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Biomedical subjects

B Ehinger

Publications and source records attributed to B Ehinger.

At least 19 recordsLinked to original sources
PubMed1999

Gap junction protein connexin43 is heterogeneously expressed among glial cells in the adult rabbit retina.

The immunohistochemical distribution and ultrastructural immunolocalization of connexin43 (Cx43) in the neural retina of the rabbit was investigated. Cx43 immunolabeling appeared in the form of distinct puncta distributed on different kinds of glial cells and exclusively in the myelinated fiber region of the neural retina. Double-label immunohistochemistry showed that the most obvious Cx43 labeling occurred at processes of glial fibrillary acidic protein-positive astrocytes and on vimentin-positive Müller cells. Cx43-immunoreactive puncta were also evident on cell bodies and processes of 2'-3'-cyclic nucleotide phosphodiesterase-labeled oligodendrocytes. As shown by electron microscopy, immunoreactivity to Cx43 was restricted to gap junctions among the macroglial cell population. The homologous interastrocytic and Müller cell-to-Müller cell, as well as the heterologous astrocyte-to-Müller cell and astrocyte/Müller-to-oligodendrocyte gap junctions were symmetrically labeled. Our results indicate a specific expression of Cx43 at gap junctions between macroglial cells located in the myelinated streak. The extensive Cx43 immunolabeling suggests a substantial amount of gap junctional coupling that establishes a macroglial syncytium.

Animals↗
PubMed1999

Partial and full-thickness neuroretinal transplants.

Adult and embryonic rabbit retinal sheets were transplanted into the subretinal space of adult rabbits. The transplants were either full-thickness with intact layering, or gelatin embedded and vibratome sectioned with the inner retina removed. The full-thickness grafts were positioned subretinally by means of a glass capillary in which they were partially folded. The vibratome sectioned ones were placed using a plastic injector in which the gelatin embedded graft was flat. The embryonic full-thickness grafts were followed clinically up to 3 months, and the other 3 transplant types up to 1 month postoperatively, after which the retina was sectioned and stained for light microscopy. Surgical complications were more common in eyes receiving vibratome sectioned grafts with 10 out of 34 eyes displaying blood in the vitreous. Four of these eyes also developed total retinal detachment. Out of 17 eyes receiving full-thickness grafts, only one displayed these complications. Histologically, 11 out of 13 embryonic full-thickness transplants revealed straight, laminated transplants with correct polarity, and with all normal retinal layers present. In these transplants, fusion with the host increased in time. Of the adult full-thickness transplants, only 1 out of 4 survived, and this graft showed signs of degeneration. The vibratome sectioned adult transplants in a few cases survived the first two postoperative weeks. In these grafts, both inner and outer retina were present, indicating an incomplete vibratome sectioning. With longer postoperative times, the number of surviving transplants in this group diminished considerably. All vibratome sectioned embryonic transplants developed into rosettes and sometimes also into laminated sections with reversed polarity. It can be concluded that in rabbits, the surgical technique used for vibratome sectioned transplants requires a larger sclerotomy and retinotomy, since they have to be kept flat in the transplanting instrument due to the surrounding gelatin. This technique is associated with a higher frequency of complications than the one used for full-thickness grafts which are more flexible and can be transplanted with a smaller instrument. Vibratome sectioning of embryonic grafts results in abnormal morphology and their adult counterparts only survive if the sectioning is incomplete. Adult full-thickness grafts show poor survival. Embryonic full-thickness transplants in the majority of cases develop into laminated retinas with layers parallel to the host retinal pigment epithelium. They also survive and integrate well with the host retina.

Animals↗
PubMed1999

MHC expression in syngeneic and allogeneic retinal cell transplants in the rat.

