Biomedical subjects

M Aleksandrov

Publications and source records attributed to M Aleksandrov.

At least 19 recordsLinked to original sources

PubMed1987

[Cultivation and demonstration of the classic swine fever virus].

Experiments were carried out for the cultivation and indication of the swine pestivirus in several continuous and in primary cell lines, using lapinized and field strains of the virus. It was demonstrated that in the various cell cultures the strains used showed varying rates of growth. In PK-15 and pig embryonic kidney cell lines, the field strains and the virulent Vratsa strain replicated with no preliminary adaptation, forming numerous large fluorescent plaques at the 16th to 18th hour. In the same cultures the lapinized strains K and Hudson had more delayed growth, forming double plaques not until the 36th hour. In rabbit kidney primary cultures the virulent K strain only exhibited growth, and up to the 4th hour at that. All results obtained were in agreement with the results from biologic experiments with pigs and rabbits. Experiments were also carried out for the indication of the swine pestivirus in infected lamellae of the cell cultures used, which were subject to additional treatment for 5 min following primary handling with the specific marked serum with the 1:40,000 solution of Evans blue. The infected cells treated by this method showed light green fluorescence of the protoplasm, with a dark nucleus, while the intact cells had tile-red cytoplasm.

Animals↗

PubMed1987

[Isolation of conjugated sera for the immunofluorescence demonstration of swine parvovirus].

High-titer, specific serum against porcine parvovirus was obtained via hyperimmunization of rabbits, with the use of a Bulgarian isolate that had been partially purified after a known, modified technique. A specific, high-titer conjugate was produced for the immunofluorescence diagnosis of porcine parvoviruses. The microscopic observation of the lamellae of cell cultures, treated with the conjugate, revealed the presence of a specific, typically granulated perinuclear (mostly unilaterally) and, in some cases nuclear fluorescence--at negative reaction in the control preparations. Immunofluorescent light was also established in cell cultures infected with the virus at highest dilution. It showed that immunofluorescence microscopy could be employed to demonstrate even the lowest amounts of the virus.

Animals↗

PubMed1987

[Replication of a local strain of swine parvovirus in swine kidney cell cultures].

The kinetics of replication of strain of parvovirus in swine was investigated in the primary cell cultures of swine kidney. The morphologic changes were traced in inoculated cultures by microscopic observation and the replication of the virus in the cells by immune-fluorescent examinations. The quality of the virus in the cell monolayer and in the nutritive medium, in the different periods after the infection, was determined by hemagglutination test. By the immune-fluorescent examinations, the virus was proved still in the first hours, while the first morphologic changes of the monolayer were determined 72 hours after the infection. The nuclear fluorescent appears at the 12-th hour and increases its intensity 24 hours after the infection. At the 72-nd hour and later predominates the cytoplasmatic fluorescent. The cell monolayer produces virus up to the 96-th hour, and the virus titer reaches its maximum 120 hours after the inoculation, which is the most appropriate moment for the yield of virus.

Animals↗

PubMed1987

[2 strains of swine parvoviruses isolated from aborted fetuses].

Two hemagglutinating virus strains were isolated (in primary cell cultures of pig kidneys) from viscera of aborted swine fetuses. A number of serologic, cytologic, physico-chemical, and laboratory investigations with the strains revealed that they belonged to the group of porcine parvovirus (PPV). The isolation of SPV from aborted fetuses pointed to the fact that the disease had been widespread among the swine population and plays a part in reproduction disturbances that have come to be known recently. The isolated strains did not produce a clear and distinguishable cytopathic effect in inoculated cell cultures. They, however, could be demonstrated in the cultures indirectly through cytologic investigation (the demonstration of intranuclear inclusion bodies, type B after Cowdry, through hemagglutination tests, and via immunofluorescent microscopy.

Abortion, Veterinary↗

PubMed1987

[Oral immunization of suckling piglets against classic swine fever].

Attempts were made to immunize suckling pigs against classic swine fever. The pigs were treated orally, originating from sows which were immunized on the 30th-40th and the 90th-100th day of pregnancy, as well as from sows which were vaccinated one month prior to impregnation. A Bulgarian lapinized K vaccine and a Soviet LK-VNIIVViM cell culture were used (immunization being carried out 1-2 hours before the newborns were allowed to suck) at the rate of 150 doses for both vaccines. It was demonstrated that the application of a live vaccine, which was patterned as cited above, eliminated the inhibiting action of colostral antibodies and induced stable postvaccinal immunity. However, the effectiveness of the immunity conferred depended on the vaccine used in each specific case. The Soviet vaccine, in which the amount of the virus per vaccinal dose was five times as much, was shown to be more appropriate to the needs for oral immunization of suckling pigs of sows that were immune to classic swine fever than the lapinized K vaccine.

Administration, Oral↗

PubMed1987

[Effect of ochratoxin on the health status of broilers].

