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Biomedical subjects

H Bleckmann

Publications and source records attributed to H Bleckmann.

At least 19 recordsLinked to original sources
PubMed2006

[Cataract extraction including posterior chamber lens implantation in the treatment of acute glaucoma].

OBJECTIVE: The aim of this study was to compare phacoemulsification in eyes with angle-closure glaucoma to the partner eyes with or without iridectomy or laser iridotomy, respectively. METHODS: Twelve eyes with an elevated intraocular pressure due to an angle closure that were treated by phacoemulsification and IOL implantation were compared with 12 partner eyes with narrow angle and iridectomy or iridotomy without intraocular pressure elevation and cataract extraction. The average follow-up period was 15.7+/-2.1 months. RESULTS: The average intraocular pressure in eyes with angle-closure glaucoma was 54.1+/-14.7 mmHg and in the partner eyes 22.4+/-8.6 mmHg preoperatively. Follow-up pressure was 19.3+/-2.0 mmHg in eyes with angle-closure glaucoma and 18.8+/-1.5 mmHg in the partner eyes. CONCLUSION: Primary cataract extraction including posterior chamber lens implantation into eyes with angle-closure glaucoma reduced intraocular pressure to normal levels, increased visual acuity, and decreased the number of antiglaucomatous drugs. Eyes with angle-closure glaucoma do not respond differently to phacoemulsification and lens implantation compared to eyes with narrow angle without pressure elevation during and after phacoemulsification.

Aged↗
PubMed2005

The spitting behavior of two species of spitting cobras.

Spitting cobras defend themselves by spitting their venom in the face of a harasser. Although it is common belief that spitting cobras direct their venom at the eyes of an aggressor, this has never been investigated. Here, we show that the spitting act of cobras (Naja nigricollis and N. pallida) can readily be triggered by a moving human face or by a moving real size photo of a human face. In contrast, a stationary human face (real or photo) or a moving or stationary human hand does not trigger the spitting act. If threatened, spitting cobras aim their venom, ejected either in two distinct jets (N. pallida) or in a fine spray (N. nigricollis), either between the eyes or at one eye. In both cobra species investigated, the width and height of the area hit by the venom was independent of eye distance (test range 5.5 cm and 11 cm). During the spitting act the cobras performed fast undulating head movements that lead to a larger distribution of their venom. This behavior increases the probability that at least one eye of the aggressor is hit.

Animals↗
PubMed2005

Preliminary results after implantation of four AlphaCor artificial corneas.

PURPOSE: The purpose was to evaluate the validity of implantation of the artificial cornea (AlphaCor) in human corneas considered too high risk for penetrating keratoplasty with donor tissue. METHODS: Four keratoprostheses, made from poly(2-hydroxyethyl methacrylate) (PHEMA) with a porous skirt and a transparent optical part, were implanted into the cornea of four patients. Keratocytes invading the skirt provide a watertight fixation with the scarred corneal tissue. Deep to the clear optical part, the posterior corneal lamella was excised to a diameter of 3.5 mm before the device was implanted, and the anterior lamella was trephined similarly 3 months after AlphaCor implantation. RESULTS: The eyes selected to receive an artificial cornea had significant neovascularisation, and 0-3 previous failed grafts. Follow-up for 6 months revealed best visual acuity between 20/400 and 20/50. Factors limiting the visual acuity outcome were optic atrophy and age-related macular disease. One patient underwent an extracapsular cataract extraction after the device was implanted, as a senile cataract was then noted. One complication occurred, a central corneal stromal melt, which was managed by covering with a 9-mm donor lamella. CONCLUSION: The flexible device AlphaCor may provide a substitute for donor corneal tissue in desperate cases. Advantages include the simple implantation technique, which avoids trauma to the surrounding structures. Visual acuity results may be limited by pre-existing pathology, but it appears that a patient's visual potential can be achieved. Further follow-up to exclude long-term complications is required.

Adult↗
PubMed2004

Nature as a model for technical sensors.

Nature has developed a stunning diversity of sensory systems. Humans and many animals mainly rely on visual information. In addition, they may use acoustic, olfactory, and tactile cues for object detection and spatial orientation. Beyond these sensory systems a large variety of highly specialized sensors have evolved. For instance, some buprestid beetles use infrared organs for the detection of forest fires. The infrared sensors of boid and crotalid snakes are used for prey detection at night. For object detection and spatial orientation many species of nocturnal fish employ active electrolocation. This review describes certain aspects of the detection and processing of infrared and electrosensory information. We show that the study of natural exotic sensory systems can lead to discoveries that are useful for the construction of technical sensors and artificial control systems. Comparative studies of animal sensory systems have the power to uncover at least a small fraction of the gigantic untapped reservoir of natural solutions for perceptive problems.

