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Biomedical subjects

N Georgiadis

Publications and source records attributed to N Georgiadis.

15 recordsLinked to original sources
PubMed2003

8-Isoprostaglandin F2a and ascorbic acid concentration in the aqueous humour of patients with exfoliation syndrome.

BACKGROUND/AIMS: The authors investigated the concentrations of 8-isoprostaglandin F(2a), a marker of oxidative stress in vivo, and ascorbic acid, a protectant against oxidative damage, in the aqueous humour of patients with exfoliation syndrome (XFS) and cataract and compared the results with those in age matched patients with cataract, but without XFS, to determine whether XFS is associated with increased oxidative stress. METHODS: Aqueous humour was aspirated at the beginning of phacoemulsification cataract surgery from 27 eyes of 27 cataract patients with XFS and 27 eyes of 27 age matched cataract patients without XFS. 8-Isoprostaglandin F(2a)concentration in the aqueous was determined with a commercial immunoassay; ascorbic acid concentration was measured with a microplate assay method. RESULTS: The mean concentration of 8-isoprostaglandin F(2a)in the aqueous from patients with XFS (2429 (SD 2940) pg/ml; range 400-10500 pg/ml) was significantly higher than that measured in the aqueous of age matched control patients (529.1 (226.8) pg/ml; range 325-1000 pg/ml); (p = 0.0028). Furthermore, mean ascorbic acid concentration in XFS patients (0.75 (0.39) mM; range 0.28-1.70 mM) was significantly lower than that found in control patients (1.19 (0.47) mM; range 0.53-2.4 mM); (p = 0.0005). There was a reverse correlation between 8-isoprostaglandin F(2a)and ascorbic acid concentration. CONCLUSION: 8-Isoprostaglandin F(2a)was significantly increased in the aqueous of patients with XFS, and ascorbic acid was decreased, providing evidence of a role for free radical induced oxidative damage in the pathobiology of XFS.

Antioxidants↗
PubMed2001

Genetic evidence for two species of elephant in Africa.

Elephants from the tropical forests of Africa are morphologically distinct from savannah or bush elephants. Dart-biopsy samples from 195 free-ranging African elephants in 21 populations were examined for DNA sequence variation in four nuclear genes (1732 base pairs). Phylogenetic distinctions between African forest elephant and savannah elephant populations corresponded to 58% of the difference in the same genes between elephant genera Loxodonta (African) and Elephas (Asian). Large genetic distance, multiple genetically fixed nucleotide site differences, morphological and habitat distinctions, and extremely limited hybridization of gene flow between forest and savannah elephants support the recognition and conservation management of two African species: Loxodonta africana and Loxodonta cyclotis.

Africa↗
PubMed2001

Transforming and insulin-like growth factors in the aqueous humour of patients with exfoliation syndrome.

BACKGROUND: Growth factors circulating with the aqueous may play an important role in the pathogenesis of exfoliation syndrome (XFS), which is characterized by excessive synthesis and accumulation of abnormal extracellular material. METHODS: We investigated the concentration of three ubiquitous growth factors (TGF-beta1, TGF-beta2 and IGF-1) in the aqueous humour of 50 patients with XFS (27 from Erlangen, 23 from Thessaloniki) and 54 age-matched controls (27 from Erlangen, 27 from Thessaloniki). This study was performed in two centres, independently of each other, using different assay systems. RESULTS: In the aqueous humour samples collected in Erlangen, both the levels of total TGF-beta1 (P<0.001) and mature TGF-beta1 (P<0.05) were significantly increased in XFS patients compared with controls. Specifically, for total TGF-beta1 patients with XFS exhibited higher a mean value (90.5 +/- 37.4 pg/ml) than controls (30.2 +/- 8.3 pg/ml). The mean level of mature TGF-beta1 was also higher in XFS (14.2 +/- 2.8 pg/ml) than in controls (4.9 +/- 5.5 pg/ml). No difference was found between XFS and controls in the levels of total or mature TGF beta2 in the aqueous or in the level of these two growth factors in the serum. In aqueous humour samples collected in Thessaloniki a significant difference between XFS and controls was also observed for mature TGF-beta1 (XFS 17.06 +/- 11.02 pg/ml vs controls 9.01 +/- 5.69 pg/ml; P=0.006). No difference was observed in TGF-beta2 concentration or IGF-1 concentration in the aqueous. No correlation could be established between protein concentration and the levels of the three growth factors measured. A significant correlation was found between age and protein concentration in XFS, but not in the controls. CONCLUSION: Since TGF-beta1 induces the synthesis and accumulation of extracellular matrix, it is hypothesized that TGF-beta1 plays an important role in the pathogenesis of XFS. Our data suggest that the increased levels of TGF-beta1 are most likely due to enhanced local synthesis.

