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Biomedical subjects

K Jahnke

Publications and source records attributed to K Jahnke.

At least 37 records · Page 2Linked to original sources
PubMed2004

Comparative investigation of the biocompatibility of various silicon nitride ceramic qualities in vitro.

There is a controversy about the biocompatibility of silicon nitride ceramics contained in the literature, which appears to be related to a factor of the individual chemical composition of different qualities of silicon nitride ceramics and of the different surface properties. This study attempts to investigate the cytotoxicity of different qualities of industrial silicon nitride ceramics applying an L929-cell culture model in a direct contact assay combined with a cell viability assessment. Five different qualities of industrial standard silicon nitride ceramics were chosen for in vitro testing. The chemical composition was determined by EDS analysis. Different biomedically approved aluminium oxide qualities, a titanium alloy, glass and polyvinylchloride (PVC) served as control materials. L929 mice fibroblasts were incubated directly on the materials for 24 h, stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy to control cell morphology, viability and cell counts compared to empty well values. Scanning electron microscopy was applied to additionally investigate cell morphology. There was no observation of cytotoxic effects on the silicon nitride ceramic samples; moreover cell morphology remained the same as on aluminium oxide and titanium. Viability testing revealed the presence of avital cells exclusively on PVC, which served as a negative control. Cell counts on all polished surfaces showed significantly higher numbers, whereas some rough surface samples showed significantly lower numbers. We conclude that silicon nitride ceramics show no cytotoxic effects and should be considered for biomedical application owing to its favourable physiochemical properties, especially its superior resistance to mechanical stress, which would be useful for compression loaded conditions. Polished surfaces would appear to promote advanced biocompatibility.

Aluminum Oxide↗
PubMed2004

[Aminoglycoside- and cisplatin-ototoxicity: from basic science to clinics].

Gentamicin and cisplatin are clinically widely used pharmacological agents which may induce irreversible hearing loss as a side effect. Concerning the pathomechanisms of ototoxicity as well as preventive strategies there are similarities but also some differences. In this review we focus on the role of reactive oxygen species, the antioxidant system, cellular iron and calcium as well as nitric oxide and neurotrophins on gentamicin- and cisplatin-ototoxicity. Furthermore we deal with apoptotic and necrotic cell death as well as the role of mitochondria in these cell injury processes.

Aminoglycosides↗
PubMed2004

[Long-term results of laser-tonsillotomy in obstructive tonsillar hyperplasia].

BACKGROUND: Carbon-dioxide-laser-tonsillotomy is reconsidered as a procedure to relieve patients in early childhood from obstructive symptoms caused by tonsillar hyperplasia such as snoring or sleep apnea without influencing the immunological function. METHODS AND PATIENTS: The protruding part of the tonsils was removed by a CO (2)-laser delivering 10 - 15 W. During 1993 to 2003, 83 children received laser-tonsillotomy, combined with adenoidectomy 51 children were available for follow-up with a standard questionnaire. The parents were surveyed in average 39 months postoperatively. 5 patients required a subsequent tonsillectomy due to a recurrence of tonsillar hyperplasia. Histological investigations were done. 15 children were reevaluated by clinical examination. RESULTS: Most of the patients were relieved from obstructive symptoms. There was no occurrence of postoperative hemorrhage or peritonsillar abscesses. The histological investigations on the specimens from later performed tonsillectomy (n = 5) showed no evidence of scarring opened crypts. The clinical examination did not reveal any signs of chronic infections. CONCLUSION: The tonsillotomy by carbon-dioxide-laser appears as a suitable and safe technique for the treatment of tonsillar hyperplasia without severe throat infection in early childhood.

Airway Obstruction↗
PubMed2004

[Biocompatibilty of silicon nitride ceramic in vitro. A comparative fluorescence-microscopic and scanning electron-microscopic study].

BACKGROUND: With regard to its favorable physical properties, silicon nitride ceramic is considered as biomaterial for human medical application. Minor controversy exists about the biocompatibility of the material. METHODS: Cytotoxicity testing, cell viability and morphology assessment was performed applying the L929-mice fibroblast cell culture model in a direct contact assay. Testing materials were silicon nitride ceramics of different surface properties and titanium alloy as a reference. Polyvinylchloride served as a negative control. The cells were stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy. Scanning electron microscopy was applied to additionally investigate cell morphology. RESULTS: No cytotoxic effects were observed on the silicon nitride ceramic samples; moreover cell morphology remained the same as on titanium. Avital cells were present exclusively on PVC. The cell growth in the silicon nitride samples showed no significant differences compared to titanium. Cell counts on all polished surfaces showed significantly higher numbers. Scanning electron microscopy revealed typical fibroblast morphology with filiform extensions. CONCLUSION: The current results indicate a favorable biocompatibility of silicon nitride ceramic. Cell growth, viability and morphology are comparable to parameters of titanium. Polished surfaces appear to promote cell growth. Further in vivo studies are mandatory prior to human medical application. Owing to its favorable physiochemical properties, especially its superior resistance to mechanical stress, silicon nitride could serve as a biomaterial for osteosynthesis of bone with mucosal attachment.

