Biomedical subjects

Peter Wiedemann

Publications and source records attributed to Peter Wiedemann.

At least 73 records · Page 4Linked to original sources

PubMed2004

Inhibition of experimental choroidal neovascularization in rats by an alpha(v)-integrin antagonist.

PURPOSE: Integrin alpha(v)beta3 is predominantly expressed on endothelial cells in choroidal neovascularization (CNV). We evaluated the efficacy of cyclic RGD (Arg-Gly-Asp) peptide, an alpha(v)-integrin antagonist, in a rat model of laser-induced CNV METHODS: We evaluated the effect of cyclic RGD on the adhesion and cell viability of bovine choroidal endothelial cells (BCECs) by cell counting and the trypan blue dye exclusion test. CNV was induced by laser photocoagulation in female Long Evans rats (day 0), followed by intravitreal administration of one dose of cyclic RGD of 200 (n = 9), 100 (n = 10), 50 (n = 4), or 0 microg (n = 9) on days 9 and 11. We assessed the area of CNV by fluorescein angiography and the thickness microscopically on histologic sections. Neovascular vessels were detected by an antibody against factor VIII. RESULTS: Cyclic RGD (0.02 to 200 microg/ml) inhibited adhesion of BCECs in a dose-dependent manner without changing the cell viability (p < 0.01). In eyes treated with two injections of 200 or 100 microg of cyclic RGD peptide, the development of CNV was significantly (p < 0.01) inhibited in the area of leakage on fluorescein angiography. Histologically, the CNV membrane was observed beneath the retina and the factor VIII-positive cells and red blood cells were involved. The thickness of the lesions was significantly (p < 0.01) reduced in eyes that received 200 or 100 microg of RGD. CONCLUSIONS: Cyclic RGD effectively inhibited CNV progression in a rat model of laser-induced CNV, suggesting that this alpha(v)-integrin antagonist may be beneficial in the treatment of CNV.

Animals↗

PubMed2004

Expression of LRP1 in retinal pigment epithelial cells and its regulation by growth factors.

PURPOSE: The retinal pigment epithelial (RPE) cells are mitotically inactive under normal conditions, but play a pivotal role in the pathogenesis of proliferative vitreoretinopathy (PVR). Triggered by changes in the concentrations of growth factors, RPE cells reenter the cell cycle, proliferate, and migrate onto the retinal surface, into the subretinal space, and into the vitreous. The receptor for alpha(2)-macroglobulin (low-density lipoprotein receptor-related protein [LRP1], or CD91) is known to be involved in the processes of cell migration and invasion, as well as in the regulation of growth factor homeostasis. The purpose of this study was to investigate the expression of this receptor and its regulation, at the protein and mRNA levels, in human (h)RPE cells. METHODS: The cell surface expression of the receptor was studied by immunocytochemistry and flow cytometry. The endocytosis-related activity of LRP1 in hRPE cells was examined by assessing the uptake of FITC-labeled, methylamine (MA)-treated alpha(2)-M (alpha(2)-M-MA). LRP1 mRNA expression was analyzed by means of the RNase protection assay (RPA) after the hRPE cells were stimulated with the growth factors TGF-beta1, TGF-beta2, PDGF, VEGF (each 10 ng/mL), or bFGF (5 ng/mL). RESULTS: hRPE cells expressed LRP1 on their cell surface. The receptor mediated rapid binding and endocytosis of FITC-labeled alpha(2)-M-MA. The expression of LRP1 mRNA strongly increased on stimulation of the cells with TGF-beta1, TGF-beta2, or VEGF, whereas PDGF or bFGF elicited only minor effects. CONCLUSIONS: The expression of functionally active LRP1 in hRPE cells suggests that the receptor may be involved in cell migration and invasion, as reported for other LRP1-expressing cells. Thus, certain growth factors may control RPE cell migration and invasion in vivo through a regulation of LRP1 expression. As LRP1 mediates the clearance of alpha(2)-M, known to regulate the homeostasis of many cytokines and growth factors, this receptor may be a promising target for therapeutic intervention in PVR.

