[Show abstract][Hide abstract] ABSTRACT: Joint instability was believed to be the main cause of osteoarthritis following non-fracture articular trauma. However, sudden high impact load through articular cartilage onto subchondral bone may also cause osteoarthritic changes.
We asked whether early osteoarthritic changes following transarticular impact may be depicted using immunofluorescence on unfixed cryosections to contribute to a more detailed understanding of degenerative processes of joint impaction.
Transarticular impacts were applied to patellofemoral joints of 12 skeletally mature beagle dogs (age: 15-16 months) using a drop tower. Biopsies of impact areas were sampled after 6 months and processed for standard light microscopy on formalin-fixed sections and for immunofluorescence for collagen type I (col I), type II (col II) and aggrecan (AC) on unfixed cryosections. Gross morphology and immunofluorescence on cryosections were documented using a semi-quantitative scaling system, compared to healthy controls and to standard light microscopy.
Four biopsies showed almost entirely fibrocartilaginous morphology, four appeared to be of preserved hyaline morphology with only minor signs of fibrocartilaginous remodelling and four showed preserved hyaline appearance. We found decrease in col II and AC expression in highly degenerative specimens as well as increase of col I expression. Increased col I expression in the pericellular matrix could even be depicted in specimens with intact hyaline morphology.
Observations suggest that joint impaction causes early osteoarthritic changes after 6 months. Collagen network disruption seems to lead to AC loss, although other researchers found isolated AC loss without denaturation of col II using immunofluorescence in formalin-fixed specimens. This is the first study on effects of transarticular impact using immunofluorescence on unfixed cryosections.
Full-text · Article · Mar 2006 · Osteoarthritis and Cartilage
[Show abstract][Hide abstract] ABSTRACT: The effect of perfusion on the temperature distribution during radio-frequency hyperthermia and laser-induced thermotherapy
was investigated with the perfused porcine kidney model. The phase shift-based proton resonance frequency shift method was
used to map the temperature distribution. In experiments with modulated perfusion rates it was demonstrated that perfusion
dissipates a significant amount of the absorbed energy and, therefore, the resulting heat distribution is strongly dependent
on the perfusion rate. The measured time course of the temperature distribution was used to estimate the thermal conductivity,
local perfusivity and heat absorption rate of the tissue. These parameters were in a good agreement with literature data.
This approach can also be extended to measure heat absorption and heat transfer parameters in vivo, which can significantly
improve the accuracy of thermotherapy session planning.
No preview · Article · Jun 2003 · Applied Magnetic Resonance
[Show abstract][Hide abstract] ABSTRACT: We investigated the use of 2-poly-hydroxyethyl-methacrylate (2-P-HEMA) as an embolic agent in swine arteriovenous malformations (AVMs).
In seven mini swine, experimental AVMs were created surgically. The aim of treatment was complete embolization of the nidus compartment filled by the feeding artery, without brain embolization. Six animals received pure liquid 2-P-HEMA, and one, 50% 2-P-HEMA. For radiopacity, liquid 2-P-HEMA was mixed with tungsten powder. Six animals underwent angiographic follow-up within 5-8 mo (mean, 6.5 mo). Evaluation criteria were controllability, procedural reproducibility, and duration of the nidus occlusion. To detect complications, brain MR imaging and CT were performed. Histopathologic studies were performed to prove occlusion and assess histopathologic responses.
2-P-HEMA was easily injected through microcatheters, with a reproducible technique. Because of the radiopacity of the mixture, deep nidus penetration was controlled with fluoroscopy and confirmed with CT and histopathologic examination. In five AVMs embolized with pure 2-P-HEMA, feeder obliteration was long term. One animal had vasospasm during embolization, and complete obliteration of the main feeder was maintained for 3 mo, but partial recanalization developed 2 mo later. One animal receiving pure 2-P-HEMA had an infarction. In the animal embolized with 50% 2-P-HEMA, angiography and CT revealed embolic material in the circle of Willis; the animal died after embolization. No marked inflammatory reaction in the vessel wall or perivascular tissue was observed in the embolized AVMs.
Experimental AVM embolization with pure 2-P-HEMA, made radiopaque with tungsten, is technically feasible in swine. Because of its properties, 2-P-HEMA has great potential as a therapeutic embolic agent.
