Biomedical subjects

M Reim

Publications and source records attributed to M Reim.

At least 19 recordsLinked to original sources

PubMed2001

Chlorite-hemoprotein interaction as key role for the pharmacological activity of the chlorite-based drug WF10.

WF10 is a chlorite-based drug that modulates macrophages functional states and can be safely administered to humans. WF10 potentially modulates disease-related up-regulation of immune responses both in vitro and in vivo. Thus immune response is influenced in a way that inappropriate inflammatory reactions are downregulated. The molecular mechanisms involved are not completely understood. Biochemical data suggest the reaction of chlorite with hemoproteins as the central step in the activation process of the drug. Thereby a chlorinating agent is generated, resulting in the oxidation of reduced sulfur-containing molecules and in the conversion of amino residues into more or less stable chloramines. The most prominent chloramine in vivo is taurine chloramine. Taurine chloramine is a long-lived molecule with immunomodulatory properties. For instance, taurine chloramine inhibits the generation of macrophage inflammatory mediators such as nitric oxide, prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6). This study on the biochemical mechanism of WF10 gives evidence that hemoprotein dependent chlorination of taurine is not only observed in vitro but also very likely in vivo. To characterize the oxidant, generated during heme activation, different methods were used: Chemiluminescence, EPR-spectroscopy, UV/VIS-spectroscopy, gas (GC) and size exclusion chromatography. In summary, the results indicate as the first products of hemoprotein catalyzed chlorite activation a chloroxygen-species (probably HOCl/OCl-) and a ferryl-oxygen species at the hemoprotein active site in analogy to the known peroxidase (compound I and II) intermediates. Moreover, hydrogen peroxide and chlorite seem to react in a similar way with heme centers. It is proposed that WF10 represents an "inactive" transport form of potentially active chlorine. Reactivity of the latter is restricted unless heme moieties in proteins or enzymes activate the "transport form" to perform reactions in analogy to peroxidases (i.e. myeloperoxidase-catalyzed formation of HOCl/OCl-).

Amino Acids, Cyclic↗

PubMed2001

[Effect of serum and osmotically active substances on metabolism in 262 tissue cultures of pig's corneas--improved preservation of donor tissue for keratoplasty].

BACKGROUND: The storage time of corneal organ cultures in limited in the closed system mainly used in European eye banks. In addition, swelling during storage reduces the quality of the donor material for keratoplasty. Therefore, dextrane was added in concentrations of 2.5%, 5%, 7.5% and 10% to the culture medium, and the energy producing metabolism was investigated. MATERIALS AND METHODS: The experiments were carried out with 262 pig corneas. MEM with some supplements was used at 31 degrees C. No serum was added, because glucose consumption, lactate production and ATP levels proved to be the same or better than with serum supplement. After 6 and 12 days, the corneas from organ cultures were extracted with perchloric acid. The levels of glucose and lactate in the stroma and of ATP and ADP in the epithelium were analysed with enzymatic-optical tests. RESULTS: Dextrane inhibited glycolysis and the production of ATP in corneal organ cultures during twelve days. With 7.5% and 10% dextrane in the medium, lactate levels in the cornea decreased from 6.09 to 4.5 and 4.6 microM/g H2O instead of increasing. At the same time, glucose increased paradoxical from 1.3 to 3.4 and 2.2 microM/g H2O, respectively. With 5% dextrane, glycolysis operated sufficiently producing an increase of lactate levels from 6.0 to 8.8 microM/g H2O and consuming glucose from levels of 1.27 down to 0.57 microM/g H2O. After 12 days with 7.5% and 10.0% dextrane, ATP levels were reduced, from 4.54 to 0.98 and 0.49 microM/g dry weight, and ATP/ADP ratios from 1.9 to 1.1 and 0.7 respectively. With 2.5% dextrane, the ATP was diminished from 4.5 to 2.2 microM/g dry weight. When 5% dextrane were added to the culture medium, the hydration was at optimum by 4.1, and ATP levels were reduced only from 4.5 to 2.6 microM/g dry weight. Moreover, the ATP/ADP ratios were at 2.1 as good as without dextrane. CONCLUSIONS: From the results it was concluded, that serum free medium may be used, and that permanent dewelling proved to be beneficial for the energy producing metabolism of the cornea in organ culture. Such conditions may improve morphological and metabolic quality of donor material. From previous publications, it was recommended, to use instead of toxic dextran the well tolerated HES (hydroxyethyl starch) and to apply a storage temperature of 21 degrees C, which slowed down glucose consumption without impairing the energy producing metabolism.

