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Biomedical subjects

M Khristova

Publications and source records attributed to M Khristova.

17 recordsLinked to original sources
PubMed2003

Copper oxide supported on carbon modified alumina as catalyst for reduction of NO with CO.

Carbon-modified alumina-supported copper oxide catalysts have been investigated. The samples have been prepared by modified incipient techniques. The gamma-Al(2)O(3)-supported carbon phase permits sufficient modification of the chemical nature of the support surface in the region of low carbon contents without changing the specific surface area and the mesoporous character of the samples as compared to those of initial gamma-Al(2)O(3). In addition, the surface oxygen groups of the carbon phase, similar to the hydroxyl groups of the alumina surface, affect the formation and type of copper oxide phase. It has been established that the catalysts investigated have high activity in the reduction of NO with CO, the highest activity belonging to the Cu17AC/AL catalyst, which contains the largest amount of carbon. This sample is also active with respect to the direct decomposition of NO.

Journal Article↗
PubMed1999

Study on Active Carbon-Supported Two-Component Catalysts for NO Conversion.

The impregnation of active carbon with two-component aqueous solutions of Cu and Co nitrates has been investigated and different deposition degrees of copper and cobalt ions have been established. Adsorption analysis has shown modification of the active carbon texture after impregnation with solutions whose concentration of Cu and Co ions exceeds 3%. A catalyst with a high activity in the reduction of NO with CO at 100 degrees C has been obtained. All samples are found to catalyze the complete reduction of NO to N2. A correlation between the catalytic activity and the Cu:Co ratio in the supported phase has been established. Copyright 1999 Academic Press.

Journal Article↗
PubMed1997

Study of Ni-Impregnated Active Carbon

The reduction of NO with CO on Ni-impregnated active carbon catalysts (AC/Ni) has been investigated. High activity toward NO reduction can be achieved on an AC/Ni catalyst obtained by thermal decomposition of the precursor nitrate at 200°C. The role of active carbon in the catalytic reduction of NO with CO at different temperatures has been discussed. At low temperatures (below 200°C), when there is no substantial gasification of the carbon, dissociative adsorption of NO along with N2 evolution and oxygen accumulation on the carbon surface has been observed. The active sites occupied by the oxygen evolved during the NO decomposition are regenerated by the CO reducing agent. At high temperatures the C-O complexes evolved from the carbon surface participate in NO reduction as a second reducing agent. The effect of the oxygen-containing functional groups and the available nitrate groups on catalyst activity has been discussed. Copyright 1997Academic Press

Journal Article↗
PubMed1990

[Enzyme histochemical changes in the myocytes of the vascular wall under the influence of sex hormones].

Estradiol, progesterone and testosterone were administered three times in the female rats of Wistar strain. Myocytes were studied in the wall of the portal vena, posterior vena cava and aorta. The used histochemical methods showed distribution of dehydrogenases, which was characteristic of predominating anaerobic oxidation in cells. They increased their activity after animals were treated with testosterone and they reduced it after treatment with progesterone. Adenosin-3-phosphatase activity was increased after administration of estradiol and was reduced after treatment with progesterone. Better manifested activity of some enzymes in the longitudinal muscular layer of the portal vena in comparison with circular layer was connected with greater functional loading of this layer. It was found to a great extent similarity in dynamics of enzyme histochemical changes in arterial and venous myocytes.

Animals↗
PubMed1989

One-incubation time-resolved fluoroimmunoassay based on monoclonal antibodies in detection of influenza A and B viruses directly in clinical specimens.

A new modified enzyme immunoassay screening method was developed for testing hybridoma cultures, so as to select antibodies useful for solid phase assays. Samples of hybridoma cultures were incubated for 1 h with purified nucleoprotein preparation in microtiter wells precoated with rabbit anti-influenza A or B immunoglobulin, followed by washing and addition of anti-mouse HRPO-conjugate. The monoclonal antibodies were then used in one-incubation time-resolved fluoroimmunoassay (TR-FIA) for detecting influenza viral proteins in nasopharyngeal aspirate specimens. The sample and europium (Eu)-labelled monoclonal detector antibody (100 microliter of each) were added simultaneously to microtiter wells precoated with anti-virus monoclonal antibody, and incubated for 1 h. After washing and addition of the enhancement solution the strips were shaken for 10 min before measurement of the fluorescence using a photon counting fluorometer. All of the monoclonal antibodies screened by our modified method and Eu-labelled worked as detector antibodies. Many of these monoclones also functioned as capture antibodies on solid phase. A total number of 309 (influenza A) and 104 (influenza B) nasopharyngeal aspirate specimens taken mainly from hospitalized children with acute respiratory disease were tested with the TR-FIA, using monoclonal antibodies produced by our modified screening method in comparison with monoclonal antibodies previously reported elsewhere (Walls et al., 1986). Results were similar, and superior to those obtained with routinely used indirect enzyme immunoassay based on polyclonal antibodies. The results of this study indicate that the one-incubation TR-FIA using monoclonal antibodies selected by the modified screening method is a highly sensitive and rapid method for detecting influenza A and influenza B virus in clinical specimens.

