Influence of the textile structure on the degradation of explanted aortic endoprostheses.

OBJECTIVES: To investigate mechanisms of textile failure in explanted human aortic endoprostheses. MATERIALS AND METHODS: Endoprostheses (n31) underwent optical and scanning electron microscopy, filament dynamometry, and saturation index measurement. RESULTS: The macroscopic lesions observed in the Stentor and Vanguard devices were holes at the extremities of the stents and slipping of the warp yarns at the level of sutures or of the longitudinal seams. The macroscopic lesions observed in AneurX endoprostheses were holes, slipping of the warp yarns and ruptures of the ligatures. The macroscopic lesions observed in the two Talent endoprostheses were sections of fibers at the level of the suture holes and few areas lesions of wear, with sometimes holes at the contact of the stent extremities. Stentor, Vanguard and AneurX all demonstrated low saturation indexes of the fabric (44-59%) with an important anisotropy. Whereas the Talent endograft demonstrated a high index of saturation (124-131%) with a low anisotropy. We did not demonstrate significant polymer degradation in any of the endoprostheses. CONCLUSIONS: It is essential to take into account the saturation index to optimally choose a woven textile for the construction of an endoprosthesis since this property of the textile may contribute to explain the macroscopic lesions observed. We did not observe significant polymer degradation by filament dynamometry but further studies are needed to confirm these data.

Mechanisms of rupture of knitted polyester vascular prostheses: an in vitro analysis of virgin prostheses.

OBJECTIVES: Previous explant retrieval studies have shown ruptures occurring on the remeshing line and the guide line of two types of warp-knitted grafts. The aim of our study was to characterize the mechanisms these ruptures. MATERIALS AND METHODS: We performed an in vitro study of the mechanical and chemical characteristics of virgin prostheses. We studied 2 virgin polyester warp-knitted grafts models: the Cooley Double Velour and the Microvel Double Velour constructed by Meadox (USA), using the following techniques: characterization and de-knitting of the textile structure, circumferential tensile strength, filament dynamometry, critical dissolution time of the filaments and scanning electron microscopy. RESULTS: Both prostheses were constructed in the same way but the texturized yarns of the Cooley graft included twice as many filaments (54) than the Microvel (27). There was more adsorbed tension in the Cooley structure than in the Microvel. The circumferential tensile strength test demonstrated that the Cooley graft always ruptured on the remeshing line and the Microvel graft always ruptured at the interface between the remeshing line and the standard line. Filament dynamometry demonstrated a heterogeneous behavior of the filaments inside the yarns, mainly at the remeshing line of the Cooley graft (27.1 cN/tex +/- 11.5% versus 26.1 cN/tex +/- 2.2% for the guide line and 28 cN/tex +/- 6.7% for the standard knit). Critical dissolution time of the filaments was significantly lower for the Microvel grafts (2.5 sec versus 17.2 sec for the Cooley). CONCLUSIONS: Rupture of knitted polyester prostheses are probably an underestimated phenomenon. They may occur at specific areas of the graft. Further studies are required to determine whether all grafts of this type are at risk.

What can we learn from explanted endovascular devices?

OBJECTIVE: To examine the durability of the Stentor and Vanguard endovascular devices in human implants. METHODS: The textile covering, the polypropylene ligatures and the stent metal of 34 devices (25 Stentor, 9 Vanguard) with a mean duration of implantation of 28.8 +/- 16 months was examined by means of stereomicroscopy and scanning electron microscopy. RESULTS: The polyester textile covering showed gaps along the sutured seam and isolated holes in the fabric. All of the examined polypropylene ligatures were worn, some ruptured. Four different types of stent corrosion were classified--pits (100%), bizarre craters (68%), large deficiencies (14%) and fractures (32%). CONCLUSION: Holes in the polyester fabric and frame dislocations are specific for the design of Stentor and Vanguard grafts. The early corrosion of the stent metal Nitinol in these devices is surprising. Until more experience is gained with other devices, we have to be reminded, that the "gold standard" for the long-term durability of artificial vascular grafts is still "today's" conventional graft.

