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Biomedical subjects

Robert Rejdak

Publications and source records attributed to Robert Rejdak.

At least 19 recordsLinked to original sources
PubMed2007

Alterations of amino acids and glutamate transport in the DBA/2J mouse retina; possible clues to degeneration.

BACKGROUND: The DBA/2J mouse spontaneously develops ocular hypertension and time-dependent progressive retinal ganglion cell (RGC) loss. This study examines changes in amino acid levels in the vitreous, and changes in the expression of retinal glutamate transporters and receptors that occur during the progression of this pathology. METHODS: Retinas were obtained from DBA/2J mice at ages 3, 6 and 11 months. C57BL/6 mice were used as age-matched controls. Vitreal amino acid content was measured with HPLC. Western blotting and immunohistochemistry were performed using specific antibodies against the glutamate transporters (GLAST, GLT-1v, EAAC-1) and glutamate receptors, particularly NMDA (NR1, NR2A, NR2B) and AMPA (GluR1, GluR2/3, GluR4) receptors. RESULTS: HPLC showed retinal concentrations of glutamate, glutamine, glycine, alanine, lysine, serine, and arginine to be significantly higher in DBA/2J mice at 11 months of age compared to age-matched controls. Western Blots revealed a moderate decrease of GLAST and GLT-1v expression in DBA/2J mice at 6 and 11 months as compared to age-matched controls while there was no change in EAAC1. Immunohistochemically, no changes in expression of NMDA and AMPA receptors were seen. CONCLUSION: Alterations of amino acid content and enhanced glutamate neurotransmission might be involved in the pathogenesis of retinal neurodegeneration in the DBA/ 2J mouse model of ocular hypertension. Moreover, these mice provide an animal model for studying excitotoxic retinal damage.

Amino Acid Transport System X-AG↗
PubMed2006

Citicoline and lithium rescue retinal ganglion cells following partial optic nerve crush in the rat.

Citicoline and lithium (Li(-)) have been shown to support retinal ganglion cell (RGC) survival and axon regeneration in vitro. Optic nerve crush (ONC) is a model of both brain axonal injury and certain aspects of the glaucomatous degeneration of RGC. We have used this model to quantify protection offered to RGC by these drugs and to determine whether their effects are mediated by enhanced expression of the antiapoptotic protein Bcl-2. Adult rats (6-12 per group) were subjected to ONC accompanied by a contralateral sham operation. Animals were treated intraperitoneally with either vehicle, citicoline sodium (1g/kg daily for up to 7 days and 300 mg/kg daily afterwards), lithium chloride (30 mg/kg daily), or both drugs combined. Fluorogold was injected bilaterally into superior colliculi 1, 5 or 19 days after ONC. Labeled cells were counted under a fluorescence microscope 2 days after tracer injection. In a separate set of experiments the effects of treatments on expression of Bcl-2 in retinas were evaluated by immunohistochemistry. In vehicle-treated animals there was a progressive decrease of RGC density after crush. This decrease was attenuated in citicoline-treated animals 1 week and 3 weeks after the crush. In the lithium-treated group protection was even more pronounced. In animals treated with both drugs RGC protection was similar to that achieved by lithium alone. Bcl-2 immunoreactivity was seen predominantly in retinal ganglion cells. Its increase was recorded in the lithium and citicoline group as well as in animals treated with the combination of both drugs. Both citicoline and lithium protect RGC and their axons in vivo against delayed degeneration triggered by the ONC. Retinoprotective action of both drugs may involve an increase in Bcl-2 expression.

Animals↗
PubMed2006

A selective method for transfection of retinal ganglion cells by retrograde transfer of antisense oligonucleotides against kynurenine aminotransferase II.

