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Biomedical subjects

A Pavlov

Publications and source records attributed to A Pavlov.

At least 19 recordsLinked to original sources
PubMed2006

Comparative genomics of the lactic acid bacteria.

Lactic acid-producing bacteria are associated with various plant and animal niches and play a key role in the production of fermented foods and beverages. We report nine genome sequences representing the phylogenetic and functional diversity of these bacteria. The small genomes of lactic acid bacteria encode a broad repertoire of transporters for efficient carbon and nitrogen acquisition from the nutritionally rich environments they inhabit and reflect a limited range of biosynthetic capabilities that indicate both prototrophic and auxotrophic strains. Phylogenetic analyses, comparison of gene content across the group, and reconstruction of ancestral gene sets indicate a combination of extensive gene loss and key gene acquisitions via horizontal gene transfer during the coevolution of lactic acid bacteria with their habitats.

Animals↗
PubMed2001

Phosphodiesterase production in an aqueous two-phase system by Nicotiana tabacum 1507.

Studies were conducted on the production of phosphodiesterases by Nicotiana tabacum 1507 cell suspension in an aqueous two-phase system formed by adding 4% polyethylene glycol (mol wt 20,000) and 7.5% dextran (mol wt 70,000) to the medium. The time course of growth, biosynthesis, secretion, and partitioning of phosphodiesterases was followed in comparison with N. tabacum 1507 cultivation as a free suspension. Partitioning of phosphodiesterases took place mainly in the bottom dextran phase, and a possibility was revealed for obtaining an enzyme preparation with high phosphodiesterase activity.

Biochemistry↗
PubMed2000

Influence of carbon dioxide clouds on early martian climate.

Recent studies have shown that clouds made of carbon dioxide ice may have warmed the surface of early Mars by reflecting not only incoming solar radiation but upwelling IR radiation as well. However, these studies have not treated scattering self-consistently in the thermal IR. Our own calculations, which treat IR scattering properly, confirm these earlier calculations but show that CO2 clouds can also cool the surface, especially if they are low and optically thick. Estimating the actual effect of CO2 clouds on early martian climate will require three-dimensional models in which cloud location, height, and optical depth, as well as surface temperature and pressure, are determined self-consistently. Our calculations further confirm that CO2 clouds should extend the outer boundary of the habitable zone around a star but that there is still a finite limit beyond which above-freezing surface temperatures cannot be maintained by a CO2-H2O atmosphere. For our own Solar System, the absolute outer edge of the habitable zone is at approximately 2.4 AU.

Atmosphere↗
PubMed1997

Evolution of RNA-binding specificity in T4 DNA polymerase.

DNA polymerase of phage T4 (T4 gp43), an essential component of the T4 DNA replicase, is a multifunctional single-chained (898-amino acid) protein that catalyzes the highly accurate synthesis of DNA in phage replication. The enzyme functions both as a DNA-binding replication protein and as a sequence-specific RNA-binding autogenous translational repressor. We have utilized a phylogenetic approach to study the relationships between the two nucleic acid-binding functions of the protein. We found that autogenous translational control of gp43 biosynthesis has been conserved in phage RB69, a distant relative of T4, although we also found that the RB69 system differs from its T4 counterpart in two regards: (a) nucleotide sequence and predicted secondary structure of the RNA target (translational operator), and (b) RNA specificity of the protein. T4 gp43 is specific to the RNA operator sequence of the T4 genome whereas RB69 gp43 can bind and repress operator RNA from both phages equally well. In studies with T4-RB69 gp43 chimeras, we mapped T4 gp43 RNA-binding specificity to a protein segment that also harbors important determinants for DNA binding and the polymerase catalytic function. Our results suggest that RNA functions as a regulator of both the dosage and activity of this DNA replication enzyme.

Bacteriophage T4↗
PubMed1995

Methods for permanent conservation of biological objects and anatomic preparations in synthetic resins.

Two methods for preparing packets of synthetic resin for permanent preservation of biological objects and anatomical tissue have been developed. The first method is applied when adding corrosive preparations to epoxide resin. The corrosive preparation is soaked in a mixture of epoxide resin and hardener in a ratio, experimentally determined. The induration proceed at room temperature for 12 h. The second method has two options and is applied for the conservation of biological objects and anatomical preparations in polymethylmethacrylate by a successive immersing of the object in a system of dehydrating mixtures: 50%, 70%, 90% and 96% water solution of methanol and ethanol and in a mixture of acetone and ethanol (1:1) and in acetone or in methylene chloride. The object, thus prepared, is impregnated in vacuum with polymer of methylmethacrylate, benzoyl peroxide and stearic acid or in a composition containing: methylmethacrylate, benzoyl peroxide, dibutylphthalate and tertiary aromatic amine, in optimum correlations of the components, experimentally determined. The induration proceed by heating in a water bath (37 + 3 degrees C) for 3 h and at 30 degrees C temperature in the course of 6-8 h in the first option or at room temperature for about 3 days in the second option. The advantages of the proposed methods are: the use of cheap and available materials for the production of a simplified technological scheme of strongly transparent packages, preserved over a long period; preserving the sizes, the form and natural colour of the objects and preparations as well as a possibility for selective tinting of the separate tissues and systems in the preserved biological objects and anatomical preparations; a possibility for stereomicroscopic observation of the objects and preparations preserved.

