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Biomedical subjects

I Hemo

Publications and source records attributed to I Hemo.

At least 19 recordsLinked to original sources
PubMed2007

Lack of benefit of early awareness to age-related macular degeneration.

AIMS: To assess the rate of early awareness to the presence of age-related macular degeneration (AMD) and whether it enables early detection of transition to neovascular AMD (NVAMD) as compared with patients whose first presentation to an ophthalmologist is already at the neovascular stage of disease. METHODS: A retrospective analysis of 268 eyes of 268 consecutive patients with newly diagnosed NVAMD that were treated in a tertiary referral centre was performed. Patients were classified into those who were unaware (Group 1), or aware (Group 2), of the fact that they had AMD before diagnosis of NVAMD. Visual acuity, lesion size and composition, and demographics were compared between both groups. RESULTS: In all, 185 patients (69%) and 83 patients (31%) were classified to Groups 1 and 2, respectively. Patients in Groups 1 and 2 had similar demographic characteristics, presenting visual acuity and lesion size, and lesion compositions. Group 1 patients were more likely to have a positive history for smoking (41 vs26% in Group 2, P=0.03), whereas Group 2 patients were more likely to have positive family history for AMD (20 vs10%, P=0.02). CONCLUSIONS: These data suggest that current screening methods fail to identify the majority of patients with AMD before the development of NVAMD. The findings also demonstrate that in the routine clinical setting, prior awareness of AMD may not facilitate early detection of treatable choroidal neovascularization lesions.

Aged↗
PubMed2006

Paediatric vs adult retinal detachment.

OBJECTIVE: To evaluate the causes, incidences, characteristics, and treatment outcomes of paediatric vs adult retinal detachment. PATIENTS AND METHODS: One hundred and sixty (136 patients) out of 2408 consecutive retinal detachments (6.6%) at our facility occurred in children under the age of 18 years. Of them, 144 eyes (90%) of 127 (93%) children were treated and compared with a sample of 56 consecutive retinal detachments in 50 adults (over the age of 18 years). The parameters for comparison included cause, type of retinal detachment, its extent, macular involvement, number of tears, number and types of surgery, and the anatomic and functional surgical outcome. RESULTS: Statistically significant differences were found in the type of retinal detachment. Rhegmatogenous RD was less common (P=0.004), and exudative RD was more common (P=0.021) in the paediatric group. Ocular trauma and ocular syndromes were more common in the paediatric group (P<0.001), while myopia, posterior vitreous detachment, and retinal detachment following cataract surgery were less common in this group compared with adults (P<0.001, <0.001, and 0.001, respectively). Ocular pathologies associated with retinal detachment were more common in the paediatric group (P<0.001). Initial and last visual acuity of >20/400, last visual acuity of >20/40, and retinal complete reattachment were higher in adults (P<0.001). CONCLUSIONS: The type of retinal detachment, causes and outcomes were statistically different between paediatric and adult cases. The less successful functional and anatomical outcomes of retinal detachment surgery in children may reflect the different aetiologies and indicate the need for aetiology-specific treatment strategies according to each aetiology.

Adolescent↗
PubMed2004

Threshold scaling limits of RO concentrates flowing in a long waste disposal pipeline.

Disposal of RO concentrates emanating from inland brackish water desalination plants presents a difficult environmental problem. The solution adopted by Mekorot--the National Water Company of Israel--is to construct a 30 km waste disposal pipeline for collecting concentrates emanating from several RO desalination plants and discharging them into the sea. The discharged concentrates are highly supersaturated with respect to CaCO3. Scale precipitation during concentrate flow through the RO module is inhibited by the presence of anti-scalants. The retention time of the concentrate solution in the discharge pipe will exceed 100 hours. This raises the issue of the risk of scale precipitation in the discharge pipe that could impair its proper functioning. The aim of the present study was to provide data for guiding the design and operation of the disposal pipeline. The extent of the induction period prior to the onset of precipitation was measured in a pilot plant simulating flow of concentrate solutions dosed with anti-scalants. The parameters investigated were the scaling potential, the anti-scalant concentration and the presence of a mixture of several anti-scalants. The results of this study provide threshold scaling limits under various conditions.

