Amniotic membrane transplantation for ocular surface burns / Transplante de membrana amniótica em queimaduras da superfície ocular

ABSTRACT Objective: To analyze the morphological and functional long-term outcomes of amniotic membrane transplantation after ocular surface chemical burns. Methods: This prospective study analyzed 7 patients who suffered from severe ocular surface burn and underwent amniotic membrane transplantation from 2015 to 2020 in Hospital de Clínicas - Universidade Federal do Paraná. Results: Out of the seven patients, six (85.7%) suffered unilateral burn and one (14.3%) suffered bilateral burn. Five of them had alkali burns (71.4%), one had acid burn (14.3%) and one suffered gunpowder fireworks burn (14.3%). Mean age was 29.4 years (±standard deviation 13.3, range 14.0 to 47.0 years). Mean visual acuity at first presentation was 1.83±0.79 logMAR (0.015 decimal) and mean VA after a follow-up of 1 year was 0.85±0.70 logMAR (0.141 decimal). The visual acuity significantly improved from 1.83±0.79 to 0.85±0.70 logMAR (p<0.05). Conclusion: Amniotic membrane transplantation is an effective adjunctive treatment in the management of ocular surface chemical burns with potential to improve the final vision outcome.

RESUMO Objetivo: Analisar os resultados morfológicos e funcionais a longo prazo do transplante de membrana amniótica após queimaduras químicas da superfície ocular. Métodos: Foi realizado um estudo prospectivo com análise de sete pacientes que sofreram queimaduras graves da superfície ocular e foram submetidos a transplante de membrana amniótica no período de 2015 a 2020 no Hospital de Clínicas da Universidade Federal do Paraná. Resultados: Dos sete pacientes, seis (85,7%) sofreram queimadura unilateral e um (14,3%) sofreu queimadura bilateral. Cinco deles sofreram queimaduras por álcali (71,4%), um por ácido (14,3%) e um por pólvora de fogo de artifício (14,3%). A média de idade foi de 29,4 anos (±desvio-padrão de 13,3, intervalo de 14,0 a 47,0 anos). A acuidade visual média na primeira apresentação foi de 1,83±0,79 logMAR (0,015 decimal) e, após 1 ano de seguimento, foi de 0,85±0,70 logMAR (0,141 decimal). A acuidade visual melhorou significativamente, de 1,83±0,79 para 0,85±0,70 logMAR (p<0,05). Conclusão: O transplante de membrana amniótica é um tratamento adjuvante eficaz no manejo de queimaduras químicas da superfície ocular com potencial para melhorar a visão final.

Placental membrane grafts for urethral replacement in a rabbit model: a pilot study.

PURPOSE: Several graft materials are available for use in the treatment of urethral stricture disease. Placental membrane is being used in a variety of settings as a graft in wound healing and tissue repair. We aim to evaluate the effect of implanting decellularized human placental membrane into rabbit urethras. METHODS: Dorsal onlay graft urethroplasty using prepared human placental membrane was performed in 10 New Zealand White rabbits (Oryctolagus cuniculus). After 3 months, the rabbits underwent cystourethroscopy to evaluate urethral patency. The rabbits were then euthanized and the urethras examined for pathological findings. RESULTS: All urethroplasties were performed without complication. There were no observed episodes of urinary retention, infection, or renal failure. Urethral patency was achieved in all rabbits 3 months postoperatively. Urothelial replacement of the placental membrane graft was observed in all rabbits without malignant transformation. CONCLUSION: Dorsal onlay urethroplasty using decellularized human placental membrane can safely be performed in a rabbit model. This pilot study demonstrated urothelial replacement of human placental membrane in the rabbit urethra without stricture formation. Placental membrane is a promising biomaterial for urethral reconstruction.

Autologous Internal Limiting Membrane Transplants Successfully Close a Large Parafoveal Retinal Hole.

　Parafoveal retinal holes (PRHs) are one of the complications that can occur after internal limiting membrane (ILM) peeling during macular surgery. Here we describe a patient in whom an exceptionally large PRH (1,069-µm dia.) was successfully closed by repeated autologous ILM transplantation.

[Modified technique of autologous transplantation of internal limiting membrane for macular hole]. / Técnica modificada de trasplante autólogo de membrana limitante interna en agujero macular.