Aged↗
PubMed2000

Contact lens fitting difficulties following refractive surgery for high myopia.

PURPOSE: To describe the clinical and optical problems encountered in contact lens fitting following refractive surgery for high myopia. METHODS: Following refractive surgery for high myopia (greater than -10.00 D) we corrected residual refractive errors with contact lenses in the four eyes of two patients. The first patient had undergone bilateral laser in situ keratomileusis (LASIK),with two subsequent LASIK retreatments in the left eye. Ten months later she was fit with rigid gas permeable (RGP) lenses in both eyes. The second patient had undergone a clear lens extraction in the right eye and radial keratotomy followed by photorefractive keratectomy(PRK) in the left eye. She was fit with toric soft lenses six years postoperatively. RESULTS: Final visual acuity obtained with contact lenses was 20/25-20/20 in all eyes. The first patient required significant minus lens power compensation. Furthermore, the RGP lens in the left eye was slightly decentered due to corneal irregularity induced by LASIK. The second patient had regular corneal surfaces and was successfully fit with daily wear toric soft lenses despite the 2.75 D of residual astigmatism in the left eye. CONCLUSIONS: Following refractive surgery for high myopia a proportion of patients will remain undercorrected. In these patients the alterations in corneal architecture that ensue make contact lens fitting more challenging. Patients with regular astigmatism may be fitted successfully with toric soft lenses. Patients with corneal irregularities should be fit with RGP lenses.

Adult↗
PubMed2000

Vital signs monitoring from home with open systems.

This study investigates the applicability of a novel codification scheme based on two healthcare informatics standards (namely the VITAL (ENV 13734) and DICOM Sup. 30 Waveform Interchange) in addressing the robust interchange of waveform and medical data in remote healthcare applications. To further address system validation and clinical acceptance issues, pilots were set-up between home-monitoring stations and a hospital-based telemedicine consultation center. The pilots focused in assessing applicability, technical feasibility and performance of the proposed codification scheme based on the two standards. This paper presents the system and services requirements as studied for a home-care application, the design goals for the preservation of security stature, the practical issues of validation and the results of integrating these codification schemes into a commercial patient connected device.

Computer Systems↗
PubMed1999

The evaluation of corneal graft tissue by the use of trypan blue.

BACKGROUND: The quality of the donor cornea, which basically depends on the condition of the endothelial sheet, is an important factor for the successful outcome of penetrating keratoplasty. PATIENTS AND METHODS: In this retrospective study, we present our experience in using trypan blue staining for the examination and evaluation of 498 consecutive corneal grafts from 251 donors, concerning their suitability for penetrating keratoplasty, during the decade 1986-1995. RESULTS: Forty-two grafts out of 498 (8.5%) were considered not suitable for surgery because of the great number of destroyed cells (cell density less than 1,500 cells/mm2) and the abnormal cell size and cell shape. Nine out of the 456 (1.97%) operated eyes exhibited primary donor failure and needed re-operation, probably because of boundary cell density of the graft (ranged in those cases from 1,600 to 1,800 cells/mm2). No infections of grafts were observed. CONCLUSION: Tissue evaluation of corneal grafts by the use of trypan blue staining is a simple, cost-effective, safe and accurate method that does not influence the vitality of the endothelial layer of the grafts.

