Stoycho Stoev - Academia.edu (original) (raw)

Papers by Stoycho Stoev

Stable radical 1, 1-dipheny-2-picrylhydrazyl (DPPH) is widely used at in vitro models to investig... more Stable radical 1, 1-dipheny-2-picrylhydrazyl (DPPH) is widely used at in vitro models to investigate antioxidant and radical scavenging abilities of natural extracts. This work presents comparative study on DPPH radical scavenging capacity before and after UV irradiation of aqueous extract of Glycyrrhiza Glabra, a plant species belonging to the Indian flora. DPPH scavenging activities of different extract concentrations (at different incubation time intervals) were analyzed and compared by in vitro spectrophotometry and electron paramagnetic resonance (EPR) spectroscopy. 9.93% and 16.79%, DPPH scavenging activities before and after UV irradiation respectively were found by spectrophotometry. By the EPR spectroscopy study statistical significant increase in DPPH radical scavenging for the Glycyrrhiza Glabra extracts was established after UV irradiation (78.39± 0.001%) comparing to the non irradiated samples (14.02± 0.02).

Authors’ addresses: 1 Radiation Biotechnology Group, Institute of Nuclear Medicine and Allied Sci... more Authors’ addresses: 1 Radiation Biotechnology Group, Institute of Nuclear Medicine and Allied Sciences, Brig. S.K. Mazumdar Marg, Defence Research and Development Organization, Delhi-110054, India. 2 Department Chemistry and Biochemistry, Medical Faculty, Trakia University, 6000 Stara Zagora, Bulgaria. 3 Department Physiology, Pathophysiology and Pharmacology, Medical Faculty, Trakia University, 6000 Stara Zagora, Bulgaria. 4 Department of General and Clinical Pathology, Faculty of Veterinary Medicine, Trakia University, 6000 Stara Zagora, Bulgaria.

Veterinary Research, 2002

Histopathological, biochemical and toxicological investigations of tissues and blood of normally ... more Histopathological, biochemical and toxicological investigations of tissues and blood of normally slaughtered chickens exhibiting different frequencies (1-2%, 40-50% and above 80%) of nephropathy changes (congested or pale and enlarged kidneys) at the slaughtering meat inspection were carried out to elucidate the aetiology of nephropathies of chickens encountered in Bulgaria. A close relationship was observed between the frequency of this nephropathy and the rate of nephrotoxic mycotoxin ochratoxin A in muscles, kidneys and livers of chickens, but the levels of ochratoxin A in corresponding feed samples (0.1-0.3 ppm) were significantly lower than the levels (2-4 ppm) required to reproduce such nephropathy. Clinicomorphological changes such as nervous symptoms, vascular and oedematous changes in various internal organs and the brain, and subcutaneous or liver and kidney haemorrhages in addition to known degenerative changes in the kidneys, liver and lymphoid organs differed from the classical description of the nephropathy made in Scandinavia. The conclusion is that the Bulgarian chicken nephropathy may have a multitoxic aetiology because it cannot be explained by the concentration of ochratoxin A alone. mycotoxic nephropathy / ochratoxicosis / mycotoxin / ochratoxin A / pathology Résumé-Néphropathie mycotoxique spontanée sans étiologie mycotoxique déterminée chez des poulets bulgares. Des études histopathologiques, biochimiques et toxicologiques des tissus et du sang de poulets montrant des fréquences variées (1-2 %, 40-50 % et supérieures à 80 %) de changements néphropathiques (reins congestionnés ou pâles et hypertrophiés) lors de l'inspection des viandes à l'abattoir, ont été entreprises afin de déterminer l'étiologie des néphropathies du poulet en Bulgarie. Une relation étroite a été observée entre la fréquence de cette néphropathie et le taux de la 83

Studies on some feed additives giving partial protection against ochratoxin A toxicity in chicks

Toxicology Letters, 2002

Significant protective effects of the feed additives: water extract of artichoke, sesame seed, Ro... more Significant protective effects of the feed additives: water extract of artichoke, sesame seed, Roxazyme-G and L-beta phenylalanine against the growth inhibitory effect of ochratoxin A (OTA) and associated pathomorphological changes were seen. Similarly, there was less OTA-induced decrease in serum total protein and increase of serum creatinine and urea in the chicks. Whereas OTA induced strong degenerative changes and an increase in weight of kidneys and liver as well as a decrease of the weight of lymphoid organs the additives variously gave protection against these changes. The protection of Roxazyme-G and sesame seed was better expressed in kidneys and liver, whereas the phenylalanine better protected the weight changes in gizzard, heart and the changes in differential WBC count. Notably, sesame seed gave strong protection against 5 ppm OTA-induced suppression of humoral immune response, for which artichoke also had some beneficial effect, whereas phenylalanine had hardly any effect.