Animals↗
PubMed1987

[Chemical composition of poultry livers].

Investigations were carried out on the basic and mineral composition of the liver of slaughtered birds. It was found that the water content of the liver depended on the age and sex, with broilers it being 73.09 g%, with laying hens--72.56 g%, and with cocks--70.62 g%. Proteins had highest percent in the liver of cocks, followed by those in the liver of hens, geese, broilers, and turkeys. The content of fats was highest in the liver of turkey, and in a descending order followed geese, broilers, hens, and cocks. Mineral salts varied from 1.20 to 1.35 g%; highest amounts of sodium were found in the liver of broilers, while highest levels of potassium, calcium, phosphorus, iron, zinc, and copper were established in the liver of turkeys.

Animals↗
PubMed1987

[Antibacterial activity of chlorquinaldol esters and 2-styryl-substituted derivatives].

Studied was the bacteriostatic activity of a total of 17 new esters and replaced 2-styryl derivatives of chlorquinaldol. Determined were also the lowest concentrations that suppressed the growth of organisms. Some of the compounds showed higher activity and broader spectrum of antibacterial qualities, mainly against Escherichia coli, Salmonella gallinarum, and Salmonella cholerae suis as compared to the initial therapeutic preparation chlorquinaldol. It was found that the presence of chlorine atoms either in the second or in the second and fourth place in the benzene nucleus of the esters studied, the presence of a NO2-group in the third place of the same nucleus, and the presence of an extranuclear hydroxyacetyl remainder in the ester grouping could lead to a rise of the antibacterial activity. The presence of an F atom in the second and third place of the benzene nucleus of the sterile grouping also raised the activity of these compounds.

Bacteria↗
PubMed1985

[Presence of Yersinia enterocolitica in raw cow's milk].

Studied were a total of 286 samples of raw milk from 12 dairy farms for the presence of Yersinia enterocolitica. Various methods and nutrient media were tested for the successful isolation of this organism. It was found that 11.89 per cent, on an average, of the investigated samples contained Y. enterocolitica. The positive samples on the individual farms varied from 0 to 33.33 per cent. Best results were obtained with the use of the phosphate buffer physiologic saline and Rappaport's modified broth at two-step enrichment. The reseeding on MacConkey and Endo agar as well as the treatment of the enriched media with weak solutions of KOH made it feasible to isolate and identify the organisms of Y. enterocolitica. It was also established that the Y. enterocolitica strains isolated from raw cow milk did not refer to the European serotypes 0:3 and 0:9 that were pathogenic for humans. Biochemically, the isolated ones were found to belong to the newly suggested Yersinia frederiksenii and Yersinia intermedia.

Animals↗
PubMed1985

[Rapid method for determining the drug resistance of gram-negative bacteria].

Comparative studies led to the working out of a new diffusion indicative method for the rapid determination of drug sensitivity in Gram-negative bacteria. It is a modification of the diffusion method, consisting in the use of an indicator medium, bromothymol blue in glucose agar, instead of the meat peptone agar or other routinely employed nutritive media. The new method makes it possible to record rapidly the drug sensitivity of bacteria--only for 4-6 hours (compared with 24 hours with the conventional method). Besides, the new method is readily applicable, precise, distinctive and rapid.

Anti-Bacterial Agents↗
PubMed1985

[Microbiological research on the production and storage of fast-frozen semiproducts].

Studies were carried out to find the sources of microbiologic contamination, and the quantitative and qualitative composition of microflora and its changes following various periods of storing of rapidly frozen meat-balls obtained under productional conditions. The investigations were performed with regard to the total count of aerobic organisms, coli forms, staphylococci, sulfite-reducing Clostridia, Salmonellae, and moulds. It was established that the machines, equipment, units, and package had no effect on the bacteriologic contamination of meat-balls. Storage at--18 degrees C in the course of six months had no effect whatever on the residual microflora and the organoleptic indices of this product. It is stated that the standard requirements concerning the total numbers of anaerobic mesophilic organisms should not exceed 5 X 10(3)/g at a coli titer of 1.0.

Animals↗
PubMed1984

[Rapid method for the simultaneous determination of bacterial urease and phenylalanine desaminase].

Tested was an accelerated method for the evaluation of urease and phenylalanine desaminase of a total of 327 strains of E. coli, S. typhimurium, S. enteritidis, S. braenderup, S. tennessee, P. vulgaris, P. mirabilis, Yersinia enterocolitica, and Citrobacter that were subjected to a preliminary identification with routine methods. It was established that the method tested had the following advantages as compared to the classical methods employed up to then in the laboratory practice: --100% positive results were obtained up to the 4th hour, i. e. the method appeared 6 times more rapid, and the overall result was obtained one day earlier; --the two enzymes were studied simultaneously; --the expenditures in connection with the use of nutrient medium per one test were several times lower. Suggested is the timely adoption of the accelerated method in the laboratory practice.