Animals↗
PubMed2004

Effects of running water on brainstem lateral line responses in trout, Oncorhynchus mykiss, to sinusoidal wave stimuli.

We investigated how single units in the medial octavolateralis nucleus of the rainbow trout, Oncorhynchus mykiss, respond to a 50-Hz vibrating sphere in still and running water. Four types of units were distinguished. Type MI units ( N=16) were flow-sensitive; their ongoing discharge rates either increased or decreased in running water, and as a consequence, responses of these units to the vibrating sphere were masked if the fish was exposed to water flow. Type MII units ( N=7) were not flow-sensitive; their ongoing discharge rates were comparable in still and running water, and thus their responses to the vibrating sphere were not masked. Type MIII units ( N=7) were also not flow-sensitive; nevertheless, their responses to the vibrating sphere were masked in running water. Type MIV units ( N=14) were flow-sensitive, but their responses to the vibrating sphere were not masked. Our data confirm previous findings in the goldfish, Carassius auratus, indicating that the organization of the peripheral lateral line is reflected to a large degree in the medial octavolateralis nucleus. We compare data from goldfish and trout and discuss differences with respect to lateral line morphology, lifestyle and habitat of these species.

Analysis of Variance↗
PubMed2004

[Removal of epikeratophakia lenticules and implantation of intraocular lenses].

Two epikeratophakia lenticules were removed from a highly myopic eye after 13 years and from an aphakic eye after 15 years, respectively. After subsequent refraction compensation, the following results were achieved. Fixation of the epikeratophakia lenticules in the corneal tissue led to a change of the K-value following the removal of the corneal transplants. The refraction compensation can be performed by an intraocular or sclera-fixated lens implantation following the complete closure of the keratotomy wounds. Neither of the two host corneas had undergone an optically relevant change so that the visual acuity was almost unchanged compared to the original data. The light microscopy examination showed a broadening of the corneal epithelium, an unclearly definable basal membrane, as well as a reduction in the number of keratocytes and plaque-shaped alteration of the unstructured matrix. Electron-microscopic examination presented many osmiophilic deposits, which were judged to be catabolic products of apoptotic keratocytes.

Age Factors↗
PubMed2002

Lateral line reception in still- and running water.

The lateral line of fish is composed of neuromasts used to detect water motions. Neuromasts occur as superficial neuromasts on the skin and as canal neuromasts in subepidermal canals. Fibres of the lateral line nerves innervate both. There have been extensive studies on the responses of lateral line nerve fibres to dipole stimuli applied in still water. However, despite the fact that many fish live in rivers and/or swim constantly, responses of lateral line nerve fibres to dipole stimuli presented in running water have never been recorded. We investigated how the peripheral lateral line of still water fish ( Carassius auratus) and riverine fish ( Oncorhynchus mykiss) responds to minute sinusoidal water motions while exposed to unidirectional water flow. Both goldfish and trout have two types of posterior lateral line nerve fibres: Type I fibres, which most likely innervate superficial neuromasts, were stimulated by running water (10 cm s(-1)). The responses of type I fibres to water motions generated by a vibrating sphere were masked if the fish was exposed to running water. Type II fibres, which most likely innervate canal neuromasts, were not stimulated by running water. Consequently, responses of type II fibres to a vibrating sphere were not masked under flow conditions.

Animals↗
PubMed2002

[Bioptic. A refractive surgery procedure for correction of high and extreme myopia].

