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Biomedical subjects

H Bleckmann

Publications and source records attributed to H Bleckmann.

At least 55 records · Page 3Linked to original sources
PubMed1990

Implantation of posterior chamber lenses in eyes with phakodonesis and lens subluxation.

Unilateral posterior chamber intraocular lens (IOL) implantation was performed after phacoemulsification or extracapsular cataract extraction in ten of 11 patients with phakodonesis or lens subluxation, which was bilateral in two cases. To facilitate placement of the IOL, the anterior capsule was opened with a YAG laser in nine patients. Intraoperative vitrectomy was performed in two patients, and posterior chamber IOL implantation was accomplished with fixation in the ciliary sulcus. Postoperative follow-up studies failed to demonstrate significant decentration or dislocation of the IOLs. Phakodonesis and lens subluxation are no longer considered absolute contraindications to implantation of posterior chamber IOLs.

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PubMed1990

Physiology of lateral-line mechanoreceptors in a teleost with highly branched, multiple lateral lines.

The physiological aspects of the lateral line of Xiphister atropurpureus--a teleost with multiple, highly branched lateral-line canals on each body side--were investigated. In terms of sensitivity and frequency response, the lateral line of Xiphister is similar to simple, unbranched lateral-line canals. For both the dorsal and the medial trunk canal the lowest displacement threshold is in the frequency range of 100-150 Hz. Within this range, a peak-to-peak displacement of 0.2-1.0 microns is sufficient to evoke a neural response. For the stimuli applied, both the dorsal and the medial lateral-line canals had well-defined, but largely overlapping, receptive fields. A comparison of the experimental results with theoretical calculations showed that the trunk lateral line of Xiphister responds in proportion to the sum of the radial and angular water displacement components caused by a vibrating sphere. Our calculations further predict that multiple lateral lines cause a substantial increase in receptive-field size if nearby objects create water displacements that are barely above threshold and/or if a stimulus is masked by background noise.

Animals↗
PubMed1990

[Raynaud syndrome following timolol-containing eyedrops].

It has been well known for a long time that beta-adrenoreceptor-blocking substances may cause Raynaud's phenomenon in hands and feet if applied orally or parenterally. Nevertheless, vasospastic phenomenons of the "Raynaud"-type have never before been described following local administration. Now a Raynaud's syndrome found in a 58-year old patient, who had been treated for glaucoma with timolol (Chibro-Timoptol-eyedrops), leaves no doubt that there is a risk of systemic vasospasm in ocular application, too. An exposition test was carried out to prove the connection between the application of timolol eyedrops and Raynaud's syndrome. It did reveal that an initially already marginally prolonged warm-up time after exposition to cold water, as measured in the thermographic test, did relevantly get worse after timolol application. At the same time, no change in arterial systolic finger blood pressure could be demonstrated using Doppler sonography. The induction of Raynaud's syndrome by beta-adrenoreceptor-blocking eyedrops may depend on an individual disposition.

Glaucoma↗
PubMed1989

Cell groups afferent to the telencephalon in a cartilaginous fish (Platyrhinoidis triseriata). A WGA-HRP study.

Cell groups projecting to the telencephalon in the guitarfish Platyrhinoidis triseriata were localized by retrograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) from injections into the basal forebrain bundle. Labeled neurons were observed bilaterally in the dorsal and ventral thalamus, hypothalamus, mesencephalon and rostral rhombencephalon. A comparison of the labeled cell groups to those which project to the telencephalon in terrestrial vertebrates reveals many parallels, including position in the brain, similarities in the afferent connections and immunoreactivity. Further data are needed to decide whether the cell groups in Platyrhinoidis are homologous or homoplasious to their counterparts in land vertebrates.

Animals↗
PubMed1989

Physiology of lateral line mechanoreceptive regions in the elasmobranch brain.

