Biomedical subjects

C Redbrake

Publications and source records attributed to C Redbrake.

At least 37 records · Page 2Linked to original sources

PubMed1997

[Tissue condition of human corneas before and after organ culture. Effect of donor cause of death].

UNLABELLED: Recent studies have shown that the human cornea reflects the metabolic status of the donor. Nevertheless, it has not yet been shown whether this leads to a different tolerance of organ culture and whether these changes are reversible or not. MATERIALS AND METHODS: Eighty-five organ-cultured human corneas were investigated. Endothelial cell density and the concentrations of glucose, lactate, ATP and ADP were determined in each cornea by enzymatic-optical methods. Obduction protocols were examined and five groups of donors could be determined: (1) donors who had died suddenly; (2) donors who had died of malignant processes; (3) donors with septicaemia; (4) renal-insufficient donors; and (5) diabetic donors. RESULTS: Endothelial cell density decreased significantly after 28 days of organ culture. Deswelling for 1 day in a medium containing dextran 500 caused additional cell loss. On the basis of biochemical parameters, the corneas showed recovery after organ culture: especially ATP and ADP concentrations increased. Glucose concentrations decreased and lactate concentration increased in the closed organ culture system. Best recovery was observed in corneas from septic donors and from those who had died of carcinoma. Overall, an equalization of all corneas after the culture period was observed. In contrast, the deswelling period causes deterioration of metabolic status; ATP concentration decreased dramatically, and ADP increase was higher than expected. CONCLUSION: From these data we conclude that there is no donor disease that could lead to exclusion of the cornea from organ culture. In fact, organ culture leads to a recovery of the metabolic status of the human cornea.

Cause of Death↗

PubMed1997

[Energy metabolism of the human cornea in various culture systems].

BACKGROUND: There are two well known systems to culture human corneas prior to transplantation. First, corneal storage at 4 degrees C especially in Optisol medium. Second, organ-culture at physiological temperatures in a modified minimal essential medium (MEM). In the cold storage system the number of endothelial cells after storage might be overestimated because the damaged cells are not able to leave the monolayer. It has been supposed that the lack in energy recruitment is the main reason for that, but has not been proven yet. It was the purpose of this study to describe the energy status of the human cornea after storage in both systems. MATERIALS AND METHODS: 32 human corneas were investigated. They were stored for 7 days in Optisol, and for 7 days in MEM plus 1 day in MEM supplemented with 5% dextran 500 and 12 days in modified MEM plus 1 day in MEM supplemented with 5% dextran 500. The endothelial cell density (ECD) as well as the hydration were determined. Glucose, lactate, ATP, ADP and AMP were measured to reflect the energy status. RESULTS: Hydration was comparable in all three groups. ECD was slightly higher in Optisol stored corneas, although the amount of damaged cells was much higher. Optisol stored corneas showed a severe anaerobic situation, especially lacate concentrations were increased. In contrast ATP and ADP concentrations were twice as high in MEM than in Optisol stored corneas. DISCUSSION: The severe anaerobic situation in Optisol stored corneas leads to a lack in energy recruitment. This reduces the ability of cell function (mitosis) and the function of the monolayer (migration, elimination). Whether these changes are reversible after transplantation has to be determined in future.

Adenine Nucleotides↗

PubMed1997

A histochemical study of the distribution of dextran 500 in human corneas during organ culture.

PURPOSE: The aim of this histochemical study was to demonstrate the absorption of dextran 500 and its distribution in the cornea after storage under standard eye bank conditions. Furthermore, an attempt was made to distinguish between the soluble and insoluble parts of dextran 500 absorbed by the cornea, in order to see how much dextran remains in the cornea after transplantation. METHODS: Forty-nine fresh and 65 organ-cultured human corneas were investigated. The corneas were cultured for 28 days in a dextran-free medium, followed by a period of 1-14 days in a medium containing 5% dextran 500. Cryosections were stained by aqueous PAS and a modified alcoholic PAS to determine the amount of dextran. RESULTS: Dextran was not found in the epithelium, stroma or endothelium of fresh human corneas. By contrast, extra- and intracellular positive staining reactions were detected in corneas following storage in a medium containing dextran. Dextran 500 absorption was relatively diffuse in the epithelium after storage in a dextran medium. Initial accumulations were found in the stroma near Bowman's and Descemet's membranes and also in the central part of the cornea, as the period of culture in the medium containing dextran lengthened. We also observed interaction between the stroma and endothelium: decreasing amounts in the endothelium were followed by an increase of same in the stroma. Intracellular deposits of dextran were detected after only one day. A much greater part of the extracellular dextran than previously described was found to be insoluble. CONCLUSIONS: As the amount of dextran in the cornea increases over a longer storage time, we conclude that the period of storage in a medium containing dextran should be limited to four days. The fact that the cornea is saturated with dextran after seven days has been shown in further studies to interfere with mitochondrial function and may also cause severe post-operative swelling of the transplant, hence leading to a longer recovery period for the patient.

