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Biomedical subjects

G Duncker

Publications and source records attributed to G Duncker.

At least 37 records · Page 2Linked to original sources
PubMed1998

[Cutting edges after automatic lamellar keratotomy].

BACKGROUND: In order to perform an automatic lamellar keratotomy microkeratomes are used, which differ from each other in several technical details. This study was done to examine, whether there are characteristics of the cutting edge, typical of each device, and whether there are some correlations between the cutting quality and technical parameters. METHODS: In Germany seven different keratomes are used today. We performed the procedure of automatic lamellar keratotomy by using each of them on 8 fresh enucleated pig eyes and we examined the corneal tissue by means of scanning electron microscopy. The cutting edges were judged by their smoothness and sharpness. RESULTS: A dominantly smooth cutting edge was found on the corneas cut by the MKM-System, the Universal Keratome and the BK-Microkeratome Set, while the Automatic Corneal Shaper, the Microtech-Mikrokeratom, the Rotor-Keratom and the Schwind-Mikrokeratom mostly produced a saw-toothed edge. CONCLUSIONS: The quality of the cutting edge may be influenced by the relationship of the speed of the pass and the rate of blade oscillation/rotation. Therefore it seems that a lower feed during one oscillation/rotation results in a more smooth pattern of the cutting edge.

Animals↗
PubMed1998

Microbiological investigations to validate the preparation of corneal transplants.

The globe and cornea are colonized by microorganisms and cannot be removed as sterile products. Antiseptic measures and storage of the cornea in medium containing antibiotics lead to an obvious reduction of the microbial flora. Unfortunately there is the possibility of secondary microbial contamination during the preparation. Large amounts of bacteria or resistant bacteria can ruin attempts to reduce the microbial flora. To validate the whole process of preparation we investigated the contamination of removed globes, environment, materials, instruments and media for each sequence of operation and eliminated sources of contamination. Recommendations are given to ensure a virtually sterile product at the end of preparation.

Bacteria↗
PubMed1997

MRI of the nasal cavity, the paranasal sinuses and orbits in Wegener's granulomatosis.

The purpose of this study was to evaluate diagnostic MRI criteria in Wegener's granulomatosis of the nasal cavity, the paranasal sinuses and orbits. Between March 1991 and January 1996, 62 patients with biopsy-proven Wegener's granulomatosis were studied with T1- and T2-weighted spin-echo (SE) sequences. In 32 patients coronal postcontrast T1-weighted images were obtained. Mucosal thickening of the nasal cavity and paranasal sinuses was demonstrated as high-intensity lesions on T2-weighted SE sequences in 57 patients (92%). Of this group, inflammatory granulomatous tissue was found on biopsy in 30 patients (48%) in the nasal cavity and in 4 patients (6%) in the paranasal sinuses. In 23 patients (37%) biopsy revealed unspecific inflammatory changes without evidence of granulomatous tissue. In 14 patients (23%) granulomas were depicted as low-signal intensity lesions on T1- and T2-weighted SE sequences in the paranasal sinuses and orbits. In 5 patients (8%) osseous destruction was found. After gadolinium injection, 12 of 14 granulomas showed inhomogeneous signal enhancement. In two granulomas no enhancement was found. The MRI technique is helpful in the diagnosis of patients with Wegener's granulomatosis. In the initial inflammatory process of Wegener's granulomatosis, it is not possible to differentiate between mucosal inflammation and granulomatous tissue in MRI. In the later stage of granulomatous transformation, granulomas can be depicted as low-signal-intensity lesions. Therefore, Wegener's granulomatosis should be included in the differential diagnosis of patients with low-signal-intensity lesions on T1- and T2-weighted SE sequences of the nasal cavity, paranasal sinuses and orbits.

Adult↗
PubMed1997

[Intraoperative skiascopy for determining the refractive value of an implantable intraocular lens].