BACKGROUND: The major histocompatibility complexes, MHC class I and II, are found only sparsely or not at all in the retina. Since the eye is immunoprivileged, we decided to investigate how the MHC class I and II antigens were influenced by a retinal transplant and whether this could be correlated to rejection of the transplant. METHODS: Fetal neural retinas of Sprague-Dawley (SD) rats were implanted in the subretinal space of adult Lewis and SD rats. After 5 weeks the retinas and the transplants were evaluated with antibodies against MHC class I and II antigens as well as microglia. RESULTS: In the syngeneic transplants no upregulation of MHC class I antigen was seen and no MHC class II-positive cells could be detected. In the allogeneic transplants, on the other hand, there was marked upregulation of MHC class I antigen. Numerous MHC class II antigen-positive cells were seen in the subretinal transplant but also in the host retina. CONCLUSION: Allogeneic retinal transplants seem to grow and thrive just as well as syngeneic transplants, but in the former there is considerable upregulation of MHC expression. Our interpretation of these results is that the allogeneic transplants are recognized as nonself, but that there is also something that modifies this reaction of the immune system at this level, preventing the rejection that would normally ensue.

Animals↗
PubMed1999

CuZn superoxide dismutase transgenic retinal transplants.

BACKGROUND: The morphology of retinal transplants is believed to depend on the extent of mechanical disruption of the donor tissue during the surgical procedure and on local factors of the host environment. We hypothesized that oxidative stress during donor tissue preparation and implantation further affects transplant development and investigated the effects of CuZn superoxide dismutase (SOD) overexpression on the survival and morphological development of mouse embryonic retinal transplants. METHODS: Retinae and livers from embryonic day 14-15 SOD overexpressing transgenic mice and CBA control mice were harvested under sterile conditions. In order to identify transgenic mouse embryos, the embryonic livers were analyzed via nondenaturing gel-electrophoresis for the presence of the human SOD protein. Neural retinae were transplanted as fragmented tissue into the subretinal space of albino BALB/c mice. At 4-8 weeks following transplantation, the grafted eyes were fixed in Bouin's solution and processed for histological analysis. RESULTS: Both SOD transgenic and control retinal transplants had developed all retinal layers except for a ganglion cell layer and exhibited a similar extent of rosette formation. Computer-assisted, quantitative assessment of retinal graft volumes revealed a significant, around 58% increase in size of SOD transgenic transplants compared with controls. CONCLUSIONS: Enhanced intracellular SOD levels do not seem to influence retinal transplant morphology as detected by light microscopy. However, volumes of the SOD transgenic transplants were found to be increased compared to control grafts.

Animals↗
PubMed1999

Expression of GABA transporter subtypes (GAT1, GAT3) in the adult rabbit retina.

PURPOSE: GABA transporters (GATs) are of importance for GABA signal systems. They have previously not been examined in rabbit retina, nor has their correlation with neurotransmitter GABA and GABA receptors been examined in the retina of any species. METHODS: The distribution of GATs, GABA and GABA receptors was examined with immunohistochemical methods. RESULTS: Both GAT1 and GAT3 immunoreactivities were found in the inner plexiform layer and in amacrine cells. GAT3 was also present in Müller cells. GAT1 appeared in amacrine cells that also had a high GABA concentration, but not in cells with moderate to low GABA concentration. GAT1 was also present in amacrine cells that did not show GABA immunoreactivity, possibly indicating a postsynaptic GABA uptake system. CONCLUSION: GAT3 is probably involved in both neuronal and glial GABA uptake whereas GAT1 is involved in predominantly neuronal uptake, and possibly also into non-GABA-ergic amacrine cells. Further, there may be at least two populations of GABA containing neurons.

Animals↗
PubMed1999

Expression of GABA transporter subtypes (GAT1, GAT3) in the developing rabbit retina.

PURPOSE: Little is known about the expression of GABA transporters (GATs) in the developing retina. We have therefore examined the expression of GABA transporters (GAT1 and GAT3) in the developing rabbit retina. METHODS: The distribution of GATs was examined with immunohistochemical methods. RESULTS: GAT3 immunoreactivity appeared at PN0, whereas GAT1 immunoreactivity appeared first at PN3, both in the inner plexiform layer. From PN5 and onwards, both GAT1 and GAT3 immunoreactivity gradually appeared in numerous amacrine cell somas. At PN10, the immunostaining patterns and the distribution of both GAT1 and GAT3 were similar to that found in the adult rabbit retina. Full staining intensity was reached at PN20. CONCLUSION: GABA neurotransmission starts to develop already the first one to three days after birth, reaches the mature neuron pattern at about PN9 to PN10 but is not fully developed until about PN20. Neither GAT1 nor GAT3 appears to be involved in trophic actions by GABA in the prenatal retina.