Adenosine Diphosphate↗

PubMed2001

Chemical and thermal injuries of the eyes. Surgical and medical treatment based on clinical and pathophysiological findings.

Light burns heal well within a few days. Severe chemical and thermal injuries of the eyes destroy surface epithelia and cause ischemic necroses of conjunctiva, cornea, sclera, iris, ciliary body, and lids. An inflammatory response follows with leucocyte infiltration and release of inflammatory mediators. Prostaglandins, lipoxygenase products, cytokines, superoxide radicals and Iysosomal enzymes are known to be active in eye burn disease. Their activities result in corneal, scleral and conjunctival ulceration, tissue proliferation and scarification, which develop within weeks, months and even years after the accident. Pathophysiological events produce defined clinical pictures. Some agents take special actions, e.g. alkali penetrates within seconds into the anterior chamber, sulfuric acid burns as well as quick lime burns forming slaked lime produce considerable heat. Hydrofluoric acid is highly toxic and induces early necroses. Heat causes deep ischemic necroses and lateron strongly shrinking scars. Onset and intensity of first aid decided on the outcome. Immediate rinsing is essential. Cool water, saline, Ringers lactate solution and BSS are good rinsing media. For first aid, buffered Previn seems suitable. Major chemical and thermal injuries need a variety of medical and surgical treatments: Necroses must be excised surgically. Tenon plasty is performed to reconstruct conjunctiva. Amnion-, limbus- and early keratoplasty or artificial epithelium are applied, initially to save the cornea from melting, and later to restore vision. Conjunctical, lid and intraocular surgery may be necessary. The aim of medical treatment is to suppress the inflammatory response and to prevent infection. Corticosteroids, antibiotics, ascorbate and inhibitors of proteolytic enzymes are used. Secondary glaucoma must not be forgotten. Extensive therapy is sometimes rewarding, results are presented.

Burns↗

PubMed2000

Eye burns: an emergency and continuing problem.

Adequate treatment of eye burns is an essential task of rescue teams. Clinical and occupational medicine studies have shown that efficient emergency treatment can prevent severe eye damage, but therapy is frequently delayed or inadequate. When initial therapy has been delayed or missed, several treatment strategies, including surgery, are available that may improve the outcome of an injury with poor visual prognosis. Discussed in this review are common accident mechanisms, causative agents and biophysical/pathogenetic aspects of eye burns, together with emergency and long-term treatment strategies including surgical procedures, and factors influencing outcome.

Antidotes↗

PubMed2000

Microbiopsy in healthy rabbit corneas. A long-term study.

PURPOSE: Corneal biopsies are important in diagnosing multiple corneal diseases. They were previously performed by way of keratectomy, a method that causes corneal opacity and topographic changes due to scarring. Microbiopsy is a new way to perform corneal biopsies. Before microbiopsy may be performed on human corneas, the safety of this procedure has to be proved concerning clinical development, histological changes and topographic changes after multiple biopsies. METHODS: The healthy right cornea of 24 rabbits was punctured. 12 microtrephinations in 4 different symmetric patterns were performed. The clinical development of the bioptic sites as well as the topographic changes were observed over 5 months. After enucleation, serial sections of the corneas were analysed histologically. RESULTS: Out of 294 performed biopsies, 291 samples could be collected. 4 perforations occurred. The initial epithelial defect closed within 3 days. A pale stromal scar remained. The histological analysis of these scars showed a facette underlined by a dense hypocellular fibrous layer and a typical star-shaped figure consisting of a loose hypercellular stromal tissue. Only dioptric power of corneas with circle-pattern showed a statistically significant decrease. CONCLUSION: Micropuncture is a safe and efficient bioptic procedure. Even 12 micropunctures do not lead to significant changes of dioptric power in most patterns. Further studies are necessary to evaluate the reproducibility of refractive changes by circle patterns and corrections of astigmatisms.

