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Biomedical subjects

B Ehinger

Publications and source records attributed to B Ehinger.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1994

Reversed ratio of color-specific cones in rabbit retinal cell transplants.

Recently, we have reported on the emergence of various retinal cell types in embryonic rabbit retina transplanted to adult rabbits. When comparing the relative numbers of the spectrally different cone types in the transplants to those in the host or age-matched control retinas, a surprising shift was observed. While in the normal rabbit retina the middle-wavelength-sensitive (M) cones are considerably more abundant than the short-wave-sensitive (S) cones, the S/M cone ratio was found to be the opposite in the graft. The number of rosettes containing only S-cones in high density was found to be considerably higher than that of M-cone rich rosettes. The number of S-cones also exceeded that of the M-cones in each rosette that contained both cell types. Our results were obtained from the systematic immunocytochemical analysis of 15 different transplants derived from transplantations of embryonic rabbit retinas into adult hosts of the same species. The emergence and proportion of the two cone types were followed between 14 and 63 days after transplantation (between 29 and 78 postconceptional days of the donor tissue). Sections from various parts of the transplants were reacted with the monoclonal antibodies COS-1 and OS-2, specific for the middle- and short-wavelength-sensitive cones, respectively. The explanation for the reverse cone ratio in these transplants is not known yet, however, the observed phenomenon may indicate differences between the specification of the two basic cone types.

Animals↗
PubMed1994

In vivo staining of oligodendroglia in the rabbit retina.

We have discovered that a strongly fluorescent dye, sulforhodamine 101, when injected intravitreally in vivo, very effectively stains a class of star-shaped cells in the innermost layers of the rabbit retina. The cells were strictly confined to the region containing medullated fibers and emitted dichotomously branching processes that ended up running some distance along the myelinated fibers. In favorable cases they could be seen to ensheath the fibers in a tube-like fashion. No other retinal cells were stained. Shortly (hours) after the injection, the stain appeared in the cell cytoplasm, but it later became progressively more localized to intracellular granules. Most of the dye had disappeared after 2 days. Oligodendrocytes and astrocytes are the only cells known to be confined to the region of the medullated fibers in the rabbit retina, and hence the sulforhodamine 101-stained cells should be one of these two types. Sulforhodamine 101-stained cells were indistinguishable from oligodendrocytes identified by 2',3'-cyclic nucleotide phosphodiesterase (CNP) immunohistochemistry, and sequential staining showed them to be the same. Sulforhodamine 101-stained cells were microinjected with lucifer yellow after lightly fixing rabbit retinas with formaldehyde and were found to be indistinguishable from oligodendrocytes. Glial fibrillary acidic protein staining for astrocytes showed fiber bundles that to some extent were similar to the bundles stained by sulforhodamine 101, but at the level of individual fibers, it was impossible to establish any concordance. Sulforhodamine 101 thus appears to stain oligodendrocytes rather than astrocytes in the rabbit retina. A related dye, rhodamine 123, also stained rabbit oligodendrocytes, but with poor contrast because many other cells and structures were also stained.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Development of cell markers in subretinal rabbit retinal transplants.

Retinas from embryonic rabbits at day E15 were transplanted to the subretinal space in adult rabbits. After survival times between 7 and 193 days, the rabbits were killed, and the transplants were processed for immunohistochemistry. The results show that subretinal transplants from embryonic rabbit retinas develop many, if not all, retinal neuronal types. The cells show approximately normal morphology and express a variety of cell-type-specific markers: photoreceptor cells express visual pigment proteins as identified by antibodies against rhodopsin (R2-15), color-specific cone pigments (COS-1, OS-2) and the cone specific antigen 50-1B11, rod bipolar cells express PKC, horizontal cells HPC-1 antigen and neurofilament 160 kDa, amacrine cells HPC-1 antigen, GABA and neurofilament 160 kDa, and glial cells express vimentin and glial fibrillary acidic protein. The high degree of rosette formation seen in many young grafts, diminishes with time; many transplant cells disappear, and the remaining cells present a less prominent formation of rosettes.

Animals↗
PubMed1994

Interphotoreceptor matrix components in retinal cell transplants.