Journal of Advanced Veterinary Research, 2021

Protective effects of herbal feed additive Silymarin against the deleterious toxic effects of och... more Protective effects of herbal feed additive Silymarin against the deleterious toxic effects of ochratoxin A (OTA) on internal organs and blood biochemistry was seen. The observed histopathological and biochemical changes were well expressed in OTA-exposed chicks without Silymarin supplementation, followed by chicks treated supplementary with Silymarin in addition to OTA treatment, whereas no pathological changes were seen in the control chicks or the chicks treated with Silymarin only. The observed increase in the serum levels of uric acid, glucose and the enzyme activity of AST and ALT in OTA treated chicks and the found decrease of the same biochemical indices in the chicks protected by Silymarin in addition to OTA treatment also supported the protective effects of this herbal additive on the kidneys and liver. The same herbal substance Silymarin could be used as a practical approach for safely utilizing of OTA-contaminated feed. Key words: ochratoxin A, protection, herbal additive...

International Journal of Molecular Sciences, 2008

Various etiological factors contributing to the development of mycotoxic nephropathy in farm anim... more Various etiological factors contributing to the development of mycotoxic nephropathy in farm animals and humans are reviewed. The possible synergistic effect between ochratoxin A (OTA) and other mycotoxins, as penicillic acid (PA) and fumonisin B 1 (FB 1 ), contributing to this nephropathy is also considered and discussed. The most convenient ways of prophylaxis and various preventive measures against OTA contamination of feeds or foods are reviewed. A reference is made concerning the most successful methods of veterinary hygiene control in the slaughterhouses in order to prevent the entering of OTA in commercial channels with a view to human health. The economic efficacy of these prophylactic procedures is also considered. An evaluation of human exposure to OTA is made.

Food Toxicology

The existing hazard of joint mycotoxin exposure of animals/humans and the significance of masked ... more The existing hazard of joint mycotoxin exposure of animals/humans and the significance of masked mycotoxins in foods or feeds and their respective contributions to the development of some food born mycotoxicoses is briefly reviewed. The importance of joint mycotoxin interaction in the complex etiology of some foodborn mycotoxicoses is covered in depth. The toxicity of low contamination levels of some combinations of mycotoxins ingested often by farm animals was carefully studied. The appropriate hygiene control and the necessary risk assessment in regard to mycotoxin contamination of foods and feeds are briefly analyzed and some useful prophylactic measures and management of the risk of mycotoxin contamination, in addition to tolerable daily intakes are also described. A reference is also made to the most suitable methods of veterinary hygiene control in some practical situations in order to prevent mycotoxins contaminating commercial food commodities and endangering public health.

Toxicon, 2021

Abstract: Carcinogenic effects of ochratoxin A (OTA) on liver, kidneys, intestine, lung and eyes ... more Abstract: Carcinogenic effects of ochratoxin A (OTA) on liver, kidneys, intestine, lung and eyes of Wistar rats exposed to 10 ppm or 5 ppm OTA in the diet and additionally supplemented or not with phenylalanine (PHE) were examined during 24-months experimental period. OTA was seen to provoke strong degenerative changes and slight pericapillary oedema in most internal organs, e.g. kidneys, liver, intestine, spleen and brain. Six of total nine neoplasms were identified as malignant and three as benign. Five of total six malignant neoplasms and two of total three benign neoplasms were seen in male rats. The pathological finding in rats after two weeks feeding with OTA-contaminated feed was dominated by degenerative changes in various internal organs, which were weaker in the group additionally supplemented with PHE. The protective effect of PHE was evident with respect to OTA-induced decrease of serum glucose and serum protein, but this protection was not singnificant with respect to serum enzymes activity. The number of neoplasms in PHE-supplemented group exposed to 10 ppm OTA was similar to that in the group exposed to twice lower feed levels of OTA alone, suggesting about a possible protective effect of PHE. The rats would not be able to serve as experimental model for humans with regard to OTA-induced tumorigenesis, because the target organ of OTA-toxicity in humans and pigs is mainly the kidney as opposed to the significant damages and carcinogenic effects seen in various organs in rats exposed to OTA.