Full-text · Article · Apr 2002 · American Journal of Neuroradiology
[Show abstract][Hide abstract] ABSTRACT: Sepsis is still a major cause of death despite well-developed therapeutical strategies such as antibiotics and supportive medication. The aim of this study was to characterize the long-term effects of a two-hit porcine sepsis model with a hemorrhagic shock as 'first hit' followed by a Pseudomonas aeruginosa infusion as 'second hit'.
Twelve juvenile healthy pigs were anesthetized and hemodynamically monitored. The two-hit group (n = 6) underwent a hemorrhagic shock with a 50% reduction of the mean arterial pressure and/or cardiac index for 45 min, followed by resuscitation, while the control group (n = 6) received no pretreatment. All chronically catheterized conscious pigs were challenged with a P. aeruginosa infusion (1.6 x 10(7) CFU/kg/h for the first 24 h followed by 1.6 x 10(6) CFU/kg/h for the next 24 h) and observed for another 48 h.
The two-hit group showed the following significant differences to the control group: higher APACHE II scores prior to sepsis induction, increased persisting mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) during bacterial challenge. In contrast, systemic vascular resistance (SVRI) was reduced at the end of the study. Throughout the observation period, the mean arterial pressure (MAP) was significantly reduced.
The present study shows that the clinical course and hemodynamic effects of a P. aeruginosa sepsis will be aggravated by a preceding hemorrhagic shock during an observation period of 96 h. This two-hit model represents a valid, clinically relevant experimental protocol in sepsis research.
No preview · Article · Mar 2002 · European Surgical Research
[Show abstract][Hide abstract] ABSTRACT: The aim of our study was to evaluate the in vivo feasibility of non-contact Er:YAG laser ablation of the internal limiting membrane (ILM), which is recommended for the treatment of macular holes.
Vitrectomy was performed in 16 eyes of 15 pigs. After perfluorodecalin filling, it was attempted to remove the ILM using a free-running fiber-guided Er:YAG laser (lambda=2.94 microm, pulse length 250 micros, repetition rate 1.7 Hz, radiant exposure 0.6-2.05 J/cm2). The eyes were enucleated either immediately (11 eyes, group 1) or 2 weeks after laser therapy (5 eyes, group 2). Furthermore, in one additional pig eye the retina was carefully treated with microforceps after vitrectomy to assess the damage produced by conventional techniques of ILM peeling. All eyes were examined histologically.
Group 1: Nine eyes could be examined (problems with fixation in two eyes). In four of nine eyes, the ILM was either removed or detached, in one eye there was a superficial retinal hemorrhage, and in four eyes the ILM was still intact. In the latter cases, there was no intraoperative whitening or bleeding and no posterior vitreous detachment was present histologically. Group 2: Four eyes (problems with fixation in one eye) could be examined. The ILM was either removed or detached in three eyes. In one eye there was a superficial retinal hemorrhage. In one eye the ILM was not removed and there had neither been intraoperative whitening or hemorrhage nor histologically visible posterior vitreous detachment. In both groups, the nerve fiber layer in treated areas was thicker than in adjacent untreated retina. In one eye the retina was gently manipulated with microforceps in an attempt to perform ILM peeling. This led to damage to all layers of the retina.
Removal of the ILM by Er:YAG laser is possible in vivo. However, the variability of the laser effects calls for further improvement such as a reliable indicator of ablation depth. In any case, any damage to the retina was lesser than that produced by microforceps.
No preview · Article · Oct 2001 · Albrecht von Graæes Archiv für Ophthalmologie
[Show abstract][Hide abstract] ABSTRACT: We report a new variation of the well-established experimental arteriovenous malformation (AVM) model in swine. To provide high flow through the rete mirabile (nidus, RM) and thereby to reduce the rate of spontaneous thrombosis of the AVM, we performed an end-to-end anastomosis of the left common carotid artery (CCA) and the external jugular vein (EJV) microsurgically in three micropigs. After 1 and 4 months the animals underwent angiograms of the CCA and vertebral artery (VA). In all cases the diversion of the blood through the RM was patent, up to the 4 months follow-up. We observed an arteriovenous fistula (arteriovenous pseudomalformation, pAVF) between the VA and the EJV in each case at both 1 and 4 months. This modification of the well-known AVM model in the micropig could be used to monitor long-term changes after embolisation, avoiding the naturally high rate of spontaneous thrombosis. This two-in-one model is thus well suited for preclinical testing of embolic materials.