PURPOSE: Intravitreal administration of specific antisense oligonucleotides (ODNs) effectively downregulates gene expression in the retina but does not modulate it exclusively in retinal ganglion cells (RGCs). Expression of kynurenine aminotransferase II (KAT II) in RGCs has been well described in the literature. We describe a new method for downregulating cellular KAT II expression via transfection of RGC by retrograde transfer of ODN. METHODS: Fluorescently labeled, specific ODNs against KAT II were injected into rats either intravitreally or into the superior colliculi. Fluorescence microscopy of retinal flat-mounts and radial sections was used to compare the location, duration, and degree of transfection for both methods of delivery. The effects of both methods on KAT II expression in RGCs were studied immunohistochemically with unlabeled ODN. Retinal kynurenic acid (KYNA) contents were measured using high pressure liquid chromatography (HPLC). RESULTS: After intravitreal injection, fluorescently labeled ODN reached all retinal layers, whereas injections into the superior colliculus resulted in transfection of the RGC layer alone. Immunohistochemistry showed that both methods of ODN application had a similar effect on downregulation of KAT II expression in RGC. Retinal KYNA content decreased significantly 4 days after both types of ODN administration. CONCLUSIONS: This study demonstrated that retrograde transfer of specific ODN into RGC is feasible and induces downregulation of KAT II cellular expression. This may become a useful tool for modulating gene expression in the retinal ganglion cell layer in vivo without direct transfer of ODN to other retinal cell layers.

Animals↗
PubMed2006

Administration of novel dyes for intraocular surgery: an in vivo toxicity animal study.

PURPOSE: To investigate the effect of intravitreal injections of new vital dyes on the retina, the retinal pigment epithelium (RPE) and the choroid in an in vivo rat model. METHODS: Rats were injected intravitreally with four dyes: light-green SF yellowish (LGSF), copper(II)phthalocyanine-tetrasulfonic acid (E68), bromphenol blue (BPB), and Chicago blue (CB) dissolved in physiologic saline solution (PSS) at concentrations of 0.5% and 0.02%. PSS served as the control. Additional animals were treated with single injections of 0.5%, 0.02%, 0.002%, and 0.0002% ICG or 0.002% E68 into one eye. Adverse effects on anterior and posterior segments were evaluated by slit lamp biomicroscopy and ophthalmoscopy. Retinal toxicity was assessed by histology and retinal ganglion cell (RGC) quantification 7 days after dye administration. RESULTS: Eyes treated with 0.5% E68, 0.5% ICG, or 0.5% CB showed discrete staining of both cornea and lens not seen at lower concentrations or with other dyes. Histology revealed dose-dependent reactions after E68 administration. ICG 0.5% induced significant thinning of inner retinal layers compared with PSS. ICG 0.02% caused focal degenerative changes of the outer retina in three of seven eyes, whereas 0.002% and 0.0002% ICG did not. CB led to heterogeneous morphologic alterations. BPB- or LGSF-treated eyes showed normal retinal morphology. ICG at all tested concentrations induced significant RGC loss, as did E68 at 0.5% but not at lower concentrations. CONCLUSIONS: BPB or LGSF produced no significantly detectable toxic effects on the retina in vivo. The safety of these new dyes must be established in other models and/or in preclinical studies before the clinical use of any of these dyes.

Animals↗
PubMed2006

[Efficacy of intravitreal triamcinolone acetonide in the visualization of the vitreous during pars plana vitrectomy].

PURPOSE: To retrospectively evaluate the efficacy of triamcinolone acetonide (TA) injection during pars plana vitrectomy, to facilitate the visualization of the internal limiting membrane (ILM), residual vitreous cortex (RVC) and preretinal membranes. MATERIAL AND METHODS: Pars plana vitrectomy was performed in 164 patients due to rhematogenous retinal detachment, vitreous hemorrhage, macular hole, lens luxation, endophthalmitis, intraocular foreign body, malignant glaucoma, preretinal membrane and proliferative diabetic retinopathy. After surgical separation of the posterior vitreous and removal of any visible epiretinal membrane, TA suspension was injected over the posterior pole into the vitreous cavity. Then, visualized RVC was removed and ILM peeling was performed. RESULTS: Upon intravitreal injection of TA, vitreous and ILM could be visualized by numerous particles of TA dispersed as white specks. RVC and ILM were completely removed in all patients. No complications related to the use of TA were encountered, even after complex procedures such as, vitrectomy combined with scleral buckling or phakoemulsification surgery in a long term follow up. CONCLUSIONS: Intraoperative visualization of RVC and ILM with intravitreal TA was found to be a useful adjunct to pars plana vitrectomy. This technique may facilitate both removal of epiretinal membrane and separation of vitreous, especially in patients with undetached vitreous.

