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T Georgieva

Publications and source records attributed to T Georgieva.

14 recordsLinked to original sources
PubMed2005

Aedes aegypti transferrin. Gene structure, expression pattern, and regulation.

Mosquitoes and all other insects so far examined have an abundant haemolymph transferrin (Tsf). The exact function of these proteins has not been determined, but they may be involved in iron transport, in oogenesis and in innate immune defence against parasites and pathogens. The Tsf gene of Aedes aegypti has been cloned and sequenced. It contains a single small intron, which contrasts it to vertebrate Tsf genes that contain up to sixteen introns. The promoter region of the gene is rich in putative NF-kappaB binding sites, which is consistent with the postulated role of Tsf in insect innate immunity. Tsf message levels are very low in embryos and early larvae, but high in late larvae, pupae and adults. Western blotting experiments revealed high levels of Tsf protein in pupae and adults. Late larvae and ovaries of blood-fed mosquitoes have little intact protein, but two prominent proteolytic degradation products. These may represent biologically active peptides, as has been shown for other organisms. Tsf message is down-regulated by inorganic iron in the diet or environment, but up-regulated by a blood meal in the adult female. The up-regulation following a blood meal may, in part, be due to the decrease in juvenile hormone (JH) that is known to follow blood feeding. Treatment of blood-fed females with methoprene, an analogue of JH, resulted in decrease of the Tsf message.

Aedes↗
PubMed2004

Potential for using thermophilic anaerobic bacteria for bioethanol production from hemicellulose.

A limited number of bacteria, yeast and fungi can convert hemicellulose or its monomers (xylose, arabinose, mannose and galactose) into ethanol with a satisfactory yield and productivity. In the present study we tested a number of thermophilic enrichment cultures, and new isolates of thermophilic anaerobic bacterial strains growing optimally at 70-80 degrees C for their ethanol production from D-xylose. The new isolates came from different natural and man-made systems such as hot springs, paper pulp mills and brewery waste water. The test was composed of three different steps; (i) test for conversion of D-xylose into ethanol; (ii) test for viability and ethanol production in pretreated wheat straw hemicellulose hydrolysate; (iii) test for tolerance against high D-xylose concentrations. A total of 86 enrichment cultures and 58 pure cultures were tested and five candidates were selected which successfully fulfilled the criteria defined for the screening test.

Acetates↗
PubMed2002

Drosophila melanogaster ferritin: cDNA encoding a light chain homologue, temporal and tissue specific expression of both subunit types.

Drosophila melanogaster secreted ferritin like the cytosolic ferritins of other organisms is composed of two subunits, a heavy chain homologue (HCH) and a light chain homologue (LCH). We report the cloning of a cDNA encoding the ferritin LCH of this insect. As predicted from the gene sequence, it contains no iron responsive element (IRE). Northern blot analysis reveals two mRNAs that differ in length due to the choice of polyadenylation signals. Message levels vary through the life cycle of the fly and are markedly increased by high levels of dietary iron. The gut is the main site of increased message synthesis and iron preferentially increases the amount of shorter messages. Western blotting reveals that LCH is the predominant ferritin subunit in all life stages. The amount of LCH protein corresponds well with the message levels in control animals, while in iron-fed animals LCH does not increase proportionally with the message levels. In contrast, the amount of HCH is less than that would be predicted from message levels in control animals, but corresponds well in iron-fed animals. Ferritin is abundant in gut and hemolymph of larvae and adults and in ovaries of adult flies. At pupariation, ferritin becomes more abundant in hemolymph than in other tissues.

Amino Acid Sequence↗
PubMed1999

Iron availability dramatically alters the distribution of ferritin subunit messages in Drosophila melanogaster.

Insect ferritins have subunits homologous to the heavy and light chains of vertebrate ferritins. Cloning and sequence of the heavy chain homologue (HCH) of Drosophila melanogaster ferritin subunit have been reported earlier. When Northern blots of D. melanogaster RNA were probed with a cDNA for this HCH, three bands were observed. It was shown that these represented at least four classes of mRNA of various lengths. The polymorphism results from alternative splicing of an intron in the 5' untranslated region (UTR) that contains the iron-responsive element (IRE) and from two alternative polyadenylation sites in the 3' UTR. This has also been reported by others [Lind, M. I., Ekengren, S., Melefors, O. & Söderhäll, K. (1998) FEBS Lett. 436, 476-482]. By hybridizing Northern blots with specific probes, it has been shown that the relative proportions of the messages vary with the life stage and especially with iron supplementation of the diet. Iron significantly increases the amount of ferritin HCH messages and dramatically shifts the balance toward those messages that lack an IRE and/or have a short 3' UTR. In the larvae this change takes place in the gut, but not in the fat body. We speculate that this dramatic shift in message distribution may result from an effect of iron on the rate of transcription or message degradation, or from an effect on the splicing process itself. Synthesis of ferritin HCH subunit mRNAs that lack an IRE may be important under conditions of iron overload.