Aged↗

PubMed2003

Recovery from hepatic retinopathy after liver transplantation.

BACKGROUND: In chronic liver disease the neuroglial cells may be affected by neurotoxic metabolites which, in turn, could be expected to affect neuronal functions. The aim of this study was to evaluate the electroretinograms (ERG) from patients before and after liver transplantation, in order to study possible functional changes of the retina. METHODS: Twelve patients with liver cirrhosis underwent routine ophthalmological examination and ERG before and after successful liver transplantation. Laboratory parameters, including ammonia, aspartate aminotransferase (AST), bilirubin, and cholinesterase, were compared. Patients were grouped according to the Child classification: three patients were Child A, six were Child B, three were Child C. RESULTS: Most obvious ERG abnormalities were found in patients with cirrhosis Child C. Before transplantation 7 of 21 ERG parameters were out of the normal range, but in the follow-up examination after transplantation only one parameter was not within the normal range. Significant ( P<0.05) postoperative improvements were found for the latencies of scotopic, mesopic and photopic b-waves and mesopic a-waves and for the photopic implicit time. Patients in the Child B group revealed less changes in the ERG. Before the transplantation only one parameter of the ERG was out of the normal range. All postoperative parameters were within the normal range. At 40+/-9 months after the liver transplantation a significant decrease in serum ammonia levels, AST and bilirubin and a significant increase in cholinesterase levels were observed. CONCLUSION: Patients with restored liver function after liver transplantation showed significantly improved ERG parameters. Our data suggest a recovery of the cells involved in hepatic retinopathy, including the Müller (glial) cells.

Adult↗

PubMed2003

Elevated proto-oncogene and collagen mRNA expression in PVR retinas.

PURPOSE: Retinal detachment is often accompanied by proliferation and migration of retinal cells and by increased synthesis of structural proteins, known as proliferative vitreoretinopathy (PVR). Herein we investigate the messenger RNA (mRNA) expression of proto-oncogenes responsible for cell proliferation and of structural proteins that have a role in membrane formation. METHODS: Retinal samples were obtained from patients undergoing vitreoretinal surgery for the treatment of retinal detachment complicated by PVR. Normal human control retinas were obtained from cornea donors. The mRNA expression of the proto-oncogenes c- myc, c- fos and the proliferation marker Ki67, as well as of collagen type III and type IV, were investigated using the ribonuclease protection assay. RESULTS: Ki67 mRNA expression was not detectable in either sample type, but c- fos and c- myc mRNA expression was found in normal and PVR retinas. Whereas the expression of c- myc showed a marginal increase, the up-regulation in c- fos expression was strongly significant (5.07-fold). The mRNA of collagen type III was detectable at widely varying levels in all the PVR retinas but was found in only 2 of the 16 analysed normal samples. Collagen type IV mRNA was expressed in both PVR and control samples but was higher (2.21-fold) in the PVR retinas. CONCLUSIONS: These results indicate that an up-regulation of the proto-oncogene c- fos occurs in human PVR retinas. An increase in mRNA expression of collagen types III and IV takes place simultaneously. These changes in mRNA expression appear to be mainly connected to the initiation of cell proliferation, dedifferentiation and formation of tractional membranes.

Adolescent↗

PubMed2003

Upregulation of purinergic P2Y receptor-mediated calcium responses in glial cells during experimental detachment of the rabbit retina.