Animals↗

PubMed1999

Metabolic changes of the human donor cornea during organ-culture.

PURPOSE: To study metabolic changes of the human cornea during organ-culture. Morphological changes have been extensively studied, whereas changes in human corneal metabolism have not been investigated yet. MATERIAL AND METHODS: 106 human corneas were stored for 1, 7, 15, 18, 21 and 28 days in a closed-system under standard eyebank conditions. After storage, glucose, lactate, ATP, ADP and AMP concentrations were determined in each cornea. RESULTS: Glucose concentration decreased during the first two weeks with a minimum on day 15. ATP and ADP concentrations increased during the same period of time, but had their minimum later, on day 18. Lactate increased during the culture period up to day 21 and decreased thereafter. CONCLUSION: From these data we conclude that the human cornea recovers during organ-culture, especially during the first two weeks. The changes occurring after a fortnight might be related to the artificial culture conditions. Nevertheless, the metabolic status is better than in post-mortem corneas. The changes may be partly avoided by changing the medium after at least two weeks of organ-culture.

Adenine Nucleotides↗

PubMed1999

The "Aachen" keratoprosthesis: a new approach towards successful keratoprosthesis-surgery.

BACKGROUND: None of the keratoprostheses available today is absolutely successful in the long term, neither the problems of extrusion, retroprosthetic membrane formation and intraocular pressure rise are yet solved. A new type of keratoprosthesis is required which can show improved ingrowth characteristics and allow intraocular pressure measurements. In order to possibly meet the above mentioned requirements we developed a flexible silicone keratoprosthesis with scleral fixation and chemical surface modification. METHODS: The one-piece keratoprosthesis is made of silicone rubber. Its optical zone has a diameter of 11 mm and is 0.3 mm thick. The surface-modified haptic consists of a scleral rim and eight branches for scleral fixation. A ridge at the back of the keratoprosthesis fitting into the trephination hole shall avoid leakage and retroprosthetic membrane formation. Optical and mechanical qualities are characterised by tensile tests, spectrophotometry and topography. RESULTS: A method for keratoprosthesis-production was established. The optical quality of the device was improved by submicron lathing of the mould. Spectrophotometry showed high visible and ultraviolet light transmission of the silicone. Mechanical tests with silicone samples revealed high tensile strength and elongation at break. The mechanical properties were not impaired by surface modification. CONCLUSIONS: The production of a flexible silicone keratoprosthesis with high optical and mechanical properties was established. Its use both for the treatment of permanently opacified corneas and as temporary keratoprosthesis seems to be possible.

Biomechanical Phenomena↗

PubMed1999

Functionally adapted surfaces on a silicone keratoprosthesis.

BACKGROUND: Silicone intraocular lenses as well as silicone sponges and encircling bands on the bulbar surface are widely used and are well tolerated. The aim of this project is a new one-piece silicone keratoprosthesis with enhanced cell adhesion in the haptic region to optimize the keratoprosthesis stability. These investigations show how enhanced profileration of conjunctival fibroblasts and, therefore, improved tissue compatibility can be achieved by hydrophilizing and by protein immobilisation on a hydrophobic silicone surface. This allows a combination of desired chemical and mechanical properties of the silicone bulk material with surfaces of improved tissue compatibility. METHODS: Silicone foils with surface modifications of different kinds were tested. Experiments were done using cell cultures with murine fibroblasts L-929 and human conjuctival fibroblasts. Cytotoxicity assays were carried out with cells grown on the material in direct contact, as well as in indirect contact, with extracts (EN 30993-5). Viability stains by means of fluoresceindiacetate and ethidiumbromide together with morphology analyses by hemalaun-staining were performed. RESULTS: For the unmodified and modified foils themselves and their extracts any negative influence on cell cultures of murine and human cells could be excluded. There was a gradual improvement of cell morphology, spreading and proliferation dependent on the degree of surface modification. Covalently immobilised fibronectin showed the best results in contrast to adsorptive binding. CONCLUSIONS: Silicone surfaces can be modified chemically with bioactive proteins. These modifications are cell compatible and do not result in toxic reactions. The degree and type of silicone hydrophilization results in improved development of cell morphology, spreading and proliferation. Even better results are obtained after covalent binding of bioactive proteins like fibronectin. Improved biocompatibility with enhanced cellular overgrowth has been demonstrated in vitro for the modified silicone of the haptic region. We believe that this type of modification will help in reducing extrusion problems observed with former keratoprostheses.

