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Biomedical subjects

I Ivanov

Publications and source records attributed to I Ivanov.

At least 55 records · Page 3Linked to original sources
PubMed1998

The diagnostic and prognostic implications of brain hyperechogenicity in hypoxic-ischaemic encephalopathy grade II.

OBJECTIVE: To study from a practical viewpoint the type, intensity and spread of brain hyperechogenicities (BHE) and their diagnostic and prognostic implications in patients with the most common, and most variable in presentation and prognosis, second grade of hypoxic-ischaemic encephalopathy (HIE). METHODS: Full-term newborns (75) with HIE gr.II were examined and divided into subgrades IIa and IIb, depending on the evidence of neurological improvement on day 7 after birth. Ultrasound examination was performed with a 5-MHz transducer. All patients were evaluated for intensity of BHE by a score system and those with focal lesions had also the number of affected loci with BHE counted. In 27 of these infants the BHE data were analyzed according to the outcome after the 11th month. A control group of 31 healthy neonates was also studied. RESULTS: We obtained 84% sensitivity and 77% specificity of BHE in HIE gr.II. Of the patients, 96% demonstrated different combinations of focal BHE, and only four demonstrated diffuse BHE. A significant correlation was found between the BHE variables (intensity score and number of loci) and clinical severity. The difference in intensity scores between HIE IIa and IIb was significant in the first 2 weeks after birth. The combination of clinical severity with the BHE variables could predict the outcome with 70.4% accuracy. CONCLUSION: BHE (focal or diffuse) could serve as additional diagnostic, grading and prognostic criterion in HIE gr.II.

Brain Ischemia↗
PubMed1998

The low level expression of chloramphenicol acetyltransferase (CAT) mRNA in Escherichia coli is not dependent on either Shine-Dalgarno or the downstream boxes in the CAT gene.

Recent studies have shown that the canonical Shine-Dalgarno (SD)-anti-SD interaction is dispensable for the initiation of translation of certain mRNAs in Escherichia coli. Alternative non-SD sequences (located upstream from the initiation codon) and also downstream sequences ("downstream boxes") complementary to 16S rRNA were found to be involved in the initiation of translation of mRNAs devoid of either SD or any leader sequences. In this study the chloramphenicol acetyltransferase (CAT) gene was modified to remove the 5' terminal non-translated region and/or the two potential downstream boxes in the CAT gene. Thus a series of ten CAT gene constructs was created and expressed in E. coli under a strong constitutive promoter. The results showed that CAT mRNAs devoid of both leader sequence nucleotides and the two downstream boxes in the CAT gene remained active in vivo and produced CAT protein in sufficient amounts for survival of the transformed cells at chloramphenicol concentrations up to 20-30 micrograms/ml.

5' Untranslated Regions↗
PubMed1998

Congenital chloride diarrhoea (presentation of two cases).

Two cases of congenital chloride diarrhoea in newborn infants are presented. The diagnosis was made by a combination of clinical findings--hydramnios, low birth weight, large abdomen, severe dehydration, dyselectrolytemia with hypochloremia and hypokalemia, and metabolic alkalosis. A crucial finding for the confirmation of the diagnosis was the fourfold rise of faecal CI exceeding the sum of sodium and potassium concentrations.

Chlorides↗
PubMed1998

West's syndrome--etiology, treatment and prognosis.

Forty two children with West's syndrome who had been treated in the Clinic of Paediatrics, Higher Medical Institute, Plovdiv in the last 10 years were entered into the present study. Analysis is made of the aetiology of the disease, the results of treatment and development of the children. All children were followed up from 6 months to 10 years. The West's syndrome was idiopathic in four children and symptomatic in 38 children (90.5%). It had perinatal aetiology in 76.5% of the patients, prenatal in 21%, and postnatal in 2.6%. Complete seizure control was achieved in 17 children (40.5%) treated only with antiepileptic drugs. Synacthen was included in the treatment of the remaining 22 children in three therapeutic doses--0.0125 mg/kg/day (n = 8), 0.025 mg/kg/day (n = 8), and > or = 0.05 mg/kg/day (n = 6). Treatment with different doses of Synacthen showed no statistically significant differences in the three groups. The side effects of the treatment occurred more frequently and were more severe in the groups with a high-dose Synacthen treatment. The follow-up established mental retardation and/or neurological deficit in 88.1% of the children. One infant died during the treatment with Synacthen and another two with severe mental retardation--one year after treatment. In about one third of the cases transition was observed to other epileptic syndromes. Synacthen is concluded to be efficacious in the treatment of West's syndrome. If antiepileptic drugs fail to produce any effect Synacthen should be included in the therapy in due time, preferably in small doses in order to avoid severe and unwanted side effects.