To investigate injury-induced alterations of purinergic P2Y receptor-mediated calcium responses in glial (Müller) cells of the rabbit retina, neural retinae were experimentally detached from the pigment epithelium. The ATP-evoked calcium responses were recorded in the endfeet of glial cells at the vitread surface of retinal wholemounts. In control retinae, approximately 7% of the glial cells investigated showed ATP-evoked calcium responses. Within 24 h of detachment, significantly more retinal glial cells (42%) showed calcium responses, and glial ATP responsiveness increased further in retinae which were detached for 48 (44%) or for 72 h (64%). The results indicate that in the detached retina, glial cells upregulate their responsiveness to extracellular ATP within 24 h of injury. Thus, P2Y receptor-mediated signalling may be involved in the early steps of glial response to retinal injury.

Animals↗

PubMed2003

Age-related decrease of potassium currents in glial (Müller) cells of the human retina.

BACKGROUND: Age-dependent alterations have been investigated far less in retinal glial cells than in retinal neurons. We investigated age-dependent alterations of inwardly rectifying potassium (Kir) currents in Müller glial cells of the human retina. METHODS: Müller cells were isolated immediately post mortem from donors without a reported history of eye disease, and the amplitudes of Kir currents and of currents through high-voltage-activated (HVA) calcium channels were measured by whole-cell patch clamping. RESULTS: The amplitude of the Kir currents was lower in the cells from donors older than 50 years than in the cells of younger donors; the decrease was strongly correlated with the donor's age (p < 0.001). The current amplitude in the cells from donors older than 60 years was about 40% lower than the amplitude in the cells from donors younger than 50 years. The amplitude of the HVA currents was greater in the cells from donors older than 55 years than in the cells from younger donors; the increase, up to about 500%, was strongly age-dependent (p < 0.001). INTERPRETATION: The age-related decrease in Kir-current amplitude in Müller cells may reflect the neuron loss in the aged retina. Our findings also indicate that retinal glial cells have enhanced cytoplasmic calcium signals in the course of aging.

Adult↗

PubMed2003

Silicone oil-RMN3 mixture ("heavy silicone oil") as internal tamponade for complicated retinal detachment.

PURPOSE: To evaluate the efficacy and safety of a silicone oil-RMN3 mixture ("heavy silicone oil") as heavier as water internal retinal tamponade after vitrectomy for complicated retinal detachment. The relative density of the heavier-than-water silicone oil was 1.03 g/cm3, and the viscosity was 3,800 cSt. Heavy silicone oil is designed to tamponade the inferior retina in complicated retinal detachment. METHODS: Patients with a complicated retinal detachment involving the inferior part of the retina requiring internal tamponade with silicone oil were recruited for this prospective study. Inclusion criteria were retinal detachment secondary to proliferative vitreoretinopathy (stage > or = C2), inferior or posterior tears, or penetrating trauma. The heavy silicone oil was injected at the end of surgery after peeling of retinal membranes or retinotomy. Follow-up examinations were scheduled at 1, 3, 6 months, and 1 year after the initial surgery. RESULTS: A total of 33 eyes of 33 patients aged from 20 to 84 years (mean, 56 +/- 18 years) were treated with heavy silicone oil. Follow-up ranged from 12 to 16 months. Rhegmatogenous retinal detachment with significant proliferative vitreoretinopathy accounted for 17 cases, inferior holes for three, and trauma with retinal detachment for three. Initial visual acuity ranged from 20/50 to hand motions. Initial retinal reattachment was achieved in all cases. Complications included increased intraocular pressure in six eyes (18%), intraocular inflammation and synechia formation in one eye (3%), a central retinal artery occlusion after heavy oil removal in one eye, and scattered retinal hemorrhages during follow-up in two eyes (6%). Significant emulsification was not observed during intraocular tamponade with heavy silicone oil. At the last follow-up, all eyes had macular attachment, and 24 eyes had a visual acuity better than or equal to 20/400. CONCLUSIONS: The results of this prospective study show the good intraocular tolerance of heavy silicone oil as tamponade in complicated retinal detachment. Its specific gravity allows for sufficient tamponade of inferior retinal tears for at least 3 months without significant side effects.

Adult↗

PubMed2003

Absence of mutations of the BRAF gene and constitutive activation of extracellular-regulated kinase in malignant melanomas of the uvea.