Calcium Carbonate↗
PubMed2000

Halofuginone: a potent inhibitor of critical steps in angiogenesis progression.

We have previously demonstrated that halofuginone, a low molecular weight quinazolinone alkaloid, is a potent inhibitor of collagen alpha1(I) and matrix metalloproteinase 2 (MMP-2) gene expression. Halofuginone also effectively suppresses tumor progression and metastasis in mice. These results together with the well-documented role of extracellular matrix (ECM) components and matrix degrading enzymes in formation of new blood vessels led us to investigate the effect of halofuginone on the angiogenic process. In a variety of experimental system, representing sequential events in the angiogenic cascade, halofuginone treatment resulted in profound inhibitory effect. Among these are the abrogation of endothelial cell MMP-2 expression and basement membrane invasion, capillary tube formation, and vascular sprouting, as well as deposition of subendothelial ECM. The most conclusive anti-angiogenic activity of halofuginone was demonstrated in vivo (mouse corneal micropocket assay) by showing a marked inhibition of basic fibroblast growth factor (bFGF) -induced neovascularization in response to systemic administration of halofuginone, either i.p. or in the diet. The ability of halofuginone to interfere with key events in neovascularization, together with its oral bioavailability and safe use as an anti-parasitic agent, make it a promising drug for further evaluation in the treatment of a wide range of diseases associated with pathological angiogenesis.

Angiogenesis Inhibitors↗
PubMed1998

Vascular endothelial growth factor upregulation in human central retinal vein occlusion.

BACKGROUND AND OBJECTIVE: Vascular endothelial growth factor (VEGF), a key mediator of intraocular neovascularization, is triggered by hypoxia and has been shown in the eyes of animal models of central retinal vein occlusion (CRVO). However, there is little information on CRVO in humans, in particular, the identity of VEGF-producing cells. STUDY DESIGN: The study design was molecular localization of the site of VEGF production in the eyes of patients with CRVO. PARTICIPANTS: Ten formaldehyde solution-fixed and paraffin-embedded eyes removed surgically from patients with CRVO and neovascular glaucoma were studied. Five eyes with uveal melanoma and no neovascularization served as control specimens. METHODS: Thin whole-eye sections were hybridized in situ with a VEGF-specific probe to identify cells producing VEGF messenger RNA (mRNA). RESULTS: All ten eyes with CRVO showed evidence of intraretinal expression of VEGF mRNA. In all eyes, the inner nuclear layer showed VEGF-upregulated expression. Upregulation of VEGF mRNA was identified in four eyes in the ganglion cell layer and in two eyes with retinal detachment in the outer nuclear layer as well. CONCLUSIONS: The population of VEGF-producing retinal cells in each eye is likely to represent cells residing in ischemic regions of the retina. Hypoxia-induced VEGF is, most likely, the linking factor between retinal ischemia and iris and retinal neovascularization in CRVO.

Aged↗
PubMed1998

A plasticity window for blood vessel remodelling is defined by pericyte coverage of the preformed endothelial network and is regulated by PDGF-B and VEGF.

Little is known about how the initial endothelial plexus is remodelled into a mature and functioning vascular network. Studying postnatal remodelling of the retina vasculature, we show that a critical step in vascular maturation, namely pericyte recruitment, proceeds by outmigration of cells positive for (alpha)-smooth muscle actin from arterioles and that coverage of primary and smaller branches lags many days behind formation of the endothelial plexus. The transient existence of a pericyte-free endothelial plexus coincides temporally and spatially with the process of hyperoxia-induced vascular pruning, which is a mechanism for fine tuning of vascular density according to available oxygen. Acquisition of a pericyte coating marks the end of this plasticity window. To substantiate that association with pericytes stabilizes the vasculature, endothelial-pericyte associations were disrupted by intraocular injection of PDGF-BB. Ectopic PDGF-BB caused the detachment of PDGF-beta receptor-positive pericytes from newly coated vessels, presumably through interference with endogenous cues, but had no effect on mature vessels. Disruption of endothelial-pericyte associations resulted in excessive regression of vascular loops and abnormal remodelling. Conversely, intraocular injection of VEGF accelerated pericyte coverage of the preformed endothelial plexus, thereby revealing a novel function of this pleiotropic angiogenic growth factor. These findings also provide a cellular basis for clinical observations that vascular regression in premature neonates subjected to oxygen therapy [i.e. in retinopathy of prematurity] drops precipitously upon maturation of retina vessels and a mechanistic explanation to our previous findings that VEGF can rescue immature vessels from hyperoxia-induced regression.