Alternative therapies in health and medicine, 2019

This review is designed to initiate a discussion we believe is necessary for the biomedical commu... more This review is designed to initiate a discussion we believe is necessary for the biomedical community, because of some recent evidences for existing of a new body anatomical system, or the primo vascular system (PVS), which could be the missing link in the scientific explanation of the unknown mechanism of action of acupuncture. Some important questions for the medical society, (eg, "What is the main source of the mistrust of Western medicine toward traditional Oriental medicine and could it be overcome?" or "Is the PVS a real one and what is its distribution, formation, and function?" or "Are there scientific proofs for intimate relationships of the PVS with meridian system and whether the PVS would be the physical basis of meridians?") are deeply studied and appropriately answered. Various pieces of knowledge are now combined to achieve a better understanding and to provide an acceptable explanation about the functions of such new system and to explai...

Purpose: To check the comparative efficacy of DNA protection by silymarin and its nanoformulation... more Purpose: To check the comparative efficacy of DNA protection by silymarin and its nanoformulation as an effective radiation countermeasure agent in ameliorating γ-radiation-induced Genotoxicity. Methods: The study performed suggests the efficacy of silymarin and its nanoformulation specifically in ameliorating γ-radiation-induced genotoxic effects at cellular, plasmid DNA levels etc. Results: The retention of super-coiled DNA following treatment of DNA with various concentrations of silymarin (parent compound) was found to be maximum at 25µg/ml, whereas better retention was seen at 10µg/ml in case of silymarin nanoformulation. Micronuclei count also reduced maximally at 10µg/ml when treated with silymarin nanoformulation as compared to 25µg/ml using parent compound. Summary : Silymarin and its nanoformulation showed no toxic effects on DNA. The nanoformulation demonstrated better results in terms of protection of genetic material against -radiation due to increase in surface area a...

Complex etiology of Endemic Nephropathy and possible prophylaxis

The progression of coccidiosis provoked by e. adenoeides was followed in turkey poults given ochr... more The progression of coccidiosis provoked by e. adenoeides was followed in turkey poults given ochratoxin A (OTA) in feed. More heavy and rapid progress of coccidiosis occurred in OTA-treated turkey poults than in those fed an OTA-free diet, as can be seen from the higher levels of oocyst and lesion indices and more rapid mortality in such birds. The concentration of total protein in serum was significantly increased in turkey poults infected with e. adenoeides and simultaneously given OTA. The serum concentration of uric acid was significantly increased in all experimental groups, especially in those exposed to OTA, and most notably in the group additionally infected with e. adenoeides. OTA induced degenerative changes in kidneys, liver and heart as well as depletion of lymphoid tissue in the lymphoid organs and a decrease in body mass. Coccidiosis also induced a growth depression in addition to caecal haemorrhages. Impairment of kidney function, histopathological changes and general...

S.D. Stoev*, M.F. Dutton, P.B. Njobeh, J.S. Mosonik and P.A. Steenkamp Department of General and ... more S.D. Stoev*, M.F. Dutton, P.B. Njobeh, J.S. Mosonik and P.A. Steenkamp Department of General and Clinical Pathology, Faculty of Veterinary Medicine, Trakia University, Students Campus, 6000 Stara Zagora, Bulgaria; Food, Environment and Health Research Group, Faculty of Health Science, University of Johannesburg, Doornfontein 2028, Gauteng, PO Box 17011, South Africa; Council for Scientific and Industrial Research, Biosciences, Ardeer Road, Private Bag x2, Modderfontein, 1645, South Africa

Acta Pharmaceutica

The aim of the study was to provide an in-depth characterization of the methanol-aqueous extract ... more The aim of the study was to provide an in-depth characterization of the methanol-aqueous extract from the aerial parts of Gypsophila glomerata Pall. Ex Adams (Caryophyllaceae) (EGG) and to assess its protective potential on carbon tetrachloride (CCl4)-induced liver and kidney damage in male Wistar rats. Twenty-two flavonoid C-, O- and C,O--glycosides in EGG were annotated by mass spectrometry--based molecular networking; nine of them are reported in this species for the first time. Fourteen-day oral administration of EGG at a dose 200 mg kg−1 bm prevented significantly CCl4-induced liver injury, discerned by an amelioration of the markers of oxidative stress (GSH and MDA) and transaminase activity. EGG decreased the serum level of urea and creatinine as well. The observed improvement of biochemical parameters was supported by histopathological observations. The protective hepatorenal effects of EGG, rich in 2“-О-pentosyl-6-С-hexosyl-apigenin/luteolin/ methylluteolin and their acetyl...