Adolescent↗
PubMed1997

A simple ocular irrigation system for alkaline burns of the eye.

An alkaline burn of the eye constitutes an ocular emergency. Emergency treatment consisting of copious irrigation begins at the site of the accident and alters the outcome of the injury. The authors describe a low-cost, simple, and effective system for continuous irrigation of the ocular surface after a severe alkaline burn of the eye. This system also can be applied by inexperienced personnel during the transport of a patient to an ophthalmologic center.

Alkalies↗
PubMed1993

Management of pseudophakic retinal detachment with various intraocular lens types.

In the last five years, 25 cases of retinal detachment (RD) after intraocular lens implantation were treated in the University Eye Clinic of Thessaloniki. The incidence of RD was lower with posterior chamber intraocular lens (PC-IOL, 0.46%) implantation than in the cases with anterior chamber IOL (AC-IOL, 2.6%) implantation. The successful reattachment rate was higher with PC-IOL (100%) than in cases with AC-IOL where the low success (87%) rate was caused by proliferative vitreoretinopathy. Therefore, the eyes with AC-IOL required reoperation more frequently, and the ultimate failure rate (despite multiple operations) was higher in the AC-IOL group. Conventional surgical techniques were used in the first procedure. In the reoperated cases, the most advanced techniques were used, such as vitrectomy combined with gas or silicone oil injection.

Cataract Extraction↗
PubMed1990

The HK/LK polymorphism of erythrocyte cation content in two wild species of east African bovids: demonstrated in wildebeest but not in African buffalo.

Concentrations of K and Na were determined in erythrocytes from wildebeest and African buffalo resident in Tanzania. The object was to determine if these species possess the HK/LK polymorphism which is typical of other bovid species, but not of other mammals. The polymorphism is characterized by individuals that are either of the HK phenotype (high K and low Na concentrations in red cells) or LK phenotype (low K and high Na concentrations in red cells). Wildebeest were shown to be polymorphic, with the distribution of phenotypes resembling that in domestic cattle. By contrast the polymorphism was not found in the African buffalo; all 59 individuals examined exhibited the HK phenotype. This was unexpected, since the polymorphism has been observed in five divergent bovid species, including two species (water buffalo and domestic cow) that are closely related to the African buffalo, and classified in the same subfamily (Bovinae). The most parsimonious interpretation of this pattern is that the trait was lost from the African buffalo after species in the Bovinae diverged. The biological significance of the HK/LK polymorphism, and reasons for its presence or absence among species in the Bovidae, remain obscure.

Animals↗
PubMed1983

Gene dosage effects in human diploid and tetraploid fibroblasts.

The effects of cell ploidy on the biochemical characteristics of cultured cells were compared using human diploid vs tetraploid fibroblasts isolated with a non-selective method. Their DNA replication was compared by thymidine incorporation, and DNA content by Feulgen staining and quantitative analysis. Their RNA and protein content, cell sizes and the specific activities of glucose-6-phosphate dehydrogenase (G-6-PD) and 6-phosphogluconate dehydrogenase (6-PGD) were assayed quantitatively. With the exception of RNA content, all other parameters demonstrated a 2-fold increase reflecting the increase in cell ploidy. These direct gene dosage effects on the genetic material and functional expression of the human genome were in contrast to previous observations in other species and validate the use of human intraspecific euploid hybrids for biochemical and genetic studies.

Adult↗
PubMed1976

Malignant tumors of the thyroid.