Actins↗
PubMed1997

Vitreoretinal surgery assisted by the 193-nm excimer laser.

PURPOSE: Ablating and cutting vitreoretinal membranes using a 193-nm excimer laser-based microsurgical system. METHODS: A 193-nm microsurgical system enables delivery of the beam into a fluid medium to cut preretinal and subretinal membranes. Two patients with proliferative diabetic retinopathy and one patient with proliferative vitreoretinopathy were treated with this new device. RESULTS: Gentle ablation and cutting of the preretinal and subretinal membranes without exerting any traction on or apparent damage to the neighboring tissue was achieved. CONCLUSIONS: The technology is applicable to a variety of intraocular vitreoretinal surgical procedures.

Aged↗
PubMed1996

Upregulated expression of vascular endothelial growth factor in proliferative diabetic retinopathy.

AIMS/BACKGROUND: Vascular endothelial growth factor (VEGF) is a hypoxia induced angiogenic factor. Recent studies have shown that high levels of VEGF accumulate in the vitreous of patients with proliferative diabetic retinopathy (PDR). The purpose of the present study was to identify the retinal cells that upregulate VEGF expression in human PDR patients representing progressive stages of retina deterioration. METHODS: Thirteen formalin fixed and paraffin embedded enucleated eyes with PDR were used (eyes were enucleated because of being blind and painful as a result of neovascular glaucoma). Thin retina sections were hybridised in situ with a VEGF specific probe, to identify cells producing VEGF mRNA. RESULTS: All eyes with PDR showed upregulated expression of VEGF mRNA, specifically in the cells of the neurosensory retina. VEGF expression was upregulated in all three nuclear layers--namely, the ganglion cell layer, the inner nuclear layer, and the outer nuclear layer. However, in each patient, VEGF producing cells were mostly distributed in a different layer, or even confined to a specific region in that layer. For example, expression by the outer nuclear layer was mostly detected in detached (presumably hypoxic) regions of the retina. CONCLUSIONS: Progression of PDR is distinguished by a sustained, upregulated expression of VEGF by the neurosensory retina. Cells in all retina layers can potentially contribute to augmented VEGF production. The restricted population of VEGF producing cells in each case is likely to represent cells residing in ischaemic regions of the retina. Thus, VEGF may function as a linking factor between retinal ischaemia and PDR associated neovascularisation.

Adult↗
PubMed1995

Efficacy of topical gentamicin treatment after 193-nm photorefractive keratectomy in an experimental Pseudomonas keratitis model.

BACKGROUND: The treatment of Pseudomonas keratitis has many limitations, and further investigation to identify more effective approaches is required. We therefore studied the possible contribution of the debridement effect of 193-nm excimer laser on Pseudomonas keratitis in rabbit eyes. METHODS: Pseudomonas keratitis was induced in 30 rabbit eyes by inflicting controlled central corneal scratches and applying a drop of Pseudomonas aeruginosa suspension. After 24 h, one cornea of each animal was photo-ablated (excimer laser: fluency 90 mJ/cm2, 10 Hz, 213 pulses), yielding 50 microns of tissue ablation, while the follow cornea served as control. Five groups of six animals each were formed and received: a subconjunctival injection of gentamicin 20 mg (group 1), topical 14 mg/ml gentamicin hourly (group 2) or every 2.5 h (group 3), or NaCl 0.9% hourly (group 4) for 8 h. In group 5, animals were sacrificed without additional treatment. After 9 h corneas were excised, homogenized, serially diluted, and plated on agar blood plates. The numbers of colony-forming units (CFU) per cornea were statistically evaluated (Mann-Whitney test). RESULTS: In control eyes, a greater decrease of CFU was observed in group 2 than in group 3 (P = 0.03). In laser-ablated eyes, there was no difference in CFU between groups 2 and 3. Comparison of the excimer-treated and control eyes revealed a greater number of bacteria (CFU) in controls only in group 3 (P = 0.02). CONCLUSION: Our study suggests that controlled debridement of cornea with excimer laser may improve the effect of topical antibiotics.

