Biomedical subjects

D Markov

Publications and source records attributed to D Markov.

At least 19 recordsLinked to original sources

PubMed1999

Localization of Escherichia coli rpoC mutations that affect RNA polymerase assembly and activity at high temperature.

We localized five rpoC (beta') mutations affecting Escherichia coli RNA polymerase assembly. The Ts4, XH56, and R120 mutations changed beta' residues conserved throughout eubacteria; the JE10092 mutation occurred in the hypervariable region; rpoC1 (TsX) changed a universally conserved residue and corresponds to yeast rpb1-1. Thus, distinct, predominantly conserved beta' residues participate in interactions holding RNA polymerase together.

Amino Acid Sequence↗

PubMed1997

A contribution to the etiopathogenesis of nasal polyps.

The first author studied nasal polyposis from the epidemiological, clinical, immunologic and histologic points of view. Based on the year-long studies, the authors have isolated three issue of common interest to rhinologists since ancient times, i.e. relationship between allergy and nasal polyposis, predilection sites of the origin of polyposis, and the development process underlying the genesis of polyps.

Humans↗

PubMed1996

Some morphological, histological, cytological and histochemical aspects of Reinke's oedema.

Using morphological criteria we divided Reinke's oedema into a pale (transparent) and a livid type. The latter is more difficult to treat because of its prolonged postoperative recovery. Ten samples of pale Reinke's oedema and 10 of livid oedema were selected for cytological, histological and histochemical analysis in order to determine some of their fundamental characteristics and differences. Tissue samples were stained by hemalaun-eosin, Mallory-azan and Paf-Halmi method (specific for visualization of elastic versus collagen fibres). Cytology (May-Grünwald Giemsa) of cellular elements was undertaken by imprint method of the excised oedematous tissue. Also, the silver-staining nuclear organizer regions (Ag NOR) were identified and quantified. We identified intracytoplasmic granula and silver-staining nuclear organizing regions (Ag NOR) in stromal cells of pale type Reinke's oedema. Thus, it may be supposed that smoke irritation provokes higher activity of stromal cells producing a special substance in Reinke's space-resulting finally in Reinke's oedema.

Adult↗

PubMed1996

Histology of nasal polyps in various conditions.

At the Salata ENT Department in Zagreb, 28 patients with nasal polyps were examined in the 1992-1993 period. Results of histologic analysis of these nasal polyps are presented. In 10 cases, nasal polyps were histologically examined at three horizontal levels, and the rest by vertical section. The method of hemalaun eoisin and histochemical methods (PAS, Alcian, Mallory, Giemsa and orcein) were used to analyze the following parameters: epithelium, stroma, basement membrane, cell infiltrate and glands. Patients were grouped according to the presence or absence of allergy, relapse of polyps and age group ( < 40 and > 40 years of age). The lateral nasal wall mucosa served as control. Histologic picture of the polyps showed some differences related to allergy and other groups of polyposis. In conclusion, histologic study of polyps should not be taken as the only indicator of the etiology of polyposis but, supplemented with other examinations, as an evidence supporting the diagnosis.

Adolescent↗

PubMed1996

Effect of mechanical pressure on c-fos and on the mitotic activity of epidermal cells.

A dosed mechanical pressure of 12.5 kg/cm2 applied for 1 min on depilated mouse skin did not cause cellular death or visible alterations of the cellular ultrastructures. However, it had a strong effect on the mitotic cycle of the epidermal cells-stimulating the cells to enter the mitotic cycle and temporarily blocking the G1-->S transition. This effect was strictly limited to the pressed area of the skin. The proto-oncogene c-fos was induced within the first 2 min following application of the pressure. The level of c-fos mRNA showed two peaks during the next 24 h. The first slight peak was preceded by a rapid increase in the cAMP level in the pressed skin, the second-by a fall in the cAMP concentration. A model is suggested to explain the observed effects by reversible functional damage of the cellular membrane affecting the enzymes maintaining the steady state level of cAMP.

Animals↗

PubMed1995

Streptolydigin-resistant mutants in an evolutionarily conserved region of the beta' subunit of Escherichia coli RNA polymerase.