BACKGROUND: Preoperative biometry for calculation of the refractive power of intraocular lenses is not sufficiently reliable in certain cases. Most frequently inaccuracies tend to occur in highly myopic eyes. Preceding refractive procedures can also impair IOL-calculation or even make it impossible. PATIENTS: In a highly myopic patient IOL-power calculation was not possible with conventional calculation formulas due to a preexisting refractive silicone lens located between the cataractuous natural lens and the iris. In another myopic patient ultrasound measurement of axial eye length produced variable and unreliable results. Therefore retinoscopy was performed intraoperatively in the aphakic eye. Refractive power of the IOL was calculated using a new formula. For validation of the method retinoscopy was performed intraoperatively in a second group of 11 patients with unproblematic ultrasound biometry. RESULTS: In 3 eyes IOL power was chosen according to intraoperative retinoscopy. A maximal deviation of 1.25 D from the aimed refraction resulted. In the second group, the retinoscopic method produced partially considerably inaccurate results as compared to the ultrasound biometry. Inaccuracies increased with the extent of hyperopia. CONCLUSIONS: In cases of difficult or inaccurate preoperative ultrasound biometry IOL power can be estimated after intraoperative retinoscopy in the aphacic highly myopic eye. IOL power can be calculated instantly using computer programs or tables. This method additionally enables the surgeon to control the refractive result of intraocular lens implantation prior to wound closure. However this method lacks reliability in higher hyperopic eyes, as in these cases small changes in corneal vertex distance of the lens used for retinoscopy highly alter the result.

Adult↗
PubMed1997

Effects of viscoelastics on bovine corneal endothelial cells in vitro.

PURPOSE: To evaluate the possible toxic effects of sodium hyaluronate and hydroxypropyl methylcellulose on corneal endothelium. METHODS: Cultured bovine corneal endothelial cells (BCEC) were treated with either original Healon (10 mg/ml) or Methocel (20 mg/ml) for 1 h, or with various dilutions of these substances in culture medium for up to one week. The toxicity of the viscoelastics was assessed in terms of lactate dehydrogenase (LDH) release into the supernatant and of cell density. RESULTS: Neither Healon nor Methocel in a dilution of 2 mg/ml enhanced LDH release after 72 h incubation, when compared with the control in a confluent model. In a proliferation model neither diluted Healon nor Methocel showed apparent inhibitory or stimulatory effects on the growth of BCEC up to the highest concentration we tested. When a BCEC monolayer was covered for 1 h with either undiluted Healon or undiluted Methocel, a significant, though transient, higher LDH release was induced. CONCLUSION: The results indicate that the diluted viscoelastics are safe for long time contact with BCEC, but undiluted they may temporarily interfere with the metabolism of the cytoplasm membranes of BCEC.

Animals↗
PubMed1997

Expression of adhesion molecule CD44 on human corneas.

AIMS: This study was undertaken to confirm the distribution and expression of the molecule CD44 on human corneas under normal and pathological conditions. METHODS: Fifty eight corneal buttons from adult patients suffering from various corneal diseases and four normal corneas were included in this study. Frozen sections were stained immunohistochemically with monoclonal antibodies against human CD44 using an APAAP method and observed under a light microscope. RESULTS: In normal corneas CD44 was predominantly expressed on the membranes of basal epithelial cells and on the keratocytes, as well as on the vascular endothelial cells of the corneal limbi, but was not expressed on corneal endothelial cells. Enhanced expression of CD44 was observed on the epithelium of corneas with inflammation and allograft rejection. In a number of abnormal conditions including allograft rejection, corneal trauma, primary and secondary corneal endothelial decompensation the remaining endothelial cells stained positively for CD44. However, in some corneas of keratitis, keratoconus, and dystrophy the endothelium which appeared relatively integral in morphology and amount remained CD44 negative. CONCLUSIONS: These results suggest that CD44, the hyaluronate receptor, may play an important role in corneal cell-cell and cell-matrix interactions. Its regulation is closely related to corneal inflammatory reactions. The induction of CD44 on corneal endothelium might play a potential role in compensatory processes when corneal endothelial cells are injured.

Aged↗
PubMed1996

Chloroquine-induced lipidosis in the rat retina: functional and morphological changes after withdrawal of the drug.