The physiology of mechanoreceptive lateral line areas was investigated in the thornback guitarfish, Platyrhinoidis triseriata, from medulla to telecephalon, using averaged evoked potentials (AEPs) and unit responses as windows to brain functions. Responses were analysed with respect to frequency sensitivity, intensity functions, influence of stimulus repetition rate, response latency, receptive field (RF) organization and multimodal interaction. 1. Following a quasi-natural vibrating sphere stimulus, neural responses were recorded in the medullary medial octavolateralis nucleus (MON), the dorsal (DMN) and anterior (AN) nucleus of the mesencephalic nuclear complex, the diencephalic lateral tuberal nucleus (LTN), and a telencephalic area which may correspond to the medial pallium (Figs. 2, 3, 13, 14, 15, 16). 2. Within the test range of 6.5-200 Hz all lateral line areas investigated responded to minute water vibrations. Best frequencies (in terms of displacement) were between 75 and 200 Hz with threshold values for AEPs as low as 0.005 microns peak-to-peak (p-p) water displacement calculated at the skin surface (Fig. 6). 3. AEP-responses to a vibrating sphere stimulus recorded in the MON are tonic or phasic-tonic, i.e., responses are strongest at stimulus onset but last for the whole stimulus duration in form of a frequency following response (Fig. 3). DMN and AN responses are phasic or phasic-tonic. Units recorded in the MON are phase coupled to the stimulus, those recorded in the DMN, AN or LTN are usually not (Figs. 5, 8, 9). Diencephalic LTN and telencephalic lateral line responses (AEPs) often are purely phasic. However, in the diencephalic LTN tonic and/or off-responses can be recorded (Fig. 11). 4. For the frequencies 25, 50, and 100 Hz, the dynamic intensity range of lateral line areas varies from 12.8 to at least 91.6 dB (AEP) respectively 8.9 and 92 dB (few unit and single unit recordings) (Fig. 7). 5. Mesencephalic, diencephalic, and telecephalic RFs, based on the evaluation of AEPs or multiunit activity (MUA), are usually contralateral (AN and LTN) or ipsi- and contralateral (telencephalon) and often complex (Figs. 10, 12, 16). 6. In many cases no obvious interactions between different modalities (vibrating sphere, electric field stimulus, and/or a light flash) were seen. However, some recording sites in the mesencephalic AN and the diencephalic LTN showed bimodal interactions in that an electric field stimulus decreased or increased the amplitude of a lateral line response and vice versa (Fig. 13 B).

Action Potentials↗
PubMed1989

[Light and electron microscopy of the human, anterior cataract capsule].

Forty-three anterior lens capsules and epithelium from cataract patients extracted during extracapsular cataract surgery were examined by light microscopy and morphometry. An additional 15 lens capsules were examined by transmission electron microscopy. Morphometric examination revealed a positive correlation between age and the lens capsule thickness of 0.08 micron/year. The medium lens-capsule thickness of a 65-year-old human being was 8.65 microns. Light microscopy of cataractous anterior lens capsule and epithelium demonstrated proliferative changes with a multilamellar arrangement of the lens epithelial cells and an increase in the pleomorphic appearance of the cell and nucleus. Examination of the lens capsule revealed intracapsular foamy and vacuolic deposits with a localized splitting of the lens capsule. Transmission electromicroscopy established certain aspects of the lens capsule and epithelium. We found intracytoplasmatic single cilia and fibrillar intracytoplasmatic structures, with a diameter of 12-20 nm arranged in a pseudocrystalline fashion. The anterior lens capsule demonstrated similarly localized deviations from the normal homogeneous structure of type IV collagen, resulting in intracapsular deposition of fibrillar material. These observations suggest that cataractogenesis is associated with ultrastructural metaplastic and degenerative alteration of the lens epithelium and capsule.

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PubMed1988

A lateral line analogue in cephalopods: water waves generate microphonic potentials in the epidermal head lines of Sepia and Lolliguncula.

