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At least 109 records · Page 6Linked to original sources
PubMed1987

Studies of the slow releasing of testosterone from radiation-polymerized testicular prostheses implanted subcutaneously in the back of castrated rabbits.

A controlled release testicular prosthesis containing testosterone, which was previously dissolved in 2-hydroxyethyl methacrylate (HEMA) at a temperature of 80 degrees C, was prepared by radiation-induced polymerization in the supercooled state at a low temperature. The daily dose of testosterone released in vitro from the poly(HEMA) testicular prosthesis was kept constant at a rate of 5.5 +/- 1.5 mg/d throughout an experimental period of 900 d. In the in vivo experiments, the poly(HEMA) testicular prosthesis was implanted subcutaneously in the back of castrated rabbits over a maximum period of 11 mnth. The cumulative amounts of testosterone released in vitro and in vivo from the poly(HEMA) testicular prosthesis for a period of 11 mnth were found to be 2.1 g (30.0 wt% of initial drug) and 0.9 g (12.8 wt% of initial drug), respectively. The serum testosterone level in castrated rabbits with a poly(HEMA) testicular prosthesis rapidly decreased for periods up to 2 mnth (after increasing during the first 2 wk), then showed a moderate decrease for a few months, and finally held constant at a level of 10 ng/ml throughout the experimental period. It was concluded that a slight amount of testosterone is continuously released in vivo from the radiation-polymerized poly(HEMA) testicular prosthesis over a long period analogous with that in vitro.

Animals↗
PubMed1992

Ultrastructural analysis of pseudo-intimal hyperplasia of polytetrafluoroethylene prostheses implanted into the venous and arterial systems.

To evaluate and compare the pathogenesis of pseudo-intimal hyperplasia (PH) of venous and arterial prostheses, a segment of the inferior vena cava (n = 16) or abdominal aorta (n = 16) was substituted by a 3 mm internal diameter polytetrafluoroethylene tube graft (PTFE, 3 cm long, 30 microns in nodal distance) in albino rabbits. At designated time intervals (3-28 days) after the replacement, graft patency was examined and the dry weights of the intraluminal deposits measured as an indicator of the degree of PH. The harvested grafts were then subjected to an ultrastructural analysis by means of light microscopy (LM), and scanning electron and transmission electron microscopy (SEM, TEM). All the grafts remained patent during the entire observation period. The PH judged by the dry weight was significantly more extensive in the venous than in the arterial prostheses. The PH on day 28, observed by light microscopes was apparently most extensive in the mid-portion of venous prostheses but in the arteria prostheses it was mostly seen at the anastomotic sites. The lining of the intraluminal surface of the prostheses with endothelial-like cells observed by SEM was faster and more extensive in venous than in arterial prostheses. The process of PH in venous prostheses observed by TEM may be divided into the following steps: early thrombosis, phagocytosis of the thrombus, appearance of fibroblasts, growth of endothelial-like cells, appearance of smooth muscle cells, and pseudointimal thickening and proliferation of fibroblasts producing collagen fibrils. The process in arterial prostheses was essentially identical to that in venous prostheses but was much slower and less extensive. From these observations, it was concluded that the formation of PH occurs much faster in venous than in arterial prostheses, although the mechanism of PH is mostly identical in venous and arterial prostheses.

Animals↗
PubMed2006

Predicting the performance of mitral prostheses implanted in children under 5 years of age.

BACKGROUND: Mitral valve replacement (MVR) is occasionally indicated in infants and young children, necessitating the use of small prostheses. The performance of these small valves during somatic growth of the patient can lead to patient-prosthesis mismatch. This study examines performance of these valves over time to establish predicted performance and timing of replacement. METHODS: Records were reviewed of all patients under 5 years of who underwent small mechanical MVR between 1988 and 2004 (n=24). Valve sizes were between 17 and 23 mm (Bileaflet 91.6%, Tilting Disc 8.3%) with a median size of 19 mm. Mean age of patients was 1.4+/-1.3 years with a mean weight of 7.8+/-3.4 kg. RESULTS: Early deaths (n=5, 20.8%) were excluded. There were two late deaths and five patients required redo-MVR: four for outgrowth and one for acute thrombosis at 3 months. Age at redo for outgrowth was 8.6+/-6.6 years with mean body weight of 22.5+/-17.5 kg. Mean time between original operation and redo was 8.6+/-6.1 years in these four patients. Follow-up was a median of 7.5 years (range 0.1-15.7 years). Overall freedom from death or valve replacement was 82.6+/-9.1% at 5 years and 75.7+/-10.6% at 10 years. The performance of the original prostheses showed a peak blood flow velocity across the valves of 1.5+/-0.6 m/s at 5 years and 2.2+/-0.5 m/s at 10 years. Seventy-five percent of the survivors still have their original valve at a mean of 8.1+/-4.4 years postoperative with New York Heart Association status of I or II. Actuarial curves suggest that gradients across the valves reach a peak of >10 mmHg at a mean between 6.5 and 7 years postoperative. CONCLUSION: MVR in children under 5 years carries a high mortality. Nevertheless, small mechanical MVR perform remarkably well in young children with durable haemodynamics despite growth of the patients well beyond more than double the initial bodyweight. Valves can be expected to last over 8 years before requiring re-replacement.

Age Factors↗
PubMed2006

The outcome of occluded above-knee femoropopliteal prostheses implanted for critical ischaemia.

OBJECTIVES: To investigate the impact of patient characteristics and treatment modality (graft thrombectomy vs thrombolysis) on the results of redo procedures for occluded above-knee prosthetic femoropopliteal grafts implanted for critical ischaemia. MATERIAL AND METHODS: Fifty-five procedures (thrombolysis 24 and thrombectomy 31) were performed on 24 prostheses (23 patients, 24 limbs) between January 1990 and December 2001. All cases were prospectively registered. Graft patency, limb salvage and survival rates were studied and subgroups of patients were compared. Risk factors were analysed with the use of log rank test and Cox proportional hazard analysis. RESULTS: Half of the 24 initial procedures to restored patency failed within one month. The outcome of second- or third-time redo procedures was similar. The primary patency rates of all 55 redo procedures were 32% at three months, 28% at six months and 12% at 12 months. The results of thrombectomy and thrombolysis were similar. Re-opened grafts additionally treated for an underlying anastomotic stenosis had significantly better patency as compared with re-opened grafts without a pre-existing stenosis on both univariate analysis (p = 0.024) and multivariate analysis (p = 0.027, hazard ratio 2.813). The one-year limb salvage rate was 76%. The one- and five-year survival rates were 87% and 52%, respectively. CONCLUSIONS: The results of redo procedures for occluded above-knee prosthetic grafts were disappointing. Grafts in which a graft-related stenosis was treated performed better than grafts in which occlusion could not be attributed to an underlying stenosis. Such cases should most likely be offered conservative treatment, amputation or a new arterial reconstruction.

Aged↗
PubMed1994

Candidates and requirements for single tooth implant prostheses.

Successful prosthodontic treatment begins with an accurate diagnosis and thorough and comprehensive treatment planning. Osseointegration is an integral part of prosthodontic treatment planning. When use of the single tooth implant is anticipated, there are several procedure objectives that should be considered: elimination of pathosis; attainment of ideal fixture alignment and stability; protection of teh adjacent teeth; preservation or augmentation of the alveolar ridge; attainment of primary closure; and avoidance of mucosal pressure. Esthetic and biologic complications are discussed.

Dental Implants↗