PubMed Health⌕ Search

Biomedical subjects

A Limberger

Publications and source records attributed to A Limberger.

7 recordsLinked to original sources
PubMed2003

[Comparative study of spatial imaging techniques in stereo-endoscopy].

PURPOSE: This study compares the two-dimensional presentation of stereo-endoscopic video data with three-dimensional presentation using polarization glasses and three-dimensional presentation with an autostereoscopic display. The aim of this study was to evaluate possible advantages of the three display technologies. MATERIAL AND METHODS: Fifty-nine test persons untrained in endoscopy had to complete three endoscopic tasks with different levels of difficulty. Each test involved a new presentation method. Different measurements were noted such as speed of task completion, accuracy of task performance, and quantity of solved tasks. The data collected were statistically evaluated. RESULTS: Neither sex, handedness, nor level of stereopsis had any statistically significant impact on the test results. The differences between the three presentation methods of stereo-endoscopic pictures were not statistically significant. CONCLUSION: Similar results were achieved with all three presentation methods. None of the presentation methods was significantly superior in the values measured. A final assessment of the possibilities of spatial endoscopy should await future technological developments in endoscopic devices (e.g., picture acquisition).

Adult↗
PubMed2002

Comparison between three-dimensional presentation of endoscopic procedures with polarization glasses and an autostereoscopic display.

BACKGROUND: Most endoscopic procedures are done with a two-dimensional (2D) view or a spatial presentation with polarization glasses. A new method of presenting three-dimensional (3D) spatial views is the autostereocopic display. We compared the performances of untrained test persons using these methods. METHODS: We designed three tests that had to be performed with one of the presentations. We used a Karl Storz 3D set with a 0 degrees stereooptic and a grasper. The autostereoscopic display was the Dresden 3D display. The 59 test persons were students who had never before worked with endoscopic devices. RESULTS: There were few differences between the tests, and none were statistically significant. The results with 2D were slightly better than those with polarization glasses, and the results with polarization glasses were slightly better than those with the autostereoscopic display. CONCLUSIONS: There are few differences between the procedures. A true spatial view is limited by the similarity of the two half-pictures.

Depth Perception↗
PubMed2001

Thyroid hormone-deficient period prior to the onset of hearing is associated with reduced levels of beta-tectorin protein in the tectorial membrane: implication for hearing loss.

The genes for alpha- and beta-tectorin encode the major non-collagenous proteins of the tectorial membrane. Recently, a targeted deletion of the mouse alpha-tectorin gene was found to cause loss of cochlear sensitivity (). Here we describe that mRNA levels for beta-tectorin, but not alpha-tectorin, are significantly reduced in the cochlear epithelium under constant hypothyroid conditions and that levels of beta-tectorin protein in the tectorial membrane are lower. A delay in the onset of thyroid hormone supply prior to onset of hearing, recently described to result in permanent hearing defects and loss of active cochlear mechanics (), can also lead to permanently reduced beta-tectorin protein levels in the tectorial membrane. beta-Tectorin protein levels remain low in the tectorial membrane up to one year after the onset of thyroid hormone supply has been delayed until postnatal day 8 or later and are associated with an abnormally structured tectorial membrane and the loss of active cochlear function. These data indicate that a simple delay in thyroid hormone supply during a critical period of development can lead to low beta-tectorin levels in the tectorial membrane and suggest for the first time that beta-tectorin may be required for development of normal hearing.

Animals↗
PubMed1999

[Hearing disorders].

Explore the source record for details and available documents.

Cochlear Implantation↗
PubMed1994

Can testosterone alone maintain the gonadotrophin-releasing hormone antagonist-induced suppression of spermatogenesis in the non-human primate?

The combination of gonadotrophin-releasing hormone (GnRH) antagonist and delayed testosterone substitution provides a promising approach towards male contraception. However, the GnRH antagonists used clinically so far cause side-effects and have to be administered continuously. We therefore used the non-human primate model to see whether the GnRH antagonist cetrorelix (which exhibits a favourable benefit-to-risk ratio in terms of anti-gonadotrophic action in normal men) induces complete and reversible suppression of spermatogenesis and whether GnRH antagonist-induced suppression of spermatogenesis can be maintained by testosterone alone. Four groups of adult cynomolgus monkeys (Macaca fascicularis; five per group) were injected daily with 450 micrograms cetrorelix/kg ([N-acetyl-D-2-naphthyl-Ala1, D-4-chloro-Phe2, D-pyridyl-Ala3, D-Cit6, D-Ala10]-GnRH). Group 1 received the GnRH antagonist for 7 weeks followed by vehicle administration for another 11 weeks; group 2 was treated with GnRH antagonist for the entire 18 weeks with each animal receiving a single testosterone implant during weeks 11-18 to restore the ejaculatory response to electrostimulation; group 3 received the GnRH antagonist for 18 weeks and testosterone buciclate (TB) was injected during week 6 of GnRH antagonist treatment; group 4 was subjected to GnRH antagonist administration for 7 weeks and received TB (200 mg/animal) during week 6. Under GnRH antagonist treatment alone serum concentrations of testosterone were suppressed. TB maintained testosterone levels two- to fourfold above baseline levels in groups 3 and 4 and prevented the recovery of LH secretion for about 20 weeks after GnRH antagonist withdrawal, whereas inhibin levels increased significantly from week 8 onwards. Group 2 animals were azoospermic during weeks 12-18 of GnRH antagonist administration. The TB-replaced groups developed azoospermia or became severely oligozoospermic. Quantitation of cell numbers by flow cytometry during weeks 6 and 18 revealed that TB (groups 3 and 4) had prevented a further decline of germ cell production compared with group 2 but had maintained the spermatogenic status present at week 6 (onset of TB substitution). All inhibitory effects of cetrorelix and/or TB were reversible after cessation of treatment. These findings demonstrate that cetrorelix reversibly inhibits spermatogenesis in a non-human primate model. Although TB maintained the GnRH antagonist-induced suppression of spermatogenesis, azoospermia was not achieved. This latter effect may reflect either a direct spermatogenesis-supporting effect of the high dose of TB or the partial recovery of inhibin secretion (indirectly reflecting FSH secretion) or a combination of both.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

A novel microperfusion system for the long-term local supply of drugs to the inner ear: implantation and function in the rat model.

Local therapy is practiced for middle and inner ear diseases but is usually restricted to cases of ear drum perforation or repeated invasive intratympanic drug application. Perfusion of drugs on the round window or through the scalae of animals using a pump system suggests that the chronic local drug treatment might also be feasible in humans. However, drug delivery systems that are currently on the market involve repeated reimplantation if they are to be used for long-term drug supply. A bone-anchored, totally implantable micro-drug delivery system (MDS) for patient-controlled drug supply has been developed [Lehner et al., 1997]. In this study, we show the first successful long-term in vivo test of the MDS micro-pump in rats. The process of implantation and first functional tests will be described. The biomaterial used to manufacture the delivery system did not cause any inflammation reaction in any of the 9 animals successfully implanted. After activation of the micro-pump, the drug reservoir and port was found to be fluid-tight. Bolus applications of tetrodotoxin (TTX) to the round window induced a transient decrease of evoked brainstem responses. In 2 animals which carried the MDS for more than 8 months the proper functioning of the pumping device was examined in a 2-3 week interval over a 3 month period. The MDS can be autoclaved even after long-term implantation and can then be reused for subsequent implantations. Designed for life-long implantation in humans, the demonstration of an effective long-term drug supply to the inner ear using the MDS provides an encouraging first step towards future long-term drug treatment of the inner ear in humans.

Administration, Topical↗