The v-raf murine sarcoma viral homolog B1 (BRAF) gene, one of the human isoforms of RAF, is activated by Ras, leading to cooperative effects in cells responsive to growth factor signals. Recently, somatic missense mutations of the BRAF gene have been detected in more than 66% of malignant melanomas of the skin. We analyzed 42 malignant melanomas of the uvea, 3 corresponding liver metastases, and 10 cutaneous melanomas for possible BRAF mutations: after microdissection, mutation analysis of BRAF and KRAS was performed. The expression of extracellular-regulated kinase 1 and 2 (ERK1/2), an important downstream point of convergence in the Ras-RAF-MEK-Erk pathway, was analyzed immunohistochemically. Interestingly, we failed to detect activating BRAF mutations in uvea melanomas and their corresponding liver metastases. There were no mutations of BRAF in corresponding non-neoplastic uvea specimens, although we detected three BRAF mutations in sporadic cutaneous melanoma that led to a substitution of valine by glutamic acid at position 599 (V599E). KRAS mutations were detected in 1 of 10 cutaneous melanoma but not in uveal or metastatic melanoma. Despite the lack of activating mutations in the BRAF gene, we identified constitutively activated ERK in almost all (86%) uveal melanoma tissues tested but not in corresponding normal retina or uveal cells. Our data indicate that BRAF gene mutations are rare to absent events in uveal melanoma. The finding of activated Erk suggests a causative role for MAPK activation in uveal melanoma independent of activating BRAF or RAS mutations.

Humans↗

PubMed2003

P2Y receptor-mediated stimulation of Müller glial cell DNA synthesis: dependence on EGF and PDGF receptor transactivation.

PURPOSE: To determine whether P2Y receptor-evoked proliferation of Müller glial cells depends on transactivation of receptor tyrosine kinases. METHODS: Primary cultures of Müller cells of the guinea pig were treated with test substances for 16 hours. The DNA synthesis rate was assessed by a bromodeoxyuridine (BrdU) immunoassay, and the phosphorylation states of the extracellular signal-regulated kinase (ERK1/2) and the p38 mitogen-activated protein kinase (p38 MAPK) were determined by Western blot analysis. RESULTS: In Müller cells, the mitogenic effect of P2Y receptor activation by extracellular adenosine triphosphate (ATP) depended on transactivation of both the platelet-derived growth factor (PDGF) and the epidermal growth factor (EGF) receptor tyrosine kinases, as suggested by the blocking effects of the tyrphostins AG1296 and AG1478 on the ATP-induced proliferation and phosphorylation of ERK1/2. Moreover, the PDGF-induced proliferation may depend on transactivation of the EGF receptor kinase. Antibodies against heparin-binding EGF (HB-EGF) or PDGF, as well as inhibition of matrix metalloproteinases (MMPs) blocked ATP-evoked proliferation. At least one metalloproteinase (MMP-9), was implicated in the signal transfer from P2Y to EGF receptors. In contrast, the mitogenic effect of fetal calf serum was independent of growth factor receptor activity. P2Y receptor activation stimulated Müller cell proliferation by activating the ERK1/2 and the phosphatidylinositol 3 (PI3) kinase signaling pathways, whereas the p38 MAPK pathway was not involved in mitogenic signaling. CONCLUSIONS: The present data suggest that P2Y-receptor-induced mitogenic signaling in Müller cells is mediated by transactivation of the PDGF and EGF receptor tyrosine kinases. The transactivation may be mediated by release of PDGF and MMP-dependent shedding of HB-EGF from the Müller cell matrix, respectively. The transactivation of the receptor tyrosine kinases may result in activation of ERK1/2 and PI3 kinase and an increase in the proliferation rate.

Adenosine Triphosphate↗

PubMed2003

Early glial cell reactivity in experimental retinal detachment: effect of suramin.

