Browsing by Author "Dimitrov K."

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Cloacal bursa morphology in turkey broilers challenged with aflatoxin b1 alone or co-administered with mycotox ng
    (2020-01-01) Grozeva N.; Valchev I.; Lazarov L.; Hristov T.; Kanakov D.; Dimitrov K.; Binev R.
    Aflatoxins are toxic metabolites of moulds from the genus Aspergillus (Aspergillus flavus and Aspergillus parasiticus being the main producers). The aim of the present investigation was to evaluate the toxic effects of aflatoxin B1 on bursa of Fabricius morphology. Also, the possibility for prevention of toxic effects of AFB1 by feed supplementation of a mycosorbent (Mycotox NB) was studied. Experiments were carried out with sixty 7-day-old female turkey broilers (meat TM strain) divided into one control and five treatment groups (n=10). Groups were as followed: Group I – control (fed standard feed according to the species and age of birds); Group II – experimental, whose feed was supplemented with 0.5 g/kg Mycotox NG, Group III– experimental, whose feed contained 0.2 mg/kg aflatoxin B1, Group IV – experimental, whose feed contained 0.4 mg/kg aflatoxin B1, Group V – experimental, supplemented with 0.2 mg/kg aflatoxin B1 and 0.5 g/kg Mycotox NG and Group VI – experimental, supplemented with 0.4 mg/kg aflatoxin B1 and 0.5 g/kg Mycotox NG. The duration of the experiments was 42 days. The changes in bursal morphology in control and treated groups were followed out after the end of the study. In birds from experimental groups ІІI and IV, atrophy and degenerative changes have occurred in the bursa of Fabricius: reduction of lymphoid cell-populations in lymphoid follicles along with dystrophy. Feed supplementation with the tested toxin binder (Groups V and VI) resulted in partial neutralisation of deleterious effects of AFB1 on severity of histological lesions: interfollicular oedema, considerably lower lymphoid follicle rarefaction.
  • No Thumbnail Available
    Item
    Effect of aflatoxin B1 alone or co-administered with mycotox ng on the renal function and morphology of Turkey broilers
    (2019-01-01) Valchev I.; Grozeva N.; Kanakov D.; Hristov T.; Lazarov L.; Dimitrov K.; Binev R.
    The changes in relative weight of kidneys, blood plasma uric acid, urea, creatinine, calcium and inorganic phosphate, and the morphology of kidneys were investigated in turkey broilers with experimentally induced aflatoxicosis B1 (AFB1) treated or not with a mycosorbent (Mycotox NB). Experiments were carried out with 60 7-day-old female turkey broilers (meat TM strain) divided into one control and five treatment groups (n=10): Group I – control (0 mg/kg AFB1 not supplemented with Mycotox NG); Group II (0.5 g/kg Mycotox NG), Group III (0.2 mg/kg AFB1), Group IV (0.4 mg/kg AFB1), Group V (0.2 mg/kg AFB1 and 0.5 g/kg Mycotox NG) and Group VI (0.4 mg/kg AFB1 and 0.5 g/kg Mycotox NG). The changes in blood parameters were assayed on day 21 and 42. Blood analysis in groups III and IV on day 21 showed increased urea and creatinine concentrations and reduction in blood uric acid, calcium and inorganic phosphate. These changes tended to become more pronounced on day 42. The relative weight of kidneys was increased in groups III and IV after the end of the experiment. Morphological alterations of renal parenchyma in Groups I and II were not present. In birds from group III, desquamation of epithelial cells from the basement membrane, dilated glomerular subcapsular space and round-cell proliferation were noted. In Group V, these changes were far more severe and comprised granular and fatty dystrophy, karyolysis and plasmolysis, necrobiotic to necrotic processes, haemorrhages, congestion. The supplementation of the feed of groups V and VI with the tested toxin binder reduced the severity of reduction of kidneys’ relative weight, magnitude of changes in blood parameters, and the frequency and severity of histological lesions.
  • No Thumbnail Available
    Item
    Effect of magnetic field on cellulose refining process and strength properties
    (2019-01-01) Todorova D.; Dimitrov K.
    This study presents the results from the investigation of the effect of constant magnetic field over the refining process of soft and hardwood pulp suspensions and an evaluation of its white waters and paper samples strength properties. In our experiment were used two types of kraft pulp - 100 % of softwood (pine and spruce) and 100 % of hardwood (acacia). The refining degree and dewatering time for 700 ml filtrate were determined by the Schopper Riegler Value °SR, according to ISO 5267-1/AC: 2004. The magnetic treatment of pulp suspensions was performed by using magnetic stator device with field intensity of 0,1 T. Aqueous stream (the paper furnish) was passed vertically downwards through the pole gap space with linear speed 0,6 - 0,8 m s-1 at quintuple and octuple crossing of the fluid. Of each pulp type were produced sheet samples 70 g/m2 without and with quintuple and octuple magnetic treatment. Tensile index, N m/g of papers was determined on a tensile testing machine Zwick/Roell, (ISO 1924-2:1985), Burst index, kPa m2/g (ISO 2759:2014) and Tear index, mNm2/g (ISO 1974:2012). The results show positive effect of the magnetic treatment over the cellulose refining time, cellulose suspensions dewatering effect and paper samples strength properties. For both investigated types of cellulose with a view of complete evaluation of the parameters studied out the quintuple magnetic treatment is optimal.
  • No Thumbnail Available
    Item
    Polycarbonate diols to produce elastic polyurethane foams - A method of immobilization of carbon dioxide into a polymer structure
    (2017-01-01) Dimitrov K.; Todorova D.; Nenkova S.; Herzog M.
    Using carbon dioxide as feedstock for polymers is a big challenge and a chance for our sustainable future. It has an immense potential for the coming decade, which comes much faster than expected. Scientists are very active lately in carbon dioxide chemistry research, especially in the field of carbon dioxide based chemicals and polymers. We report here on the stability of higher molecular weight polycarbonate diols and the formation of specialty polyurethanes such as UV stable elastomers, semi-rigid foams, and elastic sealants. These polyurethanes are produced from polycarbonate diols (ETERNACOLL®) and aromatic 4,4'-diphenyl-methane diisocyanate, from aliphatic hexane-1,6-diisocyanate, or the trimer, diisocyanates. We use butane-1,4-diol or pentane-1,5-diol as a chain extender. The thermal and mechanical properties of the polyurethanes obtained are determined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The data obtained show no phase segregation or any type of crystallinity. Any possible changes in the molecular mass distribution of the samples are investigated with the application of gel permeation chromatography (GPC). It is evidenced that only heat treatment brings about molecular mass distribution shifts to lower values.