Biomedical subjects

H Bleckmann

Publications and source records attributed to H Bleckmann.

At least 37 records · Page 2Linked to original sources

PubMed1997

Subdivisions of the olfactory system in the sterlet Acipenser ruthenus.

Subdivisions of the olfactory system of the sterlet Acipenser ruthenus were investigated by means of horseradish peroxidase (HRP) injections into the nose, and by soybean agglutinin binding studies. With both methods primary olfactory fibers were labeled which projected to the ventral part of the glomerular layer of the olfactory bulb. The dorsal part of the olfactory bulb did not bind soybean agglutinin, however, even though HRP tracing showed primary olfactory fibers in that area. This confirms earlier morphological studies which claim the existence of distinct subdivisions of the olfactory system in the sturgeon. The lack of soybean agglutinin binding in the dorsal part of the olfactory bulb suggests, however, that this part is not homologous with the accessory olfactory system of tetrapods.

Animals↗

PubMed1997

[Occlusion of finger arteries and thrombotic angiopathy of the retina during adjuvant tamoxifen therapy of a mammary carcinoma].

HISTORY AND CLINICAL FINDINGS: A 57-year-old woman had undergone partial mastectomy with subsequent radiotherapy for cancer of the breast. About 8 weeks after starting adjuvant treatment with tamoxifen (20 mg daily) pain, cooling and livid discoloration developed in her fingers and toes. Skin necroses over finger tips occurred and she was found to have visual field defects and double images. INVESTIGATIONS: There was no clinical or laboratory evidence of recurrence of the breast cancer. Tests of clotting and for inflammatory disease and complement levels were within normal limits. The antinuclear antibody titre was low (1:320) and the measured value of the rheumatoid factor reached the fourfold of normal level. Ophthalmoscopy revealed signs of retinal ischaemia, unilateral papilloedema, reduced visual acuity, visual field and abduction weakness. Duplex sonography and angiography demonstrated multiple occlusions of the finger arteries. TREATMENT AND COURSE: After tamoxifen had been discontinued and prostaglandin E1 administered (40 micrograms over one hour twice daily for 21 days) the symptoms rapidly and markedly improved, the necroses of the finger tips healed and the ophthalmoscopic changes regressed almost completely. CONCLUSION: Tamoxifen, by inducing thrombophilia, can cause thromboembolic occlusions of peripheral arteries, and must in that case be discontinued.

Alprostadil↗

PubMed1997

Sensitivity of central units in the goldfish, Carassius auratus, to transient hydrodynamic stimuli.

This study describes the discharges of central units in the medulla of the goldfish, Carassius auratus, to hydrodynamic stimuli received by the lateral line. We stimulated the animal with a small object moving in the water and recorded activity of 85 medullary lateral line units in response to different motion directions and to various object distances, velocities, accelerations and sizes. All but one unit increased discharge rate when the moving object passed the fish laterally. Five response types were distinguished based on temporal patterns of unit responses. Ten units were recorded which encoded motion direction by different temporal discharge patterns. In general, discharge rates decreased when object distance was increased and when object speed was decreased. When object size was decreased, discharge rates decreased systematically in one group of units, but they were comparable for all but the smallest object tested in a second group of units. Units responded about equally well whether an object was moved at a constant velocity or was accelerated when it passed the fish. The data indicate that medullary lateral line units in the goldfish can encode motion direction but are not tuned to other aspects of an object moving in the water. The functional properties of units in the medulla of goldfish are similar to those reported for medullary units in the catfish Ancistrus sp., suggesting that the central mechanisms for processing complex hydrodynamic stimuli may be quite similar in fish species that occupy habitats with different hydrodynamic conditions.

Animals↗

PubMed1996

Visual results of progressive multifocal posterior chamber intraocular lens implantation.

