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B Ehinger

Publications and source records attributed to B Ehinger.

At least 19 recordsLinked to original sources
PubMed1998

Correlations between cholinergic neurons and muscarinic m2 receptors in the rat retina.

Acetylcholine is well established as the neurotransmitter of starburst amacrine cells in the vertebrate retina but their function is poorly understood. We compared the distribution of muscarinic m2 receptors in the rat retina with the localization of the starburst cell processes. mAChR2 immunoreactivity appeared in a central band in the inner plexiform layer, which did not co-localize with the processes of the cholinergic amacrine cells. We found co-labelling of VAChT and ChAT making it highly unlikely that there are undetected cholinergic neurons in rat retina. Most mAChR2 receptors were located far from the cholinergic neurons, suggesting that most of them are unlikely to be associated with conventional cholinergic synapses.

Acetylcholine↗
PubMed1998

Gamma-aminobutyric acidA receptors on a bistratified amacrine cell type in the rabbit retina.

Gamma-Aminobutyric acid (GABA) is considered to be a major inhibitory neurotransmitter in the inner plexiform layer of the retinas of all vertebrate species. It is contained in and released from nearly 40% of the amacrine cells and is known to play a major role in many aspects of visual processing. By using well-characterized antibodies to several subunits of the GABA(A) receptor, we have analyzed their localization on the cell bodies and dendritic trees of two amacrine cell populations in the rabbit retina, which have been either filled intracellularly with Lucifer yellow or stained immunohistochemically. Both populations are selectively stained by intravitreal injection of the fluorescent nuclear dye 4',6-diaminidin-2-phenylindoldihydrochloride (DAPI). We have found that the most significant concentration of the alpha1 and beta2/3 GABA(A) receptor subunits is localized to the DAPI-3 type amacrine cell. The perikarya of the DAPI-3 cells are found in the proximal inner nuclear layer and send their processes into two sublayers in sublaminae a and b of the inner plexiform layer. These processes abut but do not directly overlap those of the two mirror-symmetric populations of starburst amacrine cells. Because the cell bodies of the DAPI-3 cells are the only ones in the inner nuclear layer that stain strongly for either the alpha1 or beta2/3 subunits, such staining is a diagnostic feature of these cells. Their processes also constitute the most strongly staining ones found within the inner plexiform layer. The dendritic trees of DAPI-3 cells, which range from about 150 microm up to about 300 microm, exhibit recurvate looping processes reminiscent of those described for directionally selective ganglion cells. In contrast to the DAPI-3 cell, we have also shown that the starburst amacrine cells exhibit no immunoreactivity for the alpha1 GABA(A) receptor subunit and very little for the beta2/3 subunit. Thus, we have shown that the DAPI-3 cells contain the highest concentrations of the alpha1 and beta2/3 GABA(A) receptor subunits in the rabbit retina. These cells, which costratify near the processes of both the starburst amacrine cells and the ON-OFF directionally selective ganglion cells, thus, are situated both anatomically and by virtue of their receptor content to potentially interact.

Animals↗
PubMed1998

Phenotypic expression of autosomal dominant retinitis pigmentosa in a Swedish family expressing a Phe-211-Leu variant of peripherin/RDS.