5' Untranslated Regions↗
PubMed1999

Drosophila melanogaster transferrin. Cloning, deduced protein sequence, expression during the life cycle, gene localization and up-regulation on bacterial infection.

Drosophila melanogaster transferrin cDNA was cloned from an ovarian cDNA library by using a PCR fragment amplified by two primers designed from other dipteran transferrin sequences. The clone (2035 bp) encodes a protein of 641 amino acids containing a signal peptide of 29 amino acids. Like other insect transferrins, Drosophila transferrin appears to have a functional iron-binding site only in the N-terminal lobe. The C-terminal lobe lacks iron-binding residues found in other transferrins, and has large deletions which make it much smaller than functional C-terminal lobes in other transferrins. In-situ hybridization using a digoxigenin labeled transferrin cDNA probe revealed that the gene is located at position 17B1-2 on the X chromosome. Northern blot analysis showed that transferrin mRNA was present in the larval, pupal and adult stages, but was not detectable in the embryo. Iron supplementation of the diet resulted in lower levels of transferrin mRNA. When adult flies were inoculated with bacteria (Escherichia coli), transferrin mRNA synthesis was markedly increased relative to controls.

Amino Acid Sequence↗
PubMed1999

Organization of the ferritin genes in Drosophila melanogaster.

The organization of two closely clustered genes, Fer1HCH and Fer2LCH, encoding the heavy-chain homolog (HCH) and the light-chain homolog (LCH) subunits of Drosophila melanogaster ferritin are reported here. The 5019-bp sequence of the cluster was assembled from genomic fragments obtained by polymerase chain reaction (PCR) amplification of genomic DNA and from sequences obtained from the Berkeley Drosophila Genome Project (BDGP) (http://www.fruitfly.org). These genes, located at position 99F1, have different exon-intron structures (Fer1HCH has three introns and Fer2LCH has two introns) and are divergently transcribed. Computer analysis of the possibly shared promoter regions revealed the presence of putative metal regulatory elements (MREs), a finding consistent with the upregulation of these genes by iron, and putative NF-kappaB-like binding sites. The structure of two other invertebrate ferritin genes, from the nematode Caenorhabditis elegans (located on chromosomes I and V), was also analyzed. Both nematode genes have two introns, lack iron-responsive elements (IREs), and encode ferritin subunits similar to vertebrate H chains. These findings, along with comparisons of ferritin genes from invertebrates, vertebrates, and plants, suggest that the specialization of ferritin H and L type chains, the complex exon-intron organization of plant and vertebrate genes, and the use of the IRE/iron regulatory protein (IRP) mechanism for regulation of ferritin synthesis are recent evolutionary acquisitions.

Animals↗
PubMed1998

Study of erythrocytes, hemoglobin levels, and menstrual cycle characteristics of women exposed to aromatic hydrocarbons.

OBJECTIVES: The impact of occupational hazards on erythrocyte and hemoglobin levels and menstrual cycle characteristics in women exposed to aromatic hydrocarbons was studied. The investigated cohort consisted of 110 women exposed to benzene, toluene, xylene and styrene while working in the transport and storage of petrochemical products (TSPP), the laboratory for the control of aromatic hydrocarbons (LCAH), and rubber and latex (RL) production at the biggest petrochemical plant in Bulgaria, Neftochim. Controls consisted of 45 women from the administrative personnel in the same plant. METHODS: Questionnaires were administrated to all participants to obtain self-reported demographic data, data on characteristics of the menstrual cycle, and psychosomatic symptoms. Erythrocyte counts (RBC) and hemoglobin (HGB) levels were determined by the semiautomatic hematology analyzer Serono System 190, USA. All subjects had signed an informed consent. RESULTS: The mean RBC counts and HGB levels of the women from the LCAH and TSPP departments were statistically significantly lower than those of the control group. We found statistically significant differences in all exposed groups in comparison with controls when the dose-response relationship was investigated. No statistically significant differences were found in menstrual cycle characteristics (duration of the menstrual cycle, days and quantity of bleeding) between the subjects exposed and the controls in all age groups investigated, but the numbers were too small to allow definite conclusions. CONCLUSIONS: The lowering of HGB levels and RBC counts in the investigated women were mainly due to the direct influence of aromatic hydrocarbons in the working environment on hematopoiesis. The studied group was too small to enable us to determine the impact of aromatic hydrocarbons on menstrual cycle characteristics, and the possible combination of these effects.

