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PubMed2000

Ligating clips for three-dimensional MR angiography at 1.5 T: in vitro evaluation.

Artifact size on three-dimensional (3D) magnetic resonance (MR) angiograms and safety of various vascular clips (15 titanium and three absorbable polydioxanone clips) were assessed. All evaluated clips were completely safe. Biodegradable clips rendered no artifacts; titanium clips were associated with susceptibility effects. Artifact size was dependent on clip size, clip orientation, echo time, and degree of k-space coverage. In the presence of titanium vascular clips, fast 3D MR angiography should be performed with the shortest echo time and full k-space coverage.

Artifacts↗

PubMed1983

Prevention of two-kidney, one-clip renal hypertension in rat by ablation of AV3V tissue.

This study examined the role of the anteroventral third ventricle (AV3V) in the renin-dependent two-kidney, one-clip model of renal hypertension. AV3V lesion and sham lesion rats were subjected to the placement of a clip on one renal artery or a sham operation. The sham lesion-renal artery clip rats experienced an increase in systolic blood pressure; however, AV3V lesioned animals experienced only a transient rise in arterial pressure during the 1st wk after clip. Body fluid regulation studies during the course of the hypertension revealed that there were no differences in water intake and urine volume between the lesion- and sham lesion-renal artery clip animals. Although significantly greater plasma and blood volumes were demonstrated in the AV3V lesion-sham clip rats compared with sham lesion animals, no differences in vascular volumes were detected in the renal artery clip rats. Finally, the rats were water deprived for 3 days to maximally stimulate vasopressin release. Urine osmolality increased significantly in all groups of rats except the AV3V lesion-renal artery clip animals protected against the hypertension.

Animals↗

PubMed1991

Renal atrial peptide receptors and natriuresis in two-kidney, one clip hypertension.

It has been suggested that the impaired natriuretic response of the clipped kidney in two-kidney, one clip hypertensive rats is related to downregulation of renal atrial natriuretic peptide receptors. To test this hypothesis, blood volume expansion and atrial peptide binding studies were performed in this model. Infusion of 1% and then 1.5% body weight donor blood (n = 6) caused a progressive increase in plasma immunoreactive atrial natriuretic peptide (107 +/- 26 to 168 +/- 31 to 427 +/- 154 pg/ml, p less than 0.001); the sodium excretion of the nonclipped kidney rose from 230 to 2,200 to 4,000 neq/min (p less than 0.01) but that of the clipped kidney did not rise significantly. There was a highly significant correlation between log cyclic guanosine monophosphate and log sodium excretion by the nonclipped (r2 = 0.749) but not the clipped (r2 = 0.046) kidney. Between clipped and nonclipped kidneys, the association constant (5.26 +/- 0.89 versus 5.17 +/- 0.64 x 10(9)/mol) and apparent binding site density (575 +/- 92 versus 500 +/- 74 fmol/mg protein) for atrial peptide binding in isolated glomeruli did not differ. Assay of atrial peptide-induced cyclic guanosine monophosphate release by isolated glomeruli showed that clipped and nonclipped kidneys were equally responsive. Binding affinity and receptor density did not differ in homogenates prepared from inner medullas of clipped and nonclipped kidneys. These results show that the blunted natriuretic response in clipped kidneys was not associated with any relative decrease in number or function of glomerular or papillary atrial natriuretic peptide receptors.

Animals↗

PubMed1984

Lack of evidence for the participation of tonin in the pathogenesis of one-kidney, one-clip renovascular hypertension.

It has been reported that immunization against tonin normalizes blood pressure, and that sialoadenectomy, during which the tonin-rich salivary glands are removed, decreases blood pressure in one-kidney, one-clip hypertension. To investigate the role of tonin on this form of hypertension further, we actively immunized one-kidney, one-clip hypertensive rabbits with tonin and measured both the blood pressure response and the titer of antibodies raised against tonin. In addition, because sialoadenectomy may alter food intake, we assessed the effect of sialoadenectomy on the blood pressure of one-kidney, one-clip hypertensive rats fed a liquid diet to facilitate eating. After immunization, all rabbits developed antitonin-antibody titers ranging from 1:300 to 1:56,000. However, in none of the rabbits did the blood pressure decrease significantly (114 +/- 3 mm Hg before immunization; 129 +/- 6 mm Hg at 16 weeks after immunization). In one-kidney, one-clip hypertensive rats, sialoadenectomy did not lower blood pressure (179 +/- 5 mm Hg before sialoadenectomy; 202 +/- 9 mm Hg 3 weeks after sialoadenectomy). Neither blood pressure nor body weight differed between sialoadenectomy and sham-sialoadenectomy one-kidney, one-clip hypertensive rats (n = 6). In conclusion, neither active immunization against tonin in one-kidney, one-clip hypertensive rabbits nor sialoadenectomy in one-kidney, one-clip hypertensive rats significantly reduced established hypertension. These results do not support the hypothesis that tonin is involved in the pathogenesis of one-kidney, one-clip hypertension in these animal models.