PURPOSE: To characterize the clinical phenotype, with emphasis on electrophysiology, of members of a Swedish family with autosomal dominant retinitis pigmentosa due to a novel mutation, F211L, in the peripherin/RDS gene. METHODS: Nine patients with autosomal dominant retinitis pigmentosa and two healthy family members underwent a full clinical evaluation including kinetic visual field testing, measurement of dark adaptation threshold, and full-field electroretinography. Blood samples were collected and DNA analysis was performed using denaturing gradient gel electrophoresis (DGGE). RESULTS: The grandfather, six of seven siblings from the middle generation, and two young boys carried the mutation F211L in the peripherin/RDS gene. The mutation segregated with the clinical presentation of disease. Fundus examination revealed mainly macular atrophy. All assessed parameters of retinal function (visual acuity, dark adaptation threshold, visual fields, and full-field electroretinograms) demonstrated a successive reduction with increasing age. Full-field electroretinograms showed a diminished rod response in all affected individuals and a reduction of the cone b-wave amplitudes with increasing age, indicating retinitis pigmentosa. In the affected family members, the disease seems to progress at a similar rate with increasing age. CONCLUSIONS: The peripherin/RDS gene mutation F211L is associated with a clinical phenotype and includes early loss of rod function and successive reduction of cone function with increasing age, but impressively well-preserved visual acuity and visual fields in young and middle-aged patients and moderately reduced vision in the old patient. Compared to previously described phenotypes segregating with mutations in the peripherin/RDS gene, the present family demonstrates a more benign clinical phenotype, which is concordant within the family.

Adolescent↗
PubMed1998

Transplant of full-thickness embryonic rabbit retina using pars plana vitrectomy.

PURPOSE: To develop an improved surgical technique making full-thickness retinal transplant possible, thereby achieving a normal laminated transplant with minimal rosette formation. METHODS: A total of 23 rabbits underwent vitrectomy, retinotomy, and subsequent subretinal transplant of a complete embryonic neuroretina using a specially crafted glass cannula. Of the 23 animals, 15 received a prenatal day 16 or 19 (E16 or E19) retina; the remaining eight received an E15 retina. The animals were followed from 10 to 35 days, and after this period, the transplants were sectioned and stained for light microscopy. RESULTS: In 11 of the 15 transplants with E16 or E19 donors, histology showed regions up to 1.8 mm of straight, correctly positioned transplants with layering corresponding to their age. The eight animals kept alive longest postoperatively, 31 or 35 days, all showed normal retinal layers, including photoreceptor outer segments appositioned against the host retinal pigment epithelium. Tissue from the youngest donors (E15) yielded less well-organized transplants, indicating a critical stage in retinal embryogenesis before which transplant in this respect is less favorable. CONCLUSIONS: Our procedure makes it possible to transplant embryonic retina to the appropriate position adjacent to the host retinal pigment epithelium, keeping the transplant architecture intact. The transplants show good layering and well-developed photoreceptors abutting the retinal pigment epithelium.

Animals↗
PubMed1997

Mitosis in developing rabbit retina: an immunohistochemical study.

The proliferation of cells in the embryonic and postnatal rabbit retina was studied with the MIB-1 antibody which demonstrates the Ki-67 antigen. Already at embryonic day 15 there were postmitotic cells (i.e. cells that do not stain with the MIB-1 antibody) in the basal part of the neuroblastic cell mass which are presumably the differentiating ganglion cells. After the formation of an inner plexiform layer at around embryonic day 25, postmitotic cells were seen in the proximal part of neuroblastic cell mass (presumably amacrine cells) as well as in the ganglion cell layer. Proliferating cells accumulated distal to the layer of postmitotic cells and their number gradually decreased towards the pigmented epithelium. At birth, proliferation ceased in the central parts of the retina but in the peripheral parts it continued for 7 days although rare cells could be seen for up to 15 days. After the formation of the outer plexiform layer, the proliferating cells in the outer nuclear layer accumulated close to the outer plexiform layer whereas the postmitotic cells (the differentiating photoreceptors) did so at the distal part of outer nuclear layer. Some cells in the middle of the inner nuclear layer (presumably the Müller cells) and some cells in the ganglion cell layer or nerve fiber layer (presumably the astrocytes) proliferated for the longest period of time.

Animals↗
PubMed1997

Immunocytochemical localisation of neuronal nitric oxide synthase in developing and transplanted rabbit retinas.

