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Biomedical subjects

H L Bartels

Publications and source records attributed to H L Bartels.

15 recordsLinked to original sources
PubMed2006

The "stamp method": a new treatment for perforated peptic ulcer?

BACKGROUND: The aim of this study was to develop a simple method for closure of a perforated peptic ulcer, making it more accessible for laparoscopic surgery. METHODS: An experimental pilot study was performed using five male Wistar rats. The perforation was closed by a bioabsorbable patch made of lactide-glycolid-caprolactone fixed with glue onto the outside of the stomach. RESULTS: Postoperatively, there were no signs of leakage or other complications. Histologically, there were no signs of inflammation on the inside of the stomach, and there was a 50% reduction of the perforation each successive postoperative week. No adverse reactions because of the degradable material or glue were observed. CONCLUSIONS: Treatment of a perforated peptic ulcer by placing a patch of biodegradable material like a "stamp" on the outside of the stomach is a feasible option.

Absorbable Implants↗
PubMed1995

Simultaneous transplantation and intrathymic tolerance induction. A method with clinical potential.

It has been shown that donor-specific tolerance to cardiac allografts can be induced by pretreating the prospective recipient with injections of donor splenocytes (intrathymically) and antilymphocyte serum (intraperitoneally) weeks or days before the actual transplantation. This procedure, however, lacks clinical relevance in the case of cadaver donors due to the obligatory interval between the start of the tolerance induction protocol and transplantation. We have tried to devise a protocol in which this interval is eliminated, thus allowing allotransplantation simultaneously with tolerance induction. Our results show that simultaneous cardiac allotransplantation and intrathymic tolerance induction by intrathymic injection of donor splenocytes and treatment with antilymphocyte serum is indeed possible in the PVG to AO high-responder rat strain combination, provided that low doses of cyclosporine are given intramuscularly on day 1, 2, and 3 after transplantation. As we now are able to combine the start of tolerance induction with the actual allotransplantation, this procedure may indeed have clinical potential.

Animals↗
PubMed1995

Influence of luminal pore size on the patency rate and endothelialization of polymeric microvenous prostheses.

In microvenous prosthetic surgery a continuous search for better patency rates is necessary to enable a clinical application. In this search for better patencies, modifications in the wall structure are being made. Directions found in the literature suggest that pore size plays an important role in achieving better patencies. Thus far, no study has been conducted to evaluate the influence of pore size on the patency rate of polyurethane microvenous prostheses. Since polyurethane is known to yield good patency rates, we conducted this study in which we compared different luminal pore sizes with regard to patency. Pore size varied from 0.6 to 20 microns in microvenous polyurethane-based prostheses (length 5-6 mm, internal diameter 1 mm). The results showed a favorable patency rate in the pore sizes larger than 5.0 microns (patency 75%) when compared to pore sizes smaller than 2.0 microns (patency 50%). This study demonstrates that microvenous polyurethane-based prostheses with a luminal pore size larger than 5.0 microns may yield better patency rates than prostheses with a luminal pore size smaller than 5.0 microns. Further studies are currently being performed to elucidate the very reasons for this effect.

Animals↗
PubMed1993

Healing of microvenous PTFE prostheses implanted into the rat femoral vein.

44 PTFE prostheses (Gore-Tex; ID 1 mm) were implanted into rats' femoral veins by means of the sleeve anastomotic technique and were evaluated at regular intervals from 1 h up till 24 weeks after implantation by means of light and electron microscopy to study in detail their healing process. All prostheses, except one at 1 week and one at 24 weeks after implantation, were patent at the time of removal. Upon implantation, the luminal surface of the prostheses became covered with a thin clot layer. From 1 week onwards, endothelial cells originating from the anastomotic sides grew in across the anastomoses. In addition, small capillary-like orifices were present at the anastomotic sites, from which endothelial cells also seemed to originate. At 2 weeks, in several areas in the mid-region of the prostheses, the fronts of regenerating endothelial cells had reached each other, and about 80% of the luminal surface was covered by endothelium and at 3 weeks, the prostheses were completely covered by an endothelial layer. These results demonstrate that PTFE microvenous prostheses heal exclusively by means of rapid ingrowth of endothelial cells originating from both sides at the anastomoses.

Animals↗
PubMed1993

Prosthetic microvenous grafting in the rat femoral vein.

