In vivo biocompatibility and biostability of modified polyurethanes

Modified segmented polyurethanes were examined for biostability and biocompatibility using an in vivo cage implant system for time intervals of 1, 2, 3, 5, and 10 weeks. Two types of materials were used: polyether polyurethanes and polycarbonate polyurethanes. Two unmodified polyether polyurethanes (PEUU A' and SPU-PRM), one PDMS endcapped polyether polyurethane (SPU-S), and two polycarbonate polyurethanes (SPU-PCU and SPU-C) were investigated in this study. Techniques used to characterize untreated materials were dynamic water contact angle, stress-strain analysis, and gel permeation chromatography. Cellular response was measured by exudate analysis and by macrophage and foreign body giant cell (FBGC) densities. Material characterization, postimplantation, was done by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) in order to quantify biodegradation and scanning electron microscopy (SEM) to qualitatively describe the cellular response and biodegradation. The exudate analysis showed that the acute and chronic inflammatory responses for all materials were similar. Lower FBGC densities and cell coverage on SPU-S were attributed to the hydrophobic surface provided by the PDMS endgroups. The polycarbonate polyurethanes did not show any significant differences in cell coverage or FBGC densities even though the macrophage densities were slightly lower compared to polyether polyurethanes. By 10 weeks, biodegradation in the case of PEUU A' and SPU-PRM was extensive as compared to SPU-S because the PDMS endcaps of SPU-S provided a shield against the oxygen radicals secreted by macrophages and FBGCs and lowered the rate of biodegradation. In the case of polycarbonate polyurethanes, the oxidative stability of the carbonate linkage lowered the rate of biodegradation tremendously as compared to the polyether polyurethanes (including SPU-S). The minor amount of biodegradation seen in polycarbonate polyurethanes at 10 weeks was attributed to hydrolysis of the carbonate linkage.     

Gastric duplication: endoscopic appearance and clinical features

The case of a 13-year-old female presenting with a 6 week history of significant vomiting resulting from a gastric duplication is described. At endoscopy, an antral mass which appeared to change in size and site with peristalsis was evident. Although rare, these lesions need to be considered in the differential diagnosis of patients presenting with symptoms suggestive of gastric outlet obstruction. However, in the majority of cases, the diagnosis is rarely made prior to surgery.     

The importance of behavioural studies in conservation biology

The exciting research developments in animal behaviour over the last two decades have had a negligible impact on conservation. I list 20 subjects in which the study of animal behaviour can make a significant contribution to conservation. Behaviour may in itself be worth conserving. I also suggest how behavioural ecologists could become more involved in conservation. Copyright 1998 The Association for the Study of Animal Behaviour.     

Compatibility of commonly used bone marrow transplant drugs during Y-site delivery

The morphogenesis of cirrhotic septa in chronic hepatitis B was studied assuming that they arise at the sites of hepatocellular necrosis invoked by host immune reaction against HBcAg-expressing hepatocytes. Sections from three livers with chronic hepatitis B, all in cirrhotic stage, were immunostained with HBcAg and subjected to morphometry to analyze the distribution of HBcAg(+) hepatocytes and its relation with septa. HBcAg(+) cells were not distributed randomly over the nodules but forming focal areas. The septum formation along these foci was shown by 2-D distance distribution analysis, a technique we devised. Upon a sheet of color microphotograph of immunostained section, hundreds of test points each 400 microns apart were arranged by overlaying a tessellated grid. From each of the points hitting the nodules, the distance to the nearest nodulo-septal border D(min) was measured. Measurement was performed on a total of 2,585 test points. It was shown that the mean D(min) in the HBcAg(+) areas was significantly smaller than in HBcAg(-) areas. Thus, the cirrhotic septa are considered to arise at the places of HBcAg(+) foci, connecting them by postnecrotic collapsing.     

The use of bilateral adult renal allografts - a method to optimize function from donor kidneys with suboptimal nephron mass

Alternatives to traditional organ donor usage has allowed expansion of the organ donor pool to help compensate for the increasing disparity between recipients and donors. The use of bilateral adult renal transplants is a novel idea to salvage older donor kidneys with suboptimal nephron mass that would otherwise be destined for discard. Ten renal transplants were performed utilizing both kidneys from adult cadaver donors with diminished nephron mass determined by calculated glomerular filtration rate or biopsy evidence of significant glomerulosclerosis (>10%). Nine of ten (90%) recipients have satisfactory renal function at a mean follow-up of 7 months. The single case of graft failure was due to documented medical non-compliance. Mean serum creatinine at 6 months was 1.5 mg/dl. Mean measured creatinine clearance was 43.2+/-3.4. These preliminary findings suggest that the use of bilateral renal transplants provide satisfactory early function and allows salvage of older donor kidneys with suboptimal nephron mass.