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Biomedical subjects

F Körner

Publications and source records attributed to F Körner.

At least 19 recordsLinked to original sources
PubMed2001

[Diabetic retinopathy--pathophysiological knowledge and modern treatment methods].

Diabetic retinopathy (DR) leads to visual impairment in the majority of patients suffering from diabetes mellitus for more than 20 years. Endothelial damage, capillary dropout, and vasoproliferative activity of various growth factors are some of the complex pathophysiologic events that lead to retinal damage. Insufficient blood glucose control and arterial hypertension are the leading risk factors for the progression of DR. Adequate therapeutic measures depend on timely and regular ophthalmologic examination. Laser photocoagulation prevents severe visual loss in about 50% of cases with proliferative DR and high risk factors as defined by the Diabetic Retinopathy Study Group. Dosage of laser treatment depends on the stage and severity of DR and requires appropriate experience of the surgeon. Introduction of modern vitreoretinal surgery has yielded considerable progress in the management of vitreous hemorrhages (VH) and tractional retinal detachment in advanced stages of proliferative DR. Results of vitrectomy in 765 cases with proliferative DR are presented. Visual loss can be prevented in over 70% of cases with simple VH without retinal detachment and limited neovascularization, but in only about 30% of cases of VH complicated with retinal traction detachment and extensive vasoproliferation.

Blood Glucose↗
PubMed2001

[Pharmacological therapy approaches in ocular traumatology].

Ocular trauma is the most common reason for unilateral blindness. In the last 15 years tremendous advances in diagnostics (CT, MRI, ultrasound) and surgery (pars plana vitrectomy, phacoemulsification, intraocular lenses) have been made. Furthermore new medical therapies to sustain treatment of eye accidents have been developed. On the basis of various traumatic diseases (abrasio, chemical injuries, hyphema, cataract, photothermal retina lesion and optic neuropathy) appropriate of these medical therapies are to be discussed.

Blindness↗
PubMed2001

Mutations in hepatitis C virus RNAs conferring cell culture adaptation.

As an initial approach to studying the molecular replication mechanisms of hepatitis C virus (HCV), a major causative agent of acute and chronic liver disease, we have recently developed selectable self-replicating RNAs. These replicons lacked the region encoding the structural proteins and instead carried the gene encoding the neomycin phosphotransferase. Although the replication levels of these RNAs within selected cells were high, the number of G418-resistant colonies was reproducibly low. In a search for the reason, we performed a detailed analysis of replicating HCV RNAs and identified several adaptive mutations enhancing the efficiency of colony formation by several orders of magnitude. Adaptive mutations were found in nearly every nonstructural protein but not in the 5' or 3' nontranslated regions. The most drastic effect was found with a single-amino-acid substitution in NS5B, increasing the number of colonies approximately 500-fold. This mutation was conserved with RNAs isolated from one cell line, in contrast to other amino acid substitutions enhancing the efficiency of colony formation to a much lesser extent. Interestingly, some combinations of these nonconserved mutations with the highly adaptive one reduced the efficiency of colony formation drastically, suggesting that some adaptive mutations are not compatible.

3' Untranslated Regions↗
PubMed2000

Biochemical and structural analysis of the NS5B RNA-dependent RNA polymerase of the hepatitis C virus.

Hepatitis C virus (HCV), the major causative agent of chronic and sporadic non-A, non-B hepatitis worldwide, is a distinct member of the Flaviviridae virus family. These viruses have in common a plus-strand RNA genome that is replicated in the cytoplasm of the infected cell via minus-strand RNA intermediates. Owing to the lack of reliable cell culture systems and convenient animal models for HCV, the mechanisms governing RNA replication are not known. As a first step towards the development of appropriate in vitro systems, we expressed the NS5B RNA-dependent RNA polymerase (RdRp) in insect cells, purified the protein to near homogeneity and studied its biochemical properties. It is a primer- and RNA template-dependent RNA polymerase able to copy long heteropolymeric templates without additional viral or cellular cofactors. We determined the optimal reaction parameters, the kinetic constants and the substrate specificity of the enzyme, which turned out to be similar to those described for the 3D polymerase of poliovirus. By analysing a series of nucleosidic and non-nucleosidic compounds for their effect on RdRp activity, we found that ribavirin triphosphates have no inhibitory effect, providing direct experimental proof that the therapeutic effect observed in patients is not related to a direct inhibition of the viral polymerase. Finally, mutation analysis was performed to map the minimal NS5B sequence required for enzymatic activity and to identify the 'classical' polymerase motifs important for template and NTP binding and catalysis.