Animals↗

PubMed1985

Aneurysm clip motion during magnetic resonance imaging: in vivo experimental study with metallurgical factor analysis.

Because of various mechanical, metallurgical, and commercial constraints, aneurysm clips are manufactured from different alloys, including several stainless steel and cobalt alloys. Some of the steels contain volume fractions of the crystal phase known as martensite. Martensitic alloys have body-centered cubic structure, are prone to stress corrosion failure, and are ferromagnetic. Martensitic steel can be displaced like a compass needle when exposed to a magnetic field such as that generated during magnetic resonance imaging (MRI). The force exerted by the magnetic field is proportional to the volume fraction of the magnetic phase. We investigated the martensitic content and magnetic field-induced displacement of 12 common aneurysm clips. Four clips of each of the following types were examined: Sugita, Sundt-Kees Multi-Angle, Heifetz (two types), Vari-Angle McFadden, Yasargil (two types), Scoville, Mayfield, Vari-Angle, Pivot, and Kapp. Phase homogeneity and crystal structure were analyzed by x-ray diffraction using a Phillips x-ray diffractometer. Clip deflection in an Oxford Research Systems MRI spectrometer was measured in our in vivo rat abdominal aortic aneurysm model. Results showed that the volume fraction of the martensitic phase in the various clips correlated with the magnitude of the deflection. Among the clips examined, the Yasargil, Sugita, Heifetz Elgiloy, and Vari-Angle McFadden had a nonmartensitic composition and did not deflect in the magnetic field. The Scoville contained 5% martensite and deflected only marginally. Martensite comprised 35% of the Mayfield clip, which deflected 45 degrees, and 90% of the Heifetz, Vari-Angle, Pivot, and Sundt-Kees Multi-Angle clips, which deflected approximately 70 degrees or slipped off the aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)

Alloys↗

PubMed1994

Acute phase vascular endothelial injury: a comparison of temporary arterial occlusion using an endovascular occlusive balloon catheter versus a temporary aneurysm clip in a pig model.

We compared the degree of acute endothelial injury after temporary vessel occlusion using two different occlusion modalities--external clipping and endovascular balloon occlusion. The common carotid and subclavian arteries in eight weanling pigs were temporarily occluded with either a 5 Fr occlusion balloon catheter or a temporary microvascular clip for 0 (control), 5, 10, and 30 minutes. Two animals (eight vessels; four clip and four balloon occluded) were used at each time interval. Segments of each experimental vessel were harvested and analyzed by scanning electron microscopy. Each vessel specimen was graded on the following scale: Grade 1 showed no evidence of injury; Grade 2 showed minimal evidence of endothelial cell injury; Grade 3 showed moderate evidence of endothelial cell injury; Grade 4 showed marked evidence of endothelial cell injury; Grade 5 showed severe endothelial and subendothelial injury. Control vessels showed no evidence of injury. Grade 2 injuries were seen in both clip- and balloon-occluded vessels at 5 minutes. At 10 minutes, focal Grade 2 and 3 injuries were appreciated in the clip group, with diffuse Grade 2 and 3 injuries in the balloon group. After the 30-minute occlusion, the balloon group showed Grade 2, 3, and 4 injuries, whereas the clip group showed entirely Grade 2 injuries. The degree of injury with either occlusion modality was equivalent and worsened with time. However, clip-occluded vessels displayed injury that was confined to an area closely adjacent to the clip site, whereas balloon-occluded vessels demonstrated a more widespread injury centered around the balloon site.

Animals↗

PubMed1994

Molecular characterization of two functional domains of CLIP-170 in vivo.