PURPOSE: In a rabbit model of retinal detachment, early Müller glial cell reactivity was monitored-specifically, changes in membrane features-to determine whether these changes involve an upregulation of purinergic P2 receptor-mediated responses and whether all or some of these alterations could be blocked by suramin or pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid (PPADS). In addition, the immune cell reactivity (microglial cells and blood-derived immune cells) was monitored. METHODS: A local retinal detachment was induced by subretinal injection of a sodium hyaluronate solution. Three, 24, 48, and 72 hours after surgery, Müller cells were acutely isolated, and patch-clamp records of the whole-cell potassium currents were made. The presence of P2 receptor-mediated responses was determined by measuring extracellular adenosine triphosphate (ATP)-induced membrane current increases, and by recording of ATP-induced calcium responses at the vitreal surface of retinal wholemounts. The density of isolectin B(4)-labeled immune cells was determined in the nerve fiber layer of retinal wholemounts. RESULTS: Within 24 hours of detachment, Müller cell reactivity was evident. The cells downregulated the density of their inwardly rectifying potassium currents to 60% and 47% of the control value at 48 hours and 72 hours of detachment, respectively. This downregulation was accompanied by an enhanced incidence of cells which showed calcium and current responses after ATP application (control: 14%; 24 hours of detachment: 42%; 72 hours of detachment: 80%). Müller cell hypertrophy was apparent at 48 and 72 hours of detachment. Application of suramin during surgery inhibited the downregulation of potassium currents, but not the elevated responsiveness to extracellular ATP; PPADS had no effect. Suramin also inhibited the inflammatory response that was induced by the surgical procedure and that was apparent by the increased number of immune cells. CONCLUSIONS: Reactive responses of Müller cells occur within 24 hours of detachment. Suramin inhibits several (but not all) reactive glial alterations and therefore may represent one candidate for further investigations in the search for drugs that limit detrimental effects of immune cell activation and Müller cell gliosis during retinal detachment.

Adenosine Triphosphate↗

PubMed2002

Patch-clamp recording of Müller glial cells after cryopreservation.

Human and other primate retinal Müller cells display dominating K(+) currents as well as other membrane conductances that may change in cases of retinal pathology. Because the use of human and primate tissue is limited by reasons of availability, a method for long-term storage of these cells is desirable. We describe a cryopreservation method in which isolated Müller cells are stored in liquid nitrogen. After thawing, the cells can be used for patch-clamp experiments immediately, without culturing. We show that the main electrophysiological properties are not altered by this method and that voltage- and ligand-gated currents can be recorded from cryopreserved cells even after 2-years storage.

Adenosine Triphosphate↗

PubMed2002

Advanced glycation end products quench nitric oxide in vitro.

BACKGROUND: Nitric oxide (NO) is known as an important mediator of endothelial function. The aim of this investigation was to evaluate the influence of mediators of retinal pathology - vascular endothelial growth factor (VEGF) and advanced glycation end products (AGEs) - on NO release from choroidal endothelial cells (CEC) and retinal pigment epithelial (RPE) cells to elucidate the complex role of NO. METHODS: Bovine CEC were stimulated using VEGF (1, 10, and 100 ng/ml), and RPE cells were exposed to interferon-gamma (IFN-gamma 100 U/ml) and lipopolysaccharide (LPS 1 micro g/ml). NO release into the media was assessed by an amperometric NO sensor. The influence of AGEs (10 and 100 micro g/ml) on NO release from CEC and RPE cells was investigated. The competitive NO synthase inhibitor L(omega)-nitro-L-arginine methyl ester (L-NAME 2 nmol) was used to pretreat the cells 2 h before NO measurement. RESULTS: Unstimulated CEC produced low basal levels of NO in vitro (39.1+/-13.9 nmol), and unstimulated RPE cells produced minimal basal levels of NO (15.7+/-7.0 nmol). Exposure of CEC to VEGF for 30 min resulted in a dose-dependent rise of NO in the medium, which was significantly inhibited by L-NAME. Stimulation of RPE cells with IFN-gamma and LPS resulted in a rise of NO in the bath to 125.9+/-18.5% of basal values. Basal NO release from CEC, and stimulated NO release from RPE cells, was significantly reduced by AGE treatment and L-NAME. CONCLUSIONS: These data demonstrate that AGEs formed from the nonenzymatic glycation of proteins with reducing sugars quench NO activities in vitro. The results implicate AGEs as important modulators of NO activity and may be relevant to the impairment of endothelial functions observed in diabetes and aging.

