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Mitrofanis Pavlidis

Publications and source records attributed to Mitrofanis Pavlidis.

9 recordsLinked to original sources
PubMed2006

Pathological changes in human retinal ganglion cells associated with diabetic and hypertensive retinopathy.

BACKGROUND: To examine whether systemic diseases like diabetes and arterial hypertension, which frequently cause retinopathies leading to blindness effect the morphology of retinal ganglion cells (RGC). METHODS: Histological retina material with a history of being untreated, or laser-coagulated (LC) diabetic retinopathy (DR), or arterial hypertensive retinopathy (AHR) was used. The RGC were labeled by introducing crystals of the fluorescent carbocyanine dye DiI into the nerve fiber layer, which contains ganglion cell axons. RESULTS: The typical silhouettes of both major types of RGC, parasol and midget cells, were identified. The axons in DR and AHR retinas showed morphology changes such as irregular swelling and beading. Dendritic field sizes were significantly reduced in RGC of both the hypertonic and diabetic retinas. A significant reduction in branching frequency was evident in both the diabetic and hypertonic retinas, in both the midget and the parasol cells. In LC retinas, both parasol and midget RGC were observed within the LC spots, although their numbers were dramatically decreased compared with normal retinas. CONCLUSIONS: The data suggest that diabetes and arterial hypertonia have similar effects on the morphology of RGC, in addition to causing microvascular alterations and bleeding. Therefore, therapeutic measures and prognostic outcomes in diabetic and hypertensive retinopathy should also consider regressive changes in retinal neurons.

Adult↗
PubMed2006

Morphometric examination of human and monkey retinal ganglion cells within the papillomacular area.

PURPOSE: To examine the morphology of the retinal ganglion cells (RGCs) in the lesser characterized area lying between the optic disk and the macula that consists of the central papillomacular area (PMA) and the arcuate papillomacular bundle (PMB). METHODS: Nineteen human and 10 monkey (Macaca fascicularis) retinas obtained after death were used in the study. Perikaryal, axonal, and dendritic silhouettes were examined by postvital application of the fluorescent dye DiI, which specifically labeled RGCs when placed onto the optic fiber layer. The retinas were freed from surrounding tissue, prepared as flat mounts on a nitrocellulose filter, and fixed overnight in 4% paraformaldehyde. DiI diffuses along the membranes of ganglion cell axons, thereby completely labeling them, their cell bodies, and dendrites, which enables the RGCs to be examined with fluorescence microscopy. RESULTS: In both species, midget cells represented most of the RGCs within the PMA (96.15%) and possessed small, umbrella-like dendrites oriented toward the deeper retinal layers. Parasol cells were less abundant in both species and had small, typical symmetric dendrites. Also along the PMB, midget cells represented most cells (91.52%), whereas only 8.47% could be categorized as parasol cells. In both species, parasol cells of the PMB extended dendrites, which were oriented perpendicular to the axons. CONCLUSIONS: The data show that the PMA and PMB mainly contain small midget cells of typical morphology and size but with atypically oriented dendrites, which are only characteristic for this retinal area.

Aged↗
PubMed2005

Intraocular pressure changes during high-altitude acclimatization.

BACKGROUND: To evaluate the relationship between hypobaric hypoxia acclimatization and intraocular pressure (IOP) during ascent, acclimatization, and descent between 2286 m and 5050 m. METHODS: The following acclimatization-indicative physiological parameters were compared daily with IOP changes in eight healthy climbers of the 2003 Greek Karakorum expedition in altitude stages between 500 m and 5050 m: hemoglobin oxygen saturation (PO2), resting heart rate, blood pressure, retinal findings, and the Lake Louise score for acclimatization grading. RESULTS: IOP decreased significantly in the ascent phase (0.58 mmHg/100 m) and recovered (0.71 mmHg/100 m) during acclimatization and descent. A direct proportional correlation between decreases in PO2 and IOP was evaluated. Arterial blood pulse and pressure increased during acclimatization, while IOP decreased. No retinal hemorrhages were observed in well-acclimatized and incompletely acclimatized climbers. CONCLUSIONS: Every new active exposure to hypobaric hypoxia in the ascent phase induced a decrease in the IOP parallel to the PO2 decrease and to the level of acclimatization. The results from our study suggest that IOP changes are related to hypoxia-induced respiratory alkalosis and acclimatization stage, which could be used as a simple mobile screening test for acclimatization level to reveal acute mountain sickness and its severe consequences.