Antibodies, Monoclonal↗
PubMed1979

[Resistance of the Aujeszky's disease virus to gamma ray irradiation].

Investigations on the resistance of Aujeszky's disease virus to gamma irradiation from a 60Co source were performed. The resistance of the virus was tested in vitro in a fluid medium of 50% Henk's balanced saline solution, 50% Eagle's medium MEM and a supplement of 10% normal calf serum as well as its resistance on artificially virus infected pig skin and greasy wool of sheep. It is established that virus inactivation in the fluid medium occurs following 1.6 Mrad gamma irradiation. The irradiated with lower than 1.6 Mrad gamma doses live virus particles form smaller than and with irregular oval shape and dentated plates as compared to the non-irradiated control virus. 1.5 Mrad gamma rays are needed to inactivate the virus on pig skin and greasy wheep's wool. The presence of lanoline in greasy sheep's wool, due to the alkaline pH (9--13) it produces, has an effect on the vitality of the virus both in the control and in the experimental samples.

Animals↗
PubMed1977

[Rheumatoid arthritis among the rural population of southern Bulgaria (transitory morbidity established using the Rome and New York diagnostic criteria)].

Examinations of 5021 subjects (2779 females and 2242 males) were carried out with a view to rheumatoid arthritis. En masse examinations of the population over the age of 20 were carried out in eight villages of South Bulgaria. Making use of the Roman diagnostic criteria, rheumatoid arthritis--probable form, was found in 1.47 per cent of the males and 1.40 per cent of the females (mean for both sexes-1.43%), confirmed form (including the classical) in 0.80 per cent of the males and 1.12 per cent of the females (a total of 0.98% for both sexes). With two positive New York diagnostic criteria are 1.12 per cent of the males and 1.30 per cent of the females (a total of 1.21% for both sexes). With three and four positive New York criteria are 0.45 per cent of the males and 0.76 per cent of the females (a total of 0.62% for both sexes). Only 60 per cent of the subjects with confirmed (including the classical) rheumatoid arthritis are with three or four New York diagnostic criteria. The Roman diagnostic criteria define sometimes subjects with polyarthritis as patients with rheumatoid arthritis, whereas New York criteria fail to detect the cases with rheumatoid arthritis with asymmetric joint involvement.

Adult↗
PubMed1976

[Comparative studies of the vascularization of the posterior vena cava in some laboratory animals].

The author examined the posterior caval vena in four various areas in a rat, guinea pig, rabbit, cat and dog by applying Indian inkgelatine injection and subsequent preparation of histologic and total brighter preparations. The established differences in the vascularization were determined by the thickness of the true venous wall. The later increased with an increase of the body of the examined kind of animal on behalf of the adventitial longitudinal muscular layer at comparatively small differences in the thickness of the circular muscular layer in the media. There were no capilearies in the adventicial muscular layer of a rat and guinea pig. This layer was vascular, when the thickness of the true venous wall surpassed 70 microns. The most deeply penetrated capillaries were located almost equaly from the vascular lumen: 25 microns in the rabbit and 30 microns in the cat and dog.

Animals↗
PubMed1975

[Vascularization of the myocardium in rats during various motor regimens].

The author examined the vascularization of the myocardium by impregnation of argirophil fibers according to Gomori in white rats, undergoing various motor regimens: 8 animals traned by running for a period of 90 days, 8 animals were moveless for 90 days, 8 animals trained for 90 days and then were moveless for 50 days and 7 were controls. She compared the number of capilaries with the number of muscle fibers. There was statistically significant growth of the number of capillaries and their lumen was enlarged in the trained animals. There were no significant differences in the degree of vascularization of the myocardium in the moveless and control animals. In moveless animals after preliminary training the capillary bed of the myocardium was reduced and did not differ significantly from the control animal, but the lumen of all capillaries was still not reduced. Probably we could refer also the increase of the capillary lumen to the more stable adaptation changes together with the increase of the capillaries during raised functional requirements towards the myocardium.

Animals↗
PubMedDate not supplied

[The action of lactoperoxidase, lactoferrin and lactoglobulin on Shigella sonnei in an in-vivo experiment].

The synergism of the protective action of lactoperoxidase, lactoferrin and lactoglobulin obtained from cow milk, as well as lactoferrin obtained from human milk, was shown in experiments on white mice, infected intranasally with S. sonnei and used as an experimental model. The combined administration of these preparations in doses, each one having no protective action, contributed to the elimination of the bacteria from the lungs and prevented the death of the animals. This phenomenon was found to be nonspecific and suitable for use in the development of preparations for passive immunization against a wide spectrum of microorganisms.

Animals↗