Baculoviridae↗
PubMed2000

Primary open-angle glaucoma is associated with sleep apnea syndrome.

INTRODUCTION: The etiology of primary open-angle glaucoma remains unclear. Various risk factors, including vascular abnormalities, have been associated with this disease. Sleep-associated diseases, like sleep apnea syndrome, might also represent a risk factor. Sleep apnea syndrome is characterized by repetitive upper airway obstructions during sleep, inducing hypoxia and sleep disruption with the risk of cardiovascular and neurological sequelae. In this study, we determined the prevalence of sleep apnea syndrome in primary open-angle glaucoma patients. METHODS: Overnight transcutaneous finger oximetry was performed in 30 consecutive patients having primary open-angle glaucoma. We assessed the oximetry disturbance index during night sleep, a parameter used to diagnose sleep apnea syndrome and to grade its severity. RESULTS: Sleep apnea syndrome was more prevalent among primary open-angle glaucoma patients compared to normal historic controls of the same age and sex distribution (chi(2) = 9.35, d.f. = 3, p < 0.025). The oximetry disturbance index grade was significantly larger in the primary open-angle glaucoma group compared to normal controls (U = 3, 352, p = 0.01). According to the oximetry disturbance index, 20% (6/30) of primary open-angle glaucoma patients had sleep apnea syndrome. CONCLUSION: Primary open-angle glaucoma is associated with sleep apnea syndrome. Early recognition and treatment of sleep apnea syndrome are important to avoid cardiovascular and neurological complications.

Age Distribution↗
PubMed1999

Replication of subgenomic hepatitis C virus RNAs in a hepatoma cell line.

An estimated 170 million persons worldwide are infected with hepatitis C virus (HCV), a major cause of chronic liver disease. Despite increasing knowledge of genome structure and individual viral proteins, studies on virus replication and pathogenesis have been hampered by the lack of reliable and efficient cell culture systems. A full-length consensus genome was cloned from viral RNA isolated from an infected human liver and used to construct subgenomic selectable replicons. Upon transfection into a human hepatoma cell line, these RNAs were found to replicate to high levels, permitting metabolic radiolabeling of viral RNA and proteins. This work defines the structure of HCV replicons functional in cell culture and provides the basis for a long-sought cellular system that should allow detailed molecular studies of HCV and the development of antiviral drugs.

Carcinoma, Hepatocellular↗
PubMed1998

Biochemical and kinetic analyses of NS5B RNA-dependent RNA polymerase of the hepatitis C virus.

The biochemical properties of the RNA-dependent RNA polymerase (RdRp) of the hepatitis C virus were analyzed. A hexahistidine affinity-tagged NS5B fusion protein was expressed with recombinant baculoviruses in insect cells and purified to near homogeneity. Enzymatic activity of the purified protein was inhibited by KCl or high concentrations of NaCl and was absolutely dependent on Mg2+, which could be replaced by Mn2+. NS5B was found to be processive and able to copy long heteropolymeric templates with an elongation rate of 150-200 nucleotides/min at 22 degreesC. Kinetic constants were determined for all four nucleoside triphosphates and different templates. In case of a heteropolymeric RNA template corresponding to the last 319 nucleotides of the hepatitis C virus genome, Km values for UTP, GTP, ATP, and CTP were approximately 1.0, approximately 0.5, approximately 10, and approximately 0.3 microM, respectively. The profile of several inhibitors of RdRp activity and substrate analogs indicated that the enzyme has a strong preference for ribonucleoside 5'-triphosphates and that it closely resembles 3Dpol of picornaviruses.

Hepacivirus↗
PubMed1997

Biochemical properties of hepatitis C virus NS5B RNA-dependent RNA polymerase and identification of amino acid sequence motifs essential for enzymatic activity.

