Biomedical subjects

B Juliusson

Publications and source records attributed to B Juliusson.

10 recordsLinked to original sources

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.

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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.

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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.

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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.

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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.

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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)

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PubMed1994

Complementary cone fields of the rabbit retina.

PURPOSE: Complementary cone fields have been considered a unique feature of the mouse retina. In an attempt to map the arrangement of the color-specific cones in other mammals, the authors investigated the rabbit, a commonly used experimental animal for vision research. METHODS: For the identification of the different cone types immunocytochemistry was used with two monoclonal antibodies, each specific to the middle- to long-wave (red-green) and short-wave (blue) sensitive visual pigments, respectively. RESULTS: The major part of the retinal surface, including the visual streak, exhibited a dominance of M (middle-wave sensitive) cones (6 to 13,000/mm2) versus S (short-wave sensitive) cones (1 to 2,500/mm2). In contrast, the lower 5% to 6% of the total retinal area showed a complete lack of green cones and a high density of blue cones (11,000/mm2). The authors designate this crescent-like area the blue streak of the rabbit retina. CONCLUSION: In addition to the visual streak primarily abundant in green cones, there is a specialized area of the rabbit retina that is densely and exclusively populated with blue cones. Although the relative extension of this peculiar cone field is considerably smaller than the S-field of the mouse retina, its position is similar in that it occupies the lowermost part of the retina. The functional implication of this area is unknown.

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PubMed1993

Hyperplastic neuroretinopathy and disorder of pigment epithelial cells precede accelerated retinal degeneration in the SJL/N mouse.

We have found a complex eye disease in the SJL/N mouse. This animal is closely related to the SJL/J mouse, which is homozygous for retinal degeneration (rd) and which also suffers from extraocular reticulum cell sarcomas at around 200 days of age. In the SJL/N animal, a high incidence of subretinal tumor is present at 9 days after birth. Furthermore, we have observed an extensive neuroretinal hyperplasia, a phenomenon that is termed "hyperplastic neuroretinopathy", and that is probably the consequence of elevated levels of cytokines in the animals. In addition to these anomalies, the SJL/N mouse shows progressive dystrophy of the retinal pigment epithelium (RPE) from day 4 onwards, and accelerated photoreceptor cell degeneration is completed by day 16. The early RPE dystrophy appears to be a secondary autoimmune disease, since cells in this structure and in the choroid develop MHC class II antigens, whereas we suspect that the accelerated photoreceptor cell loss is induced by a soluble toxic agent. The F1 progeny derived from cross-breeding the SJL/N and Balb/c +/+ strains also shows a high incidence of subretinal tumor and hyperplastic neuroretinopathy, but neither the RPE dystrophy nor retinal degeneration.

Age Factors↗

PubMed1992

Unique topographic separation of two spectral classes of cones in the mouse retina.

We have found two immunologically distinguishable cone types in the retina of the mouse, each localized to two opposite halves of the eye. One cone type was labelled by the monoclonal antibody COS-1 specific to the middle-to-long wave sensitive visual pigment of the mammals, while the other type was stained by the shortwave-specific monoclonal antibody (OS-2). These results were confirmed with other antibodies directed against specific sequences of the visual pigments. As a result of the uneven distribution of the two cone types the mouse retina is divided into two fields separated by an oblique meridional line. The middlewave sensitive cones were present exclusively in the dorsal half of the mouse retina (M-field). The overwhelming majority of the shortwave sensitive cones occupied the ventral half (S-field), and only a small number was scattered among the middlewave sensitive cones in the dorsal retina. The ratio of the two cone types in the M-field corresponds to what has been found in the retina of other mammals, including rodents such as the gerbil and the rat. The S-field represents an entirely unique area with the unusually great number of shortwave sensitive cones and with the complete lack of the middlewave sensitive ones. The present study provides the structural basis for dichromacy in a rodent species considered for a long time to be monochromat. In addition, it shows that the ventral retina, containing exclusively S-cones in a relatively high density, is a unique retinal field not present in other mammalian species studied so far.

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PubMedDate not supplied

Cellular organization in retinal transplants using cell suspensions or fragments of embryonic retinal tissue.

We have investigated the cellular organization in two different types of retinal transplants using cell type-specific monoclonal antibodies. Both fragments and cell suspensions of E17-E19 Sprague-Dawley rat retina were transplanted to a subretinal site in congenic adult rat hosts. After a survival time of 28 days, the transplants were stained by immunocytochemistry with antibodies against rhodopsin, which stained rods; with antibodies against HPC-1, which stained amacrine cells and outer and inner plexiform layers; and with antibodies against vimentin, which stained Müller cell fibers and horizontal cells. In the host retina, the distribution of immunocytochemical staining was similar, irrespective of transplantation technique. In the transplants, the anti-rhodopsin staining showed that fragment transplants developed photoreceptors in rosettes, whereas in cell suspension transplants, this staining showed a scattered distribution of photoreceptors. The HPC-1 staining showed that regions corresponding to the inner nuclear layer surrounded both types of transplants and made large invaginations into them. In one case, using the cell suspension technique, fibres were found to run from the inner plexiform layer of the transplant to the outer plexiform layer of the host. The vimentin staining revealed a disorganized array of Müller cell fibres in both types of transplants, but with some concentration to the regions corresponding to the inner plexiform layer.

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