Many cephalopods have lines of ciliated cells on their head and arms. In the cuttlefish Sepia and the squid Lolliguncula, electrophysiological recordings clearly identify these epidermal lines as an invertebrate analogue to the mechanoreceptive lateral lines of fish and aquatic amphibians and thus as another example of convergent evolution between a sophisticated cephalopod and vertebrate sensory system. Stimulation of the epidermal lines with local water displacements, generated by a vibrating sphere, causes receptor potentials that have many features known from lateral line microphonic potentials. The minimal threshold of the head lines is 0.2 micron peak-to-peak water displacement (calculated at the skin surface) at 75-100 Hz.

Action Potentials↗
PubMed1988

[Epikeratophakia--a new procedure in refractive surgery of the cornea].

The epikeratophakia operation developed by Kaufman represents an additional procedure in refractive surgery of the cornea. The application of individually prepared corneal tissue lenticles on top of the recipient cornea can be used in refractive (Keratolens) and tectonic (Keratopatch) problems. The most important indication for this operation is monocular aphakia in which a contact lens is not tolerated. As is pointed out in the literature, postoperative visual acuity is reduced in some patients by interface densities and incomplete epithelialization. The advantage of this newly developed method is that it offers the ophthalmic surgeon a novel procedure for the indications mentioned which does not involve any major investment in apparatus.

Cornea↗
PubMed1987

Prey localization by surface wave ray-tracing: fish track bugs like oceanographers track storms.

Surface-feeding fish accurately determine direction and distance to the center of a concentric wave stimulus, even if only a single, short lasting wave train is presented. It has been suggested that one cue used by these fish to localize the wave center is the distance dependent frequency modulation of the initial part of a wave stimulus. Here we show how the distance information contained in the fractional frequency change of a capillary wave group can be decoded. We suggest that wave source localization in surface-feeding fish in part is based on a principal similar to that used by oceanographers to track storms by the frequency change of forerunners of swell.

Animals↗
PubMed1987

The lateral line mechanoreceptive mesencephalic, diencephalic, and telencephalic regions in the thornback ray, Platyrhinoidis triseriata (Elasmobranchii).

Central lateral line pathways were mapped in the thronback ray, Platyrhinoidis triseriata, by analyzing depth profiles of averaged evoked potentials (AEPs), multiunit activity (MUA), and single unit recordings. Neural activity evoked by contra- or ipsilateral posterior lateral line nerve (pLLN) shock is restricted to the tectum mesencephali, the dorsomedial nucleus (DMN) and anterior nucleus (AN) of the mesencephalic nuclear complex, the posterior central thalamic nucleus (PCT), the lateral tuberal nucleus of the hypothalamus, and the deep medial pallium of the telencephalon (Figs. 2, 3, 4, 6, 7). Neural responses (AEPs and MUA) recorded in different lateral line areas differ with respect to shape, dynamic response properties, and/or latencies (Figs. 9, 10 and Table 1). Ipsilaterally recorded mesencephalic and diencephalic AEPs are less pronounced and of longer latency than their contralateral counterpart (Fig. 9 and Table 1). In contrast, AEP recorded in the telencephalon show a weak ipsilateral preference. If stimulated with a low amplitude water wave most DMN, AN, and tectal lateral line units respond in the frequency range 6.5 Hz to 200 Hz. Best frequencies (in terms of least displacement) are 75-150 Hz with a peak-to-peak water displacement of 0.04 micron sufficient to evoke a response in the most sensitive units (Fig. 11A, B, C). DMN and AN lateral line units have small excitatory receptive fields (RFs). Anterior, middle, and posterior body surfaces map onto the rostral, middle, and posterior brain surfaces of the contralateral DMN (Fig. 12). Some units recorded in the PCT are bimodal; they respond to a hydrodynamic flow field--generated with a ruler approaching the fish--only if the light is on and the eye facing the ruler is left uncovered (Fig. 13).

Animals↗
PubMed1987

[Treatment with betaxolol and placebo eyedrops in patients with glaucoma and reactive airway diseases].