Mutations conferring streptolydigin resistance onto Escherichia coli RNA polymerase have been found exclusively in the beta subunit (Heisler, L. M., Suzuki, H., Landick, R., and Gross, C. A. (1993) J. Biol. Chem. 268, 25369-25375). We report here the isolation of a streptolydigin-resistant mutation in the E. coli rpoC gene, encoding the beta' subunit. The mutation is the Phe793-->Ser substitution, which occurred in an evolutionarily conserved segment of the beta' subunit. The homologous segment in the eukaryotic RNA polymerase II largest subunit harbors mutations conferring alpha-amanitin resistance. Both streptolydigin and alpha-amanitin are inhibitors of transcription elongation. Thus, the two antibiotics may inhibit transcription in their respective systems by a similar mechanism, despite their very different chemical nature.

Amino Acid Sequence↗

PubMed1995

[The costoclavicular neurovascular compression syndrome].

This is a description of a great variety of abnormal compressions of nerve, arterial, and rather seldom venous structures at the base of the neck or thoracic outlet, such as supernumerary cervical rib. abnormal ligaments, musculus scalenus anterior hypertrophy and positional alterations, interfering with the normal inter-reactions between first rib and structures overlying it. With a special reference to the hypothetical mechanism of the symptomatology a wide range of denominations of this particular syndrome have been adopted, namely: scalenus anticus syndrome, cervical rib syndrome, costoclavicular syndrome, hyperabductions syndrome and thoracic outlet syndrome--a term gaining widest popularity in the Anglo-Saxon literature. It is the purpose of this study to present experience hitherto accumulated worldwide with the diagnosis and treatment of such pathology, and analyze the authors' experience based on the results of 13 operative interventions for decompressions of the costoclavicular groove against the background neurovascular costoclavicular syndrome. Special attention is focused on the surgical management of this particular pathology using the modern transaxillary approach for resection of supernumerary first rib, thoracic extrapleural sympathectomy--a method successfully introduced in Bulgaria by the authors' team for the first time in 1984. The early and long-term results in 13 patients (7 of them women) operated through transaxillary access over a 10-year period, the complication ensuing and their treatment, as well as comparative assessment with other operative procedures described in the literature, are discussed.

Clavicle↗

PubMed1993

[Morphometric evaluation of connective tissue reaction to cartilage implants].

In this paper, besides already investigated cartilage implants, we studied morphologically and histometrically possibilities to use human thyroid cartilage in reconstructive surgery, especially in nasal septum and pyramid reconstructions. Preserved human thyroid and rib cartilage as well as rabbit preserved rib cartilage were implanted under the back skin of 12 New Zealand rabbits. Animals were divided into two groups with 6 specimens in each group followed 6 and 12 weeks after implantation. Beside morphological investigation we measured histometrically the thickness of connective capsule around implants. Results obtained by our morphological and histometric studies indicate that preserved human thyroid cartilage could be used in reconstructive surgery with the same success as other cartilage implants already used.

Adult↗

PubMed1993

[The area around the wound in experimental chemical injuries to the skin].

This is an experimental assessment of the morphological patterns of skin in the area surrounding wounds, produced by exposure to sodium base, sulfuric acid and hydrochloric acid. The changes are followed up from 6th hour to 28th post-injury day, and compared with those in the skin surrounding thermal burns using the same experimental setup. The differences in healing processes, both by comparison with the control group, and between the individual chemical agents, are insignificant. Following chemical injury as well, nonspecific tissue healing processes develop in the area around the wound. The diagnostic and therapeutic problems faced, and the potentials in the wound area after chemical lesions are similar to those following other types of skin damage.

Animals↗

PubMed1993

[The experimental and clinical use of neprolizin in thermal burns of the skin].

