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Biomedical subjects

M Antoniou

Publications and source records attributed to M Antoniou.

At least 19 recordsLinked to original sources
PubMed2005

Evolving radiological features of hypothalamo-pituitary lesions in adult patients with Langerhans cell histiocytosis (LCH).

Langerhans cell histiocytosis (LCH) is a rare, systemic disease caused by monoclonal expansion of dendritic cells that shows a particular predilection for the hypothalamic-pituitary system (HPS). We studied the function (anterior and posterior pituitary hormonal secretion) and morphology using magnetic resonance imaging (MRI) of the HPS in 17 adult patients (seven males, median age 35 years, range 18-59 years) with multisystem LCH. We also evaluated the evolution of structural HPS abnormalities in relation to pituitary function and response to treatment in 12 of these patients during a median follow-up period of 3.75 years (range 1.5-10 years). Of the 17 patients, 14 (82%) had abnormal HPS imaging, and 12 (70%) had more than one area involved. Lack of the bright spot of the posterior pituitary lobe was typically found in all patients with the diagnosis of diabetes insipidus (DI). Eight patients (47%) had infundibular enlargement, six (35%) pituitary infiltration, four (24%) partially or completely empty sella, three (18%) hypothalamic involvement, and two (12%) infundibular atrophy. DI was found in 16 patients (94%) and anterior pituitary hormonal deficiency (APHD) in 10 patients (59%); two patients had single (12%) and 8 (47%) multiple APHD. During the follow-up period there was improvement of the initially demonstrated HPS pathology in seven (47%) patients, and five (33%) of them had received at least one form of treatment. APHD and DI persisted in all patients except in one in whom established gonadotrophin deficiency recovered. In summary, DI and APHD are very common in patients with multisystem LCH and are almost always associated with abnormal HPS imaging.

Adolescent↗
PubMed2003

Binge eating disorder versus overeating: a failure to replicate and common factors in severely obese treatment seeking women.

The disordered eating symptoms, general psychopathology and dieting history among obese women diagnosed with Binge Eating Disorder (BED) and obese women who overeat (OE) are examined. One hundred and thirty women (n=83 with BED and n=47 who overeat) seeking treatment for an eating disorder were diagnosed using the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria and the Eating Disorders Examination (EDE). They also completed a battery of psychometric tests. Despite adequate statistical power to detect differences, MANOVAs revealed very few significant differences between the groups. Loss of control of eating does not adequately differentiate these two groups within an eating disorders treatment-seeking context. It is likely that only the most acutely distressed from each group is seeking treatment, so that differences found in a community sample would not be found. Using a principal components analysis, factors within each group that may underlie the common psychopathology of both groups (i.e. disordered eating symptoms, general psychopathology and dieting history) were found.

Adult↗
PubMed2002

LCR-mediated, long-term tissue-specific gene expression within replicating episomal plasmid and cosmid vectors.

Locus control regions (LCRs) are transcriptional regulatory elements, which possess a dominant chromatin remodelling and transcriptional activating capability conferring full physiological levels of expression on a gene linked in cis, when integrated into the host cell genome. Using the human beta-globin LCR (betaLCR) as a model, we show that this class of control element can drive high levels of tissue-specific gene expression in stably transfected cultured cells from within an Epstein-Barr virus-based plasmid REV. Furthermore, a 38-kb betaLCR minilocus-REV cosmid vector was efficiently retained and maintained therapeutic levels of beta-globin transgene expression in the absence of drug selective pressure over a 2-month period of continuous culture equivalent to at least 60 generations. This demonstrates for the first time the feasibility of using REVs for gene therapy of the haemoglobinopathies. Importantly, our results demonstrate that as in the case of integrated transgenes, expression from within REVs is prone to silencing but that the inclusion of the betaLCR prevented this repression of gene function. Therefore, appropriate control elements to provide and maintain tissue-specific gene expression, as well as the episomal status of REVs is a crucial feature in vector design. Our data suggest that LCRs can contribute to this vital function.

Cell Line↗
PubMed2001

Isolation and functional characterisation of the promoter region of the human prion protein gene.

The human prion protein gene (PRNP) encodes a 33-35 kDa cell surface protein that is highly expressed in the central nervous system and is vital to the pathogenesis of prion diseases. We have characterised the promoter region of PRNP as a first step towards defining the mechanisms regulating its expression. Sequence analysis of a 2.7 kb genomic DNA fragment containing exon I and the 5'-flanking region of PRNP, revealed a number of putative transcriptional factor binding sites, including Sp1, Ap-1, Ap-2 and a CCAAT box. Transient transfection assays in tissue culture cells with constructs consisting of the wild-type and deletion mutants of the PRNP 2.7 kb genomic fragment driving a luciferase reporter gene, demonstrate an active promoter within a 273 bp region (-148 to +125, relative to the cap site).