An experiment was carried out with 7-day-old broiler birds to assess the effect of ochratoxin A on their health. A standard feed mixture, containing 4 mg/kg ochratoxin A in pure substance, was offered to the birds in the course of 21 days. No severe clinical symptoms and death cases were observed during the experimental period. However, both the growth and the development of the birds were arrested along with an increase in the relative weight of the kidneys and changes in their morphology--vascular disturbances and dystrophy more strongly manifested in the kidneys and to a weaker extent seen in the bursa of Fabricius, the thymus, and other organs.

Animal Feed↗

PubMed1987

[Experimentally induced aflatoxicosis in broilers].

Aflatoxicosis was induced under experimental conditions in two groups of broiler birds fed in the course of the entire fattening period upon feed, containing 0,250 and 0,600 ppm aflatoxin. Dependable changes were established in the investigated haematological and biochemical indices. There was a drop of the body weight and an increase in the feed to gain ratio. Pathologic changes were recorded in the liver.

Animal Feed↗

PubMed1986

[Development of ELISA for demonstrating antibodies to the swine pestivirus].

An indirect variant of the enzyme linked immunosorbent assay with the classic form of swine fever has been worked out. The test makes it possible to assess the level of antibodies with a great number of animals over a short period of time with no special equipment. The method has proved promising in taking prophylactic measures.

Animals↗

PubMed1986

[Enhanced luminescence intensity in immunofluorescent preparations following trypsin treatment].

Comparative investigations were carried out on the immunofluorescent preparations of cell cultures infected with bovine viruses--rota-, corona-, respiratory-syncytial, parainfluenza-3, adeno-1, and herpes-1--to test various fixatives and the effect of trypsin in raising the sensitivity of the immunofluorescence method. The effect of trypsin was manifested in fixation with formalin, ethanol, methanol, and acetone treated immunofluorescent preparations of cell cultures infected with rota- and adeno-viruses as well as in fixation with acetone of cultures infected with respiratory syncytial virus, parainfluenza-3 virus, and corona virus. Formalin, ethanol, and partly methanol were shown to be unsuitable for the purpose of fixation of cell culture preparations infected with viruses that contained a lipoprotein envelope. It was found that the treatment of immunofluorescent preparations with trypsin following fixation and prior to their treatment with conjugated antisera enhanced considerably the number of fluorescent cells and the intensity of fluorescence itself provided 0.1 per cent trypsin was used for 5 to 10 min at 37 degrees C--for cell culture preparations, and 0.1 per cent trypsin was used for 20 to 30 min at 37 degrees C--for paraffin sections of acetone-fixed tissues.

Animals↗

PubMed1986

[Mycoflora of hay and straw].

Studies were carried out on hay and straw to establish the composition of mycoflora in them. They were sampled both at the time of harvesting and after storing for four to five months. It was found that the hay and straw were most often inseminated with spores of the fungus species Alternaria tenuis, Aspergillus fumigatus, Mucor hiemalis, Penicillium sp., and more rarely with spores of Fusarium, Chaetomium, Scopulariopsis, Cladosporium, Trichoderma, and Stachybotrys alternans. It was demonstrated that when moistening of the feeds set in the period of taking in or in storage the mycoflora increased both in species composition and in extent of insemination. The presence of Alternaria tenuis was mostly demonstrated (up to 85 per cent) for hay, and (up to 100 per cent) for straw.

Animal Feed↗

PubMed1986

[Sensitivity of various cell cultures to the swine parvovirus].

Attempts were made to culture the swine parvovirus under laboratory conditions. A reference strain and a field isolate were used along with steady cell lines of pig kidney PK-15, IBAS-2, and SPEV as well as primary and secondary cell cultures of pig kidney. It was found that the steady cell lines were slightly sensitive or totally unsusceptible to the swine parvovirus. The could serve for its isolation from pathologic material and culturing in laboratory conditions. Both the primary and the secondary cell cultures proved strongly susceptible to the virus, and they could be used for the isolation of filed strains as well as for the laboratory maintenance of the virus. The strains used produced no clearly distinguishable cytopathic effects in the inoculated cell cultures. The morphologic changes that set in following inoculation with higher amounts of the virus could be seen under the light microscope and could be evaluated through cytologic investigations (the presence of intranuclear inclusion bodies). The virus could be most readily demonstrated in the infected cell cultures via the hemagglutination test.

Animals↗

PubMed1986

[The mycoflora of corn silage].

Maize silage was sampled to investigate the mycotic flora in it, the material for testing being taken at the time of preparing the silage as well 4 to 5 months later. It was found that richest mycoflora developed in the superficial layers of the silage mass, chiefly constituted by fungus species of the Aspergillus, Penicillium, Alternaria, and Mucor genera. It was also established that Aspergillus fumigatus was the most frequently isolated species. It is believed that the development of the mould fungi in maize silage was dependent on the quality of compaction and air-tight pressing of the ensiled mass.

Animal Feed↗

PubMed1985

[Demonstration of a transmissible gastroenteritis virus by contrast immunofluorescence].