Animals↗

PubMed1998

Retinal capillary density in patients with arterial hypertension: 2-year follow-up.

BACKGROUND: Arterial hypertension is known to be an important risk factor for cerebral and cardiovascular disease. Previous studies have demonstrated a decrease of capillary density in the perifoveal network in tandem with decreased capillary flow velocity in patients with essential hypertension. In a prospective study we quantified the retinal microcirculation in order to evaluate the time course of changes in the perifoveal network. METHODS: Thirty-three patients with essential hypertension (mean age 45 +/- 14 years) underwent video-fluorescein angiographic studies at baseline and at 2 years 28 +/- 6 months) thereafter. The angiograms were obtained with a scanning laser ophthalmoscope and were digitally recorded. By means of digital image analysis we quantified off-line the mean area of perifoveal intercapillary areas (PIA) and the mean capillary flow velocity. RESULTS: At baseline, the patients with hypertension showed significantly increased PIA and a significantly decreased capillary flow velocity compared with reference values. During the follow-up period the capillary flow velocity decreased further significantly, whereas the PIA showed no significant change. CONCLUSIONS: The continuous decrease of capillary flow velocity demonstrates a progression of altered microcirculation in patients with essential hypertension whose blood pressure was believed to be well controlled. Further studies with this technique may be useful to determine the influence of antihypertensive therapy and may help to identify patients at risk for cerebrovascular events.

Blood Flow Velocity↗

PubMed1998

Changes in mineral composition of rabbit corneas after alkali burn.

BACKGROUND: Mineral balance is essential for maintaining corneal transparency. In preliminary investigations, we found alterations of mineral concentrations in the human cornea after chemical burns. In this prospective study the mineral content of the rabbit cornea was quantified after experimental alkali burns. METHODS: Thirty-two eyes of rabbits were burnt for 30 s with 1 M NaOH. A short period of saline rinsing followed, but no further therapy was given. The eyes of 20 healthy rabbits served as a control. We measured the water content by weighing the cornea before and after drying. The mineral content of the cornea was determined in different stromal layers using energy-dispersive X-ray analysis in the scanning electron microscope. Groups of eight rabbits were examined on days 0, 1, 4 and 8 after the experimental burns. RESULTS: After alkali burns the mineral composition of the corneal stroma changed considerably. Sodium was present in high concentrations immediately after burning, up to 708 mmol/kg dry weight, and returned to normal on day eight. Chlorine increased significantly throughout the whole period. Sulphur concentrations stayed almost normal, showing only a minute loss of ground substance after alkali burn. A considerable and increasing edema could be concluded from the water content. CONCLUSIONS: Alkali burns resulted in a dramatic change of the corneal mineral content. Therapeutic intervention with appropriate solutions is required to restore and maintain the normal mineral composition of the denuded corneal stroma.

Animals↗

PubMed1998

Assessment of conjunctival epithelium after severe burns and surgical reconstruction with Tenon plasty by means of a modified impression cytology procedure.

