Biomedical subjects

K Arnér

Publications and source records attributed to K Arnér.

3 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.

Animals↗

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

DNA fragmentation characteristic of apoptosis and cell loss induced by kainic acid in rabbit retinas.

We have examined whether in vivo exposure to the glutamate analogue, kainic acid, induces cell loss through apoptosis and/or through necrosis. The vulnerability of rabbit retinal cells was evaluated by routine histopathology. The DNA fragmentation was examined using an in situ method (TUNEL: TdT-mediated biotin-dUTP nick-end labelling) and agarose gel electrophoresis of extracted retinal DNA. Retinas were examined at 30 min, and 4, 16, 24 and 36 h, and 2-5 days following the intraocular administration of 140 nmol kainic acid. Although pyknotic cells could be seen already at 30 min post-injection, TUNEL-labelled nuclei were first observed 4 h after the injection. A relatively large number of pyknotic cells and of TUNEL-labelled nuclei were still seen at 5 days post-injection. Pyknotic cells were seen throughout the inner nuclear layer (mostly in the proximal half of the layer) and in the ganglion cell layer. The TUNEL-labelled nuclei were almost only seen in the proximal inner nuclear layer. Analysis of DNA by electrophoresis revealed the presence of large molecular weight fragments 4 h after the injection, and of oligonucleosome-size fragments between 16 h and 2 days after the injection. The present study thus presents evidence that, in our model, the retinal cell loss induced by kainic acid is preceded, probably in most cells, by a fragmentation of DNA characteristic of apoptotic cell death. The process of cell loss following kainic acid administration was found to be relatively slow, further suggesting that a programmed type of cell death, which eventually induces apoptosis, is involved. No indication that cells were lost also through necrosis was obtained.

Animals↗