and incidence of infection for temporary hemodialysis cannulae inserted under ultrasound guidance by experienced and inexperienced operators. METHODS: The reason for insertion, patient age, reason for failed insertion, immediate complications, duration of cannula survival and reason for removal were recorded prospectively for 107 attempted cannulations by 7 operators in 72 subjects with renal failure. Operators were defined as "experienced" (more than 3 years postgraduate clinical experience and more than 25 previous central vein cannulae inserted) or "inexperienced" (less than 3 years postgraduate clinical experience and less than 3 previous central vein cannulae inserted). Rates of successful cannulation and incidence of complications were compared for experienced and inexperienced operators. Cannula survival without infection was analysed by Kaplan-Meier survival for experienced and inexperienced operators. RESULTS: The overall success rate of cannula insertion at first site was 103/107 (96.3%) with no difference between experienced and inexperienced operators (56/58 vs. 47/49). 103 internal jugular temporary haemodialysis cannulae were inserted into 72 subjects. The only immediate complication was incorrect positioning of the cannula in 6 cases requiring manipulation. The median survival of hemodialysis cannulae was 14 days (range 1-111). 64.1% cannulae functioned for as long as required. Of the remainder, 33/36 were removed because of presumed cannula related infection. There was no difference in the median duration of cannula survival between experienced and inexperienced operators (15 days versus 12 days; Mann-Whitney point estimate = -1.00; 95% confidence interval -6.00, 3.00). p = 0.66) or in the probability of cannula survival without infection by Kaplan Meier analysis. CONCLUSION: We conclude that ultrasound guided temporary haemodialysis cannulation is a safe procedure with a high rate of success, the success rate for inexperienced operators is much higher than previous studies of cannulation using the anatomical landmark technique and the rate of cannula removal due to infection is not influenced by operator experience.

Catheterization, Central Venous↗
PubMed2005

Meta-analysis of gross insertions causing human genetic disease: novel mutational mechanisms and the role of replication slippage.

Although gross insertions (>20 bp) comprise <1% of disease-causing mutations, they nevertheless represent an important category of pathological lesion. In an attempt to study these insertions in a systematic way, 158 gross insertions ranging in size between 21 bp and approximately 10 kb were identified using the Human Gene Mutation Database (www.hgmd.org). A careful meta-analytical study revealed extensive diversity in terms of the nature of the inserted DNA sequence and has provided new insights into the underlying mutational mechanisms. Some 70% of gross insertions were found to represent sequence duplications of different types (tandem, partial tandem, or complex). Although most of the tandem duplications were explicable by simple replication slippage, the three complex duplications appear to result from multiple slippage events. Some 11% of gross insertions were attributable to nonpolyglutamine repeat expansions (including octapeptide repeat expansions in the prion protein gene [PRNP] and polyalanine tract expansions) and evidence is presented to support the contention that these mutations are also caused by replication slippage rather than by unequal crossing over. Some 17% of gross insertions, all >or=276 bp in length, were found to be due to LINE-1 (L1) retrotransposition involving different types of element (L1 trans-driven Alu, L1 direct, and L1 trans-driven SVA). A second example of pathological mitochondrial-nuclear sequence transfer was identified in the USH1C gene but appears to arise via a novel mechanism, trans-replication slippage. Finally, evidence for another novel mechanism of human genetic disease, involving the possible capture of DNA oligonucleotides, is presented in the context of a 26-bp insertion into the ERCC6 gene.

Base Sequence↗
PubMed1996

Protein structural plasticity exemplified by insertion and deletion mutants in T4 lysozyme.

To further investigate the ways in which proteins respond to changes in the length of the polypeptide chain, a series of 32 insertions and five deletions were made within nine different alpha-helices of T4 lysozyme. In most cases, the inserted amino acid was a single alanine, although in some instances up to four residues, not necessarily alanine, were used. Different insertions destabilized the protein by different amounts, ranging from approximately 1 to 6 kcal/mol. In one case, no protein could be obtained. An "extension" mutant in which the carboxy terminus of the molecule was extended by four alanines increased stability by 0.3 kcal/mol. For the deletions, the loss in stability ranged from approximately 3 to 5 kcal/mol. The structures of six insertion mutants, as well as one deletion mutant and the extension mutant, were determined, three in crystal forms nonisomorphous with wild type. In all cases, including previously described insertion mutants within a single alpha-helix, there appears to be a strong tendency to preserve the helix by translocating residues so that the effects of the insertion are propagated into a bend or loop at one end or the other of the helix. In three mutants, even the hydrophobic core was disrupted so as to permit the preservation of the alpha-helix containing the insertion. Translocation (or "register shift") was also observed for the deletion mutant, in this case a loop at the end of the helix being shortened. In general, when translocation occurs, the reduction in stability is only moderate, averaging 2.5 kcal/mol. Only in the most extreme cases does "bulging" or "looping-out" occur within the body of an alpha-helix, in which case the destabilization is substantial, averaging 4.9 kcal/mol. Looping-out can occur for insertions close to the end of a helix, in which case the destabilization is less severe, averaging 2.6 kcal/mol. Mutant A73-[AAA] as well as mutants R119-[A] and V131-[A], include shifts in the backbone of 3-6 A, extending over 20 residues or more. As a result, residues 114-142, which form a "cap" on the carboxy-terminal domain, undergo substantial reorganizations such that the interface between this "cap" and the rest of the protein is altered substantially. In the case of mutant A73-[AAA], two nearby alpha-helices, which form a bend of approximately 105 degrees in the wild-type structure, reorganize in the mutant structure to form a single, essentially straight helix. These structural responses to mutation demonstrate the plasticity of protein structures and illustrate ways in which their three-dimensional structures might changes during evolution.

Amino Acid Sequence↗
PubMed1982

Copper intrauterine contraceptive device event rates following insertion 4 to 8 weeks post partum.

There is a consensus in the literature that intrauterine contraceptive devices (IUDs) should not be inserted within 8 weeks post partum because of reported greater rates of pregnancy, expulsion, and perforation. This greater incidence of event rates was observed in certain clinics that used large plastic IUDs, mainly the loops. In an effort to determine whether the interval from delivery to insertion of a copper-bearing IUD caused altered event rates, an analysis of studies of parous women who were using five different copper-bearing IUDs was undertaken. During the time of these studies, 411 women had an IUD inserted between 4 and 8 weeks post partum, whereas 1,197 women had the IUD inserted more than 8 weeks after a term delivery. At the end of 1 and 2 years of use, there were 4,164 and 6,816 woman months of experience, respectively, in the women with postpartum insertion, and 11,647 and 19,733 woman months of experience with insertion more than 8 weeks post partum. There were no uterine perforations in this experience, and there were no significant differences in the termination rates of any event between the two groups. This retrospective analysis indicates that copper IUDs can be inserted at the time of the routine postpartum examination without concern that the rate of accidental pregnancy, expulsion, or removal for bleeding and/or pain will be increased in comparison with a later insertion.

Female↗