Cosyntropin↗
PubMed1996

DNA analysis and diagnostics on oligonucleotide microchips.

We present a further development in the technology of sequencing by hybridization to oligonucleotide microchips (SHOM) and its application to diagnostics for genetic diseases. A robot has been constructed to manufacture sequencing "microchips." The microchip is an array of oligonucleotides immobilized into gel elements fixed on a glass plate. Hybridization of the microchip with fluorescently labeled DNA was monitored in real time simultaneously for all microchip elements with a two-wavelength fluorescent microscope equipped with a charge-coupled device camera. SHOM has been used to detect beta-thalassemia mutations in patients by hybridizing PCR-amplified DNA with the microchips. A contiguous stacking hybridization technique has been applied for the detection of mutations; it can simplify medical diagnostics and enhance its reliability. The use of multicolor monitoring of contiguous stacking hybridization is suggested for large-scale diagnostics and gene polymorphism studies. Other applications of the SHOM technology are discussed.

Base Sequence↗
PubMed1995

Aniridia: recent achievements in paediatric practice.

Aniridia is a rare panocular disorder which primarily involves not only the iris, but also the retina, optic nerve, lens and cornea. Visual acuity deteriorates as a result of nystagmus, glaucoma, cataract, corneal opacities and retinal hypoplasia. Aniridia may appear as an isolated disorder, most often familial with autosomal dominance or sporadically in association with at least 12 syndromes. Both familial isolated and Wilms tumour, bilateral sporadic aniridia, genitourinary abnormalities and mental retardation syndrome-associated aniridia have been traced to a mutation of the PAX6 gene on band 11p13. Since genetic diagnosis of this disorder is already possible, counselling affected families should be preceded by karyotype studies and linkage analysis in familial cases of isolated aniridia. In sporadic cases of isolated aniridia or WAGR syndrome, we suggest that PAX6 mutation analysis be employed.

Aniridia↗
PubMed1995

Domains in human interferon alpha-1 gene containing tandems of arginine codons AGG play the role of translational initiators in E. coli.

The AGG and AGA are the least used arginine codons in E. coli but they are the most preferable ones in eukaryotes. The low expression of some eucaryotic genes (such as human alpha-1 interferon gene) which contain clusters of AGG codons is explained either by the limited pool of the tRNA(AGG) (Varenne and Lazdunski, 1986) or by the competition of these clusters with the Shine-Dalgarno (SD) sequence (Ivanov et al., 1992). The aim of the present study is to demonstrate the in vivo capacity of AGG tandems to bind to bacterial ribosomes. The two tandems of AGG codons (Arg12 Arg13 and Arg163 Arg164) of hIF alpha 1 with their surrounding nucleotides were cloned in a bacterial expression plasmid containing a strong promoter and a reporter gene (chloramphenicol acetyltransferase, CAT) devoid of a ribosome binding site. The results obtained showed that both AGG tandems initiated translation of the CAT mRNA with an efficiency equal to that of the consensus SD sequence and several fold higher than the native SD sequence of the CAT gene.

Amino Acid Sequence↗
PubMed1995

[Multiple intracranial aneurysms and asymmetrical circle of Willis].

In a consecutive series of 268 patients harboring saccular aneurysms confirmed by digital subtraction angiography (DSA) all major blood vessels of the brain, 36 patients (13.4%) with multiple aneurysms were identified. Majority of them (around 58%) were between 40 to 60 years of age, around 22% were below 40 years of age, but no was younger than 30 years of age. The asymmetric Willis circle was identified in 26 patients (74.2%) A hypoplastic A1 segment of the anterior cerebral artery was revealed in 10 patients; a combination of the hypoplastic A1 segment and the fetal type of the posterior communicating artery with a hypoplastic P1 segment of the posterior cerebral artery were found in 9 cases, while 7 patients had only the fetal posterior communicating artery. A suggestion was put that the asymmetric circle of Willis, prenatal or acquired in postnatal life is inclined of developing aneurysm (multiple aneurysms) only if there exist a hemodynamic stress in postnatal life producing degenerative lesions of the circle of Willis at the site of the augmented hemodynamic vascular wave.

Adult↗
PubMed1994

Degenerative vascular changes in children with diabetes mellitus.