BACKGROUND: The antimalarial and antirheumatic drug chloroquine is one of the most infamous amphiphilic cationic drugs in clinical ophthalmology. It is known to cause lipidosis and photoreceptor degeneration in the human and the rat retina. METHODS: We treated female albino Wistar rats (mean weight 200 g) orally with chloroquine (95 mg/kg body weight) for 12 weeks, followed by a period of 4 months with normal feed. After initial electroretinography in all rats, measurements were made after 4 and 12 weeks of treatment and 16 weeks after withdrawal. The rats were prepared for histological examination. RESULTS: Treatment of rats with chloroquine caused severe lipidosis in the neuroretina; photoreceptor cell degeneration was slight. After 12 weeks of treatment, the b-wave amplitude was reduced to 30% of the initial value; the a-wave amplitude was reduced, but remained within the range of normal values. After withdrawal of chloroquine the lipidosis remitted, but the degeneration of the photoreceptor cell layer continued to progress. Despite remission of lipidosis, electroretinography demonstrated functional disturbances, marked by reduction of the a- and b-wave amplitudes to 25% and 16% of initial values, respectively. CONCLUSIONS: Seen from the point of view of function, it is doubtful whether lipidosis is the primary cause of changes in the electroretinogram or of receptor cell degeneration.

Animals↗
PubMed1996

Cross-matches on donor cadaver retinal pigment epithelial cells in corneal risk patients.

BACKGROUND: Allografts can be rejected either through the antibody-mediated or cellular pathways. The objective of this study was to look at the extent of antibody formation in patients awaiting re-keratoplasty using cross-matches on cadaver retinal pigment epithelial (RPE) cells. METHODS: Cadaver RPE cells were derived by trypsin digestion from donor eyes (n = 1200). After 3 days of cell cultivation, the cells were adherent and began to lose their pigment. By day 7 most cells were clear and grew as a polygonal monolayer. MHC class I expression by RPE cells was studied by the W6/32 (anti-HLA-A, B, C) monoclonal antibody (MoAb) and that of class II (HLA-DR) by the 136 MoAb. Normal RPE cells express few class I and no detectable class II antigens. For the induction of MHC expression, cells were subsequently stimulated with 250 U/ml of recombinant gamma-interferon for 5 days. Cells were used for tissue typing and also for cross-matches with recipient serum. Cross-matches were subsequently performed and measured by flow cytometry. RESULTS: Both class I and class II antigens were strongly enhanced, as could be shown by immunohistochemical staining. Some 20% of those patients awaiting rekeratoplasty (n = 60) were positive for anti-HLA antibodies. In one case anti-DR3 antibodies were detected in a recipient who had had several rejection episodes after keratoplasty. CONCLUSIONS: RPE cells are not only useful for cadaver post-mortem HLA typing but also for donor-specific cross-matches. The degree of antibody formation after keratoplasty in rejecting patients was, however, low. This may imply that anti-HLA antibodies are not the major cause of corneal graft loss after keratoplasty.

Antibodies, Monoclonal↗
PubMed1996

Indirect immunofluorescence study of the cornea and the conjunctiva in a xenogeneic system: analysis of humoral reactivity in patients with Wegener's granulomatosis.

BACKGROUND: Ocular involvement in patients with Wegener's granulomatosis (WG) can cause progressive loss of vision. The pathophysiological events leading to the WG-specific ocular inflammation are unknown. METHODS: A method involving indirect immunofluorescence on bovine and porcine corneoconjunctival frozen sections was used to detect antibodies to corneal and conjunctival epithelium in serum samples from patients suffering from WG with ophthalmic involvement (orbital granuloma or ocular vasculitis, both active and inactive phase). Normal persons and WG patients without ophthalmic involvement served as control groups. Anti-human IgG, IgA and IgM were tested. RESULTS: Five different immunofluorescence patterns could be distinguished in each species. There were differences in the reactivity with bovine and porcine tissue. Every pattern was caused mainly by human IgG. The antibodies were directed to the cell nuclei or to extranuclear structures. All patterns also occurred frequently in normal sera. No pattern was found that occurred specifically in the serum of patients with WG and ocular inflammation. CONCLUSIONS: The results indicate that this immunofluorescence system does not detect a characteristic antibody profile that could be attributed to the serum of WG patients. Hence the approach lacks clinical usefulness as a diagnostic procedure.

Animals↗
PubMed1996

Adhesion molecule expression in bullous keratopathy.