Animals↗

PubMed2002

Activation of P2Y receptors stimulates potassium and cation currents in acutely isolated human Müller (glial) cells.

The ability of various neurotransmitters/neuroactive substances to induce fast, transient rises of Ca(2+)-activated K(+) currents (I(BK)) caused by release of Ca(2+) from intracellular stores was investigated in Müller glial cells of the human retina. Müller cells were enzymatically isolated from retinas of healthy donors or of patients with proliferative vitreoretinopathy, and the transmembrane ionic currents were recorded using the whole-cell and the cell-attached patch-clamp techniques. The results of the screening experiments indicate that human Müller cells express, in addition to GABA(A) and perhaps glutamatergic and cholinergic receptors, predominantly P2 receptors. ATP and other nucleotides exerted two effects on membrane currents: repetitive transient increases of the I(BK) amplitude and, in a subpopulation of cells investigated, the appearance of a transient cation conductance at negative potentials. ATP and UTP increased dose-dependently the I(BK) amplitude with half-maximal effects at 0.33 and 0.50 microM, respectively. Since several different P2 receptor agonists increased the I(BK), it is assumed that human Müller cells express a mixture of different types of P2Y receptors. In cell-attached patches, extracellular application of ATP or UTP transiently increased the open probability of single putative BK channels. The increase of I(BK) and the appearance of the cation conductance in whole-cell records were abolished when intracellular Ca(2+) was buffered by a high-EGTA pipette solution or when IP(3) was included in the pipette solution. The expression of agonist-evoked transient cation currents was found to be stronger in cells from patients as compared to cells from healthy donors. It is concluded that human Müller glial cells express P2Y receptors that, via IP(3) formation, cause intracellular Ca(2+) release. The increased intracellular Ca(2+) concentration stimulates the activity of BK channels and may induce opening of cation channels. Both the ATP-induced activity of BK channels and the increased expression of Ca(2+)-gated cation channels may be important in respect to proliferative Müller cell gliosis.

Adenosine Triphosphate↗

PubMed2002

Inhibitory effects of triamcinolone acetonide on bFGF-induced migration and tube formation in choroidal microvascular endothelial cells.

BACKGROUND: Angiostatic drugs might provide desirable modulation of choroidal angiogenesis-related diseases, including histoplasmosis and the exudative form of age-related macular degeneration. However, the precise effects of this class of compounds in the choroidal neovascularization are still unclear. In the present study, we investigated the effects of triamcinolone acetonide (TA), an angiostatic steroid, on choroidal angiogenesis in vitro. METHODS: Bovine choroidal endothelial cells (CEC), which are the critical cellular component of choroidal angiogenesis in vivo, were isolated with Lycopersicon esculentum agglutinin-coated Dynabeads and cultured in EGM medium. CEC were treated with basic fibroblast growth factor (bFGF) and TA at various concentrations ranging from 50 to 300 mg/l. The capacities for CEC migration and tube formation were evaluated with the modified Boyden chamber and the Vitrogen collagen assay, respectively. The activities of matrix metalloproteinases (MMP)-2 and -9 were examined using gelatin zymography. RESULTS: The stimulation of CEC with 50 ng/ml bFGF resulted in an increase of about 100% in migration activity (P<0.01). Preincubation of CEC with TA at the indicated concentrations for 20 min inhibited the bFGF-stimulated migration in a dose-dependent manner (P<0.01). After 5 days, the bFGF-stimulated tube formation in CEC was inhibited by TA at the concentrations 100, 150 and 300 mg/l (P<0.01). Gelatin zymography of the culture media of CEC showed that the bFGF-induced activation of MMP-2 was attenuated by 300 mg/l TA (P<0.05). CONCLUSION: Downregulation of the activation of MMPs in CEC could be one of the mechanisms by which angiostatic steroids inhibit choroidal angiogenesis.

