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At least 73 records · Page 4Linked to original sources

PubMed1994

Recurrence of ICA-PCoA aneurysms after neck clipping.

Between 1975 and 1992, 2211 patients underwent aneurysmal neck clipping at the Nara Medical University clinic and associated hospitals. The aneurysm in 931 of these patients was situated at the junction of the internal carotid artery (ICA) and posterior communicating artery (PCoA). Seven patients were readmitted 4 to 17 years after the first surgery because of regrowth and rupture of an ICA-PCoA aneurysmal sac that had arisen from the residual neck. On angiograms obtained following aneurysmal neck clipping, a large primitive type of PCoA was demonstrated in six patients and a small PCoA in one. A small residual aneurysm was confirmed in only two patients and angiographically complete neck clipping in five. Recurrent ICA-PCoA aneurysms were separated into two types based on the position of the old clip in relation to the new growth. Type 1 aneurysms regrow from the entire neck and balloon eccentrically. In this type, it is possible to apply the clip at the neck as in conventional clipping for a ruptured aneurysm. Type 2 includes aneurysms in which the proximal portion of a previous clip is situated at the corner of the ICA and aneurysmal neck and the distal portion on the enlarged dome of the aneurysm, because the sac is regrowing from a portion of the residual neck. In this type of aneurysm, a Sugita fenestrated clip can occlude the residual neck, overriding the old clip. Classifying these aneurysms into two groups is very useful from a surgical point of view because it is possible to apply a new clip without removing the old clip, which was found to be adherent to surrounding tissue.

Adult↗

PubMed1992

How secure are laparoscopically placed clips? An in vitro and in vivo study.

We tested the security of laparoscopic, hemostatic clips in vitro and in vivo. In vitro, the force needed to transversely dislodge clips that were applied to silicone (Silastic) tubing ranged from a mean +/- SEM of 1.81 +/- 0.07 N (Endo Clip) to 2.68 +/- 0.04 N (Ligaclip). The force needed to axially dislodge clips that were applied to silicone tubing ranged from 4.08 +/- 0.20 N (Endo Clip) to 4.78 +/- 0.18 N (Ligaclip). In vivo, on mesenteric vessels in anesthetized pigs, 34 of 100 clips that were applied laparoscopically with the Endo Clip were moved or dislodged compared with 11 of 100 of those applied with the Ligaclip. We conclude that laparoscopically placed vascular clips applied with the Ligaclip are more secure than those applied with the Endo Clip. The laparoscopic surgeon should be aware of the relative ease with which clips may be dislodged.

Animals↗

PubMed1983

Spring clip for aneurysm surgery.

This report concerns a clip for aneurysm surgery which has (a) a stabilizing wire that prevents the scissoring of the blades, (b) a stronger coil spring that allows longer blades and a reduced possibility of slippage, and (c) grasping sites that allow the clip to be positioned in both an applier that holds the clip rigidly in one position, and in one that allows the clip to be rotated for optimal placement. The clip is made from stainless-steel wire 2 mm in diameter, which is larger than that used for other clips. The 2-mm diameter permits the clip to have wider clamping surfaces than other clips made from wire, it permits the grasping sites to be notched so that it may be held in a rotating clip applier, and permits the clip to be tooled for a stronger coil spring. The coil springs are of either a standard or a strong tension, and have opening pressures of approximately 175 g and 320 g, respectively.

Aneurysm↗

PubMed1991

Neurosurgical vascular complications associated with aneurysm clips evaluated by postmortem angiography.

Neurosurgical vascular complications were evaluated by postmortem angiography in a consecutive prospective series of 63 patients in Helsinki who suffered a fatal outcome following neurosurgery for ruptured intracranial aneurysm. Operative vascular complications were revealed in 28 (44%) of the cases. Massive intraoperative bleeding resulting from rupture of the aneurysm or adjacent major artery during dissection or clip application complicated the operation in 16 (25%) patients. Clip-induced obstruction of cerebral arteries was detected by angiography in seven cases (11%). In six of the patients an adjacent cerebral vessel was accidentally clipped. In one case a kinking of the clip had caused obstruction of the right anterior cerebellar artery with resulting frontal infarct. A combination of rupture of the internal carotid artery and accidental ligation of the left posterior cerebellar artery occurring simultaneously during the clipping of a ruptured basilar aneurysm was detected in one patient (2%). Other types of complication were revealed in four cases (6%): detachment of clip with re-bleeding; clipping of an uninvolved aneurysm instead of the ruptured one; displacement of the clip beneath the ruptured aneurysm. Operations on ruptured basilar artery aneurysm were significantly (P less than 0.01) more prone to complications. The results indicate that operative vascular complications play a significant role in the mortality of aneurysm patients. Post-mortem angiographic technique with contrast medium that vulcanizes at room temperature is particularly suitable for demonstration of the haemodynamic significance of clip-induced cerebrovascular accidental occlusions, and is the only method at autopsy to reveal an occlusion caused by a kinking of a properly placed aneurysm clip.