BACKGROUND: Adhesion molecules may play an important role in the pathogenesis of bullous keratopathy. METHODS: The expression of the integrin VLA-beta 1, alpha-subunits of the beta 2-integrins LFA-1, Mac-1, and p150,95, the members of the immunoglobulin family ICAM-1 and VCAM-1, and the selectin ELAM-1 on corneas with bullous keratopathy (BK) secondary to intraocular surgery was studied immunohistochemically using an APAAP method. RESULTS: In the corneas with BK (in contrast to normal corneas), a downregulation of VLA-beta 1 was observed throughout the corneal tissues, particularly on the epithelial layer where bullae occurred; ICAM-1 was induced on epithelial membranes in both BK and inflamed corneas; and the expression of beta 2-integrins, VCAM-1 and ELAM-1 was upregulated in some specimens with remaining endothelial cells. CONCLUSION: The results show that the investigated adhesion molecules may participate in the pathogenesis of BK. The decrease in VLA-beta 1 in patients with BK may be an important factor in the occurrence and development of recurrent bullae; the induced ICAM-1 may recruit beta 2-integrin-positive leukocytes into the epithelial layer, thus aggravating epithelial damage; and beta 2-integrins and VCAM-1 may play a role in endothelial injury and decompensation.

Aged↗
PubMed1996

[New permanent humidity chamber in dry eye disorders].

BACKGROUND: In corneal lubrication or eyelid closure disorders it may be necessary to apply a monoculus to protect the eye from drying out. Changing the monoculus involves dermal irritation. Furthermore, because the monoculus is not completely airtight, the desired humidity is not achieved. INSTRUMENT: We introduce a tape-free permanent humidity chamber fastened to a spectacle frame that achieves a relative humidity of more than 98% even over a long period of time. PATIENTS/TESTED PERSONS: Five test persons and two patients with lagophthalmus were treated with a monoculus and with the permanent humidity chamber. Comparative measurements of the humidity achieved with the two methods were done. RESULTS: For both test persons and lagophthalmus patients the permanent humidity chamber is a good alternative to the monoculus, because it maintains a humidity of more than 98% r/H over a period of eight hours or longer. It consequently provides much better conditions for successful treatment and additionally minimizes skin irritation.

Dry Eye Syndromes↗
PubMed1995

Adhesion molecules in normal and pathological corneas. An immunohistochemical study using monoclonal antibodies.

BACKGROUND: Adhesion molecules are cell surface receptors that are probably important in various cell-cell and cell-extracellular matrix interactions of the cornea. METHOD: In this immunohistochemical light-microscopic study we analyzed the expression pattern of adhesion molecules in normal and pathological human corneas (cases of corneal inflammation and degenerative disorders). The analyzed molecules included the beta 1 integrin or VLA family VLA-1-6, the beta 2 integrins or leukocyte integrins LFA-1, Mac-1, and p150,95, the immunoglobulins LFA-3, CD2, ICAM-1 and VCAM-1 and the selectins ELAM-1 and GMP-140. RESULTS: Inflamed cornea (in contrast to normal cornea). On corneal epithelium, increased expression of the alpha 2 subunit of VLA-2 was detected and ICAM-1 was induced on the basal epithelial cells. On corneal stromal keratocytes, LFA-3 was induced and expression of the alpha subunits of VLA-1-6 and ICAM-1 was increased. On vascular endothelium, VCAM-1 and ELAM-1 were induced and ICAM-1 and GMP-140 expression was increased. On corneal endothelium, ELAM-1 was induced and increased levels of the alpha 1 subunit of VLA-1 and GMP-140 were expressed. Degenerative disorders (in contrast to normal cornea): In corneas with degenerative disorders we found decreased expression of adhesion molecules. CONCLUSION: Inflammatory cytokines increase the expression of the adhesion molecules. Increased expression of the VLAs probably promotes cell-extracellular matrix and cell-cell interactions. ICAM-1, VCAM-1, LFA-3, ELAM-1 and GMP-140 expression was increased on vascular endothelium in inflamed corneas. Corresponding receptors on leukocytes probably enable a selective recruitment of different leukocyte populations in inflammatory corneal diseases. The decreased expression of adhesion molecules in corneal degenerative disorders is probably a sign of reduced cell-cell and cell-extracellular matrix interactions.