Adolescent↗
PubMed2005

Toxicity study of erucylphosphocholine in a rat model.

PURPOSE: To investigate the effect of intraocular erucylphosphocholine (ErPC) on the retina, the retinal pigment epithelium (RPE), and the choroid in an in vivo rat model. METHODS: Adult male Brown Norway rats were injected intravitreally with ErPC dissolved in balanced salt solution (BSS) at a final concentration of 10 or 100 microM with BSS serving as control. Adverse effects on the anterior and posterior segment were assessed by slit-lamp biomicroscopy and ophthalmoscopy. Retinal toxicity was assessed by electroretinography (ERG), retinal ganglion cell (RGC) quantification, and histology 7 days after intravitreal administration of ErPC. RESULTS: There was neither a statistically significant difference in the clinical examination nor in the ERG waves of treated versus control rats 7 days after intravitreal administration of ErPC. Correspondingly, the number of RGC after BSS injection did not differ significantly from ErPC-injected animals. Histologic sections of the posterior segment of 10 and 100 microM ErPC-injected rats did not show any signs of retinal toxicity. Electron microscopy did not display a difference between the 10 microM and the control group. Only the 100 microM-injected animals showed a discrete irregularity of the Müller cell and the retinal ganglion cell cytoplasm at the ultrastructural level. CONCLUSIONS: ErPC can safely be injected into the vitreous of adult rats at a concentration of 10 microM without any retinal toxicity. Even a 10-fold increase in ErPC concentration leads only to a discrete cytoplasmic irregularity of the innermost retinal layers.

Animals↗
PubMed2004

Kynurenic acid production in cultured bovine aortic endothelial cells. Homocysteine is a potent inhibitor.

Kynurenic acid (KYNA) is a broad-spectrum antagonist at all subtypes of ionotropic glutamate receptors, but is preferentially active at the strychnine-insensitive glycine allosteric site of the N-methyl-D-aspartate (NMDA) receptor and is also a non-competitive antagonist at the alpha7 nicotinic receptor. KYNA occurs in the CNS, urine, serum and amniotic fluid. Whilst it possesses anticonvulsant and neuroprotective properties in the brain, its role in the periphery, however, is unknown. In this study we demonstrated the presence of kynurenine aminotransferase (KAT) I and II in the cytoplasm of bovine aortic endothelial cells (BAEC). BAEC incubated in the presence of the KYNA precursor L-kynurenine synthesized KYNA concentration- and time-dependently. KYNA production was inhibited by the aminotransferase inhibitor aminooxyacetic acid but was not affected by a depolarising concentration of K(+) or by 4-aminopyridine. The glutamate agonists L-aspartate and L-glutamate depressed KYNA production significantly. The selective ionotropic glutamate receptor agonists alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropionic acid (AMPA) and NMDA were ineffective in this respect. D,L-Homocysteine and L-homocysteine sulphinic acid lowered KYNA production in BAEC. Further investigations are needed to assess the role and importance of KYNA in vessels and peripheral tissues.

Animals↗
PubMed2004

Retinal neurodegeneration in the DBA/2J mouse-a model for ocular hypertension.

Mice of the DBA/2J strain spontaneously develop complex ocular abnormalities, including glaucomatous loss of retinal ganglion cells (RGC). In the present study ultrastructural features of retinal neurodegeneration in DBA/2J mice of different age (3, 6, 8 and 11 months) are described. By 3 months, RGC apoptosis characterized by electron-dense karioplasm and cytoplasm of ganglion cells was observed. The occurrence of apoptotic ganglion cells peaked at the age of 6 months. Past this age, necrosis characterized by swelling and electron-rare cytoplasm appeared to be the prevailing form of cell death. Müller glia activation increased with age, but there were no signs of leukocyte infiltration. At 8 and 11 months, signs of neoangiogenesis were found both at the ultrastructural level and in clinical examinations. In these older animals myelin-like bodies, most probably representing the intracellular aggregates of phospholipids in irreversibly injured cells, were also seen. Photoreceptor cells were not affected at any age. Our observations suggest that retinal degeneration in the DBA/2J mice does not involve recruitment of blood-borne inflammatory/phagocytosing cells, and that apoptosis is gradually replaced by necrosis as the predominant pathway of RGC death. Retinal degeneration in 3- to 11-month-old DBA/2J mice partially resembles human pigment dispersion syndrome and pigmentary glaucoma with characteristic anterior segment changes and elevation of intraocular pressure. However, neovasculogenesis and myelin-like bodies are observed during aging. Therefore, the DBA/2J model requires judicious interpretation as a glaucoma model.