Adult↗

PubMed1987

Divided renal and caval vein plasma renin activity in two-kidney two-clip hypertension in rabbits and variations of blood pressure, plasma volume and renal function following unilateral nephrectomy.

Determinations were made of peripheral plasma renin activity, blood pressure, plasma volume and blood urea nitrogen in rabbit models of two-kidney one-clip, two-kidney two-clip or one-kidney one-clip hypertension that were created by staged operation to produce functionally significant renal artery stenosis. The plasma renin activity in the divided renal veins and inferior caval vein was also measured in animals with two-kidney two-clip hypertension. In rabbits with two-kidney two-clip hypertension the plasma renin activity was significantly higher in the renal vein on the more involved side and comparable in the renal vein on the less involved side and the inferior caval vein. This response pattern of renin secretion, unilateral hypersecretion with contralateral suppression, was identical with that observed in animals with two-kidney one-clip hypertension. In animals with one-kidney one-clip hypertension there was a marked increase in plasma volume and blood urea nitrogen. The renovascular hypertension was in decreasing order of severity in animals with one-kidney one-clip hypertension, those with two-kidney two-clip hypertension and those with two-kidney one-clip hypertension.

Animals↗

PubMed1995

Structural features of the invariant chain fragment CLIP controlling rapid release from HLA-DR molecules and inhibition of peptide binding.

The invariant chain (Ii) prevents binding of ligands to major histocompatibility complex (MHC) class II molecules in the endoplasmic reticulum and during intracellular transport. Stepwise removal of the Ii in a trans-Golgi compartment renders MHC class II molecules accessible for peptide loading, with CLIP (class II-associated Ii peptides) as the final fragment to be released. Here we show that CLIP can be subdivided into distinct functional regions. The C-terminal segment (residues 92-105) of the CLIP-(81-105) fragment mediates inhibition of self- and antigenic peptide binding to HLA-DR2 molecules. In contrast, the N-terminal segment CLIP-(81-98) binds to the Staphylococcus aureus enterotoxin B contact site outside the peptide-binding groove on the alpha 1 domain and does not interfere with peptide binding. Its functional significance appears to lie in the contribution to CLIP removal: the dissociation of CLIP-(81-105) is characterized by a fast off-rate, which is accelerated at endosomal pH, whereas in the absence of the N-terminal CLIP-(81-91), the off-rate of C-terminal CLIP-(92-105) is slow and remains unaltered at low pH. Mechanistically, the N-terminal segment of CLIP seems to prevent tight interactions of CLIP side chains with specificity pockets in the peptide-binding groove that normally occurs during maturation of long-lived class II-peptide complexes.

Amino Acid Sequence↗

PubMedDate not supplied

Effects of attachment clips on occlusal force transmission in removable implant-supported overdentures and cantilevered superstructures.

Attachment clips are commonly used to provide retention for removable implant-supported overdentures. In this study, the effects of attachment clips on occlusal force transmission in four implant-supported overdentures with cantilever extensions were investigated using beam theory. Distributions of moments and of forces in overdenture, clips, cantilevered superstructure, and implants were calculated as functions of position, number, and stiffness of attachment clips. Three-, four-, and five-attachment clip configurations were analyzed. Results showed that maximum bending moments and forces in all components are strong functions of position, number, and retention of attachment clips, while the effects of attachment clip stiffness are negligible. Increasing the number of attachment clips from three to five results in a significant decrease of maximum bending moments in the superstructure and implant. For a wide range of attachment clip positioning, the maximum tensile force on the implants is as high as half the applied load. At least one attachment clip for all configurations is also subjected to tensile force, which can cause it to slip out from the superstructure and increase maximum bending moment in the superstructure and implants.

Acrylic Resins↗

PubMed1995

The ability of laparoscopic clips to withstand high intraluminal pressure.