Alloys↗
PubMed2004

Coincidence of normal tension glaucoma, progressive sensorineural hearing loss, and elevated antiphosphatidylserine antibodies.

BACKGROUND: Recently, in patients with normal tension glaucoma (NTG) elevated levels of antiphosphatidylserine antibodies (APSA), a subgroup of antiphospholipid antibodies (APLA) were found. Progressive sensorineural hearing loss (PSHL) is associated with autoimmune diseases and also the presence of APLA. METHODS: To investigate a possible association between NTG and PSHL, 34 patients (age range 31-81 years) with NTG were evaluated for evidence of audiovestibular disorders. Besides ophthalmological standard examinations (slit lamp, IOP, funduscopy, perimetry) scanning laser tomography and polarimetry were performed. From all patients' audiograms, stapedial thresholds and otoacoustic emissions were obtained. The serological testing of patients and controls (40 healthy blood donors older than 50 years) concerned IgG and IgM levels of antibodies against phosphatidylserine (APSA) and beta2 glycoprotein. RESULTS: 23 of 34 NTG patients had hearing loss (PSHL n = 11; presbyacusis n = 12). The NTG patients had significantly higher APSA levels than controls. Elevated APSA concentrations were significantly more frequent in patients with NTG and hearing loss compared with NTG patients with normacusis. CONCLUSIONS: These findings show that NTG and hearing loss have a high coincidence. The elevated APSA levels may indicate an association with similar systemic autoimmune processes.

Adult↗
PubMed2002

[Reconstruction of the superstructure of the stapes in guinea pigs with biovitro ceramic and silicone foil].

BACKGROUND: The reconstruction of the stapes superstructure is still a problem. Efforts for the fixation of implants on the footplate did not show satisfying results yet. METHODS: In 6 guinea pigs a biovitro ceramic (Bioverit) was placed on the stapes footplate after removal of the superstructure. The exclusive bony fixation of the implants on the footplate should be achieved by the use of silicone foils. For control purposes replantation of autologous ossicles was done in one group of 3 animals and a sham operation was performed without any use of implants in the other group of 6 guinea pigs. RESULTS: After 21 weeks not only bony fixation of the implant with the footplate was observed, but furthermore with the wall of the middle ear. Bone formation was detected along the silicone foils. In the first control group of animals we found bony fixation of the replanted ossicles and even a bow-shaped reconstruction of the stapes superstructure in the second. CONCLUSIONS: The guinea pig was not an ideal model for questions of middle ear reconstructions due to its enormous potential for bone formation. In this animal model bony fixation of glass-ceramic with the stapes-footplate could be induced.

Animals↗
PubMed2002

[Brachytherapy with (192)Iridium in the treatment of recurrent nasopharyngeal carcinoma].

BACKGROUND: Local recurrence of nasopharyngeal carcinomas can be treated in different ways. One option is re-irradiation e. g. as stereotactically guided convergent beam. An operative approach is possible in small recurrent tumours. Brachytherapy is a good alternative because of the steep dose gradient in the pre-irradiated area. METHODS: First step is the creation of a wide approach to the nasopharynx. This leads to a tumour mass reduction and gives space for the applicator. The radioactive substance will be brought into contact with the tumour by an afterloading procedure. The advantage of this therapy is the possibility to protect the surrounding tissue whereas the tumour receives a relatively high dosage. Between 2/90 and 12/96 10 men and 3 women were treated according to this protocol. RESULTS: The median age was 56 years (37- 66 years), the average follow-up period was 49,7 months (8 -123 months). 2 non keratinising and 11 undifferentiated carcinomas were treated. 5 of 13 patients were still alive at the end of the follow-up period. The 5 year over all survival rate was 46 %. 3 patients are free of disease for 5 years or longer. The patients were treated 2 to 6 times with 7 Gy in 5 mm depth. CONCLUSIONS: The results show that good palliation can be achieved by the applied method but larger studies are required to give a definite statement.

Adult↗
PubMed2001

Mutations in the connexin26/GJB2 gene are the most common event in non-syndromic hearing loss among the German population.