Aging↗
PubMed1999

Immunohistochemical markers in full-thickness embryonic rabbit retinal transplants.

PURPOSE: To examine immunohistochemical markers in straight, well-laminated retinal transplants with special attention paid to the interphotoreceptor matrix, the Müller cells and the ganglion cells as these three retinal components have been abnormal in transplants produced by previous methods. METHODS: Nine rabbits underwent subretinal transplantation of a complete full-thickness embryonic neuroretina. After 31 or 49 days, the transplants were stained for light microscopy and processed for immunohistochemistry. RESULTS: Six of 9 eyes contained transplants with straight, well-laminated regions with all light-microscopic characteristics of a normal retina. In the outer segment region, the expression of peanut agglutinin showed segmental labeling of cone domains in the interphotoreceptor matrix, and interphotoreceptor retinoid binding protein immunoreactivity was found. Glial fibrillary acidic protein and vimentin immunoreactivity revealed normal Müller cell morphology. In 3 transplants the AB5-antibody-labeled ganglion cells in the ganglion cell layer and all transplants contained nerve fibers in the nerve fiber layer labeled by an antibody against neurofilament of 160 kD. The latter also labeled fibers connecting the transplant with the host. CONCLUSIONS: Full-thickness embryonic retinal transplants develop the normal retinal appearance and display several of the retinal components necessary for normal function which are not found in transplants produced by previous methods.

Animals↗
PubMed1999

Graft-host connections in long-term full-thickness embryonic rabbit retinal transplants.

PURPOSE: To establish neuronal connections in the rod and cone pathway between laminated rabbit retinal transplants and the host retina. METHODS: Fourteen adult rabbits received a complete full-thickness embryonic transplant. After survival times of 3 to 10 months, the retinas were studied under light microscope and with immunohistochemistry. Antibodies against protein kinase C (PKC), parvalbumin, and calbindin were used to label rod bipolar cells, AII amacrine cells, and cone bipolar cells, respectively. The AB5 antibody was used to label ganglion cells. RESULTS: The transplants displayed laminated morphology with layers parallel to the host retinal pigment epithelium. In the oldest specimens (10 months after surgery), laminated layers of graft and host approached each other and almost reconstructed the normal retinal appearance. The ganglion and cone bipolar cells of the host survived well, as was seen with AB5 and calbindin double-labeling. Connections between cone bipolar cells in the graft and ganglion cells in the host were not common. PKC-labeled rod bipolar cells and parvalbumin-labeled AII amacrine cells of host and graft showed sprouting activity directed toward an intermediate plexiform layer located between the graft and host. In specimens double-labeled with PKC and parvalbumin, this intermediate plexiform layer was seen to contain numerous PKC- and parvalbumin-labeled processes. Direct connections between rod bipolar and AII amacrine cells in host and graft were seen in the 10-month specimens. CONCLUSIONS: Full-thickness embryonic transplants survive for at least 10 months, and normal laminated morphology develops. Host and graft fuse and together contribute nerve cell processes to an intermediate plexiform layer. Direct graft-host contacts are also present between neuronal types that in the normal retina participate in the rod pathway.

Animals↗
PubMed1999

Long-term full-thickness embryonic rabbit retinal transplants.