Administration, Topical↗
PubMed1995

Vascular endothelial growth factor acts as a survival factor for newly formed retinal vessels and has implications for retinopathy of prematurity.

Retinopathy of prematurity (ROP) is initiated by hyperoxia-induced obliteration of newly formed blood vessels in the retina of the premature newborn. We propose that vessel regression is a consequence of hyperoxia-induced withdrawal of a critical vascular survival factor. We show that regression of retinal capillaries in neonatal rats exposed to high oxygen, is preceded by a shut-off of vascular endothelial growth factor (VEGF) production by nearby neuroglial cells. Vessel regression occurs via selective apoptosis of endothelial cells. Intraocular injection of VEGF at the onset of experimental hyperoxia prevents apoptotic death of endothelial cells and rescues the retinal vasculature. These findings provide evidence for a specific angiogenic factor acting as a vascular survival factor in vivo. The system also provides a paradigm for vascular remodelling as an adaptive response to an increase in oxygen tension and suggests a novel approach to prevention of ROP.

Animals↗
PubMed1995

Hypoxia-induced expression of vascular endothelial growth factor by retinal cells is a common factor in neovascularizing ocular diseases.

BACKGROUND: It is generally assumed that unwarranted, excessive neovascularization of the retina and iris is a direct response to a hypoxic retinal environment. Prompted by our previous findings that the potent angiogenic factor, vascular endothelial growth factor (VEGF), is hypoxia-inducible, we used in situ hybridization techniques to examine the thesis that VEGF functions as the link between retinal ischemia and a pathologic, intraocular, angiogenic response. EXPERIMENTAL DESIGN: To gain molecular access to human material representing progressive stages of angiogenic eye diseases, in situ hybridization analysis was carried out on sections of whole globes enucleated at the time of ongoing neovascularization. This methodology identified cells that have up-regulated VEGF expression during natural progression of the indicated diseases. A rabbit model was also used to determine whether experimentally induced retinal ischemia leads to up-regulation of VEGF expression. RESULTS: Proliferation of vascular elements in proliferative diabetic retinopathy and neovascularization of the retina and/or iris secondary to central retinal vein occlusion, retinal detachment, and intraocular tumors were always accompanied by induction of retinal VEGF expression. Furthermore, in each case, expression of VEGF was induced only in a particular layer of the retina (either the outer nuclear layer, the inner nuclear layer, or the ganglion cell layer), matching the zones affected by impaired perfusion. In a rabbit model simulating retinal vein occlusion, elevated levels of VEGF mRNA were detected within a few days of experimental induction of retinal ischemia, exclusively in the ischemic region. CONCLUSIONS: VEGF may be one of the long anticipated factors linking retinal ischemia and intraocular angiogenesis. Irrespective of the cause of retinal ischemia, sustained overproduction of VEGF by ischemic retinal cells may promote retinal and iris neovascularization in a number of neovascular eye diseases.

Animals↗
PubMed1994

Single dosage of mitomycin C for prevention of recurrent pterygium: preliminary report.

We studied the recurrence rate of pterygium after administration of a single dosage of topical mitomycin C at the completion of pterygium surgery. Forty patients who had advanced or recurrent pterygium underwent excision of pterygium, leaving the sclera bare. Patients were randomized in a masked fashion into two groups of 20 patients each. Group 1 received a single dosage of topical 0.02% mitomycin C for 5 min at the completion of the surgery whereas group 2 underwent the same procedure but received NaCl 0.9% instead of mitomycin C. Patients were followed from 6 to 15 months in a masked manner. The pterygium recurred in one patients (5%) in group 1, whereas in group 2 the recurrence rate was 45% (p = 0.0035). Formation of dellen and a delay of epithelialization for 5 weeks were found in one patient in group 2. No complications were observed in patients in group 1. This study indicates the possible advantage of administration of a single dosage of 0.02% mitomycin C for postoperative prevention of recurrence of pterygium.

Adult↗
PubMed1994

Vitreoretinal ablation with the 193-nm excimer laser in fluid media.