Congenital sensorineural hearing loss affects approximately 1/1,000 live births. Mutations in the gene encoding connexin26 (GJB2) have been described as a major cause of genetic nonsyndromic hearing impairment. Additionally, another gap junction gene, connexin30 (GJB6), was found to be responsible for hereditary hearing loss. We have studied 134 patients with severe to profound hearing loss or deafness and 13 patients with mild to moderate nonsyndromic sensorineural hearing loss in order to evaluate the prevalence of connexin26 and connexin30 mutations in Germany. Mutations in the connexin26 gene were found in 30 patients (22%) with profound to severe hearing impairment whereas only one novel single nucleotide polymorphism (396G-->A) in the connexin30 gene was detected. Among the 13 patients with mild to moderate hearing loss neither mutations in the connexin26 nor in the connexin30 gene could be detected. These results demonstrate that mutations in the connexin26 gene are also a frequent cause of hereditary non-syndromic hearing loss in Germany. Therefore a screening of mutations in the connexin26 gene should be performed in every case of non-syndromic hearing loss of unknown origin.

Adolescent↗
PubMed2001

Accelerated hyperfractionated radiotherapy with concurrent chemotherapy in locally advanced nasopharyngeal carcinoma: a phase II study.

PURPOSE: The incidence of nasopharyngeal carcinoma in Germany is relatively low in comparison with certain regions in south-east Asia. However, standardised therapeutical regimes are required in the treatment of these tumours. METHODS: Between August 1990 and December 1997, 25 patients with stage III and IV nasopharyngeal carcinoma received an accelerated and hyperfractionated radiotherapy with concurrent chemotherapy (5-FU and mitomycin C). The primary tumour and positive lymph nodes received a total dose of 72 Gy over a period of 6 weeks. In the first 3 weeks, irradiation fields were treated five times per week with 2 Gy per fraction. Thereafter, treatment was accelerated, giving two daily fractions of 1.4 Gy. Salvage surgery was offered for residual lymph node disease after radiotherapy. RESULTS: The overall response rate defined as complete and partial response of the primary was 100%. Sixteen of the 25 patients were still alive and were free of any evidence of tumour recurrence or distant metastases at a mean follow-up period of 34 months (range 7-95 months). Six patients received salvage surgery. Only one of these six patients had histologically proven evidence of vital tumour. No severe late complications such as blindness or temporal lobe necrosis were observed. CONCLUSIONS: The presented data are promising and show that the combination of hyperfractionated accelerated radiotherapy and chemotherapy is feasible and effective.

Adult↗
PubMed2001

[Connexin26 and -30 in the Cochlea and their clinical relevance].

INTRODUCTION: Gap junction channels consist of different connexin proteins and play an important role in the physiology of hearing. Connexin26 and connexin30 have been demonstrated in the inner ear by immunohistochemistry and Northern Blot analysis. Mutations in the genes for connexin26 and connexin30 have been described to be responsible for non-syndromic hearing loss. METHODS: We investigated the prevalence of connexin26 and connexin30 mutations in patients with profound hearing loss or deafness by SSCP-analysis and sequencing. RESULTS: 30 connexin26 mutations (22 %) were detected among 134 patients with profound hearing loss or deafness. The most frequent connexin26 mutation 30delG was found in 25 patients. In 5 patients other connexin26 mutations were identified. No connexin30 mutation was found. CONCLUSION: Therefore connexin26 mutations also play an important role for non-syndromic hearing loss in Germany. We propose that every patient with suspected hereditary hearing loss should be screened for a connexin26 mutation.

Adolescent↗
PubMed2001

Vascular variations of the inner ear.

Vascular anomalies of the inner ear have been documented in only a few isolated case reports. The goal of our study was to describe, qualify and quantify vascular variations of the inner ear in 122 temporal bones from 64 pediatric subjects aged between 0 and 10 years. The average age was 11.6 months. Horizontal sections of the temporal bone, examined by light microscopy, revealed vessels coursing freely through the perilymphatic space of the cochlea, especially in the apical turn. Other findings included abnormally wide vessels in the stria vascularis as well as a vascular malformation of the internal auditory canal. Our study demonstrated more atypical vessels in the cochlea than in the vestibular labyrinth. We found a statistically significant positive correlation between vascular variations of the inner ear and concomitant cardiac anomalies or endolymphatic hydrops. We also discuss the possible etiology and potential significance of these findings in terms of disturbances of the function of the inner ear.

Child↗
PubMed2001

Does metal coating improve the durability of silicone voice prostheses?