Adult↗
PubMed1997

Isolation and properties of Drosophila melanogaster ferritin--molecular cloning of a cDNA that encodes one subunit, and localization of the gene on the third chromosome.

Ferritin was purified from iron-fed Drosophila melanogaster extracts by centrifugation in a gradient of potassium bromide. On polyacrylamide gel electrophoresis, the product showed two protein bands corresponding to the ferritin monomer and dimer. Electrophoresis following dissociation with SDS and 2-mercaptoethanol revealed three strong bands of approximately 25, 26, and 28 kDa. N-terminal amino acid sequences were identical for the 25-kDa and 26-kDa subunits, but different for the 28-kDa subunit. Conserved ferritin PCR primers were used to amplify a 360-bp cDNA product, which was used to isolate a clone from a D. melanogaster cDNA library that contained the complete coding sequence for a ferritin subunit. Additional 5' sequence obtained by the RACE method revealed the presence of a putative iron regulatory element. The PCR product was also used to locate the position of the ferritin subunit gene at region 99F on the right arm of the third chromosome. The deduced amino acid sequence of the D. melanogaster ferritin subunit contained a signal sequence and resembled most closely ferritin of the mosquito Aedes aegypti. The evolution of ferritin sequences is discussed.

Amino Acid Sequence↗
PubMed1993

Pathogenetic aspects of clinico-electrophysiological differentiation of transient cerebral circulation disorders terminating with a complete clinical recovery.

The present study offers a clinico-theoretical, electrophysiological and rheoencephalographic analysis of the brain matter condition and the cerebral hemodynamics of patients with acute cerebral circulation disorders which resolve with a complete clinical recovery. The purposes of the study were (1) to achieve pathogenetic differentiation of the syndromes of transient ischemic attacks (TIA) and reversible ischemic neurologic deficit (RIND) with greater confidence than that achieved by using the clinical criterion of "the neurologic deficit duration" (24 hours for TIAs, three weeks for RIND). (2) to determine the subclinical level in a single case, and (3) to develop a new approach to secondary prophylaxis in such patients. Fifty four patients (30 men and 24 women, mean age 57.2 +/- 1.9 years) presenting with acute ischemic disorders of cerebral circulation at the Clinic of Vascular Cerebral Diseases in the Department of Neurology of Plovdiv Medical University were followed up in the period between 1989 and 1991. On the 5th and 20th days of the episode onset the central latency time (CLT) of an evoked motor potential (MEP) was investigated on the symptomatic and asymptomatic sides. The study also involved rheoencephalography not only of the clinically followed-up population but also of 59 outpatients with TIA, 129 patients with RIND and 38 patients with an ischemic cerebral stroke. The results obtained objectify the differences among the researchers and confirm their views on the most common pathogenetic mechanisms associated with the occurrence and the course of the two forms of cerebral ischemia terminating with a complete clinical recovery.

Brain Ischemia↗
PubMed1991

[The effect of electroacupuncture analgesia on the plasma levels of cortisol and aldosterone in orthopedic operations].

The effects of electroacupuncture on plasma cortisol and aldosterone levels in patients undergoing orthopedic operations were studied. Plasma cortisol and aldosterone levels were measured at three stages. Moderate activation of the hypothalamo-pituitary-adrenal system is considered an adjustment response of the organism to the operative trauma, with stable hemodynamic parameters. The total amount of analgetic drugs which the patients received during the postoperative period was three times lower than that in the control group given neuroleptanalgesia; during electroacupuncture analgesia (EAPA) opioids were not applied. It is considered that the use of EAPA lowers the degree of the stress reaction in surgical trauma, providing adequate analgesia and neurovegetative protection of patients during orthopedic operations and in the early postoperative period.

Aldosterone↗