BACKGROUND: Autologous internal limiting membrane transplantation has allowed some cases of macular holes refractory to conventional surgery techniques to be treated. The purpose of this study is to describe the anatomical and functional outcomes of a modification of this technique in a case series of naïve macular hole patients. MATERIAL AND METHODS: A consecutive case series study was performed on patients with naïve macular holes with a diameter greater than 600 µ. Best corrected visual acuity, clinical features of the macular area, and optical coherence tomography were recorded before the operation and at the end of follow-up in all patients studied. All patients underwent 23 Ga core vitrectomy, posterior hyaloid separation, and brilliant-blue assisted internal limiting membrane peeling. A small piece of the internal limiting membrane was peeled off to make a free flap, and this was trasplanted and placed inside the macular hole under perfluorocarbon liquids. Air-fluid exchange was performed and SF6 gas was injected at a non-expansile concentration. RESULTS: The study included 5 eyes of 5 patients who underwent internal limiting membrane autograft. The mean age was 50.6 (SD 12.3) years. Four of the 5 cases had macular hole closure. The case where there was no closure of the macular hole was secondary to trauma. There was an improvement in visual acuity in all patients where the closing of the macular hole was achieved at the end of follow-up. CONCLUSIONS: In this cases series of macular hole patients, the autologous internal limiting membrane transplantation was associated with an anatomical closure of the macular hole and functional improvement in most of the patients studied.

Nanofractured autologous matrix induced chondrogenesis (NAMIC©)--Further development of collagen membrane aided chondrogenesis combined with subchondral needling: A technical note.

PURPOSE: This technical note introduces a further development of the autologous matrix induced chondrogenesis (AMIC©) technology for regenerative surgery of cartilage defects considering latest data in the literature. The potential of subchondral mesenchymal stem cell stimulation for cartilage repair is combined with a membrane technique to enhance efficiency of cartilage regeneration. The nanofractured autologous matrixinduced chondrogenesis (NAMIC©) procedure is suitable for the knee, hip, ankle, shoulder and elbow joints. METHODS: A standardized subchondral needling procedure (nanofracturing) is combined with fixation of a collagen I/III membrane to regenerate cartilage defects. Its advantages over microfracturing are smaller holes, deeper perforation into the subchondral space, a standardized procedure and earlier rehabilitation of the patient. The collagen membrane protects the blood clot forming after nanofracturing. The NAMIC© procedure may be performed arthroscopically alone, or in a combined arthroscopic setting with a mini-arthrotomy. RESULTS: This is a further development of the AMIC© technology which allows earlier rehabilitation of the patient. The procedure is standardized. Early clinical results are encouraging. Nevertheless, caution is advised in the evaluation of this method as in that of any cartilage regenerating method. CONCLUSION: The development of standardized subchondral regenerative procedures is important as only reliable clinical studies will give non-biased results. The NAMIC© procedure and the nanofracturing associated with it could be a promising step. As the rehabilitation period may be significantly shortened there is an earlier re-integration of the patient into the working life as compared to the AMIC© procedure. LEVEL OF EVIDENCE: 4.

Induced membrane for treatment of critical sized bone defect: a review of experimental and clinical experiences.

PURPOSE: The purpose of this study was to review experimental and clinical experiences about the use of an induced membrane to address critical bone size defect of the limbs. METHODS: From a review of published experimental and clinical data and from our clinical experience, we present the key data about the use of an induced membrane to address critical bone size defect of the limbs. RESULTS: After reviewing the concept of critical sized bone defect, we present the different indications of an induced membrane, the key points of the surgical technique and the strategy of bone grafting given the indication, localization and importance of the critical sized bone defect. Finally, we discuss the perspective of the use of an induced membrane with various bone substitutes. CONCLUSIONS: The use of an induced membrane to treat critical sized bone defects of the limbs is a simple, reliable and reproducible technique. Certain technical steps should be pointed out and observed with great caution in order to avoid any pitfalls. This technique will probably be a key step for facilitating bone inclusion of new bone substitutes proposed by recent bioengineering.

Comparative morphometry of the antebrachial and crural interosseous membranes: preliminary study for the use of the crural interosseous membrane in the surgical repair of the antebrachial interosseous membrane tears.