Corroded nitinol wires in explanted aortic endografts: an important mechanism of failure?

PURPOSE: To analyze surface alterations and fractures observed in the nitinol stent wires of explanted endovascular grafts used for treatment of abdominal aortic aneurysm. METHODS: Twenty-one explanted Stentor devices and 1 Cragg stent were received from investigators in Germany and France. After macroscopy and photography, the explants were cleaned and the polyester coating removed. The frame was examined completely by stereomicroscopy, and irregularities were assayed by scanning electron microscopy and energy dispersive x-ray analysis (EDAX). The observed alterations were classified according to stereomicroscopic and electron microscopic morphology. RESULTS: The mean implantation interval for the endografts was 29.1 +/- 13.2 months (range 5-46). All examined explants, even those retrieved after only a few months in situ, showed pitlike surface damage 10-25 microm in diameter. Larger, irregularly shaped surface alterations were observed in approximately 70% of the explants. Older explants (age >32 months) presented vast regions of decay, with bending of the wire and stress cracks in some areas. EDAX examination revealed decreased nickel concentration in the corroded regions. CONCLUSIONS: Corrosion of the nitinol wire in endovascular grafts is confirmed. Presumably, the observed pitting and irregularly shaped corrosion defects are the precursors of material failure. They weaken the thin wire, which leads to stress cracks and eventually fracture of the stent wire under circulatory pulsation. Cell-induced electrochemical corrosion and active cellular destruction of surfaces are well-known mechanisms that must be investigated for their possible roles in the corrosion of stent metals.

[Stent wire fractures and mesh loosening in explanted endovascular prosthesis]. / Stentdrahtbrüche und Maschenlockerungen explantierter, endovaskulärer Prothesen.

UNLABELLED: Vascular grafts are available since the middle of the 50's. Explant retrieval studies still reveal not published material degradation today, after over 40 years of product development. Endovascular grafts exist since the beginning of the 90's. New developments and modifications have lead to numerous devices. The importance of explant retrieval studies grows. MATERIALS AND METHODS: Among 33 stentgrafts, retrieved 5 to 43 months after implantation, the majority were 18 MinTec devices (17 Stentor, 1 Cragg). These 18 explants were examined by endoscopy, stereomicroscopy and scanning electron microscopy. RESULTS: The following material degradation was observed. The textile coating showed holes along the longitudinal seam, the ligatures in-between the stentframes burst, allowing the frames to dislocate. Occasional fractures of the stent wire were seen accompanied by bowl-shaped alterations of the surface. CONCLUSION: The Stentor device is, since its modification 1996, not available any longer. It was one of the most applied devices world-wide. The possible material deficiencies must be known by those performing patient follow-up. The occurrence of alterations within 43 months shows the importance of a continued follow-up besides clinical trials.

Influence of production, handling, and storage on phytonutrient content of foods.

The goals of agricultural production have traditionally been to try to accommodate needs for: 1) adequate and reliable yields to provide a sufficient food supply in a growing world; 2) food safety; 3) taste; 4) convenience; 5) profit; and 6) variety. Alternative strategies to enhance any of these outcomes are typically evaluated as to their probable effects on the key outcome: yield. However, with the burgeoning consumer interest in foods that optimize health, attention is shifting from concerns over quantity alone to concerns over the constituents of foods that may promote health, and thus to the agricultural practices that will protect, and perhaps enhance these constituents of the food supply. This shift in focus requires new thinking and new strategies across all segments of the food production system. This paper summarizes selected aspects of crop production that are pivotal to the nutrient value of foods for human consumption and suggests some strategies for establishing a new research and production paradigm that will embrace nutrient quality among the priorities of agricultural research.

Enhancement of skeletal muscle regeneration.