To further investigate the functional potential of retinal transplants we have used immunocytochemistry to study the distribution of four different interphotoreceptor matrix (IPM)-specific components in rabbit retinal transplants. The different components were: interphotoreceptor retinoid-binding protein (IRBP), chondroitin-6-sulfate, F22 antigen and peanut agglutinin (PNA) binding structures. IRBP acts as a retinoid-transport protein between the neural retina and the retinal pigment epithelium. Chondroitin-6-sulfate is a glycosaminoglycan and a part of the insoluble IPM skeleton. The identity and role of the F22 antigen is not known. However, it is a 250 kDa protein localized to specific extracellular compartments such as teh IPM. PNA is a lectin with a high binding affinity for D-galactose-beta (1-3) N-acetyl-D-galactosamine disaccharide linkages and binds to IPM domains surrounding cones, but not rods. The transplants (15-day-old embryonic rabbit retina) were placed between the neural retina and retinal pigment epithelium in adult hosts. The transplants developed the typical rosette formations with photoreceptors toward the center. IRBP labeling was distinct in the IPM in the host retina. However, no IRBP labeling could be detected in the transplants. The chondroitin-6-sulfate and F22 antibodies strongly labeled the IPM in the host retina and corresponding structures in the center of rosettes. A cone-specific labeling with PNA could be seen in the host retina. In the transplants, however, PNA labeling appeared in association with many more photoreceptors than in the host retina. There is no previous study available on the IPM in retinal cell transplants.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Cataract patients in a defined Swedish population 1986-1990. II. Preoperative observations.

With the Cataract Analysis System (CAS) we have analyzed 5.878 consecutive patients undergoing cataract operations from 1986 through 1990. The material is complete enough to be regarded as representative of the cataract surgery performed in the Lund Health Care District cataract surgery referral region during this period. There has been a striking increase in the number of operations, in 1990 reaching 3.6 per 1000 inhabitants in the referral region. A number of demographic factors have been analyzed previously, and the preoperative status of the patients is reported in this paper. In 1986, the cataract patients showed more visual impairment than in 1990, but the average age at surgery did not change between the years. We therefore suggest that the increase in the number of patients which were operated on represents a new category that was added. During the period, the planned refraction has changed towards emmetropia, presumably reflecting several kinds of improvements in the procedure. About 78 per cent of the population had a preoperative astigmatism < 1.5 D. As expected males had slightly longer eyes than women, and their corneal curvature was also slightly less.

Adolescent↗
PubMed1994

Neuropeptide Y inhibits adenylyl cyclase activity in rabbit retina.

Neuropeptide Y is known to be present in significant amounts in the retina of most vertebrates, but its physiological actions are largely unknown. We have therefore studied its effects on the intracellular cyclic AMP accumulation in rabbit retina. Neuropeptide Y had no effect on the basal cyclic AMP level but was found to inhibit the forskolin induced cyclic AMP accumulation. There were no differences between the effects of neuropeptide Y 1-36 and neuropeptide Y 13-36 (2.4 x 10(-6) M) suggesting the presence of the Y2 subtype of neuropeptide Y receptor. D-myo-inositol-1,2,6-trisphosphate, a novel neuropeptide Y-antagonist, reduced per se the forskolin induced cyclic AMP production. The pronounced inhibitory effect of neuropeptide Y on the forskolin induced cyclic AMP production was, on the other hand, totally abolished by D-myo-inositol-1,2,6-trisphosphate. The results indicate that neuropeptide Y acts on Y2 receptors in the retina to cause an inhibition of the adenylyl cyclase activity which could be antagonized by D-myo-inositol-1,2,6-trisphosphate. Such an inhibitory action of neuropeptide Y is similar to what has been found in brain tissue, but it has not previously been reported in the retina for neuropeptide Y or any of the other retinal neuropeptides.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Full-field electroretinograms in patients with central areolar choroidal dystrophy.

Patients with central areolar choroidal dystrophy are often difficult to diagnose because they are similar in fundus appearance to other retinal disorders. Nineteen patients with the diagnosis were studied in order to estimate the diagnostic and prognostic value of full-field electroretinography in this disorder. Our results showed that the cone b-wave amplitude in the ERG is decreased, that there is a progression in this decrease during a follow-up period of 5 years, and that the cone b-wave implicit time is prolonged. Central areolar choroidal dystrophy is considered to be primarily a choroidal disease. Our results indicate that it also affects most or all of the retinal cones. Further, our observations suggest that the disease is slowly progressive and that full-field electroretinography is of value in its early diagnosis.

Adult↗