Amino Acid Oxidoreductases↗
PubMed1981

[Cleansing and disinfecting the skin of calves in veal production].

Investigations were carried out at 6 meat producing combines on calves intended for slaughter. The animals originated from farms of different hygiene conditions. The studies aimed at establishing the extent to which the produced meat was contaminated with organisms coming from the skin cover. The total count of bacteria as well as that of coliforms in samples taken from the coat of calves were determined prior to bathing the animals, after that and after disinfection. Following slaughter the bacteria were studied at the site of separating the skin, in the abdominal muscles and in the croup. The skin of the calves for slaughter was found to be strongly contaminated with bacteria. The bathing and the disinfection with a 2 per cent chloramine solution decreased the number of microbes, however, did not fully inactivate bacteria. This contributed to the additional surface contamination of the meat obtained.

Animals↗
PubMed1981

[Methods for the control of disinfection in meat-packing plants].

Forty-eight series of experiments were carried out to establish the effect of disinfections with 2% septin, 1% tagonin, 2.5% chloramine and 2% chlorinated lime, all applied in the meat processing shops. Determined were the total count of bacteria and that of coliforms alone, employing the methods of washings and taking impression (contact) samples (Schothorst et al., 1966). It was found that these disinfection agents did not produce a complete disinfection effect. The contact method of determining the total count of bacteria proved readily applicable and suitable to investigate subjects having smooth surfaces. The combined use of the two methods to record the effect of disinfections is, however, suggested because of the diversity of the various subjects in the meat processing shops.

Bulgaria↗
PubMed1981

[Microbiological study in pork production].

Investigations were carried out in production conditions on the sources of surface contamination of pork with regard to sanitary-indicative and pathogenic (Salmonellae) organisms. A total of 74 series of experiments were carried out, every series making use of the following: 10 fecal samples taken on the preslaughter premise; the results of studying the skin cover of 3 animals prior to washing, after washing, and after stunning, employing the method of Dryabina in studying skin areas of 25 cm2; as many as three washings taken from within the path from the place where the animals were washed to the place where they were stunned; the results of studying the surface of the meat produced (from 3 animals in each case) and at the site of starting skin removal, with sampling the abdomen muscles and the group along with sampling the meat itself after cleaning and washing it - taking impression preparations, resp., employing the contact method with a 44 cm2 surface area of the agar. No Salmonella bacteria were found in the 1628 analyses and fecal samples of the skin of pigs intended for slaughter. The washing of the animals lowered more than 70 times the total bacterial contamination of the skin cover. It was found that the site of starting skin removal and the muscles of the abdomen and those of the forelimbs were most strongly contaminated.

Animals↗
PubMed1979

[Organoleptic and biochemical changes in beef during refrigeration and storage].

Studies were carried out on the changes taking place in the organoleptic properties and the pH values of m. longissimus dorsi of carcass quarters of cattle, subjected to various ways of chilling and storage. It was found that in quickly chilled beef (immediately following slaughter) the processes of ripening were very slow, and the organoleptic indices were lower as against meat that was slowly cooled. The pH values of quickly chilled beef dropped at a very slow rate, and it was not until the ninth day that they reached the range below 6.0. The organoleptic properties of quickly chilled beef, including a preliminary phase (6 hours at 18-20 degrees C) were formed rapidly, and on the 7th-11th day the subjective evaluations became the same as those of slowly cooled beef.

Animals↗
PubMed1979

[Microfloral study of beef in refrigeration and storage].

The changes in surface microflora quantity and composition on cattle carcasses cooled and preserved in various ways were studied. It was established that immediately after production beef meat has only a small number of microorganisms on its surface -- log10 3.74 on the average.The surface microflora on slowly cooled meat increases comparatively quickly and on the eleventh day reaches the number log10 7.22. In case of fast meat cooling a considerable reduction in the total number of surface microflora is observed during the first days. Its reproduction is slowed down and the number of log10 8.00 is reached only on the 40th day. The studies were not restricted only on total number of microorganisms, but covered also some other important meat microflora groups -- psychrophyls, coliform bacteria, moulds and yeasts.

Animals↗
PubMed1978

[Express methods of determining the biochemical properties of pathogenic microorganisms].

Comparative studies were carried out to evaluate some express methods for determining the biochemical properties of microorganisms. Described are disc methods establishing the production of indol and H2S, the breakdown of urea, and the reduction of nitrates and nitrites, with which the time of investigation is shortened severalfold. The results obtained are clear and well defined, and fully agree with the results obtained by methods described in the Bulgarian State Standards. It is suggested to apply these methods in the wide laboratory practice.

Bacteriological Techniques↗