Nitric oxide (NO) acts as a modulator of neuronal transmission in mature neuronal systems, including the retina. Recently, NO has also been suggested to have a trophic function during development. We examined immunocytochemically the distribution of NO-producing cells in developing and transplanted rabbit retinas. An antibody detecting the neuronal isoform of its biosynthetic enzyme, nitric oxide synthase (NOS), was used on normal developing retinas [starting at embryonic day (E) 15] and on rabbit retinal transplants after various survival times (1-139 days after surgery). Weakly stained cell bodies were first observed in the proximal margin of the neuroblastic layer at E 29. Stained processes projecting towards a developing inner plexiform layer were also visible at this time point. Immunoreactive cells were located at later stages in the innermost part of the inner nuclear layer and in the ganglion cell layer, and are likely to correspond mainly to amacrine cells. NOS-labelled cells were also found in retinal transplants. The first NOS-labelled cells appeared, as in normal developing retinas, in ages corresponding to E 29 and were still detected in transplants corresponding to postnatal day 123. NOS-labelled cells were seen in areas between rosettes, where amacrine cells are located. NOS-labelled processes were at times seen to project for long distances, forming very distinct plexuses. NOS-containing amacrine cells thus appear both in the transplants and in developing retinas in the embryonic stages, long before synaptic function involving these cells can be expected, suggesting a role for NO not only in neuromodulation but also in retinal development.

Age Factors↗
PubMed1997

Phenotypes in three Swedish families with X-linked retinitis pigmentosa caused by different mutations in the RPGR gene.

PURPOSE: To assess the clinical phenotypes in three Swedish families with X-linked retinitis pigmentosa caused by different mutations in the RPGR gene. METHODS: Three families from different parts of Sweden, including nine patients with retinitis pigmentosa and six female carriers of X-linked retinitis pigmentosa, were examined clinically. Ophthalmologic examination included kinetic perimetry with a Goldmann perimeter using standardized objects I4e and V4e, dark adaptation final thresholds with a Goldmann-Weeker adaptometer, and full-field electroretinograms. RESULTS: The clinical findings in the patients demonstrated a severe form of retinitis pigmentosa with visual handicap early in life. Patients with a microdeletion of exons 8 through 10 of the RPGR gene had a more severe phenotype compared to the patients with single base-pair mutations in the introns 10 and 13 of the RPGR gene, resulting in splicing defects. Furthermore, heterozygous carriers in these families displayed a wide spectrum of clinical features, from minor symptoms to severe visual disability. CONCLUSION: These three families show a variable clinical phenotype resulting from different mutations in the RPGR gene. A microdeletion spanning at least parts of exons 8 through 10 seems to result in a severe phenotype compared to the splice defects. Heterozygous carriers of X-linked retinitis pigmentosa with these specific RPGR genotypes also show a variability of the phenotype; carriers with the microdeletion may be severely visually handicapped.

Adolescent↗
PubMed1997

Autosomal dominant retinitis pigmentosa with a rhodopsin mutation (Arg-135-Trp). Disease phenotype in a Swedish family.

We here present the clinical phenotype in 6 patients from a family with autosomal dominant retinitis pigmentosa found to carry a point mutation in the rhodopsin gene (arginine-135-tryptophan). The mutation is the second found by mutation screening of DNA from 20 Swedish families with dominant retinitis pigmentosa. With full-field electroretinography we could document a severe form of retinitis pigmentosa in patients belonging to the family, similar to the phenotype associated with the previously reported mutation (arginine-135-leucine). Our results indicate that different point mutations in the same region of the rhodopsin gene, resulting in amino acids with similar properties (both hydrophobic), may cause a similar clinical phenotype. Further, point mutations in this specific region seem to cause an agressive form of retinitis pigmentosa.

Adolescent↗
PubMed1997

Influence of technique and transplantation site on rosette formation in rabbit retinal transplants.