Animals↗
PubMed2000

High-level, stable expression of blood group antigens in a heterologous system.

The detection and identification of blood group antibodies in patients is crucial for successful allogeneic blood transfusions. Current methods are highly subjective and rely on red blood cells (RBCs), which simultaneously express many blood group antigens, have a short shelf-life, and carry potential biohazard risks. To overcome these problems, we have used the approach of expressing individual blood group antigen-bearing proteins in a heterologous system. We report here the high-level surface expression of type I (Knops), type II (Kell), and type III/multi-pass (Duffy) membrane proteins that carry blood group antigens in mouse erythroleukaemic (MEL) cells using a vector containing the beta-globin locus control region. Importantly, the antigens expressed were detected specifically by a panel of patients' sera containing alloantibodies at sensitivities that are comparable to antigen-positive RBCs. Furthermore, in contrast to other mammalian expression systems, antigen expression was stable following freezing and thawing of the cell lines. Thus, this system has the potential both to replace the current use of RBCs by providing a one step method to detect and identify blood group antibodies and to allow the automation of antibody identification for the clinical laboratory.

Animals↗
PubMed2000

Colonization of Phlebotomus neglectus (Diptera: Psychodidae), the major vector of visceral leishmaniasis in Greece.

Colonization of Phlebotomus neglectus Tonnoir, the major vector of visceral leishmaniasis, in Greece is reported for the first time. Starting with wild-caught specimens, a small closed colony was established that was maintained for 17 mo or 10 generations. Gonotrophic discordance, stenogamic mating behavior, low fecundity, and dormancy because of low temperature were the most important findings that characterized the colony.

Animal Feed↗
PubMed2000

Pregnancy in cystic fibrosis. Fetal and maternal outcome.

OBJECTIVE: To assess the effect of pregnancy on pulmonary function and survival in women with cystic fibrosis (CF) and to assess the fetal outcome. DESIGN: Cohort study. The data analyzed were collected from the Toronto CF database, chart review, and patient questionnaire. SETTING: Tertiary-care center. PATIENTS: All women with CF who, at the time of diagnosis or pregnancy, attended the Toronto Cystic Fibrosis Clinics between 1961 and 1998. RESULTS: From 1963 to 1998, there were 92 pregnancies in 54 women. There were 11 miscarriages and 7 therapeutic abortions. Forty-nine women gave birth to 74 children. The mean follow-up time was 11 +/- 8 years. One patient was lost to follow-up shortly after delivery, and one was lost after 12 years. The overall mortality rate was 19% (9 of 48 patients). Absence of Burkholderia cepacia (p < 0.001), pancreatic sufficiency (p = 0.01), and prepregnancy FEV(1) > 50% predicted (p = 0.03) were associated with better survival rates. When adjusted for the same parameters, pregnancy did not affect survival compared to the entire adult female CF population. The decline in FEV(1) was comparable to that in the total CF population. Three women had diabetes mellitus, and seven developed gestational diabetes. There were six preterm infants and one neonatal death. CF was diagnosed in two children. CONCLUSIONS: The maternal and fetal outcome is good for most women with CF. Risk factors for mortality are similar to those for the nonpregnant CF population. Pregnancies should be planned so that there is opportunity for counseling and optimization of the medical condition. Good communication between the CF team and the obstetrician is important.

Adolescent↗
PubMed1999

Inefficient processing impairs release of RNA from the site of transcription.

We describe here for the first time the site of retention within the nucleus of pre-mRNA processing mutants unable to be exported to the cytoplasm. Fluorescence in situ hybridization was used to detect transcripts from human beta-globin genes that are either normal or defective in splicing or 3' end formation. Nuclear transcripts of both wild-type and mutant RNAs are detected only as intranuclear foci that colocalize with the template gene locus. The kinetics of transcript release from the site of transcription was assessed by treatment of cells with the transcriptional inhibitors actinomycin D, alpha-amanitin and DRB. These drugs induce the rapid disappearance of nuclear foci corresponding to wild-type human beta-globin RNA. In contrast, pre-mRNA mutants defective in either splicing or 3' end formation and which fail to be transported to the cytoplasm, are retained at the site of transcription. Therefore, 3' end processing and splicing appear to be rate limiting for release of mRNA from the site of transcription.