Cornea↗

PubMed1997

Video fluorescein angiography of the anterior eye segment in severe eye burns.

PURPOSE: Severe eye burns often result in extensive necrosis of the conjunctiva and episcleral tissue. Video fluorescein angiography was performed to reveal the perfusion of the anterior eye segment after severe eye burns. METHODS: A scanning laser ophthalmoscope was used for anterior segment fluorescein angiography in 12 patients (14 eyes) with severe burns grade III-IV and in 7 healthy volunteers. RESULTS: Necrotic tissues occurred as non perfused areas and remained dark throughout the whole angiogram. In general, the borders from healthy to necrotic conjunctival tissue were sharply demarcated. Thus, the extent of scleral and limbal ischemia could be determined exactly. Injured vessels showed hyperfluorescence with late leakage. Damage of the subconjunctival tissue appeared as a deep weak fluorescence in the early angiography and exhibited patchy leakage in the late angiogram. CONCLUSIONS: Anterior segment angiography provides a basis for deciding the extent of surgical debridement of necrotic tissue in the acute phase of the burn. The determination of the extent of limbal and scleral ischemia may give useful information for early plastic-reconstructive procedures.

Adult↗

PubMed1997

Tenonplasty: a new surgical approach for the treatment of severe eye burns.

BACKGROUND AND OBJECTIVE: In the acute stage of most severe eye burns, the primary goal is survival of the globe. Initial tissue destruction may lead to extensive necrosis of the conjunctiva and underlying tissue down to the fornices, with resulting ischemia. These circumstances may cause a polymorphonuclear cell response, with resulting corneo-scleral ulceration and early melting of the globe. To reestablish the ocular surface, Tenonplasty was performed as a plastic procedure to reconstruct the conjunctival matrix of the globe up to the limbus. PATIENTS AND METHODS: Vital Tenon's sheets from the orbital region were prepared and advanced up to the limbus to cover the ischemic or ulcerating sclera with healthy, vascularized tissue. Fifty-nine patients with 75 severely burned eyes were treated with this procedure between 1987 and 1994. A total of 243 Tenon's flaps were prepared. RESULTS: In all cases, scleral ulcerations were prevented or healed. Epithelialization of the advanced Tenon's sheets was complete within 21 days in 80% of the cases and in all eyes within 54 days. Primary epithelialization of the burned cornea was achieved in approximately 31% of the cases. Fornices were sufficiently deep in about 74%, but severe symblepharon formation occurred in 26% of the cases. CONCLUSION: Tenonplasty may be an alternative surgical procedure to transplantation of autologous conjunctival or mucous grafts in restoring the conjunctival surface of the globe in severely burned eyes.

Adolescent↗

PubMed1996

Employment of bioluminescence for the quantification of adenosine phosphates in the human cornea.

BACKGROUND: Quantification of adenosine phosphates in human corneal extracts has been performed using spectrophotometry. We employed the bioluminescence technique to obtain a more sensitive assay for adenosine phosphates and to reduce the volume of the test sample. METHODS: The bioluminescence assay for ATP, already known from sterility control, was modified and expanded. Standard curves were established using a standard solution with equimolar concentrations of ATP, ADP and AMP. To monitor the method, adenosine phosphates were measured in 35 human corneal extracts using both spectrophometry and bioluminescence. RESULTS: Linear standard curves ranging from 1 to 45 pmol were established. The two methods yielded comparable results despite the use of a basic dilution of 1:100 for the new technique. CONCLUSION: Bioluminescence provides a highly sensitive quantification of adenosine phosphates in the human cornea and facilitates an extremely detailed evaluation of the metabolic status of the cornea.

Adenine Nucleotides↗

PubMed1996

Electrolytes in the cornea: a therapeutic challenge.

