Search PubMed⌕ Search

Biomedical subjects

D Markov

Publications and source records attributed to D Markov.

At least 19 recordsLinked to original sources
PubMed2001

Antenatal ultrasound diagnosis of perineal ectopic testis--a case report.

Perineal ectopia testis is a rare congenital anomaly with incidence of < 1% of all cases of undescended testes. We report a case of perineal ectopic testis detected by ultrasound at 38 weeks gestational age presenting as an oval echogenic structure located beneath the male fetal genitals. The diagnosis was confirmed postpartum by clinical examination and karyotyping of the neonate. Orchiopexy was performed 1 year after delivery.

Adult↗
PubMed2001

Binding of the initiation factor sigma(70) to core RNA polymerase is a multistep process.

The interaction of RNA polymerase and its initiation factors is central to the process of transcription initiation. To dissect the role of this interface, we undertook the identification of the contact sites between RNA polymerase and sigma(70), the Escherichia coli initiation factor. We identified nine mutationally verified interaction sites between sigma(70) and specific domains of RNA polymerase and provide evidence that sigma(70) and RNA polymerase interact in at least a two-step process. We propose that a cycle of changes in the interface of sigma(70) with core RNA polymerase is associated with progression through the process of transcription initiation.

Bacterial Proteins↗
PubMed2000

Chip-scale universal detection based on backscatter interferometry

An on-chip detector based on backscatter interferometry has been developed to perform subnanoliter-volume refractive index measurements. The detection system consists of a simple, folded optical train based on the interaction of a laser beam and an etched channel, consisting of two radii joined by a flat portion, thus defining a curved surface in the shape of a hemisphere in a silica (glass) plate. The backscattered light from the channel takes on the form of a high-contrast interference pattern that contains information related to the bulk properties of the fluid contained within the probe volume. Positional changes of the interference pattern (fringes) allow for the determination of deltan at the 10(-6) level, corresponding to 743 microM or 139 x 10(-15) mol or 12.8 x 10(-12) g of sucrose, in a probe volume of only 188 x 10(-12) L. A theoretical model of the on-chip backscatter interferometric detector has also been developed, evaluated, and found to be in agreement with experimental data. It is shown that the model can be used to predict general system performance for changes in the optical train such as the chip's wall thickness and channel diameter.

Journal Article↗
PubMed1999

A zinc-binding site in the largest subunit of DNA-dependent RNA polymerase is involved in enzyme assembly.

All multisubunit DNA-dependent RNA polymerases (RNAP) are zinc metalloenzymes, and at least two zinc atoms are present per enzyme molecule. RNAP residues involved in zinc binding and the functional role of zinc ions in the transcription mechanism or RNAP structure are unknown. Here, we locate four cysteine residues in the Escherichia coli RNAP largest subunit, beta', that coordinate one of the two zinc ions tightly associated with the enzyme. In the absence of zinc, or when zinc binding is prevented by mutation, the in vitro-assembled RNAP retains the proper subunit stoichiometry but is not functional. We demonstrate that zinc acts as a molecular chaperone, converting denatured beta' into a compact conformation that productively associates with other RNAP subunits. The beta' residues coordinating zinc are conserved throughout eubacteria and chloroplasts, but are absent from homologs from eukaryotes and archaea. Thus, the involvement of zinc in the RNAP assembly may be a unique feature of eubacterial-type enzymes.

Amino Acid Sequence↗
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↗
PubMed1999

Nasal polyps in children.

During the 1980-1995 period, 957 patients were admitted for nasal polyposis, 59 (6.2%) of them children. Results were analyzed with respect to localization of the polyps, allergy, histologic picture, bacteriologic tests, radiologic findings of paranasal sinuses, cytology of nasal mucosa, therapeutic approach, and tendency to relapse. Forty children (22 boys and 18 girls) were analyzed. Their mean age was 11.1 years. Unilateral polyposis was found in 29, and bilateral in 11 children. Antrochoanal polyps (ACP) were found in 30, bilateral nasal polyps in 5, polyps in maxillary sinus in 5, and allergy in 8 children. Inflammation of the maxillary sinus was present in 93% of children with ACP. Their correlation between ACP and inflammation in maxillary sinus suggested that edema of the sinus mucosa have led to protrusion through the ostium and formation of the nasal polyp.

Adolescent↗
PubMed1999

Clinical interpretation of brainstem evoked response audiometry abnormalities in cochlear pathology.

This investigation involved 45 patients with sensorineural hearing loss (SNHL): 24 with Meniere's disease, 18 with acoustic trauma, and 3 with SNHL due to ototoxic drugs. They all underwent pure tone audiometry and standard brainstem evoked response audiometry (BERA). In patients without wave I in auditory brainstem response, electrocochelography (ECochG) was performed. The findings are presented showing that cochlear lesions (beside threshold elevation) cause latency prolongation of wave I, III and V relative to normal latencies at the actual click hearing level. At high stimulation levels, this effect is almost completely compensated for by the fact that cochlear recruiting ears exhibit steeper latency-intensity curves than do normal ears. But, at the same time this pathology does not cause latency prolongation of central conduction time (CCT). Beside this, cochlear lesions will cause, in some cases, deterioration of replicability (poor waveform resolution) of waves preceding wave V. In such cases, the authors strongly recommend electrocochleography (ECochG) to make wave I visible, because they think that it is the best way to verify the diagnosis of cochlear lesion using BERA.

Adolescent↗
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↗