Amanitins↗
PubMed1999

Surveillance of brucellosis in a rural area of Greece: application of the computerized mapping programme.

Long term active surveillance of brucellosis was implemented in a rural area (Fokida) of Greece from 1989 to 1993 while the rural area of Grevena was selected as a control area. The computerised mapping programme was used to identify and protect the suspected animal brucellosis free zones. Health education of the inhabitants was further used to teach them how to avoid the risk factors. Three suspected brucellosis free zones were identified and two of them were successfully protected. The incidence for the 10 year period (1979-1988) was estimated at 1.4/1000/year for the study area and 1.6/1000/year for the control area. During the surveillance period the incidence in the study area dropped to 0.2/1000/year while in the control area it decreased to 1.0/1000/year. The methodology of identification and protection of suspected brucellosis free zones combined with health education proved to be efficient in reducing the incidence of the disease. The same methodology could be used in the country level, in countries where it is difficult to implement and maintain an animal control programme in the whole country.

Animal Husbandry↗
PubMed1999

Protease-resistant prion protein produced in vitro lacks detectable infectivity.

The 'protein-only' hypothesis of prion propagation argues that infectious prions consist of PrP(Sc), a conformational isomer of host-derived prion protein (PrP(C)), which can be distinguished from PrP(C) by its partial resistance to proteases. While protease-resistant PrP has been produced by mixing PrP(Sc) and recombinant-derived PrP(C) in vitro, bioassay of any new infectivity has been precluded by the need to use a large molar excess of same species PrP(Sc). Transgenic mice expressing a chimaeric hamster-mouse PrPC (MH2M PrP(C)) are, unlike conventional mice, highly susceptible to Sc237 hamster scrapie. In addition, they produce MH2M PrP(Sc) and infectivity which is pathogenic for conventional mice. We have therefore attempted to produce MH2M PrP(Sc) in vitro as any infectivity produced could be distinguished from the hamster PrP(Sc) used to promote the conversion by bioassay in conventional mice. Although protease-resistant MH2M PrP was produced, no infectivity was detected on bioassay. These results argue that acquisition of protease resistance by PrP(C) is not sufficient for the propagation of infectivity.

Animals↗
PubMed1998

Muscle-specific locus control region activity associated with the human desmin gene.

We describe the reproduction of the full pattern of expression of the muscle-specific desmin gene in transgenic mice using a 240-kb genomic clone spanning the human desmin locus. Analysis of RNA from adult tissues demonstrated that this fragment possesses all the necessary genetic regulatory elements required to provide reproducible, site-of-integration-independent, physiological levels of tissue-specific expression that is directly proportional to transgene copy number in all muscle cell types. In situ hybridization revealed that in marked contrast to murine desmin which is strongly expressed in the myotome of the somites, skeletal muscles, the heart, and smooth muscle of the vasculature by 9.5 days postcoitum, human desmin transgene expression was completely absent from smooth muscles, was very weak and restricted to the atrium and outflow tract within the heart, and was expressed at only 5% of murine desmin mRNA levels within the myotome of the somites. The spatial distribution and levels of human and mouse desmin expression were not coincident until 14.5 days postcoitum. Immunohistochemical analysis of human embryos at comparable stages of development showed that this transgene faithfully reproduces the human and not the mouse developmental expression pattern for this gene in transgenic mice. These results indicate that the 240-kb desmin genomic clone is capable of establishing an independent, chromatin domain in transgenic mice and provides the first definitive data for muscle-specific locus control region activity. In addition, our results demonstrate that the behavior of human transgenes in mice should, whenever possible, be compared to expression patterns for that gene in human embryonic as well as adult tissues.

Animals↗
PubMed1998

Efficient 3'-end formation of human beta-globin mRNA in vivo requires sequences within the last intron but occurs independently of the splicing reaction.