INTRODUCTION: Traumatic tears of the antebrachial interosseous membrane (AIOM) on its whole length are difficult to treat, particularly in the Essex-Lopresti syndrome. The number of ligamentoplasty techniques described in the literature witnesses the difficulty of its reconstruction and the absence of reliable and satisfying procedure. The aim of this study was to explore a new way of treatment, which consists in replacing the AIOM by the crural interosseous membrane (CIOM), harvested from the same patient. MATERIALS AND METHODS: A morphometric study of the AIOM and CIOM has been conducted on both sides of 15 formalin preserved corpses (i.e. 30 AIOM and 30 CIOM). Studied data were: length of forearms and legs, length and width (at different locations) of the membranes, in situ and after harvesting, and orientation of their fibers. The thickness of membrane was also measured but only after harvesting. RESULTS: Concerning the AIOM, the mean length was 13.3 cm in situ and 12.8 cm after harvesting. Its width was maximal at the union of middle and distal thirds with an average value of 1.7 cm in situ and 1.45 cm after harvesting. Mean thickness was 1 mm. Anterior fibers were oblique distally and medially (20.5° ± 0.95°), and posterior fibers were oblique distally and laterally (40° ± 3.4°). Concerning the CIOM, the mean length was 24.75 cm in situ and 23.9 cm after harvesting. Its width was maximal at the union of proximal and middle thirds with an average value of 2.3 cm in situ and 1.85 cm after harvesting. Mean thickness was 0.5 mm. Obliquity of its fibers was reverse of that of the AIOM: the anterior fibers were quite oblique distally and laterally (13° ± 2.6°), and the posterior fibers oblique were oblique distally and medially (24.2° ± 2.48°). DISCUSSION: From these results, one may conclude that the largest length and width of the CIOM allow its use as substitute for the injured AIOM. The orientation of its fibers should necessitate either its reversal while using the same side or the use of the CIOM of the opposite side; its relative sharpness could signify that its biomechanical properties could be worse. A biomechanical study is necessary to evaluate how this new way of replacing the AIOM could resist to the strains imposed on the forearm.

Surgical outcomes of inverted internal limiting membrane flap technique for large macular hole.

We are presenting the initial results of inverted internal limiting membrane (ILM) flap technique for large macular hole. Five eyes of five patients with large diameter macular hole (>700 µm) were selected. All patients underwent inverted ILM flap technique for macular hole. Anatomical closure and functional success were achieved in all patients. There was no loss of best-corrected visual acuity in any of the patients. Inverted ILM flap technique in macular hole surgery seems to have a better hole closure rates, especially in large diameter macular holes. Larger case series is required to assess the efficacy and safety of this technique.

Treatment of a bone defect consequent to the removal of a periapical cyst with equine bone and equine membranes: clinical and histological outcome.

AIM: While deproteinized bovine bone and bovine membranes have been well studied and can yield good results when used to treat bone defects and peri-implant dehiscences, enzymatically deantigenated equine bone and equine membranes have emerged as possible alternative biomaterials. The objective of this study was the clinical and histological assessment of such materials: equine bone granules, an equine collagen membrane and an equine pericardium membrane. METHODS: Enzymatically deantigenated equine bone and an equine collagen membrane were used to restore a bone defect caused by the removal of a bone cyst in the upper anterior maxilla. After 4.5 months, an implant was placed and a bone core sample was obtained from the grafted site. Implants threads, though, were exposed. This defect was grafted with a mixture of autogenous and equine bone and covered with an equine pericardium membrane. RESULTS: Four months after implant placement the peri-implant bone levels were maintained. A prosthesis was delivered three months later providing functional and esthetic rehabilitation. Also four-year follow-up controls showed implant success. Histological analysis of the bone core revealed that the graft material had undergone remodelling, and a fair amount of newly formed vital bone was present at the time of sample collection. CONCLUSION: The deantigenated equine bone is biocompatible and undergoes osteoclastic remodelling. Both the equine collagen and pericardium membrane acted as effective barriers for guided bone regeneration.