Male Wistar rats were used to evaluate microvenous prosthetic grafting techniques and microvenous prostheses in the femoral vein. With the end-to-end technique to implant microvenous prostheses, there was extensive exposure of vessel wall collagen especially at the suture sites. Thrombus formation then led to complete occlusion in all but one of the 32 prostheses 60 min after implantation. However, with the sleeve anastomotic technique there was only minimal exposure of collagen and minimal thrombus accumulation. Fifty-nine of the 64 microvenous prostheses implanted with the sleeve technique were patent after 1 day, 1, 3, 6, and 12 weeks (patency rate 92%). All patent microvenous prostheses were completely covered by an endothelial layer after 3 weeks. It was concluded that the rat is an appropriate experimental laboratory animal for evaluating new grafting techniques with microvenous prostheses and that the sleeve anastomotic technique gives the highest patency rates with microvenous prostheses.

Anastomosis, Surgical↗
PubMed1991

Experimental microvenous reconstructions with Gore-Tex polytetrafluoroethylene prosthesis implanted by means of the sleeve anastomotic technique.

Polytetrafluoroethylene (PTFE) prostheses (Gore-Tex; ID, 1 mm; length, 5-7 mm; wall thickness, 0.2 mm; fibril length, 30 microns, n = 28) were implanted into the rat femoral vein by means of the sleeve anastomotic technique to enhance the patency rate. In the control group, PTFE prostheses (n = 8) were implanted by means of the end-to-end technique. In the experimental group patency and healing of the PTFE prostheses were evaluated at 1 day (n = 4), 1 week (n = 6), 3 weeks (n = 6), 6 weeks (n = 6), and 12 weeks (n = 6) after implantation by means of macroscopic inspection and routine light and scanning electron microscopy. All prostheses, except one at 1 week after implantation, were patent at the time of removal. All of the microvenous prostheses were completely covered by an endothelial layer at 3, 6, and 12 weeks after implantation. Occasionally some smooth muscle-like cells could be found underneath this endothelial layer, but stenosis was never observed at the anastomotic sites. Only scarce tissue ingrowth was observed in the wall of the PTFE prostheses. In the control group, all prostheses, except one prosthesis after 3 weeks, were found to be occluded. An occlusive mural thrombus was found firmly attached at the anastomoses at 1 day, and an organized thrombus at 3 weeks after implantation. The patent prosthesis demonstrated complete endothelial healing. These results demonstrate the importance of the sleeve anastomotic technique and the potential of PTFE prostheses as a microvenous conduit when implanted by means of the sleeve anastomotic technique in experimental reconstructive microvascular procedures.

Anastomosis, Surgical↗
PubMed1991

Reduced thrombogenicity of artificial materials by coating with ADPase.

A novel coating solution for the improvement of biocompatibility of polyurethane-based vascular prostheses was tested in rabbits and rats in vivo. Segments of coated and uncoated vascular prostheses were implanted into the peritoneal cavity of rats, followed by induction of experimental haemorrhage; otherwise whole vascular prostheses were implanted in the carotid artery of rabbits using microsurgical procedures. While in both rats and rabbits, the uncoated material showed abundant formation of fibrinoid thrombi, clear reduction of thrombus formation was seen in all ADPase coated materials following implantation in vivo.

Animals↗
PubMed1989

Microarterial grafting into the carotid artery of the rabbit: some considerations concerning species-dependent thrombogenicity.

This study was undertaken to obtain more insight into the performance of microarterial prostheses in an experimental animal that resembles the human thrombogenically more closely than the rat. Therefore, microarterial polyurethane-based (PU) prostheses and polytetrafluoroethylene (PTFE) prostheses were implanted into the carotid artery of the rabbit and were compared with regard to patency and thrombus formation at 1 hour (n = 4), 1 day (n = 4), 2 days (n = 4), 1 week (n = 4), 2 weeks (n = 6), 3 weeks (n = 6) and 6 weeks (n = 6) after implantation. Arterial autografts (n = 22), followed up for 2 weeks after implantation, served as a control for the surgical procedure. All arterial autografts were patent at the time of harvesting. In contrast, although all microarterial prostheses were patent at 1 hour and some were patent at 1 day, 2 days and 1 week, none of them were patent at 2, 3 and 6 weeks. The patent PTFE prostheses showed remarkably less thrombus accumulation on the graft surface when compared to the patent PU prostheses. However, all prostheses had the same amount of thrombus formation at the distal anastomosis.

Animals↗
PubMed1989

Patency and healing of 10-cm long microarterial polytetrafluoroethylene prostheses in the rat abdominal aorta.

Many studies have been undertaken on the experimental evaluation of microarterial polytetrafluoroethylene (PTFE) prostheses of short length. This study was undertaken to obtain insight into the performance of longer microvascular PTFE prostheses, which would be of more clinical utility. Microvascular PTFE prostheses of 10 cm in length (n = 8) were implanted into the rat abdominal aorta, fixed in a loop, and were compared regarding patency and healing with microvascular PTFE prostheses of 1 cm in length (n = 8) at three months after implantation (all prostheses: I.D.--1.5 mm, fibril length--30 microns). At three months, all prostheses, except one 10-cm prosthesis, were patent. In all PTFE microarterial prostheses, healing was observed only at the anastomotic sites with ingrowth of endothelial cells for a few millimeters into the lumen. There was no evidence of healing in the central areas of the prostheses. It was concluded that microvascular PTFE prostheses of useful clinical length show encouraging patency rates in the rat, despite poor endothelial cover. For possible clinical application of microvascular PTFE prostheses, further experimental studies should be undertaken to improve their healing capabilities.