PURPOSE: To establish the light and electron microscopic morphology of long-term full-thickness embryonic rabbit retinal transplants, with special attention paid to graft- host integration. METHODS: Eighteen rabbits received a complete embryonic neuroretina 19 days after conception. The transplants were positioned under the host retina, flat against the host retinal pigment epithelium with proper polarity, using a vitrectomy technique. After surviving 3 to 10 months, the transplants were examined by light and electron microscopy. RESULTS: The outer retina of the host had degenerated in all specimens. In 16 of the 18 eyes, well-laminated transplants with correct polarity, measuring up to 3.2 mm in length, were found. The transplants displayed long outer segments facing the host retinal pigment epithelium, and they were laminated to the level of the inner plexiform layer in which fusion with the host was often evident. Fusion was more prominent in the oldest transplants. Electron microscopy revealed bundles of neurites at different levels of maturation in close contact with Müller cell fimbriae at regular intervals along the graft-host border. CONCLUSIONS: Full-thickness embryonic rabbit retinal transplants positioned with correct polarity develop into large laminated retinas and survive without immunosuppression for at least 10 months. Host and graft adapt and almost reconstruct the normal retinal appearance. Ultrastructurally, well-developed photoreceptors and many normal synapse types are seen, and neuron sprouting is evident at the graft-host border.

Animals↗
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

Endogenous hyaluronan in the normal and traumatized rabbit iris.

PURPOSE: Hyaluronan concentration in the iris tissue after iridectomy was studied in order to establish the influence of trauma on the production of hyaluronan in the anterior chamber of the eye and whether the iris participates in this process or not. METHOD: Hyaluronan was measured with a radiometric assay at different time points after surgery and identified with specific histochemical staining. RESULTS AND CONCLUSIONS: The concentration of hyaluronan in iris tissue peaked two days after surgery, reaching an average of 115.3 (S.E.M.:+/-12.2) microg/g. It then decreased slowly to almost normal values after 3 to 5 weeks. Histochemistry demonstrated the most intense hyaluronan staining in the iris stroma and in iridial processes around the iridectomy two days after the operation. Our findings indicate in situ synthesis of hyaluronan in the iris tissue.

Animals↗
PubMed1998

Survival and MHC-expression of embryonic retinal transplants in the choroid.

PURPOSE: To study the survival of syngenic versus allogenic embryonic retinal transplants in the choroid, and try to correlate the survival to the expression of MHC-expression and the presence of activated microglia. METHOD: Fetal neural retinas of Sprague-Dawley (SD) rats were implanted in the choroid of adult Lewis and SD rats. After 3 weeks the retina, the choroid and the transplants were examined by light microscope and evaluated with antibodies against MHC class I and II. RESULTS: Retinal transplants were found in all eyes. The transplants had one subretinal and one choroidal component. The syngenic transplants thrived in the subretinal space and formed rosettes and the choroidal components had to some extent rosette formation, though not as distinct as in the subretinal part. Almost no upregulation of MHC class I and II was seen. The allogenic transplants were totally deranged in the subretinal space as well as in the choroid. There was a marked upregulation of MHC class I, most pronounced in the transplants, but also in the host retina. Numerous MHC class II positive cells were seen in the transplants, but also in the host retina. All of these cells were dendritic and had the typical appearance of microglia. CONCLUSION: Syngenic choroidal transplants were seen to grow and thrive, whereas the allogenic transplants were rejected. There is a considerable upregulation of MHC expression in the allogenic transplants, but not in the syngenic.

Animals↗
PubMed1998

The expression of GABA(A) receptors during the development of the rabbit retina.

PURPOSE: Gamma-amino butyric acid (GABA) is a major inhibitory neurotransmitter in the retina, possibly participating in its normal development. The distribution of gamma-aminobutyric acid receptors was therefore examined in mature and developing rabbit retina by GABA(A) receptor alpha1 and beta2/3 subunit immunocytochemistry. RESULTS: Beta2/3 subunits appeared already at the E25 stage (25 days after gestation) although only weakly and irregularly. Alpha1 subunit immunoreactivity was first observed at birth. On the fifth postnatal day, immunostaining was clearly seen in the inner plexiform layer, and weaker, in the outer plexiform layer. There were at this stage no well-delineated sublayers in either the inner or the outer plexiform layer, but three clearly defined sublayers appeared in the inner plexiform layer at PN10. Amacrine cell bodies now also appeared, labelling for both the GABA(A) receptor alpha1 and the beta2/3 chains. A punctuate labelling appeared in the outer plexiform layer. From the 20th postnatal day, the immunoreactivity was similar to that seen in adult rabbits. CONCLUSIONS: Like in the adult, the alpha1 and beta2/3 subunits of the GABA(A) receptor thus colocalize predominantly in certain amacrine cells and in processes of the inner plexiform layer during the development of the retina. The GABA(A) receptors appear later than GABA during the development of the rabbit retina, and functioning GABA neurotransmitter circuits appear to be assembled primarily after the 3rd to 5th postnatal day. Our results support the hypothesis that GABA may have other functions than mediating classic synaptic neurotransmission before the formation of receptors containing the alpha1 and beta2/3 subunits. Like in the brain, the alpha subunits may have more selective functions during the development than the beta subunits.