BACKGROUND: The complete correction of highly or extremely myopic eyes to emmetropia can only be achieved by very few procedures: The combination of implanting phacic intraocular lenses and the use of LASIK (laser in-situ keratomileusis) - Bioptic - makes it possible to achieve this goal to a great extent. PATIENTS AND METHODS: The Bioptic procedure was carried out on 17 eyes of 10 patients. Two weeks after corneal dissection with the Hansatom,an implantable phacic lens (STAAR) was introduced into the posterior chamber and 4 weeks later the residual myopia was treated with LASIK combined with the correction of astigmatic errors. The follow-up time was 10.2 (6.7) months. RESULTS: Preoperative average values of the manifest refraction were -16.22 sph (3.86) with 1.40 cyl (1.30) which changed to -3.85 sph (2.73) with -1.50 cyl (0.87) after implantation of an ICL trade mark into the posterior chamber. Visual acuity increased from uncorrected hand motion to 0.13 (0.10) and corrected from 0.53 (0.19) to 0.63 (0.19). The refraction of implanted ICLs trade mark was 14.6 dpt (1.1). Following the LASIK procedure the uncorrected visual acuity improved to 0.68 (0.16) and fully corrected to 0.79 (0.20). The final refraction measured +0.16 sph (0.67) with -0.48 cyl (0.25). The keratectomy depth was 80.63 -m (26.9) and the optical zone showed a horizontal distance of 6.28 mm (0.39). CONCLUSION: Bioptic is able to correct highly and extremely myopic eyes with the combination of phacic lenses and subsequent LASIK. A concomitant astigmatism can be corrected up to 2.5 dpt simultaneously. With the combination of both procedures,the optical zone can be enlarged. Keeping in mind that phacic lenses reveal a constant refraction after a few days and also that LASIK is refractively safe in low myopia of -4 dpt to -5 dpt, it can be expected that the refractive deviation following the Bioptic procedure is low.

Astigmatism↗
PubMed2001

Hydrodynamic trail-following in harbor seals (Phoca vitulina).

Marine mammals often forage in dark or turbid waters. Whereas dolphins use echolocation under such conditions, pinnipeds apparently lack this sensory ability. For seals hunting in the dark, one source of sensory information may consist of fish-generated water movements, which seals can detect with their highly sensitive whiskers. Water movements in the wake of fishes persist for several minutes. Here we show that blindfolded seals can use their whiskers to detect and accurately follow hydrodynamic trails generated by a miniature submarine. This shows that hydrodynamic information can be used for long-distance prey location.

Acoustics↗
PubMed2001

[Scanning microscopy and immunohistochemical studies of an explanted phacic posterior chamber lens (ICL-M, STAAR)].

OBJECTIVE: This study was performed to find out if an explanted phacic collamer IOL (ICL/STAAR) showed structural or surface quality changes after an intraocular implantation. MATERIAL AND METHODS: We explanted an ICL 6 months after implantation and compared it to a new reference lens using scanning electron microscopy and immunohistochemical investigations. RESULTS: The explanted ICL showed no changes in comparison to a new ICL except for a coating with an unidentified material. Both the new and explanted ICL presented grooves on the surface and superficial holes of unknown origin measuring roughly 10 mu. Neither pigment nor macrophages could be found on the explanted lens. Although the lens material contained 0.1% collagen, the immunohistochemical staining for collagen was negative. CONCLUSIONS: The collagen content of the ICL could not be proven using immunohistochemistry. No changes were found between the new and the explanted lens, except for a coating of the explanted lens with an unidentified material.

Collagen↗
PubMed2000

The ability of Rhodnius prolixus (Hemiptera; Reduviidae) to approach a thermal source solely by its infrared radiation.

The ability of the haematophagous bug Rhodnius prolixus to approach a pure IR source only by its long-wave infrared radiation (IR) was investigated. To exclude any heated air from reaching the bug a cooled IR-transmitting window was placed between the IR-source (a Peltierelement heated to 35 degrees C) and the bug. Starved bugs were tested under invisible short-wave IR illumination (lambda<1 µm) in order to exclude also any visual cues. The number of bugs approaching the IR-source was significantly increased compared to the controls in which the IR-source was turned off (chi(2)-test, P<0.01). Our results show that Rhodnius prolixus can use infrared stimuli to find a host.

Journal Article↗
PubMed2000

A new type of infrared organ in the Australian "fire-beetle" Merimna atrata (Coleoptera: Buprestidae).

The Australian buprestid beetle Merimna atrata (Coleoptera: Buprestidae) approaches forest fires because its larvae develop in freshly burnt wood. So far nothing is known about possible sensory systems enabling the beetles to detect fires and to cope with the thermal environment close to the flames. We found that M. atrata has two pairs of infrared (IR) organs on the ventrolateral sides of the abdomen. Each IR organ consists of a specialized IR-absorbing area which is innervated by one thermosensitive multipolar neuron. The primary dendritic branches ramify into more than 800 closely packed terminal endings which contain a large number of mitochondria. We called the special morphology of the dendritic region a terminal dendritic mass. The type of IR receptor found in M. atrata is unique in insects and can best be compared with the IR organs of boid snakes.

