Biodegradable polymeric coatings on cochlear implant surfaces and their influence on spiral ganglion cell survival.

To improve the electrode-nerve interface of cochlear implants (CI), the role of poly(L-lactide) (PLLA) and poly(4-hydroxybutyrate) (P(4HB)) as potential coating matrices for CI was assessed both in vitro and in vivo in terms of degradation behavior and effects on spiral ganglion neurons, the main target of the electrical stimulation with a CI. Growth rates of fibroblasts on the polymers were investigated and a direct-contact test with freshly isolated spiral ganglion cells (SGC) was performed. In addition, the effects of the polymer degradation inside the inner ear were evaluated in vivo. The polymer degradation was assessed by use of scanning electron microscopy in combination with an energy-dispersive X-ray analysis. In vitro, no influence of the polymers was detected on fibroblasts' viability and on SGC survival rate. In vivo, SGC density was decreased only 6 months after implantation in the basal and middle turns of the cochlea in comparison to normal-hearing animals but not between implanted groups (coated or uncoated). The analysis of the electrode models showed that in vivo P(4HB) is characterized by a gradual degradation completed after 6 months; whereas, the PLLA coatings burst along their longitudinal axis but showed only little degradation within the same time frame. In conclusion, both polymers seem to justify further evaluation as possible coating for CI electrodes. Of the two options, due to its excellent coating adhesion/stability and optimal degradation behavior, P(4HB) may prove to be the more promising biodegradable polymer for designing a drug delivery system from the surface of CI electrodes.

Type E botulism associated with vacuum-packaged hot-smoked whitefish.

On January 16, 1997 two Germans got botulism after eating hot-smoked Canadian whitefish produced in Finland. The serum sample of one of the patients contained 6 MLD/ml of botulinum toxin. The type of toxin was identified as E by the toxin neutralization test and the botulinum neurotoxin type E (BoNT/E) gene was also amplified from the serum by polymerase chain reaction (PCR), but C. botulinum could not be isolated from the positive serum sample. The remains of the hot-smoked whitefish eaten by the patients contained botulinum toxin detected by the mouse bioassay and the BoNT/E gene as determined by PCR. C. botulinum was isolated from the fish sample and it was confirmed to be type E by the mouse bioassay and by PCR. Eleven other fish samples from the same lot did not contain botulinum toxin nor any BoNT gene. The incriminated food was processed on the 9th and 10th of January, 1997 from frozen whitefish imported to Finland from Canada. The pulsed-field gel electrophoretic pattern of the isolated C. botulinum strain resembled a reference strain of North American origin. It did not match any C. botulinum strains isolated from the Baltic sea-bottom or from the fish caught in the area indicating that the fish was contaminated by C. botulinum in Canada. The conditions resulting in toxin production could not be identified. The safety problems associated with vacuum-packaged hot-smoked fish seem to be of utmost concern and the product is one of the most important botulism food vehicles processed on an industrial scale. Temperature monitoring and the use of time-temperature indicators are to be recommended in order to ensure adequate storage temperature from processing through to consumption. Allowing the use of nitrate and nitrite together with sufficiently high NaC1 concentration in this particular product should also be considered.

Postischemic synthesis of high energy phosphates in isolated porcine hearts during reperfusion with 11 or 25 degrees C hypothermic perfluorocarbon emulsion FC 43. A 31P magnetic resonance spectroscopy study.

OBJECTIVE: One aim of coronary reperfusion after myocardial ischemia is to restore the myocardial content of high energy phosphates. The superiority of the artificial oxygen carrier perfluorocarbon emulsion FC43 over blood solution is known, therefore, in this paper we examined the temperature-dependence of this substance. METHOD: The changes of the high energy phosphates phosphocreatine (PCr) and inorganic phosphate (Pi) were documented in 29 isolated pig hearts, employing a 4.7 Tesla magnetic-resonance-spectroscope (MRS). After 15 min warm ischemia, reperfusion with warm blood and a cardioplegic ischemia period of 45 min, these hearts were reperfused with either 11 or 25 degrees C hypothermic oxygenated perfluorocarbon emulsion FC43, both under continuous spectroscopy. MRS is able to directly measure PCr as well as Pi. Their relation expresses the state of myocardial energy stores. RESULTS: Reperfusion with 11 degrees C hypothermic FC43 (n = 14) caused an increase of the relation PCr to Pi by a factor of 9, compared to an increase by a factor of 4 with 25 degrees C emulsion (n = 15) (P < 0.05). During 80 min of reperfusion with 11 degrees C cold FC43 emulsion the average flow rate was 90 +/- 12 and 96 +/- 11 ml/min during reperfusion with 25 degrees C hypothermic FC43 emulsion. Both rates fell only slightly in the course of time. CONCLUSION: We conclude that reperfusion with 11 degrees C hypothermic oxygenated FC43 in isolated ischemic porcine hearts leads to a clear increase of the index PCr/Pi compared with reperfusion at 25 degrees C. The correlation between the synthesis of myocardial high energy phosphates with postcardioplegic ventricular function is questionable. If further studies will show an improvement of myocardial function after perfusion with hypothermic oxygenated perfluorocarbon emulsion FC43, this solution may find clinical application in the storage of explanted human hearts for transplantation, during transportation to the recipient.