Morphological skin changes within the focus of lesion and in the perilesional area are studied against the background of local application of the Bulgarian enzyme preparation Neprolyzin. The experimentally induced injury includes thermal burn, mechanical crushing (conquassatio), and combination of the two. The drug is administered immediately after the trauma, or on the fourth post-injury day, with the studies performed after 4-day-long treatment. In the clinical trial Neprolyzin is applied within 3 to 4 days of a third-degree burn. In conclusion, it is stressed that Neprolyzin should be applied immediately after a thermal burn, it should not be used in handling a mechanical crush injury, whereas in the event of associated trauma it should be used on the fourth post-injury day. The clinical assessment points to the necessity of local anesthesia during application of the drug, or analgesics up to one hour after the dressing.

Animals↗

PubMed1993

[The effect of temporary skin substitutes on the area around the wound following an experimental thermal burn of the skin].

The effect of temporary skin resurfacing on processes developing in the skin surrounding post-thermal-burn wounds is morphologically studied in experiment. The burned wound region and perilesional area are immediately covered by a fresh allograft, xenograft, Ampoxen, Pharmexplant and Deflamol ointment. Tissue specimens for histological evaluation are taken within 3, 7 and 14 days. The processes developing within the wound and in the perilesional area under a fresh allograft and Deflamol ointment appear to be the most beneficial. Here the inflammatory response is substantially milder, and regardless of the latter, the regeneration and even differentiation of cells in the course of healing are more clearcut, as compared to the other resurfacing methods used in the experiment.

Animals↗

PubMed1993

[An experimental study of chemical necrectomy in chemical injuries of the skin].

The authors studied experimentally the morphological changes of injuries and the surrounding areas after a skin chemical injury caused by sodium hydroxide, sulphuric acid and chlorhydric acid under the influence of acidic necrolytics--40% benzoic acid and 40% salycilic acid in unguentus. The necrolytics are applied on the injured areas immediately upon getting the wound or on the 4th day thereafter, while the morphological study is carried out after getting off the necrosis. It has been established that the necrolysis in the case of sodium hydroxide was not effected by the 28th day. The processes in the tissues upon acidic injuries do not differ from the spontaneous healing process.

Animals↗

PubMed1991

[Stomach and duodenal lesions in patients with acute organophosphorus pesticide poisonings].

Gastric and duodenal mucosa changes were studied by means of fibrogastroduodenoscopy and targeted biopsy in 35 patients, 23 men and 12 women, aged 18 to 68 years, with acute poisoning with phosphororganic pesticides. In 33 of the patients the poisoning occurred through oral and in 2 patients through cutaneous route. 13 patients were with a light, 14--with a moderate and 8--with a severe form of poisoning. In 31 patients (88.57%) edema and hyperemia were found, in 15 patients single and in 8 p. multiple erosions and in 4 p. ulcers were found, but in the duodenum they were more rare. The microscopic examination of the biopsies revealed variable changes--from edema, through focal accumulation of siderophages and single inflammatory infiltrates up to a severe fibrino-suppurative-necrotic process. A direct correlation between the severity of the lesions and the severity of the poisoning was found.

Acute Disease↗

PubMed1990

Regulation of traumatic skin wound healing by influencing the process in the neighbouring zone of the wound.

After the burn, the authors immediately applied the albuminous hydrolysate Hydropot, a propolis-urea ointment and Trypsin compresses (3,500 E) to the burned area and its vicinity, and repeated this procedure for several days. Samples for histological examination were taken after the animals' decapitation every 2 hrs. and on the 3rd, 5th and 14th post-injury days. The morphological picture showed a difference in rate and quality of regeneration. The authors are of the opinion that the processes occurring in the neighbourhood of the traumatic skin wound can be influenced and that regeneration can be regulated.

Albumins↗

PubMed1987

[Helminthic cenosis of does in regions of Bulgaria].