CLIP-170 is a microtubule-binding protein isolated from HeLa cells that is involved in the interaction of endosomes with microtubules. The basic N-terminal domain of CLIP-170 binds to microtubules in vitro. To characterize further the functional domains of this cytoplasmic linker protein, we have transiently expressed intact and mutant forms of CLIP-170 in mammalian cells (HeLa and Vero cells) and show that the tandem repeat present in the N-terminal domain is essential for its binding to microtubules in vivo as previously found in vitro. With increasing levels of expression of CLIP-170, the sites with which the peripheral ends of microtubules interact enlarge, eventually forming large patches, which finally lead to the apparent bundling of microtubules. These patches do not form when the C-terminal domain is absent from the transfected protein. Modification of the microtubule-binding region, particularly of the tandem repeat motif, modulates the binding of CLIP-170 to microtubules. Overexpressed CLIP-170 appears neither to interact with nor to influence the organization of the intermediate filaments, and collapsing the network of intermediate filaments with microinjected antibodies against vimentin has no effect on the distribution of CLIP-170. These data suggest that CLIP-170 has at least two functional domains in vivo, an N-terminal microtubule-binding domain, and a C-terminal domain that is involved in the anchoring of microtubules to peripheral cytoplasmic structures.

Amino Acid Sequence↗

PubMed1999

Permissible arterial occlusion time in aneurysm surgery: postoperative hyperperfusion caused by temporary clipping.

The relationship between hyperperfusion and temporary clipping was evaluated to determine the safe limit for the duration of temporary clipping in aneurysm surgery. Twenty-one patients surgically treated for a ruptured aneurysm were examined using xenon-enhanced computed tomography on postoperative days 4 to 13. Eight of the 16 patients undergoing temporary clipping had focal hyperperfusion; whereas the five patients without temporary clipping had no hyperperfusion. Mean total temporary clipping time in patients with hyperperfusion was significantly longer than that in patients without (31.9 vs. 13.9 minutes, p = 0.0157) and mean maximum single temporary clipping time in patients with hyperperfusion was also significantly longer than in patients without (18.4 vs. 8.6 minutes, p = 0.0313). Moreover, cerebral infarction was related to hyperperfusion (p = 0.0027). These results support the hypothesis that temporary clipping during aneurysm surgery causes postoperative hyperperfusion and cerebral infarction. Temporary clipping may be harmful when performed for more than 20 minutes of total duration, since postoperative hyperperfusion was seen under this condition.

Adult↗

PubMed2002

Blade crossing of a pure titanium clip applied to a cerebral aneurysm--case report.

Titanium aneurysm clips are superior to cobalt clips in radiological features, biocompatibility, and hypoallergenicity, but the mechanical characteristics are less advantageous. A 56-year-old man was referred to our department due to dizziness and slurred speech. Cerebral angiography unexpectedly disclosed an aneurysm of the right middle cerebral artery. The patient underwent right frontotemporal craniotomy and neck clipping of the aneurysm with a commercially pure titanium clip. After application of the clip, the clip blades crossed and nearly sheared the wall of the aneurysm. The mechanical characteristics of titanium aneurysm clips require careful consideration because of possible clip malfunction.

Equipment Failure↗

PubMed1984

Booster clips for giant and thick-based aneurysms.

The authors describe their experience using booster clips to secure the closure of primary clips in the repair of giant and other thick-walled aneurysms. These clips were used for 21 aneurysms in 20 patients, comprising 12% of all aneurysms operated on during the 15-month period of the report, but representing about 50% of all giant aneurysms operated on during the same time frame. These clips are designed to encircle the primary clip and have fixation "shoes" to close upon the jaws of the primary clip. All aneurysms were opened for decompression and thrombectomy when necessary following temporary major vessel occlusion before placement of the primary clip. Cerebral blood flow measurements and continuous electroencephalographic monitoring were utilized to predict the brain's tolerance to temporary ligation of the internal carotid artery (ICA) in those cases with a giant aneurysm arising from that vessel. There were no complications attributable to the periods of intracranial or cervical ICA occlusion; these periods varied but did not exceed 8 minutes for the former nor the tolerance period for the latter, which was calculated as from 5 to 30 minutes. It was necessary to reoperate on two patients and reposition clips because of stenoses or occlusions identified on immediate postoperative angiography. Fifteen patients had normal neurological function at the time of discharge. Three patients had minor deficits which did not prevent employment; two of these were related to a preoperative deficit and one was a complication of delayed ischemia. There were two deaths: one from bleeding complications and probable damage to perforating vessels in a patient operated on under profound hypothermia (the only case in the series so managed), and one from respiratory complications in a patient with severe pulmonary problems.