BACKGROUND: Reported here are the results of electrolyte measurements in different layers of 70 apparently normal human corneas. METHODS: Samples were examined by energy-dispersive X-ray analysis under calibrated conditions in a scanning electron microscope. The method allows the simultaneous quantitative analysis of, among others, sodium (Na), chloride (Cl), phosphorus (P) and potassium (K). The results are related to the dry weight of the analyzed samples. Four distinct layers, subepithelium, middle stroma, posterior stroma and Descemet's membrane, were analysed in each cornea. RESULTS: In the middle stroma we found concentrations of: sodium 0.609 +/- 0.13, chloride 0.557 +/- 0.115, potassium 0.058 +/- 0.02 and phosphorus 0.038 +/- 0.01 (mol/kg dry weight) [corrected]. CONCLUSION: The collation of normal electrolyte concentrations provides reference values for future studies on changes of the corneal electrolyte composition in diseased or injured eyes. The electrolyte composition of rinsing fluids or eye drops should be adjusted to that of the corneal stroma. Phosphate buffer, for example, is not a good vehicle for topical eye treatments and should be replaced by organic buffering systems.

Adult↗

PubMed1996

[Keratoplasty with scleral rim after the most severe chemical eye burns of the anterior eye segment].

BACKGROUND: Corneo-scleral ulcerations and perforations are severe complications after most severe eye burns. One possibility to handle this situation is a keratoplasty with a scleral rim. This retrospective study was carried out to show the outcome after total replacement of the cornea after most severe eye burns. PATIENTS: Between 1986 and 1991 we carried out 12 keratoplasties with a scleral rim in 9 most severely burnt eyes of 7 patients. In 9 cases this intervention was the first transplantation. In 3 eyes a re-keratoplasty had to be carried out. RESULTS: All eyes could be saved after this surgical intervention, although all but two transplants failed. In eight cases the transplant decompensated and/or was replaced by scar tissue. Two transplants remained clear. Visual acuity was light perception in five cases, intact light projection in two cases, 1/35 in one case because of cataract formation and 0.8 in another case at the end of the observation period. The reasons for graft failure were multifactorial. Epithelial problems were the reason for graft failure in eight cases. Two of these also showed shrinkage of the eye lids with incomplete lid closure. In six cases severe vascularisation with scar formation was observed. It is remarkable that immunoreactions occurred only in four cases. This may be due to the fact that all patients were treated systemically with cyclosporin A. In one case the transplant failed after extensive surgery of the anterior segment. CONCLUSION: Our results show that the keratoplasty with a scleral rim can save the eye in the difficult situation of corneo-scleral ulceration or perforation. Nevertheless a visual rehabilitation could not be achieved in seven of nine cases. But all eyes were in a satisfying condition for further smaller transplants to achieve better visual acuity.

Accidents, Home↗

PubMed1996

[Therapy of persistent erosion after severe chemical eye burn with the excimer laser].

BACKGROUND: The course after severe eye burns is characterized by many complications which require a longlasting and intensive therapy. The success of treatment is menaced especially by superficial problems like persistent erosiones which occur also after keratoplasty. PATIENT: As a cause of persistent erosions, pathological changes of Bowmans' membrane are discussed. Therefore, it was removed by PTK (phototherapeutic keratectomy) in our patient, in order to allow better adhesion of the epithelium to the deeper, less changed layers. THERAPY AND OUTCOME: The patient suffered from a severe burn accident of his right eye with liquid cement. After proliferations were excised twice, we had to glue on a hard contact lens as an artificial epithelium due to a persistent erosion. Later, the development of a bacterial keratitis required keratoplasty. The epithelium remained intact for eleven months, but then an erosion arose and persisted for nine months. Therefore we performed a PTK and the epithelium closed subsequently within four days. CONCLUSION: The treatment of persistent erosions has been very difficult so far, and often procedures like artificial epithelium or even keratoplasty have been necessary. The astonishing course of our patient indicates, that PTK is a promising and less invasive therapy in these cases.

Adult↗

PubMed1996

Autologous transplantation of nasal mucosa after severe chemical and thermal eye burns.

Between February 1992 and March 1994, reconstruction of the fornices in 17 patients with extensive symblephara or lid fusion after most severe eye burns was performed with nasal mucosa from the inferior conchae as graft material. The time between accident and transplantation ranged from 2-64 months. All patients were followed for 6 to 31 months. Reconstruction of the fornices was achieved in 13 patients. Postoperative Schirmer-tests revealed markedly improved results. Impression cytology showed a persistence of goblet-cells and an excess of mucus. We have subsequently performed keratoplasties in 5 of these patients and are planning penetrating keratoplasties in a further 8 cases. In 4 patients, partial symblepharon formation recurred within 2-3 months after transplantation of nasal mucosa. The main advantage of nasal mucosa over buccal or labial mucosa may be the transplantation of intraepithelial goblet cells, leading to an improvement and stabilisation of the tear film.

Adolescent↗

PubMed1995

Explorative study of interleukin levels in the human cornea.