Estudo comparativo da resposta do tecido ósseo em técnica de regeneração tecidual guiada – avaliação macroscópica: parte 1 / Comparative study of bone response guided tissue regeneration technique - macroscopic evaluation: part 1

O reparo de defeitos ósseos é um desafio para diversas áreas, pois a invasão de células fibroblásticas no defeito, resulta em tecido conjuntivo cicatricial. Assim, os princípios de Regeneração Tecidual Guiada (RTG) estão bem estabelecidos para tratamento de defeitos ósseos. Essa técnica consiste na utilização de biomembranas que agem como barreiras e evitam a invasão dos fibroblastos e permite o povoamento com células osteoprogenitoras. O presente trabalho propôs-se avaliar o crescimento e potencial regenerativo em defeitos ósseos através de avaliações macroscópicas e radiográficas. Para tanto, 27 coelhos foram divididos em 3 grupos experimentais de acordo com o tratamento: Controle (A), Látex (B) e PTFE (C). Então, subdivididos em 3 grupos para análise de neoformação periódica: 15 (I); 30 (II) e 60 dias (III). As cobaias foram submetidas à cirurgia para confecção de defeitos ósseos críticos em calvária e tratamento específico de cada grupo. Após os períodos os animais foram sacrificados e obtidas as peças anatômicas para as radiografias pelo método Digora e fotografias digitais. As análises macroscópicas permitiram observar crescimento ósseo e áreas radiopacas sugestivas de tecido ósseo. No período de 15 dias a densidade óssea nos grupos experimentais no defeito foi semelhante. Contudo, aos 60 dias, verificou-se formação óssea homogênea para Látex e vários níveis de radiopacidade para PTFE e controle. Dentro das limitações, conclui-se que biomembranas são bem indicadas em processos cirúrgicos para regeneração óssea, visto que as barreiras impedem ou dificultam a migração de células incompatíveis com o tecido a ser neoformado e promove a osteogênese.

The repair of bone defects is challenge for many areas, since the invasion of fibroblast cells in the defect, resulting in scar tissue. Thus, the principles of Guided Tissue Regeneration (GTR) are well established for treatment of bone defects. This technique is the use of bio-membranes that act as barriers and prevent the invasion of fibroblasts and allows the placement of osteoprogenitor cells. The proposition of this study is evaluate the mechanical growth and regenerative potential in bone defects by macroscopic and radiographic analyses. Twenty-seven rabbits were divided into 3 groups according to treatment: control (A), Latex (B) and PTFE (C). Then divided into 3 groups for analysis of periodic neoformation: 15 (I), 30 (II) and 60 days (III). The animals were subjected to surgical preparation of bone defects in critical calvaria and specific treatment of each group. After the period, they were sacrificed and collected the body parts for X-rays by the Digora method and digital photographs. Macroscopic analysis allowed observed bone growth and areas suggestive of bone tissue. During 15 days of bone density in the experimental groups in the defect was similar. However, after 60 days, there was bone formation for homogeneous in group of Latex and various levels of radiopacity to PTFE and control. Within the experimental conditions, the biomembranes are well indicated in surgical procedures for bone regeneration, since the barriers preventing or hindering cell migration incompatible with the tissue to be newly formed and promotes osteogenesis.

[Repair of swine full-thickness cutaneous deficiency by autogenic BMSCs compounded with collagen membrane].