Animals↗

PubMed2002

Membrane conductance of Müller glial cells in proliferative diabetic retinopathy.

BACKGROUND: It is not known whether the membrane features of human Müller cells are altered in proliferative diabetic retinopathy (PDR). We performed a study to investigate the expression of several distinct forms of membrane conductance in Müller glial cells from a patient with PDR compared to cells from healthy donors (control cells). METHODS: Müller cells were isolated 2 hours after vitreoretinal surgery in the case of the patient and within 24 hours in the case of the autopsy eyes. Whole-cell voltage-clamp recordings were made. The results for the two groups were compared with the Mann-Whitney U test. RESULTS: As assayed by the whole-cell membrane capacitance, the cells from the patient with PDR showed hypertrophy in comparison to the control cells (mean 85.1 pF [standard deviation (SD) 19.7 pF] vs. 54.3 pF [SD 13.8 pF]). The cells from the patient displayed strong downregulation of inwardly rectifying potassium ion (Kir) currents (mean 0.41 [SD 0.24] pA/pF, compared to 3.43 [SD 1.86] pA/pF for the control cells). The Kir current downregulation was accompanied by a less negative membrane potential (-57.3 mV [SD 16.9 mV], compared with -82.3 mV [SD 5.3 mV] for the control cells). Both the number and the amplitude of voltage-gated sodium ion currents were enhanced in cells from the patient. When P2X7 receptors were activated by 2'-/3'-O-(4-benzoylbenzoyl)-adenosine triphosphate, cells in both groups displayed opening of a cation conductance and, simultaneously, an increase in currents through calcium ion-activated potassium ion channels. INTERPRETATION: Changes in Müller cell membrane conductance in PDR are similar to those described in proliferative vitreoretinopathy. The down-regulation of active Kir channels and the membrane depolarization likely disturb voltage-dependent Müller cell functions, such as regulation of local ion concentrations and uptake of neurotransmitters. The enhanced entry of calcium ions from the extracellular space and the subsequent stimulation of calcium-activated potassium channels support Müller cell proliferation in PDR.

Adenosine Triphosphate↗

PubMed2002

Strabological results in patients with macular translocation surgery and counterrotation of the globe as a secondary procedure.

INTRODUCTION: Age-related macular degeneration is the most common cause of irreversible loss of visual acuity, including the ability to read, in elderly patients. One of the surgical treatment options is macular translocation with 360 degrees retinotomy. The orthoptic results of torsional muscle surgery as a second procedure are demonstrated. MATERIALS AND METHODS: Between January 1999 and December 2000, the macula was rotated upward by 12-45 degrees in 10 eyes following complete artificial detachment and a 360 degrees retinotomy. In these patients, torsional surgery was carried out as a second procedure. Depending on the resulting cyclotorsion, we performed surgery on the oblique muscles only in four patients with a cyclotropia of 12-20 degrees and a combination of oblique muscle surgery with surgery of two or four rectus muscles in the remaining six eyes (cyclotropia over 21 degrees ). The pre- and postoperative diagnostic techniques included visual acuity, reading vision and the orthoptic status. RESULTS: Due to the unilateral ectopia of the macula, all patients presented postoperative strabismus with a vertical deviation of 2-10 degrees and a subjective cyclotropia between 12 degrees and 40 degrees. After surgery on the oblique muscles, the patients showed a residual cyclotropia of 0-6 degrees. In patients in whom surgery on the oblique muscles was accompanied by rectus muscle surgery, the remaining cyclotorsion was 5-13 degrees. Four patients excluded the non-operated fellow eye, six patients experienced double vision under binocular conditions and thus required prescription of additional prism glasses. CONCLUSION: Macular translocation causes diplopia under binocular conditions because of the unilateral ectopia of the macular region with cyclotropia and vertical deviation. These problems can be resolved or reduced by oblique muscle surgery or in combination with additional surgery on the rectus muscles, depending on the range of the cyclotorsion. Performing the torsional surgery as a second procedure after macular rotation with an exact preoperative measurement of the subjective cyclodeviation appears to be useful.