Abdomen↗
PubMed2000

Responses of the infrared sensilla of Melanophila acuminata (Coleoptera: Buprestidae) to monochromatic infrared stimulation.

The pit organs of the beetle Melanophila acuminata were stimulated with monochromatic infrared radiation using a continuous wave CO overtone infrared laser. Best sensitivity was in the wavelength range 2.8-3.5 micron. In this range a stimulus intensity of 14.7 mW cm(-2) was sufficient to generate single action potentials. At a wavelength of 5 microm receptor performance significantly decreased. An increase in stimulus intensity caused a decrease in response latency and an increase in the number of action potentials elicited. At a given wavelength (3.4 microm) the dynamic amplitude range of action potential responses covered 12 dB. At high stimulus intensities (94.2 mW cm(-2)) a stimulus duration of 4 ms was sufficient to generate one to two action potentials and a stimulus duration of 60 ms already caused response saturation (with up to nine action potentials). In a repetitive stimulus regime distinct receptor potentials were visible up to a frequency of 600 Hz.

Action Potentials↗
PubMed2000

The ageing of the low-frequency water disturbances caused by swimming goldfish and its possible relevance to prey detection.

Wakes caused by swimming goldfish (Carassius auratus) were measured with a particle image velocimetry system and analyzed using a cross-correlation technique. Particle velocities in a horizontal plane (size of measuring plane 24 cmx32 cm or 20 cmx27 cm) were determined, and the vorticity in the plane was derived from these data. The wake behind a swimming goldfish can show a clear vortex structure for at least 30 s. Particle velocities significantly higher than background noise could still be detected 3 min after a fish (body length 10 cm) had passed through the measuring plane. Within this time span, the lateral spread of fish-generated wakes could exceed 30 cm for a 10 cm fish and 20 cm for a 6 cm fish. Measurements in a man-made open-air pond showed that water velocities in a quasi-natural still water environment can be as small as 1 mm s(-)(1). Background velocities did not exceed 3 mm s(-)(1) as long as no moving animal was present in the measuring plane. The possible advantage for piscivorous predators of being able to detect and analyze fish-generated wakes is discussed.

Aging↗
PubMed1999

Effect of temperature and calcium on transneuronal diffusion of DiI in fixed brain preparations.

The lipophilic tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was used to label neuronal pathways in fixed goldfish brains. The normal procedure involving 4% paraformaldehyde as a fixative, applying DiI and storing the brain in the fixative at 40 degrees C resulted in many cases in a rather diffuse labeling of fiber pathways and the occurrence of transneuronally labeled cells and fibers. We found that calcium and heat both facilitate the diffusion of DiI out of membranes in vibratome sections. We modified the protocol by adding the calcium binding substance ethylenediamine tetraacetate to all solutions and incubated at room temperature. This improved the sharpness of labeled structures and eliminated the transneuronal labeling in our material. Although transneuronal transport of the tracer may still occur under certain circumstances, the present modification of the DiI staining procedure substantially increased the staining quality and reproducibility and decreased the occurrence of transneuronal labeling.

Animals↗
PubMed1999

Comparison of 3 microkeratomes used for keratomileusis in situ in a swine model.

PURPOSE: To determine whether the choice of instrumentation affects the quality and precision of corneal cuts during keratomileusis in situ. SETTING: Schlosspark-Klinik, Ophthalmology Department, Berlin, Germany. METHODS: The study was performed on 54 swine eyes and 3 human corneas using microkeratomes manufactured by Steinway, SCMD, and Eye Technology. The study results are based on micrometric and pachymetric measurements of actual slice thickness. Slice thickness and slice quality were evaluated using scanning electron microscopy. Three slices of defined thickness were made with each keratome. RESULTS: There was no significant difference in the degree of deviation of slice thickness from the intended value with any keratome. The micrometric measurement of the first lamella documented significantly less variation in the actual measurements achieved with the Eye Technology device (P < .01). All keratomes tested demonstrated a high degree of congruence between the intended values and those achieved in mean thickness and circularity of the cut. The Eye Technology device demonstrated the best profile and the cleanest margins, followed by the SCMD keratome, which caused minimal distortion of the stroma. The Steinway keratome has a high amplitude and produced 25 microns tears in the margins perpendicular to the plane of the cut. CONCLUSION: There was no overall difference in cutting precision between the 3 tested keratomes. High-oscillation frequency of the blade resulted in a smooth cut.

Animals↗