Twenty three diabetic children aged 4 to 16 years with duration of the disease from 2 months to 10 years were investigated for microvascular complications. Eight of them (34.8%) had kidney disorders (low creatinine clearance, fluctuating microproteinuria, echographic changes), and nine children (39.1%) had peripheral neuropathy (sensory disorders as assessed by electromyography). Seven children (30.4%) were found to have microscopic alterations of the capillary loops of the nail wall. Ophthalmopathy was found in two (8.7%). There was no correlation between the microvascular complications and the age of children. The duration of the disease affected the severity of the complications. Microangiopathy was related to the degree of compensation of diabetes. It is emphasized in conclusion that the degenerative vascular complications have their onset rather early in childhood diabetes. They can be detected simultaneously with the diagnosis of diabetes, and therefore should be sought, duly diagnosed and treated.

Adolescent↗
PubMed1994

Secondary diabetes in children with thalassaemia major (homozygous thalassaemia).

Life expectancy of patients suffering from homozygous beta-thalassaemia has been improved due to the modern treatment of this disease. This has allowed development of late hemosiderosis-related complications and disturbances of the endocrine and exocrine functions of the pancreas. Carbohydrate metabolism of 16 patients with thalassaemia major was studied. Three of them presented with a pronounced clinical picture and biochemical constellations of a severe diabetes mellitus. The remainder had no clinical symptoms of carbohydrate metabolism disorders. The pancreatic beta-cell function of the patients was assessed by measuring the serum concentrations of immunoreactive insulin and by a glucose tolerance test. Most patients showed very low basal insulin levels while glucose tolerance was reduced in only one of them. In this patient we also established delayed insulin response after an intravenous glucose load. We concluded that the disturbed insulin secretion found in the children studied is most likely the earliest manifestation of the pancreatic beta-cell insufficiency which precedes the changes in the glucose tolerance.

Adolescent↗
PubMed1993

Incorporation of the pancreatic membrane protein GP-2 into secretory granules in exocrine but not endocrine cells.

The pancreatic zymogen granule membrane protein GP-2 was introduced into cells of exocrine or endocrine origin by transfection of its cDNA in order to investigate the mechanisms by which proteins are specifically incorporated into the membranes of secretory granules. Permanent transformants expressing GP-2 were isolated from exocrine pancreatic-derived AR42J cells as well as AtT20 cells of anterior pituitary origin and insulinoma-derived Rin5F cells. In AR42J cells, GP-2 was localized by immunofluorescence and immunoelectron microscopy to the endogenous zymogen-like granules as well as to the plasma membrane. In experiments supporting the localization data, incubation of the AR42J transformants with the secretagogue cholecystokinin (CCK8) resulted in enhanced release of a shed form of GP-2 into the medium in parallel with amylase, suggesting that the two proteins were secreted from the same compartment. By contrast, when expressed in AtT20 cells, the protein was found by immunofluorescence microscopy on the plasma membrane as well as in intracellular vesicles that differed in size and location from the endogenous secretory vesicles. By electron microscopy, large (approximately 0.5 micron) multivesicular structures were observed. Single- and double-label immunoelectron microscopy demonstrated that these large organelles labeled with anti-GP-2 antibodies, whereas the smaller adrenocorticotropic hormone (ACTH)-containing secretory vesicles did not. In permanent transformants of Rin5F cells, GP-2 was also excluded from the insulin-containing granules and found in multivesicular bodies similar to those in the AtT20 cells and containing the endosomal/lysosomal marker endolyn-78. Despite the apparent accumulation of GP-2 in lysosome-like structures, it turned over slowly and did not undergo rapid endocytosis from the cell surface. We conclude that GP-2 is targeted to secretory granule membranes by cell type-specific mechanisms that likely involve its interaction with other membrane or content proteins expressed only in the exocrine cells.

Amylases↗
PubMed1993

Replication and encapsidation of the viroid-like satellite RNA of lucerne transient streak virus are supported in divergent hosts by cocksfoot mottle virus and turnip rosette virus.

Cocksfoot mottle sobemovirus supports replication and encapsidation of the viroid-like satellite RNA (sat-RNA) of lucerne transient streak virus (LTSV) in two monocotyledonous species, Triticum aestivum and Dactylis glomerata. Additionally, LTSV sat-RNA replicates effectively in the presence of turnip rosette sobemovirus in Brassica rapa, Raphanus raphanistrum and Sinapsis arvensis, but not in Thlaspi arvense or Nicotiana bigelovii, indicating that host species markedly influence this interaction. Previous reports of the association between LTSV sat-RNA and helper sobemoviruses were limited to dicotyledonous hosts. Our results demonstrate that the biological interaction between these two entities spans divergent dicotyledonous and monocotyledonous species.