The study communicated here was designed to evaluate the absence of pulmonary beta-blockade as detected by a histamine provocation in betaxolol-treated patients suffering from open-angle glaucoma and coexisting obstructive airway disease. The study was a randomized, double-masked crossover trial, comparing betaxolol 0.5% ophthalmic solution and placebo. Ten patients (4 male, 6 female) were eligible by demonstrating baseline off-therapy IOP values exceeding 22 mmHg and a FEV1 value that was reduced by 15% to 20% following histamine provocation. After an appropriate washout period, baseline IOP and pulmonary function (FEV1, FVC) were tested. One drop of test medication (betaxolol or placebo) was instilled in both eyes; tonometry and a pulmonary function test were performed 90 minutes later. The patients then underwent a histamine provocation test. The concentration of histamine necessary to reduce FEV1 and FVC by 15% to 20% was recorded. The IOP was significantly reduced in patients treated with betaxolol, but not in those given placebo. FEV1 and FVC values 90 minutes after treatment with betaxolol or placebo were not significantly different from baseline values. After histamine provocation the FEV1 was, as expected, significantly decreased from baseline (15% to 20%) in both treatment groups. There was no statistical difference in the histamine concentration necessary to reduce the FEV1 by 15% to 20% between placebo (5.60 mg/ml) and betaxolol (5.25 mg/ml) treatments. This demonstrates that betaxolol has no pulmonary beta-blocking effect. Our study suggests that ophthalmic treatment with betaxolol in patients with glaucoma and obstructive airway disease enhances pulmonary safety due to the beta-1 cardioselective action of the drug.

Adrenergic beta-Antagonists↗
PubMed1986

Experimental endothelial lesions by means of an ultrasound phacoemulsificator.

The current study deals with experimental use of an ultrasound generator for phacoemulsification and its effect on bovine corneal endothelium. The extent of the endothelial defect was defined by staining cell borders and nuclei. Histological examination showed that endothelial cells on the edge of a defect had no nuclei and were partially detached from the Descemet's membrane in some cases. Quantitative determinations of endothelial cell defects demonstrated the effects of distance from the generator (1, 2, and 3 mm) as well as duration of exposure. At 2 and 3 mm, addition of sodium hyaluronate (Healon) to the incubation medium was associated with a statistically significant reduction in size of the endothelial defect.

Animals↗
PubMed1986

[Therapeutic consequences of glaucoma treatment with different beta blockers in patients with obstructive respiratory tract diseases].

In patients in whom chronic obstructive bronchial disease and chronic glaucoma had been diagnosed, the most important ventilation parameters and intraocular pressures were investigated in a double-blind cross-over study. The airway resistance, the forced expiratory volume within the first second, the thoracic volume, and the mean expiratory flow in these patients exhibited significant differences after treatment with non-cardioselective beta-blocking agents, depending on the beta-receptor stimulating action of this ophthalmic solution (Pindolol 1% eye drops) or without any intrinsic sympathicomimetic action (Metipranolol 0.6% eye drops). There was no fundamental difference in the intraocular pressure-lowering effect of these two locally applied beta-blocking solutions. This study implies that when selecting a beta-blocking ophthalmic solution for anti-glaucoma treatment, the existence of an ISA effect of these eye drops is relevant only to avoid systemic side effects such as bronchopulmonary obstruction.

Adrenergic beta-Antagonists↗
PubMed1985

[Posterior chamber lenses and glaucoma].

The intraocular pressure of 100 glaucomatous eyes was followed up after extracapsular cataract extraction with implantation of a posterior chamber lens. The cataract extraction techniques employed were KPE (33), ECCE (41), ECCE with iridotomy and iris suture (15), and ECCE with iridotomy and iris suture after previous fistulizing procedures. The follow-up examinations were performed 5.5 and 16.4 months after surgery. About 1.5 years after the cataract extraction the intraocular pressure of all eyes had decreased on average by 2-3 mm Hg. The number of drug-dependent eyes decreased to 30% as compared to the situation prior to extraction. Only those patients who had undergone ECCE with iridoplasty after previous fistulizing procedures had a slightly increased, though not statistically significant pressure elevation. The proportion of drug-dependent patients in this group was also almost the same as before surgery. Follow-up at 5.5 and 16.4 months revealed no major differences in the pressure level or the number of drug-dependent glaucomatous eyes.

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