Age Factors↗
PubMed2004

Expression of kynurenine aminotransferases in the rat retina during development.

The study investigates the cellular expression of kynurenine aminotransferases (KAT I and II) in the rat retina during development. At P1 (the day of birth) and P7 (the 7th day after birth), KAT I expression was observed in the inner plexiform layer (IPL), the fiber layer (FL), and in vertically running processes in the ganglion cell layer (GCL) (but not in the cell bodies). At P14 (the 14th day after birth) a strong KAT I immunoreactivity was observed in Müller cell endfeet. KAT II was expressed in the IPL, the FL, and in cells in the GCL at P1 and P7. From P14 on, KAT II expression in the IPL decreased. Double labeling revealed that KAT I was expressed in Müller cell endfeet, whilst KAT II both on retinal ganglion cells (RGC) and Müller cell endfeet. In conclusion, KAT I and II are present in the rat retina during development. The heterogeneity of the KAT developmental profiles possibly reflects a neuromodulatory role in the retinal differentiation.

Animals↗
PubMed2004

Age-dependent decrease of retinal kynurenate and kynurenine aminotransferases in DBA/2J mice, a model of ocular hypertension.

The study examines age-dependent changes of kynurenic acid (KYNA) content and kynurenine aminotransferases (KAT I and KAT II) celluar expression in the retinas of DBA/2J mice. Retinas were obtained from DBA/2J mice of different ages (3, 6 and 11 months). C57BL6 mice were used as controls. As measured with HPLC, KYNA content decreased (p < 0.01) in the retinas of 6-month-old DBA/2J mice and continued to decrease (p < 0.0074) in the retinas of 11-month-old animals compared to the controls. Immunohistochemistry showed that expression of both KAT I and KAT II decreased markedly in the retinas of 11-month-old DBA/2J mice compared to controls. The impairment in KYNA biosynthesis in the retinas of DBA/2J mice may be one of the mechanisms of retinal neurodegeneration related to ocular hypertension.

Aging↗
PubMed2004

[Quantification of isopters using semiautomated kinetic perimetry (SKP) in glaucoma patients with advanced retinal nerve fiber layer (RNFL) loss].

PURPOSE: To quantify the area of isopters obtained using a new technique of kinetic visual field examination--semi-automated kinetic perimetry (SKP)--in case of advanced retinal nerve fiber layer (RNFL) loss, caused by glaucoma. MATERIAL AND METHODS: Forty-one subjects (19 men, 22 women; mean age 66.5 +/- 12.5 years) suffering from open-angle glaucoma (30 patients), normal tension glaucoma (5 patients), juvenile glaucoma (2 patients) and PEX glaucoma (4 patients) were examined, using SKP program implemented in Octopus 101 instrument (Haag-Streit, Koeniz, Switzerland). One eye of each patient was tested using three stimuli according to the Goldmann classification. The stimuli III4e and I4e were obligatory. Additionally one stimulus (I3e or I2e) was used depending on the character of the defect. The stimulus angular velocity was kept constant at the level of 3 degrees/s. Obtained visual field (VF) results were classified according to the Aulhorn classification into stage III (26 VF) and IV (15 VF). The areas of isopters were measured in deg2. RESULTS: The mean area of isopter III4e was 9860 deg2, I4e--5171 deg2, I3e--1093 deg2, I2e--1093 deg2 in the group of Aulhorn stage III. In the group of Aulhorn stage IV the mean area of isopter III4e was 7488 deg2, I4e--3736 deg2, I3e--1109 deg2 and I2e--818 deg2. The mean test time was 16 min. (range 9-25 min.), 15.7 min. in the group of Aulhorn stage III and 16.5 min. in the group of Aulhorn stage IV, respectively. CONCLUSION: SKP seems to be an effective method for quantitative assessment and evaluation of isopter and scotoma areas (in deg2). In this study it was demonstrated that in case of more advanced stages of glaucomatous visual field loss (Aulhorn stage IV), the areas of isopters appeared to be smaller.