We have studied the effect of adding extra satellite cells or soluble factors from crushed muscle on regeneration of minced fragments from rat tibialis muscle. The muscle mince was wrapped in an artificial epimysium to prevent adhesions and cell immigration from adjacent muscles. Regeneration was quantitatively assessed by electrophoretic determination of the muscle-specific form of creatine kinase. Control minces exhibited three periods of change in creatine kinase activity during a 7-week regeneration period. Activity fell rapidly during the first week, then rose gradually from 1-3 weeks and increased more rapidly from 3-7 weeks. To augment the original complement of myogenic cells, satellite cells were isolated from the contralateral muscle, purified by density gradient centrifugation, and expanded in culture for 3 days before adding to the muscle mince. The added cells resulted in a 3-fold enhancement of creatine kinase activity throughout the regeneration period. Soluble muscle extract incorporated into a collagen matrix also stimulated regeneration when added to muscle mince. The extract accelerated the rate of creatine kinase increase during the 1-3 week period beyond that observed in the control or cell augmented mince, suggesting that factors in the extract may facilitate revascularization or reinnervation. The specific activity of creatine kinase was increased in regenerates augmented with both cells and extract, indicating that the effects enhance primarily myogenic processes.

Post-traumatic pancreatic pseudocyst: non-operative conservative management--report on 3 cases.

The authors report on 3 cases of post-traumatic pancreatic pseudocysts in children. Complete healing occurred with non-operative conservative treatment and total parenteral nutrition. Daily follow-up with clinical evaluation, abdominal ultrasound and lab exams are detailed under definite criteria of selection and follow-up. This mode of treatment might be considered as an alternative to exploratory laparotomy and external drainage.

[Cantrell syndrome or the "shagreen skin" pentalogy. Apropos of 3 cases]. / Le syndrome de Cantrell ou la pentalogie "peau de chagrin". A propos de trois observations.

Three patients with incomplete forms of Cantrell syndrome underwent surgical therapy at the Department of Infantile Surgery in Strasbourg, France, between 1979 and 1990. One patient had a giant omphalocele. Another had a ventricular septal defect. Two of the three patients are alive and doing well. The nosology and prognostic factors in Cantrell syndrome are discussed.

[Long time hospitalization in pediatric surgical intensive care units]. / Hospitalisation de longue durée en réanimation chirurgicale pédiatrique.

If the great majority of children stay in intensive care unit only for few days, a small group of patients stay for a long period of time, varying from 3 months to five years or even more. The small group include two very different entities. On the one hand, newborns with a congenital malformation, often digestive e.a. with a short small intestine, need a long time parenteral nutrition. In such cases, the family disturbance, the opening of the unit to the parents, the awakening of the infant, his psychomotor and affective attainments are as many problems for the whole medical team. On the other hand, children severely injured in accidents, that occurred on public thoroughfares or in domestic house holds, most of the time are older than 3 years. These children may present important central neurologic sequelae, or other major sequelae (multiple trauma, burn injuries, hypoxic cervical spinal cord injury). Their education, activities, games, and family relations must be actively supported. Does the hospital structure, and particularly the intensive care unit, meet such requirements in very long time hospitalization?

Activity and Survival of Orrina phyllobia: Preliminary Investigations on the Effects of Solutes.

The motility and survival of Orrina phyllobia fourth-stage juveniles (J4) were examined in NaCl, sucrose, and synthetic soil solutions. Synthetic soil solutions (SSSs) contained Na, K, Ca(2), Mg(2), Cl, and NO at relative concentrations identical to those in a known agronomic soil. Nematode activity was dependent on solute composition and on water potential. In all solutions, motility ceased at a water potential of -30 x 10 Pa and nematodes partially desiccated. Activity inhibition in NaCl began at -5 x 10 Pa. At -15 x 10 Pa, a high level of activity was sustained only in SSS. Lethal effects occurred at -15 and -60 x 10 Pa in NaCl and SSS, respectively. No lethal effects were measured in sucrose solutions. Hydrogen ion concentration over the pH range 4.5-9.5 had no measurable effect on nematode activity.

Effects of the Ionic Composition and Water Potential of Aqueous Solution on the Activity and Survival of Orrina phyllobia.