Adult↗

PubMed1989

Magnetic resonance imaging and aneurysm clips. Magnetic properties and image artifacts.

The magnetic properties of 12 different types of aneurysm clip were investigated in order to identify which clips allow postoperative magnetic resonance (MR) imaging without risk. Clip-induced MR artifacts were also quantitatively studied using a geometrical phantom. Nonferromagnetic aneurysm clips like the Yaşargil Phynox, Sugita Elgiloy, and Vari-Angle McFadden clips do not appear to contraindicate MR studies performed with a FONAR beta-3000M imager. There is no clip movement upon introduction of the phantom into the MR imager, and the image artifacts caused by the clips are so limited that patients harboring such clips may well be considered for MR imaging. This examination may reveal information not obtainable by any other radiological modality.

Aneurysm↗

PubMed1992

[An evaluation of temporary clipping during aneurysmal surgery: a retrospective study].

A temporary clipping of a parent artery has been found convenient in facilitating an aneurysmal dissection. This is because it controls the bleeding from an unexpected rupture and keeps the sac collapsed during the operation. Such a temporary arterial occlusion, however, involves the risk of a focal ischemia that may lead to permanent postoperative neurological deficits. Therefore, to evaluate the influence of a temporary clipping on the outcome of an operation, a retrospective study of 302 patients who underwent an operation for a ruptured supratentorial aneurysm between 1981 and 1990 has been conducted. This study has revealed the information that follows: 1) Overall outcomes In patients given no temporary clipping, their postoperative activity in daily living (ADL) grade was good in 70.7%, i.e. ADL 1 or 2, whereas only 46.4% of the patients given a temporary clipping achieved a similar ADL. 2) Influence of the preoperative Hunt and Kosnik neurological classification on the outcome Irrespective of whether a temporary clip had been used, patients with a Hunt and Kosnik grade of 1 or 2 made a good recovery, whereas patients with a grade of 4 or 5 did not. The application of a temporary clip in grade 3 patients led to a poor result, whereas in grade 3 patients given no temporary clipping the results were good. This would seem to indicate that Hunt and Kosnik grade 3 rating is a critical factor in consideration whether a temporary clip should be used or not. 3) Influence of the operative timing on the outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗

PubMed1988

Effects of bacterial infection on absorbable vascular ligating clips.

Electron microscopic observations of two implanted absorbable clips, Absolok and Lactomer, infected with Escherichia coli and Streptococcus faecalis, were carried out. An overgrowth of bacteria was observed over the entire surface of the clips. The mating surfaces of the Lactomer clips and the locking mechanisms of both types of clip were more heavily infected--that is, provided better support for bacterial growth--than other areas of the clips in the initial postimplantation period. However, with longer periods (up to seven days), the initial bacterial deposits developed into a thick, plaquelike layer. This layer appeared to restrict access to the surfaces such that the infected clips degraded at a much slower rate than did the noninfected clips, particularly Lactomer clips, on which little morphologic change was detectable seven days after implantation.

Animals↗

PubMed1988

Tissue reactions to absorbable ligating clips.

Scanning electron microscopy was used in a comparative ultrastructural study of biodegradable ligating clips, the Absolok (polydioxanone) and the Lactomer (copolymer of glycolic and lactic acids), implanted subcutaneously in rabbits. The inflammatory response and tissue reactions to the implanted clips and their effects on clip breakdown were studied. By the first week after implantation, numerous inflammatory cells adhered to the clip surfaces, with occasional fibroblasts present. By two weeks after implantation there was a reduction in the number of inflammatory cells, but the number of fibroblasts gradually increased, resulting in encapsulation of the clips. The thickness of the fibrous tissue capsule, formed by a variety of collagen fibers, gradually increased 5-25 weeks after implantation. Residues from the Lactomer clips were still present within the encapsulating tissue at 25 weeks. In contrast, clips enclosed in nylon pouches were totally degraded, and no residues were detectable at 25 weeks. Tissue reactions similar to those observed for nonpouched implanted clips were seen over the entire external surface of the pouches.

Animals↗

PubMed1987

Study of renovascular hypertension in rats. IV. Renal arterial blood velocity in one-clip, two-kidney hypertensive rats.