OBJECTIVE: To determine if commercially available clips for laparoscopic surgery become displaced with high intraluminal pressures. DESIGN: In vivo model in which the splenic, renal, and mesenteric vessels together with the gallbladder of anesthetized living pigs were individually occluded using titanium and absorbable clips and then subjected to pressures of 300 mm Hg; and in vitro model in which the procedure was repeated on freshly removed human gallbladders with the attached segment of cystic duct. INTERVENTION: The intraluminal pressure of the occluded segment was increased until (1) the clip was released, (2) the vessel burst, or (3) the predetermined pressure (300 mm Hg) was obtained. RESULTS: A total of 90 clips were examined. No clip could be displaced from any porcine vessel at intraluminal pressures of up to 300 mm Hg. One vessel burst before the predetermined pressure was obtained, the clips remaining intact. Clips placed on the porcine and human models also could not be displaced by a pressure of 300 mg Hg. CONCLUSION: Commercially available titanium and absorbable clips do not disrupt when subjected to high intraluminal pressures. Postoperative bile leaks are more likely to result from necrosis of the cystic duct than displacement of the clip by the pressure within the biliary system.

Animals↗

PubMed1996

Motion and image artifacts of various intracranial aneurysm clips in a magnetic field.

Deflection angles of 36 types of Sugita intracranial aneurysm clips (Elgiloy), 2 types of Yasargil clips (Phynox), a Kirschner chip (SUS316) and a silver clip were examined by suspending each in a 1.5-tesla MRI (TOSHIBA MRT-200/FXII). Image artifacts of 5 types of intracranial aneurysm clips were also studied quantitatively with respect to their ratio of artifact/actual clip size using a spin-echo sequence with T1-weighted (Time of repetition (TR) = 500 ms, Time of echo (TE) = 20 ms) and T2-weighted (TR = 2000 ms, TE = 80 ms) images. All the Sugita clips from mini type to long type showed a deflection angle of less than 1.0 degree, the Yasargil clips less than 2.0 degrees, the Kirschner chip less than 6.0 degrees, and the silver chip did not move at all. Both brands of clips are therefore suitable for intracranial applications. The artifact size was directly proportional to the clip size and weight, though the ratio of artifact/actual width tended to decrease proportionately as the actual size and weight increased. The ratio of the width seemed slightly bigger than that of the length, but the difference did not reach statistical significance. There was no significant difference in the ratio of image artifacts/clip size between T1- and T2-weighted images.

Artifacts↗

PubMed1984

Avoidance of artifacts on computerized tomograms by selection of appropriate surgical clips.

Surgical clips (metallic or plastic) are frequently used for hemostasis and tumor marking. This study evaluated the radiographic and computerized tomographic appearance of different clips and their relative interference with computerized tomographic scans. Metallic clips (stainless steel, tantalum, and titanium) can all be seen on plain radiographs. Tantalum clips caused extensive distortion on computerized tomographic scans which would interfere with scan interpretation. Both stainless steel and titanium clips resulted in much less artifact and interference on computerized tomographic scans. Recent studies have suggested that there may be some risk of torsion of stainless steel clips in nuclear magnetic resonance scanners resulting in tissue damage. Absorbable plastic clips cannot be seen on plain film but are visualized on computerized tomographic scans and do not appear to cause scan artifact. Overall, we recommend the use of either titanium hemostatic clips when tumor marking on plain film is required or plastic clips when tumor marking is less important.

Evaluation Studies as Topic↗

PubMed1995

Binding of major histocompatibility complex class II to the invariant chain-derived peptide, CLIP, is regulated by allelic polymorphism in class II.

Major histocompatibility complex class II-associated invariant chain (Ii) provides several important functions that regulate class II expression and function. One of these is the ability to inhibit class II peptide loading early in biosynthesis. This allows for efficient class II folding and egress from the endoplasmic reticulum, and protects the class II peptide binding site from loading with peptides before entry into endosomal compartments. The ability of Ii to interact with class II and interfere with peptide loading has been mapped to Ii exon 3, which encodes amino acids 82-107. This same region of Ii has been described as a nested set of class II-associated Ii peptides (CLIPs) that are transiently associated with class II in normal cells and accumulate in human histocompatibility leukocyte antigen-DM-negative cell lines. Currently it is not clear how CLIP and the CLIP region of Ii blocks peptide binding. CLIP may bind directly to the class II peptide binding site, or may bind elsewhere on class II and modulate class II peptide binding allosterically. In this report, we show that CLIP can interact with many different murine and human class II molecules, but that the affinity of this interaction is controlled by polymorphic residues in the class II chains. Likewise, structural changes in CLIP also modulate class II binding in an allele-dependent manner. Finally, the specificity and kinetics of CLIP binding to class II molecule is similar to antigenic peptide binding to class II. These data indicate that CLIP binds to class II in an analogous fashion as conventional antigenic peptides, suggesting that the CLIP segment of Ii may actually occupy the class II peptide binding site.