The activity and survival of Orrina phyllobia fourth-stage juveniles (J4) were examined in aqueous solutions representing 96 combinations of eight predominant soil solution ions at total concentrations of 100, 200, and 1,000 meq/liter. Various water potentials were imposed by the addition of mannitol or polyethylene glycol to ionic solutions. Nematode longevity increased as water potential was decreased. Longevity was approximately doubled at a water potential of -23 x 10 Pa and more than tripled at -60 x 10 Pa. No combination oflons at 200 meq/liter was lethal after a 6-day exposure. Several ion combinations significantly increased longevity at -10 and -23 x 10 Pa. Single cation Na solutions consistently inhibited activity and more than doubled nematode longevity.

Some Factors Affecting Survival of Desiccation by Infective Juveniles of Orrina phyllobia.

The survival of desiccation by J4 Orrina phyllobia was examined at controlled relative humidities. When nematodes were transferred from water to air at 10% relative humidity (rh), 80% died within 30 minutes. When nematodes were transferred from water to air with rh at 70% or greater for ca. 15 minutes prior to being transferred to 10% rh, more than 90% of them survived desiccation. This phenomenon is referred to as preconditioning and occurred at much faster rates (2-30 minutes) than has been observed for other nematode species (24 hours). Differences in preconditioning rates may be due to technique-dependent variations in boundary layer resistance around nematodes during desiccation.

Effects of Oxygen and Temperature on the Activity and. Survival of Nothanguina phyllobia.

The effects of oxygen and temperature on the activity and survival of infective forth-stage juveniles of Nothanguina phyllobia Thorne were examined in aqueous suspension. Rate of movement was not affected by a wide range of O concentration (0.8-8.6 ppm). Activity decreased below 0.8 ppm 0 2, and at 0.15 ppm O nematodes became motionless. Activity increased as a linear function of temperature up to a thermal optimum of 24 C; beyond 24 C activity decreased. Survival was greatly prolonged at low temperature. At 23 C, 50% mortality occurred within 7 d, whereas at 4 C, 70% survived after 98 d.

Salt taste detection: an R-index approach to signal-detection measurements.

The R-index approach to the signal-detection P(A) index of sensitivity was used to measure taste sensitivity to NaCl solutions. The R-index is the predicted probability of the correct choice of a signal, for a given signal-noise pair. For flow-wise and sipwise presentation, R-indices did not fluctuate significantly, provided subjects could not see the stimuli yet to be presented, indicating a lack of systematic sensitivity drift. The simultaneous measurement of more than one signal strength with reference to a common noise stimulus was seen to be a viable and sensitive procedure. Comparison of flow-wise and sipwise presentation of stimuli using R-indices, indicated that the former elicited greater subject sensitivity to NaCl taste.

A plastic tube technique for direct vision of endodontic procedures.

A technique for the direct visualization of endodontic procedures utilizing clear plastic tubes machined to simulate root canals is described. The visualization of endodontic procedures allows for their evaluation by the clinician as well as their use as an adjunct to didactic courses in endodontics. During mechanical instrumentation it is evident that a concerted effort must be made to debride all of the walls of a canal. Hydraulic forces are seen to play a major role in irrigation and in applying root canal cement. The technique also reveals voids in the completed root canal filling when verticle condensation is used to obturate the canals.

Antibiotic sensitivities of enterococci isolated from treated root canals.

Enterococci that persisted in debrided, medicated root canals were tested by the Kirby-Bauer procedure for sensitivity to various antibiotics. The 50 strains tested were uniformly sensitive to ampicillin and vancomycin. More than 90% were also sensitive to erythromycin. Varying degrees of sensitivity and resistance were noted to bacitracin, cephaloridine, cephalothin, chloramphenicol, gentamicin, and tetracycline. All organisms were either partly or wholly resistant to clindamycin; penicillin; streptomycin; and sulfadiazine, sulfamerazine, and sulfamethazine (triple sulfas).