PURPOSE: To evaluate corrected and uncorrected near, intermediate, and distance visual acuities in eyes with a progressive multifocal intraocular lens (IOL) and to determine the effect of the lens on contrast sensitivity. SETTING: Multicenter study. METHODS: This prospective study comprised 59 eyes that had uneventful cataract surgery and implantation of a progressive multifocal IOL at three study centers. Uncorrected and corrected near, intermediate, and distance visual acuities were measured, as was contrast sensitivity at different frequencies. One year results are reported. Patient satisfaction was assessed using a subjective questionnaire. RESULTS: Distance visual acuity improved from 0.13 Snellen lines uncorrected and 0.23 with best correction preoperatively to 0.77 and 0.96 lines, respectively, postoperatively. Uncorrected preoperative near acuity was 13.28 Jaeger lines and best corrected acuity, 8.93 lines. These improved to 4.75 and 2.69 lines, respectively. The differences between visual acuity at intermediate distances and best distance and near acuities were not significant. Patient satisfaction was highest with vision under good light conditions and when viewing larger objects. CONCLUSION: Visual performance with the multifocal progressive IOL was adequate at various distances without additional correction. It was less satisfactory under poor light conditions.

Accommodation, Ocular↗

PubMed1994

Functional results of posterior chamber lens implantation with scleral fixation.

Recently, scleral fixation has been used in posterior chamber intraocular lens implantation in the absence of the posterior capsule. Fixation is achieved with a suture through the ciliary sulcus and sclera at a horizontal or vertical position. To achieve good functional results, the optical portion of the lens must lie on the optical axis. Unilateral lens implantation in the absence of the posterior capsule was performed with scleral fixation in 48 patients. Follow-up ranged from 14 months to 2.6 years. The position of the posterior chamber lens was defined in relation to the limbus and the pupillary margin. There was no evidence of lens decentration in miosis. Under conditions of extreme mydriasis, decentration of less than 1.0 mm was found in four patients; four others had approximately 1.5 mm of decentration. Magnetic resonance imaging was used to determine lens position in some cases. Scleral fixation is a viable alternative for implantation of posterior chamber lenses in the absence of the posterior capsule.

Adult↗

PubMed1994

Sensory activity in the telencephalon of the clawed toad, Xenopus laevis.

In this study data are presented providing evidence that the striatum of the clawed toad, Xenopus laevis, processes mechanosensory, acoustic, and visual information and that multisensory interaction takes place in this telencephalic structure. Multimodal processing as well as the considerable effects of stimulus repetition rate on response amplitudes are in line with the finding that the striatum of Xenopus mediates attentional processes (Traub & Elepfandt, 1990). Further physiological studies are needed to delineate the functional organization of the striatum in amphibians.

Acoustic Stimulation↗

PubMed1994

[Magnetic resonance tomography diagnosis of the posterior chamber lens].

Intraocular lenses were investigated by MRI to obtain information about the quality of this method. In experimental studies, seven lenses of between 0 and 30 diopters were visualized. By MRI it was possible to differentiate the various diameters of lenses. It was not possible to discriminate the material of the intraocular lenses. After these first studies the eyes of two corpses and eight patients were investigated. Because of the resolution of MRI it was possible to tell the diopter of implanted lenses. However, by use of MRI in the regular position, a tilting or decentration of the intraocular lens was demonstrated.

Aged↗

PubMed1993

Pit organs in axolotls: a second class of lateral line neuromasts.

The lateral line system of axolotls (Ambystoma mexicanum) consists of mechanoreceptive neuromasts and electroreceptive ampullary organs. All neuromasts in salamanders are located superficially and are organized into lines that are homologous to canal neuromasts in fishes. Ampullary organs are confined to the head and generally are located adjacent to the lines of superficial neuromasts. Axolotls, however, also possess a third class of receptors; these form restricted patches on the head and are possibly homologous to the superficial pit organs in fishes. In order to test this hypothesis the morphology of the suspected pit organs was examined with scanning electron microscopy, and a number of their physiological properties were determined. Pit organs are approximately half the size of neuromasts and have fewer hair cells, although these hair cells do possess kinocilia and stereocilia like those of neuromasts. Pit organs also possess cupulae and exhibit a pattern of innervation identical to that of neuromasts. Pit organs and neuromasts also exhibit similar rates of spontaneous activity, are excited by weak water currents but not weak electric stimuli, and are not inhibited by magnesium ions. Pit organs appear to have slightly lower rates of spontaneous discharge than neuromasts, however, and have slightly lower displacement thresholds to low frequency wave stimuli. These data support the contention that the pit organs of axolotls constitute a second class of neuromasts homologous to the pit organs of fishes.