Antibodies, Monoclonal↗
PubMed1995

Chloroquine-induced lipidosis in the rat retina: a functional and morphological study.

Corneal opacity, reversible retinal lipidosis and irreversible receptor cell degeneration are known to occur after long-term treatment with chloroquine. Female albino Wistar rats (initial age 6 weeks, weight between 100 and 150 g) were treated orally with chloroquine (40-60 mg/kg body weight) for 4 weeks and with 70-80 mg/kg body weight for the following 4 (group A) and 8 weeks (group B). The animals were submitted to electroretinography ERG, and the retinas were prepared for histological investigation. After treatment with chloroquine for 8 weeks, lipidosis-like inclusions could be seen in the rat retina. A deformation of the receptor cell layer was not observed by light microscopy. The a-wave amplitude decreased to 33% and the b-wave amplitude to 40% of the values before treatment. In contrast to group A, we found receptor cell degeneration and macrophage-like cells in the peripheral and central retina in rats treated for 12 weeks. These changes were probably responsible for a-wave and b-wave reductions of 50 and 79% of values before treatment, respectively. It can be assumed that changes in ERG parameters in the first period are caused by lipidosis. Later extremer deformation is induced by receptor cell degeneration and accompanying lipidosis.

Animals↗
PubMed1995

Recognition performance of subjects with color-vision deficiencies on a polychromatic sonar screen for ship navigation.

To facilitate differentiation between objects that are approaching, stationary, and moving away, these objects are represented in different colors on the screens of sonar locating devices used in ship navigation. Yellow represents stationary objects, and represents approaching objects, and green represents those objects moving away. A total of 46 subjects with normal color vision and 184 individuals with color-vision deficiencies, among them 29 deuteranopic, 100 deuteranomalous, 21 protanopic and 34 protanomalous individuals, were investigated for their ability to identify different signals. Ten different objects were presented for a period of 64 s each. As a minimal requirement it was established that 50% of the respective experimental group be capable of recognizing the objects within half of this time. Whereas 73.3% of the subjects with normal color vision could meet this requirement, none of the subjects in the different groups with color-vision deficiencies could do so. Only 16.1% of the deuteranopic subjects, 33.1% of the deuteranomalous individuals, 16.2% of the protanopic subjects, and 37.6% of the protanomalous individuals detected all objects within 32 s. No appreciable difference in the ability to recognize signals occurred among the different groups of subjects with color-vision deficiencies.

Color Perception↗
PubMed1994

Influence of disease manifestation and antineutrophil cytoplasmic antibody titer on the response to pulse cyclophosphamide therapy in patients with Wegener's granulomatosis.

OBJECTIVE: To assess the effectiveness of pulse cyclophosphamide (CYC) in the treatment of Wegener's granulomatosis (WG) and to identify the patients who are responsive to the treatment. METHODS: The prospective study included 43 patients with biopsy-proven WG. Clinical, radiographic, laboratory, and immunologic data were evaluated for predictive values regarding the outcome of pulse CYC therapy. RESULTS: Only 42% of the patients showed complete or partial remission that lasted at least 6 months after cessation of pulse CYC therapy. These responders had a higher frequency of disease activity limited to the upper and lower respiratory tract (39%, versus 8% in the nonresponder group; P < 0.05) and had lower titers of classic antineutrophil cytoplasmic antibody (cANCA) prior to treatment (< 1:64 42%, versus 6% in the nonresponder group; P < 0.05). In the 58% of patients who did not respond to pulse CYC treatment, there was both systemic disease involving more than 4 organ systems (mainly, the heart, nervous system, eye, and skin) and constitutional symptoms. Serious side effects induced by pulse CYC occurred in only 1 patient. CONCLUSION: Based on these findings, pulse CYC therapy appears to be effective in WG patients with moderate disease activity and low titers of cANCA, but of little benefit in patients with severe WG. Pulse CYC should therefore not be used as first-line therapy in patients with severe and rapidly progressing forms of WG associated with high titers of cANCA.

Adolescent↗