In one-clip, two-kidney hypertensive models of rats, the renal arterial blood velocity was recorded using the bidirectional Doppler velocimeter before and at various times after clipping of the renal arteries. In all the rats, immediately after placement of a clip, the blood velocity of the stenosed artery was lowered significantly. Although the blood velocity remained low 2 weeks after clipping, it recovered to the pre-clip level at 6 and at 11 to 13 weeks after clipping. The plasma renin activity tended to decrease following the acute, high-renin stage of hypertension. If it can be assumed that the blood velocity is one of the indexes representing blood flow, its return to the pre-clip normal level in the chronic stage of renovascular hypertension may signify recovery of blood flow to the clipped kidney leading to a reduction in renal renin synthesis and consequently a decrease in plasma renin activity.

Animals↗

PubMed1982

Absorbable ligating clips.

Surgical clips have gained wide spread acceptance because of speed and utility in operative fields with difficult exposure. Certain disadvantages make metallic clips less than optimal for many operative situations. Such problems include difficulty in loading metallic clips into the applier, clips falling from the applier in the transfer from nurse to surgeon or while the surgeon is positioning the clip for application and clips coming off a vessel to which it was applied. The interference which metallic clips produce in computerized tomography and their permanency must be added as factors to be evaluated in comparison with absorbable clips.

Chemical Phenomena↗

PubMed1993

Renal function conscious one kidney-one clip hypertensive rats. Effect of indomethacin.

These experiments have analyzed: a) Blood pressure (BP) and renal function in one kidney-one clip rats two weeks after clipping; b) The effect of cycloxygenase (CO) inhibition on BP and renal function regulation during the hypertensive period. Using the unanaesthetized, unrestrained and chronically instrumented animal, three groups of rats were studied: Sham, Clip 0.31 mm lumen and Clip 0.29 mm lumen. The animals were examined before (Control period) and during the infusion of indomethacin (IND, 5 mg/kg via aortic cannula, n = 11 for each group) or the buffer vehicle solution (BUF, n = 7 for each group). Effective inhibition of CO by IND was confirmed using radioimmunoassay of prostaglandin E2 (PGE2) in urine. Control BP (mmHg, mean +/- SE) differed significantly among the groups (p < 0.001): Sham, 114 +/- 3; Clip 0.31, 135 +/- 2; Clip 0.29, 154 +/- 4 and did not change by IND infusion. Along with the BP, Control Glomerular Filtration Rate and Renal Plasma Flow did not change by IND infusion, which suggests that CO eicosanoids, particularly PGG2, contribute little to basal renal hemodynamics in sham and hypertensive rats. Sodium excretion was lower in the Control period of Clip 0.29 rats (p < 0.01). A significant natriuretic effect observed in this Clip 0.29 group by the infusion of IND suggests the contribution of an AA related metabolite in renal handling of sodium in more severe renovascular hypertension.

Animals↗

PubMed1994

Telemetric blood pressure monitoring in benign 2-kidney, 1-clip renovascular hypertension: effect of chronic caffeine ingestion.

In the present study we used radiotelemetry technology to investigate: 1) the time course for development of hypertension in 2-kidney, 1-clip (2K1C) rats and 2) the effect of chronic caffeine consumption on blood pressure in 2K1C rats. Rats received water or caffeine (0.1%) in drinking water and were instrumented with radiotelemetry devices to permit continuous monitoring of blood pressure. A clip was placed on the left renal artery of rats in both the water (WATER/CLIP) and caffeine (CAFFEINE/CLIP) groups. The clip was applied briefly to, then removed from, the renal artery of caffeine- and water-treated rats randomized to the sham-operated (SHAM) group. Mean arterial blood pressure (MABP) increased by approximately 35 mm Hg within 2 hr of clipping. MABP in the WATER/CLIP and CAFFEINE/CLIP groups differed significantly from the SHAM group, but not from each other, for the first 10 days after clipping. Thereafter, MABP was greater in the CAFFEINE/CLIP rats as compared to WATER/CLIP rats. At 4.5 weeks after clipping, MABP values differed significantly in the CAFFEINE/CLIP, WATER/CLIP and SHAM rats (140 +/- 4, 122 +/- 4 and 103 +/- 2 mm Hg, respectively). Involvement of the renin-angiotensin system was assessed by treatment with the AT1 receptor antagonist, losartan, and the converting enzyme inhibitor, captopril. Results from this study indicate: 1) hypertension develops rapidly after clipping in rats monitored with telemetry; 2) the renin-angiotensin system is involved in maintaining hypertension in 2K1C rats even beyond 4 weeks after clipping; and 3) caffeine augments the increase of blood pressure in 2K1C rats, apparently through the involvement of the renin-angiotensin system.

Angiotensin II↗