Ambystoma mexicanum↗

PubMed1992

Collagel--a new viscoelastic substance for ophthalmic surgery.

A clinical trial comparing the viscoelastic properties of Collagel (human collagen) and Healon (sodium hyaluronate) was performed. Collagel was well tolerated and produced no untoward reaction in the eye. Flare cell measurement was performed during the seven day postoperative period. The initial peak and decline of flare and cell determination showed a similar course in groups treated with Collagel or Healon. A transient increase in intraocular pressure was seen. Endothelial cell loss following surgery was similar in the Collagel and Healon groups. There were no significant differences in intraocular pressure, corneal thickness, endothelial cell density, or visual acuity during the postoperative period. These results suggest that this new viscoelastic substance is comparable to Healon in respect to the parameters described.

Aged↗

PubMed1992

[Spontaneous fracture of an implanted anterior chamber lens].

This report deals with an 83-year-old patient who presented with visual deterioration. The patient had had an intracapsulary extraction with anterior chamber lens implantation. The break in the anterior chamber lens happened without any history of traumatic accident and led to dislocation of the lens and corneal decompensation. Scanning electron microscopy of the break area after explantation of the fragments revealed changes in the break zone that were characteristic of alternating tensile and compressive stress. Localization of the break at the transition of the optical part and the haptic where there is the greatest stress in the material points to insufficient strengthening in this critical part of the intraocular lens.

Aged↗

PubMed1991

Peripheral and central aspects of the acoustic and lateral line system of a bottom dwelling catfish, Ancistrus sp.

The topographical relationship between the swim bladder, the inner ear, and the otic lateral line was studied in the bottom dwelling catfish, Ancistrus sp. In addition, afferent and efferent subcomponents of the eighth and lateral line nerves were labelled with horseradish peroxidase (HRP) or with differently fluorescing dextran amines. The swim bladder of Ancistrus consists of two separate, transversely oriented parts of each of which is connected to the sinus impar of the inner ears via two Weberian ossicles and the perilymphatic sac. The osseous capsula of the ear has two foramina other than the nerve foramina. One is for the sinus impar. The other foramen, which also separates two fluid-filled spaces, exits where the horizontal canal of the ear contacts the otic lateral line. Both the otic and the postotic lateral line canal run deep below the epidermis. Each canal contains a neuromast that is innervated by the middle lateral line nerve. Further caudally, the otic lateral line canal gives rise to the postotic and finally to the truck canal whose nonossified anterior part travels through an ossified chamber that surrounds the swim bladder. Thus the anterior part of each trunk lateral line canal is in contact with a bipartite sound pressure receiver, the swim bladder. Anterior and posterior lateral line afferents terminate ipsilaterally throughout the neuropil of the electroreceptive lateral line nucleus and the mechanoreceptive nuclei medialis and caudalis of the medulla. Middle lateral line afferents terminate between the projection sites of anterior and posterior lateral line afferents. Some primary mechanosensory anterior lateral line nerve fibers continue into the ipsilateral eminentia granularis and the valvula cerebelli. In the electroreceptive lateral line projection, anterior lateral line fibers terminate more medially and posterior fibers more laterally. This somatotopy is not as clear-cut in the mechanosensory lateral line. Afferents of the sacculus and the lagena terminate predominantly in the saccular nucleus. Afferents of the utriculus, the horizontal canal, and the anterior vertical canal terminate in the magnocellular vestibular nucleus and in the medial octavolateral nucleus. The projection sites of the anterior part and the posterior part of the eighth nerve show little overlap. Eighth nerve projections to the valvula cerebelli are less prominent than the projections from the lateral line. Eighth nerve and lateral line nerve efferents arise from a common nucleus, the octavolateralis efferent nucleus. Axons of efferent cells may divide to supply two or more branches of the eighth nerve and some axons supply both lateral line and eighth nerve endorgans.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗

PubMed1991

Influence of the strength, drop size and viscosity of metipranolol eye drops on the concentration of the substance in human aqueous humour.