The NS5B protein of the hepatitis C virus (HCV) is an RNA-dependent RNA polymerase (RdRp) (S.-E. Behrens, L. Tomei, and R. De Francesco, EMBO J. 15:12-22, 1996) that is assumed to be required for replication of the viral genome. To further study the biochemical and structural properties of this enzyme, an NS5B-hexahistidine fusion protein was expressed with recombinant baculoviruses in insect cells and purified to near homogeneity. The enzyme was found to have a primer-dependent RdRp activity that was able to copy a complete in vitro-transcribed HCV genome in the absence of additional viral or cellular factors. Filter binding assays and competition experiments showed that the purified enzyme binds RNA with no clear preference for HCV 3'-end sequences. Binding to homopolymeric RNAs was also examined, and the following order of specificity was observed: poly(U) > poly(G) > poly(A) > poly(C). An inverse order was found for the RdRp activity, which used poly(C) most efficiently as a template but was inactive on poly(U) and poly(G), suggesting that a high binding affinity between polymerase and template interferes with processivity. By using a mutational analysis, four amino acid sequence motifs crucial for RdRp activity were identified. While most substitutions of conserved residues within these motifs severely reduced the enzymatic activities, a single substitution in motif D which enhanced the RdRp activity by about 50% was found. Deletion studies indicate that amino acid residues at the very termini, in particular the amino terminus, are important for RdRp activity but not for RNA binding. Finally, we found a terminal transferase activity associated with the purified enzyme. However, this activity was also detected with NS5B proteins with an inactive RdRp, with an NS4B protein purified in the same way, and with wild-type baculovirus, suggesting that it is not an inherent activity of NS5B.

Amino Acid Substitution↗
PubMed1995

[Vitrectomy in proliferative vitreoretinopathy. Anatomical and functional results in 501 patients].

BACKGROUND: Modern vitreoretinal surgery allows a successful management of most cases of retinal detachment (RD) due to proliferative vitreoretinopathy (PVR). Failure of a vitrectomy in these cases is generally caused by a recurrence of PVR. Little is known about the postoperative 'life cycle' of proliferative cellular processes within the periretinal space. An adequate retreatment of PVR recurrences may improve the anatomical and functional results of a vitrectomy. MATERIAL AND METHODS: The retrospective study comprises 501 consecutive eyes operated for non-diabetic traction RD. Conventional retinal surgery preceded the vitrectomy in 36% of the cases. PVR was staged according to the classification of the Retina Society (14) with supplemental stages for 'anterior loop' formation, epimacular and subretinal membranes. The mean follow up of 139 eyes with one single vitrectomy was 24.2 months. The time-course of recurrent PVR in 362 eyes (72%, mean follow-up 34.2 months) was analyzed. Silicone-oil tamponade was used in 343 (69%) eyes. RESULTS: Recurrent PVR occurred predominantly within 1 to 9 months (median 1.8 mos) after vitrectomy. Latencies of recurrences did not differ significantly between PVR-C and D stages. Reattachment of the retina was achieved in about 85% of PVR-C and 70% of PVR-D stages. Anatomical results were better in non-traumatic RD cases. Final visual acuity of eyes operated since 1990 was 5/200 or better in 78% C-stages and 65% D-stages (follow-up of > or = 12 months). The final visual acuity was 20/100 or better in 33% of all PVR-C cases and 9.5% of all PVR-D cases. Significantly improved visual results were achieved in eyes operated with silicone oil tamponade, and in the later series of 279 eyes operated since 1990. The rate of postoperative total blindness was reduced from 16.7% before 1990 to 3.6% after 1990. CONCLUSION: Blindness due to traction RD can be avoided by vitreoretinal surgery in about 75% of PVR-C and over 50% of PVR-D cases provided that PVR recurrences are detected early and treated adequately.

Adult↗
PubMed1995

[Results of posterior chamber lens implantation with trans-scleral sulcus suture fixation].

