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Cochlear implants are well established devices for treating severe hearing loss. However, due to the trauma caused by the insertion of the electrode and the subsequent formation of connective tissue, their clinical effectiveness varies. The aim of the current study was to achieve a long-term reduction in connective tissue growth and impedance by combining surface patterns on the electrode array with a poly-L-lactide coating containing 20% diclofenac. Three groups of six guinea pigs each (control, structure, structure with diclofenac in the coating) were implanted for four weeks. The hearing thresholds were measured before implantation and after 28 days, and impedances were monitored over time. After histological preparation, connective tissue growth and spiral ganglion neuron (SGN) survival were quantified. The hearing thresholds and impedances increased over time in all groups, showing no significant differences. The treatment groups showed increased damage in the cochlea, which appeared to be caused by the elevated parts of the microstructures. This seems to be amplified by the trauma model used in the current study. The impedances correlated with connective tissue growth near the electrode contacts. In addition, SGN survival was negatively correlated with the presence of connective tissue, both of which highlight the importance of successfully reducing connective tissue formation after cochlear implantation.

Auditory disabilities have a large impact on the human population worldwide. Research into understanding and treating hearing disabilities has increased significantly in recent years. One of the most relevant animal species in this context is the guinea pig, which has to be deafened to study several of the hearing pathologies and develop novel therapies. Applying kanamycin subcutaneously and furosemide intravenously is a long-established method in hearing research, leading to permanent hearing loss without surgical intervention at the ear. The intravenous application of furosemide requires invasive surgery in the cervical area of the animals to expose the jugular vein, since a relatively large volume (1 ml per 500 g body weight) must be injected over a period of about 2.5 min. We have established a gentler alternative by applying the furosemide by puncture of the leg veins. For this, custom-made cannula-needle devices were built to allow the vein puncture and subsequent slow injection of the furosemide. This approach was tested in 11 guinea pigs through the foreleg via the cephalic antebrachial vein and through the hind leg via the saphenous vein. Frequency-specific hearing thresholds were measured before and after the procedure to verify normal hearing and successful deafening, respectively. The novel approach of systemic deafening was successfully implemented in 10 out of 11 animals. The Vena saphena was best suited to the application. Since the animals' condition, post leg vein application, was better in comparison to animals deafened by exposure of the Vena jugularis , the postulated refinement that reduced animal stress was deemed successful.

Cochlear implants are well established to treat severe hearing impairments. Despite many different approaches to reduce the formation of connective tissue after electrode insertion and to keep electrical impedances low, results are not yet satisfying. Therefore, the aim of the current study was to combine the incorporation of 5% dexamethasone in the silicone body of the electrode array with an additional polymeric coating releasing diclofenac or the immunophilin inhibitor MM284, some anti-inflammatory substances not yet tested in the inner ear. Guinea pigs were implanted for four weeks and hearing thresholds were determined before implantation and after the observation time. Impedances were monitored over time and, finally, connective tissue and the survival of spiral ganglion neurons (SGNs) were quantified. Impedances increased in all groups to a similar extent but this increase was delayed in the groups with an additional release of diclofenac or MM284. Using Poly-L-lactide (PLLA)-coated electrodes, the damage caused during insertion was much higher than without the coating. Only in these groups, connective tissue could extend to the apex of the cochlea. Despite this, numbers of SGNs were only reduced in PLLA and PLLA plus diclofenac groups. Even though the polymeric coating was not flexible enough, MM284 seems to especially have potential for further evaluation in connection with cochlear implantation.

Several forms of microbodies have been characterized on the basis of their biochemical functions. We have investigated cucumber cotyledons which house two different microbody forms during their development. In these cells, a shift from organelles with the enzymes of beta-oxidation and glyoxylate cycle to peroxisomes with the enzymes of the photosynthetic C2-cycle can be induced by light. The transition state and the time course of changes was studied at different levels of gene expression during the first 2 days of illumination, by quantifying the rate of de novo protein synthesis in cotyledons and by measuring the mRNA activities in vitro. Synthesis and turnover of particular proteins were determined during the transition stage by immunoprecipitation of malate synthase, isocitrate lyase, catalase, multifunctional protein, and thiolase, and quantified by fluorography. From the mRNA activities and the rate of protein synthesis, gene expression for enzymes of the glyoxylate cycle and beta-oxidation started to decrease 24-36 h after onset of continuous light. At that time the rate of synthesis of glycolate oxidase, a leaf peroxisomal marker, is already maximal. By pulse-chase experiments 0-48 h after the onset of light the speed and intensity of protein turnover were measured. Rates of proteolytic degradation of individual enzymes indicated that the different enzymes were not lost simultaneously or all at once. This excludes a destruction of the whole organelle by the lytic compartment.

Fat-degrading cotyledons from cucumber seedlings were investigated with respect to the enzymes metabolizing cis-unsaturated fatty acids. Isolated glyoxysomes degrade linoleic acid, the dominating fatty acid in the storage tissue of the seed. Glyoxysomes were shown to be the sole intracellular site of enzymes responsible for the degradation of unsaturated fatty acids. All three auxiliary enzyme activities discussed for the degradation of polyunsaturated fatty acids, 2,4-dienoyl-CoA reductase, enoyl-CoA isomerase, and 3-hydroxyacyl-CoA epimerase were localized within the matrix of glyoxysomes. They were not found in mitochondria. Separation of glyoxysomal matrix proteins on CM-cellulose revealed that epimerase activity was attributable to the multifunctional protein and also to another protein which apparently exhibited no other beta-oxidation activity. Furthermore, on the basis of the high epimerase activity present in glyoxysomes compared to a much lower 2,4-dienoyl-CoA reductase activity, the metabolism of unsaturated fatty acids via delta 2-cis-enoyl-CoA is considered as alternative to the reductase-dependent pathway.

The enzymatic apparatus of fatty acid beta-oxidation in peroxisomes and glyoxysomes includes a multifunctional protein. Two forms of this protein were detected in extracts from cotyledons of germinating cucumber seeds and separated on hydroxylapatite. The two proteins purified to apparent homogeneity possessed enoyl-CoA hydratase, 3-hydroxyacyl-CoA epimerase, and 3-hydroxyacyl-CoA dehydrogenase activity; the proteins are therefore trifunctional. Analysis of molecular structures and kinetic parameters of the two enzyme forms revealed significant differences in size and amino acid composition. The two proteins were characterized as monomers exhibiting molecular weights of 74,000 and 76,500. Likewise, the data obtained with limited proteolysis proved the occurrence of two independent proteins. Immunological comparisons were performed with antibodies raised against the 76.5-kDa protein. They indicated a weak relationship between the two proteins. From that we conclude that within one type of organelle, i.e., glyoxysome, two isoenzymes with multiple functions are located.

A method for preoperative localization of non-palpable suspected microcalcifications within the mammary gland is described. This procedure is superior to the conventional methods with methylenblue.