PURPOSE: Tenon plasty has been used to reconstruct the conjunctival surface in severe burns in which ischemic sclera was exposed or undergoing ulceration. A modified impression cytology procedure was applied to investigate the conjunctival epithelium. The quality of the regenerated epithelium on the advanced Tenon sheets was assessed. METHODS: The 63 conjunctival samples of eye-burn patients were investigated. Among these, 41 patients had very severe bums. Conjunctival samples were collected from 6 weeks after surgery to 5 years after the accident. They were compared with conjunctival epithelia obtained from 53 normal eyes of healthy volunteers. A 25-mm2 Biopore membrane (Millipore Catalogue PICM 01250) was placed on the bulbar conjunctiva surface in the lower temporal quadrant, at a distance of 3-5 mm from the limbus, till it was soaked with fluid. The ablated cell sheets were stained with periodic acid-Schiff (PAS). RESULTS: In all cases, an intact conjunctival epithelium was observed. In healthy eyes, 2,338 epithelial cells/mm2 and 155 goblet cells/ mm2 were found. Eyes after a surgical reconstruction with Tenon plasty resulted only in 1,575 epithelial cells/mm2 and 72 goblet cells/mm2. The differences were highly significant. The ratio of epithelial to goblet cell counts revealed an increase of goblet cells during the postoperative period. CONCLUSION: Conjunctival epithelium as well as goblet cell densities were reduced after heat, lime, alkali, and acid burns. However, after concrete burns, cell densities were increased. Tenon plasty provided the regeneration of the fully intact conjunctival epithelium. Goblet cells were present from 6 weeks after the surgery on; their number increased gradually. The stimulation of the goblet cell mucous secretion is discussed.

Adult↗

PubMed1998

Acute effect of metipranolol on the retinal circulation.

AIM: To assess the effect of topical and systemic application of a beta adrenergic receptor blocker on retinal haemodynamics. METHODS: 24 healthy subjects were included in this double masked, randomised, placebo controlled crossover study. Metipranolol, a non-selective beta adrenergic receptor blocking agent was used as test drug. In all subjects arm-retina time, arteriovenous passage time, arterial mean dye velocity, the arterial vessel diameters, and capillary flow velocity were quantified from digital video fluorescein angiograms. RESULTS: A significant effect was observed on the arteriovenous passage time (p < 0.05), the arterial mean dye bolus velocity (p < 0.05), and capillary blood velocity (p < 0.05), but not on the arterial vessel diameter. The arterial mean dye bolus velocity and capillary blood velocity increased after application of the test drug (topical and systemic). In tandem with this a decrease of the arteriovenous passage time was observed. The perfusion pressure increased after topical application and remained unchanged after systemic application of metipranolol. CONCLUSIONS: This study shows that systemic as well as topical application of metipranolol leads to increased retinal blood flow velocities. The implications of these results for treatment with beta adrenergic receptor blockers is not clear. However, in view of these data it is very unlikely that treatment with metipranolol has a negative effect on retinal blood flow.

Administration, Oral↗

PubMed1998

Development of a surface modified silicone-keratoprosthesis with scleral fixation.

BACKGROUND: Many attempts have been made to create artificial corneas. The keratoprostheses currently available do not allow measurements of the intraocular pressure (IOP) and restrict the visual field. The main problem is extrusion due to an insufficient connection between implant and surrounding tissue. It is our aim to create a flexible keratoprosthesis with a wide field optic allowing measurements of the IOP. Surface modification will improve cell adhesion and therefore stability between implant and tissue. METHODS: The keratoprosthesis is made of silicone rubber. The optical zone is 11 mm in diameter with a thickness of 0.3 mm. The surface modified haptic consists of a scleral rim and 8 branches for scleral fixation. Optical and mechanical qualities were tested by tensile tests, spectrophotometry and topography. RESULTS: A method to produce one-piece silicone keratoprostheses was established. Submicron lathing of the mould led to an excellent optical quality. Spectrophotometry showed high degree of visible and ultraviolet light transmission of the silicone. Mechanical tests revealed high tensile strength and elongation at break which were not impaired by surface modification. CONCLUSION: The production of a flexible silicone keratoprosthesis with high optical and mechanical properties was accomplished, with possible use as both permanent and temporary keratoprosthesis.

Corneal Diseases↗

PubMed1997

The corneal stroma: an inhomogeneous structure.