Concentrations of metipranolol were determined in the aqueous humour of patients undergoing cataract surgery. At 30 min before the operation, patients were given 20- or 30 microliters drops of 0.1% or 0.3% metipranolol solutions with a viscosity of 7.5 cP or drops (20 or 30 microliters) of a 0.3% solution with a viscosity of 1.5 cP. Samples of the aqueous humour were obtained at the beginning of the cataract operation, and desacetyl-metipranolol content was determined by means of gas chromatography and mass spectroscope. The Wilcoxon signed-rank test and Jonckheere's method were used for evaluation of the results. A 3-fold increase in the strength of metipranolol was associated with an approx. 8-fold increase in the concentration of metabolite found in the aqueous humour. Drop size had no apparent effect on the concentration of this substance in the aqueous humour, but viscosity had a significant influence when large drops were applied. An increase in the amount of metipranolol applied as eye-drops was associated with an increase in the intraocular concentration of the metabolite.

Administration, Topical↗

PubMed1991

Influence of the concentration of metipranolol eye drops on the drug concentration in human aqueous humour.

The concentration of the metabolite of the beta-blocker metipranolol was determined in the aqueous humour of 89 cataract patients. At 1, 2 or 5 h before surgery, they received one drop (30 microliters) of a 0.1% or 0.3% solution of the drug. At 1, 2 or 5 h after the application of 0.1% metipranolol eye drops, desacetyl-metipranolol concentrations of 624.55, 235.29 and 88.02 ng/ml, respectively, were measured. At the same intervals after the instillation of 0.3% metipranolol eye drops, the respective values of 1289.20, 1120.88 and 327.36 ng/ml were found. The metabolite concentration in the eye drops and the values measured show no consistent correlation.

Adrenergic beta-Antagonists↗

PubMed1991

Peripheral and central nervous responses evoked by small water movements in a cephalopod.

Potentials were recorded from the epidermal head lines and from the CNS of young cuttlefish, Sepia officinalis, in response to weak water movements. 1. Within the test range 0.5-400 Hz a sinusoidal water movement elicits up to 4 components of response if the electrode is placed on a headline: (i) a positive phasic ON response; (ii) a tonic frequency-following microphonic response; (iii) a slow negative OFF response; and (iv) compound nerve impulses. 2. The amplitude of both the ON wave and the microphonic potential depends on stimulus frequency, stimulus amplitude and stimulus rise time. Frequencies around 100 Hz and short rise times are most effective in eliciting strong potentials. The minimal threshold was 0.06 microns peak-to-peak water displacement at 100 Hz (18.8 microns/s as velocity). 3. Change of direction of tangential sphere movement (parallel vs. across the head lines) has only a small effect on the microphonic and the summed nerve potentials. 4. Frequency and/or amplitude modulations of a carrier stimulus elicit responses at the onset and offset of the modulation and marked changes in the tonic microphonic response. 5. Evoked potentials can be recorded from the brain while stimulating the epidermal lines with weak water movements. The brain potentials differ in several aspects from the potentials of the head lines and show little or no onset or offset wave at the transitions of a frequency and amplitude modulation.

Animals↗

PubMed1991

The time course and frequency content of hydrodynamic events caused by moving fish, frogs, and crustaceans.