OBJECTIVE: To supply references to tissue-engineered skin clinical applications with autogenic BMSCs composited collagen membrane to repair swine full-thickness cutaneous deficiency. METHODS: Twenty mL bone marrow were obtained respectively from 4 swine, autogenic BMSCs were cultured and passed to the 3rd passage. The fresh bovine tendon treated by means of chemically cross-linked was made 5 cm diameter collagen I (Col I) membrane. The 2 x 10(7)/mL P3 swine autogenic BMSCs labeled DAPI were planted to sterile Col I membrane for 24 hours incubation, then the tissue-engineered skin was constructed. The five full-thickness skin defect of 5 cm diameter was excised to the muscle from forward to backward on the back midline two sides of swine. The tissue-engineered skin were implanted in the experimental group, while Col I membrane was implanted in control group. After 3 and 8 weeks of implantation, the two swine wound surface healing circumstance was observed and further evaluated with histology analysis and TEM. After 3 weeks of implantation, the experimental group were observed with fluorescence microscopy and staining for glycogen. RESULTS: After 3 weeks of implantation, the wound surface of control group were observed nigrescene, scab and putrescence, and after 8 weeks of implantation, also evident putrescence and scar. The wound surface of experiment group was alive after 3 weeks implantation, appearance was leveled off and flexible without evident scar. The wound surface recovered well after 8 weeks of implantation, wound surface healing rate was significantly difference between the two groups (P < 0.01). After 3 weeks of implantation, control group were observed acestoma hyperplasia and no epidermal coverage by histology analysis. The experimental group was showed integrity epidermis and dermis structure. The basal layer was crimson and continuously positive with glycogen staining. After 8 weeks of implantation, the experimental group and control group were emerged normal skin structure. After 3 weeks of implantation in control group, a lot of neutrophilic granulocytes and fibroblasts were noticed, but no epidermal structure was observed under TEM. In the experimental group, a lot of epidermal cells were observed, dermatome connection among epidermal cells and hemidesmosome connection between basilar membrane cells and basal membrane were observed in epidermis. In the dermis experimental group, blood capillary endothelial cells were noticed. Furthermore, considerable collagen fiber deposit was found in the surrounding tissue of fibroblasts. After 3 weeks of implantation, BMSCs labeled with DAPI were located reconstructed epidermal basement membrane and dermis by fluorescence microscopy. CONCLUSION: Tissue-engineered skin which is composited with autogenic BMSCs as seed cells and collagen membrane were potential prospects in application of repairing swine full-thickness cutaneous deficiency.

Comparative study of 5 different membranes for guided bone regeneration of rabbit mandibular defects beyond critical size.

BACKGROUND: Although several studies have examined use of collagen membranes in guided bone regeneration (GBR), none has examined the use of human fascia temporalis as a bioabsorbable barrier. The majority of studies related to GBR have examined critical size defects. We sought to assess the human fascia temporalis and other well-documented membranes applied for GBR in mandibular osseous defects beyond critical size. MATERIAL/METHODS: Fifty adult male New Zealand white rabbits were used in this study. Five groups of 10 animals each were used: HFL (human fascia lata membrane), HP (human pericardium), HFT (human fascia temporalis), BP (bovine pericardium), and PTFE (expanded polytetrafluoroethylene). Animals were killed 10 weeks after membrane application. In each animal, 9-mm circular mandibular defects were created bilaterally. On 1 side of the jaw, the defect was covered with 1 of the test membranes; the defect on the other side served as a control. Harvested specimens were examined histologically. RESULTS: Membranes were significantly superior to the controls in all animals (P<0.001). Paired comparisons showed that groups HFL, HP, BP, and PTFE were significantly superior to HFT (P<0.05). Conversely, comparisons of HFL-HP, HFL-BP, HFL-PTFE, HP-BP, HP-PTFE, and BP-PTFE, showed no significant differences (P>0.05). CONCLUSIONS: According to our results, the fascia temporalis is not recommended for GBR techniques. The fascia lata, human pericardium, bovine pericardium, and e-PTFE advance bone regeneration and can be successfully used as GBR membranes for osseous defects beyond the critical size.

Tissue response to a membrane of demineralized bovine cortical bone implanted in the subcutaneous tissue of rats

O tratamento de defeitos ósseos perenes tem motivado a busca por técnicas ou substitutos ósseos adequados. Na odontologia, um problema comum no tratamento de defeitos ósseos periodontais é o crescimento de tecidos competidores para o interior da lesão, como o epitélio juncional da gengiva, prejudicando a regeneração desses tecidos. Buscando melhorar a regeneração periodontal foi desenvolvida a técnica da Regeneração Tecidual Guiada (RTG) baseada na separação dos tecidos através de membranas ou barreiras. Objetivo deste estudo foi avaliar histologicamente a resposta tecidual à membrana obtida do osso cortical bovino desmineralizado, implantada em subcutâneo de ratos. Os períodos analisados foram de 1, 3, 7, 15, 30 e 60 dias após a implantação. A análise dos cortes histológicos mostrou resposta inflamatória de moderada a intensa nos períodos de 1 e 3 dias, moderada aos 7 e 15 dias, e praticamente inexistente aos 30 e 60 dias. A reabsorção da membrana se iniciou 15 dias pós-implantação e ao final de 60 dias apenas resquícios foram detectados em alguns animais. Concluímos que a membrana derivada do osso cortical bovino desmineralizado é bem tolerada pelos tecidos sendo completamente reabsorvida após 30-60 dias por células mononucleadas e células gigantes multinucleadas que desaparecem ao final do processo.