Aged↗
PubMed2004

[Comparison of SKP (semi-automated kinetic perimetry) and SASP (suprathreshold automated static perimetry) techniques in patients with advanced glaucoma].

PURPOSE: To compare the results of conventional suprathresold automated static perimetry (SASP) and a new method of kinetic visual field examination (semi-automated kinetic perimetry--SKP) in patients with advanced retinal nerve fibre layer (RNFL) defects, caused by glaucoma. MATERIAL AND METHODS: Nineteen patients (10 women and 9 men) suffering from advanced open-angle glaucoma (17 patients) and low tension glaucoma (2 patients) were enrolled in this study. The mean age was 65.3 years (range 49.0-82.9 years). One eye of each subject was examined with SKP and SASP, both implemented in Octopus 101 perimeter (Haag-Streit, Koeniz, Switzerland) on the same day. The examiner using SKP did not know the SASP results. The static visual field examination was performed first. In order to compare visual fields results obtained with both methods, only central 30 degree area of the visual fields was taken into consideration. The area obtained by creating a virtual isopter (option of SKP software) located between the position of defective and intact visual field regions of SASP and the area of I4e isopter obtained with SKP (stimulus angular velocity 3 degrees/s) were measured in deg2 and compared. RESULTS: The mean area (+/-SD) of I4e isopter obtained with SKP was 1882 deg2 (+/- 510 deg2) and the mean area of SASP 30 degree visual field was 1737 deg2 (+/- 546 deg2). This difference was not statistically significant. CONCLUSION: Quantitative comparison of static and kinetic perimetry is a difficult task to perform. The SKP software offers a possibility of direct quantitative assessment of the area of each isopters in deg2. This study shows that the results of visual field examinations obtained with both methods in this group do not differ significantly between SASP and SKP.

Aged↗
PubMed2004

[Applicability of semi-automated kinetic perimetry (SKP) in the assessment of the visual field loss due to retinitis pigmentosa].

PURPOSE: To assess the applicability of a new technique of kinetic visual field examination--semi-automated kinetic perimetry (SKP)--in patients suffering from the visual field defects due to retinitis pigmentosa. METHODS: Thirty-five patients (19 women, 16 men: mean age 38.4 years) suffering from retinitis pigmentosa (10 with with Usher syndrome, one with Bardet-Biedl syndrome and one with Refsum syndrome) were examined using SKP software, implemented in Octopus 101 instrument (Haag-Streit, Koeniz, Switzerland). Three stimuli (1114e and 14e obligatory) were used to assess the hill of vision of each patient. The area of each isopter was measured in deg2. The test time was measured automatically in minutes. RESULTS: The visual field results were classified as complete or incomplete midperipheral "ring scotoma" (group I--13 patients) and concentric loss of the visual field (group II--22 patients). The area of 1114e isopter was 6147.5 deg2 in the group I and 1961.7 deg2 in the group II. The area of 14e isopter was 1468.4 deg2 and 781.7 deg2, respectively. The mean test time was 10 min. (range 4-20 min.): 8 min. in the group I and 13 min. in the group II. CONCLUSIONS: There is a large diversity of patterns of the visual field loss in retinitis pigmentosa. SKP, in contrary to widely used manual perimeter, gives a possibility of quantification of the visual field area. Future studies may be able to monitor the progression of the visual field loss caused by retinitis pigmentosa.

Adult↗
PubMed2003

Alterations of kynurenic acid content in the retina in response to retinal ganglion cell damage.