Alleles↗

PubMed1997

A continuous central motif of invariant chain peptides, CLIP, is essential for binding to various I-A MHC class II molecules.

Invariant chain (li) associates with MHC class II molecules and performs a number of crucial functions in antigen presentation. A nested set of class II-associated li peptides (CLIP) has been isolated, comprising the li sequence between residues 82 and 107. Recently, X-ray crystallographic analysis has revealed that residues 87-101 occupy the HLA-DR3 peptide-binding groove. Based on our previous results, Lee and McConnell have also proposed a model for the binding of CLIP to various mouse I-A molecules in the binding groove. CLIP sequences are able to bind many MHC class II molecules but the molecular basis of this promiscuity has not yet been resolved. We have shown recently that CLIP binding to I-A class II molecules is generally tolerant to side chain substitutions, suggesting that the backbone structure of CLIP may provide the features critical for its interaction with class II. In pursuit of this, backbone stereochemical disruptions by serial D-alanine substitutions in CLIP86-104 have been used in competitive binding assays to I-A class II molecules. These studies have revealed that the phylogenetically conserved central continuous region, CLIP91-99, is intolerant to such configurational substitutions. Experiments with truncated and frame-shift analogues of CLIP showed that for effective binding to class II, the sequence element CLIP90-100 must be incorporated into a peptide of 13 or more residues including at least three residues N-terminal to this motif. Additionally, it appears that different I-A molecules accommodate CLIP in different binding frames. These investigations of the relationship between the structure and binding of CLIP analogues lead us to propose that there is a general backbone motif of a periodic nature within the CLIP sequence that minimizes deleterious contacts and allows promiscuous binding to class II molecules.

Amino Acid Sequence↗

PubMed1986

Autoregulation of renal blood flow in two-kidney, one-clip hypertensive rats.

Renal blood flow (RBF) autoregulation was examined in the clipped and nonclipped kidneys in two groups of two-kidney, one-clip (2K-1C) hypertensive rats 10 wk after clipping. The arterial pressure distal to the clip and the renin secretion rate (RSR) were also examined. The blood pressure (BP) was 149 +/- 4 and 162 +/- 6 mmHg in the two hypertensive groups vs. 114 +/- 3 mmHg in the controls (P less than 0.02). The RBF (in ml X min-1 X kidney-1) was 4.27 +/- 0.41 in the nonclipped and 2.18 +/- 0.23 in the clipped kidneys (P less than 0.001). The pressure distal to the clip was 104 +/- 7 mmHg. The renal vascular resistance (RVR) (in mmHg X ml-1 X min-1 X g-1) was 25.0 +/- 1.4 in the control kidneys vs. 58.4 +/- 4.5 in the nonclipped (P less than 0.001) and 39.9 +/- 6.6 in the clipped kidneys (P less than 0.01). The RBF autoregulation was well preserved in the nonclipped kidneys but reset to a higher lower pressure limit of autoregulation of 106 +/- 4 mmHg, which was significantly higher than in the normotensive controls (84 +/- 6 mmHg) (P less than 0.01). In the clipped kidneys there was complete loss of RBF autoregulation. RSR decreased with reduction of the perfusion pressure in the clipped kidneys. The increased RVR might have been due to a combination of structural and functional changes in both kidneys.

Animals↗

PubMed1986

Effect of ketanserin on pressor response to vasoactive substances in early phase of one-kidney, one clip renal artery stenosis in rats and rabbits.

The effect of ketanserin (KET), a specific 5-hydroxytryptamine2 (5-HT2) receptor blockade, on pressor response to vasoactive substances was examined in rats with one-kidney, one clip renal artery stenosis of 2 days' duration (2-day clipped rat) and in rabbits with renal artery stenosis of 3 days' duration (3-day clipped rabbits). The 2-day clipped rats showed hyperresponsiveness to norepinephrine (NE), arginine vasopressin (AVP) and 5-HT. All hyperresponsiveness were attenuated by a subdepressor dose of KET. The infusion of KET, 10 micrograms/kg/min for 30 minutes, decreased mean arterial pressure of the 3-day clipped rabbits; the dose did not alter blood pressure of the normal controls. Exaggerated pressor response to NE was observed in the 3-day clipped rabbits and was abolished by a subdepressor dose of KET, 2.5 micrograms/kg/min. These results suggest that 5-HT may be involved in the enhanced pressor response to vasoconstrictor substances in the 2-day clipped rats and 3-day clipped rabbits, and that it may also play an important role in maintaining blood pressure in the 3-day clipped rabbits.

