Transport of Escherichia coli bacteria through laboratory columns of glacial-outwash sediments: estimating model parameter values based on sediment characteristics.

Bacterial transport through cores of intact, glacial-outwash aquifer sediment was investigated with the overall goal of better understanding bacterial transport and developing a predictive capability based on the sediment characteristics. Variability was great among the cores. Normalized maximum bacterial-effluent concentrations ranged from 5.4x10(-7) to 0.36 and effluent recovery ranged from 2.9x10(-4) to 59%. Bacterial breakthrough was generally rapid with a sharp peak occurring nearly twice as early as the bromide peak. Bacterial breakthrough exhibited a long tail of relatively constant concentration averaging three orders of magnitude less than the peak concentration for up to 32 pore volumes. The tails were consistent with non-equilibrium detachment, corroborated by the results of flow interruption experiments. Bacterial breakthrough was accurately simulated with a transport model incorporating advection, dispersion and first-order non-equilibrium attachment/detachment. Relationships among bacterial transport and sediment characteristics were explored with multiple regression analyses. These analyses indicated that for these cores and experimental conditions, easily-measurable sediment characteristics--median grain size, degree of sorting, organic-matter content and hydraulic conductivity--accounted for 66%, 61% and 89% of the core-to-core variability in the bacterial effective porosity, dispersivity and attachment-rate coefficient, respectively. In addition, the bacterial effective porosity, median grain size and organic-matter content accounted for 76% of the inter-core variability in the detachment-rate coefficient. The resulting regression equations allow prediction of bacterial transport based on sediment characteristics and are a possible alternative to using colloid-filtration theory. Colloid-filtration theory, used without the benefit of running bacterial transport experiments, did not as accurately replicate the observed variability in the attachment-rate coefficient.

Reduced neutrophil superoxide generation and plasma lipoperoxide levels in pigs fed with cod liver oil.

Circulating neutrophils, isolated from pigs fed for 8 weeks with a diet supplemented with CLO, had an accentuated n-3 fatty acid incorporation into the plasma membrane, as evidenced by an approximately four-fold greater n-3/n-6 ratio as compared with the control diet group. Moreover, the neutrophils of the CLO fed pigs produced less superoxide when stimulated with PMA or f-MLP, as well as showing a more prolonged latency period before O2(-)-generation. In the plasma of pigs fed with CLO there were higher levels of thiobarbituric reactive material and lipofuscin, while the content of GSSG was similar in both dietary groups. The results of this study indicate that dietary supplementation with CLO reduces the activation of circulating neutrophils and favours the presence in the plasma of lipoperoxides.

Long-term patency of regenerated neoaortic wall following the implant of a fully biodegradable polyurethane prosthesis: experimental lipid diet model in pigs.

The degradation of a polyurethane vascular prosthesis, the time course and characteristics of tissue ingrowth and prosthesis replacement, and the incidence of thrombosis have been investigated in 50 young pigs. A 6-7 cm long cone-shaped prosthesis was implanted in the infrarenal aorta of 50 young growing pigs which were sacrificed at intervals from 60 to 365 days. Ten animals were controls, 25 were given aspirin 10 mg/kg of body weight/day, and 15 were fed with cod liver oil. Aortography, done at 30, 60, and 90 days, showed 100% of implants were thrombosed in the surviving controls, 55% of the aspirin group had patent grafts, and 100% of animals in the lipid diet group had patent grafts. At final graft retrieval, the aspirin group showed only three patencies, while in the lipid diet group seven out of nine animals were patent. The laboratory and morphological studies indicated that all patent prostheses were lined with tissue that resembled the intima of native aorta with a layer of smooth muscle cells which appeared complete at 180 days. From these data we conclude that the biodegradable polyurethane vascular prosthesis is reliable for experimental implants in a pig model. The lipid-rich diet of polyunsaturated fatty acids potentiates long-term patency, perhaps by preventing platelet aggregation and thrombosis, and allowing the growth of a neoendothelium and neomedia within the lumen of the prosthesis, which slowly degrade towards fatty tissue and form neoadventitia.

Prevention of platelet aggregation by dietary polyunsaturated fatty acids in the biodegradable polyurethane vascular prosthesis: an experimental model in pigs.

A 6-7 cm long degradable polyurethane vascular prosthesis was implanted in the infrarenal aorta of 25 young growing pigs, sacrificed from day 30 to 365 to study the processes of degradation and tissue growth, the characteristics of prosthetic substitutes and the incidence of thrombosis. Ten animals were used as controls and 15 were fed with cod liver oil (25 ml twice daily). Aortography performed at day 30, 60 and 90 showed 100% thrombosed implants in the controls, while in the lipid diet fed animals there was 100% patency. At graft retrieval, there were 7 patent grafts out of 9 in the cod liver oil fed animals. Laboratory tests indicated that the lipid diet rich in n-3 polyunsaturated fatty acids induces significant modifications of lipid metabolism preventing platelet aggregation. These data correlate well with findings of the morphological studies showing that all patent prostheses are lined with tissues similar to the endothelium of the native aorta with a mid layer made of circular and longitudinal smooth muscle cells well differentiated at day 180. These data show that the essential polyunsaturated fatty acid rich diet is able to prevent thrombosis of the biodegradable polyurethane vascular prosthesis. The combination of a synthetic material and the lipid diet experimental model, makes it possible to assess the long-term tissue-synthetic material interaction and the process of tissue growth.

Comparison of the effects of polyglycolic acid and monofilament nylon sutures in the common bile duct of pigs.

The tissue reaction and involvement of cells in the common bile duct of young pigs after surgery with two suture materials, polyglycolic acid and monofilament nylon, have been described. By comparing the different tissue reactions to the suture materials the authors observe that the use of non-absorbable polymer sutures and their long lasting presence in living tissues, may interfere with the healing process, since the sutures tend to migrate within the common duct wall and be expelled into the lumen owing perhaps to the delayed immuno-allergic reaction which develops in the common duct wall. In contrast polyglycolic acid seems to be biologically well tolerated and well integrated as a suture material, which is reabsorbed with the help of cell enzymes producing a complete restitutio ad integrum of the wall.

[Crohn's disease of the colon: anatomo-radiological correlations (author's transl)]. / La malattia di Crohn del colon. Correlazioni anatomo-radiologiche

The epicritic revision of 74 histologically proved cases permits the authors to dwell on the radiological features of the diseased colon; their correlations with pathological findings and their differential diagnosis are discussed. A number of radiographs are presented as examples.