Voice prostheses, which are used for voice rehabilitation in cancer patients after laryngectomy, usually become colonized with a mixed biofilm of bacteria and Candida after 2-4 months and lose their efficiency. It is essential to ensure the stability and biocompatibility of these implants. With the aid of surface frame analysis we have shown that local antifungal treatment is inadequate for eliminating the deep infiltration and encapsulation of Candida colonies in silicone. A surface that prevents the adhesion of microorganisms is required. Because of its special properties there are few methods available for coating silicone. We employed, for the first time, a new method of surface modification using anodic vacuum arc coating. Using this method it was possible to obtain a solid film of gold or titanium metal with a layer thickness < 100 nm. Resistance against Candida colonization and destruction of coated prostheses were tested both in vitro and in vivo. A titanium coating seemed to provide the optimal solution to the problem, because surface adhesion and the smoothness of the material appeared to be superior to those of a gold coating.

Biocompatible Materials↗
PubMed2000

PYD2 encodes 5,6-dihydropyrimidine amidohydrolase, which participates in a novel fungal catabolic pathway.

Most fungi cannot use pyrimidines or their degradation products as the sole nitrogen source. Previously, we screened several yeasts for their ability to catabolise pyrimidines. One of them, Saccharomyces kluyveri, was able to degrade the majority of pyrimidines. Here, a series of molecular techniques have been modified to clone pyrimidine catabolic genes, study their expression and purify the corresponding enzymes from this yeast. The pyd2-1 mutant, which lacked the 5,6-dihydropyrimidine amidohydrolase (DHPase) activity, was transformed with wild-type S. kluyveri genomic library. The complementing plasmid contained the full sequence of the PYD2 gene, which exhibited a high level of homology with mammalian DHPases and bacterial hydantoinases. The organisation of PYD2 showed a couple of specific features. The 542-codons open reading frame was interrupted by a 63 bp intron, which does not contain the Saccharomyces cerevisiae branch-point sequence, and the transcripts contained a long 5' untranslated leader with five or six AUG codons. The derived amino acid sequence showed similarities with dihydroorotases, allantoinases and uricases from various organisms. Surprisingly, the URA4 gene from S. cerevisiae, which encodes dihydroorotase, shows greater similarity to PYD2 and other catabolic enzymes than to dihydroorotases from several other non-fungal organisms. The S. kluyveri DHPase was purified to homogeneity and sequencing of the N-terminal region revealed that the purified enzyme corresponds to the PYD2 gene product. The enzyme is a tetramer, likely consisting of similar if not identical subunits each with a molecular mass of 59 kDa. The S. kluyveri DHPase was capable of catalysing both dihydrouracil and dihydrothymine degradation, presumably by the same reaction mechanism as that described for mammalian DHPase. On the other hand, the regulation of the yeast PYD2 gene and DHPase seem to be different from that in other organisms. DHPase activity and Northern analysis demonstrated that PYD2 expression is inducible by dihydrouracil, though not by uracil. Apparently, dihydrouracil and DHPase represent an important regulatory checkpoint of the pyrimidine catabolic pathway in S. kluyveri.

5' Untranslated Regions↗
PubMed2000

[Ambulatory rehabilitation after cochlear prosthesis implantation].

BACKGROUND AND OBJECTIVE: This study compares the results of the outpatient-based program of the Cochlear Implant Center Ruhr with inpatient-based rehabilitation, which is almost exclusively performed in Germany. PATIENTS/METHODS: The Department of Otorhinolaryngology at the University of Essen in Germany provided 52 patients with either 22- or 24-channel Nucleus cochlear implants from March 1996 to July 1999. Almost all patients (n = 49) were rehabilitated on an outpatient basis, which is the standard in many cochlear implant centers outside Germany. RESULTS: The longest follow-up period at the University of Essen Department of Otorhinolaryngology was 36 months. Minor complications occurred in 10% of the patients. After 24 months, the first three implanted patients were able to discriminate 100% of numbers and over 60% of syllables in the Freiburg speech discrimination test. The patients who developed an understanding of open speech were able to discriminate 31 words per minute with cochlear implant and without lipreading after 24 months. Children were seen to double their Schmid-Giovannini scores at 6 months postimplantation. CONCLUSIONS: The Essen outpatient-based cochlear implant program demonstrates results in speech development and speech understanding equal to those of centers providing inpatient rehabilitation. A special advantage is continuous rehabilitation with professionals known to the child for several years. In children especially, exhaustive commuting reduces school attendance and is a burden on the accompanying guardians. As an inpatient, however, the child is torn from his familiar environment. Parents with several children have particular difficulties in accompanying their child and indeed this may not always be possible.

Adult↗