Animals↗

PubMed1985

Clip with enclosed spring for aneurysm surgery. Technical note.

A clip for aneurysm surgery has been designed with several unique features. The coil spring is fully hidden and protected within two hub sections so that it cannot be handled or become entrapped in tissue. The clip is milled from a piece of solid stock of nonmagnetic stainless steel to the desired size and shape by a computer milling process, thus avoiding the stresses and structural weaknesses caused by the bending, curling, and milling needed to prepare clips made from wire or sheet metal. The only means of opening the clip is by applying pressure to the solid milled surfaces, thus the spring cannot be weakened or bent by squeezing it or by trauma applied to the clip. The clip may be grasped in either a clip applier that holds the clip in one fixed position or in an applier that allows the clip to be rotated through an arc of 180 degrees.

Aneurysm↗

PubMed1991

Laparoscopic clips. Evaluation of absorbable and titanium with regard to hemostasis and tissue reactivity.

Advanced laparoscopic techniques require laparoscopic means of providing hemostasis. We tested the hemostatic ability of laparoscopic surgical clips and their tissue reactivity as assessed by adhesion formation in an animal model. Twenty-six New Zealand white rabbits were randomized at laparotomy to one of three treatment groups: titanium surgical clips, absorbable surgical clips (both applied with a laparoscopic clip applicator) and chromic sutures of equal mass. Either the right fallopian tube was transected, with clips or sutures applied proximally and distally to control bleeding, or the clips or sutures were applied 5 mm apart and the tube transected. A clip or suture of the same material was placed on the midportion of the left fallopian tube. Necropsy was performed at 42 days, and each clip/suture site was scored for adhesions. All the materials were easily applied and effective in achieving hemostasis. The adhesion scores tended to be lower with the absorbable clips; however, there were no statistically significant differences between the groups. Laparoscopic clips are effective in providing hemostasis, are easily applied and cause no more adhesion formation than do conventional suture materials.

Animals↗

PubMed1983

[Is tubal sterilization with the Tupla-clip a reversible method?].

Between 1976 and 1981 402 tubal sterilizations were performed with Tupla-clip most of them by laparoscopic application. 11 tubes were removed between 15 and 47 months following the sterilization with the Tupla-clip. The local changes both macroscopically and microscopically to the tupla-clip were evaluated. The possibility of tubal patency following removal of the clips was tested by carbon dioxide pertubation. The tubal-occlusion with the tupla-clip is definitive since all tubes had a fibrous tissue strand where the clip had been applied which still carried blood vessels. No tube was patent with the carbon dioxide pertubation. The intra-operative testing of correct application of the clip and the documentation of this correct application is again mentioned. This is especially important in view of the recent judgements of the federal supreme court regarding liability in failed tubal sterilizations. The excellent chance of reversal by tubal anastomosis and the 100% success rate of this method of sterilization within the 6 years under observation will increase the acceptance of the tupla-clip as a method for tubal sterilizations.

Female↗

PubMedDate not supplied

The MHC class II-associated invariant chain-derived peptide clip binds to the peptide-binding groove of class II molecules.

Major Histocompatibility Complex (MHC) class II proteins bind to peptides derived from processed foreign antigens, and display them on the cell surface of antigen presenting cells for recognition by CD4+ regulatory T lymphocytes. Prior to their binding to antigenic peptides in endosomal compartments, class II molecules are associated with a nested set of peptides CLIP derived from amino acids 80 to 107 of the invariant chain (Ii). Currently the interaction between the CLIP peptide and class II molecules is not clear. Using an FITC-labeled CLIP peptide and soluble empty class II molecules synthesized in insect cells, we have investigated the direct binding of the CLIP peptide to class II molecules, and the influence of localized polymorphic residues in the peptide-binding groove on the binding. We found that the human class II HLA-DR1 molecule contains a single-binding site for the CLIP peptide as well as the antigenic peptide MP19-31, as analysed by Scatchard analysis. Further studies also showed that occupancy of the peptide-binding groove by antigenic peptides inhibited the binding of CLIP to DR1 molecules and vice versa. Most importantly, the polymorphic residues beta 85 and 86, which define the major peptide-binding pocket, strikingly influence the CLIP-DR1 interaction, as assayed by the SDS-stability of class II-peptide complexes and the affinity of class II-peptide interactions. These data indicate that the peptide-binding pocket and thus the peptide-binding groove of the class II molecule are directly involved in the association with the CLIP peptide.

Antigens, Differentiation, B-Lymphocyte↗