In order to determine mechanical and host-graft related interactions in the histogenesis of retinal transplants, a new technique for transplanting flat and comparatively large pieces of embryonic rabbit retina into adult rabbit eyes was elaborated. With the procedure, free-floating grafts in the epiretinal space survive, develop and differentiate largely without rosette formation, suggesting that the dissection and transplantation procedure is adequate for obtaining a normal development. On the other hand, subretinal transplants mature at an apparently faster pace than epiretinal transplants, but do not become regularly laminated. Outer segments do not develop well in the epiretinal transplants, whereas they do so in the subretinal ones, suggesting host-graft interactions by means of yet unknown diffusible factors.

Animals↗
PubMed1997

Intravitreal concentrations of some drugs administered with microdialysis.

Intraocular microdialysis was used to administer the drugs 5-fluorouracil, benzyl penicillin, daunomycin and dexamethasone into the vitreal space of rabbits. The purpose of the study was to investigate if therapeutic concentrations could be obtained with this administration method. After administering the drugs in labelled form, the attained concentrations were assessed by counting the radioactivity in the entire vitreous. For benzyl penicillin, the concentration was 2 microM, for dexamethasone it was 1.2 x 10(-7) M, and for daunomycin it was 1.2 microM, which are considered to be within the therapeutic ranges. For 5-fluorouracil, the corresponding concentration was 5 x 10(-5) M which probably is below the therapeutic level, when comparing with single-dose injections.

Animals↗
PubMed1997

A mild phenotype of autosomal dominant retinitis pigmentosa is associated with the rhodopsin mutation Pro-267-Leu.

By screening blood samples from patients with autosomal dominant retinitis pigmentosa, we found in one of the families a rhodopsin mutation (Pro-267-Leu), which segregates with the disease in two affected and five unaffected family members. Here, we present the results of the clinical evaluation of the family, including full-field electroretinography from the two affected family members. A 25-year-old family member with the mutation had an almost normal electrophysiological retinal response. The patient's father, who was also heterozygous for the mutation and had mild subjective symptoms of retinitis pigmentosa, demonstrated a substantially preserved retinal function. Our results suggest that the Pro-267-Leu rhodopsin mutation is associated with a very mild phenotype of retinitis pigmentosa. Young patients with the disease may have minimal pathological changes in the electroretinogram and some patients with few symptoms may be affected without acquiring a diagnosis of eye disease.

Adult↗
PubMed1996

Serum retinoids in retinitis pigmentosa patients treated with vitamin A.

BACKGROUND: Patients with retinitis pigmentosa have been suggested to benefit from treatment with moderate doses of retinyl palmitate. Retinyl palmitate is not an active retinoid in itself but is metabolised to active components in the body. To find out which metabolites of retinyl palmitate were formed and at which concentrations, we measured the concentrations of retinol, retinyl palmitate, retinoic acids and tocopherol in serum of patients treated with oral retinyl palmitate for retinitis pigmentosa. METHODS: Nine male patients and one female diagnosed as having retinitis pigmentosa after a complete ophthalmological examination including a full-field electroretinogram were given vitamin A at their own request as one daily morning dose of 16600 IU vitamin A. Blood samples were obtained before and after > 2 weeks of treatment. The concentrations of retinoids and tocopherol were measured with established methods. RESULTS: The patients were not deficient in vitamin A or vitamin E as judged from the serum vitamin concentrations. Treatment with retinyl palmitate significantly increased the serum concentration of retinyl palmitate and of 13-cis-retinoic acid but not of retinol, tocopherol or all-trans-retinoic acid. CONCLUSIONS: Neither retinyl palmitate nor 13-cis-retinoic acid, are known to be biologically active. However, 13-cis-retinoic acid can isomerise to the active vitamin A derivative, all-trans-retinoic acid. It is suggested that patients may be treated with a small dose of 13-cis-retinoic acid instead, to avoid the relatively long metabolic detour from retinyl palmitate.

Administration, Oral↗
PubMed1995

Passage of drugs through different intraocular microdialysis membranes.