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

A Swedish family with a mutation in the peripherin/RDS gene (Arg-172-Trp) associated with a progressive retinal degeneration.

PURPOSE: To clinically characterize a Swedish family with autosomal dominant retinitis pigmentosa due to a mutation, Arg-172-Trp, in the peripherin/RDS gene. METHODS: Full clinical evaluation including kinetic visual field testing, measurement of dark-adaptation threshold, and full-field electroretinography in seven patients with autosomal dominant retinitis pigmentosa and three healthy family members. Denaturing gradient gel electrophoresis (DGGE) was used for mutation screening in seven patients and six healthy members of the family. RESULTS: Three of four siblings from the middle generation and four of the younger generation were heterozygous for the peripherin /RDS Arg-172-Trp mutation. The mutation segregated with the disease. Visual acuity decreased progressively with age and visual fields were moderately constricted in young patients, while central scotoma and constriction of the fields were detected in the family members above 50 years of age. The results from full-field electrography were comparable with a widespread retinal degeneration. CONCLUSIONS: Earlier, the peripherin/RDS Arg-172-Trp mutation was associated primarily with a macular degeneration phenotype. One previous study indicated that this mutation also can give rise to a degeneration of the more peripheral parts of the retina. In the present study, a widespread retinal degeneration is seen in the patients above 50 years of age, carrying the Arg-172-Trp mutation.

Adult↗
PubMed1998

Clinical expression of X-linked retinitis pigmentosa in a Swedish family with the RP2 genotype.

PURPOSE: To examine the clinical phenotype with emphasis on electroretinograms and visual fields in a Swedish family with X-linked retinitis pigmentosa (XLRP) type 2 (RP2), and compare it with Swedish XLRP families with the RP3 genotype. METHODS: Three affected brothers and their carrier mother were examined clinically and with kinetic perimetry, dark adaptation thresholds, and full-field electroretinograms. The genotype was determined by haplotype analysis using polymorphic markers spanning the XLRP loci at the short arm of the X chromosome. RESULTS: The phenotype was consistent in the three affected males. The first subjective symptom was night blindness and the visual disability was more pronounced with increasing age. Affected individuals had a slight decrease in visual acuity and were emmetropic. They demonstrated a pathologically elevated final rod threshold. The visual fields were constricted in a somewhat atypical pattern. The three patients had an early presenting atypical cataract with multiple opacities. The fundus appearance was typical for RP with narrowing of retinal vessels and bone spicule pigmentations. The rod electroretinograms were extinguished in both eyes of the patients. The combined rod-cone responses as well as the isolated cone responses were severely reduced in amplitude; however, atypically for RP, the implicit time for the isolated cone responses was normal. The carrier female demonstrated normal ophthalmological findings, with the exception of two minimal pigmentations in the lower quadrants of the left eye. Haplotype analysis demonstrated that the disease in this family segregates with the RP2 locus. CONCLUSION: The phenotype of the studied RP2 family is associated with early onset of night blindness, emmetropia, a slight decrease in visual acuity, constriction of visual fields, and atypical cataract formation. Electroretinograms demonstrate severe rod dysfunction and surprisingly normal cone response implicit times which may indicate a milder disease progression. These findings are different from earlier descriptions of the RP2 and RP3 phenotypes.

Adolescent↗