Tested were a number of procedures to employ the immunofluorescence method for diagnosing transmissive gastroenteritis in pigs--impression preparations, frozen cross-sectioned material, and infected cell cultures of the established cell line SPEV. It was found that immunofluorescence microscopy was a dependable method for the express diagnosis of transmissive gastroenteritis. It could be employed in its three variants. The use of impression preparations, however, did not prove as dependable as the remaining ways of applying the method, and this drawback had to be compensated for with the study of a greater number of impression preparations taken from more pigs that had contracted the disease. It was also established that most promising and effective was to apply the method with the use of cell cultures infected with suspensions of organs. Cell cultures of the established SPEV cell line infected with material that contained the virus could produce dependable positive results in immunofluorescence investigations at the 24th hour following inoculation. This method could be employed for the express diagnosis of transmissive gastroenteritis.

Animals↗

PubMed1985

[Case of Pseudomonas aeruginosa infection in tropical snakes].

Microbiologic and morphologic studies were carried out with there tropical snakes (two Boa constrictor and one Pithon molurus) that contracted the disease and died. Pseudomonas aeroginosa was the only organism isolated from the affected portions of the oral cavity and the lung. It was found that all strains of the species isolated were sensitive to gentamycin, tobramycin, and polymixin B. Up to their death two of the animals were treated with tobramycin with no curative effect whatever. The morphologic lesions were confined to the oral cavity, the lung, and the skin only. Histologically, there were necrotic stomatitis and necrotic exudative pneumonia, diffuse fibrinoid degeneration of the connective tissue within all viscera, deposition of fibrinoid in the walls of the myocardial blood vessels, hyaline droplet degeneration of the hepatocytes and the kidney epithelium, and focal infiltrations of pseudoeosinophile leukocytes in the spleen. It is believed that due to the irreversible injuries of the internal parenchymal organs all treatment in the advanced stages of the disease was ineffective even with the use of antibiotics to which the etiologic agent was strongly susceptible.

Abscess↗

PubMed1984

[Pathomorphology of stachybotryotoxicosis in calves during the nursing period].

An enzootic of stachybotryotoxicosis was established on a dairy farm in 35-46-day-old calves due to the use of straw contaminated with Stachybotrys alternans. Studied were the epizootiology, the clinical picture, and chiefly the morphology of the disease. A characteristic clinical feature was the edema in the intermandibular space. Morphologically, there were numerous hemorrhages in the subcutaneous tissue, skeletal muscles, abomasal and intestinal mucosa, kidney cortex, and urinary bladder as well as ulcerous and erosive colitis, edematized mesenterial lymph nodes and occasionally catarrhal and necrotic stomatitis, icterus, and perirenal edema. Contrary to the gross lesion picture known there were no changes in the rumen, reticulum, and omasum which were not sufficiently developed during that period. Histologically, there were degenerative nephrosis, focal hemorrhagic glomerulonephritis (occasionally coupled with bacterial embolization and dystrophic calcification of the kidneys), granular degeneration of the liver and heart, hemorrhages and edema of the lungs, and edema, hyperemia, and thrombi in the brain.

Animals↗

PubMed1981

[Experiments to elucidate the role of Aspergillus fungi in the hemorrhagic syndrome in poultry].

Attempts were made to assess the role played by fungi of the Aspergillus genus in the occurrence of the hemorrhagic syndrome in birds. Groups of test birds were given continuously a forage mixture containing 30 per cent of ground nut cake which had aflatoxin at the rate of 1.5 ppm, a forage mixture 30 per cent of which was preliminarily contaminated with spores of Asp. fumigatus or Asp. flavus, and subtoxic amounts of nonpurified aflatoxin. Growth retardation was established along with the development of slightly manifested morphologic changes in some organs of the test birds. No morphologic picture characteristic of a hemorrhagic syndrome was found. In the authors' opinion the toxic Aspergillus fungi entering the body of the birds via the forage were not the sole factor contributing to the outbreak of such a syndrome.

Animal Feed↗

PubMed1980

[Microflora studies of broiler density breeding].

In rooms with a condensed raising of broilers were carried out mycological studies of samples of air, floor-covering materials, feeding mixes--degree of semination, isolation of toxic and pathogenic species, presence of mycotoxins. Experiments were carried out also on pathological materials (lungs, gizzard) from dead, ill or suspectedly healthy broilers in order to prove mycotic agents. It was proved that the semination of air with mycotic spores was considerably higher in comparison with the data of the investigations carried out in rooms housing 16--18 broilers on 1 m(2). It was also established that there was a vertical spreading of spores in the rooms, the sources of mycotic infection was a vertical spreading of spores in the rooms, the sources of mycotic infection and the most frequent species of fungi. Steps are pointed out in order to abolish mycotic diseases and reduce to a minimum their harmful effect of mycotic toxins on the organic system of poultry.

Air Microbiology↗

PubMed1978

[Effect of aflatoxin on the serum profile and antibody formation in chickens].

Experiments were carried out to follow up the effect of aflatoxin on the production of hemagglutinating antibodies in birds vaccinated against Newcastle disease and the changes in the serum profile. Birds that had been given a feed mixture with 560 and 640 mcg per kg for 20 days showed a lower titer of hemagglutinating antibodies and a drop of the alpha1, alpha2, beta1, gamma2-globulin fractions as well as a rise of the albumin and gamma1-globulin fractions. The liver and kidneys of the treated birds showed dystrophic changes.

Aflatoxins↗