Studies were carried out on the species composition of helminths as found in does in individual region of the Rhodope and Balkan Mountains and in the northeast part of this country. A total of 28 helminth species were found, belonging to 8 families as follows: class Trematoda--one family with one species; class Cestoda--one family with one species; and class Nematoda--6 families with 26 species. Most widespread were the species Chabertia ovina, with 82 per cent of infected animals; Spiculopteragia spiculoptera, with 74.1 per cent of infected animals; Ostertagia leptospicularis, with 66.6 per cent of infected animals; and Ostertagia asymetrica and Muflonagia podjapolskyi, with 33.3 per cent of infected animals. The necropsy of a doe, found in the region of the central Rhodope Mountains in a state of strongly manifested cachexia, revealed a massive Chabertia ovina infection. The severe traumatic and toxic inflammation of the intestines as caused by the parasite was characterized by oedema of the mucous membrane, with hyperaemia and pin-point hemorrhages. Similar Chabertia ovina infections were also found in does of other regions.

Animals↗

PubMed1986

Isolation and characterization of nuclear lamina from Ehrlich ascites tumor cells.

We have developed a simple and rapid method for isolation of purified nuclear lamina from Ehrlich ascites tumor cells. The procedure employs chromatin structures prepared from whole cells at low ionic strength and is carried out under conditions that minimize the formation of artifactual protein-DNA complexes. When the isolation is performed in the presence of EDTA, nuclear lamina without distinct pore complexes is obtained. In the absence of EDTA, intact pore complexes and a large amount of vimentin 100 A filaments are seen associated with nuclear lamina. The main nuclear lamina proteins are characterized using gel electrophoresis, immunoblotting, and two-dimensional peptide mapping. An extensive structural homology is found between lamin A and lamin C, whose peptide maps differ by only one major spot, whereas lamin B has apparently unrelated pattern.

Animals↗

PubMed1986

Is the nuclear matrix the site of DNA replication in eukaryotic cells?

Four types of experiment were carried out to test the recently proposed model of matrix-bound replication in eukaryotic cells. In experiments with pulse-labelling we found preferential association of newly replicated DNA with the matrix only when the procedure for isolation includes first high-salt treatment of isolated nuclei and then digestion with nucleases, or when prior to digestion the nuclei have been stored for a prolonged time. In both cases, however, evidence was found that this preferential association is due to a secondary, artifactual binding of the newly replicated chromatin region to the matrix elements. Pulse-chase experiments and experiments with continuous labelling were carried out to answer the question whether during replication the DNA is reeled through the replication complexes, i.e., whether newly replicated DNA is temporarily or permanently associated with the matrix. The results showed that at that time the matrix DNA does not move from its site of attachment. Since, according to the model of matrix-bound replication, the forks are assumed to be firmly anchored to high-salt resistant proteinaceous matrix structures, the chromatin fragments isolated with endonuclease not recognizing newly replicated DNA and purified by sucrose gradient centrifugation should be free of replication intermediates. The electronmicroscopic analysis of such fragments revealed the existence of intact replication micro-bubbles. Moreover, the fragments with replication configurations appeared as smooth chromatin fibres not attached to elements characteristic for the matrix. All these experiments suggest that the nuclear skeleton is not a native site of DNA replication in eukaryotic cells.

Animals↗

PubMed1986

Evidence for the existence in the nuclei of Friend cells of a new type of ribonucleoprotein network.

We have isolated fragments of a novel nuclear structure exhibiting the morphological and biochemical characteristics of a ribonucleoprotein network. Under transmission electron microscopy it is visualized as irregularly interconnected branches assembled by tightly packed particles with sizes between 100A and 300A. RNA extracted from this structure shows a complex pattern: as well as ribosomal 28 S and 18 S RNA, small amounts of heterogeneous nuclear RNA and small nuclear RNA are also present. The protein composition of the network indicates a strong domination of ribosomal polypeptides. This fact, considered together with the sedimentation characteristics of the prevailing type of particles isolated directly from the network, supports the conclusion that ribosomal particles are the representative particulate elements. Further electrophoretic analysis of the protein has pointed out that it also contains a significant number of acidic polypeptides. Control experiments have suggested that the site of origin of the network fragments studied is not nucleolar: the fragments are released during extraction, most probably from the nuclear periphery. It is not yet clear whether this structure is localized only at the nuclear periphery or represents an extensive structure, occupying the entire volume of the nucleus. It is speculated that the network is involved in the extranucleolar transport and maturation of ribosomes.

Autoradiography↗