The second intron (betaIVS-II) of the human beta-globin gene is essential for the accumulation of stable cytoplasmic mRNA and is implicated in promoting efficient 3'-end formation. This report presents quantitative comparisons between betaIVS-II mutants at physiological levels of expression from within a natural chromatin context in vivo which further defines it's function. In marked contrast to a beta-globin gene lacking a second intron, two mutants defective in splicing (small size or a splice donor mutation), still undergo essentially normal levels of 3'-end formation and in the absence of exon skipping. Therefore, 3' cleavage of beta-globin transcripts requires the presence of betaIVS-II sequences, but not the splicing reaction. The placement of betaIVS-II in the IVS-I position did not reduce the efficiency of 3' cleavage indicating that the distance between the necessary element(s) in this intron and the polyadenylation recognition site is not a crucial factor. Subsequent placement of betaIVS-I in the intron II position, reduced the efficiency of 3'-end formation to only 16% of normal. A direct replacement of intron II by the heterologous introns betaIVS-I or alpha-globin IVS-II, only partially substitute (16 and 30% respectively) for betaIVS-II. Hybrid introns show that efficient 3'-end formation is strongly enhanced by the presence of the terminal 60 nt of betaIVS-II. These data imply that the last intervening sequence of multiple intron containing genes is a principal determinant of the efficiency of 3'-end formation and may act as a post-transcriptional regulatory step in gene expression.

Animals↗
PubMed1997

A focus of Fasciola hepatica in Crete without human cases.

In Greece, Fasciola hepatica, the sheep liver fluke, is common in sheep but only three human cases of fascioliasis have been reported. An epidemiological study was conducted in central Crete which proved to be a focus of F. hepatica. Sheep and snails were found positive for this parasite, but none of the 205 persons tested serologically.

Animals↗
PubMed1996

Selective proton permeability and pH regulation of the influenza virus M2 channel expressed in mouse erythroleukaemia cells.

1. The M2 protein of influenza A virus is implicated in transmembrane pH regulation during infection. Whole-cell patch clamp of mouse erythroleukaemia cells expressing the M2 protein in the surface membrane showed a conductance due to M2 which was specifically blocked by the anti-influenza drug rimantadine. 2. The ion selectivity of the rimantadine-sensitive current through M2 was determined. Reversal potentials were close to equilibrium potentials for transmembrane pH gradients and not to those for Na+, K+ or Cl- concentration gradients. M2 permeability to Na+ relative to H+ was estimated to be less than 6 x 10(-7). 3. The M2 conductance increased as external pH decreased below 8.5 and approached saturation at an external pH of 4, effects attributable to increased permeability due to increased driving potential and to activation by low external pH. Both activation and permeation could be described by interaction of protons with sites on M2, with apparent dissociation constants of approximately 0.1 microM and 1 microM, respectively, under physiological conditions. 4. The M2 protein can transfer protons selectively across membranes with the H+ electrochemical gradient, properties consistent with its role in modifying virion and trans-Golgi pH during virus infection.

Animals↗
PubMed1996

GATA transcription factors associate with a novel class of nuclear bodies in erythroblasts and megakaryocytes.

The nuclear distribution of GATA transcription factors in murine haemopoietic cells was examined by indirect immunofluorescence. Specific bright foci of GATA-1 fluorescence were observed in erythroleukaemia cells and primary murine erythroblasts and megakaryocytes, in addition to diffuse nucleoplasmic localization. These foci, which were preferentially found adjacent to nucleoli or at the nuclear periphery, did not represent sites of active transcription or binding of GATA-1 to consensus sites in the beta-globin loci. Immunoelectron microscopy demonstrated the presence of intensely labelled structures likely to represent the GATA-1 foci seen by immunofluorescence. The GATA-1 nuclear bodies differed from previously described nuclear structures and there was no co-localization with nuclear antigens involved in RNA processing or other ubiquitous (Spl, c-Jun and TBP) or haemopoietic (NF-E2) transcription factors. Interestingly, GATA-2 and GATA-3 proteins also localized to the same nuclear bodies in cell lines co-expressing GATA-1 and -2 or GATA-1 and -3 gene products. This pattern of distribution is, thus far, unique to the GATA transcription factors and suggests a protein-protein interaction with other components of the nuclear bodies via the GATA zinc finger domain.

Animals↗
PubMed1995

TBP binding and the rate of transcription initiation from the human beta-globin gene.

DNA-protein interaction studies in vitro revealed several factors binding over the TATA box and the region of transcription initiation (cap) site of the human beta-globin promoter; TATA binding protein TBP at -30, Sp1 at -19, GATA-1 at -12 and +5, YY1 at -9 and a novel factor C1 over the site of initiation (-4 to +7). Point mutants which specifically abolish the binding of each of these proteins were tested in a beta-globin locus control region (LCR) construct which allows quantitative comparisons at physiological levels of transcription. Only mutants which drastically affect the binding of TBP resulted in decreased levels of transcription. A threshold value of TBP binding of 15-30% of wild type was sufficient to give normal levels of transcription. This indicates that the association of TF IID with the TATA box is not limiting in the rate of initiation of transcription.

Animals↗