PURPOSE: To ablate retina and vitreous membranes using the 193-nm argon fluoride excimer laser in a fluid medium. METHODS: A special delivery system for the 193-nm excimer laser was developed that enabled the delivery of the laser into high-absorption liquid environments. The system was tested on the retina in an in vitro cup preparation of cow's eyes, and also in vivo on retina and vitreous membranes of rabbit eyes. The depth of cut as a function of laser energy was determined for an ablating needle with a 0.25-mm exit diameter. RESULTS: Gentle cutting of retinal tissue and of vitreous membranes was obtained in an energy range of 0.075 to 0.25 mJ/pulse. At the energy level of 0.075 mJ/pulse, four pulses were required for full-depth cut formation in rabbit retina, whereas at energy levels greater than 0.17 mJ/pulse, one pulse was sufficient for full-depth cut formation. The maximal rate of cutting achieved for the bovine retina was 2 mm/sec at a 20-Hz repetition rate of the laser. Ablation occurred only when the tip was held in contact with the tissue. CONCLUSIONS: The technology described herein appears to be advantageous and applicable to a variety of vitreoretinal surgical procedures.

Animals↗
PubMed1993

Efficacy of doxycycline and tetracycline in ocular rosacea.

We compared the effects of doxycycline and tetracycline hydrochloride on the subjective symptoms in ocular rosacea. Twenty-four patients with symptomatic ocular rosacea were randomly assigned to two groups and treated with doxycycline 100 mg/day (group 1, 16 patients) or tetracycline hydrochloride 1 g/day (group 2, eight patients). The dosages of each drug were gradually tapered and discontinued according to symptomatic response. At each examination all the manifesting symptoms were scored by the patients. Patients were followed up from six weeks to three years. After six weeks of drug treatment, all patients except one had symptomatic improvement. Although most of the scores of the symptoms were significantly decreased in both groups, greater symptomatic relief occurred in the tetracycline hydrochloride-treated patients (P = .041). However, after three months of treatment there was no significant difference in symptoms between the two groups. Gastrointestinal tract complications occurred in two of the 16 patients (12.5%) in group 1 and in three of the eight patients (37.5%) in group 2. Both tetracycline hydrochloride and doxycycline can control the symptoms of ocular rosacea.

Administration, Oral↗
PubMed1993

Effect of eye patching on ocular surface.

We studied the effect of pressure patching in 27 medical students. Fourteen students had pressure patching in one eye (group 1) and 13 (group 2) had light patching. The fellow eye of each volunteer remained unpatched (group 3). Clinical signs and symptoms were scored and evaluated at the first and the following (after overnight) examinations. Before patching no subject had any of the clinical signs or symptoms. After the patch was removed in groups 1 and 2, all except one volunteer in each group had clinical signs or symptoms, or both, whereas in group 3, none had clinical signs or symptoms. Group 1 had greater scores for clinical signs (P = .019) and for symptoms (P = .038) as compared to group 2. In group 1, two participants did not complete the study period (by removal of the patch) because of severe discomfort and three had temporary irregularities in corneal surface with temporary decrease of vision. We suggest that pressure patching may cause discomfort and changes in visual acuity that are usually attributed to other reasons.

Adolescent↗
PubMed1993

Silicone oil tamponade for retinal detachment and delayed treatment of retinal tears.

Four patients underwent a vitrectomy procedure for retinal detachment associated with anterior and posterior proliferative vitreoretinopathy (D-1 type). In each patient, an internal tamponade was achieved with 1000-centistoke silicone oil. Preretinal and/or subretinal hemorrhage that was difficult to remove during surgery, as well as remnants of subretinal fluid, prevented complete intraoperative treatment of the retinal tears or the retinotomy with endolaser photocoagulation. The silicone oil tamponade kept the retina flat until laser treatment was applied to the retinal tears several weeks later, when the retinal blood and subretinal fluid had reabsorbed. When circumstances make achieving intraoperative laser marks difficult, silicone oil tamponade appears to be superior to a long-lasting gas tamponade. It provides a more permanent tamponade than gas and excellent visualization of the fundus several weeks after surgery, at which time laser marks can be completed.

Adult↗