BACKGROUND: Transscleral fixation of a posterior chamber intraocular lens has been proposed in eyes lacking adequate posterior capsular support. METHODS: We performed a retrospective review of 38 eyes of 38 patients who had a 12 months follow-up. Visual acuity, intraocular pressure and complications have been studied. We performed a transscleral fixation of posterior chamber lens with the following indications: 1. planned intraocular cataract extraction; 2. following intraoperative complications of phacoemulsification; 3. in combination with perforating keratoplasty; 4. in combination with parsplana vitrectomy. RESULTS: There were no serious intra- or shortly postoperative complications. 34% of the implanted lenses were not perfectly positioned. Up to 12 months, there were only minor problems in the anterior segment (suture erosions, anterior synechiae, iris capture). As longterm postoperative complications one patient developed retinal detachment, 3 others proliferative vitreoretinopathy after previous retinal detachment surgery. Two patients developed new onset glaucoma, and 3 glaucoma patients showed a medically uncontrollable intraocular pressure postoperatively. CONCLUSIONS: The transscleral fixation of a posterior chamber intraocular lens has been performed in combination with a vitrectomy in order to minimize postoperative complications. Especially in combination with a pars-plana vitrectomy and silicone oil filing the transsclerally fixated posterior chamber intraocular lens is superior to the anterior chamber IOLs.

Follow-Up Studies↗
PubMed1995

[Implantation of a silicone tube in therapy refractory glaucoma].

BACKGROUND: Hemorrhagic and neovascular glaucomas are difficult to treat. Trabeculectomy often fails. Cyclophotocoagulation or cyclocryotherapy are destructive procedures and are frequently followed by further visual loss. Fistulizing operations with silicone implants appear more promising in regulating the intraocular pressure (IOP) while preserving vision. Results of a modified implantation technique are compared with previously published studies. METHOD: A von Denffer silicone tube was implanted in 53 eyes of 50 patients with untreatable glaucomas. The follow-up was at least 6 months. The surgical procedure consisted of an oblique scleral stab incision into the anterior chamber without preparation of a scleral flap. The tapered silicone tube was inserted into the tunnel and fixed with 3 episcleral 9-0 prolene sutures. The conjunctiva was adapted watertight at the limbus. RESULTS: The IOP was regulated in 71% eyes (< 21 mm Hg). 30% of the eyes needed additional antiglaucomatous measures. Postoperative visual acuity remained stable or improved in 58% of the eyes. CONCLUSION: The described technique of a fistulizing operation with a von Denffer silicone tube was proven to be a valuable alternative for the treatment of refractory hemorrhagic or neovascular secondary glaucomas.

Diabetic Retinopathy↗
PubMed1995

[Change in therapy of acute endophthalmitis: an analysis of 92 cases 1980-1993].

BACKGROUND: The aim of our study was to develop possible criteria for the choice of vitrectomy in the treatment of endophthalmitis. MATERIALS AND METHODS: Ninety-two patients with endophthalmitis who were seen between 1980 and 1993 were reviewed retrospectively and analysed regarding pathogenesis, bacteriological aetiology, as well as pre- and postoperative visual acuity comparing intravenous (i.v.) therapy alone to a combination with vitrectomy in 3 pretherapeutic visual acuity classes (class I < 0.02, class II 0.02- < 0.1 and class III > or = 0.1). RESULTS: Endophthalmitis most commonly occurred after cataract extraction (39%). The best prognosis regarding final visual acuity was found with Staph. epidermidis infection, the worst with Streptococci. Postoperative visual acuity in class I was significantly better after vitrectomy with 0.18 +/- 0.06 (Standard Error = SE) compared to i.v. therapy alone (0.06 +/- 0.03 SE) (p < 0.05 unpaired Student t-Test). In class II, no such difference could be demonstrated. In class III, i.v. therapy yielded significantly better results (0.8 +/- 0.09 SE) than vitrectomy (0.53 +/- 0.14 SE), however only by comparing the final - but not the best - obtained posttherapeutic visual acuity. CONCLUSION: The more favourable results after vitrectomy in patients with very poor pretherapeutic vision suggest an important role of vitrectomy in the presence of extensive vitreous opacifications. The better outcome after i.v. therapy in patients with pretherapeutic vision > or = 0.1 could be influenced by the very short follow-up period which renders an evaluation of a potential loss of vision due to late complications after endophthalmitis impossible.

Acute Disease↗
PubMed1995

[Evaluation of published recommendations for screening studies of retinopathy of prematurity].