In a mycological study, a total of 95 human food samples were investigated to evaluate the incide... more In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.

Journal of Aquaculture Engineering and Fisheries Research, 2015

The main clinical and pathomorphological changes in Aeromonas hydrophila infection in carp provok... more The main clinical and pathomorphological changes in Aeromonas hydrophila infection in carp provoked by different field strains of this bacterium were studied. The strongest histopathological damages were seen in the functional epithelium of liver and kidneys, followed by intestine and hearth damages in addition to various haemorrhages in interstitial tissues of visceral organs and some skin haemorrhages on the ventral surface of the body and the anal region. As a whole, pathological damages consisted of degenerative changes as cloudy swelling, granular and/or hyaline droplet degeneration or vacuolation in functional epithelium in the respective internal organs in addition to some target vascular disturbances, which appeared to be good biomarkers for field assessment of that disease. Pathological damages in internal organs and haemorrhages were stronger in experimental fishes exposed to higher levels of the respective pathogens, especially those isolated from dead anaconda or the referent strain, and less pronounced damages were seen in fishes infected with of Aeromonas hydrophila isolated from a silver carp with marked signs of septicaemia.

Oxidative-protective effects of Tinospora cordifolia extract on plasma and spleen cells after experimental ochratoxicosis

Comparative Clinical Pathology

The importance of Tinospora cordifolia extract was investigated for its possible protective effec... more The importance of Tinospora cordifolia extract was investigated for its possible protective effect in spleen and blood in male ICR albino mice against ochratoxin A-induced toxicity (OTA). OTA instigates oxidative changes and results in the overproduction of free radicals, changes in body/organ weight, and the food consumption and is considered as a risk factor for animals and humans. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and consequent lipid-peroxidative damages caused by OTA are considered to be the main mechanisms leading to oxidative stress disorders in organs and blood. TC oral administrations prevent the physiological status of animals and improve the biochemical parameters of the urine and plasma. Moreover, EPR analysis show that TC administration decreased Asc • and NO • radicals and ROS productions in the spleen and serum, even in OTA-treated group. The significant decrease in MDA formation in the spleen and serum and the increased expression of SOD activity in TC and TC + OTA groups confirm the positive modulatory effect of TC extract on the cellular antioxidant system. TC and TC + OTA treatment caused significant reduction of genotoxic potential (8-OHdG) of OTA, followed by a decreased oxidative activity and gradual recovery of ROS-induced DNA damage. The results suggested that TC extract protect against OTA-induced oxidative disorders and other abnormalities. As typical antioxidant TC could protect splenic macrophages and regain intracellular antioxidant capacity.

Balkan Endemic Nephropathy – Still continuing enigma, risk assessment and underestimated hazard of joint mycotoxin exposure of animals or humans

Chemico-Biological Interactions

Research in Veterinary Science, 2016

The possible interaction between Pasteurella multocida and the mycotoxin fumonisin B1 (FB1), reco... more The possible interaction between Pasteurella multocida and the mycotoxin fumonisin B1 (FB1), recognised as one of the most often food/feed contaminant, was studied with the aim to evaluate whether and how FB1 can influence and/or complicate the development and severity of various pathological damages provoked by Pasteurella multocida in some internal organs of pigs. Heavier lung pathology was seen in pigs experimentally infected with Pasteurella multocida, when the same were exposed to 20 ppm dietary levels of fumonisin B 1 (FB 1) as was assessed by gross pathology, pathomorphological examinations, clinical biochemistry and some immunological investigations. The most typical damages in FB 1 treated pigs were the strong oedema in the lung and the slight oedema in the other internal organs and mild degenerative changes in the kidneys, whereas the typical pathomorphological findings in pigs infected with Pasteurella multocida was broncho-interstitial pneumonia. FB1 was found to aggravate pneumonic changes provoked by P. multocida in the cranial lobes of the lung and to complicate pneumonic damages with interstitial oedema in the lung. No macroscopic damages were observed in the pigs infected only with Pasteurella multocida. It can be concluded that the feed intake of FB1 in pigs may complicate or exacerbate the course of P. multocida serotype A infection.