BACKGROUND: The presence of interleukins has been demonstrated in the cornea and other ocular tissues. Although pathogenic mechanisms are unknown, interleukins seem to be involved in inflammatory disorders of the cornea. The present study was undertaken to analyse concentrations of interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) in human corneas with various clinical diagnoses. METHODS: Immediately after keratoplasty 127 explanted human corneas with various corneal diseases were snap frozen and cryosections were prepared for histological examination. Furthermore, the protein content was measured according to the method of Bradford and the concentration of IL-1 beta and IL-6 were determined using a specific immunosorbent test (ELISA). RESULTS: It was found that IL-1 beta and IL-6 level were clearly higher in corneas with ulcerations and distinct inflammatory signs. Lower levels of both interleukins were found in corneas with a weak expression of inflammatory signs. CONCLUSIONS: Keratitis, keratoconus with inflammatory signs, and ulcerating processes showed higher interleukin levels than corneas with non-inflammatory disorders like scar formation, corneal dystrophy and keratoconus. The results could show that, depending on the clinical diagnosis, the inflammatory status of the cornea may be evaluated by the interleukin levels determined in the corneal tissue.

Cornea↗

PubMed1995

[Therapeutic hydrophilic bandage lenses after perforating keratoplasty in severe eye chemical burns].

BACKGROUND: The prognosis of penetrating keratoplasty after severe eye burns is uncertain. Beside of immune reactions the outcome is determined by surface problems. PATIENTS AND METHODS: Between July 1991 and October 1993 in 15 patients (16 eyes) with grade IV eye burns penetrating keratoplasties with large diameters (11-16 mm) were carried out. Cultured corneas were used with an intact epithelium. In 9 eyes hydrophilic bandage lenses (Geaflex 70, Fa. Wöhlk, Kiel) were applied initially, in the remainder 7 eyes within 7 days postoperatively. RESULTS: The lens radius best suited was found out by trial, because corneal topography was not possible for many weeks. In 12 (75%) eyes the lens had to be fitted steep, with a radius from < or = 8.7. A change in lens radius during the healing course was rare. The frequent use of artificial tear drops was important, because many eyes showed clinical manifestations of dry eye syndrome. Complications during soft contact lens wearing were rare. In 5 eyes microbiological examination was positive, but successfully treated. Under the protection of soft contact lenses 9 eyes maintained an intact epithelium. In the remainder eyes severe vascularisation with large persistent epithelial defects occurred mostly as a consequence of immune reactions. These keratoplasties developed on growth of inflammatory pannus or progressive ulceration. The average of the follow-up time was 22 months. CONCLUSION: The use of large diameter keratoplasties in combination with hydrophilic bandage lenses proved to be successful to maintain the integrity of the epithelium in these high-risk keratoplasties. The prognosis of these transplants is, however, determined by immune reactions.

Adolescent↗

PubMed1995

[Effect of donor illness on endothelial cell number of human corneas].

BACKGROUND: In most clinical centers donor material can not be obtained in necessary amounts. Therefore corneas from long-suffering donors have to be accepted, too. It was the aim of this study to demonstrate the influence of the cause of death on the endothelial cell density of fresh human corneas. MATERIAL AND METHODS: The endothelial cell count of 81 donor corneas was determined after preparation of the corneo-scleral disc. For all donors the premortal history was evaluated concerning the cause of death and therapy. In this manner donors were divided into five groups: sudden death, carcinoma, septicemia, renal insufficiency and diabetes mellitus. RESULTS: There were no significant differences in endothelial cell count between these five groups. Even chemotherapy and radiatio of the donor had no influence on the cell density. CONCLUSION: It may be concluded, that clear corneas have a sufficient endothelial cell density and that the cause of death has no influence on this parameter. Therefore also corneas from donors with long-standing diseases may be accepted for transplantation.

Adult↗

PubMed1995

[Tenon-plasty and early keratoplasty in severe chemical eye burns].

In severe eye burns with destruction of extensive areas of the conjunctiva and epibulbar tissue, Tenon plasty has proved to be successful. Because the epithelium fails to cover the denuded stroma, the corneal surface must be protected by an artificial epithelium. If necrolysis occurs, a tectonic keratoplasty must be performed early. The clinical courses of 12 patients with 14 very severely burned eyes are reported. In addition to Tenon plasty, early penetrating keratoplasies with large diameters 10-16 mm were performed up to 3 months after the accident. The follow-up time was between 6 and 34 months (mean 15.1 months). In five cases the Tenon tissue showed marked inflammation, and the keratoplasties developed large, persistent epithelial defects and had to be covered by conjunctiva. In the other cases it was possible to preserve a healthy epithelial layer by applying soft contact lenses. In 79% of the cases an endothelial graft rejection was observed. In about 50% the transplants were lost. Early keratoplasties are mainly for tectonic repair in severely burned eyes. Optical rehabilitation was achieved in only a few cases.