Anastomosis, Surgical↗
PubMed1988

Small-calibre vascular grafting into the rat abdominal aorta with biodegradable prostheses.

130 Male Wistar rats, 2-3 months old and weighing 250-350 g were operated on to implant biodegradable small-calibre vascular prostheses (length 10 mm; internal diameter 1.5 mm) in their infrarenal abdominal aorta. The mean operation time was 40 min, the mean aortic cross-clamping time 25 min. The early patency rate was 100%, the late patency rate was 97.7%, and the operative mortality was 3.1%. Microscopical examination of the biodegradable prostheses from 1 h up to 1 year after implantation demonstrated reproducible morphological results; in these prostheses a new arterial wall regenerated which had a structure very similar to the normal arterial wall. It was concluded that the rat is an appropriate experimental laboratory animal for testing new types of small-calibre vascular prostheses.

Animals↗
PubMed1985

Microporous, complaint, biodegradable vascular grafts for the regeneration of the arterial wall in rat abdominal aorta.

Microporous, complaint, biodegradable vascular grafts prepared from mixtures of polyurethane (PU) and poly-L-lactic acid (PLLA) can function as temporary scaffolds for the regeneration of the arterial wall in small-caliber arteries. This study was undertaken to determine the most suitable composition for PU/PLLA vascular grafts to ensure an optimal regeneration. Four types of PU/PLLA vascular grafts differing in percent weight of the PU/PLLA mixture, molecular weight of PLLA, and pore size were implanted into the abdominal aorta of rats (n = 32). Six weeks after implantation two implants of each graft type were evaluated by means of scanning electron microscopy and six implants were evaluated by means of light microscopy. In two types of the PU/PLLA vascular grafts, both of which were prepared from a 95%/5% weight PU/PLLA mixture with PLLA of molecular weight 500,000 but which had a different pore size, there was (I) absence of aneurysm formation and maintenance of arterial implant pulsations, (II) regeneration of a complete antithrombogenic neointima, (III) regeneration of a neomedia of comparable thickness to the media of normal rat abdominal aorta with the regeneration of elastic laminae almost throughout its thickness, and (IV) regeneration of a sufficiently supporting neoadventitia. These results demonstrate that a 95%/5% weight PU/PLLA mixture with PLLA of molecular weight 500,000 is the most suitable composition for PU/PLLA vascular grafts to ensure an optimal regeneration of a neoarterial wall that is of sufficient strength, compliance, and thromboresistance to function as a small-caliber arterial substitute. Pore size of these PU/PLLA grafts does not affect regeneration.

Animals↗
PubMedDate not supplied

Reduced thrombogenicity of vascular prostheses by coating with ADP-ase.

In this pilot study ADP-ase coated polyurethane (PU) vascular prostheses and noncoated (control) PU vascular prostheses (all vascular prostheses: ID 1.5 mm, length 1.5 cm) were implanted into the carotid artery of the rabbit to test whether ADP-ase might function as an adequate anti-thrombogenic coating. The prostheses were evaluated after 1 hour (n = 4) and 3 weeks (n = 8). After 1 hour, there was extensive accumulation of thrombus on the inner surface of the control PU vascular prostheses, in contrast to the ADP-ase coated prostheses. At 3 weeks, all control PU vascular prostheses (n = 8) were occluded, whereas only 1 of the 8 ADP-ase coated PU vascular prostheses. The patient ADP-ase coated PU prostheses showed already extensive endothelial healing. These results indicate the potential of ADP-ase to function as an effective antithrombogenic coating of small-caliber and microvascular PU prostheses.

Animals↗
PubMedDate not supplied

Why are lung allografts more vigorously rejected than hearts?

The fact that lungs are more prone to rejection than hearts was studied in a fully allogeneic rat strains combination. Between these strains, lung rejection was significantly faster than that of the heart (mean survival time of 4.0 versus 6.8 days). The mucosal immune system transplanted within the lung allograft was found to intensify the recipient's immune response in several ways. First, it facilitates the infiltration of the graft by recipient lymphocytes. Secondly, it provides a strong stimulus for the local immune response in the graft itself, and lastly, the dissimination of donor lymphocytes from the graft into the recipient generates a systemic immune response.

Animals↗