PURPOSE: This study was conducted to determine the elemental composition of the human cornea. Special attention was paid to corneal stroma inhomogeneity. METHODS: Seventy human corneas were examined by means of energy-dispersive X-ray analysis. Epithelium, subepithelium, middle stroma, sub-Descemet layer, Descemet's membrane and endothelium were subjected to repeated measurements. RESULTS: In the cellular layers the phosphorus concentrations were high [0.35 mol/kg dry weight (dw) in the epithelium and 0.403 mol/kg dw in the endothelium]. Similar concentrations were found for sulphur (0.38 mol/kg dw in the epithelium). Stromal layers showed high contents of sulphur: 0.26 mol/kg dw. The phosphorus concentration was found to be higher in the subepithelium than in the middle stroma. Sulphur concentrations were highest in Descemet's membrane, followed by the subepithelium and the middle stroma. DISCUSSION: Nucleic acids and energy-containing phosphates explain the high levels of phosphorus in the cellular layers. The high sulphur concentrations may be related to the phosphoadenosinphosphosulfate and protein turnover in the epithelium. We interpret the inhomogeneous distribution of phosphorus in the stroma as a function of the density of keratocytes. An evaluation of all known sulphur-containing biochemical components of the stroma (0.217 mol sulphur/kg dw) corresponds to our measurements. In contrast to former results we find the corneal stroma to be an inhomogeneous structure.

Aged↗

PubMed1997

[Temperature changes of the cornea by applying an eye bandage].

BACKGROUND: The corneal temperature is not often measured, but it may be useful to evaluate the temperature-changing effect of the application of eye bandages. The reason for applying an eye bandage is to calm an inflamed eye and to provide mechanical protection. Everyone knows that some patients have more complaints after an eye bandage has been applied. This phenomenon might be caused by the inflamed eye being warmed up by bandage application. MATERIALS AND METHODS: In 40 apparently healthy subjects 24 +/- 1.93 years of age we examined the temperature changes caused by two different types of eye bandage. The measurements were done with a Jeol infrared camera. Twenty probands received a monocular bandage consisting of a perforated plastic cap and another 20 subjects a monocular mull bandage with a perforated plastic cap. RESULTS: The mean corneal apex temperature was 32.05 +/- 0.74 degrees C. Both bandages caused the corneal temperature to go up considerably. The perforated plastic cap increased the mean apex temperature by 0.58 +/- 0.48 degree K and the combined mull bandage by 1.15 +/- 0.57 degrees K (P < 0.05). CONCLUSIONS: Application of an eye bandage increases the corneal temperature significantly. This is known to change enzyme activities and to cause prostaglandin liberation and pain. A change in the bacterial spectrum may result. Cooling as a universal principle in antiphlogistic therapy might be a supplementary therapy in treating sterile, but inflamed eyes.

Adult↗

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

Perifoveal capillary network in patients with acute central retinal vein occlusion.

PURPOSE: Reduction of visual acuity in patients with central retinal vein occlusion (CRVO) is often caused by macular edema and ischemia. The major causative factor for macular changes may be a disturbance in the macular microcirculation. The authors studied the perifoveal microcirculation in patients with central retinal vein occlusion to quantify the extent of circulatory deficiency in the macular circulation. METHODS: Twenty-four patients (8 men, 16 women) with recently diagnosed CRVO were included in this study. The following data were quantified: mean capillary blood velocity (CBV), foveal avascular zone (FAZ), and mean perifoveal intercapillary area (PIA). RESULTS: In patients with CRVO, the mean flow velocity was significantly reduced compared with healthy subjects (1.63 +/- 0.220 mm/sec vs. 2.89 +/- 0.41 mm/sec, P < 0.01). The FAZ and the mean PIA characterizing capillary density were significantly enlarged in CRVO (5548 +/- 1151 microm2 vs. 3872 +/- 529 microm2; P < 0.01). CONCLUSIONS: The present study demonstrates that CRVO not only led to a decrease in capillary blood velocities, but also to an enlargement of perifoveal intercapillary areas in early stages of the disease.

Acute Disease↗

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↗