The present study is the first to examine the modulation of retinal kynurenic acid (KYNA) content in response to N-methyl-D-aspartate (NMDA)-induced cell death in adult rat retinal ganglion cells (RGC). Adult Brown Norway rats were intravitreally injected with NMDA or PBS. Surviving RGC were retrogradely labeled with fluorogold and counted in wholemounts of retinas 2, 7 and 14 days after injection. Retinal KYNA content was measured by HPLC at the same time points. RGC numbers decreased significantly 2, 7 and 14 days after NMDA injection if compared to control retinas. KYNA concentration increased significantly two days after NMDA-injection. However, 7 and 14 days after injection retinal KYNA content was found markedly decreased in NMDA-treated eyes as compared to controls. It is conceivable that KYNA deficiency is causally related to the pathology of excitotoxic retinal diseases.

Animals↗
PubMed2003

Ontogenic changes of kynurenine aminotransferase I activity and its expression in the chicken retina.

Kynurenine aminotransferases are key enzymes for the synthesis of kynurenic acid (KYNA), an endogenous glutamate receptor antagonist. The study described here examined ontogenic changes of kynurenine aminotransferase I (KAT I) activity and its expression in the chicken retina. KAT I activity measured on embryonic day 16 (E16) was significantly higher than at all other stages (E12, P0 and P7). Double labeling with antibodies against glutamine synthetase showed that on P7 KAT I was expressed in Müller cell endfeet and their processes in the inner retina. Since KAT I activity is high in the late embryonic stages, it is conceivable that it plays a neuromodulatory role in the retina during the late phase of embryogenesis.

Animals↗
PubMed2003

Oral citicoline treatment improves visual pathway function in glaucoma.

BACKGROUND: Increased latency and reduced amplitude of visual evoked potentials (VEP), frequently encountered in ocular hypertension or open-angle glaucoma, suggest slowed neural conduction in the visual pathways. An improvement in VEP latency and amplitude has been reported following repeated intramuscular injections of citicoline, a neuroprotective drug. Our aim was to find whether citicoline given orally would produce a similar effect. MATERIAL/METHODS: VEP latency and amplitude were measured in 21 glaucomatous eyes prior to and after two bi-weekly courses of citicoline taken orally in a dose of 1 gram/day. The treatment courses were separated by a two-week break; post-treatment VEP measurement was performed two weeks after the end of the second treatment. RESULTS: 62% of the eyes showed a response to the treatment, with VEP latency reduced from 123.5 (3.9 SEM) ms to 111.9 (1.9 SEM) ms (P=0.0008), and VEP amplitude increased from 6.56 (1.39 SEM) to 7.88 (1.16 SEM) (P=0.04). CONCLUSIONS: Citicoline given orally improves visual evoked potentials in some glaucoma patients.

Administration, Oral↗
PubMed2002

Changes of kynurenic acid content in the rat and chicken retina during ontogeny.

BACKGROUND: Kynurenic acid (KYNA) is the only known endogenous glutamate receptor antagonist and neuroprotectant. After showing the presence of KYNA and its synthesising enzymes in the adult rat retina, we examined developmental changes of KYNA content in both vascularised rat and avascular chicken retinas. METHODS: Retinas from Brown Norway rats and White Leghorn chickens at different developmental stages between the embryonic and the adult stages were used. KYNA levels were investigated with HPLC. RESULTS: KYNA was present in both rat and chicken retinas during ontogeny. The mean (+/- SE) concentration of KYNA found in the embryonic rat retina (E20) was 95+/-10 pmol/g wet wt. The KYNA content sharply increased within the following 3 days reaching a peak at birth (P0) of 702+/-77 pmol/g wet wt. At the end of the second postnatal week KYNA content decreased to 211+/-29 pmol/g wet wt. A further decrease was observed subsequently, with KYNA levels of 100+/-24.6 pmol/g wet wt at 3 month and 58+/-4 pmol/g wet wt at 12 month. Significant differences in KYNA concentrations between the embryonic and post-hatching stages were also observed in the chicken retina. In 12-day-old embryonic (E12) retinas the KYNA level was 364+/-48 pmol/g wet wt, and in E16 embryos it was 440+/-80 pmol/g wet wt. It significantly decreased to 200+/-38 pmol/g wet wt at P0 and stayed more or less at this level until P21 (217.5+/-23.5 pmol/g wet wt). CONCLUSION: KYNA is present in the rat and chicken retinas in high concentrations during early developmental stages. This suggests that KYNA may play a neuromodulatory role in the retina during development.

Animals↗