Defective Viruses↗
PubMed1993

Comparison of methods used for detection of mycoplasma contamination in cell cultures, sera, and live-virus vaccines.

Two methods for detection of mycoplasma contamination in cell cultures, sera, and live-virus vaccines were compared: the direct culture test and the DNA staining method employing bisBenzimide (Hoechst No. 33258). Contamination by different species of mycoplasma was found in 39% samples tested. It is recommended to use both techniques for a reliable detection of mycoplasma contamination.

Blood↗
PubMed1992

Effect of tandemly repeated AGG triplets on the translation of CAT-mRNA in E. coli.

It has been shown that tandems of rare arginine codons AGG have a strong inhibitory effect on translation of mRNA in E. coli [5]. This has been explained by the rate-limiting interaction of these codons with the less abundant tRNA(AGG) [6]. In this study tandemly repeated AGG triplets were introduced into the chloramphenicol acetyltransferase (CAT) gene either upstream of the initiation ATG codon or downstream of it (both in frame and out of frame) and the expression of the modified genes was investigated. We report that the addition of AGG clusters resulted in a substantial inhibitory effect on CAT gene expression independently of their localization in mRNA. This inhibitory effect is explained by a competition of the tandem AGGAGG with the natural Shine-Dalgarno (SD) sequence (consensus AAGGAGGU) for the 3'-end of the 16S small ribosomal RNA (rRNA).

Amino Acid Sequence↗
PubMed1992

A stable line of turkey bone marrow cells transformed by the myelocytomatosis virus strain MC31. Ultrastructural characteristics and localization of the DNA replication sites.

Attempts were made to characterize cells of the LSTC-SF2 line by scanning electron microscopy and transmission electron microscopy on the ultrastructural level. The virus-transformed cells are of oval, slightly elongated shape with an undulating surface. The cell nucleus is well outlined, poor in heterochromatin but with a strongly developed nucleolus. The cytoplasm is not rich in organelles except for an abundance of mitochondria with dense granules that are often found in them. With high-resolution autoradiography the DNA synthesis sites were identified mainly in proximity to the nuclear membrane and in the perinuclear spaces. The cells under study can be regarded as immature forms of the blood series and most likely as precursors of cells of the granulocyte or monocyte series.

Animals↗
PubMed1992

Microtubules and regulation of granulosa cell steroidogenesis by porcine granulosa cell conditioned medium.

Possible involvement of microtubules in the regulation of granulosa cell steroidogenesis by large follicle granulosa cell conditioned media (LGCCM) was assessed by monitoring the effect of agents that alter the cytoplasmic microtubule-tubulin equilibrium. The changes in microtubule organization and cell shape were examined by immunohistochemical procedure and morphometric analysis. Progesterone production stimulated by LGCCM was reduced by colchicine (agent that polymerizes microtubules) in a dose-dependent manner. In contrast, LGCCM stimulated progesterone secretion was significantly decreased by microtubule stabilizing agent (taxol: 1-10 microM). Cultured granulosa cells with a flattened appearance and projections after 24 h of incubation assumed a spherical configuration and were devoid of cytoplasmic processes when cultured with these agents. LGCCM stimulated GCs showed a reduction in the perimeter as compared with controls, although some cytoplasmic processes were observed. These findings suggest the involvement of microtubules in the regulation of cultured granulosa cell progesterone production by LGCCM, possibly through an effect on subcellular organelle distribution by altering the morphology of granulosa cells.

Animals↗
PubMed1991

Secretion of oligomeric Val8-human calcitonin by Saccharomyces cerevisiae.

Monomeric human calcitonin (hCT) gene and oligomeric hCT genes composed of two, three or four head-to-tail linked monomers were fused in-frame to the yeast alpha-factor leader coding sequence wild-type and fragile mutant Saccharomyces cerevisiae strains were transformed with the constructed plasmids and the yield of recombinant protein secreted into the culture medium was measured. The yeast cells secreted equal (molar) amounts of all of the hCT variants. The recombinant proteins remained stable in the growth medium for at least 3 days. The fragile cells secreted about 30% more hCT as compared to the wild-type yeast cells.

Amino Acid Sequence↗