Adult↗

PubMed1995

[Long-term results of Tenon-plasty in treatment of severe chemical eye burns].

From November 1986 to December 1993, 50 patients with 62 very severe eye burns were treated with Tenon plasty. Forty-one eyes showed widespread scleral ischemia, while 21 eyes had developed corneoscleral ulcerations. Surgery was done 3-126 days after the injury. A total of 210 quadrants was treated with Tenon plasty. Epithelization of the Tenon sheets was complete within 21 days in 79% and in all eyes up to 51 days. In all eyes corneoscleral ulcerations could be prevented or healed. In 48% isolated symblepharon formation or severe scarring of the fornices developed within 3 months after Tenon plasty. In these cases restoration of the conjunctiva was achieved by transplantation of autologous conjunctiva or nasal and buccal mucosa. Spontaneous epithelization of the burned cornea was achieved in 25.8%. In 36 eyes penetrating keratoplasty was performed. Sixteen (44.5%) grafts failed due to surface problems, while 12 (33.3%) grafts failed because of an endothelial immune reaction. Tenon plasty proved to be successful in preventing early necrolysis of the anterior eye segment in very severe eye burns. However, the prognosis for penetrating keratoplasty in these eyes is limited due to surface problems and immune reactions.

Adolescent↗

PubMed1995

Remarks on the vitality of the human cornea after organ culture.

The purpose of this study was to obtain further information on the viability of organ-cultured human cornea. We thus used a specific staining method for succinate dehydrogenase (SDH), which is located in the membrane system of vital mitochondria. We examined fresh and long-term-cultured human corneas. After an initial incubation period in dextran-free culture medium, corneas were stored in a medium containing dextran. With respect to different appearances of the SDH staining, minimal essential medium without dextran seems to have a positive effect on the condition of epithelial cells. After renewal of the medium, keratocytes showed a brief improvement followed by a delayed deterioration, while the endothelial cells were severely damaged. However, best results for all three cell types were observed on the fourth day in a medium containing dextran. We therefore conclude that these corneas were best suited for transplantation.

Adolescent↗

PubMed1994

The influence of the cause of death and age on human corneal metabolism.

PURPOSE: Little is known about the metabolic status of human corneas before transplantation. The authors attempted to determine the influence of both cause of death and age on the corneal metabolism. METHODS: Adenosine-triphosphate (ATP), adenosine-diphosphate (ADP), glucose, and lactate were measured in the stroma and endothelium of 30 human corneas. The corneas were divided into four groups according to cause of death and four groups according to age. Corneas from donors with diabetes were excluded. RESULTS: Corneas from patients who died suddenly--because of cardiac infarction, for example--have good metabolic status even 24 hours after death. In corneas of patients with cancer or sepsis, the metabolism has run down. In comparison, corneas from patients with cancer are in better metabolic condition than those from donors with sepsis because they have adapted to catabolism. Corneas donated from patients with renal insufficiency show results somewhere in between. Statistical evaluation revealed significant differences in ATP concentrations for corneas from donors who died suddenly and from patients with renal insufficiency compared to corneas from patients with sepsis. It could be shown that glucose concentrations as a resource for metabolism increase with age. The best ATP-ADP ratios were found in the group of 40- to 59-year-old donors. Nevertheless, differences between the age groups were not statistically significant. CONCLUSION: From our results it can be concluded that the cause of death and systemic metabolism have an influence on corneal metabolism. Results concerning donor age reflect the well-known fact that donor age has no influence on the quality of keratoplasty material.

Adenosine Diphosphate↗

PubMed1993

Immunological reactions against PMMA lens material?

We investigated the kind of reactions that occur after injection of a PMMA lens powder into the back skin of rabbit. The lens powder was suspended in NaCl and incomplete Freund's adjuvant to reinforce the immunological reaction. The ELISA test was carried out to detect antibodies against the lens material as a whole and against the UV absorber Tinuvin in particular. We also performed histological and immunohistochemical examinations of the back skin. We did not detect antibodies against either the lens material or against Tinuvin. Histological examination showed a foreign-body or delayed allergic reaction against the lens material. Lymphocytes surrounding the PMMA were found to be mainly of the T-type, which supports the results of the ELISA test.

Animals↗