PURPOSE: Evaluation of different and partially contradictory guidelines for screening for retinopathy of prematurity published in Germany. PATIENTS: The data on 1219 preterm infants examined in Bern (n = 900) and Berlin (n = 319) were analyzed. A total of 680 preterm infants (56%) had a birth weight below 1500 g. The remaining infants were examined because oxygen had to be supplied or surgery done before or around the estimated delivery time. RESULTS: Stage 3 retinopathy was found in 88/1219 (7.2%) preterm infants. Only 5/88 infants weighed more than 1500 g at birth. Three of these infants had a birth weight below 2000 g and needed supplemental oxygen for a prolonged period of time. The other 2 infants had birth weights of more than 2000 g and were severely ill. Of 1219 preterm infants, 37 (3%) developed threshold retinopathy (according to the criteria of the multicenter trial); 35/37 infants weighed less than 1230 g at birth. The remaining 2 children (1650 g and 2185 g birth weight) were severely ill. CONCLUSIONS: Preterm infants should be screened for retinopathy of prematurity: (1) if the birth weight is below 1500 g; (2) if the birth weight is below 2000 g and oxygen supply was necessary for more than 30 days; (3) if infants are very sick or must undergo multiple surgery before term. The first examination should be scheduled for the 6th week postnatal and not before 31 weeks postmenstrual age.

Berlin↗
PubMed1993

[Eye complications in chronic juvenile arthritis].

BACKGROUND: The relationship between uveitis anterior in childhood and juvenile chronic arthritis (JCA, respectively JRA) has been known since 1950. In a review, the clinical picture of uveitis anterior, its prevalence, pathogenesis, prognosis and current therapy of ocular complications are presented. In addition, we will report our results of a clinical study. PATIENTS AND METHODS: In a cross-sectional study, 64 patients with juvenile chronic arthritis (JCA) had an ophthalmological screening for eye complications either from the disease itself or from the treatment. RESULTS: In 16% of the patients, an iridocyclitis was found, in one case acute, in 9 cases chronic. The cases of chronic uveitis anterior showed in 43% a combination with the classic risk factors (ANA-positive, oligoarticular, female). At the beginning of uveitis, the patients had a mean age of 81 months, at the beginning of JCA disease a mean age of 37 months. Four of 10 patients (= 40%) had eye complications from uveitis (cataract, posterior synechiae, glaucoma). Complications from therapy were found in 27%, mostly cataract as a complication of systemic and topical steroid treatment. Eighteen % had a visual acuity of 0.4 or less. CONCLUSIONS: Because of the often asymptomatic progression of chronic uveitis anterior, the risk of severe undetected eye complications is high. Therefore, an intensive interdisciplinary cooperation between rheumatologists, pediatrics and ophthalmologists is required.

Adolescent↗
PubMed1993

[Vitrectomy in oculocerebral non-Hodgkin's lymphoma].

Ocular non-Hodgkin lymphoma (NHL) is thought to be a rare intraocular tumor; the clinical diagnosis, however, is difficult, and ocular NHL might occur more frequently than we thought. Vitrectomy is essential for establishing the diagnosis. During the last 6 years, we performed vitrectomies for ocular NHL in seven eyes of four patients. We report on the visual outcome and cytological findings. In three patients, we suspected the oculocerebral form of the disease; one patient suffered from a systemic lymphoma. The mean observation time was 19 months (5-30 months). In one patient, we failed to examine the vitreous fluid; this patient has since died. The other three patients underwent radiation treatment and/or chemotherapy; they are alive, and no recurrence of the NHL has since occurred. In all five cases in which cytological examination of the vitreous fluid was performed, we were able to establish the diagnosis of NHL on the first attempt. This accuracy is due to rapid and careful processing by the cytologist. Vision improved considerably in most cases. In only one eye with heavy retinal infiltration could vision not be restored. Secondary cataract extraction was necessary in five cases; otherwise, vision remained stable. We conclude that vitrectomy has to be done early in atypical vitreous "inflammations". Immediate processing and cytological examination of the vitreous fluid establishes the diagnosis of NHL and permits accurate radiation or chemotherapy. Early vitrectomy is greatly beneficial not only for visual rehabilitation but maybe even for a longer life expectancy.

Aged↗