Carcinoma of the thyroid gland is not common. The majority of lesions in this series were differentiated in type. The treatment of choice is almost total thyroidectomy supplemented by I131 in some cases. L-thyroxine was prescribed routinely for all patients postoperatively for replacement and depression treatment. The immediate postoperative mortality was about 1% and prognosis is relatively good. Undifferentiated thyroid carcinomas are fast growing and very lethal and unfortunately no method of treatment is effective. Only four patients in this group survived more than a year.

Adenocarcinoma↗
PubMedDate not supplied

HK/LK polymorphism and its genetic determination in Speke's gazelle.

Concentrations of potassium (K) and sodium (Na) were determined in the erythrocytes of 28 members of an interbreeding herd of Speke's gazelle. The distribution of K concentrations and Na/K concentration ratios suggested the presence of the high-K/low-K (HK/LK) polymorphism known in erythrocytes of domestic bovids. The pedigree of the herd of gazelles is known completely, permitting examination of the inheritance of HK/LK polymorphism by overlaying the distribution of phenotypes on the pedigree. Statistical analyses clearly indicate a strong genetic component in the phenotypic variability that is entirely consistent with a single autosomal locus, two-allele mode of inheritance, with the LK allele being dominant. This is the first demonstration of HK/LK polymorphism in a wild bovid species. The evidence indicates that HK/LK polymorphism is of considerable evolutionary age, is of monophyletic origin, and is maintained by selection.

Alleles↗
PubMedDate not supplied

Structure and history of African elephant populations: I. Eastern and southern Africa.

Patterns of restriction site variation within mitochondrial DNA (mtDNA) of 270 individuals were used to examine the current structure of savanna elephant populations and to infer historical patterns of gene flow across eastern and southern Africa. Elephants have a complex population structure characterized by marked subdivision at the continental level (Fst = 0.39; 95% confidence interval 0.19-0.58), and isolation by distance at the regional level. However, phylogeographic analysis revealed evidence of protracted gene flow across the continent. First, one relatively derived haplotype was found at all sampling locations. Second, haplotypes representing exceptionally divergent (up to 8.3%) mitochondrial clades were found to coexist at distant (> 2,000 km) sampling locations. In the few other species characterized by sympatric individuals bearing such divergent haplotypes, all such individuals were found to coexist within limited geographical regions. Accordingly, pronounced mitochondrial divergence within populations is often attributed to ancestral isolation in allopatry, followed by secondary contact. The patterns within elephants do not accord with ancestral isolation in allopatry. Given the exceptional mobility of elephants, a geographical barrier is unlikely to have obstructed gene flow between regions for long enough to produce the observed mitochondrial divergence. Rather, the patterns are consistent with the more parsimonious hypothesis, based on neutral coalescent theory, that gene flow has maintained a sufficiently large effective population size (> 50,000 females) for representatives of clades that diverged at least 4 million years ago to have persisted by chance within a population that was subdivided, but not strictly isolated in allopatry.

Africa, Eastern↗
PubMedDate not supplied

Isolated ocular ischemic syndrome with no cerebral involvement in common carotid artery occlusion.

PURPOSE: The ocular ischemic syndrome (OIS) is sometimes a complication of common carotid artery (CCA) occlusion causing complete interruption of blood flow through both the internal and external carotid arteries we investigated a single case of an isolated OIS that remained undiagnosed for two years, because the underlying CCA pathology caused no cerebral involvement. CASE REPORT: A 57-year-old man presented with subacute painful visual loss in the right eye in a setting of hypertension, smoking and coronary artery disease. RESULTS. Neurological examination, a brain CT and MRI scan were all normal. Extensive laboratory work-up excluded small artery disease, inflammatory arteritis or cardiac causes of retinal embolism. Ophthalmologic evaluation and fluorescein angiography gave findings consistent with OIS, while vascular ultrasound evaluation and aortic arch angiography verified right CCA occlusion accompanied by an extensive collateral network. CONCLUSIONS: Had this patient been referred sooner for a simple carotid artery work-up, both the CCA occlusion and the OIS could probably had been prevented.

Aorta, Thoracic↗