A comparison of parietal and iliac crest bone grafts for orbital reconstruction.

PURPOSE: This study evaluated the results of cranial (membranous) versus iliac crest (endochondral) bone grafts as implants to correct post-traumatic globe malposition and/or diplopia. PATIENTS AND METHODS: Twenty-two patients underwent 25 orbital reconstructions with bone for enophthalmos, hypophthalmos, and diplopia after trauma to the orbit. Inclusion criteria consisted of at least 4 months postsurgical follow-up, pre- and postsurgical quantitative orbital measurements, photographic documentation, and complete medical records regarding inpatient and outpatient data. RESULTS: Nine cranial bone grafts and 16 iliac crest grafts were placed. Ages were similar in both groups. The average follow-up was 24 months for the cranial graft group (range, 4 to 54 months) and 18 months for the iliac crest graft group (range, 4 to 51 months). Preoperative enophthalmos averaged 4.11 and 5.06 mm in the cranial and iliac crest groups, respectively, and postoperatively the measurements were 1.78 and 1.37 mm, respectively. Changes in hypophthalmos generally reflected changes in the enophthalmos correction. In 10 patients diplopia was corrected by the procedure. There was a statistically significant change in the enophthalmos of patients when comparing pre- and postoperative status, but no statistically significant difference between the results of the cranial and iliac crest graft groups. CONCLUSION: There is no difference in the ability of cranial and iliac crest bone grafts to correct post-traumatic enophthalmos.

Inhibition of epidural scar tissue formation after spinal surgery: external irradiation vs. spinal membrane application.

PURPOSE: The scar tissue that forms after lumbar dissection is a severe complication and a cause of lumbar and radicular pain. It was recently shown that radiotherapy could inhibit peridural fibrosis after laminectomy. In this study, the efficiency of external irradiation was compared with spinal membrane application. METHOD AND MATERIALS: Thirty male New Zealand rabbits underwent L5 laminectomy. Ten rabbits each received a single fraction of 900-cGy external irradiation administered by 9-MeV electron beam 24 h after the surgery. Ten other rabbits each had spinal membrane applied during laminectomy. The remaining 10 rabbits constituted the control group. All of the rabbits were killed 30 days after the laminectomy. Axial histologic sections through the laminectomy defect were evaluated. Each specimen was scored for the extent and density of fibrosis and arachnoidal adherence. RESULTS: The extent and density of fibrosis and arachnoidal adherence differed significantly between the control group and the treatment groups (p < 0.05). However, the extent and density of fibrosis and arachnoidal adherence did not differ significantly between the spinal membrane and irradiation groups (p > 0.05). CONCLUSION: This preliminary study showed that high-single-fraction/low-total-dose administered postoperatively can successfully inhibit postsurgical epidural fibrosis as effectively as applied spinal membrane.

[Treatment of trophic ulcers in chronic venous insufficiency using bio-transplants]. / Ispol'zovanie biotransplantata dlia lecheniia troficheskoi iazvy pri khronicheskoi venoznoi nedostatochnosti.

The results of treatment of 66 patients with trophic ulcer in postthrombophlebitic syndrome, using biological lining, manufactured from mollusc of Cephalopoda genus owing properties of semipermeable biological membrane, were analyzed. Application of biogenic linings had promoted the results of patients treatment improvement due to quickening of epithelization and formation of ripe granular tissue.

Guanine nucleotides, including GMP, antagonize kainate responses in Xenopus oocytes injected with chick cerebellar membranes.