Aged↗

PubMed2002

Role of apoptosis in the cytotoxic effect mediated by daunorubicin in cultured human retinal pigment epithelial cells.

To investigate whether apoptosis is involved in the therapeutic effect of daunorubicin on proliferative vitreoretinopathy (PVR), cultured human retinal pigment epithelial cells (RPE) were exposed to a cytotoxic dose of 180 microg/l daunorubicin. After 12-hour treatment with the drug and 24-hour prolonged post-incubation in the drug-free medium, progressive condensation, shrinkage of cytoplasm and nucleus, and fragmented nuclei were identified by light and electron microscopy. TUNEL assay showed the characteristic apoptotic patterns of circumscribed clumps and sometimes even dark masses in nuclei. The expression of bax protein was enhanced, and the integral optical density values for immunocytochemical expression of bax protein increased by 22.0% in the drug-treated group (P < 0.05). The results demonstrated the pivotal role of apoptotic mechanism in the cytotoxic effect mediated by daunorubicin, and confirmed the relationship between the drug-induced apoptosis and overexpression of bax protein. It suggested that the upregulation of bax mediated by daunorubicin could lead to the onset of apoptosis, and therefore contribute to its therapeutic mechanisms for the treatment of PVR.

Antibiotics, Antineoplastic↗

PubMed2002

Determination of the solubility of perfluorocarbon liquids in silicone oil in vitro and in vivo.

PURPOSE: To investigate the solubility of perfluorocarbon liquids (PFCL) in silicone oil. METHODS: Forty-eight samples of silicone oil (1,300 mPas, n = 22; 5,000 mPas, n = 26) were analyzed for dissolved fluorocarbon molecules after surgical removal from patients who had initially undergone vitreoretinal surgery with (n = 41) and as control without (n = 7) the use of perfluorodecalin in headspace gas chromatography. In vitro, the solubility of three different PFCL-perfluorooctane (PFO), perfluorodecalin (PFD), and fluoromethylcyclohexane (FMCH)-in silicone oil of various viscosities was determined. The diffusion phenomena during a direct exchange were studied. RESULTS: In 39 of 41 silicone oil samples removed from patients who had undergone vitreoretinal surgery with the use of PFD, small amounts of dissolved perfluorocarbons could be detected. The mean value in 5,000-mPas silicone oil was 939.0 x 10-4 m/% and in 1,300-mPas silicone oil was 322.75 x10(-4) m/%. No perfluorocarbon molecules were found in seven control patients. In vitro, the following maximum solubilities in 1,000-mPas silicone oil were measured at room temperature: PFO, 3.2 m/%; PFD, 5.1 m/%; and FMCH, 10.3 m/%. The maximum values measured in 5,000-mPas silicone oil were PFO, 3.3 m/%; PFD, 5.7 m/%; and FMCH, 8.5 m/%; and in 100-mPas silicone oil were PFO, 2.4 m/%, and PFD, 5.1 m/%. CONCLUSION: Perfluorocarbon liquids dissolve in silicone oil. This may lead to transient formation of "heavy silicone oil," but no stable heavy silicone oil can be created adding PFCL. Intraocularly, retained PFCL vanish in silicone oil and are removed during silicone oil removal.

Chromatography, Gas↗