BACKGROUND: Since drug penetration from the blood to the vitreous body is very poor, it is important to find means other than systemic delivery to reach necessary intraocular concentrations of drugs. This study represents a step in this direction. METHOD: Microdialysis probes implanted intraocularly in rabbits were perfused with different substances, mainly drugs. The substances belonged to three groups, antibiotics, corticosteroids and cytostatics, and were: benzylpenicillin and cefuroxim; triamcinolone and dexamethasone; daunomycin and 5-fluorouracil. In addition, three substances of different molecular weights were tested: formic acid (MW 70), glucose (MW 189) and insulin (MW ca. 5200). RESULTS: When used in tracer concentrations, some lipophilic drugs stick to polycarbonate but not to polyamide membranes. The latter material has therefore been used in all intraocular perfusions. All substances except inulin were found to diffuse through the polyamide membrane into the vitreous at a rate of about 10-20% of the perfusate concentration. Membranes with different dimensions and the above-mentioned two materials have also been screened for their transport properties in vitro. No differences were found between the two membrane materials, polycarbonate and polyamide. The net dialysis is strongly dependent on the probe geometry. CONCLUSIONS: We have shown that the above-mentioned substances penetrate into the vitreous body of rabbits through an implanted microdialysis membrane. This is of importance for the development of new means of intraocular drug administration.

Animals↗
PubMed1995

Localisation of neuronal nitric oxide synthase-immunoreactivity in rat and rabbit retinas.

The distribution of neuronal nitric oxide synthase (NOS) immunoreactivity was examined in rat and rabbit retinas and was compared with the distribution of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase reactivity and vasoactive intestinal peptide (VIP) immunoreactivity. An antibody raised against a C-terminal fragment of a cloned rat cerebellar NOS was used to localise NOS immunoreactivity. NOS immunoreactive cells were not detected in rat retinas at postnatal day 1 or 4, but were seen from postnatal day 7 onwards. NOS immunolabelling was seen in a small population of cells in the proximal inner nuclear layer. Most of the labelled cells had the position of amacrine cells and were seen to send processes into the inner plexiform layer. A few labelled cells were at times also seen in the ganglion cell layer, which are likely to correspond to displaced amacrine cells. The same NOS-labelling pattern was seen in rat and rabbit retinas. NADPH-diaphorase staining was observed in both species, in photoreceptor inner segments, in cells with the position of horizontal cells, in a subset of amacrine and displaced amacrine cells, in large cell bodies in the ganglion cell layer, in both plexiform layers, and in endothelium. Colocalisation of NOS immunoreactivity and NADPH-diaphorase staining was only observed among amacrine cells. However, not all NADPH-diaphorase-reactive amacrine cells were found to be NOS immunoreactive. VIP immunoreactivity was also localised in rat retinas in a subpopulation of amacrine cells, but no colocalisation of NOS and VIP immunoreactivity was observed. Our observations indicate that only amacrine cells contain the NOS form recognisable by the antibody used, and suggest that different isoforms of neuronal NOS may be present in retinal cells. Further, the onset of NOS expression in rat amacrine cells appears to occur independently of neuronal activity.

Amino Acid Oxidoreductases↗
PubMed1995

Phenotype variations within a choroideremia family lacking the entire CHM gene.

A Swedish family with choroideremia and a deletion of the CHM gene has been studied with ophthalmological examination, full-field electroretinography, and DNA analysis in order to characterize the phenotype of the disease. Although all four patients studied had a complete deletion of the gene, they showed a considerable variability regarding the phenotype, including the electroretinogram tracings. Two of the affected males demonstrated a severe form of choroideremia with low or nondetectable ERG recordings, while the other two affected males showed a less severe phenotype with only a slight reduction of the ERG amplitudes. The variation of the clinical phenotype among family members carrying the same mutation indicates that the severity of choroideremia is not solely a function of the CHM gene.

Adult↗