Injection of chick cerebellar membranes, rich in kainate binding sites, into Xenopus oocytes resulted in the structural integration of chick membrane patches into the oocyte plasma membrane that could be easily identified by specific immunofluorescent staining. Application of kainate to the oocyte perfusion medium, under voltage-clamp conditions, induced dose-dependent (EC50 = 87+/-14 microM) inward currents, confirming the functional incorporation to the oocyte of kainate-driven channels. Responses to kainate were consistently nondesensitizing and strongly potentiated by cyclothiazide, suggesting the selective involvement of alpha-amino-3-hydroxy-5-methyl-4isoxazolepropionate (AMPA)-preferring receptors. Binding experiments with (S)-[3H]AMPA confirmed the presence in the chick membrane preparation of low-affinity AMPA receptors (K(D) = 278 nM) amounting to <2% of the total population of kainate binding sites. A tenfold concentration of guanine nucleotides, with different degrees of phosphorylation, blocked the responses to 100 microM kainate by approximately 90%. In the case of GMP, additional concentration-inhibition studies yielded an IC50 of 180+/-11 microM. Our results illustrate the apparent failure of kainate-binding proteins to form functional channels, even when maintaining their own native membrane environment, and confirm the antagonistic behavior of guanine nucleotides, including GMP, toward glutamate receptors, in agreement with previous results of ligand-binding experiments and, more interestingly, with the marked neuroprotective effects of some guanine nucleotides in different excitotoxicity experimental paradigms.

Amniotic membrane transplantation for ocular surface reconstruction in patients with chemical and thermal burns.

OBJECTIVE: The purpose of the study is to examine the usefulness of preserved human amniotic membrane transplantation in patients with chemical and thermal burns. DESIGN: The study design was a nonrandomized clinical trial. PARTICIPANTS: Seven eyes of six patients with severe chemical (n = 5) and thermal (n = 2) burns were studied. INTERVENTION: Eyes were treated with excision of cicatricial tissues followed by a placement of amniotic membrane on the sclera. Transplantation of limbal grafts from an opposite eye (n = 4) or from donor eyes preserved at -80 degrees C (n = 2) was performed simultaneously. MAIN OUTCOME MEASURES: Reconstruction of ocular surface epithelia and visual acuity were measured. RESULTS: With the mean observation period of 53.3 weeks, central corneal epithelium was reconstructed successfully in all eyes. Neither amniotic membrane nor limbal grafts were rejected. A persistent epithelial defect developed in one eye, which was treated successfully by tarsorrhaphy. After surgery, the corneal epithelium showed normal arrangements on specular microscopy, and its barrier function recovered to seminormal. Corrected visual acuity markedly improved in each eye. Regenerated conjunctiva on the amniotic membrane was stable and uninflammed with minimum-to-mild scarring. Slight recurrence of conjunctivalization was noted in three eyes. However, because these eyes were stable and central cornea was clear, no further surgery was needed. CONCLUSIONS: Amniotic membrane transplantation promotes normal conjunctival epithelialization while suppressing fibrosis formation. The procedure, especially when performed with limbal autograft transplantation, appears to be effective for the treatment of chemical or thermal burns of the ocular surface.

New surgical technique for treatment of extraarticular knee ankylosis.

Laboratory and clinical studies were conducted to evaluate a treatment regimen for extraarticular ankylosis of the knee. The study evaluated the use of a porcine biomembrane to prevent quadriceps adhesions. A canine model was studied to determine the cellular response to the membrane by evaluating biopsies at 3, 7, 14, and 21 days after surgery using light and scanning electron microscopy. The results showed that there was nonspecific inflammatory cell infiltration into the base (rough) layer of the biomembrane during the first few days, although fibroblasts were the dominant cellular response 7 days later. No significant tissue ingrowth was seen on the smooth (muscular interface) surface of the membrane. The clinical study applied the information gained from the canine model to a series of 23 patients who suffered from extraarticular knee ankylosis and who were treated with a surgical procedure in which the released interface between the femur and the muscle groups was protected with a piece of porcine biomembrane. Subjects were observed from 16 to 30 months (mean, 26 months) after surgery. An average increase in knee range of motion of 86 degrees was documented, and a 100% patient satisfaction rate was noted. The technique yields satisfactory results in terms of cost, range of motion, and postoperative pain.

Reconstruction of the flexor tendon sheath. An experimental study in rabbits.

The role of the tendon sheath in flexor tendon healing was investigated in rabbits. Tendon sheath was reconstructed with syngeneic parietal peritoneum or a non-tanned processed porcine collagen membrane. Resection of the tendon sheath led to adhesions. Reconstruction of the sheath with either graft resulted in a synovial-like lining, resembling a neo-tendon sheath. Even when combined with tendon repair a neo-tendon sheath was seen after reconstruction with both grafts, without adhesions. Subcutaneously implanted processed porcine collagen membrane was completely resorbed in less than 3 months.