In the present study the time course and spectral-amplitude distribution of hydrodynamic flow fields caused by moving fish, frogs, and crustaceans were investigated with the aid of laser-Doppler-anemometry. In the vicinity of a hovering fish sinusoidal water movements can be recorded whose velocity spectra peak below 10 Hz. Single strokes during startle responses or during steady swimming of fish, frogs, and crustaceans cause short-lasting, low-frequency (less than 10 Hz), transient water movements. Low-frequency transients also occur if a frog approaches and passes a velocity-sensitive hydrodynamic sensor. In contrast, transient water movements caused by a rapidly struggling or startled fish or water motions measured in the wake of a slowly swimming (less than or equal to 47 cm/s) trout can be broadbanded, i.e., these water movements can contain frequency components up to at least 100 Hz. High-frequency hydrodynamic events can also be measured behind obstacles submerged in running water. The possible biological advantage of the ability to detect high-frequency hydroynamic events is discussed with respect to the natural occurrence of high frequencies and its potential role in orientation and predator-prey interactions of aquatic animals.

Animals↗

PubMed1991

[Clinical results with soft intraocular lenses of poly-HEMA].

In a prospective study 28 patients were unilaterally implanted with a flexible posterior chamber lens made of poly-HEMA. Clinical results of 18 months follow up is reported. Implantation of the one-piece lens was more difficult in some patients according to the elastic property of the lens in comparison to PMMA-lenses. This is expressed in 8 patients in which a asymmetric sulcus-bag fixation of the lens was found. Postoperative visual acuity of better than 20/40 was found in 21 patients, which is rather the same as with hard intraocular implants. According to a lower refraction index of poly-HEMA the refractive power had to be chosen about 1 dpt higher than in PMMA-lenses. Early observation of the soft intraocular implants revealed 3 decentered lenses, in later follow up 5 implants were in an excentric position. One lens removal was performed due to diplopia. 16 of 28 patients revealed capsular fibrosis after 18 months follow up, in 8 patients a YAG-capsulotomy was performed. As an advantage of soft intraocular implants of poly-HEMA a good biocompatibility can be ruled out which is demonstrated in poor cell deposits on the lens surface and no synechias. The minor tendency to adheresis seems to favour on the other hand a destable fixation of the lens, which is expressed in the number of decentered lenses, possibly also in the observed capsular fibrosis.

Aged↗

PubMed1991

[Anti-inflammatory treatment after argon laser trabeculoplasty].

After argon trabeculoplasty procedures in patients with chronic open angle glaucoma, the protein appearance and cell circulation were observed within the anterior chamber. Flare and cell measurements of the anterior compartment are parameters of aqueous blood barrier break down. This investigation was performed in 50 patients suffering from elevated intraocular pressure and treated with argon laser trabeculoplasty. Two different anti-inflammatory drugs (prednisolone acetate and cyclooxygenase inhibitor) were applied to the treated eyes and checked for their effect on inflammation reduction. The protein and cell concentrations within the anterior chamber were measured before and 6 and 24 h after trabeculoplasty with a flare cell meter (KOWA) and compared to a control group. Argon laser trabeculoplasty induces an increase in protein concentration within the anterior chamber. This investigation demonstrates a clear drop in the inflammatory reaction of treated eyes during prednisolone acetate and cyclooxygenase inhibitor application. The intraocular pressure was reduced to about 6 mm Hg in treated eyes from an average pressure of 26 mm Hg.

Aged↗

PubMed1990

A discrete projection of the sacculus and lagena to a distinct brainstem nucleus in a catfish.

The projection of individual inner ear maculae of the catfish, Ancistrus spec. were labelled with horseradish peroxidases (HRP) or fluorescent dextran amines. In ostariophysans, fibres which innervate epithelia known or assumed to be sensitive to the pressure component of aquatic sound, i.e. acoustic fibres which come from the sacculus and lagena, have projections separate from those of the utriculus and canal organs. In Ancistrus afferents of sacculus and lagena terminate in an area which is distinct based on its cytoarchitecture. This area, previously believed to be a secondary auditory nucleus, is therefore an identifiable primary auditory nucleus in a subtetrapod vertebrate. This is different from other pressure sensitive teleosts (clupeids, osteoglossomorphs) in which acoustic fibres also terminate separately from vestibular fibres, but within parts of a larger cytoarchitectonic entity.

Animals↗