Acclimatization↗
PubMed2005

Lens epithelium supports axonal regeneration of retinal ganglion cells in a coculture model in vitro.

The purpose of this study was to determine whether the lens epithelium influences the survival or axonal growth of regenerating retinal ganglion cells. The optic nerves of adult albino rats were injured in order to induce axonal regeneration, and axon growth was then studied in retinal explants in the presence of cocultivated lens capsules carrying living epithelial cells. In the first series of experiments, cocultivation of retinal explants with lens epithelium in immediate proximity resulted in penetration of fibers into the lens epithelium, indicating that it supported axonal growth. In the second series of experiments, co-explants were placed 0.5-1.0mm from each other. The numbers of outgrowing retinal axons were determined both with respect to the retinal eccentricity and the topological relationship with the lenticular co-explant. The Wilcoxon matched-pairs signed-rank test was used to determine if the numbers of axons differed significantly between four regions of the explants. Significantly more axons grew out from the retinal edge facing the lenticular explant than from its opposite side, indicating that the lens epithelium supports axon growth. The numbers of surviving retinal ganglion cells in culture were determined after retrograde prelabelling with a neuroanatomical tracer. The number of fluorescent ganglion cells within the retinal explants did not significantly differ between the groups (Mann-Whitney test). These findings indicate that the lens epithelium influences both the amount of axonal regeneration and the direction of growth without affecting the survival rate of retinal ganglion cells in vitro.

Animals↗
PubMed2004

Ultrasonic visualization of the effect of blinking on the lacrimal pump mechanism.

BACKGROUND: The role of the lacrimal sac (LS) and the medial canthal tendon in the lacrimal pump mechanism is controversial. This study used ultrasonic visualization to analyze this phenomenon. METHODS: Movements of the LS and the medial canthal tendon during blinking were visualized with sonography. In addition, the maximal profile area of the LS was measured before and after blinking using 15-MHz sonography in 14 individuals with a normal lacrimal drainage system and in six patients with lacrimal duct obstruction. RESULTS: The upper part of the LS could be located as an echolucent structure between the lacrimal bone and the medial canthal tendon. The medial canthal tendon appeared to compress the LS during lid closure and release the LS during lid opening. The measured profile area of the visible normal LS at the compression time decreased by 50%. The dilated LS of patients with obstruction could also be compressed by the orbital muscle on blinking, but the maximum area decrease was only 15.5%. CONCLUSION: The findings imply that the lacrimal part of the orbicularis muscle contracts during blinking, with the medial canthal tendon compressing the LS in a cranial direction. Completion of lid closure then compresses both canaliculi and LS, forcing the intrasacral fluid through the drainage system. The expansion of the LS during the opening phase of the blink causes suction, and after opening of the punctal areas the canaliculi and LS vacuum breaks to reload with tear fluid. These findings demonstrate the importance of the orbicularis muscle and the medial canthal tendon for the lacrimal pump mechanism during blinking.

Adult↗
PubMed2004

Presurgical and postsurgical ultrasound assessment of lacrimal drainage dysfunction.

PURPOSE: In addition to the obligatory clinical tests, imaging of the lacrimal drainage system (LDS) is useful in its clinical evaluation. The purpose of this study was to examine the usability and reliability of ultrasonography in the evaluation of the lacrimal drainage system. DESIGN: Observational cohort study. METHODS: A prospective study was conducted at a single institution. We performed ultrasound examinations on 17 patients with epiphora before and after surgery, and on 17 asymptomatic volunteers, to visualize and evaluate the anatomic and functional condition or pathologic abnormalities of the LDS. RESULTS: Echographic evaluation of the LDS was possible in all individuals. Pathologic abnormalities (canaliculitis, diverticulitis, concretion, or dilation of the lacrimal sac, and reduced functionality of the orbicular muscle and/or lacrimal sac pump) could be well demonstrated. In the postsurgical course, functional patency of the dacryocystorhinostomy opening could be verified in all cases. CONCLUSIONS: Sonography of the LDS appears to represent a reliable diagnostic technique supplementary to clinical tests in the presurgical and postsurgical examination of patients with epiphora. Pathologic abnormalities that may not be apparent in routine x-ray dacryocystography can be demonstrated with ultrasound techniques. Patients also benefit from the avoidance of exposure to ionizing radiation. However, ultrasound is not suitable for imaging the lower part of the lacrimal sac and the lacrimal duct because of the presence of overlying bony structures.

Adult↗
PubMed2003

Retinal ganglion cells resistant to advanced glaucoma: a postmortem study of human retinas with the carbocyanine dye DiI.

PURPOSE: The present study was conducted to examine whether the morphology of the retinal ganglion cells is altered in advanced glaucoma. Perikaryal, axonal, and dendritic alterations were monitored in glaucoma-resistant retinal ganglion cells by postvitam application of the fluorescent dye DiI. METHODS: The retinas of four amaurotic glaucomatous eyes and four normal eyes enucleated after death were used in this study. The retinas were freed from surrounding tissue, prepared as flatmounts on a nitrocellulose filter, and fixed overnight in 4% paraformaldehyde. The retinal ganglion cells were labeled by introducing crystals of the fluorescent carbocyanine dye DiI, into the optic fiber layer. This dye diffuses along membranes of ganglion cell axons, completely labeling them and their cell bodies and dendrites. Further characterization of the retinas and optic nerves included hematoxylin-eosin and van Gieson histochemical staining as well as immunohistochemistry against glial fibrillary acidic protein. RESULTS: Because of the advanced stage of the disease, the retinas were almost completely depleted of ganglion cells, which had degenerated and therefore could not be stained. The few remaining ganglion cells were considered to be resistant to glaucoma. They showed drastic morphologic alterations, such as abnormal axonal beading, the cell bodies were normal in size but had irregular silhouettes or swellings, and there were fewer dendritic bifurcations. The size of the dendritic trees was smaller, implicating pruning of smaller dendritic branches. Glial cells were also detected immunocytochemically indicating their involvement in the pathologic course of glaucoma. CONCLUSIONS: The data suggest that the few ganglion cells that survive the elevated intraocular pressure associated with loss of visual function display morphologic changes that are manifested both on the cell body and on their intraretinal processes, including axons and dendrites.

Adult↗
PubMedDate not supplied

Multifocal electroretinography changes in the macula at high altitude: a report of three cases.

BACKGROUND: To evaluate the short- and long-term effects of high-altitude hypobaric hypoxia on macula morphology and function during ascents, acclimatizations, and descents between 500 m and 5,650 m, macula function was evaluated in three healthy climbers of a trekking expedition. METHODS: Macula physiology was tested with multifocal electroretinography (MF ERG), near and farvisual acuity, and Amsler grid tests. Macula morphology was tested with optical coherence tomography (OCT) and with stereoscopic fundoscopy obtained 1 week before ascent, as well as 1 week and 2 weeks after high-altitude exposure. The following physiological parameters indicative of acclimatization were compared daily during the expedition at altitudes between 500 m and 5,050 m: hemoglobin, oxygen saturation, resting heart rate, retinal findings, and the Lake Louise score of acclimatization. RESULTS: The central macula MF ERG responses were significantly reduced 1 week after high-altitude exposure, and had recovered by the follow-up examination performed during the following week. Near visual acuity and Amsler grid tests remained unaffected at both follow-up examinations. No significant changes were found in the follow-up OCT and daily fundoscopy examinations in all three well-acclimatized climbers. CONCLUSIONS: High-altitude hypobaric hypoxia affects the function of the highly sensitive macula region. This suggests that the exposure of persons with macula diseases such as age-related macula degeneration, tapetoretinal degeneration, or diabetic retinopathy to high altitudes may influence the disease progression. For this reason, this population should avoid prolonged and unnecessary high-altitude exposure without proper acclimatization.

Acclimatization↗